The pH dependent Raman spectroscopic study of caffeine

Science.gov (United States)

Kang, Jian; Gu, Huaimin; Zhong, Liang; Hu, Yongjun; Liu, Fang

2011-02-01

First of all the surface enhanced Raman spectroscopy (SERS) and normal Raman spectra of caffeine aqueous solution were obtained at different pH values. In order to obtain the detailed vibrational assignments of the Raman spectroscopy, the geometry of caffeine molecule was optimized by density functional theory (DFT) calculation. By comparing the SERS of caffeine with its normal spectra at different pH values; it is concluded that pH value can dramatically affect the SERS of caffeine, but barely affect the normal Raman spectrum of caffeine aqueous solution. It can essentially affect the reorientation of caffeine molecule to the Ag colloid surface, but cannot impact the vibration of functional groups and chemical bonds in caffeine molecule.

Kinetics of an acid-base catalyzed reaction (aspartame degradation) as affected by polyol-induced changes in buffer pH and pK values.

Science.gov (United States)

Chuy, S; Bell, L N

2009-01-01

The kinetics of an acid-base catalyzed reaction, aspartame degradation, were examined as affected by the changes in pH and pK(a) values caused by adding polyols (sucrose, glycerol) to phosphate buffer. Sucrose-containing phosphate buffer solutions had a lower pH than that of phosphate buffer alone, which contributed, in part, to reduced aspartame reactivity. A kinetic model was introduced for aspartame degradation that encompassed pH and buffer salt concentrations, both of which change with a shift in the apparent pK(a) value. Aspartame degradation rate constants in sucrose-containing solutions were successfully predicted using this model when corrections (that is, lower pH, lower apparent pK(a) value, buffer dilution from the polyol) were applied. The change in buffer properties (pH, pK(a)) from adding sucrose to phosphate buffer does impact food chemical stability. These effects can be successfully incorporated into predictive kinetic models. Therefore, pH and pK(a) changes from adding polyols to buffer should be considered during food product development.

Temperature and pH driven association in uranyl aqueous solutions

Directory of Open Access Journals (Sweden)

M. Druchok

2012-12-01

Full Text Available An association behavior of uranyl ions in aqueous solutions is explored. For this purpose a set of all-atom molecular dynamics simulations is performed. During the simulation, the fractions of uranyl ions involved in dimer and trimer formations were monitored. To accompany the fraction statistics one also collected distributions characterizing average times of the dimer and trimer associates. Two factors effecting the uranyl association were considered: temperature and pH. As one can expect, an increase of the temperature decreases an uranyl capability of forming the associates, thus lowering bound fractions/times and vice versa. The effect of pH was modeled by adding H+ or OH- ions to a "neutral" solution. The addition of hydroxide ions OH- favors the formation of the associates, thus increasing bound times and fractions. The extra H+ ions in a solution produce an opposite effect, thus lowering the uranyl association capability. We also made a structural analysis for all the observed associates to reveal the mutual orientation of the uranyl ions.

Automated pH Control of Nutrient Solution in a Hydroponic Plant Growth System

Science.gov (United States)

Smith, B.; Dogan, N.; Aglan, H.; Mortley, D.; Loretan, P.

1998-01-01

Over, the years, NASA has played an important role in providing to and the development of automated nutrient delivery and monitoring, systems for growing crops hydroponically for long term space missions. One example are the systems used in the Biomass Production Chamber (BPC) at Kennedy Space Center (KSC). The current KSC monitoring system is based on an engineering workstation using standard analog/digital input/output hardware and custom written software. The monitoring system uses completely separate sensors to provide a check of control sensor accuracy and has the ability to graphically display and store data form past experiment so that they are available for data analysis [Fortson, 1992]. In many cases, growing systems have not been fitted with the kind of automated control systems as used at KSC. The Center for Food and Environmental Systems for Human Exploration of Space (CFESH) located on the campus of Tuskegee University, has effectively grown sweetpotatoes and peanuts hydroponically for the past five years. However they have adjusted the pH electrical conductivity and volume of the hydroponic nutrient solution only manually at times when the solution was to be replenished or changed out according to its protocol (e.g. one-week, two-week, or two-day cycle). But the pH of the nutrient solution flowing through the channel is neither known nor controlled between the update, change out, or replenishment period. Thus, the pH of the nutrient solution is not held at an optimum level over the span of the plant's growth cycle. To solve this dilemma, an automated system for the control and data logging of pH data relative to sweetpotato production using the nutrient film technique (NFT) has been developed, This paper discusses a microprocessor-based system, which was designed to monitor, control, and record the pH of a nutrient solution used for growing sweetpotatoes using NFT.

A study of specific sorption of neptunium(V) on smectite in low pH solution

International Nuclear Information System (INIS)

Kozai, Naofumi; Ohnuki, Toshihiko; Matsumoto, Junko; Banba, Tsunetaka; Ito, Yoshimoto

1996-01-01

The 'specific sorption' of neptunium(V) on smectite, in other words, a strong sorption undesorbable by 1 M KCl, is studied with a combination of batch type sorption and desorption experiments over a pH range of 2 to 5. Six types of homoionic smectite (Li-, Na-, K-, Cs-, Mg-, and Ca-smectite) are used in this study. Distribution coefficients (K d ) of neptunium for smectite vary over a wide pH range; the maximum K d value of ∝300 cm 3 x g -1 at around pH 2 for Li- and Na-smectite and the minimum value of ∝2 cm 3 x g -1 for Cs-smectite. The specific sorption of neptunium depends on pH and on the affinity of the exchangeable cation for smectite; the lower the pH of solution or the affinity, the larger the specific sorption. The neptunium-smectite association varies with the elapse of contact time. Within the first day of the neptunium-smectite contact the neptunium sorbed on na-smectite at low pH is desorbable by 1 M KCl solution, and on the passage of time most of the neuptunium sorbed becomes undesorbable by KCl (the specific sorption). Hydronium ion in solution is sorbed on smectite at low pH and dissociates the exchangeable cation from smectite into solution, and the specific sorption of neuptunium increases with increasing the exchangeable cation that is dissociated from smectite. (orig.)

Effect of initial pH and temperature of iron salt solutions on formation of magnetite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Gnanaprakash, G. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Mahadevan, S. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Jayakumar, T. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Kalyanasundaram, P. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Philip, John [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)]. E-mail: philip@igcar.gov.in; Raj, Baldev [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)

2007-05-15

We report the effect of initial pH and temperature of iron salt solutions on formation of magnetite (Fe{sub 3}O{sub 4}) nanoparticles during co-precipitation. We synthesized nanoparticles by keeping the initial pH at 0.7, 1.5, 3.0, 4.7, 5.7, 6.7 for two different temperatures of 30 and 60 deg. C. When the initial pH (prior to alkali addition) of the salt solution was below 5, the nanoparticles formed were 100% spinel iron oxide. Average size of the magnetite particles increases with initial pH until ferrihydrite is formed at a pH of 3 and the size remains the same till 4.7 pH. The percentage of goethite formed along with non-stoichiometric magnetite was 35 and 78%, respectively, when the initial pH of the solution was 5.7 and 6.7. As the reaction temperature was increased to 60 deg. C, maintaining a pH of 6.7, the amount of goethite increased from 78 to 100%. These results show that the initial pH and temperature of the ferrous and ferric salt solution before initiation of the precipitation reaction are critical parameters controlling the composition and size of nanoparticles formed. We characterize the samples using X-ray diffraction, transmission electron microscopy and vibrating sample magnetometer. The results of the present work provide the right conditions to synthesis pure magnetite nanoparticles, without goethite impurities, through co-precipitation technique for ferrofluid applications.

Effect of nitrogen form and pH of nutrient solution on the changes in pH and EC of spinach rhizosphere in hydroponic culture

OpenAIRE

M. Parsazadeh; N. Najafi

2011-01-01

In this study, the effect of nitrate to ammonium ratio and pH of nutrient solution on the changes in pH and EC of rhizosphere during spinach growth period in perlite culture, under greenhouse conditions, was investigated. A split factorial experiment in a completely randomized design with four replications was conducted with three factors including nutrient solution’s pH in three levels (4.5, 6.5 and 8), nitrate to ammonium ratio of nutrient solution in five levels (100:0, 75:25, 50:50, 25:75...

Effect of Solution pH on the Adsorption of Paracetamol on Chemically Modified Activated Carbons

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Valentina Bernal

2017-06-01

Full Text Available Paracetamol adsorption in acidic, neutral and basic media on three activated carbons with different chemistry surfaces was studied. A granular activated carbon (GAC was prepared from coconut shell; starting from this sample, an oxidized activated carbon (GACo was obtained by treating the GAC with a boiling solution of 6 M nitric acid, so to generate a greater number of oxygenated surface groups. In addition, a reduced activated carbon (GACr was obtained by heating the GAC at 1173 K, to remove the oxygenated surface groups. Paracetamol adsorption was higher for GACr due to the lower presence of oxygenated surface functional groups. Moreover, adsorption was highest at neutral pH. The magnitude of the interactions between paracetamol molecules and activated carbons was studied by measuring the immersion enthalpies of activated carbons in solution of paracetamol at different concentrations and pH values and by calculating the interaction enthalpy. The highest value was obtained for GACr in a paracetamol solution of 1000 mg L−1 at pH 7, confirming that paracetamol adsorption is favoured on basic activated carbons at pH values near to neutrality. Finally, the Gibbs energy changes confirmed the latter result, allowing explaining the different magnitudes of the interactions between paracetamol and activated carbons, as a function of solution pH.

Ph3CCOOSnPh3.Ph3PO AND Ph3CCOOSnPh3.Ph3AsO: SYNTHESIS AND INFRARED STUDY

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ABDOU MBAYE

2014-08-01

Full Text Available The mixture of ethanolic solutions of Ph3CCOOSnPh3 and Ph3PO or Ph3AsO gives Ph3CCOOSnPh3.Ph3PO and Ph3CCOOSnPh3.Ph3AsO adducts which have been characterized by infrared spectroscopy. A discrete structure is suggested for both, the environment around the tin centre being trigonal bipyramidal, the triphenylacetate anion behaving as a mondentate ligand.

Integrating chemical imaging of cationic trace metal solutes and pH into a single hydrogel layer

Energy Technology Data Exchange (ETDEWEB)

Hoefer, Christoph [Department of Forest and Soil Sciences, Institute of Soil Research, University of Natural Resources and Life Sciences, Vienna, Konrad-Lorenz-Strasse 24, A-3430 Tulln (Austria); Santner, Jakob, E-mail: jakob.santner@boku.ac.at [Department of Forest and Soil Sciences, Institute of Soil Research, University of Natural Resources and Life Sciences, Vienna, Konrad-Lorenz-Strasse 24, A-3430 Tulln (Austria); Department of Crop Sciences, Division of Agronomy, University of Natural Resources and Life Sciences, Vienna, Konrad-Lorenz-Strasse 24, 3430 Tulln (Austria); Borisov, Sergey M. [Institute of Analytical Chemistry and Food Chemistry, Graz University of Technology, Stremayrgasse 9, A-8010, Graz (Austria); Wenzel, Walter W.; Puschenreiter, Markus [Department of Forest and Soil Sciences, Institute of Soil Research, University of Natural Resources and Life Sciences, Vienna, Konrad-Lorenz-Strasse 24, A-3430 Tulln (Austria)

2017-01-15

Gel-based, two-dimensional (2D) chemical imaging techniques are versatile methods for investigating biogeochemically active environments at high spatial resolution (sub-mm). State-of-the-art solute imaging techniques, such as diffusive gradients in thin films (DGT) and planar optodes (PO), employ passive solute sampling or sensing. Combining these methods will provide powerful tools for studying the biogeochemistry of biological niches in soils and sediments. In this study we aimed at developing a combined single-layer gel for direct pH imaging using PO and sampling of anionic and cationic solutes by DGT, with subsequent analysis of the bound solutes by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). We tested three ultra-thin (<100 μm) polyurethane-based gels, incorporating anion and cation binding materials and the fluorescent pH indicator DCIFODA (2′,7′-dichloro-5(6)-N-octadecyl-carboxamidofluorescein). Results showed that PO-based pH sensing using DCIFODA was impossible in the presence of the anion binding materials due to interferences with DCIFODA protonation. One gel, containing only a cation binding material and DCIFODA, was fully characterized and showed similar performance characteristics as comparable DGT-only gels (applicable pH range: pH 5–8, applicable ionic strength range: 1–20 mmol L{sup -1}, cation binding capacity ∼24 μg cm{sup −2}). The dynamic range for PO-based pH mapping was between pH 5.5 and 7.5 with t{sub 90} response time of ∼60 min. In a case study we demonstrated the gel's suitability for multi-analyte solute imaging and mapped pH gradients and concurrent metal solubility patterns in the rhizosphere of Salix smithiana. pH decreases in the rooted soil were co-localized with elevated solute fluxes of Al{sup 3+}, Co{sup 2+}, Cu{sup 2+}, Fe, Mn{sup 2+}, Ni{sup 2+} and Pb{sup 2+}, indicating pH-induced metal solubilisation. - Highlights: • Diffusive gradients in thin films (DGT) and planar

Integrating chemical imaging of cationic trace metal solutes and pH into a single hydrogel layer

International Nuclear Information System (INIS)

Hoefer, Christoph; Santner, Jakob; Borisov, Sergey M.; Wenzel, Walter W.; Puschenreiter, Markus

2017-01-01

Gel-based, two-dimensional (2D) chemical imaging techniques are versatile methods for investigating biogeochemically active environments at high spatial resolution (sub-mm). State-of-the-art solute imaging techniques, such as diffusive gradients in thin films (DGT) and planar optodes (PO), employ passive solute sampling or sensing. Combining these methods will provide powerful tools for studying the biogeochemistry of biological niches in soils and sediments. In this study we aimed at developing a combined single-layer gel for direct pH imaging using PO and sampling of anionic and cationic solutes by DGT, with subsequent analysis of the bound solutes by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). We tested three ultra-thin (<100 μm) polyurethane-based gels, incorporating anion and cation binding materials and the fluorescent pH indicator DCIFODA (2′,7′-dichloro-5(6)-N-octadecyl-carboxamidofluorescein). Results showed that PO-based pH sensing using DCIFODA was impossible in the presence of the anion binding materials due to interferences with DCIFODA protonation. One gel, containing only a cation binding material and DCIFODA, was fully characterized and showed similar performance characteristics as comparable DGT-only gels (applicable pH range: pH 5–8, applicable ionic strength range: 1–20 mmol L"-"1, cation binding capacity ∼24 μg cm"−"2). The dynamic range for PO-based pH mapping was between pH 5.5 and 7.5 with t_9_0 response time of ∼60 min. In a case study we demonstrated the gel's suitability for multi-analyte solute imaging and mapped pH gradients and concurrent metal solubility patterns in the rhizosphere of Salix smithiana. pH decreases in the rooted soil were co-localized with elevated solute fluxes of Al"3"+, Co"2"+, Cu"2"+, Fe, Mn"2"+, Ni"2"+ and Pb"2"+, indicating pH-induced metal solubilisation. - Highlights: • Diffusive gradients in thin films (DGT) and planar optode (PO) imaging is combined. • A

Influence of pH of spray solution on optoelectronic properties of cadmium oxide thin films

International Nuclear Information System (INIS)

Hodlur, R. M.; Rabinal, M. K.

2015-01-01

Highly conducting transparent cadmium oxide thin films were prepared by the conventional spray pyrolysis technique. The pH of the spray solution is varied by adding ammonia/hydrochloric acid. The effect of pH on the morphology, crystallinity and optoelectronic properties of these films is studied. The structural analysis showed all the films in the cubic phase. For the films with pH < 7 (acidic condition), the preferred orientation is along the (111) direction and for those with pH >7 (alkaline condition), the preferred orientation is along the (200) direction. A lowest resistivity of 9.9 × 10 −4 Ω·cm (with carrier concentration = 5.1 × 10 20 cm −3 , mobility = 12.4 cm 2 /(V·s)) is observed for pH ≈ 12. The resistivity is tuned almost by three orders of magnitude by controlling the bath pH with optical transmittance more than 70%. Thus, the electrical conductivity of CdO films could be easily tuned by simply varying the pH of the spray solution without compromising the optical transparency. (paper)

Comparative study of buffered 50% glycolic acid (pH 3.0) + 0.5% salicylic acid solution vs Jessner's solution in patients with acne vulgaris.

Science.gov (United States)

In Jae, Jeong; Dong Ju, Hyun; Dong Hyun, Kim; Yoon, Moon Soo; Lee, Hee Jung

2017-11-21

Superficial chemical peels are frequently used in acne vulgaris treatment. Although glycolic acid (GA) has been widely used in clinical practice, its pH ranges from 0.08-2.75 and thus should be neutralized after application to avoid burns. To evaluate treatment efficacy and safety of chemical peeling using buffered 50% GA (pH 3.0) + 0.5% salicylic acid (SA) solution that does not need to be neutralized in the treatment of acne vulgaris compared to the conventional peeling using Jessner's solution. We performed a prospective, randomized, evaluator-blind, split-face clinical trial. Twenty patients were randomized by assigning one side of each patient's face to receive a 50% GA (pH 3.0) + 0.5% SA peel (GA side) and the other side to receive the Jessner's solution (Jessner's solution side). All patients underwent 2 sessions of treatment spaced 2 weeks apart. Lesion count, acne severity, subjective efficacy assessment, and side effects were evaluated. The total lesion count was significantly reduced for the GA and Jessner's solution sides (P  .05). The GA side had fewer side effects than the Jessner's solution side. The results of this study suggest that chemical peeling using the 50% GA (pH 3.0) + 0.5% SA solution can be as effective and convenient as the conventional peeling using Jessner's solution in the treatment of acne vulgaris and may show fewer adverse events than the conventional peeling. © 2017 Wiley Periodicals, Inc.

Biodesulfurization of vanadium-bearing titanomagnetite concentrates and pH control of bioleaching solution

Science.gov (United States)

Liu, Xiao-rong; Jiang, Sheng-cai; Liu, Yan-jun; Li, Hui; Wang, Hua-jun

2013-10-01

Vanadium-bearing titanomagnetite concentrates were desulfurized with Acidithiobacillus ferrooxidans ( A. ferrooxidans). The sulfur content of the concentrates was reduced from 0.69wt% to 0.14wt% after bioleaching for 15 d with a 10% pulp density at 30°C. Maintaining a stable pH value during biodesulfurization was critical because of high acid consumption, resulting from a combination of nonoxidative and oxidative dissolution of pyrrhotite in acid solution. It is discovered that the citric acid-disodium hydrogen phosphate buffer of pH 2.0 can control the solution pH value smoothly in the optimal range of 2.0-3.0 for A. ferrooxidans growth. Using the buffer in the volume fraction range of 5.0%-15.0% stimulates A. ferrooxidans growth and improves the biodesulfurization efficiency. Compared with the buffer-free control case, the maximum increase of biodesulfurization rate is 29.7% using a 10.0vol% buffer. Bioleaching provides an alternative process for desulfurization of vanadium-bearing titanomagnetite ores.

Changes in soil solution Zn and pH and uptake of Zn by arbuscular mycorrhizal red clover in Zn-contaminated soil.

Science.gov (United States)

Li, X; Christie, P

2001-01-01

Red clover plants inoculated with Glomus mosseae were grown in a sterile pasture soil containing 50 mg Zn kg(-1) in 'Plexiglas' (acrylic) containers with nylon net partitions (30 microm mesh) designed to separate the soil into a central root zone and two outer zones for hyphal growth with no root penetration. Two porous plastic soil moisture samplers were installed in each pot, one in the root compartment and the other in one of the hyphal compartments. The soil in the outer compartments was amended with one of the four application rates of Zn (as ZnSO4) ranging from 0 to 1000 mg kg(-1). Non-mycorrhizal controls were included, and there were five replicates of each treatment in a randomised block in a glasshouse. Uninoculated plants received supplementary P to avoid yield limitation due to low soil P status. Plants grew in the central compartment for nine weeks. Soil moisture samples were collected 4, 24 and 62 days after sowing to monitor changes in the Zn concentration and pH of the soil solution. At harvest, the mean mycorrhizal infection rate of inoculated plants ranged from 29% to 34% of total root length and was little affected by Zn application. Root and shoot yields were not affected by mycorrhizal infection. Plant Zn concentration and uptake were lower in mycorrhizal plants than non-mycorrhizal controls, and this effect was more pronounced with increasing Zn application rate to the soil. Soil solution Zn concentrations were lower and pH values were higher in mycorrhizal treatments than non-mycorrhizal controls and the mycorrhiza effect was more pronounced at higher Zn application rates. The protective effect of mycorrhiza against plant Zn uptake may have been associated with changes in Zn solubility mediated by changes in the soil solution pH, or by immobilisation of Zn in the extraradical mycelium.

Initial pH of medium affects organic acids production but do not affect phosphate solubilization.

Science.gov (United States)

Marra, Leandro M; de Oliveira-Longatti, Silvia M; Soares, Cláudio R F S; de Lima, José M; Olivares, Fabio L; Moreira, Fatima M S

2015-06-01

The pH of the culture medium directly influences the growth of microorganisms and the chemical processes that they perform. The aim of this study was to assess the influence of the initial pH of the culture medium on the production of 11 low-molecular-weight organic acids and on the solubilization of calcium phosphate by bacteria in growth medium (NBRIP). The following strains isolated from cowpea nodules were studied: UFLA03-08 (Rhizobium tropici), UFLA03-09 (Acinetobacter sp.), UFLA03-10 (Paenibacillus kribbensis), UFLA03-106 (Paenibacillus kribbensis) and UFLA03-116 (Paenibacillus sp.). The strains UFLA03-08, UFLA03-09, UFLA03-10 and UFLA03-106 solubilized Ca3(PO4)2 in liquid medium regardless of the initial pH, although without a significant difference between the treatments. The production of organic acids by these strains was assessed for all of the initial pH values investigated, and differences between the treatments were observed. Strains UFLA03-09 and UFLA03-10 produced the same acids at different initial pH values in the culture medium. There was no correlation between phosphorus solubilized from Ca3(PO4)2 in NBRIP liquid medium and the concentration of total organic acids at the different initial pH values. Therefore, the initial pH of the culture medium influences the production of organic acids by the strains UFLA03-08, UFLA03-09, UFLA03-10 and UFLA03-106 but it does not affect calcium phosphate solubilization.

Effect of pH on corrosion behavior of CuCrZr in solution without and with NaCl

Energy Technology Data Exchange (ETDEWEB)

Kwok, C.T.; Wong, P.K. [Department of Electromechanical Engineering, University of Macau (China); Man, H.C. [Department of Industrial and Systems Engineering, Hong Kong Polytechnic University (Hong Kong); Cheng, F.T., E-mail: apaftche@polyu.edu.h [Department of Applied Physics, Hong Kong Polytechnic University (Hong Kong)

2009-10-01

CuCrZr is a high copper alloy widely used as electrical and thermal conducting material, especially in heat exchangers in nuclear reactors. In this respect, the physical and fatigue properties of CuCrZr have been extensively studied. The electrochemical behavior of CuCrZr, on the other hand, has not been adequately investigated. In the present study, the effect of pH on the corrosion behavior of CuCrZr in aqueous solutions without and with chloride (0.6 M NaCl) was studied. The pH of the solutions is found to exert significant influence on the corrosion behavior of CuCrZr. In acidic solutions without chloride, the corrosion of CuCrZr is ascribed to active dissolution with soluble products. In neutral and alkaline solutions without NaCl, the presence of oxides on the surface of CuCrZr leads to a noble shift in corrosion potential and passivation results in increased corrosion resistance. In chloride solutions at various pH values, the chloride ions influence the formation of the surface layers and the anodic dissolution process during polarization. At high pH, CuCrZr shows significant passivity and high corrosion resistance due to the growth of Cu{sub 2}O/Cu(OH) film which hinders further dissolution whereas at low pH the corrosion resistance is lowered due to active dissolution of Cu.

Effect of pH on corrosion behavior of CuCrZr in solution without and with NaCl

International Nuclear Information System (INIS)

Kwok, C.T.; Wong, P.K.; Man, H.C.; Cheng, F.T.

2009-01-01

CuCrZr is a high copper alloy widely used as electrical and thermal conducting material, especially in heat exchangers in nuclear reactors. In this respect, the physical and fatigue properties of CuCrZr have been extensively studied. The electrochemical behavior of CuCrZr, on the other hand, has not been adequately investigated. In the present study, the effect of pH on the corrosion behavior of CuCrZr in aqueous solutions without and with chloride (0.6 M NaCl) was studied. The pH of the solutions is found to exert significant influence on the corrosion behavior of CuCrZr. In acidic solutions without chloride, the corrosion of CuCrZr is ascribed to active dissolution with soluble products. In neutral and alkaline solutions without NaCl, the presence of oxides on the surface of CuCrZr leads to a noble shift in corrosion potential and passivation results in increased corrosion resistance. In chloride solutions at various pH values, the chloride ions influence the formation of the surface layers and the anodic dissolution process during polarization. At high pH, CuCrZr shows significant passivity and high corrosion resistance due to the growth of Cu 2 O/Cu(OH) film which hinders further dissolution whereas at low pH the corrosion resistance is lowered due to active dissolution of Cu.

Calorimetric and diffractometric evidence for the sequential crystallization of buffer components and the consequential pH swing in frozen solutions.

Science.gov (United States)

Sundaramurthi, Prakash; Shalaev, Evgenyi; Suryanarayanan, Raj

2010-04-15

Sequential crystallization of succinate buffer components in the frozen solution has been studied by differential scanning calorimetry and X-ray diffractometry (both laboratory and synchrotron sources). The consequential pH shifts were monitored using a low-temperature electrode. When a solution buffered to pH pK(a)(2), the freeze-concentrate pH first decreased and then increased due to the sequential crystallization of the basic (disodium succinate) followed by the acidic (monosodium succinate and succinic acid) buffer components. XRD provided direct evidence of the crystallization events in the frozen buffer solutions, including the formation of disodium succinate hexahydrate [Na(2)(CH(2)COO)(2).6H(2)O]. When the frozen solution was warmed in a differential scanning calorimeter, multiple endotherms attributable to the melting of buffer components and ice were observed. When the frozen solutions were dried under reduced pressure, ice sublimation was followed by dehydration of the crystalline hexahydrate to a poorly crystalline anhydrate. However, crystalline succinic acid and monosodium succinate were retained in the final lyophiles. The pH and the buffer salt concentration of the prelyo solution influenced the crystalline salt content in the final lyophile. The direction and magnitude of the pH shift in the frozen solution depended on both the initial pH and the buffer concentration. In light of the pH-sensitive nature of a significant fraction of pharmaceuticals (especially proteins), extreme care is needed in both the buffer selection and its concentration.

Factors affecting intra-oral pH - a review.

Science.gov (United States)

Loke, C; Lee, J; Sander, S; Mei, L; Farella, M

2016-10-01

One of the greatest challenges to modern dentistry is the progressive destruction of tooth material due to chemical erosion. Dental erosion is the loss of dental hard tissue, without the action of bacteria, in which demineralisation of enamel and dentine results due to a decrease in intra-oral pH. The aim of this review was to appraise the scientific literature on the factors that can affect intra-oral pH. The review will examine (i) the protective role of human saliva, in terms of its mineral composition, flow rates and buffering systems and (ii) sources of in-mouth acids such as extrinsic acids, which are derived from the diet and environment, as well as intrinsic acids, which are related to disorders of the gastro-oesophageal tract. This review may assist clinicians to identify the risk factors for tooth wear and to recommend adequate preventive measures to patients. © 2016 John Wiley & Sons Ltd.

How Helicobacter pylori urease may affect external pH and influence growth and motility in the mucus environment: evidence from in-vitro studies.

Science.gov (United States)

Sidebotham, Ramon L; Worku, Mulugeta L; Karim, Q Najma; Dhir, Nirmal K; Baron, J Hugh

2003-04-01

Survival of Helicobacter pylori is dependent upon urease in the cytoplasm and at the bacterial surface. We have sought to clarify how alkaline ammonium salts, released from urea by this enzyme, might alter mucus pH and so affect growth and motility of the bacterium in the gastric mucus environment. Experiments were conducted in vitro to determine how the growth and motility of H. pylori are affected by changes in external pH, and how the bacterium, by hydrolysing urea, alters the pH of the bicarbonate buffer that occurs at the gastric mucosal surface. These data were fitted into experimental models that describe how pH varies within the mucus layer in the acid-secreting stomach. H. pylori was motile between pH 5 and 8, with optimal motility at pH 5. It grew between pH 6 and 8, with optimal growth at pH 6. The bacterium had urease activity between pH 2.7 and 7.4, as evidenced by pH rises in bicarbonate-buffered solutions of urea. Changes in buffer pH were dependent upon initial pH and urea concentration, with the greatest rate of pH change occurring at pH 3. Modelling experiments utilizing these data indicated that (1) in the absence of urease, H. pylori growth and motility in the mucus layer would be restricted severely by low mucus pH in the acid-secreting stomach, and (2) urease will sometimes inhibit H. pylori growth and motility in the mucus layer by elevating the pH of the mucus environment above pH 8. Urease is essential to the growth and motility of H. pylori in the mucus layer in the acid-secreting stomach, but, paradoxically, sometimes it might suppress colonization by raising the mucus pH above 8. This latter effect may protect the bacteria from the adverse consequences of overpopulation.

THE PREDICTION OF pH BY GIBBS FREE ENERGY MINIMIZATION IN THE SUMP SOLUTION UNDER LOCA CONDITION OF PWR

Directory of Open Access Journals (Sweden)

HYOUNGJU YOON

2013-02-01

Full Text Available It is required that the pH of the sump solution should be above 7.0 to retain iodine in a liquid phase and be within the material compatibility constraints under LOCA condition of PWR. The pH of the sump solution can be determined by conventional chemical equilibrium constants or by the minimization of Gibbs free energy. The latter method developed as a computer code called SOLGASMIX-PV is more convenient than the former since various chemical components can be easily treated under LOCA conditions. In this study, SOLGASMIX-PV code was modified to accommodate the acidic and basic materials produced by radiolysis reactions and to calculate the pH of the sump solution. When the computed pH was compared with measured by the ORNL experiment to verify the reliability of the modified code, the error between two values was within 0.3 pH. Finally, two cases of calculation were performed for the SKN 3&4 and UCN 1&2. As results, pH of the sump solution for the SKN 3&4 was between 7.02 and 7.45, and for the UCN 1&2 plant between 8.07 and 9.41. Furthermore, it was found that the radiolysis reactions have insignificant effects on pH because the relative concentrations of HCl, HNO3, and Cs are very low.

Mesenchymal stem cell proliferation and mineralization but not osteogenic differentiation are strongly affected by extracellular pH.

Science.gov (United States)

Fliefel, Riham; Popov, Cvetan; Tröltzsch, Matthias; Kühnisch, Jan; Ehrenfeld, Michael; Otto, Sven

2016-06-01

Osteomyelitis is a serious complication in oral and maxillofacial surgery affecting bone healing. Bone remodeling is not only controlled by cellular components but also by ionic and molecular composition of the extracellular fluids in which calcium phosphate salts are precipitated in a pH dependent manner. To determine the effect of pH on self-renewal, osteogenic differentiation and matrix mineralization of mesenchymal stem cells (MSCs). We selected three different pH values; acidic (6.3, 6.7), physiological (7.0-8.0) and severe alkaline (8.5). MSCs were cultured at different pH ranges, cell viability measured by WST-1, apoptosis detected by JC-1, senescence was analyzed by β-galactosidase whereas mineralization was detected by Alizarin Red and osteogenic differentiation analyzed by Real-time PCR. Self-renewal was affected by pH as well as matrix mineralization in which pH other than physiologic inhibited the deposition of extracellular matrix but did not affect MSCs differentiation as osteoblast markers were upregulated. The expression of osteocalcin and alkaline phosphatase activity was upregulated whereas osteopontin was downregulated under acidic pH. pH affected MSCs self-renewal and mineralization without influencing osteogenic differentiation. Thus, future therapies, based on shifting acid-base balance toward the alkaline direction might be beneficial for prevention or treatment of osteomyelitis. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

The increase in pH during aging of porous sol-gel silica spheres

NARCIS (Netherlands)

Titulaer, M.K.; Kegel, W.K.; Jansen, J.B.H.; Geus, John W.

1994-01-01

The increase in pH in the hydrothermal fluid is studied after hydrothermal aging of porous silica gel spheres of 1–3 mm diameter. The porous silica spheres are formed by the sol-gel process from a supersaturated silica solution. The increase of the pH of the hydrothermal solution affects the silica

Effect of Aging Temperature on Corrosion Behavior of Sintered 17-4 PH Stainless Steel in Dilute Sulfuric Acid Solution

Science.gov (United States)

Szewczyk-Nykiel, Aneta; Kazior, Jan

2017-07-01

The general corrosion behavior of sintered 17-4 PH stainless steel processed under different processing conditions in dilute sulfuric acid solution at 25 °C was studied by open-circuit potential measurement and potentiodynamic polarization technique. The corrosion resistance was evaluated based on electrochemical parameters, such as polarization resistance, corrosion potential, corrosion current density as well as corrosion rate. The results showed that the precipitation-hardening treatment could significantly improve the corrosion resistance of the sintered 17-4 PH stainless steel in studied environment. As far as the influence of aging temperature on corrosion behavior of the sintered 17-4 PH stainless steel is concerned, polarization resistance and corrosion rate are reduced with increasing aging temperature from 480 up to 500 °C regardless of the temperature of solution treatment. It can be concluded that the highest corrosion resistance in 0.5 M H2SO4 solution exhibits 17-4 PH after solution treatment at 1040 °C followed by aging at 480 °C.

Zn availability in nutrient solutions for cucumber (Cucumis sativus L) in hydroponics as affected by Fe-chelates and pH

NARCIS (Netherlands)

Voogt, W.; Sonneveld, C.

2017-01-01

In soil-less culture systems Fe is usually supplied as chelate to ensure an adequate availability of this element. As chelates have affinity for many metal ions these chelates will interact with other cation nutrients in nutrient solutions. This affects the availability of Fe and other nutrients.

Low-temperature solution processing of palladium/palladium oxide films and their pH sensing performance.

Science.gov (United States)

Qin, Yiheng; Alam, Arif U; Pan, Si; Howlader, Matiar M R; Ghosh, Raja; Selvaganapathy, P Ravi; Wu, Yiliang; Deen, M Jamal

2016-01-01

Highly sensitive, easy-to-fabricate, and low-cost pH sensors with small dimensions are required to monitor human bodily fluids, drinking water quality and chemical/biological processes. In this study, a low-temperature, solution-based process is developed to prepare palladium/palladium oxide (Pd/PdO) thin films for pH sensing. A precursor solution for Pd is spin coated onto pre-cleaned glass substrates and annealed at low temperature to generate Pd and PdO. The percentages of PdO at the surface and in the bulk of the electrodes are correlated to their sensing performance, which was studied by using the X-ray photoelectron spectroscope. Large amounts of PdO introduced by prolonged annealing improve the electrode's sensitivity and long-term stability. Atomic force microscopy study showed that the low-temperature annealing results in a smooth electrode surface, which contributes to a fast response. Nano-voids at the electrode surfaces were observed by scanning electron microscope, indicating a reason for the long-term degradation of the pH sensitivity. Using the optimized annealing parameters of 200°C for 48 h, a linear pH response with sensitivity of 64.71±0.56 mV/pH is obtained for pH between 2 and 12. These electrodes show a response time shorter than 18 s, hysteresis less than 8 mV and stability over 60 days. High reproducibility in the sensing performance is achieved. This low-temperature solution-processed sensing electrode shows the potential for the development of pH sensing systems on flexible substrates over a large area at low cost without using vacuum equipment. Copyright © 2015 Elsevier B.V. All rights reserved.

Gammaradiation effect on spectral properties of oxyhemoglobin solutions of different pH in the presence of serotonin

International Nuclear Information System (INIS)

Artyukhov, V.G.

1979-01-01

Changes in spectral properties of oxyhemoglobin solutions (pH 3 to 12) of mice exposed to gammaradiation (6000R) in the presence of serotonin have been studied. It was established that serotonin (5x10 -5 M) exerts a radioprotective effect in respect of oxyhemoglobin solutions of pH 5 to 9. Serotonin fails to protect protein in the presence of catalase (1x10 -6 M). It is stated that the process of formation of hydrogen peroxide/serotonin complex appreciably contributes to the protective action of the radioprotective agent in respect of gammairradiated oxyhemoglobin solutions

Gravity-driven pH adjustment for site-specific protein pKa measurement by solution-state NMR

Science.gov (United States)

Li, Wei

2017-12-01

To automate pH adjustment in site-specific protein pKa measurement by solution-state NMR, I present a funnel with two caps for the standard 5 mm NMR tube. The novelty of this simple-to-build and inexpensive apparatus is that it allows automatic gravity-driven pH adjustment within the magnet, and consequently results in a fully automated NMR-monitored pH titration without any hardware modification on the NMR spectrometer.

Effects of pH on the stability of cyanidin and cyanidin 3-O-β-glucopyranoside in aqueous solution

Directory of Open Access Journals (Sweden)

Rakić Violeta P.

2015-01-01

Full Text Available The colour variation, colour intensity and stability at various pH values (2.0, 4.0, 7.0 and 9.0 of cyanidin 3-O-β-glucopyranoside (Cy3Glc and its aglycone cyanidin was investigated during a period of 8 hours storage at 25ºC. Our data showed that pH of aqueous solution had impact on spectroscopic profile of cyanidin and Cy3Glc. Beginning with the most acidic solutions, increasing the pH induce bathochromic shifts of absorbance maximum in the visible range for all examined pH values (with the exception pH 4.0 for cyanidin, while the presence of the 3-glucosidic substitution induce hypsochromic shift. Compared to cyanidin, Cy3Glc has higher colour intensity and higher stability in the whole pH range, except at pH 7.0. The 3-glucosidic substitution influences on the colour intensity of Cy3Glc in the alkaline region. After 8-hour incubation of Cy3Glc and cyanidin at pH 2.0 and 25 ºC, 99% of Cy3Glc and only 27% of cyanidin remained unchanged.

Effect of pH Changes on Antioxidant Capacity and the Content of Betalain Pigments During the Heating of a Solution of Red Beet Betalains

Directory of Open Access Journals (Sweden)

Mikołajczyk-Bator Katarzyna

2017-06-01

Full Text Available Red beets and their products are mainly consumed after processing. In this study, the effect of pH on changes in antioxidant capacity (AC and the content of betalain pigments were analysed during the heating of a betalain preparation solution. With pH ranging from 4 to 9 during the heat-treatment, the content of red pigments decreased depending on the pH level of the sample. The losses of red pigments in the investigated betalain preparation solution increased along with rising pH levels of the heated solution. The greatest losses were recorded at pH of 9.0. An opposite correlation was observed for yellow pigments. The content of yellow pigments in the heated betalain preparation solution was increasing along with increasing pH. The most pronounced increase in the content of yellow pigments was found at pH of 6.5 and 7.0. At the same time, the heated betalain preparation solution was shown to exhibit a higher antioxidant capacity at pH of 6.0 (14.9 μmol Trolox/mL than at pH of 4.0 (12.6 μmol Trolox/mL. It was observed that the increase in the antioxidant capacity in heated betalain preparation solutions with pH in the 6.0–6.5 range occurred as a result of increased concentrations of neobetanin, assessed by HPLC, within the pH range from 5.0 to 6.5.

Effect of pH Value on the Electrochemical and Stress Corrosion Cracking Behavior of X70 Pipeline Steel in the Dilute Bicarbonate Solutions

Science.gov (United States)

Cui, Z. Y.; Liu, Z. Y.; Wang, L. W.; Ma, H. C.; Du, C. W.; Li, X. G.; Wang, X.

2015-11-01

In this work, effects of pH value on the electrochemical and stress corrosion cracking (SCC) behavior of X70 pipeline steel in the dilute bicarbonate solutions were investigated using electrochemical measurements, slow strain rate tensile tests and surface analysis techniques. Decrease of the solution pH from 6.8 to 6.0 promotes the anodic dissolution and cathodic reduction simultaneously. Further decrease of the pH value mainly accelerates the cathodic reduction of X70 pipeline steel. As a result, when the solution pH decreases form 6.8 to 5.5, SCC susceptibility decreases because of the enhancement of the anodic dissolution. When the solution pH decreases from 5.5 to 4.0, SCC susceptibility increases gradually because of the acceleration of cathodic reactions.

Effects of solution pH and complexing reagents on uranium and thorium desorption under saturated equilibrium conditions

International Nuclear Information System (INIS)

Wang, Yug-Yea; Yu, C.

1992-01-01

Three contaminated bulk surface soils were used for investigating the effect of solution pH and complexing reagents on uranium and thorium desorption. At a low solution pH, the major chemical species of uranium and thorium, uranyl UO 2 +2 , thorium dihydroxide Th(OH) 2 +2 , and thorium hydroxide Th(OH) +3 , tend to form complexes with acetates in the solution phase, which increases the fractions of uranium and thorium desorbed into this phase. At a high solution pH, important uranium and thorium species such as uranyl tricarbonate complex UO 2 (CO) 33 -4 and thorium tetrahydroxide complex Th(OH) 4 tend to resist complexation with acetates. The presence of complexing reagents in solution can release radionuclides such as uranium and/or thorium from the soil to the solution by forming soluble complexes. Sodium bicarbonate (NaHCO 3 ) and diethylenetriaminepentaacetic acid (DTPA) are strong complex formers that released 38% to 62% of total uranium activity and 78% to 86% of total thorium activity, respectively, from the soil samples investigated. Solutions of 0.1 molar sodium nitrate (NaNO 3 ) and 0.1 molar sodium sulfate (Na 2 SO 4 ) were not effective complex formers with uranium and thorium under the experimental conditions. Fractions of uranium and thorium desorbed by 0.15g/200ml humic acid ranged from 4.62% to 6.17% and 1.59% to 7.09%, respectively. This work demonstrates the importance of a knowledge of solution chemistry in investigating the desorption of radionuclides

Methodologically controlled variations in laboratory and field pH measurements in waterlogged soils

DEFF Research Database (Denmark)

Elberling, Bo; Matthiesen, Henning

2007-01-01

artefacts is critical. But the study includes agricultural and forest soils for comparison. At a waterlogged site, Laboratory results were compared with three different field methods: calomel pH probes inserted in the soil from pits, pH measurements of soil solution extracted from the soil, and pH profiles...... using a solid-state pH electrode pushed into the soil from the surface. Comparisons between in situ and laboratory methods revealed differences of more than 1 pH unit. The content of dissolved ions in soil solution and field observations of O2 and CO2 concentrations were used in the speciation model...... PHREEQE in order to predict gas exchange processes. Changes in pH in soil solution following equilibrium in the laboratory could be explained mainly by CO2 degassing. Only soil pH measured in situ using either calomel or solid-state probes inserted directly into the soil was not affected by gas exchange...

Revealing the Dimeric Crystal and Solution Structure of β-Lactoglobulin at pH 4 and Its pH and Salt Dependent Monomer–Dimer Equilibrium

DEFF Research Database (Denmark)

Khan, Sanaullah; Ipsen, Richard; Almdal, Kristoffer

2018-01-01

The dimeric structure of bovine β-lactoglobulin A (BLGA) at pH 4.0 was solved to 2.0 Å resolution. Fitting the BLGA pH 4.0 structure to SAXS data at low ionic strength (goodness of fit R-factor = 3.6%) verified the dimeric state in solution. Analysis of the monomer–dimer equilibrium at varying pH...... and ionic strength by SAXS and scattering modeling showed that BLGA is dimeric at pH 3.0 and 4.0, shifting toward a monomer at pH 2.2, 2.6, and 7.0 yielding monomer/dimer ratios of 80/20%, 50/50%, and 25/75%, respectively. BLGA remained a dimer at pH 3.0 and 4.0 in 50–150 mM NaCl, whereas the electrostatic...... shielding raised the dimer content at pH 2.2, 2.6, and 7.0, i.e., below and above the pI. Overall, the findings provide new insights into the molecular characteristics of BLGA relevant for dairy product formulations and for various biotechnological and pharmaceutical applications....

Redox properties of phenosafranine at zeolite-modified electrodes-Effect of surface modification and solution pH

International Nuclear Information System (INIS)

Easwaramoorthi, S.; Natarajan, P.

2008-01-01

Redox properties of cationic dye phenosafranine (3,7-diamino-5-phenylphenazenium chloride) (PS + ) were studied at zeolite-modified electrodes using Zeolite-Y and NaZSM-5. The peak current and peak potential of phenosafranine-adsorbed zeolite were found to be influenced by the pH of the electrolyte solution. Observation of a second redox couple is suggested to be due to formation of new species at low concentration from the reduced phenosafranine at the zeolite-modified electrodes. Titanium dioxide nanoparticles encapsulated in the cavities of the zeolite or anchored on the external surface of the zeolite do not seem to affect the redox properties of adsorbed PS + . When the cyclic voltammograms are recorded immediately after the electrode is immersed into the solution, the redox potential of PS + is found to be sensitive to the nature of the zeolite surface. The peak potential shifts towards positive region under continuous cycles as the surface hydroxyl groups get protonated in acidic electrolyte solution thereby forcing the movement of dye molecules from the zeolite surface to the zeolite electrode solution interface. The electron transfer rate constants for the adsorbed dye at the electrode are calculated to be 2.5 ± 0.2 s -1 and 3.5 ± 0.2 s -1 for the zeolite-Y electrode and the ZSM-5 electrode, respectively by the Laviron equation

pH Sensing Properties of Flexible, Bias-Free Graphene Microelectrodes in Complex Fluids: From Phosphate Buffer Solution to Human Serum.

Science.gov (United States)

Ping, Jinglei; Blum, Jacquelyn E; Vishnubhotla, Ramya; Vrudhula, Amey; Naylor, Carl H; Gao, Zhaoli; Saven, Jeffery G; Johnson, Alan T Charlie

2017-08-01

Advances in techniques for monitoring pH in complex fluids can have a significant impact on analytical and biomedical applications. This study develops flexible graphene microelectrodes (GEs) for rapid (pH of complex biofluids by measuring real-time Faradaic charge transfer between the GE and a solution at zero electrical bias. For an idealized sample of phosphate buffer solution (PBS), the Faradaic current is varied monotonically and systematically with the pH, with a resolution of ≈0.2 pH unit. The current-pH dependence is well described by a hybrid analytical-computational model, where the electric double layer derives from an intrinsic, pH-independent (positive) charge associated with the graphene-water interface and ionizable (negative) charged groups. For ferritin solution, the relative Faradaic current, defined as the difference between the measured current response and a baseline response due to PBS, shows a strong signal associated with ferritin disassembly and the release of ferric ions at pH ≈2.0. For samples of human serum, the Faradaic current shows a reproducible rapid (pH. By combining the Faradaic current and real-time current variation, the methodology is potentially suitable for use to detect tumor-induced changes in extracellular pH. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stability of the Stevia-Derived Sweetener Rebaudioside A in Solution as Affected by Ultraviolet Light Exposure.

Science.gov (United States)

Zhang, Jiewen; Bell, Leonard N

2017-04-01

Rebaudioside A is a natural noncaloric high-potency sweetener extracted from the leaves of Stevia rebaudiana. With rebaudioside A use increasing in foods, understanding the factors affecting its stability is necessary. This project evaluated the degradation rate constants of rebaudioside A in water, 0.1 M phosphate buffer, and 0.1 M citrate buffer at pH 3 and 7 as a function of ultraviolet (UV) light intensity (365 nm, 0 μW/cm 2 for dark conditions, 27 μW/cm 2 for low intensity, and 190 μW/cm 2 for high intensity) at 32.5 °C. Rebaudioside A stability was adversely affected by light exposure. The pseudo-1st-order degradation rate constants increased significantly (P < 0.05) with increasing light intensity in all solutions. Under dark conditions, rebaudioside A in phosphate buffers was more susceptible to breakdown than in water and citrate buffers at both pH levels. However, exposure to UV light resulted in rebaudioside A degradation occurring approximately 10 times faster in citrate than in phosphate buffers at both pH levels. The sensitivity of rebaudioside A to UV light was greater in citrate buffers than in water or phosphate buffers. The use of light-protective packaging for beverages containing rebaudioside A will improve its stability. © 2017 Institute of Food Technologists®.

Effect of Nutrition Solution pH and Electrical Conductivity on Fusarium Wilt on Strawberry Plants in Hydroponic Culture

Directory of Open Access Journals (Sweden)

Myeong Hyeon Nam

2018-03-01

Full Text Available Fusarium wilt on strawberry plants caused by Fusarium oxysporum f. sp. fragariae (Fof is a major disease in Korea. The prevalence of this disease is increasing, especially in hydroponic cultivation in strawberry field. This study assessed the effect of nutrition solution pH and electrical conductivity (EC on Fusarium wilt in vitro and in field trials. pH levels of 5.0, 5.5, 6.0, 6.5, 7.0, and 7.5 were assayed in vitro and in field trials. EC levels at 0, 0.5, 0.8, 1.0, and 1.5 dS∙m⁻¹ were assayed in field trials. Mycelial growth of Fof increased with increasing pH and was highest at 25°C pH 7 and lowest at 20°C, pH 5.0 in vitro. The incidence of Fusarium wilt was lowest in the pH 6.5 treatment and highest in the pH 5 treatment in field trials. At higher pH levels, the EC decreased in the drain solution and the potassium content of strawberry leaves increased. In the EC assay, the severity of Fusarium wilt and nitrogen content of leaves increased as the EC increased. These results indicate that Fusarium wilt is related to pH and EC in hydroponic culture of strawberry plants.

Estimation of Hydrazine Decomposition on Measuring the High-Temperature pH in Hydrazine/ETA Solutions at 553 K

International Nuclear Information System (INIS)

Hwang, Jae Sik; Yeon, Jei Won; Yun, Myung Hee; Song, Kyu Seok; Lee, Sang Ill

2010-01-01

Hydrazine is one of the most excellent oxygen scavengers used in the secondary circuit of nuclear power plants. Furthermore, in some pants, the hydrazine is used as a source of hydrogen required to suppress radiolysis of the coolant water in the primary loop. When hydrazine was exposed in the high temperature and high pressure water, it can be decomposed into the various products such as NH 3 , N 2 , H 2 , and NO 3 ions. As the result, the pH of solution containing hydrazine in the condition of the high temperature and high pressure can be changed by those decomposed products. In the present work, we investigated the decomposition behavior of hydrazine in ETA (ethanol amine) solution. In addition, we measured the high temperature pH at 553 K on the various hydrazine/ETA solutions for confirming the applicability of the yttria stabilized zirconia (YSZ)- based pH electrode in secondary circuit of the nuclear power plants

Influence of alkaline (PH 8.3-12.0) and saline solutions on chemical, mineralogical and physical properties of two different bentonites - batch experiments at 25 deg. C

International Nuclear Information System (INIS)

Heikola, Tiina; Vuorinen, Ulla; Kumpulainen, Sirpa; Kiviranta, Leena; Korkeakoski, Petri

2012-01-01

Document available in extended abstract form only. Construction of a spent fuel repository deep in the bedrock will need supporting structures using cement materials. A part of them can be removed before closure but still it is estimated that about 1000 tonnes will remain in the host rock. Degradation of cementitious materials produces leachates of high pH. If such an alkaline plume reaches the bentonite buffer, it may induce mineralogical and chemical changes in bentonite over long term, and further affect the safety functions of the buffer. Laboratory experiments were done with the objective to gain data of possible alterations in mineralogical, chemical and physical properties of bentonites contacted with high-pH saline solutions. Two untreated, high grade, Na- and Ca-bentonites, were used in batch experiments, which were carried out in an anaerobic glove-box at 25±1 deg. C for 554 days. Each bentonite sample (20 g) was leached with approximately 3.8 L of leaching solution, which equals 190 mL/g of bentonite. The bentonites were leached with three types of simulated cement waters (pH 9.7, 11.3 and 12.0) and one saline groundwater simulate (pH 8.3) as a reference. The leaching solutions were 0.3 M, and contained NaCl and CaCl 2 , and trace amounts of SiO 2 , K, Br, Mg and SO 4 . Dissolved oxygen and carbon dioxide were removed from leaching solutions before mixing of bentonite in PC bottles. The samples were placed on a platform shaker in order to allow better contact between bentonite and the leaching solution. The evolution of pH in the samples was followed by measuring the pH-value of each sample in the solution phase approximately twice a week and the solution was renewed when values of two to three consecutive measurements did not change. On average, the leaching solution was renewed once a month. For each renewal of the leaching solution the phases were separated, the reacted solution withdrawn, and the chemical composition analysed. Before analysis the

New analytical methodology for analysing S(IV) species at low pH solutions by one stage titration method (bichromatometry) with a clear colour change. Could potentially replace the state-of-art-method iodometry at low pH analysis due higher accuracy.

Science.gov (United States)

Santasalo-Aarnio, Annukka; Galfi, Istvan; Virtanen, Jorma; Gasik, Michael M

2017-01-01

A new, faster and more reliable analytical methodology for S(IV) species analysis at low pH solutions by bichromatometry is proposed. For decades the state of the art methodology has been iodometry that is still well justified method for neutral solutions, thus at low pH media possess various side reactions increasing inaccuracy. In contrast, the new methodology has no side reactions at low pH media, requires only one titration step and provides a clear color change if S(IV) species are present in the solution. The method is validated using model solutions with known concentrations and applied to analyses of gaseous SO2 from purged solution in low pH media samples. The results indicate that bichromatometry can accurately analyze SO2 from liquid samples having pH even below 0 relevant to metallurgical industrial processes.

Effect of pH on the corrosion behaviour of SUS321 in the ammonia aqueous solution

International Nuclear Information System (INIS)

Park, Sang Yoon; Jeong, Y. H.; Baek, J. H.; Choi, B. K.; Lee, M. H.; Choi, B. S.; Yoon, J. H.; Lee, D. J.

2003-02-01

The corrosion characteristics of SUS321 for pressure vessel of SMART in pure water, ammonia aqueous solutions of pH 8.5 ∼ 11.5 at 300 .deg. C were evaluated by using static autoclaves. SUS321 specimen in the high temperature ammonia aqueous solution has weight gain or loss by the 4 reactions. And it depends on the refreshing period of the aqueous solution. So additional experiments by recirculating loop system were required to evaluate the corrosion behaviour of SUS321 in the ammonia aqueous solution

The role of pH in heavy metal detoxification by biosorption from ...

African Journals Online (AJOL)

The high level of toxic metal pollution in the environment is a result of increased human activities. The hydrogen ion concentration of solutions has been known to affect reactions in solutions. The role of pH in As(V), Pb(II) and Hg(II) ions detoxification by bio-sorption from aqueous solutions using coconut fiber and sawdust ...

Influence of pH and oxygen content of buffer solutions on the corrosion behaviour of metallic materials

International Nuclear Information System (INIS)

Wiedemann, K.H.

1977-05-01

The application of solutions to the decontamination of materials in nuclear installations is based on the condition that their corrosion behaviour is clearly understood. Since electrochemical corrosion is due to cathodic and anodic partial reactions which are influenced in different ways by the pH of the solution and the oxygen content it is suggested that the results of electrochemical experiments with buffer solutions be used as a model for predicting the corrosion behaviour of materials in other solutions. In the tests described here potentio-kinetic current-potential-curves have been traced and galvanic corrosion tests have been made. The results obtained in ascorbic acid, potassium hydrogen phthalate, ammonium citrate and acetate, sodium and potassium tartrate, ammonium hydrogen phosphate, sodium carbonate, hexamethylene tetramin, ethylene diamine enable - on the basis of summarized current-potential-curves - the metals studied to be classified in four groups characterized by clear differences concerning the influence of pH on the corrosion behaviour. (Auth.)

Pb and Cd binding to natural freshwater biofilms developed at different pH: the important role of culture pH.

Science.gov (United States)

Hua, Xiuyi; Dong, Deming; Ding, Xiaoou; Yang, Fan; Jiang, Xu; Guo, Zhiyong

2013-01-01

The effects of solution pH on adsorption of trace metals to different types of natural aquatic solid materials have been studied extensively, but few studies have been carried out to investigate the effect of pH at which the solid materials were formed on the adsorption. The purpose of present study is to examine this effect of culture pH on metal adsorption to natural freshwater biofilms. The adsorption of Pb and Cd to biofilms which were developed at different culture pH values (ranging from 6.5 to 9.0) was measured at the same adsorption pH value (6.5). The culture pH had considerable effects on both composition and metal adsorption ability of the biofilms. Higher culture pH usually promoted the accumulation of organic material and Fe oxides in the biofilms. The culture pH also affected the quantity and species of algae in the biofilms. The adsorption of Pb and Cd to the biofilms generally increased with the increase of culture pH. This increase was minor at lower pH range and significant at higher pH range and was more remarkable for Cd adsorption than for Pb adsorption. The notable contribution of organic material to the adsorption at higher culture pH values was also observed. The profound impacts of culture pH on adsorption behavior of biofilms mainly resulted from the variation of total contents of the biofilm components and were also affected by the alteration of composition and properties of the components.

[Aluminum dissolution and changes of pH in soil solution during sorption of copper by aggregates of paddy soil].

Science.gov (United States)

Xu, Hai-Bo; Zhao, Dao-Yuan; Qin, Chao; Li, Yu-Jiao; Dong, Chang-Xun

2014-01-01

Size fractions of soil aggregates in Lake Tai region were collected by the low-energy ultrasonic dispersion and the freeze-desiccation methods. The dissolution of aluminum and changes of pH in soil solution during sorption of Cu2+ and changes of the dissolution of aluminum at different pH in the solution of Cu2+ by aggregates were studied by the equilibrium sorption method. The results showed that in the process of Cu2+ sorption by aggregates, the aluminum was dissoluted and the pH decreased. The elution amount of aluminum and the decrease of pH changed with the sorption of Cu2+, both increasing with the increase of Cu2+ sorption. Under the same conditions, the dissolution of aluminum and the decrease of pH were in the order of coarse silt fraction > silt fraction > sand fraction > clay fraction, which was negatively correlated with the amount of iron oxide, aluminum and organic matter. It suggested that iron oxide, aluminum and organic matters had inhibitory and buffering effect on the aluminum dissolution and the decrease of pH during the sorption of Cu2+.

Effects of solution P H on the adsorption of aromatic compounds from aqueous solutions by activated carbon

International Nuclear Information System (INIS)

Nouri, S.; Haghseresht, F.; Lu, M.

2002-01-01

Absorption of p-Cresol, Benzoic acid and Nitro Benzene by activated carbon from dilute aqueous solutions was carried out under controlled ph conditions at 310 k. In acidic conditions, well below the pK a of all solutes, it was observed that the adsorbate solubility and the electron density of its aromatic ring were the influencing factors on the extent of the adsorption by affecting the extent of London dispersion forces. In higher solution ph conditions, on the other hand, it was found that the electrostatic forces played a significant role on the extent of adsorption. The Effect of ph must be considered from its combined effects on the carbon surface and on the solute molecules. It was found that the uptake of the molecular forms of the aromatic solutes was dependent on the substituents of the aromatic ring. Adsorption of the solutes in higher P H values was found to be dependent on the concentration of anionic form of the solutes. All isotherms were fitted into Freundlich Isotherm Equations

Dansyl-8-aminoquinoline as a sensitive pH fluorescent probe with dual-responsive ranges in aqueous solutions.

Science.gov (United States)

Zhang, Min; Zheng, Shuyu; Ma, Liguo; Zhao, Meili; Deng, Lengfang; Yang, Liting; Ma, Li-Jun

2014-04-24

A sensitive pH fluorescent probe based on dansyl group, dansyl-8-aminoquinoline (DAQ), has been synthesized. The probe showed dual-responsive ranges to pH changes, one range from 2.00 to 7.95 and another one from 7.95 to 10.87 in aqueous solution, as it showed pKa values of 5.73 and 8.56 under acid and basic conditions, respectively. Furthermore, the pH response mechanism of the probe was explored successfully by using NMR spectra. The results indicated that the responses of DAQ to pH changes should attribute to the protonation of the nitrogen atom in the dimethylamino group and deprotonation of sulfonamide group. Copyright © 2014. Published by Elsevier B.V.

Peroxidase-mediated polymerization of 1-naphthol: impact of solution pH and ionic strength.

Science.gov (United States)

Bhandari, Alok; Xu, Fangxiang; Koch, David E; Hunter, Robert P

2009-01-01

Peroxidase-mediated oxidation has been proposed as a treatment method for naphthol-contaminated water. However, the impact of solution chemistry on naphthol polymerization and removal has not been documented. This research investigated the impact of pH and ionic strength on peroxidase-mediated removal of 1-naphthol in completely mixed batch reactors. The impact of hydrogen peroxide to 1-naphthol ratio and activity of horseradish peroxidase was also studied. Size exclusion chromatography was used to estimate the molecular weight distribution of oligomeric products, and liquid chromatography/mass spectrometry was used to estimate product structure. Naphthol transformation decreased with ionic strength, and substrate removal was lowest at neutral pHs. Solution pH influenced the size and the composition of the oligomeric products. An equimolar ratio of H(2)O(2):naphthol was sufficient for optimal naphthol removal. Polymerization products included naphthoquinones and oligomers derived from two, three, and four naphthol molecules. Our results illustrate the importance of water chemistry when considering a peroxidase-based approach for treatment of naphthol-contaminated waters.

Contribution of solution pH and buffer capacity to suppress intergranular stress corrosion cracking of sensitized type 304 stainless steel at 95 C

International Nuclear Information System (INIS)

Zhang, S.; Shibata, T.; Haruna, T.

1999-01-01

Controlling pH of high-temperature water to ∼pH 7 at 300 C by adding lithium hydroxide (LiOH) into the coolant system of a pressurized water reactor (PWR) successfully has been mitigating the corrosion of PWR component materials. The effects of solution pH and buffer capacity on intergranular stress corrosion cracking (IGSCC) of sensitized type 304 stainless steel ([SS] UNS S30400) was examined at 95 C by slow strain rate technique (SSRT) with an in-situ cracking observation system. It was found that an increase in solution pH or buffer capacity increased crack initiation time and decreased mean crack initiation frequency, but exerted almost no effect on crack propagation. This inhibition effect on IGSCC initiation was explained as resulting from a retarding effect of solution pH and buffer capacity on the decrease in pH at crack nuclei caused by the hydrolysis of metal ions dissolved when the passive film was ruptured by strain in SSRT

Behaviour of lactose with the presence of lactic acid and Ca as affected by pH.

Science.gov (United States)

Chandrapala, Jayani; Gauthier, Claire; Vasiljevic, Todor

2017-11-01

Contradictory statements about the effects of pH change on crystallisation behaviour of lactose exist in the literature. Considering the importance of addressing the processability issue of acid whey, a systematic study is required to establish lactose crystallisation behaviour in the presence of LA and Ca at concentrations present in real acid whey waste streams emphasising impact of pH. Structural modifications of lactose were evident at elevated, more neutral pH in the presence of 1% w/w LA and 0·12% w/w Ca. These structural changes led to changes in the anomeric equilibrium of lactose, which manipulated the water-lactose behaviour and increased the crystallinity. Therefore, altering pH to 6·5 may be the solution to proper industrial processing of acid whey, enhancing the ability of lactose to crystallise properly.

pH sensing characteristics and biosensing application of solution-gated reduced graphene oxide field-effect transistors.

Science.gov (United States)

Sohn, Il-Yung; Kim, Duck-Jin; Jung, Jin-Heak; Yoon, Ok Ja; Thanh, Tien Nguyen; Quang, Trung Tran; Lee, Nae-Eung

2013-07-15

Solution-gated reduced graphene oxide field-effect transistors (R-GO FETs) were investigated for pH sensing and biochemical sensing applications. A channel of a networked R-GO film formed by self-assembly was incorporated as a sensing layer into a solution-gated FET structure for pH sensing and the detection of acetylcholine (Ach), which is a neurotransmitter in the nerve system, through enzymatic reactions. The fabricated R-GO FET was sensitive to protons (H(+)) with a pH sensitivity of 29 mV/pH in terms of the shift of the charge neutrality point (CNP), which is attributed to changes in the surface potential caused by the interaction of protons with OH surface functional groups present on the R-GO surface. The R-GO FET immobilized with acetylcholinesterase (AchE) was used to detect Ach in the concentration range of 0.1-10mM by sensing protons generated during the enzymatic reactions. The results indicate that R-GO FETs provide the capability to detect protons, demonstrating their applicability as a biosensing device for enzymatic reactions. Copyright © 2013 Elsevier B.V. All rights reserved.

Spectroscopic determination of pH

International Nuclear Information System (INIS)

Faanu, A.; Glover, E.T.; Bailey, E.; Rochelle, C.

2009-01-01

A technique of measuring pH at temperature range of 20 - 70 0 C and high pressure conditions of 1 - 200 atmospheres has been developed by relating the ratio of absorbance peaks of indicator solutions (basic and acidic) as a function of pH, using ultraviolet-visible spectrophotometer. The pH values of the buffer solutions measured at 20 0 C and 70 0 C indicated slight temperature dependence, while the pressure had no effect. The pH of the buffer solutions increased with temperature with relative standard deviations in the range 0.4 - 0.5 % at 95 % confidence interval. The possible causes of the temperature dependence were attributed to changes in pH values as the temperature changed. (au)

Influence of the pH value of a colloidal gold solution on the absorption spectra of an LSPR-assisted sensor

International Nuclear Information System (INIS)

Zhu, Jin; Li, Wenbin; Zhu, Mao; Zhang, Wei; Niu, Wencheng; Liu, Guohua

2014-01-01

The localized surface plasmon resonances (LSPRs) of gold particles assembled on a crystal plate are a powerful tool for biological sensors. Here, we prepare gold colloids in different pH solutions. We monitor the effects of the particle radius and particle coverage on the absorption spectra of AT-cut (r-face dihedral angle of about 3°) crystal plates supporting gold nanoparticles. The surface morphologies were monitored on silicon dioxide substrates using ultraviolet and visible (UV-vis) spectroscopy, and atomic force microscopy (AFM). The results showed that the gold particle coverage decreases with increasing pH value of the gold colloid solution. This phenomenon demonstrates that self-assembled gold surfaces were formed via the electrostatic adsorption of gold particles on the positively charged, ionized amino groups on the crystal plates in the acidic solution. The spectrum of gold nanoparticles with different coverage degree on the crystal plates showed that the LSPR properties are highly dependent on pH

Migration characteristics of cobalt-60 through sandy soil in high pH solution

International Nuclear Information System (INIS)

Ohnuki, Toshihiko

1992-01-01

Migration characteristics of 60 Co through sandy soil in high pH solution has been investigated by both column and batch techniques. The association of 60 Co with the sandy soil and its components were studied by sequential extraction techniques. The concentration profile of 60 Co in the sandy soil column was composed of two exponential curves showing that 60 Co would consist of immobile and mobile fractions. The immobile 60 Co was retained by the sandy soil and was distributed near the top. Though the mobile 60 Co was little sorbed by soil and migrated through the soil column, maximum concentration of 60 Co in the effluents decreased slightly with increasing path length of the soil column. The sequential extraction of 60 Co from the sandy soil and from its components showed that 60 Co was sorbed by both manganese oxide and clay minerals. And manganese oxide is one of the responsible soil components for the observed decrease in the maximum concentration of 60 Co in the effluents. Although the content of manganese oxide in the sandy soil was 0.13%, manganese oxide is the important component to prevent from the migration of 60 Co in the high pH solution. (author)

The electrochemical behaviour of stainless steel AISI 304 in alkaline solutions with different pH in the presence of chlorides

International Nuclear Information System (INIS)

Freire, L.; Carmezim, M.J.; Ferreira, M.G.S.; Montemor, M.F.

2011-01-01

Highlights: → The passivation and passivation breakdown of AISI 304 in alkaline solutions with different pH was studied. → The electrochemical behaviour and the corrosion resistance in chloride environments were evaluated using d.c. potentiodynamic polarization and electrochemical impedance spectroscopy. → The results were modelled using a hierarchically distributed circuit and revealed a more susceptible surface at pH 9. → The passive film characterization was carried out by SEM and EDS analysis, revealing the existence of MnS inclusions and the increase of Cr/Fe ratio in the attacked areas, preferably the vicinity of those inclusions. - Abstract: Nowadays, stainless steel reinforcements appear as an effective solution to increase the durability of reinforced concrete structures exposed to very aggressive environments. AISI 304 is widely used for this purpose. Although the improved durability of reinforcing AISI 304, when compared to carbon steel, there is a high probability of pitting susceptibility in the presence of chlorides. Thus, the present work aims at studying the passivation and passivation breakdown of AISI 304 in alkaline solutions of different pH (pH from 13 to 9), simulating the interstitial concrete electrolyte. These solutions were contaminated with different concentrations of chloride ions (3% and 10%, as NaCl). The electrochemical behaviour was evaluated by d.c. potentiodynamic polarization and by electrochemical impedance spectroscopy (EIS). The morphological features and the changes observed in the surface composition were evaluated by Scanning Electron Microscopy (SEM) together with EDS chemical analysis. The results evidence that pH plays an important role in the evolution of the film resistance and charge transfer processes. Moreover, the effect is highly dependent upon the chloride content and immersion time.

Dendritic Zinc Growth in Acid Electrolyte: Effect of the pH

Science.gov (United States)

Bengoa, Leandro N.; Pary, Paola; Seré, Pablo R.; Conconi, M. Susana; Egli, Walter A.

2018-03-01

In this paper, dendritic growth at the edges of electrogalvanized steel strip has been studied using a specially designed rotating washer electrode which simulates the fluid dynamic conditions and the current density distribution at the steel strip edge found in a production line. The effect of electrolyte pH and current density on dendritic growth in an acidic zinc plating bath (ZnSO4 and H2SO4) was addressed. The temperature was kept constant at 60 °C. Solution pH was adjusted to 1, 2 or 3 using different amounts of H2SO4. In addition, the influence of temperature on the pH of the solution was determined. The current density was set at 40 or 60 A/dm2, similar to that used in the industry. Deposits were characterized using SEM and XRD. The results showed that pH strongly affects dendrites shape, length and texture. Furthermore, the morphology of dendrites at the washer edge and of deposits on the flat portion of the washer changed considerably as solution pH was increased from 1 to 3. It was found that the morphology of dendrites at the washer edge stems from the morphology of the deposit on its flat portion, which in turn determines their shape.

Calculation of the equilibrium pH in a multiple-buffered aqueous solution based on partitioning of proton buffering: a new predictive formula.

Science.gov (United States)

Nguyen, Minhtri K; Kao, Liyo; Kurtz, Ira

2009-06-01

Upon the addition of protons to an aqueous solution containing multiple buffers, the final H+ concentration ([H+]) at equilibrium is determined by the partitioning of added H+ among the various buffer components. In the analysis of acid-base chemistry, the Henderson-Hasselbalch equation and the Stewart strong ion formulation can only describe (rather than predict) the equilibrium pH following a proton load since these formulas calculate the equilibrium pH only when the reactant concentrations at equilibrium(1) 1The term "equilibrium" refers to the steady state proton and reactant concentrations when the buffering of excess protons by the various buffers is complete. are already known. In this regard, it is simpler to directly measure the equilibrium pH rather than measure the equilibrium reactant concentrations to calculate the equilibrium pH. As these formulas cannot predict the final equilibrium [H+] following a proton load to a multiple-buffered aqueous solution, we developed a new quantitative approach for predicting the equilibrium [H+] that is based on the preequilibrium(2)2 The term "preequilibrium" refers to the initial proton and reactant concentrations immediately upon addition of protons and before the buffering of excess protons by the various buffers. concentrations of all buffers in an aqueous solution. The mathematical model used to derive our equation is based on proton transfer buffer equilibria without requiring the incorporation of electroneutrality considerations. The model consists of a quartic polynomial equation that is derived based solely on the partitioning of H+ among the various buffer components. We tested the accuracy of the model using aqueous solutions with various buffers and measured the equilibrium pH values following the addition of HCl. Our results confirmed the accuracy of our new equation (r2 = 1; measured pH vs. predicted pH), indicating that it quantitatively accounts for the underlying acid-base phenomenology.

Calculation of the equilibrium pH in a multiple-buffered aqueous solution based on partitioning of proton buffering: a new predictive formula

Science.gov (United States)

Nguyen, Minhtri K.; Kao, Liyo; Kurtz, Ira

2009-01-01

Upon the addition of protons to an aqueous solution containing multiple buffers, the final H+ concentration ([H+]) at equilibrium is determined by the partitioning of added H+ among the various buffer components. In the analysis of acid-base chemistry, the Henderson-Hasselbalch equation and the Stewart strong ion formulation can only describe (rather than predict) the equilibrium pH following a proton load since these formulas calculate the equilibrium pH only when the reactant concentrations at equilibrium1 1The term “equilibrium” refers to the steady state proton and reactant concentrations when the buffering of excess protons by the various buffers is complete. are already known. In this regard, it is simpler to directly measure the equilibrium pH rather than measure the equilibrium reactant concentrations to calculate the equilibrium pH. As these formulas cannot predict the final equilibrium [H+] following a proton load to a multiple-buffered aqueous solution, we developed a new quantitative approach for predicting the equilibrium [H+] that is based on the preequilibrium22The term “preequilibrium” refers to the initial proton and reactant concentrations immediately upon addition of protons and before the buffering of excess protons by the various buffers. concentrations of all buffers in an aqueous solution. The mathematical model used to derive our equation is based on proton transfer buffer equilibria without requiring the incorporation of electroneutrality considerations. The model consists of a quartic polynomial equation that is derived based solely on the partitioning of H+ among the various buffer components. We tested the accuracy of the model using aqueous solutions with various buffers and measured the equilibrium pH values following the addition of HCl. Our results confirmed the accuracy of our new equation (r2 = 1; measured pH vs. predicted pH), indicating that it quantitatively accounts for the underlying acid-base phenomenology. PMID

The passivation of calcite by acid mine water. Column experiments with ferric sulfate and ferric chloride solutions at pH 2

Energy Technology Data Exchange (ETDEWEB)

Soler, Josep M. [Institute of Earth Sciences ' Jaume Almera' (CSIC), Lluis Sole i Sabaris s/n, 08028 Barcelona, Catalonia (Spain); Institute of Environmental Assessment and Water Research (CSIC), Jordi Girona 18, 08034 Barcelona, Catalonia (Spain)], E-mail: jsoler@ija.csic.es; Boi, Marco [Institute of Earth Sciences ' Jaume Almera' (CSIC), Lluis Sole i Sabaris s/n, 08028 Barcelona, Catalonia (Spain); Institute of Environmental Assessment and Water Research (CSIC), Jordi Girona 18, 08034 Barcelona, Catalonia (Spain); Mogollon, Jose Luis [Institute of Earth Sciences ' Jaume Almera' (CSIC), Lluis Sole i Sabaris s/n, 08028 Barcelona, Catalonia (Spain); Instituto de Ciencias de la Tierra, Universidad Central de Venezuela, Caracas 1020-A (Venezuela, Bolivarian Republic of); Cama, Jordi; Ayora, Carlos [Institute of Earth Sciences ' Jaume Almera' (CSIC), Lluis Sole i Sabaris s/n, 08028 Barcelona, Catalonia (Spain); Institute of Environmental Assessment and Water Research (CSIC), Jordi Girona 18, 08034 Barcelona, Catalonia (Spain); Nico, Peter S.; Tamura, Nobumichi; Kunz, Martin [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States)

2008-12-15

Column experiments, simulating the behavior of passive treatment systems for acid mine drainage, have been performed. Acid solutions (HCl or H{sub 2}SO{sub 4}, pH 2), with initial concentrations of Fe(III) ranging from 250 to 1500 mg L{sup -1}, were injected into column reactors packed with calcite grains at a constant flow rate. The composition of the solutions was monitored during the experiments. At the end of the experiments (passivation of the columns), the composition and structure of the solids were measured. The dissolution of calcite in the columns caused an increase in pH and the release of Ca into the solution, leading to the precipitation of gypsum and Fe-oxyhydroxysulfates (Fe(III)-SO{sub 4}-H{sup +} solutions) or Fe-oxyhydroxychlorides (Fe(III)-Cl-H{sup +} solutions). The columns worked as an efficient barrier for some time, increasing the pH of the circulating solutions from 2 to {approx}6-7 and removing its metal content. However, after some time (several weeks, depending on the conditions), the columns became chemically inert. The results showed that passivation time increased with decreasing anion and metal content of the solutions. Gypsum was the phase responsible for the passivation of calcite in the experiments with Fe(III)-SO{sub 4}-H{sup +} solutions. Schwertmannite and goethite appeared as the Fe(III) secondary phases in those experiments. Akaganeite was the phase responsible for the passivation of the system in the experiments with Fe(III)-Cl-H{sup +} solutions.

Addressing a Common Misconception: Ammonium Acetate as Neutral pH "Buffer" for Native Electrospray Mass Spectrometry

Science.gov (United States)

Konermann, Lars

2017-09-01

Native ESI-MS involves the transfer of intact proteins and biomolecular complexes from solution into the gas phase. One potential pitfall is the occurrence of pH-induced changes that can affect the analyte while it is still surrounded by solvent. Most native ESI-MS studies employ neutral aqueous ammonium acetate solutions. It is a widely perpetuated misconception that ammonium acetate buffers the analyte solution at neutral pH. By definition, a buffer consists of a weak acid and its conjugate weak base. The buffering range covers the weak acid pKa ± 1 pH unit. NH4 + and CH3-COO- are not a conjugate acid/base pair, which means that they do not constitute a buffer at pH 7. Dissolution of ammonium acetate salt in water results in pH 7, but this pH is highly labile. Ammonium acetate does provide buffering around pH 4.75 (the pKa of acetic acid) and around pH 9.25 (the pKa of ammonium). This implies that neutral ammonium acetate solutions electrosprayed in positive ion mode will likely undergo acidification down to pH 4.75 ± 1 in the ESI plume. Ammonium acetate nonetheless remains a useful additive for native ESI-MS. It is a volatile electrolyte that can mimic the solvation properties experienced by proteins under physiological conditions. Also, a drop from pH 7 to around pH 4.75 is less dramatic than the acidification that would take place in pure water. It is hoped that the habit of referring to pH 7 solutions as ammonium acetate "buffer" will disappear from the literature. Ammonium acetate "solution" should be used instead. [Figure not available: see fulltext.

Kinetic Rate Law Parameter Measurements on a Borosilicate Waste Glass: Effect of Temperature, pH, and Solution Composition on Alkali Ion Exchange

International Nuclear Information System (INIS)

Pierce, Eric M.; McGrail, B PETER.; Icenhower, J P.; Rodriguez, Elsa A.; Steele, Jackie L.; Baum, Steven R.

2004-01-01

The reaction kinetics of glass is controlled by matrix dissolution and ion exchange (IEX). Dissolution of an alkali-rich simulated borosilicate waste glass was investigated using single-pass flow-through (SPFT) experiments. Experiments were conducted as a function of temperature, pH, and solution composition by varying the SiO 2 (aq) activity in the influent solution. Results showed that under dilute conditions matrix dissolution increased with increasing pH and temperature, and decreased with increasing SiO 2 (aq) activity. IEX rates decreased with increasing pH and temperature, and increased with increasing SiO 2 (aq) activity. Over the solution composition range interrogated in this study the dominant dissolution mechanism changed from matrix dissolution to IEX. These results suggest that ''secondary'' reactions may become dominant under certain environmental conditions and emphasize the need to incorporate these reactions into dissolution rate models

Fate of cadmium at the soil-solution interface: a thermodynamic study as influenced by varying pH at South 24 Parganas, West Bengal, India.

Science.gov (United States)

Karak, Tanmoy; Paul, Ranjit Kumar; Das, Sampa; Das, Dilip K; Dutta, Amrit Kumar; Boruah, Romesh K

2015-11-01

A study on the sorption kinetics of Cd from soil solution to soils was conducted to assess the persistence of Cd in soil solution as it is related to the leaching, bioavailability, and potential toxicity of Cd. The kinetics of Cd sorption on two non-contaminated alkaline soils from Canning (22° 18' 48.02″ N and 88° 39' 29.0″ E) and Lakshmikantapur (22° 06' 16.61″ N and 88° 19' 08.66″ E) of South 24 Parganas, West Bengal, India, were studied using conventional batch experiment. The variable soil suspension parameters were pH (4.00, 6.00, 8.18, and 9.00), temperatures (308, 318, and 328 K) and Cd concentrations (5-100 mg L(-1)). The average rate coefficient (kavg) and half-life (t1/2) values indicate that the persistence of Cd in soil solution is influenced by both temperature and soil suspension pH. The concentration of Cd in soil solution decreases with increase of temperature; therefore, Cd sorption on the soil-solution interface is an endothermic one. Higher pH decreases the t 1/2 of Cd in soil solution, indicating that higher pH (alkaline) is not a serious concern in Cd toxicity than lower pH (acidic). Based on the energy of activation (Ea) values, Cd sorption in acidic pH (14.76±0.29 to 64.45±4.50 kJ mol(-1)) is a surface control phenomenon and in alkaline pH (9.33±0.09 to 44.60±2.01 kJ mol(-1)) is a diffusion control phenomenon The enthalpy of activation (ΔH∓) values were found to be between 7.28 and 61.73 kJ mol(-1). Additionally, higher positive energy of activation (ΔG∓) values (46.82±2.01 to 94.47±2.36 kJ mol(-1)) suggested that there is an energy barrier for product formation.

Method for producing rapid pH changes

Science.gov (United States)

Clark, J.H.; Campillo, A.J.; Shapiro, S.L.; Winn, K.R.

A method of initiating a rapid pH change in a solution comprises irradiating the solution with an intense flux of electromagnetic radiation of a frequency which produces a substantial pK change to a compound in solution. To optimize the resulting pH change, the compound being irradiated in solution should have an excited state lifetime substantially longer than the time required to establish an excited state acid-base equilibrium in the solution. Desired pH changes can be accomplished in nanoseconds or less by means of picosecond pulses of laser radiation.

Influence of pH, temperature and thermal treatment on site corrosion of SAE 304 steel in chlorinated solutions

International Nuclear Information System (INIS)

Konrad, I.B.

1982-01-01

The electrochemical behaviour and fracture morphology of homogenized and sensitized type SAE 304 stainless steel U bent specimens, in 3% NaCl solution, at pH=2.0 and pH=7.0 both at room temperature and 100 0 C was studied. Polarization curves, galvanostatic and potentiostatic experiments were run. It could be observed that high temperature and low pH favour transgranular cracking and longer sensitization times lower fracture time and tend to give rise to intergranular fracture. Light sensitization can produce transgranular cracking even at room temperature, when the homogenized alloy does not present stress-corrosion cracking for the same condition. (Author) [pt

X-ray absorption spectroscopic study of trivalent and tetravalent actinides in solution at varying pH values

Energy Technology Data Exchange (ETDEWEB)

Brendebach, B.; Banik, N.L.; Marquardt, C.M.; Rothe, J.; Denecke, M.A.; Geckeis, H. [Forschungszentrum Karlsruhe (Germany). Inst. fuer Nukleare Entsorgung

2009-07-01

We perform X-ray absorption spectroscopy (XAS) investigations to monitor the stabilization of redox sensitive trivalent and tetravalent actinide ions in solution at acidic conditions in a pH range from 0 to 3 after treatment with holding reductants, hydroxylamine hydrochloride (NH{sub 2}OHHCl) and Rongalite (sodium hydroxymethanesulfinate, CH{sub 3}NaO{sub 3}S). X-ray absorption near edge structure (XANES) measurements clearly demonstrate the stability of the actinide species for several hours under the given experimental conditions. Hence, structural parameters can be accurately derived by extended X-ray absorption fine structure (EXAFS) investigations. The coordination structure of oxygen atoms belonging to water ligands surrounding the actinide ions does not change with increasing pH value (approximately 11 O atoms at 2.42 A in the case of U(IV) at pH 1, 9 0 atoms at 2.52 A for Np(III) at pH 1.5, and 10 O atoms at 2.49 A for Pu(III) up to pH 3), indicating that hydrolysis reactions are suppressed under the given chemical conditions. (orig.)

Chemical Composition and Evaluation of Nicotine, Tobacco Alkaloids, pH and Selected Flavors in e-Cigarette Cartridges and Refill Solutions

Science.gov (United States)

Lisko, Joseph G.; Tran, Hang; Stanfill, Stephen B.; Blount, Benjamin C.; Watson, Clifford H.

2015-01-01

Introduction Electronic cigarette (e-cigarette) use is increasing dramatically in developed countries, but little is known about these rapidly evolving products. This study analyzed and evaluated the chemical composition including nicotine, tobacco alkaloids, pH and flavors in 36 e-liquids brands from four manufacturers. Methods We determined the concentrations of nicotine, alkaloids, and select flavors and measured pH in solutions used in e-cigarettes. E-cigarette products were chosen based upon favorable consumer approval ratings from online review websites. Quantitative analyses were performed using strict quality assurance/quality control (QC) validated methods previously established by our lab for the measurement of nicotine, alkaloids, pH and flavors. Results Three-quarters of the products contained lower measured nicotine levels than the stated label values (6% - 42% by concentration). The pH for e-liquids ranged from 5.1 – 9.1. Minor tobacco alkaloids were found in all samples containing nicotine, and their relative concentrations varied widely among manufacturers. A number of common flavor compounds were analyzed in all e-liquids. Conclusions Free nicotine levels calculated from the measurement of pH correlated with total nicotine content. The direct correlation between the total nicotine concentration and pH suggests that the alkalinity of nicotine drives the pH of e-cigarette solutions. A higher percentage of nicotine exists in the more absorbable free form as total nicotine concentration increases. A number of products contained tobacco alkaloids at concentrations that exceed U.S. Pharmacopeia limits for impurities in nicotine used in pharmaceutical and food products. PMID:25636907

Molecular water motions of skim milk powder solutions during acidification studied by 17O and 1H nuclear magnetic resonance and rheology

DEFF Research Database (Denmark)

Møller, S M; Whittaker, A. K.; Stokes, J. R.

2011-01-01

The molecular motion of water was studied in glucono-δ-lactone-acidified skim milk powder (SMP) solutions with various pH values and dry matter contents. NMR relaxometry measurements revealed that lowering the pH in SMP solutions affected 17O and 1HT2 relaxation rates almost identically. Conseque......The molecular motion of water was studied in glucono-δ-lactone-acidified skim milk powder (SMP) solutions with various pH values and dry matter contents. NMR relaxometry measurements revealed that lowering the pH in SMP solutions affected 17O and 1HT2 relaxation rates almost identically...... could contribute to the initial decrease in 17O and 1Hrelaxation rate in the pH range between 6.6 and 5.5 for 15% SMP and in the pH range between 6.6 and 5.9 for 25% SMP. However, below pH 5.5 the viscosity and 17Oand 1HNMRrelaxation rates did not correlate, revealing that the aggregation of casein...... micelles, which increases viscosity below pH 5.5, does not involve major repartitioning of water....

Deletion of pH Regulator pac-3 Affects Cellulase and Xylanase Activity during Sugarcane Bagasse Degradation by Neurospora crassa.

Directory of Open Access Journals (Sweden)

Amanda Cristina Campos Antoniêto

Full Text Available Microorganisms play a vital role in bioethanol production whose usage as fuel energy is increasing worldwide. The filamentous fungus Neurospora crassa synthesize and secrete the major enzymes involved in plant cell wall deconstruction. The production of cellulases and hemicellulases is known to be affected by the environmental pH; however, the regulatory mechanisms of this process are still poorly understood. In this study, we investigated the role of the pH regulator PAC-3 in N. crassa during their growth on sugarcane bagasse at different pH conditions. Our data indicate that secretion of cellulolytic enzymes is reduced in the mutant Δpac-3 at alkaline pH, whereas xylanases are positively regulated by PAC-3 in acidic (pH 5.0, neutral (pH 7.0, and alkaline (pH 10.0 medium. Gene expression profiles, evaluated by real-time qPCR, revealed that genes encoding cellulases and hemicellulases are also subject to PAC-3 control. Moreover, deletion of pac-3 affects the expression of transcription factor-encoding genes. Together, the results suggest that the regulation of holocellulase genes by PAC-3 can occur as directly as in indirect manner. Our study helps improve the understanding of holocellulolytic performance in response to PAC-3 and should thereby contribute to the better use of N. crassa in the biotechnology industry.

pH sensing in aqueous solutions using a MnO2 thin film electrodeposited on a glassy carbon electrode

International Nuclear Information System (INIS)

Cherchour, N.; Deslouis, C.; Messaoudi, B.; Pailleret, A.

2011-01-01

An electrolysis technique at a constant potential was used to develop a highly reproducible and fast elaboration method of adherent manganese dioxide thin films on a glassy carbon electrode from aqueous solutions containing sulfuric acid and manganese sulfate. The resulting films were found to have a nanostructured character presumably due rather to birnessite (δ-MnO 2 ) than to γ-MnO 2 , as suggested by their Raman and XRD signatures. They lead to modified electrodes that present an obvious although complex pH dependent potentiometric response. This sensor indeed showed a single slope non-Nernstian linear behaviour over the 1.5-12 pH range for increasing pH direction ('trace'), whereas a Nernstian two slopes linear behaviour was observed for decreasing pH direction ('re-trace'). Preliminary EIS experiments carried out at a pH value of 1.8 seem to reveal a sensitivity mechanism based on proton insertion process at least at highly acidic pH values.

Changes of organic acid exudation and rhizosphere pH in rice plants under chromium stress

International Nuclear Information System (INIS)

Zeng Fanrong; Chen Song; Miao Ying; Wu Feibo; Zhang Guoping

2008-01-01

The effect of chromium (Cr) stress on the changes of rhizosphere pH, organic acid exudation, and Cr accumulation in plants was studied using two rice genotypes differing in grain Cr accumulation. The results showed that rhizosphere pH increased with increasing level of Cr in the culture solution and with an extended time of Cr exposure. Among the six organic acids examined in this experiment, oxalic and malic acid contents were relatively higher, and had a significant positive correlation with the rhizosphere pH, indicating that they play an important role in changing rhizosphere pH. The Cr content in roots was significantly higher than that in stems and leaves. Cr accumulation in plants was significantly and positively correlated with rhizosphere pH, and the exudation of oxalic, malic and citric acids, suggesting that an increase in rhizosphere pH, and exudation of oxalic, malic and citric acid enhances Cr accumulation in rice plants. - Rhizosphere pH and organic acid exudation of rice roots are markedly affected by chromium level in culture solution

The study on the pH behavior of the HFSC leached solution. The development of model considering the pozzolanic reaction

International Nuclear Information System (INIS)

Yoshida, Yasushi; Mihara, Morihiro

2005-09-01

The development of low alkalinity cement (high fly-ash contained silica-fume cement, HFSC) has been carried out in JNC. Low alkalinity for this cement is achieved by adding pozzolan materials to ordinary portland cement and Ca ion attributed to high alkalinity is consumed by forming CHS gel. This report shows the calculation model to predict the composition for HFSC reacted solution which considers cement mineral dissolution/precipitation as equilibrium reactions and dissolution for pozzolan material as a kinetic reaction. The dissolution kinetic equation for pozzolan material is also derived from leaching experiment. This calculation model is applied to the leaching experiment where powdered HFSC was reacted with distilled water. As a result of comparison between calculation and experimental measurement at the early stage for leaching the tendency for pH, pH decrease from 12.5 to 11.5 drastically, could be interpreted by this calculation model, however, after this drastic pH decreasing pH predicted by calculation model also shows drastic decrease whereas pH for experiment decreased mildly around pH 11.5. It could be thought that this difference between experiment and calculation is caused by inappropriate modelling for CSH gel dissolution/precipitation of C/S value lower than 1.0. For this C/S range thermodynamic data for intermediate and end member for solid solution for CSH gel and in addition the reaction kinetic for CSH gel should be examined in detail. (author)

Effect of Nitrogen Form and pH of Nutrient Solution on the Shoot Concentration of Phosphorus, Nitrate, and Nitrogen of Spinach in Hydroponic Culture

OpenAIRE

N. Najafi; M. Parsazadeh

2010-01-01

In order to study the effect of nitrogen form and pH of nutrient solution on the shoot concentration of P, nitrate, organic N + inorganic ammonium, and total N of spinach, a factorial experiment was conducted with two factors including pH of nutrient solution in three levels (4.5, 6.5 and 8.0) and nitrate to ammonium ratio of nutrient solution in five levels (100:0, 75:25, 50:50, 25:75 and 0:100). This factorial experiment was carried out in a completely randomized design with four replicatio...

Removal of phosphate and nitrate from aqueous solution using ...

African Journals Online (AJOL)

sunny t

water, 3.5 g of NaCl were dissolved to obtain 3.5 g/l salinity final solution. When the ... The nitrate adsorption was highly pH dependent, which affects the ... adsorption mechanism that the optimum pH for phosphate removal by .... Biosorption of copper(ii) from aqueous ... Accumulation and detoxification of toxic elements by ...

Minimization of sucrose losses in sugar industry by pH and temperature optimization

International Nuclear Information System (INIS)

Panpae, Kornvalai; Jaturonrusmee, Wasna; Mingvanish, Withawat; Santudrob, Kittisak; Triphanpitak, Siriphan

2008-01-01

Invert sugar has several disadvantage properties that play an important role in many food applications. It has a high affinity for water and is the cause of making products retain moisture. Invert sugar also affects the carmelization process, producing a browning effect. In this study, the possibility of minimization of sucrose inversion during the industrial production of sugar cane was investigated by the variation of the important parameters, i.e. temperature and pH of sugar cane juice for each of samples. The amounts of sucrose and reducing sugar alerting during the sucrose inversion process were determined by the values of % Pol and % reducing sugar (% RS), respectively. Starting with the study of temperature and pH effects of the sucrose solution with the concentration of 16 Brix, used as a sample model, it was found that no change in amounts of reducing sugar and sucrose was observed at room temperature (34 degree Celsius) in the pH range of 5-11. At pH 3, the amounts of reducing sugar increased and the amount of sucrose decreased as the time increased. These indicated that the process of sucrose inversion should better occur in more acidic solutions. Compared to the room temperature, it was found that the increment of temperature led to enhance the process of sucrose inversion. This was depicted by higher values of % RS and lower value of % Pol as the temperatures were elevated. The experiments were also done with real sugar cane juice, i.e. first, last, and mixed juice. The tendency of changes of the amounts of reducing sugar and sucrose in sugar cane samples by varying temperature and pH were found to resemble to those for the sample model. The increment of temperatures have also affected on a reduction of amounts of sucrose in each sugar cane juice. In addition, it could be concluded that the acidity of the solution affects sucrose easier to be broken down to glucose and fructose molecules. (author)

Some effects of pH on iodine volatility in containment

International Nuclear Information System (INIS)

Ashmore, C.B.; Gwyther, J.R.; Sims, H.E.

1994-01-01

The behaviour of iodine in containment in the event of an accident involving fission product release would be strongly dependent on pH. High pH leads to a lower rate of radiolytic oxidation and in alkaline conditions the thermally stable form is IO 3 - . Much of the work on effects of pH on radiolytic oxidation reported in the literature may be erroneous or misleading because of postirradiation reaction and in this report some new experiments are described which were designed to overcome these problems involving sparged irradiated solutions of CsI spiked with 131 I. The rate of radiolytic oxidation has been measured as a function of pH between pH 4.6 and pH 9 and iodide concentrations between 10 -4 and 10 -6 mol dm -3 . Also discussed in the paper are factors which can affect the pH of the sump water and the effects of high pH in sprays. It is concluded that high pH is beneficial and it is important not only to achieve high pH but to maintain it. (author). 10 refs., 1 tab., 6 figs

Semi-mechanistic partial buffer approach to modeling pH, the buffer properties, and the distribution of ionic species in complex solutions.

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Dougherty, Daniel P; Da Conceicao Neta, Edith Ramos; McFeeters, Roger F; Lubkin, Sharon R; Breidt, Frederick

2006-08-09

In many biological science and food processing applications, it is very important to control or modify pH. However, the complex, unknown composition of biological media and foods often limits the utility of purely theoretical approaches to modeling pH and calculating the distributions of ionizable species. This paper provides general formulas and efficient algorithms for predicting the pH, titration, ionic species concentrations, buffer capacity, and ionic strength of buffer solutions containing both defined and undefined components. A flexible, semi-mechanistic, partial buffering (SMPB) approach is presented that uses local polynomial regression to model the buffering influence of complex or undefined components in a solution, while identified components of known concentration are modeled using expressions based on extensions of the standard acid-base theory. The SMPB method is implemented in a freeware package, (pH)Tools, for use with Matlab. We validated the predictive accuracy of these methods by using strong acid titrations of cucumber slurries to predict the amount of a weak acid required to adjust pH to selected target values.

Influence of pH on Cr(VI) ions removal from aqueous solutions using carboxymethyl cellulose-based hydrogel as adsorbent

Science.gov (United States)

Anah, L.; Astrini, N.

2017-03-01

The major problem in heavy metal pollution is that these metals are not biodegradable and accordingly accumulate in the bodies of living organisms, causing dangerous diseases and serious cell disorder. According to World Health Organization (WHO), the long term exposure of Cr(VI) levels of over 0.1 ppm causes respiratory problems, liver and kidney damage, and carcinogenicity.Due to its easy operation and of various cheap adsorbents development, adsorption has been proved to be efficient and most economically attractive technique and feasible to the removal of toxic heavy metal from wastewater. The study aimed to report the removal of Cr(VI) ions from aqueous solutions through adsorption process using carboxymethyl cellulose-graft-poly(acrylic acid) (CMC-g-PAA) hydrogel as adsorbent.Effect of pH was studied to remove hexavalent chromium.Graft copolymerization of poly(acrylic acid) onto carboxymethyl cellulose was carried out in the presence of benzoyl peroxide redox initiator and methylenbisacrylamide as crosslinker agent. Batch experiments were carried out to investigate the effects ofinitial pH.The adsorption of Cr(VI) ions as a function of pH was conducted in the initial pH range of 1 to 8. The results indicated that acidic pH strongly favored the adsorption. The optimum pH for adsorption of Cr(VI) ranged from 1 to 3, and the maximum uptake of Cr(VI) from the solution was 6.53 mg/g at pH 1 and 30°C. FTIR spectroscopy, SEM analyses were performed on the adsorbent before and after Cr(VI) binding. All analyses confirmed the complexation of Cr(VI) ions on the adsorbent.

Microneedle pH Sensor: Direct, Label-Free, Real-Time Detection of Cerebrospinal Fluid and Bladder pH.

Science.gov (United States)

Mani, Ganesh Kumar; Miyakoda, Kousei; Saito, Asuka; Yasoda, Yutaka; Kajiwara, Kagemasa; Kimura, Minoru; Tsuchiya, Kazuyoshi

2017-07-05

Acid-base homeostasis (body pH) inside the body is precisely controlled by the kidneys and lungs and buffer systems, such that even a minor pH change could severely affect many organs. Blood and urine pH tests are common in day-to-day clinical trials and require little effort for diagnosis. There is always a great demand for in vivo testing to understand more about body metabolism and to provide effective diagnosis and therapy. In this article, we report the simple fabrication of microneedle-based direct, label-free, and real-time pH sensors. The reference and working electrodes were Ag/AgCl thick films and ZnO thin films on tungsten (W) microneedles, respectively. The morphological and structural characteristics of microneedles were carefully investigated through various analytical methods. The developed sensor exhibited a Nernstian response of -46 mV/pH. Different conditions were used to test the sensor to confirm their accuracy and stability, such as various buffer solutions, with respect to time, and we compared the reading with commercial pH electrodes. Besides that, the fabricated microneedle sensor ability is proven by in vivo testing in mouse cerebrospinal fluid (CSF) and bladders. The pH sensor procedure reported here is totally reversible, and results were reproducible after several rounds of testing.

Degradation kinetics of fisetin and quercetin in solutions affected by medium pH, temperature and co-existed proteins

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Wang Jing

2016-01-01

Full Text Available Impacts of medium pH, temperature and coexisted proteins on the degradation of two flavonoids fisetin and quercetin were assessed by spectroscopic method in the present study. Based on the measured degradation rate constants (k, fisetin was more stable than quercetin in all cases. Increasing medium pH from 6.0 to 7.5 at 37°C enhanced respective k values of fisetin and quercetin from 8.30x10−3 and 2.81x10−2 to 0.202 and 0.375 h-1 (P<0.05. In comparison with their degradation at 37°C, fisetin and quercetin showed larger k values at higher temperature (0.124 and 0.245 h−1 at 50°C, or 0.490 and 1.42 h−1 at 65°C. Four protein products in medium could stabilize the two flavonoids (P<0.05, as these proteins at 0.10 g L-1 decreased respective k values of fisetin and quercetin to 2.28x10−2-2.98x10−2 and 4.37´10−2-5.97x10−2 h−1. Hydrophobic interaction between the proteins and the two flavonoids was evidenced responsible for the stabilization, as sodium dodecyl sulfate could destroy the stabilization significantly (P<0.05. Casein and soybean protein provided greater stabilization than whey protein isolate. It is thus concluded that higher temperature and alkaline pH can enhance flavonoid loss, whereas coexisted proteins as flavonoid stabilizers can inhibit flavonoid degradation.

Trans-life cycle acclimation to experimental ocean acidification affects gastric pH homeostasis and larval recruitment in the sea star Asterias rubens.

Science.gov (United States)

Hu, Marian Y; Lein, Etienne; Bleich, Markus; Melzner, Frank; Stumpp, Meike

2018-04-16

Experimental simulation of near-future ocean acidification (OA) has been demonstrated to affect growth and development of echinoderm larval stages through energy allocation towards ion and pH compensatory processes. To date, it remains largely unknown how major pH regulatory systems and their energetics are affected by trans-generational exposure to near-future acidification levels. Here we used the common sea star Asterias rubens in a reciprocal transplant experiment comprising different combinations of OA scenarios, in order to study trans-generational plasticity using morphological and physiological endpoints. Acclimation of adults to pH T 7.2 (pCO 2 3500μatm) led to reductions in feeding rates, gonad weight, and fecundity. No effects were evident at moderate acidification levels (pH T 7.4; pCO 2 2000μatm). Parental pre-acclimation to pH T 7.2 for 85 days reduced developmental rates even when larvae were raised under moderate and high pH conditions, whereas pre-acclimation to pH T 7.4 did not alter offspring performance. Microelectrode measurements and pharmacological inhibitor studies carried out on larval stages demonstrated that maintenance of alkaline gastric pH represents a substantial energy sink under acidified conditions that may contribute up to 30% to the total energy budget. Parental pre-acclimation to acidification levels that are beyond the pH that is encountered by this population in its natural habitat (e.g. pH T 7.2) negatively affected larval size and development, potentially through reduced energy transfer. Maintenance of alkaline gastric pH and reductions in maternal energy reserves probably constitute the main factors for a reduced juvenile recruitment of this marine keystone species under simulated OA. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

The effect of pH on the corrosion behavior of intermetallic compounds Ni{sub 3}(Si,Ti) and Ni{sub 3}(Si,Ti) + 2Mo in sodium chloride solutions

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Priyotomo, Gadang, E-mail: gada001@lipi.go.id; Nuraini, Lutviasari, E-mail: Lutviasari@gmail.com [Research Center for Metallurgy and Material, Indonesian Institute of Sciences, Kawasan PUSPIPTEK Gd.474, Setu, Tangerang Selatan, Banten 15314 (Indonesia); Kaneno, Yasuyuki, E-mail: kaneno@mtr.osakafu-u.ac.id [Department of Materials Science, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531 (Japan)

2015-12-29

The corrosion behavior of the intermetallic compounds, Ni{sub 3}(Si,Ti) (L1{sub 2}: single phase) and Ni{sub 3}(Si,Ti) + 2Mo (L1{sub 2} and (L12 + Ni{sub ss}) mixture region), has been investigated using an immersion test, electrochemical method and surface analytical method (SEM; scanning electron microscope and EDAX: Energy Dispersive X-ray) in 0.5 kmol/m{sup 3} NaCl solutions at various pH. The corrosion behavior of nickel alloy C-276 was studied under the same experimental conditions as a reference. It was found that the uniform attack was observed on Ni{sub 3}(Si,Ti) for the immersion test at lower pH, while the pitting attack was observed on this compound for this test at neutral solution. Furthermore, Ni{sub 3}(Si,Ti)+2Mo had the preferential dissolution of L1{sub 2} compared to (L1{sub 2} + Ni{sub ss}) mixture region at lower pH, while pitting attack occurred in (L1{sub 2} + Ni{sub ss}) mixture region at neutral solution. For both intermetallic compounds, the magnitude of pitting and uniform attack decrease with increasing pH of solutions. From the immersion test and polarization curves, the corrosion resistance of Ni{sub 3}(Si,Ti)+2Mo is lower than that of Ni{sub 3}(Si,Ti), while the nickel alloy C-276 is the highest one at various pH of solutions. On the other hand, in the lower pH of solutions, the corrosion resistance of tested materials decreased significantly compared to those in neutral and higher pH of solutions.

Performance study of ultrafiltration membrane with bovine serum albumin as feed solution

International Nuclear Information System (INIS)

Syahril Ahmad

2009-01-01

Bovine serum albumin solutions at different temperature, pH, flow rate and operation pressure have been used as feed solution for studying performance of ultrafiltration membrane. Polysulfone membranes used for this experiment were in form of hollow fibers that have Molecular Weight Cut Off (MWCO) 60 kDa. Observation was focused on flux parameter and rejection coefficient towards protein during the process. Result shows that temperature, pH of BSA feed solution, flow rate and operation pressure can affect the flux and rejection coefficient of membrane. High temperature feed solution tend to decrease the flux but increase rejection coefficient. Rejection coefficient of membrane will increase while flux decreasing at pH of feed solution near to protein isoelectric point. High pressure of feed solution will increase flux but decrease rejection of membrane. Rejection of membrane will decrease and flux will increase when the process operated in slow flow rate. (author)

Methods of pH determination in Calcareous soils of Oman: The effect of Electrolyte and soil solution ratio

International Nuclear Information System (INIS)

Al-Busaidi, A.; Cookson, P.

2002-01-01

Determination of pH assists in understanding many reactions that occur in soil. Soil pH values are highly sensitive to the procedure used for determination. In this study, pH was measured in different electrolytes [distilled water (pHw), 0.01MCaCl2 (pHCa), 1MKCl (pHk), and 0.01MBaCl2 (pHba)] with different soil: electrolyte ratios (i.e. 1:1, 1:2.5 and 1:5). The objective was to determine the effect of each electrolyte and dilution ratio on pH of saline and non-saline soils from Oman. It was found that ph values varied significantly between electrolytes and with different dilution ratios. Linear regression equations were generated between electrolytes, dilution ratios and were mostly significant. Soil pH values determined in different electrolytes were significantly interrelated. Water appeared as a highly suitable solvent for soil pH measurements because it is simple and values familiar to soil users. However, alkaline errors and electrode instabilities due to liquid junction and soluble salt effects, affected soil pH measurements, especially in water, and resulted in alkaline errors during pH measurements. Errors were minimized when pH was measured in electrolytes rather than in water. (author)

Effect of pH value on particle morphology and electrochemical properties of LiFePO4 by hydrothermal method

International Nuclear Information System (INIS)

Song, Qingzhu; Ou, Xiuqin; Wang, Li; Liang, Guangchuan; Wang, Zuorui

2011-01-01

Graphical abstract: The pH value of system is adjusted in the range of 2.5-8.8 by using dilute sulfuric acid and ammonia water. The results indicated that the particle exhibits acute angle diamond flake-like morphology at pH = 2.5. With increase of pH value, the particle gradually becomes to round flake-like and irregular flake-like morphology. The optimal sample synthesized at pH = 6.4 exhibits discharge capacities of 151.8 mAh g -1 at 0.2 C rate and 129.3 mAh g -1 at 3 C rate. Highlights: → The pH value of solution affects greatly on particle morphology. → The solubility product determined the transition of interphases. → The disorder of atoms in crystal is affected by pH value. → LiFePO 4 with high capacity could be synthesized at slight acid or neutral conditions. -- Abstract: Lithium iron phosphate was prepared by hydrothermal synthesis using LiOH.H 2 O, FeSO 4 .7H 2 O and H 3 PO 4 as raw materials. The effects of pH value of reaction solution on particle morphology and electrochemical property were investigated. The pH value of the reaction solution was adjusted in the range of 2.5-8.8 by dilute sulfuric acid and ammonia water. The samples were characterized by field-emission scanning electronic microscope (FE-SEM), X-ray powder diffraction (XRD), constant-current charge/discharge cycling tests and chemical analysis. The results indicated that the particles exhibited acute angle diamond flake-like morphology at pH = 2.5, and as the pH value increased, the particle became hexagon flake-like, round flake-like and irregular flake-like morphology gradually. The optimal sample synthesized at pH = 6.4 exhibited discharge capacities of 151.8 mAh g -1 at 0.2 C rate and 129.3 mAh g -1 at 3 C rate. It was found that pH value affected the morphologies and properties of the product by means of different crystal growth rates.

Effect of chitosan on the heat stability of whey protein solution as a function of pH.

Science.gov (United States)

Zhao, Zhengtao; Xiao, Qian

2017-03-01

Chitosan was reported to interact with proteins through electrostatic interactions. Their interaction was influenced by pH, which was not fully characterized. Further research on the interactions between protein and chitosan at different pH and their influence on the thermal denaturation of proteins is necessary. In this research, the effect of chitosan on the heat stability of whey protein solution at pH 4.0-6.0 was studied. At pH 4.0, a small amount chitosan was able to prevent the heat-induced denaturation and aggregation of whey protein molecules. At higher pH values (5.5 and 6.0), whey proteins complexed with chitosan through electrostatic attraction. The formation of chitosan-whey protein complexes at pH 5.5 improved the heat stability of dispersions and no precipitation could be detected up to 20 days. The dispersion with a medium amount of chitosan (chitosan:whey protein 1:5) produced the most stable particles, which had an average radius of 135 ± 14 nm and a zeta potential value of 36 ± 1 mV. In contrast, at pH 6.0 only the dispersion with a high amount of chitosan (chitosan:whey protein 1:2) showed good shelf stability up to 20 days. It was possible to produce heat-stable whey protein beverages by regulating the interaction between chitosan and whey protein molecules. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

The influence of surface modification, coating agents and pH value of aqueous solutions on physical properties of magnetite nanoparticles investigated by ESR method

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Dobosz, Bernadeta, E-mail: benia@amu.edu.pl [Medical Physics Division, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Krzyminiewski, Ryszard [Medical Physics Division, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Kurczewska, Joanna; Schroeder, Grzegorz [Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89B, 61-614 Poznań (Poland)

2017-05-01

The article presents the results of electron spin resonance (ESR) studies for aqueous solutions of functionalized superparamagnetic iron(II,III) oxide nanoparticles. The samples studied differed in type of organic ligands at the magnetite surface, type of coating agent and pH value of aqueous solutions. The ESR spectra of the samples were obtained at room temperature and at 230 K. The field cooling (FC) experiment was performed for selected samples, and the effective anisotropy field (H{sub K2}) and the first order magnetocrystalline anisotropy constant (K{sub 1}) was calculated. The process of the nanoparticles diffusion in different environments (human blood, human serum) forced by an inhomogeneous magnetic field was monitored and their interactions with different solvents have been discussed. It has been shown that ESR method is useful to observe the impact of organic ligands at the magnetite surface, type of coating agent and pH value of aqueous solutions on the properties of iron(II,III) oxide nanoparticles. - Highlights: • The influence of different organic ligands, coatings and pH values of aqueous solutions on the physical properties of the magnetite nanoparticles studied by ESR method. • Nanoparticles diffusion forced by inhomogeneous magnetic field monitored by ESR and explained. • A narrow line separated in ESR spectra by CREM. • The influence of different coatings and pH values of aqueous solutions on ESR spectra of TEMPO attached to the magnetite core.

Passivation Characteristics of Alloy Corrosion-Resistant Steel Cr10Mo1 in Simulating Concrete Pore Solutions: Combination Effects of pH and Chloride.

Science.gov (United States)

Ai, Zhiyong; Sun, Wei; Jiang, Jinyang; Song, Dan; Ma, Han; Zhang, Jianchun; Wang, Danqian

2016-09-01

The electrochemical behaviour for passivation of new alloy corrosion-resistant steel Cr10Mo1 immersed in alkaline solutions with different pH values (13.3, 12.0, 10.5, and 9.0) and chloride contents (0.2 M and 1.0 M), was investigated by various electrochemical techniques: linear polarization resistance, electrochemical impedance spectroscopy and capacitance measurements. The chemical composition and structure of passive films were determined by XPS. The morphological features and surface composition of the immersed steel were evaluated by SEM together with EDS chemical analysis. The results evidence that pH plays an important role in the passivation of the corrosion-resistant steel and the effect is highly dependent upon the chloride contents. In solutions with low chloride (0.2 M), the corrosion-resistant steel has notably enhanced passivity with pH falling from 13.3 to 9.0, but does conversely when in presence of high chloride (1.0 M). The passive film on the corrosion-resistant steel presents a bilayer structure: an outer layer enriched in Fe oxides and hydroxides, and an inner layer, rich in Cr species. The film composition varies with pH values and chloride contents. As the pH drops, more Cr oxides are enriched in the film while Fe oxides gradually decompose. Increasing chloride promotes Cr oxides and Fe oxides to transform into their hydroxides with little protection, and this is more significant at lower pH (10.5 and 9.0). These changes annotate passivation characteristics of the corrosion-resistant steel in the solutions of different electrolyte.

Ph responsive permeability and Ion- exchange characteristics of (PE/EPDM)-g-PMAA membranes

International Nuclear Information System (INIS)

El- Awady, M.M.; El-Awady, N.I.; Eissa, A.M.

2005-01-01

Chemical grafting of methacrylic acid (MAA) on low density exchange membranes for recovery of different cations from their solutions was investigated. When the dialysis permeability of two solutes (glucose + urea) through the membrane were tested at different ph values and compared, glucose was found to be less efficient than urea for permeation through the membrane. The permeability response of such solute was noticed only at higher ph value (ph 8). The grafted film (membrane) with graft yield of 185% is experimentally adequate to permeate all molecules with radius of lower than 4.3 x 10 polyethylene blended with EPDM with a ratio (90/10) films was carried out using sodium bisulphite as initiator. Factors affecting grafting and the properties of the grafted films were studied in details and showed improved hydrophilic properties, good thermal stability and nearly unaffected strength properties which make them acceptable for practical uses.In the present work, the possibility of practical uses of such grafted films as ph-responsive membranes in a dialysis process and as ion--7 mm. Grafted membranes in different forms (COOH-form), (Na-methacrylate form) and (K methacrylate- form) were prepared to evaluate the membranes uptake selectivity to different mono, di-and trivalent cations from their solutions. The results obtained showed very good efficiency of the prepared membranes as compared with the values obtained for the commercial cation exchange resin (Dowex)

Soil solution Zn and pH dynamics in non-rhizosphere soil and in the rhizosphere of Thlaspi caerulescens grown in a Zn/Cd-contaminated soil.

Science.gov (United States)

Luo, Y M; Christie, P; Baker, A J

2000-07-01

Temporal changes in soil solution properties and metal speciation were studied in non-rhizosphere soil and in the rhizosphere of the hyperaccumulator Thlaspi caerulescens J. & C. Presl (population from Prayon, Belgium) grown in a Zn- and Cd-contaminated soil. This paper focuses on soil solution Zn and pH dynamics during phytoextraction. The concentration of Zn in both non-rhizosphere and rhizosphere soil solutions decreased from 23 mg/l at the beginning to 2 mg/l at the end of the experiment (84 days after transplanting of seedlings), mainly due to chemical sorption. There was no significant difference in overall Zn concentration between the planted and the unplanted soil solutions (P > 0.05). Soil solution pH decreased initially and then increased slightly in both planted and unplanted soil zones. From 60 to 84 days after transplanting, the pH of the rhizosphere soil solution was higher than that of non-rhizosphere soil solution (P<0.05). Zn uptake by the hyperaccumulator plants was 8.8 mg per pot (each containing 1 kg oven-dry soil) on average. The data indicate that the potential of T. caerulescens to remove Zn from contaminated soil may not be related to acidification of the rhizosphere.

Influence of the solution pH in the 6-mercaptopurine self-assembled monolayer (6MP-SAM) on a Au(111) single-crystal electrode.

Science.gov (United States)

Madueño, Rafael; García-Raya, Daniel; Viudez, Alfonso J; Sevilla, José M; Pineda, Teresa; Blázquez, Manuel

2007-10-23

Self-assembled monolayers (SAMs) of 6-mercaptopurine (6MP) have been prepared on a Au(111) single-crystal electrode by immersion of the metal surface in a 100 microM 6MP and 0.01 M HClO4 solution. The 6MP-SAM Au(111) single-crystal electrodes were transferred to the cell and allowed to equilibrate with the different aqueous working solutions before the electrochemical experiments. The influence of the solution pH was studied by cyclic voltammetry, double layer capacitance curves, and electrochemical impedance spectroscopy. The electrochemical behavior of the 6MP-SAM in acetic acid at pH 4 presents important differences in comparison to that obtained in 0.1 M KOH solutions. Cyclic voltammograms for the reductive desorption process in acid medium are broad and show some features that can be explained by a phase transition between a chemisorbed and a physisorbed state of the 6MP molecules. The low solubility of these molecules in acid medium could explain this phenomenon and the readsorption of the complete monolayer when the potential is scanned in the positive direction. The variation of the double-layer capacitance values in the potential range of monolayer stability with the pH suggests that the acid-base chemistry of the 6MP molecules is playing a role. This fact has been studied by following the variations of the electron-transfer rate constant of the highly charged redox probes as are Fe(CN)(6)-3/-4 and Ru(NH3)(6)+3/+2 as a function of solution pH. The apparent surface pKa value for the 6MP-SAM (pKa approximately 8) is explained by the total conversion of the different 6MP tautomers that exist in solution to the thiol species in the adsorbed state.

pH sensing in aqueous solutions using a MnO{sub 2} thin film electrodeposited on a glassy carbon electrode

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Cherchour, N. [Laboratoire de Technologie des Materiaux et Genie des Procedes (LTMGP), Departement de Genie des Procedes, Universite A. Mira, Route de Targa Ouzemmour, 06000 Bejaia (Algeria); CNRS, UPR 15, Laboratoire Interfaces et Systemes Electrochimiques (LISE, case courrier 133), 4 Place Jussieu, F-75005 Paris (France); UPMC Univ. Paris VI, UPR 15, Laboratoire Interfaces et Systemes Electrochimiques (LISE, case courrier 133), 4 Place Jussieu, F-75005 Paris (France); Deslouis, C. [CNRS, UPR 15, Laboratoire Interfaces et Systemes Electrochimiques (LISE, case courrier 133), 4 Place Jussieu, F-75005 Paris (France); UPMC Univ. Paris VI, UPR 15, Laboratoire Interfaces et Systemes Electrochimiques (LISE, case courrier 133), 4 Place Jussieu, F-75005 Paris (France); Messaoudi, B. [Laboratoire de Technologie des Materiaux et Genie des Procedes (LTMGP), Departement de Genie des Procedes, Universite A. Mira, Route de Targa Ouzemmour, 06000 Bejaia (Algeria); Pailleret, A., E-mail: alain.pailleret@upmc.fr [CNRS, UPR 15, Laboratoire Interfaces et Systemes Electrochimiques (LISE, case courrier 133), 4 Place Jussieu, F-75005 Paris (France); UPMC Univ. Paris VI, UPR 15, Laboratoire Interfaces et Systemes Electrochimiques (LISE, case courrier 133), 4 Place Jussieu, F-75005 Paris (France)

2011-11-30

An electrolysis technique at a constant potential was used to develop a highly reproducible and fast elaboration method of adherent manganese dioxide thin films on a glassy carbon electrode from aqueous solutions containing sulfuric acid and manganese sulfate. The resulting films were found to have a nanostructured character presumably due rather to birnessite ({delta}-MnO{sub 2}) than to {gamma}-MnO{sub 2}, as suggested by their Raman and XRD signatures. They lead to modified electrodes that present an obvious although complex pH dependent potentiometric response. This sensor indeed showed a single slope non-Nernstian linear behaviour over the 1.5-12 pH range for increasing pH direction ('trace'), whereas a Nernstian two slopes linear behaviour was observed for decreasing pH direction ('re-trace'). Preliminary EIS experiments carried out at a pH value of 1.8 seem to reveal a sensitivity mechanism based on proton insertion process at least at highly acidic pH values.

Iron biofortification of wheat grains through integrated use of organic and chemical fertilizers in pH affected calcareous soil.

Science.gov (United States)

Ramzani, Pia Muhammad Adnan; Khalid, Muhammad; Naveed, Muhammad; Ahmad, Rashid; Shahid, Muhammad

2016-07-01

Incidence of iron (Fe) deficiency in human populations is an emerging global challenge. This study was conducted to evaluate the potential of iron sulphate combined with biochar and poultry manure for Fe biofortification of wheat grains in pH affected calcareous soil. In first two incubation studies, rates of sulfur (S) and Fe combined with various organic amendments for lowering pH and Fe availability in calcareous soil were optimized. In pot experiment, best rate of Fe along with biochar (BC) and poultry manure (PM) was evaluated for Fe biofortification of wheat in normal and S treated low pH calcareous soil. Fe applied with BC provided fair increase in root-shoot biomass and photosynthesis up to 79, 53 and 67%, respectively in S treated low pH soil than control. Grain Fe and ferritin concentration was increased up to 1.4 and 1.2 fold, respectively while phytate and polyphenol was decreased 35 and 44%, respectively than control in treatment where Fe was applied with BC and S. In conclusion, combined use of Fe and BC could be an effective approach to improve growth and grain Fe biofortification of wheat in pH affected calcareous soil. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Chemical Composition and Evaluation of Nicotine, Tobacco Alkaloids, pH, and Selected Flavors in E-Cigarette Cartridges and Refill Solutions.

Science.gov (United States)

Lisko, Joseph G; Tran, Hang; Stanfill, Stephen B; Blount, Benjamin C; Watson, Clifford H

2015-10-01

Electronic cigarette (e-cigarette) use is increasing dramatically in developed countries, but little is known about these rapidly evolving products. This study analyzed and evaluated the chemical composition including nicotine, tobacco alkaloids, pH, and flavors in 36 e-liquids brands from 4 manufacturers. We determined the concentrations of nicotine, alkaloids, and select flavors and measured pH in solutions used in e-cigarettes. E-cigarette products were chosen based upon favorable consumer approval ratings from online review websites. Quantitative analyses were performed using strict quality assurance/quality control validated methods previously established by our lab for the measurement of nicotine, alkaloids, pH, and flavors. Three-quarters of the products contained lower measured nicotine levels than the stated label values (6%-42% by concentration). The pH for e-liquids ranged from 5.1-9.1. Minor tobacco alkaloids were found in all samples containing nicotine, and their relative concentrations varied widely among manufacturers. A number of common flavor compounds were analyzed in all e-liquids. Free nicotine levels calculated from the measurement of pH correlated with total nicotine content. The direct correlation between the total nicotine concentration and pH suggests that the alkalinity of nicotine drives the pH of e-cigarette solutions. A higher percentage of nicotine exists in the more absorbable free form as total nicotine concentration increases. A number of products contained tobacco alkaloids at concentrations that exceed U.S. pharmacopeia limits for impurities in nicotine used in pharmaceutical and food products. © Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Adsorption of phenol by activated carbon: Influence of activation methods and solution pH

International Nuclear Information System (INIS)

Beker, Ulker; Ganbold, Batchimeg; Dertli, Halil; Guelbayir, Dilek Duranoglu

2010-01-01

Cherry stone based activated carbon derived from a canning industry was evaluated for its ability to remove phenol from an aqueous solution in a batch process. A comparative adsorption on the uptake of phenol by using commercial activated carbon (Chemviron CPG-LF), and two non-functional commercial polymeric adsorbents (MN-200 and XAD-2) containing a styrene-divinylbenzene macroporous hyperreticulated network have been also examined. Equilibrium studies were conducted in 25 mg L -1 initial phenol concentrations, 6.5-9 solution pH and at temperature of 30 deg. C. The experimental data were analyzed by the Langmuir and Freundlich isotherm models. Besides, the cherry stone based activated carbons were carried out by using zinc chloride and KOH activation agents at different chemical ratios (activating agent/precursor), to develop carbons with well-developed porosity. The cherry stone activated carbon prepared using KOH as a chemical agent showed a high surface area. According to the results, activated carbons had excellent adsorptive characteristics in comparison with polymeric sorbents and commercial activated carbon for the phenol removal from the aqueous solutions.

SPATIAL AND TEMPORAL PATTERN OF SOIL pH AND Eh AND THEIR IMPACT ON SOLUTE IRON CONTENT IN A WETLAND (TRANSDANUBIA, HUNGARY

Directory of Open Access Journals (Sweden)

SZALAI ZOLTÁN

2008-06-01

Full Text Available Land mosaics have direct and indirect influence on chemical reaction and redox condition of soils. The present paper deals with the relationship between some environmental factors (such as soil andvegetation patterns, micro-relief, water regime, temperature and incident solar radiation and the pH, Eh of soils and solute iron in a headwater wetland in Transdanubia, Hungary. Measurements have been taken in four different patches and along their boundaries: sedge (Carex vulpina, Carex riparia, three patches and two species, horsetail (Equisetum arvense, common nettle (Urtica dioica. Thespatial pattern of the studied parameters are influenced by the water regime, micro-topography, climatic conditions and by direct and indirect effects of vegetation. The indirect effect can be the shading, which has influence on soil temperature and on the incident solar radiation (PAR. Root respiration and excretion of organic acids appear as direct effects.. There have been measured individual pH and Eh characteristic in the studied patches. Soil Eh, pH and solute iron have shown seasonal dynamics. Higher redox potentials (increasingly oxidative conditions and higher pH values were measured between late autumn and early spring. The increasing physiological activity of plants causes lower pH and Eh and it leads to higher spatial differences. Although temperature is an essential determining factor for Eh and pH, but our results suggest it rather has indirect effectsthrough plants on wetlands.

The radiation chemistry of aqueous sodium terephthalate solutions

International Nuclear Information System (INIS)

Matthews, R.W.

1980-04-01

The radiation chemistry of cobalt-60 gamma-irradiated aqueous sodium terephthalate solutions has been studied. In aerated 4 x 10 -4 M sodium hydroxide solutions, the main products are hydroxyterephthalate (HTA) (G = 0.99 +- 0.01), carbonate (G = 1.31 +- 0.08), and peroxides (G = 2.84 +- 0.04). The HTA and carbonate species are both formed as a result of hydroxyl radical attack and account for approximately 90 per cent of hydroxyl radical reactions. Oxygen needs to be present for efficient conversion of the terephthalate-OH radical adduct to HTA and oxygenation increases G(HTA) above the aerated solution value. G(HTA) is unaffected by changes in terephthalate concentration between 1 x 10 -4 M and 1 x 10 -2 M in sodium hydroxide solutions at pH 10. Decreasing the solution pH does however affect G(HTA). In phosphate buffered solutions pH 6.85, G(HTA) is 0.93 +- 0.01 and lower values are obtained with further decrease in solution pH. The lowering of the G(HTA) value is attributed to recombination reactions between the terephthalate-OH radical products and reducing radical products. Experimental evidence supporting the recombination postulate was obtained from the measurement of a parallel decrease in the peroxide yield and the observation of a dose rate effect on G(HTA). Competition kinetic studies with the added solutes carbonate and bicarbonate gave the rate ratios k (OH + TA 2- ) : k(OH + CO 3 2- ) : k(OH + HCO 3 - ) = 1 : 0.105 : 0.0036

Effect of the pH in the adsorption and in the immersion enthalpy of monohydroxylated phenols from aqueous solutions on activated carbons.

Science.gov (United States)

Blanco-Martínez, D A; Giraldo, L; Moreno-Piraján, J C

2009-09-30

An activated carbon Carbochem--PS230 was modified by chemical and thermal treatment in flow of H(2) in order to evaluate the influence of the activated carbon chemical surface in the adsorption of the monohydroxylated phenols. The solid-solution interaction was determined by analyzing the adsorption isotherms at 298 K at pH 7, 9 and 11 during 48 h. The adsorption capacity of activated carbons increases when the pH solution decreases. The amount adsorbed increases in the reduced carbon at the maximum adsorption pH and decreases in the oxidized carbon. In the sample of granulated activated carbon, CAG, the monohydroxylated phenols adsorption capacity diminishes in the following order catechol >hydroquinone >resorcinol, at the three pH values. The experimental data are evaluated with Freundlich's and Langmuir's models. The immersion enthalpies are determined and increase with the retained amount, ranging between 21.5 and 45.7 J g(-1). In addition, the immersion enthalpies show more interaction with the reduced activated carbon that has lower total acidity contents.

The Shampoo pH can Affect the Hair: Myth or Reality?

Science.gov (United States)

Gavazzoni Dias, Maria Fernanda Reis; de Almeida, Andréia Munck; Cecato, Patricia Makino Rezende; Adriano, Andre Ricardo; Pichler, Janine

2014-07-01

Dermatologists most frequently prescribe shampoos for the treatment of hair shed and scalp disorders. Prescription of hair care products is often focused on improving scalp hair density, whereas the over-the-counter products focus on hair damage prevention. Little is taught in medical schools about the hair cosmetics, so that the prescriptions are based only on the treatment of the scalp and usually disregards the hair fiber health. In this work, we review the current literature about the mode of action of a low-pH shampoo regarding the hair shaft's health and analyze the pH of 123 shampoos of international brands. All shampoo pH values ranged from 3.5 to 9.0. 38.21% of all 123 shampoos presented a pH ≤ 5.5 (IC: 29.9-47%) and 61.78% presented a pH > 5.5. 26 anti-dandruff shampoos were analyzed. About 19.23% presented pH ≤ 5.5.(IC: 7.4-37.6%). 80.77% of all anti-dandruffs shampoos presented a pH > 5.5. The dermatological shampoo group (n = 19) presented 42.10% with pH ≤ 5.5 (IC: 21.8-64.6%), and 57.90% with pH > 5.5. Among the commercial (popular) products (n = 96), 34.37% presented pH ≤ 5.5 (IC: 25.4-44.3%) and 65.62% presented pH > 5.5. 15 professional products (used in hair salons) were analyzed, of which 75% had a pH ≤ 5.5 (IC: 18-65, 4%), and 25% had a pH > 5.5. 100% of the children's shampoos presented a pH > 5.5. Alkaline pH may increase the negative electrical charge of the hair fiber surface and, therefore, increase friction between the fibers. This may lead to cuticle damage and fiber breakage. It is a reality and not a myth that lower pH of shampoos may cause less frizzing for generating less negative static electricity on the fiber surface. Interestingly, only 38% of the popular brand shampoos against 75% of the salons shampoos presented a pH ≤ 5.0. Pediatric shampoos had the pH of 7.0 because of the "no-tear" concept. There is no standardized value for the final pH. The authors believe that it is important to reveal the pH value on the

Comparative study of polypyrrole films electrosynthesized in alkaline and acid solutions

International Nuclear Information System (INIS)

Lehr, I.L.; Quinzani, O.V.; Saidman, S.B.

2009-01-01

The influence of the pH of electropolymerization solutions on the properties of polypyrrole films has been studied using potentiodynamic techniques and faradaic impedance spectroscopy. Scanning electron microscopy (SEM), IR and Raman spectroscopies, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were also used for products characterization. Results indicate that, contrary to what happen with the polymer electrogenerated in acid solutions, the films prepared in alkaline media are stable and present good electrochemical activity in basic solutions. Possible explanations for the observed differences are discussed and it is proposed that the pH of electropolymerization medium directly affects chains organization. Electrosynthesis in solutions of increased basicity results in a more compact and closed polymer structure.

pH effect on pit potential and protection potential of stainless steels AISI-304, 310 and 316 in NaCl solution

International Nuclear Information System (INIS)

Cabral, U.Q.; Sathler, L.; Mariano Neto, F.

1973-06-01

For three austenitic stainless steels, AISI 304, 310 and 316, the pH influence on the rupture, protection and corrosion potentials was studied in a 0,5N NACl solution. The pit potentials determined by the chronogalvonometric method, are pH independent within the acid range. They showed a rough linear variation within the basic range having a maximum corresponding to the pH value of 8.8. The electrochemical hysteresis method, employed for determining the protection potential, presented a total pH independence for the AISI 316. The other steels showed a small dependence within the basic range but with a tendency for the protection potential to become slightly more active with increasing pH, within the acid range. It was also noted for the three steels studied that the corrosion potental became more active with increasing pH, within the basic range [pt

Effects of pH on the degradation of aqueous ferricyanide by photolysis and photocatalysis under solar radiation

Energy Technology Data Exchange (ETDEWEB)

Arellano, Carlos Antonio Pineda [Posgrado en Ingenieria y Ciencias Aplicadas, FCQI-CIICAp, Universidad Autonoma del Estado de Morelos (Mexico); Martinez, Susana Silva [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Universidad Autonoma del Estado de Morelos, Avenida Universidad 1001, Col. Chamilpa, Cuernavaca, Morelos 62209 (Mexico)

2010-02-15

Results of voltammetry and spectrophotometry analyses revealed that upon sunlight exposure, the conversion of ferricyanide to ferrocyanide, and the reverse reaction, in the absence and in the presence of TiO{sub 2} catalyst depends strongly on pH. Thus, the pH of the solution dictates whether the redox reactions will proceed under illumination. In addition, the extent of the heterogeneous photocatalytic degradation of ferricyanide was influenced by pH. The initial concentration of ferricyanide did not affect its degradation. (author)

pH variation and influence in an autotrophic nitrogen removing biofilm system using an efficient numerical solution strategy.

Science.gov (United States)

Vangsgaard, Anna Katrine; Mauricio-Iglesias, Miguel; Valverde-Pérez, Borja; Gernaey, Krist V; Sin, Gürkan

2013-01-01

A pH simulator consisting of an efficient numerical solver of a system of nine nonlinear equations was constructed and implemented in the modeling software MATLAB. The pH simulator was integrated in a granular biofilm model and used to simulate the pH profiles within granules performing the nitritation-anammox process for a range of operating points. The simulation results showed that pH profiles were consistently increasing with increasing depth into the granule, since the proton-producing aerobic ammonium-oxidizing bacteria (AOB) were located close to the granule surface. Despite this pH profile, more NH3 was available for AOB than for anaerobic ammonium oxidizers, located in the center of the granules. However, operating at a higher oxygen loading resulted in steeper changes in pH over the depth of the granule and caused the NH3 concentration profile to increase from the granule surface towards the center. The initial value of the background charge and influent bicarbonate concentration were found to greatly influence the simulation result and should be accurately measured. Since the change in pH over the depth of the biofilm was relatively small, the activity potential of the microbial groups affected by the pH did not change more than 5% over the depth of the granules.

Magnetite synthesis from ferrous iron solution at pH 6.8 in a continuous stirred tank reactor.

Science.gov (United States)

Mos, Yvonne M; Zorzano, Karin Bertens; Buisman, Cees J N; Weijma, Jan

2018-04-01

Partial oxidation of defined Fe 2+ solutions is a well-known method for magnetite synthesis in batch systems. The partial oxidation method could serve as basis for an iron removal process in drinking water production, yielding magnetite (Fe 3 O 4 ) as a compact and valuable product. As a first step toward such a process, a series of experiments was carried out, in which magnetite was synthesized from an Fe 2+ solution in a 2 L continuous stirred tank reactor (CSTR) at atmospheric pressure and 32 °C. In four experiments, elevating the pH from an initial value of 5.5 or 6.0 to a final value of 6.8, 7.0 or 7.5 caused green rust to form, eventually leading to magnetite. Formation of NH 4 + in the reactor indicated that NO 3 - and subsequently NO 2 - served as the oxidant. However, mass flow analysis revealed an influx of O 2 to the reactor. In a subsequent experiment, magnetite formation was achieved in the absence of added nitrate. In another experiment, seeding with magnetite particles led to additional magnetite precipitation without the need for a pH elevation step. Our results show, for the first time, that continuous magnetite formation from an Fe 2+ solution is possible under mild conditions, without the need for extensive addition of chemicals.

Corrosion behaviour of the UO2 pellet in corrosive solutions using electrochemical Technique

International Nuclear Information System (INIS)

Taftanzani, A.; Sucipto; Lahagu, F.; Irianto, B.

1996-01-01

The UO 2 electrodes has been made from the local product of UO 2 pellets. The corrosion behaviour of the UO 2 pellets is affected by solution, by pH value and by concentration of salt solution. Investigation into corrosion behaviour of UO 2 electrodes have been carried out in saturated salt solutions using electrochemical technique. The saturated solutions have been made from salts NaCl, Na 2 CO 3 , Na 2 SO 4 and Na 3 PO 4 . The pH value have been done over range 1 pH 10 and the salt concentration (C) over range 0,001 mol/l C 1,0 mol/l, Na 2 CO 3 solution produced the lowest corrosion rates of UO 2 pellets. Those rates were relative constant in the range of pH = 4 - 8. The results indicate an influence of the Na 2 CO 3 concentrations on the corrosions on the corrosion rate, and the lowest rates occur in 0,10 mol/l Na 2 CO 3 . The lowest corrosion rate was 0.3388 mil/year in 0.10 mol/l Na 2 CO 3 by pH = 4. (author)

ph Sensitive hydrogel as colon specific drug delivery

International Nuclear Information System (INIS)

Alarifi, A.S.

2011-01-01

γ-radiation induced graft copolymerization and crosslinking was for the synthesis of ph-sensitive hydrogels composed of poly (vinyl pyrrolidone) acrylic acid. The prepared hydrogels were subjected to swelling test to evaluate the effects of ph and ionic strength of the surrounding solution. Drastic changes in the swelling parameters where observed by changing the surrounding solution ph values. The release of ibuprofen from hydrogels was monitored as a function of time at ph 1 and ph 7 in order to evaluate the prepared copolymer ability for colon- specific drug carrier uses.

Photoproduction of hydroxyl radicals in aqueous solution with algae under high-pressure mercury lamp.

Science.gov (United States)

Liu, Xianli; Wu, Feng; Deng, Nansheng

2004-01-01

Photoproduction of hydroxyl radicals (*OH) could be induced in aqueous solution with algae (Nitzschia hantzschiana, etc.) and (or not) Fe3+ under high-pressure mercury lamp with an exposure time of 4 h. *OH was determined by HPLC using benzene as a probe. The photoproduction of *OH increased with increasing algae concentration. Fe3+ could enhance the photoproduction of *OH in aqueous solution with algae. The results showed that the photoproduction of *OH in algal solution with Fe3+ was greater than that in algal solution without Fe3+. The light intensity and pH affected the photoproduction of *OH in aqueous solution with algae with/without Fe3+. The photoproduction of *OH in aqueous solution with algae and Fe3+ under 250 W was greater than that under 125 W HPML. The photoproduction of *OH in algal solution (pH ranged from 4.0 to 7.0) with (or not) Fe3+ at pH 4 was the greatest.

Corrosion of zirconium alloys in alternating pH environment

International Nuclear Information System (INIS)

Mayer, P.; Manolescu, A.V.

1985-01-01

Behaviour of two commercial alloys, Zircaloy-2 and zirconium-2.5 wt% niobium were investigated in an environment of alternating pH. Corrosion advancement and scale morphology of coupons exposed to aqueous solution of LiOH (pH 10.2 and 14) were followed as a function of temperature (300-360 degreesC) and time (up to 165 days). The test sequence consisted of short term exposure to high pH and re-exposure to low pH solutions for extended period of time followed by a short term test in high pH. The results of these tests and detailed post-corrosion analysis indicate a fundamental difference between the corrosion behaviour of these two materials. Both alloys corrode fast in high pH environments, but only zirconium-2.5 wt% niobium continues to form detectable new oxide in low pH solution

A new slurry pH model accounting for effects of ammonia and carbon dioxide volatilization on solution speciation

DEFF Research Database (Denmark)

Petersen, V.; Markfoged, R.; Hafner, S. D.

2014-01-01

a reduced variable that combines time and location and an analytical approach to solving the resulting system of equations using Mathematica. To evaluate the model, we made measurements of pH at a resolution of 0.1 mm in the top 30 mm of an ammonium bicarbonate solution. These measurements show the creation...

Surface hardness of hybrid ionomer cement after immersion in antiseptic solution

Directory of Open Access Journals (Sweden)

Anita Yuliati

2006-06-01

Full Text Available Hybrid ionomer cement or resin modified glass ionomer cement is a developed form of conventional glass ionomer cement. This hybrid ionomer cement can be eroded if in direct contact with acid solution which will affect surface hardness. The aim of this study is to learn surface hardness of hybrid ionomer cement after immersion in methyl salicylate 0.06% (pH 3.6 and povidon iodine 1% (pH 2.9 solution. Sample of hybrid ionomer cement with 5 mm diameter and 3 mm thickness was immersed in sterile aquadest solution (control, methyl salicylate pH 3.6, povidon iodine pH 2.9 for 1 minute, 7 and 14 minutes. Surface hardness was measured with Micro Vickers Hardness Tester. The obtained data was analyzed statistically with ANOVA followed by LSD test. The result of hybrid ionomer cement after immersion in sterile aquadest, methyl salicylate 0.06% pH 3.6 and povidon iodine 1% pH 2.9 for one minute, showed no significant difference; while immersion for 7 and 14 minutes showed a significant difference. The conclusion states that hybrid ionomer cement after 14 minutes immersion in povidon iodine 1% pH 2.9 has the lowest surface hardness.

Enzymatic characterization of peptidic materials isolated from aqueous solutions of ammonium cyanide (pH 9) and hydrocyanic acid (pH 6) exposed to ionizing radiation.

Science.gov (United States)

Niketic, V; Draganić, Z; Nesković, S; Draganić, I

1982-01-01

The enzymatic digestion of some radiolytically produced peptidic materials was examined. The substrates were compounds isolated from 0.1 molar solutions of NH4CN (pH 9) and HCN (pH 6), after their exposure to gamma rays from a 60Co source (15-20 Mrad doses). Commercial proteolytic enzymes pronase and aminopeptidase M were used. The examined materials were of composite nature and proteolytic action was systematically observed after their subsequent purification. In some fractions the effect was found to be positive with up to 30% of peptide bonds cleaved with respect to the amino acid content. These findings support our previous conclusions on the free radical induced formation of peptidic backbones without the intervention of amino acids. Some side effects were also noted which might be of interest in observations on enzymatic cleavage of other composite peptidic materials of abiotic origin.

Salt type and concentration affect the viscoelasticity of polyelectrolyte solutions

Science.gov (United States)

Turkoz, Emre; Perazzo, Antonio; Arnold, Craig B.; Stone, Howard A.

2018-05-01

The addition of small amounts of xanthan gum to water yields viscoelastic solutions. In this letter, we show that the viscoelasticity of aqueous xanthan gum solutions can be tuned by different types of salts. In particular, we find that the decrease in viscoelasticity not only depends, as is known, on the salt concentration, but also is affected by the counterion ionic radius and the valence of the salt.

Effects of EDTA on the electronic properties of passive film formed on Fe-20Cr in pH 8.5 buffer solution

International Nuclear Information System (INIS)

Cho, Eun Ae; Kwon, Hyuk Sang; Beranrd, Frederic

2003-01-01

The electronic properties of the passive film formed on Fe-20Cr ferritic stainless steel in pH 8.5 buffer solution containing 0.05 M EDTA (ethylene diammine tetraacetic acid) were examined by the photocurrent measurements and Mott-Schottky analysis for the film. XPS depth profile for the film demonstrated that Cr content in the outermost layer of the passive film was higher in the solution with EDTA than that in the solution without EDTA, due to selective dissolution of Fe by EDTA. In the solution with EDTA, the passive film showed characteristics of an amorphous or highly disordered n-type semiconductor. The band gap energies of the passive film are estimated to be ∼ 3.0 eV, irrespective of film formation potential from 0 to 700 mV SCE and of presence of EDTA. However, the donor density of the passive film formed in the solution with EDTA is much higher than that formed in the solution without EDTA, due to an increase in oxygen vacancy resulted from the dissolution of Fe-oxide in the outermost layer of the passive film. These results support the proposed model that the passive film formed on Fe-20Cr in pH 8.5 buffer solution mainly consists of Cr-substituted γ-Fe 2 O 3

Continuous measurement of electrical characteristics in plants. 3. Shokubutsu seitai no denki tokusei sokuteiho. 3. ; Suikoeki pH chosei heno tekiyo

Energy Technology Data Exchange (ETDEWEB)

Sekiyama, T; Haniyu, H; Saiki, H

1989-09-01

Controlling pH of nutrient solution and keeping the other conditions unchanged, measurements of variation in electric potential difference between leaf and hypocotyl of a bush bean plant was performed for about seven days. Silver electrodes 0.3mm in diameter were glued on the surface of the plant using conductive paste prepared by dissolving gelatine in Ringel {prime} s solution. The results obtained are summarized as follws: first, when pH of the solution is suddenly increased or decreased, the potential of leave becomes high or low with respect to that of hypocotyl respectively; second, the variation in potential difference between them is affected by the rate at which pH of the solution is adjusted, although the total variation of pH is controlled to be the same, and in particular by mild adjustment (0.02 - 0.05pH/min) it is reduced to 1/2 - 1/4 of that produced by sudden change; third, abrupt change in pH of the solution cause to the plant the temporary suppression of its water absorption having a duration of 7 - 15 minutes. A short account is given of a non-contact type measurement of bioelectric potential performanced by making use of a Faraday {prime} s cage. 11 refs., 12 figs.

A miniature integrated multimodal sensor for measuring pH, EC and temperature for precision agriculture.

Science.gov (United States)

Futagawa, Masato; Iwasaki, Taichi; Murata, Hiroaki; Ishida, Makoto; Sawada, Kazuaki

2012-01-01

Making several simultaneous measurements with different kinds of sensors at the same location in a solution is difficult because of crosstalk between the sensors. In addition, because the conditions at different locations in plant beds differ, in situ measurements in agriculture need to be done in small localized areas. We have fabricated a multimodal sensor on a small Si chip in which a pH sensor was integrated with electrical conductivity (EC) and temperature sensors. An ISFET with a Si(3)N(4) membrane was used for the pH sensor. For the EC sensor, the electrical conductivity between platinum electrodes was measured, and the temperature sensor was a p-n junction diode. These are some of the most important measurements required for controlling the conditions in plant beds. The multimodal sensor can be inserted into a plant bed for in situ monitoring. To confirm the absence of crosstalk between the sensors, we made simultaneous measurements of pH, EC, and temperature of a pH buffer solution in a plant bed. When the solution was diluted with hot or cold water, the real time measurements showed changes to the EC and temperature, but no change in pH. We also demonstrated that our sensor was capable of simultaneous in situ measurements in rock wool without being affected by crosstalk.

Stabilization of pH in solid-matrix hydroponic systems

Science.gov (United States)

Frick, J.; Mitchell, C. A.

1993-01-01

2-[N-morpholino]ethanesulfonic acid (MES) buffer or Amberlite DP-1 (cation-exchange resin beads) were used to stabilize substrate pH of passive-wicking, solid-matrix hydroponic systems in which small canopies of Brassica napus L. (CrGC 5-2, genome : ACaacc) were grown to maturity. Two concentrations of MES (5 or 10 mM) were included in Hoagland 1 nutrient solution. Alternatively, resin beads were incorporated into the 2 vermiculite : 1 perlite (v/v) growth medium at 6% or 12% of total substrate volume. Both strategies stabilized pH without toxic side effects on plants. Average seed yield rates for all four pH stabilization treatments (13.3 to 16.9 g m-2 day-1) were about double that of the control (8.2 g m-2 day-1), for which there was no attempt to buffer substrate pH. Both the highest canopy seed yield rate (16.9 g m-2 day-1) and the highest shoot harvest index (19.5%) occurred with the 6% resin bead treatment, even though the 10 mM MES and 12% bead treatments maintained pH within the narrowest limits. The pH stabilization methods tested did not significantly affect seed oil and protein contents.

A method for measuring pH at high temperatures is presented

International Nuclear Information System (INIS)

Chaudon, Luc.

1979-01-01

Two hydrogen electrodes are used and set up in a PTFE cell comprising two chambers connected through a saturated potassium chloride solution bridge. This cell is put in an autoclave containing hydrogen. The potential difference of the following cell is measured: H 2 , Pt, R solution - KCl saturated solution at 25 0 C - X solution, Pt, H 2 - The pH of the reference solution R is known up to 300 0 C and the X solution must have its pH to be determined. The precision of the measures at 300 0 C is estimated about +-0,1 pH unit. The dissociation constant of water is calculated from pH variations of alcaline solutions up to 300 0 C. The method has helped to measure the pH at 300 0 C of some boric acid solutions, with or without lithium hydroxide additions, in the following concentration range: B: 250 to 1500 ppm and Li: 0 to 3 ppm. Some concentrations are in fact those chosen for the primary circuits of pressurized water reactors. The pH of ammoniacal solutions is measured too and helped to determine the variations of the dissociation constant of ammonia with temperature [fr

Polyelectrolyte multilayer assembly as a function of pH and ionic strength using the polysaccharides chitosan and heparin.

Science.gov (United States)

Boddohi, Soheil; Killingsworth, Christopher E; Kipper, Matt J

2008-07-01

The goal of this work is to explore the effects of solution ionic strength and pH on polyelectrolyte multilayer (PEM) assembly, using biologically derived polysaccharides as the polyelectrolytes. We used the layer-by-layer (LBL) technique to assemble PEM of the polysaccharides heparin (a strong polyanion) and chitosan (a weak polycation) and characterized the sensitivity of the PEM composition and layer thickness to changes in processing parameters. Fourier-transform surface plasmon resonance (FT-SPR) and spectroscopic ellipsometry provided in situ and ex situ measurements of the PEM thickness, respectively. Vibrational spectroscopy and X-ray photoelectron spectroscopy (XPS) provided details of the chemistry (i.e., composition, electrostatic interactions) of the PEM. We found that when PEM were assembled from 0.2 M buffer, the PEM thickness could be increased from less than 2 nm per bilayer to greater than 4 nm per bilayer by changing the solution pH; higher and lower ionic strength buffer solutions resulted in narrower ranges of accessible thickness. Molar composition of the PEM was not very sensitive to solution pH or ionic strength, but pH did affect the interactions between the sulfonates in heparin and amines in chitosan when PEM were assembled from 0.2 M buffer. Changes in the PEM thickness with pH and ionic strength can be interpreted through descriptions of the charge density and conformation of the polyelectrolyte chains in solution.

Effects of Iodide and Hydrogen Peroxide on Measuring High Temperature pH in Various Lithium Borate Buffer Solutions

Energy Technology Data Exchange (ETDEWEB)

Hwang, Jae Sik; Yun, Myung Hee; Yeon, Jei Won; Song, Kyu Seok [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2008-10-15

In a reactor coolant system of nuclear power plants, the need for reliable high temperature pH electrodes has resulted from interests in the corrosion and corrosion product behaviors of the structural materials in a high temperature coolant system. In developing the electrodes for measuring the high temperature pH of aqueous solutions, it is necessary to note two major problems: the chemical stability of an electrode against other chemical impurities, and an electrode's integrity as the temperature and pressure are varied between operational extremes. Over the past decade Macdonald et al. and Danielson et al. have developed many ceramic membrane pH electrodes based on a yttrium stabilized zirconium oxide. However, there are still many experimental difficulties associated with the problems in obtaining electrochemical information across different pressure boundaries and against many kinds of chemical impurities caused by the radiolysis of water and the leakage of a fuel clad. In the present work, we investigated the effects of the environmental factors on a high temperature pH. The selected environmental factors are as follows: system pressure, and chemical species such as iodide and hydrogen peroxide ions.

Measurements of spectral responses for developing fiber-optic pH sensor

Science.gov (United States)

Yoo, Wook Jae; Heo, Ji Yeon; Jang, Kyoung Won; Seo, Jeong Ki; Moon, Jin Soo; Park, Jang-Yeon; Park, Byung Gi; Cho, Seunghyun; Lee, Bongsoo

2011-01-01

In this study, we have fabricated a fiber-optic pH sensor, which is composed of a light source, a pH-sensing probe, plastic optical fibers and a spectrometer, for determining the degree of infection by Helicobacter pylori in the stomach. As pH indicators, phenol red and m-cresol purple are used, and pH liquid solutions are prepared by mixing phenol red or m-cresol purple solutions and various kinds of pH buffer solutions. The light emitted by a light source is guided by plastic optical fibers to the pH liquid solution, and the optical characteristic of a reflected light is changed according to the color variations of the pH indicator in the pH-sensing probe. Therefore, we have measured the intensities and wavelength shifts of the reflected lights, which change according to the color variations of indicators at different pH values, by using a spectrometer for spectral analysis. Also, the relationships between the pH values of liquid solutions and the optical properties of the modulated lights are obtained on the basis of the changes of the colors of indicators.

The investigation of parameters affecting boron removal by electrocoagulation method

International Nuclear Information System (INIS)

Yilmaz, A. Erdem; Boncukcuoglu, Recep; Kocakerim, M. Muhtar; Keskinler, Buelent

2005-01-01

Boron removal from wastewaters by electrocoagulation using aluminum electrode material was investigated in this paper. Several working parameters, such as pH, current density, boron concentration and type and concentration of supporting electrolyte were studied in an attempt to achieve a higher removal capacity. The experiments were carried out by keeping the pH of solution constant and optimum pH of solution was determined 8.0 for the aluminum electrode. Although energy consumption increased with decreasing boron concentration, which conductivity of these solutions were low, boron removal efficiency was higher at 100 mg/L than that of 1000 mg/L. Current density was an important parameter affecting removal efficiency. Boron removal efficiency and energy consumption increased with increasing current density from 1.2 to 6.0 mA/cm 2 . The types of different supporting electrolyte were experimented in order to investigate to this parameter effect on boron removal. The highest boron removal efficiency, 97%, was found by CaCl 2 . Added CaCl 2 increased more the conductivity of solution according to other supporting electrolytes, but decreased energy consumption. The results showed to have a high effectiveness of the electrocoagulation method in removing boron from aqueous solutions

Root uptake of uranium (6) in solution by a higher plant: speciation in hydroponic solution, bioavailability, micro-localisation and biological effects induced

International Nuclear Information System (INIS)

Laroche, L.

2005-01-01

Uranium exists naturally in the environment, usually present in trace quantities. In soil solution and oxic conditions, uranium is present in the +VI oxidation state and forms a large number of inorganic and organic complexes. The exposure medium, an artificial soil solution, was designed in such a way as to control the uranium species in solution. The geochemical speciation code JCHESS was used to calculate the uranium aqueous species concentration and to define the domains of interest, each of them characterized by a limited number of dominant U species. These domains were defined as follows: pH 4.9 with uranyl ions as dominant species, pH 5.8 with hydroxyl complexes and pH 7 where carbonates play a major role. For each pH, short-duration (5 hours of exposure) well-defined laboratory experiments were carried out with Phaseolus vulgaris as plant model. The effect of competitive ions such as Ca 2+ or the presence of ligands such as phosphate or citrate on root assimilation efficiency was explored. Results have shown that uranium transfer was not affected by the presence of calcium, phosphate or citrate (but was decreased of 60% with citrate (10 μM) at pH 5.8) in our experimental conditions. Moreover, observation in Transmission Electronic Microscopy (TEM), equipped with an EDAX probe, have shown that uranium was associated with granules rich in phosphorus and that there were some chloroplast anomalies. Finally, the presence of uranium affects root CEC by reducing it and stimulates root elongation at low uranium concentrations (100 nM, 400 nM and 2 μM at pHs 4.9, 5.8 and 7 respectively) and inhibits it at high uranium concentrations. (author)

Evaluation method of iodine re-evolution from an in-containment water pool after a loss of coolant accident, Part I: pH estimation of a solution with various chemicals

International Nuclear Information System (INIS)

Kim, Tae Hyeon; Jeong, Ji Hwan

2016-01-01

Highlights: • It is required to evaluate re-evolved iodine from sump water after LOCA. • pH evaluation based on Gibbs free energy minimization. • Program was developed to evaluate chemical equilibrium and pH solutions. • Predictions are in good agreement with experimental data. - Abstract: Radioactive iodine, which is released into the atmosphere of the containment building, is absorbed into the containment spray water and dissolved to be ionized. This iodine-rich water is then transported to the in-containment refueling water storage tank (IRWST) in APR1400 nuclear power plants. When the pH of the water is below 7, the dissolved iodine converts to molecular iodine and re-evolves from the water and returns to the atmosphere. A series of studies have been conducted in order to evaluate the iodine re-evolution from the IRWST. This study consists of two parts: the pH evaluation method and the evaluation of the iodine re-evolution. This paper presents the first part, i.e. the pH evaluation method. The equilibrium concentrations of various chemicals in a solution are determined at the minimum Gibbs’ free energy. This method is useful for complex reactant problems rather than equilibrium constants method because the latter method requires numerous equilibrium constants and there might be missing equilibrium constants associated with the solution. The calculated pH values of solutions are compared with the experimental measurements in order to validate this method and the thermodynamic data of the chemicals incorporated into the program. The estimated values for solutions are in good agreement with the experimental measurements within a difference of less than 3.3%.

Effect of pH values on the extracellular polysaccharide secreted by Acidithiobacillus ferrooxidans during chalcopyrite bioleaching

Science.gov (United States)

Yu, Run-lan; Liu, Jing; Tan, Jian-xi; Zeng, Wei-min; Shi, Li-juan; Gu, Guo-hua; Qin, Wen-qing; Qiu, Guan-zhou

2014-04-01

The pH value plays an important role in the bioleaching of sulphide minerals. The effect of pH values on the extracellular polysaccharide secreted by Acidithiobacillus ferrooxidans was investigated in different phases of bacterial growth during chalcopyrite bioleaching. It is found that extracellular polysaccharide secretion from the cells attached to chalcopyrite is more efficiently than that of the free cells in the bioleaching solution. Three factors, pH values, the concentration of soluble metal ions, and the bacterial growth and metabolism, affect extracellular polysaccharide secretion in the free cells, and are related to the bacterial growth phase. Extracellular polysaccharide secretion from the attached cells is mainly dependent on the pH value of the bacterial culture.

In vitro simulation of fretting-corrosion in hip implant modular junctions: The influence of pH.

Science.gov (United States)

Royhman, Dmitry; Patel, Megha; Jacobs, Joshua J; Wimmer, Markus A; Hallab, Nadim J; Mathew, Mathew T

2018-02-01

The fretting-corrosion behavior of mixed metal contacts is affected by various mechanical and electrochemical parameters. Crevice conditions at the junction and patient-specific pathologies can affect the pH of the prosthetic environment. The main objective of this study is to understand the effect of pH variation at the stem/head junction of the hip implant under fretting corrosion exposure. We hypothesized that pH will have a significant influence on the fretting-corrosion behavior hip implant modular junctions. A custom-made setup was used to evaluate the fretting corrosion behavior of hip implant modular junctions. A Newborn calf serum solution (30 g/L protein content) was used to simulate the synovial fluid environment. A sinusoidal fretting motion, with a displacement amplitude of +50 µm, was applied to the Ti alloy rod. The effects of pathology driven, periprosthetic pH variation were simulated at four different pH levels (3.0, 4.5, 6.0 and 7.6). Electrochemical and mechanical properties were evaluated before, during, and after the applied fretting motion. The impedance of the system was increased in response to the fretting motion. The hysteresis tangential load/displacement behavior was not affected by pH level. The worn surfaces of CoCrMo pins exhibited the presence of tribolayer or organic deposits, in the pH 4.5 group, which may explain the lower drop in potential and mass loss observed in that group. Mechanically dominated wear mechanisms, namely, adhesive wear was shown in the pH 7.6 group, which may account for a higher potential drop and metal content loss. This study suggests that the fretting-corrosion mechanisms in hip implant are affected by the pH levels of the surrounding environment and patient-specific factors. Copyright © 2017. Published by Elsevier Ltd.

Influence of pH on the localized corrosion of iron

International Nuclear Information System (INIS)

Webley, R.; Henry, R.

1986-06-01

The influence of pH on the pitting corrosion of iron in chloride and sulfate solutions was determined using two artificial pit apparatuses to obtain the pH near the surface of the pit bottom. A glass membrane electrode and an antimony electrode were used to measure pH in the two apparatuses. Using solutions of NaCl and Na 2 SO 4 at current densities of 0.5, 5.0, and 10 mA/cm 2 pH's in the range 5 to 6 were obtained with the first apparatus. The antimony probe did not measure pH accurately in solutions of 1 N NaCl and 1 N Na 2 SO 4 and had an error of approximately 2 pH units. A one-dimensional transport model was developed to predict pH variations around the pit mouth and inside the pit. The validity of this model was not verified due to the relative lack of precision with pH measurement techniques

Root uptake of uranium (6) in solution by a higher plant: speciation in hydroponic solution, bioavailability, micro-localisation and biological effects induced; Transfert racinaire de l'uranium (6) en solution chez une plante superieure: speciation en solution hydroponique, prise en charge par la plante, microlocalisation et effets biologiques induits

Energy Technology Data Exchange (ETDEWEB)

Laroche, L

2005-01-15

Uranium exists naturally in the environment, usually present in trace quantities. In soil solution and oxic conditions, uranium is present in the +VI oxidation state and forms a large number of inorganic and organic complexes. The exposure medium, an artificial soil solution, was designed in such a way as to control the uranium species in solution. The geochemical speciation code JCHESS was used to calculate the uranium aqueous species concentration and to define the domains of interest, each of them characterized by a limited number of dominant U species. These domains were defined as follows: pH 4.9 with uranyl ions as dominant species, pH 5.8 with hydroxyl complexes and pH 7 where carbonates play a major role. For each pH, short-duration (5 hours of exposure) well-defined laboratory experiments were carried out with Phaseolus vulgaris as plant model. The effect of competitive ions such as Ca{sup 2+} or the presence of ligands such as phosphate or citrate on root assimilation efficiency was explored. Results have shown that uranium transfer was not affected by the presence of calcium, phosphate or citrate (but was decreased of 60% with citrate (10 {mu}M) at pH 5.8) in our experimental conditions. Moreover, observation in Transmission Electronic Microscopy (TEM), equipped with an EDAX probe, have shown that uranium was associated with granules rich in phosphorus and that there were some chloroplast anomalies. Finally, the presence of uranium affects root CEC by reducing it and stimulates root elongation at low uranium concentrations (100 nM, 400 nM and 2 {mu}M at pHs 4.9, 5.8 and 7 respectively) and inhibits it at high uranium concentrations. (author)

Effect of surface chemistry, solution pH, and ionic strength on the removal of herbicides diuron and amitrole from water by an activated carbon fiber.

Science.gov (United States)

Fontecha-Cámara, M A; López-Ramón, M V; Alvarez-Merino, M A; Moreno-Castilla, C

2007-01-30

A study was conducted on the effects of carbon surface chemistry, solution pH, and ionic strength on the removal of diuron and amitrole from aqueous solutions by adsorption on an as-received and oxidized activated carbon fiber. Results obtained were explained by the surface characteristics of the adsorbents and the characteristics of the herbicide molecules. Under the experimental conditions used, diuron uptake was much higher than that of amitrole, despite its larger molecular dimensions, due to the lesser water solubility, greater hydrophobicity, and larger dipolar moment of diuron compared with amitrole. Uptake variations associated with differences in carbon surface oxidation, solution pH, and ionic strength were explained by corresponding changes in electrostatic, hydrophobic, and van der Waals interactions.

pH in atomic scale simulations of electrochemical interfaces

DEFF Research Database (Denmark)

Rossmeisl, Jan; Chan, Karen; Ahmed, Rizwan

2013-01-01

Electrochemical reaction rates can strongly depend on pH, and there is increasing interest in electrocatalysis in alkaline solution. To date, no method has been devised to address pH in atomic scale simulations. We present a simple method to determine the atomic structure of the metal......|solution interface at a given pH and electrode potential. Using Pt(111)|water as an example, we show the effect of pH on the interfacial structure, and discuss its impact on reaction energies and barriers. This method paves the way for ab initio studies of pH effects on the structure and electrocatalytic activity...

Role of Metal Cations on the corrosion behaviour of 8090-T851 in a pH 2.0 solution

DEFF Research Database (Denmark)

Murthy, K.S.N.; Ambat, Rajan; Dwarakadasa, E.S.

1994-01-01

The influence of cations such as Cu2+, Al3+ and Li+ on the corrosion behaviour of 8090-T851(Al-Li) alloy in a pH 2.0 HCl solution was investigated by weight loss and polarisation techniques. Weight loss experiments showed that the effect of cation is a strong function of its nature...

Application of Activated Carbon for Removal of Arsenic Ions from Aqueous Solutions

Directory of Open Access Journals (Sweden)

R. Ansari

2007-01-01

Full Text Available The activated carbon (AC was used for removal of As(III and As(V ions from aqueous solutions. Sorption experiments were conducted using both batch and column systems. The effect of some important parameters on sorption of these by AC was studied. It was found that among the different factors affecting sorption capacity and efficiency in removal of arsenic from aqueous solutions, the effect of pH and the oxidation state were the most prominent. The optimum pH values for removal of As(III and As(V from aqueous solutions using AC was found 12 and 3 respectively. Impregnation of AC with sulphur contain organic dyes, it is possible to improve As(III uptake considerably.

Light acclimation and pH perturbations affect photosynthetic performance in

NARCIS (Netherlands)

Ihnken, S.; Beardall, J.; Kromkamp, J.C.; Gómez Serrano, C.; Torres, M.A.; Masojídek, J.; Malpartida, I.; Abdala, R.; Gil Jerez, C.; Malapascua, J.R.; Navarro, E.; Rico, R.M.; Peralta, E.; Ferreira Ezequil, J.P.; Lopez Figueroa, F

2014-01-01

Chlorella spp. are robust chlorophyte microalgal species frequently used in mass culture. The pH optimum for growth is close to neutrality; at this pH, theoretically little energy is required to maintain homeostasis. In the present study, we grew Chlorella fusca cells in an open, outdoor, thin-layer

A Miniature Integrated Multimodal Sensor for Measuring pH, EC and Temperature for Precision Agriculture

Directory of Open Access Journals (Sweden)

Hiroaki Murata

2012-06-01

Full Text Available Making several simultaneous measurements with different kinds of sensors at the same location in a solution is difficult because of crosstalk between the sensors. In addition, because the conditions at different locations in plant beds differ, in situ measurements in agriculture need to be done in small localized areas. We have fabricated a multimodal sensor on a small Si chip in which a pH sensor was integrated with electrical conductivity (EC and temperature sensors. An ISFET with a Si₃N₄ membrane was used for the pH sensor. For the EC sensor, the electrical conductivity between platinum electrodes was measured, and the temperature sensor was a p-n junction diode. These are some of the most important measurements required for controlling the conditions in plant beds. The multimodal sensor can be inserted into a plant bed for in situ monitoring. To confirm the absence of crosstalk between the sensors, we made simultaneous measurements of pH, EC, and temperature of a pH buffer solution in a plant bed. When the solution was diluted with hot or cold water, the real time measurements showed changes to the EC and temperature, but no change in pH. We also demonstrated that our sensor was capable of simultaneous in situ measurements in rock wool without being affected by crosstalk.

Identification of some factors affecting pharmaceutical active compounds (PhACs) removal in real wastewater. Case study of fungal treatment of reverse osmosis concentrate.

Science.gov (United States)

Badia-Fabregat, Marina; Lucas, Daniel; Gros, Meritxell; Rodríguez-Mozaz, Sara; Barceló, Damià; Caminal, Glòria; Vicent, Teresa

2015-01-01

Many technologies are being developed for the efficient removal of micropollutants from wastewater and, among them, fungal degradation is one of the possible alternative biological treatments. In this article, some factors that might affect pharmaceutically active compounds (PhACs) removal in a fungal treatment of real wastewater were identified in batch bioreactor treating reverse osmosis concentrate (ROC) from urban wastewater treatment plant (WWTP). We found that degradation of PhACs by Trametes versicolor was enhanced by addition of external nutrients (global removal of 44%). Moreover, our results point out that high aeration might be involved in the increase in the concentration of some PhACs. In fact, conjugation and deconjugation processes (among others) affect the removal assessment of emerging contaminants when working with real concentrations in comparison to experiments with spiked samples. Moreover, factors that could affect the quantification of micropollutants at lab-scale experiments were studied. Copyright © 2014 Elsevier B.V. All rights reserved.

Consideration of Factors Affecting Strip Effluent PH and Sodium Content

Energy Technology Data Exchange (ETDEWEB)

Peters, T. [Savannah River Site (SRS), Aiken, SC (United States)

2015-07-29

A number of factors were investigated to determine possible reasons for why the Strip Effluent (SE) can sometimes have higher than expected pH values and/or sodium content, both of which have prescribed limits. All of the factors likely have some impact on the pH values and Na content.

Progress of research on the influence of alkaline cation and alkaline solution on bentonite properties

International Nuclear Information System (INIS)

Ye Weimin; Zheng Zhenji; Chen Bao; Chen Yonggui

2011-01-01

Based on the previous laboratory studies and numerical simulation on bentonite in alkaline environments, the effects of alkaline cation and alkaline solution on mineral composition, microstructure, swelling capacity and hydraulic properties of bentonite are emphasized in this paper, temperature, pH values and concentration are discussed as main affecting factors. When bentonite is exposed to alkaline cation or alkaline solution, microstructure of bentonite will be changed due to the dissolution of montmorillonite and the formation of secondary minerals, which results in the decrease of swelling pressure. The amount of the reduction of swelling pressure depends on the concentration of alkaline solution. Temperature, polyvalent cation, salinity and concentration are the main factors affecting hydraulic properties of bentonite under alkaline conditions. Therefore, future research should focus on the mechanism of coupling effects of weak alkaline solutions on the mineral composition, microstructure, swelling capacity and hydraulic properties of bentonite under different temperatures and different pH values. (authors)

Effects of phytoextraction on heavy metal concentrations and pH of pore-water of biosolids determined using an in situ sampling technique.

Science.gov (United States)

Huynh, T T; Laidlaw, W S; Singh, B; Gregory, D; Baker, A J M

2008-12-01

Heavy metal concentrations and pH of pore-water in contaminated substrates are important factors in controlling metal uptake by plants. We investigated the effects of phytoextraction on these properties in the solution phase of biosolids and diluted biosolids in a 12-month phytoextraction column experiment. Phytoextraction using Salix and Populus spp. temporarily decreased pore-water pH of the substrates over the experimental period followed by a return to initial pH conditions. Salixxreichardtii and Populus balsamifera effectively extracted Ni, Zn and Cd and actively mobilized these metals from the solid to the solution phase. S.xreichardtii had the stronger effect on mobilization of metals due to its larger root system. Phytoextraction did not affect Cu in the solution phase of the biosolids. Heavy metals were leached down to lower depths of the columns during the phytoextraction process.

The investigation of parameters affecting boron removal by electrocoagulation method

Energy Technology Data Exchange (ETDEWEB)

Yilmaz, A. Erdem [Department of Environmental Engineering, Atatuerk University, Faculty of Engineering, Erzurum (Turkey)]. E-mail: aerdemy@atauni.edu.tr; Boncukcuoglu, Recep [Department of Environmental Engineering, Atatuerk University, Faculty of Engineering, Erzurum (Turkey); Kocakerim, M. Muhtar [Department of Chemical Engineering, 25240, Atatuerk University, Faculty of Engineering Erzurum (Turkey); Keskinler, Buelent [Department of Environmental Engineering, Gebze Institute of Technology, Gebze/Kocaeli 41400 (Turkey)

2005-10-17

Boron removal from wastewaters by electrocoagulation using aluminum electrode material was investigated in this paper. Several working parameters, such as pH, current density, boron concentration and type and concentration of supporting electrolyte were studied in an attempt to achieve a higher removal capacity. The experiments were carried out by keeping the pH of solution constant and optimum pH of solution was determined 8.0 for the aluminum electrode. Although energy consumption increased with decreasing boron concentration, which conductivity of these solutions were low, boron removal efficiency was higher at 100 mg/L than that of 1000 mg/L. Current density was an important parameter affecting removal efficiency. Boron removal efficiency and energy consumption increased with increasing current density from 1.2 to 6.0 mA/cm{sup 2}. The types of different supporting electrolyte were experimented in order to investigate to this parameter effect on boron removal. The highest boron removal efficiency, 97%, was found by CaCl{sub 2}. Added CaCl{sub 2} increased more the conductivity of solution according to other supporting electrolytes, but decreased energy consumption. The results showed to have a high effectiveness of the electrocoagulation method in removing boron from aqueous solutions.

pH dependent polymeric micelle adsorption

Energy Technology Data Exchange (ETDEWEB)

McLean, S C; Gee, M L [The University of Melbourne, VIC (Australia). School of Chemistry

2003-07-01

Full text: Poly(2-vinylpyridine)-poly(ethylene oxide) (P2VP-PEO) shows potential as a possible drug delivery system for anti-tumour drugs since it forms pH dependent polymeric micelles. Hence to better understand the adsorption behaviour of this polymer we have studied the interaction forces between layers of P2VP-PEO adsorbed onto silica as a function of solution pH using an Atomic Force Microscope (AFM). When P2VP-PEO is initially adsorbed above the pKa of the P2VP block, P2VP-PEO adsorbs from solution as micelles that exist as either partially collapsed- or a hemi-micelles at the silica surface. Below the pKa of P2VP, the P2VP-PEO adsorbs as unimers, forming a compact layer with little looping and tailing into solution. When initial adsorption of P2VP-PEO is in the form of unimers, any driving force to self-assembly of the now charge neutral polymer is kinetically hindered. Hence, after initial adsorption at pH 3.6, a subsequent increase in pH to 6.6 results in a slow surface restructuring towards self-assembly and equilibrium. When the pH is increased from pH 6.6 to 9.7 there is a continuation of the evolution of the system to its equilibrium position during which the adsorbed P2VP-PEO unimers continue to 'unravel' from the surface, extending away from it, towards eventual complete surface self-assembly.

pH tolerance of Daphnia pulex (leydig, emend. , richard)

Energy Technology Data Exchange (ETDEWEB)

Davis, P; Ozburn, G W

1969-01-01

The survival time and reproduction of female Daphnia pulex in solutions varying in pH have been observed. Dilute sodium hydroxide or sulfuric acid solutions were added to four different diluent waters: distilled water, aerated tap water, aerated and filtered tap water from an aquarium containing Dace minnows, and Mcintyre River water. D. Pulex (initially up to 72 hours old) survived for the duration of the experiment (32 hours) in river water within a pH range of 6.1 to 10.3; in aquarium water within a pH range of 4.3 to 10.4; only at pH 6.4 and pH 7.6 in distilled water; and in none of the solutions using aerated tap water. The dissolved oxygen content was measured at the beginning and end of every experiment and was found never to fall below 6.2 p.p.M. Those individuals which survived were cultured in the laboratory and parthenogenesis was observed at pH values between 7.0 and 8.7.

Intracellular pH in rat pancreatic ducts

DEFF Research Database (Denmark)

Novak, I; Hug, M; Greger, R

1997-01-01

In order to study the mechanism of H+ and HCO3- transport in a HCO3- secreting epithelium, pancreatic ducts, we have measured the intracellular pH (pHi) in this tissue using the pH sensitive probe BCECF. We found that exposures of ducts to solutions containing acetate/acetic acid or NH4+/NH3...... buffers (20 mmol/l) led to pHi changes in accordance with entry of lipid-soluble forms of the buffers, followed by back-regulation of pHi by duct cells. In another type of experiment, changes in extracellular pH of solutions containing HEPES or HCO3-/CO2 buffers led to significant changes in pHi that did....... Under some conditions, these exchangers can be invoked to regulate cell pH....

Economical wireless optical ratiometric pH sensor

International Nuclear Information System (INIS)

Vuppu, Sandeep; Kostov, Yordan; Rao, Govind

2009-01-01

The development and application of a portable, wireless fluorescence-based optical pH sensor is presented. The design incorporates the MSP430 microcontroller as the control unit, an RF transceiver for wireless communication, digital filters and amplifiers and a USB-based communication module for data transmission. The pH sensor is based on ratiometric fluorescence detection from pH sensitive dye incorporated in a peel-and-stick patch. The ability of the instrument to detect the pH of the solution with contact only between the sensor patch and the solution makes it partially non-invasive. The instrument also has the ability to transmit data wirelessly, enabling its use in processes that entail stringent temperature control and sterility. The use of the microcontroller makes it a reliable, low-cost and low-power device. The luminous intensity of the light source can be digitally controlled to maximize the sensitivity of the instrument. It has a resolution of 0.05 pH. The sensor is accurate and reversible over the pH range of 6.5–9

Radiolysis of permanganate and its mixtures with bromate and nitrate ions in solution at pH 10

International Nuclear Information System (INIS)

Dedgaonkar, V.G.; Kulkarni, S.A.; Mahajan, C.T.

1981-01-01

γ-radiolysis of aqueous solutions of pure permanganate and its binary mixture with nitrite and bromate ions at pH 10 is studied as a function of concentration and dose. In pure system G(-MnO 4 - ) increases with the increase in initial concentration from 0.68 to a maximum of 25. The rise is sharp above 10 -2 M concentration which indicates the occurrence of a chain mechanism. In the presence of bromate or nitrite the G value decreases: the G(-MnO 4 - ) in 10 -3 M permanganate solution is 1.07, with 10 -1 M bromate it is 0.2 and with 10 -2 M nitrite it is 0.7. A mechanism based on the cometitive kinetics is envisaged to explain the observed results. (author)

Ocean acidification affects parameters of immune response and extracellular pH in tropical sea urchins Lytechinus variegatus and Echinometra luccunter.

Science.gov (United States)

Leite Figueiredo, Débora Alvares; Branco, Paola Cristina; Dos Santos, Douglas Amaral; Emerenciano, Andrews Krupinski; Iunes, Renata Stecca; Shimada Borges, João Carlos; Machado Cunha da Silva, José Roberto

2016-11-01

The rising concentration of atmospheric CO 2 by anthropogenic activities is changing the chemistry of the oceans, resulting in a decreased pH. Several studies have shown that the decrease in pH can affect calcification rates and reproduction of marine invertebrates, but little attention has been drawn to their immune response. Thus this study evaluated in two adult tropical sea urchin species, Lytechinus variegatus and Echinometra lucunter, the effects of ocean acidification over a period of 24h and 5days, on parameters of the immune response, the extracellular acid base balance, and the ability to recover these parameters. For this reason, the phagocytic capacity (PC), the phagocytic index (PI), the capacity of cell adhesion, cell spreading, cell spreading area of phagocytic amebocytes in vitro, and the coelomic fluid pH were analyzed in animals exposed to a pH of 8.0 (control group), 7.6 and 7.3. Experimental pH's were predicted by IPCC for the future of the two species. Furthermore, a recovery test was conducted to verify whether animals have the ability to restore these physiological parameters after being re-exposed to control conditions. Both species presented a significant decrease in PC, in the pH of coelomic fluid and in the cell spreading area. Besides that, Echinometra lucunter showed a significant decrease in cell spreading and significant differences in coelomocyte proportions. The recovery test showed that the PC of both species increased, also being below the control values. Even so, they were still significantly higher than those exposed to acidified seawater, indicating that with the re-establishment of the pH value the phagocytic capacity of cells tends to restore control conditions. These results demonstrate that the immune system and the coelomic fluid pH of these animals can be affected by ocean acidification. However, the effects of a short-term exposure can be reversible if the natural values ​​are re-established. Thus, the effects of

Characteristics of separation of carnitine and metal ions in cheese whey model solution by loose reverse osmosis membrane

Energy Technology Data Exchange (ETDEWEB)

Xu, J.; Echizen, H.; Xing, X.; Yamamoto, S.; Unno, H. [Tokyo Institute of Technology, Tokyo (Japan)

1996-04-20

Aiming at recovering carnitine from cheese whey by using loose reverse osmosis membranes, rejection characteristics of several components in the whey were examined by using model solutions. An electroneutral membrane was found to be most effective for the separation. The rejection of carnitine was above 0.95 independent of the pH of solutions, while monovalent metal ions showed low rejections of 0.1-0.3. On the other hand, the rejections of divalent metal ions deceased with increase of the pH, and reached a minimum of about 0.5. As a result, mono-and divalent metal ions could be removed simultaneously by adjusting the pH of the feed solutions. To clarify the effect of pH on the rejection the permeate of MgCl2 aqueous solution was examined. The rejections of MgCl2 were greatly affected by the pH and showed the same tendency as the mixed station. The effect of the pH on permeation of electrolyte was considered to be caused mainly by the adsorption of ions on the membrane. 16 refs., 6 figs., 2 tabs.

Programmable pH buffers

Science.gov (United States)

Gough, Dara Van; Huber, Dale L.; Bunker, Bruce C.; Roberts, Mark E.

2017-01-24

A programmable pH buffer comprises a copolymer that changes pK.sub.a at a lower critical solution temperature (LCST) in water. The copolymer comprises a thermally programmable polymer that undergoes a hydrophobic-to-hydrophilic phase change at the LCST and an electrolytic polymer that exhibits acid-base properties that are responsive to the phase change. The programmable pH buffer can be used to sequester CO.sub.2 into water.

Cadmium and Zn availability as affected by pH manipulation and its assessment by soil extraction, DGT and indicator plants

International Nuclear Information System (INIS)

Muhammad, Iqbal; Puschenreiter, Markus; Wenzel, Walter W.

2012-01-01

Manipulation of soil pH by soil additives and / or rhizosphere processes may enhance the efficiency of metal phytoextraction. Here we report on the effect of nitric acid additions to four polluted soils on Cd and Zn concentrations in soil solution (C soln ) and 0.005 M Ca(NO 3 ) 2 extracts, and related changes in the diffusive fluxes and resupply of the metals as assessed by diffusive gradients in thin films (DGT). The responses of these chemical indicators of bioavailability were compared to metal uptake in two indicator plant species, common dandelion (Taraxacum officinale F.H. Wigg) and narrow leaf plantain (Plantago lanceolata L.) grown for 75 days in a pot experiment. Lowering soil pH increased C soln , the 0.005 M Ca(NO 3 ) 2 -soluble fractions and the DGT-measured Cd and Zn concentrations (C DGT ) in the experimental soils. This was associated with enhanced uptake of Cd and Zn on soils acidified to pH 4.5 whereas plants did not survive at pH 3.5. Toxicity along with decreased kinetics of metal resupply (calculated by the 2D DIFS model) in the strong acidification treatment suggests that moderate acidification is more appropriate to enhance the phytoextraction process. Each of the chemical indicators of bioavailability predicted well (R 2 > 0.70) the Cd and Zn concentrations in plantain shoots but due to metal toxicity not for dandelion. Concentration factors, i.e. the ratio between metal concentrations in shoots and in soil solution (CF) indicate that Cd and Zn uptake in plantain was not limited by diffusion which may explain that DGT did not perform better than C soln . However, DGT is expected to predict plant uptake better in diffusion-limited conditions such as in the rhizosphere of metal-accumulating phytoextraction crops. - Highlights: ► The effect of soil acidification was assessed for four Zn and Cd polluted soils. ► For some soils moderate acidification could enhance the metal uptake efficiency. ► Chemical assessment of bioavailability using

Cadmium and Zn availability as affected by pH manipulation and its assessment by soil extraction, DGT and indicator plants

Energy Technology Data Exchange (ETDEWEB)

Muhammad, Iqbal; Puschenreiter, Markus, E-mail: markus.puschenreiter@boku.ac.at; Wenzel, Walter W.

2012-02-01

Manipulation of soil pH by soil additives and / or rhizosphere processes may enhance the efficiency of metal phytoextraction. Here we report on the effect of nitric acid additions to four polluted soils on Cd and Zn concentrations in soil solution (C{sub soln}) and 0.005 M Ca(NO{sub 3}){sub 2} extracts, and related changes in the diffusive fluxes and resupply of the metals as assessed by diffusive gradients in thin films (DGT). The responses of these chemical indicators of bioavailability were compared to metal uptake in two indicator plant species, common dandelion (Taraxacum officinale F.H. Wigg) and narrow leaf plantain (Plantago lanceolata L.) grown for 75 days in a pot experiment. Lowering soil pH increased C{sub soln}, the 0.005 M Ca(NO{sub 3}){sub 2}-soluble fractions and the DGT-measured Cd and Zn concentrations (C{sub DGT}) in the experimental soils. This was associated with enhanced uptake of Cd and Zn on soils acidified to pH 4.5 whereas plants did not survive at pH 3.5. Toxicity along with decreased kinetics of metal resupply (calculated by the 2D DIFS model) in the strong acidification treatment suggests that moderate acidification is more appropriate to enhance the phytoextraction process. Each of the chemical indicators of bioavailability predicted well (R{sup 2} > 0.70) the Cd and Zn concentrations in plantain shoots but due to metal toxicity not for dandelion. Concentration factors, i.e. the ratio between metal concentrations in shoots and in soil solution (CF) indicate that Cd and Zn uptake in plantain was not limited by diffusion which may explain that DGT did not perform better than C{sub soln}. However, DGT is expected to predict plant uptake better in diffusion-limited conditions such as in the rhizosphere of metal-accumulating phytoextraction crops. - Highlights: Black-Right-Pointing-Pointer The effect of soil acidification was assessed for four Zn and Cd polluted soils. Black-Right-Pointing-Pointer For some soils moderate acidification could

Dielectrophoresis Aligned Single-Walled Carbon Nanotubes as pH Sensors.

Science.gov (United States)

Li, Pengfei; Martin, Caleb M; Yeung, Kan Kan; Xue, Wei

2011-01-31

Here we report the fabrication and characterization of pH sensors using aligned single-walled carbon nanotubes (SWNTs). The SWNTs are dispersed in deionized (DI) water after chemical functionalization and filtration. They are deposited and organized on silicon substrates with the dielectrophoresis process. Electrodes with "teeth"-like patterns-fabricated with photolithography and wet etching-are used to generate concentrated electric fields and strong dielectrophoretic forces for the SWNTs to deposit and align in desired locations. The device fabrication is inexpensive, solution-based, and conducted at room temperature. The devices are used as pH sensors with the electrodes as the testing pads and the dielectrophoretically captured SWNTs as the sensing elements. When exposed to aqueous solutions with various pH values, the SWNTs change their resistance accordingly. The SWNT-based sensors demonstrate a linear relationship between the sensor resistance and the pH values in the range of 5-9. The characterization of multiple sensors proves that their pH sensitivity is highly repeatable. The real-time data acquisition shows that the sensor response time depends on the pH value, ranging from 2.26 s for the pH-5 solution to 23.82 s for the pH-9 solution. The long-term stability tests illustrate that the sensors can maintain their original sensitivity for a long period of time. The simple fabrication process, high sensitivity, and fast response of the SWNT-based sensors facilitate their applications in a wide range of areas.

Computer simulation of the effect of temperature on pH.

Science.gov (United States)

Kipp, J E; Schuck, D F

1995-11-01

The effect of temperature on solution pH was simulated by computer (program PHTEMP). We have determined that the change in pH due to shifts in acid-base equilibria [delta pH = pH(60 degrees C) - pH(25 degrees C)] can be substantial for compounds such as aliphatic amines that have high enthalpies for acid dissociation. This is of particular significance during elevated temperature experiments in which changes in the pKa values of formulation components, and hence the solution pH, can accelerate decomposition as compared to those formulations where sensitive functionality is absent. PHTEMP afforded the following results at initial pH = 7 (25 degrees C): (a) 0.1 M triethylamine (delta H zero = 10.4 kcal/mol) delta pH approximately -0.8; (b) 0.1 M acetic acid (delta H zero = -0.1 kcal/mol) delta pH approximately 0; (c) 0.1 M sulfuric acid (delta H zero 1 = -12 kcal/mol; delta H zero 2 = -5.4 kcal/mol) delta pH approximately -0.4. Solutions of general pharmaceutical interest were also studied and included a 12-component amino acid mixture, 0.1 M glycine, and 0.1 M triethylamine in either 0.02 M citric acid or 0.05 M TRIS buffer. In each case the pH change with temperature was dependent on the concentrations of components, the enthalpies for each acid dissociation, and the starting pH. At lower pH ( 9). These results are interpreted as the effect of a relative change in hydronium ion activity, delta H+/H+(initial), due to temperature-induced shifts in equilibria (acid dissociation, water autoprotolysis). This relative change must become larger as H+ decreases (pH increases). The output of PHTEMP was experimentally verified with 0.1 M glycine and with a multiple component amino acid solution. In both cases, agreement with prediction was excellent. The results of this investigation underscore the need to critically review formulation choices for both thermodynamic and traditional kinetic effects on the resulting product stability.

Hemoglobin bioconjugates with surface-protected gold nanoparticles in aqueous media: The stability depends on solution pH and protein properties.

Science.gov (United States)

Del Caño, Rafael; Mateus, Lucia; Sánchez-Obrero, Guadalupe; Sevilla, José Manuel; Madueño, Rafael; Blázquez, Manuel; Pineda, Teresa

2017-11-01

The identification of the factors that dictate the formation and physicochemical properties of protein-nanomaterial bioconjugates are important to understand their behavior in biological systems. The present work deals with the formation and characterization of bioconjugates made of the protein hemoglobin (Hb) and gold nanoparticles (AuNP) capped with three different molecular layers (citrate anions (c), 6-mercaptopurine (MP) and ω-mercaptoundecanoic acid (MUA)). The main focus is on the behavior of the bioconjugates in aqueous buffered solutions in a wide pH range. The stability of the bioconjugates have been studied by UV-visible spectroscopy by following the changes in the localized surface resonance plasmon band (LSRP), Dynamic light scattering (DLS) and zeta-potential pH titrations. It has been found that they are stable in neutral and alkaline solutions and, at pH lower than the protein isoelectric point, aggregation takes place. Although the surface chemical properties of the AuNPs confer different properties in respect to colloidal stability, once the bioconjugates are formed their properties are dictated by the Hb protein corona. The protein secondary structure, as analyzed by Attenuated total reflectance infrared (ATR-IR) spectroscopy, seems to be maintained under the conditions of colloidal stability but some small changes in protein conformation take place when the bioconjugates aggregate. These findings highlight the importance to keep the protein structure upon interaction with nanomaterials to drive the stability of the bioconjugates. Copyright © 2017 Elsevier Inc. All rights reserved.

Effect of Strength and Microstructure on Stress Corrosion Cracking Behavior and Mechanism of X80 Pipeline Steel in High pH Carbonate/Bicarbonate Solution

Science.gov (United States)

Zhu, Min; Du, Cuiwei; Li, Xiaogang; Liu, Zhiyong; Wang, Shengrong; Zhao, Tianliang; Jia, Jinghuan

2014-04-01

The stress corrosion cracking (SCC) behaviors and mechanisms of X80 pipeline steels with different strength and microstructure in high pH carbonate/bicarbonate solution were investigated by slow strain rate testing and electrochemical test. The results showed that the cracking mode of low strength X80 steel composed of bulky polygonal ferrite and granular bainite in high pH solution was intergranular (IGSCC), and the SCC mechanism was anodic dissolution (AD). While the mixed cracking mode of high strength X80 steel consisted of fine acicular ferrite and granular bainite was intergranular (IGSCC) in the early stage, and transgranular (TGSCC) in the later stage. The decrease of pH value of crack tip was probably the key reason for the occurrence of TGSCC. The SCC mechanism may be a mixed mode of AD and hydrogen embrittlement (HE), and the HE mechanism may play a significant role in the deep crack propagation at the later stage. The cracking modes and SCC mechanisms of the two X80 steels were associated with its microstructure and strength.

[How aliphatic alcohols and ph affect reactional capability of the horse blood serum cholinesterase at its interaction with organophosphorus inhibitors].

Science.gov (United States)

Basova, N E; Kormilitsin, B N; Perchenok, A Iu; Rozengart, E V; Saakov, V S; Suvorov, A A

2013-01-01

There was studied action of aliphatic alcohols (ethanol, propanol, isopropanol, n-butanol, isobutanol, secbutanol, tretbetanol) and pH on various kinds of reactional capability the serum cholinesterase. At the alcohols-affected inhibition of the cholinesterase hydrolytic activity, the determining role was played not the total number carbon atoms in the alcohol molecule, but by the "effective length" of the carbohydrate chain. The fact that the presence of alcohols did not affect parameters of the reverse cholinesterase inhibition with onium ions tetramethylammonium and choline allows suggesting the absence of effect solvents on specific acetylcholine sorption in the enzyme active center. With aid of two rows of hydrophobic organophosphorus inhibitors (OPI), we have managed to estimate both the degree and the character itself of the modifying action of alcohols and pH on the process of irreversible inhibition of serum cholinesterase.

A highly selective chemosensor for colorimetric detection of Hg2+ and fluorescence detection of pH changes in aqueous solution

International Nuclear Information System (INIS)

Kavitha, Ramasamy; Stalin, Thambusamy

2014-01-01

A naturally existing and unmodified simple chemosensor, 2-hydroxy-1,4-naphthoquinone (2HNQ), was identified and used for both the colorimetric detection of Hg 2+ and the fluorescent (on-off) detection of pH. The distinct color change and quenching of fluorescence emission was visible to the naked eye. More importantly, the chemosensor was used in combination with β-cyclodextrin (β-CD), which enabled the sensor to be solubilized and stabilized in aqueous solutions. The sensor selectively detected Hg 2+ via the stable 1:1 complexation of the CåO and OH groups with Hg 2+ and reflected pH changes in the range from 6 to 12 via a fluorescence on–off response resulting from the deprotonation of the hydroxyl group in 2HNQ. - Highlights: • The 2-Hydroxy-1,4-Naphthoquinone (2HNQ) chemosensor is capable of both colorimetric detection of Hg 2+ and a fluorescence on-off response to pH. • The distinct color change and quenching of fluorescence emission are detectable with the naked eye. • The on– off fluorescence response in the pH range from 6– to 12 is due to the deprotonation of the hydroxyl group in 2HNQ

Self-assembly behavior of pH- and thermosensitive amphiphilic triblock copolymers in solution: experimental studies and self-consistent field theory simulations.

Science.gov (United States)

Cai, Chunhua; Zhang, Liangshun; Lin, Jiaping; Wang, Liquan

2008-10-09

We investigated, both experimentally and theoretically, the self-assembly behaviors of pH- and thermosensitive poly(L-glutamic acid)- b-poly(propylene oxide)-b-poly(L-glutamic acid) (PLGA-b-PPO-b-PLGA) triblock copolymers in aqueous solution by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM), dynamic light scattering (DLS), circular dichroism (CD), and self-consistent field theory (SCFT) simulations. Vesicles were observed when the hydrophilic PLGA block length is shorter or the pH value of solution is lower. The vesicles were found to transform to spherical micelles when the PLGA block length increases or its conformation changes from helix to coil with increasing the pH value. In addition, increasing temperature gives rise to a decrease in the size of aggregates, which is related to the dehydration of the PPO segments at higher temperatures. The SCFT simulation results show that the vesicles transform to the spherical micelles with increasing the fraction or statistical length of A block in model ABA triblock copolymer, which corresponds to the increase in the PLGA length or its conformation change from helix to coil in experiments, respectively. The SCFT calculations also provide chain distribution information in the aggregates. On the basis of both experimental and SCFT results, the mechanism of the structure change of the PLGA- b-PPO- b-PLGA aggregates was proposed.

Chemical Speciation and Bond Lengths of Organic Solutes by Core-Level Spectroscopy: pH and Solvent Influence on p-Aminobenzoic Acid.

Science.gov (United States)

Stevens, Joanna S; Gainar, Adrian; Suljoti, Edlira; Xiao, Jie; Golnak, Ronny; Aziz, Emad F; Schroeder, Sven L M

2015-05-04

Through X-ray absorption and emission spectroscopies, the chemical, electronic and structural properties of organic species in solution can be observed. Near-edge X-ray absorption fine structure (NEXAFS) and resonant inelastic X-ray scattering (RIXS) measurements at the nitrogen K-edge of para-aminobenzoic acid reveal both pH- and solvent-dependent variations in the ionisation potential (IP), 1s→π* resonances and HOMO-LUMO gap. These changes unequivocally identify the chemical species (neutral, cationic or anionic) present in solution. It is shown how this incisive chemical state sensitivity is further enhanced by the possibility of quantitative bond length determination, based on the analysis of chemical shifts in IPs and σ* shape resonances in the NEXAFS spectra. This provides experimental access to detecting even minor variations in the molecular structure of solutes in solution, thereby providing an avenue to examining computational predictions of solute properties and solute-solvent interactions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Acid Rain, pH & Acidity: A Common Misinterpretation.

Science.gov (United States)

Clark, David B.; Thompson, Ronald E.

1989-01-01

Illustrates the basis for misleading statements about the relationship between pH and acid content in acid rain. Explains why pH cannot be used as a measure of acidity for rain or any other solution. Suggests that teachers present acidity and pH as two separate and distinct concepts. (RT)

Biosorption of mercury from aqueous solutions using highly characterised peats

Directory of Open Access Journals (Sweden)

A.M. Rizzuti

2015-02-01

Full Text Available This research investigated the biosorption of mercury from aqueous solutions by six highly characterised peats. Samples of the peats were tested both in unaltered condition and after being treated with hydrochloric acid (HCl to free up any occupied exchange sites. Other variables tested were sample dose, contact time, mixing temperature, and the concentration and pH of the mercury solution. Desorption studies were also performed, and tests were done to determine whether the peats could be re-used for mercury biosorption. The results indicate that all six peat types biosorb mercury from aqueous solutions extremely well (92−100 % removal and that their mercury removal capacities are not significantly affected by manipulation of the various factors tested. The factor that had the greatest impact on the mercury removal capacities of the peats was the pH of the mercury solution. The optimal mercury solution pH for mercury removal was in the range 5−7 for four of the peats and in the range 2−3 for the other two. The desorption results indicate that it may be possible to recover up to 41 % of the removed mercury. All of the peat types tested can be repeatedly re-used for additional mercury biosorption cycles. Hence, their disposal should not become a hazardous waste problem.

Synthesis and characterization of pH sensitive carboxySNARF-1 nanoreactors

International Nuclear Information System (INIS)

Chen Yenchi; Ostafin, Agnes; Mizukami, Hiroshi

2010-01-01

A rapid response dual wavelength emission pH sensor consisting of carboxySNARF-1 nanoreactors has been synthesized and shown to provide accurate pH measurements even in complex biological media, where the unprotected pH responsive dyes have failed. The carboxySNARF-1 nanoreactor is made of a calcium phosphate shell covering phosphatidylcholine liposomes filled with the dye. Its mean diameter is 150 nm with dynamic light scattering, the shell thickness is 5-7 nm with TEM, and it contains about 10 dyes/particle. The nanoreactor's response time to pH change nearly equals that of the dye in solution. Its pH titration curves at two different wavelengths are equivalent to those of the dye in solution and fluorescence intensity ratio dependent pH analysis is possible using the modified Henderson-Hasselbalch equation. However, the pH dependent fluorescence ratios of the dye in solution in the presence of plasma and albumin are distorted, and application of the Henderson-Hasselbalch equation is not possible. We have found that the distortions may be restored using cSNARF-1 nanoreactors and the pK a of the dye in the nanoreactor then equals that in solution. These results suggest that the interference to the dye for the pH analyses with the environmental molecules may be reduced or prohibited by usage of cSNARF-1 nanoreactors.

Synthesis and characterization of pH sensitive carboxySNARF-1 nanoreactors

Energy Technology Data Exchange (ETDEWEB)

Chen Yenchi; Ostafin, Agnes [Department of Materials Science, University of Utah, Salt Lake City, UT (United States); Mizukami, Hiroshi, E-mail: a.ostafin@utah.edu [Department of Biological Science, Wayne State University, Detroit, MI (United States)

2010-05-28

A rapid response dual wavelength emission pH sensor consisting of carboxySNARF-1 nanoreactors has been synthesized and shown to provide accurate pH measurements even in complex biological media, where the unprotected pH responsive dyes have failed. The carboxySNARF-1 nanoreactor is made of a calcium phosphate shell covering phosphatidylcholine liposomes filled with the dye. Its mean diameter is 150 nm with dynamic light scattering, the shell thickness is 5-7 nm with TEM, and it contains about 10 dyes/particle. The nanoreactor's response time to pH change nearly equals that of the dye in solution. Its pH titration curves at two different wavelengths are equivalent to those of the dye in solution and fluorescence intensity ratio dependent pH analysis is possible using the modified Henderson-Hasselbalch equation. However, the pH dependent fluorescence ratios of the dye in solution in the presence of plasma and albumin are distorted, and application of the Henderson-Hasselbalch equation is not possible. We have found that the distortions may be restored using cSNARF-1 nanoreactors and the pK{sub a} of the dye in the nanoreactor then equals that in solution. These results suggest that the interference to the dye for the pH analyses with the environmental molecules may be reduced or prohibited by usage of cSNARF-1 nanoreactors.

Influence of variation in mobile phase pH and solute pK(a) with the change of organic modifier fraction on QSRRs of hydrophobicity and RP-HPLC retention of weakly acidic compounds.

Science.gov (United States)

Han, Shu-ying; Liang, Chao; Zou, Kuan; Qiao, Jun-qin; Lian, Hong-zhen; Ge, Xin

2012-11-15

The variation in mobile phase pH and ionizable solute dissociation constant (pK(a)) with the change of organic modifier fraction in hydroorganic mobile phase has seemingly been a troublesome problem in studies and applications of reversed phase high performance liquid chromatography (RP-HPLC). Most of the early studies regarding the RP-HPLC of acid-base compounds have to measure the actual pH of the mixed mobile phase rigorously, sometimes bringing difficulties in the practices of liquid chromatographic separation. In this paper, the effect of this variation on the apparent n-octanol/water partition coefficient (K(ow)″) and the related quantitative structure-retention relationship (QSRR) of logK(ow)″ vs. logk(w), the logarithm of retention factor of analytes in neat aqueous mobile phases, was investigated for weakly acidic compounds. This QSRR is commonly used as a classical method for K(ow) measurement by RP-HPLC. The theoretical and experimental derivation revealed that the variation in mobile phase pH and solute pK(a) will not affect the QSRRs of acidic compounds. This conclusion is proved to be suitable for various types of ion-suppressors, i.e., strong acid (perchloric acid), weak acid (acetic acid) and buffer salt (potassium dihydrogen phosphate/phosphoric acid, PBS). The QSRRs of logK(ow)″ vs. logk(w) were modeled by 11 substituted benzoic acids using different types of ion-suppressors in a binary methanol-water mobile phase to confirm our deduction. Although different types of ion-suppressor all can be used as mobile phase pH modifiers, the QSRR model obtained by using perchloric acid as the ion-suppressor was found to have the best result, and the slightly inferior QSRRs were obtained by using acetic acid or PBS as the ion-suppressor. Copyright © 2012 Elsevier B.V. All rights reserved.

Acid skim milk gels: The gelation process as affected by preheated pH

NARCIS (Netherlands)

Lakemond, C.M.M.; Vliet, van T.

2008-01-01

The effect of preheating milk (10 min 80 [degree sign]C) at pH values from 6.20 to 6.90 on formation of acid skim milk gels was studied by dynamic oscillation measurements. Up to pH 6.65 a higher pH of heating (pHheating) resulted in a higher G'. Since below pH 4.9 the development of

Effects of phytoextraction on heavy metal concentrations and pH of pore-water of biosolids determined using an in situ sampling technique

Energy Technology Data Exchange (ETDEWEB)

Huynh, T.T. [Applied Ecology Research Group, School of Botany, University of Melbourne, Parkville, VIC 3010 (Australia)], E-mail: t.huynh11@pgrad.unimelb.edu.au; Laidlaw, W.S. [Applied Ecology Research Group, School of Botany, University of Melbourne, Parkville, VIC 3010 (Australia); Singh, B. [Faculty of Agriculture, Food and Natural Resources, University of Sydney, Sydney, NSW 2006 (Australia); Gregory, D. [Research and Technology Division, Melbourne Water, Melbourne, VIC 3001 (Australia); Baker, A.J.M. [Applied Ecology Research Group, School of Botany, University of Melbourne, Parkville, VIC 3010 (Australia)

2008-12-15

Heavy metal concentrations and pH of pore-water in contaminated substrates are important factors in controlling metal uptake by plants. We investigated the effects of phytoextraction on these properties in the solution phase of biosolids and diluted biosolids in a 12-month phytoextraction column experiment. Phytoextraction using Salix and Populus spp. temporarily decreased pore-water pH of the substrates over the experimental period followed by a return to initial pH conditions. Salix x reichardtii and Populus balsamifera effectively extracted Ni, Zn and Cd and actively mobilized these metals from the solid to the solution phase. S. x reichardtii had the stronger effect on mobilization of metals due to its larger root system. Phytoextraction did not affect Cu in the solution phase of the biosolids. Heavy metals were leached down to lower depths of the columns during the phytoextraction process. - Salix x reichardtii and Populus balsamifera extracted Ni, Zn and Cd and mobilized these metals in biosolids during phytoextraction.

Effects of phytoextraction on heavy metal concentrations and pH of pore-water of biosolids determined using an in situ sampling technique

International Nuclear Information System (INIS)

Huynh, T.T.; Laidlaw, W.S.; Singh, B.; Gregory, D.; Baker, A.J.M.

2008-01-01

Heavy metal concentrations and pH of pore-water in contaminated substrates are important factors in controlling metal uptake by plants. We investigated the effects of phytoextraction on these properties in the solution phase of biosolids and diluted biosolids in a 12-month phytoextraction column experiment. Phytoextraction using Salix and Populus spp. temporarily decreased pore-water pH of the substrates over the experimental period followed by a return to initial pH conditions. Salix x reichardtii and Populus balsamifera effectively extracted Ni, Zn and Cd and actively mobilized these metals from the solid to the solution phase. S. x reichardtii had the stronger effect on mobilization of metals due to its larger root system. Phytoextraction did not affect Cu in the solution phase of the biosolids. Heavy metals were leached down to lower depths of the columns during the phytoextraction process. - Salix x reichardtii and Populus balsamifera extracted Ni, Zn and Cd and mobilized these metals in biosolids during phytoextraction

Consideration of factors affecting strip effluent pH and sodium content

Energy Technology Data Exchange (ETDEWEB)

Peters, T. B. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2015-07-29

A number of factors were investigated to determine possible reasons for why the Strip Effluent (SE) can sometimes have higher than expected pH values and/or sodium content, both of which have prescribed limits. All of the factors likely have some impact on the pH values and Na content.

Dielectrophoresis Aligned Single-Walled Carbon Nanotubes as pH Sensors

Directory of Open Access Journals (Sweden)

Wei Xue

2011-01-01

Full Text Available Here we report the fabrication and characterization of pH sensors using aligned single-walled carbon nanotubes (SWNTs. The SWNTs are dispersed in deionized (DI water after chemical functionalization and filtration. They are deposited and organized on silicon substrates with the dielectrophoresis process. Electrodes with “teeth”-like patterns—fabricated with photolithography and wet etching—are used to generate concentrated electric fields and strong dielectrophoretic forces for the SWNTs to deposit and align in desired locations. The device fabrication is inexpensive, solution-based, and conducted at room temperature. The devices are used as pH sensors with the electrodes as the testing pads and the dielectrophoretically captured SWNTs as the sensing elements. When exposed to aqueous solutions with various pH values, the SWNTs change their resistance accordingly. The SWNT-based sensors demonstrate a linear relationship between the sensor resistance and the pH values in the range of 5–9. The characterization of multiple sensors proves that their pH sensitivity is highly repeatable. The real-time data acquisition shows that the sensor response time depends on the pH value, ranging from 2.26 s for the pH-5 solution to 23.82 s for the pH-9 solution. The long-term stability tests illustrate that the sensors can maintain their original sensitivity for a long period of time. The simple fabrication process, high sensitivity, and fast response of the SWNT-based sensors facilitate their applications in a wide range of areas.

Determining pH of strip-mine spoils

Science.gov (United States)

W. A. Berg

1969-01-01

Results with the LaMotte-Morgan method for determining soil pH-or the solution modification of this method-usually agreed fairly well with the results from using a pH meter, the recognized standard. Results obtained with the Soiltex and Hellige-Truog methods often deviated somewhat from the pH meter readings; and the Hydrion papers and the Kelway pH tester often gave...

Technetium recovery from high alkaline solution

Energy Technology Data Exchange (ETDEWEB)

Nash, Charles A.

2016-07-12

Disclosed are methods for recovering technetium from a highly alkaline solution. The highly alkaline solution can be a liquid waste solution from a nuclear waste processing system. Methods can include combining the solution with a reductant capable of reducing technetium at the high pH of the solution and adding to or forming in the solution an adsorbent capable of adsorbing the precipitated technetium at the high pH of the solution.

PhD students and integrative research

NARCIS (Netherlands)

Fry, G.; Tress, B.; Tress, G.

2006-01-01

The training of PhD students is currently very dynamic and varies widely from place to place. We present some examples of this variation and comment on how it may affect the way PhD students cope with integrative studies. Our focus is on the training needs of PhD students studying integrative

Sugar-based gemini surfactant with a vesicle-to-micelle transition at acidic pH and a reversible vesicle flocculation near neutral pH

NARCIS (Netherlands)

Johnsson, M; Wagenaar, A; Engberts, JBFN

2003-01-01

A sugar-based (reduced glucose) gemini surfactant forms vesicles in dilute aqueous solution near neutral pH. At lower pH, there is a vesicle-to-micelle transition within a narrow pH region (pH 6.0-5.6). The vesicles are transformed into large cylindrical micelles that in turn are transformed into

Study of the crystallographic phase change on copper (I) selenide thin films prepared through chemical bath deposition by varying the pH of the solution

Energy Technology Data Exchange (ETDEWEB)

Sandoval-Paz, M.G., E-mail: myrnasandoval@udec.cl [Departament of Physics, Faculty of Physical Sciences and Mathematics, University of Concepcion, Box 160-C, Concepción (Chile); Rodríguez, C.A. [Department of Materials Engineering, Faculty of Engineering, University of Concepción, Edmundo Larenas 270, Concepción 4070409 (Chile); Porcile-Saavedra, P.F. [Departament of Physics, Faculty of Physical Sciences and Mathematics, University of Concepcion, Box 160-C, Concepción (Chile); Trejo-Cruz, C. [Department of Physics, Faculty of Science, University of Biobío, Avenue Collao 1202, Box 5C, Concepción 4051381 (Chile)

2016-07-15

Copper (I) selenide thin films with orthorhombic and cubic structure were deposited on glass substrates by using the chemical bath deposition technique. The effects of the solution pH on the films growth and subsequently the structural, optical and electrical properties of the films were studied. Films with orthorhombic structure were obtained from baths wherein both metal complex and hydroxide coexist; while films with cubic structure were obtained from baths where the metal hydroxide there is no present. The structural modifications are accompanied by changes in bandgap energy, morphology and electrical resistivity of the films. - Graphical abstract: “Study of the crystallographic phase change on copper (I) selenide thin films prepared through chemical bath deposition by varying the pH of the solution” by M. G. Sandoval-Paz, C. A. Rodríguez, P. F. Porcile-Saavedra, C. Trejo-Cruz. Display Omitted - Highlights: • Copper (I) selenide thin films were obtained by chemical bath deposition. • Orthorhombic to cubic phase change was induced by varying the reaction solution pH. • Orthorhombic phase is obtained mainly from a hydroxides cluster mechanism. • Cubic phase is obtained mainly from an ion by ion mechanism. • Structural, optical and electrical properties are presented as a function of pH.

Effect of organic matter and pH on the adsorption of metalaxyl and penconazole by soils

Energy Technology Data Exchange (ETDEWEB)

Gondar, Dora; López, Rocío [Departamento de Química Física, Facultad de Química, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela (Spain); Antelo, Juan [Departamento de Edafología y Química Agrícola, Facultad de Biología, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela (Spain); Fiol, Sarah, E-mail: sarah.fiol@usc.es [Departamento de Química Física, Facultad de Química, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela (Spain); Arce, Florencio [Departamento de Química Física, Facultad de Química, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela (Spain)

2013-09-15

Highlights: • The adsorption of non-ionic pesticides on soils is affected by pH. • At pH < 5, the C{sub s}{sup OC}/C{sub e} ratio increased as the pH of the medium decreased. • The effect of pH on adsorption is related to the ionization of carboxylic groups. • SOM charge had similar effect on C{sub s}{sup OC}/C{sub e} in the four soils under study. -- Abstract: Soil organic matter (SOM) is considered to be the primary adsorbent of non-ionic pesticides, and it is therefore thought to determine the concentration of such pesticides in the soil solution and how they are transported throughout the medium. It is generally assumed that the sorption capacity of different soils is the same per unit mass of SOM; however, the reactivity also depends on the SOM composition and the pH of the medium. We carried out experiments to study the effects of pH and ionic strength on the adsorption of the non-ionic fungicides metalaxyl and penconazole on four soils containing different amounts of organic carbon. The adsorption isotherms fitted a Freundlich equation. For pH > 5, partitioning of the fungicides between the solid phase and the soil solution did not vary with the pH, while at lower pH, the fraction adsorbed on the solid phase increased as the pH decreased. The response was related to the effect of pH on the ionization of the carboxylic groups of the SOM and therefore to the hydrophilic nature of the SOM. Analysis of the charge effect on the partitioning of both fungicides revealed a common response in all four soils. Adsorption appears to be related to the magnitude of the charge developed at the SOM due to ionization of the carboxylic acid groups.

The pH Value of Fungicide, Insecticide and Mineral Fertilizer Mixtures Depending on Water Quality

Directory of Open Access Journals (Sweden)

Dušanka Inđić

2008-01-01

Full Text Available The paper deals with the effect of water quality on the pH value of fungicides, insecticides, mineral fertilizers and their mixtures. The fungicides propineb (Antracol WP-70 and mancozeb (Dithane M-70, insecticides pirimiphos-methyl (Actellic-50 and imidacloprid(Confidor 200-SL, several fertilizers (Ferticare I, Ferticare II, Ferticare III and Wuxal Super and their mixtures were analyzed for pH value under laboratory conditions using a potentiometric pH meter. Measurements were made directly after preparation or mixing with tap and well water and 24 hours later. Tap water exhibited a neutral reaction. A slightly alkaline reaction of well water was mostlikely due to high ammonium content. The suspensions of Antracol WP-70 exhibited slightly alkaline reactions with both water types during 24 hours. The spray liquids of Dithane M-70 mixed with tap or well water had neutral reaction after preparation and slightly alkaline reaction after 24 hours. The emulsions of Actellic-50 showed neutral reaction with both water types, followed by a pH increase in tap water after 24 hours. The solutions of Confidor200-SL had a slightly alkaline reaction after mixing and the pH value increased with both water types after 24 hours. It is therefore recommended to apply these insecticides directly after preparation. Mineral fertilizers considerably reduced pH values of the fungicide and insecticide components in double and triple mixtures, especially Ferticare nutrients which had a moderately acid reaction. Wuxal Super had a neutral reaction with both water types.The mixtures with well water increased pH values, which indicates that water pH does affect the pH value of the mixture. Both individual fertilizers and all mixtures (double and triple with Ferticare had pH values between 2.4 and 6, which allows their active liquids to be stored for 12 to 24 hours. The suspensions (Antracol WP-70, double and triple mixtures, emulsions (Actellic-50 and Actellic-50+Wuxal Super

Microfabricated Collector-Generator Electrode Sensor for Measuring Absolute pH and Oxygen Concentrations.

Science.gov (United States)

Dengler, Adam K; Wightman, R Mark; McCarty, Gregory S

2015-10-20

Fast-scan cyclic voltammetry (FSCV) has attracted attention for studying in vivo neurotransmission due to its subsecond temporal resolution, selectivity, and sensitivity. Traditional FSCV measurements use background subtraction to isolate changes in the local electrochemical environment, providing detailed information on fluctuations in the concentration of electroactive species. This background subtraction removes information about constant or slowly changing concentrations. However, determination of background concentrations is still important for understanding functioning brain tissue. For example, neural activity is known to consume oxygen and produce carbon dioxide which affects local levels of oxygen and pH. Here, we present a microfabricated microelectrode array which uses FSCV to detect the absolute levels of oxygen and pH in vitro. The sensor is a collector-generator electrode array with carbon microelectrodes spaced 5 μm apart. In this work, a periodic potential step is applied at the generator producing transient local changes in the electrochemical environment. The collector electrode continuously performs FSCV enabling these induced changes in concentration to be recorded with the sensitivity and selectivity of FSCV. A negative potential step applied at the generator produces a transient local pH shift at the collector. The generator-induced pH signal is detected using FSCV at the collector and correlated to absolute solution pH by postcalibration of the anodic peak position. In addition, in oxygenated solutions a negative potential step at the generator produces hydrogen peroxide by reducing oxygen. Hydrogen peroxide is detected with FSCV at the collector electrode, and the magnitude of the oxidative peak is proportional to absolute oxygen concentrations. Oxygen interference on the pH signal is minimal and can be accounted for with a postcalibration.

Metal/Metal Oxide Differential Electrode pH Sensors

Science.gov (United States)

West, William; Buehler, Martin; Keymeulen, Didier

2007-01-01

Solid-state electrochemical sensors for measuring the degrees of acidity or alkalinity (in terms of pH values) of liquid solutions are being developed. These sensors are intended to supplant older electrochemical pH sensors that include glass electrode structures and reference solutions. The older sensors are fragile and subject to drift. The present developmental solid-state sensors are more rugged and are expected to be usable in harsh environments. The present sensors are based on a differential-electrode measurement principle. Each sensor includes two electrodes, made of different materials, in equilibrium with the solution of interest.

Influence of storage solution on enamel demineralization submitted to pH cycling Influência da solução de armazenagem na desmineralização do esmalte submetido à ciclagem de pH

Directory of Open Access Journals (Sweden)

Juliana Silva Moura

2004-09-01

Full Text Available Extracted human teeth are frequently used for research or educational purposes. Therefore, it is necessary to store them in disinfectant solutions that do not alter dental structures. Thus, this study evaluated the influence of storage solution on enamel demineralization. For that purpose, sixty samples were divided into the following groups: enamel stored in formaldehyde (F1, stored in thymol (T1, stored in formaldehyde and submitted to pH cycling (F2, stored in thymol and submitted to pH cycling (T2. All samples were evaluated by cross-sectional microhardness analysis and had their percentage of mineral volume versus micrometer (integrated area determined. Differences between groups were found up to 30-µm depth from the enamel surface (p Dentes humanos extraídos são freqüentemente utilizados para propósitos educacionais ou de pesquisa. Desta forma, é necessário o armazenamento dos mesmos em soluções desinfetantes que não alterem a estrutura dental. Para tanto, sessenta espécimes foram divididos nos seguintes grupos: esmalte armazenado em formol (F1, armazenado em timol (T1, armazenado em formol e submetido à ciclagem de pH (F2 e armazenado em timol e submetido à ciclagem de pH (T2, sendo avaliados por meio de análise de microdureza longitudinal e tiveram a porcentagem de volume mineral pro micrômetro determinada. Diferenças entre os grupos foram encontradas até a profundidade de 30µm da superfície do esmalte (p<0,05, onde o grupo mais desmineralizado era T2. Foi concluído que a solução de armazenagem influenciou na reação do substrato dental a um desafio cariogênico, sugerindo que o formaldeído pode aumentar a resistência do esmalte à desmineralização promovida pelo modelo de ciclagem de pH, quando comparado à desmineralização ocorrida no esmalte armazenado em timol.

Traceability of pH to the Mole

Directory of Open Access Journals (Sweden)

Maria Filomena Camões

2015-08-01

Full Text Available Free acidity of aqueous solutions was initially defined in 1909 by Søren Peter Lauritz Sørensen as pH = −lgcH+ (c/mol·dm−3 or m/mol·kg−1 of the free hydrogen ions in solution, H+ soon (1910 was changed to pH = paH+ = −lgaH+, integrating the new concepts of activity, ai and activity coefficient γi, for the ionic species i under concern, H+ in this case; it is ai = −lg(miγi. Since individual ions do not exist alone in solution, primary pH values cannot be assigned solely by experimental measurements, requiring extra thermodynamic model assumptions for the activity coefficient, γH+, which has put pH in a unique situation of not being fully traceable to the International System of Units (SI. Also the concept of activity is often not felt to be as perceptible as that of concentration which may present difficulties, namely with the interpretation of data. pH measurements on unknown samples rely on calibration of the measuring setup with adequate reference pH buffers. In this work, the assignment of pH values to buffers closely matching the samples, e.g., seawater, is revisited. An approach is presented to assess the quantity pmH+ = −lgmH+ profiting from the fact that, contrary to single ion activity coefficients, mean activity coefficients,   can be assessed based on experimentally assessed quantities alone, γExp ±, thus ensuring traceability to the mole, the SI base unit for amount of substance. Compatibility between γExp ± and mean activity coefficient calculated by means of Pitzer model equations, γPtz ±, validates the model for its intended use.

Recovery of uranium from sulphate solutions containing molybdenum

International Nuclear Information System (INIS)

Weir, D.R.; Genik-Sas-Berezowsky, R.M.

1983-01-01

A process for recovering uranium from a sulphate solution containing dissolved uranium and molybdenum includes reacting the solution with ammonia (pH 8 to 10), the pH of the original solution must not exceed 5.5 and after the addition of ammonia the pH must not be in the vicinity of 7 for a significant time. The resultant uranium precipitate is relatively uncontaminated by molybdenum. The precipitate is then separated from the remaining solution while the pH is maintained within the stated range

An All-Solid-State pH Sensor Employing Fluorine-Terminated Polycrystalline Boron-Doped Diamond as a pH-Insensitive Solution-Gate Field-Effect Transistor.

Science.gov (United States)

Shintani, Yukihiro; Kobayashi, Mikinori; Kawarada, Hiroshi

2017-05-05

A fluorine-terminated polycrystalline boron-doped diamond surface is successfully employed as a pH-insensitive SGFET (solution-gate field-effect transistor) for an all-solid-state pH sensor. The fluorinated polycrystalline boron-doped diamond (BDD) channel possesses a pH-insensitivity of less than 3mV/pH compared with a pH-sensitive oxygenated channel. With differential FET (field-effect transistor) sensing, a sensitivity of 27 mv/pH was obtained in the pH range of 2-10; therefore, it demonstrated excellent performance for an all-solid-state pH sensor with a pH-sensitive oxygen-terminated polycrystalline BDD SGFET and a platinum quasi-reference electrode, respectively.

Ex situ characterization of metallurgical inclusions in X100 pipeline steel before and after immersion in a neutral pH bicarbonate solution

International Nuclear Information System (INIS)

Li, Yingbo; Liu, Jie; Deng, Yida; Han, Xiaopeng; Hu, Wenbin; Zhong, Cheng

2016-01-01

The initiation of corrosion pits in pipeline steels plays an important role in the development of stress corrosion cracking. In order to reveal the effect of inclusions on corrosion initiation sites and also to clarify contradictory results from previous literature, we proposed an ex situ characterization method that is allowed to characterize exactly the same inclusion or location of the surface of steel before and after corrosion tests. The time-dependent corrosion behaviour of the inclusions and the surrounding X100 steel matrix at the same area before and after early stage immersion in a near-neutral pH bicarbonate solution was investigated by ex situ scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis and localized electrochemical impedance spectroscopy (LEIS). The sizes of most inclusions in X100 steel are below 3 μm. The results challenge the long-held opinion of previous work that corrosion pit initiations are related with the inclusions. It has been found that most of the inclusions remain stable (intact) during the whole testing time although severe corrosion occurs on the matrix of the steel. The chemical composition of the inclusion greatly affects the chemical stability of the inclusion. SiO_2 inclusions and complex inclusions with a high SiO_2 content remain intact although obvious general corrosion occurs on the steel matrix under the investigated immersion period. Inclusions with little Si, such as Al–Mg–Ca–O enriched inclusions, totally disappear after certain immersion time. During the immersion, the corrosion product tends to deposit at the interstice between the inclusion and steel matrix. - Highlights: • Ex situ characterization of metallurgical inclusions in X100 pipeline steel. • The pipeline steel was immersed in neutral pH bicarbonate solution. • Majority of inclusions remain stable during the whole testing time. • The chemical stability of metallurgical inclusions depends on the SiO_2 content.

Ex situ characterization of metallurgical inclusions in X100 pipeline steel before and after immersion in a neutral pH bicarbonate solution

Energy Technology Data Exchange (ETDEWEB)

Li, Yingbo; Liu, Jie [Key Laboratory of Advanced Ceramics and Machining Technology (Ministry of Education), School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Deng, Yida [Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin 300072 (China); Han, Xiaopeng [Key Laboratory of Advanced Ceramics and Machining Technology (Ministry of Education), School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Hu, Wenbin [Key Laboratory of Advanced Ceramics and Machining Technology (Ministry of Education), School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin 300072 (China); Zhong, Cheng, E-mail: cheng.zhong@tju.edu.cn [Key Laboratory of Advanced Ceramics and Machining Technology (Ministry of Education), School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China)

2016-07-15

The initiation of corrosion pits in pipeline steels plays an important role in the development of stress corrosion cracking. In order to reveal the effect of inclusions on corrosion initiation sites and also to clarify contradictory results from previous literature, we proposed an ex situ characterization method that is allowed to characterize exactly the same inclusion or location of the surface of steel before and after corrosion tests. The time-dependent corrosion behaviour of the inclusions and the surrounding X100 steel matrix at the same area before and after early stage immersion in a near-neutral pH bicarbonate solution was investigated by ex situ scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis and localized electrochemical impedance spectroscopy (LEIS). The sizes of most inclusions in X100 steel are below 3 μm. The results challenge the long-held opinion of previous work that corrosion pit initiations are related with the inclusions. It has been found that most of the inclusions remain stable (intact) during the whole testing time although severe corrosion occurs on the matrix of the steel. The chemical composition of the inclusion greatly affects the chemical stability of the inclusion. SiO{sub 2} inclusions and complex inclusions with a high SiO{sub 2} content remain intact although obvious general corrosion occurs on the steel matrix under the investigated immersion period. Inclusions with little Si, such as Al–Mg–Ca–O enriched inclusions, totally disappear after certain immersion time. During the immersion, the corrosion product tends to deposit at the interstice between the inclusion and steel matrix. - Highlights: • Ex situ characterization of metallurgical inclusions in X100 pipeline steel. • The pipeline steel was immersed in neutral pH bicarbonate solution. • Majority of inclusions remain stable during the whole testing time. • The chemical stability of metallurgical inclusions depends on the SiO{sub 2

Analysis of the electric conductivity and pH behaviors in recycled drainage solution of rose cv. Charlotte plants grown in substrate

Directory of Open Access Journals (Sweden)

Luis Fernando Yepes V

2013-12-01

Full Text Available In open soilless cropping systems contamination from nutrient lixiviation is generated making it necessary to design closed or semi-closed systems, which require the determination of the maximum saline levels in recycling solutions. In this study, the electric conductivity (EC and pH behaviors were analyzed in drainage solution intended for recycling in the crop; in addition, parameters were used to estimate nutrient availability for the plants in a substrate based cropping system. This research project was carried out under greenhouse conditions in the municipality of Mosquera (Colombia. Rose cv. Charlotte grafted on "Natal briar" stocks were used, sown in pots arranged on elevated beds, 15 m in length. This project was carried out using a split-plot design with sub-plots (with the substrate as the main plot and the recycling as the sub-plot, three kinds of substrate and three recycling percentages (0, 50, and 100%, for a total of 27 experimental units. Substrate mixtures based on burned rice husk and coconut fiber were used. Recycling during one harvest cycle of the roses did not show EC and pH values above those that are considered to have a negative impact on production; however, an increasing behavior in the EC and pH values was observed. Likewise, no significant differences between the 50 and 100% recycling were observed, which means 100% recycling can be used, optimizing nutrient use and water conservation

Structure evolution of gelatin particles induced by pH and ionic strength.

Science.gov (United States)

Xu, Jing; Li, Tianduo; Tao, Furong; Cui, Yuezhi; Xia, Yongmei

2013-03-01

Microstructure of gelatin particles played a key role in determining the physicochemical properties of gelatin. Ionic strength and pH as systematic manners were considered to affect gelatin particles structure on the micrometer scale. Scanning electron microscopy was used for depicting the morphologies of gelatin particles. Increasing pH to 10.0 or decreasing pH to 4.0, spherical, spindle, and irregular aggregates of gelatin particles at 2, 6, 10, and 14% solution (w/w) were all transformed to spindle aggregates. When NaCl was added to the system, the molecular chains of gelatin possibly rearranged themselves in a stretched state, and the ribbon aggregates was observed. The structural transitions of gelatin aggregates were strongly depended on the electrostatic repulsion. In the gelatin-sodium dodecyl sulfate (SDS) case, the micrometer scale of aggregates was larger and the different degrees of cross-links were induced through hydrophobic interaction and electrostatic repulsion. Copyright © 2012 Wiley Periodicals, Inc.

An empirical model for parameters affecting energy consumption in boron removal from boron-containing wastewaters by electrocoagulation.

Science.gov (United States)

Yilmaz, A Erdem; Boncukcuoğlu, Recep; Kocakerim, M Muhtar

2007-06-01

In this study, it was investigated parameters affecting energy consumption in boron removal from boron containing wastewaters prepared synthetically, via electrocoagulation method. The solution pH, initial boron concentration, dose of supporting electrolyte, current density and temperature of solution were selected as experimental parameters affecting energy consumption. The obtained experimental results showed that boron removal efficiency reached up to 99% under optimum conditions, in which solution pH was 8.0, current density 6.0 mA/cm(2), initial boron concentration 100mg/L and solution temperature 293 K. The current density was an important parameter affecting energy consumption too. High current density applied to electrocoagulation cell increased energy consumption. Increasing solution temperature caused to decrease energy consumption that high temperature decreased potential applied under constant current density. That increasing initial boron concentration and dose of supporting electrolyte caused to increase specific conductivity of solution decreased energy consumption. As a result, it was seen that energy consumption for boron removal via electrocoagulation method could be minimized at optimum conditions. An empirical model was predicted by statistically. Experimentally obtained values were fitted with values predicted from empirical model being as following; [formula in text]. Unfortunately, the conditions obtained for optimum boron removal were not the conditions obtained for minimum energy consumption. It was determined that support electrolyte must be used for increase boron removal and decrease electrical energy consumption.

Reclamation of cadmium-contaminated soil using dissolved organic matter solution originating from wine-processing waste sludge.

Science.gov (United States)

Liu, Cheng-Chung; Chen, Guan-Bu

2013-01-15

Soil washing using an acid solution is a common practice for removing heavy metals from contaminated soil in Taiwan. However, serious loss of nutrients from soil is a major drawback of the washing. Distillery sludge can be used to prepare a dissolved organic matter (DOM) solution by extracting its organic constituents with alkaline solutions. This study employed DOM solutions to remediate Cd-contaminated soil (with concentrations up to 21.5 mg kg(-1)) and determine the factors affecting removal of Cd, such as pH, initial concentration of DOM solution, temperature, and washing frequency. When washing with pH 3.0 and 1250 mg L(-1) DOM solution, about 80% and 81% of Cd were removed from the topsoil at 27 °C and subsoil at 40 °C, respectively. To summarize the changes in fertility during DOM washing with various pH solutions: the increase in organic matter content ranged from 7.7% to 23.7%; cation exchange capacity (CEC) ranged from 4.6% to 13.9%; available ammonium (NNH(4)) content ranged from 39.4% to 2175%; and available phosphorus content ranged from 34.5% to 182%. Exchangeable K, Ca, and Mg remained in the topsoil after DOM washing, with concentrations of 1.1, 2.4, and 1.5 times higher than those treated with HCl solution at the same pH, respectively. Copyright © 2012 Elsevier B.V. All rights reserved.

Complexing Agents and pH Influence on Chemical Durability of Type I Molded Glass Containers.

Science.gov (United States)

Biavati, Alberto; Poncini, Michele; Ferrarini, Arianna; Favaro, Nicola; Scarpa, Martina; Vallotto, Marta

2017-01-01

Among the factors that affect the glass surface chemical durability, pH and complexing agents present in aqueous solution have the main role. Glass surface attack can be also related to the delamination issue causing glass particles' appearance in the pharmaceutical preparation. A few methods to check for glass containers delamination propensity and some control guidelines have been proposed. The present study emphasizes the possible synergy between a few complexing agents with pH on borosilicate glass chemical durability.Hydrolytic attack was performed in small-volume 23 mL type I glass containers autoclaved according to the European Pharmacopoeia or United States Pharmacopeia for 1 h at 121 °C, in order to enhance the chemical attack due to time, temperature, and the unfavorable surface/volume ratio. Solutions of 0.048 M or 0.024 M (M/L) of the acids citric, glutaric, acetic, EDTA (ethylenediaminetetraacetic acid), together with sodium phosphate with water for comparison, were used for the trials. The pH was adjusted ±0.05 units at fixed values 5.5, 6.6, 7, 7.4, 8, and 9 by LiOH diluted solution.Because silicon is the main glass network former, silicon release into the attack solutions was chosen as the main index of the glass surface attack and analysed by inductively coupled plasma atomic emission spectrophotometry. The work was completed by the analysis of the silicon release in the worst attack conditions of molded glass, soda lime type II glass, and tubing borosilicate glass vials to compare different glass compositions and forming technologies. Surface analysis by scanning electron microscopy was finally performed to check for the surface status after the worst chemical attack condition by citric acid. LAY ABSTRACT: Glass, like every packaging material, can have some usage limits, mainly in basic pH solutions. The issue of glass surface degradation particles that appear in vials (delamination) has forced a number of drug product recalls in recent years

Effect of pH and phosphate on calcium carbonate polymorphs precipitated at near-freezing temperature

NARCIS (Netherlands)

Hu, Yu-Bin; Wolthers, Mariëtte; Wolf-Gladrow, Dieter A.; Nehrke, Gernot

2015-01-01

The effects of pH and phosphate on the precipitation of calcium carbonate polymorphs from aqueous solution were investigated. Experiments were carried out at near-freezing temperature and two different pH conditions (pH 13.4 and 9.0). At each pH condition, solutions having different concentrations

Alterations in seawater pH and CO 2 affect calcification and photosynthesis in the tropical coralline alga, Hydrolithon sp. (Rhodophyta)

Science.gov (United States)

Semesi, I. Sware; Kangwe, Juma; Björk, Mats

2009-09-01

Calcification in the marine environment is the basis for the accretion of carbonate in structures such as coral reefs, algal ridges and carbonate sands. Among the organisms responsible for such calcification are the Corallinaceae (Rhodophyta), recognised as major contributors to the process world-wide. Hydrolithon sp. is a coralline alga that often forms rhodoliths in the Western Indian Ocean. In Zanzibar, it is commonly found in shallow lagoons, where it often grows within seagrass beds and/or surrounded by green algae such as Ulva sp. Since seagrasses in Zanzibar have recently been shown to raise the pH of the surrounding seawater during the day, and since calcification rates are sensitive to pH, which changes the saturation state of calcium carbonate, we measured the effects of pH on photosynthetic and calcification rates of this alga. It was found that pH had significant effects on both calcification and photosynthesis. While increased pH enhanced calcification rates both in the light and in the dark at pH >8.6, photosynthetic rates decreased. On the other hand, an increase in dissolved CO 2 concentration to ˜26 μmol kg -1 (by bubbling with air containing 0.9 mbar CO 2) caused a decrease in seawater pH which resulted in 20% less calcification after 5 days of exposure, while enhancing photosynthetic rates by 13%. The ecological implications of these findings is that photosynthetically driven changes in water chemistry by surrounding plants can affect calcification rates of coralline algae, as may future ocean acidification resulting from elevated atmospheric CO 2.

ISFET pH Sensitivity: Counter-Ions Play a Key Role.

Science.gov (United States)

Parizi, Kokab B; Xu, Xiaoqing; Pal, Ashish; Hu, Xiaolin; Wong, H S Philip

2017-02-02

The Field Effect sensors are broadly used for detecting various target analytes in chemical and biological solutions. We report the conditions under which the pH sensitivity of an Ion Sensitive Field Effect transistor (ISFET) sensor can be significantly enhanced. Our theory and simulations show that by using pH buffer solutions containing counter-ions that are beyond a specific size, the sensor shows significantly higher sensitivity which can exceed the Nernst limit. We validate the theory by measuring the pH response of an extended gate ISFET pH sensor. The consistency and reproducibility of the measurement results have been recorded in hysteresis free and stable operations. Different conditions have been tested to confirm the accuracy and validity of our experiment results such as using different solutions, various oxide dielectrics as the sensing layer and off-the-shelf versus IC fabricated transistors as the basis of the ISFET sensor.

Continuous pH monitoring in a perfused bioreactor system using an optical pH sensor

Science.gov (United States)

Jeevarajan, Antony S.; Vani, Sundeep; Taylor, Thomas D.; Anderson, Melody M.

2002-01-01

Monitoring and regulating the pH of the solution in a bioprocess is one of the key steps in the success of bioreactor operation. An in-line optical pH sensor, based on the optical absorption properties of phenol red present in the medium, was developed and tested in this work for use in NASA space bioreactors based on a rotating wall-perfused vessel system supporting a baby hamster kidney (BHK-21) cell culture. The sensor was tested over three 30-day and one 124-day cell runs. The pH sensor initially was calibrated and then used during the entire cell culture interval. The pH reported by the sensor was compared to that measured by a fiber optically coupled Shimadzu spectrophotometer and a blood gas analyzer. The maximum standard error of prediction for all the four cell runs for development pH sensor against BGA was +/-0.06 pH unit and for the fiber optically coupled Shimadzu spectrophotometer against the blood gas analyzer was +/-0.05 pH unit. The pH sensor system performed well without need of recalibration for 124 days. Copyright 2002 Wiley Periodicals, Inc.

Radiolysis of nitrite, bromate and permanganate ions and their binary mixtures in aqueous solutions at pH 10

International Nuclear Information System (INIS)

Dedgaonkar, V.G.; Kulkarni, S.A.; Mahajan, C.T.

1981-01-01

#betta#-radiolysis of pure systems viz. nitrite, bromate and permanganate and their binary mixtures (MNO 4- /NO 2- , MnO 4- /BrO 3- ) in aqueous solution at pH 10 is studied as a function of dose and concentration. In pure systems the G(NO 3- ), G(Br - ) and G(-MnO 4- ) increase with increasing concentration. The first two show an identical limiting value of approximately 0.5 while the last increases from 0.68 below 10 4 M and reaches 2.5 at 10 - 2 M concentration. Presence of 10 - 1 M BrO 3- or 10 - 2 M NO 2- reduces the G(-MnO 4- ) from 1.07 for the pure 10 - 3 M permanganate solution to 0.2 and 0.7 respectively. A mechanism based on the competitive kinetics is envisaged to explain the observed results. (author)

Applications of Fertilizer Cations Affect Cadmium and Zinc Concentrations in Soil Solutions and Uptake by Plants

DEFF Research Database (Denmark)

Lorenz, S. E.; Hamon, R. E.; McGrath, S. P.

1994-01-01

A pot experiment was conducted to study changes over time of Cd and Zn in soil solution and in plants. Radish was grown in a soil which had been contaminated with heavy metals prior to 1961. Constant amounts of a fertilizer solution (NH4N03, KN03) were added daily. Soil solution was obtained......-metal (Cd, Zn) ions in soil solutions and a decrease in soil pH, probably due to ion-exchange mechanisms and the dissolution of carbonates. Uptake of Cd and Zn into leaves was correlated with the mass flow of Cd (adjusted r2 = 0.798) and Zn (adjusted r2=0.859). Uptake of K, Ca and Mg by the plants...... at intervals by displacement with water. The cumulative additions of small amounts of fertilizers were made equal to the plants' requirements at the final harvest but were found to exceed them during most of the experiment. Excess fertilizers caused substantial increases of major (K, Ca, Mg) and heavy...

Effect of interactions between carbon dioxide enrichment and NH4+/NO3- ratio on pH of culturing nutrient solution,growth and vigor of tomato root system

Institute of Scientific and Technical Information of China (English)

Juan LI; Jianmin ZHOU

2008-01-01

A growth chamber experiment was conducted to investigate the influence of NH4+/NO3- ratio and elevated CO2 concentration on the pH in nutrient solution,growth and root vigor system of tomato seedling roots,which attempts to understand whether the elevated CO2 concentration can alleviate the harmful effects of higher NH4+-N concentration in nutrient solutions on the tomato root system.Tomato (Lycopersicon esculenturn Mill.var.Hezuo 906) was grown in pots with nutrient solutions varying in NH4+/NO3- ratio (0:1,1:3,1:1,3:1and 1:0) and the growth chambers were supplied with with the growth process and CO2 concentration increased.At both CO2 levels,pH increased when 100% NO3--N was supplied and decreased in other treatments.The pH decrease in the nutrient solution was directly correlated to the NH4+-N proportion.The pH value was more reduced in 100% NH4+-N nutrient solution than increased in the 100% NO3--N nutrient solution.CO2 enrichment increased the dry weight of shoots and roots,root vigor system,total absorbing area and active absorbing area of tomato seedlings.All the measurement indexes above were increased in the elevated CO2 concentration treatment with the NO3- proportion increase in the nutrient solutions.Thus,under the elevated CO2 concentration,the dry weights of shoots and roots,root vigor system,total root absorbing area and active absorbing area were found to be inversely correlated to NH4+/NO3- ratio,leading to about 65.8%,78.0%,18.9%,12.9% and 18.9% increase,respectively,compared with that under the ambient CO2 concentration.Our results indicated that tomato seedling roots may benefit mostly from CO2 enrichment when 100% NO3--N nutrient solutions was supplied,but the CO2 concentration elevation did not alleviate the harmful effects when 100% NHa+-N was supplied.

Salt-specific effects in lysozyme solutions

Directory of Open Access Journals (Sweden)

T. Janc

2016-03-01

Full Text Available The effects of additions of low-molecular-mass salts on the properties of aqueous lysozyme solutions are examined by using the cloud-point temperature, T_{cloud}, measurements. Mixtures of protein, buffer, and simple salt in water are studied at pH=6.8 (phosphate buffer and pH=4.6 (acetate buffer. We show that an addition of buffer in the amount above I_{buffer} = 0.6 mol dm^{-3} does not affect the T_{cloud} values. However, by replacing a certain amount of the buffer electrolyte by another salt, keeping the total ionic strength constant, we can significantly change the cloud-point temperature. All the salts de-stabilize the solution and the magnitude of the effect depends on the nature of the salt. Experimental results are analyzed within the framework of the one-component model, which treats the protein-protein interaction as highly directional and of short-range. We use this approach to predict the second virial coefficients, and liquid-liquid phase diagrams under conditions, where T_{cloud} is determined experimentally.

Stability of Adrenaline in Irrigating Solution for Intraocular Surgery.

Science.gov (United States)

Shibata, Yuuka; Kimura, Yasuhiro; Taogoshi, Takanori; Matsuo, Hiroaki; Kihira, Kenji

2016-01-01

Intraocular irrigating solution containing 1 µg/mL adrenaline is widely used during cataract surgery to maintain pupil dilation. Prepared intraocular irrigating solutions are recommended for use within 6 h. After the irrigating solution is admistered for dilution, the adrenaline may become oxidized, and this may result in a decrease in its biological activity. However, the stability of adrenaline in intraocular irrigating solution is not fully understood. The aim of this study was to evaluate the stability of adrenaline in clinically used irrigating solutions of varying pH. Six hours after mixing, the adrenaline percentages remaining were 90.6%±3.7 (pH 7.2), 91.1%±2.2 (pH 7.5), and 65.2%±2.8 (pH 8.0) of the initial concentration. One hour after mixing, the percentages remaining were 97.6%±2.0 (pH 7.2), 97.4%±2.7 (pH 7.5), and 95.6%±3.3 (pH 8.0). The degradation was especially remarkable and time dependent in the solution at pH 8.0. These results indicate that the concentration of adrenaline is decreased after preparation. Moreover, we investigated the influence of sodium bisulfite on adrenaline stability in irrigating solution. The percentage adrenaline remaining at 6 h after mixing in irrigating solution (pH 8.0) containing sodium bisulfite at 0.5 µg/mL (concentration in irrigating solution) or at 500 µg/mL (concentration in the undiluted adrenaline preparation) were 57.5 and 97.3%, respectively. Therefore, the low concentration of sodium bisulfite in the irrigating solution may be a cause of the adrenaline loss. In conclusion, intraocular irrigation solution with adrenaline should be prepared just prior to its use in surgery.

Solution pH and oligoamine molecular weight dependence of the transition from monolayer to multilayer adsorption at the air-water interface from sodium dodecyl sulfate/oligoamine mixtures.

Science.gov (United States)

Halacheva, S S; Penfold, J; Thomas, R K; Webster, J R P

2013-05-14

Neutron reflectivity and surface tension have been used to investigate the solution pH and oligoamine molecular weight dependence of the adsorption of sodium dodecyl sulfate (SDS)/oligoamine mixtures at the air-water interface. For diethylenetriamine, triamine, or triethylenetetramine, tetramine mixed with SDS, there is monolayer adsorption at pH 7 and 10, and multilayer adsorption at pH 3. For the slightly higher molecular weight tetraethylenepentamine, pentamine, and pentaethylenehexamine, hexamine, the adsorption is in the form of a monolayer at pH 3 and multilayers at pH 7 and 10. Hence, there is a pH driven transition from monolayer to multilayer adsorption, which shifts from low pH to higher pH as the oligoamine molecular weight increases from tetramine to pentamine. This results from the relative balance between the electrostatic attraction between the SDS and amine nitrogen group which decreases as the charge density decreases with increasing pH, the ion-dipole interaction between the amine nitrogen and SDS sulfate group which is dominant at higher pH, and the hydrophobic interalkyl chain interaction between bound SDS molecules which changes with oligoamine molecular weight.

Stabilizing sodium hypochlorite at high pH: effects on soft tissue and dentin.

Science.gov (United States)

Jungbluth, Holger; Marending, Monika; De-Deus, Gustavo; Sener, Beatrice; Zehnder, Matthias

2011-05-01

When sodium hypochlorite solutions react with tissue, their pH drops and tissue sorption decreases. We studied whether stabilizing a NaOCl solution at a high pH would increase its soft-tissue dissolution capacity and effects on the dentin matrix compared with a standard NaOCl solution of the same concentration and similar initial pH. NaOCl solutions were prepared by mixing (1:1) a 10% stock solution with water (standard) or 2 mol/L NaOH (stabilized). Physiological saline and 1 mol/L NaOH served as the controls. Chlorine content and alkaline capacity of NaOCl solutions were determined. Standardized porcine palatal soft-tissue specimens and human root dentin bars were exposed to test and control solutions. Weight loss percentage was assessed in the soft-tissue dissolution assay. Three-point bending tests were performed on the root dentin bars to determine the modulus of elasticity and flexural strength. Values between groups were compared using one-way analysis of variance with the Bonferroni correction for multiple testing (α pH level of 7.5, respectively. The stabilized NaOCl dissolved significantly more soft tissue than the standard solution, and the pH remained high. It also caused a higher loss in elastic modulus and flexure strength (P < .05) than the control solutions, whereas the standard solution did not. NaOH-stabilized NaOCl solutions have a higher alkaline capacity and are thus more proteolytic than standard counterparts. Copyright © 2011 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Effect of pH on Pulp Potential and Sulphide Mineral Flotation

OpenAIRE

GÖKTEPE, Ferihan

2014-01-01

Control of pH is one of the most widely applied methods for the modulation of mineral flotation. In this study the effect of pH on potential in solution and sulphur minerals flotation is discussed with various electrodes. The electrodes were platinum, gold, chalcopyrite, pyrite and galena. In solution, potentials were linearly dependent on pH with a different slope for each electrode. Chalcopyrite, pyrite, sphalerite and galena minerals flotation tests were performed in a microflot...

Investigating the sensitivity of PMMA optical fibres for use as an evanescent field absorption sensor in aqueous solutions

International Nuclear Information System (INIS)

Lye, P G; Boerkamp, M; Ernest, A; Lamb, D W

2005-01-01

Polymethylmethacrylate (PMMA) optical fibres are low-cost polymer fibres that are generally more physically robust than silica fibres, are more flexible, yet like silica fibres have the potential to be used for practical evanescent field absorption sensors in aqueous solutions. However, evanescent field absorption in aqueous solutions is influenced by more than just the specific absorptivity of the solution in question. The physical configuration of the optical fibre itself, as well as surface charge interactions between the fibre and the chromophore in the solution also significantly affects the sensitivity of the fibre to evanescent field absorption. This paper reports on an investigation of numerous physical phenomena that influence evanescent field absorption for PMMA fibres using an aqueous solution of the dye Amidoblack. Parameters investigated included fibre coiling configuration and bend radius, fibre interaction length, and effect of solution pH. Coiled fibres were found to be more sensitive to evanescent field absorption than straight (uncoiled) lengths, and sensitivity was found to increase with a further reduction in bend radius. At high solution pH, the absorption versus solution concentration proved to be linear whereas at low pH the absorption versus concentration relationship exhibited a clear deviation from linearity. The observed nonlinearity at low pH points to the importance of accounting for electrostatic interactions between chromophore and fibre surface when designing a PMMA sensor for evanescent field absorption measurements in aqueous solutions

Modelling the Interaction of Low pH Cements and Bentonite. Issues Affecting the Geochemical Evolution of Repositories for Radioactive Waste

International Nuclear Information System (INIS)

Watson, Claire; Benbow, Steven; Savage, David

2007-05-01

It is well known that in the hyperalkaline conditions (pH > 12) of standard cement pore fluids, there is potential for deleterious effects upon the host rock and other EBS materials, notably bentonite, in geological repositories for radioactive waste. Low pH cements are beginning to be considered as a potential alternative material that may address some of these concerns. Low pH cement (also known as low heat cement) was developed by the cement industry for use where large masses of cement (e.g. dams) could cause problems regarding heat generated during curing. In low pH cements, the amount of cement is reduced by substitution of materials such as fly ash, blast furnace slag, silica fume, and/or non pozzolanic silica flour. NUMO, Posiva and SKB have defined a pH limit ≤ 11 for cement grout leachates. To attain this pH, blending agents must comprise at least 50 wt % of dry materials. Because low pH cement has little, or no free portlandite, the cement consists predominantly of calcium silicate hydrate (CSH) gel with a Ca/Si ratio ≤ 0.8. In this report we give the results of a preliminary modelling study to investigate the potential impacts of low pH cement water. We compare the evolution of a bentonite sample under the influence of several invading cement porewaters over a pH range from 10 to 13.2. The porewater compositions are taken from published CSH gel leaching experiments and published cement-bentonite modelling studies. The models suggest that the amount of degradation that is likely to be observed when low pH cement water interacts with bentonite is likely to be much less than when OPC water is the invading fluid. Below pH 11 there was not an observable Na montmorillonite dissolution front which would tend to support the pH ≤ 11 target suggested by NUMO, Posiva and SKB. The models used in this study could be improved upon by including a cement component to the model (rather than representing cement as a fixed boundary condition). Solid-solution models

A ph sensor based on a flexible substrate

Science.gov (United States)

Huang, Wen-Ding

pH sensor is an essential component used in many chemical, food, and bio-material industries. Conventional glass electrodes have been used to construct pH sensors, however, have some disadvantages. Glass electrodes are easily affected by alkaline or HF solution, they require a high input impedance pH meter, they often exhibit a sluggish response. In some specific applications, it is also difficult to use glass electrodes for in vivo biomedical or food monitoring applications due to the difficulty of size miniaturization, planarization and polymerization based on current manufacturing technologies. In this work, we have demonstrated a novel flexible pH sensor based on low-cost sol-gel fabrication process of iridium oxide (IrOx) sensing film (IROF). A pair of flexible miniature IrOx/AgCl electrode generated the action potential from the solution by electrochemical mechanism to obtain the pH level of the reagent. The fabrication process including sol-gel, thermal oxidation, and the electro-plating process of the silver chloride (AgCl) reference electrode were reported in the work. The IrOx film was verified and characterized using electron dispersive analysis (EDAX), scanning electron microscope (SEM), and x-ray diffraction (XRD). The flexible pH sensor's performance and characterization have been investigated with different testing parameters such as sensitivity, response time, stability, reversibility, repeatability, selectivity and temperature dependence. The flexible IrOx pH sensors exhibited promising sensing performance with a near-Nernstian response of sensitivity which is between --51.1mV/pH and --51.7mV/pH in different pH levels ranging from 1.5 to 12 at 25°C. Two applications including gastroesophageal reflux disease (GERD) diagnosis and food freshness wireless monitoring using our micro-flexible IrOx pH sensors were demonstrated. For the GERD diagnosing system, we embedded the micro flexible pH sensor on a 1.2cmx3.8cm of the capsule size of wireless sensor

Soil solution dynamics of Cu and Zn in a Cu- and Zn-polluted soil as influenced by gamma-irradiation and Cu-Zn interaction.

Science.gov (United States)

Luo, Y M; Yan, W D; Christie, P

2001-01-01

A pot experiment was conducted to study soil solution dynamics of Cu and Zn in a Cu/Zn-polluted soil as influenced by gamma-irradiation and Cu-Zn interaction. A slightly acid sandy loam was amended with Cu and Zn (as nitrates) either singly or in combination (100 mg Cu and 150 mg Zn kg(-1) soil) and was then gamma-irradiated (10 kGy). Unamended and unirradiated controls were included, and spring barley (Hordeum vulgare L. cv. Forrester) was grown for 50 days. Soil solution samples obtained using soil moisture samplers immediately before transplantation and every ten days thereafter were used directly for determination of Cu, Zn, pH and absorbance at 360 nm (A360). Cu and Zn concentrations in the solution of metal-polluted soil changed with time and were affected by gamma-irradiation and metal interaction. gamma-Irradiation raised soil solution Cu substantially but generally decreased soil solution Zn. These trends were consistent with increased dissolved organic matter (A360) and solution pH after gamma-irradiation. Combined addition of Cu and Zn usually gave higher soil solution concentrations of Cu or Zn compared with single addition of Cu or Zn in gamma-irradiated and non-irradiated soils, indicating an interaction between Cu and Zn. Cu would have been organically complexed and consequently maintained a relatively high concentration in the soil solution under higher pH conditions. Zn tends to occur mainly as free ion forms in the soil solution and is therefore sensitive to changes in pH. The extent to which gamma-irradiation and metal interaction affected solubility and bioavailability of Cu and Zn was a function of time during plant growth. Studies on soil solution metal dynamics provide very useful information for understanding metal mobility and bioavailability.

Effect of pH and uranium concentration on interaction of uranium(VI) and uranium(IV) with organic ligands in aqueous solutions

International Nuclear Information System (INIS)

Li, W.C.; Victor, D.M.; Chakrabarti, C.L.

1980-01-01

The effect of pH and uranium concentration on the interactions of uranium(VI) and uranium(IV) with organic ligands was studied by employing dialysis and ultrafiltration techniques. The interactions of U(VI) and U(IV) with organic ligands in nitrate or chloride aqueous solution have been found to be pH-dependent. The stability constants of uranium-organic complexes decrease in the order: fulvic acid>humic acid>tannic acid for U(VI) and humic acid>tannic acid>fulvic acid for U(IV). Scatchard plots for the uranium-organic acid systems indicate two types of binding sites with a difference in stability constants of about 10 2 . Ultrafiltration of uranium-humic acid complexes indicates that U(VI) and U(IV) ions are concentrated in larger molecular size fractions (>5.1 nm) at pH less than or equal to 3 and in smaller molecular size fractions (in the range 5.1 to 3.1 nm and 2.4 to 1.9 nm) at pH greater than or equal to 5. 7 figures, 4 tables

CMOS COLOUR SENSOR BASED pH MEASUREMENT FOR WATER QUALITY ANALYSIS

OpenAIRE

Sanjay Kumar; Arvind Singh

2016-01-01

A Real-Time pH measurement system using a novel design Programmable CMOS optical Colour light to frequency converter TCS230 is presented. The system uses Bogen’s universal indicator solution combined with a white light source and the Programmable CMOS colour sensor TCS230 to measure pH as a function of colour change in a sample. Bogen’s universal indicator solution causes a colour change in a sample according to the pH of the sample. The output frequency from the colour-sensitive CM...

Electrocatalytic hydrogen evolution under densely buffered neutral pH conditions

KAUST Repository

Shinagawa, Tatsuya

2015-08-18

Under buffered neutral pH conditions, solute concentrations drastically influence the hydrogen evolution reaction (HER). The iR-free HER performance as a function of solute concentration was found to exhibit a volcano-shaped trend in sodium phosphate solution at pH 5, with the maximum occurring at 2 M. A detailed microkinetic model that includes calculated activity coefficients, solution resistance, and mass-transport parameters accurately describes the measured values, clarifying that the overall HER performance is predominantly governed by mass-transport of slow phosphate ions (weak acid). In the HER at the optimum concentration of approximately 2 M sodium phosphate at pH 5, our theoretical model predicts that the concentration overpotential accounts for more than half of the required overpotential. The substantial concentration overpotential would originate from the electrolyte property, suggesting that the proper electrolyte engineering will result in an improved apparent HER performances. The significance of concentration overpotential shown in the study is critical in the advancement of electrocatalysis, biocatalysis, and photocatalysis.

Electrocatalytic hydrogen evolution under densely buffered neutral pH conditions

KAUST Repository

Shinagawa, Tatsuya; Takanabe, Kazuhiro

2015-01-01

Under buffered neutral pH conditions, solute concentrations drastically influence the hydrogen evolution reaction (HER). The iR-free HER performance as a function of solute concentration was found to exhibit a volcano-shaped trend in sodium phosphate solution at pH 5, with the maximum occurring at 2 M. A detailed microkinetic model that includes calculated activity coefficients, solution resistance, and mass-transport parameters accurately describes the measured values, clarifying that the overall HER performance is predominantly governed by mass-transport of slow phosphate ions (weak acid). In the HER at the optimum concentration of approximately 2 M sodium phosphate at pH 5, our theoretical model predicts that the concentration overpotential accounts for more than half of the required overpotential. The substantial concentration overpotential would originate from the electrolyte property, suggesting that the proper electrolyte engineering will result in an improved apparent HER performances. The significance of concentration overpotential shown in the study is critical in the advancement of electrocatalysis, biocatalysis, and photocatalysis.

Isotopic equilibria between sulphur solute species at high temperature

International Nuclear Information System (INIS)

Robinson, B.W.

1978-01-01

Sulphur solute species in ore solutions and geothermal discharges include HSO 4 - , SO 4 2- , H 2 S, and HS - , as well as the ion-paired species, NaHS 0 , NaHSO 4 - and Na 2 SO 4 0 . Observed sulphate-sulphide fractionation factors and the rates of attainment of isotopic equilibrium are likely to depend on the nature of the sulphur species actually taking part in these isotopic equilibria. Preliminary experiments in alkaline solution (pH 10.1 at 20 0 C) were carried out in a gold cell. No significant isotope fractionation was observed between the SO 4 2- and HS - in 29 days at 200 0 C, 63days at 300 0 C, or 90 days at 250 0 C. However, similar experiments at 350 0 C in sealed gold capsules at room temperature pH 8.5 showed slow exchange(t( 1 / 2 ) was calculated to be 510 days for the SO 4 2- -HS - exchange reaction using the theoretical fractionation of 20.2 0 / 00 ). The addition of NaCl appeared to have no affect on the exchange. However, pH strongly controls the reaction rate, and exchange probably involves H 2 S and the HSO 4 - ion. Additional preliminary experiments were conducted with a fivefold increase in the sulphur concentration; a decrease in t( 1 / 2 ) to 142 days resulted. Some inter-relationship between sulphur concentration and exchange rate thus exists. The important controlling parameters of isotope exchange (temperature, pH, and ΣS) can be seen to have influenced exchange in natural systems.(auth.)

Reduction of exchangeable calcium and magnesium in soil with increasing pH

Directory of Open Access Journals (Sweden)

Miyazawa Mário

2001-01-01

Full Text Available A laboratory study was conducted with soil samples and synthetic solutions to investigate possible mechanisms related with reduction in KCl exchangeable Ca and Mg with increasing pH. Increasing soil pH over 5.3 with CaCO3 added to the soil and with NaOH solution added to soil/KCl suspension increased adsorptions of Ca and Mg. The reduction of Mg was greater than Ca and was related to the concentration of soil exchangeable Al. The decreases of soluble Ca and Mg following addition of Al in synthetic solution were at pH > 7.5. The isomorphic coprecipitation reaction with Al compounds may be the most possible mechanism responsible for the decrease of exchangeable Ca and Mg with increasing pH. Possible chemical reactions are presented.

Preparation of fluorescent polyaniline nanoparticles in aqueous solutions

Energy Technology Data Exchange (ETDEWEB)

Alves, Kleber G. B. [Universidade Federal de Pernambuco, Departamento de Engenharia Mecanica (Brazil); Melo, Etelino F. de [Universidade Federal de Pernambuco, Departamento de Quimica Fundamental (Brazil); Andrade, Cesar A. S. [Universidade Federal de Pernambuco, Departamento de Bioquimica (Brazil); Melo, Celso P. de, E-mail: celso@df.ufpe.br [Universidade Federal de Pernambuco, Departamento de Fisica (Brazil)

2013-01-15

We report the synthesis of stable polyaniline nanoparticles (PANI{sub N}Ps) based on the chemical oxidative polymerization of aniline in aqueous solutions of surfactants. Surfactants of three different types-cationic (dodecyltrimethylammonium bromide-DTAB), anionic (sodium dodecyl sulfate-SDS), and non-ionic (Triton X-405-TX-405)-were used. The resulting PANI{sub N}Ps{sub s}urfactant samples were characterized through UV-Vis, fluorescence and Fourier transform infrared spectroscopies, and scanning electronic microscopy (SEM). We have verified that the color of the PANI{sub N}Ps{sub s}urfactant dispersions is affected by a change in the pH of the solution. The PANI-NPs{sub s}urfactant colloidal suspensions in aqueous solution present a surprising high fluorescence quantum yield value (ranging from 1.9 Multiplication-Sign 10{sup -3} to 6.9 Multiplication-Sign 10{sup -3}) that can be controlled as a function of the pH, a fact that we associate to the corresponding protonation degree of the PANI polymeric chains. We suggest that these fluorescent nanocomposites can find important technological applications in different areas such as organic light emitting devices, biosensors, and pigments for coatings.

Preparation of fluorescent polyaniline nanoparticles in aqueous solutions

International Nuclear Information System (INIS)

Alves, Kleber G. B.; Melo, Etelino F. de; Andrade, César A. S.; Melo, Celso P. de

2013-01-01

We report the synthesis of stable polyaniline nanoparticles (PANI N Ps) based on the chemical oxidative polymerization of aniline in aqueous solutions of surfactants. Surfactants of three different types—cationic (dodecyltrimethylammonium bromide—DTAB), anionic (sodium dodecyl sulfate—SDS), and non-ionic (Triton X-405–TX-405)—were used. The resulting PANI N Ps s urfactant samples were characterized through UV–Vis, fluorescence and Fourier transform infrared spectroscopies, and scanning electronic microscopy (SEM). We have verified that the color of the PANI N Ps s urfactant dispersions is affected by a change in the pH of the solution. The PANI-NPs s urfactant colloidal suspensions in aqueous solution present a surprising high fluorescence quantum yield value (ranging from 1.9 × 10 −3 to 6.9 × 10 −3 ) that can be controlled as a function of the pH, a fact that we associate to the corresponding protonation degree of the PANI polymeric chains. We suggest that these fluorescent nanocomposites can find important technological applications in different areas such as organic light emitting devices, biosensors, and pigments for coatings.

A simple protocol for the routine calibration of pH meters

Directory of Open Access Journals (Sweden)

A. FEDERMAN NETO

2009-01-01

Full Text Available

A simplified laboratory protocol for the calibration of pH meters is described and tested. It is based on the use of two analytical primary buffer solutions, potassium hydrogen phthalate and Borax (sodium tetraborate decahydrate of precisely known concentrations and pH. The solutions may be stored at room temperature for long periods, without decomposition and used directly. The calibration of the meter can be checked with standard solutions of sodium dihydrogen phosphate, sodium carbonate, sodium benzoate, sodium salicylate or potassium oxalate. Methods for the purification of Borax and potassium chloride are also given, and a new method for the neutralization of 0.9% saline is suggested. Keywords: pH meters (calibration; saline (0.9%; pH standards; potassium biphthalate; Borax.

Peroxidase activity in roots of arracacha affected by pH and temperature = Atividade da peroxidase em raízes de batata-baroa afetada pelo pH e temperatura

Directory of Open Access Journals (Sweden)

Luciana Nunes Menolli

2011-07-01

Full Text Available In this paper, roots of arracacha (Arracacia xanthorrhyza Bancroft were stored at 5ºC to induce chilling injury symptoms and stress-related peroxidase activity. Later, peroxidase kinetic activity was determined in different pH and temperature conditions. For this, soluble crude extract was sequentially saturated with ammonium sulfate, obtaining a semi-purified enzyme solution used for the analysis. Activity of peroxidase induced by the chilling at 5oC was determined from pH 2.5 to 9.0 and at temperature ranging from 10 to80oC. The peroxidase had higher activity when the reaction occurred between pH 5.5 and 6.0 and at temperature of 30oC. Complete inactivation of the activity was observed in pH 2.5 after 60 minutes of pre-incubation or at 60oC for 10 minutes or alternatively at 70oCafter 5 minutes of pre-incubation. The enzyme is more susceptible to inactivation in acid than alkaline pHs or alternatively using heat treatment.Neste trabalho, raízes de batata-baroa (Arracacia xanthorrhiza Bancroft foram armazenadas a 5oC para induzir injúria por frio e expressar atividade da peroxidase de estresse. Posteriormente, a cinética de atividade foi determinada em diferentes condições depHs e temperatura. Para isto, extrato solúvel da raiz foi sequencialmente saturado com sulfato de amônio, obtendo-se uma preparação semi-purificada para a análise enzimática. Atividade peroxidativa induzida pela temperatura de armazenamento de 5oC foideterminada em pHs de 2,5 a 9,0 e a temperaturas de 10 a 80oC. A atividade da peroxidase foi maior quando a reação foi realizada nos pHs de 5,5 e 6,0 e temperatura de 30oC. A inativação completa da enzima ocorreu em pH de 2,5 após 60 min. de pré-incubação ou a60oC por 10 min., e alternativamente a 70oC após 5 min. de pré-incubação. A enzima foi mais susceptível à inativação em pH ácido do que alcalino, podendo também ser inativada pelo tratamento de calor.

BSA-coated nanoparticles for improved SERS-based intracellular pH sensing.

Science.gov (United States)

Zheng, Xiao-Shan; Hu, Pei; Cui, Yan; Zong, Cheng; Feng, Jia-Min; Wang, Xin; Ren, Bin

2014-12-16

Local microenvironment pH sensing is one of the key parameters for the understanding of many biological processes. As a noninvasive and high sensitive technique, surface-enhanced Raman spectroscopy (SERS) has attracted considerable interest in the detection of the local pH of live cells. We herein develop a facile way to prepare Au-(4-MPy)-BSA (AMB) pH nanosensor. The 4-MPy (4-mercaptopyridine) was used as the pH sensing molecule. The modification of the nanoparticles with BSA not only provides a high sensitive response to pH changes ranging from pH 4.0 to 9.0 but also exhibits a high sensitivity and good biocompatibility, stability, and reliability in various solutions (including the solutions of high ionic strength or with complex composition such as the cell culture medium), both in the aggregation state or after long-term storage. The AMB pH nanosensor shows great advantages for reliable intracellular pH analysis and has been successfully used to monitor the pH distribution of live cells and can address the grand challenges in SERS-based pH sensing for practical biological applications.

Chapter A6. Section 6.4. pH

Science.gov (United States)

Wilde, Franceska D.; Busenberg, Eurybiades; Radtke, Dean B.

2006-01-01

Measurement of pH is critical to the understanding of the viability and vulnerability of environmental waters and is considered a master variable in determining the aqueous geochemistry of an aqueous system. pH is a measure that represents the hydrogen-ion concentration (activity) of a solution. This section of the National Field Manual (NFM) describes U.S. Geological Survey (USGS) guidance and protocols for measurement of pH in ground and surface waters.

O pH da calda de aplicação e a absorção de ácido giberélico por frutas de laranja cv. ‘Valência’ The solution pH on gibberellic acid uptake by cv. ‘Valência’ orange fruits

Directory of Open Access Journals (Sweden)

João Guilherme Casagrande Jr.

1999-10-01

different solution pH. The treatments consisted of 5 concentrations of gibberellic acid (0; 5; 10; 15; and 20 ppm and 3 pHs (3; 4.5; and 6. The aplication was made in May, when fruits were at green-yellow stage, and samples were collected every 30 days until November. The variables studied were coloration and thickness of the peel, total soluble solids (TSS, pH of juice, percent of juice, total acid (TA, ratio TSS/TA and technological index. The results obtained did not allow to conclude that gibberellic acid had any influence on the characteristics of the juice. The thickness of the peel was not affected by gibberellic acid. However, gibberellic acid caused a retaintion of the green color of the peel with increasing concentration, causing the fruits to remain greener. This was observed for all solution pHs. At pH 3, the fruits were greener than under the other pHs, and at the normal pH (4.5 The green coloration in the fruits persisted for a louger time than at pH=6, suggesting that acid pHs increase the uptake of gibberelic acid by the plants. It was also observed that gibberellic acid delayed the regreening of the fruits, what happens when the temperature becomes higher.

Effect of pH on boron adsorption in some soils of Paraná, Brazil

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Fábio Steiner

2013-06-01

Full Text Available Temporary B deficiency can be triggered by liming of acid soils because of increased B adsorption at higher soil pH. Plants respond directly to the activity of B in soil solution and only indirectly to B adsorbed on soil constituents. Because the range between deficient and toxic B concentration is relatively narrow, this poses difficulty in maintaining appropriate B levels in soil solution. Thus, knowledge of the chemical behavior of B in the soil is particularly important. The present study investigated the effect of soil pH on B adsorption in four soils of Paraná State, and to correlate these values with the physical and chemical properties of the soils. Surface samples were taken from a Rhodic Hapludox, Arenic Hapludalf, Arenic Hapludult, and one Typic Usthorthent. To evaluate the effect of pH on B adsorption, subsamples soil received the application of increasing rates of calcium carbonate. Boron adsorption was accomplished by shaking 2.0 g soil, for 24 h, with 20 mL of 0.01 mol L¹ NaCl solution containing different concentrations (0.0, 0.1, 0.2, 0.4, 0.8, 1.2, 1.6, 2.0, and 4.0 mg B L-1. Sorption was fitted to non-linear form of the Langmuir adsorption isotherm. Boron adsorption increased as concentration increased. Boron adsorption was dependent on soil pH, increasing as a function of pH in the range between 4.6 and 7.4, although the bonding energy has decreased. Maximum adsorption capacity (MAC of B was observed in the Arenic Hapludalf (49.8 mg B kg-1 soil followed by Arenic Hapludult (22.5 mg kg-1, Rhodic Hapludox (17.4 mg kg-1, and Typic Usthorthent (7.0 mg kg-1. The organic matter content, clay content, and aluminum oxide content (Al2O3 were the soils properties that affecting the B adsorption on Paraná soils.

Electrical Conductivity and Chemical Composition of Soil Solution: Comparison of Solution Samplers in Tropical Soils

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Davi Lopes do Carmo

2016-01-01

Full Text Available ABSTRACT Soil solution samplers may have the same working principle, but they differ in relation to chemical and physical characteristics, cost and handling, and these aspects exert influence on the chemical composition of the soil solution obtained. This study was carried out to evaluate, over time, the chemical composition of solutions extracted by Suolo Acqua, with the hydrophilic membrane (HM as a standard, using soils with contrasting characteristics, and to determine the relationship between electrical conductivity (EC and concentration of ions and pH of soil solution samples. This study was carried out under laboratory conditions, using three soils samples with different clay and organic matter (OM contents. Soil solution contents of F−, Cl−, NO−3, Br−, SO42−, Na+, NH4+, K+, Mg2+, Ca2+, were analyzed, as well as inorganic, organic, and total C contents, pH, and EC, in four successive sampling times. Soil solution chemical composition extracted by the Suolo Acqua sampler is similar to that collected by the HM, but the Suolo Acqua extracted more Na+ and soluble organic C than the HM solution. Solution EC, cation and anion concentrations, and soluble C levels are higher in the soil with greater clay and OM contents (Latossolo and Cambissolo in this case. Soil solution composition varied over time, with considerable changes in pH, EC, and nutrient concentrations, especially associated with soil OM. Thus, single and isolated sampling of the soil solution must be avoided, otherwise composition of the soil solution may not be correctly evaluated. Soil solution EC was regulated by pH, as well as the sum of cation and anion concentrations, and the C contents determined in the soil liquid phase.

Influence of pH on extracellular matrix preservation during lung decellularization.

Science.gov (United States)

Tsuchiya, Tomoshi; Balestrini, Jenna L; Mendez, Julio; Calle, Elizabeth A; Zhao, Liping; Niklason, Laura E

2014-12-01

The creation of decellularized organs for use in regenerative medicine requires the preservation of the organ extracellular matrix (ECM) as a means to provide critical cues for differentiation and migration of cells that are seeded onto the organ scaffold. The purpose of this study was to assess the influence of varying pH levels on the preservation of key ECM components during the decellularization of rat lungs. Herein, we show that the pH of the 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS)-based decellularization solution influences ECM retention, cell removal, and also the potential for host response upon implantation of acellular lung tissue. The preservation of ECM components, including elastin, fibronectin, and laminin, were better retained in the lower pH conditions that were tested (pH ranges tested: 8, 10, 12); glycosaminoglycans were preserved to a higher extent in the lower pH groups as well. The DNA content following decellularization of the rat lung was inversely correlated with the pH of the decellularization solution. Despite detectible levels of cyotoskeletal proteins and significant residual DNA, tissues decellularized at pH 8 demonstrated the greatest tissue architecture maintenance and the least induction of host response of all acellular conditions. These results highlight the effect of pH on the results obtained by organ decellularization and suggest that altering the pH of the solutions used for decellularization may influence the ability of cells to properly differentiate and home to appropriate locations within the scaffold, based on the preservation of key ECM components and implantation results.

No-core fiber-based highly sensitive optical fiber pH sensor.

Science.gov (United States)

Bhardwaj, Vanita; Pathak, Akhilesh Kumar; Singh, Vinod Kumar

2017-05-01

The present work describes the fabrication and characterization of an optical fiber pH sensor using a sol–gel technique. The sensing head configuration is incorporated using a short section of no-core fiber, coated with tetraethyl orthosilicate and spliced at the end of a single mode fiber with a bulge. Different types of indicators (bromophenol blue, cresol red, and chlorophenol red) were used to achieve a wide pH range from 2 to 13. High sensitivities of the fabricated device were found to be 1.02 and ? 0.93 ?? nm / pH for acidic and alkaline solutions, respectively. From the characterization results, it was noted that there is an impact of ionic strength and an effect of the temperature of liquid on the response characteristic, which is an advantage of the existing device over the other pH sensors. The fabricated sensor exhibited good reflection spectrum, indicating a blueshift in resonance wavelength for alkaline solutions and a redshift for acidic solutions.

Differential Sensor for PH Monitoring of Environmental Objects

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Romanenko Sergey

2016-01-01

Full Text Available Differential pH sensor is proposed. Reference electrode and measuring electrode are the same type. Reference electrode is immersed in standard buffer solution with known pH value. The differential pH sensor has longer service life as compared with the traditionally used sensors with silver chloride reference electrode. Ultrasonic cleaning system is proposed to clean the primary measuring transducer from pollution that form as result of silting during long-term operation with the sensor.

An electrochemical approach to monitor pH change in agar media during plant tissue culture.

Science.gov (United States)

Wang, Min; Ha, Yang

2007-05-15

In this work, metal oxide microelectrodes were developed to monitor pH change in agar media during plant tissue culture. An antimony wire was produced by a new approach "capillary melt method". The surface of the obtained antimony wire was oxidized in a potassium nitrate melt to fabricate an antimony oxide film for pH sensing. Characterization results show that the oxide layer grown on the wire surface consists of Sb(2)O(3) crystal phase. The sensing response, open-circuit potential, of the electrode has a good linear relationship (R(2)=1.00) with pH value of the test solution. Adding organic compounds into the test media would not affect the linear relationship, although the slope of the lines varied with different ingredients added. The antimony oxide electrodes were employed to continuously monitor pH change of agar culture media during a 2-week plant tissue culture of Dendrobium candidum. The antimony oxide electrode fabricated this way has the advantages of low cost, easy fabrication, fast response, and almost no contamination introduced into the system. It would be suitable for in situ and continuous pH measurement in many bio applications.

Adsorption of copper from the sulphate solution of low copper contents using the cationic resin Amberlite IR 120

International Nuclear Information System (INIS)

Jha, Manis Kumar; Nghiem Van Nguyen; Lee, Jae-chun; Jeong, Jinki; Yoo, Jae-Min

2009-01-01

In view of the increasing importance of the waste processing and recycling to meet the strict environmental regulations, the present investigation reports an adsorption process using the cationic exchanger Amberlite IR 120 for the recovery/removal of copper from the synthetic sulphate solution containing copper ≤0.7 mg/mL similar to the CMP waste effluent of electronic industry. Various process parameters, viz. contact time, solution pH, resin dose, and acid concentration of eluant were investigated for the adsorption of copper from the effluents. The 99.99% copper was found to be adsorbed from the sulphate solution containing copper 0.3-0.7 mg/mL of solution (feed pH 5) at A/R ratio 100 and eq. pH 2.5 in contact time 14 min. The mechanism for the adsorption of copper was found to follow Langmuir isotherm and second order rate. From the loaded organic, copper was eluted effectively by 1.8 M sulphuric acid at A/R ratio 25. The raffinate obtained after the recovery copper could be disposed safely without affecting the environment.

Complexing agents and pH influence on chemical durability of type I moulded glass containers.

Science.gov (United States)

Biavati, Alberto; Poncini, Michele; Ferrarini, Arianna; Favaro, Nicola; Scarpa, Martina; Vallotto, Marta

2017-06-16

Among the factors that affect the glass surface chemical durability, pH and complexing agents presence in aqueous solution have the main role (1). Glass surface attack can be also related to the delamination issue with glass particles appearance in the pharmaceutical preparation. A few methods to check for glass containers delamination propensity and some control guidelines have been proposed (2,3). The present study emphasizes the possible synergy between a few complexing agents with pH on the borosilicate glass chemical durability. Hydrolytic attack was performed in small volume 23 ml type I glass containers autoclaved according to EP or USP for 1 hour at 121°C, in order to enhance the chemical attack due to time, temperature and the unfavourable surface/volume ratio. 0,048 M or 0.024 M (moles/liter) solutions of the acids citric, glutaric, acetic, EDTA (ethylenediaminetetraacetic acid) and sodium phosphate with water for comparison, were used for the trials. The pH was adjusted ± 0,05 units at fixed values 5,5-6,6-7-7,4-8-9 by LiOH diluted solution. Since silicon is the main glass network former, silicon release into the attack solutions was chosen as the main index of the glass surface attack and analysed by ICPAES. The work was completed by the analysis of the silicon release in the worst attack conditions, of moulded glass, soda lime type II and tubing borosilicate glass vials to compare different glass compositions and forming technologies. Surface analysis by SEM was finally performed to check for the surface status after the worst chemical attack condition by citric acid. Copyright © 2017, Parenteral Drug Association.

Colorimetric study of malvidin-3-O-glucoside copigmented by phenolic compounds: The effect of molar ratio, temperature, pH, and ethanol content on color expression of red wine model solutions.

Science.gov (United States)

Zhang, Bo; Yang, Xue-Shan; Li, Ning-Ning; Zhu, Xia; Sheng, Wen-Jun; He, Fei; Duan, Chang-Qing; Han, Shun-Yu

2017-12-01

In the recent research, the copigmentations of malvidin-3-O-glucoside with eight types of phenolic copigments have been investigated. The influence of the pigment/copigment molar ratio, the reaction temperature, the pH and the ethanol content of solutions has been examined. The results showed that the copigmentation effect was dependent on not only the particular structures of the phenolic compounds but also the factors of the reaction systems. The increase of the copigment concentration can strengthen the copigmentation effect, improve the solution color, and enhance the red-purple features. Different temperatures had different influences on the copigmentation reactions. The destruction of the copigmentation complexes can result in the hypsochromic shift of the reaction solution when the temperature was higher than 20°C. The bathochromic shift of the solution gradually progressed with the increase of the pH value. A significant copigmentation feature was spotted when pH reached 3.0, which demonstrates obvious red-purple characterization. The addition of the ethanol weakened the copigmentation effect. According to measurement through color analysis, it was found that the color differences caused by ethanol in red wine were typically attributed to quantitative changes. Remarkably, all of the above delicate color deviations caused by the structural or environmental factors can be precisely and conveniently depicted via the CIELAB space analysis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Spectrophotometric Determination of Chromium (III) in Egyptian 11 manite from phosphate solution using Ewes as a selective adsorbent

International Nuclear Information System (INIS)

Abdu, A. A.

2012-12-01

Egyptian white sand (EWS) was used as an adsorbent for the selective separation of Cr(III) from phosphate solution to be determined colorimetrically using 1,5-diphenylcarbazide. The experimental factors affecting maximum selective adsorption/desorption of Cr(III) on / from EWS were the amount of adsorption (g), pH of initial concentration of Cr(III) in solution, contact time temperature and initial concentration of Cr(III) in solution were investigated. No effect of [PO 4 ] 3- , Ti(IV) and Fe(III) on Cr(III) sorption were verified. Accuracy and relative standard deviations (RSD) were acceptable for all analyses. The maximum sorption capacity, Q e , of adsorbed Cr(III) per gram of sand was 93.5 mg/g, at EWS concentration 20 g/1, pH 0.8 contact time 120 min and temperature 30 o C for adsorption of Cr(III) on EWS and pH 0.4, contact time 6 min and temperature 25o C for desorption of Cr(III) from EWS. (Author)

pH dependent green synthesis of gold nanoparticles by completely C6-carboxylated curdlan under high temperature and various pH conditions.

Science.gov (United States)

Qiu, Wen-Yi; Wang, Kai; Wang, Yao-Yao; Ding, Zhi-Chao; Wu, Li-Xia; Cai, Wu-Dan; Yan, Jing-Kun

2018-01-01

A C6-carboxylated curdlan (C6-Cc) obtained from 4-acetamido-TEMPO-mediated oxidation of curdlan was used both as a reducing and stabilizing agent for green synthesis of pH-responsive AuNPs, which was carried out by controlling the pH of the C6-Cc solution at a high temperature (100°C). C6-Cc presented a semi-flexible random coil chain in the aqueous medium at pH 5.5 and became more expanded and rigid in alkaline conditions (pH 7.1-12.0), though the primary chemical structure of C6-Cc was virtually unchanged with the pH variation. The AuNPs prepared with C6-Cc at various pHs were characterized by various instrumental measurements. The shapes and sizes of AuNPs were found to be strongly dependent on the pH of the C6-Cc solution. The C6-Cc-decorated AuNPs exhibited a more well-dispersed spherical morphology with smaller particle sizes under alkaline conditions (pH 7.1-12.0). Through this study, a facile, simple, and green method has been demonstrated for preparation of stimuli-sensitive AuNPs using biocompatible polyanionic polysaccharides. Copyright © 2017 Elsevier B.V. All rights reserved.

Biological and analytical studies of peritoneal dialysis solutions

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N. Hudz

2018-04-01

Full Text Available The purpose of our work was to conduct biological and analytical studies of the peritoneal dialysis (PD solutions containing glucose and sodium lactate and establish correlations between cell viability of the Vero cell line and values of analytical indexes of the tested solutions. The results of this study confirm the cytotoxicity of the PD solutions even compared with the isotonic solution of sodium chloride, which may be due to the low pH of the solutions, presence of glucose degradation products (GDPs and high osmolarity of the solutions, and unphysiological concentrations of glucose and sodium lactate. However, it is not yet known what factors or their combination and to what extent cause the cytotoxicity of PD solutions. In the neutral red (NR test the weak, almost middle (r = -0.496 and 0.498, respectively and unexpected correlations were found between reduced viability of monkey kidney cells and increased pH of the PD solutions and between increased cell viability and increased absorbance at 228 nm of the tested PD solutions. These two correlations can be explained by a strong correlation (r = -0.948 between a decrease in pH and an increase in the solution absorbance at 228 nm. The opposite effect was observed in the MTT test. The weak, but expected correlations (r = 0.32 and -0.202, respectively were found between increased cell viability and increased pH in the PD solutions and between decreased cell viability and increased absorbance at 228 nm of the tested PD solutions. The middle and weak correlations (r = 0.56 and 0.29, respectively were detected between increased cell viability and increased lactate concentration in the NR test and MTT test. The data of these correlations can be partially explained by the fact that a correlation with a coefficient r = -0.34 was found between decreased pH in the solutions and increased lactate concentration. The very weak correlations (0.138 and 0.196, respectively were found between increased cell

Electrochemical characteristics of bioresorbable binary MgCa alloys in Ringer's solution: Revealing the impact of local pH distributions during in-vitro dissolution

Energy Technology Data Exchange (ETDEWEB)

Mareci, D., E-mail: danmareci@yahoo.com [Faculty of Chemical Engineering and Environmental Protection, The “Gheorghe Asachi” Technical University of Iasi, 700050, Iasi (Romania); Bolat, G. [Faculty of Chemical Engineering and Environmental Protection, The “Gheorghe Asachi” Technical University of Iasi, 700050, Iasi (Romania); Izquierdo, J. [Department of Chemistry, University of La Laguna, P.O. Box 456, E-38200 La Laguna (Tenerife) (Spain); Crimu, C.; Munteanu, C. [Faculty of Mechanical Engineering, The “Gheorghe Asachi” Technical University of Iasi, 700050, Iasi (Romania); Antoniac, I. [Faculty of Materials Science and Engineering, Politehnica of Bucharest, 060042 Bucharest (Romania); Souto, R.M., E-mail: rsouto@ull.es [Department of Chemistry, University of La Laguna, P.O. Box 456, E-38200 La Laguna (Tenerife) (Spain); Faculty of Materials Science and Engineering, Politehnica of Bucharest, 060042 Bucharest (Romania)

2016-03-01

Biodegradable magnesium–calcium (MgCa) alloy is a very attractive biomaterial. Two MgCa alloys below the solid solubility of Ca were considered, as to solely investigate the effect of Ca content on the behavior of magnesium and the pH changes associated to metal dissolution. X-ray diffraction analysis and optical microscopy showed that both Mg–0.63Ca and Mg–0.89Ca alloys were solely composed of α(Mg) phase. Degradation characteristics and electrochemical characterization of MgCa alloys were investigated during exposure to Ringer's solution at 37 °C by electrochemical impedance spectroscopy and scanning electrochemical microscopy. The impedance behavior showed both capacitive and inductive features that are related to the alloy charge transfer reaction and the relaxation of the absorbed corrosion compounds, and can be described in terms of an equivalent circuit. Scanning electron microscopy (SEM) was employed to view the surface morphology of the MgCa samples after 1 week immersion in Ringer's solution showing extensive precipitation of corrosion products, whereas the substrate shows evidence of a non-uniform corrosion process. Energy dispersive analysis showed that the precipitates contained oxygen, calcium, magnesium and chlorine, and the Mg:Ca ratios were smaller than in the alloys. Scanning electrochemical microscopy (SECM) was used to visualize local pH changes associated to these physicochemical processes with high spatial resolution. The occurrence of pH variations in excess of 3 units between anodic and cathodic half-cell reactions was monitored in situ. - Highlights: • Spontaneous degradation of MgCa alloys in Ringer's solution characterized at 37 °C • Reactivity differences between Mg0.63Ca and Mg0.89Ca are evidenced using multiscale electrochemical characterization. • Electrochemical activation occurs heterogeneously on the alloy surface. • Metal dissolution is accompanied by local pH changes. • Mg0.63Ca degrades faster

Effects of pH and chloride concentration on pitting corrosion of AA6061 aluminum alloy

International Nuclear Information System (INIS)

Zaid, B.; Saidi, D.; Benzaid, A.; Hadji, S.

2008-01-01

Effects of pH solution and chloride (Cl - ) ion concentration on the corrosion behaviour of alloy AA6061 immersed in aqueous solutions of NaCl have been investigated using measurements of weight loss, potentiodynamic polarisation, linear polarisation, cyclic polarisation experiment combined with open circuit potential transient technique and optical or scanning electron microscopy. The corrosion behaviour of the AA6061 aluminum alloy was found to be dependant on the pH and chloride concentration [NaCl] of solution. In acidic or slightly neutral solutions, general and pitting corrosion occurred simultaneously. In contrast, exposure to alkaline solutions results in general corrosion. Experience revealed that the alloy AA6061 was susceptible to pitting corrosion in all chloride solution of concentration ranging between 0.003 wt% and 5.5 wt% NaCl and an increase in the chloride concentration slightly shifted both the pitting E pit and corrosion E cor potentials to more active values. In function of the conditions of treatment, the sheets of the alloy AA6061 undergo two types of localised corrosion process, leading to the formation of hemispherical and crystallographic pits. Polarisation resistance measurements in acidic (pH = 2) and alkaline chloride solutions (pH = 12) which are in good agreement with those of weight loss, show that the corrosion kinetic is minimised in slightly neutral solutions (pH = 6)

Influence of oxidation state on the pH dependence of hydrous iridium oxide films

International Nuclear Information System (INIS)

Steegstra, Patrick; Ahlberg, Elisabet

2012-01-01

Many electrochemical reactions taking place in aqueous solution consume or produce protons. The pH in the diffusion layer can therefore be significantly altered during the reaction and there is a need for in situ pH measurements tracing this near surface pH. In the present paper the rotating ring disc technique was used to measure near surface pH changes during oxygen reduction, utilising hydrous iridium oxide as the pH sensing probe. Before such experiments a good understanding of the pH sensing properties of these films is required and the impact of the oxidation state of the film on the pH sensing properties was investigated as well as the influence of solution redox species. The pH sensitivity (depicted by dE/dpH) was found to depend on the average oxidation state of the film in a manner resembling the cyclic voltammetry response. In all cases the pH response is “supernernstian” with more than one proton per electron. The origin of this behaviour is discussed in the context of acid-base properties of the film and the existence of both hydrous and anhydrous oxide phases. The pH response depends also on the redox properties of the solution but can be optimised for various purposes by conditioning the film at different potentials. This was clearly illustrated by adding hydrogen peroxide, an intermediate in the oxygen reduction reaction, to the solution. It was shown that hydrous iridium oxide can be used as a reliable in situ pH sensor provided that care is taken to optimise the oxidation state of the film.

An empirical model for parameters affecting energy consumption in boron removal from boron-containing wastewaters by electrocoagulation

Energy Technology Data Exchange (ETDEWEB)

Yilmaz, A. Erdem [Atatuerk University, Faculty of Engineering, Department of Environmental Engineering, 25240 Erzurum (Turkey)]. E-mail: aerdemy@atauni.edu.tr; Boncukcuoglu, Recep [Atatuerk University, Faculty of Engineering, Department of Environmental Engineering, 25240 Erzurum (Turkey); Kocakerim, M. Muhtar [Atatuerk University, Faculty of Engineering, Department of Chemical Engineering, 25240 Erzurum (Turkey)

2007-06-01

In this study, it was investigated parameters affecting energy consumption in boron removal from boron containing wastewaters prepared synthetically, via electrocoagulation method. The solution pH, initial boron concentration, dose of supporting electrolyte, current density and temperature of solution were selected as experimental parameters affecting energy consumption. The obtained experimental results showed that boron removal efficiency reached up to 99% under optimum conditions, in which solution pH was 8.0, current density 6.0mA/cm{sup 2}, initial boron concentration 100mg/L and solution temperature 293K. The current density was an important parameter affecting energy consumption too. High current density applied to electrocoagulation cell increased energy consumption. Increasing solution temperature caused to decrease energy consumption that high temperature decreased potential applied under constant current density. That increasing initial boron concentration and dose of supporting electrolyte caused to increase specific conductivity of solution decreased energy consumption. As a result, it was seen that energy consumption for boron removal via electrocoagulation method could be minimized at optimum conditions. An empirical model was predicted by statistically. Experimentally obtained values were fitted with values predicted from empirical model being as following;[ECB]=7.6x10{sup 6}x[OH]{sup 0.11}x[CD]{sup 0.62}x[IBC]{sup -0.57}x[DSE]{sup -0.}= {sup 04}x[T]{sup -2.98}x[t] Unfortunately, the conditions obtained for optimum boron removal were not the conditions obtained for minimum energy consumption. It was determined that support electrolyte must be used for increase boron removal and decrease electrical energy consumption.

An empirical model for parameters affecting energy consumption in boron removal from boron-containing wastewaters by electrocoagulation

International Nuclear Information System (INIS)

Yilmaz, A. Erdem; Boncukcuoglu, Recep; Kocakerim, M. Muhtar

2007-01-01

In this study, it was investigated parameters affecting energy consumption in boron removal from boron containing wastewaters prepared synthetically, via electrocoagulation method. The solution pH, initial boron concentration, dose of supporting electrolyte, current density and temperature of solution were selected as experimental parameters affecting energy consumption. The obtained experimental results showed that boron removal efficiency reached up to 99% under optimum conditions, in which solution pH was 8.0, current density 6.0mA/cm 2 , initial boron concentration 100mg/L and solution temperature 293K. The current density was an important parameter affecting energy consumption too. High current density applied to electrocoagulation cell increased energy consumption. Increasing solution temperature caused to decrease energy consumption that high temperature decreased potential applied under constant current density. That increasing initial boron concentration and dose of supporting electrolyte caused to increase specific conductivity of solution decreased energy consumption. As a result, it was seen that energy consumption for boron removal via electrocoagulation method could be minimized at optimum conditions. An empirical model was predicted by statistically. Experimentally obtained values were fitted with values predicted from empirical model being as following;[ECB]=7.6x10 6 x[OH] 0.11 x[CD] 0.62 x[IBC] -0.57 x[DSE] -0.04 x[T] -2.98 x[t] Unfortunately, the conditions obtained for optimum boron removal were not the conditions obtained for minimum energy consumption. It was determined that support electrolyte must be used for increase boron removal and decrease electrical energy consumption.

Removing Phosphorus from Aqueous Solutions Using Lanthanum Modified Pine Needles.

Directory of Open Access Journals (Sweden)

Xianze Wang

Full Text Available The renewable pine needles was used as an adsorbent to remove phosphorus from aqueous solutions. Using batch experiments, pine needles pretreated with alkali-isopropanol (AI failed to effectively remove phosphorus, while pine needles modified with lanthanum hydroxide (LH showed relatively high removal efficiency. LH pine needles were effective at a wide pH ranges, with the highest removal efficiency reaching approximately 85% at a pH of 3. The removal efficiency was kept above 65% using 10 mg/L phosphorus solutions at desired pH values. There was no apparent significant competitive behavior between co-existing anions of sulfate, nitrate, and chloride (SO4(2-, NO3(- and Cl(-; however, CO3(2- exhibited increased interfering behavior as concentrations increased. An intraparticle diffusion model showed that the adsorption process occurred in three phases, suggesting that a boundary layer adsorption phenomena slightly affected the adsorption process, and that intraparticle diffusion was dominant. The adsorption process was thermodynamically unfavorable and non-spontaneous; temperature increases improved phosphorus removal. Total organic carbon (TOC assays indicated that chemical modification reduced the release of soluble organic compounds from 135.6 mg/L to 7.76 mg/L. This new information about adsorption performances provides valuable information, and can inform future technological applications designed to remove phosphorus from aqueous solutions.

Effect of Sulfur Concentration and PH Conditions on Akaganeite Formation: Understanding Akaganeite Formation Conditions in Yellowknife Bay, Gale Crater, Mars

Science.gov (United States)

Fox, A.; Peretyazhko, T.; Sutter, B.; Niles, P.; Ming, D. W.; Morris, R. V.

2015-01-01

The Chemistry and Mineralogy Instrument (CHEMIN) on board the Mars Science Laboratory (MSL) Curiosity Rover identified minor amounts of akaganeite (beta-FeOOH) at Yellowknife Bay, Mars. There is also evidence for akaganeite at other localities on Mars from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). Akaganeite is an iron(III) hydroxide with a hollandite- like structure and Cl in its tunnels. Terrestrial akaganeite usually forms in Cl-rich environments under acidic, oxidizing conditions. Previous studies of akaganeite have revealed that akaganeite formation is affected by the presence of sulfate (hereafter denoted as S. The prediction of circumneutral pH coupled with the detection of S at Yellowknife Bay dictate that work is needed to determine how S and pH together affect akaganeite formation. The goal of this work is to study how changes in both S concentration and pH influence akaganeite precipitation. Akaganeite formation was investigated at S/Cl molar ratios of 0, 0.017, 0.083, 0.17 and 0.33 at pH 1.5, 2, and 4. Results are anticipated to provide combined S concentration and pH constraints on akaganeite formation in Yellowknife Bay and elsewhere on Mars. Knowledge of solution pH and S concentrations can be utilized in understanding microbial habitability potential on the Martian surface.

Passive behaviour of alloy corrosion-resistant steel Cr10Mo1 in simulating concrete pore solutions with different pH

International Nuclear Information System (INIS)

Ai, Zhiyong; Jiang, Jinyang; Sun, Wei; Song, Dan; Ma, Han; Zhang, Jianchun; Wang, Danqian

2016-01-01

Highlights: • A new alloy corrosion-resistant steel Cr10Mo1 is developed for reinforcing rebar of concrete in severe environments. • The effects of pH on the passive behaviour of Cr10Mo1 steel compared with plain carbon steel were studied systematically by electrochemical techniques and surface analysis. • The mechanism for self-reinforcing passivity against carbonation of the corrosion-resistant steel is revealed. - Abstract: The passive behaviour of new alloy corrosion-resistant steel Cr10Mo1 and plain carbon steel (as a comparison) in simulating concrete pore solutions of different pH (ranging from 13.5 to 9.0) under open circuit potential conditions, was evaluated by various electrochemical techniques: potentiodynamic polarization, capacitance measurements and electrochemical impedance spectroscopy. The chemical composition and structure of passive films were investigated by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). The electrochemical responses of passive films show that Cr10Mo1 steel has an increasing passivity with pH decreasing while carbon steel dose conversely, revealing carbonation does no negative effect on passivation of the corrosion-resistant steel. SIMS reveals that the passive film on the corrosion-resistant steel presents a bilayer structure: an outer layer mainly consisting of Fe oxides and hydroxides, and an inner layer enriched in Cr species, while only a Fe-concentrated layer for carbon steel. According to the XPS analysis results, as the pH decreases, more stable and protective Cr oxides are enriched in the film on Cr10Mo1 steel while Fe oxides gradually decompose. Higher content of Cr oxides in the film layer provides Cr10Mo1 corrosion-resistant steel more excellent passivity at lower pH.

Passive behaviour of alloy corrosion-resistant steel Cr10Mo1 in simulating concrete pore solutions with different pH

Energy Technology Data Exchange (ETDEWEB)

Ai, Zhiyong, E-mail: 230139452@seu.edu.cn [School of Materials Science and Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Jiangsu Key Laboratory of Construction Materials, Nanjing 211189, Jiangsu (China); Jiang, Jinyang, E-mail: jiangjinyang16@163.com [School of Materials Science and Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Jiangsu Key Laboratory of Construction Materials, Nanjing 211189, Jiangsu (China); Sun, Wei, E-mail: sunwei@seu.edu.cn [School of Materials Science and Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Jiangsu Key Laboratory of Construction Materials, Nanjing 211189, Jiangsu (China); Song, Dan, E-mail: songdancharls@hhu.edu.cn [School of Materials Science and Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Jiangsu Key Laboratory of Construction Materials, Nanjing 211189, Jiangsu (China); College of Mechanics and Materials, Hohai University, Nanjing 210098, Jiangsu (China); Ma, Han, E-mail: mahan-iris@shasteel.cn [Research Institute of Jiangsu Shasteel Iron and Steel, Zhangjiagang 215625, Jiangsu (China); Zhang, Jianchun, E-mail: Zhangjc-iris@shasteel.cn [Research Institute of Jiangsu Shasteel Iron and Steel, Zhangjiagang 215625, Jiangsu (China); Wang, Danqian, E-mail: wonderbaba@126.com [School of Materials Science and Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Jiangsu Key Laboratory of Construction Materials, Nanjing 211189, Jiangsu (China)

2016-12-15

Highlights: • A new alloy corrosion-resistant steel Cr10Mo1 is developed for reinforcing rebar of concrete in severe environments. • The effects of pH on the passive behaviour of Cr10Mo1 steel compared with plain carbon steel were studied systematically by electrochemical techniques and surface analysis. • The mechanism for self-reinforcing passivity against carbonation of the corrosion-resistant steel is revealed. - Abstract: The passive behaviour of new alloy corrosion-resistant steel Cr10Mo1 and plain carbon steel (as a comparison) in simulating concrete pore solutions of different pH (ranging from 13.5 to 9.0) under open circuit potential conditions, was evaluated by various electrochemical techniques: potentiodynamic polarization, capacitance measurements and electrochemical impedance spectroscopy. The chemical composition and structure of passive films were investigated by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). The electrochemical responses of passive films show that Cr10Mo1 steel has an increasing passivity with pH decreasing while carbon steel dose conversely, revealing carbonation does no negative effect on passivation of the corrosion-resistant steel. SIMS reveals that the passive film on the corrosion-resistant steel presents a bilayer structure: an outer layer mainly consisting of Fe oxides and hydroxides, and an inner layer enriched in Cr species, while only a Fe-concentrated layer for carbon steel. According to the XPS analysis results, as the pH decreases, more stable and protective Cr oxides are enriched in the film on Cr10Mo1 steel while Fe oxides gradually decompose. Higher content of Cr oxides in the film layer provides Cr10Mo1 corrosion-resistant steel more excellent passivity at lower pH.

REMOVAL OF ASTROZON RED FROM AQUEOUS SOLUTIONS BY THE ADSORBENTS PRODUCED FROM LIGNITE COAL

Directory of Open Access Journals (Sweden)

Mehmet MAHRAMANLIOĞLU

2002-01-01

Full Text Available The adsorption of Astrozone Red on the activated coal from aqueous solutions was studied.The adsorption process followed the Lagergren first order kinetics equation. The adsorbent concentration affected the adsorption of Astrozone Red significiantly.The equilibrium data fit well in the Langmuir model and isotherm constants were calculated. The adsorption of Astrozon Red increased with increase of the pH value in the solution.The thermodynamics of adsorption indicated spontaneous and exothermic nature of the process.

Formation of Hg(II) Tetrathiolate Complexes with Cysteine at Neutral pH.

Science.gov (United States)

Warner, Thomas; Jalilehvand, Farideh

2016-04-01

Mercury(II) ions precipitate from aqueous cysteine (H 2 Cys) solutions containing H 2 Cys/Hg(II) mole ratio ≥ 2.0 as Hg( S -HCys) 2 . In absence of additional cysteine, the precipitate dissolves at pH ~12 with the [Hg( S,N -Cys) 2 ] 2- complex dominating. With excess cysteine (H 2 Cys/Hg(II) mole ratio ≥ 4.0), higher complexes form and the precipitate dissolves at lower pH values. Previously, we found that tetrathiolate [Hg( S -Cys) 4 ] 6- complexes form at pH = 11.0; in this work we extend the investigation to pH values of physiological interest. We examined two series of Hg(II)-cysteine solutions in which C Hg(II) varied between 8 - 9 mM and 80 - 100 mM, respectively, with H 2 Cys/Hg(II) mole ratios from 4 to ~20. The solutions were prepared in the pH range 7.1 - 8.8, at the pH at which the initial Hg( S -HCys) 2 precipitate dissolved. The variations in the Hg(II) speciation were followed by 199 Hg NMR, X-ray absorption and Raman spectroscopic techniques. Our results show that in the dilute solutions ( C Hg(II) = 8 - 9 mM), mixtures of di-, tri- (major) and tetrathiolate complexes exist at moderate cysteine excess ( C H2Cys ~ 0.16 M) at pH 7.1. In the more concentrated solutions ( C Hg(II) = 80 - 100 mM) with high cysteine excess ( C H2Cys > 0.9 M), tetrathiolate [Hg( S -cysteinate) 4 ] m -6 ( m = 0 - 4) complexes dominate in the pH range 7.3 - 7.8, with lower charge than for the [Hg( S -Cys) 4 ] 6- complex due to protonation of some ( m ) of the amino groups of the coordinated cysteine ligands. The results of this investigation could provide a key to the mechanism of biosorption and accumulation of Hg(II) ions in biological / environmental systems.

Solution chemistry of lanthanide complexes

International Nuclear Information System (INIS)

Brittain, H.G.

1979-01-01

Intermolecular energy transfer from Tb 3+ to Eu 3+ , luminescence intensity measurements, potentiometric titrations, differential absorption spectroscopy, and spectroscopic titrations were all used to study the binding of lanthanide ions by serine and threonine. At low pH (3.0 to 6.0) the complexes are mononuclear and ligand is only weakly bound. In the pH interval of 6.0 to 8.5 stronger interaction takes place between the ligand and the metal (with possible coordination of the undissociated hydroxyl group), and self-association of complexes becomes important. Above pH 8.5, base hydrolysis of the complexes leads to highly associated species in solution and shortly above this pH an insoluble precipitate is formed. It was found that energy could be transferred from Tb 3+ to Eu 3+ more efficiently among complexes prepared from racemic ligands than in complexes made from resolved ligand, but this stereoselectivity was only observed at pH values greater than 6.5 and in solutions having a 1:10 ratio of metal-to-ligand. No stereoselectivity was found in solutions having 1:5 ratios, and this observation was explained by the existence of 1:2 metal-ligand complexes existing in solutions having the higher ratio of metal-to-ligand (only 1:1 complexes are then found at lower ratios of metal-to-ligand). (author)

Reclamation of cadmium-contaminated soil using dissolved organic matter solution originating from wine-processing waste sludge

International Nuclear Information System (INIS)

Liu, Cheng-Chung; Chen, Guan-Bu

2013-01-01

Highlights: ► Increases in acidity, washing frequency, and operational temperature enhance the Cd removal. ► Approximately 80% of Cd can be removed from the soil by dissolved organic matter (DOM) washing. ► The DOM washing can moderate the loss of soil fertility. ► The DOM washing will have a great improvement if we employ NaOH, KOH, Ca(OH) 2 , and Mg(OH) 2 to prepare the DOM solution together. -- Abstract: Soil washing using an acid solution is a common practice for removing heavy metals from contaminated soil in Taiwan. However, serious loss of nutrients from soil is a major drawback of the washing. Distillery sludge can be used to prepare a dissolved organic matter (DOM) solution by extracting its organic constituents with alkaline solutions. This study employed DOM solutions to remediate Cd-contaminated soil (with concentrations up to 21.5 mg kg −1 ) and determine the factors affecting removal of Cd, such as pH, initial concentration of DOM solution, temperature, and washing frequency. When washing with pH 3.0 and 1250 mg L −1 DOM solution, about 80% and 81% of Cd were removed from the topsoil at 27 °C and subsoil at 40 °C, respectively. To summarize the changes in fertility during DOM washing with various pH solutions: the increase in organic matter content ranged from 7.7% to 23.7%; cation exchange capacity (CEC) ranged from 4.6% to 13.9%; available ammonium (N-NH 4 ) content ranged from 39.4% to 2175%; and available phosphorus content ranged from 34.5% to 182%. Exchangeable K, Ca, and Mg remained in the topsoil after DOM washing, with concentrations of 1.1, 2.4, and 1.5 times higher than those treated with HCl solution at the same pH, respectively

Reclamation of cadmium-contaminated soil using dissolved organic matter solution originating from wine-processing waste sludge

Energy Technology Data Exchange (ETDEWEB)

Liu, Cheng-Chung, E-mail: ccliu@niu.edu.tw [Department of Environmental Engineering, National Ilan University, Ilan, 260, Taiwan (China); Chen, Guan-Bu [Department of Environmental Engineering, National Ilan University, Ilan, 260, Taiwan (China)

2013-01-15

Highlights: ► Increases in acidity, washing frequency, and operational temperature enhance the Cd removal. ► Approximately 80% of Cd can be removed from the soil by dissolved organic matter (DOM) washing. ► The DOM washing can moderate the loss of soil fertility. ► The DOM washing will have a great improvement if we employ NaOH, KOH, Ca(OH){sub 2}, and Mg(OH){sub 2} to prepare the DOM solution together. -- Abstract: Soil washing using an acid solution is a common practice for removing heavy metals from contaminated soil in Taiwan. However, serious loss of nutrients from soil is a major drawback of the washing. Distillery sludge can be used to prepare a dissolved organic matter (DOM) solution by extracting its organic constituents with alkaline solutions. This study employed DOM solutions to remediate Cd-contaminated soil (with concentrations up to 21.5 mg kg{sup −1}) and determine the factors affecting removal of Cd, such as pH, initial concentration of DOM solution, temperature, and washing frequency. When washing with pH 3.0 and 1250 mg L{sup −1} DOM solution, about 80% and 81% of Cd were removed from the topsoil at 27 °C and subsoil at 40 °C, respectively. To summarize the changes in fertility during DOM washing with various pH solutions: the increase in organic matter content ranged from 7.7% to 23.7%; cation exchange capacity (CEC) ranged from 4.6% to 13.9%; available ammonium (N-NH{sub 4}) content ranged from 39.4% to 2175%; and available phosphorus content ranged from 34.5% to 182%. Exchangeable K, Ca, and Mg remained in the topsoil after DOM washing, with concentrations of 1.1, 2.4, and 1.5 times higher than those treated with HCl solution at the same pH, respectively.

Adsorption of Remazol Black 5 from aqueous solution by the templated crosslinked-chitosans

International Nuclear Information System (INIS)

Chen, Arh-Hwang; Huang, Yao-Yi

2010-01-01

The templated crosslinked-chitosan microparticles prepared using the imprinting method with the Remazol Black5 (RB5) dye as a template, epichlorohydrin (ECH) as a crosslinker, and sodium hydroxide (NaOH) solution used for the microparticle formation showed the highest adsorption capacity for the RB5 dye compared with those that used other methods with or without a template, three crosslinkers, and two microparticle formations. The results showed that the adsorption of the RB5 dye on the microparticles was affected by the microparticle size, the initial dye concentration, the initial pH value, as well as the temperature. Both kinetics and thermodynamic parameters of the adsorption process were estimated. These data indicated an exothermic spontaneous adsorption process that kinetically followed the second-order adsorption process. Equilibrium experiments fitted well the Langmuir isotherm model, and the maximum monolayer adsorption capacity for the RB5 dye was 2941 mg/g. The competition study showed that the adsorption of the RB5 dye on the microparticles in the mixture solution was much less affected by the existence of the 3R dye than the other way around. Furthermore, the microparticles could be regenerated through the desorption of the dye in pH 10.0 of NaOH solution and could be reused to adsorb the dye again.

Pyrite oxidation at circumneutral pH

Science.gov (United States)

Moses, Carl O.; Herman, Janet S.

1991-02-01

Previous studies of pyrite oxidation kinetics have concentrated primarily on the reaction at low pH, where Fe(III) has been assumed to be the dominant oxidant. Studies at circumneutral pH, necessitated by effective pH buffering in some pyrite oxidation systems, have often implicitly assumed that the dominant oxidant must be dissolved oxygen (DO), owing to the diminished solubility of Fe(III). In fact, Fe(III)(aq) is an effective pyrite oxidant at circumneutral pH, but the reaction cannot be sustained in the absence of DO. The purpose of this experimental study was to ascertain the relative roles of Fe(III) and DO in pyrite oxidation at circumneutral pH. The rate of pyrite oxidation was first-order with respect to the ratio of surface area to solution volume. Direct determinations of both Fe(II) (aq)> and Fe(III) (aq) demonstrated a dramatic loss of Fe(II) from the solution phase in excess of the loss for which oxidation alone could account. Based on rate data, we have concluded that Fe(II) is adsorbed onto the pyrite surface. Furthermore, Fe(II) is preferred as an adsorbate to Fe(III), which we attribute to both electrostatic and acid-base selectivity. We also found that the rate of pyrite oxidation by either Fe(III) (aq) or DO is reduced in the presence of aqueous Fe(II), which leads us to conclude that, under most natural conditions, neither Fe(III) (aq) nor DO directly attacks the pyrite surface. The present evidence suggests a mechanism for pyrite oxidation that involves adsorbed Fe( II ) giving up electrons to DO and the resulting Fe(III) rapidly accepting electrons from the pyrite. The adsorbed Fe is, thus, cyclically oxidized and reduced, while it acts as a conduit for electrons traveling from pyrite to DO. Oxygen is transferred from the hydration sphere of the adsorbed Fe to pyrite S. The cycle of adsorbed Fe oxidation and reduction and the successive addition of oxygen to pyrite S continues until a stable sulfoxy species dissociates from the surface. Prior

Adsorption and colloidal behaviour of carrier-free 7Be in aqueous solutions

International Nuclear Information System (INIS)

Benes, P.; Jiranek, V.

1974-01-01

The state of carrier-free 7 Be in aqueous nitrate solutions was studied by electrophoresis, centrifugation and dialysis. In solutions of pH 2+ cation. At pH > 4 hydrolysis of beryllium proceeds which results in the formation of BeOH + ions and Be(OH) 2 molecules. The larger part of these molecules is adsorbed on the surface of colloidal impurities present in the solution. The pseudocolloids thus formed are positively charged up to pH 11. In alkaline solutions (pH > 11), negatively charged pseudocolloids and anionic hydroxocomplexes of beryllium exist. Adsorption and desorption of carrier-free beryllium was studied on glass, plexiglass and polyethylene as a function of pH, age and ionic strength (NaNO 3 ) of the solution. It has been found that the adsorption begins at pH 3-5, passes through a maximum at pH 8-11 and decreases to a very low value at pH 14. Probable mechanismus of the adsorption were discussed. (orig.) [de

Accumulation of thorium and uranium by microbes. The effect of pH, concentration of metals, and time course on the accumulation of both elements using streptomyces levoris

International Nuclear Information System (INIS)

Tsuruta, Takehiko

2006-01-01

The accumulation of thorium and uranium by various microorganisms from a solution containing both metals at pH 3.5 was examined. Among the tested species, a high accumulation ability for thorium was exhibited by strains of gram-positive bacteria, such as Arthrobacter nicotianae, Bacillus megaterium, B. subtilis, Micrococcus luteus, Rhodococcus erythropolis, and Streptomyces levoris. Though uranium was accumulated in small amounts by most of microorganisms. A. nicotianae, S. flavoviridis, and S. levoris had relatively high uranium accumulation abilities. In these high performance thorium- and uranium-accumulating microorganisms, S. levoris, which accumulated the largest amount of uranium from the solution containing only uranium at pH 3.5, accumulated about 300 μmol thorium and 133 μmol uranium per gram dry weight of microbial cells from a solution containing both thorium and uranium at pH 3.5. The amount and time course of the thorium accumulation were almost unaffected by the co-existing uranium, while those of uranium were strongly affected by the co-existing thorium. The effects of pH, the thorium and uranium concentrations, and time course on both metal accumulations were also evaluated by numerical formulas. (author)

In vitro synthesis and purification of PhIP-deoxyguanosine and PhIP-DNA oligomer covalent complexes

Energy Technology Data Exchange (ETDEWEB)

Freeman, J.

1994-12-01

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a heterocyclic amine compound formed when meats are cooked at high temperatures. PhIP damages DNA by forming covalent complexes with DNA carcinogen. In an effort to understand how the binding of PhIP to DNA may cause cancer, it is important to characterize the structures of PhIP-damaged DNA molecules. Our HPLC data support fluorescence and {sup 32}P Post-labeling studies which indicate the formation of several species of 2{prime}deoxyguanosine-(dG) or oligodeoxynucleotide-PhIP adducts. The reaction of PhIP with dG resulted in a reddish precipitate that was likely the major adduct, N-(deoxyguanosin-8-yl)-PhIP (dG-C8-PhIP) adduct, with a more polar adduct fraction remaining in the supernatant. Reversed-phase HPLC analysis of the adducts in the supernatant revealed the existence of species of much shorter retention times than the dG-C8-PhIP adduct, confirming that these species are more polar than dG-C8-PhIP. At least four adducts were formed in the reaction of PhIP with DNA oligomer. HPLC analysis of the PhIP-DNA oligomer supernatant after butanol extractions revealed four unresolved peaks which spectra had maximum wavelengths between 340 and 360 nm. Though adduct peaks were not completely resolved, there was {approximately}3 minutes interval between the DNA oligomer peak and the adduct peaks. Furthermore, fluorescence emission data of the DNA oligomer-PhIP adduct solution show heterogeneous binding. The more polar PhIP adducts were fraction-collected and their structures will be solved by nuclear magnetic resonance or x-ray crystallography.

Label-Free Carbon-Dots-Based Ratiometric Fluorescence pH Nanoprobes for Intracellular pH Sensing.

Science.gov (United States)

Shangguan, Jingfang; He, Dinggeng; He, Xiaoxiao; Wang, Kemin; Xu, Fengzhou; Liu, Jinquan; Tang, Jinlu; Yang, Xue; Huang, Jin

2016-08-02

Measuring pH in living cells is of great importance for better understanding cellular functions as well as providing pivotal assistance for early diagnosis of diseases. In this work, we report the first use of a novel kind of label-free carbon dots for intracellular ratiometric fluorescence pH sensing. By simple one-pot hydrothermal treatment of citric acid and basic fuchsin, the carbon dots showing dual emission bands at 475 and 545 nm under single-wavelength excitation were synthesized. It is demonstrated that the fluorescence intensities of the as-synthesized carbon dots at the two emissions are pH-sensitive simultaneously. The intensity ratio (I475 nm/I545 nm) is linear against pH values from 5.2 to 8.8 in buffer solution, affording the capability as ratiometric probes for intracellular pH sensing. It also displays that the carbon dots show excellent reversibility and photostability in pH measurements. With this nanoprobe, quantitative fluorescence imaging using the ratio of two emissions (I475 nm/I545 nm) for the detection of intracellular pH were successfully applied in HeLa cells. In contrast to most of the reported nanomaterials-based ratiometric pH sensors which rely on the attachment of additional dyes, these carbon-dots-based ratiometric probes are low in toxicity, easy to synthesize, and free from labels.

Plaque pH changes following consumption of two types of plain and bulky bread

Directory of Open Access Journals (Sweden)

Shiva Mortazavi

2011-01-01

Full Text Available Background: Consistency, backing process and content differences could influence cariogenic potential of foods. The aim was to compare plaque pH changes following consumption of two types of bread with different physical characteristics. Methods : In this clinical trial, interproximal plaque pH of 10 volunteers with high risk of dental caries (saliva Streptococcus mutans > 10 5 , high dental caries experience, and average DMFT =6.10 ± 1.56 was measured. Plain traditionally backed "Sangak bread" and soft bulky "Baguette bread" and %10 sucrose solution were tested in a cross over designed experiment. Baseline plaque pH was recorded and followed by 1, 5, 10, 15, 20, and 30 minutes intervals. Data was analyzed using ANOVA and Tukey test (α = 0.05. Results: Sucrose solution caused the most pronounced pH and ∆pH drop from 7.15 ± 0.33 at baseline to 6.78 ± 0.29. Means plaque pH of 10% sucrose solution and Baguette were not statistically different at 1, 20 and 30 minutes (P > 0.05. Mean plaque pH of Sangak and Baguette showed significant differences at 0, 1, 20 and30 minutes (P < 0.05. Sucrose solution caused a dramatic plaque pH drop during first 10 minutes and then within 30 minutes returned to baseline pH. For two bread samples within first 10 minutes, pH increased and then started to decrease during tenth to fifteenth minutes. Conclusion: During all experiment phases, the mean pH of Baguette with less consistency and carbohydrate content and higher rate of starch gelatination was lower compared to Sangak.

Transport and Retention of TiO2 Rutile Nanoparticles in Saturated Porous Media: Influence of Solution pH, Ionic Strength, and the Presence of Humic Acid

Science.gov (United States)

The influence of solution pH, ionic strength, and varying concentrations of the Suwannee River Humic Acid (SRHA) on the transport of titanium dioxide (TiO2, rutile) nanoparticle aggregates (nTiO2) in saturated porous media was investigated through systematically examining the tra...

Nitrite-cured color and phosphate-mediated water binding of pork muscle proteins as affected by calcium in the curing solution.

Science.gov (United States)

Zhao, Jing; Xiong, Youling L

2012-07-01

Calcium is a mineral naturally present in water and may be included into meat products during processing thereby influencing meat quality. Phosphates improve myofibril swelling and meat water-holding capacity (WHC) but can be sensitive to calcium precipitation. In this study, pork shoulder meat was used to investigate the impact of calcium at 0, 250, and 500 ppm and phosphate type [sodium pyrophosphate (PP), tripolyphosphate (TPP), and hexametaphopshate (HMP)] at 10 mM on nitrite-cured protein extract color at various pH levels (5.5, 6.0, and 6.5) and crude myofibril WHC at pH 6.0. Neither calcium nor phosphates present in the curing brines significantly affected the cured color. Increasing the pH tended to promote the formation of metmyoglobin instead of nitrosylmyoglobin. The ability of PP to enhance myofibril WHC was hampered (P meat products. Although not affecting nitrite-cured color, calcium hampers the efficacy of phosphates to promote water binding by muscle proteins, underscoring the importance of water quality for brine-enhanced meat products. © 2012 Institute of Food Technologists®

Influence of Bath Composition at Acidic pH on Electrodeposition of Nickel-Layered Silicate Nanocomposites for Corrosion Protection

Directory of Open Access Journals (Sweden)

Jeerapan Tientong

2013-01-01

Full Text Available Nickel-layered silicates were electrochemically deposited from acidic bath solutions. Citrate was used as a ligand to stabilize nickel (II ions in the plating solution. The silicate, montmorillonite, was exfoliated by stirring in aqueous solution over 24 hours. The plating solutions were analyzed for zeta-potential, particle size, viscosity, and conductivity to investigate the effects of the composition at various pHs. The solution particles at pH 2.5 (−22.2 mV and pH 3.0 (−21.9 mV were more stable than at pH 1.6 (−10.1 mV as shown by zeta-potential analysis of the nickel-citrate-montmorillonite plating solution. Ecorr for the films ranged from −0.32 to −0.39 V with varying pH from 1.6 to 3.0. The films were immersed in 3.5% NaCl and the open circuit potential monitored for one month. The coatings deposited at pH 3.0 were stable 13 days longer in the salt solution than the other coatings. X-ray diffraction showed a change in the (111/(200 ratio for the coatings at the various pHs. The scanning electron microscopy and hardness results also support that the electrodeposition of nickel-montmorillonite at pH 3.0 (234 GPa had improved hardness and morphology compared to pH 2.5 (174 GPa and pH 1.6 (147 GPa.

Separation of uranium and rare earth elements from Rirang ore leach solution by two-step precipitation

International Nuclear Information System (INIS)

Sradjono; Erni Rifandriyah, A.; Zahardi

1995-01-01

Separation of uranium and rare-earth elements from Rirang ore leach solution was carried out through a two-step precipitation. Several condition affecting the separation processes were examined including solution pH, reagent concentration, and reaction prepitation time. Optimum conditions for the first and second precipitation steps include adjustment of precipitation pH to 1.3 and 2.3, respectively by the addition of 7.3% of NH 4 OH solution and allowing 60 minutes precipitation/reaction time. Based on the conditions, about 6% of Th, 3% of U, 0.9% of PO 4 3- , and none of RE were recovered in the first precipitation step meanwhile, about 99% of RE, 55% of U, 76% of PO 4 3- , and of the Th were recovered in the second step. (author). 3 refs. 4 tabs. 4 figs

Water-rock interactions and the pH stability of groundwater from Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Ebinger, M.H.

1992-01-01

Titrations of acidic solutions in waters from the tuff and carbonate aquifers at Yucca Mountain were simulated using the geochemical codes PHREEQE and EQ3/6. The simulations tested pH stability of the waters in the presence of different minerals and in their absence. Two acidic solutions, 10 -4 HCl and 10 -4 M UO 2 (NO 3 ) 2 , were titrated in to the water. Little pH and/or compositional change resulted in the groundwater when the HCl solution was titrated, but significant pH and CO 2 fugacity changes were observed when UO 2 (NO 3 ) 2 was titrated. Water interactions with alkali feldspar, quartz or cristobalite, and Ca-smectite buffered the pH and compositional changes in the carbonate water and decreased the magnitude of pH and compositional changes when small volumes of UO 2 (NO 3 ) 2 added to the tuffaceous waters

Electrochemical characteristics of bioresorbable binary MgCa alloys in Ringer's solution: Revealing the impact of local pH distributions during in-vitro dissolution.

Science.gov (United States)

Mareci, D; Bolat, G; Izquierdo, J; Crimu, C; Munteanu, C; Antoniac, I; Souto, R M

2016-03-01

Biodegradable magnesium-calcium (MgCa) alloy is a very attractive biomaterial. Two MgCa alloys below the solid solubility of Ca were considered, as to solely investigate the effect of Ca content on the behavior of magnesium and the pH changes associated to metal dissolution. X-ray diffraction analysis and optical microscopy showed that both Mg-0.63Ca and Mg-0.89Ca alloys were solely composed of α(Mg) phase. Degradation characteristics and electrochemical characterization of MgCa alloys were investigated during exposure to Ringer's solution at 37 °C by electrochemical impedance spectroscopy and scanning electrochemical microscopy. The impedance behavior showed both capacitive and inductive features that are related to the alloy charge transfer reaction and the relaxation of the absorbed corrosion compounds, and can be described in terms of an equivalent circuit. Scanning electron microscopy (SEM) was employed to view the surface morphology of the MgCa samples after 1 week immersion in Ringer's solution showing extensive precipitation of corrosion products, whereas the substrate shows evidence of a non-uniform corrosion process. Energy dispersive analysis showed that the precipitates contained oxygen, calcium, magnesium and chlorine, and the Mg:Ca ratios were smaller than in the alloys. Scanning electrochemical microscopy (SECM) was used to visualize local pH changes associated to these physicochemical processes with high spatial resolution. The occurrence of pH variations in excess of 3 units between anodic and cathodic half-cell reactions was monitored in situ. Copyright © 2015 Elsevier B.V. All rights reserved.

SEPARATION OF BARIUM VALUES FROM URANYL NITRATE SOLUTIONS

Science.gov (United States)

Tompkins, E.R.

1959-02-24

The separation of radioactive barium values from a uranyl nitrate solution of neutron-irradiated uranium is described. The 10 to 20% uranyl nitrate solution is passed through a flrst column of a cation exchange resin under conditions favoring the adsorption of barium and certain other cations. The loaded resin is first washed with dilute sulfuric acid to remove a portion of the other cations, and then wash with a citric acid solution at pH of 5 to 7 to recover the barium along with a lesser amount of the other cations. The PH of the resulting eluate is adjusted to about 2.3 to 3.5 and diluted prior to passing through a smaller second column of exchange resin. The loaded resin is first washed with a citric acid solution at a pH of 3 to elute undesired cations and then with citric acid solution at a pH of 6 to eluts the barium, which is substantially free of undesired cations.

Aqueous solutions/nuclear glasses interactions

International Nuclear Information System (INIS)

Delage, F.; Advocat, T.; Vernaz, E.; Crovisier, J.L.

1991-01-01

Interactions results of the borosilicate glass used in radioactive wastes confinement and aqueous solutions at various temperature and PH show that for the glass components: - the release rate evolution follows an Arrhenius law, - in acid PH, there is a selective dissolution, - in basic PH, there is a stoechiometric dissolution [fr

PH measurement under pressure and at high temperatures; Mesure du pH sous pression et a temperature elevee

Energy Technology Data Exchange (ETDEWEB)

Fournie, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Le Peintre, M; Mahieu, C [Centre National de la Recherche Scientifique (CNRS), 91 - Gif-sur-Yvette (France)

1961-07-01

In the first part the development and operation of a glass electrode under pressure at room temperature is described. The pressure equilibrium between the inside and outside of the glass membrane several centimetres thick is obtained instantaneously by means of a siphon. The use of a silicone oil as electrical insulator makes possible the working of the glass electrode with the siphon at high pressures (100 kg/cm{sup 2}). In the second part, we determined the pH of various buffer solutions up to 250 deg. C using a cell of our design having two hydrogen electrodes. The values thus obtained for the buffer solutions make it possible to verify and calibrate the pH electrodes independently of the oxido-reduction potential of the medium. In the third part we give the results obtained up to 200 deg. C with the glass electrodes developed in conjunction with the Societe St Gobain. (author) [French] Dans une premiere partie, nous exposons la mise au point et le fonctionnement d'une electrode en verre sous pression a la temperature ordinaire. L'equilibrage instantane de la pression a l'interieur et a l'exterieur de la membrane en verre de quelques diziemes de millimetres d'epaisseur s'effectue par l'intermediaire d'un siphon. L'emploi d'une huile de silicone comme isolant electrique a permis le fonctionnement de l'electrode en verre a siphon sous haute pression (1000 kg/cm{sup 2}). Dans une deuxieme partie, nous avons determine jusqu'a 250 deg. C les valeurs du pH des diverses solutions tampons avec une cellule de notre conception a deux electrodes d'hydrogene. Les valeurs des solutions tampons ainsi obtenues permettent de verifier et d'etalonner les electrodes a pH independantes du potentiel d'oxydo-reduction du milieu. Dans une troisieme partie, nous relatons les resultats obtenus jusqu'a 200 deg. C avec les electrodes en verre mis au point en collaboration avec la Societe Saint-Gobain. (auteur)

Antimicrobial activity and pH of a endodontic sealer containing MTA

DEFF Research Database (Denmark)

Maliza, Amanda GA; de Andrade, Flaviana Bombarda; Arias, Marcela C

Objective: To investigate the antimicrobial activity, calcium release, and pH of a new mineral trioxide aggregate endodontic sealer when compared to endodontic sealers containing calcium hydroxide and/or epoxy resin. Method: Specimens were fabricated from MTA Fillapex, Sealer 26, Sealapex, and AH...... Plus immediately, 24 or 48 hours prior to the tests. The antimicrobial activity against Enterococcus faecalis and Candida albicans was evaluated by the direct contact and the agar diffusion methods. Calcium release was determined by atomic absorption spectrometry. The pH from solutions containing...... in solution with an alkaline pH. Conclusion: The new mineral trioxide aggregate endodontic sealer presented higher antimicrobial activity when compared to the sealers containing calcium hydroxide and/or epoxy resin. As for pH and calcium release, the sealers containing calcium hydroxide resulted in presented...

Adsorption of Radioactive Strontium and Caesium from Mixtures of Solutions

International Nuclear Information System (INIS)

Haznedaroglu, H.N.

2002-07-01

In this thesis, the adsorption of the radioactive Cs and Sr on two different types of cement, Sulfate Resistant Cement and Portland Composed Cement, was investigated. The gamma-active Cs-137 and Sr-85 were used as tracers. Four different mixtures of solutions of Cs and Sr were used in experiments; a) The solution containing trace amount of Sr-85 and Cs-137 b) 1.10 - 5 - 1.10 - 1 M *SrCl 2 solutions containing trace amount of Cs-137 c) 1.10 - 5 - 1.10 - 1 M *CsCl solutions containing trace amount of Sr-85 d) The equal amount of mixtures of 1.10 - 5 - 1.10 - 1 M SrCl 2 and 1.10 - 5 - 1.10 - 1 M CsCl solutions. It was shown that the convenient ph values for the comparison of Cs and Sr adsorption on both cement were 2.5 and 11.0. It was observed that the adsorption capacity of Sr on Sulfate Resistant Cement was twice that for the Portland Composed Cement in the solutions containing trace amount of Cs-137 and 1.10 - 5 - 1.10 - 1 *SrCl 2 . The in cease in adsorption capacity is related to the Ca to Sr ion exchange in Sulfate Resistant Cement containing appreciable amount of C 3 S. The adsorption of Cs and Sr on both types of cement in solutions containing equal amount of CsCl and SrCl 2 was greater than that of individual solutions of CsCl and SrCl 2 . This latter behavior is related to the ion charge, the hydration of ions and the interaction of the Cs with the Sr on the surface of adsorbent. It was observed that although Portland Composed Cement adsorbs Cs selectively, Sulfate Resistant Cement has a greater affinity for Sr. Cs adsorption is not affected by ph changes whilst Sr adsorption is highly dependent on ph

Reclamation of zinc-contaminated soil using a dissolved organic carbon solution prepared using liquid fertilizer from food-waste composting

International Nuclear Information System (INIS)

Chiang, Po-Neng; Tong, Ou-Yang; Chiou, Chyow-San; Lin, Yu-An; Wang, Ming-Kuang; Liu, Cheng-Chung

2016-01-01

Highlights: • Nitrogen, phosphorus, and potassium contents in soil are substantially increased after the DOC washing. • The removal of Zn is dominated by proton replacement at pH 2.0, rather than by complexation with DOC. • The removal of Zn is dominated by DOC complexation between pH 3.0 and pH 5.0. - Abstract: A liquid fertilizer obtained through food-waste composting can be used for the preparation of a dissolved organic carbon (DOC) solution. In this study, we used the DOC solutions for the remediation of a Zn-contaminated soil (with Zn concentrations up to 992 and 757 mg kg −1 in topsoil and subsoil, respectively). We then determined the factors that affect Zn removal, such as pH, initial concentration of DOC solution, and washing frequency. Measurements using a Fourier Transform infrared spectrometer (FT-IR) revealed that carboxyl and amide were the major functional groups in the DOC solution obtained from the liquid fertilizer. Two soil washes using 1,500 mg L −1 DOC solution with a of pH 2.0 at 25 °C removed about 43% and 21% of the initial Zn from the topsoil and subsoil, respectively. Following this treatment, the pH of the soil declined from 5.4 to 4.1; organic matter content slightly increased from 6.2 to 6.5%; available ammonium (NH 4 + -N) content increased to 2.4 times the original level; and in the topsoil, the available phosphorus content and the exchangeable potassium content increased by 1.65 and 2.53 times their initial levels, respectively.

Reclamation of zinc-contaminated soil using a dissolved organic carbon solution prepared using liquid fertilizer from food-waste composting

Energy Technology Data Exchange (ETDEWEB)

Chiang, Po-Neng [Experimental Forest, National Taiwan University, Chushan, Nantou County, 55750, Taiwan (China); Tong, Ou-Yang [Department of Environment Engineering, College of the Environment and Ecology, and The Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, Xiamen University, Xiamen (China); Chiou, Chyow-San; Lin, Yu-An [Department of Environmental Engineering, National Ilan University, Ilan 26047, Taiwan (China); Wang, Ming-Kuang [Department of Animal Science, National Ilan University, Ilan 26047, Taiwan (China); Liu, Cheng-Chung, E-mail: ccliu@niu.edu.tw [Department of Agricultural Chemistry, National Taiwan University, Taipei 10617, Taiwan (China)

2016-01-15

Highlights: • Nitrogen, phosphorus, and potassium contents in soil are substantially increased after the DOC washing. • The removal of Zn is dominated by proton replacement at pH 2.0, rather than by complexation with DOC. • The removal of Zn is dominated by DOC complexation between pH 3.0 and pH 5.0. - Abstract: A liquid fertilizer obtained through food-waste composting can be used for the preparation of a dissolved organic carbon (DOC) solution. In this study, we used the DOC solutions for the remediation of a Zn-contaminated soil (with Zn concentrations up to 992 and 757 mg kg{sup −1} in topsoil and subsoil, respectively). We then determined the factors that affect Zn removal, such as pH, initial concentration of DOC solution, and washing frequency. Measurements using a Fourier Transform infrared spectrometer (FT-IR) revealed that carboxyl and amide were the major functional groups in the DOC solution obtained from the liquid fertilizer. Two soil washes using 1,500 mg L{sup −1} DOC solution with a of pH 2.0 at 25 °C removed about 43% and 21% of the initial Zn from the topsoil and subsoil, respectively. Following this treatment, the pH of the soil declined from 5.4 to 4.1; organic matter content slightly increased from 6.2 to 6.5%; available ammonium (NH{sub 4}{sup +}-N) content increased to 2.4 times the original level; and in the topsoil, the available phosphorus content and the exchangeable potassium content increased by 1.65 and 2.53 times their initial levels, respectively.

Acid-base equilibria in the reaction of tantalum pentafluoride with O,O-diphenyl-H-benzoylamidophosphate (PhO)2P(0)NHC(O)Ph

International Nuclear Information System (INIS)

Il'in, E.G.; Kharrmann, Eh.; Shcherbakova, M.N.; Buslaev, Yu.A.

1987-01-01

Method of 19 F NMR was used to study TaF 5 interaction with imidodiphosphoric acid ester (PhO) 2 P(O)NHC(O)Ph(LH) in methylene chloride. Dimeric molecular LH(TaF 5 ) 2 complex was the main form in the solution with towfold TaF 5 excess; phosphoryl and carbonyl groups partisipate in complexing at that. Increase of ligand content in the solution up to equimolar one results to preliminary ligand coordination via P=O-group. Introduction of the base excess to the solution results to formation of L - anion which is coordinated to TaF 5 in a monodentate way via phosphoryl group or in a chelate way with fluorine ion substitution and formation of LTaF 4 + cationw

Overexpression of PhEXPA1 increases cell size, modifies cell wall polymer composition and affects the timing of axillary meristem development in Petunia hybrida.

Science.gov (United States)

Zenoni, Sara; Fasoli, Marianna; Tornielli, Giovanni Battista; Dal Santo, Silvia; Sanson, Andrea; de Groot, Peter; Sordo, Sara; Citterio, Sandra; Monti, Francesca; Pezzotti, Mario

2011-08-01

• Expansins are cell wall proteins required for cell enlargement and cell wall loosening during many developmental processes. The involvement of the Petunia hybrida expansin A1 (PhEXPA1) gene in cell expansion, the control of organ size and cell wall polysaccharide composition was investigated by overexpressing PhEXPA1 in petunia plants. • PhEXPA1 promoter activity was evaluated using a promoter-GUS assay and the protein's subcellular localization was established by expressing a PhEXPA1-GFP fusion protein. PhEXPA1 was overexpressed in transgenic plants using the cauliflower mosaic virus (CaMV) 35S promoter. Fourier transform infrared (FTIR) and chemical analysis were used for the quantitative analysis of cell wall polymers. • The GUS and GFP assays demonstrated that PhEXPA1 is present in the cell walls of expanding tissues. The constitutive overexpression of PhEXPA1 significantly affected expansin activity and organ size, leading to changes in the architecture of petunia plants by initiating premature axillary meristem outgrowth. Moreover, a significant change in cell wall polymer composition in the petal limbs of transgenic plants was observed. • These results support a role for expansins in the determination of organ shape, in lateral branching, and in the variation of cell wall polymer composition, probably reflecting a complex role in cell wall metabolism. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

Resorcinol adsorption from aqueous solution over activated carbon

International Nuclear Information System (INIS)

Blanco, Diego A; Giraldo, Liliana; Moreno, Juan C

2007-01-01

In this paper, the adsorption behavior of Resorcinol a monohydroxylated phenol, poorly acid to 298 K, over activated carbon is analyzed by studying the solution's pH influence and the surface reduction in the adsorption process. To do this, an activated carbon of lignocellulose origin and a reduced activated carbon was used. The interaction solid solution is characterized by the analyses of adsorption in the isotherms to 298 K and pH values of 7. 00, 9.00 and 11.00 for a period of 48 hours. The capacity adsorption of activated carbons increases when the solution's pH decreases and the retained amount increases in the reduced coal to the pH of maximum adsorption.

The potential of curcumin reagent as a natural pH indicator for the development of an optical pH sensor

International Nuclear Information System (INIS)

Rosmawani Mohammad; Musa Ahmad; Jamaluddin Mohd Daud

2007-01-01

The potential of curcumin reagent as a natural pH indicator for the development of an optical pH sensor was discussed in this study. Curcumin has been chosen because it has never been reported before for use in the development of an optical pH sensor. Curcumin is a coloring constituent of turmeric that giving yellow pigmentation. Curcumin showed clear color changes, for example yellow in acidic and reddish-brown in basic solutions. The color change is fast for example within 5 seconds. Results from the study showed that a linear pH range for this reagent was observed at pH 8-12 (R 2 =0.9854). Curcumin has a good photo stability with RSD value of 1.42 % for a study period of 6 months. The RSD values of the reproducibility study were found to be 1.43 % and 0.37 % for pH 9 and pH 12, respectively. Characterisation of the immobilised curcumin reagent also showed promising results, hence a good potential for use as a sensing reagent for an optical pH sensor. (author)

Effect of pH on cadmium biosorption by coconut copra meal

International Nuclear Information System (INIS)

Ofomaja, Augustine E.; Ho, Y.-S.

2007-01-01

Biosorption of cadmium ion by coconut copra meal, an agricultural waste product was investigated as a function of initial solution pH and initial cadmium concentration. Pseudo-second-order kinetic analyses were performed to determine the rate constant of biosorption, the equilibrium capacity, and initial biosorption rate. Cadmium biosorption by copra meal was found to be dependent on the initial solution pH and initial cadmium concentration. Ion exchange occurred in the initial biosorption period. In addition, mathematical relationships were drawn to relate the change in the solution hydrogen ion concentration with equilibrium biosorption capacity, initial cadmium concentration, and equilibrium biosorption capacity

The impact of pH inhomogeneities on CHO cell physiology and fed-batch process performance - two-compartment scale-down modelling and intracellular pH excursion.

Science.gov (United States)

Brunner, Matthias; Braun, Philipp; Doppler, Philipp; Posch, Christoph; Behrens, Dirk; Herwig, Christoph; Fricke, Jens

2017-07-01

Due to high mixing times and base addition from top of the vessel, pH inhomogeneities are most likely to occur during large-scale mammalian processes. The goal of this study was to set-up a scale-down model of a 10-12 m 3 stirred tank bioreactor and to investigate the effect of pH perturbations on CHO cell physiology and process performance. Short-term changes in extracellular pH are hypothesized to affect intracellular pH and thus cell physiology. Therefore, batch fermentations, including pH shifts to 9.0 and 7.8, in regular one-compartment systems are conducted. The short-term adaption of the cells intracellular pH are showed an immediate increase due to elevated extracellular pH. With this basis of fundamental knowledge, a two-compartment system is established which is capable of simulating defined pH inhomogeneities. In contrast to state-of-the-art literature, the scale-down model is included parameters (e.g. volume of the inhomogeneous zone) as they might occur during large-scale processes. pH inhomogeneity studies in the two-compartment system are performed with simulation of temporary pH zones of pH 9.0. The specific growth rate especially during the exponential growth phase is strongly affected resulting in a decreased maximum viable cell density and final product titer. The gathered results indicate that even short-term exposure of cells to elevated pH values during large-scale processes can affect cell physiology and overall process performance. In particular, it could be shown for the first time that pH perturbations, which might occur during the early process phase, have to be considered in scale-down models of mammalian processes. Copyright © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reactive solute transport in acidic streams

Science.gov (United States)

Broshears, R.E.

1996-01-01

Spatial and temporal profiles of Ph and concentrations of toxic metals in streams affected by acid mine drainage are the result of the interplay of physical and biogeochemical processes. This paper describes a reactive solute transport model that provides a physically and thermodynamically quantitative interpretation of these profiles. The model combines a transport module that includes advection-dispersion and transient storage with a geochemical speciation module based on MINTEQA2. Input to the model includes stream hydrologic properties derived from tracer-dilution experiments, headwater and lateral inflow concentrations analyzed in field samples, and a thermodynamic database. Simulations reproduced the general features of steady-state patterns of observed pH and concentrations of aluminum and sulfate in St. Kevin Gulch, an acid mine drainage stream near Leadville, Colorado. These patterns were altered temporarily by injection of sodium carbonate into the stream. A transient simulation reproduced the observed effects of the base injection.

Study of the pitting and repassiv,tion corrosion potential of zicaloy-4 halides solutions at 250C and several pH

International Nuclear Information System (INIS)

Gardiazabal, J.I.; Cordova, R.; Gomez, H.; Layana, G.; Schrebler, R.

1987-01-01

The electrochemical behaviour of Zircaloy-4 electrode in chloride, bromide and iodide acid solution was investigated at 25 0 C employing stationary, quasi-stationary and potentiodynamic techniques. The results show that the pitting and repassivation potentials are independent on pH but both are dependent on halice concentration, following linear relation ships in these cases. It is also possible to correlate the pitting potential with the ionic radius of the anions, allowing thus to establish an order in their agressive properties. This order was extrapolated for fluoride ion and further experimental measurements show that the corrosion potential of Zircaloy-4 in acid or neutra solution of this ion (which undergoes active dissolution) is coincident with that predicted from the Ep v/s ionic radius determined for the other halides. (Author) [pt

Digestibility and antigenicity of β-lactoglobulin as affected by heat, pH and applied shear.

Science.gov (United States)

Rahaman, Toheder; Vasiljevic, Todor; Ramchandran, Lata

2017-02-15

Processing induced conformational changes can modulate digestibility of food allergens and thereby their antigenicity. Effect of different pH (3, 5, 7), temperature (room temperature, 120°C) and shear (0s(-1), 1000s(-1)) on simulated gastrointestinal digestibility of β-lg and post digestion antigenic characteristics have been studied. At all pH levels unheated β-lg showed resistance to peptic digestion with high antigenic value while it was fairly susceptible to pancreatin with moderate reduction in antigenicity. Heating at 120°C significantly improved both peptic and pancreatic digestion attributed to structural alterations that resulted in much lower antigenicity; the level of reduction being pH dependant. The lowest antigenicity was recorded at pH 5. Shearing (1000s(-1)) had a minor impact reducing digestibility and thereby enhancing antigenicity of unheated β-lg at pH 5 and 7 slightly; however in conjunction with heating (120°C) it reduced antigenicity further irrespective of the pH. Overall, treatment at pH 5, 120°C and 1000s(-1) could potentially reduce post digestion antigenicity of β-lg. Copyright © 2016. Published by Elsevier Ltd.

Dependence of precipitation of trace elements on pH in standard water

Science.gov (United States)

Verma, Shivcharan; Mohanty, Biraja P.; Singh, K. P.; Behera, B. R.; Kumar, Ashok

2018-04-01

The present work aimed to study the dependence of precipitation of trace elements on the pH of solution. A standard solution was prepared by using ultrapure deionized water (18.2 MΩ/cm) as the solvent and 11 water-soluble salts having different elements as solutes. Five samples of different pH values (2 acidic, 2 basic, and 1 neutral) were prepared from this standard solution. Sodium-diethyldithiocarbamate was used as the chelating agent to precipitate the metal ions present in these samples of different pH values. The targets were prepared by collecting these precipitates on mixed cellulose esters filter of 0.4 μm pore size by vacuum filtration. Elemental analysis of these targets was performed by particle-induced X-ray emission (PIXE) using 2.7 MeV protons from the single Dee variable energy cyclotron at Panjab University, Chandigarh, India. PIXE data were analyzed using GUPIXWIN software. For most of the elements, except Hg with oxidation state +2, such as Co, Ni, Zn, Ba, and Cd, a general trend of enhancement in precipitation was observed with the increase in pH. However, for other elements such as V, As, Mo, Ag, and Bi, which have oxidation state other than +2, no definite pattern was observed. Precipitation of Ba and As using this method was negligible at all five pH values. From these results, it can be concluded that the precipitation and recovery of elements depend strongly on the pH of the water sample.

The role of pH in the decomposition of organic micropollutants during the heterogeneous photocatalysis process

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Kudlek Edyta

2017-01-01

Full Text Available The study investigated that the change in the pH ranged from 5 to 7 affects the adsorption degree of selected organic micropollutants such as: polycyclic aromatic hydrocarbons (anthracene, benzo[a]pyrene, pharmaceutical compounds (diclofenac and industrial additives (octylphenol and pentachlorophenol on the photocatalyst surface (100 mg TiO2/dm3. For example, in suspension of pH 5 a 12% reduction in the concentration of octylphenol was noted, while in the suspension of pH 7 the concentration of this compound was reduced by 64%. In the case of anthracene an inverse relationship was observed. The concentration of this micropollutant decreased by 94% for pH 5 and only by 61% for pH 7 suspension. With the commencement of UV irradiation of reaction mixtures a gradual increase in the concentration of micropollutants reduction in aqueous solutions was observed. This indicates the decomposition of compounds as a result of their reaction with highly reactive OH• radicals or other reactive oxygen species generated during the process. For reaction mixtures of pH 7, already in the first 15 minutes, higher degrees of removal of micropollutants ware observed compared to suspension of pH 6. The obtained micropollutants removal degrees exceeded 91% for diclofenac, octylphenol, pentachlorophenol and amounted to 100% for anthracene and benzo(apyrene.

The role of Eh and pH in leaching Saskatchewan uranium ores with chloride and nitrate leaching systems

International Nuclear Information System (INIS)

Nirdosh, I.; Muthuswami, S.V.

1992-01-01

The effects of solution E h and pH on the extractions of U, 230 Th, 226 Ra, As and Ni from two typical uranium ores from the province of Saskatchewan in Canada are discussed for the leachants ferric chloride, ferric nitrate, nitric acid and hydrochloric acid. It is concluded that E h > 700 mV and pH 230 Th extraction is more sensitive to solution pH than to E h whereas Ni extraction is sensitive mainly to the solution E h . Arsenic extraction is very sensitive to solution E h , and for a given E h , is high at pH 1.3. (orig.) [de

Influence of pH on the adsorption of uranium ions by oxidized activated carbon and chitosan

International Nuclear Information System (INIS)

Park, G.I.; Park, H.S.; Woo, S.I.

1999-01-01

The adsorption characteristics of uranyl ions on surface-oxidized carbon were compared with those of powdered chitosan over a wide pH range. In particular, an extensive analysis was made on solution pH variation during the adsorption process or after adsorption equilibrium. Uranium adsorption on the two adsorbents was revealed to be strongly dependent on the initial pH of the solution. A quantitative comparison of the adsorption capacities of the two adsorbents was made, based on the isotherm data obtained at initial pH 3, 4, and 5. In order to analyze the adsorption kinetics incorporated with pH effects, batch experiments at various initial pH values were carried out, and solution pH profiles with the adsorption time were also evaluated. The breakthrough behavior in a column packed with oxidized carbon was also characterized with respect to the variation of effluent pH. Based on these experimental results, the practical applicability of oxidized carbon for uranium removal from acidic radioactive liquid waste was suggested

Rapid pH and PO2 changes in the tissue recording chamber during stoppage of a gas-equilibrated perfusate: effects on calcium currents in ventral horn neurons.

Science.gov (United States)

Carlin, K P; Brownstone, R M

2006-09-01

In vitro studies often use bicarbonate-buffered saline solutions to mimic the normal extracellular environment of tissues. These solutions are typically equilibrated with gaseous O2 and CO2, the latter interacting with bicarbonate ions to maintain a physiological pH. In vitro tissue chambers, like those used for electrophysiology, are usually continually perfused with the gassed buffer, but stopping the perfusion to add expensive chemicals or acquire imaging data is a common practice. The present study demonstrates that this procedure leads to rapid (PO2 of the detained solution in the tissue chamber. During the first 200 s, pH increased by 0.4 units and resulted in a 25% PO2 reduction of the detained solution. The rates of these changes were dependent on the volume of solution in the chamber. In experiments using acute transverse slices from the lumbar spinal cord of neonatal (postnatal day 0-10) mice, perfusion stoppage of the same duration was accompanied by a 34.7% enhancement of the peak voltage-gated calcium current recorded from ventral horn neurons. In these cells both low voltage-activated and high voltage-activated currents were affected. These currents were unaffected by decreasing PO2 when a CO2-independent buffer was used, suggesting that changes in pH were responsible for the observed effects. It is concluded that the procedure of stopping a bicarbonate/CO2-buffered perfusate results in rapid changes in pH and PO2 of the solution detained in the tissue chamber, and that these changes have the potential to covertly influence experimental results.

The pH behavior of a 2-aminoethyl dihydrogen phosphate zwitterion studied with NMR-titrations

Science.gov (United States)

Myller, A. T.; Karhe, J. J.; Haukka, M.; Pakkanen, T. T.

2013-02-01

In this study a bifunctional 2-aminoethyl dihydrogen phosphate (AEPH2) was 1H and 31P NMR characterized in a pH range of 1-12 in order to determine the zwitterion properties in different pH regions in H2O and D2O solutions. NMR was also used to determine the pH range where AEPH2 exists as a zwitterion. The phosphate group has two deprotonation points, around pH 1 and 6, while the amino group deprotonates at pH 11. The zwitterion form of AEPH2 (NH3+sbnd CHsbnd CHsbnd OPOH) exists as the main ion between pH 1 and 6 in water solutions and also in the solid state.

Iridium Oxide pH Sensor Based on Stainless Steel Wire for pH Mapping on Metal Surface

Science.gov (United States)

Shahrestani, S.; Ismail, M. C.; Kakooei, S.; Beheshti, M.; Zabihiazadboni, M.; Zavareh, M. A.

2018-03-01

A simple technique to fabricate the iridium oxide pH sensor is useful in several applications such as medical, food processing and engineering material where it is able to detect the changes of pH. Generally, the fabrication technique can be classified into three types: electro-deposition iridium oxide film (EIrOF), activated iridium oxide film (AIROF) and sputtering iridium oxide film (SIROF). This study focuses on fabricating electrode, calibration and test. Electro-deposition iridium oxide film is a simple and effective method of fabricating this kind of sensor via cyclic voltammetry process. The iridium oxide thick film was successfully electrodeposited on the surface of stainless steel wire with 500 cycles of sweep potential. A further analysis under FESEM shows detailed image of iridium oxide film which has cauliflower-liked microstructure. EDX analysis shows the highest element present are iridium and oxygen which concluded that the process is successful. The iridium oxide based pH sensor has shown a good performance in comparison to conventional glass pH sensor when it is being calibrated in buffer solutions with 2, 4, 7 and 9 pH values. The iridium oxide pH sensor is specifically designed to measure the pH on the surface of metal plate.

Shelf-Life of Chlorine Solutions Recommended in Ebola Virus Disease Response.

Science.gov (United States)

Iqbal, Qais; Lubeck-Schricker, Maya; Wells, Emma; Wolfe, Marlene K; Lantagne, Daniele

2016-01-01

In Ebola Virus Disease (EVD) outbreaks, it is widely recommended to wash living things (handwashing) with 0.05% (500 mg/L) chlorine solution and non-living things (surfaces, personal protective equipment, dead bodies) with 0.5% (5,000 mg/L) chlorine solution. Chlorine solutions used in EVD response are primarily made from powdered calcium hypochlorite (HTH), granular sodium dichloroisocyanurate (NaDCC), and liquid sodium hypochlorite (NaOCl), and have a pH range of 5-11. Chlorine solutions degrade following a reaction highly dependent on, and unusually sensitive to, pH, temperature, and concentration. We determined the shelf-life of 0.05% and 0.5% chlorine solutions used in EVD response, including HTH, NaDCC, stabilized NaOCl, generated NaOCl, and neutralized NaOCl solutions. Solutions were stored for 30 days at 25, 30, and 35°C, and tested daily for chlorine concentration and pH. Maximum shelf-life was defined as days until initial concentration fell to pH = 7) had a maximum shelf-life of a few hours, NaDCC solutions (pH = 6) 2 days, generated NaOCl solutions (pH = 9) 6 days, and HTH and stabilized NaOCl solutions (pH 9-11) >30 days. Models were developed for solutions with maximum shelf-lives between 1-30 days. Extrapolating to 40°C, the maximum predicted shelf-life for 0.05% and 0.5% NaDCC solutions were 0.38 and 0.82 hours, respectively; predicted shelf-life for 0.05% and 0.5% generated NaOCl solutions were >30 and 5.4 days, respectively. Each chlorine solution type offers advantages and disadvantages to responders, as: NaDCC is an easy-to-import high-concentration effervescent powder; HTH is similar, but forms a precipitate that may clog pipes; and, NaOCl solutions can be made locally, but are difficult to transport. We recommend responders chose the most appropriate source chlorine compound for their use, and ensure solutions are stored at appropriate temperatures and used or replaced before expiring.

Adsorção de cromo (VI por carvão ativado granular de soluções diluídas utilizando um sistema batelada sob pH controlado Chromium (VI adsorption by GAC from diluted solutions in batch system and controlled ph

Directory of Open Access Journals (Sweden)

Renata Santos Souza

2009-09-01

solutions, and batch systems with controlled pH. The functional groups on the CAG surface was carried out by the Boehm method. In addition, effect of pH on the Cr(VI adsorption, adsorption equilibrium, and kinetic were studied under experimental conditions (pH = 6, MA = 6g, for 90min.. On the GAC surface, carboxylic groups were found to be in higher concentrations (MAS=0,43 mmol/gCAG, which increase the Cr(VI adsorption, principally in acidic pH values. The adsorption capacity is dependent on the pH of the solution, due to its influence on the surface properties of the CAG and different ionic forms of the Cr(VI solutions. The adsorption equilibrium data was adjusted satisfactorily by the Langmuir isotherm (R²=0,988, favorable type. From kinetics adsorption of 20 mg/L and 5 mg/L, the results were compatible with the national legislation (Res. nº 357/05. Therefore, the experimental system using (CAG was efficient in removing the Cr(VI from liquid streams containing low concentrations of the metal.

Physicochemistry of the plasma-electrolyte solution interface

International Nuclear Information System (INIS)

Chen Qiang; Saito, Kenji; Takemura, Yu-ichiro; Shirai, Hajime

2008-01-01

The atmospheric rf plasma discharge was successfully investigated using NaOH or HCl electrolyte solutions as a counter electrode at different pH values. The emission intensities of solution components, self bias, and electron density strongly depend on the pH value of electrolyte. An addition of ethanol to the electrolyte solutions enhanced the dehydration, which markedly promoted the emissions of solution components as well as electrons from the solution. An acidification of the solution was always observed after the plasma exposure and two coexisting mechanisms were proposed to give a reasonable interpretation. The plasma-electrolyte interface was discussed based on a model of hydrogen cycle

Influences of salt concentration, loading and pH on strontium adsorption

International Nuclear Information System (INIS)

Atun, G.; Kaplan, Z.

1996-01-01

The adsorption of Sr on clay with contains zeolites and montmorillonite mixtures was investigated in solutions of NaCl by means of a batch technique. Sr retention was reduced with increasing NaCl concentration from 5*10 -4 to 5*10 -1 M. Distribution coefficients (K d ) linearly increased with pH in the acidic region but they were almost independent of pH in neutral and alkaline solutions. By fitting the data of the Dubinin-Radushkevich (D-R) isotherm, the mean energies of adsorption and adsorption capacities of Sr at different pH values were calculated. The results showed that the mode of adsorption below pH 4.5 is ion exchange, while above that value a multilayer adsorption occurs. Adsorption data were fitted to the Freundlich isotherm and from empirical Freundlich parameters a site distribution function was calculated. (author)

EFFECT OF TEMPERATURE AND pH OF MODIFICATION PROCESS ON THE PHYSICAL-MECHANICAL PROPERTIES OF MODIFIED CASSAVA STARCH

Directory of Open Access Journals (Sweden)

Yudi Wicaksono

2016-11-01

Full Text Available The use of cassava starch for excipient in the manufacturing of the tablet has some problems, especially on physical-mechanical properties. The purpose of this study was to determine the effect of the differentness of temperature and pH in the process of modification on the physical-mechanical properties of modified cassava starch. Modifications were performed by suspending cassava starch into a solution of 3 % (w/v PVP K30. The effect of the difference of temperature was observed at temperatures of 25; 45 and 65 0C, while the effect of the difference of pH was observed at pH of 4.0; 7.0 and 12.0. The results showed that the temperature and pH did not affect the physical-mechanical properties of the modified cassava starch. Modification of cassava starch at pH and temperature of 7.0 and 45 0C was produced modified cassava starch with the most excellent solubility, while the best swelling power were formed by the modification process at pH and temperature of 7.0 and 25 0C. Overall, the most excellent compression properties of modified cassava starch resulted from the modification process at pH 12.

Equilibrium leach tests with cobalt in the system cemented waste form/container material/aqueous solution

International Nuclear Information System (INIS)

Vejmelka, P.; Koester, R.; Lee, M. J.; Han, K. W.

1991-01-01

The equilibrium concentrations of Co in the system of cemented waste form/aqueous solutions were determined including the effect of the container material and its corrosion products under the respective conditions. The chemical conditions in the near field of the waste form were characterized by measurement of the pH and E h value. As disposal relevant solutions, saturated sodium chloride, Q-brine (main constituent MgCl 2 ) and a granitic type groundwater were used. For comparison, also experiments using deionized water were performed. In all systems investigated the cemented waste form itself has a strong influence on the chemical conditions in the near field. The pH and E h values are affected in all cases by the addition of the cemented waste form. There is no or only a slight difference between the E h values if iron powder or iron hydroxide is added to the cemented waste form/solution systems, but the E h is markedly decreased when iron powder is added to the solution free of cement. The Co concentration is decreased in all solutions by the addition of the cemented waste form, the largest effect is observed in Q-brine and this can be attributed either to the sorption of the Co-ions on the corrosion products of the cement or to the coprecipitation of Co-hydroxide and Mg-hydroxide. In the other solutions the Co concentration is decreased by precipitation of Co-hydroxide due to the high pH value of 12.5, and the concentrations are comparable for the different solutions

The effect of high pH alkaline solutions on the mineral stability of the Boom Clay - Batch experiments at 60 deg. C

International Nuclear Information System (INIS)

Honty, M.; De Craen, M.; Wang, L.; Madejova, J.; Czimerova, A.; Pentrak, M.; Stricek, I.; Van Geet, M.

2010-01-01

Boom Clay is currently viewed as a reference host formation for studies on deep geological disposal of radioactive waste in Belgium. The interactions between bulk rock Boom Clay and 0.1 M KOH, 0.1 M NaOH, 0.1 M Ca(OH) 2 , young cement water and evolved cement water solutions, ranging in pH from 12.5 to 13.2, were examined as static batch experiments at 60 deg. C to simulate alkaline plume perturbations, which are expected to occur in the repository due to the presence of concrete. Both liquids and solids were investigated at specific times between 90 and 510 days in order to control the elemental budget and to search for potential mineralogical alterations. Also, the clay fraction was separated from the whole-rock Boom Clay at the end of each run and characterized for its mineralogical composition. Thereby, the importance of the mineral matrix to buffer the alkaline attack and the role of organic matter to protect clay minerals were also addressed. The results indicate that the degree of geochemical perturbation in Boom Clay is dependent on the initial pH of the applied solution together with the nature of the major cation in the reactant fluids. The higher the initial pH of the media, the stronger its interaction with Boom Clay. No major non-clay mineralogical alteration of the Boom Clay was detected, but dissolution of kaolinite, smectite and illite occurred within the studied experimental conditions. The dissolution of clays is accompanied by the decrease in the layer charge, followed by a decrease in the cation-exchange capacity. The highest TOC values coincide with the highest total elemental concentrations in the leachates, and correspondingly, the highest dissolution degree. However, no quantitative link could be established between the degree of organic matter decomposition and clay dissolution.

Biosynthesis of schwertmannite by Acidithiobacillus ferrooxidans cell suspensions under different pH condition

Energy Technology Data Exchange (ETDEWEB)

Liao Yuehua [Department of Environmental Engineering, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China); Zhou Lixiang [Department of Environmental Engineering, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China)], E-mail: lxzhou@njau.edu.cn; Liang Jianru; Xiong Huixin [Department of Environmental Engineering, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China)

2009-01-01

Oxidation of FeSO{sub 4} solution with initial pH in the range of 1.40-3.51 by Acidithiobacillus ferrooxidans LX5 cell at 26 deg. C and subsequent precipitation of resulting Fe(III) were investigated in the present study. Results showed that the oxidation rate of Fe(II) was around 1.2-3.9 mmol l{sup -1} h{sup -1}. X-ray diffraction (XRD) indicated that the formed precipitates were composed of natrojarosite with schwertmannite when the initial pH was 3.51, while only schwertmannite was produced when initial pH was in the range of 1.60-3.44 and no precipitate occurred when initial pH {<=} 1.40. Scanning electron microscope (SEM) analyses showed that precipitates formed in solution with initial pH 3.51 were spherical particles of about 0.4 {mu}m in diameter and had a smooth surface, whereas precipitates in solution with initial pH {<=} 3.44 were spherical particles of approximately 1.0 {mu}m in diameter, having specific sea-urchin morphology. Specific surface area of the precipitates varied from 3.42 to 23.45 m{sup 2} g{sup -1}. X-ray fluorescence analyses revealed that schwertmannite formed in solution with initial pH in the range of 2.00-3.44 had similar elemental composition and could be expressed as Fe{sub 8}O{sub 8}(OH){sub 4.42}(SO{sub 4}){sub 1.79,} whereas Fe{sub 8}O{sub 8}(OH){sub 4.36}(SO{sub 4}){sub 1.82} and Fe{sub 8}O{sub 8}(OH){sub 4.29}(SO{sub 4}){sub 1.86} as its chemical formula when the initial pH was 1.80 and 1.60, respectively.

Solid phase extraction of uranium and thorium on octadecyl bonded silica modified with Cyanex 302 from aqueous solutions

International Nuclear Information System (INIS)

Nilchi, A.; Shariati Dehaghan, T.; Rasouli Garmarodi, S.

2013-01-01

A simple and reliable method for rapid extraction and determination of uranium and thorium using octadecyl-bonded silica modified with Cyanex 302 is presented. Extraction efficiency and the influence of various parameters such as aqueous phase pH, flow rate of sample solution and amount of extractant has been investigated. The study showed that the extraction of uranium and thorium increase with increasing pH value and was found to be quantitative at pH 6; and the retention of ions was not affected significantly by the flow rate of sample solution. The extraction percent were found to be 89.55 and 86.27 % for uranium and thorium, respectively. The maximal capacity of the cartridges modified by 30 mg of Cyanex 302 was found to be 20 mg of uranium and thorium. The method was successfully applied to the extraction and determination of uranium and thorium in aqueous solutions. The percentage recovery of uranium and thorium in a number of natural as well as seawater samples of Iran were also investigated and found to be in the range of 85-95%. (author)

Sorghum grain supplementation affects rumen pH of animals fed ...

African Journals Online (AJOL)

Martin Aguerre

Ruminal pH was measured immediately and NH3-N concentration was determined by ... when using sorghum as a supplement of a rye grass hay. The aim of this ... Increasing grain level in a diet often results in higher rumen fermentation (Rymer & .... and in situ degradability and the in vitro gas production profile of the diet.

Alteration behavior of bentonite barrier of radioactive waste disposal by alkaline solutions. Part 1. Permeability change of compacted bentonite immersed in alkaline solutions

International Nuclear Information System (INIS)

Yokoyama, Shingo; Nakamura, Kunihiko

2010-01-01

Permeability tests using the compacted bentonites and alkaline solutions were carried out to estimate of alteration behavior and the change of permeability during the alteration reaction. The permeability tests of the compacted bentonites were carried out at 23degC for one week after they were immersed in alkaline solution at 60degC for four weeks (immersing test). After permeability tests, the compacted bentonites were repeatedly tested as the same procedure (i.e. repetition of permeability test and immersing test) at 11 cycles. The compacted bentonites with initial dry density of 1.6 Mg/m 3 were reacted with the different type of the alkaline solutions (deionized water, NaOH (pH=12 and 14), KOH (pH=12 and 14) and Ca(OH) 2 (pH=12)) in each experiments. In the case of deionized water and alkaline solutions of pH12, the mineral compositions of altered bentonite were similar to original bentonite while the exchangeable cations of altered bentonites were changed. No changes of the mineralogical features of montmorillonite in altered bentonites (i.e. illitization, baideritization and increasing of layer charge) were observed in the case of deionized water, pH12-NaOH and pH12-Ca(OH) 2 . The montmorillonite was changed to the illite/smectite interstratified mineral containing about 40% illite like component during the reaction with pH12-KOH. In the case of alkaline solutions with pH14, the component minerals of bentonite (e.g. montmorillonite, quartz and clinoptilolite) were dissolved, consequently secondly minerals (e.g. analcime and phillipsite) were crystallized during experiments. Furthermore, the mineralogical features of montmorillonite were changed as illitization (pH14-KOH), beidellitization (pH14-NaOH and pH14-KOH) and increasing of layer charge (pH14-NaOH and pH14-KOH). No increasing of permeability were observed during the experiment using pH12-NaOH and pH12-Ca(OH) 2 as well as the case of deionized water. In the case of pH12-KOH, the permeability continually

Emulsifier type, metal chelation and pH affect oxidative stability of n-3-enriched emulsions

DEFF Research Database (Denmark)

Haahr, Anne-Mette; Jacobsen, Charlotte

2008-01-01

-enriched oil-in-water emulsion. The selected food emulsifiers were Tween 80, Citrem, sodium caseinate and lecithin. Lipid oxidation was evaluated by determination of peroxide values and secondary volatile oxidation products. Moreover, the zeta potential and the droplet sizes were determined. Twen resulted...... in the least oxidatively stable emulsions, followed by Citrem. When iron was present, caseinate-stabilized emulsions oxidized slower than lecithin emulsions at pH 3, whereas the opposite was the case at pH 7. Oxidation generally progressed faster at pH 3 than at pH 7, irrespective of the addition of iron. EDTA...

An accurate coarse-grained model for chitosan polysaccharides in aqueous solution.

Directory of Open Access Journals (Sweden)

Levan Tsereteli

Full Text Available Computational models can provide detailed information about molecular conformations and interactions in solution, which is currently inaccessible by other means in many cases. Here we describe an efficient and precise coarse-grained model for long polysaccharides in aqueous solution at different physico-chemical conditions such as pH and ionic strength. The Model is carefully constructed based on all-atom simulations of small saccharides and metadynamics sampling of the dihedral angles in the glycosidic links, which represent the most flexible degrees of freedom of the polysaccharides. The model is validated against experimental data for Chitosan molecules in solution with various degree of deacetylation, and is shown to closely reproduce the available experimental data. For long polymers, subtle differences of the free energy maps of the glycosidic links are found to significantly affect the measurable polymer properties. Therefore, for titratable monomers the free energy maps of the corresponding links are updated according to the current charge of the monomers. We then characterize the microscopic and mesoscopic structural properties of large chitosan polysaccharides in solution for a wide range of solvent pH and ionic strength, and investigate the effect of polymer length and degree and pattern of deacetylation on the polymer properties.

An accurate coarse-grained model for chitosan polysaccharides in aqueous solution.

Science.gov (United States)

Tsereteli, Levan; Grafmüller, Andrea

2017-01-01

Computational models can provide detailed information about molecular conformations and interactions in solution, which is currently inaccessible by other means in many cases. Here we describe an efficient and precise coarse-grained model for long polysaccharides in aqueous solution at different physico-chemical conditions such as pH and ionic strength. The Model is carefully constructed based on all-atom simulations of small saccharides and metadynamics sampling of the dihedral angles in the glycosidic links, which represent the most flexible degrees of freedom of the polysaccharides. The model is validated against experimental data for Chitosan molecules in solution with various degree of deacetylation, and is shown to closely reproduce the available experimental data. For long polymers, subtle differences of the free energy maps of the glycosidic links are found to significantly affect the measurable polymer properties. Therefore, for titratable monomers the free energy maps of the corresponding links are updated according to the current charge of the monomers. We then characterize the microscopic and mesoscopic structural properties of large chitosan polysaccharides in solution for a wide range of solvent pH and ionic strength, and investigate the effect of polymer length and degree and pattern of deacetylation on the polymer properties.

Effect of solution chemistry on the adsorption of perfluorooctane sulfonate onto mineral surfaces.

Science.gov (United States)

Tang, Chuyang Y; Shiang Fu, Q; Gao, Dawen; Criddle, Craig S; Leckie, James O

2010-04-01

Perfluorooctane sulfonate (PFOS) is an emergent contaminant of substantial environmental concerns, yet very limited information has been available on PFOS adsorption onto mineral surfaces. PFOS adsorption onto goethite and silica was investigated by batch adsorption experiments under various solution compositions. Adsorption onto silica was only marginally affected by pH, ionic strength, and calcium concentration, likely due to the dominance of non-electrostatic interactions. In contrast, PFOS uptake by goethite increased significantly at high [H+] and [Ca2+], which was likely due to enhanced electrostatic attraction between the negatively charged PFOS molecules and positively charged goethite surface. The effect of pH was less significant at high ionic strength, likely due to electrical double layer compression. PFOS uptake was reduced at higher ionic strength for a strongly positively charged goethite surface (pH 3), while it increased for a weakly charged surface (pH 7 and 9), which could be attributed to the competition between PFOS-surface electrostatic attraction and PFOS-PFOS electrostatic repulsion. A conceptual model that captures PFOS-surface and PFOS-PFOS electrostatic interactions as well as non-electrostatic interaction was also formulated to understand the effect of solution chemistry on PFOS adsorption onto goethite and silica surfaces. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Electrochemical Impedance Spectroscopic Analysis of RuO2 Based Thick Film pH Sensors

International Nuclear Information System (INIS)

Manjakkal, Libu; Djurdjic, Elvira; Cvejin, Katarina; Kulawik, Jan; Zaraska, Krzysztof; Szwagierczak, Dorota

2015-01-01

The conductimetric interdigitated thick film pH sensors based on RuO 2 were fabricated and their electrochemical reactions with solutions of different pH values were studied by electrochemical impedance spectroscopy (EIS) technique. The microstructural properties and composition of the sensitive films were examined by scanning electron microscopy, X-ray energy dispersive spectroscopy and Raman spectroscopy. The EIS analysis of the sensor was carried out in the frequency range 10 mHz–2 MHz for pH values of test solutions 2–12. The electrical parameters of the sensor were found to vary with changing pH. The conductance and capacitance of the film were distinctly dependent on pH in the low frequency range. The Nyquist and Bode plots derived from the impedance data for the metal oxide thick film pH sensor provided information about the underlying electrochemical reactions

Development of a microprocessor-controlled coulometric system for stable ph control

NARCIS (Netherlands)

Bergveld, Piet; van der Schoot, B.H.

1983-01-01

The coulometric pH control system utilizes a programmable coulostat for controlling the pH of a certain volume of unbuffered solution. Based on theoretical considerations, conditions are established which guarantee stable operation with maximum suppression of disturbances from the dissolution of

Decomposition kinetics of aminoborane in aqueous solutions

International Nuclear Information System (INIS)

Shvets, I.B.; Erusalimchik, I.G.

1984-01-01

Kinetics of aminoborane hydrolysis has been studied using the method of polarization galvanostatical curves on a platinum electrode in buffer solutions at pH 3; 5; 7. The supposition that the reaction of aminoborane hydrolysis is the reaction of the first order by aminoborane is proved. The rate constant of aminoborane decomposition in the solution with pH 5 is equal to: K=2.5x10 -5 s -1 and with pH 3 it equals K=1.12x10 -4 s -1

Reclamation of zinc-contaminated soil using a dissolved organic carbon solution prepared using liquid fertilizer from food-waste composting.

Science.gov (United States)

Chiang, Po-Neng; Tong, Ou-Yang; Chiou, Chyow-San; Lin, Yu-An; Wang, Ming-Kuang; Liu, Cheng-Chung

2016-01-15

A liquid fertilizer obtained through food-waste composting can be used for the preparation of a dissolved organic carbon (DOC) solution. In this study, we used the DOC solutions for the remediation of a Zn-contaminated soil (with Zn concentrations up to 992 and 757 mg kg(-1) in topsoil and subsoil, respectively). We then determined the factors that affect Zn removal, such as pH, initial concentration of DOC solution, and washing frequency. Measurements using a Fourier Transform infrared spectrometer (FT-IR) revealed that carboxyl and amide were the major functional groups in the DOC solution obtained from the liquid fertilizer. Two soil washes using 1,500 mg L(-1) DOC solution with a of pH 2.0 at 25°C removed about 43% and 21% of the initial Zn from the topsoil and subsoil, respectively. Following this treatment, the pH of the soil declined from 5.4 to 4.1; organic matter content slightly increased from 6.2 to 6.5%; available ammonium (NH4(+)-N) content increased to 2.4 times the original level; and in the topsoil, the available phosphorus content and the exchangeable potassium content increased by 1.65 and 2.53 times their initial levels, respectively. Copyright © 2015 Elsevier B.V. All rights reserved.

Modified Organosilica Core-Shell Nanoparticles for Stable pH Sensing in Biological Solutions.

Science.gov (United States)

Robinson, Kye J; Huynh, Gabriel T; Kouskousis, Betty P; Fletcher, Nicholas L; Houston, Zachary H; Thurecht, Kristofer J; Corrie, Simon R

2018-04-19

Continuous monitoring using nanoparticle-based sensors has been successfully employed in complex biological systems, yet the sensors still suffer from poor long-term stability partially because of the scaffold materials chosen to date. Organosilica core-shell nanoparticles containing a mixture of covalently incorporated pH-sensitive (shell) and pH-insensitive (core) fluorophores is presented as a continuous pH sensor for application in biological media. In contrast to previous studies focusing on similar materials, we sought to investigate the sensor characteristics (dynamic range, sensitivity, response time, stability) as a function of material properties. The ratio of the fluorescence intensities at specific wavelengths was found to be highly sensitive to pH over a physiologically relevant range (4.5-8) with a response time of pH-specific signals when stored at room temperature for more than 80 days. Finally, we demonstrated that the nanosensors successfully monitored the pH of a bacterial culture over 15 h and that pH changes in the skin of mouse cadavers could also be observed via in vivo fluorescence imaging following subcutaneous injection. The understanding gained from linking sensor characteristics and material properties will inform the next generation of optical nanosensors for continuous-monitoring applications.

Tuning interionic interaction by rationally controlling solution pH for highly selective colorimetric sensing of arginine.

Science.gov (United States)

Qian, Qin; Hao, Jie; Ma, Wenjie; Yu, Ping; Mao, Lanqun

2016-04-01

Direct selective sensing of arginine in central nervous systems remains very essential to understanding of the molecular basis of some physiological events. This study presents the first demonstration on a simple yet effective method for arginine sensing with gold nanoparticles (Au-NPs) as the signal readout. The rationale for the method is based on the pH-dependent feature of the interionic interaction between cysteine and arginine. At pH 6.0, cysteine can only interact with arginine through the ion-pair interaction and such interaction can lead to the changes in both the solution color and UV-vis spectrum of the cysteine-protected Au-NPs upon the addition of arginine. These changes are further developed into an analytical strategy for effective sensing of arginine by rationally controlling the pH values of Au-NP dispersions with the ratio of the absorbance at 650 nm (A 650) to that at 520 nm (A 520) (A 650/A 520) as a parameter for analysis. The method is responsive to arginine without the interference from other species in the cerebral system; under the optimized conditions, the A 650/A 520 values are linear with the concentration of arginine within a concentration range from 0.80 to 64 μM, yet remain unchanged with the addition of other kinds of amino acids or the species in the central nervous system into the Au-NPs dispersion containing cysteine. The method demonstrated here is reliable and robust and could thus be used for detection of the increase of arginine in central nervous systems.

Effects of pH on the crystallographic structure and magnetic properties of electrodeposited cobalt nanowires

International Nuclear Information System (INIS)

Zafar, N.; Shamaila, S.; Sharif, R.; Wali, H.; Naseem, S.; Riaz, S.; Khaleeq-ur-Rahman, M.

2015-01-01

Anodic aluminum oxide templates with pore diameter of 40 nm and inter pore separation of 100 nm are prepared by two step anodization in 0.3 M oxalic acid solution. These templates are used to fabricate dc-deposited Co nanowires at different pH values of acidic bath. Continuous and densely packed nanowires having length ∼8 µm are observed. The hcp configuration appeared at moderate and high pH whereas both fcc and hcp phases are observed at low pH. However the crystallinity distorted at high pH due to formation of polycrystalline structure of cobalt nanowires. Alignment of easy-axis of nanowires can be tailored by varying pH of solution. - Highlights: • Variation in the structure of dc deposited cobalt nanowires can be obtained by varying pH of acidic bath. • The hcp structure is stable at room temperature with low voltage deposition for electrodeposited Co nanowires. Co with fcc structure, is stable at temperatures above 422 °C or at pH<3 with high potential. • The hcp (100) plane is obtained with pH∼3.5 and (101) is stable at pH∼5.5 due to variation in temperature inside the pores with respect to the pH. • Alignment of easy-axis of nanowires can be tailored by varying pH of solution

Iodine evolution and pH control

International Nuclear Information System (INIS)

Beahm, E.C.; Lorenz, R.A.; Weber, C.F.

1993-01-01

The pH is the major factor in determining the extent of I 2 in solution. In containment where no pH-control chemicals are present, the acidity or basicity of the water pool will be determined by materials that are introduced into containment as a result of the accident itself. These materials may be fission products (i.e., cesium compounds), thermally produced products (i.e., core-concrete aerosols), or compounds produced by radiation (i.e., nitric acid). In situations where pH levels fall below ∼7, the formation of I 2 will occur in irradiated iodide solutions. A correlation between pH and iodine formation is needed so that the amounts I 2 in water pools can be assessed. This, in turn, determines the amount of I 2 in the atmosphere available for escape by containment leakage. A number of calculational routines based on more than 100 differential equations representing individual reactions can be found in the literature. In this work, it is shown that a simpler approach based on the steady-state decomposition of hydrogen peroxide should correctly describe iodine formation in severe accidents. Comparisons with test data show this approach to be valid. The most important acids in containment will be nitric acid (HNO 3 ), produced by irradiation of water and air, and hydrochloric acid (HCl), produced by irradiation or heating of electrical cable insulation. The most important bases in containment will be cesium hydroxide, cesium borate (or cesium carbonate), and in some plants pH additives, such as sodium hydroxide or sodium phosphate

Capturing intracellular pH dynamics by coupling its molecular mechanisms within a fully tractable mathematical model.

Directory of Open Access Journals (Sweden)

Yann Bouret

Full Text Available We describe the construction of a fully tractable mathematical model for intracellular pH. This work is based on coupling the kinetic equations depicting the molecular mechanisms for pumps, transporters and chemical reactions, which determine this parameter in eukaryotic cells. Thus, our system also calculates the membrane potential and the cytosolic ionic composition. Such a model required the development of a novel algebraic method that couples differential equations for slow relaxation processes to steady-state equations for fast chemical reactions. Compared to classical heuristic approaches based on fitted curves and ad hoc constants, this yields significant improvements. This model is mathematically self-consistent and allows for the first time to establish analytical solutions for steady-state pH and a reduced differential equation for pH regulation. Because of its modular structure, it can integrate any additional mechanism that will directly or indirectly affect pH. In addition, it provides mathematical clarifications for widely observed biological phenomena such as overshooting in regulatory loops. Finally, instead of including a limited set of experimental results to fit our model, we show examples of numerical calculations that are extremely consistent with the wide body of intracellular pH experimental measurements gathered by different groups in many different cellular systems.

Dependency of the band gap of electrodeposited Copper oxide thin films on the concentration of copper sulfate (CuSO4.5H2O) and pH in bath solution for photovoltaic applications

KAUST Repository

Islam, Md. Anisul

2016-03-10

In this study, Copper oxide thin films were deposited on copper plate by electrodeposition process in an electrolytic bath containing CuSO4.5H2O, 3M lactic acid and NaOH. Copper oxide films were electrodeposited at different pH and different concentration of CuSO4.5H2O and the optical band gap was determined from their absorption spectrum which was obtained from UV-Vis absorption spectroscopy. It was found that copper oxide films which were deposited at low concentration of CuSO4.5H2O have higher band gap than those deposited at higher bath concentration. The band gap of copper oxide films also significantly changes with pH of the bath solution. It was also observed that with the increase of the pH of bath solution band gap of copper oxide film decreased. © 2015 IEEE.

The role of pH variation on the growth of zinc oxide nanostructures

International Nuclear Information System (INIS)

Wahab, Rizwan; Ansari, S.G.; Kim, Young Soon; Song, Minwu; Shin, Hyung-Shik

2009-01-01

In this paper we present a systematic study on the morphological variation of ZnO nanostructure by varying the pH of precursor solution via solution method. Zinc acetate dihydrate and sodium hydroxide were used as a precursor, which was refluxed at 90 deg. C for an hour. The pH of the precursor solution (zinc acetate di hydrate) was increased from 6 to 12 by the controlled addition of sodium hydroxide (NaOH). Morphology of ZnO nanorods markedly varies from sheet-like (at pH 6) to rod-like structure of zinc oxide (pH 10-12). Diffraction patterns match well with standard ZnO at all pH values. Crystallinity and nanostructures were confirmed by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) pattern, which indicates structure grew along [0 0 0 1] direction with an ideal lattice fringes distance 0.52 nm. FTIR spectroscopic measurement showed a standard peak of zinc oxide at 464 cm -1 . Amount of H + and OH - ions are found key to the structure control of studied material, as discussed in the growth mechanism.

Trimerization Dictates Solution Opalescence of a Monoclonal Antibody.

Science.gov (United States)

Yang, Teng-Chieh; Langford, Alex Jacob; Kumar, Sandeep; Ruesch, John Carl; Wang, Wei

2016-08-01

Opalescence, sometimes observed in antibody solutions, is thought to be mediated by light scattering of soluble oligomers or insoluble particulates. However, mechanistic features, such as stoichiometry and self-association affinity of oligomeric species related to opalescence, are poorly understood. Here, opalescence behavior of a monoclonal antibody (mAb-1) solution was studied over a wide range of solution conditions including different protein concentrations, pH, and in the presence or absence of salt. Hydrodynamic and thermodynamic properties of mAb-1 solutions were studied by analytical ultracentrifugation and dynamic light scattering. Opalescence in mAb-1 solutions is pH and concentration dependent. The degree of opalescence correlates with reversible monomer-trimer equilibrium detected by analytical ultracentrifugation. Increased trimer formation corresponds to increased opalescence in mAb-1 solutions at higher pH and protein concentrations. Addition of NaCl shifts this equilibrium toward monomer and reduces solution opalescence. This study demonstrates that opalescence in mAb-1 solutions does not arise from the light scattering of monomer or random molecular self-associations but is strongly correlated with a specific self-association stoichiometry and affinity. Importantly, at pH 5.5 (far below isoelectric point of mAb-1), the solution is not opalescent and with nonideal behavior. This study also dissects several parameters to describe the hydrodynamic and thermodynamic nonideality. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Response surface methodology for the optimization of lanthanum removal from an aqueous solution using a Fe{sub 3}O{sub 4}/chitosan nanocomposite

Energy Technology Data Exchange (ETDEWEB)

Haldorai, Yuvaraj [Department of Energy and Materials Engineering, Dongguk University-Seoul, Seoul (Korea, Republic of); Rengaraj, Arunkumar [Department of Biological Engineering, Biohybrid Systems Research Center (BSRC), Inha University, Incheon 402-751 (Korea, Republic of); Ryu, Taegong; Shin, Junho [Mineral Resources Research Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 305-350 (Korea, Republic of); Huh, Yun Suk, E-mail: yunsuk.huh0311@gmail.com [Department of Biological Engineering, Biohybrid Systems Research Center (BSRC), Inha University, Incheon 402-751 (Korea, Republic of); Han, Young-Kyu, E-mail: ykenergy@dongguk.edu [Department of Energy and Materials Engineering, Dongguk University-Seoul, Seoul (Korea, Republic of)

2015-05-15

Highlights: • Magnetite/chitosan composite for lanthanum removal. • Response surface methodology was used for optimization. • A 99.88% removal of La{sup 3+} was observed at 40 °C, pH 11, and 50 min. • Adsorption process was significantly affected by pH and adsorbent dosage. • Biocompatible, eco-friendly and a low-cost adsorbent. - Abstract: In the present work, magnetite nanoparticles/chitosan composites (Fe{sub 3}O{sub 4}/CS) were prepared by a chemical precipitation method. We demonstrated the efficient removal of a rare earth metal, lanthanum (La{sup 3+}), from an aqueous solution using the composite. The removal of La{sup 3+} was optimized by using response surface methodology. Analysis of variance and Fisher's F-test were used to determine the reaction parameters which affect the removal of La{sup 3+}. Optimal conditions, including adsorbent dosage, pH, temperature, and contact time for the removal of La{sup 3+}, were found to be 6.5 mg, pH 11, 40 °C, and 50 min, respectively. The adsorption capacity was 99.88%. The rate of La{sup 3+} adsorption was significantly affected by the solution pH and adsorbent amount. An adsorption isotherm was fitted well by the Freundlich model with a linear regression correlation value of 0.9975. The adsorption of La{sup 3+} using the composite followed pseudo second-order kinetics. Thermodynamic studies have revealed that the negative values of Gibbs free energy confirmed the spontaneous and feasible nature of adsorption.

Microbially-Enhanced Redox Solution Reoxidation for Sour Natural Gas Sweetening

Energy Technology Data Exchange (ETDEWEB)

Kenneth Brezinsky

2008-01-15

The specific objective of this project are to advance the technology and improve the economics of the commercial iron-based chelate processes such as LO-CAT II and SulFerox process utilizing biologically enhanced reoxidation of the redox solutions used in these processes. The project is based on the use of chelated ferric iron as the catalyst for the production of elemental sulfur, and then oxidizing bacteria, such as Thiobacillus Ferrooxidans (ATCC 23270) as an oxidizer. The regeneration of Fe{sup 3+} - chelate is accomplished by the use of these same microbes under mild conditions at 25-30 C and at atmospheric pressure to minimize the chelate degradation process. The pH of the redox solution was observed to be a key process parameter. Other parameters such as temperature, total iron concentration, gas to liquid ratio and bacterial cell densities also influence the overall process. The second part of this project includes experimental data and a kinetic model of microbial H{sub 2}S removal from sour natural gas using thiobacillus species. In the experimental part, a series of experiments were conducted with a commercial chelated iron catalyst at pH ranges from 8.7 to 9.2 using a total iron concentration range from 925 ppm to 1050 ppm in the solution. Regeneration of the solution was carried out by passing air through the solution. Iron oxidizing bacteria were used at cell densities of 2.3 x 10{sup 7}cells/ml for optimum effective performance. In the modeling part, oxidation of Fe{sup 2+} ions by the iron oxidizing bacteria - Thiobacillus Ferrooxidans was studied for application to a continuous stirred tank reactor (CSTR). The factors that can directly affect the oxidation rate such as dilution rate, temperature, and pH were analyzed. The growth of the microorganism was assumed to follow Monod type of growth kinetics. Dilution rate had influence on the rate of oxidation of ferrous iron. Higher dilution rates caused washout of the biomass. The oxidation rate was

Modelling of the effect of solute structure and mobile phase pH and composition on the retention of phenoxy acid herbicides in reversed-phase high-performance liquid chromatography

International Nuclear Information System (INIS)

Aschi, Massimiliano; D'Archivio, Angelo Antonio; Mazzeo, Pietro; Pierabella, Mirko; Ruggieri, Fabrizio

2008-01-01

A feed-forward artificial neural network (ANN) learned by error back-propagation is used to generate a retention predictive model for phenoxy acid herbicides in isocratic reversed-phase high-performance liquid chromatography. The investigated solutes (18 compounds), apart from the most common herbicides of this class, include some derivatives of benzoic acid and phenylacetic acid structurally related to phenoxy acids, as a whole covering a pK a range between 2.3 and 4.3. A mixed model in terms of both solute descriptors and eluent attributes is built with the aim of predicting retention in water-acetonitrile mobile phases within a large range of composition (acetonitrile from 30% to 70%, v/v) and acidity (pH of water before mixing with acetonitrile ranging between 2 and 5). The set of input variables consists of solute pK a and quantum chemical molecular descriptors of both the neutral and dissociated form, %v/v of acetonitrile in the mobile phase and pH of aqueous phase before mixing with acetonitrile. After elimination of redundant variables, a nine-dimensional model is identified and its prediction ability is evaluated by external validation based on three solutes not involved in model generation and by cross-validation. A multilinear counterpart in terms of the same descriptors is seen to provide a noticeably poorer retention prediction

Modelling of the effect of solute structure and mobile phase pH and composition on the retention of phenoxy acid herbicides in reversed-phase high-performance liquid chromatography

Energy Technology Data Exchange (ETDEWEB)

Aschi, Massimiliano [Dipartimento di Chimica, Ingegneria Chimica e Materiali, Universita degli Studi di L' Aquila, Via Vetoio, 67010 Coppito, L' Aquila (Italy); D' Archivio, Angelo Antonio [Dipartimento di Chimica, Ingegneria Chimica e Materiali, Universita degli Studi di L' Aquila, Via Vetoio, 67010 Coppito, L' Aquila (Italy)], E-mail: darchivi@univaq.it; Mazzeo, Pietro; Pierabella, Mirko; Ruggieri, Fabrizio [Dipartimento di Chimica, Ingegneria Chimica e Materiali, Universita degli Studi di L' Aquila, Via Vetoio, 67010 Coppito, L' Aquila (Italy)

2008-06-02

A feed-forward artificial neural network (ANN) learned by error back-propagation is used to generate a retention predictive model for phenoxy acid herbicides in isocratic reversed-phase high-performance liquid chromatography. The investigated solutes (18 compounds), apart from the most common herbicides of this class, include some derivatives of benzoic acid and phenylacetic acid structurally related to phenoxy acids, as a whole covering a pK{sub a} range between 2.3 and 4.3. A mixed model in terms of both solute descriptors and eluent attributes is built with the aim of predicting retention in water-acetonitrile mobile phases within a large range of composition (acetonitrile from 30% to 70%, v/v) and acidity (pH of water before mixing with acetonitrile ranging between 2 and 5). The set of input variables consists of solute pK{sub a} and quantum chemical molecular descriptors of both the neutral and dissociated form, %v/v of acetonitrile in the mobile phase and pH of aqueous phase before mixing with acetonitrile. After elimination of redundant variables, a nine-dimensional model is identified and its prediction ability is evaluated by external validation based on three solutes not involved in model generation and by cross-validation. A multilinear counterpart in terms of the same descriptors is seen to provide a noticeably poorer retention prediction.

Motion-Based pH Sensing Based on the Cartridge-Case-like Micromotor.

Science.gov (United States)

Su, Yajun; Ge, Ya; Liu, Limei; Zhang, Lina; Liu, Mei; Sun, Yunyu; Zhang, Hui; Dong, Bin

2016-02-17

In this paper, we report a novel cartridge-case-like micromotor. The micromotor, which is fabricated by the template synthesis method, consists of a gelatin shell with platinum nanoparticles decorating its inner surface. Intriguingly, the resulting cartridge-case-like structure exhibits a pH-dependent "open and close" feature, which originates from the pH responsiveness of the gelatin material. On the basis of the catalytic activity of the platinum nanoparticle inside the gelatin shell, the resulting cartridge-case-like structure is capable of moving autonomously in the aqueous solution containing the hydrogen peroxide fuel. More interestingly, we find out that the micromotor can be utilized as a motion-based pH sensor over the whole pH range. The moving velocity of the micromotor increases monotonically with the increase of pH of the analyte solution. Three different factors are considered to be responsible for the proportional relation between the motion speed and pH of the analyte solution: the peroxidase-like and oxidase-like catalytic behavior of the platinum nanoparticle at low and high pH, the volumetric decomposition of the hydrogen peroxide under the basic condition and the pH-dependent catalytic activity of the platinum nanoparticle caused by the swelling/deswelling behavior of the gelatin material. The current work highlights the impact of the material properties on the motion behavior of a micromotor, thus paving the way toward its application in the motion-based sensing field.

Synthesis of xenotime(YPO4) by precipitation from aqueous solution

International Nuclear Information System (INIS)

Hikichi, Yasuo; Hukuo, Ken-iti; Shiokawa, Jiro.

1978-01-01

Xenotime (tetragonal YPO 4 ) was synthesized by the precipitation from a mixed solution of yttrium chloride and orthophosphoric acid or orthophosphate above 50 0 C. At 50 0 C, the initial precipitate from the solutions in the pH range from 0.8 to 2.9 was crystalline weinschenkite (monoclinic YPO 4 .2H 2 O) and amorphous phosphate was formed at pH above 3, while precipitation did not take place at pH 0.5. Weinschenkite was stable at 50 0 C, but amorphous phosphate gradually crystallized by aging and became crystalline xenotime at pH 3.7 after 5 days and at pH 5.0 after 28 days. At 90 0 C, xenotime was detected in the precipitate from the solution of pH 0.5, and was also obtained by aging weinschenkite at pH between 0.8 and 2.9 or amorphous phosphate at pH above 3. The unit cell parameters of the synthesized xenotime were as follows: a=b=6.893A, c=6.026A. (auth.)

Mechanisms of intragastric pH sensing.

Science.gov (United States)

Goo, Tyralee; Akiba, Yasutada; Kaunitz, Jonathan D

2010-12-01

Luminal amino acids and lack of luminal acidity as a result of acid neutralization by intragastric foodstuffs are powerful signals for acid secretion. Although the hormonal and neural pathways underlying this regulatory mechanism are well understood, the nature of the gastric luminal pH sensor has been enigmatic. In clinical studies, high pH, tryptic peptides, and luminal divalent metals (Ca(2+) and Mg(2+)) increase gastrin release and acid production. The calcium-sensing receptor (CaSR), first described in the parathyroid gland but expressed on gastric G cells, is a logical candidate for the gastric acid sensor. Because CaSR ligands include amino acids and divalent metals, and because extracellular pH affects ligand binding in the pH range of the gastric content, its pH, metal, and nutrient-sensing functions are consistent with physiologic observations. The CaSR is thus an attractive candidate for the gastric luminal sensor that is part of the neuroendocrine negative regulatory loop for acid secretion.

Plaque pH Changes Following Consumption of Two Types of Plain and Bulky Bread.

Science.gov (United States)

Mortazavi, Shiva; Noin, Sogol

2011-01-01

Consistency, backing process and content differences could influence cariogenic potential of foods. The aim was to compare plaque pH changes following consumption of two types of bread with different physical characteristics. In this clinical trial, interproximal plaque pH of 10 volunteers with high risk of dental caries (saliva Streptococcus mutans > 10(5), high dental caries experience, and average DMFT =6.10 ± 1.56) was measured. Plain traditionally backed "Sangak bread" and soft bulky "Baguette bread" and %10 sucrose solution were tested in a cross over designed experiment. Baseline plaque pH was recorded and followed by 1, 5, 10, 15, 20, and 30 minutes intervals. Data was analyzed using ANOVA and Tukey test (α = 0.05). Sucrose solution caused the most pronounced pH and ΔpH drop from 7.15 ± 0.33 at baseline to 6.78 ± 0.29. Means plaque pH of 10% sucrose solution and Baguette were not statistically different at 1, 20 and 30 minutes (P > 0.05). Mean plaque pH of Sangak and Baguette showed significant differences at 0, 1, 20 and30 minutes (P bread samples within first 10 minutes, pH increased and then started to decrease during tenth to fifteenth minutes. During all experiment phases, the mean pH of Baguette with less consistency and carbohydrate content and higher rate of starch gelatination was lower compared to Sangak.

Antimony removal from aqueous solutions using Zirconium hydroxide

International Nuclear Information System (INIS)

Petrescu, D.; Velciu, L.; Bucur, C.

2016-01-01

In this paper it is presented an experimental test for non-radioactive antimony removal from aqueous solutions using zirconium hydroxide powder. Also, it was studied how the temperature and pH influences antimony adsorption onto zirconium hydroxide surface. After the adsorption, solutions were filtered on Cellulose Mixed Ester Membrane with 0.2 μm pore size to remove the zirconium powder and then the aqueous solutions were sent to Inductively Coupled Plasma Optic Emission Spectrometry (ICP-OES) for quantitative analysis of Sb. Zirconium hydroxide powders were examined by optical microscopy. For the solutions that were tested at pH 4.5 and 10.2 the antimony concentration dropped below the detection limit of ICP-OES device, proof of antimony adsorption on zirconium hydroxide. Also, for the other tested solutions which had pH=12 the antimony concentration reduced with 77% and 80%. The temperature had no influence upon adsorption mechanism. (authors)

pH and effects on Streptococcus mutans growth of denture adhesives: an in vitro study.

Science.gov (United States)

Chen, Fengying; Mao, Tiantian; Cheng, Xiangrong

2014-06-01

To evaluate the pH and effects on Streptococcus mutans growth of denture adhesives. There is little information regarding the pH of contemporary adhesives and their influences on S. mutans growth. The adhesives tested were Polident® cream, Protefix® cream and Protefix® powder. Samples of each adhesive were added to deionized water to produce solutions of 10.0, 5.0, 2.5 and 1.0% w/v (cream formulations) or 5.0, 2.5,1.0 and 0.5% (powder formulation). The pH values were measured immediately after preparation and at 1-, 2-, 3-, 6-, 12-, and 24-h intervals using a digital pH meter. Streptococcus mutans UA159 was inoculated in the Brain Heart Infusion medium with or without the adhesive extracts (control). Bacterial growth was observed by measuring absorption at 600 nm every 1 h for 12 h using a spectrophotometer. The tested adhesives generally remained relatively pH-stable over 24 h, ranging from 5.5 to 7.0. There were no statistically significant differences in S. mutans growth rates between the extract-treated and control cultures (p>0.5). Some adhesives produce a pH below the critical pH of hydroxyapatite and may not be suitable for patients with natural teeth. None of the tested adhesives significantly affect S. mutans growth. © 2012 The Gerodontology Society and John Wiley & Sons A/S.

pH Mapping on Tooth Surfaces for Quantitative Caries Diagnosis Using Micro Ir/IrOx pH Sensor.

Science.gov (United States)

Ratanaporncharoen, Chindanai; Tabata, Miyuki; Kitasako, Yuichi; Ikeda, Masaomi; Goda, Tatsuro; Matsumoto, Akira; Tagami, Junji; Miyahara, Yuji

2018-04-03

A quantitative diagnostic method for dental caries would improve oral health, which directly affects the quality of life. Here we describe the preparation and application of Ir/IrOx pH sensors, which are used to measure the surface pH of dental caries. The pH level is used as an indicator to distinguish between active and arrested caries. After a dentist visually inspected and defined 18 extracted dentinal caries at various positions as active or arrested caries, the surface pH values of sound and caries areas were directly measured with an Ir/IrOx pH sensor with a diameter of 300 μm as a dental explorer. The average pH values of the sound root, the arrested caries, and active caries were 6.85, 6.07, and 5.30, respectively. The pH obtained with an Ir/IrOx sensor was highly correlated with the inspection results by the dentist, indicating that the types of caries were successfully categorized. This caries testing technique using a micro Ir/IrOx pH sensor provides an accurate quantitative caries evaluation and has potential in clinical diagnosis.

Influence of soil solution cation composition on boron adsorption by soils

Science.gov (United States)

Boron (B) adsorption on five arid-zone soil samples from California was investigated as a function of solution pH (4-10) and cation composition (Na, Ca, or Mg). Boron adsorption increased with increasing solution pH, reached an adsorption maximum near pH 9, and decreased with further increases with...

Chemical dosimetry at less than 1000 rad: aqueous trimesic acid solutions

International Nuclear Information System (INIS)

Matthews, R.W.; Wilson, J.G.

1981-01-01

Aqueous solutions of trimesic acid were investigated for possible use as a chemical dosimeter. In aerated 10 -2 M sulphuric acid solution containing 10 -3 M trimesic acid, a highly fluorescent product is formed with its maximum fluorescence at 450nm when excited by 350nm light. The product has fluorescence characteristics very similar to quinine in 0.05 M sulphuric acid. The fluorescence intensity is linear with dose in the range 1-1000 rad and a precision of +-2% was obtained from a number of runs. Solutions are stable for at least several days before and after irradiation. The yield is little affected by moderate changes in trimesic acid concentration, oxygen concentration, water purity, energy of radiation and irradiation temperature. The small dependence of the yield on dose rate and the effect of measurement temperature on the fluorescence signal have been quantified. The most significant factor affecting the fluorescence signal is the hydrogen ion concentration of the solution. In aerated neutral and alkaline (pH 10) solutions, hydroxytrimesic acid (HTMA) is formed with G(HTMA) equal to 2.07 +- 0.04 and 2.21 +- 0.04, for 10 -3 M trimesate. In these solutions, G(HTMA) increases appreciably with increase in the trimesate concentration. The main fluorescent product formed in irradiated acid solutions was not identified but it was not HTMA. (author)

pH variations during diafiltration due to buffer nonidealities.

Science.gov (United States)

Baek, Youngbin; Yang, Deyu; Singh, Nripen; Arunkumar, Abhiram; Ghose, Sanchayita; Li, Zheng Jian; Zydney, Andrew L

2017-11-01

Diafiltration is used for final formulation of essentially all biotherapeutics. Several studies have demonstrated that buffer/excipient concentrations in the final diafiltered product can be different than that in the diafiltration buffer due to interactions between buffer species and the protein product. However, recent work in our lab has shown variations in solution pH that are largely independent of the protein concentration during the first few diavolumes. Our hypothesis is that these pH variations are due to nonidealities in the acid-base equilibrium coefficient. A model was developed for the diafiltration process accounting for the ionic strength dependence of the pK a . Experimental results obtained using phosphate and histidine buffers were in excellent agreement with model predictions. A decrease in ionic strength leads to an increase in the pK a for the phosphate buffer, causing a shift in the solution pH, even under conditions where the initial feed and the diafiltration buffer are at the same pH. This effect could be eliminated by matching the ionic strength of the feed and diafiltration buffer. The experimental data and model provide new insights into the factors controlling the pH profile during diafiltration processes. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1555-1560, 2017. © 2017 American Institute of Chemical Engineers.

Monosilicate adsorption by ferrihydrite and goethite at pH 3-6

DEFF Research Database (Denmark)

Hansen, Hans Christian Bruun; Raben-Lange, B.; Raulund-Rasmussen, Karsten

1994-01-01

The constant capacitance model and the Elovich equation were combined in the following mathematical expression enabling calculation of the amount of silicic acid adsorbed by iron oxides as a function of the Si concentration, pH, soil:solution ratio, and reaction time: [GRAPHICS] K(a1) is the prot......The constant capacitance model and the Elovich equation were combined in the following mathematical expression enabling calculation of the amount of silicic acid adsorbed by iron oxides as a function of the Si concentration, pH, soil:solution ratio, and reaction time: [GRAPHICS] K(a1...

Photogeneration of H2O2 in SPEEK/PVA aqueous polymer solutions.

Science.gov (United States)

Little, Brian K; Lockhart, PaviElle; Slaten, B L; Mills, G

2013-05-23

Photolysis of air-saturated aqueous solutions containing sulphonated poly(ether etherketone) and poly(vinyl alcohol) results in the generation of hydrogen peroxide. Consumption of oxygen and H2O2 formation are initially concurrent processes with a quantum yield of peroxide generation of 0.02 in stirred or unstirred solutions within the range of 7 ≤ pH ≤ 9. The results are rationalized in terms of O2 reduction by photogenerated α-hydroxy radicals of the polymeric ketone in competition with radical-radical processes that consume the macromolecular reducing agents. Generation of H2O2 is controlled by the photochemical transformation that produces the polymer radicals, which is most efficient in neutral and slightly alkaline solutions. Quenching of the excited state of the polyketone by both H3O(+) and OH(-) affect the yields of the reducing macromolecular radicals and of H2O2. Deprotonation of the α-hydroxy polymeric radicals at pH > 9 accelerate their decay and contribute to suppressing the peroxide yields in basic solutions. Maxima in [H2O2] are observed when illuminations are performed with static systems, where O2 reduction is faster than diffusion of oxygen into the solutions. Under such conditions H2O2 can compete with O2 for the reducing radicals resulting in a consumption of the peroxide.

Solution-mediated phase transformation of haloperidol mesylate in the presence of sodium lauryl sulfate.

Science.gov (United States)

Greco, Kristyn; Bogner, Robin

2011-09-01

Forming a salt is a common way to increase the solubility of a poorly soluble compound. However, the solubility enhancement gained by salt formation may be lost due to solution-mediated phase transformation (SMPT) during dissolution. The SMPT of a salt can occur due to a supersaturated solution near the dissolving surface caused by pH or other solution conditions. In addition to changes in pH, surfactants are also known to affect SMPT. In this study, SMPT of a highly soluble salt, haloperidol mesylate, at pH 7 in the presence of a commonly used surfactant, sodium lauryl sulfate (SLS), was investigated. Dissolution experiments were performed using a flow-through dissolution apparatus with solutions containing various concentrations of SLS. Compacts of haloperidol mesylate were observed during dissolution in the flow-through apparatus using a stereomicroscope. Raman microscopy was used to characterize solids. The dissolution of haloperidol mesylate was significantly influenced by the addition of sodium lauryl sulfate. In conditions where SMPT was expected, the addition of SLS at low concentrations (0.1-0.2 mM) reduced the dissolution of haloperidol mesylate. In solutions containing concentrations of SLS above the critical micelle concentration (CMC) (10-15 mM), the dissolution of haloperidol mesylate increased compared to below the CMC. The solids recovered from solubility experiments of haloperidol mesylate indicated that haloperidol free base precipitated at all concentrations of SLS. Above 5 mM of SLS, Raman microscopy suggested a new form, perhaps the estolate salt. The addition of surfactant in solids that undergo solution-mediated phase transformation can add complexity to the dissolution profiles and conversion.

Regulating NETosis: Increasing pH Promotes NADPH Oxidase-Dependent NETosis

Science.gov (United States)

Khan, Meraj A.; Philip, Lijy M.; Cheung, Guillaume; Vadakepeedika, Shawn; Grasemann, Hartmut; Sweezey, Neil; Palaniyar, Nades

2018-01-01

Neutrophils migrating from the blood (pH 7.35–7.45) into the surrounding tissues encounter changes in extracellular pH (pHe) conditions. Upon activation of NADPH oxidase 2 (Nox), neutrophils generate large amounts of H+ ions reducing the intracellular pH (pHi). Nevertheless, how extracellular pH regulates neutrophil extracellular trap (NET) formation (NETosis) is not clearly established. We hypothesized that increasing pH increases Nox-mediated production of reactive oxygen species (ROS) and neutrophil protease activity, stimulating NETosis. Here, we found that raising pHe (ranging from 6.6 to 7.8; every 0.2 units) increased pHi of both activated and resting neutrophils within 10–20 min (Seminaphtharhodafluor dual fluorescence measurements). Since Nox activity generates H+ ions, pHi is lower in neutrophils that are activated compared to resting. We also found that higher pH stimulated Nox-dependent ROS production (R123 generation; flow cytometry, plate reader assay, and imaging) during spontaneous and phorbol myristate acetate-induced NETosis (Sytox Green assays, immunoconfocal microscopy, and quantifying NETs). In neutrophils that are activated and not resting, higher pH stimulated histone H4 cleavage (Western blots) and NETosis. Raising pH increased Escherichia coli lipopolysaccharide-, Pseudomonas aeruginosa (Gram-negative)-, and Staphylococcus aureus (Gram-positive)-induced NETosis. Thus, higher pHe promoted Nox-dependent ROS production, protease activity, and NETosis; lower pH has the opposite effect. These studies provided mechanistic steps of pHe-mediated regulation of Nox-dependent NETosis. Raising pH either by sodium bicarbonate or Tris base (clinically known as Tris hydroxymethyl aminomethane, tromethamine, or THAM) increases NETosis. Each Tris molecule can bind 3H+ ions, whereas each bicarbonate HCO3− ion binds 1H+ ion. Therefore, the amount of Tris solution required to cause the same increase in pH level is less than that of equimolar

Regulating NETosis: Increasing pH Promotes NADPH Oxidase-Dependent NETosis

Directory of Open Access Journals (Sweden)

Meraj A. Khan

2018-02-01

Full Text Available Neutrophils migrating from the blood (pH 7.35–7.45 into the surrounding tissues encounter changes in extracellular pH (pHe conditions. Upon activation of NADPH oxidase 2 (Nox, neutrophils generate large amounts of H+ ions reducing the intracellular pH (pHi. Nevertheless, how extracellular pH regulates neutrophil extracellular trap (NET formation (NETosis is not clearly established. We hypothesized that increasing pH increases Nox-mediated production of reactive oxygen species (ROS and neutrophil protease activity, stimulating NETosis. Here, we found that raising pHe (ranging from 6.6 to 7.8; every 0.2 units increased pHi of both activated and resting neutrophils within 10–20 min (Seminaphtharhodafluor dual fluorescence measurements. Since Nox activity generates H+ ions, pHi is lower in neutrophils that are activated compared to resting. We also found that higher pH stimulated Nox-dependent ROS production (R123 generation; flow cytometry, plate reader assay, and imaging during spontaneous and phorbol myristate acetate-induced NETosis (Sytox Green assays, immunoconfocal microscopy, and quantifying NETs. In neutrophils that are activated and not resting, higher pH stimulated histone H4 cleavage (Western blots and NETosis. Raising pH increased Escherichia coli lipopolysaccharide-, Pseudomonas aeruginosa (Gram-negative-, and Staphylococcus aureus (Gram-positive-induced NETosis. Thus, higher pHe promoted Nox-dependent ROS production, protease activity, and NETosis; lower pH has the opposite effect. These studies provided mechanistic steps of pHe-mediated regulation of Nox-dependent NETosis. Raising pH either by sodium bicarbonate or Tris base (clinically known as Tris hydroxymethyl aminomethane, tromethamine, or THAM increases NETosis. Each Tris molecule can bind 3H+ ions, whereas each bicarbonate HCO3− ion binds 1H+ ion. Therefore, the amount of Tris solution required to cause the same increase in pH level is less than that of equimolar

The effect of emulsifying salts on the turbidity of a diluted milk system with varying pH and protein concentration.

Science.gov (United States)

Culler, M D; Saricay, Y; Harte, F M

2017-06-01

Solutions of 10 commonly used emulsifying salts (ES) listed in the Code of Federal Regulations (21CFR133.179) for pasteurized process cheese were tested for their effect on the turbidity of a diluted milk system at different pH and protein concentrations to characterize the conditions that affect micellar structure. Emulsifying salt solutions were made by mixing the ES in a 1-in-20 dilution of water in skim milk ultrafiltrate (3 kDa molecular weight cut-off) to obtain ES concentrations from 0 to 248 mM. Skim milk was added to solutions containing nanopure water, skim milk ultrafiltrate, and a specific ES ranging in concentration from 0 to 248 mM and pH 5, 5.8, 6.8, 7.8, and 8.8. The turbidity of the samples was measured as the optical density at 400 nm immediately after mixing (time, t = 0), after 30 s (t = 30s), and after 30 min (t = 30min). Emulsifying salts were found to cause a decrease in the turbidity of the system, which was modeled using an exponential decay model, where C* represents a threshold salt concentration at which rapid dissociation occurs. At pH values 5.8 and 6.8, the ES caused the greatest decrease in turbidity of the diluted milk system. At pH 5, the ES had the least effect on the turbidity of the system. Sodium hexametaphosphate was found to have the strongest dissociative effect, with a C* value of 0.33 mM for t = 0 at pH 6.8. In contrast, the largest C* value calculated at pH 6.8 was monosodium phosphate at 278.22 mM. Increased time resulted in lower C* values. The model established for this study can be used to predict the dissociation of casein micelles in the presence of various types of ES. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Fluoresence quenching of riboflavin in aqueous solution by methionin and cystein

International Nuclear Information System (INIS)

Droessler, P.; Holzer, W.; Penzkofer, A.; Hegemann, P.

2003-01-01

The fluorescence quantum distributions, fluorescence quantum yields, and fluorescence lifetimes of riboflavin in methanol, DMSO, water, and aqueous solutions of the sulphur atom containing amino acids methionin and cystein have been determined. In methanol, DMSO, and water (pH=4-8) only dynamic fluorescence reduction due to intersystem crossing and internal conversion is observed. In aqueous methionin solutions of pH=5.25-9 a pH independent static and dynamic fluorescence quenching occurs probably due to riboflavin anion-methionin cation pair formation. In aqueous cystein solutions (pH range from 4.15 to 9) the fluorescence quenching increases with rising pH due to cystein thiolate formation. The cystein thiol form present at low pH does not react with neutral riboflavin. Cystein thiolate present at high pH seems to react with neutral riboflavin causing riboflavin deprotonation (anion formation) by cystein thiolate reduction to the cystein thiol form

Oxidative stability of soybean oil in oleosomes as affected by pH and iron.

Science.gov (United States)

Kapchie, Virginie N; Yao, Linxing; Hauck, Catherine C; Wang, Tong; Murphy, Patricia A

2013-12-01

The oxidative stability of oil in soybean oleosomes, isolated using the Enzyme-Assisted Aqueous Extraction Process (EAEP), was evaluated. The effects of ferric chloride, at two concentration levels (100 and 500 μM), on lipid oxidation, was examined under pH 2 and 7. The peroxide value (PV) and thiobarbituric acid-reactive substance (TBARS) value of oil, in oleosome suspensions stored at 60 °C, were measured over a 12 day period. The presence of ferric chloride significantly (Poil in the isolated oleosome, as measured by the PV and TBARS. Greater lipid oxidation occurred under an acidic pH. In the pH 7 samples, the positively charged transition metals were strongly attracted to the negatively charged droplets. However, the low ζ-potential and the high creaming rate at this pH, may have limited the oxidation. Freezing, freeze-drying or heating of oleosomes have an insignificant impact on the oxidative stability of oil in isolated soybean oleosomes. Manufacturers should be cautious when adding oleosomes as ingredients in food systems containing transition metal ions. Published by Elsevier Ltd.

FLEXIBLE PH SENSOR WITH POLYANILINE LAYER BASED ON IMPEDANCE MEASUREMENT

OpenAIRE

Chuang, Cheng-Hsin; Wu, Hsun-Pei; Chen, Cheng-Ho; Wu, Peng-Rong

2012-01-01

A flexible sensor with conducting polyaniline layer for detecting pH value based on the impedance measurement is fabricated and demonstrated in this study. The pH sensor consists of an interdigital electrode array on a flexible printed circuit and a thin-film polyaniline as the sensing layer. As the conductivity of polyaniline depends on the redox state, the impedance change of the polyaniline after it has reacted with different pH value solutions works as the sensing mechanism. In order to o...

Isolation of an oxomanganese(V) porphyrin intermediate in the reaction of a manganese(III) porphyrin complex and H2O2 in aqueous solution.

Science.gov (United States)

Nam, Wonwoo; Kim, Inwoo; Lim, Mi Hee; Choi, Hye Jin; Lee, Je Seung; Jang, Ho G

2002-05-03

The reaction of [Mn(TF(4)TMAP)](CF(3)SO(3))(5) (TF(4)TMAP=meso-tetrakis(2,3,5,6-tetrafluoro-N,N,N-trimethyl-4-aniliniumyl)porphinato dianion) with H(2)O(2) (2 equiv) at pH 10.5 and 0 degrees C yielded an oxomanganese(V) porphyrin complex 1 in aqueous solution, whereas an oxomanganese(IV) porphyrin complex 2 was generated in the reactions of tert-alkyl hydroperoxides such as tert-butyl hydroperoxide and 2-methyl-1-phenyl-2-propyl hydroperoxide. Complex 1 was capable of epoxidizing olefins and exchanging its oxygen with H(2) (18)O, whereas 2 did not epoxidize olefins. From the reactions of [Mn(TF(4)TMAP)](5+) with various oxidants in the pH range 3-11, the O-O bond cleavage of hydroperoxides was found to be sensitive to the hydroperoxide substituent and the pH of the reaction solution. Whereas the O-O bond of hydroperoxides containing an electron-donating tert-alkyl group is cleaved homolytically, an electron-withdrawing substituent such as an acyl group in m-chloroperoxybenzoic acid (m-CPBA) facilitates O-O bond heterolysis. The mechanism of the O-O bond cleavage of H(2)O(2) depends on the pH of the reaction solution: O-O bond homolysis prevails at low pH and O-O bond heterolysis becomes a predominant pathway at high pH. The effect of pH on (18)O incorporation from H(2) (18)O into oxygenated products was examined over a wide pH range, by carrying out the epoxidation of carbamazepine (CBZ) with [Mn(TF(4)TMAP)](5+) and KHSO(5) in buffered H(2) (18)O solutions. A high proportion of (18)O was incorporated into the CBZ-10,11-oxide product at all pH values but this proportion was not affected significantly by the pH of the reaction solution.

Evaluating Nanoparticle Sensor Design for Intracellular pH Measurements

DEFF Research Database (Denmark)

Benjaminsen, Rikke Vicki; Sun, Honghao; Henriksen, Jonas Rosager

2011-01-01

Particle-based nanosensors have over the last decade been designed for optical fluorescent-based ratiometric measurements of pH in living cells. However, quantitative and time-resolved intracellular measurements of pH in endosomes and lysosomes using particle nanosensors is challenging...... and there is a need to improve measurement methodology. In the present paper, we have successfully carried out time resolved pH measurements in endosomes and lyosomes in living cells using nanoparticle sensors and show the importance of sensor choice for successful quantification. We have studied two nanoparticle...... quantification of pH is an unfortunate result when measuring pH too close to the limit of the sensitive range of the sensors. Triple-labeled nanosensors with a pH measurement range of 3.2-7.0, which was synthesized by adding two pH-sensitive fluorophores with different pKa to each sensor, seem to be a solution...

An ultrasensitive method of real time pH monitoring with complementary metal oxide semiconductor image sensor.

Science.gov (United States)

Devadhasan, Jasmine Pramila; Kim, Sanghyo

2015-02-09

CMOS sensors are becoming a powerful tool in the biological and chemical field. In this work, we introduce a new approach on quantifying various pH solutions with a CMOS image sensor. The CMOS image sensor based pH measurement produces high-accuracy analysis, making it a truly portable and user friendly system. pH indicator blended hydrogel matrix was fabricated as a thin film to the accurate color development. A distinct color change of red, green and blue (RGB) develops in the hydrogel film by applying various pH solutions (pH 1-14). The semi-quantitative pH evolution was acquired by visual read out. Further, CMOS image sensor absorbs the RGB color intensity of the film and hue value converted into digital numbers with the aid of an analog-to-digital converter (ADC) to determine the pH ranges of solutions. Chromaticity diagram and Euclidean distance represent the RGB color space and differentiation of pH ranges, respectively. This technique is applicable to sense the various toxic chemicals and chemical vapors by situ sensing. Ultimately, the entire approach can be integrated into smartphone and operable with the user friendly manner. Copyright © 2014 Elsevier B.V. All rights reserved.

pCO2 And pH regulation of cerebral blood flow

Directory of Open Access Journals (Sweden)

SeongHun eYoon

2012-09-01

Full Text Available CO2 Serves as one of the fundamental regulators of cerebral blood flow. It is widely considered that this regulation occurs through pCO2-driven changes in pH of the cerebral spinal fluid, with elevated and lowered pH causing direct relaxation and contraction of the smooth muscle, respectively. However, some findings also suggest that pCO2 acts independently of and/or in conjunction with altered pH. This action may be due to a direct effect of cerebral spinal fluid pCO2 on the smooth muscle as well as on the endothelium, nerves, and astrocytes. Findings may also point to an action of arterial pCO2 on the endothelium to regulate smooth muscle contractility. Thus, the effects of pH and pCO2 may be influenced by the absence/presence of different cell types in the various experimental preparations. Results may also be influenced by experimental parameters including myogenic tone as well as solutions containing significantly altered HCO3- concentrations, i.e., solutions routinely employed to differentiate the effects of pH from pCO2. In sum, it appears that pCO2, independently and in conjunction with pH, may regulate cerebral blood flow.

Graphite Screen-Printed Electrodes Applied for the Accurate and Reagentless Sensing of pH.

Science.gov (United States)

Galdino, Flávia E; Smith, Jamie P; Kwamou, Sophie I; Kampouris, Dimitrios K; Iniesta, Jesus; Smith, Graham C; Bonacin, Juliano A; Banks, Craig E

2015-12-01

A reagentless pH sensor based upon disposable and economical graphite screen-printed electrodes (GSPEs) is demonstrated for the first time. The voltammetric pH sensor utilizes GSPEs which are chemically pretreated to form surface immobilized oxygenated species that, when their redox behavior is monitored, give a Nernstian response over a large pH range (1-13). An excellent experimental correlation is observed between the voltammetric potential and pH over the entire pH range of 1-13 providing a simple approach with which to monitor solution pH. Such a linear response over this dynamic pH range is not usually expected but rather deviation from linearity is encountered at alkaline pH values; absence of this has previously been attributed to a change in the pKa value of surface immobilized groups from that of solution phase species. This non-deviation, which is observed here in the case of our facile produced reagentless pH sensor and also reported in the literature for pH sensitive compounds immobilized upon carbon electrodes/surfaces, where a linear response is observed over the entire pH range, is explained alternatively for the first time. The performance of the GSPE pH sensor is also directly compared with a glass pH probe and applied to the measurement of pH in "real" unbuffered samples where an excellent correlation between the two protocols is observed validating the proposed GSPE pH sensor.

Bioaccumulation of uranium and thorium from the solution containing both elements using various microorganisms

International Nuclear Information System (INIS)

Tsuruta, T.

2006-01-01

The effects of proton, thorium and uranium on the bioaccumulation of thorium and uranium from the solution (pH 3.5) containing uranium and thorium using Streptomyces levoris cells were examined. The amount of thorium accumulated using the cells decreased by the pre-contact between the cells and the solution (pH 3.5) containing no metals, whereas that of uranium was almost unaffected by the treatment. The amount of thorium was almost unaffected by the existence of uranium. On the other hand, the amount of uranium accumulated was strongly affected by the thorium, especially thorium addition after uranium accumulation. The decrease of uranium accumulated by the addition of thorium after the accumulation of uranium was higher than that from the solution containing both elements. Therefore, the contribution of uranium-thorium exchange reaction was higher than that of competition reaction. Accordingly, proton-uranium-thorium exchange reaction was occurred in the accumulation of thorium from the solution containing thorium and uranium. The gram-positive bacteria, such as Micrococcus luteus, Arthrobacter nicotianae, Bacillus subtilis and B. megaterium, has a much higher separation factor as thorium/uranium than that of actinomycetes. These gram-positive bacterial strains can be used for the accumulation of thorium from the solution containing uranium and thorium

Hydrogen production by sodium borohydride in NaOH aqueous solution

Science.gov (United States)

Wang, Q.; Zhang, L. F.; Zhao, Z. G.

2018-01-01

The kinetics of hydrolysis reaction of NaBH4 in NaOH aqueous solution is studied. The influence of pH of the NaOH aqueous solution on the rate of hydrogen production and the hydrogen production efficiency are studied for the hydrolysis reaction of NaBH4. The results show that the activation energy of hydrolysis reaction of NaBH4 increased with the increase of the initial pH of NaOH aqueous solution.With the increasing of the initial pH of NaOH aqueous solution, the rate of hydrogen production and hydrogen production efficiency of NaBH4 hydrolysis decrease.

Taxonomy of Means and Ends in Aquaculture Production—Part 2: The Technical Solutions of Controlling Solids, Dissolved Gasses and pH

Directory of Open Access Journals (Sweden)

Bjorgvin Vilbergsson

2016-09-01

Full Text Available In engineering design, knowing the relationship between the means (technique and the end (desired function or outcome is essential. The means in Aquaculture are technical solutions like airlifts that are used to achive desired functionality (an end like controlling dissolved gasses. In previous work, the authors identified possible functions by viewing aquaculture production systems as transformation processes in which inputs are transformed by treatment techniques (means and produce outputs (ends. The current work creates an overview of technical solutions of treatment functions for both design and research purposes. A comprehensive literature review of all areas of technical solutions is identified and categorized into a visual taxonomy of the treatment functions for controlling solids, controlling dissolved gasses and controlling pH alkalinity and hardness. This article is the second in a sequence of four and partly presents the treatments functions in the taxonomy. The other articles in this series present complementary aspects of this research: Part 1, A transformational view on aquaculture and functions divided into input, treatment and output functions; Part 2, The current taxonomy paper; Part 3, The second part of the taxonomy; and Part 4, Mapping of the means (techniques for multiple treatment functions.

Effect of pH on the adsorption of dodecylamine on montmorillonite: Insights from experiments and molecular dynamics simulations

Science.gov (United States)

Peng, Chenliang; Min, Fanfei; Liu, Lingyun

2017-12-01

The hydrophobic aggregation in cationic surfactant suspension is an effective method to enhance the dewatering of clay-rich tailing. The solution pH can affect the adsorption behavior of cationic surfactant on clay mineral. The effect of pH on the adsorption of dodecylamine (DDA) on montmorillonite was investigated by the sedimentation test and the characterization of flocs images, contact angle, adsorption quantity, and fourier transform infrared (FTIR) spectroscopy, as well as molecular dynamics (MD) simulation. It was found that DDA ions were adsorbed on montmorillonite basal surfaces mainly by physical adsorption, including the electrostatic attraction and hydrogen bonding. A certain number of neutral DDA molecules can favor the adsorption of DDA. At pH around 8, the effect of hydrophobic modification was the best because DDA molecules and ions form compact and well-organized monolayer. The MD simulation results were in good agreement with that of contact angle, adsorption quantity and FTIR.

Factors influencing hydroquinone degradation in aqueous solution using a modified microelectrolysis method.

Science.gov (United States)

Li, Tong; Li, Tingting; Xiong, Houfeng; Zou, Donglei

2015-01-01

The discharge of hydroquinone (HQ), an important chemical raw material, to natural waters poses different ecological threats to aquatic organisms. In this study, we investigated the removal performance of traditional and modified microelectrolysis methods in aqueous solutions. The traditional microelectrolysis packing was modified by adding manganese (Mn), zinc (Zn), and copper (Cu) powder as additives. The factors affecting the removal performance of HQ, such as catalytic metal type, mass fraction of additive, reaction time, and initial pH, were examined. The results showed that the Mn modified packing exhibited the best performance compared to Zn and Cu powder. The removal rate of HQ using Mn modified packing can reach 94% after 4 h. In addition, 9% of Mn packing has a higher removal rate than other mass fractions. The acidic solution pH shows a more favorable degradation than a neutral and alkaline solution. The intermediates of HQ degradation by modified microelectrolysis were identified and then the pathway of HQ degradation was proposed. Our result indicates that Mn as catalytic metal holds promising potential to enhance HQ removal in water using the microelectrolysis method.

Intracellular pH determination by a 31P-NMR technique. The second dissociation constant of phosphoric acid in a biological system.

Science.gov (United States)

Seo, Y; Murakami, M; Watari, H; Imai, Y; Yoshizaki, K; Nishikawa, H; Morimoto, T

1983-09-01

To evaluate the accuracy of pH determination by 31P-NMR, factors which influence the pK value of phosphate were appraised on the basis of the titration of 1 mM phosphate buffer solution. When the method is used for the determination of cytoplasmic pH, ionic strength is the major factor causing shifts of apparent pK (pK') value, and the magnitude of the shift can be predicted from the ionic strength calculated by means of the Debye-Hückel equation. Ions (Na+, K+, Mg2+, and Ca2+) and salivary protein affected the pK' value by 0.1 to 0.3 units in solution with a given ionic strength depending on the species of ion. The form of the titration curve varied with temperature. Based on these results, the value of 6.75 was obtained with the uncertainty of 0.12 for the intracellular pK' of frog muscle at 24 degrees C.

Round robin test for define an accurate protocol to measure the pore fluid pH of low-pH cementitious materials

International Nuclear Information System (INIS)

Alonso, M.C.; Garcia Calvo, J.L.; Pettersson, S.; Puigdomenech, I.; Cunado, M.A.; Vuorio, M.; Weber, H.; Ueda, H.; Naito, M.; Walker, C.; Takeshi, Y.; Cau Dit Coumes, C.

2012-01-01

The present research belongs to an international project where several of the main nuclear waste management agencies have been involved. The main objective is the development of agreed procedures or protocols for measuring the pH value using low-pH cementitious products (LopHC). The Pore Fluid Expression (PFE) has been identified as reference method and Ex-situ Leaching methods (ELS) with two variants (filtering and without filtering the obtained suspension) have been identified as routine methods. Both methodologies are based on the extraction of the pore solution of the concrete before pH determination. The protocols employed were based on a broad literature review and in fitting the more critical parameters, such as the sample size, the carbonation affection, the leaching of cement hydrates during the measurement, etc. Moreover, the routine methods were validated with respect to the pore fluid expression results. It appears that the repeatability of the 3 pH measurement protocols is very good and that the results obtained with both ESL procedures agree well with the results given by the PFE technique in the case of low-pH cementitious materials and are acceptable in the case of cementitious materials with high pore fluid pH values, in that case some corrections considering the Ca content of the solution may be needed

pH and Protein Sensing with Functionalized Semiconducting Oxide Nanobelt FETs

Science.gov (United States)

Cheng, Yi; Yun, C. S.; Strouse, G. F.; Xiong, P.; Yang, R. S.; Wang, Z. L.

2008-03-01

We report solution pH sensing and selective protein detection with high-performance channel-limited field-effect transistors (FETs) based on single semiconducting oxide (ZnO and SnO2) nanobelts^1. The devices were integrated with PDMS microfluidic channels for analyte delivery and the source/drain contacts were passivated for in-solution sensing. pH sensing experiments were performed on FETs with functionalized and unmodified nanobelts. Functionalization of the nanobelts by APTES was found to greatly improve the pH sensitivity. The change in nanobelt conductance as functions of pH values at different gate voltages and ionic strengths showed high sensitivity and consistency. For the protein detection, we achieved highly selective biotinylation of the nanobelt channel with through APTES linkage. The specific binding of fluorescently-tagged streptavidin to the biotinylated nanobelt was verified by fluorescence microscopy; non-specific binding to the substrate was largely eliminated using PEG-silane passivation. The electrical responses of the biotinylated FETs to the streptavidin binding in PBS buffers of different pH values were systematically measured. The results will be presented and discussed. ^1Y. Cheng et al., Appl. Phys. Lett. 89, 093114 (2006). *Supported by NSF NIRT Grant ECS-0210332.

pH Sensitivity of Novel PANI/PVB/PS3 Composite Films

Directory of Open Access Journals (Sweden)

Olga Korostynska

2007-12-01

Full Text Available This paper reports on the results from the investigation into the pH sensitivity ofnovel PANI/PVB/PS3 composite films. The conductimetric sensing mode was chosen as itis one of the most promising alternatives to the mainstream pH-sensing methods and it is theleast investigated due to the popularity of other approaches. The films were deposited usingboth screen-printing and a drop-coating method. It was found that the best response to pHwas obtained from the screen-printed thick films, which demonstrated a change inconductance by as much as three orders of magnitude over the pH range pH2-pH11. Thedevices exhibited a stable response over 96 hours of operation. Several films were immersedin buffer solutions of different pH values for 96 hours and these were then investigated usingXPS. The resulting N 1s spectra for the various films confirmed that the change inconductance was due to deprotonation of the PANI polymer backbone. SEM andProfilometry were also undertaken and showed that no considerable changes in themorphology of the films took place and that the films did not swell or contract due toexposure to test solutions.

Heat-denaturation and aggregation of quinoa (Chenopodium quinoa) globulins as affected by the pH value.

Science.gov (United States)

Mäkinen, Outi E; Zannini, Emanuele; Koehler, Peter; Arendt, Elke K

2016-04-01

The influence of heating (100 °C; 0-15 min) on the relative molecular mass, protein unfolding and secondary structure of quinoa globulins was studied at pH 6.5 (low solubility), 8.5 and 10.5 (high solubility). The patterns of denaturation and aggregation varied with pH. Heating triggered the disruption of the disulfide bonds connecting the acidic and basic chains of the chenopodin subunits at pH 8.5 and 10.5, but not at pH 6.5. Large aggregates unable to enter a 4% SDS-PAGE gel were formed at pH 6.5 and 8.5, which became soluble under reducing conditions. Heating at pH 10.5 lead to a rapid dissociation of the native chenopodin and to the disruption of the subunits, but no SDS-insoluble aggregates were formed. No major changes in secondary structure occurred during a 15 min heating, but an increase in hydrophobicity indicated unfolding of the tertiary structure in all samples. Copyright © 2015 Elsevier Ltd. All rights reserved.

Influence of the Dentinal Wall on the pH of Sodium Hypochlorite during Root Canal Irrigation

NARCIS (Netherlands)

Macedo, Ricardo Gomes; Herrero, Noemi Pascual; Wesselink, Paul; Versluis, Michel; van der Sluis, Luc

Introduction: The purpose of this study was to evaluate the influence of dentin on the pH levels of different concentrations of sodium hypochlorite (NaOCl) solutions over time and to evaluate if preconditioning of dentin with 17% EDTA or agitation of the NaOCl solution influences these pH levels.

Evolution of pH during in-situ leaching in small concrete cavities

Energy Technology Data Exchange (ETDEWEB)

Saguees, A.A. [Univ. of South Florida, Tampa, FL (United States). Dept. of Civil and Environmental Engineering; Moreno, E.I. [Univ. of South Florida, Tampa, FL (United States). Dept. of Civil and Environmental Engineering]|[CINVESTAV Merida-Unit (Mexico); Andrade, C. [CSIC, Madrid (Spain). Inst. Eduardo Torroja de Ciencias de la Construccion

1997-11-01

Small amounts (0.4 cc) of neutral water placed in small cylindrical cavities (5 mm diameter) in concrete exposed to 100% relative humidity first developed a pH comparable to that of a saturated Ca(OH){sub 2} solution. The pH then increased over a period of days-weeks toward a higher terminal value. A micro pH electrode arrangement was used. This behavior was observed in samples of 12 different concrete mix designs, including some with pozzolanic additions. The average terminal cavity pH closely approached that of expressed pore water from the same concretes. A simplified mathematical model reproduced the experimentally observed behavior. The model assumed inward diffusional transport of the pH-determining species in the surrounding concrete pore solution. The experimental results were consistent with the model predictions when using diffusion parameters on the order of those previously reported for alkali cations in concrete. The cavity size, cavity water content, and exposure to atmospheric CO{sub 2} should be minimized when attempting to obtain cavity pH values approaching those of the surrounding pore water.

Dolomitic lime amendment affects pine bark substrate pH, nutrient availability, and plant growth: A review

Science.gov (United States)

Dolomitic lime (DL) is one of the most commonly used fertilizer amendments in nursery container substrates. It is used to adjust pH of pine bark substrates from their native pH, 4.1 to 5.1, up to about pH 6. Additions of DL have been shown to be beneficial, inconsequential, or detrimental dependin...

The influence of pH on the adsorption of lead by Na-clinoptilolite ...

African Journals Online (AJOL)

The influence of pH on the adsorption of lead by Na-clinoptilolite: Kinetic and equilibrium studies. ... At high pH of the contact solution, the adsorption process occurs by ion exchange and at low pH; i.e., it is physical. The variation of the Gibbs free energy demonstrates that adsorption occurs spontaneously. The process was ...

Engineering a pH responsive pore forming protein.

Science.gov (United States)

Kisovec, Matic; Rezelj, Saša; Knap, Primož; Cajnko, Miša Mojca; Caserman, Simon; Flašker, Ajda; Žnidaršič, Nada; Repič, Matej; Mavri, Janez; Ruan, Yi; Scheuring, Simon; Podobnik, Marjetka; Anderluh, Gregor

2017-02-08

Listeriolysin O (LLO) is a cytolysin capable of forming pores in cholesterol-rich lipid membranes of host cells. It is conveniently suited for engineering a pH-governed responsiveness, due to a pH sensor identified in its structure that was shown before to affect its stability. Here we introduced a new level of control of its hemolytic activity by making a variant with hemolytic activity that was pH-dependent. Based on detailed structural analysis coupled with molecular dynamics and mutational analysis, we found that the bulky side chain of Tyr406 allosterically affects the pH sensor. Molecular dynamics simulation further suggested which other amino acid residues may also allosterically influence the pH-sensor. LLO was engineered to the point where it can, in a pH-regulated manner, perforate artificial and cellular membranes. The single mutant Tyr406Ala bound to membranes and oligomerized similarly to the wild-type LLO, however, the final membrane insertion step was pH-affected by the introduced mutation. We show that the mutant toxin can be activated at the surface of artificial membranes or living cells by a single wash with slightly acidic pH buffer. Y406A mutant has a high potential in development of novel nanobiotechnological applications such as controlled release of substances or as a sensor of environmental pH.

Engineering a pH responsive pore forming protein

Science.gov (United States)

Kisovec, Matic; Rezelj, Saša; Knap, Primož; Cajnko, Miša Mojca; Caserman, Simon; Flašker, Ajda; Žnidaršič, Nada; Repič, Matej; Mavri, Janez; Ruan, Yi; Scheuring, Simon; Podobnik, Marjetka; Anderluh, Gregor

2017-02-01

Listeriolysin O (LLO) is a cytolysin capable of forming pores in cholesterol-rich lipid membranes of host cells. It is conveniently suited for engineering a pH-governed responsiveness, due to a pH sensor identified in its structure that was shown before to affect its stability. Here we introduced a new level of control of its hemolytic activity by making a variant with hemolytic activity that was pH-dependent. Based on detailed structural analysis coupled with molecular dynamics and mutational analysis, we found that the bulky side chain of Tyr406 allosterically affects the pH sensor. Molecular dynamics simulation further suggested which other amino acid residues may also allosterically influence the pH-sensor. LLO was engineered to the point where it can, in a pH-regulated manner, perforate artificial and cellular membranes. The single mutant Tyr406Ala bound to membranes and oligomerized similarly to the wild-type LLO, however, the final membrane insertion step was pH-affected by the introduced mutation. We show that the mutant toxin can be activated at the surface of artificial membranes or living cells by a single wash with slightly acidic pH buffer. Y406A mutant has a high potential in development of novel nanobiotechnological applications such as controlled release of substances or as a sensor of environmental pH.

Reassessment of pH reference values with improved methodology for the evaluation of ionic strength

International Nuclear Information System (INIS)

Lito, M.J. Guiomar H.M.; Camoes, M. Filomena G.F.C.

2005-01-01

The conflict between pH as empirical number in routine control and the pH value regarded as conveying some information concerning the effective concentration or activity of hydrogen ions, a H , has caused much confusion. There are, however, reasons to conclude that the overwhelming amount of thermodynamic data is not sufficiently accurate--either due to ignorance of metrological concepts or due to insufficiently specified measurement processes of fundamental chemical quantities pH. The commonly used seven reference buffer solutions to which primary pH values have been conventional assigned, represent a selection out of a more extensive list, recommended by NBS (now NIST) in 1962. From then onwards conventions concerning the Debye-Hueckel model of electrolyte solutions and ionic strength have been revised and the pH(S) values reassessed in conformity but only for these seven reference buffer solutions. The others have, so far remained unchanged, locking harmonisation of the conventionally assigned pH(S) values. In this work, ionic strength is calculated through complete equations derived from the acidity constants. Concentrations of the various species involved in the conventional assignment of pH and their corresponding activity coefficients are therefore, more rigorously known. The process proves particularly useful for poliprotic acids with overlapping acidity constants, where the ratio is less than 10 3 . As a consequence, conventionally assigned pH values of reference buffer solutions are recalculated and corrections are introduced as appropriate

Corrosion of Dental Au-Ag-Cu-Pd Alloys in 0.9 % Sodium Chloride Solution

International Nuclear Information System (INIS)

Chiba, Atsushi; Kusayanagi, Yukiharu

2005-01-01

Two Au-Ag-Cu-Pd dental casting alloys (Au:12% and 20%) used. The test solutions used 0.9 % NaCl solution (isotonic sodium chloride solution), 0.9 % NaCl solution containing 1 % lactic acid, and 0.9 % NaCl solution containing 1 % lactic acid and 0.1 mol dm -3 Na 2 S. The surface of two samples in three sample solutions was not natural discoloration during one year. The alloy containing 12 % gold was easily alloyed and the composition was uniform comparing with the alloy containing 20 % gold. The rest potentials have not a little effect after three months. The kinds of metals could not definitely from the oxidation and reduction waves of metal on the cyclic voltammograms. The dissolutions of gold and palladium were 12 % Au sample in the 0.9 % NaCl solution containing 1 % lactic acid and 0.1 mol dm -3 Na 2 S. The pH of solution had an affect on dissolution of copper, and sulfur ion had an affect on dissolution of silver. The copper dissolved amount from 20 % gold sample was about 26 times comparing with that of 12 % gold sample in the 0.9 % solution containing 1 % lactic acid. Corrosion products were silver chloride and copper chloride in NaCl solution, and silver sulfide and copper sulfide in NaCl solution containing Na 2 S

Theory of pH changes in water desalination by capacitive deionization

NARCIS (Netherlands)

Dykstra, J.E.; Keesman, K.J.; Biesheuvel, P.M.; Wal, van der A.

2017-01-01

In electrochemical water desalination, a large difference in pH can develop between feed and effluent water. These pH changes can affect the long-term stability of membranes and electrodes. Often Faradaic reactions are implicated to explain these pH changes. However, quantitative theory has not

Simultaneous removal of NO and SO2 with hexamminecobalt(II) solution coupled with the hexamminecobalt(II) regeneration catalyzed by activated carbon

International Nuclear Information System (INIS)

Long, Xiang-Li; Xin, Zhi-Ling; Wang, Hong-Xin; Xiao, Wen-De; Yuan, Wei-Kang

2004-01-01

The wet ammonia desulfurization process can be retrofitted for combined removal of SO 2 and NO from the flue gases by adding soluble cobalt(II) salt into the aqueous ammonia solution. Activated carbon is used to catalyze the reduction of hexamminecobalt(III) to hexamminecobalt(II) to maintain the capability of removing NO of the hexamminecobalt solution. The effects of temperature, pH, activated carbon particle size, and superficial liquid flow velocity on hexamminecobalt(III) conversion have been investigated. An apparent activation energy is obtained. According to the experimental results, the catalytic reduction reaction rate increases with temperature. The batch reactor experiments show that the best pH range lies in between 3.5 and 6.5. In a fixed-bed reactor, superficial liquid flow velocity obviously affects the reaction and a high yield of cobalt(II) is obtained at a pH value lower than 9.0. The experiments manifest that the hexamminecobalt solution coupled with catalytic regeneration of hexamminecobalt(II) can maintain a high nitric oxide removal efficiency during a period of time

Removal of Methyl Red from Aqueous Solution by Adsorption on Treated Banana Pseudo stem Fibers Using Response Surface Method (RSM)

International Nuclear Information System (INIS)

Zaida Rahayu Yet; Mohd Zulkhairi Abdul Rahim

2014-01-01

The effect of adsorbent dose, pH and contact times on the removal of Methyl Red (MR) from aqueous solution by using agriculture waste (NaOH treated banana pseudo stem fibers) were studied. The influence of these parameters on the removal of Methyl Red was examined by using a response surface method (RSM). The experiment was conducted by combining three parameters: adsorbent dose (500-1500 mg/L), pH (2-8) dan contact time (5-75 minutes ). The Box-Behnken Design (BBD) in Response Surface Methodology (RSM) by Design Expert Version 8.0.4 (Stat Ease, USA) was used for designing the experiments. Results showed that the optimum conditions for removal of Methyl Red from an aqueous solution (100 mg/L) were as follows: adsorbent dose (1417.70 mg/L), pH (2.08) and contact time (42.94 minutes) with the value of a coefficient of determination, R2 is 98.98 %. Meanwhile, the second-order polynomial equation indicates that pH and contact times mostly affect the removal of Methyl Red. (author)

Effects of 42 deg. C hyperthermia on intracellular pH in ovarian carcinoma cells during acute or chronic exposure to low extracellular pH

International Nuclear Information System (INIS)

Wahl, Miriam L.; Bobyock, Suzanne B.; Leeper, Dennis B.; Owen, Charles S.

1997-01-01

Purpose: To determine whether intracellular pH (pH i ) is affected during hyperthermia in substrate-attached cells and whether acute extracellular acidification potentiates the cytotoxicity of hyperthermia via an effect on pH i . Methods and Materials: The pH i was determined in cells attached to extracellular matrix proteins loaded with the fluorescent indicator dye BCECF at 37 deg. C and during 42 deg. C hyperthermia at an extracellular pH (pH e ) of 6.7 or 7.3 in cells. Effects on pH i during hyperthermia are compared to effects on clonogenic survival after hyperthermia at pH e 7.3 and 6.7 of cells grown at pH e 7.3, or of cells grown and monitored at pH e 6.7. Results: The results show that pH i values are affected by substrate attachments. Cells attached to extracellular matrix proteins had better signal stability, low dye leakage and evidence of homeostatic regulation of pH i during heating. The net decrease in pH i in cells grown and assayed at pH e = 7.3 during 42 deg. C hyperthermia was 0.28 units and the decrease in low pH adapted cells heated at pH e = 6.7 was 0.14 units. Acute acidification from pH e = 7.3 to pH e = 6.7 at 37 deg. C caused an initial reduction of 0.5-0.8 unit in pH i , but a partial recovery followed during the next 60-90 min. Concurrent 42 deg. C hyperthermia caused the same initial reduction in pH i in acutely acidified cells, but inhibited the partial recovery that occurred during the next 60-90 min at 37 deg. C. After 4 h at 37 deg. C, the net change in pH i in acutely acidified cells was 0.30 pH unit, but at 42 deg. C is 0.63 pH units. The net change in pH i correlated inversely with clonogenic survival. Conclusions: Hyperthermia causes a pH i reduction in cells which was smaller in magnitude by 50% in low pH adapted cells. Hyperthermia inhibited the partial recovery from acute acidification that was observed at 37 deg. C in substrate attached cells, in parallel with a lower subsequent clonogenic survival

Modelling of niobium sorption on clay minerals in sodium and calcium perchlorate solutions

Energy Technology Data Exchange (ETDEWEB)

Ervanne, Heini; Hakanen, Martti; Lehto, Jukka [Helsinki Univ. (Finland). Laboratory of Radiochemistry

2014-11-01

The sorption behaviour of niobium on kaolinite and illite minerals in sodium and calcium perchlorate solutions was evaluated with use of the mass distribution coefficient, Rd, obtained in batch sorption experiments. Very high distribution coefficient values, about 100 m{sup 3}/kg, were obtained for both minerals in the neutral pH range between 6 and 8. Values were somewhat lower at pH 5. In NaClO{sub 4} solution, the sorption of niobium starts to decrease at pH higher than 8. This is in agreement with the increase, with pH, in the proportion of anionic niobate species, which are presumed to be low or non-sorbing. A similar decrease was not observed in Ca(ClO{sub 4}){sub 2} solution, probably owing to the influence of Ca on niobium solution speciation and surface species. The surface complexation model was applied to model the Rd values. The model fitted well for the NaClO{sub 4} solution but only at pH below 9 for the Ca(ClO{sub 4}){sub 2} solution. The discrepancy between the strong sorption of niobium in calcium-bearing solution at high pH and the calculated speciation is due in part to the non-inclusion of calcium niobate solution species and Ca-Nb compounds in the present NEA and other similar thermodynamic databases.

The role of preservation solution on acid-base regulation during machine perfusion of kidneys.

Science.gov (United States)

Baicu, Simona C; Taylor, Michael J; Brockbank, Kelvin G M

2006-01-01

To meet the current clinical organ demand, efficient preservation methods and solutions are needed to increase the number of viable kidneys for transplantation. In the present study, the influence of perfusion solution buffering strength on renal pH dynamics and regulation mechanisms during kidney ex vivo preservation was determined. Porcine kidneys were hypothermically machine perfused for 72 h with either Unisol-UHK or Belzer-Machine Perfusion solution, Belzer-MP solution. Renal perfusate samples were periodically collected and biochemically analyzed. The UHK solution, a Hepes-based solution (35 mM), provided a more efficient control of renal pH that, in turn, resulted in minor changes in the perfusate pH relative to baseline, in response to tissue CO2 and HCO3- production. In the perfusate of Belzer-MP kidney group a wider range of pH values were recorded and a pronounced pH reduction was seen in response to significant rises in pCO2 and HCO3- concentrations. The Belzer-MP solution, containing phosphate (25 mM) as its main buffer, and only 10 mM Hepes, had a greater buffering requirement to attenuate larger pH changes.

Early Development of the Threespine Stickleback in Relation to Water pH

Directory of Open Access Journals (Sweden)

Olivier Glippa

2017-12-01

Full Text Available Ocean acidification is a growing environmental problem, and there is a need to investigate how the decreasing pH will affect marine organisms. Here we studied the effects of lowered pH on the growth and development of the threespine stickleback (Gasterosteus aculeatus eggs. Adult fish, collected from the natural environment, were allowed to mate in aquaria and the newly produced eggs were incubated in an experiment. Eggs and larvae from ambient conditions (produced in the laboratory were reared at three different pH concentrations (control: pH 7.8; and reduced pH treatments: pH 7.5 and 7.0 for 21 days in the laboratory. Dissolved oxygen concentration (8.1 ± 0.1 mg l−1 and temperature (18.6 ± 0.02°C were monitored regularly. Then, egg diameter, larval length, weight and survival were measured. There was no relationship between egg diameter and pH or oxygen, but a negative relationship was found with temperature. Survival of larvae was not affected by pH or temperature, whereas dissolved oxygen concentration had a positive effect on number of survivors. The pH did not have a significant effect on the final larval length on day 21, but interacted significantly with dissolved oxygen. Higher temperatures were found to have a positive effect on the final larval length and weight. Larval weight, on the other hand, was not related to pH nor oxygen. Coastal zones are characterized by pH levels that fluctuate due to natural processes, such as upwelling and river runoff. Our results suggest that the threespine stickleback larvae are well adapted to the different pHs tested, and egg development will likely not be affected by decreasing pH, but even slight temperature and oxygen changes can have a great impact on the threespine stickleback development.

Similarity of salt influences on the pH of buffers, polyelectrolytes, and proteins.

Science.gov (United States)

Voinescu, Alina E; Bauduin, Pierre; Pinna, M Cristina; Touraud, Didier; Ninham, Barry W; Kunz, Werner

2006-05-04

Changes in pH induced by the addition of electrolytes to buffers, polyelectrolytes (a polycarboxy polymethylene and a polyethyleneimine), and proteins (casein, whey, and lysozyme) solutions are explored systematically. The two buffer systems are triethanolamine/triethanolammonium chloride and citric acid/sodium citrate. These are chosen because of the similarity of their acid-base equilibria with those of amino acids predominant in most proteins, that is, amino acids that include carboxylate or ammonium groups in their structures. The pH of triethanolamine and of citrate buffers respectively increases and decreases when salt is added. At low electrolyte concentrations (buffer solutions. It is even possible to qualitatively predict these changes in protein solutions simply from the primary protein structure. At least in the systems considered here, the specific ion effects on pH seem to correlate with the bulk activity coefficients of the added electrolytes, at least at moderate salt concentrations.

Regulation of pH During Amelogenesis.

Science.gov (United States)