Sampling and characterisation of groundwater colloids in ONKALO at Olkiluoto, Finland 2009-2010

International Nuclear Information System (INIS)

Jaervinen, E.; Manninen, P.; Takala, M.; Vilhunen, S.

2011-04-01

The purpose of this study was to estimate the concentration of colloids and composition of the colloid phase on the basis of the water chemistry results of filtered and unfiltered water samples and to compare the results with the previous ones. The water samples were collected from groundwater stations ONK-PVA1 in December 2009 and ONKPVA5 in June 2010. The colloid concentrations were determined from scanning electron microscopy (SEM) micrographs taken from the filters. The change in the water chemistry due to filtration was also analysed. The decrease of element concentrations due to filtration would possibly reflect the composition of the colloid phase. Because the concentration of the colloids is very low, three parallel water samples were analysed three times with an Inductively Coupled Plasma - Mass Spectrometry (ICP-MS) analyser so that the chemical differences between the filtered and unfiltered water could be evaluated. The colloid concentration in ONK-PVA1, determined by the single particle analysis of SEM micrographs, was 0.5 μg/l while the colloid concentration in ONK-PVA5 was 0.15 μg/l. The colloid phase composition could not be reliably determined due to the low colloid concentration. (orig.)

Colloid transport in model fracture filling materials

Science.gov (United States)

Wold, S.; Garcia-Garcia, S.; Jonsson, M.

2010-12-01

Colloid transport in model fracture filling materials Susanna Wold*, Sandra García-García and Mats Jonsson KTH Chemical Science and Engineering Royal Institute of Technology, SE-100 44 Stockholm, Sweden *Corresponding author: E-mail: wold@kth.se Phone: +46 8 790 6295 In colloid transport in water-bearing fractures, the retardation depends on interactions with the fracture surface by sorption or filtration. These mechanisms are difficult to separate. A rougher surface will give a larger area available for sorption, and also when a particle is physically hindered, it approaches the surface and enables further sorption. Sorption can be explained by electrostatics were the strongest sorption on minerals always is observed at pH below pHpzc (Filby et al., 2008). The adhesion of colloids to mineral surfaces is related to the surface roughness according to a recent study (Darbha et al., 2010). There is a large variation in the characteristics of water-bearing fractures in bedrock in terms of aperture distribution, flow velocity, surface roughness, mineral distributions, presence of fracture filling material, and biological and organic material, which is hard to implement in modeling. The aim of this work was to study the transport of negatively charged colloids in model fracture filling material in relation to flow, porosity, mineral type, colloid size, and surface charge distribution. In addition, the impact on transport of colloids of mixing model fracture filling materials with different retention and immobilization capacities, determined by batch sorption experiments, was investigated. The transport of Na-montmorillonite colloids and well-defined negatively charged latex microspheres of 50, 100, and 200 nm diameter were studied in either columns containing quartz or quartz mixed with biotite. The ionic strength in the solution was exclusively 0.001 and pH 6 or 8.5. The flow rates used were 0.002, 0.03, and 0.6 mL min-1. Sorption of the colloids on the model fracture

New innovative electrocoagulation (EC) treatment technology for BWR colloidal iron utilizing the seeding and filtration electronically (SAFETTM) system

International Nuclear Information System (INIS)

Denton, Mark S.; Bostick, William D.

2007-01-01

The presence of iron (iron oxide from carbon steel piping) buildup in Boiling Water Reactor (BWR) circuits and wastewaters is decades old. In, perhaps the last decade, the advent of precoatless filters for condensate blow down has compounded this problem due to the lack of a solid substrate (e.g., Powdex resin pre-coat) to help drop the iron out of solution. The presence and buildup of this iron in condensate phase separators (CPS) further confounds the problem when the tank is decanted back to the plant. Iron carryover here is unavoidable without further treatment steps. The form of iron in these tanks, which partially settles and is pumped to a de-waterable high integrity container (HIC), is particularly difficult and time consuming to de-water (low shear strength, high water content). The addition upstream from the condensate phase separator (CPS) of chemicals, such as polymers, to carry out the iron, only produces an iron form even more difficult to filter and de-water (even less shear strength, higher water content, and a gel/slime consistency). Typical, untreated colloidal material contains both sub-micron particles up to, let's say 100 micron. It is believed that the sub-micron particles penetrate filters, or sheet filters, thus plugging the pores for what should have been the successful filtration of the larger micron particles. Like BWR iron wastewaters, fuel pools/storage basins (especially in the decon. phase) often contain colloids which make clarity and the resulting visibility nearly impossible. Likewise, miscellaneous, often high conductivity, waste streams at various plants contain such colloids, iron, salts (sometimes seawater intrusion and referred to as Salt Water Collection Tanks), dirt/clay, surfactants, waxes, chelants, etc. Such waste streams are not ideally suited for standard dead-end (cartridges) or cross-flow filtration (UF/RO) followed even by demineralizers. Filter and bed plugging are almost assured. The key to solving these dilemmas

Magnetic-seeding filtration

Energy Technology Data Exchange (ETDEWEB)

DePaoli, D.W.; Tsouris, C. [Oak Ridge National Lab., TN (United States); Yiacoumi, Sotira

1997-10-01

Magnetic-seeding filtration is a technology under development for the enhanced removal of magnetic and non-magnetic particulates from liquids. This process involves the addition of a small amount of magnetic seed particles (such as naturally occurring iron oxide) to a waste suspension, followed by treatment with a magnetic filter. Non-magnetic and weakly magnetic particles are made to undergo nonhomogeneous flocculation with the seed particles, forming flocs of high magnetic susceptibility that are readily removed by a conventional high-gradient magnetic filter. This technology is applicable to a wide range of liquid wastes, including groundwater, process waters, and tank supernatants. Magnetic-seeding filtration may be used in several aspects of treatment, such as (1) removal of solids, particularly those in the colloidal size range that are difficult to remove by conventional means; (2) removal of contaminants by precipitation processes; and (3) removal of contaminants by sorption processes. Waste stream characteristics for which the technology may be applicable include (1) particle sizes ranging from relatively coarse (several microns) to colloidal particles, (2) high or low radiation levels, (3) broad-ranging flow rates, (4) low to moderate solids concentration, (5) cases requiring high decontamination factors, and (6) aqueous or non-aqueous liquids. At this point, the technology is at the bench-scale stage of development; laboratory studies and fundamental modeling are currently being employed to determine the capabilities of the process.

Magnetic-seeding filtration

International Nuclear Information System (INIS)

DePaoli, D.W.; Tsouris, C.; Yiacoumi, Sotira.

1997-01-01

Magnetic-seeding filtration is a technology under development for the enhanced removal of magnetic and non-magnetic particulates from liquids. This process involves the addition of a small amount of magnetic seed particles (such as naturally occurring iron oxide) to a waste suspension, followed by treatment with a magnetic filter. Non-magnetic and weakly magnetic particles are made to undergo nonhomogeneous flocculation with the seed particles, forming flocs of high magnetic susceptibility that are readily removed by a conventional high-gradient magnetic filter. This technology is applicable to a wide range of liquid wastes, including groundwater, process waters, and tank supernatants. Magnetic-seeding filtration may be used in several aspects of treatment, such as (1) removal of solids, particularly those in the colloidal size range that are difficult to remove by conventional means; (2) removal of contaminants by precipitation processes; and (3) removal of contaminants by sorption processes. Waste stream characteristics for which the technology may be applicable include (1) particle sizes ranging from relatively coarse (several microns) to colloidal particles, (2) high or low radiation levels, (3) broad-ranging flow rates, (4) low to moderate solids concentration, (5) cases requiring high decontamination factors, and (6) aqueous or non-aqueous liquids. At this point, the technology is at the bench-scale stage of development; laboratory studies and fundamental modeling are currently being employed to determine the capabilities of the process

Experimental and Numerical Investigations on Colloid-facilitated Plutonium Reactive Transport in Fractured Tuffaceous Rocks

Science.gov (United States)

Dai, Z.; Wolfsberg, A. V.; Zhu, L.; Reimus, P. W.

2017-12-01

Colloids have the potential to enhance mobility of strongly sorbing radionuclide contaminants in fractured rocks at underground nuclear test sites. This study presents an experimental and numerical investigation of colloid-facilitated plutonium reactive transport in fractured porous media for identifying plutonium sorption/filtration processes. The transport parameters for dispersion, diffusion, sorption, and filtration are estimated with inverse modeling for minimizing the least squares objective function of multicomponent concentration data from multiple transport experiments with the Shuffled Complex Evolution Metropolis (SCEM). Capitalizing on an unplanned experimental artifact that led to colloid formation and migration, we adopt a stepwise strategy to first interpret the data from each experiment separately and then to incorporate multiple experiments simultaneously to identify a suite of plutonium-colloid transport processes. Nonequilibrium or kinetic attachment and detachment of plutonium-colloid in fractures was clearly demonstrated and captured in the inverted modeling parameters along with estimates of the source plutonium fraction that formed plutonium-colloids. The results from this study provide valuable insights for understanding the transport mechanisms and environmental impacts of plutonium in fractured formations and groundwater aquifers.

Colloid transport in saturated porous media: Elimination of attachment efficiency in a new colloid transport model

Science.gov (United States)

Landkamer, Lee L.; Harvey, Ronald W.; Scheibe, Timothy D.; Ryan, Joseph N.

2013-01-01

A colloid transport model is introduced that is conceptually simple yet captures the essential features of colloid transport and retention in saturated porous media when colloid retention is dominated by the secondary minimum because an electrostatic barrier inhibits substantial deposition in the primary minimum. This model is based on conventional colloid filtration theory (CFT) but eliminates the empirical concept of attachment efficiency. The colloid deposition rate is computed directly from CFT by assuming all predicted interceptions of colloids by collectors result in at least temporary deposition in the secondary minimum. Also, a new paradigm for colloid re-entrainment based on colloid population heterogeneity is introduced. To accomplish this, the initial colloid population is divided into two fractions. One fraction, by virtue of physiochemical characteristics (e.g., size and charge), will always be re-entrained after capture in a secondary minimum. The remaining fraction of colloids, again as a result of physiochemical characteristics, will be retained “irreversibly” when captured by a secondary minimum. Assuming the dispersion coefficient can be estimated from tracer behavior, this model has only two fitting parameters: (1) the fraction of the initial colloid population that will be retained “irreversibly” upon interception by a secondary minimum, and (2) the rate at which reversibly retained colloids leave the secondary minimum. These two parameters were correlated to the depth of the Derjaguin-Landau-Verwey-Overbeek (DLVO) secondary energy minimum and pore-water velocity, two physical forces that influence colloid transport. Given this correlation, the model serves as a heuristic tool for exploring the influence of physical parameters such as surface potential and fluid velocity on colloid transport.

Colloid molecular weight estimation by gel chromatography/acrylamide gel electrophoresis

International Nuclear Information System (INIS)

Liberatore, F.A.; Dearborn, C.; Nigam, S.; Poon, C.; Camin, L.; Liteplo, M.

1984-01-01

Size or molecular weight (MW) estimation of radiolabeled collides in aqueous solutions has long been a problem. The authors have prepared several minimicroaggregated albumin colloids (mμAA) by heat denaturation of stannous-containing HSA solutions at pH 7.0, 7.5, and 8.5). The resulting colloids were labeled with Tc-99m and compared with Au-198 colloid and Tc-99m-antimony sulfide colloid (Tc-99m-Sb/sub 2/S3) by gel chromatography and gel electrophoresis. Tc-99mm-mμAA aggregated at pH 7.0 and the Au-198 colloid appeared in the external void volume of a BioRad A5.0 agarose column indicating an apparent MW of > 5 x 10/sup 6/ daltons. The pH7.5 Tc-99m-mμAA, migrated within the filtration range of the column as did a small fraction of Tc-99m-Sb/sub 2/S/sub 3/, suggesting that the MW is between 6 x 10/sup 4/ - 5 x 10/sup 6/ daltons. The Tc-99m-mμAA, aggregated at pH 8.5, had an apparent MW on gel filtration similar to that of untreated albumin, MW 6.6 x 10-/sup 4/ daltons. The mobilities of the colloids, on acrylamide disc gel electrophoresis, were consistent with the results on gel chromatography. The largest colloids, Au-198 colloid and pH 7.0 Tc-99m-mμAA, barely entered the separating gel; intermediate sized colloids, a small fraction of Tc-99m-Sb/sub 2/S/sub 3/ and pH 7.5 Tc-99m-mμAA migrated farther into the separating gel; while pH 8.5 Tc-99m-mμAA had mobility approaching that of untreated albumin. Lymphoscintigraphy studies using these colloids in animals showed the predicted, particle size-related differences in migration and clearance. The authors conclude that gel chromatography and gel electrophoresis are useful methods for estimating the apparent size of the colloidal particles

Grimsel colloid exercise

International Nuclear Information System (INIS)

Degueldre, C.; Longworth, G.; Vilks, P.

1989-11-01

The Grimsel Colloid Exercise was an intercomparison exercise which consisted of an in situ sampling phase followed by a colloid characterisation step. The goal of this benchmark exercise, which involved 12 laboratories, was to evaluate both sampling and characterisation techniques with emphasis on the colloid specific size distribution. The sampling phase took place at the Grimsel Test Site between February 1 and 13, 1988 and the participating groups produced colloid samples using the following methods: 1. Cross-flow ultrafiltration with production of membranes loaded with colloids. 2. Tangential diaultrafiltration and production of colloid concentrates. 3. Filtrates produced by each group. 4. Unfiltered water was also collected by PSI in glass bottles, under controlled anaerobic conditions, and by the other sampling groups in various plastic bottles. In addition, on-line monitoring of pH, χ, [O-2] and T of the water and of [O-2] in the atmosphere of the sampling units was carried out routinely. All samples were shipped according to the CoCo Club scheme for characterisation, with emphasis on the size distribution. The exercise differentiates the colloid samples produced on site from those obtained after transfer of the fluid samples to the laboratories. The colloid concentration and size distribution can be determined by scanning electron microscopy (SEM), gravimetry (GRAV), chemical analysis of fluid samples after micro/ultrafiltration (MF/UF) and by transmission single particle counting (PC). The colloid concentration can also be evaluated by transmission electron microscopy (TEM), static and dynamic light scattering (SLS,DLS) and by laser-induced photoacoustic spectroscopy (LPAS). The results are discussed on the basis of the detection limit, lateral resolution and counting conditions of the technique (precision) as well as sample preparation, artefact production and measurement optimisation (accuracy). A good agreement between size distribution results was

Behavior of colloids in radionuclide migration in deep geologic formation

International Nuclear Information System (INIS)

Kanno, Takuji

1994-01-01

In case high level waste is isolated in deep strata, it is important to elucidate the behavior of movement that radionuclides take in the strata. Recently, it has been recognized that the participation of colloids is very important, and it has been studied actively. In this study, as to the mechanism of the adsorption of colloids to geological media or buffers, analysis was carried out for a number of systems, and it was clarified in what case they are caught or they move without being caught. Also it is considered what research is necessary hereafter. First, the kinds of colloids are shown. As the properties of colloids that control the movement of colloids in groundwater in deep strata, the surface potential, shape, size and so on of colloids are conceivable. These properties are briefly discussed. As the interaction of colloids and geological media, the interaction by electrostatic attraction, the fast and slow movement of colloids through rock crevices, and the filtration of colloids in buffers and porous media are described. The experimental results on the movement of colloids are reported. (K.I.)

Impact of colloid formation on safety assessment of waste disposal in brine

International Nuclear Information System (INIS)

Nagasaki, S.

2014-01-01

The transport model, which had been developed at low ionic strength in an ion - colloid - solid ternary system, was applied to the transport of Np(V) (NpO 2 + ) and humic acid through a quartz-packed column at 2 M NaCl. It was found that the model was useful to simulate the transport behaviors of Np(V) and humic acid by the modification of filtration coefficient which depends on the colloid size. Using this model, the impact of colloids on the transport of actinides was evaluated. It was found that the influence of the colloids in brine is limited or negligible. (author)

Saturated Zone Colloid Transport

International Nuclear Information System (INIS)

H. S. Viswanathan

2004-01-01

This scientific analysis provides retardation factors for colloids transporting in the saturated zone (SZ) and the unsaturated zone (UZ). These retardation factors represent the reversible chemical and physical filtration of colloids in the SZ. The value of the colloid retardation factor, R col is dependent on several factors, such as colloid size, colloid type, and geochemical conditions (e.g., pH, Eh, and ionic strength). These factors are folded into the distributions of R col that have been developed from field and experimental data collected under varying geochemical conditions with different colloid types and sizes. Attachment rate constants, k att , and detachment rate constants, k det , of colloids to the fracture surface have been measured for the fractured volcanics, and separate R col uncertainty distributions have been developed for attachment and detachment to clastic material and mineral grains in the alluvium. Radionuclides such as plutonium and americium sorb mostly (90 to 99 percent) irreversibly to colloids (BSC 2004 [DIRS 170025], Section 6.3.3.2). The colloid retardation factors developed in this analysis are needed to simulate the transport of radionuclides that are irreversibly sorbed onto colloids; this transport is discussed in the model report ''Site-Scale Saturated Zone Transport'' (BSC 2004 [DIRS 170036]). Although it is not exclusive to any particular radionuclide release scenario, this scientific analysis especially addresses those scenarios pertaining to evidence from waste-degradation experiments, which indicate that plutonium and americium may be irreversibly attached to colloids for the time scales of interest. A section of this report will also discuss the validity of using microspheres as analogs to colloids in some of the lab and field experiments used to obtain the colloid retardation factors. In addition, a small fraction of colloids travels with the groundwater without any significant retardation. Radionuclides irreversibly

PCR detection of groundwater bacteria associated with colloidal transport

Energy Technology Data Exchange (ETDEWEB)

Cruz-Perez, P.; Stetzenbach, L.D.; Alvarez, A.J.

1996-02-29

Colloidal transport may increase the amount of contaminant material than that which could be transported by water flow alone. The role of colloids in groundwater contaminant transport is complicated and may involve many different processes, including sorption of elements onto colloidal particles, coagulation/dissolution, adsorption onto solid surfaces, filtration, and migration. Bacteria are known to concentrate minerals and influence the transport of compounds in aqueous environments and may also serve as organic colloids, thereby influencing subsurface transport of radionuclides and other contaminants. The initial phase of the project consisted of assembling a list of bacteria capable of sequestering or facilitating mineral transport. The development and optimization of the PCR amplification assay for the detection of the organisms of interest, and the examination of regional groundwaters for those organisms, are presented for subsequent research.

PCR detection of groundwater bacteria associated with colloidal transport

International Nuclear Information System (INIS)

Cruz-Perez, P.; Stetzenbach, L.D.; Alvarez, A.J.

1996-01-01

Colloidal transport may increase the amount of contaminant material than that which could be transported by water flow alone. The role of colloids in groundwater contaminant transport is complicated and may involve many different processes, including sorption of elements onto colloidal particles, coagulation/dissolution, adsorption onto solid surfaces, filtration, and migration. Bacteria are known to concentrate minerals and influence the transport of compounds in aqueous environments and may also serve as organic colloids, thereby influencing subsurface transport of radionuclides and other contaminants. The initial phase of the project consisted of assembling a list of bacteria capable of sequestering or facilitating mineral transport. The development and optimization of the PCR amplification assay for the detection of the organisms of interest, and the examination of regional groundwaters for those organisms, are presented for subsequent research

Impact of colloid formation on safety assessment of waste disposal in brine

Energy Technology Data Exchange (ETDEWEB)

Nagasaki, S. [McMaster Univ., Hamilton, ON (Canada)

2014-07-01

The transport model, which had been developed at low ionic strength in an ion - colloid - solid ternary system, was applied to the transport of Np(V) (NpO{sub 2}{sup +} ) and humic acid through a quartz-packed column at 2 M NaCl. It was found that the model was useful to simulate the transport behaviors of Np(V) and humic acid by the modification of filtration coefficient which depends on the colloid size. Using this model, the impact of colloids on the transport of actinides was evaluated. It was found that the influence of the colloids in brine is limited or negligible. (author)

Application of Colloidal Filtration Theory on Textile Fibrous Media: Effect of Fiber Orientation on Bacterial Removal Efficiency and Attachment

Science.gov (United States)

Roy, Sukumar; Ghosh, Subrata; Bhowmick, Niranjan

2018-05-01

A mechanism to remove the Pseudomonas bacteria from contaminated water by using textile fibrous media has been proposed in this article. The attachment of Pseudomonas bacteria on nylon fibrous media was studied in laboratory column experiment. A systematic study was carried out to investigate the attachment of bacteria on the fibrous material as a function of fiber orientation to the direction of the liquid flow. Three types of textiles media with different orientation fiber were selected for the experiment (i.e. 0°, 45° and 90°). It was found that the bacteria removal efficiency was comparatively higher at 90° orientation as compared to that of 45° and 0° orientation of fibrous media, suggesting that the removal efficiency of bacteria (1 - Fp) was depended on fiber orientation. The removal trends were explained on the basis of colloidal filtration theory. This is due to the higher single collector contact efficiency and attachment/collision efficiency as observed from the experimental data of removal efficiency.

Experimental evidence of colloids and nanoparticles presence from 25 waste leachates

Energy Technology Data Exchange (ETDEWEB)

Hennebert, Pierre, E-mail: pierre.hennebert@ineris.fr [INERIS – Institut National de l’Environnement Industriel et des Risques, Domaine du Petit Arbois BP33, F-13545 Aix-en-Provence (France); Avellan, Astrid; Yan, Junfang [INERIS – Institut National de l’Environnement Industriel et des Risques, Domaine du Petit Arbois BP33, F-13545 Aix-en-Provence (France); Aguerre-Chariol, Olivier [INERIS, Parc Technologique ALATA, BP No. 2, 60550 Verneuil en Halatte (France)

2013-09-15

Highlights: • This work is the first assessment of colloids in waste leachates. • Analytical methods are proposed and discussed. • All the waste have at least one element in colloidal form, and some elements are always colloidal. • Man-made nanoparticles are observed. • It can change the interpretation of leachate elemental concentration. - Abstract: The potential colloids release from a large panel of 25 solid industrial and municipal waste leachates, contaminated soil, contaminated sediments and landfill leachates was studied. Standardized leaching, cascade filtrations and measurement of element concentrations in the microfiltrate (MF) and ultrafiltrate (UF) fraction were used to easily detect colloids potentially released by waste. Precautions against CO{sub 2} capture by alkaline leachates, or bacterial re-growth in leachates from wastes containing organic matter should be taken. Most of the colloidal particles were visible by transmission electron microscopy with energy dispersion spectrometry (TEM–EDS) if their elemental MF concentration is greater than 200 μg l{sup −1}. If the samples are dried during the preparation for microscopy, neoformation of particles can occur from the soluble part of the element. Size distribution analysis measured by photon correlation spectroscopy (PCS) were frequently unvalid, particularly due to polydispersity and/or too low concentrations in the leachates. A low sensitivity device is required, and further improvement is desirable in that field. For some waste leachates, particles had a zeta potential strong enough to remain in suspension. Mn, As, Co, Pb, Sn, Zn had always a colloidal form (MF concentration/UF concentration > 1.5) and total organic carbon (TOC), Fe, P, Ba, Cr, Cu, Ni are partly colloidal for more than half of the samples). Nearly all the micro-pollutants (As, Ba, Co, Cr, Cu, Mo, Ni, Pb, Sb, Sn, V and Zn) were found at least once in colloidal form greater than 100 μg l{sup −1}. In particular

Increasing Wet Green Strength of Alumina Body During Microfabrication by Colloidal Isopressing

National Research Council Canada - National Science Library

Zhang, Zhuo

2004-01-01

Colloidal Isopressing involves formulating a slurry with a weakly attractive particle network that can be pre-consolidated to a high relative density by pressure filtration and still retain fluid-like characteristics...

Deposition behavior of colloid in filtration process through glass beads packed bed

International Nuclear Information System (INIS)

Chinju, Hirofumi; Nagasaki, Shinya; Tanaka, Satoru; Tanaka, Tadao; Takebe, Shinichi; Ogawa, Hiromichi

1999-01-01

We investigated the deposition behavior in colloid transport through porous media by conducting column experiments and batch experiments using polystyrene latex particles and spherical glass beads. The conclusion of this present work are summarized as follows: (1) The comparison between the results of the batch and the column experiments indicated that the deposition was enhanced in the column experiments compared with the batch experiments due to particles trapped by the effect of slow field. (2) Colloid BTCs showed three different stages of deposition which can be characterized by the different rate of the change in the C/C O . Three stages can be explained by the existence of large area of weak deposition sites and small area of strong deposition sites on the collector surfaces. (3) The amount of deposited particles until the beginning of the third stage was larger for lower flow velocity. (4) The results of the column experiments revealed that breakthrough behavior of colloidal particles of the second run after back wash process is affected by remaining particles on collector surfaces. (J.P.N.)

CALCULATION OF LONG-TERM FILTRATION IN A POROUS MEDIUM

Directory of Open Access Journals (Sweden)

Ludmila I. Kuzmina

2018-03-01

Full Text Available he filtration problem in a porous medium is an important part of underground hydromechanics. Filtration of suspensions and colloids determines the processes of strengthening the soil and creating waterproof walls in the ground while building the foundations of buildings and underground structures. It is assumed that the formation of a deposit is dominated by the size-exclusion mechanism of pore blocking: solid particles pass freely through large pores and get stuck at the inlet of pores smaller than the diameter of the particles. A one-dimensional mathematical model for the filtration of a monodisperse suspension includes the equation for the mass balance of suspended and retained particles and the kinetic equation for the growth of the deposit. For the blocking filtration coefficient with a double root, the exact solution is given implicitly. The asymptotics of the filtration problem is constructed for large time. The numerical calculation of the problem is carried out by the finite differences method. It is shown that asymptotic approximations rapidly converge to a solution with the increase of the expansion order.

Saturated Zone Colloid Transport

Energy Technology Data Exchange (ETDEWEB)

H. S. Viswanathan

2004-10-07

This scientific analysis provides retardation factors for colloids transporting in the saturated zone (SZ) and the unsaturated zone (UZ). These retardation factors represent the reversible chemical and physical filtration of colloids in the SZ. The value of the colloid retardation factor, R{sub col} is dependent on several factors, such as colloid size, colloid type, and geochemical conditions (e.g., pH, Eh, and ionic strength). These factors are folded into the distributions of R{sub col} that have been developed from field and experimental data collected under varying geochemical conditions with different colloid types and sizes. Attachment rate constants, k{sub att}, and detachment rate constants, k{sub det}, of colloids to the fracture surface have been measured for the fractured volcanics, and separate R{sub col} uncertainty distributions have been developed for attachment and detachment to clastic material and mineral grains in the alluvium. Radionuclides such as plutonium and americium sorb mostly (90 to 99 percent) irreversibly to colloids (BSC 2004 [DIRS 170025], Section 6.3.3.2). The colloid retardation factors developed in this analysis are needed to simulate the transport of radionuclides that are irreversibly sorbed onto colloids; this transport is discussed in the model report ''Site-Scale Saturated Zone Transport'' (BSC 2004 [DIRS 170036]). Although it is not exclusive to any particular radionuclide release scenario, this scientific analysis especially addresses those scenarios pertaining to evidence from waste-degradation experiments, which indicate that plutonium and americium may be irreversibly attached to colloids for the time scales of interest. A section of this report will also discuss the validity of using microspheres as analogs to colloids in some of the lab and field experiments used to obtain the colloid retardation factors. In addition, a small fraction of colloids travels with the groundwater without any significant

Physico-chemical characterisation and biological evaluation of 188-Rhenium colloids for radiosynovectomy

International Nuclear Information System (INIS)

Ures, Ma Cristina; Savio, Eduardo; Malanga, Antonio; Fernández, Marcelo; Paolino, Andrea; Gaudiano, Javier

2002-01-01

Radiosynovectomy is a type of radiotherapy used to relieve pain and inflammation from rheumatoid arthritis. In this study, 188-Rhenium ( 188 Re) colloids were characterized by physical and biological methodologies. This was used to assess which parameters of the kit formulation would be the basis in the development of a more effective radiopharmaceutical for synovectomy. Intraarticular injection in knees of rabbits assessed cavity leakage of activity. The physical characteristics of tin (Sn) and sulphur (S) colloids were determined to assess the formulation with suitable properties. Particles were grouped in three ranges for analyzing their distribution according to their number, volume and surface. The ideal particle size range was considered to be from 2 to 10 microns. Membrane filtration and laser diffraction characterization methodologies were used. While membrane filtration could give misleading data, laser diffraction proportions more reliable results. The Sn colloid showed a better distribution of particle volume and surface than S colloid, in the 2 to 10 microns range. The 188 Re-Sn colloid was obtained with a radiochemical purity higher than 95% after 30 minutes of autoclaving. While Sn colloid kit stability was verified for 60 days, the 188 Re-Sn preparation was stable in the first 24 hrs. No significant intrabatch variability (n = 3) was detected. Biodistribution and scintigraphic studies in rabbits after intraarticular injection showed relevant activity only in knee, being 90% at 48 hours. The 188 Re-Sn colloid is easy to prepare, is stable for 24 hours and shows minimal cavity leakage after intraarticular injection into rabbit knees, suggesting this radiotherapeutical agent has suitable physical properties for evaluation for joint treatment in humans

Migration of colloids of radionuclides in geologic media

International Nuclear Information System (INIS)

Tanaka, Satoru; Ogawa, Hiromichi

2001-01-01

Radionuclide migration in underground environment is affected by the presence of colloids in ground water. As the colloids in flow systems may be trapped or collected to solid surfaces, filtration effect results from. In the present study, dependence of collector efficiency on flow velocity and on heterogeneity of solid surfaces were theoretically and experimentally investigated using DLVO (Electric double-layer and Van der Waals force) and Smoluchowski-Levich approximation and the following results were obtained: Effluent to inflow ratio of colloids obtained from the column experiments can be analyzed to give collector efficiency for single particle. The dependence of collector efficiency on flow velocity was found to be smaller than that deduced from the previously proposed models. A model in which flow system affects the Brownian motion of colloids gives a smaller flow-velocity dependence of collector efficiency. On the contrary, the heterogeneity of solid surface taken into consideration in the model increases the flow velocity dependence. (S. Ohno)

Measurement of water filtration in skeletal muscle in man by an osmotic transient method

DEFF Research Database (Denmark)

Palm, T; Nielsen, S L; Lassen, N A

1983-01-01

Water filtration in the human forearm was determined with a new method using a hyperoncotic transient of albumin solution infused into the brachial artery. Baseline dilution of labelled albumin in deep forearm vein plasma in excess of the contribution from arterial blood and from infusate...... was assumed to originate from extravascular water filtered into the blood by the transient. The filtration coefficient (Fc) was determined as the ratio between filtered water and increase in colloid osmotic pressure in the blood samples, and gives the filtrative water permeability in the exchange areas...... muscles, but it is of the same order of magnitude as the capillary filtration coefficient (CFC) determined plethysmographically for the entire forearm by the venous stasis technique....

Association of uranium with colloidal and suspended particulate matter in Arabian sea near the west coast of Maharashtra (India)

International Nuclear Information System (INIS)

Singhal, R.K.; Joshi, S.N.; Hegde, A.G.

2004-01-01

Association of natural uranium in seawater with colloidal and suspended-particulate matter was determined. The separation of suspended particulate material (>0.45 ) and colloidal fraction (as dissolved fractions) in seawater were done by suction and ultra filtration techniques. Seawater samples were collected at 1 km away from the shore and subjected to sequential fractionation in nine stages ranging from 2.7 μm to 1.1 nm. Suspended particulate matter were separated in three different size groups namely >2.7 μm, 0.45 μm and 0.22 μm by suction filtration using cellulose acetate and nitrate membranes filters. To concentrate the solution with colloidal particles <0.22 μm-1.1 nm (0.5 k Nominal Molecular Weight cut-off Limit (NMWL), the solution obtained from filtration through <0.22 μm was passed through stirred ultra-filtration cell. The pH and conductivity at different stages of fractionation (dissolved) showed minor variations. The concentration of uranium was measured in suspended and dissolved fractions by using a pulsed nitrogen laser at 337.1 nm. In order to evaluate the role of mineral colloids in various stages of filtration, concentration of calcium, magnesium, potassium were measured by using ion chromatography and atomic absorption spectrometry. The clay mineral at seawater pH (approximately 8) behave as negative ions and provides binding site for the positively charge species of uranium. Among the dissolved fraction, the maximum concentrations of colloidal uranium was observed about 4 times higher than that compared to average concentration of 6.93 ± 3.10 ppb in other fractions. In the case of suspended particulate matter, the concentration of uranium was below detection limits (<1 ppb). The maximum concentration of Ca, Mg and K in the dissolved fraction were in the <1.1 nm fraction, while for suspended particulate matter, the concentration of Ca, Mg and K decreased with the decrease in size and it is highest in the fraction of 0.22 -0.45 μm.(author)

Particle phase distribution of polycyclic aromatic hydrocarbons in stormwater — Using humic acid and iron nano-sized colloids as test particles

DEFF Research Database (Denmark)

Nielsen, Katrine; Kalmykova, Yuliya; Strömvall, Ann-Margret

2015-01-01

The distribution of polycyclic aromatic hydrocarbons (PAHs) in different particulate fractions in stormwater: Total, Particulate, Filtrated, Colloidal and Dissolved fractions, were examined and compared to synthetic suspensions of humic acid colloids and iron nano-sized particles. The distribution...

Problems of multiphase fluid filtration

CERN Document Server

Konovalov, AN

1994-01-01

This book deals with a spectrum of problems related to the mathematical modeling of multiphase filtration. Emphasis is placed on an inseparable triad: model - algorithm - computer code. An analysis of new and traditional filtration problems from the point of view of both their numerical implementation and the reproduction of one or another technological characteristics of the processes under consideration is given. The basic principles which underlie the construction of efficient numerical methods taking into account the filtration problems are discussed: non-evolutionary nature, degeneration,

Colloid-facilitated radionuclide transport in the fractured rock: effects of decay chain and limited matrix diffusion

International Nuclear Information System (INIS)

Park, J. B.; Park, J. W.; Lee, E. Y.; Kim, C. R.

2002-01-01

Colloid-facilitated radionuclide transport in the fractured rock is studies by considering radioactive decay chain and limited matrix diffusion into surrounding porous media. Semi-analytical solution in the Laplace domain is obtained from the mass balance equation of radionuclides and colloid particles. Numerical inversion of the Laplace solution is used to get the concentration profiles both in a fracture and in rock matrix. There issues are analyzed for the radionuclide concentration in a fracture by 1) formation constant of pseudo-colloid, 2) filtration coefficient of radio-colloid and 3) effective diffusion depth into the surrounding porous rock media

Uncertainty and Sensitivity Analysis of Filtration Models for Non-Fickian transport and Hyperexponential deposition

DEFF Research Database (Denmark)

Yuan, Hao; Sin, Gürkan

2011-01-01

Uncertainty and sensitivity analyses are carried out to investigate the predictive accuracy of the filtration models for describing non-Fickian transport and hyperexponential deposition. Five different modeling approaches, involving the elliptic equation with different types of distributed...... filtration coefficients and the CTRW equation expressed in Laplace space, are selected to simulate eight experiments. These experiments involve both porous media and colloid-medium interactions of different heterogeneity degrees. The uncertainty of elliptic equation predictions with distributed filtration...... coefficients is larger than that with a single filtration coefficient. The uncertainties of model predictions from the elliptic equation and CTRW equation in Laplace space are minimal for solute transport. Higher uncertainties of parameter estimation and model outputs are observed in the cases with the porous...

Particle clogging in porous media. Filtration of a smectite solution

Energy Technology Data Exchange (ETDEWEB)

Richards, Tobias (Chalmers University of Technology, Goeteborg (Sweden))

2010-01-15

The goal of this project is to find out if it is possible for bentonite clay to self heal during leaching with deionized water. The investigation has focused on the formation of a filter cake made of accessory material from MX 80 and the separation of solid material when a smectite solution (1%) is pushed through the cake using a pressure difference of 5 bar. It was also in the scope of this project to design and build the necessary equipment for these experiments. In the literature review it was not found any example that the phenomenon of clogging has been used as a self-healing method previously. It was rather separated also between the clogging of a filter cake (deep bed filtration or cake filtration) and the filtration of colloidal particles. Probably because the latter are in such low concentrations in natural systems and the focus have mainly been in the transport properties of colloids within a filter cake or deep bed filter. An experimental equipment was designed and built. It consists of seven filtration cells that could operate in parallel. All of them are connected to the same source of pressure to ensure equal conditions. A system was also prepared to prevent air from dissolving in the solution because it could create an unwanted expansion in the filter cake due to lower solubility at lower pressure. The experiment showed good separation of smectite particles from the solution when it passed through the filter cake. In all tested cases, the separation was almost complete after long enough time, indicating that the cake has small enough pores to act as a geometrical hinder for the small particles. Comparison between the materials prepared at Chalmers University of Technology and at Clay Technology showed a very good agreement indicating similar properties of the produced smectite

Particle clogging in porous media. Filtration of a smectite solution

International Nuclear Information System (INIS)

Richards, Tobias

2010-01-01

The goal of this project is to find out if it is possible for bentonite clay to self heal during leaching with deionized water. The investigation has focused on the formation of a filter cake made of accessory material from MX 80 and the separation of solid material when a smectite solution (1%) is pushed through the cake using a pressure difference of 5 bar. It was also in the scope of this project to design and build the necessary equipment for these experiments. In the literature review it was not found any example that the phenomenon of clogging has been used as a self-healing method previously. It was rather separated also between the clogging of a filter cake (deep bed filtration or cake filtration) and the filtration of colloidal particles. Probably because the latter are in such low concentrations in natural systems and the focus have mainly been in the transport properties of colloids within a filter cake or deep bed filter. An experimental equipment was designed and built. It consists of seven filtration cells that could operate in parallel. All of them are connected to the same source of pressure to ensure equal conditions. A system was also prepared to prevent air from dissolving in the solution because it could create an unwanted expansion in the filter cake due to lower solubility at lower pressure. The experiment showed good separation of smectite particles from the solution when it passed through the filter cake. In all tested cases, the separation was almost complete after long enough time, indicating that the cake has small enough pores to act as a geometrical hinder for the small particles. Comparison between the materials prepared at Chalmers University of Technology and at Clay Technology showed a very good agreement indicating similar properties of the produced smectite

Colloidal paradigm in supercapattery electrode systems

Science.gov (United States)

Chen, Kunfeng; Xue, Dongfeng

2018-01-01

Among decades of development, electrochemical energy storage systems are now sorely in need of a new design paradigm at the nano size and ion level to satisfy the higher energy and power demands. In this review paper, we introduce a new colloidal electrode paradigm for supercapattery that integrates multiple-scale forms of matter, i.e. ion clusters, colloidal ions, and nanosized materials, into one colloid system, coupled with multiple interactions, i.e. electrostatic, van der Waals forces, and chemical bonding, thus leading to the formation of many redox reactive centers. This colloidal electrode not only keeps the original ionic nature in colloidal materials, but also creates a new attribute of high electroactivity. Colloidal supercapattery is a perfect application example of the novel colloidal electrode, leading to higher specific capacitance than traditional electrode materials. The high electroactivity of the colloidal electrode mainly comes from the contribution of exposed reactive centers, owing to the confinement effect of carbon and a binder matrix. Systematic and thorough research on the colloidal system will significantly promote the development of fundamental science and the progress of advanced energy storage technology.

A pilot test of methods for determination of trace metals bound to colloids in surface waters

Energy Technology Data Exchange (ETDEWEB)

Nilsson, Kersti (Geosigma AB (Sweden))

2011-01-15

Two methods have been tested for the determination of trace metals associated with colloid species in surface waters, using test water from Eckarfjaerden (PFM000070) in Forsmark; 1) fractionation (ultra filtration) using special membrane filters with cut-offs of 1 kD and 5 kD and 2) filtration using a system of standard membrane filters with varying pore sizes connected in series. Both methods were somewhat modified compared to previous methods for colloid determination in groundwater within the site investigations at Forsmark and Laxemar (PLU). The results show that, in general, the largest amounts of metals associated with a colloid phase were recovered in the fraction between 1kD and 5 kD which indicates that the metal ions are associated with low molecular weight organic acids. Similar amounts were recovered on the filters in the filtration experiment. A minor part of the colloidal phase metals was recovered in the fraction larger than 5 kD i.e. metal ions associated with larger organic acids or colloidal size clay minerals. The metals present preferably as colloids in the fractionation experiment were: iron, thorium, cerium, uranium, neodymium, titanium, zirconium and yttrium. The filtering experiment showed larger parts of titanium and aluminum in the colloid phase than the fractionation experiment while the iron and cerium portions were equal and the uranium, yttrium and neodymium portions were lower. The results from the fractionation test showed that the dissolved parts were large for barium, manganese, strontium and rubidium. In the filtration test, uranium, yttrium and rubidium, were also present mainly as dissolved ions. The detection limit for filter analysis of thorium was high, and the part of thorium present as colloids was determined to <50%. Issues and methodological problems: - Severe contamination caused interpretation difficulties for several metal ions, especially chromium, nickel and zinc. - Both methods are time consuming and difficult to

Colloidal agglomerates in tank sludge: Impact on waste processing. 1997 annual progress report

Energy Technology Data Exchange (ETDEWEB)

Virden, J.W.

1997-06-01

'Disposal of millions of gallons of existing radioactive wastes is a major remediation problem for the Department of Energy (DOE). Although radionuclides are the most hazardous waste con- stituents. the components of greatest concern from a waste processing standpoint are insoluble sludges consisting of submicron colloidal particles. Depending on processing conditions, these colloidal particles can form agglomerate networks that could clog transfer lines or interfere with solid-liquid separations such as settle-decant operations. Under different conditions, the particles can be dispersed to form very fine suspended particles that will not create sediment in settle- decant steps and that can foul and contaminate downstream treatment components including ion exchangers or filtrations systems. Given the wide range of tank chemistries present at Hanford and other DOE sites, it is impractical to measure the properties of all potential processing conditions to design effective treatment procedures. Instead. a framework needs to be established to allow sludge property trends to be predicted on a sound scientific basis. The scientific principles of greatest utility in characterizing, understanding, and controlling the physical properties of sludge fall in the realm of colloid chemistry. The objectives of this work are to accomplish the following: understand the factors controlling the nature and extent of colloidal agglomeration under expected waste processing conditions determine how agglomeration phenomena influence physical properties relevant to waste processing including rheology, sedimentation. and filtration develop strategies for optimizing processing conditions via control of agglomeration phenomena.'

Colloidal agglomerates in tank sludge: Impact on waste processing. 1997 annual progress report

International Nuclear Information System (INIS)

Virden, J.W.

1997-01-01

'Disposal of millions of gallons of existing radioactive wastes is a major remediation problem for the Department of Energy (DOE). Although radionuclides are the most hazardous waste constituents. the components of greatest concern from a waste processing standpoint are insoluble sludges consisting of submicron colloidal particles. Depending on processing conditions, these colloidal particles can form agglomerate networks that could clog transfer lines or interfere with solid-liquid separations such as settle-decant operations. Under different conditions, the particles can be dispersed to form very fine suspended particles that will not create sediment in settle- decant steps and that can foul and contaminate downstream treatment components including ion exchangers or filtrations systems. Given the wide range of tank chemistries present at Hanford and other DOE sites, it is impractical to measure the properties of all potential processing conditions to design effective treatment procedures. Instead. a framework needs to be established to allow sludge property trends to be predicted on a sound scientific basis. The scientific principles of greatest utility in characterizing, understanding, and controlling the physical properties of sludge fall in the realm of colloid chemistry. The objectives of this work are to accomplish the following: understand the factors controlling the nature and extent of colloidal agglomeration under expected waste processing conditions determine how agglomeration phenomena influence physical properties relevant to waste processing including rheology, sedimentation. and filtration develop strategies for optimizing processing conditions via control of agglomeration phenomena.'

Fabrication of bioinspired nanostructured materials via colloidal self-assembly

Science.gov (United States)

Huang, Wei-Han

ultimate strains than nacre and pure GO paper (also synthesized by filtration). Specifically, it exhibits ˜30 times higher fracture energy than filtrated graphene paper and nacre, ˜100 times tougher than filtrated GO paper. Besides reinforced nanocomposites, we further explored the self-assembly of spherical colloids and the templating nanofabrication of moth-eye-inspired broadband antireflection coatings. Binary crystalline structures can be easily accomplished by spin-coating double-layer nonclose-packed colloidal crystals as templates, followed by colloidal templating. The polymer matrix between self-assembled colloidal crystal has been used as a sacrificial template to define the resulting periodic binary nanostructures, including intercalated arrays of silica spheres and polymer posts, gold nanohole arrays with binary sizes, and dimple-nipple antireflection coatings. The binary-structured antireflection coatings exhibit better antireflective properties than unitary coatings. Natural optical structures and nanocomposites teach us a great deal on how to create high performance artificial materials. The bottom-up technologies developed in this thesis are scalable and compatible with standard industrial processes, promising for manufacturing high-performance materials for the benefits of human beings.

A Study on Liver Scan using 113mIn Colloid

International Nuclear Information System (INIS)

Koh, Chang Soon; Rhee, Chong Hoen; Chang, Kochang; Hong, Chang Gi

1969-01-01

There have been reported numberous cases of liver scanning in use of 198 Au colloid by many investigators, however, one in use of 113m In colloid has not been reported as yet in this country. The dose of 113 mIn for high diagnostic value in examination of each organ was determined and the diagnostic interpretability of liver scanning with the use of 113m In was carefully evaluated in comparison with the results of the liver scanning by the conventionally applied radioisotope. The comparative study of both figures of liver scanning with the use of 113m In colloid and 198 Au colloid delivered following results:1) The liver uptake rate and clearance into peripheral blood were accentuated more in case of 113m In colloid than in case of 198 Au colloid. 2) The interpretability of space occupying lesion in liver scanning with 113m In was also superior to one with 198 Au. 3) The figure of liver scanning with 113m In colloid corresponds not always to the figure with 198 Au. This difference can be explained by difference of phagocytic ability of reticuloendothelial system within liver. 4) In the liver scanning with 113m In colloid, the spleen is also visualized even in normal examine. 5) In the cases of disturbed liver function, uptake is more decreased in use of 113m In colloid than in 198 Au, in the spleen, however, the way is contrary. 6) With use of 113m In colloid, the time required for scanning could be shortened in comparison with 198 Au. 7) The filtration of 113m In colloid for scanning prior to human administration gives an expectation for better scanning figure.

Mathematical Basis and Test Cases for Colloid-Facilitated Radionuclide Transport Modeling in GDSA-PFLOTRAN

Energy Technology Data Exchange (ETDEWEB)

Reimus, Paul William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-07-31

This report provides documentation of the mathematical basis for a colloid-facilitated radionuclide transport modeling capability that can be incorporated into GDSA-PFLOTRAN. It also provides numerous test cases against which the modeling capability can be benchmarked once the model is implemented numerically in GDSA-PFLOTRAN. The test cases were run using a 1-D numerical model developed by the author, and the inputs and outputs from the 1-D model are provided in an electronic spreadsheet supplement to this report so that all cases can be reproduced in GDSA-PFLOTRAN, and the outputs can be directly compared with the 1-D model. The cases include examples of all potential scenarios in which colloid-facilitated transport could result in the accelerated transport of a radionuclide relative to its transport in the absence of colloids. Although it cannot be claimed that all the model features that are described in the mathematical basis were rigorously exercised in the test cases, the goal was to test the features that matter the most for colloid-facilitated transport; i.e., slow desorption of radionuclides from colloids, slow filtration of colloids, and equilibrium radionuclide partitioning to colloids that is strongly favored over partitioning to immobile surfaces, resulting in a substantial fraction of radionuclide mass being associated with mobile colloids.

Self Cleaning HEPA Filtration without Interrupting Process Flow

International Nuclear Information System (INIS)

Wylde, M.

2009-01-01

The strategy of protecting the traditional glass fibre HEPA filtration train from it's blinding contamination and the recovery of dust by the means of self cleaning, pre-filtration is a proven means in the reduction of ultimate disposal volumes and has been used within the Fuel Production Industry. However, there is an increasing demand in nuclear applications requiring elevated operating temperatures, fire resistance, moisture resistance and chemical composition that the existing glass fibre HEPA filtration cannot accommodate, which can be remedied by the use of a metallic HEPA filter media. Previous research (Bergman et al 1997, Moore et al 1992) suggests that the then costs to the DOE, based on a five year life cycle, was $29.5 million for the installation, testing, removal and disposal of glass fibre HEPA filtration trains. Within these costs, $300 was the value given to the filter and $4,450 was given to the peripheral activity. Development of a low cost, cleanable, metallic, direct replacement of the traditional filter train will the clear solution. The Bergman et al work has suggested that a 1000 ft 3 /min, cleanable, stainless HEPA could be commercially available for $5,000 each, whereas the industry has determined that the truer cost of such an item in isolation would be closer to $15,000. This results in a conflict within the requirement between 'low cost' and 'stainless HEPA'. By proposing a system that combines metallic HEPA filtration with the ability to self clean without interrupting the process flow, the need for a tradition HEPA filtration train will be eliminated and this dramatically reduces the resources required for cleaning or disposal, thus presenting a route to reducing ultimate costs. The paper will examine the performance characteristics, filtration efficiency, flow verses differential pressure and cleanability of a self cleaning HEPA grade sintered metal filter element, together with data to prove the contention. (authors)

Association of trace elements with colloidal fractions in leachates from closed and active municipal solid waste landfills

Czech Academy of Sciences Publication Activity Database

Matura, M.; Ettler, V.; Ježek, J.; Mihaljevič, M.; Šebek, O.; Sýkora, V.; Klementová, Mariana

2010-01-01

Roč. 183, 1-3 (2010), s. 541-548 ISSN 0304-3894 Institutional research plan: CEZ:AV0Z40320502 Keywords : Landfill * leachate * trace elements * colloids * cascade filtration Subject RIV: DD - Geochemistry Impact factor: 3.723, year: 2010

Large-scale assembly of colloidal particles

Science.gov (United States)

Yang, Hongta

increase of the effective refractive index of the diffractive medium, resulting in the red-shift of the optical stop bands. The wavelength shift is linearly proportional to the vapor partial pressure for a spectrum of vapors. Optical simulation and theoretical prediction based on Kelvin equation suggest that a liquid film is formed on the walls of the macropores during vapor condensation. The third topic describes introducing doctor blade coating fabricated large area and low cost macroporous films for thermochromic smart windows, which are useful for energy control in glazed buildings. The fabricated macroporous polymer films exhibit brilliant colors and are capable of reflecting solar radiation when in-situ heated, and become transparent as cavities are filled with a solvent which has the same refractive index as that of the polymer when cooled to building temperature. The fourth topic reports the roll-to roll fabricated excellent water-repelling and self-cleaning macroporous polymer films. The size of the voids can be easily controlled by tuning the duration of an oxygen reactive-ion etching process prior to the removal of the templating silica spheres from silica colloidal-polymer composites. After surface functionalization with fluorosilane, superhydrophobic surface with large apparent water contact angle and small sliding angle can be obtained. The self-cleaning functionality can be achieved on superhydrophobic macroporous coatings by preventing bacterial contamination is further demonstrated. The fifth topic presented is that the template macroporous polymer films with interconnected voids and uniform interconnecting nanopores can be directly used as filtration membranes to achieve size-exclusive separation of particles. The results also demonstrate that more than 85% of small sized particles are recovered after filtration. The results also demonstrate that Escherichia coli can be filtrated by the from macroporous polymer films aqueous solution.

Experimental analysis of colloid capture by a cylindrical collector in laminar overland flow.

Science.gov (United States)

Wu, Lei; Gao, Bin; Muñoz-Carpena, Rafael

2011-09-15

Although colloid-facilitated contaminant transport in water flow is a well-known contamination process, little research has been conducted to investigate the transport of colloidal particles through emergent vegetation in overland flow. In this work, a series of laboratory experiments were conducted to measure the single-collector contact efficiency (η(0)) of colloid capture by a simulated plant stem in laminar lateral flow. Fluorescent microspheres of various sizes were used as experimental colloids. The colloid suspensions were applied to a glass cylinder installed in a small size flow chamber at different flow rates. Two cylinder sizes were tested in the experiment and silicone grease was applied to the cylinder surface to make it favorable for colloid deposition. Our results showed that increases in flow rate and collector size reduced the value of η(0) and a minimum value of η(0) might exist for a colloid size. The experimental data were compared to theoretical predictions of different single-collector contact efficiency models. The results indicated that existing single-collector contact efficiency models underestimated the η(0) of colloid capture by the cylinders in laminar overland flow. A regression equation of η(0) as a function of collector Reynolds number (Re(c)) and Peclet number (N(Pe)) was developed and fit the experimental data very well (R(2) > 0.98). This regression equation can be used to help construct and refine mathematical models of colloid transport and filtration in laminar overland flow on vegetated surfaces.

Characterization samples of Tigris river water treated with nano colloidal silver (physically, chemically, microbiologically)

International Nuclear Information System (INIS)

Dumboos, H. I.; Beden, S. J.; Zouari, K.; Chkir, N.; Ahmed, H. A.

2012-12-01

Many researches of using nano silver in purification of drinking water from bacteria and its effect on stan dared properties as drinking water were established. Two stages accomplished in these projects. First stage include preparation of colloidal silver with characterization process and prepare water samples through sedimentation, filtration process, PH and turbidity measure then treated with colloidal silver in volume ratio (0.1-Λ) ml/100ml. The second stage represent select the better results from stage one and take samples to determine the standard characterization values with chemical, physical and microbiological taste. Results will be compared with Iraq standard certification. (Author)

Development of COLLAGE 3; Role for colloids in the transport of radionuclides

Energy Technology Data Exchange (ETDEWEB)

Klos, Richard (Aleksandria Sciences, Sheffield (United Kingdom)); Bath, Adrian (Intellisci Ltd., Loughborough (United Kingdom))

2010-03-15

The issue of colloid-facilitated radionuclide transport (CFRT) was last addressed by the Swedish nuclear regulators in 2001 - 2002. SKI had commissioned the Collage code with subsequent development as Collage 2. This code was employed to investigate the potential role for colloids to have been involved in the transport of radionuclides at the Nevada Test Site and to examine the implications for CFRT in the Swedish disposal programme. It was concluded that colloids could not be ruled out as a mechanism for rapid transport and early release from the geosphere. Recently the 'bentonite erosion scenario' has become of concern. In it the generation of large quantities of bentonite colloids in fractures as a result of fresh water ingress at repository depth is possible. Potentially, these could carry radiologically significant quantities of radionuclides to an early release to the surface system. The objectives of this work are to update the knowledge of colloid-facilitated radionuclide transport through a fractured geosphere and to provide review capability within the SSM. Recent developments in CFRT (reviewed here) indicate that additional parameters needed to be added to the existing Collage 2 plus code in order to adequately represent colloid transport in fractures. This report looks at modifications to the model and discusses the implications of the implementation of the new processes. Authors conclude that the process of colloid filtration is an important mitigating mechanism. A new code - Collage 3 - is demonstrated and suggestions for further work are given

Sampling and characterisation of groundwater colloids at ONKALO, Olkiluoto, Finland

International Nuclear Information System (INIS)

Takala, M.; Manninen, P.

2006-11-01

The purpose of this sampling campaign was to test different filtering methods and filter membranes, to determine the colloid concentration and to characterise the composition of the colloid phase at ONKALO groundwater station ONK-PVA1 at Olkiluoto. The sampling was done on 18 to 19 April 2006. The filtering methods tested were downhole in-situ filtration and in-line syringe filtration. The membranes tested were Anopore 0.2-μm membrane and Nuclepore 0.05 -μm membrane. The Anopore filter was designed to be 0.02 -μm, but according to the SEM micrograph the nominal pore size of the membranes was 0.2 -μm. The size distributions were determined by single particle analysis of the SEM micrographs taken from the used filter membranes. The size distribution can be expressed as a function of the Pareto power law (Buffle, 1988). Parameters A and b of the Pareto power law distribution were determined by using the least square sum method. The particle and mass concentrations were then calculated using the Pareto power law. The size distribution varied between the filtering methods, so that the syringe filtered samples indicated less aggregation than the downhole filtered samples. The colloid concentrations were higher in the Nuclepore filter membranes. This is probably due to the shorter settling time prior to the sampling or differences in the membrane pore size and material. The concentration of the colloid phase determined from the anopore membranes (0.05-1 -μm) was 0.2-0.4 mg/L. The water samples were analysed at the accredited laboratory of Consulting Engineers Paavo Ristola Ltd. The differences in the element concentrations were not detectable between the filtered and unfiltered samples. Contamination with, e.g., nickel, aluminium and organic carbon was evident. The valves, fittings and filter membranes probably caused the contamination. An EDS spectrum was taken from the downhole filtered Nuclepore membrane. The filter cake showed traces of aluminium, silicon and

Graphene nanoplatelets as high-performance filtration control material in water-based drilling fluids

Science.gov (United States)

Ridha, Syahrir; Ibrahim, Arif; Shahari, Radzi; Fonna, Syarizal

2018-05-01

The main objective of this work is to evaluate the effectiveness of graphene nanoplatelets (GNP) as filtration control materials in water based drilling fluids. Three (3) general samples of water based drilling fluids were prepared including basic potassium chloride (KCl) drilling fluids, nanosilica (NS) drilling fluids and GNP drilling fluids. Several concentrations of NS and GNP were dispersed in controlled formulations of water based drilling fluids. Standard API filtration tests were carried out for comparison purposes as well as High Temperature High Pressure (HTHP) filtration tests at 150 °F (∼66 °C), 250 °F (∼121 °C) and 350 °F (∼177 °C) at a fixed 500 (∼3.45MPa) psi to study the filtration trend as a function of temperature. Mud cake samples from several tests were selectively chosen and analyzed under Field Emission Scanning Electron Microscope (FESEM) for its morphology. Results from this work show that nanoparticle concentrations play a factor in filtration ability of colloid materials in water based drilling fluids when studied at elevated temperature. Low temperature filtration, however, shows only small differences in volume in all the drilling fluid samples. 0.1 ppb concentrations of GNP reduced the fluid loss of 350 °F by 4.6 mL as compared to the similar concentration of NS drilling fluids.

Fouling behavior of microstructured hollow fibers in cross-flow filtrations: Critical flux determination and direct visual observation of particle deposition

NARCIS (Netherlands)

Culfaz, P.Z.; Haddad, M.; Wessling, Matthias; Lammertink, Rob G.H.

2011-01-01

The fouling behavior of microstructured hollow fiber membranes was investigated in cross-flow filtrations of colloidal silica and yeast. In addition to the as-fabricated microstructured fibers, twisted fibers made by twisting the microstructured fibers around their own axes were tested and compared

Preventing colloidal fouling in reverse osmosis and nano filtration system. Application of electron beam surface analysis; Prevencion del ensuciamiento coloidal en sistemas de osmosis inversa y nanofiltracion. Aplicacion del analisis de superficies con haces de electrones.

Energy Technology Data Exchange (ETDEWEB)

Sanz Ataz, J.; Guerrero Gallego, L.; Taberna Camprubi, E.; Pena Garcia, N.M; Carulla Contreras, C.; Blavia Bergos, J.

2003-07-01

Particulate matter in natural waters and wastewaters can cause fouling in reverse osmosis and nano filtration membranes. Common foulants includes organic and inorganic colloids; hydrous aluminum and iron silicates, silt, iron and manganese oxides, calcium carbonate, microorganisms, polysaccharides, lipoproteins, biological debris, etc. Predicting fouling of dispersed materials on membrane surface and brine flow channels uses the silt density index (SDI) and modified fouling index (MFI). Scanning electron microscopy (SEM) coupled with energy X-ray microanalysis (EDX) of SDI filters contributes to obtain information about shape, size and chemical composition of foulants and cake layer. (Author) 6 refs.

An integrated colloid fractionation approach applied to the characterisation of porewater uranium-humic interactions at a depleted uranium contaminated site

International Nuclear Information System (INIS)

Graham, Margaret C.; Oliver, Ian W.; MacKenzie, Angus B.; Ellam, Robert M.; Farmer, John G.

2008-01-01

Methods for the fractionation of aquatic colloids require careful application to ensure efficient, accurate and reproducible separations. This paper describes the novel combination of mild colloidal fractionation and characterisation methods, namely centrifugal ultrafiltration, gel electrophoresis and gel filtration along with spectroscopic (UV-visible) and elemental (Inductively Coupled Plasma-Optical Emission Spectroscopy, Inductively Coupled Plasma-Mass Spectrometry) analysis, an approach which produced highly consistent results, providing improved confidence in these methods. Application to the study of the colloidal and dissolved components of soil porewaters from one soil at a depleted uranium (DU)-contaminated site revealed uranium (U) associations with both large (100 kDa-0.2 μm) and small (3-30 kDa) humic colloids. For a nearby soil with lower organic matter content, however, association with large (100 kDa-0.2 μm) iron (Fe)-aluminium (Al) colloids in addition to an association with small (3-30 kDa) humic colloids was observed. The integrated colloid fractionation approach presented herein can now be applied with confidence to investigate U and indeed other trace metal migration in soil and aquatic systems

Sampling and characterisation of groundwater colloids in ONKALO at Olkiluoto, Finland in 2007

International Nuclear Information System (INIS)

Takala, M.; Manninen, P.

2008-08-01

Colloid samples were collected from ONKALO groundwater station ONK-PVA1 in October 2007 and an additional sample was taken from groundwater station ONK-PVA3 in November 2007. The colloids were collected by filtering the groundwater on site with an Anopore 0.02 μm aluminium oxide filter. In the sampling in October, water samples were also collected to analyse the differences in the water chemistry before and after filtration. The water samples were freeze-dried so that the elements would be concentrated in the water. The colloid concentrations were determined by counting the particles from the SEM micrographs and by calculating the concentration using the micrograph area, the filter area and the filtered volume. The colloid concentration in ONK-PVA1 was very low. The particle concentration within the size range from 0.1 μm to 1 μm was 1.6 x 10 4 pt/L and the mass concentration within the same size range 0.001 μg/L. Owing to the very low concentration, an additional colloid sample was taken from ONK-PVA3. The colloid concentration in ONK-PVA3 within the size range from 0.1 μm to 1 μm was 8.2 x 10 7 pt/L and the mass concentration 0.013 mg/L. When studying the ONKALO groundwater monitoring data it was noticed that in the samples where the colloid concentration was elevated also the sodium fluorescein concentration was probably elevated. This indicated that process water (e.g. drilling water) was present in the water samples. The ONK-PVA1 water probably also contained process water during the colloid sampling performed in 2006. The composition of the colloid phase could not be determined by analysing the differences in the filtered and unfiltered water owing to the low colloid concentration. Furthermore, the aluminium oxide filter caused aluminium contamination. (orig.)

Colloid suspension stability and transport through unsaturated porous media

International Nuclear Information System (INIS)

McGraw, M.A.; Kaplan, D.I.

1997-04-01

Contaminant transport is traditionally modeled in a two-phase system: a mobile aqueous phase and an immobile solid phase. Over the last 15 years, there has been an increasing awareness of a third, mobile solid phase. This mobile solid phase, or mobile colloids, are organic or inorganic submicron-sized particles that move with groundwater flow. When colloids are present, the net effect on radionuclide transport is that radionuclides can move faster through the system. It is not known whether mobile colloids exist in the subsurface environment of the Hanford Site. Furthermore, it is not known if mobile colloids would likely exist in a plume emanating from a Low Level Waste (LLW) disposal site. No attempt was made in this study to ascertain whether colloids would form. Instead, experiments and calculations were conducted to evaluate the likelihood that colloids, if formed, would remain in suspension and move through saturated and unsaturated sediments. The objectives of this study were to evaluate three aspects of colloid-facilitated transport of radionuclides as they specifically relate to the LLW Performance Assessment. These objectives were: (1) determine if the chemical conditions likely to exist in the near and far field of the proposed disposal site are prone to induce flocculation (settling of colloids from suspension) or dispersion of naturally occurring Hanford colloids, (2) identify the important mechanisms likely involved in the removal of colloids from a Hanford sediment, and (3) determine if colloids can move through unsaturated porous media

Colloid stable sorbents for cesium removal: Preparation and application of latex particles functionalized with transition metals ferrocyanides

Energy Technology Data Exchange (ETDEWEB)

Avramenko, Valentin [Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159 ave 100-letiya Vladivostoka, Vladivostok 690022 (Russian Federation); Bratskaya, Svetlana, E-mail: sbratska@ich.dvo.ru [Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159 ave 100-letiya Vladivostoka, Vladivostok 690022 (Russian Federation); Zheleznov, Veniamin; Sheveleva, Irina [Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159 ave 100-letiya Vladivostoka, Vladivostok 690022 (Russian Federation); Voitenko, Oleg [Far Eastern Federal University, Laboratory of Electron Microscopy and Image Processing, 27, Oktyabr' skaya Street, Vladivostok 690950 (Russian Federation); Sergienko, Valentin [Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159 ave 100-letiya Vladivostoka, Vladivostok 690022 (Russian Federation)

2011-02-28

In this paper we suggest a principally new approach to preparation of colloid stable selective sorbents for cesium uptake using immobilization of transition metals (cobalt, nickel, and copper) ferrocyanides in nanosized carboxylic latex emulsions. The effects of ferrocyanide composition, pH, and media salinity on the sorption properties of the colloid stable sorbents toward cesium ions were studied in solutions containing up to 200 g/L of sodium nitrate or potassium chloride. The sorption capacities of the colloid sorbents based on mixed potassium/transition metals ferrocyanides were in the range 1.3-1.5 mol Cs/mol ferrocyanide with the highest value found for the copper ferrocyanide. It was shown that the obtained colloid-stable sorbents were capable to penetrate through bulk materials without filtration that made them applicable for decontamination of solids, e.g. soils, zeolites, spent ion-exchange resins contaminated with cesium radionuclides. After decontamination of liquid or solid radioactive wastes the colloid-stable sorbents can be easily separated from solutions by precipitation with cationic flocculants providing localization of radionuclides in a small volume of the precipitates formed.

Colloidal agglomerates in tank sludge: Impact on waste processing

International Nuclear Information System (INIS)

Bunker, B.C.; Martin, J.E.

1998-01-01

'Insoluble colloidal sludges in hazardous waste streams such as tank wastes can pose serious problems for waste processing, interfering with retrieval, transport, separation, and solidification procedures. Properties of sediment layers and sludge suspensions such as slurry viscosities, sedimentation rates, and final sediment densities can vary by orders of magnitude depending on the particle types present, the degree to which the particles agglomerate or stick to each other, and on a wide range of processing parameters such as solution shear rates, pH, salt content, and temperature. The objectives of this work are to: (1) understand the factors controlling the nature and extent of colloidal agglomeration under expected waste processing conditions; (2) determine how agglomeration phenomena influence physical properties relevant to waste processing including rheology, sedimentation, and filtration; and (3) develop strategies for optimizing processing conditions via control of agglomeration phenomena. Insoluble colloidal sludges in hazardous waste streams such as tank wastes can pose serious problems for waste processing, interfering with retrieval, transport, separation, and solidification procedures. Properties of sediment layers and sludge suspensions such as slurry viscosities, sedimentation rates, and final sediment densities can vary by orders of magnitude depending on the particle types present, the degree to which the particles agglomerate or stick to each other, and on a wide range of processing parameters such as solution shear rates, pH, salt content, and temperature. The objectives of this work are to: (1) understand the factors controlling the nature and extent of colloidal agglomeration under expected waste processing conditions; (2) determine how agglomeration phenomena influence physical properties relevant to waste processing including rheology, sedimentation, and filtration; and (3) develop strategies for optimizing processing conditions via control

Isotopic investigation of the colloidal mobility of depleted uranium in a podsolic soil

International Nuclear Information System (INIS)

Harguindeguy, S.; Crancon, P.; Pointurier, F.; Potin-Gautier, M.; Lespes, G.

2014-01-01

The mobility and colloidal migration of uranium were investigated in a soil where limited amounts of anthropogenic uranium (depleted in the "2"3"5U isotope) were deposited, adding to the naturally occurring uranium. The colloidal fraction was assumed to correspond to the operational fraction between 10 kDa and 1.2 μm after (ultra)filtration. Experimental leaching tests indicate that approximately 8-15% of uranium is desorbed from the soil. Significant enrichment of the leachate in the depleted uranium (DU) content indicates that uranium from recent anthropogenic DU deposit is weakly bound to soil aggregates and more mobile than geologically occurring natural uranium (NU). Moreover, 80% of uranium in leachates was located in the colloidal fractions. Nevertheless, the percentage of DU in the colloidal and dissolved fractions suggests that NU is mainly associated with the non-mobile coarser fractions of the soil. A field investigation revealed that the calculated percentages of DU in soil and groundwater samples result in the enhanced mobility of uranium downstream from the deposit area. Colloidal uranium represents between 10% and 32% of uranium in surface water and between 68% and 90% of uranium in groundwater where physicochemical parameters are similar to those of the leachates. Finally, as observed in batch leaching tests, the colloidal fractions of groundwater contain slightly less DU than the dissolved fraction, indicating that DU is primarily associated with macromolecules in dissolved fraction. (authors)

Amagnetic field-enhanced filtration/sorption Device and its potential for inexpensive water and wastewater treatment

International Nuclear Information System (INIS)

Navratil, J.D.

2000-01-01

A magnetic field-enhanced filtration/sorption device is described for removal of radioactive and heavy metals from water and wastewater. The device consists of a column of supported magnetite surrounded by a movable permanent magnet. The mineral magnetite, or synthetically prepared iron ferrite (Fe O Fe 2 O 3 ), is typically supported on various materials to permit adequate water passage through the column. In the presence of the external magnetic field, enhanced capacity was observed in using supported magnetite for removal of actinides and heavy metals from wastewater. The enhanced capacity is primarily due to magnetic filtration of colloidal and submicron particles along with some complex and ion exchange sorption mechanisms. The loaded magnetite can easily be regenerated by the removal of the magnetic field and use of a regenerating solution. This paper will review previous work on the use of iron oxides for wastewater treatment and discuss the development and potential of the magnetic filtration/sorption process for water and wastewater treatment

Organic-inorganic membranes for filtration of corn distillery

Directory of Open Access Journals (Sweden)

Myronchuk Valeriy G.

2016-01-01

Full Text Available Organic-inorganic membranes were obtained by modification of polymer microfiltration membrane with inorganic ion-exchangers, which form secondary porosity inside macroporous substrate (zirconium hydrophosphate or simultaneously in the macroporous substrate and active layer, depending of the particle size (from ≈50 nm up to several microns. Precipitation of the inorganic constituent is considered from the point of view of Ostwald-Freundlich equation. Such processes as pressing test in deionized water and filtration of corn distillery at 1-6 bar were investigated. Theoretical model allowing to establish fouling mechanism, was applied. It was found that the particles both in the substrate and active layer prevent fouling of the membrane with organics and provide rejection of colloidal particles.

Crystalloids versus colloids: implications in fluid therapy of dogs with intestinal obstruction.

Science.gov (United States)

Allen, D; Kvietys, P R; Granger, D N

1986-08-01

Responses of jejunal transcapillary and transmucosal fluid fluxes to IV infusion of crystalloid or colloid solutions were evaluated in 12 dogs. One isolated intestinal segment in each dog was used as the control segment, and 2 segments were distended to a intraluminal hydrostatic pressure of 10 cm of H2O. The artery supplying 1 of the 2 distended (autoperfused) segments was cannulated and perfused with blood from the femoral artery. One of the 2 distended segments was autoperfused from the femoral artery. Intraluminal pressure was increased in the autoperfused segment and in 1 other segment for three, 20-minute periods after administration of the crystalloid or colloid solution. Net transmucosal fluid flux was estimated, using a volume recovery method. In each autoperfused segment, blood flow, capillary pressure, lymph flow, and plasma protein and lymph protein concentrations were measured during each 20-minute distention period. Systemic arterial pressure was monitored throughout the procedure. Plasma and tissue oncotic pressures were calculated from the plasma protein and lymph protein concentrations. Total vascular resistance and precapillary and postcapillary resistances were determined. Capillary pressure increased after infusion with colloids and crystalloids, with the effects being more prolonged in the colloid group. Plasma oncotic pressure transiently increased after infusion with colloids and decreased after infusion with crystalloids. Lymph flow increased only in crystalloid-treated dogs. Due to alterations in transcapillary fluid filtration, crystalloids induced a net loss of fluid into the intestinal lumen, whereas the fluid absorptive capacity of the jejunum was unaltered by colloid treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Self Cleaning High Efficiency Particulate Air (HEPA) Filtration without Interrupting Process Flow - 59347

International Nuclear Information System (INIS)

Chadwick, Chris

2012-01-01

The strategy of protecting the traditional glass fibre HEPA filtration train from it's blinding contamination and the recovery of dust by the means of self cleaning, pre-filtration is a proven means in the reduction of ultimate disposal volumes and has been used within the Fuel Production Industry. However, there is an increasing demand in nuclear applications requiring elevated operating temperatures, fire resistance, moisture resistance and chemical composition that the existing glass fibre HEPA filtration cannot accommodate, which can be remedied by the use of a metallic HEPA filter media. Previous research suggests that the then costs to the Department of Energy (DOE), based on a five year life cycle, was $29.5 million for the installation, testing, removal and disposal of glass fibre HEPA filtration trains. Within these costs, $300 was the value given to the filter and $4, 450 was given to the peripheral activity. Development of a low cost, cleanable, metallic, direct replacement of the traditional filter train will the clear solution. The Bergman et al work has suggested that a 1000 ft 3 /min, cleanable, stainless HEPA could be commercially available for $5, 000 each, whereas the industry has determined that the truer cost of such an item in isolation would be closer to $15, 000. This results in a conflict within the requirement between 'low cost' and 'stainless HEPA'. By proposing a system that combines metallic HEPA filtration with the ability to self clean without interrupting the process flow, the need for a tradition HEPA filtration train will be eliminated and this dramatically reduces the resources required for cleaning or disposal, thus presenting a route to reducing ultimate costs. The paper will examine the performance characteristics, filtration efficiency, flow verses differential pressure and cleanability of a self cleaning HEPA grade sintered metal filter element, together with data to prove the contention. (authors)

Shape-shifting colloids via stimulated dewetting

Science.gov (United States)

Youssef, Mena; Hueckel, Theodore; Yi, Gi-Ra; Sacanna, Stefano

2016-01-01

The ability to reconfigure elementary building blocks from one structure to another is key to many biological systems. Bringing the intrinsic adaptability of biological systems to traditional synthetic materials is currently one of the biggest scientific challenges in material engineering. Here we introduce a new design concept for the experimental realization of self-assembling systems with built-in shape-shifting elements. We demonstrate that dewetting forces between an oil phase and solid colloidal substrates can be exploited to engineer shape-shifting particles whose geometry can be changed on demand by a chemical or optical signal. We find this approach to be quite general and applicable to a broad spectrum of materials, including polymers, semiconductors and magnetic materials. This synthetic methodology can be further adopted as a new experimental platform for designing and rapidly prototyping functional colloids, such as reconfigurable micro swimmers, colloidal surfactants and switchable building blocks for self-assembly. PMID:27426418

The impact of metallic filter media on HEPA filtration

International Nuclear Information System (INIS)

Chadwick, Chris; Kaufman, Seth

2006-01-01

Traditional HEPA filter systems have limitations that often prevent them from solving many of the filtration problems in the nuclear industry; particularly in applications where long service or storage life, high levels of radioactivity, dangerous decomposition products, chemical aggression, organic solvents, elevated operating temperatures, fire resistance and resistance to moisture are issues. This paper addresses several of these matters of concern by considering the use of metallic filter media to solve HEPA filtration problems ranging from the long term storage of transuranic waste at the WIPP site, spent and damaged fuel assemblies, in glove box ventilation and tank venting to the venting of fumes at elevated temperatures from incinerators, vitrification processes and conversion and sintering furnaces as well as downstream of iodine absorbers in gas cooled reactors in the UK. The paper reviews the basic technology, development, performance characteristics and filtration efficiency, flow versus differential pressure, cleanability and costs of sintered metal fiber in comparison with traditional resin bonded glass fiber filter media and sintered metal powder filter media. Examples of typical filter element and system configurations and applications will be presented The paper will also address the economic case for installing self cleaning pre-filtration, using metallic media, to recover the small volumes of dust that would otherwise blind large volumes of final disposable HEPA filters, thus presenting a route to reduce ultimate disposal volumes and secondary waste streams. (authors)

Cross-flow filtration and axial filtration

International Nuclear Information System (INIS)

Kraus, K.A.

1974-01-01

Two relatively novel alternative solid-liquid-separation techniques of filtration are discussed. In cross-flow filtration, the feed is pumped past the filtering surface. While in axial filtration the filter, mounted on a rotor, is moved with respect to the feed. While large-scale application of the axial filter is still in doubt, it permits with little expenditure of time and money, duplication of many hydrodynamic aspects of cross-flow filtration for fine-particle handling problems. The technique has been applied to municipal wastes, low-level radioactive waste treatment plant, lead removal from industrial wastes, removal of pulp-mill contaminants, textile-mill wastes, and pretreatment of saline waters by lime-soda process in preparation for hyperfiltration. Economics and energy requirements are also discussed

Active colloids

International Nuclear Information System (INIS)

Aranson, Igor S

2013-01-01

A colloidal suspension is a heterogeneous fluid containing solid microscopic particles. Colloids play an important role in our everyday life, from food and pharmaceutical industries to medicine and nanotechnology. It is useful to distinguish two major classes of colloidal suspensions: equilibrium and active, i.e., maintained out of thermodynamic equilibrium by external electric or magnetic fields, light, chemical reactions, or hydrodynamic shear flow. While the properties of equilibrium colloidal suspensions are fairly well understood, active colloids pose a formidable challenge, and the research is in its early exploratory stage. One of the most remarkable properties of active colloids is the possibility of dynamic self-assembly, a natural tendency of simple building blocks to organize into complex functional architectures. Examples range from tunable, self-healing colloidal crystals and membranes to self-assembled microswimmers and robots. Active colloidal suspensions may exhibit material properties not present in their equilibrium counterparts, e.g., reduced viscosity and enhanced self-diffusivity, etc. This study surveys the most recent developments in the physics of active colloids, both in synthetic and living systems, with the aim of elucidation of the fundamental physical mechanisms governing self-assembly and collective behavior. (physics of our days)

Colloidal organization

CERN Document Server

Okubo, Tsuneo

2015-01-01

Colloidal Organization presents a chemical and physical study on colloidal organization phenomena including equilibrium systems such as colloidal crystallization, drying patterns as an example of a dissipative system and similar sized aggregation. This book outlines the fundamental science behind colloid and surface chemistry and the findings from the author's own laboratory. The text goes on to discuss in-depth colloidal crystallization, gel crystallization, drying dissipative structures of solutions, suspensions and gels, and similar-sized aggregates from nanosized particles. Special emphas

Bentonite as a colloid source in groundwaters at Olkiluoto

International Nuclear Information System (INIS)

Vuorinen, U.; Hirvonen, H.

2005-02-01

In this work bentonite was studied as a potential source of colloids in Olkiluoto groundwaters. Samples were collected at two groundwater stations, PVA1 at 37.5 m dept and PVA3 at 95.6 m depth, in the VLJ-tunnel. The deeper groundwater at PVA3 was more saline (2.6g/L of Cl-) than the shallow at PVA1 (0.8g/L of Cl-). A bentonite source had been assembled at each groundwater station so that two sample lines were available for water samples; one for collecting a sample before and the other for collecting a sample after interaction with bentonite. Before starting the actual colloid sampling groundwaters from both sample lines at both stations were analysed. Only minor alterations, mostly within the uncertainty limits of the analysis methods, were brought about in the water chemistries after interaction with the bentonite sources. The only clear changes were seen in the concentration of iron which decreased after interaction with bentonite in the groundwaters at both stations. After groundwater sampling the actual colloid sampling was performed. The water samples were collected and treated inside a movable nitrogen filled glove-box. The samples could be collected from each sampling line directly in the glove-box via two quick-couplings that had been assembled on the front face of the box. The sample lines had been assembled with 0.45 μm filters before entering the glove-box, because only colloids smaller than 0.45 μm were of interest, as they are not prone to sedimentation in slow groundwater flows and therefore could act as potential radionuclide carriers. Colloid samples were collected and treated similarly from both sampling lines at both groundwater stations. For estimating the colloid content the groundwater samples were filtered with centrifugal ultrafiltration tubes of different cut-off values (0.3 μm, 300kD and 10kD). The ultrafiltrations produced the colloid-containing concentrate fractions and the soluble substances-containing filtrate fractions. In

Particulate, colloidal, and solution phase associations of plutonium, americium, and uranium in surface and groundwater at the Rocky Flats Plant, Colorado

International Nuclear Information System (INIS)

Harnish, R.A.; McKnight, D.M.; Ranville, J.F.; Stephens, V.C.; Honeyman, B.D.

1993-01-01

With the cessation of plutonium processing at the D.O.E.-administered Rocky Flats Plant near Denver, CO, the focus of activities at the facility has switched to contaminant assessment and potential remediation strategies. In this context the authors began a study in 1991 to determine the potential for colloid-facilitated transport of the actinides Pu, Am, and in surface- and groundwater at this site. Using the technique of tangential flow ultrafiltration, the authors isolated particles from four size fractions at one groundwater well and two surface water seeps to determine the distribution of Pu, Am, and U among particulate, colloidal, and dissolved aqueous phases. Analysis of particle isolates and filtrate fractions showed significant associations of Am and Pu with colloidal and particulate size particles; uranium isotopes were associated mainly with low molecular weight organic species. The results indicate a potential for colloidal-facilitated transport of the actinides Pu and Am and a significant contribution by low molecular weight natural organic matter to uranium transport

Concentrations and compositions of colloidal particles in groundwater near the ICPP, Idaho National Laboratory, Idaho

International Nuclear Information System (INIS)

Estes, M.; McCurry, M.

1994-01-01

The presence of colloidal material is being investigated in groundwater near the ICPP to determine whether the concentrations and chemical compositions are suitable to have an impact on the transport of Sr-90. Colloids are proposed as a viable transport mechanism, and may have an influence on the chemical trends observed in three wells near the ICPP. Ultrafiltration of groundwater samples has been performed on difFerent intervals in USGS wells 45, 46, and Site 14, has provided filtrate samples, for analyses by ICP-MS, and filters for analyses by SEM/EDS. Preliminary results indicate that concentrations of colloids are from 2.1-0.8 ppm for the >0.45 μm size fraction, and 2.3-9.8 ppm for the <0.45 μm size fractions. Compositions consist of calcite, silicic acid, ferrihydrite, clay, and possibly dolomite. Calcium was shown to have the largest contribution from both EDS and ICP-MS. Magnesium and silicon were also found to filter out in large concentrations. Iron and aluminum are minor constituents of the colloidal mass and contain concentrations of <10ppb and <1ppb, respectively. These results indicate that if colloids are going to have a major impact on contaminant migration then the coprecipitation of Sr-90 with calcite and dolomite would have to be a sorption mechanism. Sorption onto Fe and Al colloids probably does not have a major impact because of the low concentrations. Clay colloids were noted to be relatively abundant and may also have an impact on Sr-90 migration, due to the exchange of Sr with other cations in the clay structure. 14 refs., 4 figs., 2 tabs

On the Failure of Upscaling the Single-Collector Efficiency to the Transport of Colloids in an Array of Collectors

Science.gov (United States)

Messina, F.; Tosco, T.; Sethi, R.

2017-12-01

Colloidal transport and deposition in saturated porous media are phenomena of considerable importance in a large number of natural processes and engineering applications, such as the contaminant and microorganism propagation in aquifer systems, the development of innovative groundwater remediation technologies, air and water filtration, and many others. Therefore, a thorough understanding of particle filtration is essential for predicting the transport and fate of colloids in the subsurface environment. The removal efficiency of a filter is a key aspect for colloid transport in porous media. Several efforts were devoted to derive accurate correlations for the single collector efficiency, one of the key concept in the filtration theory. However, up scaling this parameter to the entire porous medium is still a challenge. The common up-scaling approach assumes the deposition to be independent of the transport history, which means that the collector efficiency is considered uniform along the porous medium. However, previous works showed that this approach is inadequate under unfavorable deposition conditions. This study demonstrates that it is not adequate even in the simplest case of favorable deposition. Computational Fluid Dynamics simulations were run for a simplify porous media geometry, composed of a vertical array of 50 identical spherical collectors. A combination of Lagrangian and Eulerian simulations were performed to analyze the particle transport under a broad range of parameters (i.e., particle size, particle density, water velocity). The results show the limits of the existing models to interpret the experimental data. In fact, the outcome evidenced that when particle deposition is not controlled by Brownian diffusion, non-exponential concentration profiles are retrieved, in contrast with the assumption of uniform efficiency. Moreover, when the deposition mechanisms of sedimentation and interception dominate, the efficiency of the first sphere of the

A Binomial Modeling Approach for Upscaling Colloid Transport Under Unfavorable Attachment Conditions: Emergent Prediction of Nonmonotonic Retention Profiles

Science.gov (United States)

Hilpert, Markus; Johnson, William P.

2018-01-01

We used a recently developed simple mathematical network model to upscale pore-scale colloid transport information determined under unfavorable attachment conditions. Classical log-linear and nonmonotonic retention profiles, both well-reported under favorable and unfavorable attachment conditions, respectively, emerged from our upscaling. The primary attribute of the network is colloid transfer between bulk pore fluid, the near-surface fluid domain (NSFD), and attachment (treated as irreversible). The network model accounts for colloid transfer to the NSFD of downgradient grains and for reentrainment to bulk pore fluid via diffusion or via expulsion at rear flow stagnation zones (RFSZs). The model describes colloid transport by a sequence of random trials in a one-dimensional (1-D) network of Happel cells, which contain a grain and a pore. Using combinatorial analysis that capitalizes on the binomial coefficient, we derived from the pore-scale information the theoretical residence time distribution of colloids in the network. The transition from log-linear to nonmonotonic retention profiles occurs when the conditions underlying classical filtration theory are not fulfilled, i.e., when an NSFD colloid population is maintained. Then, nonmonotonic retention profiles result potentially both for attached and NSFD colloids. The concentration maxima shift downgradient depending on specific parameter choice. The concentration maxima were also shown to shift downgradient temporally (with continued elution) under conditions where attachment is negligible, explaining experimentally observed downgradient transport of retained concentration maxima of adhesion-deficient bacteria. For the case of zero reentrainment, we develop closed-form, analytical expressions for the shape, and the maximum of the colloid retention profile.

Towards an assessment of colloid transport in undisturbed clay stone

International Nuclear Information System (INIS)

Durce, D.; Landesman, C.; Grambow, B.; Giffaut, E.

2010-01-01

Document available in abstract form only. Full text of publication follows: Colloids are known as a potentially important transport vector for sparingly soluble radionuclides in natural water environments. For assessing the mass transfer resistance of the Callovo-Oxfordian clay rock formation for colloid transport, a series of percolation experiments have been performed, using high pressure stainless steel advection cells of different diameters containing clay cores machined to about 50 μm of accuracy to the inner diameter of the cells. Synthetic clay pore water was pushed by a high pressure syringe pump across the clay core. In order to assess the cut-off size for colloid transport, molecules of different molecular weight were injected. C 14 labeled polymaleic acid (PMA) of sizes of 2 and 50 kDa were used. The effect of clay permeability, of water flow rate (injection pressure) and of ionic strength was studied. Low ionic strength experiments (I = 0.001) were realized by replacing the pore water by advective displacement with the required composition. Clay rock permeabilities were between 10 -12 and 10 -14 m/s. Hydrodynamic parameters were determined by HTO and 36 Cl injection. The results show already at 2 kDa and a permeability of 10 -12 m/s strong retention by partial filtration. The experimental results were modeled using simple chromatographic theory. (authors)

Accumulation of Colloidal Particles in Flow Junctions Induced by Fluid Flow and Diffusiophoresis

Science.gov (United States)

Shin, Sangwoo; Ault, Jesse T.; Warren, Patrick B.; Stone, Howard A.

2017-10-01

The flow of solutions containing solutes and colloidal particles in porous media is widely found in systems including underground aquifers, hydraulic fractures, estuarine or coastal habitats, water filtration systems, etc. In such systems, solute gradients occur when there is a local change in the solute concentration. While the effects of solute gradients have been found to be important for many applications, we observe an unexpected colloidal behavior in porous media driven by the combination of solute gradients and the fluid flow. When two flows with different solute concentrations are in contact near a junction, a sharp solute gradient is formed at the interface, which may allow strong diffusiophoresis of the particles directed against the flow. Consequently, the particles accumulate near the pore entrance, rapidly approaching the packing limit. These colloidal dynamics have important implications for the clogging of a porous medium, where particles that are orders of magnitude smaller than the pore width can accumulate and block the pores within a short period of time. We also show that this effect can be exploited as a useful tool for preconcentrating biomolecules for rapid bioassays.

Accumulation of Colloidal Particles in Flow Junctions Induced by Fluid Flow and Diffusiophoresis

Energy Technology Data Exchange (ETDEWEB)

Shin, Sangwoo [Univ. of Hawaii at Manoa, Honolulu, HI (United States); Ault, Jesse T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Warren, Patrick B. [Unilever R& D Port Sunlight, Wirral (United Kingdom); Stone, Howard A. [Princeton Univ., Princeton, NJ (United States)

2017-11-16

The flow of solutions containing solutes and colloidal particles in porous media is widely found in systems including underground aquifers, hydraulic fractures, estuarine or coastal habitats, water filtration systems, etc. In such systems, solute gradients occur when there is a local change in the solute concentration. While the effects of solute gradients have been found to be important for many applications, we observe an unexpected colloidal behavior in porous media driven by the combination of solute gradients and the fluid flow. When two flows with different solute concentrations are in contact near a junction, a sharp solute gradient is formed at the interface, which may allow strong diffusiophoresis of the particles directed against the flow. Consequently, the particles accumulate near the pore entrance, rapidly approaching the packing limit. These colloidal dynamics have important implications for the clogging of a porous medium, where particles that are orders of magnitude smaller than the pore width can accumulate and block the pores within a short period of time. As a result, we also show that this effect can be exploited as a useful tool for preconcentrating biomolecules for rapid bioassays.

Band-gap engineering by molecular mechanical strain-induced giant tuning of the luminescence in colloidal amorphous porous silicon nanostructures.

Science.gov (United States)

Mughal, A; El Demellawi, J K; Chaieb, Sahraoui

2014-12-14

Nano-silicon is a nanostructured material in which quantum or spatial confinement is the origin of the material's luminescence. When nano-silicon is broken into colloidal crystalline nanoparticles, its luminescence can be tuned across the visible spectrum only when the sizes of the nanoparticles, which are obtained via painstaking filtration methods that are difficult to scale up because of low yield, vary. Bright and tunable colloidal amorphous porous silicon nanostructures have not yet been reported. In this letter, we report on a 100 nm modulation in the emission of freestanding colloidal amorphous porous silicon nanostructures via band-gap engineering. The mechanism responsible for this tunable modulation, which is independent of the size of the individual particles and their distribution, is the distortion of the molecular orbitals by a strained silicon-silicon bond angle. This mechanism is also responsible for the amorphous-to-crystalline transformation of silicon.

Band-gap engineering by molecular mechanical strain-induced giant tuning of the luminescence in colloidal amorphous porous silicon nanostructures

KAUST Repository

Mughal, Asad Jahangir

2014-01-01

Nano-silicon is a nanostructured material in which quantum or spatial confinement is the origin of the material\\'s luminescence. When nano-silicon is broken into colloidal crystalline nanoparticles, its luminescence can be tuned across the visible spectrum only when the sizes of the nanoparticles, which are obtained via painstaking filtration methods that are difficult to scale up because of low yield, vary. Bright and tunable colloidal amorphous porous silicon nanostructures have not yet been reported. In this letter, we report on a 100 nm modulation in the emission of freestanding colloidal amorphous porous silicon nanostructures via band-gap engineering. The mechanism responsible for this tunable modulation, which is independent of the size of the individual particles and their distribution, is the distortion of the molecular orbitals by a strained silicon-silicon bond angle. This mechanism is also responsible for the amorphous-to-crystalline transformation of silicon. This journal is

Natural colloids in groundwater from granite and their potential impact on radionuclide transport

International Nuclear Information System (INIS)

Vilks, P.; Bachinski, D.B.

1997-03-01

AECL has submitted an Environmental Impact Statement (EIS) to evaluate the concept of nuclear fuel disposal at depth in crystalline rock of the Canadian Shield. As part of geochemical studies carried out in support of the EIS, the role of natural groundwater colloids (0.001 to 0.45 μm) and suspended particles (>0.45 μm) in radionuclide transport in granite rock has been investigated. This report summarizes the results of investigations carried out in groundwaters from the Whiteshell Research Area (WRA) of southern Manitoba and the Atikokan Research Area (ARA) of northwestern Ontario to determine the concentrations, size distributions, and compositions of natural particles in groundwaters from the Canadian Shield. Particles from groundwater were isolated by ultrafiltration under a nitrogen atmosphere and particle concentrations and size distributions were determined by filtration, and by laser-based particle counting and size analysis. Groundwaters from Canadian Shield granites contain particles in a broad range of sizes, with no one particular size being dominant. Particle compositions include aluminosilicates, Fe oxides, carbonate and organics. Suspended particles are most likely generated by the mobilization of fracture-lining minerals by groundwater flow, while colloids are formed by a combination of precipitation and mobilization of colloidal material from fracture surfaces. The average concentration of 0.01 to 0.45 μm colloids in WRA groundwaters was 1.05 ± 0.14 mg/L. Average colloid concentrations were slightly higher in the more highly fractured ARA, although the highest observed colloid concentration in the ARA was below the 7 mg/L maximum observed in a sample from the WRA. The existence of colloids in the 0.001 to 0.01 μm size range was demonstrated using the results of chemical analysis of particle concentrates and data obtained with the laser-based Ultrafine Particle Size Analyzer (UPA). The WRA groundwaters contain on average about 2.7 mg/L of 0

Tangential Flow Filtration of Colloidal Silver Nanoparticles: A "Green" Laboratory Experiment for Chemistry and Engineering Students

Science.gov (United States)

Dorney, Kevin M.; Baker, Joshua D.; Edwards, Michelle L.; Kanel, Sushil R.; O'Malley, Matthew; Pavel Sizemore, Ioana E.

2014-01-01

Numerous nanoparticle (NP) fabrication methodologies employ "bottom-up" syntheses, which may result in heterogeneous mixtures of NPs or may require toxic capping agents to reduce NP polydispersity. Tangential flow filtration (TFF) is an alternative "green" technique for the purification, concentration, and size-selection of…

Removal of heavy metals and radionuclides by seeded magnetic filtration

International Nuclear Information System (INIS)

Bibler, J.P.; Norrell, G.; Hemmings, R.L.; Bradbury, D.; Dunn, M.J.; Kalinauskas, G.L.

1991-01-01

Removal of traces of heavy metal or radionuclide contamination from solution at high flow rate presents a considerable technical challenge. Low flow methods of treatment such as particle gravity settling require expensive large volume equipment, whereas traditional methods of filtration can cause significant energy costs. Magnetic filtration can be used to provide a low cost method of solid-liquid separation at high flow rate, provided contaminants can be selectively bound to a magnetic solid particle. This paper describes the use of such selective magnetic particles made up of inorganic particles coupled with organic polymers

Changes in colloid solution sales in Nordic countries.

Science.gov (United States)

Kongsgaard, U E; Holtan, A; Perner, A

2018-04-01

Administration of resuscitation fluid is a common intervention in the treatment of critically ill patients, but the right choice of fluid is still a matter of debate. Changes in medical practice are based on new evidence and guidelines as well as traditions and personal preferences. Official warnings against the use of hydroxyl-ethyl-starch (HES) solutions have been issued. Nordic guidelines have issued several strong recommendations favouring crystalloids over colloids in all patient groups. Our objective was to describe the patterns of colloid use in Nordic countries from 2012 to 2016. The data were obtained from companies that provide pharmaceutical statistics in different countries. The data are sales figures from pharmaceutical companies to pharmacies and health institutions. We found a 56% reduction in the total sales of all colloids in Nordic countries over a 5-year period. These findings were mainly related to a 92% reduction in the sales of HES solutions. A reduction in sales of other synthetic colloids has also occurred. During the same period, we found a 46% increase in albumin sales, but these numbers varied between Nordic countries. The general reduction in colloid sales likely reflects the recommendation that colloids should be used only in special circumstances. The dramatic reduction in the sales of HES solutions was expected given evidence of harm and the official warnings. The steady increase in albumin sales and the notable differences between the five Nordic countries cannot be explained. © 2018 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Dynamic behaviour of river colloidal and dissolved organic matter through cross-flow ultrafiltration system.

Science.gov (United States)

Wilding, Andrew; Liu, Ruixia; Zhou, John L

2005-07-01

Through cross-flow filtration (CFF) with a 1-kDa regenerated cellulose Pellicon 2 module, the ultrafiltration characteristics of river organic matter from Longford Stream, UK, were investigated. The concentration of organic carbon (OC) in the retentate in the Longford Stream samples increased substantially with the concentration factor (cf), reaching approximately 40 mg/L at cf 15. The results of dissolved organic carbon (DOC) and colloidal organic carbon (COC) analysis, tracking the isolation of colloids from river waters, show that 2 mg/L of COC was present in those samples and good OC mass balance (77-101%) was achieved. Fluorescence measurements were carried out for the investigation of retentate and permeate behaviour of coloured dissolved organic materials (CDOM). The concentrations of CDOM in both the retentate and permeate increased with increasing cf, although CDOM were significantly more concentrated in the retentate. The permeation model expressing the correlation between log[CDOM] in the permeate and logcf was able to describe the permeation behaviour of CDOM in the river water with regression coefficients (r(2)) of 0.94 and 0.98. Dry weight analysis indicated that the levels of organic colloidal particles were from 49 to 71%, and between 29 and 51% of colloidal particles present were inorganic. COC as a percentage of DOC was found to be 10-16% for Longford Stream samples.

An assessment of existing common traditional methods of water ...

African Journals Online (AJOL)

Classical water purification methods include boiling, filtration, irradiation and the use of chemicals while traditional water purification methods in use are boiling, filtration, sedimentation, long storage and solar radiation. Waterborne diseases are m ore common in the rural communities where potable water supply coverage ...

Anisotropic Model Colloids

NARCIS (Netherlands)

van Kats, C.M.

2008-01-01

The driving forces for fundamental research in colloid science are the ability to manage the material properties of colloids and to unravel the forces that play a role between colloids to be able to control and understand the processes where colloids play an important role. Therefore we are

Use of ultra-filtration in organic-rich groundwater for the physical separation of thorium

International Nuclear Information System (INIS)

Singhal, R.K.; Basu, H.; Pimple, M.V.; Manisha, V.; Bassan, M.K.T.; Reddy, A.V.R.

2014-01-01

During this work, size fractionation technique 'ultra filtration' is used in physical speciation of thorium in organic rich groundwater. Laboratory simulated experiments were carried out to study the physical speciation of thorium in aquatic environment having elevated level of dissolved humus material classified as dissolved organic carbon (DOC). Samples were collected from organic rich environment having DOC in the range of 50-60 μg mL -1 . Th(IV) ions are extremely particle reactive having K d value of the order of 105-6, hence to avoid adsorption on suspended particulate matter, spiking of the solution with Th(NO 3 )4 was carried out in ground water samples after filtering through 450 nm pore size using suction filtration. Particles in dissolved state (colloids) ranging between 220 nm were separated using suction filtration assembly having a membrane with a pore diameter of 220 nm. Thereafter, solution was sequentially passed through the ultra-filtration membranes having pore diameters of 14 nm [300 k NMWL (nominal molecular weight limit)], 3.1 nm (50 k NMWL), 2.2 nm (30 k NMWL), 1.6 nm (10 k NMWL) and 1.1 nm (0.5 k NMWL) by using 'Stirred Ultra-filtration Cells', operating in concentration mode. Thorium has only one stable oxidation state i.e. IV, under all redox conditions in natural waters and therefore, its speciation is dominated by its interaction with various fractions of DOC. Experimental results show 50-60 % of the spiked Th is in association with fraction enriched with particles of 10 k NMWL (1.6 nm) followed by fraction enriched with particle of 0.5 k NMWL and <220 nm. (author)

Magnetic-seeding filtration

International Nuclear Information System (INIS)

Ying, T.Y.; Chin, C.J.; Lu, S.C.; Yiacoumi, S.

1997-10-01

Magnetic-seeding filtration consists of two steps: heterogeneous particle flocculation of magnetic and nonmagnetic particles in a stirred tank and high-gradient magnetic filtration (HGMF). The effects of various parameters affecting magnetic-seeding filtration (HGMF). The effects of various parameters affecting magnetic seeding filtration are theoretically and experimentally investigated. A trajectory model that includes hydrodynamic resistance, van der Waals, and electrostatic forces is developed to calculate the flocculation frequency in a turbulent-shear regime. Fractal dimension is introduced to simulate the open structure of aggregates. A magnetic-filtration model that consists of trajectory analysis, a particle build-up model, a breakthrough model, and a bivariate population-balance model is developed to predict the breakthrough curve of magnetic-seeding filtration. A good agreement between modeling results and experimental data is obtained. The results show that the model developed in this study can be used to predict the performance of magnetic-seeding filtration without using empirical coefficients or fitting parameters. 35 refs., 7 figs., 1 tab

Colloidal nanoparticles as catalysts and catalyst precursors for nitrite hydrogenation

NARCIS (Netherlands)

Zhao, Yingnan

2015-01-01

The most distinguished advantage to use colloidal methods for catalyst preparation is that the size and the shape of nanoparticles can be manipulated easily under good control, which is normally difficult to achieve by using traditional methods, such as impregnation and precipitation. This

Comparison of pressure-driven membrane processes and traditional ...

African Journals Online (AJOL)

In this article a comparison is made between drinking water production from surface water using pressure-driven membrane processes and using traditional surface water treatment systems. Three alternatives are considered: Traditional treatment using coagulation/flocculation, sand filtration, physicochemical softening, ...

Decrease of concentration and colloidal fraction of organic carbon and trace elements in response to the anomalously hot summer 2010 in a humic boreal lake

International Nuclear Information System (INIS)

Shirokova, L.S.; Pokrovsky, O.S.; Moreva, O.Yu.; Chupakov, A.V.; Zabelina, S.A.; Klimov, S.I.; Shorina, N.V.; Vorobieva, T.Ya.

2013-01-01

The colloidal distribution and size fractionation of organic carbon (OC), major elements and trace elements (TE) were studied in a seasonally stratified, organic-rich boreal lake, Lake Svyatoe, located in the European subarctic zone (NW Russia, Arkhangelsk region). This study took place over the course of 4 years in both winter and summer periods using an in situ dialysis technique (1 kDa, 10 kDa and 50 kDa) and traditional frontal filtration and ultrafiltration (5, 0.22 and 0.025 μm). We observed a systematic difference in dissolved elements and colloidal fractions between summer and winter periods with the highest proportion of organic and organo-ferric colloids (1 kDa–0.22 μm) observed during winter periods. The anomalously hot summer of 2010 in European Russia produced surface water temperatures of approximately 30 °C, which were 10° above the usual summer temperatures and brought about crucial changes in element speciation and size fractionation. In August 2010, the concentration of dissolved organic carbon (DOC) decreased by more than 30% compared to normal period, while the relative proportion of organic colloids decreased from 70–80% to only 20–30% over the full depth of the water column. Similarly, the proportion of colloidal Fe decreased from 90–98% in most summers and winters to approximately 60–70% in August 2010. During this hot summer, measurable and significant (> 30% compared to other periods) decreases in the colloidal fractions of Ca, Mg, Sr, Ba, Al, Ti, Ni, As, V, Co, Y, all rare earth elements (REEs), Zr, Hf, Th and U were also observed. In addition, dissolved ( 100 for Co), the second and third factors could have brought about the decrease of allochthonous DOC concentration as well as the concentration and proportion of organic and organo-mineral colloidal forms of non-essential low-soluble trace elements present in the form of organic colloids (Al, Y, Ti, Zr, Hf, Th, Pb, all REEs). It can be hypothesized that climate warming in

Decrease of concentration and colloidal fraction of organic carbon and trace elements in response to the anomalously hot summer 2010 in a humic boreal lake.

Science.gov (United States)

Shirokova, L S; Pokrovsky, O S; Moreva, O Yu; Chupakov, A V; Zabelina, S A; Klimov, S I; Shorina, N V; Vorobieva, T Ya

2013-10-01

The colloidal distribution and size fractionation of organic carbon (OC), major elements and trace elements (TE) were studied in a seasonally stratified, organic-rich boreal lake, Lake Svyatoe, located in the European subarctic zone (NW Russia, Arkhangelsk region). This study took place over the course of 4 years in both winter and summer periods using an in situ dialysis technique (1 kDa, 10 kDa and 50 kDa) and traditional frontal filtration and ultrafiltration (5, 0.22 and 0.025 μm). We observed a systematic difference in dissolved elements and colloidal fractions between summer and winter periods with the highest proportion of organic and organo-ferric colloids (1 kDa-0.22 μm) observed during winter periods. The anomalously hot summer of 2010 in European Russia produced surface water temperatures of approximately 30°C, which were 10° above the usual summer temperatures and brought about crucial changes in element speciation and size fractionation. In August 2010, the concentration of dissolved organic carbon (DOC) decreased by more than 30% compared to normal period, while the relative proportion of organic colloids decreased from 70-80% to only 20-30% over the full depth of the water column. Similarly, the proportion of colloidal Fe decreased from 90-98% in most summers and winters to approximately 60-70% in August 2010. During this hot summer, measurable and significant (>30% compared to other periods) decreases in the colloidal fractions of Ca, Mg, Sr, Ba, Al, Ti, Ni, As, V, Co, Y, all rare earth elements (REEs), Zr, Hf, Th and U were also observed. In addition, dissolved (organic matter by heterotrophic aerobic bacterioplankton and 3) photo-degradation of DOM and photo-chemical liberation of organic-bound TE. While the first process may have caused significant decreases in the total dissolved concentration of micronutrients (a factor of 2 to 5 for Cr, Mn, Fe, Ni, Cu, Zn and Cd and a factor of >100 for Co), the second and third factors could have brought

The Fundamentals of Waste Water Sludge Characterization and Filtration

Energy Technology Data Exchange (ETDEWEB)

Scales, Peter J.; Dixon, David R.; Harbour, Peter J.; Stickland, Anthony D.

2003-07-01

The move to greater emphasis on the disposal of waste water sludges through routes such as incineration and the added cost of landfill emplacement puts high demands on dewatering technology for these sludges. A dear problem in this area is that waste water sludges are slow and difficult to dewater and traditional methods of laboratory measurement for prediction of filtration performance are inadequate. This is highly problematic for the design and operational optimisation of centrifuges, filters and settling devices in the waste water industry. The behaviour is assessed as being due to non-linear behaviour of these sludges which negates the use of classical approaches. These approaches utilise the linear portion of a t versus V{sup 2} plot (where t is the time to filtration and V is the specific filtrate volume) to extract a simple Darcian permeability. Without this parameter, a predictive capacity for dewatering using current theory is negated. (author)

Modeling the filtration ability of stockpiled filtering facepiece

Science.gov (United States)

Rottach, Dana R.

2016-03-01

Filtering facepiece respirators (FFR) are often stockpiled for use during public health emergencies such as an infectious disease outbreak or pandemic. While many stockpile administrators are aware of shelf life limitations, environmental conditions can lead to premature degradation. Filtration performance of a set of FFR retrieved from a storage room with failed environmental controls was measured. Though within the expected shelf life, the filtration ability of several respirators was degraded, allowing twice the penetration of fresh samples. The traditional picture of small particle capture by fibrous filter media qualitatively separates the effect of inertial impaction, interception from the streamline, diffusion, settling, and electrostatic attraction. Most of these mechanisms depend upon stable conformational properties. However, common FFR rely on electrets to achieve their high performance, and over time heat and humidity can cause the electrostatic media to degrade. An extension of the Langevin model with correlations to classical filtration concepts will be presented. The new computational model will be used to predict the change in filter effectiveness as the filter media changes with time.

Characterisation and Treatment of Nano-sized Particles, Colloids and Associated Polycyclic Aromatic Hydrocarbons in Stormwater

DEFF Research Database (Denmark)

Nielsen, Katrine

such as pH, Total Suspended Solid(TSS), turbidity, and electrical conductivity.The five sites where stormwater was sampled from used two different methods of stormwater treatment: settling and filtration, and four different treatment techniques: detention ponds, stormwater pond, disc filter and combined...... sedimentation tanks. From all sites, inlet and outlet stormwater were collected,and pollutant concentrations were quantified as well as the removal efficiencies calculated. The colloidal and nano-sized particle-enhanced transportation of pollutants was also scrutinised in the stormwater.The μm-range PSD...

Rapid electrostatics-assisted layer-by-layer assembly of near-infrared-active colloidal photonic crystals.

Science.gov (United States)

Askar, Khalid; Leo, Sin-Yen; Xu, Can; Liu, Danielle; Jiang, Peng

2016-11-15

Here we report a rapid and scalable bottom-up technique for layer-by-layer (LBL) assembling near-infrared-active colloidal photonic crystals consisting of large (⩾1μm) silica microspheres. By combining a new electrostatics-assisted colloidal transferring approach with spontaneous colloidal crystallization at an air/water interface, we have demonstrated that the crystal transfer speed of traditional Langmuir-Blodgett-based colloidal assembly technologies can be enhanced by nearly 2 orders of magnitude. Importantly, the crystalline quality of the resultant photonic crystals is not compromised by this rapid colloidal assembly approach. They exhibit thickness-dependent near-infrared stop bands and well-defined Fabry-Perot fringes in the specular transmission and reflection spectra, which match well with the theoretical calculations using a scalar-wave approximation model and Fabry-Perot analysis. This simple yet scalable bottom-up technology can significantly improve the throughput in assembling large-area, multilayer colloidal crystals, which are of great technological importance in a variety of optical and non-optical applications ranging from all-optical integrated circuits to tissue engineering. Copyright © 2016 Elsevier Inc. All rights reserved.

Colloid Transport and Retention

DEFF Research Database (Denmark)

Yuan, Hao; Shapiro, Alexander

2012-01-01

related to historical prospective, synthesis, characterization, theoretical modeling and application of unique class of colloidal materials starting from colloidal gold to coated silica colloid and platinum, titania colloids. This book is unique in its design, content, providing depth of science about...

Colloid chemistry: available sorption models and the question of colloid adhesion

International Nuclear Information System (INIS)

Grauer, R.

1990-05-01

A safety analysis of a radioactive waste repository should consider the possibility of nuclide transport by colloids. This would involve describing the sorption properties of the colloids and their transport in porous and fissured media. This report deals with a few selected aspects of the chemistry of this complex subject. Because the mechanisms of ion adsorption onto surfaces are material-specific, increased attention should be paid to identifying the material constitution of aquatic colloids. Suitable models already exist for describing reversible adsorption; these models describe sorption using mass action equations. The surface coordination model, developed for hydrous oxide surfaces, allows a uniform approach to be adopted for different classes of materials. This model is also predictive and has been applied successfully to natural systems. From the point of view of nuclide transport by colloids, irreversible sorption represents the most unfavourable situation. There is virtually no information available on the extent of reversibility and on the desorption kinetics of important nuclide/colloid combinations. Experimental investigations are therefore necessary in this respect. The only question considered in connection with colloid transport and its modelling is that of colloid sticking. Natural colloids, and the surfaces of the rock on which they may be collected, generally have negative surface charges so that colloid sticking will be difficult. The DLVO theory contains an approach for calculating the sticking factor from the surface potentials of the solid phases and the ionic strength of the water. However, it has been shown that this theory is inapplicable because of inherent shortcomings which lead to completely unrealistic predictions. The sticking probability of colloids should therefore be determined experimentally for systems which correspond as closely as possible to reality. (author) 66 figs., 12 tabs., 204 refs

Investigation of Microgranular Adsorptive Filtration System

Science.gov (United States)

Cai, Zhenxiao

Over the past few decades, enormous advances have been made in the application of low-pressure membrane filtration to both drinking water and wastewater treatment. Nevertheless, the full potential of this technology has not been reached, due primarily to limitations imposed by membrane fouling. In drinking water treatment, much of the fouling is caused by soluble and particulate natural organic matter (NOM). Efforts to overcome the problem have focused on removal of NOM from the feed solution, usually by addition of conventional coagulants like alum and ferric chloride (FeCl3) or adsorbents like powdered activated carbon (PAC). While coagulants and adsorbents can remove a portion of the NOM, their performance with respect to fouling control has been inconsistent, often reducing fouling but sometimes having no effect or even exacerbating fouling. This research investigated microgranular adsorptive filtration (muGAF), a process that combines three existing technologies---granular media filtration, packed bed adsorption, and membrane filtration---in a novel way to reduce membrane fouling while simultaneously removing NOM from water. In this technology, a thin layer of micron-sized adsorbent particles is deposited on the membrane prior to delivering the feed to the system. The research reported here represents the first systematic study of muGAF, and the results demonstrate the promising potential of this process. A new, aluminum-oxide-based adsorbent---heated aluminum oxide particles (HAOPs)---was synthesized and shown to be very effective for NOM removal as well as fouling reduction in muGAF systems. muGAF has also been demonstrated to work well with powdered activated carbon (PAC) as the adsorbent, but not as well as when HAOPs are used; the process has also been successful when used with several different membrane types and configurations. Experiments using a wide range of operational parameters and several analytical tools lead to the conclusion that the fouling

Ultra-thin layer chromatography with integrated silver colloid-based SERS detection.

Science.gov (United States)

Wallace, Ryan A; Lavrik, Nickolay V; Sepaniak, Michael J

2017-01-01

Simplified lab-on-a-chip techniques are desirable for quick and efficient detection of analytes of interest in the field. The following work involves the use of deterministic pillar arrays on the micro-scale as a platform to separate compounds, and the use of Ag colloid within the arrays as a source of increased signal via surface enhanced Raman spectroscopy (SERS). One problem traditionally seen with SERS surfaces containing Ag colloid is oxidation; however, our platforms are superhydrophobic, reducing the amount of oxidation taking place on the surface of the Ag colloid. This work includes the successful separation and SERS detection of a fluorescent dye compounds (resorufin and sulforhodamine 640), fluorescent anti-tumor drugs (Adriamycin and Daunomycin), and purine and pyrimidine bases (adenine, cytosine, guanine, hypoxanthine, and thymine). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transport of 152Eu colloids in a system of fine sand and water containing humic substances

International Nuclear Information System (INIS)

Klotz, D.

1995-01-01

The migration of 152 Eu in a system of fine sand and water containing humic substances was investigated in a flow column system under realistic conditions. In this system, the trivalent Eu forms colloids with the water. These Eu humates are transported without retardation at recovery rates significantly below 100 per cent. Recovery is more or less a measure of the physical process of filtration of Eu bonded to particulates. In the range of natural filtering rates, the recovery rates decrease with decreasing filtering rate. (orig.) [de

Colloid Titration--A Rapid Method for the Determination of Charged Colloid.

Science.gov (United States)

Ueno, Keihei; Kina, Ken'yu

1985-01-01

"Colloid titration" is a volumetric method for determining charged polyelectrolytes in aqueous solutions. The principle of colloid titration, reagents used in the procedure, methods of endpoint detection, preparation of reagent solutions, general procedure used, results obtained, and pH profile of colloid titration are considered. (JN)

[AgBr colloids prepared by electrolysis and their SERS activity research].

Science.gov (United States)

Si, Min-Zhen; Fang, Yan; Dong, Gang; Zhang, Peng-Xiang

2008-01-01

Ivory-white AgBr colloids were prepared by means of electrolysis. Two silver rods 1.0 cm in diameter and 10.0 cm long were respectively used as the negative and positive electrodes, the aqueous solution of hexadecyl trimethyl ammonium bromide was used as the electrolyte, and a 7 V direct current was applied on the silver rods for three hours. The obtained AgBr colloids were characterized by UV-Vis spectroscopy, transmission electron microscopy, and SERS using a 514. 5 nm laser line on Renishaw 2000 Raman spectrometer. These particles are about nanometer size and their shapes are as spherical or elliptic, with a slight degree of particle aggregation. The UV-Vis spectra exhibit a large plasmon resonance band at about 292.5 nm, similar to that reported in the literature. The AgBr colloids were very stable at room temperature for months. In order to test if these AgBr colloids can be used for SERS research, methyl orange, Sudan red and pyridine were used. It was found that AgBr colloids have SERS activity to these three molicules. For methyl orange, the intense Raman peaks are at 1 123, 1 146, 1 392, 1 448 and 1 594 cm(-1); for Sudan red, the intense Raman peaks are at 1 141, 1 179, 1 433 and 1 590 cm(-1); and for pyridine, the intense Raman peaks are at 1 003, 1 034 and 1 121 cm(-1). It is noticeable that SERS of methyl orange was observed on AgBr colloids, but not on the gray and yellow silver colloids prepared by traditional means. The possible reason was explained. One major advantage of this means is the absence of the spectral interference such as citrate, BH4- arising from reaction products of the colloids formation process. On AgBr colloids, one can get some molecular SERS impossible to get on the gray and yellow silver colloids.

INTRODUCTION: New trends in simulating colloids and self-assembling systems New trends in simulating colloids and self-assembling systems

Science.gov (United States)

Foffi, Giuseppe; Kahl, Gerhard

2010-03-01

relatively high number of contributions as an indicator that the topics presented at these workshops represent substantial scientific developments. The particular motivation to organize these two workshops came from the fact that experimental work in colloidal physics is advancing rapidly around the globe. In contrast, theoretical and simulation approaches to investigate the wide range of new and surprising physical phenomena of colloidal systems is lagging behind this experimental progress. This is the more deploring since theory and simulation might provide a more profound understanding of many phenomena in soft and bio-related physics, such as phase behaviour, self-assembly strategies, or rheological properties, to name but a few. Furthermore this insight might help to guide experiment to design new colloid-based materials with desired properties. The declared aim of the two workshops was thus to bring together scientists who have contributed in recent time to new developments in colloidal physics and to share and discuss their latest innovations. While CECAM workshops traditionally bring together scientists from the theoretical and simulator communities, from the very beginning the organizers considered it an indispensable necessity to invite experimentalists. And indeed, the organizers are happy to confirm that the participation of experimentalists, theoreticians, and simulators was highly fruitful and mutually inspiring: discussions between all communities did help to understand the possibilities and limitations imposed by experiment, theory, and simulations. Reuniting thus all forces, the workshop did contribute to a deeper understanding in colloidal physics and has helped to address future aspects that might lead to more applied problems of technological relevance. The first workshop, entitled 'Computer Simulation Approaches to Study Self-Assembly: From Patchy Nano-Colloids to Virus Capsides', (organized by Jonathan Doye—University Of Oxford, Ard A Louis�

GSPEL - Air Filtration Laboratory

Data.gov (United States)

Federal Laboratory Consortium — Evaluation capabilities for air filtration devicesThe Air Filtration Lab provides testing of air filtration devices to demonstrate and validate new or legacy system...

Dissociation behavior of Np(IV) from humic acid colloid

Energy Technology Data Exchange (ETDEWEB)

Iijima, K.; Tobitsuka, S. [Japan Nuclear Cycle Development Institute, 4-33 Muramatsu, Tokai, Naka-gun, Ibaraki 319-1194 (Japan); Kohara, Y. [Inspection Development Corporation, 4-33, Muramatsu, Tokai, Nakagun, Ibaraki 319-1112 (Japan)

2005-07-01

Full text of publication follows: Dissociation behavior of Np(IV) from humic colloid, which was prepared with purified Aldrich humic acid (PAHA) was investigated. The complexation experiments were carried out in 0.1 M NaClO{sub 4} - 0.05 M Na{sub 2}S{sub 2}O{sub 4} solution at pH 8 with PAHA concentration between 0 and 500 mg L-1 under anaerobic condition. Np-237 was added as Np(V) solution so that its concentration becomes 1.1 x 10-5 mol L-1. After shaking from 1 to 156 days, aliquots of experimental solution were filtered through the membranes with 50, 10 and 3 kD of MWCO to obtain the size distribution of colloid, followed by adding the filtrate into the 6 M HCl for dissociation. At the end of experiments for 596 days, 0.1 M NaHCO{sub 3} was used for dissociation solution. The concentration of Np released into this solution was evaluated by measuring a activity of Np-237. The concentration of Np becomes constant by 112 days. Since Eh of the solution has been kept between -300 and -100 mV vs. SHE during experimental duration, Np is presumed to be reduced into tetravalent. In the case of higher PAHA concentration than 50 mg L{sup -1}, the Np concentration is close to that of initially added Np. Since the size of the dissolved species of Np during complexation experiments varies from 3 to 50 kD, the Np is sorbed on humic acid colloid. In the dissociation experiments, the Np dissociated by 6 M HCl decreases with increasing complexation time and PAHA concentration. After 156 days complexation with 500 mg L{sup -1} of PAHA, 35% of Np can be dissociated from the colloid. Such a tendency, however, is not observed in case of the lowest PAHA concentration, 5 mg L{sup -1}. After 596 days complexation, the dissociation experiments were carried out by adding 0.1 M NaHCO{sub 3} solution to avoid the precipitation which might hinder the dissociation of Np in the aforementioned experiments with HCl. As a result, 50% of Np is dissociated in the presence of 50 and 100 mg L-1 of

40 CFR 141.173 - Filtration.

Science.gov (United States)

2010-07-01

... PRIMARY DRINKING WATER REGULATIONS Enhanced Filtration and Disinfection-Systems Serving 10,000 or More People § 141.173 Filtration. A public water system subject to the requirements of this subpart that does... treatment, direct filtration, slow sand filtration, or diatomaceous earth filtration. A public water system...

Colloid process engineering

CERN Document Server

Peukert, Wolfgang; Rehage, Heinz; Schuchmann, Heike

2015-01-01

This book deals with colloidal systems in technical processes and the influence of colloidal systems by technical processes. It explores how new measurement capabilities can offer the potential for a dynamic development of scientific and engineering, and examines the origin of colloidal systems and its use for new products. The future challenges to colloidal process engineering are the development of appropriate equipment and processes for the production and obtainment of multi-phase structures and energetic interactions in market-relevant quantities. The book explores the relevant processes and for controlled production and how they can be used across all scales.

A case of generalized argyria after ingestion of colloidal silver solution.

Science.gov (United States)

Kim, Yangho; Suh, Ho Seok; Cha, Hee Jeong; Kim, Suk Hwan; Jeong, Kyoung Sook; Kim, Dong Hoon

2009-03-01

A 58-year-old woman was referred to our hospital due to progressive skin darkening, which began 5 months previously. The patient had strikingly diffuse blue-gray discoloration of the skin, most prominent in sun-exposed areas, especially her face and hands. The oral mucosa, tongue, gums, eye conjunctiva, ears, nail beds, and trunk were also involved. Bluish-gray discoloration of all nails was aggravated by cold weather. She had ingested 1 L of colloidal silver solution daily for approximately 16 months as a traditional remedy. Her serum silver concentration was 381 ng/ml which was a very high (reference level: silver and sulfur in the dense black deposits. The ingestion of colloidal silver appears to be an increasing practice among patients using alternative health practices. All silver-containing products including colloidal silver should be labeled with a clear warning to prevent argyria, especially in alternative health practices.

Colloids as a sink for certain pharmaceuticals in the aquatic environment.

Science.gov (United States)

Maskaoui, Khalid; Zhou, John L

2010-05-01

filtrate (observed partition coefficients, Kobsp, Kobsoc), between SPM and soluble phase (intrinsic partition coefficients, Kintp, Kintoc), and between colloids and soluble phase (Kcoc) showed that intrinsic partition coefficients (Kintp, Kintoc) are between 25% and 96%, and between 18% and 82% higher than relevant observed partition coefficients values, and are much less variable. Secondly, Kcoc values are 3-4 orders of magnitude greater than Kintoc values, indicating that aquatic colloids are substantially more powerful sorbents for accumulating pharmaceuticals than sediments. Furthermore, mass balance calculations of pharmaceutical concentrations demonstrate that between 23% and 70% of propranolol, 17-62% of sulfamethoxazole, 7-58% of carbamazepine, 19-84% of indomethacine, and 9-74% of diclofenac are present in the colloidal phase. The results provide direct evidence that sorption to colloids provides an important sink for the pharmaceuticals in the aquatic environment. Such strong pharmaceutical/colloid interactions may provide a long-term storage of pharmaceuticals, hence, increasing their persistence while reducing their bioavailability in the environment. Pharmaceutical compounds have been detected not only in the aqueous phase but also in suspended particles; it is important, therefore, to have a holistic approach in future environmental fate investigation of pharmaceuticals. For example, more research is needed to assess the storage and long-term record of pharmaceutical residues in aquatic sediments by which benthic organisms will be most affected. Aquatic colloids have been shown to account for the accumulation of major fractions of total pharmaceutical concentrations in the aquatic environment, demonstrating unequivocally the importance of aquatic colloids as a sink for such residues in the aquatic systems. As aquatic colloids are abundant, ubiquitous, and highly powerful sorbents, they are expected to influence the bioavailability and bioaccumulation of such

Radioactive colloids

International Nuclear Information System (INIS)

Bergqvist, L.

1987-01-01

Different techniques for the characterization of radioactive colloids, used in nuclear medicine, have been evaluated and compared. Several radioactive colloids have been characterized in vitro and in vivo and tested experimentally. Colloid biokinetics following interstitial or intravenous injection were evaluated with a scintillation camera technique. Lymphoscintigraphy with a Tc-99-labelled antimony sulphur colloid was performed in 32 patients with malignant melanoma in order to evaluate the technique. Based on the biokinetic results, absorbed doses in tissues and organs were calculated. The function of the reticuloendothelial system has been evaluated in rats after inoculation with tumour cells. Microfiltration and photon correlation spectroscopy were found to be suitable in determining activity-size and particle size distributions, respectively. Maximal lymph node uptake following subcutaneous injection was found to correspond to a colloid particle size between 10 and 50 nm. Lymphoscintigraphy was found to be useful in the study of lymphatic drainage from the primary tumour site in patients with malignant melanoma on the trunk. Quantitative analysis of ilio-inguinal lymph node uptake in patients with malignant melanoma on the lower extremities was, however, found to be of no value for the detection of metastatic disease in lymph nodes. High absorbed doses may be received in lymph nodes (up to 1 mGy/MBq) and at the injection site (about 10 mGy/MBq). In an experimental study it was found that the relative colloid uptake in bone marrow and spleen depended on the total number of intravenously injected particles. This may considerably affect the absorbed dose in these organs. (author)

Task 9 - centrifugal membrane filtration. Semi-annual report April 1--September 30, 1996

International Nuclear Information System (INIS)

Stepan, D.J.; Moe, T.A.; Collings, M.E.

1997-01-01

This report assesses a centrifugal membrane filtration technology developed by SpinTek Membrane Systems, Inc. The technology uses supported microporous membranes rotating at high rpm, under pressure, to separate suspended and colloidal solids from liquid streams, yielding a solids-free permeate stream and a highly concentrated solids stream. The Tank Waste Focus Area was chosen for study. Membrane-screening tests were performed with the STC-X4 static test cell filtration unit, using five ceramic membranes with different pore size and composition. Based on permeate flux, a 0.25-μm TiO 2 /Al 2 O 3 membrane was selected for detailed performance evaluation using the centrifugal membrane filtration unit with a surrogate tank waste solution. The performance of the unit was evaluated with a statistical test design that determined the effect of temperature, pressure, membrane rotational speed, and solids loading on permeate flux. All four variables were found to be statistically significant, with the magnitude of the effect in the order of temperature, solids loading, rotor speed, and pressure. Temperature, rotor speed, and pressure had an increasing effect on flux with increasing value, while increases in solids loading showed a decrease in permeate flux. Significant interactions between rotor speed and solids loading and pressure and solids loading were also observed. The regression equation derived from test data had a correlation coefficient of 0.934, which represents a useful predictive capability for integrating the technology into DOE cleanup efforts. An extended test run performed on surrogate waste showed some deterioration in filtration performance, based on flux, apparently due to the buildup of solids near the inner portion of the membrane where relative membrane velocities were low. Continued testing of the system will focus on modifications to the shear pattern across the entire membrane surface to affect improved long-term performance

Dynamic Heterogeneous Multiscale Filtration Model: Probing Micro- and Macroscopic Filtration Characteristics of Gasoline Particulate Filters.

Science.gov (United States)

Gong, Jian; Viswanathan, Sandeep; Rothamer, David A; Foster, David E; Rutland, Christopher J

2017-10-03

Motivated by high filtration efficiency (mass- and number-based) and low pressure drop requirements for gasoline particulate filters (GPFs), a previously developed heterogeneous multiscale filtration (HMF) model is extended to simulate dynamic filtration characteristics of GPFs. This dynamic HMF model is based on a probability density function (PDF) description of the pore size distribution and classical filtration theory. The microstructure of the porous substrate in a GPF is resolved and included in the model. Fundamental particulate filtration experiments were conducted using an exhaust filtration analysis (EFA) system for model validation. The particulate in the filtration experiments was sampled from a spark-ignition direct-injection (SIDI) gasoline engine. With the dynamic HMF model, evolution of the microscopic characteristics of the substrate (pore size distribution, porosity, permeability, and deposited particulate inside the porous substrate) during filtration can be probed. Also, predicted macroscopic filtration characteristics including particle number concentration and normalized pressure drop show good agreement with the experimental data. The resulting dynamic HMF model can be used to study the dynamic particulate filtration process in GPFs with distinct microstructures, serving as a powerful tool for GPF design and optimization.

Colloid formation in groundwater by subsurface aeration: characterisation of the geo-colloids and their counterparts

International Nuclear Information System (INIS)

Wolthoorn, Anke; Temminghoff, Erwin J.M.; Riemsdijk, Willem H. van

2004-01-01

Subsurface aeration is used to oxidise Fe in situ in groundwater to make the water potable. In a groundwater system with pH > 7, subsurface aeration results in a non-mobile Fe precipitate and mobile Fe colloids. Since originally the goal of subsurface aeration is to remove Fe in situ, the formation of non-mobile Fe precipitate is the desired result. In addition to this intended effect, subsurface aeration may also strongly enhance the microbiological removal of NH 4 in the purification station. A hypothesis is that mobile Fe colloids may be the link between subsurface aeration and the positive effect on the microbiological removal of NH 4 . The objective of this study is to characterise the mobile Fe colloids and to derive a synthetic substitute for the naturally formed Fe colloids in order to be able to apply the Fe colloids as a management tool to enhance the removal of NH 4 in the process of producing drinking water from groundwater. At a purification station in The Netherlands natural Fe colloids from an aerated well were sampled. Furthermore, eight synthetic Fe colloids were prepared by oxidising synthetic solutions differing in elemental composition. The colloids were analysed using chemical analysis and electron microscopy (SEM and SEM-EDAX). The Fe colloids sampled in the field contained Fe, Ca, Na, PO 4 and Mn. Also in the synthetic Fe colloids PO 4 , Ca, Na and Mn were the most important elements next to Fe. Phosphate and dissolved organic C strongly influenced the morphology of the synthetic Fe colloids. When both the elemental composition and the morphology of the Fe colloids are taken into account, the synthetic Fe colloids formed in the synthetic solution containing Fe, Mn, PO 4 , SiO 4 and dissolved organic matter best match the Fe colloids from the field

Colloid formation in groundwater by subsurface aeration: characterisation of the geo-colloids and their counterparts

Energy Technology Data Exchange (ETDEWEB)

Wolthoorn, Anke; Temminghoff, Erwin J.M.; Riemsdijk, Willem H. van

2004-09-01

Subsurface aeration is used to oxidise Fe in situ in groundwater to make the water potable. In a groundwater system with pH > 7, subsurface aeration results in a non-mobile Fe precipitate and mobile Fe colloids. Since originally the goal of subsurface aeration is to remove Fe in situ, the formation of non-mobile Fe precipitate is the desired result. In addition to this intended effect, subsurface aeration may also strongly enhance the microbiological removal of NH{sub 4} in the purification station. A hypothesis is that mobile Fe colloids may be the link between subsurface aeration and the positive effect on the microbiological removal of NH{sub 4}. The objective of this study is to characterise the mobile Fe colloids and to derive a synthetic substitute for the naturally formed Fe colloids in order to be able to apply the Fe colloids as a management tool to enhance the removal of NH{sub 4} in the process of producing drinking water from groundwater. At a purification station in The Netherlands natural Fe colloids from an aerated well were sampled. Furthermore, eight synthetic Fe colloids were prepared by oxidising synthetic solutions differing in elemental composition. The colloids were analysed using chemical analysis and electron microscopy (SEM and SEM-EDAX). The Fe colloids sampled in the field contained Fe, Ca, Na, PO{sub 4} and Mn. Also in the synthetic Fe colloids PO{sub 4}, Ca, Na and Mn were the most important elements next to Fe. Phosphate and dissolved organic C strongly influenced the morphology of the synthetic Fe colloids. When both the elemental composition and the morphology of the Fe colloids are taken into account, the synthetic Fe colloids formed in the synthetic solution containing Fe, Mn, PO{sub 4}, SiO{sub 4} and dissolved organic matter best match the Fe colloids from the field.

A binomial modeling approach for upscaling colloid transport under unfavorable conditions: Emergent prediction of extended tailing

Science.gov (United States)

Hilpert, Markus; Rasmuson, Anna; Johnson, William P.

2017-07-01

Colloid transport in saturated porous media is significantly influenced by colloidal interactions with grain surfaces. Near-surface fluid domain colloids experience relatively low fluid drag and relatively strong colloidal forces that slow their downgradient translation relative to colloids in bulk fluid. Near-surface fluid domain colloids may reenter into the bulk fluid via diffusion (nanoparticles) or expulsion at rear flow stagnation zones, they may immobilize (attach) via primary minimum interactions, or they may move along a grain-to-grain contact to the near-surface fluid domain of an adjacent grain. We introduce a simple model that accounts for all possible permutations of mass transfer within a dual pore and grain network. The primary phenomena thereby represented in the model are mass transfer of colloids between the bulk and near-surface fluid domains and immobilization. Colloid movement is described by a Markov chain, i.e., a sequence of trials in a 1-D network of unit cells, which contain a pore and a grain. Using combinatorial analysis, which utilizes the binomial coefficient, we derive the residence time distribution, i.e., an inventory of the discrete colloid travel times through the network and of their probabilities to occur. To parameterize the network model, we performed mechanistic pore-scale simulations in a single unit cell that determined the likelihoods and timescales associated with the above colloid mass transfer processes. We found that intergrain transport of colloids in the near-surface fluid domain can cause extended tailing, which has traditionally been attributed to hydrodynamic dispersion emanating from flow tortuosity of solute trajectories.

Colloidal glasses

Indian Academy of Sciences (India)

First page Back Continue Last page Overview Graphics. Colloidal glasses. Glassy state is attained when system fails to reach equilibrium due to crowding of constituent particles. In molecular glasses, glassy state is reached by rapidly lowering the temperature. In colloidal glasses, glassy state is reached by increasing the ...

Colloidal nematostatics

Directory of Open Access Journals (Sweden)

V.M. Pergamenshchik

2010-01-01

Full Text Available We give a review of the theory of large distance colloidal interaction via the nematic director field. The new area of nematic colloidal systems (or nematic emulsions has been guided by the analogy between the colloidal nematostatics and electrostatics. The elastic charge density representation of the colloidal nematostatics [V.M. Pergamenshchik, V.O. Uzunova, Eur. Phys. J. E, 2007, 23, 161; Phys. Rev. E, 2007, 76, 011707] develops this analogy at the level of charge density and Coulomb interaction. The analogy is shown to lie in common mathematics based on the solutions of Laplace equation. However, the 3d colloidal nematostatics substantially differs from electrostatics both in its mathematical structure and physical implications. The elastic charge is a vector fully determined by the torque exerted upon colloid, the role of Gauss' theorem is played by conservation of the torque components. Elastic multipoles consist of two tensors (dyads. Formulas for the elastic multipoles, the Coulomb-like, dipole-dipole, and quadrupole-quadrupole pair interaction potentials are derived and illustrated by particular examples. Based on the tensorial structure, we list possible types of elastic dipoles and quadrupoles. An elastic dipole is characterized by its isotropic strength, anisotropy, chirality, and its longitudinal component. An elastic quadrupole can be uniaxial and biaxial. Relation between the multipole type and its symmetry is discussed, sketches of some types of multipoles are given. Using the mirror image method of electrostatics as a guiding idea, we develop the mirror image method in nematostatics for arbitrary director tilt at the wall. The method is applied to the charge-wall and dipole-wall interaction.

Colloidal Photoluminescent Amorphous Porous Silicon, Methods Of Making Colloidal Photoluminescent Amorphous Porous Silicon, And Methods Of Using Colloidal Photoluminescent Amorphous Porous Silicon

KAUST Repository

Chaieb, Sahraoui

2015-04-09

Embodiments of the present disclosure provide for a colloidal photoluminescent amorphous porous silicon particle suspension, methods of making a colloidal photoluminescent amorphous porous silicon particle suspension, methods of using a colloidal photoluminescent amorphous porous silicon particle suspension, and the like.

Colloidal Photoluminescent Amorphous Porous Silicon, Methods Of Making Colloidal Photoluminescent Amorphous Porous Silicon, And Methods Of Using Colloidal Photoluminescent Amorphous Porous Silicon

KAUST Repository

Chaieb, Saharoui; Mughal, Asad Jahangir

2015-01-01

Embodiments of the present disclosure provide for a colloidal photoluminescent amorphous porous silicon particle suspension, methods of making a colloidal photoluminescent amorphous porous silicon particle suspension, methods of using a colloidal photoluminescent amorphous porous silicon particle suspension, and the like.

Colloid formation during waste glass corrosion

International Nuclear Information System (INIS)

Mertz, C.J.; Buck, E.C.; Fortner, J.A.; Bates, J.K.

1996-01-01

The long-term behavior of nuclear waste glass in a geologic repository may require a technical consideration of the role of colloids in the release and transport of radionuclides. The neglect of colloidal properties in assessing the near- and far-field migration behavior of actinides may lead to significant underestimates and poor predictions of biosphere exposure from high-level waste (HLW) disposal. Existing data on colloid-facilitated transport suggests that radionuclide migration may be enhanced, but the importance of colloids is not adequately assessed. Indeed, the occurrence of radionuclide transport, attributed to colloidal species, has been reported at Mortandad Canyon, Los Alamos and at the Nevada Test Site; both unsaturated regions are similar to the proposed HLW repository at Yucca Mountain. Although some developments have been made on understanding the transport characteristics of colloids, the characterization of colloids generated from the corrosion of the waste form has been limited. Colloids are known to incorporate radionuclides either from hydrolysis of dissolved species (real colloids) or from adsorption of dissolved species onto existing groundwater colloids (pseudocolloids); however, these colloids may be considered secondary and solubility limited when compared to the colloids generated during glass alteration

Actinide colloid generation in groundwater

International Nuclear Information System (INIS)

Kim, J.I.

1990-05-01

The progress made in the investigation of actinide colloid generation in groundwaters is summarized and discussed with particular examples relevant to an understanding of the migration behaviour of actinides in natural aquifer systems. The first part deals with the characterization of colloids: groundwater colloids, actinide real-colloids and actinide pseudocolloids. The second part concentrates on the generation processes and migration behaviour of actinide pseudocolloids, which are discussed with some notable experimental examples. Importance is stressed more on the chemical aspects of the actinide colloid generation in groundwater. This work is a contribution to the CEC project MIRAGE II, particularly, to research area: complexation and colloids. (orig.)

Contribution of non-traditional lipid profiles to reduced glomerular filtration rate in H-type hypertension population of rural China.

Science.gov (United States)

Wang, Haoyu; Li, Zhao; Guo, Xiaofan; Chen, Yintao; Chen, Shuang; Tian, Yichen; Sun, Yingxian

2018-05-01

Despite current interest in the unfavourable impact of non-traditional lipid profiles on cardiovascular disease, information regarding its relations to reduced glomerular filtration rate (GFR) in H-type hypertension population has not been systemically elucidated. Analyses were based upon a cross-sectional study of 3259 participants with H-type hypertension who underwent assessment of biochemical, anthropometric and blood pressure values. Reduced GFR was considered if meeting estimated GFR <60 ml/min/1.73 m 2 . A stepwise multivariate regression analysis indicated that non-traditional lipid parameters remained as independent determinants of estimated GFR (all p < .001). In multivariable models, we observed a 50%, 51%, 31%, and 24% higher risk for decreased GFR with each SD increment in TC/HDL-C, TG/HDL-C, LDL-C/HDL-C ratios and non-HDL-C levels, respectively. The highest quartile of TC/HDL-C, TG/HDL-C and LDL-C/HDL-C ratios carried reduced GFR odds (confidence intervals) of 5.50 (2.50 to 12.09), 6.63 (2.58 to 17.05) and 2.22 (1.15 to 4.29), respectively. The relative independent contribution of non-traditional lipid profiles, as indexed by TC/HDL-C, TG/HDL-C, LDL-C/HDL-C ratios and non-HDL-C, towards reduced GFR putting research evidence at the very heart of lipoprotein-mediated renal injury set a vital example for applying a clinical and public health recommendation for reducing the burden of chronic kidney disease. KEY MESSAGES Non-traditional lipid profiles has been linked with the occurrence of cardiovascular disease, but none of the studies that address the effect of non-traditional lipid profiles on reduced GFR risk in H-type hypertension population has been specifically established. A greater emphasis of this study resided in the intrinsic value of TC/HDL-C, TG/HDL-C, LDL-C/HDL-C ratios and non-HDL-C that integrate atherogenic and anti-atherogenic lipid molecules to predict the risk of reduced GFR among H-type hypertension population and provide

UZ Colloid Transport Model

International Nuclear Information System (INIS)

McGraw, M.

2000-01-01

The UZ Colloid Transport model development plan states that the objective of this Analysis/Model Report (AMR) is to document the development of a model for simulating unsaturated colloid transport. This objective includes the following: (1) use of a process level model to evaluate the potential mechanisms for colloid transport at Yucca Mountain; (2) Provide ranges of parameters for significant colloid transport processes to Performance Assessment (PA) for the unsaturated zone (UZ); (3) Provide a basis for development of an abstracted model for use in PA calculations

LONG-TERM COLLOID MOBILIZATION AND COLLOID-FACILITATED TRANSPORT OF RADIONUCLIDES IN A SEMI-ARID VADOSE ZONE

Energy Technology Data Exchange (ETDEWEB)

Markus Flury; James B. Harsh; Fred Zhang; Glendon W. Gee; Earl D. Mattson; Peter C. L

2012-08-01

The main purpose of this project was to improve the fundamental mechanistic understanding and quantification of long-term colloid mobilization and colloid-facilitated transport of radionuclides in the vadose zone, with special emphasis on the semi-arid Hanford site. While we focused some of the experiments on hydrogeological and geochemical conditions of the Hanford site, many of our results apply to colloid and colloid-facilitated transport in general. Specific objectives were (1) to determine the mechanisms of colloid mobilization and colloid-facilitated radionuclide transport in undisturbed Hanford sediments under unsaturated flow, (2) to quantify in situ colloid mobilization and colloid-facilitated radionuclidetransport from Hanford sediments under field conditions, and (3) to develop a field-scale conceptual and numerical model for colloid mobilization and transport at the Hanford vadose zone, and use that model to predict long-term colloid and colloid- facilitated radionuclide transport. To achieve these goals and objectives, we have used a combination of experimental, theoretical, and numerical methods at different spatial scales, ranging from microscopic investigationsof single particle attachment and detachment to larger-scale field experiments using outdoor lysimeters at the Hanford site. Microscopic and single particle investigations provided fundamental insight into mechanisms of colloid interactions with the air-water interface. We could show that a moving air water interface (such as a moving water front during infiltration and drainage) is very effective in removing and mobilizing particles from a stationary surface. We further demonstrated that it is particularly the advancing air-water interface which is mainly responsible for colloid mobilization. Forces acting on the colloids calculated from theory corroborated our experimental results, and confirm that the detachment forces (surface tension forces) during the advancing air-water interface

Programming Hierarchical Self-Assembly of Patchy Particles into Colloidal Crystals via Colloidal Molecules.

Science.gov (United States)

Morphew, Daniel; Shaw, James; Avins, Christopher; Chakrabarti, Dwaipayan

2018-03-27

Colloidal self-assembly is a promising bottom-up route to a wide variety of three-dimensional structures, from clusters to crystals. Programming hierarchical self-assembly of colloidal building blocks, which can give rise to structures ordered at multiple levels to rival biological complexity, poses a multiscale design problem. Here we explore a generic design principle that exploits a hierarchy of interaction strengths and employ this design principle in computer simulations to demonstrate the hierarchical self-assembly of triblock patchy colloidal particles into two distinct colloidal crystals. We obtain cubic diamond and body-centered cubic crystals via distinct clusters of uniform size and shape, namely, tetrahedra and octahedra, respectively. Such a conceptual design framework has the potential to reliably encode hierarchical self-assembly of colloidal particles into a high level of sophistication. Moreover, the design framework underpins a bottom-up route to cubic diamond colloidal crystals, which have remained elusive despite being much sought after for their attractive photonic applications.

Filtration behaviors of rod-shaped bacterial broths in unsteady-state phase of cross-flow filtration

Energy Technology Data Exchange (ETDEWEB)

Tanaka, T.; Usui, K.; Koda, K.; Nakanishi, K. [Okayama University, Okayama (Japan). Faculty of Engineering

1996-12-20

Filtration behaviors in the unsteady-state phase of crossflow filtration of broths of Bacillus subtilis, Escherichia coli, and Lactobacillus delbrueckii, which are rod-shaped, were studied from the viewpoint of the changes in the specific resistance and in the structure of the microbial cake formed on the membrane surface. The permeation flux followed the cake filtration law at the initial stage of the crossflow filtration of the broths of B. subtilis and E. coli, where the cells deposited randomly on the membrane. In the case of the crossflow filtration of a L. delbrueckii broth, the period of random deposition was shorter. The specific resistance for the cake formed at the initial stage agreed with that measured in dead-end filtration. Then, the specific resistance started to increase in comparison with that measured in dead-end filtration due to shear-induced arrangement of the cells. The extent of the increase in specific resistance became higher and the time taken to start the cell arrangement became shorter with increasing circulation flow rate. The increase in specific resistance due to the shear-induced arrangement was more appreciable in the crossflow filtration of the broth of L. delbrueckii than that of B. subtilis and E. coli. The average permeation flux was increased considerably by applying periodical backwashing with appropriate time intervals. The permeation flux was well predicted by the cake filtration law, since the cells deposited in a way similar to that for dead-end filtration during a sufficiently short period of crossflow filtration in a backwashing mode. 21 refs., 11 figs.

Colloid migration in fractured media

International Nuclear Information System (INIS)

Hunt, J.R.

1989-01-01

Field studies at the Nevada Test Site by researchers at Lawrence Livermore National Laboratory have demonstrated that radionuclides are being transported by colloidal material suspended in groundwater. This observation is counter to most predictions from contaminant transport models because the models assume adsorbed species are immobile. The purpose of this research is to quantify the transport processes for colloidal materials and develop the mechanistic understanding necessary to predict radionuclide transport in fractured media. There were three areas of investigation during this year that have addressed these issues: chemical control of colloid deposition on clean mineral surfaces, colloid accumulation on fracture surfaces, and the influence of deposited colloids on colloid and tracer migration. 7 refs

Filtration and compression of organic materials

DEFF Research Database (Denmark)

Christensen, Morten Lykkegaard; Keiding, Kristian

is to use more simple systems. Dextran-MnO2 particles and polystyrene particles with a water-swollen polyacrylic acid shell have therefore been synthesised. These particles have been filtered and used to study the non-linear filtration behaviour. The compressibility of the formed cake has been investigated......The conventional filtration theory has been based on filtrations of incompressible particles such as anatase, kaolin and clay. The filtration models have later been used for organic slurries but can often not explain the observed experimental data. At constant pressure, the filtrate volume does...... and the discrepancy between the filtration theory and the observed filtration behaviour explained as a time-dependent collapse of the formed cake (creep). Thus, the creep phenomenon has been adopted in the conventional filtration models and it will be shown that the model can be used to simulate filtration data...

Colloid migration in groundwaters: Geochemical interactions of radionuclides with natural colloids. Final report

International Nuclear Information System (INIS)

Kim, J.J.; Longworth, G.; Hasler, S.E.; Gardiner, M.; Fritz, P.; Klotz, D.; Lazik, D.; Wolf, M.; Geyer, S.; Alexander, J.L.; Read, D.; Thomas, J.B.

1994-08-01

In this joint research programme the significance of groundwater colloids in far field radionuclide migration has been studied. The characterization, quantification and theoretical interpretation of colloid-borne transport phenomena for radionuclides were the main objectives of this research programme. Groundwaters, colloids and sediments were sampled from aquifer system overlying a saltdome in the Gorleben area in northern Germany and were characterized by various analytical methods (ICP-MS, ICP-AES, neutron activation analysis (NAA), DOC-Analyser, HPIC, potentiometric titration). Different natural isotopes ( 2 H, 3 H, 13 C, 14 C, 18 O, 34 S, U/Th decay series) were determined and their ratios were compared with one another in the order to ascertain the provenance of the groundwater colloids. The investigated groundwaters contain substantial amounts of colloids mainly composed of humic and fulvic acids loaded with various metal ions. The chemical interaction of radionuclide ions of various oxidation states (Am, Eu, for M(III), Th, Pu for M(IV), Np for M(V) and U for M(VI)) with groundwater colloids was investigated in order to elucidate the colloid facilitated migration behaviour of actinides in a given aquifer system. Transport process studies with generated pseudocolloids of radionuclides in various oxidation states were undertaken in scaled column experiments, pre-equilibrated with colloid rich Gorleben groundwater. A modelling programme was developed to predict chemical transport of radionuclides in the presence of humic colloids using a modified version of the CHEMTARD code. Modelling predictions have generated acceptable results for Eu, Am and U and poorer agreement between experimental and modelling results for Th and Np as a result of more limited data. (orig.)

Colloid migration in groundwaters: Geochemical interactions of radionuclides with natural colloids. Final report

Energy Technology Data Exchange (ETDEWEB)

Kim, J.J. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Radiochemie; Delakowitz, B. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Radiochemie; Zeh, P. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Radiochemie; Probst, T. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Radiochemie; Lin, X. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Radiochemie; Ehrlicher, U. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Radiochemie; Schauer, C. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Radiochemie; Ivanovich, M. [AEA Environment and Energy, Harwell (United Kingdom); Longworth, G. [AEA Environment and Energy, Harwell (United Kingdom); Hasler, S.E. [AEA Environment and Energy, Harwell (United Kingdom); Gardiner, M. [AEA Decommissioning and Radwaste, Harwell (United Kingdom); Fritz, P. [Gesellschaft fuer Strahlen- und Umweltforschung mbH Muenchen, Neuherberg (Germany); Klotz, D. [Gesellschaft fuer Strahlen- und Umweltforschung mbH Muenchen, Neuherberg (Germany); Lazik, D. [Gesellschaft fuer Strahlen- und Umweltforschung mbH Muenchen, Neuherberg (Germany); Wolf, M. [Gesellschaft fuer Strahlen- und Umweltforschung mbH Muenchen, Neuherberg (Germany); Geyer, S. [Gesellschaft fuer Strahlen- und Umweltforschung mbH Muenchen, Neuherberg (Germany); Alexander, J.L. [Atkins (W.S.) Engineering Sciences, Epsom (United Kingdom); Read, D. [Atkins (W.S.) Engineering Sciences, Epsom (United Kingdom); Thomas, J.B. [Atkins (W.S.) Engineering Sciences, Epsom (United Kingdom)

1994-08-01

In this joint research programme the significance of groundwater colloids in far field radionuclide migration has been studied. The characterization, quantification and theoretical interpretation of colloid-borne transport phenomena for radionuclides were the main objectives of this research programme. Groundwaters, colloids and sediments were sampled from aquifer system overlying a saltdome in the Gorleben area in northern Germany and were characterized by various analytical methods (ICP-MS, ICP-AES, neutron activation analysis (NAA), DOC-Analyser, HPIC, potentiometric titration). Different natural isotopes ({sup 2}H, {sup 3}H, {sup 13}C, {sup 14}C, {sup 18}O, {sup 34}S, U/Th decay series) were determined and their ratios were compared with one another in the order to ascertain the provenance of the groundwater colloids. The investigated groundwaters contain substantial amounts of colloids mainly composed of humic and fulvic acids loaded with various metal ions. The chemical interaction of radionuclide ions of various oxidation states (Am, Eu, for M(III), Th, Pu for M(IV), Np for M(V) and U for M(VI)) with groundwater colloids was investigated in order to elucidate the colloid facilitated migration behaviour of actinides in a given aquifer system. Transport process studies with generated pseudocolloids of radionuclides in various oxidation states were undertaken in scaled column experiments, pre-equilibrated with colloid rich Gorleben groundwater. A modelling programme was developed to predict chemical transport of radionuclides in the presence of humic colloids using a modified version of the CHEMTARD code. Modelling predictions have generated acceptable results for Eu, Am and U and poorer agreement between experimental and modelling results for Th and Np as a result of more limited data. (orig.)

Liquid crystal boojum-colloids

International Nuclear Information System (INIS)

Tasinkevych, M; Silvestre, N M; Telo da Gama, M M

2012-01-01

Colloidal particles dispersed in a liquid crystal (LC) lead to distortions of the director field. The distortions are responsible for long-range effective colloidal interactions whose asymptotic behaviour is well understood. The short-distance behaviour depends on the structure and dynamics of the topological defects nucleated near the colloidal particles and a full nonlinear theory is required to describe it. Spherical colloidal particles with strong planar degenerate anchoring nucleate a pair of antipodal surface topological defects, known as boojums. We use the Landau-de Gennes theory to resolve the mesoscopic structure of the boojum cores and to determine the pairwise colloidal interactions. We compare the results in three (3D) and two (2D) spatial dimensions for spherical and disc-like colloidal particles, respectively. The corresponding free energy functionals are minimized numerically using finite elements with adaptive meshes. Boojums are always point-like in 2D, but acquire a rather complex structure in 3D, which depends on the combination of the anchoring potential, the radius of the colloid, the temperature and the LC elastic anisotropy. We identify three types of defect cores in 3D that we call single, double and split-core boojums, and investigate the associated structural transitions. The split-core structure is favoured by low temperatures, strong anchoring and small twist to splay or bend ratios. For sufficiently strong anchoring potentials characterized by a well-defined uniaxial minimum, the split-core boojums are the only stable configuration. In the presence of two colloidal particles, we observe substantial re-arrangements of the inner defects in both 3D and 2D. These re-arrangements lead to qualitative changes in the force-distance profile when compared to the asymptotic quadrupole-quadrupole interaction. In line with the experimental results, the presence of the defects prevents coalescence of the colloidal particles in 2D, but not in 3D

Colloids in Biotechnology

CERN Document Server

Fanun, Monzer

2010-01-01

Colloids have come a long way from when Thomas Graham coined the term colloid to describe 'pseudo solutions'. This book enables scientists to close the gap between extensive research and translation into commercial options in biomedicine and biotechnology. It covers biosurfactants and surface properties, phase behavior, and orientational change of surfactant mixtures with peptides at the interface. It also covers adsorption of polymers and biopolymers on the surface and interface, discusses colloidal nanoparticles and their use in biotechnology, and delves into bioadhesion and microencapsulati

EDITORIAL: Colloidal dispersions in external fields Colloidal dispersions in external fields

Science.gov (United States)

Löwen, Hartmut

2012-11-01

Colloidal dispersions have long been proven as pivotal model systems for equilibrium phase transition such as crystallization, melting and liquid-gas phase transition. The last decades have revealed that this is also true for nonequilibrium phenomena. In fact, the fascinating possibility to track the individual trajectories of colloidal particles has greatly advanced our understanding of collective behaviour in classical many-body systems and has helped to reveal the underlying physical principles of glass transition, crystal nucleation, and interfacial dynamics (to name just a few typical nonequilibrium effects). External fields can be used to bring colloids out of equilibrium in a controlled way. Different kinds of external fields can be applied to colloidal dispersions, namely shear flow, electric, magnetic and laser-optical fields, and confinement. Typical research areas can be sketched with the by now traditional complexity diagram (figure 1). The complexity of the colloidal system itself as embodied in statistical degrees of freedom is shown on the x-axis while the complexity of the problem posed, namely bulk, an inhomogeneity in equilibrium, steady state nonequilibrium and full time-dependent nonequilibrium are shown on the y-axis. The different external fields which can be imposed are indicated by the different hatched areas. figure1 Figure 1. Diagram of complexity for colloidal dispersions in external fields: while the x-axis shows the complexity of the system, the y-axis shows the complexity of the problem. Regions which can be accessed by different kinds of external fields are indicated. The arrows indicate recent research directions. Active particles are also indicated with a special complexity of internal degrees of freedom [1]. This collection of papers reflects the scientific programme of the International Conference on Colloidal Dispersions in External Fields III (CODEF III) which took place in Bonn-Bad Godesberg from 20-23 March 2012. This was the

Filtration in Porous Media

DEFF Research Database (Denmark)

Yuan, Hao; Shapiro, Alexander

There is a considerable and ongoing effort aimed at understanding the transport and the deposition of suspended particles in porous media, especially non-Fickian transport and non-exponential deposition of particles. In this work, the influential parameters in filtration models are studied...... to understand their effects on the non-Fickian transport and the non-exponential deposition. The filtration models are validated by the comparisons between the modelling results and the experimental data.The elliptic equation with distributed filtration coefficients may be applied to model non-Fickian transport...... and hyperexponential deposition. The filtration model accounting for the migration of surface associated particles may be applied for non-monotonic deposition....

Effect of colloids on the occurrence, distribution and photolysis of emerging organic contaminants in wastewaters

Energy Technology Data Exchange (ETDEWEB)

Yan, Caixia [School of Geography and Environment, Key Laboratory of Poyang Lake Wetland and Watershed Research, Ministry of Education, Jiangxi Normal University, No. 99, Ziyang Road, Nanchang 330022 (China); State Key Laboratory of Estuarine and Coastal Research, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062 (China); SmartState Center for Environmental Nanoscience and Risk, Arnold School of Public Health, University of South Carolina, 921 Assembly Street, Columbia 29208,USA (United States); Nie, Minghua [School of Geography and Environment, Key Laboratory of Poyang Lake Wetland and Watershed Research, Ministry of Education, Jiangxi Normal University, No. 99, Ziyang Road, Nanchang 330022 (China); Department of Environmental Science and Engineering, Fudan University, 220Handan Road, Shanghai 200433 (China); Yang, Yi, E-mail: yyang@geo.ecnu.edu.cn [State Key Laboratory of Estuarine and Coastal Research, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062 (China); Key Laboratory of Geographic Information Science of the Ministry of Education, Department of Geosciences, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062 (China); Zhou, Junliang [State Key Laboratory of Estuarine and Coastal Research, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062 (China); Liu, Min [Key Laboratory of Geographic Information Science of the Ministry of Education, Department of Geosciences, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062 (China); Baalousha, Mohammed; Lead, Jamie R. [SmartState Center for Environmental Nanoscience and Risk, Arnold School of Public Health, University of South Carolina, 921 Assembly Street, Columbia 29208,USA (United States)

2015-12-15

Highlights: • Colloidal fractions in wastewaters were isolated using cross flow ultrafiltration. • EOCs exhibited a pseudo - first - order degradation kinetics in all water samples. • Photolysis of EOCs in permeate were accelerated, while inhibited in the retentates. • EOCs with higher degradation rates were detected at low level in natural water. - Abstract: The effect of colloids on the occurrence, phase distribution and photolysis of twenty-seven emerging organic contaminants (EOCs) was studied in domestic and livestock wastewaters (DW and LW), respectively. Filtered water (<1 μm) was separated into permeate (<1 kDa) and retentate (1 kDa-1 μm) by cross flow ultrafiltration. Results indicated that total concentration of EOCs ranged from 1220 ng L{sup −1} in permeate of DW to 5065 ng L{sup −1} in retentate of LW. The average EOC fraction associated with colloids was 13.5% and 14.4% in DW and LW. Most of the EOCs exhibited pseudo-first-order degradation kinetics in all water samples. Control experiments using glass and quartz reactors showed that UV light was more effective on the photolysis of most EOCs. The EOCs photolysis in the three fractions of DW and LW could be accelerated or inhibited compared to ultrapure water with the enhancement factor ranging from −0.94 to 7.33. The impact of colloids on the photolysis of EOCs depended on the compound and the source of water. The photolysis of most EOCs in permeates and filtrates was generally accelerated, while inhibited in the retentates, which could be attributed to the relatively high dissolved organic carbon contents in retentates.

Filtration Efficiency of Functionalized Ceramic Foam Filters for Aluminum Melt Filtration

Science.gov (United States)

Voigt, Claudia; Jäckel, Eva; Taina, Fabio; Zienert, Tilo; Salomon, Anton; Wolf, Gotthard; Aneziris, Christos G.; Le Brun, Pierre

2017-02-01

The influence of filter surface chemistry on the filtration efficiency of cast aluminum alloys was evaluated for four different filter coating compositions (Al2O3—alumina, MgAl2O4—spinel, 3Al2O3·2SiO2—mullite, and TiO2—rutile). The tests were conducted on a laboratory scale with a filtration pilot plant, which facilitates long-term filtration tests (40 to 76 minutes). This test set-up allows the simultaneous use of two LiMCAs (before and after the filter) for the determination of the efficiency of inclusion removal. The four tested filter surface chemistries exhibited good thermal stability and mechanical robustness after 750 kg of molten aluminum had been cast. All four filter types exhibited a mean filtration efficiency of at least 80 pct. However, differences were also observed. The highest filtration efficiencies were obtained with alumina- and spinel-coated filter surfaces (>90 pct), and the complete removal of the largest inclusions (>90 µm) was observed. The efficiency was slightly lower with mullite- and rutile-coated filter surfaces, in particular for large inclusions. These observations are discussed in relation to the properties of the filters, in particular in terms of, for example, the surface roughness.

Applications of the spline filter for areal filtration

International Nuclear Information System (INIS)

Tong, Mingsi; Zhang, Hao; Ott, Daniel; Chu, Wei; Song, John

2015-01-01

This paper proposes a general use isotropic areal spline filter. This new areal spline filter can achieve isotropy by approximating the transmission characteristic of the Gaussian filter. It can also eliminate the effect of void areas using a weighting factor, and resolve end-effect issues by applying new boundary conditions, which replace the first order finite difference in the traditional spline formulation. These improvements make the spline filter widely applicable to 3D surfaces and extend the applications of the spline filter in areal filtration. (technical note)

Improved Filtration Technology for Pathogen Reduction in Rural Water Supplies

Directory of Open Access Journals (Sweden)

Valentine Tellen

2010-06-01

Full Text Available Intermittent bio-sand filtration (BSF is a low-cost process for improving water quality in rural households. This study addresses its two drawbacks: flow limitations requiring excessive waiting, and inadequate purification when high flows are imposed. Two modifications were examined: increasing the sand’s effective size, and adding zero-valent iron (ZVI into the media as a disinfectant. After 65 days, percent reductions in total coliform, fecal coliform, and fecal streptococci averaged 98.9% for traditional BSF and 99% for the improved BSF. Both modifications showed statistically significant improvements. Increased sand size and ZVI addition can counter the drawbacks of traditional BSF.

Integrated photonics using colloidal quantum dots

Science.gov (United States)

Menon, Vinod M.; Husaini, Saima; Okoye, Nicky; Valappil, Nikesh V.

2009-11-01

Integrated photonic devices were realized using colloidal quantum dot composites such as flexible microcavity laser, microdisk emitters and integrated active-passive waveguides. The microcavity laser structure was realized using spin coating and consisted of an all-polymer distributed Bragg reflector with a poly-vinyl carbazole cavity layer embedded with InGaP/ZnS colloidal quantum dots. These microcavities can be peeled off the substrate yielding a flexible structure that can conform to any shape and whose emission spectra can be mechanically tuned. Planar photonic devices consisting of vertically coupled microring resonators, microdisk emitters, active-passive integrated waveguide structures and coupled active microdisk resonators were realized using soft lithography, photo-lithography, and electron beam lithography, respectively. The gain medium in all these devices was a composite consisting of quantum dots embedded in SU8 matrix. Finally, the effect of the host matrix on the optical properties of the quantum dots using results of steady-state and time-resolved luminescence measurements was determined. In addition to their specific functionalities, these novel device demonstrations and their development present a low-cost alternative to the traditional photonic device fabrication techniques.

Efficient, air-stable colloidal quantum dot solar cells encapsulated using atomic layer deposition of a nanolaminate barrier

KAUST Repository

Ip, Alexander H.; Labelle, André J.; Sargent, Edward H.

2013-01-01

Atomic layer deposition was used to encapsulate colloidal quantum dot solar cells. A nanolaminate layer consisting of alternating alumina and zirconia films provided a robust gas permeation barrier which prevented device performance degradation over a period of multiple weeks. Unencapsulated cells stored in ambient and nitrogen environments demonstrated significant performance losses over the same period. The encapsulated cell also exhibited stable performance under constant simulated solar illumination without filtration of harsh ultraviolet photons. This monolithically integrated thin film encapsulation method is promising for roll-to-roll processed high efficiency nanocrystal solar cells. © 2013 AIP Publishing LLC.

Efficient, air-stable colloidal quantum dot solar cells encapsulated using atomic layer deposition of a nanolaminate barrier

KAUST Repository

Ip, Alexander H.

2013-12-23

Atomic layer deposition was used to encapsulate colloidal quantum dot solar cells. A nanolaminate layer consisting of alternating alumina and zirconia films provided a robust gas permeation barrier which prevented device performance degradation over a period of multiple weeks. Unencapsulated cells stored in ambient and nitrogen environments demonstrated significant performance losses over the same period. The encapsulated cell also exhibited stable performance under constant simulated solar illumination without filtration of harsh ultraviolet photons. This monolithically integrated thin film encapsulation method is promising for roll-to-roll processed high efficiency nanocrystal solar cells. © 2013 AIP Publishing LLC.

PROBLEMS OF NONSTATIONARY FILTRATION

Directory of Open Access Journals (Sweden)

Vsevolod A. Shabanov

2018-03-01

Full Text Available he article deals with the classical hydrodynamic theory of filtration. Discusses models of soil, fluid and nature of fluid flow that formed the basis for the creation of the classic filtration theory. Also discusses the assumptions made for the linearization of the equations. Evaluated the scope of the classical filtration theory. Proposed a new model of filtration through a porous medium, based on the application of the laws of theoretical mechanics. It is based on the classical model of soil: the soil is composed of capillaries with ..parallel axes, in which the liquid moves. For tasks of infiltration equations of motion. Considered special cases of unsteady motion of a finite volume of liquid. Numerical example a machine experiment.

Liquid crystal colloids

CERN Document Server

Muševič, Igor

2017-01-01

This book brings together the many concepts and discoveries in liquid crystal colloids contributed over the last twenty years and scattered across numerous articles and book chapters. It provides both a historical overview of the development of the field and a clear perspective on the future applications in photonics. The book covers all phenomena observed in liquid crystal colloids with an emphasis on experimental tools and applications of topology in condensed matter, as well as practical micro-photonics applications. It includes a number of spectacular manifestations of new topological phenomena not found or difficult to observe in other systems. Starting from the early works on nematic colloids, it explains the basics of topological defects in ordered media, charge and winding, and the elastic forces between colloidal particles in nematics. Following a detailed description of experimental methods, such as optical tweezing and particle tracking, the book eases the reader into the theoretical part, which de...

Liquid Crystal Colloids

Science.gov (United States)

Smalyukh, Ivan I.

2018-03-01

Colloids are abundant in nature, science, and technology, with examples ranging from milk to quantum dots and the colloidal atom paradigm. Similarly, liquid crystal ordering is important in contexts ranging from biological membranes to laboratory models of cosmic strings and liquid crystal displays in consumer devices. Some of the most exciting recent developments in both of these soft matter fields emerge at their interface, in the fast-growing research arena of liquid crystal colloids. Mesoscale self-assembly in such systems may lead to artificial materials and to structures with emergent physical behavior arising from patterning of molecular order and nano- or microparticles into precisely controlled configurations. Liquid crystal colloids show exceptional promise for new discovery that may impinge on composite material fabrication, low-dimensional topology, photonics, and so on. Starting from physical underpinnings, I review the state of the art in this fast-growing field, with a focus on its scientific and technological potential.

EDITORIAL: Colloidal suspensions Colloidal suspensions

Science.gov (United States)

Petukhov, Andrei; Kegel, Willem; van Duijneveldt, Jeroen

2011-05-01

Special issue in honour of Henk Lekkerkerker's 65th birthday Professor Henk N W Lekkerkerker is a world-leading authority in the field of experimental and theoretical soft condensed matter. On the occasion of his 65th birthday in the summer of 2011, this special issue celebrates his many contributions to science. Henk Lekkerkerker obtained his undergraduate degree in chemistry at the University of Utrecht (1968) and moved to Calgary where he received his PhD in 1971. He moved to Brussels as a NATO fellow at the Université Libre de Bruxelles and was appointed to an assistant professorship (1974), an associate professorship (1977) and a full professorship (1980) in physical chemistry at the Vrije Universiteit Brussel. In 1985 he returned to The Netherlands to take up a professorship at the Van 't Hoff Laboratory, where he has been ever since. He has received a series of awards during his career, including the Onsager Medal (1999) of the University of Trondheim, the Bakhuys Roozeboom Gold Medal (2003) of the Royal Dutch Academy of Arts and Sciences (KNAW), the ECIS-Rhodia European Colloid and Interface Prize (2003), and the Liquid Matter Prize of the European Physical Society (2008). He was elected a member of KNAW in 1996, was awarded an Academy Chair position in 2005, and has held several visiting lectureships. Henk's work focuses on phase transitions in soft condensed matter, and he has made seminal contributions to both the theoretical and experimental aspects of this field. Here we highlight three major themes running through his work, and a few selected publications. So-called depletion interactions may lead to phase separation in colloid-polymer mixtures, and Henk realised that the partitioning of polymer needs to be taken into account to describe the phase behaviour correctly [1]. Colloidal suspensions can be used as model fluids, with the time- and length-scales involved leading to novel opportunities, notably the direct observation of capillary waves at a

Driving dynamic colloidal assembly using eccentric self-propelled colloids

OpenAIRE

Ma, Zhan; Lei, Qun-li; Ni, Ran

2017-01-01

Designing protocols to dynamically direct the self-assembly of colloidal particles has become an important direction in soft matter physics because of the promising applications in fabrication of dynamic responsive functional materials. Here using computer simulations, we found that in the mixture of passive colloids and eccentric self-propelled active particles, when the eccentricity and self-propulsion of active particles are high enough, the eccentric active particles can push passive coll...

Pharmacological study of radioactive-gold colloid transport by blood and by serous exudate; Contribution a l'etude pharmacologique du transport des colloides d'or radioactif par le sang et les exsudats sereux

Energy Technology Data Exchange (ETDEWEB)

Rousselet, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1966-06-01

transport de l'or colloidal radioactif. Les fractions sanguines qui peuvent participer au transport de l'or colloidal sont les hematies, les leucocytes et elements histiocytaires, et le plasma. La repartition de la radioactivite dans ces elements est precisee en pratiquant des autoradiographies de coupes de culots de sang centrifuge et congele apres incubation avec de l'or colloidal. Cette etude montre l'importance du plasma dans le transport des particules radioactives. Nous avons alors recherche une fixation eventuelle de l'or colloidal 198 sur les diverses proteines seriques en appliquant certaines methodes de separation a savoir une filtration-exclusion sur colonne de gel de Sephadex G-200 et un fractionnement electrophoretique sur papier et sur acetate de cellulose gelatineux (cellogel). Nous avons etudie la liaison ''in vitro'' et ''in vivo'' des particules colloidales d'or 198 d'abord avec les proteines seriques de sujets sains puis avec les proteines des liquides d'epanchement d'origine pathologique, chez l'homme, ou du a une inflammation experimentale a la carragenine chez le rat. Les particules d'or colloidal 198 de 30 m{mu} (S-2) sont liees dans une certaine mesure aux {alpha}2 globulines sanguines ou ascitiques, celles de 5 m{mu} (S-6) sont liees aux {alpha}1 globulines de meme que les grains contenus dans l'or polydisperse. Cette liaison semble intervenir grace a la couche protectrice de macromolecules constituees par la gelatine. Seules les caracteristiques physicochimiques de grains colloidaux peuvent expliquer leur difference de localisation sur l'electrophoregramme. L'or sous forme ionique, par contre, est combine, aux seules albumines si la quantite de metal presente ne depasse pas une certaine limite. (auteur)

Crystallization of DNA-coated colloids

Science.gov (United States)

Wang, Yu; Wang, Yufeng; Zheng, Xiaolong; Ducrot, Étienne; Yodh, Jeremy S.; Weck, Marcus; Pine, David J.

2015-01-01

DNA-coated colloids hold great promise for self-assembly of programmed heterogeneous microstructures, provided they not only bind when cooled below their melting temperature, but also rearrange so that aggregated particles can anneal into the structure that minimizes the free energy. Unfortunately, DNA-coated colloids generally collide and stick forming kinetically arrested random aggregates when the thickness of the DNA coating is much smaller than the particles. Here we report DNA-coated colloids that can rearrange and anneal, thus enabling the growth of large colloidal crystals from a wide range of micrometre-sized DNA-coated colloids for the first time. The kinetics of aggregation, crystallization and defect formation are followed in real time. The crystallization rate exhibits the familiar maximum for intermediate temperature quenches observed in metallic alloys, but over a temperature range smaller by two orders of magnitude, owing to the highly temperature-sensitive diffusion between aggregated DNA-coated colloids. PMID:26078020

Glass/Jamming Transition in Colloidal Aggregation

Science.gov (United States)

Segre, Philip N.; Prasad, Vikram; Weitz, David A.; Rose, M. Franklin (Technical Monitor)

2000-01-01

We have studied colloidal aggregation in a model colloid plus polymer system with short-range attractive interactions. By varying the colloid concentration and the strength of the attraction, we explored regions where the equilibrium phase is expected to consist of colloidal crystallites in coexistance with colloidal gas (i.e. monomers). This occurs for moderate values of the potential depth, U approximately equal to 2-5 kT. Crystallization was not always observed. Rather, over an extended sub-region two new metastable phases appear, one fluid-like and one solid-like. These were examined in detail with light scattering and microscopy techniques. Both phases consist of a near uniform distribution of small irregular shaped clusters of colloidal particles. The dynamical and structural characteristics of the ergodic-nonergodic transition between the two phases share much in common with the colloidal hard sphere glass transition.

Distribution of cesium between colloid-rock phases-establishment of experimental system and investigation of Cs distribution between colloid and rock

International Nuclear Information System (INIS)

Nakata, Kotaro

2006-01-01

Distribution and re-distribution of cesium between 3-phases (colloid, rock and water) was investigated. Analcite and bentonite colloid ware used as colloid phase and muscovite was used as rock phase. Before investigating the distribution between 3-phases, sorption and desorption behavior of Cs on analcite colloid, bentonite colloid and muscovite was investigated. It was found some fraction of Cs sorbed irreversibly on analcite colloid, while Cs sorbed reversibly on bentonite colloid. The experimental system was established for assessment of the distribution of nuclides between 3-phases by using combination of membrane filter and experimental cell. Since colloid and muscovite were separated by membrane filter, sorption of colloid on muscovite could be prevented and we could obtain distribution of Cs as ion. The distribution of Cs between 3-phases were obtained by this experimental system. Furthermore, re-distribution experiment was also carried out by using this system. After 7 days contact of colloid with Cs, distribution of sorbed Cs on colloid to liquid or muscovite phase was investigated. Comparing sorption and desorption isotherm with the distribution of Cs between 3-phases, it was found that Kd value of colloid (ratio of Cs concentration in liquid phase to amount of sorbed Cs on colloid phase) estimated in 2-phases (water and colloid) is different from that in 3-phases. Furthermore, in the case of analcite colloid, Kd value of colloid obtained in 3-phases distribution experiment was different from that obtained in re-distribution experiment. This is considered because of the irreversibility of Cs sorption on analcite colloid. Thus, it was found distribution of Cs in 3-phases was not predictable from sorption and desorption isotherm or Kd value of 2-phases (water-rock, water-colloid). (author)

A short textbook of colloid chemistry

CERN Document Server

Jirgensons, B

1962-01-01

A Short Textbook of Colloid Chemistry, Second Revised Edition details the factual aspect of colloid chemistry that includes the basic facts, established empirical and mathematical relationships, and practical applications. The chapters of the title are organized into two parts. In the first part, the text discusses the general concepts of colloid chemistry, such as the history and scope, basic terms, and basic methods in experiment with colloids. Part Two covers the technical aspect of colloid chemistry, such as the optical properties, electrical properties, and viscosity. The book will be of

Actinide colloid generation in groundwater. Part 2

International Nuclear Information System (INIS)

Kim, J.I.

1991-01-01

The progress made in the investigation of actinide colloid generation in groundwater is summarized and discussed with particular examples relevant to an understanding of the migration behaviour of actinides in natural aquifer systems. The first part deals with the characterization of colloids: groundwater colloids, actinide real-colloids and actinide pseudocolloids. The second part concentrates on the generation processes and migration behaviour of actinide pseudo colloids, which are discussed with some notable experimental examples. Importance is stressed more on the chemical aspects of the actinide colloid generation in groundwater. This work is a contribution to the CEC Mirage II project, in particular the complexation and colloids research area

Crack formation and prevention in colloidal drops

Science.gov (United States)

Kim, Jin Young; Cho, Kun; Ryu, Seul-A.; Kim, So Youn; Weon, Byung Mook

2015-08-01

Crack formation is a frequent result of residual stress release from colloidal films made by the evaporation of colloidal droplets containing nanoparticles. Crack prevention is a significant task in industrial applications such as painting and inkjet printing with colloidal nanoparticles. Here, we illustrate how colloidal drops evaporate and how crack generation is dependent on the particle size and initial volume fraction, through direct visualization of the individual colloids with confocal laser microscopy. To prevent crack formation, we suggest use of a versatile method to control the colloid-polymer interactions by mixing a nonadsorbing polymer with the colloidal suspension, which is known to drive gelation of the particles with short-range attraction. Gelation-driven crack prevention is a feasible and simple method to obtain crack-free, uniform coatings through drying-mediated assembly of colloidal nanoparticles.

Colloid remediation in groundwater by polyelectrolyte capture

International Nuclear Information System (INIS)

Nuttall, H.E.; Rao, S.; Jain, R.

1992-01-01

This paper describes an ongoing study to characterize groundwater colloids, to understand the geochemical factors affecting colloid transport in groundwater, and to develop an in-situ colloid remediation process. The colloids and suspended particulate matter used in this study were collected from a perched aquifer site that has radiation levels several hundred times the natural background and where previous researchers have measured and reported the presence of radiocolloids containing plutonium and americium. At this site, radionuclides have spread over several kilometers. Inorganic colloids collected from water samples are characterized with respect to concentration, mineralogy, size distribution, electrophoretic mobility (zeta potential), and radioactivity levels. Presented are the methods used to investigate the physiochemical factors affecting colloid transport and the preliminary analytical results. Included below are a description of a colloid transport model and the corresponding computational code, water analyses, characterization of the inorganic colloids, and a conceptual description of a process for in-situ colloid remediation using the phenomenon of polyelectrolyte capture

Clusters in attractive colloids

Energy Technology Data Exchange (ETDEWEB)

Coniglio, A [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' , Complesso Universitario di Monte Sant' Angelo, via Cintia 80126 Naples (Italy); Arcangelis, L de [Dipartimento di Ingegneria dell' Informazione and CNISM II Universita di Napoli, Aversa (CE) (Italy); Candia, A de [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' , Complesso Universitario di Monte Sant' Angelo, via Cintia 80126 Naples (Italy); Gado, E Del [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' , Complesso Universitario di Monte Sant' Angelo, via Cintia 80126 Naples (Italy); Fierro, A [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' , Complesso Universitario di Monte Sant' Angelo, via Cintia 80126 Naples (Italy); Sator, N [Laboratoire de Physique Theorique de la Matiere Condensee, Universite Pierre et Marie Curie-Paris6, UMR (CNRS) 7600 Case 121, 4 Place Jussieu 75252 Paris Cedex 05 (France)

2006-09-13

We discuss how the anomalous increase of the viscosity in colloidal systems with short-range attraction can be related to the formation of long-living clusters. Based on molecular dynamics and Monte Carlo numerical simulations of different models, we propose a similar picture for colloidal gelation at low and intermediate volume fractions. On this basis, we analyze the distinct role played by the formation of long-living bonds and the crowding of the particles in the slow dynamics of attractive colloidal systems.

Grimsel colloid exercise, an international intercomparison exercise on the sampling and characterization of groundwater colloids

International Nuclear Information System (INIS)

Degueldre, C.

1990-01-01

The Grimsel colloid exercise was an intercomparison exercise which consisted of an in situ sampling phase followed by a colloid characterization step. The goal of this benchmark exercise, which involved 12 laboratories, was to evaluate both sampling and characterization techniques with emphasis on the colloid specific size distribution. The sampling phase took place at the Grimsel test site between 1 and 13 February 1988 and the participating groups produced colloid samples using various methods. This work was carried out within the Community COCO Club, as a component of the Mirage project (second phase)

Filtrations of free groups as intersections

OpenAIRE

Efrat, Ido

2013-01-01

For several natural filtrations of a free group S we express the n-th term of the filtration as the intersection of all kernels of homomorphisms from S to certain groups of upper-triangular unipotent matrices. This generalizes a classical result of Grun for the lower central filtration. In particular, we do this for the n-th term in the lower p-central filtration of S.

Colloid-Associated Radionuclide Concentration Limits: ANL

International Nuclear Information System (INIS)

Mertz, C.

2000-01-01

The purpose and scope of this report is to describe the analysis of available colloidal data from waste form corrosion tests at Argonne National Laboratory (ANL) to extract characteristics of these colloids that can be used in modeling their contribution to the source term for sparingly soluble radioelements (e.g., Pu). Specifically, the focus is on developing a useful description of the following waste form colloid characteristics: (1) composition, (2) size distribution, and (3) quantification of the rate of waste form colloid generation. The composition and size distribution information are intended to support analysis of the potential transport of the sparingly soluble radionuclides associated with the waste form colloids. The rate of colloid generation is intended to support analysis of the waste form colloid-associated radionuclide concentrations. In addressing the above characteristics, available data are interpreted to address mechanisms controlling colloid formation and stability. This report was developed in accordance with the ''Technical Work Plan for Waste Form Degradation Process Model Report for SR'' (CRWMS M and O 2000). Because the end objective is to support the source term modeling we have organized the conclusions into two categories: (1) data analysis conclusions and (2) recommendations for colloid source term modeling. The second category is included to facilitate use of the conclusions from the data analysis in the abstraction of a colloid source term model. The data analyses and conclusions that are presented in this report are based on small-scale laboratory tests conducted on a limited number of waste glass compositions and spent fuel types

Colloid transport in dual-permeability media

Science.gov (United States)

Leij, Feike J.; Bradford, Scott A.

2013-07-01

It has been widely reported that colloids can travel faster and over longer distances in natural structured porous media than in uniform structureless media used in laboratory studies. The presence of preferential pathways for colloids in the subsurface environment is of concern because of the increased risks for disease caused by microorganisms and colloid-associated contaminants. This study presents a model for colloid transport in dual-permeability media that includes reversible and irreversible retention of colloids and first-order exchange between the aqueous phases of the two regions. The model may also be used to describe transport of other reactive solutes in dual-permeability media. Analytical solutions for colloid concentrations in aqueous and solid phases were obtained using Laplace transformation and matrix decomposition. The solutions proved convenient to assess the effect of model parameters on the colloid distribution. The analytical model was used to describe effluent concentrations for a bromide tracer and 3.2- or 1-μm-colloids that were observed after transport through a composite 10-cm long porous medium made up of a cylindrical lens or core of sand and a surrounding matrix with sand of a different grain size. The tracer data were described very well and realistic estimates were obtained for the pore-water velocity in the two flow domains. An accurate description was also achieved for most colloid breakthrough curves. Dispersivity and retention parameters were typically greater for the larger 3.2-μm-colloids while both reversible and irreversible retention rates tended to be higher for the finer sands than the coarser sand. The relatively small sample size and the complex flow pattern in the composite medium made it difficult to reach definitive conclusions regarding transport parameters for colloid transport.

Colloid properties in groundwaters from crystalline formations

International Nuclear Information System (INIS)

Degueldre, C.A.

1994-09-01

Colloids are present in all groundwaters. The role they may play in the migration of safety-relevant radionuclides in the geosphere therefore must be studied. Colloid sampling and characterisation campaigns have been carried out in Switzerland. On the bases of the results from studies in the Grimsel area, Northern Switzerland and the Black Forest, as well as those obtained by other groups concerned with crystalline waters, a consistent picture is emerging. The groundwater colloids in crystalline formations are predominantly comprised of phyllosilicates and silica originating from the aquifer rock. Under constant hydrogeochemical conditions, the colloid concentration is not expected to exceed 100 ng.ml -1 when the calcium concentration is greater than 10 -4 . However, under transient chemical or physical conditions, such as geothermal or tectonic activity, colloid generation may be enhanced and the colloid concentration may reach 10 μg.ml -1 or more, if both the calcium and sodium concentrations are low. In the Nagra Crystalline Reference Water the expected colloid concentration is -1 . This can be compared, for example, to a colloid concentration of about 10 ng.ml -1 found in Zurzach water. The small colloid concentration in the reference water is a consequence of an attachment factor for clay colloids (monmorillonite) close to 1. A model indicates that at pH 8, the nuclide partition coefficients between water and colloid (K p ) must be smaller than 10 7 ml.g -1 if sorption takes place by surface complexation on colloids, = AIOH active groups forming the dominant sorption sites. This pragmatic model is based on the competition between the formation of nuclide hydroxo complexes in solution and their sorption on colloids. Experimental nuclide sorption data on colloids are compared with those obtained by applying this model. For a low colloid concentration, a sorption capacity of the order of 10 -9 M and reversible surface complexation, their presence in the

Optimization of suspensions filtration with compressible cake

Directory of Open Access Journals (Sweden)

Janacova Dagmar

2016-01-01

Full Text Available In this paper there is described filtering process for separating reaction mixture after enzymatic hydrolysis to process the chromium tanning waste. Filtration of this mixture is very complicated because it is case of mixture filtration with compressible cake. Successful process strongly depends on mathematical describing of filtration, calculating optimal values of pressure difference, specific resistant of filtration cake and temperature maintenance which is connected with viscosity change. The mathematic model of filtration with compressible cake we verified in laboratory conditions on special filtration device developed on our department.

Fabricating colloidal crystals and construction of ordered nanostructures

Directory of Open Access Journals (Sweden)

Sun Zhiqiang

2006-01-01

Full Text Available AbstractColloidal crystals of polymeric or inorganic microspheres are of extensive interest due to their potential applications in such as sensing, optics, photonic bandgap and surface patterning. The article highlights a set of approaches developed in our group, which are efficient to prepare colloidal crystals with ordered voids, patterned colloidal crystals on non-planar surfaces, heterogeneous colloidal crystals of different building blocks, colloidal crystals composed of non-spherical polyhedrons, and colloidal crystals of non-close-packed colloidal microspheres in particular. The use of these colloidal crystals as templates for different microstructures range from nanoscale to micron-scale is also summarized.

Detection of serum anti-sperm antibody in infertile couples with dot-immunogold filtration assay (DIGFA)

International Nuclear Information System (INIS)

Xie Xiaoxian

2005-01-01

Objective: To develop a new method for rapid detection of serum anti-sperm antibody in infertile couples. Methods: Human sperm antigen was prepared from pooled semen specimens of fertile males. Nitro-cellulose membrane was used as solid-phase carrier of the antigen. Colloidal gold pellet combined goat anti-human IgG was taken as labelled antibody. A dot-immunogold filtration assay system was established for test of serum anti-human sperm antibody. Serum specimens from 137 infertile couples were tested and the result compared with flat from ELISA. Results: The human sperm antigen would react with the anti-sperm antibody in the tested serum over the cellulose membrane through filtration and the result could be read with naked eye within 6 minutes. In this study of 137 infertile coupled, the anti-sperm antibody was positive in 21.9% of the female serum specimens and 13.19% of the males. Compared with the result from ELISA, the consistency rate was 96.1%. The sensitivity of the assay was 90.2% and specificity was 95.4%. The p reparation was stable after 6 months refrigerator storage. Conclusion: This newly developed DIGFA is very adequate for rap id detection of anti-sperm antibody and deserves popularization. (authors)

Water Filtration Products

Science.gov (United States)

1986-01-01

American Water Corporation manufactures water filtration products which incorporate technology originally developed for manned space operations. The formula involves granular activated charcoal and other ingredients, and removes substances by catalytic reactions, mechanical filtration, and absorption. Details are proprietary. A NASA literature search contributed to development of the compound. The technology is being extended to a deodorizing compound called Biofresh which traps gas and moisture inside the unit. Further applications are anticipated.

Quantitative uptake of colloidal particles by cell cultures

Energy Technology Data Exchange (ETDEWEB)

Feliu, Neus [Department of Physics, Philipps University Marburg, Marburg (Germany); Department for Clinical Science, Intervention and Technology (CLINTEC),Karolinska Institutet, Stockholm (Sweden); Hühn, Jonas; Zyuzin, Mikhail V.; Ashraf, Sumaira; Valdeperez, Daniel; Masood, Atif [Department of Physics, Philipps University Marburg, Marburg (Germany); Said, Alaa Hassan [Department of Physics, Philipps University Marburg, Marburg (Germany); Physics Department, Faculty of Science, South Valley University (Egypt); Escudero, Alberto [Department of Physics, Philipps University Marburg, Marburg (Germany); Instituto de Ciencia de Materiales de Sevilla, CSIC — Universidad de Sevilla, Seville (Spain); Pelaz, Beatriz [Department of Physics, Philipps University Marburg, Marburg (Germany); Gonzalez, Elena [Department of Physics, Philipps University Marburg, Marburg (Germany); University of Vigo, Vigo (Spain); Duarte, Miguel A. Correa [University of Vigo, Vigo (Spain); Roy, Sathi [Department of Physics, Philipps University Marburg, Marburg (Germany); Chakraborty, Indranath [Department of Chemistry, University of Illinois at Urbana Champaign, Urbana, IL (United States); Lim, Mei L.; Sjöqvist, Sebastian [Department for Clinical Science, Intervention and Technology (CLINTEC),Karolinska Institutet, Stockholm (Sweden); Jungebluth, Philipp [Department of Thoracic Surgery, Thoraxklinik, Heidelberg University, Heidelberg (Germany); Parak, Wolfgang J., E-mail: wolfgang.parak@physik.uni-marburg.de [Department of Physics, Philipps University Marburg, Marburg (Germany); CIC biomaGUNE, San Sebastian (Spain)

2016-10-15

The use of nanotechnologies involving nano- and microparticles has increased tremendously in the recent past. There are various beneficial characteristics that make particles attractive for a wide range of technologies. However, colloidal particles on the other hand can potentially be harmful for humans and environment. Today, complete understanding of the interaction of colloidal particles with biological systems still remains a challenge. Indeed, their uptake, effects, and final cell cycle including their life span fate and degradation in biological systems are not fully understood. This is mainly due to the complexity of multiple parameters which need to be taken in consideration to perform the nanosafety research. Therefore, we will provide an overview of the common denominators and ideas to achieve universal metrics to assess their safety. The review discusses aspects including how biological media could change the physicochemical properties of colloids, how colloids are endocytosed by cells, how to distinguish between internalized versus membrane-attached colloids, possible correlation of cellular uptake of colloids with their physicochemical properties, and how the colloidal stability of colloids may vary upon cell internalization. In conclusion three main statements are given. First, in typically exposure scenarios only part of the colloids associated with cells are internalized while a significant part remain outside cells attached to their membrane. For quantitative uptake studies false positive counts in the form of only adherent but not internalized colloids have to be avoided. pH sensitive fluorophores attached to the colloids, which can discriminate between acidic endosomal/lysosomal and neutral extracellular environment around colloids offer a possible solution. Second, the metrics selected for uptake studies is of utmost importance. Counting the internalized colloids by number or by volume may lead to significantly different results. Third, colloids

Pore water colloid properties in argillaceous sedimentary rocks

Energy Technology Data Exchange (ETDEWEB)

Degueldre, Claude, E-mail: c.degueldre@lancaster.ac.uk [Engineering Department, University of Lancaster, LA1 4YW Lancaster (United Kingdom); ChiAM & Institute of Environment, University of Geneva, 1211 Genève 4, Swizerland (Switzerland); Earlier, NES, Paul Scherrer Institute, 5232 Villigen (Switzerland); Cloet, Veerle [NAGRA, Hardstrasse 73, 5430 Wettingen (Switzerland)

2016-11-01

The focus of this work is to evaluate the colloid nature, concentration and size distribution in the pore water of Opalinus Clay and other sedimentary host rocks identified for a potential radioactive waste repository in Switzerland. Because colloids could not be measured in representative undisturbed porewater of these host rocks, predictive modelling based on data from field and laboratory studies is applied. This approach allowed estimating the nature, concentration and size distributions of the colloids in the pore water of these host rocks. As a result of field campaigns, groundwater colloid concentrations are investigated on the basis of their size distribution quantified experimentally using single particle counting techniques. The colloid properties are estimated considering data gained from analogue hydrogeochemical systems ranging from mylonite features in crystalline fissures to sedimentary formations. The colloid concentrations were analysed as a function of the alkaline and alkaline earth element concentrations. Laboratory batch results on clay colloid generation from compacted pellets in quasi-stagnant water are also reported. Experiments with colloids in batch containers indicate that the size distribution of a colloidal suspension evolves toward a common particle size distribution independently of initial conditions. The final suspension size distribution was found to be a function of the attachment factor of the colloids. Finally, calculations were performed using a novel colloid distribution model based on colloid generation, aggregation and sedimentation rates to predict under in-situ conditions what makes colloid concentrations and size distributions batch- or fracture-size dependent. The data presented so far are compared with the field and laboratory data. The colloid occurrence, stability and mobility have been evaluated for the water of the considered potential host rocks. In the pore water of the considered sedimentary host rocks, the clay

Dissolved and colloidal trace elements in the Mississippi River delta outflow after Hurricanes Katrina and Rita

Science.gov (United States)

Shim, Moo-Joon; Swarzenski, Peter W.; Shiller, Alan M.

2012-07-01

The Mississippi River delta outflow region is periodically disturbed by tropical weather systems including major hurricanes, which can terminate seasonal bottom water hypoxia and cause the resuspension of shelf bottom sediments which could result in the injection of trace elements into the water column. In the summer of 2005, Hurricanes Katrina and Rita passed over the Louisiana Shelf within a month of each other. Three weeks after Rita, we collected water samples in the Mississippi River delta outflow, examining the distributions of trace elements to study the effect of Hurricanes Katrina and Rita. We observed limited stratification on the shelf and bottom waters that were no longer hypoxic. This resulted, for instance, in bottom water dissolved Mn being lower than is typically observed during hypoxia, but with concentrations still compatible with Mn-O2 trends previously reported. Interestingly, for no element were we able to identify an obvious effect of sediment resuspension on its distribution. In general, elemental distributions were compatible with previous observations in the Mississippi outflow system. Co and Re, which have not been reported for this system previously, showed behavior consistent with other systems: input for Co likely from desorption and conservative mixing for Re. For Cs, an element for which there is little information regarding its estuarine behavior, conservative mixing was also observed. Our filtration method, which allowed us to distinguish the dissolved (<0.02 μm) from colloidal (0.02-0.45 μm) phase, revealed significant colloidal fractions for Fe and Zn, only. For Fe, the colloidal phase was the dominant fraction and was rapidly removed at low salinity. Dissolved Fe, in contrast, persisted out to mid-salinities, being removed in a similar fashion to nitrate. This ability to distinguish the smaller Fe (likely dominantly organically complexed) from larger colloidal suspensates may be useful in better interpreting the bioavailablity

Marine phages as excellent tracers for reactive colloidal transport in porous media

Science.gov (United States)

Ghanem, Nawras; Chatzinotas, Antonis; Harms, Hauke; Wick, Lukas Y.

2016-04-01

Question: Here we evaluate marine phages as specific markers of hydrological flow and reactive transport of colloidal particles in the Earth's critical zone (CZ). Marine phages and their bacterial hosts are naturally absent in the CZ, and can be detected with extremely high sensitivity. In the framework of the DFG Collaborative Research Center AquaDiva, we asked the following questions: (1) Are marine phages useful specific markers of hydrological flow and reactive transport in porous media? and (2) Which phage properties are relevant drivers for the transport of marine phages in porous media? Methods: Seven marine phages from different families (as well two commonly used terrestrial phages) were selected based on their morphology, size and physico-chemical surface properties (surface charge and hydrophobicity). Phage properties were assessed by electron microscopy, dynamic light scattering and water contact angle analysis (CA). Sand-filled laboratory percolation columns were used to study transport. The breakthrough curves of the phages were analyzed using the clean bed filtration theory and the XDLVO theory of colloid stability, respectively. Phages were quantified by a modified high- throughput plaque assay and a culture-independent particle counting method approach. Results: Our data show that most marine tested phages exhibited highly variable transport rates and deposition efficiency, yet generally high colloidal stability and viability. We find that size, morphology and hydrophobicity are key factors shaping the transport efficiency of phages. Differing deposition efficiencies of the phages were also supported by calculated XDLVO interaction energy profile. Conclusion: Marine phages have a high potential for the use as sensitive tracers in terrestrial habitats with their surface properties playing a crucial role for their transport. Marine phages however, exhibit differences in their deposition efficiency depending on their morphology, hydrophobicity and

Health Benefits of Particle Filtration

Energy Technology Data Exchange (ETDEWEB)

Fisk, William J.

2013-10-01

The evidence of health benefits of particle filtration in homes and commercial buildings is reviewed. Prior reviews of papers published before 2000 are summarized. The results of 16 more recent intervention studies are compiled and analyzed. Also, reviewed are four studies that modeled health benefits of using filtration to reduce indoor exposures to particles from outdoors. Prior reviews generally concluded that particle filtration is, at best, a source of small improvements in allergy and asthma health effects; however, many early studies had weak designs. A majority of recent intervention studies employed strong designs and more of these studies report statistically significant improvements in health symptoms or objective health outcomes, particularly for subjects with allergies or asthma. The percent age improvement in health outcomes is typically modest, for example, 7percent to 25percent. Delivery of filtered air to the breathing zone of sleeping allergic or asthmatic persons may be more consistently effective in improving health than room air filtration. Notable are two studies that report statistically significant improvements, with filtration, in markers that predict future adverse coronary events. From modeling, the largest potential benefits of indoor particle filtration may be reductions in morbidity and mortality from reducing indoor exposures to particles from outdoor air.

Health Benefits of Particle Filtration

Energy Technology Data Exchange (ETDEWEB)

Fisk, William J.

2013-10-01

The evidence of health benefits of particle filtration in homes and commercial buildings is reviewed. Prior reviews of papers published before 2000 are summarized. The results of 16 more recent intervention studies are compiled and analyzed. Also reviewed are four studies that modeled health benefits of using filtration to reduce indoor exposures to particles from outdoors. Prior reviews generally concluded that particle filtration is, at best, a source of small improvements in allergy and asthma health effects; however, many early studies had weak designs. A majority of recent intervention studies employed strong designs and more of these studies report statistically significant improvements in health symptoms or objective health outcomes, particularly for subjects with allergies or asthma. The percentage improvement in health outcomes is typically modest, e.g., 7percent to 25percent. Delivery of filtered air to the breathing zone of sleeping allergic or asthmatic persons may be more consistently effective in improving health than room air filtration. Notable are two studies that report statistically significant improvements, with filtration, in markers that predict future adverse coronary events. From modeling, the largest potential benefits of indoor particle filtration may be reductions in morbidity and mortality from reducing indoor exposures to particles from outdoor air.

Filtration Behaviour and Fouling Mechanisms of Polysaccharides

Directory of Open Access Journals (Sweden)

Sondus Jamal

2014-07-01

Full Text Available This study investigated filtration behaviors of polysaccharides solutions, both alone and in mixture with proteins, in the short-time constant flux filtration with the focus on factors affecting the transmembrane pressure (TMP increase rate, the irreversible filtration resistance, and the membrane rejection behavior. The results showed that the TMP increase rates in the short-time constant flux filtration of alginate solutions were significantly affected by the calcium addition, alginate concentration, and flux. Although the addition of calcium resulted in a decrease in the TMP increase rate, it was found that the irreversible fouling developed during the filtration increased with the calcium addition, implying that the double-sided effect of calcium on membrane filtration and that the TMP increase rate observed in the filtration does not always reflect the irreversible membrane fouling development. It was also found that for the filtration of solutions containing mixed alginate and BSA, alginate exerted a dominant effect on the TMP increase rate and the membrane exhibited a reduced rejection to both alginate and BSA molecules compared to that in the filtration of the pure alginate or BSA.

Colloid mobilization and transport during capillary fringe fluctuations.

Science.gov (United States)

Aramrak, Surachet; Flury, Markus; Harsh, James B; Zollars, Richard L

2014-07-01

Capillary fringe fluctuations due to changing water tables lead to displacement of air-water interfaces in soils and sediments. These moving air-water interfaces can mobilize colloids. We visualized colloids interacting with moving air-water interfaces during capillary fringe fluctuations by confocal microscopy. We simulated capillary fringe fluctuations in a glass-bead-filled column. We studied four specific conditions: (1) colloids suspended in the aqueous phase, (2) colloids attached to the glass beads in an initially wet porous medium, (3) colloids attached to the glass beads in an initially dry porous medium, and (4) colloids suspended in the aqueous phase with the presence of a static air bubble. Confocal images confirmed that the capillary fringe fluctuations affect colloid transport behavior. Hydrophilic negatively charged colloids initially suspended in the aqueous phase were deposited at the solid-water interface after a drainage passage, but then were removed by subsequent capillary fringe fluctuations. The colloids that were initially attached to the wet or dry glass bead surface were detached by moving air-water interfaces in the capillary fringe. Hydrophilic negatively charged colloids did not attach to static air-bubbles, but hydrophobic negatively charged and hydrophilic positively charged colloids did. Our results demonstrate that capillary fringe fluctuations are an effective means for colloid mobilization.

Colloidal phytosterols: synthesis, characterization and bioaccessibility

NARCIS (Netherlands)

Rossi, L.; Seijen ten Hoorn, J.W.M.; Melnikov, S.M.; Velikov, K.P.

2010-01-01

We demonstrate the synthesis of phytosterol colloidal particles using a simple food grade method based on antisolvent precipitation in the presence of a non-ionic surfactant. The resulting colloidal particles have a rod-like shape with some degree of crystallinity. The colloidal dispersions display

Health Benefits of Particle Filtration

OpenAIRE

Fisk, William J.

2013-01-01

The evidence of health benefits of particle filtration in homes and commercial buildings is reviewed. Prior reviews of papers published before 2000 are summarized. The results of 16 more recent intervention studies are compiled and analyzed. Also reviewed are four studies that modeled health benefits of using filtration to reduce indoor exposures to particles from outdoors. Prior reviews generally concluded that particle filtration is, at best, a source of small improvements in allergy and as...

Assessing colloid-bound metal export in response to short term changes in runoff from a forested catchment

Science.gov (United States)

Neubauer, E.; Kammer, F. v. d.; Knorr, K.-H.; Pfeiffer, S.; Reichert, M.; Hofmann, T.

2012-04-01

Soils can act as a source of metals and natural organic matter (NOM) in runoff from catchments. Amounts and intensity of rainfall may influence NOM export from catchments. The presence of NOM and other colloids in water may not only enhance metal export, but also significantly change metal speciation. In this study, we investigated the response of metal-colloid associations to short-term discharge variations in the runoff from a small forested catchment (Lehstenbach, Bavaria, Germany). Here, the discharge from the catchment outlet responds within hours to rain events. Near-surface flow in organic-rich layers and peat soils has been identified to increase dissolved organic carbon (DOC) concentrations during stormwater runoff. Flow Field-Flow Fractionation coupled to ICP-MS (FlowFFF-ICPMS) is a high-resolution size separation technique which was used for the detection and quantification of colloids and associated metals. Colloid-associated metals, dissolved metals and metals associated with low-molecular weight organic ligands were also separated by filtration (0.2 µm) and ultrafiltration (1000 g/mol MWCO). During baseflow DOC concentration was pH ranged between 4.6 and 5.0. The DOC concentration exported at a given discharge was subject to strong seasonal variation and depended on the water level before the discharge event. DOC concentrations were up to 8 fold higher during stormwater runoff compared to baseflow. The export of aluminum, arsenic, rare earth elements (REE) and uranium from the catchment increased during stormwater runoff showing a strong correlation with NOM concentrations. This result was supported by FlowFFF-ICPMS data revealing that NOM was the only colloid type available for metal complexation during all hydrological conditions. A clear temporal pattern in the association with the NOM was observed for most of the metals under study: During baseflow, 70-100% (Fe), 90% (Al), 60-100% (REE) and 80-85% (U) were associated with the NOM. During

Relation Between Filtration and Soil Consolidation Theories

Directory of Open Access Journals (Sweden)

Strzelecki Tomasz

2015-03-01

Full Text Available This paper presents a different, than commonly used, form of equations describing the filtration of a viscous compressible fluid through a porous medium in isothermal conditions. This mathematical model is compared with the liquid flow equations used in the theory of consolidation. It is shown that the current commonly used filtration model representation significantly differs from the filtration process representation in Biot’s and Terzaghi’s soil consolidation models, which has a bearing on the use of the methods of determining the filtration coefficient on the basis of oedometer test results. The present analysis of the filtration theory equations should help interpret effective parameters of the non-steady filtration model. Moreover, equations for the flow of a gas through a porous medium and an interpretation of the filtration model effective parameters in this case are presented.

Particle filtration in consolidated granular systems

International Nuclear Information System (INIS)

Schwartz, L.M.; Wilkinson, D.J.; Bolsterli, M.; Hammond, P.

1993-01-01

Grain-packing algorithms are used to model the mechanical trapping of dilute suspensions of particles by consolidated granular media. We study the distribution of filtrate particles, the formation of a damage zone (internal filter cake), and the transport properties of the host--filter-cake composite. At the early stages of filtration, our simulations suggest simple relationships between the structure of the internal filter cake and the characteristics of the underlying host matrix. These relationships are then used to describe the dynamics of the filtration process. Depending on the grain size and porosity of the host matrix, calculated filtration rates may either be greater than (spurt loss) or less than (due to internal clogging) those predicted by standard surface-filtration models

Simulation of bentonite colloid migration through granite

International Nuclear Information System (INIS)

Rosicka, Dana; Hokr, Milan

2012-01-01

Document available in extended abstract form only. Full text of publication follows: Colloidal bentonite particles generate at the interface of buffer and host rock in spent nuclear fuel repository due to an erosion process and migrate through granite by the water flow. Stability of these colloids and their migration possibilities have been studied on account of radionuclide transport possibility as colloid could carry adsorbed radionuclides in groundwater through granite. That is why a simulation of bentonite colloid migration in the surrounding of a repository might be requested. According to chemical condition as ionic strength and pH, the colloidal particles coagulate into clusters and that influence the migration of particles. The coagulation kinetics of natural bentonite colloids were experimentally studied in many articles, for example by light scattering techniques. We created a model of coagulation of bentonite colloids and simulation of a chosen experiment with use of the multicomponent reactive transport equation. The coagulation model describes clustering of particles due to attractive van der Waals forces as result of collision of particles due to heat fluctuation and different velocity of particles during sedimentation and velocity gradient of water flow. Next, the model includes influence of repulsive electrostatic forces among colloidal particles leading to stability of particles provided high surface charge of colloids. In the model, each group of clusters is transported as one solution component and the kinetics of coagulation are implemented as reactions between the components: a shift of particles among groups of particles with similar migration properties, according to size of the clusters of colloids. The simulation of migration of bentonite colloid through granite using the coagulation model was calibrated according to experiment results. On the basis of the simulation, one can estimate the basic processes that occur during bentonite colloid

Wave oscillations in colloid oxyhydrates wave oscillations in colloid oxyhydrates

CERN Document Server

Sucharev, Yuri I

2010-01-01

The importance of coherent chemistry, that is, the chemistry of periodic oscillatory processes, is increasing at a rapid rate in specific chemical disciplines. While being perfectly understood and highly developed in the fields of physical chemistry, chemical physics and biological chemistry, the periodic developmental paradigm of processes and phenomena still remains poorly developed and misunderstood in classical inorganic chemistry and related branches, such as colloid chemistry. The probability is that we miss subtle colloid chemical phenomena that could be of utmost importance if taken into consideration when catalysis or adsorption is involved. The author here reveals all of the astonishing vistas that periodic wave paradigms open up to researchers in certain colloid chemical systems, and will doubtless stimulate researchers to look at them in a new light.Review from Book News Inc.: Coherent chemistry, the chemistry of periodical oscillatory processes, is well established in physical chemistry, chemical...

Self-Assembly of Faceted Colloidal Particles

NARCIS (Netherlands)

Gantapara, A.P.

2015-01-01

A colloidal dispersion consists of insoluble microscopic particles that are suspended in a solvent. Typically, a colloid is a particle for which at least one of its dimension is within the size range of a nanometer to a micron. Due to collisions with much smaller solvent molecules, colloids perform

Health benefits of particle filtration.

Science.gov (United States)

Fisk, W J

2013-10-01

The evidence of health benefits of particle filtration in homes and commercial buildings is reviewed. Prior reviews of papers published before 2000 are summarized. The results of 16 more recent intervention studies are compiled and analyzed. Also, reviewed are four studies that modeled health benefits of using filtration to reduce indoor exposures to particles from outdoors. Prior reviews generally concluded that particle filtration is, at best, a source of small improvements in allergy and asthma health effects; however, many early studies had weak designs. A majority of recent intervention studies employed strong designs and more of these studies report statistically significant improvements in health symptoms or objective health outcomes, particularly for subjects with allergies or asthma. The percentage improvement in health outcomes is typically modest, for example, 7% to 25%. Delivery of filtered air to the breathing zone of sleeping allergic or asthmatic persons may be more consistently effective in improving health than room air filtration. Notable are two studies that report statistically significant improvements, with filtration, in markers that predict future adverse coronary events. From modeling, the largest potential benefits of indoor particle filtration may be reductions in morbidity and mortality from reducing indoor exposures to particles from outdoor air. Published 2013. This article is a US Government work and is in the public domain in the USA.

Surface patterning of polymeric separation membranes and its influence on the filtration performance

Science.gov (United States)

Maruf, Sajjad

Polymeric membrane based separation technologies are crucial for addressing the global issues such as water purification. However, continuous operations of these processes are often hindered by fouling which increases mass transport resistance of the membrane to permeation and thus the energy cost, and eventually replacement of the membrane in the system. In comparison to other anti-fouling strategies, the use of controlled surface topography to mitigate fouling has not been realized mainly due to the lack of methods to create targeted topography on the porous membrane surface. This thesis aims to develop a new methodology to create surface-patterned polymeric separation membrane to improve their anti-fouling characteristics during filtration. First, successful fabrication of sub-micron surface patterns directly on a commercial ultrafiltration (UF) membrane surface using nanoimprint lithographic (NIL) technique was demonstrated. Comprehensive filtration studies revealed that the presence of these sub-micron surface patterns mitigates not only the onset of colloidal particle deposition, but also lowers the rate of growth of cake layer after initial deposition, in comparison with un-patterned membranes. The anti-fouling effects were also observed for model protein solutions. Staged filtration experiments, with backwash cleaning, revealed that the permeate flux of the patterned membrane after protein fouling was considerably higher than that of the pristine or un-patterned membrane. In addition to the surface-patterning of UF membranes, successful fabrication of a surface-patterned thin film composite (TFC) membrane was shown for the first time. A two-step fabrication process was carried out by (1) nanoimprinting a polyethersulfone (PES) support using NIL, and (2) forming a thin dense film atop the PES support via interfacial polymerization (IP). Fouling experiments suggest that the surface patterns alter the hydrodynamics at the membrane-feed interface, which is

Preparation of radioactive colloidal gold 198Au

International Nuclear Information System (INIS)

Cammarosano, S.A.

1979-01-01

The preparation with simple equipment of radioactive colloidal gold of particle size about approximately 300 A from seed colloid stabilized by gelatine is described. Some physico-chemical parameters which can affect the process of formation of these colloidal particles are analysed; particle size has been meassured with an electron microscope. The colloid stability has been studied as a function of dilution, age and pH. Nucleation and growth of radioactive colloidal gold have been studied using spectrophotometry. Absorption spectra of the two ones are presented and compared. Quality control of the production process is verified through measurement of parameters, such as radioactive and radiochemical purity and biological distribution in laboratorial animals. This distribution was evalusted for rats injected endovenously with the gold colloidal solution.(Author) [pt

Saturated Zone Colloid-Facilitated Transport

International Nuclear Information System (INIS)

Wolfsberg, A.; Reimus, P.

2001-01-01

The purpose of the Saturated Zone Colloid-Facilitated Transport Analysis and Modeling Report (AMR), as outlined in its Work Direction and Planning Document (CRWMS MandO 1999a), is to provide retardation factors for colloids with irreversibly-attached radionuclides, such as plutonium, in the saturated zone (SZ) between their point of entrance from the unsaturated zone (UZ) and downgradient compliance points. Although it is not exclusive to any particular radionuclide release scenario, this AMR especially addresses those scenarios pertaining to evidence from waste degradation experiments, which indicate that plutonium and perhaps other radionuclides may be irreversibly attached to colloids. This report establishes the requirements and elements of the design of a methodology for calculating colloid transport in the saturated zone at Yucca Mountain. In previous Total Systems Performance Assessment (TSPA) analyses, radionuclide-bearing colloids were assumed to be unretarded in their migration. Field experiments in fractured tuff at Yucca Mountain and in porous media at other sites indicate that colloids may, in fact, experience retardation relative to the mean pore-water velocity, suggesting that contaminants associated with colloids should also experience some retardation. Therefore, this analysis incorporates field data where available and a theoretical framework when site-specific data are not available for estimating plausible ranges of retardation factors in both saturated fractured tuff and saturated alluvium. The distribution of retardation factors for tuff and alluvium are developed in a form consistent with the Performance Assessment (PA) analysis framework for simulating radionuclide transport in the saturated zone. To improve on the work performed so far for the saturated-zone flow and transport modeling, concerted effort has been made in quantifying colloid retardation factors in both fractured tuff and alluvium. The fractured tuff analysis used recent data

Direct filtration of Biesbosch water and Algae and water treatment in the Netherlands : 3rd Direct Filtration Seminar

NARCIS (Netherlands)

Petrusevski, B.; Vlaski, A.; Van Breemen, A.N.; Alaerts, G.J.

1993-01-01

This presentation summarises basic information on direct filtration, and demonstrates the main research findings, related to the performance of simple in-line direct filtration. The results reported are part of a comprehensive ongoing research programm "Direct filtration of Biesbosch water"

Active structuring of colloidal armour on liquid drops

Science.gov (United States)

Dommersnes, Paul; Rozynek, Zbigniew; Mikkelsen, Alexander; Castberg, Rene; Kjerstad, Knut; Hersvik, Kjetil; Otto Fossum, Jon

2013-06-01

Adsorption and assembly of colloidal particles at the surface of liquid droplets are at the base of particle-stabilized emulsions and templating. Here we report that electrohydrodynamic and electro-rheological effects in leaky-dielectric liquid drops can be used to structure and dynamically control colloidal particle assemblies at drop surfaces, including electric-field-assisted convective assembly of jammed colloidal ‘ribbons’, electro-rheological colloidal chains confined to a two-dimensional surface and spinning colloidal domains on that surface. In addition, we demonstrate the size control of ‘pupil’-like openings in colloidal shells. We anticipate that electric field manipulation of colloids in leaky dielectrics can lead to new routes of colloidosome assembly and design for ‘smart armoured’ droplets.

Thermophoretic torque in colloidal particles with mass asymmetry

Science.gov (United States)

Olarte-Plata, Juan; Rubi, J. Miguel; Bresme, Fernando

2018-05-01

We investigate the response of anisotropic colloids suspended in a fluid under a thermal field. Using nonequilibrium molecular dynamics computer simulations and nonequilibrium thermodynamics theory, we show that an anisotropic mass distribution inside the colloid rectifies the rotational Brownian motion and the colloids experience transient torques that orient the colloid along the direction of the thermal field. This physical effect gives rise to distinctive changes in the dependence of the Soret coefficient with colloid mass, which features a maximum, unlike the monotonic increase of the thermophoretic force with mass observed in homogeneous colloids.

Filtration approach to mitigate indoor Thoron progeny concentration

International Nuclear Information System (INIS)

Wang, J.; Meisenberg, O.; Karg, E.; Tschiersch, J.; Chen, Y.

2010-01-01

This study investigates filtration of air as potential mitigation method of thoron progeny exposure. The experiments were conducted in a model room (volume 7.1 m 3 ) which was equipped with a pump and an HEPA (high efficiency particulate air) filter. Filtration at a rate of 0.2, 0.4, 0.5 and 0.8 h -1 during 88 h proved an effective practice in reducing the total indoor thoron decay product concentration. The results indicate that 0.4-0.8 h -1 filtration rate had almost the same filtration efficiency in decreasing the total thoron EEC (equilibrium equivalent concentration) by 97% while 80% of total thoron EEC were reduced by 0.2 h -1 filtration rate; meanwhile, the unattached thoron EEC rose significantly by 190, 270, 290%, respectively under 0.4-0.8 h -1 filtration rate, whereas 0.2 h -1 filtration rate increased unattached thoron EEC by 40%. The aerosol number size distribution variation reveals that filtration operation removes smaller particles faster or earlier than the larger ones. The annual effective dose calculated was reduced by 91-92% at a filtration rate of 0.4-0.8 h -1 while 75% reduced at 0.2 h -1 filtration rate after 88 h filtration process. (authors)

Portable field water sample filtration unit

International Nuclear Information System (INIS)

Hebert, A.J.; Young, G.G.

1977-01-01

A lightweight back-packable field-tested filtration unit is described. The unit is easily cleaned without cross contamination at the part-per-billion level and allows rapid filtration of boiling hot and sometimes muddy water. The filtration results in samples that are free of bacteria and particulates and which resist algae growth even after storage for months. 3 figures

Characterization of colloids in groundwater

International Nuclear Information System (INIS)

Kim, J.I.; Buckau, G.; Klenze, R.

1987-07-01

Natural colloids in the Gorleben aquifer systems have been investigated as for their chemical composition, quantification and size distribution. Humic substances appear to be the major organic materials in these groundwaters, generating humic colloids which are analysed to be humic acid (and fulvic acid) loaded with a large number of trace heavy metal ions. These metal ions include natural homologues of actinides and some fission products in trivalent, tetravalent and hexavalent state. Concentrations of trivalent and tetravalent heavy metal ions are linearly correlated with the dissolved organic carbon (DDC) concentration in different groundwaters. The DOC is found to be present as humic colloids. The Am 3+ ions introduced in such a groundwater readily undergo the generation of its pseudocolloids through sorption or ion exchange reactions with humic colloids. The chemical behaviour of Am(III), being similar to the trivalent metal ions, e.g. Fe 3+ , REE etc. found in natural colloids, has been investigated by laser induced photoacoustic spectroscopy (LPAS). Groundwaters from Ispra, Markham Clinton and Felslabor Grimsel. Bidistilled water and one of Gorleben groundwaters, Gohy 1011, are taken for the purpose of comparison. This groundwater contains the least amount of natural colloids of all Gorleben groundwaters hitherto investigated. An indirect quantification is made by comparison of the LPAS results with experiment from Latex solution. (orig./IRB)

Pore water colloid properties in argillaceous sedimentary rocks.

Science.gov (United States)

Degueldre, Claude; Cloet, Veerle

2016-11-01

The focus of this work is to evaluate the colloid nature, concentration and size distribution in the pore water of Opalinus Clay and other sedimentary host rocks identified for a potential radioactive waste repository in Switzerland. Because colloids could not be measured in representative undisturbed porewater of these host rocks, predictive modelling based on data from field and laboratory studies is applied. This approach allowed estimating the nature, concentration and size distributions of the colloids in the pore water of these host rocks. As a result of field campaigns, groundwater colloid concentrations are investigated on the basis of their size distribution quantified experimentally using single particle counting techniques. The colloid properties are estimated considering data gained from analogue hydrogeochemical systems ranging from mylonite features in crystalline fissures to sedimentary formations. The colloid concentrations were analysed as a function of the alkaline and alkaline earth element concentrations. Laboratory batch results on clay colloid generation from compacted pellets in quasi-stagnant water are also reported. Experiments with colloids in batch containers indicate that the size distribution of a colloidal suspension evolves toward a common particle size distribution independently of initial conditions. The final suspension size distribution was found to be a function of the attachment factor of the colloids. Finally, calculations were performed using a novel colloid distribution model based on colloid generation, aggregation and sedimentation rates to predict under in-situ conditions what makes colloid concentrations and size distributions batch- or fracture-size dependent. The data presented so far are compared with the field and laboratory data. The colloid occurrence, stability and mobility have been evaluated for the water of the considered potential host rocks. In the pore water of the considered sedimentary host rocks, the clay

Colloid-facilitated radionuclide transport: a regulatory perspective

Science.gov (United States)

Dam, W. L.; Pickett, D. A.; Codell, R. B.; Nicholson, T. J.

2001-12-01

What hydrogeologic-geochemical-microbial conditions and processes affect migration of radionuclides sorbed onto microparticles or native colloid-sized radionuclide particles? The U.S. Nuclear Regulatory Commission (NRC) is responsible for protecting public health, safety, and the environment at numerous nuclear facilities including a potential high-level nuclear waste disposal site. To fulfill these obligations, NRC needs to understand the mechanisms controlling radionuclide release and transport and their importance to performance. The current focus of NRC staff reviews and technical interactions dealing with colloid-facilitated transport relates to the potential nuclear-waste repository at Yucca Mountain, Nevada. NRC staff performed bounding calculations to quantify radionuclide releases available for ground-water transport to potential receptors from a Yucca Mountain repository. Preliminary analyses suggest insignificant doses of plutonium and americium colloids could be derived from spent nuclear fuel. Using surface complexation models, NRC staff found that colloids can potentially lower actinide retardation factors by up to several orders of magnitude. Performance assessment calculations, in which colloidal transport of plutonium and americium was simulated by assuming no sorption or matrix diffusion, indicated no effect of colloids on human dose within the 10,000 year compliance period due largely to long waste-package lifetimes. NRC staff have identified information gaps and developed technical agreements with the U.S. Department of Energy (DOE) to ensure sufficient information will be presented in any potential future Yucca Mountain license application. DOE has agreed to identify which radionuclides could be transported via colloids, incorporate uncertainties in colloid formation, release and transport parameters, and conceptual models, and address the applicability of field data using synthetic microspheres as colloid analogs. NRC is currently

Migration of uranium in the presence of clay colloids in a sandy aquifer

International Nuclear Information System (INIS)

Le Cointe, P.; Grambow, B.; Piscitelli, A.; Montavon, G.; Van der Lee, J.; Giffaut, E.; Schneider, V.

2010-01-01

polystyrene standards on different sediment samples (core sample, reconsolidated auger sample and clay-free reconsolidated auger sample). The filtration threshold has been defined between 70 and 100 nm, except for the clay-free sample, for which it is above 500 nm. Laboratory column experiments were performed with 70 nm clay colloids, U(VI) and clay colloids + U(VI). To make the system simpler, the clay fraction was removed from the sediment and the experiments were carried out at a low ionic strength, to avoid clay colloids flocculation. The breakthrough behaviour of clay colloids and U(VI) was monitored and compared to conservative tracers (HTO and 36 Cl). The data were modelled with the HYTEC reactive transport code developed at the Paris School of Mines, considering both hydrodynamic properties of the porous system (porosity of 30%, Darcy velocity fixed to 3.10 -6 m/s, close to the one measured in situ) and the parameters quantifying U(VI)-Quartz and U(VI)-Clay interactions. An in situ tracing experiment was also conducted with both conservative (D 2 O, H 2 18 O) and colloidal (polystyrene nanoparticles) tracers. The objective is to ensure the reactive transport model, based on laboratory experiments, can be extended to a parcel of the site, and finally to the whole site, using experimental and modelling data collected by Andra. (authors)

Migration of uranium in the presence of clay colloids in a sandy aquifer

Energy Technology Data Exchange (ETDEWEB)

Le Cointe, P. [Laboratoire SUBATECH, UMR 6457 Ecole des Mines/CNRS/Universite, 4 rue A. Kastler, BP 20722, 44307 Nantes Cedex 03 (France); Centre de Geosciences, Ecole des Mines de Paris, 35 rue St-Honore, 77305 Fontainebleau Cedex (France); ANDRA 1/7 rue Jean Monnet - 92298 Chatenay Malabry Cedex (France); Grambow, B.; Piscitelli, A.; Montavon, G. [Laboratoire SUBATECH, UMR 6457 Ecole des Mines/CNRS/Universite, 4 rue A. Kastler, BP 20722, 44307 Nantes Cedex 03 (France); Van der Lee, J. [EDF R ete D, Site des Renardieres, Route de Sens - Ecuelles, 77250 Moret sur Loing (France); Giffaut, E.; Schneider, V. [ANDRA 1/7 rue Jean Monnet - 92298 Chatenay Malabry Cedex (France)

2010-07-01

polystyrene standards on different sediment samples (core sample, reconsolidated auger sample and clay-free reconsolidated auger sample). The filtration threshold has been defined between 70 and 100 nm, except for the clay-free sample, for which it is above 500 nm. Laboratory column experiments were performed with 70 nm clay colloids, U(VI) and clay colloids + U(VI). To make the system simpler, the clay fraction was removed from the sediment and the experiments were carried out at a low ionic strength, to avoid clay colloids flocculation. The breakthrough behaviour of clay colloids and U(VI) was monitored and compared to conservative tracers (HTO and {sup 36}Cl). The data were modelled with the HYTEC reactive transport code developed at the Paris School of Mines, considering both hydrodynamic properties of the porous system (porosity of 30%, Darcy velocity fixed to 3.10{sup -6} m/s, close to the one measured in situ) and the parameters quantifying U(VI)-Quartz and U(VI)-Clay interactions. An in situ tracing experiment was also conducted with both conservative (D{sub 2}O, H{sub 2}{sup 18}O) and colloidal (polystyrene nanoparticles) tracers. The objective is to ensure the reactive transport model, based on laboratory experiments, can be extended to a parcel of the site, and finally to the whole site, using experimental and modelling data collected by Andra. (authors)

EOS9nT: A TOUGH2 module for the simulation of flow and solute/colloid transport

International Nuclear Information System (INIS)

Moridis, G.J.; Wu, Y.S.; Pruess, K.

1998-04-01

EOS9nT is a new TOUGH2 module for the simulation of flow and transport of an arbitrary number n of tracers (solutes and/or colloids) in the subsurface. The module first solves the flow-related equations, which are comprised of (a) the Richards equation and, depending on conditions, may also include (b) the flow equation of a dense brine or aqueous suspension and/or (c) the heat equation. A second set of transport equations, corresponding to the n tracers, are then solved sequentially. The low concentrations of the n tracers are considered to have no effect on the liquid phase, thus making possible the decoupling of their equations. The first set of equations in EOS9nT provides the flow regime and account for fluid density variations due to thermal and/or solute concentration effects. The n tracer transport equations account for sorption, radioactive decay, advection, hydrodynamic dispersion, molecular diffusion, as well as filtration (for colloids only). EOS9nT can handle gridblocks or irregular geometry in three-dimensional domains. Preliminary results from four 1-D verification problems show an excellent agreement between the numerical predictions and the known analytical solutions

Latest aspects of mechanical filtration

Directory of Open Access Journals (Sweden)

Stanislav Koláček

2013-01-01

Full Text Available The aim of this study was to describe and unify all knowledge about mechanic filtration. The first part deals with the parameters and properties of filtration. Here some important basic concepts are explained such as pressure gradient, filter life, etc. There’s also a description of convenient filtration technology for coarse and fine materials, such as sand, smoke or soot. The second part primarily focuses on the real use and application of filters for liquid and gaseous media. The differences in construction between different types of filters for filtration of fuels, oils, hydraulic fluids, air and cabin filters are described. The last section is focused mainly on new materials for the production of filters. These materials are ceramic or nanomaterials, which can actually be enriched for example with antibacterial silver or some fungicides.

Towards conducting inks: Polypyrrole–silver colloids

International Nuclear Information System (INIS)

Omastová, Mária; Bober, Patrycja; Morávková, Zuzana; Peřinka, Nikola; Kaplanová, Marie; Syrový, Tomáš; Hromádková, Jiřina; Trchová, Miroslava; Stejskal, Jaroslav

2014-01-01

Graphical abstract: - Highlights: • Composite colloidal particles combining conducting polymer and metal have been prepared. • Conducting colloids are suitable for printing applications. • Polypyrrole/silver colloids are prepared in a single reaction step. • The conductivity control is discussed and still needs improvement. - Abstract: The oxidation of pyrrole with silver nitrate in the presence of suitable water-soluble polymers yields composite polypyrrole–silver colloids. The polypyrrole–silver nanoparticles stabilized with poly(N-vinylpyrrolidone) have a typical size around 350 nm and polydispersity index 0.20, i.e. a moderate polydispersity in size. Similar results have been obtained with poly(vinyl alcohol) as stabilizer. The effect of stabilizer concentration on the particle size is marginal. In the present study, several types of stabilizers have been tested in addition to currently used poly(N-vinylpyrrolidone). Transmission electron microscopy and optical microscopy revealed the gemini morphology of polypyrrole and silver colloidal nanoparticles and confirmed their size and size-distribution determined by dynamic light scattering. The use of colloidal dispersions provides an efficient tool for the UV–vis and FT Raman spectroscopic characterization of polypyrrole, including the transition between polypyrrole salt and corresponding polypyrrole base. The dispersions were used for the preparation of coatings on polyethylene terephthalate foils, and the properties for polypyrrole–silver composites have been compared with those produced from polypyrrole colloids alone

Quantum-size colloid metal systems

International Nuclear Information System (INIS)

Roldugin, V.I.

2000-01-01

In the review dealing with quantum-dimensional metallic colloid systems the methods of preparation, electronic, optical and thermodynamic properties of metal nanoparticles and thin films are considered, the effect of ionizing radiation on stability of silver colloid sols and existence of a threshold radiation dose affecting loss of stability being discussed. It is shown that sol stability loss stems from particles charge neutralization due to reduction of sorbed silver ions induced by radiation, which results in destruction of double electric layer on colloid particles boundary [ru

FEBEX bentonite colloid stability in ground water

Energy Technology Data Exchange (ETDEWEB)

Seher, H.; Schaefer, T.; Geckeis, H. [Inst. fuer Nukleare Entsorgung (INE), Forschungszentrum Karlsruhe, 76021 Karlsruhe (Germany)]. e-mail: holger.seher@ine.fzk .de; Fanghaenel, T. [Ruprecht-Karls-Univ. Heidelberg, Physikalisch-Chemisches In st., D-69120 Heidelberg (Germany)

2007-06-15

Coagulation experiments are accomplished to identify the geochemical conditions for the stability of Febex bentonite colloids in granite ground water. The experiments are carried out by varying pH, ionic strength and type of electrolyte. The dynamic light scattering technique (photon correlation spectroscopy) is used to measure the size evolution of the colloids with time. Agglomeration rates are higher in MgCl{sub 2} and CaCl{sub 2} than in NaCl solution. Relative agglomeration rates follow approximately the Schulze-Hardy rule. Increasing agglomeration rates at pH>8 are observed in experiments with MgCl{sub 2} and CaCl{sub 2} which are, however, caused by coprecipitation phenomena. Bentonite colloid stability fields derived from the colloid agglomeration experiments predict low colloid stabilization in granite ground water taken from Aespoe, Sweden, and relatively high colloid stability in Grimsel ground water (Switzerland)

Interface colloidal robotic manipulator

Science.gov (United States)

Aronson, Igor; Snezhko, Oleksiy

2015-08-04

A magnetic colloidal system confined at the interface between two immiscible liquids and energized by an alternating magnetic field dynamically self-assembles into localized asters and arrays of asters. The colloidal system exhibits locomotion and shape change. By controlling a small external magnetic field applied parallel to the interface, structures can capture, transport, and position target particles.

Molecular Recognition in the Colloidal World.

Science.gov (United States)

Elacqua, Elizabeth; Zheng, Xiaolong; Shillingford, Cicely; Liu, Mingzhu; Weck, Marcus

2017-11-21

Colloidal self-assembly is a bottom-up technique to fabricate functional nanomaterials, with paramount interest stemming from programmable assembly of smaller building blocks into dynamic crystalline domains and photonic materials. Multiple established colloidal platforms feature diverse shapes and bonding interactions, while achieving specific orientations along with short- and long-range order. A major impediment to their universal use as building blocks for predesigned architectures is the inability to precisely dictate and control particle functionalization and concomitant reversible self-assembly. Progress in colloidal self-assembly necessitates the development of strategies that endow bonding specificity and directionality within assemblies. Methodologies that emulate molecular and polymeric three-dimensional (3D) architectures feature elements of covalent bonding, while high-fidelity molecular recognition events have been installed to realize responsive reconfigurable assemblies. The emergence of anisotropic 'colloidal molecules', coupled with the ability to site-specifically decorate particle surfaces with supramolecular recognition motifs, has facilitated the formation of superstructures via directional interactions and shape recognition. In this Account, we describe supramolecular assembly routes to drive colloidal particles into precisely assembled architectures or crystalline lattices via directional noncovalent molecular interactions. The design principles are based upon the fabrication of colloidal particles bearing surface-exposed functional groups that can undergo programmable conjugation to install recognition motifs with high fidelity. Modular and versatile by design, our strategy allows for the introduction and integration of molecular recognition principles into the colloidal world. We define noncovalent molecular interactions as site-specific forces that are predictable (i.e., feature selective and controllable complementary bonding partners

40 CFR 141.174 - Filtration sampling requirements.

Science.gov (United States)

2010-07-01

... PROGRAMS (CONTINUED) NATIONAL PRIMARY DRINKING WATER REGULATIONS Enhanced Filtration and Disinfection... water system subject to the requirements of this subpart that provides conventional filtration treatment... 40 Protection of Environment 22 2010-07-01 2010-07-01 false Filtration sampling requirements. 141...

Sampling and analysis of groundwater colloids. A literature review

International Nuclear Information System (INIS)

Takala, M.; Manninen, P.

2006-03-01

The purpose of this literature study was to give basic information of colloids: their formation, colloid material, sampling and characterisation of groundwater colloids. Colloids are commonly refereed to as particles in the size range of 1 nm to 1000 nm. They are defined as a suspension of solid material in a liquid that does not appear to separate even after a long period of time. Colloids can be formed from a variety of inorganic or organic material. Inorganic colloids in natural groundwaters are formed by physical fragmentation of the host rock or by precipitation. The water chemistry strongly controls the stability of colloids. The amount of colloid particles in a solution tends to decrease with the increasing ionic strength of the solution. Increases in pH and organic material tend to increase the stability of colloids. The mobility of colloids in a porous medium is controlled mainly by groundwater movement, sedimentation, diffusion and interception. Factors controlling sampling artefacts are oxygen diffusion: leads to e.g. calcite precipitation, pumping rates and filtering techniques. Efforts to minimise artefact formation should be taken if the scope of the sampling programme is to study the colloid particles. The colloid phase size distribution can be determined by light scattering systems, laser induced break down or by single particle analysis using SEM micrographs. Elemental compositions can be analysed with EDS spectrometry from single colloid particles. Bulk compositions of the colloid phase can be analysed with e.g. ICP-MS analyser. The results of this study can be used as guidelines for groundwater colloid samplings. Recommendations for future work are listed in the conclusions of this report. (orig.)

Simulation study on the structural properties of colloidal particles with offset dipoles.

Science.gov (United States)

Rutkowski, David M; Velev, Orlin D; Klapp, Sabine H L; Hall, Carol K

2017-05-03

A major research theme in materials science is determining how the self-assembly of new generations of colloidal particles of complex shape and surface charge is guided by their interparticle interactions. In this paper, we describe results from quasi-2D Monte Carlo simulations of systems of colloidal particles with offset transversely-oriented extended dipole-like charge distributions interacting via an intermediate-ranged Yukawa potential. The systems are cooled slowly through an annealing procedure during which the temperature is lowered in discrete steps, allowing the system to equilibrate. We perform ground state calculations for two, three and four particles at several shifts of the dipole vector from the particle center. We create state diagrams in the plane spanned by the temperature and the area fraction outlining the boundaries between fluid, string-fluid and percolated states at various values of the shift. Remarkably we find that the effective cooling rate in our simulations has an impact on the structures formed, with chains being more prevalent if the system is cooled quickly and cyclic structures more prevalent if the system is cooled slowly. As the dipole is further shifted from the center, there is an increased tendency to assemble into small cyclic structures at intermediate temperatures. These systems further self-assemble into open lattice-like arrangements at very low temperatures. The novel structures identified might be useful for photonic applications, new types of porous media for filtration and catalysis, and gel matrices with unusual properties.

Pharmacological study of radioactive-gold colloid transport by blood and by serous exudate; Contribution a l'etude pharmacologique du transport des colloides d'or radioactif par le sang et les exsudats sereux

Energy Technology Data Exchange (ETDEWEB)

Rousselet, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1966-06-01

substances et particulierement dans le transport de l'or colloidal radioactif. Les fractions sanguines qui peuvent participer au transport de l'or colloidal sont les hematies, les leucocytes et elements histiocytaires, et le plasma. La repartition de la radioactivite dans ces elements est precisee en pratiquant des autoradiographies de coupes de culots de sang centrifuge et congele apres incubation avec de l'or colloidal. Cette etude montre l'importance du plasma dans le transport des particules radioactives. Nous avons alors recherche une fixation eventuelle de l'or colloidal 198 sur les diverses proteines seriques en appliquant certaines methodes de separation a savoir une filtration-exclusion sur colonne de gel de Sephadex G-200 et un fractionnement electrophoretique sur papier et sur acetate de cellulose gelatineux (cellogel). Nous avons etudie la liaison ''in vitro'' et ''in vivo'' des particules colloidales d'or 198 d'abord avec les proteines seriques de sujets sains puis avec les proteines des liquides d'epanchement d'origine pathologique, chez l'homme, ou du a une inflammation experimentale a la carragenine chez le rat. Les particules d'or colloidal 198 de 30 m{mu} (S-2) sont liees dans une certaine mesure aux {alpha}2 globulines sanguines ou ascitiques, celles de 5 m{mu} (S-6) sont liees aux {alpha}1 globulines de meme que les grains contenus dans l'or polydisperse. Cette liaison semble intervenir grace a la couche protectrice de macromolecules constituees par la gelatine. Seules les caracteristiques physicochimiques de grains colloidaux peuvent expliquer leur difference de localisation sur l'electrophoregramme. L'or sous forme ionique, par contre, est combine, aux seules albumines si la quantite de metal presente ne depasse pas une certaine limite. (auteur)

Formation of a barrier to groundwater contaminants by the injection of zero-valent iron colloids: Suspension properties

International Nuclear Information System (INIS)

Kaplan, D.I.; Cantrell, K.J.; Wietsma, T.W.

1994-01-01

Zero-valent iron (Fe 0 ) (metallic iron) is a strong chemical reductant that is capable of degrading several halogenated-hydrocarbon compounds (e.g., trichloroethene and tetrachloroethene) and chemically reducing several highly mobile oxidized oxyanions and oxycations to their immobile forms. A series of studies was undertaken to develop methods of injecting micrometer-sized Fe 0 colloids into the subsurface environment to form a chemical barrier to these highly mobile contaminants. Forming a barrier by means of this technique may have the distinct advantage over traditional trench-and-fill technologies: it may be safer, more cost-effective, and may be used at greater depths. Several commercially available Fe 0 colloids were evaluated. One type was selected for further study based on its small size (1 to 2 microm) and the presence of an organic coating. This organic coating was weathered away within 7 days by Hanford ground water (CaCO 3 system, pH 8.1) and exposed the chemically active Fe 0 -colloid surface. Through the use of surfactants in a low ionic strength solution, the length of time that these extremely dense (7.8 g cm -3 ) colloids remained in suspension increased as much as 250%. The efficiency of quartz-sand columns to remove surfactant-coated Fe 0 colloids appeared to be at least partially controlled by injection rate; the filter coefficient values at injection rates of 6, 124, and 248 ml min -1 were 0.30, 0.05, and 0.02 cm -1 , respectively. Studies are underway to develop further understanding of this relationship and to determine the interactive effect of influent colloid concentration and injection flow rate on colloid placement in aquifer sediments for barrier formation

Presence of Fe-Al binary oxide adsorbent cake layer in ceramic membrane filtration and their impact for removal of HA and BSA.

Science.gov (United States)

Kim, Kyung-Jo; Jang, Am

2018-04-01

To enhance the removal of natural organic matter (NOM) in ceramic (Ce) membrane filtration, an iron-aluminum binary oxide (FAO) was applied to the ceramic membrane surface as the adsorbent cake layer, and it was compared with heated aluminum oxide (HAO) for the evaluation of the control of NOM. Both the HAO and FAO adsorbent cake layers efficiently removed the NOM regardless of NOM's hydrophobic/hydrophilic characteristics, and the dissolved organic carbon (DOC) removal in NOM for FAO was 1-1.12 times greater than that for HAO, which means FAO was more efficient in the removal of DOC in NOM. FAO (0.03 μm), which is smaller in size than HAO (0.4 μm), had greater flux reduction than HAO. The flux reduction increased as the filtration proceeded because most of the organic foulants (colloid/particles and soluble NOM) were captured by the adsorbent cake layer, which caused fouling between the membrane surface and the adsorbent cake layer. However, no chemically irreversible fouling was observed on the Ce membrane at the end of the FAO adsorbent cake layer filtration. This means that a stable adsorbent cake layer by FAO formed on the Ce membrane, and that the reduced pure water flux of the Ce membrane, resulting from the NOM fouling, can easily be recovered through physicochemical cleaning. Copyright © 2018 Elsevier Ltd. All rights reserved.

40 CFR 141.73 - Filtration.

Science.gov (United States)

2010-07-01

... Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) WATER PROGRAMS (CONTINUED) NATIONAL PRIMARY DRINKING WATER REGULATIONS Filtration and Disinfection § 141.73 Filtration. A public water system that uses a surface water source or a ground water source under the direct influence of surface water...

Clustering and self-assembly in colloidal systems

NARCIS (Netherlands)

Smallenburg, F.

2012-01-01

A colloidal dispersion consists of small particles called colloids, typically tens of nanometers to a few micrometers in size, suspended in a solvent. Due to collisions with the much smaller particles in the solvent, colloids perform Brownian motion: randomly directed movements that cause the

Colloid-Facilitated Transport of Radionuclides Through The Vadose Zone

International Nuclear Information System (INIS)

Markus Flury; James B. Harsh; John F. McCarthy' Peter C. Lichtner; John M. Zachara

2007-01-01

The main purpose of this project was to advance the basic scientific understanding of colloid and colloid-facilitated Cs transport of radionuclides in the vadose zone. We focused our research on the hydrological and geochemical conditions beneath the leaking waste tanks at the USDOE Hanford reservation. Specific objectives were (1) to determine the lability and thermodynamic stability of colloidal materials, which form after reacting Hanford sediments with simulated Hanford Tank Waste, (2) to characterize the interactions between colloidal particles and contaminants, i.e., Cs and Eu, (3) to determine the potential of Hanford sediments for in situ mobilization of colloids, (4) to evaluate colloid-facilitated radionuclide transport through sediments under unsaturated flow, (5) to implement colloid-facilitated contaminant transport mechanisms into a transport model, and (6) to improve conceptual characterization of colloid-contaminant-soil interactions and colloid-facilitated transport for clean-up procedures and long-term risk assessment

The physics of the colloidal glass transition.

Science.gov (United States)

Hunter, Gary L; Weeks, Eric R

2012-06-01

As one increases the concentration of a colloidal suspension, the system exhibits a dramatic increase in viscosity. Beyond a certain concentration, the system is said to be a colloidal glass; structurally, the system resembles a liquid, yet motions within the suspension are slow enough that it can be considered essentially frozen. For several decades, colloids have served as a valuable model system for understanding the glass transition in molecular systems. The spatial and temporal scales involved allow these systems to be studied by a wide variety of experimental techniques. The focus of this review is the current state of understanding of the colloidal glass transition, with an emphasis on experimental observations. A brief introduction is given to important experimental techniques used to study the glass transition in colloids. We describe features of colloidal systems near and in glassy states, including increases in viscosity and relaxation times, dynamical heterogeneity and ageing, among others. We also compare and contrast the glass transition in colloids to that in molecular liquids. Other glassy systems are briefly discussed, as well as recently developed synthesis techniques that will keep these systems rich with interesting physics for years to come.

The physics of the colloidal glass transition

International Nuclear Information System (INIS)

Hunter, Gary L; Weeks, Eric R

2012-01-01

As one increases the concentration of a colloidal suspension, the system exhibits a dramatic increase in viscosity. Beyond a certain concentration, the system is said to be a colloidal glass; structurally, the system resembles a liquid, yet motions within the suspension are slow enough that it can be considered essentially frozen. For several decades, colloids have served as a valuable model system for understanding the glass transition in molecular systems. The spatial and temporal scales involved allow these systems to be studied by a wide variety of experimental techniques. The focus of this review is the current state of understanding of the colloidal glass transition, with an emphasis on experimental observations. A brief introduction is given to important experimental techniques used to study the glass transition in colloids. We describe features of colloidal systems near and in glassy states, including increases in viscosity and relaxation times, dynamical heterogeneity and ageing, among others. We also compare and contrast the glass transition in colloids to that in molecular liquids. Other glassy systems are briefly discussed, as well as recently developed synthesis techniques that will keep these systems rich with interesting physics for years to come. (review article)

40 CFR 141.719 - Additional filtration toolbox components.

Science.gov (United States)

2010-07-01

... taken from a surface water or GWUDI source. A cap, such as GAC, on a single stage of filtration is not... separate stage of filtration if both filtration stages treat entire plant flow taken from a surface water... 40 Protection of Environment 22 2010-07-01 2010-07-01 false Additional filtration toolbox...

Colloids from the aqueous corrosion of uranium nuclear fuel

Science.gov (United States)

Kaminski, M. D.; Dimitrijevic, N. M.; Mertz, C. J.; Goldberg, M. M.

2005-12-01

Colloids may enhance the subsurface transport of radionuclides and potentially compromise the long-term safe operation of the proposed radioactive waste repository at Yucca Mountain. Little data is available on colloid formation for the many different waste forms expected to be buried in the repository. This work expands the sparse database on colloids formed during the corrosion of metallic uranium nuclear fuel. We characterized spherical UO 2 and nickel-rich montmorilonite smectite-clay colloids formed during the corrosion of uranium metal fuel under bathtub conditions at 90 °C. Iron and chromium oxides and calcium carbonate colloids were present but were a minor population. The estimated upper concentration of the UO 2 and clays was 4 × 10 11 and 7 × 10 11-3 × 10 12 particles/L, respectively. However, oxygen eventually oxidized the UO 2 colloids, forming long filaments of weeksite K 2(UO 2) 2Si 6O 15 · 4H 2O that settled from solution, reducing the UO 2 colloid population and leaving predominantly clay colloids. The smectite colloids were not affected by oxygen. Plutonium was not directly observed within the UO 2 colloids but partitioned completely to the colloid size fraction. The plutonium concentration in the colloidal fraction was slightly higher than the value used in the viability assessment model, and does not change in concentration with exposure to oxygen. This paper provides conclusive evidence for single-phase radioactive colloids composed of UO 2. However, its impact on repository safety is probably small since oxygen and silica availability will oxidize and effectively precipitate the UO 2 colloids from concentrated solutions.

Removal of actinides from dilute waste waters using polymer filtration

International Nuclear Information System (INIS)

Smith, B.F.; Robison, T.W.; Gibson, R.R.

1995-01-01

More stringent US Department of Energy discharge regulations for waste waters containing radionuclides (30 pCi/L total alpha) require the development of new processes to meet the new discharge limits for actinide metal ions, particularly americium and plutonium, while minimizing waste. We have been investigating a new technology, polymer filtration, that has the potential for effectively meeting these new limits. Traditional technology uses basic iron precipitation which produces large amounts of waste sludge. The new technology is based on using water-soluble chelating polymers with ultrafiltration for physical separation. The actinide metal ions are selectively bound to the polymer and can not pass through the membrane. Small molecules and nonbinding metals pass through the membrane. Advantages of polymer filtration technology compared to ion, exchange include rapid kinetics because the binding is occurring in a homogenous solution and no mechanical strength requirement on the polymer. We will present our results on the systematic development of a new class of water-soluble chelating polymers and their binding ability from dilute acid to near neutral waters

Aerosol filtration

International Nuclear Information System (INIS)

First, M.W.; Gilbert, H.

1981-01-01

Significant developments in high efficiency filtration for nuclear applications are reviewed for the period 1968 to 1980. Topics of special interest include factory (bench) and in-place test methods, new developments in paper and filter unit construction methods, vented containment air cleaning systems for LMFBR and light water moderated reactors, and decontamination of offgases from nuclear waste volume reduction processes. It is noted that standards development has been vigorously pursued during this period but that advances in filtration theory have been few. One of the significant changes likely to occur in the immediate future is adoption of the European style of HEPA filters for those that have been in service for the past three decades to obtain the benefits of having almost twice as much filter paper in the same filter cartridge. 71 references

Filtration by eyelashes

Science.gov (United States)

Vistarakula, Krishna; Bergin, Mike; Hu, David

2010-11-01

Nearly every mammalian and avian eye is rimmed with lashes. We investigate experimentally the ability of lashes to reduce airborne particle deposition in the eye. We hypothesize that there is an optimum eyelash length that maximizes both filtration ability and extent of peripheral vision. This hypothesis is tested using a dual approach. Using preserved heads from 36 species of animals at the American Museum of Natural History, we determine the relationship between eye size and eyelash geometry (length and spacing). We test the filtration efficacy of these geometries by deploying outdoor manikins and measuring particle deposition rate as a function of eyelash length.

Dynamic Colloidal Molecules Maneuvered by Light-Controlled Janus Micromotors.

Science.gov (United States)

Gao, Yirong; Mou, Fangzhi; Feng, Yizheng; Che, Shengping; Li, Wei; Xu, Leilei; Guan, Jianguo

2017-07-12

In this work, we propose and demonstrate a dynamic colloidal molecule that is capable of moving autonomously and performing swift, reversible, and in-place assembly dissociation in a high accuracy by manipulating a TiO 2 /Pt Janus micromotor with light irradiation. Due to the efficient motion of the TiO 2 /Pt Janus motor and the light-switchable electrostatic interactions between the micromotor and colloidal particles, the colloidal particles can be captured and assembled one by one on the fly, subsequently forming into swimming colloidal molecules by mimicking space-filling models of simple molecules with central atoms. The as-demonstrated dynamic colloidal molecules have a configuration accurately controlled and stabilized by regulating the time-dependent intensity of UV light, which controls the stop-and-go motion of the colloidal molecules. The dynamic colloidal molecules are dissociated when the light irradiation is turned off due to the disappearance of light-switchable electrostatic interaction between the motor and the colloidal particles. The strategy for the assembly of dynamic colloidal molecules is applicable to various charged colloidal particles. The simulated optical properties of a dynamic colloidal molecule imply that the results here may provide a novel approach for in-place building functional microdevices, such as microlens arrays, in a swift and reversible manner.

Near-field light design with colloidal quantum dots for photonics and plasmonics.

Science.gov (United States)

Kress, Stephan J P; Richner, Patrizia; Jayanti, Sriharsha V; Galliker, Patrick; Kim, David K; Poulikakos, Dimos; Norris, David J

2014-10-08

Colloidal quantum-dots are bright, tunable emitters that are ideal for studying near-field quantum-optical interactions. However, their colloidal nature has hindered their facile and precise placement at desired near-field positions, particularly on the structured substrates prevalent in plasmonics. Here, we use high-resolution electro-hydrodynamic printing (quantum dots on both flat and structured substrates with a few nanometer precision. We also demonstrate that the autofocusing capability of the printing method enables placement of quantum dots preferentially at plasmonic hot spots. We exploit this control and design diffraction-limited photonic and plasmonic sources with arbitrary wavelength, shape, and intensity. We show that simple far-field illumination can excite these near-field sources and generate fundamental plasmonic wave-patterns (plane and spherical waves). The ability to tailor subdiffraction sources of plasmons with quantum dots provides a complementary technique to traditional scattering approaches, offering new capabilities for nanophotonics.

Colloidal CdSe Quantum Rings.

Science.gov (United States)

Fedin, Igor; Talapin, Dmitri V

2016-08-10

Semiconductor quantum rings are of great fundamental interest because their non-trivial topology creates novel physical properties. At the same time, toroidal topology is difficult to achieve for colloidal nanocrystals and epitaxially grown semiconductor nanostructures. In this work, we introduce the synthesis of luminescent colloidal CdSe nanorings and nanostructures with double and triple toroidal topology. The nanorings form during controlled etching and rearrangement of two-dimensional nanoplatelets. We discuss a possible mechanism of the transformation of nanoplatelets into nanorings and potential utility of colloidal nanorings for magneto-optical (e.g., Aharonov-Bohm effect) and other applications.

Side Stream Filtration for Cooling Towers

Energy Technology Data Exchange (ETDEWEB)

None

2012-10-20

This technology evaluation assesses side stream filtration options for cooling towers, with an objective to assess key attributes that optimize energy and water savings along with providing information on specific technology and implementation options. This information can be used to assist Federal sites to determine which options may be most appropriate for their applications. This evaluation provides an overview of the characterization of side stream filtration technology, describes typical applications, and details specific types of filtration technology.

Conductivity maximum in a charged colloidal suspension

Energy Technology Data Exchange (ETDEWEB)

Bastea, S

2009-01-27

Molecular dynamics simulations of a charged colloidal suspension in the salt-free regime show that the system exhibits an electrical conductivity maximum as a function of colloid charge. We attribute this behavior to two main competing effects: colloid effective charge saturation due to counterion 'condensation' and diffusion slowdown due to the relaxation effect. In agreement with previous observations, we also find that the effective transported charge is larger than the one determined by the Stern layer and suggest that it corresponds to the boundary fluid layer at the surface of the colloidal particles.

Formation, characterization, and stability of plutonium (IV) colloid

International Nuclear Information System (INIS)

Hobart, D.E.; Morris, D.E.; Palmer, P.D.; Newton, T.W.

1989-01-01

Plutonium is expected to be a major component of the waste element package in any high-level nuclear waste repository. Plutonium(IV) is known to form colloids under chemical conditions similar to those found in typical groundwaters. In the event of a breach of a repository, these colloids represent a source of radionuclide transport to the far-field environment, in parallel with the transport of dissolved waste element species. In addition, the colloids may decompose or disaggregate into soluble ionic species. Thus, colloids represent an additional term in determining waste element solubility limits. A thorough characterization of the physical and chemical properties of these colloids under relevant conditions is essential to assess the concentration limits and transport mechanisms for the waste elements at the proposed Yucca Mountain Repository site. This report is concerned primarily with recent results obtained by the Yucca Mountain Project (YMP) Solubility Determination Task pertaining to the characterization of the structural and chemical properties of Pu(IV) colloid. Important results will be presented which provides further evidence that colloidal plutonium(IV) is structurally similar to plutonium dioxide and that colloidal plutonium(IV) is electrochemically reactive. 13 refs., 7 figs

Photonic emitters and circuits based on colloidal quantum dot composites

Science.gov (United States)

Menon, Vinod M.; Husaini, Saima; Valappil, Nikesh; Luberto, Matthew

2009-02-01

We discuss our work on light emitters and photonic circuits realized using colloidal quantum dot composites. Specifically we will report our recent work on flexible microcavity laser, microdisk emitters and integrated active - passive waveguides. The entire microcavity laser structure was realized using spin coating and consisted of an all-polymer distributed Bragg reflector with a poly-vinyl carbazole cavity layer embedded with InGaP/ZnS colloidal quantum dots. These microcavities can be peeled off the substrate yielding a flexible structure that can conform to any shape and whose emission spectra can be mechanically tuned. The microdisk emitters and the integrated waveguide structures were realized using soft lithography and photo-lithography, respectively and were fabricated using a composite consisting of quantum dots embedded in SU8 matrix. Finally, we will discuss the effect of the host matrix on the optical properties of the quantum dots using results of steady-state and time-resolved luminescence measurements. In addition to their specific functionalities, these novel device demonstrations and their development present a low cost alternative to the traditional photonic device fabrication techniques.

Dissolved and colloidal trace elements in the Mississippi River Delta outflow after Hurricanes Katrina and Rita

Science.gov (United States)

Shim, Moo-Joon; Swarzenski, Peter W.; Shiller, Alan M.

2012-01-01

The Mississippi River delta outflow region is periodically disturbed by tropical weather systems including major hurricanes, which can terminate seasonal bottom water hypoxia and cause the resuspension of shelf bottom sediments which could result in the injection of trace elements into the water column. In the summer of 2005, Hurricanes Katrina and Rita passed over the Louisiana Shelf within a month of each other. Three weeks after Rita, we collected water samples in the Mississippi River delta outflow, examining the distributions of trace elements to study the effect of Hurricanes Katrina and Rita. We observed limited stratification on the shelf and bottom waters that were no longer hypoxic. This resulted, for instance, in bottom water dissolved Mn being lower than is typically observed during hypoxia, but with concentrations still compatible with Mn–O2 trends previously reported. Interestingly, for no element were we able to identify an obvious effect of sediment resuspension on its distribution. In general, elemental distributions were compatible with previous observations in the Mississippi outflow system. Co and Re, which have not been reported for this system previously, showed behavior consistent with other systems: input for Co likely from desorption and conservative mixing for Re. For Cs, an element for which there is little information regarding its estuarine behavior, conservative mixing was also observed. Our filtration method, which allowed us to distinguish the dissolved (<0.02 μm) from colloidal (0.02–0.45 μm) phase, revealed significant colloidal fractions for Fe and Zn, only. For Fe, the colloidal phase was the dominant fraction and was rapidly removed at low salinity. Dissolved Fe, in contrast, persisted out to mid-salinities, being removed in a similar fashion to nitrate. This ability to distinguish the smaller Fe (likely dominantly organically complexed) from larger colloidal suspensates may be useful in better interpreting the

Active structuring of colloidal armour on liquid drops

OpenAIRE

Dommersnes, Paul; Rozynek, Zbigniew; Mikkelsen, Alexander; Castberg, Rene; Kjerstad, Knut; Hersvik, Kjetil; Fossum, Jon Otto

2013-01-01

Adsorption and assembly of colloidal particles at the surface of liquid droplets are at the base of particle-stabilized emulsions and templating. Here we report that electrohydrodynamic and electro-rheological effects in leaky-dielectric liquid drops can be used to structure and dynamically control colloidal particle assemblies at drop surfaces, including electric-fieldassisted convective assembly of jammed colloidal ‘ribbons’, electro-rheological colloidal chains confined to a...

Formation and stability of aluminosilicate colloids by coprecipitation

Energy Technology Data Exchange (ETDEWEB)

Putri, Kirana Yuniati

2011-02-15

Colloids are ubiquitous in natural waters. Colloid-facilitated migration is of importance in safety assessment of a nuclear waste disposal. Aluminosilicate colloids are considered to be the kernel of aquatic colloids. Their stability is affected by a number of geochemical parameters. This work aims to study qualitatively and quantitatively the stability of aluminosilicate colloids formed by coprecipitation under various geochemical conditions, i.e. pH, concentration of Al and Si metal ions, ionic strength, and omnipresent cations (Na{sup +}, Ca{sup 2+}, and Mg{sup 2+}). The work is performed by colorimetric method and laser-induced breakdown detection (LIBD). Two consecutive phase separations at 450 nm and 1 kDa are applied to separate the precipitates and colloids from the ionic species. By means of colorimetry, Si and Al can be detected down to 5.8 x10{sup -8} M and 7.4x10{sup -7} M, respectively. On the other hand, LIBD is able to quantify the colloidal size and its number density down to several ppt. Depending on the concentration of Al and Si metal ions, the formation trend of aluminosilicate colloid changes following its solubility curve. The lower the concentration, the higher the pH range in which the colloids start to emerge. Furthermore, the colloids are stable at higher Al and Si concentration and at low ionic strength. In the low pH range, cations provide different effects at low and high ionic strengths. At high ionic strength, the colloids are stable in the presence of a larger cation, while all cations exhibit similar effects at low ionic strength. However, in the high pH range, valence seems to have a stronger effect than ionic radius; colloids are more stable in the presence of monovalent cations than divalent ones. Meanwhile, XRD shows non- and/or poor crystalline structure of the aluminosilicate species. Nevertheless, results from XPS may suggest that the chemical composition (Si/Al ∼ 0.6) of the aluminosilicate precipitates is sillimanite or

Radiolytic reduction reaction of colloidal silver bromide solution

International Nuclear Information System (INIS)

Oya, Yasuhisa; Zushi, Takehiro; Hasegawa, Kunihiko; Matsuura, Tatsuo.

1995-01-01

The reduction reaction of colloidal silver bromide (AgBr 3 ) 2- in nitrous oxide gas saturated solution of some alcohols: methanol, ethanol, 2-propanol and 2-methyl-2-propanol by γ-irradiation was studied spectrophotometrically in order to elucidate the mechanism of the formation of colloidal silver bromide (AgBr 3 ) 3- at ambient temperature. The amount of colloidal silver bromide formed increases in the order: i-PrOH, EtOH, MeOH. In t-BuOH, colloidal silver bromide did not form. The relative reactivities of alcohols for colloidal silver bromide was also studied kinetically. (author)

21 CFR 177.2910 - Ultra-filtration membranes.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ultra-filtration membranes. 177.2910 Section 177... Components of Articles Intended for Repeated Use § 177.2910 Ultra-filtration membranes. Ultra-filtration membranes identified in paragraphs (a)(1), (a)(2), (a)(3), and (a)(4) of this section may be safely used in...

Colloid Thrusters, Physics, Fabrication and Performance

National Research Council Canada - National Science Library

Martinez-Sanchez, Manuel; Akinwande, Akintunde I

2005-01-01

... discovered pure ionic mode, the microfabrication in Silicon of two types of arrays of colloid or electrospray emitters, and the development of a quantitative theory for the colloidal regime (no ions...

Colloid-Facilitated Transport of Radionuclides through the Vadose Zone

International Nuclear Information System (INIS)

Flury, Markus; Harsh, James B.; Zachara, John M.; McCarthy, John F.; Lichtner, Peter C.

2006-01-01

This project seeks to improve the basic understanding of the role of colloids in facilitating the transport of contaminants in the vadose zone. We focus on three major thrusts: (1) thermodynamic stability and mobility of colloids formed by reactions of sediments with highly alkaline tank waste solutions, (2) colloid-contaminant interactions, and (3) in-situ colloid mobilization and colloid facilitated contaminant transport occurring in both contaminated and uncontaminated Hanford sediments

Impact of Redox Reactions on Colloid Transport in Saturated Porous Media: An Example of Ferrihydrite Colloids Transport in the Presence of Sulfide.

Science.gov (United States)

Liao, Peng; Yuan, Songhu; Wang, Dengjun

2016-10-18

Transport of colloids in the subsurface is an important environmental process with most research interests centered on the transport in chemically stable conditions. While colloids can be formed under dynamic redox conditions, the impact of redox reactions on their transport is largely overlooked. Taking the redox reactions between ferrihydrite colloids and sulfide as an example, we investigated how and to what extent the redox reactions modulated the transport of ferrihydrite colloids in anoxic sand columns over a range of environmentally relevant conditions. Our results reveal that the presence of sulfide (7.8-46.9 μM) significantly decreased the breakthrough of ferrihydrite colloids in the sand column. The estimated travel distance of ferrihydrite colloids in the absence of sulfide was nearly 7-fold larger than that in the presence of 46.9 μM sulfide. The reduced breakthrough was primarily attributed to the reductive dissolution of ferrihydrite colloids by sulfide in parallel with formation of elemental sulfur (S(0)) particles from sulfide oxidation. Reductive dissolution decreased the total mass of ferrihydrite colloids, while the negatively charged S(0) decreased the overall zeta potential of ferrihydrite colloids by attaching onto their surfaces and thus enhanced their retention in the sand. Our findings provide novel insights into the critical role of redox reactions on the transport of redox-sensitive colloids in saturated porous media.

Aerosol filtration

International Nuclear Information System (INIS)

First, M.W.; Gilbert, H.

1982-01-01

Significant developments in high-efficiency filtration for nuclear applications are reviewed for the period 1968 to 1980. Topics of special interest include (1) factory (bench) and in-place test methods, (2) new developments in paper and filter unit construction methods, (3) vented containment air cleaning systems for liquid-metal fast breeder reactors and light-water-moderated reactors, and (4) decontamination of off-gases from nuclear waste volume-reduction processes. Standards development has been vigorously pursued during this period, but advances in filtration theory have been few. One of the significant changes likely to occur in the immediate future is adoption of the European style of high-efficiency particulate air filters instead of those which have been in service for the past three decades to obtain the benefits of having almost twice as much filter paper in the same filter cartridge

Flocking ferromagnetic colloids.

Science.gov (United States)

Kaiser, Andreas; Snezhko, Alexey; Aranson, Igor S

2017-02-01

Assemblages of microscopic colloidal particles exhibit fascinating collective motion when energized by electric or magnetic fields. The behaviors range from coherent vortical motion to phase separation and dynamic self-assembly. Although colloidal systems are relatively simple, understanding their collective response, especially under out-of-equilibrium conditions, remains elusive. We report on the emergence of flocking and global rotation in the system of rolling ferromagnetic microparticles energized by a vertical alternating magnetic field. By combing experiments and discrete particle simulations, we have identified primary physical mechanisms, leading to the emergence of large-scale collective motion: spontaneous symmetry breaking of the clockwise/counterclockwise particle rotation, collisional alignment of particle velocities, and random particle reorientations due to shape imperfections. We have also shown that hydrodynamic interactions between the particles do not have a qualitative effect on the collective dynamics. Our findings shed light on the onset of spatial and temporal coherence in a large class of active systems, both synthetic (colloids, swarms of robots, and biopolymers) and living (suspensions of bacteria, cell colonies, and bird flocks).

Colloids related to low level and intermediate level waste

International Nuclear Information System (INIS)

Ramsay, J.D.F.; Russell, P.J.; Avery, R.G.

1991-03-01

A comprehensive investigation has been undertaken to improve the understanding of the potential role of colloids in the context of disposal and storage of low and intermediate level waste immobilised in cement. Several topics have been investigated using a wide range of advanced physico-chemical and analytical techniques. These include: (a) the study of formation and characteristics of colloids in cement leachates, (b) the effects of the near-field aqueous chemistry on the characteristics of colloids in repository environments, (c) colloid sorption behaviour, (d) interactions of near-field materials with leachates, and (e) preliminary assessment of colloid migration behaviour. It has been shown that the generation of colloids in cement leachates can arise from a process of nucleation and growth leading to an amorphous phase which is predominantly calcium silicate hydrate. Such colloidal material has a capacity for association with polyvalent rare earths and actinides and these may be significant in the source term and processes involving radionuclide retention in the near field. It has also been shown that the near-field aqueous chemistry (pH, Ca 2+ concentration) has a marked effect on colloid behaviour (deposition and stability). A mechanistic approach to predict colloid sorption affinity has been developed which highlights the importance of colloid characteristics and the nature of the ionic species. (author)

Pharmacology of colloids and crystalloids.

Science.gov (United States)

Griffel, M I; Kaufman, B S

1992-04-01

We have attempted to review body fluid distribution by compartments so that the reader understands the physiology of ICF and ECF, and the relationship between interstitial and intravascular fluids. Crystalloids such as NS and RL are distributed to the ECF, whereas colloids primarily remain intravascular for longer periods. Although effective, crystalloids tend to require larger volumes for infusion, and edema remains a problem. Colloids as a group are extremely effective volume expanders, but none is ideal. Albumin, hetastarch, dextran, and the less commonly used colloids each have significant toxicities that must be considered when using them. Intelligent choices can be made to optimize use of these fluids.

The radiation chemistry of colloids

International Nuclear Information System (INIS)

Sellers, R.M.

1976-08-01

One of the most important problems associated with water cooled reactors is the accumulation on the pipework of radio-active deposits. These are formed from corrosion products which become activated during their passage through the reactor core. The first step of the activation process involves the deposition of the corrosion products, which are present as either colloidal or particulate matter, onto surfaces in the reactor core, i.e. within the radiation zone. A review of the literature on the effect of radiation on colloids is presented. Particular emphasis is given to the dependence of colloidal parameters such as particle size, turbidity and electrophoretic mobility on radiation dose. Most of the data available is of a qualitative nature only. Evidence is presented that colloids of iron are affected (in some cases precipitated) by radiation, and it is suggested that this process plays a part in the deposition of corrosion products in nuclear reactor cores. The bulk of the information available can be rationalized in terms of the radiation chemistry of aqueous solutions, and the interaction of the radicals produced with the atoms or molecules at the surface of the colloidal particles. This approach is very successful in explaining the variation of the mean particle size of monodisperse sulphur hydrosols with dose, for which quantitative experimental data are available. (author)

Structure and stability of charged colloid-nanoparticle mixtures

Science.gov (United States)

Weight, Braden M.; Denton, Alan R.

2018-03-01

Physical properties of colloidal materials can be modified by addition of nanoparticles. Within a model of like-charged mixtures of particles governed by effective electrostatic interactions, we explore the influence of charged nanoparticles on the structure and thermodynamic phase stability of charge-stabilized colloidal suspensions. Focusing on salt-free mixtures of particles of high size and charge asymmetry, interacting via repulsive Yukawa effective pair potentials, we perform molecular dynamics simulations and compute radial distribution functions and static structure factors. Analysis of these structural properties indicates that increasing the charge and concentration of nanoparticles progressively weakens correlations between charged colloids. We show that addition of charged nanoparticles to a suspension of like-charged colloids can induce a colloidal crystal to melt and can facilitate aggregation of a fluid suspension due to attractive van der Waals interactions. We attribute the destabilizing influence of charged nanoparticles to enhanced screening of electrostatic interactions, which weakens repulsion between charged colloids. This interpretation is consistent with recent predictions of an effective interaction theory of charged colloid-nanoparticle mixtures.

Structural properties of dendrimer-colloid mixtures

International Nuclear Information System (INIS)

Lenz, Dominic A; Blaak, Ronald; Likos, Christos N

2012-01-01

We consider binary mixtures of colloidal particles and amphiphilic dendrimers of the second generation by means of Monte Carlo simulations. By using the effective interactions between monomer-resolved dendrimers and colloids, we compare the results of simulations of mixtures stemming from a full monomer-resolved description with the effective two-component description at different densities, composition ratios, colloid diameters and interaction strengths. Additionally, we map the two-component system onto an effective one-component model for the colloids in the presence of the dendrimers. Simulations based on the resulting depletion potentials allow us to extend the comparison to yet another level of coarse graining and to examine under which conditions this two-step approach is valid. In addition, a preliminary outlook into the phase behavior of this system is given. (paper)

Influences on physicians' choices of intravenous colloids.

Science.gov (United States)

Miletin, Michael S; Stewart, Thomas E; Norton, Peter G

2002-07-01

Controversy over the optimal intravenous fluid for volume resuscitation continues unabated. Our objectives were to characterize the demographics of physicians who prescribe intravenous colloids and determine factors that enter into their decision to choose a colloid. Questionnaire with 61 items. Ten percent ( n = 364) of frequent intravenous fluid prescribers in the province of Ontario, Canada. The response rate was 74%. Colloid use in the past year was reported by 79% of the responding physicians. Important reasons for choosing a colloid included blood loss and manipulation of oncotic pressure. Physicians tended to prefer either albumin or pentastarch, but no important reasons were found for choosing between the two. Albumin with or without crystalloid was preferred in 5/13 scenarios by more than 50% of the respondents, whereas pentastarch was not favored by more than 50% of respondents in any scenario. Physicians practising in critical care areas and teaching hospitals generally preferred pentastarch to albumin. Physicians reporting pentastarch as representing greater than 90% of total colloid use were more likely to have been visited by a drug detailer for pentastarch than those who used less synthetic colloid (54 vs 22%, p distribution. Although albumin appeared to be preferred in more clinical niches, most physicians did not state reasons for choosing between products. Marketing, specialty, location of practice and clinical scenario appear to play significant roles in the utilization of colloid products.

Characterization of magnetic colloids by means of magnetooptics

OpenAIRE

Baraban, Larysa; Erbe, Artur; Leiderer, Paul

2007-01-01

A new, efficient method for the characterization of magnetic colloids based on the Faraday effect is proposed. According to the main principles of this technique, it is possible to detect the stray magnetic field of the colloidal particles induced inside the magnetooptical layer. The magnetic properties of individual particles can be determined providing measurements in a wide range of magnetic fields. The magnetization curves of capped colloids and paramagnetic colloids were measured by mean...

Bletilla colloid as a vascular embolization agent: experimental studies

International Nuclear Information System (INIS)

Zheng Chuansheng; Feng Gansheng; Zhang Yanfang

1998-01-01

Purpose: To study the efficacy, safety and related characteristics of bletilla colloid as a vascular embolization agent. Materials and methods: The authors prepared bletilla colloid as a vascular embolization agent from the stem tubers of bletilla of Chinese medicinal herb. Related characteristics of bletilla colloid were studied. In four pigs hepatic arterial embolization was performed with the bletilla colloid. Results: The bletilla colloid was a homogenous viscous colloid whose relative viscosity was 2324.6 mm 2 /s. It was easily injected through 4-F catheter and hyperattenuating under fluoroscopy, meanwhile, with good histocompatibility and hemo-compatibility, without pyrogenetic response and toxicity. In vitro, the mixture of bletilla colloid and MMC did not produce separation and suspension phenomena but released 50% of MMC at 1.8h and 100% at 3.4h. The bletilla colloid mainly embolized peripheral arteries, maintaining occlusion for 5 weeks and without formation of collateral circulation. The injuries of normal hepatic tissues were slight, without hepatic cytonecrosis. Conclusions: Bletilla colloid, safe and effective in use with angioembolic function and characteristics of carrier and slow-release, is a potential peripheral embolization agent

Technetium migration in Boom Clay - Assessing the role of colloid-facilitated transport in a deep clay formation

International Nuclear Information System (INIS)

Bruggeman, C.; Martens, E.; Maes, N.; Jacops, E.; Van Gompel, M.; Van Ravestyn, L.

2010-01-01

independent study on the migration of natural organic matter was used to extract migration parameters. This independent study relied on both lab-scale and in situ large-scale migration experiments with 14 C-labelled NOM which were performed over a period of 15 years. A classic diffusion-advection equation, including a colloid filtration term and/or non-linear sorption, simulated the experimental data quite well and could also account for the anisotropy of the Boom Clay formation. By using information from independent experiments on processes that were assumed to occur upon transport of Tc through the Boom Clay formation, the degree of freedom of the model was seriously constrained. All parameters used in the reactive transport model (Tc solubility, complexation with inorganic ligands, stability constant for the 'colloid-colloid' interaction process, solid-solution distribution coefficient of aqueous inorganic Tc species) were either taken from established thermodynamic data sources, or from published data of batch experiments. Only the first-order kinetic rate that accounted for slow decoupling of the Tc colloid and the organic matter colloids was fitted. An accurate model simulation could be obtained both for the Tc concentration in the outflowing solution, and the Tc tracer profile across the clay cores used in the setup. The good accuracy between the reactive transport model, batch experimental data and the experimental percolation data shows that the conceptual model is strong enough to handle different types of experimental setups, and allows to make interpolations for different geochemical conditions. Moreover, the model was adapted to make predictions of Tc migration as a NOM-associated colloid over the entire height of the overlying formation. Based on these predictions, we are now able to assess the potential for colloid-facilitated transport of radionuclides by dissolved NOM in Boom Clay. (authors)

Transport of Intrinsic Plutonium Colloids in Saturated Porous Media

Science.gov (United States)

Zhou, D.; Abdel-Fattah, A.; Boukhalfa, H.; Ware, S. D.; Tarimala, S.; Keller, A. A.

2011-12-01

Actinide contaminants were introduced to the subsurface environment as a result of nuclear weapons development and testing, as well as for nuclear power generation and related research activities for defense and civilian applications. Even though most actinide species were believed to be fairly immobile once in the subsurface, recent studies have shown the transport of actinides kilometers away from their disposal sites. For example, the treated liquid wastes released into Mortandad Canyon at the Los Alamos National Laboratory were predicted to travel less than a few meters; however, plutonium and americium have been detected 3.4 km away from the waste outfall. A colloid-facilitated mechanism has been suggested to account for this unexpected transport of these radioactive wastes. Clays, oxides, organic matters, and actinide hydroxides have all been proposed as the possible mobile phase. Pu ions associated with natural colloids are often referred to as pseudo-Pu colloids, in contrast with the intrinsic Pu colloids that consist of Pu oxides. Significant efforts have been made to investigate the role of pseudo-Pu colloids, while few studies have evaluated the environmental behavior of the intrinsic Pu colloids. Given the fact that Pu (IV) has extremely low solubility product constant, it can be inferred that the transport of Pu in the intrinsic form is highly likely at suitable environmental conditions. This study investigates the transport of intrinsic Pu colloids in a saturated alluvium material packed in a cylindrical column (2.5-cm Dia. x 30-cm high) and compares the results to previous data on the transport of pseudo Pu colloids in the same material. A procedure to prepare a stable intrinsic Pu colloid suspension that produced consistent and reproducible electrokinetic and stability data was developed. Electrokinetic properties and aggregation stability were characterized. The Pu colloids, together with trillium as a conservative tracer, were injected into the

Projective Dimension in Filtrated K-Theory

DEFF Research Database (Denmark)

Bentmann, Rasmus Moritz

2013-01-01

Under mild assumptions, we characterise modules with projective resolutions of length n∈N in the target category of filtrated K-theory over a finite topological space in terms of two conditions involving certain Tor -groups. We show that the filtrated K-theory of any separable C∗dash-algebra over...... any topological space with at most four points has projective dimension 2 or less. We observe that this implies a universal coefficient theorem for rational equivariant KK-theory over these spaces. As a contrasting example, we find a separable C∗dash-algebra in the bootstrap class over a certain five......-point space, the filtrated K-theory of which has projective dimension 3. Finally, as an application of our investigations, we exhibit Cuntz-Krieger algebras which have projective dimension 2 in filtrated K-theory over their respective primitive spectrum....

Phosphate binding by natural iron-rich colloids in streams

NARCIS (Netherlands)

Baken, S.; Moens, C.; Griffioen, J.J.; Smolders, E.

2016-01-01

Phosphorus (P) in natural waters may be bound to iron (Fe) bearing colloids. However, the natural variation in composition and P binding strength of these colloids remain unclear. We related the composition of "coarse colloids" (colloids in the 0.1-1.2 μm size range) in 47 Belgian streams to the

Microbial effects on colloidal agglomeration

International Nuclear Information System (INIS)

Hersman, L.

1995-11-01

Colloidal particles are known to enhance the transport of radioactive metals through soil and rock systems. This study was performed to determine if a soil microorganism, isolated from the surface samples collected at Yucca Mountain, NV, could affect the colloidal properties of day particles. The agglomeration of a Wyoming bentonite clay in a sterile uninoculated microbial growth medium was compared to the agglomeration in the medium inoculated with a Pseudomonas sp. In a second experiment, microorganisms were cultured in the succinate medium for 50 h and removed by centrifugation. The agglomeration of the clay in this spent was compared to sterile uninoculated medium. In both experiments, the agglomeration of the clay was greater than that of the sterile, uninoculated control. Based on these results, which indicate that this microorganism enhanced the agglomeration of the bentonite clay, it is possible to say that in the presence of microorganisms colloidal movement through a rock matrix could be reduced because of an overall increase in the size of colloidal particle agglomerates. 32 refs

Air filtration in HVAC systems

CERN Document Server

Ginestet, Alain; Tronville, Paolo; Hyttinen, Marko

2010-01-01

Air filtration Guidebook will help the designer and user to understand the background and criteria for air filtration, how to select air filters and avoid problems associated with hygienic and other conditions at operation of air filters. The selection of air filters is based on external conditions such as levels of existing pollutants, indoor air quality and energy efficiency requirements.

Active osmotic exchanger for advanced filtration at the nano scale

Science.gov (United States)

Marbach, Sophie; Bocquet, Lyderic

2015-11-01

One of the main functions of the kidney is to remove the waste products of an organism, mostly by excreting concentrated urea while reabsorbing water and other molecules. The human kidney is capable of recycling about 200 liters of water per day, at the relatively low cost of 0.5 kJ/L (standard dialysis requiring at least 150 kJ/L). Kidneys are constituted of millions of parallel filtration networks called nephrons. The nephrons of all mammalian kidneys present a specific loop geometry, the Loop of Henle, that is believed to play a key role in the urinary concentrating mechanism. One limb of the loop is permeable to water and the other contains sodium pumps that exchange with a common interstitium. In this work, we take inspiration from this osmotic exchanger design to propose new nanofiltration principles. We first establish simple analytical results to derive general operating principles, based on coupled water permeable pores and osmotic pumps. The best filtration geometry, in terms of power required for a given water recycling ratio, is comparable in many ways to the mammalian nephron. It is not only more efficient than traditional reverse osmosis systems, but can also work at much smaller pressures (of the order of the blood pressure, 0.13 bar, as compared to more than 30 bars for pressure-retarded osmosis systems). We anticipate that our proof of principle will be a starting point for the development of new filtration systems relying on the active osmotic exchanger principle.

Colloid transport in porous media: impact of hyper-saline solutions.

Science.gov (United States)

Magal, Einat; Weisbrod, Noam; Yechieli, Yoseph; Walker, Sharon L; Yakirevich, Alexander

2011-05-01

The transport of colloids suspended in natural saline solutions with a wide range of ionic strengths, up to that of Dead Sea brines (10(0.9) M) was explored. Migration of microspheres through saturated sand columns of different sizes was studied in laboratory experiments and simulated with mathematical models. Colloid transport was found to be related to the solution salinity as expected. The relative concentration of colloids at the columns outlet decreased (after 2-3 pore volumes) as the solution ionic strength increased until a critical value was reached (ionic strength > 10(-1.8) M) and then remained constant above this level of salinity. The colloids were found to be mobile even in the extremely saline brines of the Dead Sea. At such high ionic strength no energetic barrier to colloid attachment was presumed to exist and colloid deposition was expected to be a favorable process. However, even at these salinity levels, colloid attachment was not complete and the transport of ∼ 30% of the colloids through the 30-cm long columns was detected. To further explore the deposition of colloids on sand surfaces in Dead Sea brines, transport was studied using 7-cm long columns through which hundreds of pore volumes were introduced. The resulting breakthrough curves exhibited a bimodal shape whereby the relative concentration (C/C(0)) of colloids at the outlet rose to a value of 0.8, and it remained relatively constant (for the ∼ 18 pore volumes during which the colloid suspension was flushed through the column) and then the relative concentration increased to a value of one. The bimodal nature of the breakthrough suggests different rates of colloid attachment. Colloid transport processes were successfully modeled using the limited entrapment model, which assumes that the colloid attachment rate is dependent on the concentration of the attached colloids. Application of this model provided confirmation of the colloid aggregation and their accelerated attachment during

Suspensions of colloidal particles and aggregates

CERN Document Server

Babick, Frank

2016-01-01

This book addresses the properties of particles in colloidal suspensions. It has a focus on particle aggregates and the dependency of their physical behaviour on morphological parameters. For this purpose, relevant theories and methodological tools are reviewed and applied to selected examples. The book is divided into four main chapters. The first of them introduces important measurement techniques for the determination of particle size and interfacial properties in colloidal suspensions. A further chapter is devoted to the physico-chemical properties of colloidal particles—highlighting the interfacial phenomena and the corresponding interactions between particles. The book’s central chapter examines the structure-property relations of colloidal aggregates. This comprises concepts to quantify size and structure of aggregates, models and numerical tools for calculating the (light) scattering and hydrodynamic properties of aggregates, and a discussion on van-der-Waals and double layer interactions between ...

Measurement and characterization of filtration efficiencies for prefilter materials used in aerosol filtration

International Nuclear Information System (INIS)

Sciortino, J.

1991-01-01

In applications where the filtration of large quantities of mixed (liquid and solid) aerosols is desired, a multistage filtration system is often employed. This system consists of a prefilter, a High Efficiency Particulate Air (HEPA) filter, and any number of specialized filters particular to the filtration application. The prefilter removes liquids and any large particles from the air stream, keeping them from prematurely loading the HEPA filter downstream. The HEPA filter eliminates 99.97% of all particulates in the aerosol. The specialized filters downstream of the HEPA filter can be used to remove organic volatiles or other vapors. While the properties of HEPA filters have been extensively investigated, literature characterizing the prefilter is scarce. The purpose of this report is to characterize the efficiency of the prefilter as a function of particle size, nature of the particle (solid or liquid), and the gas flow rate across the face of the prefilter. 1 ref., 4 figs

Size determinations of plutonium colloids using autocorrelation photon spectroscopy

International Nuclear Information System (INIS)

Triay, I.R.; Rundberg, R.S.; Mitchell, A.J.; Ott, M.A.; Hobart, D.E.; Palmer, P.D.; Newton, T.W.; Thompson, J.L.

1989-01-01

Autocorrelation Photon Spectroscopy (APS) is a light-scattering technique utilized to determine the size distribution of colloidal suspensions. The capabilities of the APS methodology have been assessed by analyzing colloids of known sizes. Plutonium(IV) colloid samples were prepared by a variety of methods including: dilution; peptization; and alpha-induced auto-oxidation of Pu(III). The size of theses Pu colloids was analyzed using APS. The sizes determined for the Pu colloids studied varied from 1 to 370 nanometers. 7 refs., 5 figs., 3 tabs

Silica colloids and their effect on radionuclide sorption. A literature review

International Nuclear Information System (INIS)

Hoelttae, P.; Hakanen, M.

2008-05-01

Silica sol, commercial colloidal silica manufactured by Eka Chemicals in Bohus, Sweden is a promising inorganic grout material for sealing small fractures in low permeable rock. This literature review collects information about the use of silica sol as an injection grout material, the properties of inorganic, especially silica colloids, colloid contents in granitic groundwater conditions, essential characterization methods and colloid-mediated transport of radionuclides. Objective was to evaluate the release and mobility of silica sol colloids, the effect of the groundwater conditions, the amount of colloids compared with natural colloids in Olkiluoto conditions, radionuclide sorption on colloids and their contribution to radionuclide transport. Silica sol seems to be a feasible material to seal fractures with an aperture as small as 10 μm in low permeable rock. The silica sol gel is sufficiently stable to limit to water ingress during the operational phase, the requirement that the pH should be below 11 is fulfilled and the compatibility with Engineered Barrier System (EBS) materials is expected to be good. No significant influence on the bentonite properties caused by the silica sol is expected when calcium chloride is used as an accelerator but the influence of sodium chloride has not been examined. No significant release of colloids is expected under prevailing groundwater conditions. The long-term (100 y) stability of silica sol gel has not yet been clearly demonstrated and a long-term release of silica colloids cannot be excluded. The question is the amount of colloids, how mobile they are and the influence of possible glacial melt waters. The bentonite buffer used in the EBS system is assumed to be a potential source of colloids. In a study in Olkiluoto, bentonite colloids were found only in low salinity groundwater. In general, low salinity water (total dissolved solids -1 ) favours colloid stability and bentonite colloids can remain stable over long

Determination of radiochemical purity and pharmacokinetic parameters of sup(99m)Tc-sulphur colloid and sup(99m)Tc-tin colloid

International Nuclear Information System (INIS)

Jovanovic, V.; Konstantinovska, D.; Milivojevic, K.; Bzenic, J.

1981-01-01

Labelling yield and radiochemical purity, higher than 95%, of sup(99m)Tc-colloid preparations were determined by using the paper chromatography method. Less than 3% of labelled citric acid, added to the preparation as a buffer solution, has been found in sup(99m)Tc-sulphur colloid. High radiochemical purity and optimum size of colloid particles has also been proved by biodistribution studies on experimental animals. The analysis performed has shown that more than 50% of sup(99m)Tc-colloid preparations excreted by urine is sup(99m)TcO - , the remaining past 50% being protein bound sup(99m)Tc. Biological half-time of excretion of the fast phase is the same for both preparations, i.e. 10 min, while for the slow component it is 120 min in sup(99m)Tc-S-colloid and 160 min in sup(99m)Tc-Sn colloid. (orig.) [de

Analysis report for WIPP colloid model constraints and performance assessment parameters

Energy Technology Data Exchange (ETDEWEB)

Mariner, Paul E.; Sassani, David Carl

2014-03-01

An analysis of the Waste Isolation Pilot Plant (WIPP) colloid model constraints and parameter values was performed. The focus of this work was primarily on intrinsic colloids, mineral fragment colloids, and humic substance colloids, with a lesser focus on microbial colloids. Comments by the US Environmental Protection Agency (EPA) concerning intrinsic Th(IV) colloids and Mg-Cl-OH mineral fragment colloids were addressed in detail, assumptions and data used to constrain colloid model calculations were evaluated, and inconsistencies between data and model parameter values were identified. This work resulted in a list of specific conclusions regarding model integrity, model conservatism, and opportunities for improvement related to each of the four colloid types included in the WIPP performance assessment.

Review on influences of colloids on geologic disposal of high level radioactive waste. For better understanding of natural colloidal materials

International Nuclear Information System (INIS)

Kanai, Yutaka; Suzuki, Masaya; Kamioka, Hikari; Yoshida, Takahiro; Suko, Takeshi

2007-01-01

Although the influences of colloidal materials on radionuclide transport in geological media are pointed out, their behaviors in natural environment have not yet been well elucidated and therefore their influences on the geologic disposal of high-level radioactive waste (HLW) are not fully estimated quantitatively. This paper reviewed the studies on natural colloids, especially focused on inorganic, organic and biological colloids, and discussed the future works to be carried out. Much attention should be paid to the sampling and analysis. Excellent techniques for in-situ observation, concentration without changing the state of colloid, standard procedure for analysis, are necessary to be developed. More research studies on the behaviors of colloids are required in not only far- and near-fields but also items on effects of the environments and its evolution. (author)

EM Task 9 - Centrifugal membrane filtration

International Nuclear Information System (INIS)

Stepan, Daniel J.; Stevens, Bradley G.; Hetland, Melanie D.

1999-01-01

The overall project consists of several integrated research phases related to the applicability, continued development, demonstration, and commercialization of the SpinTek centrifugal membrane filtration process. Work performed during this reporting period consisted of Phase 2 evaluation of the SpinTek centrifugal membrane filtration technology and Phase 3, Technology Partnering. During Phase 1 testing conducted at the EERC using the SpinTek ST-IIL unit operating on a surrogate tank waste, a solids cake developed on the membrane surface. The solids cake was observed where linear membrane velocities were less than 17.5 ft/s and reduced the unobstructed membrane surface area up to 25%, reducing overall filtration performance. The primary goal of the Phase 2 research effort was to enhance filtration performance through the development and testing of alternative turbulence promoter designs. The turbulence promoters were designed to generate a shear force across the entire membrane surface sufficient to maintain a self-cleaning membrane capability and improve filtration efficiency and long-term performance. Specific Phase 2 research activities included the following: System modifications to accommodate an 11-in.-diameter, two-disk rotating membrane assembly; Development and fabrication of alternative turbulence promoter designs; Testing and evaluation of the existing and alternative turbulence promoters under selected operating conditions using a statistically designed test matrix; and Data reduction and analysis; The objective of Phase 3 research was to demonstrate the effectiveness of SpinTek's centrifugal membrane filtration as a pretreatment to remove suspended solids from a liquid waste upstream of 3M's WWL cartridge technology for the selective removal of technetium (Tc)

Cation colloidal particles in alkaline-earth halides

Energy Technology Data Exchange (ETDEWEB)

Alcala, R; Orera, V M [Zaragoza Univ. (Spain). Facultad da Ciencias

1976-01-01

The formation of calcium, strontium and barium colloids both in heavily electron irradiated samples and in additively colored crystals of CaF/sub 2/, SrF/sub 2/ and BaF/sub 2/ has been investigated. Detailed data on the temperature dependence of the efficiency of colloid formation by irradiation have been obained. The growth of metallic particles in additively colored samples containing F and M centers has been studied for different color center concentrations and annealing temperatures. The optical absorption bands due to metallic colloids have been calculated using the theory of Mie. To take account of the pressure exerted by the matrix on the metallic particles several corrections to the optical constants of the metals have been introduced. A good agreement between theoretical calculations and experimental results has been obtained. The evolution of colloids along several thermal annealing experiments has also been investigated. A diffusion-limited model has been used which accounts for the dependence of the colloid radii with the annealing time.

Vibrating membrane filtration as improved technology for microalgae dewatering.

Science.gov (United States)

Nurra, Claudia; Clavero, Ester; Salvadó, Joan; Torras, Carles

2014-04-01

The effect of shear-enhanced filtration by vibratory process in microalgae dewatering is presented in this paper. The aim of this research was to investigate the technical performance and improvement of vibrating membrane filtration compared with conventional tangential cross-flow filtration in microalgae concentration. An industrial-scale available commercial set-up was used. Several membrane materials as polyethersulfone, polyacrylonitrile, etc., and mean pore sizes (from 7000Da to 0.2μm) were tested and compared in both filtration set-ups. Experiments were carried-out with Nannochloropsis gaditana and Phaeodactylum tricornutum microalgae. It has been demonstrated that, even if the choice of the membrane depends on its cut-off, its material and the type of microalgae filtrated, dynamic filtration is always the best technology over a conventional one. If with conventional filtration permeability values were in the vicinity of 10L/h/m(2)/bar in steady state phase, with dynamic filtration these values increased to 30L/h/m(2)/bar or more. Copyright © 2014 Elsevier Ltd. All rights reserved.

Simulating colloid hydrodynamics with lattice Boltzmann methods

International Nuclear Information System (INIS)

Cates, M E; Stratford, K; Adhikari, R; Stansell, P; Desplat, J-C; Pagonabarraga, I; Wagner, A J

2004-01-01

We present a progress report on our work on lattice Boltzmann methods for colloidal suspensions. We focus on the treatment of colloidal particles in binary solvents and on the inclusion of thermal noise. For a benchmark problem of colloids sedimenting and becoming trapped by capillary forces at a horizontal interface between two fluids, we discuss the criteria for parameter selection, and address the inevitable compromise between computational resources and simulation accuracy

Evaluation of the liver scintigraphy with /sup 99m/Tc-Sn-colloid. II. C Clinical studies by comparison with /sup 198/Au-colloid

Energy Technology Data Exchange (ETDEWEB)

Kimura, K; Nishimura, T; Takeda, H; Furukawa, T [Osaka Univ. (Japan). Faculty of Medicine; Kajiya, Fumihiko

1975-08-01

Clinical significance of the liver scintigraphy with sup(99m)Tc-Sn-colloid was evaluated in comparison with those with /sup 198/Au-colloid. The liver scintigrams with sup(99m)Tc-Sn-colloid and /sup 198/Au-colloid were done in 36 cases of various hepatic diseases and RI accumulation curves in the liver and the spleen, and the blood disapearance curves were also obtained. The conclusions were as follows. The liver scintigrams with sup(99m)Tc-Sn-colloid proved to be more sensitive in the detection of tumors, especially, in the lower margin, left lobe and superficial layers of the liver than those with /sup 198/Au-colloid. In all cases, including normal and cirrhotic subjects, visualizations of the spleen were seen on the scintigrams with sup(99m)Tc-Sn-colloid. In diffuse hepatic diseases, comparing both radiopharmaceuticals, the splenic accumulations were studied qualitatively and quantitatively. As a result, the ratio (spleen/liver) was thought to be useful for the differentiation of diffuse hepatic diseases concerned with splenic function and/or size. It was also shown that sup(99m)Tc-Sn-colloid was useful as a spleen scanning agent. The Tl/2 in the liver accumulation curves with sup(99m)Tc-Sn-colloid were not as clearly differentiated in the various hepatic diseases as those with /sup 198/Au-colloid where those indexes were useful in the evaluation of liver functions.

Investigation on the Stability of Aluminosilicate Colloids by Various Analytical Tools

Energy Technology Data Exchange (ETDEWEB)

Putri, Kirana Y.; Lee, D. H.; Yun, J. I. [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

2010-05-15

Colloids are ubiquitous in natural aquatic systems. Aquatic colloids may play a significant carrier role for radionuclide migration in aquifer systems. Being omnipresent in natural aquatic systems, aluminosilicate colloids are considered as a kernel for various aquatic colloids. Characterization of aluminosilicate colloids formed under various geochemical conditions is of importance to understand their chemical behavior in natural aquatic systems. In this work, a preliminary study on the formation of aluminosilicate colloids with a help of colorimetry and other colloid detection techniques is presented

The effect of filter cake viscoelasticity on filtration

DEFF Research Database (Denmark)

Christensen, Morten Lykkegaard

, it is difficult to use the existing mathematical filtration models to simulate and optimise the filtration process. Activated sludge as well as synthetic model particles has been filtrated in this project. The study shows that compression of the formed filter cake is a time dependent process, and not only...

40 CFR 141.71 - Criteria for avoiding filtration.

Science.gov (United States)

2010-07-01

... PROGRAMS (CONTINUED) NATIONAL PRIMARY DRINKING WATER REGULATIONS Filtration and Disinfection § 141.71 Criteria for avoiding filtration. A public water system that uses a surface water source must meet all of...)(C)(iii), that filtration is required. A public water system that uses a ground water source under...

Entropy favours open colloidal lattices

Science.gov (United States)

Mao, Xiaoming; Chen, Qian; Granick, Steve

2013-03-01

Burgeoning experimental and simulation activity seeks to understand the existence of self-assembled colloidal structures that are not close-packed. Here we describe an analytical theory based on lattice dynamics and supported by experiments that reveals the fundamental role entropy can play in stabilizing open lattices. The entropy we consider is associated with the rotational and vibrational modes unique to colloids interacting through extended attractive patches. The theory makes predictions of the implied temperature, pressure and patch-size dependence of the phase diagram of open and close-packed structures. More generally, it provides guidance for the conditions at which targeted patchy colloidal assemblies in two and three dimensions are stable, thus overcoming the difficulty in exploring by experiment or simulation the full range of conceivable parameters.

Patterned Colloidal Photonic Crystals.

Science.gov (United States)

Hou, Jue; Li, Mingzhu; Song, Yanlin

2018-03-01

Colloidal photonic crystals (PCs) have been well developed because they are easy to prepare, cost-effective, and versatile with regards to modification and functionalization. Patterned colloidal PCs contribute a novel approach to constructing high-performance PC devices with unique structures and specific functions. In this review, an overview of the strategies for fabricating patterned colloidal PCs, including patterned substrate-induced assembly, inkjet printing, and selective immobilization and modification, is presented. The advantages of patterned PC devices are also discussed in detail, for example, improved detection sensitivity and response speed of the sensors, control over the flow direction and wicking rate of microfluidic channels, recognition of cross-reactive molecules through an array-patterned microchip, fabrication of display devices with tunable patterns, well-arranged RGB units, and wide viewing-angles, and the ability to construct anti-counterfeiting devices with different security strategies. Finally, the perspective of future developments and challenges is presented. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The influence of colloids on the migration of radionuclides

International Nuclear Information System (INIS)

Seher, Holger

2011-01-01

For a concept of deep geological disposal of high level nuclear waste, the repository will be designed as a multiple-barrier system including bentonite as the buffer/backfill material and the host rock formation as the geological barrier. The engineered barrier (compacted bentonite) will be in contact with the host rock formation (e.g. granite). Consequently the bentonite will be saturated over time with formation groundwater, which will induce swelling and gel formation of the bentonite. At the gel-groundwater boundary, colloid detachment might be a possible colloid source and therefore might enhance the mobility of strong sorbing actinides. This work will focus on three aspects of colloidal transport: (a) Colloid stability in the mixing zone between granite groundwater and bentonite pore water, including its description with an extended DLVO model. (b) Colloid generation and erosion of the bentonite at the interface between compacted bentonite and granitic groundwater, as well as formation of new colloids in the mixing zone between the bentonite porewater and the granitic groundwater. (c) Colloid transport and the interaction of U, Th, Hf, Tb, Eu and Cm with bentonite colloids and fracture filling material, as well as their mobility in a natural fracture.

Relation Between Filtration and Soil Consolidation Theories

OpenAIRE

Strzelecki Tomasz; Strzelecki Michał

2015-01-01

This paper presents a different, than commonly used, form of equations describing the filtration of a viscous compressible fluid through a porous medium in isothermal conditions. This mathematical model is compared with the liquid flow equations used in the theory of consolidation. It is shown that the current commonly used filtration model representation significantly differs from the filtration process representation in Biot’s and Terzaghi’s soil consolidation models, which has a bearing on...

Hydrodynamic interactions in active colloidal crystal microrheology

OpenAIRE

Weeber, R; Harting, JDR Jens

2012-01-01

In dense colloids it is commonly assumed that hydrodynamic interactions do not play a role. However, a found theoretical quantification is often missing. We present computer simulations that are motivated by experiments where a large colloidal particle is dragged through a colloidal crystal. To qualify the influence of long-ranged hydrodynamics, we model the setup by conventional Langevin dynamics simulations and by an improved scheme with limited hydrodynamic interactions. This scheme signif...

Characterization of Complex Colloidal Suspensions

Science.gov (United States)

Seaman, J. C.; Guerin, M.; Jackson, B. P.; Ranville, J. M.

2003-04-01

Surface chemical reactions play a major role in controlling contaminant fate and transport in the subsurface environment. Recent field and laboratory evidence suggests that mobile soil and groundwater colloids may facilitate the migration of sparingly soluble groundwater contaminants. Colloidal suspensions collected in the field or generated in laboratory column experiments tend to be fairly dilute in nature and comprised of relatively small particulates (reserved for studying ideal systems to the characterization of mobile colloids. However, many of these analytical techniques, including total/selective dissolution methods, dynamic light scattering, micro-electrophoresis, streaming potential, and even scanning electron microscopy (SEM), can be biased in of larger size fractions, and therefore, extremely sensitive to sampling, storage, and fractionation artifacts. In addition, surface modifiers such as sorbed oxides or organics can alter particulate appearance, composition, and behavior when compared to synthetic analogues or mineral standards. The current presentation will discuss the limitations and inherent biases associated with a number of analytical characterization techniques that are commonly applied to the study of mobile soil and groundwater colloids, including field flow fractionation (FFF) and acoustic based methods that have only recently become available.

Extraction and characterisation of colloids in waste repository leachate

International Nuclear Information System (INIS)

Verrall, K.E.

1998-10-01

Inorganic colloids are ubiquitous in environmental waters and are thought to be potential transporters of radionuclides and other toxic metals. Colloids present large surface areas to pollutants and contaminants present in waters and are therefore capable of sorbing and transporting them via groundwater and surface water movement. Much research has been and is currently being undertaken to understand more fully the stability of colloids in different water chemistries, factors which affect metal sorption onto colloids, and the processes which affect metal-colloid transport. This thesis first investigates groundwater and surface water sampling and characterisation techniques for the investigation of the colloids present in and around a low-level waste repository. Samples were collected anaerobically using micro-purge low-flow methodology (MPLF) and then subjected to sequential ultrafiltration, again anaerobically. After separation into size fractions the solids were analysed for radiochemical content, colloid population and morphology. It was found that colloids were present in large numbers in the groundwaters extracted from the trench waste burial area (anaerobic environment), but in the surface drain waters (aerobic environment) colloid population was comparable to levels found in waters extracted from above the trenches. There was evidence that the non-tritium activity was associated with the colloids and particulates in the trenches, but outside of the trenches the evidence was not conclusive because the activity and colloid concentrations were low. Secondly this thesis investigates the stability of inorganic colloids, mainly haematite, in the presence of humic acid, varying pH and electrolyte concentrations. The applicability of the SchuIze-Hardy rule to haematite and haematite/humic acid mixtures was investigated using photon correlation spectroscopy to measure the rate of fast and slow coagulation after the addition of mono, di and trivalent ions. It was

Bonding assembled colloids without loss of colloidal stability

NARCIS (Netherlands)

Vutukuri, H.R.; Stiefelhagen, J.C.P.; Vissers, T; Imhof, A.; van Blaaderen, A.

2012-01-01

In recent years the diversity of self-assembled colloidal structures has strongly increased, as it is fueled by a wide range of applications in materials science and also in soft condensed-matter physics.[1–4] Some potential applications include photonic bandgap (PBG) crystals, materials for

Real-time observation of template-assisted colloidal aggregation and colloidal dispersion under an alternating electric field

International Nuclear Information System (INIS)

Chao-Rong, Li; Shu-Wen, Li; Jie, Mei; Qing, Xu; Ying-Ying, Zheng; Wen-Jun, Dong

2011-01-01

A fascinating colloid phenomenon was observed in a specially designed template-assisted cell under an alternating electrical field. Most colloidal particles experienced the processes of aggregation, dispersion and climbing up to the plateaus of the patterns pre-lithographed on the indium tin oxide glass as the frequency of the alternating electrical field increased. Two critical frequencies f crit1 ≈ 15 kHz and f crit2 ≈ 40 kHz, corresponding to the transitions of the colloid behaviour were observed. When f < 15 kHz, the particles were forced to aggregate along the grooves of the negative photoresist patterned template. When 15 kHz < f < 40 kHz, the particle clusters became unstable and most particles started to disperse and were blocked by the fringes of the negative photoresist patterns. As the frequency increased to above 40 kHz, the majority of particles started to climb up to the plateaus of the patterns. Furthermore, the dynamics analysis for the behaviour of the colloids was given and we found out that positive or negative dielectrophoresis force, electrohydrodynamic force, particle—particle interactions and Brownian motion change with the frequency of the alternating electric field. Thus, changes of the related forces affect or control the behaviour of the colloids. (interdisciplinary physics and related areas of science and technology)

Colloid Mobilization in Two Atlantic Coastal Plain Aquifers: Field Studies

Science.gov (United States)

Ryan, Joseph N.; Gschwend, Philip M.

1990-02-01

The geochemical mechanisms leading to the mobilization of colloids in groundwater were investigated in the Pine Barrens of New Jersey and in rural central Delaware by sampling pairs of wells screened in oxic and anoxic groundwaters in the same geologic formations. Samples were carefully taken at very low flow rates (˜100 mL min-1) to avoid suspending immobilized particles. The colloidal matter was characterized by light-scattering photometry, scanning electron microscopy, energy-dispersive X ray analysis, microelectrophoresis, and Fe, Al, Si, and organic carbon analyses. The colloids, composed primarily of clays, were observed at high concentrations (up to 60 mg colloids/L) in the anoxic groundwaters, while the oxic groundwaters exhibited ≤1 mg colloids/L. Colloidal organic carbon was present in all groundwaters; but under anoxic conditions, one-third to one-half of the total organic carbon was associated with the inorganic colloids. The field evidence indicates that anoxic conditions cause the mobilization of soil colloids by dissolving the ferric oxyhydroxide coatings cementing the clay particles to the aquifer solids. The depletion of oxidized iron on the surfaces of immobile particles and the addition of organic carbon coatings on the soil particles and colloids apparently stabilizes the colloidal suspension in the anoxic groundwaters.

Rotating Ceramic Water Filter Discs System for Water Filtration

Directory of Open Access Journals (Sweden)

Riyadh Z. Al Zubaidy

2017-04-01

Full Text Available This work aimed to design, construct and operate a new laboratory scale water filtration system. This system was used to examine the efficiency of two ceramic filter discs as a medium for water filtration. These filters were made from two different ceramic mixtures of local red clay, sawdust, and water. The filtration system was designed with two rotating interfered modules of these filters. Rotating these modules generates shear force between water and the surfaces of filter discs of the filtration modules that works to reduce thickness of layer of rejected materials on the filters surfaces. Each module consists of seven filtration units and each unit consists of two ceramic filter discs. The average measured hydraulic conductivity of the first module was 13.7mm/day and that for the second module was 50mm/day. Results showed that the water filtration system can be operated continuously with a constant flow rate and the filtration process was controlled by a skin thin layer of rejected materials. The ceramic water filters of both filtration modules have high removal efficiency of total suspended solids up to 100% and of turbidity up to 99.94%.

Colloid cyst in pituitary gland: a case report

International Nuclear Information System (INIS)

Koo, Hee Youn; Lee, Myung Jun; Lee, Chang Joon; Yoo, Jeong Hyun

2001-01-01

Colloid cyst is a congenital lesion which is thought to be derived from the primitive neuro epithelium, and is most frequently located in the anterior half of the third ventricle. Colloid cysts rarely occur in the pituitary gland, and we describe a case of pituitary colloid cyst, including the CT, MRI and pathologic findings

Sodium caseinate stabilized zein colloidal particles.

Science.gov (United States)

Patel, Ashok R; Bouwens, Elisabeth C M; Velikov, Krassimir P

2010-12-08

The present work deals with the preparation and stabilization of zein colloidal particles using sodium caseinate as electrosteric stabilizer. Colloidal particles with well-defined size range (120-150 nm) and negative surface potential (-29 to -47 mV) were obtained using a simple antisolvent precipitation method. Due to the presence of caseinate, the stabilized colloidal particles showed a shift of isoelectric point (IEP) from 6.0 to around pH 5.0 and thus prevent the aggregation of zein near its native IEP (pH 6.2). The particles also showed good stability to varying ionic strength (15 mM-1.5 M NaCl). Furthermore, stabilized particles retained the property of redispersibility after drying. In vitro protein hydrolysis study confirmed that the presence of caseinate did not alter the digestibility of zein. Such colloidal particles could potentially serve as all-natural delivery systems for bioactive molecules in food, pharmaceutical, and agricultural formulations.

Linear Optical Properties of Gold Colloid

Directory of Open Access Journals (Sweden)

Jingmin XIA

2015-11-01

Full Text Available Gold colloid was prepared by reducing HAuCl4·4H2O with Na3C6H5O7·2H2O. The morphology, size of gold nanoparticles and the optical property of colloid were characterized by transmission electron microscope and UV-Vis spectrophotometer, respectively. It shows that the gold nanoparticles are in the shape of spheres with diameters less than 8 nm, and the surface plasmon resonance absorption peak is located at about 438 nm. As the volume fraction of gold particles increases, the intensity of absorption peak strengthens. The optical property of gold colloid was analyzed by Maxwell-Garnett (MG effective medium theory in the company of Drude dispersion model. The results show that the matrix dielectric constant is a main factor, which influences the optical property of gold colloid.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9558

Solid colloids with surface-mobile linkers

International Nuclear Information System (INIS)

Van der Meulen, Stef A J; Helms, Gesa; Dogterom, Marileen

2015-01-01

In this report we review the possibilities of using colloids with surface mobile linkers for the study of colloidal self-assembly processes. A promising route to create systems with mobile linkers is the use of lipid (bi-)layers. These lipid layers can be either used in the form of vesicles or as coatings for hard colloids and emulsion droplets. Inside the lipid bilayers molecules can be inserted via membrane anchors. Due to the fluidity of the lipid bilayer, the anchored molecules remain mobile. The use of different lipid mixtures even allows creating Janus-like particles that exhibit directional bonding if linkers are used which have a preference for a certain lipid phase. In nature mobile linkers can be found e.g. as receptors in cells. Therefore, towards the end of the review, we also briefly address the possibility of using colloids with surface mobile linkers as model systems to mimic cell–cell interactions and cell adhesion processes. (topical review)

Salt disposition alternatives filtration at SRTC

International Nuclear Information System (INIS)

Walker, B. W.; Hobbs, D.

2000-01-01

Several of the prospective salt disposition alternative technologies require a monosodium titanate (MST) contact to remove strontium and actinides from inorganic salt solution feedstock. This feedstock also contains sludge solids from waste removal operations and may contain defoamers added in the evaporator systems. Filtration is required to remove the sludge and MST solids before sending the salt solution for further processing. This report describes testing performed using the Parallel Theological Experimental Filter (PREF). The PREF contains two single tube Mott sintered metal crossflow filters. For this test one filter was isolated so that the maximum velocities could be achieved. Previous studies showed slurries of MST and sludge in the presence of sodium tetraphenylborate (NaTPB) were filterable since the NaTPB slurry formed a filter cake which aided in removing the smaller MST and sludge particles. Some of the salt disposition alternative technologies do not use NaTPB raising the question of how effective crossflow filtration is with a feed stream containing only sludge and MST. Variables investigated included axial velocity, transmembrane pressure, defoamer effects, and solids concentration (MST and sludge). Details of the tests are outlined in the technical report WSRC-RP-98-O0691. Key conclusions from this study are: (1) Severe fouling of the Mott sintered metal filter did not occur with any of the solutions filtered. (2) The highest fluxes, in the range of .46 to 1.02 gpm/f 2 , were obtained when salt solution decanted from settled solids was fed to the filter. These fluxes would achieve 92 to 204 gpm filtrate production for the current ITP filters. The filtrate fluxes were close to the flux of 0.42 gpm/f 2 reported for In Tank Precipitation Salt Solution by Morrisey. (3) For the range of solids loading studied, the filter flux ranged from .04 to .17 gpm/f 2 which would result in a filtrate production rate of 9 to 31 gpm for the current HP filter. (4

Filtration Systems Design for Universal Oils in Agricultural Tractors

Directory of Open Access Journals (Sweden)

R. Majdan

2017-12-01

Full Text Available Three filtration systems using the tractor hydraulic circuit were proposed and verified during the tractors operation. Using the tractor-implement hydraulic system and filter body with accessories the universally useful filtration systems were designed. The designed filtration systems are the second stage of universal oil filtration whereas the first stage is the standard tractor filter. The decrease in the content of iron reached the values 25.53 %, 32.95 % and 41.55 % and the average decrease in oil contamination characterized by average value of decrease in content of iron, copper and silicium reached values 24.3 %, 24.7 % and 35.53 % in dependence on the filtration system and an oil contamination level. The decrease in contamination level verified the ability of designed filtration systems for agricultural tractors.

Evaluation of sup(99m)Tc-Sn-colloid on liver scintigram

Energy Technology Data Exchange (ETDEWEB)

Matsuyuki, Y; Kanao, K; Honda, M; Ishihara, S [Sumitomo Hospital, Osaka (Japan)

1975-04-01

sup(99m)Tc-Sn-colloid injectable solution and Sn-colloid preparation set were used for nuclear medical examination of the liver and their efficiency was discussed. Both sup(99m)Tc-Sn-colloid injectable solution and Sn-colloid preparation set showed the same kinetics in vivo, and the sup(99m)Tc-Sn-colloid rapidly disappeared from the serum and concentrated to the liver and spleen. Comparing /sup 198/Au-colloid, sup(99m)Tc-Sn-colloid could be increased the administration dose, and provided easy examination within short time period, easy observation from multiple directions, and improvement of resolution by scinticamera. Imaging of the spleen with sup(99m)Tc-Sn-colloid was slightly superior to that with sup(99m)Tc-sulfur-colloid. sup(99m)Tc-Sn-colloid injectable solution which required no procedure of labeling was evaluated as the most safe and easy technique. Side effects were not recognized. As the results, already made preparation, such as sup(99m)Tc-Sn-colloid injectable solution, which provided easy preparation with less absorbed dose of the tissue and high resolution would be frequently required.

Evaluation of sup(99m)Tc-Sn-colloid on liver scintigram

International Nuclear Information System (INIS)

Matsuyuki, Yoshihiko; Kanao, Keisuke; Honda, Minoru; Ishihara, Shizumori

1975-01-01

sup(99m)Tc-Sn-colloid injectable solution and Sn-colloid preparation set were used for nuclear medical examination of the liver and their efficiency was discussed. Both sup(99m)Tc-Sn-colloid injectable solution and Sn-colloid preparation set showed the same kinetics in vivo, and the sup(99m)Tc-Sn-colloid rapidly disappeared from the serum and concentrated to the liver and spleen. Comparing 198 Au-colloid, sup(99m)Tc-Sn-colloid could be increased the administration dose, and provided easy examination within short time period, easy observation from multiple directions, and improvement of resolution by scinticamera. Imaging of the spleen with sup(99m)Tc-Sn-colloid was slightly superior to that with sup(99m)Tc-sulfur-colloid. sup(99m)Tc-Sn-colloid injectable solution which required no procedure of labeling was evaluated as the most safe and easy technique. Side effects were not recognized. As the results, already made preparation, such as sup(99m)Tc-Sn-colloid injectable solution, which provided easy preparation with less absorbed dose of the tissue and high resolution would be frequently required. (Mukohata, S.)

Factorial analysis of the trihalomethane formation in the reaction of colloidal, hydrophobic, and transphilic fractions of DOM with free chlorine.

Science.gov (United States)

Platikanov, Stefan; Tauler, Roma; Rodrigues, Pedro M S M; Antunes, Maria Cristina G; Pereira, Dilson; Esteves da Silva, Joaquim C G

2010-09-01

analysis of the fractions, is important issue in the revealing of the quality and quantity characteristics of DOM. Systematic study composed from DOM fraction investigation and factorial analysis of the responsible parameters in the THM formation reaction can, after an evaluation of the adjustment of the models with the reality, serves well for the evaluation of the spatial and temporal variability in the THM formation in dependence of DOM. However, taking into consideration the natural complexity of DOM, different operations and a strict control of them (like coagulation/flocculation and filtration) has to be used to quantitatively remove DOM from the raw water. Assuming that this study represents a local case study, similar experiments can be easily applied and will supply with relevant information every local water treatment plant meeting problems with THM formation. The coagulation/flocculation and the filtration stages are the main mechanisms to remove DOM, particularly the colloidal DOM fraction. With the objective to minimize THMs generation, different unit operation designed to quantitatively remove DOM from water must be optimized.

Determination of chromate ion in drilling mud filtrates

International Nuclear Information System (INIS)

Whitfill, D.

1980-01-01

A method of determining the amount of chromate ion in an aqueous drilling mud filtrate containing organic color bodies such as lignosulfate wherein the method comprises: (A) treating the aqueous filtrate with an effective amount of hydrogen peroxide to destroy said color bodies, and (B) measuring the amount of chromate ion in the filtrate by means of a spectrophotometer

Monodisperse, submicrometer-scale platinum colloidal spheres with high electrocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Zhang, Lixue; Wang, Liang; Guo, Shaojun; Zhai, Junfeng; Dong, Shaojun; Wang, Erkang [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, 130022 Jilin, Changchun (China)

2009-02-15

Monodisperse, submicrometer-scale platinum (Pt) colloidal spheres were prepared through a simple direct chemical reduction of p-phenylenediamine (PPD)-chloroplatinic acid (H{sub 2}PtCl{sub 6}) coordination polymer colloids. It was found that the prepared Pt colloids had the similar size and morphology with their coordination polymer precursors, and the prepared Pt colloids with rough surfaces were three-dimensional (3D) structured assemblies of high-density small Pt nanoparticles. The electrochemical experiments confirmed that the prepared Pt colloids possessed a high electrocatalytic activity towards mainly four-electron reduction of dioxygen to water, making the prepared Pt colloids potential candidates for the efficient cathode material in fuel cells. (author)

Filtration of Sludge and Sodium Nonatitanate Solutions

International Nuclear Information System (INIS)

Poirier, M.R.

2000-01-01

The proposed facility designs for the ion exchange and solvent extraction flowsheets under development to treat high level waste at the Savannah River Site use crossflow filtration to remove entrained sludge and monosodium titanate (MST). Bench-scale and pilot-scale testing performed with simulated feed streams showed much lower filtration rates than desired for the process. This report documents an investigation of the impact on filtration of using Honeywell sodium nonatitanate (ST), rather than MST, for strontium and actinide removal

The Perspective of Riverbank Filtration in China

Science.gov (United States)

Li, J.; Teng, Y.; Zhai, Y.; Zuo, R.

2014-12-01

Sustainable drinking water supply can affect the health of people, and the surrounding ecosystems. According to statistics of the monitoring program of drinking water sources in 309 at or above prefecture level of China in 2013, the major pollutants index were total phosphorus, ammonia and manganese in surface drinking water sources, respectively, iron, ammonia and manganese in groundwater drinking water sources, respectively. More than 150 drinking water emergency environmental accidents happened since 2006, 52 of these accidents led to the disruption of water supply in waterworks, and a population of over ten million were affected. It indicated that there is a potential risk for people's health by the use of river water directly and it is necessary to require alternative techniques such as riverbank filtration for improving the drinking water quality. Riverbank filtration is an inexpensive natural process, not only smoothing out normal pollutant concentration found in surface water but also significantly reducing the risk from such emergency events as chemical spill into the river. Riverbank filtration technique has been used in many countries more than 100 years, including China. In China, in 1950s, the bank infiltration technique was first applied in northeast of China. Extensive bank infiltration application was conducted in 1980s, and more than 300 drinking water sources utilities bank infiltration established mainly near the Songhua River Basin, the Yellow River Basin, Haihe River Basin. However, the comparative lack of application and researches on riverbank filtration have formed critical scientific data gap in China. As the performance of riverbank filtration technique depend on not only the design and setting such as well type, pumping rate, but also the local hydrogeology and environmental properties. We recommend more riverbank filtration project and studies to be conducted to collect related significant environmental geology data in China

Modeling of Hydrodynamic Chromatography for Colloid Migration in Fractured Rock

International Nuclear Information System (INIS)

Li Shihhai; Jen, C.-P.

2001-01-01

The role of colloids in the migration of radionuclides in the geosphere has been emphasized in the performance assessment of high-level radioactive waste disposal. The literature indicates that the colloid velocity may not be equal to the velocity of groundwater owing to hydrodynamic chromatography. A theoretical model for hydrodynamic chromatography of colloid migration in the fracture is proposed in the present work. In this model, the colloids are treated as nonreactive and the external forces acting on colloidal particles are considered including the inertial force, the van der Waals attractive force, and the electrical double-layer repulsive force, as well as the gravitational force. A fully developed concentration profile for colloids is obtained to elucidate migration behavior for colloids in the fracture. The effects of parameters governing these forces and the aperture of the fracture are determined using a theoretical model

Mobility of radioactive colloidal particles in groundwater

International Nuclear Information System (INIS)

Nuttall, H.E.; Long, R.L.

1993-01-01

Radiocolloids are a major factor in the rapid migration of radioactive waste in groundwater. For at least two Los Alamos National Laboratory (LANL) sites, researchers have shown that groundwater colloidal particles were responsible for the rapid transport of radioactive waste material in groundwater. On an international scale, a review of reported field observations, laboratory column studies, and carefully collected field samples provides compelling evidence that colloidal particles enhance both radioactive and toxic waste migration. The objective of this project is to understand and predict colloid-contaminant migration through fundamental mathematical models, water sampling, and laboratory experiments and use this information to develop an effective and scientifically based colloid immobilization strategy. The article focuses on solving the suspected radiocolloid transport problems at LANL's Mortandad Canyon site. (author) 6 figs., 5 tabs., 18 refs

A general method to coat colloidal particles with titiana

NARCIS (Netherlands)

Demirors, A.F.; van Blaaderen, A.; Imhof, A.

2010-01-01

We describe a general one-pot method for coating colloidal particles with amorphous titania. Various colloidal particles such as silica particles, large silver colloids, gibbsite platelets, and polystyrene spheres were successfully coated with a titania shell. Although there are several ways of

[Management of chronic kidney disease guided by the theory of Traditional Chinese Medicine: an experimental study].

Science.gov (United States)

Wen, Ji; Xie, Xi-Sheng; Zhang, Ming-Hua; Mao, Nan; Zhang, Cheng-Long; Xie, Lin-Shen; Cheng, Yuan; Zhang, Zi-Yuan; Fan, Jun-Ming

2014-01-01

To determine the impact of Traditional Chinese Medicine on patients with chronic kidney disease (CKD). A total of 225 CKD patients in an outpatient department were recruited for this study, among whom 170 received regular Western and Chinese medicine treatments (control group) and 55 received treatments guided by the theory of Traditional Chinese Medicine (experimental group). The effectiveness of the treatments was determined through a pre-post comparison. Significant pre-intervention differences in age (P control group. No significant differences between the groups were found in changes of uric acid (P = 0.475), urine protein (P = 0.058), urine red cells (P = 0.577), and urine white cells (P = 0.01). A greater level of increase in estimated glomerular filtration rate was found in the experimental group compared with the control (P theory of Traditional Chinese Medicine can improve renal function through influencing glomerular filtration rate. The effect is more prominent than the regular treatment regime.

Micro-rheology on (polymer-grafted) colloids using optical tweezers

International Nuclear Information System (INIS)

Gutsche, C; Elmahdy, M M; Kegler, K; Semenov, I; Stangner, T; Otto, O; Ueberschaer, O; Kremer, F; Keyser, U F; Krueger, M; Rauscher, M; Weeber, R; Harting, J; Kim, Y W; Lobaskin, V; Netz, R R

2011-01-01

Optical tweezers are experimental tools with extraordinary resolution in positioning (± 1 nm) a micron-sized colloid and in the measurement of forces (± 50 fN) acting on it-without any mechanical contact. This enables one to carry out a multitude of novel experiments in nano- and microfluidics, of which the following will be presented in this review: (i) forces within single pairs of colloids in media of varying concentration and valency of the surrounding ionic solution, (ii) measurements of the electrophoretic mobility of single colloids in different solvents (concentration, valency of the ionic solution and pH), (iii) similar experiments as in (i) with DNA-grafted colloids, (iv) the nonlinear response of single DNA-grafted colloids in shear flow and (v) the drag force on single colloids pulled through a polymer solution. The experiments will be described in detail and their analysis discussed.

Field-scale colloid migration experiments in a granite fracture

International Nuclear Information System (INIS)

Vilks, P.; Frost, L.H.; Bachinski, D.B.

1997-01-01

An understanding of particle migration in fractured rock, required to assess the potential for colloid-facilitated transport of radionuclides, can best be evaluated when the results of laboratory experiments are demonstrated in the field. Field-scale migration experiments with silica colloids were carried out at AECL's Underground Research Laboratory (URL), located in southern Manitoba, to develop the methodology for large-scale migration experiments and to determine whether colloid transport is possible over distances up to 17 m. In addition, these experiments were designed to evaluate the effects of flow rate and flow path geometry, and to determine whether colloid tracers could be used to provide additional information on subsurface transport to that provided by conservative tracers alone. The colloid migration studies were carried out as part of AECL's Transport Properties in Highly Fractured Rock Experiment, the objective of which was to develop and demonstrate methods for evaluating the solute transport characteristics of zones of highly fractured rock. The experiments were carried out within fracture zone 2 as two-well recirculating, two-well non-recirculating, and convergent flow tests, using injection rates of 5 and 101 min -1 . Silica colloids with a 20 nm size were used because they are potentially mobile due to their stability, small size and negative surface charge. The shapes of elution profiles for colloids and conservative tracers were similar, demonstrating that colloids can migrate over distances of 17 m. The local region of drawdown towards the URL shaft affected colloid migration and, to a lesser extent, conservative tracer migration within the flow field established by the two-well tracer tests. These results indicate that stable colloids, with sizes as small as 20 nm, have different migration properties from dissolved conservative tracers. (author)

Study on liver scintigram using sup(99m)Tc-Sn colloid

International Nuclear Information System (INIS)

Nagase, Katsuya; Maruo, Kuninobu

1975-01-01

First of all, the liver scintigram was taken using 198 Au-colloid in cases of liver diseases, especially cases which seemed to have morphological changes in the liver. Of these cases, in cases which were found to have lesions the liver scintigram was subsequently taken using sup(99m)Tc-Sn colloid. In addition, in order to compare the state of lesions in both liver scintigrams with 198 Au-colloid and sup(99m)Tc-Sn colloid, ultrasonic tomogram was taken at each time. The scintigram using sup(99m)Tc-Sn colloid seemed to more clearly reveal the state of lesions and their sizes in the thin liver regions, especially the right border, the lower border and the left lobe in the liver, compared with 198 Au-colloid scintigram. The lesions in the thick liver tissues, especially the central right lobe, sometimes became unclear using sup(99m)Tc-Sn colloid. Therefore, 198 Au-colloid seemed to be available in these lesions. The scintigram using sup(99m)Tc-Sn colloid was found more useful for the diagnosis of lesions of patients with liver, cirrhosis whom the uptake rate of 198 Au-colloid is poor, compared with 198 Au-colloid scintigram. (Namekawa, K.)

Colloidal assemblies modified by ion irradiation

NARCIS (Netherlands)

Snoeks, E.; Blaaderen, A. van; Dillen, T. van; Kats, C.M. van; Velikov, K.P.; Brongersma, M.L.; Polman, A.

2001-01-01

Spherical SiO2 and ZnS colloidal particles show a dramatic anisotropic plastic deformation under 4 MeV Xe ion irradiation, that changes their shape into oblate into oblate ellipsional, with an aspect ratio that can be precisely controlled by the ion fluence. The 290 nm and 1.1 um diameter colloids

The effects of corrosion product colloids on actinide transport

International Nuclear Information System (INIS)

Gardiner, M.P.; Smith, A.J.; Williams, S.J.

1991-11-01

This report assesses the possible effects of colloidal corrosion products on the transport of actinides from the near field of radioactive waste repositories. The desorption of plutonium and americium from colloidal corrosion products of iron and zirconium was studied under conditions simulating a transition from near-field to far-field environmental conditions. Desorption of actinides occurred slowly from the colloids under far-field conditions. Measurements of particle stability showed all the colloids to be unstable in the near field. Stability increased under far-field conditions or as a result of the evolution of the near field. Migration of colloids from the near field is unlikely except in the presence of organic materials. (Author)

Transport and Deposition of Suspended Soil-Colloids in Saturated Sand Columns

DEFF Research Database (Denmark)

Sharma, Anu; Kawamoto, Ken; Møldrup, Per

2011-01-01

Understanding colloid mobilization, transport and deposition in the subsurface is a prerequisite for predicting colloid‐facilitated transport of strongly adsorbing contaminants and further developing remedial activities. This study investigated the transport behavior of soil‐colloids extracted from...... caused tailing of colloid BTCs with higher reversible entrapment and release of colloids than high flow velocity. The finer Toyoura sand retained more colloids than the coarser Narita sand at low pH conditions. The deposition profile and particle size distribution of colloids in the Toyoura sand clearly...

Shape recognition of microbial cells by colloidal cell imprints

NARCIS (Netherlands)

Borovicka, J.; Stoyanov, S.D.; Paunov, V.N.

2013-01-01

We have engineered a class of colloids which can recognize the shape and size of targeted microbial cells and selectively bind to their surfaces. These imprinted colloid particles, which we called "colloid antibodies", were fabricated by partial fragmentation of silica shells obtained by templating

Hanford underground storage tank waste filtration process evaluation

International Nuclear Information System (INIS)

Walker, B.W.; McCabe, D.J.

1997-01-01

The purpose of this filter study was to evaluate cross-flow filtration as effective solid-liquid separation technology for treating Hanford wastes, outline operating conditions for equipment, examine the expected filter flow rates, and determine proper cleaning. Two Hanford waste processing applications have been identified as candidates for the use of cross-flow filtration. The first of the Hanford applications involves filtration of the decanted supernate from sludge leaching and washing operations. This process involves the concentration and removal of dilute (0.05 wt percent) fines from the bulk of the supernate. The second application involves filtration to wash and concentrate the sludge during out-of-tank processing. This process employs a relatively concentrated (8 wt percent) solids feed stream. Filter studies were conducted with simulants to evaluate whether 0.5 micron cross-flow sintered metal Mott filters and 0.1 micron cross-flow Graver filters can perform solid-liquid separation of the solid/liquid waste streams effectively. In cross-flow filtration the fluid to be filtered flows in parallel to the membrane surface and generates shearing forces and/or turbulence across the filter medium. This shearing influences formation of filter cake stabilizing the filtrate flow rate

Magnetic Assisted Colloidal Pattern Formation

Science.gov (United States)

Yang, Ye

Pattern formation is a mysterious phenomenon occurring at all scales in nature. The beauty of the resulting structures and myriad of resulting properties occurring in naturally forming patterns have attracted great interest from scientists and engineers. One of the most convenient experimental models for studying pattern formation are colloidal particle suspensions, which can be used both to explore condensed matter phenomena and as a powerful fabrication technique for forming advanced materials. In my thesis, I have focused on the study of colloidal patterns, which can be conveniently tracked in an optical microscope yet can also be thermally equilibrated on experimentally relevant time scales, allowing for ground states and transitions between them to be studied with optical tracking algorithms. In particular, I have focused on systems that spontaneously organize due to particle-surface and particle-particle interactions, paying close attention to systems that can be dynamically adjusted with an externally applied magnetic or acoustic field. In the early stages of my doctoral studies, I developed a magnetic field manipulation technique to quantify the adhesion force between particles and surfaces. This manipulation technique is based on the magnetic dipolar interactions between colloidal particles and their "image dipoles" that appear within planar substrate. Since the particles interact with their own images, this system enables massively parallel surface force measurements (>100 measurements) in a single experiment, and allows statistical properties of particle-surface adhesion energies to be extracted as a function of loading rate. With this approach, I was able to probe sub-picoNewton surface interactions between colloidal particles and several substrates at the lowest force loading rates ever achieved. In the later stages of my doctoral studies, I focused on studying patterns formed from particle-particle interaction, which serve as an experimental model of

Spontaneous water filtration of bio-inspired membrane

Science.gov (United States)

Kim, Kiwoong; Kim, Hyejeong; Lee, Sang Joon

2016-11-01

Water is one of the most important elements for plants, because it is essential for various metabolic activities. Thus, water management systems of vascular plants, such as water collection and water filtration have been optimized through a long history. In this view point, bio-inspired technologies can be developed by mimicking the nature's strategies for the survival of the fittest. However, most of the underlying biophysical features of the optimized water management systems remain unsolved In this study, the biophysical characteristics of water filtration phenomena in the roots of mangrove are experimentally investigated. To understand water-filtration features of the mangrove, the morphological structures of its roots are analyzed. The electrokinetic properties of the root surface are also examined. Based on the quantitatively analyzed information, filtration of sodium ions in the roots are visualized. Motivated by this mechanism, spontaneous desalination mechanism in the root of mangrove is proposed by combining the electrokinetics and hydrodynamic transportation of ions. This study would be helpful for understanding the water-filtration mechanism of the roots of mangrove and developing a new bio-inspired desalination technology. This research was financially supported by the National Research Foundation (NRF) of Korea (Contract Grant Number: 2008-0061991).

Colloidal superballs

NARCIS (Netherlands)

Rossi, L.

2012-01-01

This thesis is organized in four parts as follows. Part 1 focuses on the synthetic aspects of the colloidal model systems that will be used throughout the work described in this thesis. In Chapter 2 we describe synthetic procedures for the preparation of polycrystalline hematite superballs and

Efficient filtration system for paraffin-catalyst slurry separation

Directory of Open Access Journals (Sweden)

Khodagholi Mohammad Ali

2013-01-01

Full Text Available The filtration efficiency for separating liquid paraffin (or water from a slurry consisting of 25 weight% spherical alumina in a Slurry Bubble Column Reactor (SBCR comprised of a cylindrical tube of 10 cm diameter and 150 cm length was studied. Various differential pressures (ΔP were applied to two separate tubular sintered metal stainless steel filter elements with nominal pore size of 4 and 16μm. The experimental results disclosed that the rate of filtrations increased on applying higher differential pressure to the filter element. Albeit this phenomenon is limited to moderate ΔPs and for ΔP more than 1 bar is neither harmful nor helpful. The highest filtration rates at ΔPs higher than 1 bar were 170 and 248 ml/minute for 4 and 16μm respectively. Using water as the liquid in slurry the rate of filtration enhanced to 4 folds, and this issue reveals impact of viscosity on filtration efficiency clearly. In all situations, the total amount of particles present in the filtrate part never exceeded a few parts per million (ppm. The statistical analysis of the SEM image of the filtrate indicated that by applying higher pressure difference to the filter element the frequency percent of larger particle size increases. The operation of filter cake removing was performed with back flashing of 300 ml of clean liquid with pressures of 3-5 bar of N2 gas.

Self-assembled three-dimensional chiral colloidal architecture

Science.gov (United States)

Ben Zion, Matan Yah; He, Xiaojin; Maass, Corinna C.; Sha, Ruojie; Seeman, Nadrian C.; Chaikin, Paul M.

2017-11-01

Although stereochemistry has been a central focus of the molecular sciences since Pasteur, its province has previously been restricted to the nanometric scale. We have programmed the self-assembly of micron-sized colloidal clusters with structural information stemming from a nanometric arrangement. This was done by combining DNA nanotechnology with colloidal science. Using the functional flexibility of DNA origami in conjunction with the structural rigidity of colloidal particles, we demonstrate the parallel self-assembly of three-dimensional microconstructs, evincing highly specific geometry that includes control over position, dihedral angles, and cluster chirality.

Interplay between Colloids and Interfaces : Emulsions, Foams and Microtubes

NARCIS (Netherlands)

de Folter, J.W.J.

2013-01-01

The central theme of this thesis is the interplay between colloids and interfaces. The adsorption of colloids at fluid-fluid interfaces is the main topic and covers Chapters 2-6. Pickering emulsions where colloidal particles act as emulsion stabilizers in the absence of surfactants are studied in a

Colloidal nanocrystals for quality lighting and displays: milestones and recent developments

Directory of Open Access Journals (Sweden)

Erdem Talha

2016-06-01

Full Text Available Recent advances in colloidal synthesis of nanocrystals have enabled high-quality high-efficiency light-emitting diodes, displays with significantly broader color gamut, and optically-pumped lasers spanning the whole visible regime. Here we review these colloidal platforms covering the milestone studies together with recent developments. In the review, we focus on the devices made of colloidal quantum dots (nanocrystals, colloidal quantum rods (nanorods, and colloidal quantum wells (nanoplatelets as well as those of solution processed perovskites and phosphor nanocrystals. The review starts with an introduction to colloidal nanocrystal photonics emphasizing the importance of colloidal materials for light-emitting devices. Subsequently,we continue with the summary of important reports on light-emitting diodes, in which colloids are used as the color converters and then as the emissive layers in electroluminescent devices. Also,we review the developments in color enrichment and electroluminescent displays. Next, we present a summary of important reports on the lasing of colloidal semiconductors. Finally, we summarize and conclude the review presenting a future outlook.

Colloid cysts of the third ventricle

International Nuclear Information System (INIS)

Pina, J.I.; Medrano, J.; Benito, J.L. de; Lasierra, R.; Lopez, S.; Fernandez, J.A.; Villavieja, J.L.

1994-01-01

Colloid cysts (CC) are uncommon cystic endo dermal tumors located in the roof of the third ventricle. The clinical features depend on their capacity for obstructing the foramen of Monro, which results in univentricular or biventricular hydrocephalus. We present three cases of colloid cysts of the third ventricle, diagnosed by CT, reviewing their diagnostic, clinical and pathological features

40 CFR 141.717 - Pre-filtration treatment toolbox components.

Science.gov (United States)

2010-07-01

... surface water or GWUDI source. (c) Bank filtration. Systems receive Cryptosporidium treatment credit for... paragraph. Systems using bank filtration when they begin source water monitoring under § 141.701(a) must... 40 Protection of Environment 22 2010-07-01 2010-07-01 false Pre-filtration treatment toolbox...

Colloidal characterization of silicon nitride and silicon carbide

Science.gov (United States)

Feke, Donald L.

1986-01-01

The colloidal behavior of aqueous ceramic slips strongly affects the forming and sintering behavior and the ultimate mechanical strength of the final ceramic product. The colloidal behavior of these materials, which is dominated by electrical interactions between the particles, is complex due to the strong interaction of the solids with the processing fluids. A surface titration methodology, modified to account for this interaction, was developed and used to provide fundamental insights into the interfacial chemistry of these systems. Various powder pretreatment strategies were explored to differentiate between true surface chemistry and artifacts due to exposure history. The colloidal behavior of both silicon nitride and carbide is dominated by silanol groups on the powder surfaces. However, the colloid chemistry of silicon nitride is apparently influenced by an additional amine group. With the proper powder treatments, silicon nitride and carbide powder can be made to appear colloidally equivalent. The impact of these results on processing control will be discussed.

Automated preparation method for colloidal crystal arrays of monodisperse and binary colloid mixtures by contact printing with a pintool plotter.

Science.gov (United States)

Burkert, Klaus; Neumann, Thomas; Wang, Jianjun; Jonas, Ulrich; Knoll, Wolfgang; Ottleben, Holger

2007-03-13

Photonic crystals and photonic band gap materials with periodic variation of the dielectric constant in the submicrometer range exhibit unique optical properties such as opalescence, optical stop bands, and photonic band gaps. As such, they represent attractive materials for the active elements in sensor arrays. Colloidal crystals, which are 3D gratings leading to Bragg diffraction, are one potential precursor of such optical materials. They have gained particular interest in many technological areas as a result of their specific properties and ease of fabrication. Although basic techniques for the preparation of regular patterns of colloidal crystals on structured substrates by self-assembly of mesoscopic particles are known, the efficient fabrication of colloidal crystal arrays by simple contact printing has not yet been reported. In this article, we present a spotting technique used to produce a microarray comprising up to 9600 single addressable sensor fields of colloidal crystal structures with dimensions down to 100 mum on a microfabricated substrate in different formats. Both monodisperse colloidal crystals and binary colloidal crystal systems were prepared by contact printing of polystyrene particles in aqueous suspension. The array morphology was characterized by optical light microscopy and scanning electron microscopy, which revealed regularly ordered crystalline structures for both systems. In the case of binary crystals, the influence of the concentration ratio of the large and small particles in the printing suspension on the obtained crystal structure was investigated. The optical properties of the colloidal crystal arrays were characterized by reflection spectroscopy. To examine the stop bands of the colloidal crystal arrays in a high-throughput fashion, an optical setup based on a CCD camera was realized that allowed the simultaneous readout of all of the reflection spectra of several thousand sensor fields per array in parallel. In agreement with

Adsorption of ions by colloids in electrolyte solutions

International Nuclear Information System (INIS)

Kallay, N.

1977-01-01

The adsorption isotherm for ionic adsorption by colloid particles was evaluated. The adsorption process was treated as the reaction between colloid particles and ions. The colloid particle has been here considered as a reaction entity. The possibility of the surface potential determination was presented. The analyses of the experimental data showed, that (at electrolyte concentration higher than the critical coagulation one) the surface potential reaches its zero value

Wetting in a colloidal liquid-gas system

NARCIS (Netherlands)

Wijting, W.K.; Besseling, N.A.M.; Cohen Stuart, M.A.

2003-01-01

We present first observations of wetting phenomena in depletion interaction driven, phase separated colloidal dispersions (coated silica-cyclohexane-polydimethylsiloxane). The contact angle of the colloidal liquid-gas interface at a solid substrate (coated glass) was determined for a series of

Dynamic optimization of dead-end membrane filtration

NARCIS (Netherlands)

Blankert, B.; Betlem, Bernardus H.L.; Roffel, B.; Marquardt, Wolfgang; Pantelides, Costas

2006-01-01

An operating strategy aimed at minimizing the energy consumption during the filtration phase of dead-end membrane filtration has been formulated. A method allowing fast calculation of trajectories is used to allow incorporation in a hierarchical optimization scheme. The optimal trajectory can be

Colloidal silver: a novel treatment for Staphylococcus aureus biofilms?

Science.gov (United States)

Goggin, Rachel; Jardeleza, Camille; Wormald, Peter-John; Vreugde, Sarah

2014-03-01

Colloidal silver is an alternative medicine consisting of silver particles suspended in water. After using this solution as a nasal spray, the symptoms of a previously recalcitrant Staphylococcus aureus (S. aureus)-infected chronic rhinosinusitis patient were observed to have improved markedly. The aim of this study was to determine whether colloidal silver has any direct bactericidal effects on these biofilms in vitro. S. aureus biofilms were grown from the ATCC 25923 reference strain on Minimum Biofilm Eradication Concentration (MBEC) device pegs, and treated with colloidal silver. Concentrations tested ranged from 10 to 150 μL colloidal silver diluted to 200 μL with sterile water in 50 μL cerebrospinal fluid (CSF) broth. Control pegs were exposed to equivalent volumes of CSF broth and sterile water. The sample size was 4 biomass values per treatment or control group. Confocal scanning laser microscopy and COMSTAT software were used to quantify biofilms 24 hours after treatment. Significant differences from control were found for all concentrations tested bar the lowest of 10 μL colloidal silver in 200 μL. At 20 μL colloidal silver, the reduction in biomass was 98.9% (mean difference between control and treatment = -4.0317 μm(3) /μm(2) , p colloidal silver (mean differences = -4.0681 and -4.0675μm(3) /μm(2) , respectively, p Colloidal silver directly attenuates in vitro S. aureus biofilms. © 2014 ARS-AAOA, LLC.

Giant Leaking Colloid Cyst Presenting with Aseptic Meningitis

DEFF Research Database (Denmark)

Bakhtevari, Mehrdad Hosseinzadeh; Sharifi, Guive; Jabbari, Reza

2015-01-01

BACKGROUND: Colloid cysts are benign third ventricle lesions that need to be diagnosed correctly because of their association with sudden death. Chemical or aseptic meningitis is a rare presentation of a colloid cyst. METHODS: We present a case of a 69-year-old man with fever, alteration of mental...... status, and meningismus. Microbiological examination of the cerebrospinal fluid revealed aseptic meningitis. Brain imaging revealed a third ventricular colloid cyst with hydrocephalus. RESULTS: The tumor was resected via endoscopic intervention. There were no persistent operative complications related...... to the endoscopic procedure. CONCLUSIONS: Chemical or aseptic meningitis is an unusual clinical manifestation of a colloid cyst, complicating the differential diagnosis, especially in the elderly....

Colloidal alloys with preassembled clusters and spheres.

Science.gov (United States)

Ducrot, Étienne; He, Mingxin; Yi, Gi-Ra; Pine, David J

2017-06-01

Self-assembly is a powerful approach for constructing colloidal crystals, where spheres, rods or faceted particles can build up a myriad of structures. Nevertheless, many complex or low-coordination architectures, such as diamond, pyrochlore and other sought-after lattices, have eluded self-assembly. Here we introduce a new design principle based on preassembled components of the desired superstructure and programmed nearest-neighbour DNA-mediated interactions, which allows the formation of otherwise unattainable structures. We demonstrate the approach using preassembled colloidal tetrahedra and spheres, obtaining a class of colloidal superstructures, including cubic and tetragonal colloidal crystals, with no known atomic analogues, as well as percolating low-coordination diamond and pyrochlore sublattices never assembled before.

Field-scale variation in colloid dispersibility and transport

DEFF Research Database (Denmark)

Nørgaard, Trine; Møldrup, Per; Ferré, T. P. A.

2014-01-01

comparison parameters including textural, chemical, and structural (e.g. air permeability) 8 soil properties. The soil dispersibility was determined (i) using a laser diffraction method on 1-2 mm aggregates equilibrated to an initial matric potential of -100 cm H2O, (ii) using an end-over-end shaking on 6......Colloids are potential carriers for strongly sorbing chemicals in macroporous soils, but predicting the amount of colloids readily available for facilitated chemical transport is an unsolved challenge. This study addresses potential key parameters and predictive indicators when assessing colloid....... Predictions of soil dispersibility and the risk of colloid-facilitated chemical transport will therefore need to be highly scale- and area-specific....

Fast microbial reduction of ferrihydrite colloids from a soil effluent

Science.gov (United States)

Fritzsche, Andreas; Bosch, Julian; Rennert, Thilo; Heister, Katja; Braunschweig, Juliane; Meckenstock, Rainer U.; Totsche, Kai U.

2012-01-01

Recent studies on the microbial reduction of synthetic iron oxide colloids showed their superior electron accepting property in comparison to bulk iron oxides. However, natural colloidal iron oxides differ in composition from their synthetic counterparts. Besides a potential effect of colloid size, microbial iron reduction may be accelerated by electron-shuttling dissolved organic matter (DOM) as well as slowed down by inhibitors such as arsenic. We examined the microbial reduction of OM- and arsenic-containing ferrihydrite colloids. Four effluent fractions were collected from a soil column experiment run under water-saturated conditions. Ferrihydrite colloids precipitated from the soil effluent and exhibited stable hydrodynamic diameters ranging from 281 (±146) nm in the effluent fraction that was collected first and 100 (±43) nm in a subsequently obtained effluent fraction. Aliquots of these oxic effluent fractions were added to anoxic low salt medium containing diluted suspensions of Geobacter sulfurreducens. Independent of the initial colloid size, the soil effluent ferrihydrite colloids were quickly and completely reduced. The rates of Fe2+ formation ranged between 1.9 and 3.3 fmol h-1 cell-1, and are in the range of or slightly exceeding previously reported rates of synthetic ferrihydrite colloids (1.3 fmol h-1 cell-1), but greatly exceeding previously known rates of macroaggregate-ferrihydrite reduction (0.07 fmol h-1 cell-1). The inhibition of microbial Fe(III) reduction by arsenic is unlikely or overridden by the concurrent enhancement induced by soil effluent DOM. These organic species may have increased the already high intrinsic reducibility of colloidal ferrihydrite owing to quinone-mediated electron shuttling. Additionally, OM, which is structurally associated with the soil effluent ferrihydrite colloids, may also contribute to the higher reactivity due to increasing solubility and specific surface area of ferrihydrite. In conclusion, ferrihydrite

Colloidal silver fabrication using the spark discharge system and its antimicrobial effect on Staphylococcus aureus.

Science.gov (United States)

Tien, Der-Chi; Tseng, Kuo-Hsiung; Liao, Chih-Yu; Tsung, Tsing-Tshih

2008-10-01

Nanoscale techniques for silver production may assist the resurgence of the medical use of silver, especially given that pathogens are showing increasing resistance to antibiotics. Traditional chemical synthesis methods for colloidal silver (CS) may lead to the presence of toxic chemical species or chemical residues, which may inhibit the effectiveness of CS as an antibacterial agent. To counter these problems a spark discharge system (SDS) was used to fabricate a suspension of colloidal silver in deionized water with no added chemical surfactants. SDS-CS contains both metallic silver nanoparticles (Ag(0)) and ionic silver forms (Ag(+)). The antimicrobial affect of SDS-CS on Staphylococcus aureus was studied. The results show that CS solutions with an ionic silver concentration of 30 ppm or higher are strong enough to destroy S. aureus. In addition, it was found that a solution's antimicrobial potency is directly related to its level of silver ion concentration.

Effects of levosimendan on glomerular filtration rate, renal blood flow, and renal oxygenation after cardiac surgery with cardiopulmonary bypass: a randomized placebo-controlled study.

Science.gov (United States)

Bragadottir, Gudrun; Redfors, Bengt; Ricksten, Sven-Erik

2013-10-01

Acute kidney injury develops in a large proportion of patients after cardiac surgery because of the low cardiac output syndrome. The inodilator levosimendan increases cardiac output after cardiac surgery with cardiopulmonary bypass, but a detailed analysis of its effects on renal perfusion, glomerular filtration, and renal oxygenation in this group of patients is lacking. We therefore evaluated the effects of levosimendan on renal blood flow, glomerular filtration rate, renal oxygen consumption, and renal oxygen demand/supply relationship, i.e., renal oxygen extraction, early after cardiac surgery with cardiopulmonary bypass. Prospective, placebo-controlled, and randomized trial. Cardiothoracic ICU of a tertiary center. Postcardiac surgery patients (n=30). The patients were randomized to receive levosimendan, 0.1 µg/kg/min after a loading dose of 12 µg/kg (n=15), or placebo (n=15). The experimental procedure started 4-6 hours after surgery in the ICU during propofol sedation and mechanical ventilation. Systemic hemodynamic were evaluated by a pulmonary artery thermodilution catheter. Renal blood flow and glomerular filtration rate were measured by the renal vein retrograde thermodilution technique and by renal extraction of Cr-EDTA, respectively. Central venous pressure was kept constant by colloid/crystalloid infusion. Compared to placebo, levosimendan increased cardiac index (22%), stroke volume index (15%), and heart rate (7%) and decreased systemic vascular resistance index (21%), whereas mean arterial pressure was not affected. Levosimendan induced significant increases in renal blood flow (12%, prenal vascular resistance (18%, prenal oxygen consumption, or renal oxygen extraction, compared to placebo. After cardiac surgery with cardiopulmonary bypass, levosimendan induces a vasodilation, preferentially of preglomerular resistance vessels, increasing both renal blood flow and glomerular filtration rate without jeopardizing renal oxygenation. Due to its

Transport and Deposition of Variably Charged Soil Colloids in Saturated Porous Media

DEFF Research Database (Denmark)

Sharma, Anu; Kawamoto, Ken; Møldrup, Per

2011-01-01

Okinawa (RYS colloids) in Japan. The VAS colloids exhibited a negative surface charge with a high pH dependency, whereas the RYS colloids exhibited a negative surface charge with less pH dependency. The soil colloids were applied as colloidal suspensions to 10-cm-long saturated sand columns packed...

Diffusion of organic colloids in compacted bentonite. The influence of ionic strength on molecular size and transport capacity of the colloids

International Nuclear Information System (INIS)

Wold, S.; Eriksen, Trygve E.

2000-09-01

Diffusion of radionuclides in compacted bentonite can be affected by inorganic and organic colloids if the radionuclides form complexes with the colloids. Formation and mobility of the colloid-radionuclide complexes will be governed by the properties of the colloids as well as the competition between complexation and sorption of the radionuclides on bentonite. This report presents the results of experiments with organic colloids humic acid (HA) and lignosulfonate (LS). The aim of the experiments has been to describe the HA and LS properties: size distribution, acidity, sorption on bentonite, diffusivity in compacted bentonite, complexation with strontium, and diffusion of strontium in bentonite in the presence of HA. This study indicates that the diffusion of cationic radionuclides like Sr 2+ is not affected by the presence of HA in high ionic strength solution. In 0.1 M NaClO 4 solution, HA is most probably not available for complexation due to coiling and shielding of the negative sites

Evaluation of colloid transport issues and recommendations for SKI performance assessments

International Nuclear Information System (INIS)

Wickham, S. M.; Bennett, D. G.; Higgo, J. J. W.

2000-08-01

The primary objective of this project was to develop recommendations to SKI for evaluating the potential significance of colloids in performance assessment (PA) studies by: Updating a previous review of the treatment of colloids in PA studies for radioactive waste repositories and to include information on PAs published in the period 1997-1999. We have reviewed sixteen PAs conducted in nine countries and have made the following observations: All PAs include colloid formation and colloid transport in their FEP list. Although some programmes have deferred consideration of colloidal radionuclide transport until further research has been performed, more recent PAs do account for the effects of colloids. PAs of disposal systems in which the waste canister is surrounded by a bentonite buffer do not consider the effect of colloids on the source term. These PAs assume that all colloids are filtered by the bentonite buffer and cannot escape from the near-field. PAs of disposal systems with no bentonite buffer have to account for mobilisation of radionuclides from the waste by colloids. The concentration of colloids that may form in the repository is a key uncertainty. Many PA programmes have modelled colloidal radionuclide transport in the geosphere using one-dimensional transport equations. No PA has included a comprehensive treatment of colloid transport using mechanistic modelling. Some PAs have not undertaken modelling of colloid transport in the geosphere, but have relied instead on arguments that such transport processes will be of low consequence to the performance of the disposal system. Five PAs have shown the effects of colloid transport through the geosphere to be potentially significant. For the disposal of spent nuclear fuel, SKB has developed the KBS-3 concept. For the disposal of long-lived low-level and intermediate-level radioactive waste, SKB has developed the SFL 3-5 concept. In the SFL 3-5 concept, waste is placed in underground disposal caverns and

Reversibility of sorption of plutonium-239 onto hematite and goethite colloids

International Nuclear Information System (INIS)

Lu, N.; Cotter, C.R.; Kitten, H.D.; Bentley, J.; Triay, I.R.

1998-01-01

Laboratory batch sorption experiments were conducted to evaluate: (1) sorption of plutonium-239 ( 239 Pu) on different iron oxide colloids (hematite and geothite), (2) sorption kinetics of colloidal Pu(IV) and soluble Pu(V) onto these two colloids, and (3) desorption of colloidal Pu(IV) and soluble Pu(V) from 239 Pu-loaded colloids as a function of time. Natural groundwater and carbonate-rich synthetic groundwater were used in this study. To examine the possible influence of bicarbonate on 239 Pu sorption, an additional set of experiments was conducted in sodium nitrate (NaNO 3 ) solutions under carbon dioxide free environments. Our results show that colloidal Pu(IV) as well as soluble Pu(V) was rapidly adsorbed by hematite and goethite colloids in both natural and synthetic groundwater. The amount of 239 Pu adsorbed by both iron oxide colloids in synthetic groundwater was higher than in natural groundwater. The presence of carbonate did not influence the sorption of 239 Pu. While sorption of soluble Pu(V) is a slow process, sorption of colloidal Pu(IV) occurs rapidly. Desorption of Pu from iron oxide colloids is much slower than the sorption processes. Our findings suggest that different sorption and desorption behaviors of 239 Pu by iron oxide colloids in groundwater may facilitate the transport of 239 Pu along potential flowpaths from the areas contaminated by radionuclide and release to the accessible environment. (orig.)

Characterization, origin and aggregation behavior of colloids in eutrophic shallow lake.

Science.gov (United States)

Xu, Huacheng; Xu, Mengwen; Li, Yani; Liu, Xin; Guo, Laodong; Jiang, Helong

2018-05-31

Stability of colloidal particles contributes to the turbidity in the water column, which significantly influences water quality and ecological functions in aquatic environments especially shallow lakes. Here we report characterization, origin and aggregation behavior of aquatic colloids, including natural colloidal particles (NCPs) and total inorganic colloidal particles (TICPs), in a highly turbid shallow lake, via field observations, simulation experiments, ultrafiltration, spectral and microscopic, and light scattering techniques. The colloidal particles were characterized with various shapes (spherical, polygonal and elliptical) and aluminum-, silicon-, and ferric-containing mineralogical structures, with a size range of 20-200 nm. The process of sediment re-suspension under environmentally relevant conditions contributed 78-80% of TICPs and 54-55% of NCPs in Lake Taihu, representing an important source of colloids in the water column. Both mono- and divalent electrolytes enhanced colloidal aggregation, while a reverse trend was observed in the presence of natural organic matter (NOM). The influence of NOM on colloidal stability was highly related to molecular weight (MW) properties with the high MW fraction exhibiting higher stability efficiency than the low MW counterparts. However, the MW-dependent aggregation behavior for NCPs was less significant than that for TICPs, implying that previous results on colloidal behavior using model inorganic colloids alone should be reevaluated. Further studies are needed to better understand the mobility/stability and transformation of aquatic colloids and their role in governing the fate and transport of pollutants in natural waters. Copyright © 2018. Published by Elsevier Ltd.

Filter aids influence on pressure drop across a filtration system

Science.gov (United States)

Hajar, S.; Rashid, M.; Nurnadia, A.; Ammar, M. R.; Hasfalina, C. M.

2017-06-01

Filter aids is commonly used to reduce pressure drop across air filtration system as it helps to increase the efficiency of filtration of accumulated filter cake. Filtration velocity is one of the main parameters that affect the performance of filter aids material. In this study, a formulated filter aids consisting of PreKot™ and activated carbon mixture (designated as PrekotAC) was tested on PTFE filter media under various filtration velocities of 5, 6, and 8 m/min at a constant material loading of 0.2 mg/mm2. Results showed that pressure drop is highly influenced by filtration velocity where higher filtration velocity leads to a higher pressure drop across the filter cake. It was found that PrekotAC performed better in terms of reducing the pressure drop across the filter cake even at the highest filtration velocity. The diversity in different particle size distribution of non-uniform particle size in the formulated PrekotAC mixture presents a higher permeability causes a lower pressure drop across the accumulated filter cake. The finding suggests that PrekotAC is a promising filter aids material that helps reducing the pressure drop across fabric filtration system.

Colloid-templated multisectional porous polymeric fibers.

Science.gov (United States)

Song, Jung Hun; Kretzschmar, Ilona

2008-10-07

A fabrication method for porous polymeric fibers (PPFs) is reported. We show that a multisectional colloidal crystal can be assembled within a microcapillary by alternating dipping into colloidal solutions of varying size. Subsequent infiltration with curable polymer and washing with suitable solvents results in porous fibers with a cylindrical cross section. Along the length of the fiber, alternating sections of controlled length, pore size, and pore size distribution exist. These fibers present interesting materials for neural scaffolding, catalysis, and possibly photonics if produced with a high degree of crystallinity. The surface pores and bulk porosity of the fibers are characterized by variable-pressure scanning electron microscopy (vp-SEM). Careful analysis shows that the surface pores vary with the colloidal template diameter and polymer infiltration time.

Characteristics of colloids generated during the corrosion of nuclear waste glasses in groundwater

International Nuclear Information System (INIS)

Feng, X.; Buck, E.C.; Mertz, C.; Bates, J.K.; Cunnane, J.C.; Chaiko, D.

1993-10-01

Aqueous colloidal suspensions were generated by reacting nuclear waste glasses with groundwater at 90 degrees C at different ratios of the glass surface area to solution volume (S/V). The colloids have been characterized in terms of size, charge, identity, and stability with respect to salt concentration, pH, and time, by examination using dynamic light scattering, electrophoretic mobility, and transmission electron microscopy. The colloids are predominately produced by precipitation from solution, possibly with contribution from reacted layers that have spallated from the glass. These colloids are silicon-rich minerals. The colloidal suspensions agglomerate when the salinity of the solutions increase. The following implications for modeling the colloidal transport of contaminants have been derived from this study: (1) The sources of the colloids are not only solubility-limited real colloids and the pseudo colloids formed by adsorption of radionuclides onto a groundwater colloid, but also from the spalled surface layers of reacted waste glasses. (2) In a repository, the local environment is likely to be glass-reaction dominated and the salt concentration is likely to be high, leading to rapid colloid agglomeration and settling; thus, colloid transport may be insignificant. (3) If large volumes of groundwater contact the glass reaction site, the precipitated colloids may become resuspended, and colloid transport may become important. (4) Under most conditions, the colloids are negatively charged and will deposit readily on positively charged surfaces. Negatively charged surfaces will, in general, facilitate colloid stability and transport

The colloid investigations conducted at the Aespoe Hard Rock Laboratory during 2000-2004

Energy Technology Data Exchange (ETDEWEB)

Laaksoharju, Marcus [Geopoint AB, Stockholm (Sweden); Wold, Susanna [Royal Inst. of Tech., Stockholm (Sweden). School of Chemical Science and Engineering, Nuclear Chemistry] (eds.)

2005-12-15

In 2000, SKB decided to initiate an international colloid project at the Aespoe Hard Rock Laboratory in Sweden. The objectives of the colloid project are to: (i) study the role of bentonite as a colloid source, (ii) verify the background colloid concentration at Aespoe HRL and, (iii) investigate the potential for colloid formation/transport in natural groundwater concentrations. The experimental concepts for the colloid project are: laboratory experiments with bentonite, background field measurements of natural colloids, borehole specific bentonite colloid stability experiments and a fracture specific transport experiment. The activities concerning the laboratory experiments and background field measurements are described in this work; the other activities are ongoing or planned. The following conclusions were made: The bentonite colloid stability is strongly dependent on the groundwater ionic strength. Natural colloids are organic degradation products such as humic and fulvic acids, inorganic colloids (clay, calcite, iron hydroxide) and microbes. Microbes form few but large particles and their concentration increase with increasing organic carbon concentrations. The small organic colloids are present in very low concentrations in deep granitic groundwater. The concentrations can be rather high in shallow waters. The colloid concentration decreases with depth and salinity, since colloids are less stable in saline waters. The colloid content at Aespoe is less than 300 ppb. The colloid content at repository level is less than 50 ppb. The groundwater variability obtained in the boreholes reflects well the natural groundwater variability along the whole HRL tunnel.

The colloid investigations conducted at the Aespoe Hard Rock Laboratory during 2000-2004

International Nuclear Information System (INIS)

Laaksoharju, Marcus; Wold, Susanna

2005-12-01

In 2000, SKB decided to initiate an international colloid project at the Aespoe Hard Rock Laboratory in Sweden. The objectives of the colloid project are to: (i) study the role of bentonite as a colloid source, (ii) verify the background colloid concentration at Aespoe HRL and, (iii) investigate the potential for colloid formation/transport in natural groundwater concentrations. The experimental concepts for the colloid project are: laboratory experiments with bentonite, background field measurements of natural colloids, borehole specific bentonite colloid stability experiments and a fracture specific transport experiment. The activities concerning the laboratory experiments and background field measurements are described in this work; the other activities are ongoing or planned. The following conclusions were made: The bentonite colloid stability is strongly dependent on the groundwater ionic strength. Natural colloids are organic degradation products such as humic and fulvic acids, inorganic colloids (clay, calcite, iron hydroxide) and microbes. Microbes form few but large particles and their concentration increase with increasing organic carbon concentrations. The small organic colloids are present in very low concentrations in deep granitic groundwater. The concentrations can be rather high in shallow waters. The colloid concentration decreases with depth and salinity, since colloids are less stable in saline waters. The colloid content at Aespoe is less than 300 ppb. The colloid content at repository level is less than 50 ppb. The groundwater variability obtained in the boreholes reflects well the natural groundwater variability along the whole HRL tunnel

Composition inversion in mixtures of binary colloids and polymer

Science.gov (United States)

Zhang, Isla; Pinchaipat, Rattachai; Wilding, Nigel B.; Faers, Malcolm A.; Bartlett, Paul; Evans, Robert; Royall, C. Patrick

2018-05-01

Understanding the phase behaviour of mixtures continues to pose challenges, even for systems that might be considered "simple." Here, we consider a very simple mixture of two colloidal and one non-adsorbing polymer species, which can be simplified even further to a size-asymmetrical binary mixture, in which the effective colloid-colloid interactions depend on the polymer concentration. We show that this basic system exhibits surprisingly rich phase behaviour. In particular, we enquire whether such a system features only a liquid-vapor phase separation (as in one-component colloid-polymer mixtures) or whether, additionally, liquid-liquid demixing of two colloidal phases can occur. Particle-resolved experiments show demixing-like behaviour, but when combined with bespoke Monte Carlo simulations, this proves illusory, and we reveal that only a single liquid-vapor transition occurs. Progressive migration of the small particles to the liquid phase as the polymer concentration increases gives rise to composition inversion—a maximum in the large particle concentration in the liquid phase. Close to criticality, the density fluctuations are found to be dominated by the larger colloids.

Hydrodynamic interactions in active colloidal crystal microrheology.

Science.gov (United States)

Weeber, R; Harting, J

2012-11-01

In dense colloids it is commonly assumed that hydrodynamic interactions do not play a role. However, a found theoretical quantification is often missing. We present computer simulations that are motivated by experiments where a large colloidal particle is dragged through a colloidal crystal. To qualify the influence of long-ranged hydrodynamics, we model the setup by conventional Langevin dynamics simulations and by an improved scheme with limited hydrodynamic interactions. This scheme significantly improves our results and allows to show that hydrodynamics strongly impacts the development of defects, the crystal regeneration, as well as the jamming behavior.

Characterization of natural groundwater colloids at Palmottu

International Nuclear Information System (INIS)

Vuorinen, U.; Kumpulainen, H.

1993-01-01

Characterization of groundwater colloids (size range from 2 nm to 500 nm) in the Palmottu natural analogue (for radioactive waste disposal in Finland) area was continued by sampling another drill hole, 346, at three depths. Results evaluated so far indicate the presence of both organic and inorganic colloids. In terms of chemical composition and morphology, the inorganic colloids differ from those found in previous studies. According to SEM/EDS and STEM/EDS they mostly contain Ca and are spherical in shape. At this stage further characterization and evaluation of results is provisional and does not allow very accurate conclusions to be drawn

Anomalous interactions in confined charge-stabilized colloid

International Nuclear Information System (INIS)

Grier, D G; Han, Y

2004-01-01

Charge-stabilized colloidal spheres dispersed in weak 1:1 electrolytes are supposed to repel each other. Consequently, experimental evidence for anomalous long-ranged like-charged attractions induced by geometric confinement inspired a burst of activity. This has largely subsided because of nagging doubts regarding the experiments' reliability and interpretation. We describe a new class of thermodynamically self-consistent colloidal interaction measurements that confirm the appearance of pairwise attractions among colloidal spheres confined by one or two bounding walls. In addition to supporting previous claims for this as-yet unexplained effect, these measurements also cast new light on its mechanism

Sorption behavior of cesium onto bentonite colloid

International Nuclear Information System (INIS)

Iijima, Kazuki; Masuda, Tsuguya; Tomura, Tsutomu

2004-01-01

It is considered that bentonite colloid might be generated from bentonite which will be used as buffer material in geological disposal system, and can facilitate the migration of radionuclides by means of sorption. In order to examine this characteristic, sorption and desorption experiments of Cs onto bentonite colloid were carried out to obtain its distribution coefficient (Kd) and information on the reversibility of its sorption. In addition, particle size distribution and shape of colloid were investigated and their effect on the sorption behavior was discussed. Kds for Cs were around 20 m 3 /kg for sorption and 30 m 3 /kg for desorption, in which sorbed Cs was desorbed by 8.4x10 -4 mol/l of NaCl solution. These values did not show any dependencies on Cs concentration and duration of sorption and desorption. The first 20% of sorbed Cs was desorbed reversibly at least. Most of colloidal particles were larger than 200 nm and TEM micrographs showed they had only several sheets of the clay crystal. Obtained Kds for colloidal bentonite were larger than those for powdered bentonite. This can be caused by difference of competing ions in the solution, characteristics of contained smectite, or sorption site density. (author)

Colloid Release from Soil Aggregates

DEFF Research Database (Denmark)

Vendelboe, Anders Lindblad; Møldrup, Per; Schjønning, Per

2012-01-01

The content of water-dispersible colloids (WDC) has a major impact on soil functions and structural stability. In addition, the presence of mobile colloids may increase the risk of colloid-facilitated transport of strongly sorbing environmental contaminants. The WDC content was measured in 39 soils......, using laser diffraction, by agitating the samples using a wet-dispersion unit. This approach eliminated the need for long sedimentation times required by the more classical end-over-end shaking approach and provided information about the time-dependent release of WDC. The total clay content of the soils...... ranged from 0.1 to 0.44 kg kg−1. The WDC content was measured on air-dry and moist 1- to 2-mm aggregates. The WDC content at a reference time was highly correlated to the total clay content (r > 0.91, P soils. Only for two sites was the WDC content correlated to the content of clay...

Growth and Interaction of Colloid Nuclei

Science.gov (United States)

Lam, Michael-Angelo; Khusid, Boris; Meyer, William; Kondic, Lou

2017-11-01

We study evolution of colloid systems under zero-gravity conditions. In particular, we focus on the regime where there is a coexistence between a liquid and a solid state. Under zero gravity, the dominating process in the bulk of the fluid phase and the solid phase is diffusion. At the moving solid/liquid interface, osmotic pressure is balanced by surface tension, as well as balancing fluxes (conservation of mass) with the kinematics of nuclei growth (Wilson-Frenkel law). Due to the highly nonlinear boundary condition at the moving boundary, care has to be taken when performing numerical simulations. In this work, we present a nonlinear model for colloid nuclei growth. Numerical simulations using a finite volume method are compared with asymptotic analysis of the governing equation and experimental results for nuclei growth. Novel component in our numerical simulations is the inclusion of nonlinear (collective) diffusion terms that depend on the chemical potentials of the colloid in the solid and fluid phase. The results include growth and dissolution of a single colloidal nucleus, as well as evolution of multiple interacting nuclei. Supported by NASA Grant No. NNX16AQ79G.

Manipulating colloids with charges and electric fields

NARCIS (Netherlands)

Leunissen, M.E.

2007-01-01

This thesis presents the results of experimental investigations on a variety of colloidal suspensions. Colloidal particles are at least a hundred times larger than atoms or molecules, but suspended in a liquid they display the same phase behavior, including fluid and crystalline phases. Due to their

Mesoscopic electrohydrodynamic simulations of binary colloidal suspensions

Science.gov (United States)

Rivas, Nicolas; Frijters, Stefan; Pagonabarraga, Ignacio; Harting, Jens

2018-04-01

A model is presented for the solution of electrokinetic phenomena of colloidal suspensions in fluid mixtures. We solve the discrete Boltzmann equation with a Bhatnagar-Gross-Krook collision operator using the lattice Boltzmann method to simulate binary fluid flows. Solvent-solvent and solvent-solute interactions are implemented using a pseudopotential model. The Nernst-Planck equation, describing the kinetics of dissolved ion species, is solved using a finite difference discretization based on the link-flux method. The colloids are resolved on the lattice and coupled to the hydrodynamics and electrokinetics through appropriate boundary conditions. We present the first full integration of these three elements. The model is validated by comparing with known analytic solutions of ionic distributions at fluid interfaces, dielectric droplet deformations, and the electrophoretic mobility of colloidal suspensions. Its possibilities are explored by considering various physical systems, such as breakup of charged and neutral droplets and colloidal dynamics at either planar or spherical fluid interfaces.

Colloidal nanocrystals for photoelectrochemical and photocatalytic water splitting

Science.gov (United States)

Gadiyar, Chethana; Loiudice, Anna; Buonsanti, Raffaella

2017-02-01

Colloidal nanocrystals (NCs) are among the most modular and versatile nanomaterial platforms for studying emerging phenomena in different fields thanks to their superb compositional and morphological tunability. A promising, yet challenging, application involves the use of colloidal NCs as light absorbers and electrocatalysts for water splitting. In this review we discuss how the tunability of these materials is ideal to understand the complex phenomena behind storing energy in chemical bonds and to optimize performance through structural and compositional modification. First, we describe the colloidal synthesis method as a means to achieve a high degree of control over single material NCs and NC heterostructures, including examples of the role of the ligands in modulating size and shape. Next, we focus on the use of NCs as light absorbers and catalysts to drive both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), together with some of the challenges related to the use of colloidal NCs as model systems and/or technological solution in water splitting. We conclude with a broader prospective on the use of colloidal chemistry for new material discovery.

Evaluation of colloid transport issues and recommendations for SKI performance assessments

Energy Technology Data Exchange (ETDEWEB)

Wickham, S. M.; Bennett, D. G.; Higgo, J. J. W. [Galson Sciences Ltd., Oakham (United Kingdom)

2000-08-01

The primary objective of this project was to develop recommendations to SKI for evaluating the potential significance of colloids in performance assessment (PA) studies by: Updating a previous review of the treatment of colloids in PA studies for radioactive waste repositories and to include information on PAs published in the period 1997-1999. We have reviewed sixteen PAs conducted in nine countries and have made the following observations: All PAs include colloid formation and colloid transport in their FEP list. Although some programmes have deferred consideration of colloidal radionuclide transport until further research has been performed, more recent PAs do account for the effects of colloids. PAs of disposal systems in which the waste canister is surrounded by a bentonite buffer do not consider the effect of colloids on the source term. These PAs assume that all colloids are filtered by the bentonite buffer and cannot escape from the near-field. PAs of disposal systems with no bentonite buffer have to account for mobilisation of radionuclides from the waste by colloids. The concentration of colloids that may form in the repository is a key uncertainty. Many PA programmes have modelled colloidal radionuclide transport in the geosphere using one-dimensional transport equations. No PA has included a comprehensive treatment of colloid transport using mechanistic modelling. Some PAs have not undertaken modelling of colloid transport in the geosphere, but have relied instead on arguments that such transport processes will be of low consequence to the performance of the disposal system. Five PAs have shown the effects of colloid transport through the geosphere to be potentially significant. For the disposal of spent nuclear fuel, SKB has developed the KBS-3 concept. For the disposal of long-lived low-level and intermediate-level radioactive waste, SKB has developed the SFL 3-5 concept. In the SFL 3-5 concept, waste is placed in underground disposal caverns and

Wind Turbine Gearbox Oil Filtration and Condition Monitoring

Energy Technology Data Exchange (ETDEWEB)

Sheng, Shuangwen

2015-10-25

This is an invited presentation for a pre-conference workshop, titled advances and opportunities in lubrication: wind turbine, at the 2015 Society of Tribologists and Lubrication Engineers (STLE) Tribology Frontiers Conference held in Denver, CO. It gives a brief overview of wind turbine gearbox oil filtration and condition monitoring by highlighting typical industry practices and challenges. The presentation starts with an introduction by covering recent growth of global wind industry, reliability challenges, benefits of oil filtration and condition monitoring, and financial incentives to conduct wind operation and maintenance research, which includes gearbox oil filtration and condition monitoring work presented herein. Then, the presentation moves on to oil filtration by stressing the benefits of filtration, discussing typical main- and offline-loop practices, highlighting important factors considered when specifying a filtration system, and illustrating real-world application challenges through a cold-start example. In the next section on oil condition monitoring, a discussion on oil sample analysis, oil debris monitoring, oil cleanliness measurements and filter analysis is given based on testing results mostly obtained by and at NREL, and by pointing out a few challenges with oil sample analysis. The presentation concludes with a brief touch on future research and development (R and D) opportunities. It is hoping that the information presented can inform the STLE community to start or redirect their R and D work to help the wind industry advance.

Search for an optimal colloid for sentinel node imaging

International Nuclear Information System (INIS)

Imam, S.K.; Killingsworth, M.

2005-01-01

This study aims at finding a cost-effective and stable colloid of appropriate size to replace antimony sulfide colloid which is now in routine use in Australia for sentinel lymph node (SLN) imaging. For this reason we evaluated three colloids; namely phytate, hepatate and stannous fluoride (SnF 2 ). As colloids of particle size of 100-200 nm seem to be appropriate for sentinel node imaging, the three radiolabelled colloid preparations were filtered through 0.1 and 0.22 μm filters and then studied on electron microscope. Electron microscopy showed that unlike phytate, the particle size of the hepatate and SnF 2 colloids did not increase beyond the size limit of 200 nm over a period of as long as 26 hours. Instead, they remained well within the size limits chosen. The stability of particle size is required for intra-operative gamma probe lymphatic mapping that sometimes may be performed on the following day. Hepatate and SnF 2 colloids appeared to be more suited for sentinel lymph node imaging, the latter being an inhouse product is more cost-effective. Further studies based on nodal uptake and the behavior of these two radiopharmaceuticals in animals is suggested in order to evaluate their potential for future wide-spread application in human sentinel node imaging. (author)

Life Support Filtration System Trade Study for Deep Space Missions

Science.gov (United States)

Agui, Juan H.; Perry, Jay L.

2017-01-01

The National Aeronautics and Space Administrations (NASA) technical developments for highly reliable life support systems aim to maximize the viability of long duration deep space missions. Among the life support system functions, airborne particulate matter filtration is a significant driver of launch mass because of the large geometry required to provide adequate filtration performance and because of the number of replacement filters needed to a sustain a mission. A trade analysis incorporating various launch, operational and maintenance parameters was conducted to investigate the trade-offs between the various particulate matter filtration configurations. In addition to typical launch parameters such as mass, volume and power, the amount of crew time dedicated to system maintenance becomes an increasingly crucial factor for long duration missions. The trade analysis evaluated these parameters for conventional particulate matter filtration technologies and a new multi-stage particulate matter filtration system under development by NASAs Glenn Research Center. The multi-stage filtration system features modular components that allow for physical configuration flexibility. Specifically, the filtration system components can be configured in distributed, centralized, and hybrid physical layouts that can result in considerable mass savings compared to conventional particulate matter filtration technologies. The trade analysis results are presented and implications for future transit and surface missions are discussed.

Dynamic optimization of a dead-end filtration trajectory: Blocking filtration laws

NARCIS (Netherlands)

Blankert, B.; Betlem, Bernardus H.L.; Roffel, B.

2006-01-01

An operating model for dead-end membrane filtration is proposed based on the well-known blocking laws. The resulting model contains three parameters representing, the operating strategy, the fouling mechanism and the fouling potential of the feed. The optimal control strategy is determined by

Statistical Physics of Colloidal Dispersions.

Science.gov (United States)

Canessa, E.

Available from UMI in association with The British Library. Requires signed TDF. This thesis is concerned with the equilibrium statistical mechanics of colloidal dispersions which represent useful model systems for the study of condensed matter physics; namely, charge stabilized colloidal dispersions and polymer stabilized colloidal dispersions. A one-component macroparticle approach is adopted in order to treat the macroscopic and microscopic properties of these systems in a simple and comprehensive manner. The thesis opens with the description of the nature of the colloidal state before reviewing some basic definitions and theory in Chapter II. In Chapter III a variational theory of phase equilibria based on the Gibbs-Bogolyobov inequality is applied to sterically stabilized colloidal dispersions. Hard spheres are chosen as the reference system for the disordered phases while an Einstein model is used for the ordered phases. The new choice of pair potential, taken for mathematical convenience, is a superposition of two Yukawa functions. By matching a double Yukawa potential to the van der Waals attractive potential at different temperatures and introducing a purely temperature dependent coefficient to the repulsive part, a rich variety of observed phase separation phenomena is qualitatively described. The behaviour of the potential is found to be consistent with a small decrease of the polymer layer thickness with increasing temperature. Using the same concept of a collapse transition the non-monotonic second virial coefficient is also explained and quantified. It is shown that a reduction of the effective macroparticle diameter with increasing temperature can only be partially examined from the point of view of a (binary-) polymer solution theory. This chapter concludes with the description of the observed, reversible, depletion flocculation behaviour. This is accomplished by using the variational formalism and by invoking the double Yukawa potential to allow

Humic colloid-borne migration of uranium in sand columns

International Nuclear Information System (INIS)

Artinger, R.; Rabung, T.; Kim, J.I.; Sachs, S.; Schmeide, K.; Heise, K.H.; Bernhard, G.; Nitsche, H.

2002-09-01

Column experiments were carried out to investigate the influence of humic colloids on subsurface uranium migration. The columns were packed with well-characterized aeolian quartz sand and equilibrated with groundwater rich in humic colloids (dissolved organic carbon (DOC): 30 mg dm -3 ). U migration was studied under an Ar/1% CO 2 gas atmosphere as a function of the migration time, which was controlled by the flow velocity or the column length. In addition, the contact time of U with groundwater prior to introduction into a column was varied. U(VI) was found to be the dominant oxidation state in the spiked groundwater. The breakthrough curves indicate that U was transported as a humic colloid-borne species with a velocity up to 5% faster than the mean groundwater flow. The fraction of humic colloid-borne species increases with increasing prior contact time and also with decreasing migration time. The migration behavior was attributed to a kinetically controlled association/dissociation of U onto and from humic colloids and also a subsequent sorption of U onto the sediment surface. The column experiments provide an insight into humic colloid-mediated U migration in subsurface aquifers

The electrostatic interaction between interfacial colloidal particles

Science.gov (United States)

Hurd, A. J.

1985-11-01

The electrostatic interaction between charged, colloidal particles trapped at an air-water interface is considered using linearised Poisson-Boltzmann results for point particles. In addition to the expected screened-Coulomb contribution, which decays exponentially, an algebraic dipole-dipole interaction occurs that may account for long-range interactions in interfacial colloidal systems.

Solution to the colloidal silica problem in the San Luis Potosi power plant; Solucion del problema de silice coloidal en la central termoelectrica San Luis Potosi

Energy Technology Data Exchange (ETDEWEB)

Lopez Rubalcava, Humberto [Comision Federal de Electricidad (CFE), Mexico, D. F. (Mexico); Mercado, Sergio [Instituto de Investigaciones Electricas, Cuernavaca (Mexico); Guerra, Protasio [Comision Federal de Electricidad (CFE), Mexico, D. F. (Mexico)

1988-12-31

In June 1986 the Comision Federal de Electricidad (CFE) made tests to raise the load of the first normalized unit of 350 MW of the San Luis Potosi Power Plant; although the new system for colloidal silica removal had not yet been installed, consisting of a hollow fibers ultra-filtration system with a capacity of 110 m{sup 3}, that for the first time would be applied in a Mexican power plant. It was decided to install this system due to the fact that the well water supplying this power plant comes from a geothermal reservoir, with water at 38 degrees Celsius and a silica content of 15 to 250 parts per billion (ppb) of colloidal silica, which makes it necessary to eliminate it in order to enable the boiler operation at its design conditions (175 bars (2573 psig) and 540 degrees Celsius). Although a demineralizing plant existed for the boiler feed water make up, the ion exchange resins were not able to retain the colloidal silica. Also, the First Unit operation was held at 25% of its rated capacity; in trying to raise the output to 50%, the silica concentration in the boiler water went over the allowed limits, resulting in a concentration of 1,500 ppb in the boiler water and 28 ppb in the steam. One the ultra-filtration plant was installed, the power plant operated at full rated capacity with silica concentrations in the steam lower than the permitted concentration, i.e. 10 ppb . By the end of 1987 the Second Unit of 350 MW was put into operation with the ultra-filtration system in operation, reaching full load without any problem. Once confirmed the efficiency of the ultra-filtration for the colloidal silica removal, CFE will apply this system in other power plants of the country having the same problem. [Espanol] En junio de 1986, la Comision Federal de Electricidad (CFE) efectuo pruebas de elevacion de carga en la primera unidad normalizada de 350 MW de la central termoelectrica San Luis Potosi; sin embargo, aun no se terminaba de instalar el nuevo sistema para la

Spectrum of antimicrobial activity associated with ionic colloidal silver.

Science.gov (United States)

Morrill, Kira; May, Kathleen; Leek, Daniel; Langland, Nicole; Jeane, La Deana; Ventura, Jose; Skubisz, Corey; Scherer, Sean; Lopez, Eric; Crocker, Ephraim; Peters, Rachel; Oertle, John; Nguyen, Krystine; Just, Scott; Orian, Michael; Humphrey, Meaghan; Payne, David; Jacobs, Bertram; Waters, Robert; Langland, Jeffrey

2013-03-01

Silver has historically and extensively been used as a broad-spectrum antimicrobial agent. However, the Food and Drug Administration currently does not recognize colloidal silver as a safe and effective antimicrobial agent. The goal of this study was to further evaluate the antimicrobial efficacy of colloidal silver. Several strains of bacteria, fungi, and viruses were grown under multicycle growth conditions in the presence or absence of ionic colloidal silver in order to assess the antimicrobial activity. For bacteria grown under aerobic or anaerobic conditions, significant growth inhibition was observed, although multiple treatments were typically required. For fungal cultures, the effects of ionic colloidal silver varied significantly between different genera. No viral growth inhibition was observed with any strains tested. The study data support ionic colloidal silver as a broad-spectrum antimicrobial agent against aerobic and anaerobic bacteria, while having a more limited and specific spectrum of activity against fungi.

Colloids related to low level and intermediate level waste

International Nuclear Information System (INIS)

Ramsay, J.D.F.; Russell, P.J.; Avery, R.G.

1991-01-01

A comprehensive research investigation has been undertaken to improve the understanding of the potential role of colloids in the context of disposal and storage of low level and intermediate level waste immobilized in cement. Several topics have been investigated which include: (a) the study of the formation and characteristics of colloids in cement leachates; (b) the effects of the near-field aqueous chemistry on the characteristics of colloids in repository environments; (c) colloid sorption behaviour; (d) interactions of near-field materials with leachates; (e) characteristics of near-field materials in EC repository simulation tests; and (f) colloid migration behaviour. These experimental investigations should provide data and a basis for the development of transport models and leaching mechanisms, and thus relate directly to the part of the Task 3 programme concerned with migration and retention of radionuclides in the near field. 114 Figs.; 39 Tabs.; 12 Refs

Groundwater colloids: Their mobilization from subsurface deposits. Final report

International Nuclear Information System (INIS)

1998-01-01

The overall goal of this program has involved developing basic understandings of the mechanisms controlling the presence of colloidal phases in groundwaters. The presence of colloids in groundwater is extremely important in that they may enable the subsurface transport of otherwise immobile pollutants like plutonium or PCBs. The major findings of this work have included: (1) Sampling groundwaters must be performed with great care in order to avoid false positives; (2) Much of the colloidal load moving below ground derives from the aquifer solids themselves; and (3) The detachment of colloids from the aquifer solids occurs in response to changes in the groundwater solution chemistry

Mitigation of radon and thoron decay products by filtration

International Nuclear Information System (INIS)

Wang Jin; Meisenberg, Oliver; Chen Yongheng; Karg, Erwin; Tschiersch, Jochen

2011-01-01

Inhalation of indoor radon ( 222 Rn) and thoron ( 220 Rn) decay products is the most important source of exposure to ionizing radiation for the human respiratory tract. Decreasing ventilation rates due to energy saving reasons in new buildings suggest additional active mitigation techniques to reduce the exposure in homes with high radon and thoron concentrations but poor ventilation. Filtration techniques with HEPA filters and simple surgical mask material have been tested for their potential to reduce the indoor exposure in terms of the total effective dose for mixed radon and thoron indoor atmospheres. The tests were performed inside an experimental room providing stable conditions. Filtration (at filtration rates of 0.2 h -1 and larger) removes attached radon and thoron decay products effectively but indoor aerosol as well. Therefore the concentration of unattached decay products (which have a higher dose coefficient) may increase. The decrease of the attached decay product concentrations could be theoretically described by a slowly decreasing exponential process. For attached radon decay products, it exhibited a faster but weaker removal process compared to attached thoron decay products (- 70% for attached radon decay products and - 80% for attached thoron decay products at a filtration rate of 0.5 h -1 with an HEPA filter). The concentration of unattached thoron decay products increased distinctly during the filtration process (+ 300%) while that of unattached radon decay products rose only slightly though at a much higher level (+ 17%). In the theoretical description these observed differences could be attributed to the different half-lives of the nuclides. Considering both effects, reduced attached and increased unattached decay product concentrations, filtration could significantly decrease the total effective dose from thoron whereas the overall effect on radon dose is small. A permanent filtration is recommended because of the slow decrease of the

An overview of filtration methods that can provide protection from the macrofouling zebra mussel at hydroelectric facilities

Energy Technology Data Exchange (ETDEWEB)

Smythe, A.G.; Short, T.M. [Acres International Corp., Amherst, NY (United States)

1995-12-31

The non-indigenous freshwater zebra and quagga mussels (Dreissena, spp.) threaten to foul freshwater conduits throughout much of the United States and southern Canada. Initially, many electric facilities within the lower Great Lakes drainage were fouled. More recently, other systems both in and out of the Great Lakes, have been exposed to infested water facilitated by canals and boat traffic and impacted by the mussels. Mussels have clogged conduits and fouled equipment and monitoring sensors in relatively distant regions including the Hudson River, the Mississippi River south to New Orleans, and the Arkansas River into Oklahoma. Chemicals can effectively control the mussels, however, filtration methods promise to be a relatively cost effective, environmentally safe alternative control approach. Information on traditional filtration methods will be presented in this paper along with recent research results for in-line filters.

A study of dynamic filtration; Um estudo sobre filtracao dinamica

Energy Technology Data Exchange (ETDEWEB)

Girao, Joaquim Helder S [PETROBRAS, Natal, RN (Brazil). Distrito de Perfuracao da Bacia Potiguar. Div. de Tecnicas de Perfuracao

1990-12-31

The problems that cause cost increase such as: formation damage and borehole swelling or caving lead us to study the filtration of the liquid part of formation drilling fluid. With the aim of comparing static and dynamic filtration rates, we developed a modest dynamic filtration equipment, consisting of a modified API filter, connected to reservoir by means of a positive injection pump. We carried out various tests, and the results were set in charts and tables. Through these, it is possible to notice how the static and dynamic filtration curves come apart for a same pressure value. We also evaluated the effects of circulation speed, starch concentration and counter pressure. This paper does not include calculations or mathematical models accounting for filtrate invasion radii, but it demonstrates, for example, that cleaning circulation will cause lower filtration rates at lower flows. (author) 5 refs., 11 figs., 14 tabs.

A study of dynamic filtration; Um estudo sobre filtracao dinamica

Energy Technology Data Exchange (ETDEWEB)

Girao, Joaquim Helder S. [PETROBRAS, Natal, RN (Brazil). Distrito de Perfuracao da Bacia Potiguar. Div. de Tecnicas de Perfuracao

1989-12-31

The problems that cause cost increase such as: formation damage and borehole swelling or caving lead us to study the filtration of the liquid part of formation drilling fluid. With the aim of comparing static and dynamic filtration rates, we developed a modest dynamic filtration equipment, consisting of a modified API filter, connected to reservoir by means of a positive injection pump. We carried out various tests, and the results were set in charts and tables. Through these, it is possible to notice how the static and dynamic filtration curves come apart for a same pressure value. We also evaluated the effects of circulation speed, starch concentration and counter pressure. This paper does not include calculations or mathematical models accounting for filtrate invasion radii, but it demonstrates, for example, that cleaning circulation will cause lower filtration rates at lower flows. (author) 5 refs., 11 figs., 14 tabs.

Temperature-Triggered Colloidal Gelation through Well-Defined Grafted Polymeric Surfaces

Directory of Open Access Journals (Sweden)

Jan Maarten van Doorn

2017-06-01

Full Text Available Sufficiently strong interparticle attractions can lead to aggregation of a colloidal suspension and, at high enough volume fractions, form a mechanically rigid percolating network known as a colloidal gel. We synthesize a model thermo-responsive colloidal system for systematically studying the effect of surface properties, grafting density and chain length, on the particle dynamics within colloidal gels. After inducing an attraction between particles by heating, aggregates undergo thermal fluctuation which we observe and analyze microscopically; the magnitude of the variance in bond angle is larger for lower grafting densities. Macroscopically, a clear increase of the linear mechanical behavior of the gels on both the grafting density and chain length arises, as measured by rheology, which is inversely proportional to the magnitude of local bond angle fluctuations. This colloidal system will allow for further elucidation of the microscopic origins to the complex macroscopic mechanical behavior of colloidal gels including bending modes within the network.

Zeta potential in colloid science principles and applications

CERN Document Server

Hunter, Robert J; Rowell, R L

2013-01-01

Zeta Potential in Colloid Science: Principles and Applications covers the concept of the zeta potential in colloid chemical theory. The book discusses the charge and potential distribution at interfaces; the calculation of the zeta potential; and the experimental techniques used in the measurement of electrokinetic parameters. The text also describes the electroviscous and viscoelectric effects; applications of the zeta potential to areas of colloid science; and the influence of simple inorganic ions or more complex adsorbates on zeta potential. Physical chemists and people involved in the stu

Depletion interactions in two-dimensional colloid-polymer mixtures: molecular dynamics simulations

International Nuclear Information System (INIS)

Kim, Soon-Chul; Seong, Baek-Seok; Suh, Soong-Hyuck

2009-01-01

The depletion interactions acting between two hard colloids immersed in a bath of polymers, in which the interaction potentials include the soft repulsion/attraction, are extensively studied by using the molecular dynamics simulations. The collision frequencies and collision angle distributions for both incidental and reflection conditions are computed to study the dynamic properties of the colloidal mixtures. The depletion effect induced by the polymer-polymer and colloid-polymer interactions are investigated as well as the size ratio of the colloid and polymer. The simulated results show that the strong depletion interaction between two hard colloids appears for the highly asymmetric hard-disc mixtures. The attractive depletion force at contact becomes deeper and the repulsive barrier becomes wider as the asymmetry in size ratio increases. The strong polymer-polymer attraction leads to the purely attractive depletion interaction between two hard colloids, whereas the purely repulsive depletion interaction is induced by the strong colloid-polymer attraction.

Waste Form and Indrift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary

International Nuclear Information System (INIS)

Aguilar, R.

2003-01-01

This Model Report describes the analysis and abstractions of the colloids process model for the waste form and engineered barrier system components of the total system performance assessment calculations to be performed with the Total System Performance Assessment-License Application model. Included in this report is a description of (1) the types and concentrations of colloids that could be generated in the waste package from degradation of waste forms and the corrosion of the waste package materials, (2) types and concentrations of colloids produced from the steel components of the repository and their potential role in radionuclide transport, and (3) types and concentrations of colloids present in natural waters in the vicinity of Yucca Mountain. Additionally, attachment/detachment characteristics and mechanisms of colloids anticipated in the repository are addressed and discussed. The abstraction of the process model is intended to capture the most important characteristics of radionuclide-colloid behavior for use in predicting the potential impact of colloid-facilitated radionuclide transport on repository performance

Waste Form and Indrift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary

Energy Technology Data Exchange (ETDEWEB)

R. Aguilar

2003-06-24

This Model Report describes the analysis and abstractions of the colloids process model for the waste form and engineered barrier system components of the total system performance assessment calculations to be performed with the Total System Performance Assessment-License Application model. Included in this report is a description of (1) the types and concentrations of colloids that could be generated in the waste package from degradation of waste forms and the corrosion of the waste package materials, (2) types and concentrations of colloids produced from the steel components of the repository and their potential role in radionuclide transport, and (3) types and concentrations of colloids present in natural waters in the vicinity of Yucca Mountain. Additionally, attachment/detachment characteristics and mechanisms of colloids anticipated in the repository are addressed and discussed. The abstraction of the process model is intended to capture the most important characteristics of radionuclide-colloid behavior for use in predicting the potential impact of colloid-facilitated radionuclide transport on repository performance.

Test of precoat filtration technology for treatment of swimming pool water.

Science.gov (United States)

Christensen, Morten Lykkegaard; Klausen, Morten Møller; Christensen, Peter Vittrup

2018-02-01

The technical performance of a precoat filter was compared with that of a traditional sand filter. Particle concentration and size distribution were measured before and after the filtration of swimming pool water. Both the sand and precoat filters could reduce the particle concentration in the effluent. However, higher particle removal efficiency was generally observed for the precoat filter, especially for particles smaller than 10 μm in diameter. Adding flocculant improved the removal efficiency of the sand filter, resulting in removal efficiencies comparable to those of the precoat filter. Three powders, i.e., two types of perlite (Harbolite ® and Aquatec perlite) and cellulose fibers (Arbocel ® ), were tested for the precoat filter, but no significant difference in particle removal efficiency was observed among them. The maximum efficiency was reached within 30-40 min of filtration. The energy required for the pumps increased by approximately 35% over a period of 14 days. The energy consumption could be reduced by replacing the powder on the filter cloth. The sand filter was backwashed once a week, while the powder on the precoat filter was replaced every two weeks. Under these conditions, it was possible to reduce the water used for cleaning by 88% if the precoat filter was used instead of the sand filter.

Transport of synthetic colloids through single saturated fractures: A literature review

International Nuclear Information System (INIS)

Reimus, P.W.

1995-07-01

Colloids having the same surface charge sign as the bulk of the geologic media in a groundwater system may be able to travel through the system faster than soluble species because they will follow fluid streamlines more closely and they should have less tendency to diffuse into pores or dead spaces in the media than soluble species. Synthetic colloids with uniform, controlled properties may be ideal for serving as open-quotes worst-caseclose quotes tracers that provide lower-bound estimates of contaminant travel times in hydrologic systems. This report discusses a review of the literature pertaining to colloid transport in single saturated natural fractures. After a brief background discussion to put the literature review in perspective, the phenomenon of colloid transport in saturated fractures is divided into three major topics, each of which is reviewed in detail: (1) saturated fluid flow through fractures; (2) colloid transport by convection, diffusion, and force fields; and (3) colloid interactions with surfaces. It is suggested that these phenomena be accounted for in colloid transport models by using (1) lubrication theory to describe water flow through fractures, (2) particle tracking methods to describe colloid transport in fractures, and (3) a kinetic boundary layer approximation to describe colloid interactions with fracture walls. These methods offer better computational efficiency and better experimental accessibility to model parameters than rigorously solving the complete governing equations

Detection of colloidal silver chloride near solubility limit

Science.gov (United States)

Putri, K. Y.; Adawiah, R.

2018-03-01

Detection of nanoparticles in solution has been made possible by several means; one of them is laser-induced breakdown detection (LIBD). LIBD is able to distinguish colloids of various sizes and concentrations. This technique has been used in several solubility studies. In this study, the formation of colloids in a mixed system of silver nitrate and sodium chloride was observed by acoustic LIBD. Silver chloride has low solubility limit, therefore LIBD measurement is appropriate. Silver and chloride solutions with equal concentrations, set at below and above the solubility of silver chloride as the expected solid product, were mixed and the resulting colloids were observed. The result of LIBD measurement showed that larger particles were present as more silver and chloride introduced. However, once the concentrations exceeded the solubility limit of silver chloride, the detected particle size seemed to be decreasing, hence suggested the occurrence of coprecipitation process. This phenomenon indicated that the ability of LIBD to detect even small changes in colloid amounts might be a useful tool in study on formation and stability of colloids, i.e. to confirm whether nanoparticles synthesis has been successfully performed and whether the system is stable or not.

Adsorption, immobilization, and activity of beta-glucosidase on different soil colloids.

Science.gov (United States)

Yan, Jinlong; Pan, Genxing; Li, Lianqing; Quan, Guixiang; Ding, Cheng; Luo, Ailan

2010-08-15

For a better understanding of enzyme stabilization and the subsequent catalytic process in a soil environment, the adsorption, immobilization, and activity of beta-glucosidase on various soil colloids from a paddy soil were studied. The calculated parameters maximum adsorption capacity (q(0)) for fine soil colloids ranged from 169.6 to 203.7 microg mg(-1), which was higher than coarse soil colloids in the range of 81.0-94.6 microg mg(-1), but the lower adsorption affinity (K(L)) was found on fine soil colloids. The percentages of beta-glucosidase desorbed from external surfaces of the coarse soil colloids (27.6-28.5%) were higher than those from the fine soil colloids (17.5-20.2%). Beta-glucosidase immobilized on the coarse inorganic and organic soil colloids retained 72.4% and 69.8% of activity, respectively, which indicated the facilitated effect of soil organic matter in the inhibition of enzyme activity. The residual activity for the fine soil clay is 79-81%. After 30 days of storage at 40 degrees C the free beta-glucosidase retained 66.2% of its initial activity, whereas the soil colloidal particle-immobilized enzyme retained 77.1-82.4% of its activity. The half-lives of free beta-glucosidase appeared to be 95.9 and 50.4 days at 25 and 40 degrees C. Immobilization of beta-glucosidase on various soil colloids enhanced the thermal stability at all temperatures, and the thermal stability was greatly affected by the affinity between the beta-glucosidase molecules and the surface of soil colloidal particles. Due to the protective effect of supports, soil colloidal particle-immobilized enzymes were less sensitive to pH and temperature changes than free enzymes. Data obtained in this study are helpful for further research on the enzymatic mechanisms in carbon cycling and soil carbon storage. Copyright 2010 Elsevier Inc. All rights reserved.

Manipulating semiconductor colloidal stability through doping.

Science.gov (United States)

Fleharty, Mark E; van Swol, Frank; Petsev, Dimiter N

2014-10-10

The interface between a doped semiconductor material and electrolyte solution is of considerable fundamental interest, and is relevant to systems of practical importance. Both adjacent domains contain mobile charges, which respond to potential variations. This is exploited to design electronic and optoelectronic sensors, and other enabling semiconductor colloidal materials. We show that the charge mobility in both phases leads to a new type of interaction between semiconductor colloids suspended in aqueous electrolyte solutions. This interaction is due to the electrostatic response of the semiconductor interior to disturbances in the external field upon the approach of two particles. The electrostatic repulsion between two charged colloids is reduced from the one governed by the charged groups present at the particles surfaces. This type of interaction is unique to semiconductor particles and may have a substantial effect on the suspension dynamics and stability.

Filtration and retention capacities of filter aids

International Nuclear Information System (INIS)

Mellah, A.; Boualia, A.

1992-01-01

The present work involves the filtration of impure uranyl nitrate solutions by different filter aids such as kieselguhr, celite and bleaching clay. The retention of substances contained in uranyl nitrate solution was determined using the three filter aids. A study of the effects of granulometry and filter earths treatment (thermal and chemical) on the filtration rate was performed

Rheological State Diagrams for Rough Colloids in Shear Flow.

Science.gov (United States)

Hsiao, Lilian C; Jamali, Safa; Glynos, Emmanouil; Green, Peter F; Larson, Ronald G; Solomon, Michael J

2017-10-13

To assess the role of particle roughness in the rheological phenomena of concentrated colloidal suspensions, we develop model colloids with varying surface roughness length scales up to 10% of the particle radius. Increasing surface roughness shifts the onset of both shear thickening and dilatancy towards lower volume fractions and critical stresses. Experimental data are supported by computer simulations of spherical colloids with adjustable friction coefficients, demonstrating that a reduction in the onset stress of thickening and a sign change in the first normal stresses occur when friction competes with lubrication. In the quasi-Newtonian flow regime, roughness increases the effective packing fraction of colloids. As the shear stress increases and suspensions of rough colloids approach jamming, the first normal stresses switch signs and the critical force required to generate contacts is drastically reduced. This is likely a signature of the lubrication films giving way to roughness-induced tangential interactions that bring about load-bearing contacts in the compression axis of flow.

Nonlinear machine learning and design of reconfigurable digital colloids.

Science.gov (United States)

Long, Andrew W; Phillips, Carolyn L; Jankowksi, Eric; Ferguson, Andrew L

2016-09-14

Digital colloids, a cluster of freely rotating "halo" particles tethered to the surface of a central particle, were recently proposed as ultra-high density memory elements for information storage. Rational design of these digital colloids for memory storage applications requires a quantitative understanding of the thermodynamic and kinetic stability of the configurational states within which information is stored. We apply nonlinear machine learning to Brownian dynamics simulations of these digital colloids to extract the low-dimensional intrinsic manifold governing digital colloid morphology, thermodynamics, and kinetics. By modulating the relative size ratio between halo particles and central particles, we investigate the size-dependent configurational stability and transition kinetics for the 2-state tetrahedral (N = 4) and 30-state octahedral (N = 6) digital colloids. We demonstrate the use of this framework to guide the rational design of a memory storage element to hold a block of text that trades off the competing design criteria of memory addressability and volatility.

Rheological State Diagrams for Rough Colloids in Shear Flow

Science.gov (United States)

Hsiao, Lilian C.; Jamali, Safa; Glynos, Emmanouil; Green, Peter F.; Larson, Ronald G.; Solomon, Michael J.

2017-10-01

To assess the role of particle roughness in the rheological phenomena of concentrated colloidal suspensions, we develop model colloids with varying surface roughness length scales up to 10% of the particle radius. Increasing surface roughness shifts the onset of both shear thickening and dilatancy towards lower volume fractions and critical stresses. Experimental data are supported by computer simulations of spherical colloids with adjustable friction coefficients, demonstrating that a reduction in the onset stress of thickening and a sign change in the first normal stresses occur when friction competes with lubrication. In the quasi-Newtonian flow regime, roughness increases the effective packing fraction of colloids. As the shear stress increases and suspensions of rough colloids approach jamming, the first normal stresses switch signs and the critical force required to generate contacts is drastically reduced. This is likely a signature of the lubrication films giving way to roughness-induced tangential interactions that bring about load-bearing contacts in the compression axis of flow.

Wetting in a Colloidal Liquid-Gas System

Science.gov (United States)

Wijting, W. K.; Besseling, N. A.; Stuart, M. A.

2003-05-01

We present first observations of wetting phenomena in depletion interaction driven, phase separated colloidal dispersions (coated silica cyclohexane-polydimethylsiloxane). The contact angle of the colloidal liquid-gas interface at a solid substrate (coated glass) was determined for a series of compositions. Upon approach to the critical point, a transition occurs from partial to complete wetting.

Wetting in a colloidal liquid-gas system

OpenAIRE

Wijting, W.K.; Besseling, N.A.M.; Cohen Stuart, M.A.

2003-01-01

We present first observations of wetting phenomena in depletion interaction driven, phase separated colloidal dispersions (coated silica-cyclohexane-polydimethylsiloxane). The contact angle of the colloidal liquid-gas interface at a solid substrate (coated glass) was determined for a series of compositions. Upon approach to the critical point, a transition occurs from partial to complete wetting.

Fabrication of Phase-Change Polymer Colloidal Photonic Crystals

Directory of Open Access Journals (Sweden)

Tianyi Zhao

2014-01-01

Full Text Available This paper presents the preparation of phase-change polymer colloidal photonic crystals (PCs by assembling hollow latex spheres encapsulated with dodecanol for the first time. The monodispersed hollow latex spheres were obtained by phase reversion of monodispersed core-shell latex spheres in the n-hexane, which dissolves the PS core and retains the PMMA/PAA shell. The as-prepared phase-change colloidal PCs show stable phase-change behavior. This fabrication of phase-change colloidal PCs would be significant for PC’s applications in functional coatings and various optic devices.

Continuous separation of colloidal particles using dielectrophoresis.

Science.gov (United States)

Yunus, Nurul Amziah Md; Nili, Hossein; Green, Nicolas G

2013-04-01

Dielectrophoresis is the movement of particles in nonuniform electric fields and has been of interest for application to manipulation and separation at and below the microscale. This technique has the advantages of being noninvasive, nondestructive, and noncontact, with the movement of particle achieved by means of electric fields generated by miniaturized electrodes and microfluidic systems. Although the majority of applications have been above the microscale, there is increasing interest in application to colloidal particles around a micron and smaller. This paper begins with a review of colloidal and nanoscale dielectrophoresis with specific attention paid to separation applications. An innovative design of integrated microelectrode array and its application to flow-through, continuous separation of colloidal particles is then presented. The details of the angled chevron microelectrode array and the test microfluidic system are then discussed. The variation in device operation with applied signal voltage is presented and discussed in terms of separation efficiency, demonstrating 99.9% separation of a mixture of colloidal latex spheres. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Glass transition of soft colloids

Science.gov (United States)

Philippe, Adrian-Marie; Truzzolillo, Domenico; Galvan-Myoshi, Julian; Dieudonné-George, Philippe; Trappe, Véronique; Berthier, Ludovic; Cipelletti, Luca

2018-04-01

We explore the glassy dynamics of soft colloids using microgels and charged particles interacting by steric and screened Coulomb interactions, respectively. In the supercooled regime, the structural relaxation time τα of both systems grows steeply with volume fraction, reminiscent of the behavior of colloidal hard spheres. Computer simulations confirm that the growth of τα on approaching the glass transition is independent of particle softness. By contrast, softness becomes relevant at very large packing fractions when the system falls out of equilibrium. In this nonequilibrium regime, τα depends surprisingly weakly on packing fraction, and time correlation functions exhibit a compressed exponential decay consistent with stress-driven relaxation. The transition to this novel regime coincides with the onset of an anomalous decrease in local order with increasing density typical of ultrasoft systems. We propose that these peculiar dynamics results from the combination of the nonequilibrium aging dynamics expected in the glassy state and the tendency of colloids interacting through soft potentials to refluidize at high packing fractions.

C-cells in colloid goiter

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Lima Marcus A.

2003-01-01

Full Text Available PURPOSE: The aim of this investigation was to quantitatively evaluate C-cells in colloid goiters, analyzing 36 thyroids that were obtained through thyroidectomy from 24 patients with goiter and 12 normal glands from adult patients without thyroid disease, which were used as the control group. MATERIAL AND METHODS: On average, 6 different thyroid areas were sampled and labeled by immunohistochemistry with a monoclonal anticalcitonin antibody, utilizing the avidin-biotin-peroxidase complex. C-cells were counted in fields measuring 1 square centimeter, and the mean number of cells per field was then calculated. Data were statistically analyzed using the Mann-Whitney test. RESULTS: In the colloid goiter group, the number of C-cells ranged from 0 to 23 per field, while in normal controls they ranged from 20 to 148 per field. CONCLUSIONS: These results demonstrate a significant decrease of C-cell number in the colloid goiter group compared with control group, indicating that the hyperplastic process is restricted to follicular cells, to the detriment of C-cells, which probably cease to receive trophic stimuli.

40 CFR 141.171 - Criteria for avoiding filtration.

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 22 2010-07-01 2010-07-01 false Criteria for avoiding filtration. 141.171 Section 141.171 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) WATER PROGRAMS (CONTINUED) NATIONAL PRIMARY DRINKING WATER REGULATIONS Enhanced Filtration and Disinfection...

Component-Customizable Porous Rare-Earth-Based Colloidal Spheres towards Highly Effective Catalysts and Bioimaging Applications.

Science.gov (United States)

Li, Cheng Chao; Rui, Xianhong; Wei, Weifeng; Chen, Libao; Yu, Yan

2017-11-16

Multicomponent porous colloidal spheres are of interest because they not only show a combination of the properties associated with all different components, but also usually present synergy effects. However, a combination of different components in a single porous sphere is still greatly challenged due to the different precipitation behaviors of each component. In this work, we have developed a general synthetic route to prepare several categories of porous monodisperse rare-earth (RE)-based colloidal spheres with customizable elemental compositions and a uniform element distribution. The two-step synthetic strategy is based on the integration of coordination chemistry precipitation of RE ions and a subsequent ion-exchange process, which steers clear of obstacles, such as differences in solubility product constant, that are to be found in traditional co-precipitation methods. Our approach provides a new mixing mechanism to realize homogeneous distribution of each element within the porous spheres. An array of binary, ternary, and even senary RE colloidal porous spheres with diameters of 500 nm to 700 nm has been successfully synthesized. Taking advantage of their good dispersibility, porosity, and customizable components, these porous RE oxide spheres show excellent catalytic activity for the reduction of 4-nitrophenol, and promising application in single-phase multifunctional bioprobes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The application of polyelectrolytes to improve liquid radwaste treatment system radionuclide removal efficiency

International Nuclear Information System (INIS)

Homyk, W.A.; Spall, M.J.; Vance, J.N.

1990-01-01

At nuclear plants, miscellaneous waste water treated in the liquid radwaste processing system contains a significant fraction of suspended particulate materials ranging in size from a few microns down to the submicron region. The fewer particles that typically exist as colloids are generally negatively charged by virtue of inorganic and organic anions absorbed onto the particle surfaces. Because many of the radionuclides exist as colloids and resist agglomeration and settling they are not easily removed by mechanical filtration or ion exchange processes. The colloidal materials will easily pass through most filters with conventional pore size ratings and through most ion exchange media. This leads to poor decontamination Factors (dFs) and higher radionuclide releases to the environment. A laboratory-scale testing program was conducted at Indian Point Unit No. 2 to determine the effectiveness of the use of organic polyelectrolytes to destabilize colloidal suspensions in liquid radwaste. Destabilizing colloidal suspensions will improve the removal efficiencies of the suspended material by typical filtration and ion exchange processes. The increased removal efficiencies will provide increased dFs in the liquid radwaste treatment system. The testing focused on identifying the specific organic polyelectrolytes and the associated dosages which would be effective in destabilizing the colloidal suspensions on actual waste water samples. The testing also examined the filtration characteristics of the water source to determine filter parameters such as: body feed material, body feed dosages, specific flow rates, etc., which would provide the basis for the design of filtration systems for these applications. The testing effort and the major conclusions from this investigation are given. 4 refs., 8 figs., 2 tabs

Vibrating membrane filtration as improved technology for microalgae dewatering

OpenAIRE

Nurra, C.; Clavero, E.; Salvadó, J.; Torras, C.

2014-01-01

10.1016/j.biortech.2014.01.115 The effect of shear-enhanced filtration by vibratory process in microalgae dewatering is presented in this paper. The aim of this research was to investigate the technical performance and improvement of vibrating membrane filtration compared with conventional tangential cross-flow filtration in microalgae concentration. An industrial-scale available commercial set-up was used. Several membrane materials as polyethersulfone, polyacrylonitrile, etc., and mean ...

Small-angle neutron scattering from colloidal dispersions

International Nuclear Information System (INIS)

Ottewill, R.H.

1991-01-01

A survey is given of recent work on the use of small-angle neutron scattering to examine colloidal dispersions. Particular attention is given to the determination of particle size and polydispersity, the determination of particle morphology and the behaviour of concentrated colloidal dispersions, both at rest and under the influence of an applied shear field. (orig.)

Scaling and particulate fouling in membrane filtration systems

NARCIS (Netherlands)

Boerlage, S.F.E.

2001-01-01

In the last decade, pressure driven membrane filtration processes; reverse osmosis, nano, ultra and micro-filtration have undergone steady growth. Drivers for this growth include desalination to combat water scarcity and the removal of various material from water to comply with increasingly

Sampling silica and ferrihydrite colloids with fiberglass wicks under unsaturated conditions.

Science.gov (United States)

Shira, Jason M; Williams, Barbara C; Flury, Markus; Czigány, Szabolcs; Tuller, Markus

2006-01-01

The suitability of passive capillary samplers (PCAPS) for collection of representative colloid samples under partially saturated conditions was evaluated by investigating the transport of negatively and positively charged colloids in fiberglass wicks. A synthetic pore water solution was used to suspend silica microspheres (330 nm in diameter) and ferrihydrite (172 nm in diameter) for transport experiments on fiberglass wicks. Breakthrough curves were collected for three unsaturated flow rates with silica microspheres and one unsaturated flow rate with ferrihydrite colloids. A moisture characteristic curve, relating tensiometer measurements of matric potential to moisture content, was developed for the fiberglass wick. Results indicate that retention of the silica and the ferrihydrite on the wick occurred; that is, the wicks did not facilitate quantitative sampling of the colloids. For silica microspheres, 90% of the colloids were transmitted through the wicks. For ferrihydrite, 80 to 90% of the colloids were transmitted. The mechanisms responsible for the retention of the colloids on the fiberglass wicks appeared to be physicochemical attachment and not thin-film, triple-phase entrapment, or mechanical straining. Visualization of pathways by iron staining indicates that flow is preferential at the center of twisted bundles of filaments. Although axial preferential flow in PCAPS may enhance their hydraulic suitability for sampling mobile colloids, we conclude that without specific preparation to reduce attachment or retention, fiberglass wicks should only be used for qualitative sampling of pore water colloids.

Sorption and mechanism of aqueous U(Ⅵ) onto red soil-colloid

International Nuclear Information System (INIS)

Xia Liangshu; Huang Xin; Cao Cuncun; Chen Wei; Lu Junwen

2013-01-01

By static adsorption experiments, the effects of pH, ionic strength, adsorption time, uranium initial concentration, adsorbent dosage, red soil-colloid size, and organic matters on the biosorption capacity of red soil-colloid extracted from the soil around uranium tailing for uranium were studied. The adsorption process was analyzed by thermodynamics and kinetics, and the adsorption mechanism was characterized by the element analysis, infrared spectroscopy and scanning electron microscopy. The results show that the adsorption capacity for U (Ⅵ) on red soil-colloid increases with the decrease of ionic strength or particle size, increases with the initial concentration of uranium, decreases with the increase of the amount of red soil-colloid; the saturated adsorption capacity q max can be up to 76.76 μg/mg by red soil-colloid which diameter is less than 1 μm at 25 ℃ and pH=3.5, when the ionic strength is 0.001 mol/L. FT-IR micrograph before and after red soil-colloid adsorbed uranyl ions indicates that the red soil-colloid are mainly composed of hydroxyl, carbonyl, Si-O, Si-O-Fe, etc. The adsorption of U (Ⅵ) on red soil-colloid follows Langmuir adsorption isotherm, and the pseudo-second-order equation provides the best correlation for the adsorption process. (authors)

COLLOIDS IN SEPTIC TANK EFFLUENT AND THEIR INFLUENCE ON FILTER PERMEABILITY

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Marcin Spychała

2015-09-01

Full Text Available The aim of the study was to evaluate the content of colloids in septic tank effluent and their impact on textile filter permeability. Measurements were performed on septic tank effluent without suspended solids but containing colloids and without colloids - including only dissolved substances (filtered by micro-filters and centrifuged. The study was conducted on unclogged and clogged textile filter coupons. During the study the following measurements were determined: turbidity, chemical oxygen demand and hydraulic conductivity of textile filter coupons. The colloid size range was assumed to be less than 1.2 microns according to the literature. Despite the relatively low content in the septic tank effluent the colloids played an important role in the clogging process. Both the filtering media, filled with low (unclogged and high content of biomass (clogged were sensitive to the clogging process of colloid acceleration due to the possibility of small diameter pore closure and oxygen access termination. Moreover, small size pores were probably sensitive to closing or bridging by small size colloidal particles.

Vacuum distillation/vapor filtration water recovery

Science.gov (United States)

Honegger, R. J.; Neveril, R. B.; Remus, G. A.

1974-01-01

The development and evaluation of a vacuum distillation/vapor filtration (VD/VF) water recovery system are considered. As a functional model, the system converts urine and condensates waste water from six men to potable water on a steady-state basis. The system is designed for 180-day operating durations and for function on the ground, on zero-g aircraft, and in orbit. Preparatory tasks are summarized for conducting low gravity tests of a vacuum distillation/vapor filtration system for recovering water from urine.

Depletion and the dynamics in colloid-polymer mixtures

NARCIS (Netherlands)

Tuinier, R.; Fan, T.H.; Taniguchi, T.

2015-01-01

The status of work on the influence of nonadsorbing polymers on depletion dynamics in colloidal dispersions is reviewed. In the past focus has been paid to equilibrium properties of colloid-polymer mixtures. In practice the dynamical behaviour is equally important. Dynamic properties including

Advanced Colloids Experiment (ACE) Science Overview

Science.gov (United States)

Meyer, William V.; Sicker, Ronald J.; Chiaramonte, Francis P.; Luna, Unique J.; Chaiken, Paul M.; Hollingsworth, Andrew; Secanna, Stefano; Weitz, David; Lu, Peter; Yodh, Arjun;

Industrial Application of Open Pore Ceramic Foam for Molten Metal Filtration

Science.gov (United States)

Gauckler, L. J.; Waeber, M. M.; Conti, C.; Jacob-Dulière, M.

Ceramic foam filters were used for industrial filtration of aluminum. Results are compared with laboratory experiments which are in good agreement with trajectory analyses of deep bed filtration for the early stage of filtration.

Colloid and interface chemistry for nanotechnology

CERN Document Server

Kralchevsky, Peter; Ravera, Francesca

2016-01-01

Colloid and interface science dealt with nanoscale objects for nearly a century before the term nanotechnology was coined. An interdisciplinary field, it bridges the macroscopic world and the small world of atoms and molecules. Colloid and Interface Chemistry for Nanotechnology is a collection of manuscripts reflecting the activities of research teams that have been involved in the networking project Colloid and Interface Chemistry for Nanotechnology (2006-2011), Action D43, the European Science Foundation. The project was a part of the intergovernmental framework for Cooperation in Science and Technology (COST), allowing the coordination of nationally funded research across Europe. With contributions by leading experts, this book covers a wide range of topics. Chapters are grouped into three sections: "Nanoparticle Synthesis and Characterization," "New Experimental Tools and Interpretation," and "Nanocolloidal Dispersions and Interfaces." The topics covered belong to six basic research areas: (1) The synthes...

Dynamic properties of polydisperse colloidal particles in the presence of thermal gradient studied by a modified Brownian dynamic model

Science.gov (United States)

Song, Dongxing; Jin, Hui; Jing, Dengwei; Wang, Xin

2018-03-01

Aggregation and migration of colloidal particles under the thermal gradient widely exists in nature and many industrial processes. In this study, dynamic properties of polydisperse colloidal particles in the presence of thermal gradient were studied by a modified Brownian dynamic model. Other than the traditional forces on colloidal particles, including Brownian force, hydrodynamic force, and electrostatic force from other particles, the electrostatic force from the asymmetric ionic diffusion layer under a thermal gradient has been considered and introduced into the Brownian dynamic model. The aggregation ratio of particles (R A), the balance time (t B) indicating the time threshold when {{R}A} becomes constant, the porosity ({{P}BA} ), fractal dimension (D f) and distributions of concentration (DISC) and aggregation (DISA) for the aggregated particles were discussed based on this model. The aggregated structures formed by polydisperse particles are less dense and the particles therein are loosely bonded. Also it showed a quite large compressibility as the increases of concentration and interparticle potential can significantly increase the fractal dimension. The thermal gradient can induce two competitive factors leading to a two-stage migration of particles. When t{{t}B} , the thermophoresis becomes dominant thus the migrations of particles are against the thermal gradient. The effect of thermophoresis on the aggregate structures was found to be similar to the effect of increasing particle concentration. This study demonstrates how the thermal gradient affects the aggregation of monodisperse and polydisperse particles and can be a guide for the biomimetics and precise control of colloid system under the thermal gradient. Moreover, our model can be easily extended to other more complex colloidal systems considering shear, temperature fluctuation, surfactant, etc.

Scattering from correlations in colloidal systems

International Nuclear Information System (INIS)

Hayter, J.B.

1984-01-01

Colloidal suspensions typically exhibit spatial correlations over distances of order 10-10 4 A, corresponding either to the size of individual particles (e.g., polymer chains, surfactant micelles) or to the range of interaction between particles (e.g., charged polymer lattices at low ionic strength). Apart from having fundamental intrinsic interest, such systems are also extremely useful as model systems with which to study, for example, non-Newtonian hydrodynamics, since temporal correlations are generally much longer lived (10 -8 -10 -3 sec) than those found in simple atomic or small molecular systems (10 -13 -10 -10 sec). Colloids have long been the subject of macroscopic phenomenological research (on rheological properties, for example), but it is only recently that microscopic light, x-ray and neutron scattering techniques have been applied to their study, in large part because of theoretical difficulties in understanding the scattering from dense liquid-like systems of interacting particles. For spherical colloids, such theoretical problems have now been largely overcome, and for anisotropic colloids experimental techniques are being developed which circumvent the intractable theoretical areas. This paper will first review some static light and small-angle neutron scattering (SANS) results on colloidal suspensions, both at equilibrium and in steady-state non-equilibrium situations, and will then discuss some dynamic measurements on polymer solutions and melts made using the neutron spin-echo (NSE) technique. Emphasis is placed on experiments which have a possible counterpart in synchrotron radiation studies. In particular, NSE extends the results of photon correlation spectroscopy (PCS) to larger momentum transfers and shorter time-scales than are available with visible light, and the extension of PCS to short wavelength on a synchrotron source would be of similar fundamental interest

Rheology modification in mixed shape colloidal dispersions. Part I: pure components

NARCIS (Netherlands)

ten Brinke, A.J.W.; Bailey, L.; Lekkerkerker, H.N.W.; Matiland, G.C.

2007-01-01

The flow behaviour and rheology of colloidal dispersions are of considerable interest in many applications, for example colloidal clay particles find applications in oilfield and constructiondrilling fluids. The rheological properties of such fluids can be enhanced significantly by adding colloidal

Baleen Hydrodynamics and Morphology of Cross-Flow Filtration in Balaenid Whale Suspension Feeding.

Directory of Open Access Journals (Sweden)

Alexander J Werth

Full Text Available The traditional view of mysticete feeding involves static baleen directly sieving particles from seawater using a simple, dead-end flow-through filtration mechanism. Flow tank experiments on bowhead (Balaena mysticetus baleen indicate the long-standing model of dead-end filtration, at least in balaenid (bowhead and right whales, is not merely simplistic but wrong. To recreate continuous intraoral flow, sections of baleen were tested in a flume through which water and buoyant particles circulated with variable flow velocity. Kinematic sequences were analyzed to investigate movement and capture of particles by baleen plates and fringes. Results indicate that very few particles flow directly through the baleen rack; instead much water flows anteroposteriorly along the interior (lingual side of the rack, allowing items to be carried posteriorly and accumulate at the posterior of the mouth where they might readily be swallowed. Since water flows mainly parallel to rather than directly through the filter, the cross-flow mechanism significantly reduces entrapment and tangling of minute items in baleen fringes, obviating the need to clean the filter. The absence of copepods or other prey found trapped in the baleen of necropsied right and bowhead whales supports this hypothesis. Reduced through-baleen flow was observed with and without boundaries modeling the tongue and lips, indicating that baleen itself is the main if not sole agent of crossflow. Preliminary investigation of baleen from balaenopterid whales that use intermittent filter feeding suggests that although the biomechanics and hydrodynamics of oral flow differ, cross-flow filtration may occur to some degree in all mysticetes.

Water quality and treatment of river bank filtrate

Directory of Open Access Journals (Sweden)

W. W. J. M. de Vet

2010-06-01

Full Text Available In drinking water production, river bank filtration has the advantages of dampening peak concentrations of many dissolved components, substantially removing many micropollutants and removing, virtually completely, the pathogens and suspended solids. The production aquifer is not only fed by the river bank infiltrate but also by water percolating through covering layers. In the polder areas, these top layers consist of peat and deposits from river sediments and sea intrusions.

This paper discusses the origin and fate of macro components in river bank filtrate, based on extensive full-scale measurements in well fields and treatment systems of the Drinking Water Company Oasen in the Netherlands. First, it clarifies and illustrates redox reactions and the mixing of river bank filtrate and PW as the dominant processes determining the raw water quality for drinking water production. Next, full-scale results are elaborated on to evaluate trickling filtration as an efficient and proven one-step process to remove methane, iron, ammonium and manganese. The interaction of methane and manganese removal with nitrification in these systems is further analyzed. Methane is mostly stripped during trickling filtration and its removal hardly interferes with nitrification. Under specific conditions, microbial manganese removal may play a dominant role.

H51E-1535: Biogeochemical factors influencing the transport and fate of colloids and colloid-associated contaminants in the vadose zone

Science.gov (United States)

The vadose zone exhibits large spatial and temporal variability in many physical, chemical, and biological factors that strongly influence the transport and fate of colloids (e.g., microbes, nanoparticles, clays, and dissolved organic matter) and colloid-associated contaminants (e.g., heavy metals, ...

Anisotropic colloids: bulk phase behavior and equilibrium sedimentation

NARCIS (Netherlands)

Marechal, M.A.T.

2009-01-01

This thesis focuses on the phase behavior of anisotropically shaped (i.e. non-spherical) colloids using computer simulations. Only hard-core interactions between the colloids are taken into account to investigate the effects of shape alone. The bulk phase behavior of three different shapes of

COLLOID-FACILITATED TRANSPORT OF RADIONUCLIDES THROUGH THE VADOSE ZONE

International Nuclear Information System (INIS)

Flury, Markus

2003-01-01

Contaminants have leaked into the vadose zone at the USDOE Hanford reservation. It is important to understand the fate and transport of these contaminants to design remediation strategies and long-term waste management plans at the Hanford reservation. Colloids may play an important role in fate and transport of strongly sorbing contaminants, such as Cs or Pu. This project seeks to improve the basic understanding of colloid and colloid-facilitated transport of contaminants in the vadose zone. The specific objectives addressed are: (1) Determine the structure, composition, and surface charge characteristics of colloidal particles formed under conditions similar to those occurring during leakage of waste typical of Hanford tank supernatants into soils and sediments surrounding the tanks. (2) Characterize the mutual interactions between colloids, contaminant, and soil matrix in batch experiments under various ionic strength and pH conditions. We will investigate the nature of the solid-liquid interactions and the kinetics of the reactions. (3) Evaluate mobility of colloids through soil under different degrees of water saturation and solution chemistry (ionic strength and pH). (4) Determine the potential of colloids to act as carriers to transport the contaminant through the vadose zone and verify the results through comparison with field samples collected under leaking tanks. (5) Improve conceptual characterization of colloid-contaminant-soil interactions and colloid-facilitated transport for implementation into reactive chemical transport models. This project was in part supported by an NSF-IGERT grant to Washington State University. The IGERT grant provided funding for graduate student research and education, and two graduate students were involved in the EMSP project. The IGERT program also supported undergraduate internships. The project is part of a larger EMSP program to study fate and transport of contaminants under leaking Hanford waste tanks. The project has

Agglomeration of Luminescent Porous Silicon Nanoparticles in Colloidal Solutions.

Science.gov (United States)

Herynková, Kateřina; Šlechta, Miroslav; Šimáková, Petra; Fučíková, Anna; Cibulka, Ondřej

2016-12-01

We have prepared colloidal solutions of clusters composed from porous silicon nanoparticles in methanol, water and phosphate-buffered saline (PBS). Even if the size of the nanoclusters is between 60 and 500 nm, due to their highly porous "cauliflower"-like structure, the porous silicon nanoparticles are composed of interconnected nanocrystals having around 2.5 nm in size and showing strong visible luminescence in the orange-red spectral region (centred at 600-700 nm). Hydrophilic behaviour and good solubility of the nanoclusters in water and water-based solutions were obtained by adding hydrogen peroxide into the etching solution during preparation and 16 min long after-bath in hydrogen peroxide. By simple filtration of the solutions with syringe filters, we have extracted smaller nanoclusters with sizes of approx. 60-70 nm; however, these nanoclusters in water and PBS solution (pH neutral) are prone to agglomeration, as was confirmed by zeta potential measurements. When the samples were left at ambient conditions for several weeks, the typical nanocluster size increased to approx. 330-400 nm and then remained stable. However, both freshly filtered and aged samples (with agglomerated porous silicon nanoparticles) of porous silicon in water and PBS solutions can be further used for biological studies or as luminescent markers in living cells.

Dynamic optimization of a dead-end filtration trajectory: non-ideal cake filtration

NARCIS (Netherlands)

Blankert, B.; Kattenbelt, C.; Betlem, Bernardus H.L.; Roffel, B.

2007-01-01

A control strategy aimed at minimizing energy consumption is formulated for non-ideal dead-end cake filtration with an inside-out hollow fiber ultrafiltration membrane system. The non-ideal behavior was assumed to originate from cake compression, non-linear cake resistance and a variable pump

Secondary Emission From Synthetic Opal Infiltrated by Colloidal Gold and Glycine

International Nuclear Information System (INIS)

Dovbeshko, G.I.; Fesenko, O.M.; Boyko, V.V.; Romanyuk, V.R.; Gorelik, V.S.; Moiseyenko, V.N.; Sobolev, V.B.; Shvalagin, V.V.

2012-01-01

A comparison of the secondary emission (photoluminescence) and Bragg reflection spectra of photonic crystals (PC), namely, synthetic opals, opals infiltrated by colloidal gold, glycine, and a complex of colloidal gold with glycine is performed. The infiltration of colloidal gold and a complex of colloidal gold with glycine into the pores of PC causes a short-wavelength shift (about 5-15 nm) of the Bragg reflection and increases the intensity of this band by 1.5-3 times. In photoluminescence, the infiltration of PC by colloidal gold and colloidal gold with glycine suppresses the PC emission band near 375-450 nm and enhances the shoulder of the stop-zone band of PC in the region of 470-510 nm. The shape of the observed PC emission band connected with defects in synthetic opal is determined by the type of infiltrates and the excitation wavelength. Possible mechanisms of the effects are discussed.

Strontium migration in a crystalline medium: effects of the presence of bentonite colloids.

Science.gov (United States)

Albarran, Nairoby; Missana, Tiziana; García-Gutiérrez, Miguel; Alonso, Ursula; Mingarro, Manuel

2011-03-25

The effects of bentonite colloids on strontium migration in fractured crystalline medium were investigated. We analyzed first the transport behaviour of bentonite colloids alone at different flow rates; then we compared the transport behaviour of strontium as solute and of strontium previously adsorbed onto stable bentonite colloids at a water velocity of approximately 7.1·10(-6)m/s-224m/yr. Experiments with bentonite colloids alone showed that - at the lowest water flow rate used in our experiments (7.1·10(-6)m/s) - approximately 70% of the initially injected colloids were retained in the fracture. Nevertheless, the mobile colloidal fraction, moved through the fracture without retardation, at any flow rate. Bentonite colloids deposited over the fracture surface were identified during post-mortem analyses. The breakthrough curve of strontium as a solute, presented a retardation factor, R(f)~6, in agreement with its sorption onto the granite fracture surface. The breakthrough curve of strontium in the presence of bentonite colloids was much more complex, suggesting additional contributions of colloids to strontium transport. A very small fraction of strontium adsorbed on mobile colloids moved un-retarded (R(f)=1) and this fraction was much lower than the expected, considering the quantity of strontium initially adsorbed onto colloids (90%). This behaviour suggests the hypothesis of strontium sorption reversibility from colloids. On the other hand, bentonite colloids retained within the granite fracture played a major role, contributing to a slower strontium transport in comparison with strontium as a solute. This was shown by a clear peak in the breakthrough curve corresponding to a retardation factor of approximately 20. Copyright © 2010 Elsevier B.V. All rights reserved.

Functional principal component analysis of glomerular filtration rate curves after kidney transplant.

Science.gov (United States)

Dong, Jianghu J; Wang, Liangliang; Gill, Jagbir; Cao, Jiguo

2017-01-01

This article is motivated by some longitudinal clinical data of kidney transplant recipients, where kidney function progression is recorded as the estimated glomerular filtration rates at multiple time points post kidney transplantation. We propose to use the functional principal component analysis method to explore the major source of variations of glomerular filtration rate curves. We find that the estimated functional principal component scores can be used to cluster glomerular filtration rate curves. Ordering functional principal component scores can detect abnormal glomerular filtration rate curves. Finally, functional principal component analysis can effectively estimate missing glomerular filtration rate values and predict future glomerular filtration rate values.

Colloidal silica films for high-capacity DNA arrays

Science.gov (United States)

Glazer, Marc Irving

The human genome project has greatly expanded the amount of genetic information available to researchers, but before this vast new source of data can be fully utilized, techniques for rapid, large-scale analysis of DNA and RNA must continue to develop. DNA arrays have emerged as a powerful new technology for analyzing genomic samples in a highly parallel format. The detection sensitivity of these arrays is dependent on the quantity and density of immobilized probe molecules. We have investigated substrates with a porous, "three-dimensional" surface layer as a means of increasing the surface area available for the synthesis of oligonucleotide probes, thereby increasing the number of available probes and the amount of detectable bound target. Porous colloidal silica films were created by two techniques. In the first approach, films were deposited by spin-coating silica colloid suspensions onto flat glass substrates, with the pores being formed by the natural voids between the solid particles (typically 23nm pores, 35% porosity). In the second approach, latex particles were co-deposited with the silica and then pyrolyzed, creating films with larger pores (36 nm), higher porosity (65%), and higher surface area. For 0.3 mum films, enhancements of eight to ten-fold and 12- to 14-fold were achieved with the pure silica films and the films "templated" with polymer latex, respectively. In gene expression assays for up to 7,000 genes using complex biological samples, the high-capacity films provided enhanced signals and performed equivalently or better than planar glass on all other functional measures, confirming that colloidal silica films are a promising platform for high-capacity DNA arrays. We have also investigated the kinetics of hybridization on planar glass and high-capacity substrates. Adsorption on planar arrays is similar to ideal Langmuir-type adsorption, although with an "overshoot" at high solution concentration. Hybridization on high-capacity films is

Charge-extraction strategies for colloidal quantum dot photovoltaics

KAUST Repository

Lan, Xinzheng

2014-02-20

The solar-power conversion efficiencies of colloidal quantum dot solar cells have advanced from sub-1% reported in 2005 to a record value of 8.5% in 2013. Much focus has deservedly been placed on densifying, passivating and crosslinking the colloidal quantum dot solid. Here we review progress in improving charge extraction, achieved by engineering the composition and structure of the electrode materials that contact the colloidal quantum dot film. New classes of structured electrodes have been developed and integrated to form bulk heterojunction devices that enhance photocharge extraction. Control over band offsets, doping and interfacial trap state densities have been essential for achieving improved electrical communication with colloidal quantum dot solids. Quantum junction devices that not only tune the optical absorption spectrum, but also provide inherently matched bands across the interface between p-and n-materials, have proven that charge separation can occur efficiently across an all-quantum-tuned rectifying junction. © 2014 Macmillan Publishers Limited.

Diffusing colloidal probes of protein-carbohydrate interactions.

Science.gov (United States)

Eichmann, Shannon L; Meric, Gulsum; Swavola, Julia C; Bevan, Michael A

2013-02-19

We present diffusing colloidal probe measurements of weak, multivalent, specific protein-polysaccharide interactions mediated by a competing monosaccharide. Specifically, we used integrated evanescent wave and video microscopy methods to monitor the three-dimensional Brownian excursions of conconavilin A (ConA) decorated colloids interacting with dextran-functionalized surfaces in the presence of glucose. Particle trajectories were interpreted as binding lifetime histograms, binding isotherms, and potentials of mean force. Binding lifetimes and isotherms showed clear trends of decreasing ConA-dextran-specific binding with increasing glucose concentration, consistent with expectations. Net potentials were accurately captured by superposition of a short-range, glucose-independent ConA-dextran repulsion and a longer-range, glucose-dependent dextran bridging attraction modeled as a harmonic potential. For glucose concentrations greater than 100 mM, the net ConA-dextran potential was found to have only a nonspecific repulsion, similar to that of bovine serum albumin (BSA) decorated colloids over dextran determined in control experiments. Our results demonstrate the first use of optical microscopy methods to quantify the connections between potentials of mean force and the binding behavior of ConA-decorated colloids on dextran-functionalized surfaces.

Active colloidal propulsion over a crystalline surface

Science.gov (United States)

Choudhury, Udit; Straube, Arthur V.; Fischer, Peer; Gibbs, John G.; Höfling, Felix

2017-12-01

We study both experimentally and theoretically the dynamics of chemically self-propelled Janus colloids moving atop a two-dimensional crystalline surface. The surface is a hexagonally close-packed monolayer of colloidal particles of the same size as the mobile one. The dynamics of the self-propelled colloid reflects the competition between hindered diffusion due to the periodic surface and enhanced diffusion due to active motion. Which contribution dominates depends on the propulsion strength, which can be systematically tuned by changing the concentration of a chemical fuel. The mean-square displacements (MSDs) obtained from the experiment exhibit enhanced diffusion at long lag times. Our experimental data are consistent with a Langevin model for the effectively two-dimensional translational motion of an active Brownian particle in a periodic potential, combining the confining effects of gravity and the crystalline surface with the free rotational diffusion of the colloid. Approximate analytical predictions are made for the MSD describing the crossover from free Brownian motion at short times to active diffusion at long times. The results are in semi-quantitative agreement with numerical results of a refined Langevin model that treats translational and rotational degrees of freedom on the same footing.

Colloid migration in groundwaters: Geochemical interactions of radionuclides with natural colloids. 5. progress report. Period covered: July - December 1993

Energy Technology Data Exchange (ETDEWEB)

Kim, J.I. [Technische Univ. Muenchen, Garching (Germany); Delakowitz, B. [Technische Univ. Muenchen, Garching (Germany); Zeh, P. [Technische Univ. Muenchen, Garching (Germany); Probst, T. [Technische Univ. Muenchen, Garching (Germany); Lin, X. [Technische Univ. Muenchen, Garching (Germany); Ehrlicher, U. [Technische Univ. Muenchen, Garching (Germany); Schauer, C. [Technische Univ. Muenchen, Garching (Germany); Ivanovich, M. [Harwell Lab., AEA Environment and Energy, Oxon (United Kingdom); Longworth, G. [Harwell Lab., AEA Environment and Energy, Oxon (United Kingdom); Hasler, S.E. [Harwell Lab., AEA Environment and Energy, Oxon (United Kingdom); Gardiner, M. [Harwell Lab., AEA Decommissioning and RadWaste, Oxon (United Kingdom); Fritz, P. [GSF - Forschungszentrum fuer Umwelt und Gesundheit GmbH, Neuherberg (Germany); Klotz, D. [GSF - Forschungszentrum fuer Umwelt und Gesundheit GmbH, Neuherberg (Germany); Lazik, D. [GSF - Forschungszentrum fuer Umwelt und Gesundheit GmbH, Neuherberg (Germany); Wolf, M. [GSF - Forschungszentrum fuer Umwelt und Gesundheit GmbH, Neuherberg (Germany); Geyer, S. [GSF - Forschungszentrum fuer Umwelt und Gesundheit GmbH, Neuherberg (Germany); Alexander, J.L. [Atkins (W.S.) Engineering Sciences, Epsom (United Kingdom); Read, D. [Atkins (W.S.) Engineering Sciences, Epsom (United Kingdom); Thomas, J.B. [Atkins (W.S.) Engineering Sciences, Epsom (United Kingdom)

1994-02-01

The aim of the joint research programme is to determine the significance of groundwater colloids in far field radionuclide migration. The characterization, quantification and theoretical interpretation of colloid-borne transport phenomena of radionuclides in selected Gorleben aquifer systems are the main objectives of the present research programme. Gorleben aquifer systems are chosen because they are well characterized in terms of their hydrological and geological properties and because they contain substantial amounts of colloids of different chemical compositions as well as considerable quantities of chemical homologues and natural analogues of radionuclides, e.g. M(III), M(IV), M(VI), and Th and U decay series. The research tasks are investigated jointly by the four laboratories (listed below) in close coordination of experimental capacities of each laboratory. (orig.)

Investigation of factors affecting adhesion of 99Tcm labelled colloids to glass vials

International Nuclear Information System (INIS)

Elliott, A.T.; Murray, T.; Hilditch, T.E.; Whateley, T.L.

1990-01-01

Factors which may possibly influence the adhesion of 99 Tc m labelled colloid to glass vials were investigated. Of five colloids studied, two protein-free tin colloids were affected most by the problem, some 12-18% being lost by adhesion to the glass vial when the colloid was left resting on the bench, or 60-87% when it was rotated for a period of 4 h. The proportion of activity which adhered to the vial was dependent on the time the product had been contained within it, whether on the bench or rotated. Two of the colloids, both of which contained protein, were affected only slightly by the problem, one being a tin colloid and the other a sulphur colloid. An antimony sulphide colloid, which contained no added protein, was virtually unaffected by the problem. The degree of adhesion was not related to the pH of the product, or to the temperature at which the product was stored, nor to the tendency of the colloidal particles to grow in size upon vigorous agitation. (author)

Colloids in the mortar backfill of a cementitious repository for radioactive waste

International Nuclear Information System (INIS)

Wieland, E.; Spieler, P.

1999-01-01

Colloids are present in groundwater aquifers and water-permeable engineered barrier systems and may facilitate the migration of radionuclides. A careful evaluation of colloid concentrations is required to assess the potential effect of colloids on nuclide migration and, consequently, on the safety of a repository for radioactive waste. A highly permeable mortar is foreseen to be used as backfill for the engineered barrier of the Swiss repository for low- and intermediate-level waste (L/ILW). The backfill is considered to be a chemical environment with a potential for colloid generation and, due to its high porosity, for colloid mobility. In this contribution a novel in-house built particle counting device is described, and measurements of colloid concentrations in the pore water of backfill mortar are presented. (author)

Capillary evaporation in colloid-polymer mixtures selectively confined to a planar slit

International Nuclear Information System (INIS)

Schmidt, Matthias; Fortini, Andrea; Dijkstra, Marjolein

2004-01-01

Using density functional theory and Monte Carlo simulations we investigate the Asakura-Oosawa-Vrij mixture of hard sphere colloids and non-adsorbing ideal polymers under selective confinement of the colloids to a planar slab geometry. This is a model for confinement of colloid-polymer mixtures by either two parallel walls with a semi-permeable polymer coating or through the use of laser tweezers. We find that such a pore favours the colloidal gas over the colloidal liquid phase and induces capillary evaporation. A treatment based on the Kelvin equation gives a good account of the location of the capillary binodal for large slit widths. The colloid density profile is found to exhibit a minimum (maximum) at contact with the wall for large (small) slit widths

Correlation between physical structure and magnetic anisotropy of a magnetic nanoparticle colloid

Science.gov (United States)

Dennis, C. L.; Jackson, A. J.; Borchers, J. A.; Gruettner, C.; Ivkov, R.

2018-05-01

We show the effects of a time-invariant magnetic field on the physical structure and magnetic properties of a colloid comprising 44 nm diameter magnetite magnetic nanoparticles, with a 24 nm dextran shell, in water. Structural ordering in this colloid parallel to the magnetic field occurs simultaneously with the onset of a colloidal uniaxial anisotropy. Further increases in the applied magnetic field cause the nanoparticles to order perpendicular to the field, producing unexpected colloidal unidirectional and trigonal anisotropies. This magnetic behavior is distinct from the cubic magnetocrystalline anisotropy of the magnetite and has its origins in the magnetic interactions among the mobile nanoparticles within the colloid. Specifically, these field-induced anisotropies and colloidal rearrangements result from the delicate balance between the magnetostatic and steric forces between magnetic nanoparticles. These magnetic and structural rearrangements are anticipated to influence applications that rely upon time-dependent relaxation of the magnetic colloids and fluid viscosity, such as magnetic hyperthermia and shock absorption.

Implant materials modified by colloids

Directory of Open Access Journals (Sweden)

Zboromirska-Wnukiewicz Beata

2016-03-01

Full Text Available Recent advances in general medicine led to the development of biomaterials. Implant material should be characterized by a high biocompatibility to the tissue and appropriate functionality, i.e. to have high mechanical and electrical strength and be stable in an electrolyte environment – these are the most important properties of bioceramic materials. Considerations of biomaterials design embrace also electrical properties occurring on the implant-body fluid interface and consequently the electrokinetic potential, which can be altered by modifying the surface of the implant. In this work, the surface of the implants was modified to decrease the risk of infection by using metal colloids. Nanocolloids were obtained using different chemical and electrical methods. It was found that the colloids obtained by physical and electrical methods are more stable than colloids obtained by chemical route. In this work the surface of modified corundum implants was investigated. The implant modified by nanosilver, obtained by electrical method was selected. The in vivo research on animals was carried out. Clinical observations showed that the implants with modified surface could be applied to wounds caused by atherosclerotic skeleton, for curing the chronic and bacterial inflammations as well as for skeletal reconstruction surgery.

Studies of colloids and their importance for repository performance assessment

International Nuclear Information System (INIS)

Laaksoharju, M.; Skaarman, C.; Degueldre, C.

1995-12-01

The processes, parameters and data used to evaluate the potential of nuclide transport by a colloid facilitated mechanism are reviewed and discussed in this report. Both steady-state (present situation) and possible future non-steady-state hydrogeochemistry in the geosphere are covered. In the steady-state scenario, the colloid (clay, silica, iron(III)hydroxide) concentration is around 20-45 micrograms/l which is considered to be a low value. The low colloid concentration is justified by the large attachment factor to the rock which reduces the stability of the colloids in the aquifer. Both reversible and irreversible sorption processes are reviewed. In the non-steady-state scenario, changes of hydrogeochemical properties may induce larger colloid concentrations. The increase of concentration is however limited and relaxation is always observed after any change. Emphasis is placed on the glaciation-deglaciation scenario. 53 refs, 12 figs, 3 tabs

Sensitive chemical neutron dosimetry using silver colloids

International Nuclear Information System (INIS)

Brede, O.; Boes, J.; Hoesselbarth, B.

1982-01-01

The radiation-induced formation of silver colloid was checked for its use as a sensitive dosimeter for neutron irradiation. For non-monoenergetic pulsed neutron irradiation in the Dubna IBR-30 reactor, the colloid dosimeter was found to be suitable to indicate the chemical neutron effect, i.e., to determine the sum concentration of the primary particles of water radiolysis: esub(aq)sup(-), OH and H. (author)

Green synthesis of silver nanoparticles and silver colloidal solutions

International Nuclear Information System (INIS)

Nguyen Thi Phuong Phong; Ngo Hoang Minh; Ngo Vo Ke Thanh; Dang Mau Chien

2009-01-01

In this paper, silver colloidal solutions have been synthesized rapidly in green conditions by using microwave irradiation and non-toxic chemistry substances (acid oxalic, silver nitrate, polyvinyl pyrolidone (PVP; Mw = 55 000)). The particle size and morphology of these solutions can be controlled by altering several factors like the time, the power of microwave exposure, and the ratio of silver oxalate and PVP etc. The silver nanoparticles were fabricated by thermal decomposition of silver oxalate. The synthesized silver colloidal solutions and silver nanoparticles were characterized by several analytical techniques like UV- VIS, XRD, TEM, FESEM/EDS and ICP-AAS studies. Finally, we used the synthesized silver colloidal solutions for antibacterial purpose. The obtained results showed that the synthesized silver colloidal solutions, even at very low concentrations, have highly efficient anti-bacterial property.

Open channels in fractures maintained by deposition and erosion of colloids

International Nuclear Information System (INIS)

Kessler, J.H.; Hunt, J.R.

1993-01-01

Material in the colloidal size range is present in many natural groundwater systems at existing or proposed radioactive waste storage locations. Colloids initially suspended in the water in fractures can deposit onto the fracture surfaces, and will partially or fully clog the fracture. The amount of clogging will depend on whether the deposited colloidal material can erode from the fracture surfaces. If the fracture remains only partially clogged the unclogged regions take the form of open channels. The purpose of this paper is to assess under what conditions these open channels form. An analytical model of a steady state, average open channel width is presented which is a function of the fluid flow rate and viscosity, fracture aperture, and the permeability and shear strength of the deposited colloidal material. The implications of the presence of open channels for colloidal transport is also discussed. However, for most repository conditions the fractures are expected to fully clog with colloids

Particulate Matter Filtration Design Considerations for Crewed Spacecraft Life Support Systems

Science.gov (United States)

Agui, Juan H.; Vijayakumar, R.; Perry, Jay L.

2016-01-01

Particulate matter filtration is a key component of crewed spacecraft cabin ventilation and life support system (LSS) architectures. The basic particulate matter filtration functional requirements as they relate to an exploration vehicle LSS architecture are presented. Particulate matter filtration concepts are reviewed and design considerations are discussed. A concept for a particulate matter filtration architecture suitable for exploration missions is presented. The conceptual architecture considers the results from developmental work and incorporates best practice design considerations.

Immobilized Filters for Air Filtration

National Research Council Canada - National Science Library

Mahle, John J; Zaiee, Saeed

2002-01-01

... (settling performance) and attrition resistance. The fabricated filter samples will be analyzed in order to determine the physical and chemical factors affecting mechanical strength and chemical filtration...

Polymers at interfaces and in colloidal dispersions.

Science.gov (United States)

Fleer, Gerard J

2010-09-15

This review is an extended version of the Overbeek lecture 2009, given at the occasion of the 23rd Conference of ECIS (European Colloid and Interface Society) in Antalya, where I received the fifth Overbeek Gold Medal awarded by ECIS. I first summarize the basics of numerical SF-SCF: the Scheutjens-Fleer version of Self-Consistent-Field theory for inhomogeneous systems, including polymer adsorption and depletion. The conformational statistics are taken from the (non-SCF) DiMarzio-Rubin lattice model for homopolymer adsorption, which enumerates the conformational details exactly by a discrete propagator for the endpoint distribution but does not account for polymer-solvent interaction and for the volume-filling constraint. SF-SCF corrects for this by adjusting the field such that it becomes self-consistent. The model can be generalized to more complex systems: polydispersity, brushes, random and block copolymers, polyelectrolytes, branching, surfactants, micelles, membranes, vesicles, wetting, etc. On a mean-field level the results are exact; the disadvantage is that only numerical data are obtained. Extensions to excluded-volume polymers are in progress. Analytical approximations for simple systems are based upon solving the Edwards diffusion equation. This equation is the continuum variant of the lattice propagator, but ignores the finite segment size (analogous to the Poisson-Boltzmann equation without a Stern layer). By using the discrete propagator for segments next to the surface as the boundary condition in the continuum model, the finite segment size can be introduced into the continuum description, like the ion size in the Stern-Poisson-Boltzmann model. In most cases a ground-state approximation is needed to find analytical solutions. In this way realistic analytical approximations for simple cases can be found, including depletion effects that occur in mixtures of colloids plus non-adsorbing polymers. In the final part of this review I discuss a

Hydrothermal synthesis of highly water-dispersible anatase nanocrystals from transparent aqueous sols of titanate colloids

International Nuclear Information System (INIS)

Ban, Takayuki; Tanaka, Yusuke; Ohya, Yutaka

2011-01-01

Transparent colloidal aqueous solutions of anatase nanocrystals were hydrothermally synthesized from aqueous transparent sols with tetramethylammonium titanate colloids, the surfaces of which were modified with citric acid, by structural conversion of the titanate to anatase. This modification hindered coalescence of the titanate colloids during the hydrothermal synthesis. Although the amount of citric acid adsorbed on the colloids was reduced during hydrothermal treatment, a small amount of citric acid was adsorbed on the resulting anatase nanocrystals. Moreover, the use of the titanate colloids as a precursor was compared with the use of a citrato Ti complex, tetramethylammonium citratotitanate. The hydrothermal treatment of the transparent aqueous solutions of the Ti complex yielded opaque solutions with large anatase colloids, suggesting that the titanate colloids were useful for preparing transparent anatase colloidal solutions. Because the shape and size of resulting colloids may be dependent on the size and shape of starting colloids, the use of titanate colloids as a precursor may make it easy to control size and shape of anatase colloids.

Method of electrostatic filtration

International Nuclear Information System (INIS)

Devienne, F.M.

1975-01-01

Electrostatic filtration of secondary ions of mass m in a given mass ratio with a primary ion of mass M which has formed the secondary ions by fission is carried out by a method which consists in forming a singly-charged primary ion of the substance having a molecular mass M and extracting the ion at a voltage V 1 with respect to ground. The primary ion crosses a potential barrier V 2 , in producing the dissociation of the ion into at least two fragments of secondary ions and in extracting the fragment ion of mass m at a voltage V 2 . Filtration is carried out in an electrostatic analyzer through which only the ions of energy eV'' are permitted to pass, detecting the ions which have been filtered. The mass m of the ions is such that (M/m) = (V 1 - V 2 )/(V'' - V 2 )

Is the use of particle air filtration justified? Costs and benefits of filtration with regard to health effects, building cleaning and occupant productivity

DEFF Research Database (Denmark)

Bekö, Gabriel; Clausen, Geo; Weschler, Charles J.

2008-01-01

Estimates of costs and the corresponding benefits of particle filtration have been derived for a standard office building. Reduction in occupants’ exposure to particles during their workday is anticipated to reduce their morbidity and mortality. Filtration may also reduce the costs associated......, the sensitivity of the results to these parameters was evaluated as part of this study. The study also acknowledges that the benefits-to-costs ratio depends on the perspective of the stakeholder: the employer renting the building is impacted by occupant performance and building energy costs; the building owner...... is impacted by maintenance of the building and its HVAC system; society is impacted by the employees’ health and welfare. Regardless of perspective, particle filtration is anticipated to lead to annual savings significantly exceeding the running costs for filtration. However, economic losses resulting from...

Iron colloids reduce the bioavailability of phosphorus to the green alga Raphidocelis subcapitata.

Science.gov (United States)

Baken, Stijn; Nawara, Sophie; Van Moorleghem, Christoff; Smolders, Erik

2014-08-01

Phosphorus (P) is a limiting nutrient in many aquatic systems. The bioavailability of P in natural waters strongly depends on its speciation. In this study, structural properties of iron colloids were determined and related to their effect on P sorption and P bioavailability. The freshwater green alga Raphidocelis subcapitata was exposed to media spiked with radiolabelled (33)PO4, and the uptake of (33)P was monitored for 1 h. The media contained various concentrations of synthetic iron colloids with a size between 10 kDa and 0.45 μm. The iron colloids were stabilised by natural organic matter. EXAFS spectroscopy showed that these colloids predominantly consisted of ferrihydrite with small amounts of organically complexed Fe. In colloid-free treatments, the P uptake flux by the algae obeyed Michaelis-Menten kinetics. In the presence of iron colloids at 9 or 90 μM Fe, corresponding to molar P:Fe ratios between 0.02 and 0.17, the truly dissolved P (<10 kDa) was between 4 and 60% of the total dissolved P (<0.45 μm). These colloids reduced the P uptake flux by R. subcapitata compared to colloid-free treatments at the same total dissolved P concentration. However, the P uptake flux from colloid containing solutions equalled that from colloid-free ones when expressed as truly dissolved P. This demonstrates that colloidal P did not contribute to the P uptake flux. It is concluded that, on the short term, phosphate adsorbed to ferrihydrite colloids is not available to the green alga R. subcapitata. Copyright © 2014 Elsevier Ltd. All rights reserved.

Irreversible colloidal agglomeration in presence of associative inhibitors: Computer simulation study

International Nuclear Information System (INIS)

Barcenas, Mariana; Duda, Yurko

2007-01-01

Monte Carlo simulation is employed to study the irreversible particle-cluster agglomeration of valence-limited colloids affected by associative inhibitors. The cluster size distribution and number of connections between colloids are analyzed as a function of density and inhibitor concentration. The influence of colloid functionality on its aggregation is discussed

Cross-flow micro-filtration using ceramic membranes