Leaching of boron, arsenic and selenium from sedimentary rocks: II. pH dependence, speciation and mechanisms of release

Energy Technology Data Exchange (ETDEWEB)

Tabelin, Carlito Baltazar, E-mail: carlito@trans-er.eng.hokudai.ac.jp [Laboratory of Soil Environment Engineering, Faculty of Engineering, Hokkaido University, Sapporo (Japan); Hashimoto, Ayaka, E-mail: a.hashimoto@diaconsult.co.jp [DIA Consultants Co. Ltd., Sapporo (Japan); Igarashi, Toshifumi, E-mail: tosifumi@eng.hokudai.ac.jp [Laboratory of Groundwater and Mass Transport, Faculty of Engineering, Hokkaido University, Sapporo (Japan); Yoneda, Tetsuro, E-mail: yonet@eng.hokudai.ac.jp [Laboratory of Soil Environment Engineering, Faculty of Engineering, Hokkaido University, Sapporo (Japan)

2014-03-01

Sedimentary rocks excavated in Japan from road- and railway-tunnel projects contain relatively low concentrations of hazardous trace elements like boron (B), arsenic (As) and selenium (Se). However, these seemingly harmless waste rocks often produced leachates with concentrations of hazardous trace elements that exceeded the environmental standards. In this study, the leaching behaviors and release mechanisms of B, As and Se were evaluated using batch leaching experiments, sequential extraction and geochemical modeling calculations. The results showed that B was mostly partitioned with the residual/crystalline phase that is relatively stable under normal environmental conditions. In contrast, the majority of As and Se were associated with the exchangeable and organics/sulfides phases that are unstable under oxidizing conditions. Dissolution of water-soluble phases controlled the leaching of B, As and Se from these rocks in the short term, but pyrite oxidation, calcite dissolution and adsorption/desorption reactions became more important in the long term. The mobilities of these trace elements were also strongly influenced by the pH of the rock-water system. Although the leaching of Se only increased in the acidic region, those of B and As were enhanced under both acidic and alkaline conditions. Under strongly acidic conditions, the primarily release mechanism of B, As and Se was the dissolution of mineral phases that incorporated and/or adsorbed these elements. Lower concentrations of these trace elements in the circumneutral pH range could be attributed to their strong adsorption onto minerals like Al-/Fe-oxyhydroxides and clays, which are inherently present and/or precipitated in the rock-water system. The leaching of As and B increased under strongly alkaline conditions because of enhanced desorption and pyrite oxidation while that of Se remained minimal due to its adsorption onto Fe-oxyhydroxides and co-precipitation with calcite. - Highlights: • The bulk of

Research on the Characteristics and Mechanism of the Cumulative Release of Antimony from an Antimony Smelting Slag Stacking Area under Rainfall Leaching

Science.gov (United States)

Zhou, Yingying; Deng, Renjian

2017-01-01

We aimed to study the characteristics and the mechanism of the cumulative release of antimony at an antimony smelting slag stacking area in southern China. A series of dynamic and static leaching experiments to simulate the effects of rainfall were carried out. The results showed that the release of antimony from smelting slag increased with a decrease in the solid-liquid ratio, and the maximum accumulated release was found to be 42.13 mg Sb/kg waste and 34.26 mg Sb/kg waste with a solid/liquid ratio of 1 : 20; the maximum amount of antimony was released within 149–420 μm size fraction with 7.09 mg/L of the cumulative leaching. Also, the antimony release was the greatest and most rapid at pH 7.0 with the minimum release found at pH 4.0. With an increase in rainfall duration, the antimony release increased. The influence of variation in rainfall intensity on the release of antimony from smelting slag was small. PMID:28804669

Leach test methodology for the Waste/Rock Interactions Technology Program

International Nuclear Information System (INIS)

Bradley, D.J.; McVay, G.L.; Coles, D.G.

1980-05-01

Experimental leach studies in the WRIT Program have two primary functions. The first is to determine radionuclide release from waste forms in laboratory environments which attempt to simulate repository conditions. The second is to elucidate leach mechanisms which can ultimately be incorporated into nearfield transport models. The tests have been utilized to generate rates of removal of elements from various waste forms and to provide specimens for surface analysis. Correlation between constituents released to the solution and corresponding solid state profiles is invaluable in the development of a leach mechanism. Several tests methods are employed in our studies which simulate various proposed leach incident scenarios. Static tests include low temperature (below 100 0 C) and high temperature (above 100 0 C) hydrothermal tests. These tests reproduce nonflow or low-flow repository conditions and can be used to compare materials and leach solution effects. The dynamic tests include single-pass, continuous-flow(SPCF) and solution-change (IAA)-type tests in which the leach solutions are changed at specific time intervals. These tests simulate repository conditions of higher flow rates and can also be used to compare materials and leach solution effects under dynamic conditions. The modified IAEA test is somewhat simpler to use than the one-pass flow and gives adequate results for comparative purposes. The static leach test models the condition of near-zero flow in a repository and provides information on element readsorption and solubility limits. The SPCF test is used to study the effects of flowing solutions at velocities that may be anticipated for geologic groundwaters within breached repositories. These two testing methods, coupled with the use of autoclaves, constitute the current thrust of WRIT leach testing

Leaching mechanisms

International Nuclear Information System (INIS)

Dougherty, D.R.; Colombo, P.

1984-01-01

Sufficient data are lacking to provide a basis for adequately assessing the long term leaching behavior of solidified low level radioactive waste forms in their disposal environment. Although the release of radioactivity from a waste form to an aqueous environment is recognized to be due to one or more mechanisms such as diffusion, dissolution, corrosion or ion exchange, the leaching mechanisms and the factors which control the leaching behavior of waste forms are not fully understood. This study will determine the prevailing mechanisms for a variety of selected LLW solidification agents which are being considered for use by defense and commercial generators and which will cover the broadest possible number of mechanisms. The investigation will proceed by the postulation of mathematical models representative of the prevailing mechanism(s) and the use of statistically designed experiments to test the actual leaching behavior of laborattory samples against the postulated representations. Maximum use of existing leach data in the literature will be made by incorporating literature results into a computerized data base along with the experimental results generated in this task

Performance of waste-based amendments to reduce metal release from mine tailings: One-year leaching behaviour.

Science.gov (United States)

Rodríguez, Luis; Gómez, Rocío; Sánchez, Virtudes; Villaseñor, José; Alonso-Azcárate, Jacinto

2018-03-01

A one-year leaching experiment has been conducted in order to assess the effectiveness of several amendments on metal immobilization in mine tailings from an old Pb/Zn mining area of Central Spain (San Quintín mine). Demineralized water was used as leaching solution, selecting doses equivalent to the annual rainfall conditions of the studied area. Columns with mine tailings without any amendment and others treated with 10% of sugar foam (SF), 15% of drinking water treatment sludge (DWS), 30% of paper mill sludge (PMS) and 15% of olive mill waste (OMW) were used. SF, DWS and PMS amendments increased the pH of leachates from values of approximately 4 to around neutrality. Additionally, the release of sulfate ions from the oxidation of pyritic residues was decreased in some extent by SF and DWS amendments. Metal leaching was effectively reduced by the amendments reaching overall decreases with respect to the unamended columns of 79-96% for Pb, 36-100% for Zn, 50-99% for Cu and 44-100% for Cd. The effect of the amendments in leachate pH, sulfate concentration and metal release from mine tailings was kept throughout the whole experimental period. Our results showed that the application of different organic and inorganic amendments based on by-products and waste materials may be a feasible alternative for the restoration of soils around abandoned metal mines. Copyright © 2017 Elsevier Ltd. All rights reserved.

pH-dependent release of trace elements including platinum group elements (PGEs) from gasoline and diesel catalysts

Science.gov (United States)

Sucha, Veronika; Mihaljevic, Martin; Ettler, Vojtech; Strnad, Ladislav

2014-05-01

The release of trace metals and platinum group elements (PGEs) from automobile exhaust catalysts represents a remarkable source of higly dispersed environmental contamination. Especially, PGEs have shown increasing research interest due to their possible bioaccessibility. In our research, we focused on leaching behaviour of trace metals from gasoline and diesel automobile catalysts. While catalysts for gasoline engines contain a mixture of Pt-Pd-Rh or Pd-Rh, catalysts for diesel engines are composed only of Pt. We used dust from two crushed gasoline and two crushed diesel catalysts (new and aged). The dust of gasoline catalysts contains significant concentrations of Pt (700 mg.kg-1), Pd (11 000 mg.kg-1) and Rh (700 mg.kg-1). And the dust of diesel catalysts are composed of Pt (3 900 mg.kg-1) and they contains negligible amounts of Pd dan Rh (leaching of trace metals from dust we used pH-stat leaching test according to the European standard CEN/TS 14997. The concentrations of cations: PGEs (Pt, Pd a Rh), K, Na, Ca, Mg, Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, La and Ce were determined by inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS), and anions: F-, Cl-, SO42- and NO3- by high-performance liquid chromatography. Although the dusts from catalysts were relatively stable to acid/base influence, the leaching of trace metals from catalysts showed a dependence on pH. Generally, the highest concentrations were released under acidic conditions. The leaching of PGEs was higher for Pt in diesel catalysts and for Pd and Rh in gasoline catalysts. The highest concentrations of Zn and Pb were observed in old catalysts. The rare earth metals were released more from gasoline catalysts. Catalysts particles represent health risk especially with respect to their PGEs contents.

Dynamic leaching test of personal computer components.

Science.gov (United States)

Li, Yadong; Richardson, Jay B; Niu, Xiaojun; Jackson, Ollie J; Laster, Jeremy D; Walker, Aaron K

2009-11-15

A dynamic leaching test (DLT) was developed and used to evaluate the leaching of toxic substances for electronic waste in the environment. The major components in personal computers (PCs) including motherboards, hard disc drives, floppy disc drives, and compact disc drives were tested. The tests lasted for 2 years for motherboards and 1.5 year for the disc drives. The extraction fluids for the standard toxicity characteristic leaching procedure (TCLP) and synthetic precipitation leaching procedure (SPLP) were used as the DLT leaching solutions. A total of 18 elements including Ag, Al, As, Au, Ba, Be, Cd, Cr, Cu, Fe, Ga, Ni, Pd, Pb, Sb, Se, Sn, and Zn were analyzed in the DLT leachates. Only Al, Cu, Fe, Ni, Pb, and Zn were commonly found in the DLT leachates of the PC components. Their leaching levels were much higher in TCLP extraction fluid than in SPLP extraction fluid. The toxic heavy metal Pb was found to continuously leach out of the components over the entire test periods. The cumulative amounts of Pb leached out of the motherboards in TCLP extraction fluid reached 2.0 g per motherboard over the 2-year test period, and that in SPLP extraction fluid were 75-90% less. The leaching rates or levels of Pb were largely affected by the content of galvanized steel in the PC components. The higher was the steel content, the lower the Pb leaching rate would be. The findings suggest that the obsolete PCs disposed of in landfills or discarded in the environment continuously release Pb for years when subjected to landfill leachate or rains.

Nanoscale Coloristic Pigments: Upper Limits on Releases from Pigmented Plastic during Environmental Aging, In Food Contact, and by Leaching.

Science.gov (United States)

Neubauer, Nicole; Scifo, Lorette; Navratilova, Jana; Gondikas, Andreas; Mackevica, Aiga; Borschneck, Daniel; Chaurand, Perrine; Vidal, Vladimir; Rose, Jerome; von der Kammer, Frank; Wohlleben, Wendel

2017-10-17

The life cycle of nanoscale pigments in plastics may cause environmental or human exposure by various release scenarios. We investigated spontaneous and induced release with mechanical stress during/after simulated sunlight and rain degradation of polyethylene (PE) with organic and inorganic pigments. Additionally, primary leaching in food contact and secondary leaching from nanocomposite fragments with an increased surface into environmental media was examined. Standardized protocols/methods for release sampling, detection, and characterization of release rate and form were applied: Transformation of the bulk material was analyzed by Scanning Electron Microscopy (SEM), X-ray-tomography and Fourier-Transform Infrared spectroscopy (FTIR); releases were quantified by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), single-particle-ICP-MS (sp-ICP-MS), Transmission Electron Microscopy (TEM), Analytical Ultracentrifugation (AUC), and UV/Vis spectroscopy. In all scenarios, the detectable particulate releases were attributed primarily to contaminations from handling and machining of the plastics, and were not identified with the pigments, although the contamination of 4 mg/kg (Fe) was dwarfed by the intentional content of 5800 mg/kg (Fe as Fe 2 O 3 pigment). We observed modulations (which were at least partially preventable by UV stabilizers) when comparing as-produced and aged nanocomposites, but no significant increase of releases. Release of pigments was negligible within the experimental error for all investigated scenarios, with upper limits of 10 mg/m 2 or 1600 particles/mL. This is the first holistic confirmation that pigment nanomaterials remain strongly contained in a plastic that has low diffusion and high persistence such as the polyolefin High Density Polyethylene (HDPE).

Reduced rates of controlled-release fertilizer lower potential nitrogen leaching from a Wisconsin bare-root tree nursery

Science.gov (United States)

Ryosuke Fujinuma; Nick J. Balster; Hyung-Kyung. Lee

2011-01-01

Controlled-release fertilizer (CRF) typically increases nitrogen (N) fertilizer uptake and lowers N lost from the rooting zone via leaching. However, questions remain as to whether lower rates of CRF could further increase this efficiency, especially in sandy bare-root nurseries in Wisconsin. We hypothesized that: 1) a reduced CRF application at 60 percent of the...

Optimizing conditions for an accelerated leach test

International Nuclear Information System (INIS)

Pietrzak, R.F.; Fuhrmann, M.; Heiser, J.; Franz, E.M.; Colombo, P.

1988-01-01

An accelerated leach test for low-level radioactive waste forms is being developed to provide, in a short time, data that can be extrapolated to long time periods. The approach is to provide experimental conditions that will accelerate leaching without changing the dominant release mechanism. Experimental efforts have focused on combining individual factors that have been observed to accelerate leaching. These include elevated temperature, increased leachant volume, and reduced specimen size. The response of diffusion coefficients to various acceleration factors have been evaluated and provide information on experimental parameters that need to be optimized to increase leach rates. Preliminary modeling using a diffusion mechanism (allowing for depletion) of a finite cylinder geometry indicates that during early portions of experiments (daily sampling intervals), leaching is diffusion controlled and more rapid than later in the same experiments (weekly or greater sampling intervals). For cement waste forms, this reduction in rate may be partially controlled by changes in physical structure and chemistry (sometimes related to environmental influences such as CO 2 ), but it is more likely associated with the duration of the sampling interval. By using a combination of mathematical modeling and by experimentally investigating various leach rate controlling factors, a more complete understanding of leaching processes is being developed. This, in turn, is leading to optimized accelerating conditions for a leach test

Comparison of leaching tests to determine and quantify the release of inorganic contaminants in demolition waste

International Nuclear Information System (INIS)

Delay, Markus; Lager, Tanja; Schulz, Horst D.; Frimmel, Fritz H.

2007-01-01

The changes in waste management policy caused by the massive generation of waste materials (e.g. construction and demolition waste material, municipal waste incineration products) has led to an increase in the reuse and recycling of waste materials. For environmental risk assessment, test procedures are necessary to examine waste materials before they can be reused. In this article, results of column and lysimeter leaching tests having been applied to inorganic compounds in a reference demolition waste material are presented. The results show a good agreement between the leaching behaviour determined with the lysimeter unit and the column units used in the laboratory. In view of less time and system requirements compared to lysimeter systems, laboratory column units can be considered as a practicable instrument to assess the time-dependent release of inorganic compounds under conditions similar to those encountered in a natural environment. The high concentrations of elements in the seepage water at the initial stage of elution are reflected by the laboratory column leaching tests. In particular, authorities or laboratories might benefit and have an easy-to-use, but nevertheless reliable, method to serve as a basis for decision-making

Instant release fraction and matrix release of high burn-up UO{sub 2} spent nuclear fuel: Effect of high burn-up structure and leaching solution composition

Energy Technology Data Exchange (ETDEWEB)

Serrano-Purroy, D., E-mail: Daniel.serrano-purroy@ec.europa.eu [European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, D-76125 Karlsruhe (Germany); Clarens, F.; Gonzalez-Robles, E. [CTM Centre Tecnologic, Avda. Bases de Manresa 1, 08240 Barcelona (Spain); Glatz, J.P.; Wegen, D.H. [European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, D-76125 Karlsruhe (Germany); Pablo, J. de [CTM Centre Tecnologic, Avda. Bases de Manresa 1, 08240 Barcelona (Spain); Department of Chemical Engineering, Universitat Politecnica de Catalunya, Avda. Diagonal 647, 08028 Barcelona (Spain); Casas, I.; Gimenez, J. [Department of Chemical Engineering, Universitat Politecnica de Catalunya, Avda. Diagonal 647, 08028 Barcelona (Spain); Martinez-Esparza, A. [ENRESA, C/Emilio Vargas 7, 28043 Madrid (Spain)

2012-08-15

Two weak points in Performance Assessment (PA) exercises regarding the alteration of Spent Nuclear Fuel (SNF) are the contribution of the so-called Instant Release Fraction (IRF) and the effect of High Burn-Up Structure (HBS). This manuscript focuses on the effect of HBS in matrix (long term) and instant release of a Pressurised Water Reactor (PWR) SNF irradiated in a commercial reactor with a mean Burn-Up (BU) of 60 GWd/tU. In order to study the HBS contribution, two samples from different radial positions have been prepared. One from the centre of the SNF, labelled CORE, and one from the periphery, enriched with HBS and labelled OUT. Static leaching experiments have been carried out with two synthetic leaching solutions: bicarbonate (BIC) and Bentonitic Granitic Groundwater (BGW), and in all cases under oxidising conditions. IRF values have been calculated from the determined Fraction of Inventory in Aqueous Phase (FIAP). In all studied cases, some radionuclides (RN): Rb, Sr and Cs, have shown higher release rates than uranium, especially at the beginning of the experiment, and have been considered as IRF. Redox sensitive RN like Mo and Tc have been found to dissolve slightly faster than uranium and further studies might be needed to confirm if they can also be considered part of the IRF. Most of the remaining studied RN, mainly actinides and lanthanides, have been found to dissolve congruently with the uranium matrix. Finally, Zr, Ru and Rh presented lower release rates than the matrix. Higher matrix release has been determined for CORE than for OUT samples showing that the formation of HBS might have a protective effect against the oxidative corrosion of the SNF. On the contrary, no significant differences have been observed between the two studied leaching solutions (BIC and BGW). Two different IRF contributions have been determined. One corresponding to the fraction of inventory segregated in the external open grain boundaries, directly available to water and

Groundwater leaching of neutralized and untreated acid-leached uranium-mill tailings

International Nuclear Information System (INIS)

Gee, G.W.; Begej, C.W.; Campbell, A.C.; Sauter, N.N.; Opitz, B.E.; Sherwood, D.R.

1981-01-01

Tailings neutralization was examined to determine the effect of neutralization on contaminant release. Column leaching of acid extracted uranium mill tailings from Exxon Highland Mill, Wyoming, Pathfinder Gas Hills Mill, Wyoming, and the Dawn Midnite Mill, Washington, resulted in the flushing of high concentrations of salts in the first four pore volumes of leachate, followed by a steady decrease to the original groundwater salt concentrations. Neutralization decreased the concentration of salts and radionuclides leaching from the tailings and decreased the volume of solution required to return the solution to the groundwater pH and EC. Radium-226 and uranium-238 leached quickly from the tailings in the initial pore volumes of both neutralized and unneutralized tailings, and then decreased significantly. 6 figures, 5 tables

Optimizing conditions for an accelerated leach test

International Nuclear Information System (INIS)

Pietrzak, R.F.; Fuhrmann, M.; Heiser, J.; Franz, E.M.; Colombo, P.

1988-01-01

An accelerated leach test for low-level radioactive waste forms is being developed to provide, in a short time, data that can be extrapolated to long time periods. The approach is to provide experimental conditions that will accelerate leaching without changing the dominant release mechanism. Experimental efforts have focused on combining individual factors that have been observed to accelerate leaching. These include elevated temperature, increased leachant volume, and reduced specimen size. The response of diffusion coefficients to various acceleration factors have been evaluated and provide information on experimental parameters that need to be optimized to increase leach rates. For example, these data show that large volumes of leachant are required when leaching portland cement waste forms at elevated temperatures because of high concentrations of dissolved species. Sr-85 leaching is particularly susceptible to suppression due to concentration effects while Cs-137 leaching is less so. Preliminary modeling using a diffusion mechanism (allowing for depletion) of a finite cylinder geometry indicates that during early portions of experiments (daily sampling intervals), leaching is diffusion controlled and more rapid than later in the same experiments (weekly or greater sampling intervals). For cement waste forms, this reduction in rate may be partially controlled by changes in physical structure and chemistry (sometimes related to environmental influences such as CO 2 ), but it is more likely associated with the duration of the sampling interval. 9 refs., 6 figs

Leaching of irradiated CANDU UO2 fuel

International Nuclear Information System (INIS)

Vandergraaf, T.T.; Johnson, L.H.; Lau, D.W.P.

1980-01-01

Irradiated fuel, leached at room temperature with distilled water and with slightly chlorinated river water, releases approx. 4% of its cesium inventory over a comparatively sort period of a few days but releases its actinides and rare earths more slowly. The matrix itself dissolves at a rate conservatively calculated to be less than approx. 2 x 10 -6 g UO 2 /cm 2 day and, with time, the leach rates of the various nuclides approach this value

Evaluation of the leaching behavior of incineration bottom ash using seawater: A comparison with standard leaching tests.

Science.gov (United States)

Lin, Wenlin Yvonne; Heng, Kim Soon; Nguyen, Minh Quan; Ho, Jin Rui Ivan; Mohamed Noh, Omar Ahmad Bin; Zhou, Xue Dong; Liu, Alec; Ren, Fei; Wang, Jing-Yuan

2017-04-01

Batch and column tests were conducted on untreated incineration bottom ash (IBA) samples from two incineration plants in Singapore, using seawater as the leachant. The main objective of this study was to investigate the change in the leaching behavior of certain elements (i.e. As, Cd, Cr, Cu, Ni, Pb, Sb, Se and Zn) when IBA comes into contact with seawater. Such an investigation using seawater as leachant was not commonly carried out when investigating leaching behavior in IBA. The leaching tests were then carried out on the same IBA samples using DI water, as a comparison. Lower level of leaching was observed for Pb and Zn when seawater was used as the leachant. Cr and Sb showed significant cumulative release at Liquid-to-Solids (L/S) ratio 5 in the seawater column leaching. The influence of Dissolved Organic Carbon (DOC) on Cu leaching seems to decrease after L/S 2 when using seawater in the column test. Although the leaching behavior of IBA was affected when seawater was used, for the column test, there was no significant difference during the initial release when compared to DI water. The initial L/S fractions collected were important as the low L/S ratios represent the pore water concentration and the maximum output in an actual application. The results from this study would be useful for the future study on using IBA in marine applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Leaching of actinides and technetium from simulated high-level waste glass

International Nuclear Information System (INIS)

Bradley, D.J.; Harvey, C.O.; Turcotte, R.P.

1979-08-01

Leach tests were conducted using a modified version of the IAEA procedure to study the behavior of glass waste-solution interactions. Release rates were determined for Tc, U, Np, Pu, Am, Cm, and Si in the following solutions: WIPP B salt brine, NaCl (287 g/l), NaCl (1.76 g/1), CaCl 2 (1.66 g/l), NaHCO 3 (2.52 g/l), and deionized water. The leach rates for all elements decreased an order of magnitude from their initial values during the first 20 to 30 days leaching time. The sodium bicarbonate solution produced the highest elemental release rates, while the saturated salt brine and deionized water in general gave the lowest release. Technetium has the highest initial release of all elements studied. The technetium release rates, however, decreased by over four orders of magnitude in 150 days of leaching time. In the prepared glass, technetium was phase separated, concentrating on internal pore surfaces. Neptunium, in all cases except CaCl 2 solution, shows the highest actinide release rate. In general, curium and uranium have the lowest release rates. The range of actinide release rates is from 10 -5 to 10 -8 g/cm 2 /day. 25 figures, 7 tables

Characterization of phosphorus leaching from phosphate waste rock in the Xiangxi River watershed, Three Gorges Reservoir, China.

Science.gov (United States)

Jiang, Li-Guo; Liang, Bing; Xue, Qiang; Yin, Cheng-Wei

2016-05-01

Phosphate mining waste rocks dumped in the Xiangxi River (XXR) bay, which is the largest backwater zone of the Three Gorges Reservoir (TGR), are treated as Type I industry solid wastes by the Chinese government. To evaluate the potential pollution risk of phosphorus leaching from phosphate waste rocks, the phosphorus leaching behaviors of six phosphate waste rock samples with different weathering degrees under both neutral and acidic conditions were investigated using a series of column leaching experiments, following the Method 1314 standard of the US EPA. The results indicate that the phosphorus release mechanism is solubility-controlled. Phosphorus release from waste rocks increases as pH decreases. The phosphorus leaching concentration and cumulative phosphorus released in acidic leaching conditions were found to be one order of magnitude greater than that in neutral leaching conditions. In addition, the phosphorus was released faster during the period when environmental pH turned from weak alkalinity to slight acidity, with this accelerated release period appearing when L/S was in the range of 0.5-2.0 mL/g. In both neutral and acidic conditions, the average values of Total Phosphorus (TP), including orthophosphates, polyphosphates and organic phosphate, leaching concentration exceed the availability by regulatory (0.5 mg/L) in the whole L/S range, suggesting that the phosphate waste rocks stacked within the XXR watershed should be considered as Type II industry solid wastes. Therefore, the phosphate waste rocks deposited within the study area should be considered as phosphorus point pollution sources, which could threaten the adjacent surface-water environment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Antimony leaching release from brake pads: Effect of pH, temperature and organic acids.

Science.gov (United States)

Hu, Xingyun; He, Mengchang; Li, Sisi

2015-03-01

Metals from automotive brake pads pollute water, soils and the ambient air. The environmental effect on water of antimony (Sb) contained in brake pads has been largely untested. The content of Sb in one abandoned brake pad reached up to 1.62×10(4) mg/kg. Effects of initial pH, temperature and four organic acids (acetic acid, oxalic acid, citric acid and humic acid) on Sb release from brake pads were studied using batch reactors. Approximately 30% (97 mg/L) of the total Sb contained in the brake pads was released in alkaline aqueous solution and at higher temperature after 30 days of leaching. The organic acids tested restrained Sb release, especially acetic acid and oxalic acid. The pH-dependent concentration change of Sb in aqueous solution was best fitted by a logarithmic function. In addition, Sb contained in topsoil from land where brake pads were discarded (average 9×10(3) mg/kg) was 3000 times that in uncontaminated soils (2.7±1 mg/kg) in the same areas. Because potentially high amounts of Sb may be released from brake pads, it is important that producers and environmental authorities take precautions. Copyright © 2015. Published by Elsevier B.V.

Glass-surface area to solution-volume ratio and its implications to accelerated leach testing

International Nuclear Information System (INIS)

Pederson, L.R.; Buckwalter, C.Q.; McVay, G.L.; Riddle, B.L.

1982-10-01

The value of glass surface area to solution volume ratio (SA/V) can strongly influence the leaching rate of PNL 76-68 glass. The leaching rate is largely governed by silicon solubility constraints. Silicic acid in solution reduced the elemental release of all glass components. No components are leached to depths greater than that of silicon. The presence of the reaction layer had no measurable effect on the rate of leaching. Accelerated leach testing is possible since PNL 76-68 glass leaching is solubility-controlled (except at very low SA/V values). A series of glasses leached with SA/V x time = constant will yield identical elemental release

Column leaching from biomass combustion ashes

DEFF Research Database (Denmark)

Maresca, Alberto; Astrup, Thomas Fruergaard

2015-01-01

The utilization of biomass combustion ashes for forest soil liming and fertilizing has been addressed in literature. Though, a deep understanding of the ash chemical composition and leaching behavior is necessary to predict potential benefits and environmental risks related to this practice....... In this study, a fly ash sample from an operating Danish power plant based on wood biomass was collected, chemically characterized and investigated for its leaching release of nutrients and heavy metals. A column leaching test was employed. The strongly alkaline pH of all the collected eluates suggested...

Long-time leaching on full size radioactive waste blocks

International Nuclear Information System (INIS)

Bernard, Andre; Nomine, J.-C.; Cornec, Georges; Bonnet, Andre; Farges, Louis.

1980-12-01

Leaching is generally accepted as the fundamental characteristic when judging the quality of radioactive waste packaging. Long duration leaching tests have been carried out on full size waste blocks at the Commissariat a l'Energie Atomique. The monoliths studied are 200 litre cylinders made up of α, β and γ emitting liquid or solid waste embedded in cement or bitumen. Leaching takes place in accordance with rules based on I.A.E.A. recommendations embodying the specific concerns of safety and radiological capacity of storage sites. The tests are carried out at a Testing Station purpose built at Saclay. It includes several loops with instrumentation (volume: 3000 litres). The counting and analyses of the leached products have enabled the aggregated released fractions of the radionuclides and the structural and chemical modifications of the matrices to be assessed. The fractions of 137 Cs and 239 Pu released at 18 months are 10 -2 and 5x10 -6 for the cement coated wastes, and 10 -4 and 10 -5 for the bitumen coated wastes. The evaluation of the changes in the matrices made it possible, in particular, to observe the start of carbonation in the cement coated wastes. These trials are to be pursued for several years so as to obtain a better understanding of the exchange mechanics between the packaged wastes and the environment [fr

Leaching test of bituminized waste and waste solidified by epoxy resin

International Nuclear Information System (INIS)

Yoshinaka, Kazuyuki; Sugaya, Atsushi; Onizawa, Toshikazu; Takano, Yugo; Kimura, Yukihiko

2008-10-01

About 30,000 bituminized waste drums and about 1800 drums of waste solidified by epoxy resin, generated from Tokai Reprocessing Plant, were stored in storage facilities. And study for disposal of these waste is performed. It was considered that radioactive nuclides and chemical components were released from these waste by contact of underground water, when disposed there waste. This paper is reported that result of leaching tests for these waste, done from 2003 to 2006. We've get precious knowledge and data, as follows. (1) In leaching tests for bituminized waste, it has detected iodine-129 peak, considered difficult too low energy gamma to detect. We've get data and knowledge of iodine-129 behavior first. Leached radioactivity for 50 days calculated by peak area was equal for about 40% and 100% of including radioactivity in bituminized waste sample. And we've get data of behavior of nitric acid ion and so on, important to study for disposal, in various condition of sample shape or leaching liquid temperature. (2) In leaching test for waste solidified by epoxy resin, we've get data of behavior of TBP, radionuclides and so on, important to study for disposal. Leached TBP was equal about 1% of including of sample. And we've get data of iodine-129 behavior, too. It was confirmed that leached iodine-129 was equal for about 60% and 100% of including sample, for 90 days. (author)

Leaching studies of low-level radioactive waste forms

International Nuclear Information System (INIS)

Dayal, R.; Arora, H.; Milian, L.; Clinton, J.

1985-01-01

A research program has been underway at the Brookhaven National Laboratory to investigate the release of radionuclides from low-level waste forms under laboratory conditions. This paper describes the leaching behavior of Cs-137 from two major low-level waste streams, that is, ion exchange bead resin and boric acid concentrate, solidified in Portland cement. The resultant leach data are employed to evaluate and predict the release behavior of Cs-137 from low-level waste forms under field burial conditions

Evaluation through column leaching tests of metal release from contaminated estuarine sediment subject to CO2 leakages from Carbon Capture and Storage sites

International Nuclear Information System (INIS)

Payán, M. Cruz; Galan, Berta; Coz, Alberto; Vandecasteele, Carlo; Viguri, Javier R.

2012-01-01

The pH change and the release of organic matter and metals from sediment, due to the potential CO 2 acidified seawater leakages from a CCS (Carbon Capture and Storage) site are presented. Column leaching test is used to simulate a scenario where a flow of acidified seawater is in contact with recent contaminated sediment. The behavior of pH, dissolved organic carbon (DOC) and metals As, Cd, Cr, Cu, Ni, Pb, Zn, with liquid to solid (L/S) ratio and pH is analyzed. A stepwise strategy using empirical expressions and a geochemical model was conducted to fit experimental release concentrations. Despite the neutralization capacity of the seawater-carbonate rich sediment system, important acidification and releases are expected at local scale at lower pH. The obtained results would be relevant as a line of evidence input of CCS risk assessment, in an International context where strategies to mitigate the climate change would be applied. - Highlights: ► Tier structured approach for assessment of the release of metals from sediment. ► Standard column leaching test to simulate CO 2 acidified seawater CCS leakages. ► Metal and DOC release from marine sediment in contact to CO 2 acidified seawater. ► From empirical to geochemical modeling approaches of DOC and metals release in column tests. ► Contamination line of evidence input of CCS risk assessment. - Column metal release from CO 2 acidified seawater leakages in contact with estuarine contaminated sediment in CCS sites

Full-scale leaching study of commercial reactor waste forms

International Nuclear Information System (INIS)

Kalb, P.D.; Colombo, P.

1984-01-01

This paper describes a full-scale leaching experiment which has been conducted at Brookhaven National Laboratory (BNL) to study the release of radionuclides from actual commercial reactor waste forms. While many studies characterizing the leaching behavior of simulated laboratory-scale waste forms have been performed, this program represents one of the first attempts in the United States to quantify activity releases for real, full-scale waste forms. 5 references, 5 figures, 1 table

Uranium and thorium leached from uranium mill tailing of Guangdong province (CN)) and its implication for radiological risk

International Nuclear Information System (INIS)

Wang, J.; Liu, J.; Zhu, L.; Qi, J. Y.; Chen, Y. H.; Xiao, T. F.; Fu, S. M.; Wang, C. L.; Li, J. W.

2012-01-01

The paper focused on the leaching behaviour of uranium (U) and thorium (Th) from uranium mill tailing collected from the Uranium Mill Plant in Northern Guangdong Province (CN)). Distilled water (pH 6) and sulphuric acid solution (pH 4 and 3) were used as solvent for the leaching over 22 weeks. It was found that the cumulative leach fraction from the mill tailing was 0.1, 0.1 and 0.7 % for U release, and overall 0.01 % for Th release, using distilled water, sulphuric acid solution of pH 4 and pH 3 as leaching agents, respectively. The results indicate that (1) the release of U and Th in uranium mill tailing is a slow and long-term process; (2) surface dissolution is the main mechanism for the release of U and Th when sulphuric acid solution of pH 3 is employed as the leaching agent; (3) both U and Th are released by diffusion when using sulphuric acid solution of pH 4 as the leaching agent and (4) U is released by surface dissolution, while Th is released by diffusion when using distilled water as the leaching agent. The implication for radiological risk in the real environment was also discussed. (authors)

Kinetics of steel slag leaching: Batch tests and modeling

International Nuclear Information System (INIS)

De Windt, Laurent; Chaurand, Perrine; Rose, Jerome

2011-01-01

Reusing steel slag as an aggregate for road construction requires to characterize the leaching kinetics and metal releases. In this study, basic oxygen furnace (BOF) steel slag were subjected to batch leaching tests at liquid to solid ratios (L/S) of 10 and 100 over 30 days; the leachate chemistry being regularly sampled in time. A geochemical model of the steel slag is developed and validated from experimental data, particularly the evolution with leaching of mineralogical composition of the slag and trace element speciation. Kinetics is necessary for modeling the primary phase leaching, whereas a simple thermodynamic equilibrium approach can be used for secondary phase precipitation. The proposed model simulates the kinetically-controlled dissolution (hydrolysis) of primary phases, the precipitation of secondary phases (C-S-H, hydroxide and spinel), the pH and redox conditions, and the progressive release of major elements as well as the metals Cr and V. Modeling indicates that the dilution effect of the L/S ratio is often coupled to solubility-controlled processes, which are sensitive to both the pH and the redox potential. A sensitivity analysis of kinetic uncertainties on the modeling of element releases is performed.

Investigation of the leaching behavior of lead in stabilized/solidified waste using a two-year semi-dynamic leaching test.

Science.gov (United States)

Xue, Qiang; Wang, Ping; Li, Jiang-Shan; Zhang, Ting-Ting; Wang, Shan-Yong

2017-01-01

Long-term leaching behavior of contaminant from stabilization/solidification (S/S) treated waste stays unclear. For the purpose of studying long-term leaching behavior and leaching mechanism of lead from cement stabilized soil under different pH environment, semi-dynamic leaching test was extended to two years to investigate leaching behaviors of S/S treated lead contaminated soil. Effectiveness of S/S treatment in different scenarios was evaluated by leachability index (LX) and effective diffusion coefficient (D e ). In addition, the long-term leaching mechanism was investigated at different leaching periods. Results showed that no significant difference was observed among the values of the cumulative release of Pb, D e and LX in weakly alkaline and weakly acidic environment (pH value varied from 5.00 to 10.00), and all the controlling leaching mechanisms of the samples immersed in weakly alkaline and weakly acidic environments turned out to be diffusion. Strong acid environment would significantly affect the leaching behavior and leaching mechanism of lead from S/S monolith. The two-year variation of D e appeared to be time dependent, and D e values increased after the 210 th day in weakly alkaline and weakly acidic environment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Extended Leach Testing of Simulated LAW Cast Stone Monoliths

Energy Technology Data Exchange (ETDEWEB)

Serne, R. Jeffrey [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lanigan, David C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Westsik, Joseph H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Williams, Benjamin D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Jung, H. B. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wang, Guohui [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2016-08-12

This revision to the original report adds two longer term leach sets of data to the report and provides more discussion and graphics on how to interpret the results from long-term laboratory leach tests. The leach tests were performed at Pacific Northwest National Laboratory (PNNL) for Washington River Protection Solutions (WRPS) to evaluate the release of key constituents from monoliths of Cast Stone prepared with four simulated low-activity waste (LAW) liquid waste streams.

Leaching of cadmium, chromium, copper, lead, and zinc from two slag dumps with different environmental exposure periods under dynamic acidic condition.

Science.gov (United States)

Jin, Zhisheng; Liu, Taoze; Yang, Yuangen; Jackson, Daniel

2014-06-01

Over the past few decades, zinc smelting activities in Guizhou, China have produced numerous slag dumps, which are often dispersed on roadsides and hill slopes throughout the region. During periods of acid rain, these exposed slags release heavy metals into surface water bodies. A column leaching study was designed to test the potential release of the heavy metals cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), and zinc (Zn) under simulated acid rain events. Two slags with varying environmental exposure periods were packed in columns and subjected to leaching solutions of pH 3.5, 5.5, or DI H2O at intervals of 1, 7, 14, 28, 56d. Pulse concentrations of Cd in leachate were found above 5μg/L, Cr, Pb, and Zn >10μg/L, whereas, Cu reached 10μg/L. After five leaching events, the leachability (percentage of cumulative heavy metal leached after five leaching events as in its respective total concentration in slags) of Cd was 0.05 percent and 0.035 percent from the old and young slag, respectively. Cr (0.035 percent and 0.05 percent) was greater than Cu (0.002 percent and 0.005 percent) and Zn (0.006 percent and 0.003 percent), while the lowest leachability was observed for Pb (0.0005 percent and 0.0002 percent) from the old and young slags, respectively. Reaction rates (release amount of heavy metals in certain period of leaching) of heavy metals in the leachates demonstrated the sequence of Zn>Cr>Cd, Cu>Pb. Leaching release of heavy metals was jointly affected by the pH of leaching solution and mineral composition of slags (including chemical forms of Cd, Cr, Cu, Pb, and Zn). Environmental exposure period of slags, resulting in the alteration of minerals, could affect the release process of heavy metals in leaching as well. Copyright © 2014 Elsevier Inc. All rights reserved.

Mass Loss and Nutrient Release through Leaching in Tectona ...

African Journals Online (AJOL)

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West African Journal of Applied Ecology, vol. 24(1), 2016: 43–58. ... utilization of organic compounds in litter, and also leaching .... Department of Physics and Engineering. Physics ... The analysis was done following the method described by ...

Microfluidic Leaching of Soil Minerals: Release of K+ from K Feldspar

Science.gov (United States)

Ciceri, Davide; Allanore, Antoine

2015-01-01

The rate of K+ leaching from soil minerals such as K-feldspar is believed to be too slow to provide agronomic benefit. Currently, theories and methods available to interpret kinetics of mineral processes in soil fail to consider its microfluidic nature. In this study, we measure the leaching rate of K+ ions from a K-feldspar-bearing rock (syenite) in a microfluidic environment, and demonstrate that at the spatial and temporal scales experienced by crop roots, K+ is available at a faster rate than that measured with conventional apparatuses. We present a device to investigate kinetics of mineral leaching at an unprecedented simultaneous resolution of space (~101-102 μm), time (~101-102 min) and fluid volume (~100-101 mL). Results obtained from such a device challenge the notion that silicate minerals cannot be used as alternative fertilizers for tropical soils. PMID:26485160

Some factors affecting agitation leach test during in-situ leaching of uranium

International Nuclear Information System (INIS)

Liao Wensheng; Jiang Yan; Wang Limin; Shi Zhenfeng; Zhao Qiaofu; MARMAR

2014-01-01

The agitation leaching test is one of the most fundamental research works in in-situ leaching of uranium. Some factors affecting the test results were analyzed including stirring, leaching time, oxidizer used in alkaline leach, washing solution, the amount and size of ore samples. The results indicate that stirring can enhance diffusion velocity. The leach time l or 2 days is suitable for the samples containing accessible uranium and low acid consumption minerals; whereas 3 or 4 days for those containing refractory ore to leach and slowly acid consuming minerals. For the oxidizer used in alkaline leach, potassium permanganate is better than hydrogen peroxide. Recovery calculated by the leach solution can be directly obtained by its uranium level and the original volume of lixiviant without analyzing and calculating the washing solution. The appropriate amount and size of ore samples for the agitation leaching test are 60 g and <1 mm. By controlling the above factors, the agitation leach test can improve the applicability of the different ore samples and give the more reliable data. (authors)

Leaching of solidified TRU-contaminated incinerator ash

International Nuclear Information System (INIS)

Fuhrmann, M.; Colombo, P.

1984-01-01

Leach rate and cumulative fractional releases of plutonium were determined for a series of laboratory-scale waste forms containing transuranic (TRU) contaminated incinerator ash. The solidification agents from which these waste forms were produced are commercially available materials for radioactive waste disposal. The leachants simulate groundwaters with chemical compositions that are indiginous to different geological media proposed for repositories. In this study TRU-contaminated ash was incorporated into waste forms fabricated with portland type I cement, urea-formaldehyde, polyester-styrene or Pioneer 221 bitumen. The ash was generated at the dual-chamber incinerator at the Rocky Flats Plant. These waste forms contained between 1.25 x 10 -2 and 4.4 x 10 -2 Ci (depending on the solidification agent) of mixed TRU isotopes comprised primarily of 239 Pu and 240 Pu. Five leachant solutions were prepared consisting of: (1) demineralized water, (2) simulated brine, (3) simplified sodium-dominated groundwater (30 meq NaCl/liter), (4) simplified calcium-dominated groundwater (30 meq CaCl 2 /liter), and (5) simplified bicarbonate-dominated groundwater (30 meq NaHCO 3 /liter). Cumulative fractional releases were found to vary significantly with different leachants and solidification agents. In all cases waste forms leached in brine gave the lowest leach rates. Urea-formaldehyde had the greatest release of radionuclides while polyester-styrene and portland cement had approximately equivalent fractional releases. Cement cured for 210 days retained radionuclides three times more effectively than cement cured only 30 days

Leaching of heavy metals from steelmaking slags

International Nuclear Information System (INIS)

Gomez, J. F. P.; Pino, C. G.

2006-01-01

Leaching tests with EAF and Ladle slags were performed, using a flow through tests and the standard batch test DIN 38414-S4. The previous method was used to simulate the leaching behaviour of steel slags under landfill. the chemical analysis of the leachates during this period shows, in general, for both types of slag, and increase of heavy metal releases with ageing. Standard test method DIN 38414-S4 was used to evaluate leachability of heavy metals by water in unprocessed slags. After more than one year of trials, slang samples submitted to these trials presented very low total leaching levels. The most extracted elements are calcium and magnesium. Nevertheless, in flow-though test, calcium and magnesium leached from solid slags are below 0.5% and all other metals below 0.1%. Leachates obtained with DIN 38414-S4 present, as expected, higher leaching values; however, these are inferior to 5% (Ca) and 1% (other elements). (Author) 12 refs

Stability and leaching of cobalt smelter fly ash

DEFF Research Database (Denmark)

Vítková, Martina; Hyks, Jiri; Ettler, Vojtěch

2013-01-01

The leaching behaviour of fly ash from a Co smelter situated in the Zambian Copperbelt was studied as a function of pH (5–12) using the pH-static leaching test (CEN/TS 14997). Various experimental time intervals (48h and 168h) were evaluated. The leaching results were combined with the ORCHESTRA...... modelling framework and a detailed mineralogical investigation was performed on the original FA and leached solid residues. The largest amounts of Co, Cu, Pb and Zn were leached at pH 5, generally with the lowest concentrations between pH 9 and 11 and slightly increased concentrations at pH 12. For most...... detected using SEM/EDS and/or TEM/EDS. The leaching of metals was mainly attributed to the dissolution of metallic particles. Partial dissolution of silicate and glass fractions was assumed to significantly influence the release of Ca, Mg, Fe, K, Al and Si as well as Cu, Co and Zn. The formation of illite...

Chapter 14: Evaluating the Leaching of Biocides from Preservative-Treated Wood Products

Science.gov (United States)

Stan T. Lebow

2014-01-01

Leaching of biocides is an important consideration in the long term durability and any potential for environmental impact of treated wood products. This chapter discusses factors affecting biocide leaching, as well as methods of evaluating rate and quantity of biocide released. The extent of leaching is a function of preservative formulation, treatment methods, wood...

Acid pre-treatment method for in situ ore leaching

International Nuclear Information System (INIS)

Mallon, R.G.; Braun, R.L.

1975-01-01

An acid leaching method is described for the recovery of a desired element from a subterranean rubblized body of primary ore containing the element and also having associated therewith a carbonate mineral wherein the rubblized ore body is flooded with an aqueous acidic solution in order to release carbon dioxide from the associated carbonate mineral. After a substantial portion of the available carbon dioxide is released and removed from the ore body, as by venting to the atmosphere, an oxidizing gas is introduced into the flooded, rubblized ore to oxidize the ore and form an acid leach solution effective in the presence of the dissolved oxidizing gas to dissolve the ore and cause the desired element to go into solution. The leach solution is then circulated to the surface where the metal values are recovered therefrom

Leaching of saltstone: Laboratory and field testing and mathematical modeling

International Nuclear Information System (INIS)

Grant, M.W.; Langton, C.A.; Oblath, S.B.; Pepper, D.W.; Wallace, R.M.; Wilhite, E.L.; Yau, W.W.F.

1987-01-01

A low-level alkaline salt solution will be a byproduct in the processing of high-level waste at the Savannah River Plant (SRP). This solution will be incorporated into a wasteform, saltstone, and disposed of in surface vaults. Laboratory and field leach testing and mathematical modeling have demonstrated the predictability of contaminant release from cement wasteforms. Saltstone disposal in surface vaults will meet the design objective, which is to meet drinking water standards in shallow groundwater at the disposal area boundary. Diffusion is the predominant mechanism for release of contaminants to the environment. Leach testing in unsaturated soil, at soil moisture levels above 1 wt %, has shown no difference in leach rate compared to leaching in distilled water. Field leach testing of three thirty-ton blocks of saltstone in lysimeters has been underway since January 1984. Mathematical models were applied to assess design features for saltstone disposal. One dimensional infinite-composite and semi-infinite analytical models were developed for assessing diffusion of nitrate from saltstone through a cement barrier. Numerical models, both finite element and finite difference, were validated by comparison of model predictions with the saltstone lysimeter results. Validated models were used to assess the long-term performance of the saltstone stored in surface vaults. The maximum concentrations of all contaminants released from saltstone to shallow groundwater are predicted to be below drinking water standards at the disposal area boundary. 5 refs., 11 figs., 5 tabs

Determining leach rates of monolithic waste forms

International Nuclear Information System (INIS)

Gilliam, T.M.; Dole, L.R.

1986-01-01

The ANS 16.1 Leach Procedure provides a conservative means of predicting long-term release from monolithic waste forms, offering a simple and relatively quick means of determining effective solid diffusion coefficients. As presented here, these coefficients can be used in a simple model to predict maximum release rates or be used in more complex site-specific models to predict actual site performance. For waste forms that pass the structural integrity test, this model also allows the prediction of EP-Tox leachate concentrations from these coefficients. Thus, the results of the ANS 16.1 Leach Procedure provide a powerful tool that can be used to predict the waste concentration limits in order to comply with the EP-Toxicity criteria for characteristically nonhazardous waste. 12 refs., 3 figs

THE INFLUENCE OF SELECTED FACTORS ON THE LEACHING OF HEAVY METALS FROM SMELTER WASTE

OpenAIRE

Kamila Mizerna; Anna Król

2015-01-01

The paper presents the results of leaching research of selected heavy metals (Pb, Cu, Zn, Ni, Cd, Cr) from industrial waste. The impact of waste fragmentation on the level of heavy metals leaching was analyzed. The decrease of copper and zinc release and the increase of nickel leaching were observed with increasing grain size fraction of waste. Furthermore, release of contaminants in different ratio of liquid to solid (L/S = 10 dm3/kg and 2 dm3/kg) was studied. Higher concentrations of heavy ...

Leaching assessment of road materials containing primary lead and zinc slags.

Science.gov (United States)

Barna, R; Moszkowicz, P; Gervais, C

2004-01-01

Characterisation of the leaching behaviour of waste-containing materials is a crucial step in the environmental assessment for reuse scenarios. In our research we applied the multi-step European methodology ENV 12-920 to the leaching assessment of road materials containing metallurgical slag. A Zn slag from an imperial smelting furnace (ISF) and a Pb slag from a lead blast furnace (LBF) are investigated. The two slags contain up to 11.2 wt% of lead and 3.5 wt% of zinc and were introduced as a partial substitute for sand in two road materials, namely sand-cement and sand-bitumen. At the laboratory scale, a leaching assessment was performed first through batch equilibrium leaching tests. Second, the release rate of the contaminants was evaluated using saturated leaching tests on monolithic material. Third, laboratory tests were conducted on monolithic samples under intermittent wetting conditions. Pilot-scale tests were conducted for field testing of intermittent wetting conditions. The results show that the release of Pb and Zn from the materials in a saturated scenario was controlled by the pH of the leachates. For the intermittent wetting conditions, an additional factor, blocking of the pores by precipitation during the drying phase is proposed. Pilot-scale leaching behaviour only partially matched with the laboratory-scale test results: new mass transfer mechanisms and adapted laboratory leaching tests are discussed.

Leaching of copper and zinc from spent antifouling paint particles

International Nuclear Information System (INIS)

Singh, Nimisha; Turner, Andrew

2009-01-01

Leaching of Cu and Zn from a composite of spent antifouling paint particles, containing about 300 mg g -1 and 110 mg g -1 of the respective metals, was studied in batch experiments. For a given set of simulated environmental conditions, release of Cu was independent of paint particle concentration due to attainment of pseudo-saturation, but Zn was less constrained by solubility effects and release increased with increasing particle concentration. Leaching of Cu increased but Zn decreased with increasing salinity, consistent with mechanisms governing the dissolution of Cu 2 O in the presence of chloride and Zn acrylates in the presence of seawater cations. Because of complex reaction kinetics and the presence of calcium carbonate in the paint matrix, metal leaching appeared to be greater at 4 deg. C than 19 deg. C under many conditions. These findings have important environmental and biological implications regarding the deliberate or inadvertent disposal of antifouling paint residues. - Copper and zinc are readily leached from particles of spent antifouling paint under a range of environmental conditions

Leaching of copper and zinc from spent antifouling paint particles

Energy Technology Data Exchange (ETDEWEB)

Singh, Nimisha [School of Earth, Ocean and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom); Turner, Andrew [School of Earth, Ocean and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom)], E-mail: aturner@plymouth.ac.uk

2009-02-15

Leaching of Cu and Zn from a composite of spent antifouling paint particles, containing about 300 mg g{sup -1} and 110 mg g{sup -1} of the respective metals, was studied in batch experiments. For a given set of simulated environmental conditions, release of Cu was independent of paint particle concentration due to attainment of pseudo-saturation, but Zn was less constrained by solubility effects and release increased with increasing particle concentration. Leaching of Cu increased but Zn decreased with increasing salinity, consistent with mechanisms governing the dissolution of Cu{sub 2}O in the presence of chloride and Zn acrylates in the presence of seawater cations. Because of complex reaction kinetics and the presence of calcium carbonate in the paint matrix, metal leaching appeared to be greater at 4 deg. C than 19 deg. C under many conditions. These findings have important environmental and biological implications regarding the deliberate or inadvertent disposal of antifouling paint residues. - Copper and zinc are readily leached from particles of spent antifouling paint under a range of environmental conditions.

Speciation analysis and leaching behaviors of selected trace elements in spent SCR catalyst.

Science.gov (United States)

Dai, Zejun; Wang, Lele; Tang, Hao; Sun, Zhijun; Liu, Wei; Sun, Yi; Su, Sheng; Hu, Song; Wang, Yi; Xu, Kai; Liu, Liang; Ling, Peng; Xiang, Jun

2018-09-01

This study investigated heavy metal chemical speciation and leaching behavior from a board-type spent selective catalytic reduction (SCR) catalyst containing high concentrations of vanadium, chromium, nickel, copper, zinc, and lead. A three-step sequential extraction method, standard toxicity characteristic leaching procedure (TCLP), and leaching characteristic tests have been performed. It was found that the mobility of six heavy metals in the spent SCR catalyst was significantly different. The mobility of the six heavy metals exhibited the following order: Ni > Zn > V > Cr > As > Cu. Meanwhile, TCLP test results revealed relatively high Zn and Cr leaching rate of 83.20% and 10.35%, respectively. It was found that leaching rate was positively correlated with available contents (sum of acid soluble, reducible and oxidizable fractions). Leaching characteristics tests indicated that pH substantially affected the leaching of these heavy metals. In particular, the leaching of Cr, Ni, Cu, and Zn was positively influenced by strong acid, while V and As were easily released in the presence of strong acid and strong alkali (pH 11). In terms of kinetics, the leaching of Cr, Ni, Cu, Zn, and As within the spent catalyst was dominated by erosion and dissolution processes, which were rapid reaction processes. V was released in large amounts within 1 h, but its leaching amount sharply decreased with time due to readsorption. Copyright © 2018 Elsevier Ltd. All rights reserved.

Biocide leaching from CBA treated wood — A mechanistic interpretation

International Nuclear Information System (INIS)

Lupsea, Maria; Mathies, Helena; Schoknecht, Ute; Tiruta-Barna, Ligia; Schiopu, Nicoleta

2013-01-01

Treated wood is frequently used for construction. However, there is a need to ensure that biocides used for the treatment are not a threat for people or environment. The paper focused on Pinus sylvestris treated with copper–boron–azole (CBA), containing tebuconazole as organic biocide and monoethanolamine (Mea). This study investigates chemical mechanisms of fixation and mobilisation involved in the leaching process of the used inorganic and organic biocides in CBA. A pH dependent leaching test was performed, followed by a set of complementary analysis methods in order to identify and quantify the species released from wood. The main findings of this study are: -Organic compounds are released from untreated and treated wood; the quantity of released total organic carbon, carboxylic and phenolic functions increasing with the pH. -Nitrogen containing compounds, i.e. mainly Mea and its reaction products with extractives, are released in important quantities from CBA treated wood, especially at low pH. -The release of copper is the result of competitive reactions: fixation via complexation reactions and complexation with extractives in the liquid phase. The specific pH dependency of Cu leaching is explained by the competition of ligands for protonation and complexation. -Tebuconazole is released to a lesser extent relative to its initial content. Its fixation on solid wood structure seems to be influenced by pH, suggesting interactions with -OH groups on wood. Boron release appears to be pH independent and very high. This confirms its weak fixation on wood and also no or weak interaction with the extractives. - Highlights: ► A pH dependent leaching mechanism for CBA treated wood is described. ► The fixation and mobilisation of inorganic and organic biocides was investigated. ► Extractives' quantity and nature depend on pH. ► Competition of ligands for protonation and complexation explains Cu behaviour. ► Tebuconazole seems to interact with -OH groups on

Biocide leaching from CBA treated wood — A mechanistic interpretation

Energy Technology Data Exchange (ETDEWEB)

Lupsea, Maria [University of Toulouse, INSA, UPS, INP, LISBP, 135 Avenue de Rangueil, F-31077 Toulouse (France); INRA, UMR 792, F-31400 Toulouse (France); CNRS, UMR 5504, F-31400 Toulouse (France); Paris-Est University, CSTB — Scientific and Technical Centre for the Building Industry, ESE/Environment, 24 rue Joseph Fourier, F-38400 Saint Martin d' Hères (France); Mathies, Helena; Schoknecht, Ute [BAM — Federal Institute for Materials Research and Testing, Division 4.1, Unter den Eichen 87, 12205 Berlin (Germany); Tiruta-Barna, Ligia, E-mail: ligia.barna@insa-toulouse.fr [University of Toulouse, INSA, UPS, INP, LISBP, 135 Avenue de Rangueil, F-31077 Toulouse (France); INRA, UMR 792, F-31400 Toulouse (France); CNRS, UMR 5504, F-31400 Toulouse (France); Schiopu, Nicoleta [Paris-Est University, CSTB — Scientific and Technical Centre for the Building Industry, ESE/Environment, 24 rue Joseph Fourier, F-38400 Saint Martin d' Hères (France)

2013-02-01

Treated wood is frequently used for construction. However, there is a need to ensure that biocides used for the treatment are not a threat for people or environment. The paper focused on Pinus sylvestris treated with copper–boron–azole (CBA), containing tebuconazole as organic biocide and monoethanolamine (Mea). This study investigates chemical mechanisms of fixation and mobilisation involved in the leaching process of the used inorganic and organic biocides in CBA. A pH dependent leaching test was performed, followed by a set of complementary analysis methods in order to identify and quantify the species released from wood. The main findings of this study are: -Organic compounds are released from untreated and treated wood; the quantity of released total organic carbon, carboxylic and phenolic functions increasing with the pH. -Nitrogen containing compounds, i.e. mainly Mea and its reaction products with extractives, are released in important quantities from CBA treated wood, especially at low pH. -The release of copper is the result of competitive reactions: fixation via complexation reactions and complexation with extractives in the liquid phase. The specific pH dependency of Cu leaching is explained by the competition of ligands for protonation and complexation. -Tebuconazole is released to a lesser extent relative to its initial content. Its fixation on solid wood structure seems to be influenced by pH, suggesting interactions with -OH groups on wood. Boron release appears to be pH independent and very high. This confirms its weak fixation on wood and also no or weak interaction with the extractives. - Highlights: ► A pH dependent leaching mechanism for CBA treated wood is described. ► The fixation and mobilisation of inorganic and organic biocides was investigated. ► Extractives' quantity and nature depend on pH. ► Competition of ligands for protonation and complexation explains Cu behaviour. ► Tebuconazole seems to interact with -OH groups

Leaching and geochemical behavior of fired bricks containing coal wastes.

Science.gov (United States)

Taha, Yassine; Benzaazoua, Mostafa; Edahbi, Mohamed; Mansori, Mohammed; Hakkou, Rachid

2018-03-01

High amounts of mine wastes are continuously produced by the mining industry all over the world. Recycling possibility of some wastes in fired brick making has been investigated and showed promising results. However, little attention is given to the leaching behavior of mine wastes based fired bricks. The objective of this paper is to evaluate the geochemical behavior of fired bricks containing different types of coal wastes. The leachates were analyzed for their concentration of As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, Zn and sulfates using different leaching tests; namely Tank Leaching tests (NEN 7375), Toxicity Characteristic Leaching Procedure (TCLP) and pH dependence test (EPA, 1313). The results showed that the release of constituents of potential interest was highly reduced after thermal treatment and were immobilized within the glassy matrix of the fired bricks. Moreover, it was also highlighted that the final pH of all fired samples changed and stabilized around 8-8.5 when the initial pH of leaching solution was in the range 2.5-11.5. The release of heavy metals and metalloids (As) tended to decrease with the increase of pH from acidic to alkaline solutions while Mo displayed a different trend. Copyright © 2017 Elsevier Ltd. All rights reserved.

Impact of pre-equilibration and diffusion limited release kinetics on effluent concentration in column leaching tests: Insights from numerical simulations.

Science.gov (United States)

Finkel, Michael; Grathwohl, Peter

2017-05-01

Column leaching tests have become a standard method for assessing leaching of pollutants from materials used, e.g., for road and railway constructions and in landscaping measures. Column tests showed to be practical in laboratories yielding robust and reproducible results. However, considerable uncertainty still exists related particularly to the degree of equilibration of the pore water with the solids during preparation (pre-equilibration) and percolation of the column. We analyse equilibration time scales and sensitivity of concentrations in column leachate with respect to initial conditions in a series of numerical experiments covering a broad spectrum of material and solute properties. Slow release of pollutants from solid materials is described by a spherical diffusion model of kinetic sorption accounting for multiple grain size fractions and sorption capacities. Results show that the cumulative concentrations are rather independent of the pre-equilibration level for a broad spectrum of parameter settings, e.g. if intra-particle porosity is high, grain size is small, or if the sorption coefficient is large. Sensitivity increases with decreasing liquid solid ratios and contact time during percolation. Significant variations with initial column conditions are to be expected for material and compound properties leading to slow release kinetics. In these cases, sensitivity to initial conditions may have to be considered. Copyright © 2016 Elsevier Ltd. All rights reserved.

LCA of management strategies for RDF incineration and gasification bottom ash based on experimental leaching data

DEFF Research Database (Denmark)

Gianfilippo, Martina Di; Costa, Giulia; Pantini, Sara

2016-01-01

data were used to estimate the potential release from each of the two types of residues. Specific attention was placed on the sensitivity of leaching properties and the determination of emissions by leaching, including: leaching data selection, material properties and assumptions related to emission......The main characteristics and environmental properties of the bottom ash (BA) generated from thermal treatment of waste may vary significantly depending on the type of waste and thermal technology employed. Thus, to ensure that the strategies selected for the management of these residues do...... not cause adverse environmental impacts, the specific properties of BA, in particular its leaching behavior, should be taken into account. This study focuses on the evaluation of potential environmental impacts associated with two different management options for BA from thermal treatment of Refuse Derived...

Leaching of biomass from semi-natural grasslands – Effects on chemical composition and ash high-temperature behaviour

International Nuclear Information System (INIS)

Tonn, Bettina; Thumm, Ulrich; Lewandowski, Iris; Claupein, Wilhelm

2012-01-01

Combustion of biodiversity-rich semi-natural grassland biomass no longer needed for forage allows nature conservation to be combined with bioenergy production. Natural leaching by rainfall during the period between biomass harvest and collection can reduce the content of elements detrimental for the combustion of grassland biomass. This study assesses the influence of biomass characteristics on leaching efficiency and the potential effects of leaching on ash melting behaviour and elemental release. Grassland biomass harvested from five sites at two harvest dates was leached at two intensities. Low-temperature ash was heated to 700, 800, 900 and 1000 °C respectively and classified into four ash fusion classes. Ash mass loss was determined as a measure of high-temperature elemental release. Weather data were used to calculate the frequency of weather conditions favourable to on-field leaching. K and Cl were leached most strongly and were reduced by 30 and 45% respectively by a leaching treatment corresponding to 30–40 mm of rain. The effects of site and harvest date on leaching efficiency were significant but small. Ash melting behaviour and elemental release between 700 and 900 °C were favourably influenced by leaching. The K/(Ca + Mg) and Si/ash ratios were related to increased ash melting. In this respect, semi-natural grassland biomass differs from other, less Ca-rich, herbaceous biofuels. Even if suitable weather conditions are not occurring frequently at the study sites, on-field leaching can offer an additional low-cost, on-farm strategy option for farmers and nature conservation agencies to improve biomass quality of nature conservation grasslands for combustion. -- Graphical abstract: Highlights: ► Combustion of biomass from biodiversity-rich nature conservation grassland. ► Leaching by rain during the field period reduces K and Cl concentrations. ► Increasing K/(Ca + Mg) and decreasing (K + Ca + Mg)/ash ratios increase ash melting. ► Leaching

Leaching behavior of a simulated bituminized radioactive waste form under deep geological conditions

International Nuclear Information System (INIS)

Nakayama, Shinichi; Iida, Yoshihisa; Nagano, Tetsushi; Akimoto, Toshiyuki

2003-01-01

The leaching behavior of a simulated bituminized waste form was studied to acquire data for the performance assessment of the geologic disposal of bituminized radioactive waste. Laboratory-scale leaching tests were performed for radioactive and non-radioactive waste specimens simulating bituminized waste of a French reprocessing company, COGEMA. The simulated waste was contacted with deionized water, an alkaline solution (0.03-mol/l KOH), and a saline solution (0.5-mol/l KCl) under atmospheric and anoxic conditions. The concentrations of Na, Ba, Cs, Sr, Np, Pu, NO 3 , SO 4 and I in the leachates were determined. Swelling of the bituminized waste progressed in deionized water and KOH. The release of the soluble components, Na and Cs, was enhanced by the swelling, and considered to be diffusion-controlled in the swelled layers of the specimens. The release of sparingly soluble components such as Ba and Np was solubility-limited in addition to the progression of leaching. Neptunium, a redox-sensitive element, showed a distinct difference in release between anoxic and atmospheric conditions. The elemental release from the bituminized waste specimens leached in the KCl was very low, which is likely due to the suppression of swelling of the specimens at high ionic strength. (author)

Selective Leaching of Gray Cast Iron: Electrochemical Aspects

International Nuclear Information System (INIS)

Na, Kyung Hwan; Yun, Eun Sub; Park, Young Sheop

2010-01-01

Currently, to keep step with increases in energy consumption, much attention has been paid to the construction of new nuclear power plants (NPPs) and to the continued operation of NPPs. For continued operation, the selective leaching of materials should be evaluated by visual inspections and hardness measurements as a part of One-Time Inspection Program according to the requirements of the guidelines for continued operation of pressured water reactors (PWRs) in Korea and license renewals in the United States, entitled the 'Generic Aging Lessons Learned (GALL) report.' However, the acceptance criteria for hardness have yet to be provided. Recently, USNRC released a new draft of the GALL report for comment and plans to publish its formal version by the end of 2010. In the new draft, the quantitative acceptance criteria for hardness are given at last: no more than a 20 percent decrease in hardness for gray cast iron and brass containing more than 15 percent zinc. Selective leaching is the preferential removal of one of the alloying elements from a solid alloy by corrosion processes, leaving behind a weakened spongy or porous residual structure. The materials susceptible to selective leaching include gray cast iron and brass, which are mainly used as pump casings and valve bodies in the fire protection systems of NPPs. Since selective leaching proceeds slowly during a long period of time and causes a decrease in strength without changing the overall dimensions of original material, it is difficult to identify. In the present work, the selective leaching of gray cast iron is investigated in terms of its electrochemical aspects as part of an ongoing research project to study the changes in metal properties by selective leaching

Leaching of hazardous substances from a composite construction product – An experimental and modelling approach for fibre-cement sheets

Energy Technology Data Exchange (ETDEWEB)

Lupsea, Maria [University of Toulouse, INSA, UPS, INP, LISBP, 135 Avenue de Rangueil, F-31077 Toulouse (France); INRA, UMR 792, F-31400 Toulouse (France); CNRS, UMR 5504, F-31400 Toulouse (France); Paris–Est University, CSTB–Scientific and Technical Centre for the Building Industry, DEE/Environmentand Life Cycle Engineering Team, 24 rue Joseph Fourier, F–38400 Saint Martin d’Hères (France); Tiruta-Barna, Ligia, E-mail: ligia.barna@insa-toulouse.fr [University of Toulouse, INSA, UPS, INP, LISBP, 135 Avenue de Rangueil, F-31077 Toulouse (France); INRA, UMR 792, F-31400 Toulouse (France); CNRS, UMR 5504, F-31400 Toulouse (France); Schiopu, Nicoleta [Paris–Est University, CSTB–Scientific and Technical Centre for the Building Industry, DEE/Environmentand Life Cycle Engineering Team, 24 rue Joseph Fourier, F–38400 Saint Martin d’Hères (France)

2014-01-15

Highlights: • Biocide and heavy metals leaching from fibre-cement sheet was investigated. • Equilibrium and dynamic leaching tests were used as modelling support. • The chemical-transport model identifies the main fixation/solubilisation mechanisms. • Biocides as terbutryn and boron were released by the commercial product. • FCS exhibit a cement-like leaching behaviour with high organic carbon release. -- Abstract: The leaching behaviour of a commercial fibre-cement sheet (FCS) product has been investigated. A static pH dependency test and a dynamic surface leaching test have been performed at lab scale. These tests allowed the development of a chemical-transport model capable to predict the release of major and trace elements over the entire pH range, in function of time. FCS exhibits a cement-type leaching behaviour with respect to the mineral species. Potentially hazardous species are released in significant quantities when compared to their total content. These are mainly heavy metals commonly encountered in cement matrixes and boron (probably added as biocide). Organic compounds considered as global dissolved carbon are released in significant concentrations, originating probably from the partial degradation of the organic fibres. The pesticide terbutryn (probably added during the preservative treatment of the organic fibres) was systematically identified in the leachates. The simulation of an upscaled runoff scenario allowed the evaluation of the cumulative release over long periods and the distribution of the released quantities in time, in function of the local exposure conditions. After 10 years of exposure the release reaches significant fractions of the species’ total content – going from 4% for Cu to near 100% for B.

Leaching of PAHs from agricultural soils treated with oil shale combustion ash: an experimental study.

Science.gov (United States)

Jefimova, Jekaterina; Adamson, Jasper; Reinik, Janek; Irha, Natalya

2016-10-01

The present study focuses on the fate of polycyclic aromatic hydrocarbons (PAHs) in soils amended with oil shale ash (OSA). Leachability studies to assess the release of PAHs to the environment are essential before the application of OSA in agriculture. A quantitative estimation of the leaching of PAHs from two types of soil and two types of OSA was undertaken in this study. Two leaching approaches were chosen: (1) a traditional one step leaching scheme and (2) a leaching scheme with pretreatment, i.e.., incubation of the material in wet conditions imitating the field conditions, followed by a traditional leaching procedure keeping the total amount of water constant. The total amount of PAHs leached from soil/OSA mixtures was in the range of 15 to 48 μg/kg. The amount of total PAHs leached was higher for the incubation method, compared to the traditional leaching method, particularly for Podzolic Gleysols soil. This suggests that for the incubation method, the content of organic matter and clay minerals of the soil influence the fate of PAHs more strongly compared to the traditional leaching scheme. The amount of PAHs leached from OSA samples is higher than from soil/OSA mixtures, which suggests soils to inhibit the release of PAHs. Calculated amount of PAHs from experimental soil and OSA leaching experiments differed considerably from real values. Thus, it is not possible to estimate the amount of PAHs leached from soil/OSA mixtures based on the knowledge of the amount of PAHs leached from soil and OSA samples separately.

Quinoa seeds leach phytoecdysteroids and other compounds with anti-diabetic properties

Science.gov (United States)

Graf, Brittany L.; Poulev, Alexander; Kuhn, Peter; Grace, Mary H.; Lila, Mary Ann; Raskin, Ilya

2014-01-01

Quinoa (Chenopodium quinoa Willd.) contains high levels of biologically active phytoecdysteroids, which have been implicated in plant defense from insects, and have shown a range of beneficial pharmacological effects in mammals. We demonstrated that the most prevalent phytoecdysteroid, 20-hydroxyecdysone (20HE), was secreted (leached) from intact quinoa seeds into water during the initial stages of seed germination. Leaching efficiency was optimized by ethanol concentration (70% ethanol), temperature (80°C), time (4 h), and solvent ratio (5 ml/g seed). When compared to extraction of macerated seeds, the leaching procedure released essentially all the 20HE available in the seeds (491 μg/g seed). The optimized quinoa leachate (QL), containing 0.86% 20HE, 1.00% total phytoecdysteroids, 2.59% flavonoid glycosides, 11.9% oil, and 20.4% protein, significantly lowered fasting blood glucose in obese, hyperglycemic mice. Leaching effectively releases and concentrates bioactive phytochemicals from quinoa seeds, providing an efficient means to produce a food-grade mixture that may be useful for anti-diabetic applications. PMID:24912714

Environmental Hazard Assessment of Jarosite Waste Using Batch Leaching Tests

Directory of Open Access Journals (Sweden)

M. Kerolli – Mustafa

2018-01-01

Full Text Available Jarosite waste samples from Trepça Zinc Industry in Kosovo were subjected to two batch leaching tests as an attempt to characterize the leaching behavior and mobility of minor and major elements of jarosite waste. To achieve this, deionized water and synthetic acidic rain leaching tests were employed. A two-step acidic treatment in microwave digestion system were used to dissolve jarosite waste samples, followed by determination of Al, Ag, As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, P, Pb, S, Si, Sr, and Zn by inductively coupled plasma optical emission spectrometry (ICP-OES. The validation of the procedure was performed by the analysis of two geochemical reference materials, S JR-3 and S Jsy-1. Two toxicity leaching tests revealed a high metal releasing of Cd, Cu, Ni, Mn, Pb, Zn, and As, and the metal release risk for these elements is still very high due the low pH and acid rain. The statistical analysis showed useful data information on the relationship between elements in jarosite samples in two different extraction conditions (deionized water and synthetic acid rain.

Relationship between reaction layer thickness and leach rate for nuclear waste glasses

International Nuclear Information System (INIS)

Chick, L.A.; Pederson, L.R.

1984-02-01

Three leaching tests, devised to distinguish among several proposed nuclear waste glass leaching mechanisms, were carried out for four different waste glasses. In the first test, the influence of a pre-formed reaction layer on elemental release was evaluated. In the second test, glass specimens were replaced with fresh samples halfway through the leaching experiment, to evaluate the influence of the concentration of glass components in leaching. Finally, regular replacement of the leachant at fixed time intervals essentially removed the variable changing solution concentration, and allowed an assessment of the influence of reaction layer thickness on the leaching rate. Results for all glasses tested indicated that the reaction layer presented little or no barrier to leaching, and that most of the retardation on leaching rates generally observed are attributable to saturation effects. 20 references, 6 figures, 1 table

Leaching behavior of mineral processing waste: Comparison of batch and column investigations

Energy Technology Data Exchange (ETDEWEB)

Al-Abed, Souhail R. [National Risk Management Research Laboratory, U.S. Environmental Protection Agency, 26 West Martin Luther King Drive, Cincinnati, OH 45268 (United States)], E-mail: al-abed.souhail@epa.gov; Jegadeesan, G. [Pegasus Technical Services Inc., 46 East Hollister Street, Cincinnati, OH 45219 (United States); Purandare, J. [Englandgeosystem Inc., 15375 Barranca Pkwy, Suite F-106, Irvine, CA 92618 (United States); Allen, D. [National Risk Management Research Laboratory, U.S. Environmental Protection Agency, 26 West Martin Luther King Drive, Cincinnati, OH 45268 (United States)

2008-05-30

In this study, a comparison of laboratory batch and column experiments on metal release profile from a mineral processing waste (MPW) is presented. Batch (equilibrium) and column (dynamic) leaching tests were conducted on ground MPW at different liquid-solid ratios (LS) to determine the mechanisms controlling metal release. Additionally, the effect of pH on metal release is also discussed. It was observed that acidic pH conditions induced dissolution of As, Zn and Cu. Negligible leaching at alkaline pH was observed. However, Se depicted amphoteric behavior with high release at low and high pH. The batch and column data showed that As and Se release increased with LS ratio, while that of Cu and Zn increased initially and tapered towards equilibrium values at high LS ratios. The results on metal release from the MPW suggested that dissolution of the metal was the controlling mechanism. Leaching profiles from the batch and column data corresponded well for most LS ratios. This is most likely due to the acidic character of the waste, minimal changes in pH during the column operation and granular structure of the waste. From a waste management perspective, low cost batch equilibrium studies in lieu of high cost column experiments can be used for decision making on its disposal only when the waste exhibits characteristics similar to the mineral processing waste.

Leaching behavior of mineral processing waste: Comparison of batch and column investigations

International Nuclear Information System (INIS)

Al-Abed, Souhail R.; Jegadeesan, G.; Purandare, J.; Allen, D.

2008-01-01

In this study, a comparison of laboratory batch and column experiments on metal release profile from a mineral processing waste (MPW) is presented. Batch (equilibrium) and column (dynamic) leaching tests were conducted on ground MPW at different liquid-solid ratios (LS) to determine the mechanisms controlling metal release. Additionally, the effect of pH on metal release is also discussed. It was observed that acidic pH conditions induced dissolution of As, Zn and Cu. Negligible leaching at alkaline pH was observed. However, Se depicted amphoteric behavior with high release at low and high pH. The batch and column data showed that As and Se release increased with LS ratio, while that of Cu and Zn increased initially and tapered towards equilibrium values at high LS ratios. The results on metal release from the MPW suggested that dissolution of the metal was the controlling mechanism. Leaching profiles from the batch and column data corresponded well for most LS ratios. This is most likely due to the acidic character of the waste, minimal changes in pH during the column operation and granular structure of the waste. From a waste management perspective, low cost batch equilibrium studies in lieu of high cost column experiments can be used for decision making on its disposal only when the waste exhibits characteristics similar to the mineral processing waste

Radionuclide release from low-level waste in field lysimeters

International Nuclear Information System (INIS)

Oblath, S.B.

1986-01-01

A field program has been in operation for 8 years at the Savannah River Plant (SRP) to determine the leaching/migration behavior of low-level radioactive waste using lysimeters. The lysimeters are soil-filled caissons containing well characterized wastes, with each lysimeter serving as a model of a shallow land burial trench. Sampling and analysis of percolate water and vegetation from the lysimeters provide a determination of the release rates of the radionuclides from the waste/soil system. Vegetative uptake appears to be a major pathway for migration. Fractional release rates from the waste/soil system are less than 0.01% per year. Waste-to-soil leach rates up to 10% per year have been determined by coring several of the lysimeters. The leaching of solidified wasteforms under unsaturated field conditions has agreed well with static, immersion leaching of the same type waste in the laboratory. However, releases from the waste/soil system in the lysimeter may be greater than predicted based on leaching alone, due to complexation of the radionuclides by other components leached from the wastes to form mobile, anionic species

LCA of management strategies for RDF incineration and gasification bottom ash based on experimental leaching data.

Science.gov (United States)

Di Gianfilippo, Martina; Costa, Giulia; Pantini, Sara; Allegrini, Elisa; Lombardi, Francesco; Astrup, Thomas Fruergaard

2016-01-01

The main characteristics and environmental properties of the bottom ash (BA) generated from thermal treatment of waste may vary significantly depending on the type of waste and thermal technology employed. Thus, to ensure that the strategies selected for the management of these residues do not cause adverse environmental impacts, the specific properties of BA, in particular its leaching behavior, should be taken into account. This study focuses on the evaluation of potential environmental impacts associated with two different management options for BA from thermal treatment of Refuse Derived Fuel (RDF): landfilling and recycling as a filler for road sub bases. Two types of thermal treatment were considered: incineration and gasification. Potential environmental impacts were evaluated by life-cycle assessment (LCA) using the EASETECH model. Both non-toxicity related impact categories (i.e. global warming and mineral abiotic resource depletion) and toxic impact categories (i.e. human toxicity and ecotoxicity) were assessed. The system boundaries included BA transport from the incineration/gasification plants to the landfills and road construction sites, leaching of potentially toxic metals from the BA, the avoided extraction, crushing, transport and leaching of virgin raw materials for the road scenarios, and material and energy consumption for the construction of the landfills. To provide a quantitative assessment of the leaching properties of the two types of BA, experimental leaching data were used to estimate the potential release from each of the two types of residues. Specific attention was placed on the sensitivity of leaching properties and the determination of emissions by leaching, including: leaching data selection, material properties and assumptions related to emission modeling. The LCA results showed that for both types of BA, landfilling was associated with the highest environmental impacts in the non-toxicity related categories. For the toxicity

Leaching of radioactive waste forms under saturated and unsaturated flow conditions

International Nuclear Information System (INIS)

Petelka, M.F.

1987-01-01

To predict the environmental impact of shallow land burial sites for radioactive waste, the mobilization and migration of waste nuclides must be estimated. The theoretical understanding that in potential leaching mechanisms leach-rate variations may arise from changes in both moisture content and volumetric flow rate was tested in column flow leach experiments using labeled vermiculite particles as a simulated waste form. As far as possible, conditions of flow rate and solution ion concentration were chosen to roughly approximate expected field conditions. A modified pressure-plate apparatus was developed, tested, and found suitable for the production of steady-state unsaturated conditions with leachate flow. Water content was determined using the gamma-ray attenuation method. The effects of several parameters on leaching were studied, including moisture content and pore velocity. Pore velocity effects were found to be negligible. It was found that the leach rate depends on the fraction of the exposed waste surface that is wetted and varies with the mobile water content in a non-linear fashion. The experimental results indicate that the release rate of radionuclides placed within a properly sited low-level waste disposal site may be two to three times smaller than that predicted assuming saturated conditions. This study was performed using a homogeneous fine-grained synthetic waste form, at room temperature, with a near neutral pH leachant and oxidizing conditions

Modelling and simulation of concrete leaching under outdoor exposure conditions

International Nuclear Information System (INIS)

Schiopu, Nicoleta; Tiruta-Barna, Ligia; Jayr, Emmanuel; Mehu, Jacques; Moszkowicz, Pierre

2009-01-01

Recently, a demand regarding the assessment of release of dangerous substances from construction products was raised by European Commission which has issued the Mandate M/366 addressed to CEN. This action is in relation with the Essential Requirement No. 3 'Hygiene, Health and Environment' of the Construction Products Directive (89/106/EC). The potential hazard for environment and health may arise in different life cycle stages of a construction product. During the service life stage, the release of substances due to contact with the rain water is the main potential hazard source, as a consequence of the leaching phenomenon. The objective of this paper is to present the development of a coupled chemical-transport model for the case of a concrete based construction product, i.e. concrete paving slabs, exposed to rain water under outdoor exposure conditions. The development of the model is based on an iterative process of comparing the experimental results with the simulated results up to an acceptable fit. The experiments were conducted at laboratory scale (equilibrium and dynamic leaching tests) and field scale. The product was exposed for one year in two types of leaching scenarios under outdoor conditions, 'runoff' and 'stagnation', and the element release was monitored. The model was calibrated using the experimental data obtained at laboratory scale and validated against measured field data, by taking into account the specific rain water balance and the atmospheric CO 2 uptake as input parameters. The numerical tool used in order to model and simulate the leaching behaviour was PHREEQC, coupled with the Lawrence Livermore National Laboratory (LLNL) thermodynamic data base. The simulation results are satisfying and the paper demonstrates the feasibility of the modelling approach for the leaching behaviour assessment of concrete type construction materials

Effects of extraction methods and factors on leaching of metals from recycled concrete aggregates.

Science.gov (United States)

Bestgen, Janile O; Cetin, Bora; Tanyu, Burak F

2016-07-01

Leaching of metals (calcium (Ca), chromium (Cr), copper, (Cu), iron (Fe), and zinc (Zn)) of recycled concrete aggregates (RCAs) were investigated with four different leachate extraction methods (batch water leach tests (WLTs), toxicity leaching procedure test (TCLP), synthetic precipitation leaching procedure test (SPLP), and pH-dependent leach tests). WLTs were also used to perform a parametric study to evaluate factors including (i) effects of reaction time, (ii) atmosphere, (iii) liquid-to-solid (L/S) ratio, and (iv) particle size of RCA. The results from WLTs showed that reaction time and exposure to atmosphere had impact on leaching behavior of metals. An increase in L/S ratio decreased the effluent pH and all metal concentrations. Particle size of the RCA had impact on some metals but not all. Comparison of the leached concentrations of metals from select RCA samples with WLT method to leached concentrations from TCLP and SPLP methods revealed significant differences. For the same RCA samples, the highest metal concentrations were obtained with TCLP method, followed by WLT and SPLP methods. However, in all tests, the concentrations of all four (Cr, Cu, Fe, and Zn) metals were below the regulatory limits determined by EPA MCLs in all tests with few exceptions. pH-dependent batch water leach tests revealed that leaching pattern for Ca is more cationic whereas for other metals showed more amphoteric. The results obtained from the pH-dependent tests were evaluated with geochemical modeling (MINTEQA2) to estimate the governing leaching mechanisms for different metals. The results indicated that the releases of the elements were solubility-controlled except Cr.

FIELD-SCALE LEACHING OF ARSENIC, CHROMIUM AND COPPER FROM WEATHERED TREATED WOOD

Science.gov (United States)

Hasan, A. Rasem; Hu, Ligang; Solo-Gabriele, Helena M.; Fieber, Lynne; Cai, Yong; Townsend, Timothy G.

2010-01-01

Earlier studies documented the loss of wood preservatives from new wood. The objective of this study was to evaluate losses from weathered treated wood under field conditions by collecting rainfall leachate from 5 different wood types, all with a surface area of 0.21 m2. Wood samples included weathered chromate copper arsenate (CCA) treated wood at low (2.7 kg/m3), medium (4.8 kg/m3) and high (35.4 kg/m3) retention levels, new alkaline copper quat (ACQ) treated wood (1.1 kg/m3 as CuO) and new untreated wood. Arsenic was found to leach at a higher rate (100 mg in 1 year for low retention) than chromium and copper (leached at the highest rate from the ACQ sample (670 mg). Overall results suggest that metals’ leaching is a continuous process driven by rainfall, and that the mechanism of release from the wood matrix changes as wood weathers. PMID:20053493

Leaching of metals from sewage sludge during one year and their relationship to particle size

International Nuclear Information System (INIS)

Ahlberg, G.; Gustafsson, O.; Wedel, P.

2006-01-01

Leaching of metals from sewage sludge can lead to their accumulation in topsoil and can also contaminate groundwater. Our objectives were to document the metal leachates and the size distribution of leached particles from sewage sludge and to identify possible correlations with physical factors. Results from monthly lysimeter sampling showed an initial release followed by decline for most metals. Cadmium, Ca, Sr, Li, Mn, Ni and Zn showed a 'cyclic' behaviour. Filtration revealed that this 'cyclicity' had no correlation to the size of released particles, but Al, Cr, Fe, Cu, Ag and Pb were clearly related to release of coarser particles most of the year. Total metal amounts leached during one year, relative to original sludge content, had the order Na > Ca = Mg > Mn > Sr > Zn > K > Li = Ni > Cd > Co > Rb > Ag > Cr > Ba = Cu > Ga > Al = Pb = Fe. There were no simple correlations between monthly measured leachate concentrations and precipitation, temperature or pH of precipitation. Occasional leachate sampling might give misleading values for metals with 'cyclic' behaviour. - Cyclic leaching patterns of metals from sewage sludge deserve attention

Microstructural characteristics of PWR [pressurized water reactor] spent fuel relative to its leaching behavior

International Nuclear Information System (INIS)

Wilson, C.N.

1986-01-01

Microstructural, compositional and thermochemical properties of spent nuclear fuel are discussed relative to its potential performance as a high-level waste form under proposed Nevada Nuclear Waste Storage Investigations Project tuff repository conditions. Pressurized water reactor spent fuel specimens with various artificially induced cladding defects were leach tested in deionized water and in a reference tuff groundwater under ambient hot cell air and temperature conditions. Greater fractional actinide release was observed with bare fuel than with clad fuel leached through a cladding defect. Congruent actinide release and preferential release of cesium and technetium were observed in both water types. Selected summary radionuclide release data are presented and correlated to pre- and post-test microstructural characterization data

Leaching from municipal solid waste incineration residues

Energy Technology Data Exchange (ETDEWEB)

Hyks, J.

2008-02-15

Leaching of pollutants from Municipal Solid Waste Incineration (MSWI) residues has been investigated combining a range of laboratory leaching experiments with geochemical modeling. Special attention was paid to assessing the applicability of laboratory data for subsequent modeling with respect to presumed full-scale conditions; both sample pretreatment and actual influence of leaching conditions on the results of laboratory experiments were considered. It was shown that sample pretreatment may have large impact on leaching test data. In particular, a significant fraction of Pb was shown mobile during the washing of residues with water. In addition, drying of residues (i.e. slow oxidation) prior to leaching experiments increased the leaching of Cr significantly. Significant differences regarding the leaching behavior of individual elements with respect to (non)equilibrium conditions in column percolation experiments were observed in the study. As a result, three groups of elements were identified based on the predominant leaching control and the influence of (non)equilibrium on the results of the laboratory column experiments: I. Predominantly availability-controlled elements (e.g. Na, K, Cl) II. Solubility-controlled elements (e.g. Ca, S, Si, Al, Ba, and Zn) III. Complexation-controlled elements (e.g. Cu and Ni) With respect to the above groups it was suggested that results of laboratory column experiments can, with consideration, be used to estimate full-scale leaching of elements from Group I and II. However, in order to avoid large underestimations in the assessment of leaching from Group III, it is imperative to describe the time-dependent transport of dissolved organic carbon (DOC) in the tested system or to minimize the physical non-equilibrium during laboratory experiments (e.g. bigger column, slower flow velocity). Forward geochemical modeling was applied to simulate long-term release of elements from a MSWI air-pollution-control residue. Leaching of a

Directions of development of research methods in the assessment of leaching of heavy metals from mineral waste

Directory of Open Access Journals (Sweden)

Król Anna

2016-01-01

Full Text Available There are many test methods to assess the level of the release of heavy metals into the environment from mineral waste materials. Leaching methods can be different depending on the leaching time periods, leaching dynamics, sample preparation method or the pH of the elution medium. In Poland, little attention is paid to the research on the relationship between the leaching of particular heavy metals from mineral wastes and changes in environmental conditions, including the pH of the environment. Tests being carried out abroad have started to pay great attention to the pH-dependent impact of the environment and the liquid being in contact with the material on the degree of leaching contaminants from wastes. The solubility of all metals depends on the value of the pH. Authors of the paper will try to prove that Polish methods of waste characterization is incomplete and inconsistent with opinions prevailing in the global literature. The procedure described in the Polish standards are insufficient to determine the actual level of leaching of heavy metals having regard to the impact of multiple external conditions on the level of leaching of heavy metals. Paper will present a directions of development of research methods in the assessment of leaching of heavy metals from mineral waste.

Leaching of DOC, DN, and inorganic constituents from scrap tires.

Science.gov (United States)

Selbes, Meric; Yilmaz, Ozge; Khan, Abdul A; Karanfil, Tanju

2015-11-01

One concern for recycle and reuse of scrap tires is the leaching of tire constituents (organic and inorganic) with time, and their subsequent potential harmful impacts in environment. The main objective of this study was to examine the leaching of dissolved organic carbon (DOC), dissolved nitrogen (DN), and selected inorganic constituents from scrap tires. Different sizes of tire chips and crumb rubber were exposed to leaching solutions with pH's ranging from 3.0 to 10.0 for 28days. The leaching of DOC and DN were found to be higher for smaller size tire chips; however, the leaching of inorganic constituents was independent of the size. In general, basic pH conditions increased the leaching of DOC and DN, whereas acidic pH conditions led to elevated concentrations of metals. Leaching was minimal around the neutral pH values for all the monitored parameters. Analysis of the leaching rates showed that components associated with the rubbery portion of the tires (DOC, DN, zinc, calcium, magnesium, etc.) exhibited an initial rapid followed by a slow release. On the other hand, a constant rate of leaching was observed for iron and manganese, which are attributed to the metal wires present inside the tires. Although the total amounts that leached varied, the observed leaching rates were similar for all tire chip sizes and leaching solutions. Operation under neutral pH conditions, use of larger size tire chips, prewashing of tires, and removal of metal wires prior to application will reduce the impact of tire recycle and reuse. Copyright © 2015 Elsevier Ltd. All rights reserved.

Counter-current acid leaching process for copper azole treated wood waste.

Science.gov (United States)

Janin, Amélie; Riche, Pauline; Blais, Jean-François; Mercier, Guy; Cooper, Paul; Morris, Paul

2012-09-01

This study explores the performance of a counter-current leaching process (CCLP) for copper extraction from copper azole treated wood waste for recycling of wood and copper. The leaching process uses three acid leaching steps with 0.1 M H2SO4 at 75degrees C and 15% slurry density followed by three rinses with water. Copper is recovered from the leachate using electrodeposition at 5 amperes (A) for 75 min. Ten counter-current remediation cycles were completed achieving > or = 94% copper extraction from the wood during the 10 cycles; 80-90% of the copper was recovered from the extract solution by electrodeposition. The counter-current leaching process reduced acid consumption by 86% and effluent discharge volume was 12 times lower compared with the same process without use of counter-current leaching. However, the reuse of leachates from one leaching step to another released dissolved organic carbon and caused its build-up in the early cycles.

Long-term leach testing of solidified radioactive waste forms (International Standard Publication ISO 6961:1982)

International Nuclear Information System (INIS)

Stefanik, J.

2001-01-01

Processes are developed for the immobilization of radionuclides by solidification of radioactive wastes. The resulting solidification products are characterized by strong resistance to leaching aimed at low release rates of the radionuclides to the environment. To measure this resistance to leaching of the solidified materials: glass, glass-ceramics, bitumen, cement, concrete, plastics, a long-term leach test is presented. The long-term leach test is aimed at: a) the comparison of different kinds or compositions of solidified waste forms; b) the intercomparison between leach test results from different laboratories on one product; c) the intercomparison between leach test results on products from different processes

Life cycle assessment and residue leaching: The importance of parameter, scenario and leaching data selection

Energy Technology Data Exchange (ETDEWEB)

Allegrini, E., E-mail: elia@env.dtu.dk [Technical University of Denmark, Department of Environmental Engineering, Building 115, 2800 Lyngby (Denmark); Butera, S. [Technical University of Denmark, Department of Environmental Engineering, Building 115, 2800 Lyngby (Denmark); Kosson, D.S. [Vanderbilt University, Department of Civil and Environmental Engineering, Box 1831 Station B, Nashville, TN 37235 (United States); Van Zomeren, A. [Energy Research Centre of the Netherlands (ECN), Department of Environmental Risk Assessment, P.O. Box 1, 1755 ZG Petten (Netherlands); Van der Sloot, H.A. [Hans van der Sloot Consultancy, Dorpsstraat 216, 1721 BV Langedijk (Netherlands); Astrup, T.F. [Technical University of Denmark, Department of Environmental Engineering, Building 115, 2800 Lyngby (Denmark)

2015-04-15

Highlights: • Relevance of metal leaching in waste management system LCAs was assessed. • Toxic impacts from leaching could not be disregarded. • Uncertainty of toxicity, due to background activities, determines LCA outcomes. • Parameters such as pH and L/S affect LCA results. • Data modelling consistency and coverage within an LCA are crucial. - Abstract: Residues from industrial processes and waste management systems (WMSs) have been increasingly reutilised, leading to landfilling rate reductions and the optimisation of mineral resource utilisation in society. Life cycle assessment (LCA) is a holistic methodology allowing for the analysis of systems and products and can be applied to waste management systems to identify environmental benefits and critical aspects thereof. From an LCA perspective, residue utilisation provides benefits such as avoiding the production and depletion of primary materials, but it can lead to environmental burdens, due to the potential leaching of toxic substances. In waste LCA studies where residue utilisation is included, leaching has generally been neglected. In this study, municipal solid waste incineration bottom ash (MSWI BA) was used as a case study into three LCA scenarios having different system boundaries. The importance of data quality and parameter selection in the overall LCA results was evaluated, and an innovative method to assess metal transport into the environment was applied, in order to determine emissions to the soil and water compartments for use in an LCA. It was found that toxic impacts as a result of leaching were dominant in systems including only MSWI BA utilisation, while leaching appeared negligible in larger scenarios including the entire waste system. However, leaching could not be disregarded a priori, due to large uncertainties characterising other activities in the scenario (e.g. electricity production). Based on the analysis of relevant parameters relative to leaching, and on general results

Modelling inorganic and organic biocide leaching from CBA-amine (Copper–Boron–Azole) treated wood based on characterisation leaching tests

Energy Technology Data Exchange (ETDEWEB)

Lupsea, Maria [University of Toulouse, INSA, UPS, INP, LISBP, 135 Avenue de Rangueil, F–31077 Toulouse (France); INRA, UMR 792, F-31400 Toulouse (France); CNRS, UMR 5504, F-31400 Toulouse (France); Paris-Est University, CSTB — Scientific and Technical Centre for the Building Industry, DEE/Environment and Life Cycle Engineering Team, 24 Rue Joseph Fourier, F-38400 Saint Martin d' Hères (France); Tiruta-Barna, Ligia, E-mail: ligia.barna@insa-toulouse.fr [University of Toulouse, INSA, UPS, INP, LISBP, 135 Avenue de Rangueil, F–31077 Toulouse (France); INRA, UMR 792, F-31400 Toulouse (France); CNRS, UMR 5504, F-31400 Toulouse (France); Schiopu, Nicoleta [Paris-Est University, CSTB — Scientific and Technical Centre for the Building Industry, DEE/Environment and Life Cycle Engineering Team, 24 Rue Joseph Fourier, F-38400 Saint Martin d' Hères (France); Schoknecht, Ute [BAM — Federal Institute for Materials Research and Testing, Division 4.1, Unter den Eichen 87, 12205 Berlin (Germany)

2013-09-01

Numerical simulation of the leaching behaviour of treated wood is the most pertinent and less expensive method for the prediction of biocides' release in water. Few studies based on mechanistic leaching models have been carried out so far. In this work, a coupled chemistry-mass transport model is developed for simulating the leaching behaviour of inorganic (Cu, B) and organic (Tebuconazole) biocides from CBA-amine treated wood. The model is based on experimental investigations (lab-scale leaching tests coupled with chemical and structural analysis). It considers biocides' interactions with wood solid components and with extractives (literature confirmed reactions), as well as transport mechanisms (diffusion, convection) in different compartments. Simulation results helped at identifying the main fixation mechanisms, like (i) direct complexation of Cu by wood-phenolic and -carboxylic sites (and not via monoethanolamine; complex) on lignin and hemicellulose and strong dependence on extractives' nature, (ii) pH dependent binding of tebuconazole on polarized -OH moieties on wood. The role of monoethanolamine is to provide a pore-solution pH of about 7.5, when copper solubility is found to be weakest. The capability of the developed model to simulate the chemical and transport behaviour is the main result of this study. Moreover, it proved that characterization leaching tests (pH dependency and dynamic tests), combined with appropriate analytical methods are useful experimental tools. Due to its flexibility for representing and simulating various leaching conditions, chemical-transport model developed could be used to further simulate the leaching behaviour of CBA treated wood at larger scales. - Highlights: • Biocide and extractives leaching from ammonia-CBA treated wood were modelled. • The chemical-transport model identifies the main fixation/solubilisation mechanisms. • The model describes well the results of equilibrium and dynamic leaching

Leach studies of chelating agents and influence on radionuclide leaching from simulated LLW/ILW cement waste forms

International Nuclear Information System (INIS)

Vejmelka, P.; Koester, R.; Ferrara, D.; Wacks, M.E.

1990-01-01

Leach studies were performed on cemented waste forms containing sodium nitrate, trace amounts of cesium-137, and cobalt-60, and a chelating agent (ethylene diamine tetraacetic acid (EDTA), nitrilotriacetic acid (NTA), or citric acid). Leaching of the chelates was measured in water and the effect of the chelates on the release of the Cs-137 and Co-60 was studied. The time dependence of the release rate of the chelates is comparable but the chelate concentration in solution and the released fractions are different. EDTA shows the highest release rate followed by NTA and citrate. The release of the non complex forming cesium is not affected by the presence of the chelates. Independent from the strong complex formation of cobalt with EDTA, NTA, and citrate in the alkaline region the cobalt release is also not affected by the presence of the chelates. The high calcium content of the system decreases the stability of the Co complexes in the high pH region (12-13). Experiments were performed to determine the equilibrium concentration of the chelates between liquid and solid phases. The liquid phases were deionized water, saturated sodium chloride, 24 percent magnesium chloride and Q-brine. The equilibrium studies are based on the assumption that in time a stable final condition is to be established in the near field of the waste form in which each compound is at chemical equilibrium between the dissolved and the various solid phases. The total release may be assessed from the concentration in solution and flow rate out of the near field. The fraction of EDTA released from the cement ranged from 0.2 in the Q-brine to 0.5 in the saturated sodium chloride. The concentration of EDSA in solution was dependent on the original amount in the cement sample, but the released fraction was independent of the initial loading. Indicating, EDTA concentration is not affected by solubility limits. 11 refs., 3 figs., 2 tabs

Life cycle assessment and residue leaching: the importance of parameter, scenario and leaching data selection.

Science.gov (United States)

Allegrini, E; Butera, S; Kosson, D S; Van Zomeren, A; Van der Sloot, H A; Astrup, T F

2015-04-01

Residues from industrial processes and waste management systems (WMSs) have been increasingly reutilised, leading to landfilling rate reductions and the optimisation of mineral resource utilisation in society. Life cycle assessment (LCA) is a holistic methodology allowing for the analysis of systems and products and can be applied to waste management systems to identify environmental benefits and critical aspects thereof. From an LCA perspective, residue utilisation provides benefits such as avoiding the production and depletion of primary materials, but it can lead to environmental burdens, due to the potential leaching of toxic substances. In waste LCA studies where residue utilisation is included, leaching has generally been neglected. In this study, municipal solid waste incineration bottom ash (MSWI BA) was used as a case study into three LCA scenarios having different system boundaries. The importance of data quality and parameter selection in the overall LCA results was evaluated, and an innovative method to assess metal transport into the environment was applied, in order to determine emissions to the soil and water compartments for use in an LCA. It was found that toxic impacts as a result of leaching were dominant in systems including only MSWI BA utilisation, while leaching appeared negligible in larger scenarios including the entire waste system. However, leaching could not be disregarded a priori, due to large uncertainties characterising other activities in the scenario (e.g. electricity production). Based on the analysis of relevant parameters relative to leaching, and on general results of the study, recommendations are provided regarding the use of leaching data in LCA studies. Copyright © 2014 Elsevier Ltd. All rights reserved.

Pollution potential leaching index as a tool to assess water leaching risk of arsenic in excavated urban soils.

Science.gov (United States)

Li, Jining; Kosugi, Tomoya; Riya, Shohei; Hashimoto, Yohey; Hou, Hong; Terada, Akihiko; Hosomi, Masaaki

2018-01-01

Leaching of hazardous trace elements from excavated urban soils during construction of cities has received considerable attention in recent years in Japan. A new concept, the pollution potential leaching index (PPLI), was applied to assess the risk of arsenic (As) leaching from excavated soils. Sequential leaching tests (SLT) with two liquid-to-solid (L/S) ratios (10 and 20Lkg -1 ) were conducted to determine the PPLI values, which represent the critical cumulative L/S ratios at which the average As concentrations in the cumulative leachates are reduced to critical values (10 or 5µgL -1 ). Two models (a logarithmic function model and an empirical two-site first-order leaching model) were compared to estimate the PPLI values. The fractionations of As before and after SLT were extracted according to a five-step sequential extraction procedure. Ten alkaline excavated soils were obtained from different construction projects in Japan. Although their total As contents were low (from 6.75 to 79.4mgkg -1 ), the As leaching was not negligible. Different L/S ratios at each step of the SLT had little influence on the cumulative As release or PPLI values. Experimentally determined PPLI values were in agreement with those from model estimations. A five-step SLT with an L/S of 10Lkg -1 at each step, combined with a logarithmic function fitting was suggested for the easy estimation of PPLI. Results of the sequential extraction procedure showed that large portions of more labile As fractions (non-specifically and specifically sorbed fractions) were removed during long-term leaching and so were small, but non-negligible, portions of strongly bound As fractions. Copyright © 2017 Elsevier Inc. All rights reserved.

THE INFLUENCE OF SELECTED FACTORS ON THE LEACHING OF HEAVY METALS FROM SMELTER WASTE

Directory of Open Access Journals (Sweden)

Kamila Mizerna

2015-07-01

Full Text Available The paper presents the results of leaching research of selected heavy metals (Pb, Cu, Zn, Ni, Cd, Cr from industrial waste. The impact of waste fragmentation on the level of heavy metals leaching was analyzed. The decrease of copper and zinc release and the increase of nickel leaching were observed with increasing grain size fraction of waste. Furthermore, release of contaminants in different ratio of liquid to solid (L/S = 10 dm3/kg and 2 dm3/kg was studied. Higher concentrations of heavy metals were determined in ratio of L/S = 10 dm3/kg. In order to determine the risk of tested waste to the environment, the results were compared with the current law. This allowed the classification of the waste to hazardous waste.

Pesticide leaching through sandy and loamy fields - long-term lessons learnt from the Danish Pesticide Leaching Assessment Programme.

Science.gov (United States)

Rosenbom, Annette E; Olsen, Preben; Plauborg, Finn; Grant, Ruth; Juhler, René K; Brüsch, Walter; Kjær, Jeanne

2015-06-01

The European Union authorization procedure for pesticides includes an assessment of the leaching risk posed by pesticides and their degradation products (DP) with the aim of avoiding any unacceptable influence on groundwater. Twelve-year's results of the Danish Pesticide Leaching Assessment Programme reveal shortcomings to the procedure by having assessed leaching into groundwater of 43 pesticides applied in accordance with current regulations on agricultural fields, and 47 of their DP. Three types of leaching scenario were not fully captured by the procedure: long-term leaching of DP of pesticides applied on potato crops cultivated in sand, leaching of strongly sorbing pesticides after autumn application on loam, and leaching of various pesticides and their DP following early summer application on loam. Rapid preferential transport that bypasses the retardation of the plow layer primarily in autumn, but also during early summer, seems to dominate leaching in a number of those scenarios. Copyright © 2015 Elsevier Ltd. All rights reserved.

Comparison of leach results from field and laboratory prepared samples

International Nuclear Information System (INIS)

Oblath, S.B.; Langton, C.A.

1985-01-01

The leach behavior of saltstone prepared in the laboratory agrees well with that from samples mixed in the field using the Littleford mixer. Leach rates of nitrates and cesium from the current reference formulation saltstone were compared. The laboratory samples were prepared using simulated salt solution; those in the field used Tank 50 decontaminated supernate. For both nitrate and cesium, the field and laboratory samples showed nearly identical leach rates for the first 30 to 50 days. For the remaining period of the test, the field samples showed higher leach rates with the maximum difference being less than a factor of three. Ruthenium and antimony were present in the Tank 50 supernate in known amounts. Antimony-125 was observed in the leachate and a fractional leach rate was calculated to be at least a factor of ten less than that of 137 Cs. No 106 Ru was observed in the leachate, and the release rate was not calculated. However, based on the detection limits for the analysis, the ruthenium leach rate must also be at least a factor of ten less than cesium. These data are the first measurements of the leach rates of Ru and Sb from saltstone. The nitrate leach rates for these samples were 5 x 10 -5 grams of nitrate per square cm per day after 100 days for the laboratory samples and after 200 days for the field samples. These values are consistent with the previously measured leach rates for reference formulation saltstone. The relative standard deviation in the leach rate is about 15% for the field samples, which all were produced from one batch of saltstone, and about 35% for the laboratory samples, which came from different batches. These are the first recorded estimates of the error in leach rates for saltstone

Extended Leach Testing of Simulated LAW Cast Stone Monoliths

Energy Technology Data Exchange (ETDEWEB)

Serne, R. Jeffrey [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Westsik, Joseph H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Williams, Benjamin D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Jung, H. B. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wang, Guohui [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2015-07-09

This report describes the results from long-term laboratory leach tests performed at Pacific Northwest National Laboratory (PNNL) for Washington River Protection Solutions (WRPS) to evaluate the release of key constituents from monoliths of Cast Stone prepared with four simulated low-activity waste (LAW) liquid waste streams. Specific objectives of the Cast Stone long-term leach tests described in this report focused on four activities: 1. Extending the leaching times for selected ongoing EPA-1315 tests on monoliths made with LAW simulants beyond the conventional 63-day time period up to 609 days reported herein (with some tests continuing that will be documented later) in an effort to evaluate long-term leaching properties of Cast Stone to support future performance assessment activities. 2. Starting new EPA-1315 leach tests on archived Cast Stone monoliths made with four LAW simulants using two leachants (deionized water [DIW] and simulated Hanford Integrated Disposal Facility (IDF) Site vadose zone pore water [VZP]). 3. Evaluating the impacts of varying the iodide loading (starting iodide concentrations) in one LAW simulant (7.8 M Na Hanford Tank Waste Operations Simulator (HTWOS) Average) by manufacturing new Cast Stone monoliths and repeating the EPA-1315 leach tests using DIW and the VZP leachants. 4. Evaluating the impacts of using a non-pertechnetate form of Tc that is present in some Hanford tanks. In this activity one LAW simulant (7.8 M Na HTWOS Average) was spiked with a Tc(I)-tricarbonyl gluconate species and then solidified into Cast Stone monoliths. Cured monoliths were leached using the EPA-1315 leach protocol with DIW and VZP. The leach results for the Tc-Gluconate Cast Stone monoliths were compared to Cast Stone monoliths pertechnetate.

The structure of leached sodium borosilicate glass

International Nuclear Information System (INIS)

Bunker, B.C.; Tallant, D.R.; Headley, T.J.; Turner, G.L.; Kirkpatrick, R.J.

1988-01-01

Raman spectroscopy, solid state 29 Si, 11 B, 17 O, and 23 Na nuclear magnetic resonance spectroscopy, and transmission electron microscopy have been used to investigate how the structures of sodium borosilicate glasses change during leaching in water at pH 1, 9, and 12. Results show that the random network structure present prior to leaching is transformed into a network of small condensed ring structures and/or colloidal silica particles. The restructuring of leached glass can be rationalised on the basis of simple hydrolysis (depolymerisation) and condensation (repolymerisation) reactions involving Si-O-Si and Si-O-B bonds. The structural changes that occur during leaching influence the properties of the leached layer, including leaching kinetics, crazing and spalling, and slow crack growth. (author)

Presence and leaching of bisphenol a (BPA) from dental materials

Science.gov (United States)

Becher, Rune; Wellendorf, Hanne; Sakhi, Amrit Kaur; Samuelsen, Jan Tore; Thomsen, Cathrine; Bølling, Anette Kocbach; Kopperud, Hilde Molvig

2018-01-01

Abstract BPA has been reported to leach from some resin based dental restorative materials and materials used for orthodontic treatment. To confirm and update previous findings, especially in light of the new temporary lower threshold value for tolerable daily BPA intake, we have investigated the leaching of BPA from 4 composite filling materials, 3 sealants and 2 orthodontic bonding materials. The materials were either uncured and dissolved in methanol or cured. The cured materials were kept in deionized water for 24 hours or 2 weeks. Samples were subsequently analyzed by ultra-performance liquid chromatography coupled to mass spectrometry (UPLC-MS-MS). The composite filling material Tetric EvoFlow® and the fissure sealant DELTON® showed significantly higher levels of BPA leaching compared to control samples for all test conditions (uncured, 24 h leaching and 2 weeks leaching). There were no significant differences in amount of leached BPA for any of the tested materials after 24 hours compared to 2 weeks. These results show that BPA is still released from some dental materials despite the general concern about potential adverse effects of BPA. However, the amounts of BPA were relatively low and most likely represent a very small contribution to the total BPA exposure. PMID:29868625

Standard leach tests for nuclear waste materials

International Nuclear Information System (INIS)

Strachan, D.M.; Barnes, B.O.; Turcotte, R.P.

1980-01-01

Five leach tests were conducted to study time-dependent leaching of waste forms (glass). The first four tests include temperature as a variable and the use of three standard leachants. Three of the tests are static and two are dynamic (flow). This paper discusses the waste-form leach tests and presents some representative data. 4 figures

Study on the leaching behavior of actinides from nuclear fuel debris

Science.gov (United States)

Kirishima, Akira; Hirano, Masahiko; Akiyama, Daisuke; Sasaki, Takayuki; Sato, Nobuaki

2018-04-01

For the prediction of the leaching behavior of actinides contained in the nuclear fuel debris generated by the Fukushima Daiichi nuclear power plant accident in Japan, simulated fuel debris consisting of a UO2-ZrO2 solid solution doped with 137Cs, 237Np, 236Pu, and 241Am tracers was synthesized and investigated. The synthesis of the debris was carried out by heat treatment at 1200 °C at different oxygen partial pressures, and the samples were subsequently used for leaching tests with Milli-Q water and seawater. The results of the leaching tests indicate that the leaching of actinides depends on the redox conditions under which the debris was generated; for example, debris generated under oxidative conditions releases more actinide nuclides to water than that generated under reductive conditions. Furthermore, we found that, as Zr(IV) increasingly substituted U(IV) in the fluorite crystal structure of the debris, the actinide leaching from the debris decreased. In addition, we found that seawater leached more actinides from the debris than pure water, which seems to be caused by the complexation of actinides by carbonate ions in seawater.

Acid mine drainage simulated leaching behavior of goethite and cobalt substituted goethite

Science.gov (United States)

Penprase, S. B.; Kimball, B. E.

2015-12-01

Though most modern day mining aims to eliminate the seepage of acid mine drainage (AMD) to the local watershed, historical mines regularly receive little to no remediation, and often release acidic, metal-rich drainage and particles to the environment. Treatment of AMD often includes neutralizing pH to facilitate the precipitation of Fe-oxides and dissolved trace metals, thereby forming Trace Metal Substituted (TMS) forms of known minerals, such as goethite (α-FeOOH). The stability of TMS precipitates is not fully understood. As a result, we conducted a 20 day leach experiment using laboratory synthesized pure (Gt) and cobalt-substituted (CoGt) goethites with a dilute ultrapure HCl solution (pH = 3.61) at T = 23.3±2.5ºC. Leached solids were characterized using X-ray diffraction (XRD) and scanning electron microscopy paired with energy dispersive spectroscopy (SEM-EDS). Leach solutions were sampled for pH and conductivity, and dissolved chemistry was determined with Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). Preliminary results indicate Gt and CoGt filtered leach solutions experienced constant pH (Gt = 3.9 ± 0.1, CoGt = 6.8 ± 0.2) and conductivity (Gt = 69 ± 6.6 μS/cm, CoGt = 81 ± 16 μS/cm) for t = 0-20 days. Micro-focused XRD results indicate that leached solids did not change in mineralogy throughout the experiment, and SEM images show minor disintegration along mineral grain edges, but little overall change in shape. Preliminary ICP-MS results show lower dissolved Fe concentrations for CoGt (1.1 ± 1.1 ppb) compared to Gt (17 ± 8.9 ppb) over time. Dissolved Co concentrations ranged from 560 - 830 ppb and increased over time. Compared to leaching of pure Gt, leaching of CoGt generated significantly higher pH, slightly higher conductivity, and significantly less dissolved Fe. During the CoGt leach, Co was preferentially leached over Fe. The differences in leaching behavior between pure and TMS goethite in the laboratory have implications for

Antimony leaching from polyethylene terephthalate (PET) plastic used for bottled drinking water.

Science.gov (United States)

Westerhoff, Paul; Prapaipong, Panjai; Shock, Everett; Hillaireau, Alice

2008-02-01

Antimony is a regulated contaminant that poses both acute and chronic health effects in drinking water. Previous reports suggest that polyethylene terephthalate (PET) plastics used for water bottles in Europe and Canada leach antimony, but no studies on bottled water in the United States have previously been conducted. Nine commercially available bottled waters in the southwestern US (Arizona) were purchased and tested for antimony concentrations as well as for potential antimony release by the plastics that compose the bottles. The southwestern US was chosen for the study because of its high consumption of bottled water and elevated temperatures, which could increase antimony leaching from PET plastics. Antimony concentrations in the bottled waters ranged from 0.095 to 0.521 ppb, well below the US Environmental Protection Agency (USEPA) maximum contaminant level (MCL) of 6 ppb. The average concentration was 0.195+/-0.116 ppb at the beginning of the study and 0.226+/-0.160 ppb 3 months later, with no statistical differences; samples were stored at 22 degrees C. However, storage at higher temperatures had a significant effect on the time-dependent release of antimony. The rate of antimony (Sb) release could be fit by a power function model (Sb(t)=Sb 0 x[Time, h]k; k=8.7 x 10(-6)x[Temperature ( degrees C)](2.55); Sb 0 is the initial antimony concentration). For exposure temperatures of 60, 65, 70, 75, 80, and 85 degrees C, the exposure durations necessary to exceed the 6 ppb MCL are 176, 38, 12, 4.7, 2.3, and 1.3 days, respectively. Summertime temperatures inside of cars, garages, and enclosed storage areas can exceed 65 degrees C in Arizona, and thus could promote antimony leaching from PET bottled waters. Microwave digestion revealed that the PET plastic used by one brand contained 213+/-35 mgSb/kg plastic; leaching of all the antimony from this plastic into 0.5L of water in a bottle could result in an antimony concentration of 376 ppb. Clearly, only a small

Evaluation of leaching behavior and immobilization of zinc in cement-based solidified products

Directory of Open Access Journals (Sweden)

Krolo Petar

2012-01-01

Full Text Available This study has examined leaching behavior of monolithic stabilized/solidified products contaminated with zinc by performing modified dynamic leaching test. The effectiveness of cement-based stabilization/solidification treatment was evaluated by determining the cumulative release of Zn and diffusion coefficients, De. The experimental results indicated that the cumulative release of Zn decreases as the addition of binder increases. The values of the Zn diffusion coefficients for all samples ranged from 1.210-8 to 1.1610-12 cm2 s-1. The samples with higher amounts of binder had lower De values. The test results showed that cement-based stabilization/solidification treatment was effective in immobilization of electroplating sludge and waste zeolite. A model developed by de Groot and van der Sloot was used to clarify the controlling mechanisms. The controlling leaching mechanism was found to be diffusion for samples with small amounts of waste material, and dissolution for higher waste contents.

Leaching of biocides from building facades: Upscaling of a local two-region leaching model to the city scale

Science.gov (United States)

Coutu, S.; Rota, C.; Rossi, L.; Barry, D. A.

2011-12-01

Facades are protected by paints that contain biocides as protection against degradation. These biocides are leached by rainfall (albeit at low concentrations). At the city scale, however, the surface area of building facades is significant, and leached biocides are a potential environmental risk to receiving waters. A city-scale biocide-leaching model was developed based on two main steps. In the first step, laboratory experiments on a single facade were used to calibrate and validate a 1D, two-region phenomenological model of biocide leaching. The same data set was analyzed independently by another research group who found empirically that biocide leachate breakthrough curves were well represented by a sum of two exponentials. Interestingly, the two-region model was found analytically to reproduce this functional form as a special case. The second step in the method is site-specific, and involves upscaling the validated single facade model to a particular city. In this step, (i) GIS-based estimates of facade heights and areas are deduced using the city's cadastral data, (ii) facade flow is estimated using local meteorological data (rainfall, wind direction) and (iii) paint application rates are modeled as a stochastic process based on manufacturers' recommendations. The methodology was applied to Lausanne, Switzerland, a city of about 200,000 inhabitants. Approximately 30% of the annually applied mass of biocides was estimated to be released to the environment.

Leaching for recovery of copper from municipal solid waste incineration fly ash: influence of ash properties and metal speciation.

Science.gov (United States)

Lassesson, Henric; Fedje, Karin Karlfeldt; Steenari, Britt-Marie

2014-08-01

Recovery of metals occurring in significant amounts in municipal solid waste incineration fly ash, such as copper, could offer several advantages: a decreased amount of potentially mobile metal compounds going to landfill, saving of natural resources and a monetary value. A combination of leaching and solvent extraction may constitute a feasible recovery path for metals from municipal solid waste incineration fly ash. However, it has been shown that the initial dissolution and leaching is a limiting step in such a recovery process. The work described in this article was focused on elucidating physical and chemical differences between two ash samples with the aim of explaining the differences in copper release from these samples in two leaching methods. The results showed that the chemical speciation is an important factor affecting the release of copper. The occurrence of copper as phosphate or silicate will hinder leaching, while sulphate and chloride will facilitate leaching. © The Author(s) 2014.

Characterizing the release of different composition of dissolved organic matter in soil under acid rain leaching using three-dimensional excitation-emission matrix spectroscopy.

Science.gov (United States)

Liu, Li; Song, Cunyi; Yan, Zengguang; Li, Fasheng

2009-09-01

Although excitation-emission matrix spectroscopy (EEMS) has been widely used to characterize dissolved organic matter (DOM), there has no report that EEMS has been used to study the effects of acid rain on DOM and its composition in soil. In this work, we employed three-dimensional EEMS to characterize the compositions of DOM leached by simulated acid rain from red soil. The red soil was subjected to leaching of simulated acid rain of different acidity, and the leached DOM presented five main peaks in its EEMS: peak-A, related to humic acid-like (HA-like) material, at Ex/Em of 310-330/395-420nm; peak-B, related to UV fulvic acid-like (FA-like) material, at Ex/Em of 230-280/400-435nm; peak-C and peak-D, both related to microbial byproduct-like material, at Ex/Em of 250-280/335-355nm and 260-280/290-320nm, respectively; and peak-E, related to simple aromatic proteins, at Ex/Em of 210-240/290-340nm. EEMS analysis results indicated that most DOM could be lost from red soil in the early phase of acid rain leaching. In addition to the effects of the pH of acid rain, the loss of DOM also depended on the properties of its compositions and the solubility of their complexes with aluminum. HA-like and microbial byproduct-like materials could be more easily released from red soil by acid rain at both higher pH (4.5 and 5.6) and lower pH (2.5 and 3) than that at middle pH (3.5). On the contrary, FA-like material lost in a similar manner under the action of different acid rains with pH ranging from 2.5 to 5.6.

Statistical Evaluation and Optimization of Factors Affecting the Leaching Performance of Copper Flotation Waste

Directory of Open Access Journals (Sweden)

Semra Çoruh

2012-01-01

Full Text Available Copper flotation waste is an industrial by-product material produced from the process of manufacturing copper. The main concern with respect to landfilling of copper flotation waste is the release of elements (e.g., salts and heavy metals when in contact with water, that is, leaching. Copper flotation waste generally contains a significant amount of Cu together with trace elements of other toxic metals, such as Zn, Co, and Pb. The release of heavy metals into the environment has resulted in a number of environmental problems. The aim of this study is to investigate the leaching characteristics of copper flotation waste by use of the Box-Behnken experimental design approach. In order to obtain the optimized condition of leachability, a second-order model was examined. The best leaching conditions achieved were as follows: pH = 9, stirring time = 5 min, and temperature = 41.5°C.

Statistical evaluation and optimization of factors affecting the leaching performance of copper flotation waste.

Science.gov (United States)

Coruh, Semra; Elevli, Sermin; Geyikçi, Feza

2012-01-01

Copper flotation waste is an industrial by-product material produced from the process of manufacturing copper. The main concern with respect to landfilling of copper flotation waste is the release of elements (e.g., salts and heavy metals) when in contact with water, that is, leaching. Copper flotation waste generally contains a significant amount of Cu together with trace elements of other toxic metals, such as Zn, Co, and Pb. The release of heavy metals into the environment has resulted in a number of environmental problems. The aim of this study is to investigate the leaching characteristics of copper flotation waste by use of the Box-Behnken experimental design approach. In order to obtain the optimized condition of leachability, a second-order model was examined. The best leaching conditions achieved were as follows: pH = 9, stirring time = 5 min, and temperature = 41.5 °C.

LEACH-A: An Adaptive Method for Improving LEACH Protocol

Directory of Open Access Journals (Sweden)

Jianli ZHAO

2014-01-01

Full Text Available Energy has become one of the most important constraints on wireless sensor networks. Hence, many researchers in this field focus on how to design a routing protocol to prolong the lifetime of the network. The classical hierarchical protocols such as LEACH and LEACH-C have better performance in saving the energy consumption. However, the choosing strategy only based on the largest residue energy or shortest distance will still consume more energy. In this paper an adaptive routing protocol named “LEACH-A” which has an energy threshold E0 is proposed. If there are cluster nodes whose residual energy are greater than E0, the node of largest residual energy is selected to communicated with the base station; When all the cluster nodes energy are less than E0, the node nearest to the base station is select to communication with the base station. Simulations show that our improved protocol LEACH-A performs better than the LEACH and the LEACH-C.

Assessment of metal contaminations leaching out from recycling plastic bottles upon treatments.

Science.gov (United States)

Cheng, Xiaoliang; Shi, Honglan; Adams, Craig D; Ma, Yinfa

2010-08-01

Heavy metal contaminants in environment, especially in drinking water, are always of great concern due to their health impact. Due to the use of heavy metals as catalysts during plastic syntheses, particularly antimony, human exposure to metal release from plastic bottles has been a serious concern in recent years. The aim and scope of this study were to assess metal contaminations leaching out from a series of recycling plastic bottles upon treatments. In this study, leaching concentrations of 16 metal elements were determined in 21 different types of plastic bottles from five commercial brands, which were made of recycling materials ranging from no. 1 to no. 7. Several sets of experiments were conducted to study the factors that could potentially affect the metal elements leaching from plastic bottles, which include cooling with frozen water, heating with boiling water, microwave, incubating with low-pH water, outdoor sunlight irradiation, and in-car storage. Heating and microwave can lead to a noticeable increase of antimony leaching relative to the controls in bottle samples A to G, and some even reached to a higher level than the maximum contamination level (MCL) of the US Environmental Protection Agency (USEPA) regulations. Incubation with low-pH water, outdoor sunlight irradiation, and in-car storage had no significant effect on antimony leaching relative to controls in bottle samples A to G, and the levels of antimony leaching detected were below 6 ppb which is the MCL of USEPA regulations. Cooling had almost no effect on antimony leaching based on our results. For the other interested 15 metal elements (Al, V, Cr, Mn, Co, Ni, Cu, As, Se, Mo, Ag, Cd, Ba, Tl, Pb), no significant leaching was detected or the level was far below the MCL of USEPA regulations in all bottle samples in this study. In addition, washing procedure did contribute to the antimony leaching concentration for polyethylene terephthalate (PET) bottles. The difference of antimony leaching

Comparative leaching of six toxic metals from raw and chemically stabilized MSWI fly ash using citric acid.

Science.gov (United States)

Wang, Huawei; Fan, Xinxiu; Wang, Ya-Nan; Li, Weihua; Sun, Yingjie; Zhan, Meili; Wu, Guizhi

2018-02-15

The leaching behavior of six typical toxic metals (Pb, Zn, Cr, Cd, Cu and Ni) from raw and chemically stabilized (phosphate and chelating agent) municipal solid waste incineration (MSWI) fly ash were investigated using citric acid. Leaching tests indicated that phosphate stabilization can effectively decrease the leaching of Zn, Cd and Cr; whereas chelating agent stabilization shows a strong ability to lower the release of Pb, Cd and Cu, but instead increases the solubility of Zn and Cr at low pH conditions. Sequential extraction results suggested that the leaching of Pb, Zn and Cd in both the stabilized MSWI fly ash samples led to the decrease in Fe/Mn oxide fraction and the increase in exchangeable and carbonate fractions. The leaching of Cr was due to the decrease in exchangeable, carbonate and Fe/Mn oxide fractions in phosphate-stabilized and chelating agent-stabilized MSWI fly ash. The leaching of Cu in both stabilized MSWI fly ash was greatly ascribed to the decrease in Fe/Mn oxide and oxidisable fractions. Moreover, predicted curves by geochemical model indicated that both stabilized MSWI fly ash have the risk of releasing toxic metals under strong acid environment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Comprehensive evaluation on effective leaching of critical metals from spent lithium-ion batteries.

Science.gov (United States)

Gao, Wenfang; Liu, Chenming; Cao, Hongbin; Zheng, Xiaohong; Lin, Xiao; Wang, Haijuan; Zhang, Yi; Sun, Zhi

2018-05-01

Recovery of metals from spent lithium-ion batteries (LIBs) has attracted worldwide attention because of issues from both environmental impacts and resource supply. Leaching, for instance using an acidic solution, is a critical step for effective recovery of metals from spent LIBs. To achieve both high leaching efficiency and selectivity of the targeted metals, improved understanding on the interactive features of the materials and leaching solutions is highly required. However, such understanding is still limited at least caused by the variation on physiochemical properties of different leaching solutions. In this research, a comprehensive investigation and evaluation on the leaching process using acidic solutions to recycle spent LIBs is carried out. Through analyzing two important parameters, i.e. leaching speed and recovery rate of the corresponding metals, the effects of hydrogen ion concentration, acid species and concentration on these two parameters were evaluated. It was found that a leachant with organic acids may leach Co and Li from the cathode scrap and leave Al foil as metallic form with high leaching selectivity, while that with inorganic acids typically leach all metals into the solution. Inconsistency between the leaching selectivity and efficiency during spent LIBs recycling is frequently noticed. In order to achieve an optimal status with both high leaching selectivity and efficiency (especially at high solid-to-liquid ratios), it is important to manipulate the average leaching speed and recovery rate of metals to optimize the leaching conditions. Subsequently, it is found that the leaching speed is significantly dependent on the hydrogen ion concentration and the capability of releasing hydrogen ions of the acidic leachant during leaching. With this research, it is expected to improve understanding on controlling the physiochemical properties of a leaching solution and to potentially design processes for spent LIBs recycling with high industrial

Leaching behaviour of municipal solid waste incineration bottom ash: From granular material to monolithic concrete.

Science.gov (United States)

Sorlini, Sabrina; Collivignarelli, Maria Cristina; Abbà, Alessandro

2017-09-01

The aim of this work was to assess the leaching behaviour of the bottom ash derived from municipal solid waste incineration (MSWI) used in concrete production. In particular, the release of pollutants was evaluated by the application of different leaching tests, both on granular materials and monolithic samples (concrete mixtures cast with bottom ash). The results confirmed that, according to Italian regulations, unwashed bottom ashes present critical issues for the use as alternative aggregates in the construction sector due to the excessive release of pollutants; instead, the leachate from washed bottom ashes was similar to natural aggregates. The concentration of pollutants in the leachate from concrete mixtures was lower than regulation limits for reuse. The crushing process significantly influenced the release of pollutants: this behaviour was due both to the increase in surface area and the release of contaminants from cement. Moreover, the increase in contact time (up to 64 days) involved more heavy metals to be released.

Leaching behavior of heavy metals from municipal solid wastes incineration (MSWI) fly ash used in concrete

International Nuclear Information System (INIS)

Shi Huisheng; Kan Lili

2009-01-01

The characteristics of municipal solid waste incineration (MSWI) fly ash, surface leaching toxicity and successive leaching concentration of heavy metals from MSWI fly ash-cement hardened pastes were studied. And, the relationships between leaching concentrations of heavy metals and leaching time were also discussed. Experimental results showed that immobilization effect of cement on MSWI fly ash is good. Even if MSWI fly ash-cement hardened pastes were damaged, the leaching toxicity is still in a safety range. In early leaching stage, the surface leaching rate is relatively a little high, up to 10 -5 -10 -4 cm d -1 order of magnitude, in the later time of leaching, its rate rapidly declined, down to 10 -7 . Most of leached heavy metals are produced at early ages. The leaching concentration of heavy metals and leaching time has strong positive relationships. In factual utilizing circumstances, heavy metals' leaching from MSWI fly ash-cement hardened pastes is a very slow and gradually diluting process. The leaching toxicity of heavy metals is far lower than that of the National Standard of China, and minimum harmful matters can be contained and released in the environment. Reusing of MSWI fly ash as partial replacement for cement in concrete mixes is potentially feasible.

RMDF leach-field decontamination. Final report

International Nuclear Information System (INIS)

Carroll, J.W.; Marzec, J.M.; Stelle, A.M.

1982-01-01

The objective of the decontamination effort was to place the Radioactive Materials Disposal Facility (RMDF) leach field in a condition suitable for release for unrestricted use. Radioactively contaminated soil was excavated from the leach field to produce a condition of contamination as low as reasonably achievable (ALARA). The contaminated soil was boxed and shipped to an NRC-licensed burial site at Beatty, Nevada, and to the DOE burial site at Hanford, Washington. The soil excavation project successfully reduced the contamination level in the leach field to background levels, except for less than 0.6 mCi of Sr-90 and trace amounts of Cs-137 that are isolated in cracks in the bedrock. The cracks are greater than 10 ft below the surface and have been sealed with a bituminous asphalt mastic. A pathways analysis for radiation exposure to humans from the remaining radionuclides was performed, assuming intensive home gardening, and the results show that the total first year whole body dose equivalent would be about 0.1 mrem/year. This dose equivalent is a projection for the hypothetical ingestion of vegetables grown on the site. Assuming that an average adult consumes 64 kg of green leafy vegetables per year and that the entire yearly supply could be grown on the site, the amount of ingested Sr-90 and Cs-137 is calculated to be 1100 pCi/year and 200 pCi/year. This ingested quantity would produce a total first year whole body dose equivalent of 0.10 mrem, using the accepted soil-to-plant transfer factors of 0.0172 and 0.010 for Sr-90 and Cs-137, respectively. The whole body dose equivalent exposure value of 0.1 mrem/year is far below the tentative limit established by NRC of 5 mrem/year for areas released for unrestricted use

Gamma radiolysis and post-irradiation leaching of ion exchange resins

International Nuclear Information System (INIS)

Traboulsi, A.

2012-01-01

The knowledge of the behavior under irradiation and in presence of water of Ion Exchange Resins (IER) is very necessary to predict their impact on the environment during the storage phase and in a possible deep geological disposal. The IER studied are the MB400 mixed bed resin and its 'pure' anionic and cationic components. The experimental strategy used in this work was based on the use of chemometric tools permitting to estimate the effect of the irradiation atmosphere, the dose rate, the absorbed dose and the leaching temperature. The gaseous and water-soluble radiolysis products were analyzed by gas Mass Spectrometry (MS) and Ion Chromatography (IC). The IER generated principally H 2 g, CO 2 g and amines for which quantities depended of the resin nature and the irradiation conditions. The analysis of solid irradiated resins was investigated by Fourier Transformed Infrared (FTIR) and Nuclear Magnetic Resonance ( 13 C NMR) techniques. The last ones revealed structural modifications of the IER solid matrix in function of the experimental conditions. Their behavior in presence of water was studied during 143 days by characterization of the organic matter released after their post-irradiation leaching. The kinetics showed that all the water-soluble components were releasing at the first contact with water. The Total Organic Carbon (TOC) quantity released depends, according to the resin nature, either on the dose, either on the irradiation atmosphere. The dose rate has no effect on the degradation and the leaching of the MB400 resin, which behaved differently than its pure components. (author) [fr

Different low-molecular-mass organic acids specifically control leaching of arsenic and lead from contaminated soil.

Science.gov (United States)

Ash, Christopher; Tejnecký, Václav; Borůvka, Luboš; Drábek, Ondřej

2016-04-01

Low-molecular-mass organic acids (LMMOA) are of key importance for mobilisation and fate of metals in soil, by functioning as ligands that increase the amount of dissolved metal in solution or by dissociation of metal binding minerals. Column leaching experiments were performed on soil polluted with As and Pb, in order to determine the specificity of LMMOA related release for individual elements, at varying organic acid concentrations. Acetic, citric and oxalic acids were applied in 12h leaching experiments over a concentration range (0.5-25 mM) to soil samples that represent organic and mineral horizons. The leaching of As followed the order: oxalic>citric>acetic acid in both soils. Arsenic leaching was attributed primarily to ligand-enhanced dissolution of mineral oxides followed by As released into solution, as shown by significant correlation between oxalic and citric acids and content of Al and Fe in leaching solutions. Results suggest that subsurface mineral soil layers are more vulnerable to As toxicity. Leaching of Pb from both soils followed the order: citric>oxalic>acetic acid. Mineral soil samples were shown to be more susceptible to leaching of Pb than samples characterised by a high content of organic matter. The leaching efficiency of citric acid was attributed to formation of stable complexes with Pb ions, which other acids are not capable of. Results obtained in the study are evidence that the extent of As and Pb leaching in contaminated surface and subsurface soil depends significantly on the types of carboxylic acid involved. The implications of the type of acid and the specific element that can be mobilised become increasingly significant where LMMOA concentrations are highest, such as in rhizosphere soil. Copyright © 2016 Elsevier B.V. All rights reserved.

Pesticide leaching through sandy and loamy fields – Long-term lessons learnt from the Danish Pesticide Leaching Assessment Programme

International Nuclear Information System (INIS)

Rosenbom, Annette E.; Olsen, Preben; Plauborg, Finn; Grant, Ruth; Juhler, René K.; Brüsch, Walter; Kjær, Jeanne

2015-01-01

The European Union authorization procedure for pesticides includes an assessment of the leaching risk posed by pesticides and their degradation products (DP) with the aim of avoiding any unacceptable influence on groundwater. Twelve-year's results of the Danish Pesticide Leaching Assessment Programme reveal shortcomings to the procedure by having assessed leaching into groundwater of 43 pesticides applied in accordance with current regulations on agricultural fields, and 47 of their DP. Three types of leaching scenario were not fully captured by the procedure: long-term leaching of DP of pesticides applied on potato crops cultivated in sand, leaching of strongly sorbing pesticides after autumn application on loam, and leaching of various pesticides and their DP following early summer application on loam. Rapid preferential transport that bypasses the retardation of the plow layer primarily in autumn, but also during early summer, seems to dominate leaching in a number of those scenarios. - Highlights: • Field-results reveal shortcomings in the EU authorization procedure for pesticides. • The plough layer can be bypassed via preferential transport in e.g. wormholes. • Pesticides properties are decisive for leaching pattern on the sandy fields. • The hydrogeological settings control the leaching patterns on the loamy fields. • Pesticide detection frequency seems to be independent of the month of the year. - Long-term lessons learnt from the Danish Pesticide Leaching Assessment Programme reveals shortcomings in the European Union authorization procedure for pesticides

Fertilizer source effects on phosphate and nitrate leaching through simulated golf greens

International Nuclear Information System (INIS)

Shuman, L.M.

2003-01-01

In general, more P than N leached from both field and greenhouse lysimeters. - Phosphorus and nitrogen leached from high-porosity golf greens can adversely affect surface water and groundwater quality. Greenhouse and field lysimeter experiments were carried out to determine the effects of eight fertilizer sources on P and N leaching from simulated golf greens. Phosphorus appeared in the leachate later than nitrate-N, and the highest concentrations were for the soluble 20-20-20 and the 16-25-12 starter fertilizers. The other six sources resulted in lower P concentrations. The soluble 20-20-20 and the 16-25-12 sources each resulted in 43% of the added P eluting in the leachate, whereas the others varied from 15 to 25%. For nitrate-N the lowest cumulative mass was for the controlled-release 13-13-13 and sulfur-coated urea. A higher percentage of applied P than applied N leached from both field and greenhouse lysimeters. However, the amounts of P leached for the field lysimeters were lower than for the greenhouse columns

Toxicity assessment and geochemical model of chromium leaching from AOD slag.

Science.gov (United States)

Liu, Bao; Li, Junguo; Zeng, Yanan; Wang, Ziming

2016-02-01

AOD (Argon Oxygen Decarburization) slag is a by-product of the stainless steel refining process. The leaching toxicity of chromium from AOD slag cannot be ignored in the recycling process of the AOD slag. To assess the leaching toxicity of the AOD slag, batch leaching tests have been performed. PHREEQC simulations combined with FactSage were carried out based on the detailed mineralogical analysis and petrophysical data. Moreover, Pourbaix diagram of the Cr-H2O system was protracted by HSC 5.0 software to explore the chromium speciation in leachates. It was found that AOD slag leachate is an alkaline and reductive solution. The Pourbaix diagram of the Cr-H2O system indicated that trivalent chromium, such as Cr(OH)4(-), is the major chromium species in the experimental Eh-pH region considered. However, toxic hexavalent chromium was released with maximum concentrations of 30 µg L(-1) and 18 µg L(-1) at L/S 10 and 100, respectively, during the earlier leaching stage. It concluded that the AOD slag possessed a certain leaching toxicity. After 10 d of leaching, trivalent chromium was the dominant species in the leachates, which corresponded to the results of PHREEQC simulation. Leaching toxicity of AOD slag is based on the chromium speciation and its transformation. Great attention should be focused on such factors as aging, crystal form of chromium-enriched minerals, and electrochemical characteristics of the leachates. Copyright © 2015 Elsevier Ltd. All rights reserved.

Leaching of concrete : the leaching process : extrapolation of deterioration : effect on the structural stability

OpenAIRE

Fagerlund, Göran

2000-01-01

The leaching process when water attacks concrete, and the effect of leaching on the strength and durability of a concrete structure, is analysed theoretically. Technique for prediction of the future leaching and structural stability is outlined. The analysis is to a certain extent supported by data from literature. The leaching process is divided in five different types: 1: Pure surface leaching 2: Surface leaching involving erosion 3: Homogeneous leaching over the entire structure 4...

Leaching from denture base materials in vitro

Energy Technology Data Exchange (ETDEWEB)

Lygre, H.; Solheim, E.; Gjerdet, N.R. [School of Medicine, Univ. of Bergen (Norway)

1995-04-01

Specimens made from denture base materials were leached in Ringer Solution and in ethanol. The specimens comprised a heat-cured product processed in two different ways and two cold-cured materials. The organic compounds leaching from the specimens to the solutions were separated, identified, and quantified by a combined gas-chromatography and gas-chromatography/mass-spectrometry technique. Additives and degradation products, possibly made by free radical reactions, were released from the denture base materials. In Ringer solution only phthalates could be quantified. In ethanol solvent, biphenyl, dibutyl phthalate, dicyclohexyl phthalate, phenyl benzoate, and phenyl salicylate were quantified. In addition, copper was found in the ethanol solvent from one of the denture base materials. The amount of leachable organic compounds varies among different materials. Processing temperature influences the initial amount of leachable compounds. 36 refs., 7 figs., 1 tab.

Effect of uniaxially pressing ordinary Portland cement pastes containing metal hydroxides on porosity, density, and leaching

International Nuclear Information System (INIS)

Cheeseman, C.R.; Asavapisit, S.; Knight, J.

1998-01-01

Synthetic metal hydroxide wastes containing Zn and Pb have been mixed with partially hydrated cement and uniaxially pressed. The effect on porosity, pore size distribution, and bulk and skeletal densities has been characterized using mercury intrusion porosimetry. Ca(OH) 2 formation has been determined using differential thermal analysis and metal leaching has been assessed in a series of static leach tests completed on monolithic samples. Pressed solidified materials have increased density, reduced porosity, and reduced Ca(OH) 2 . They exhibit increased resistance to acid attack in terms of sample weight loss during leaching due to reduced release of alkalis. Leaching of Zn and Pb is primarily determined by pH. A peak observed in Zn leaching from pressed samples is due to the effect of changing leachate pH on the dominant Zn species present

Renewal of corrosion progress after long-term leaching

International Nuclear Information System (INIS)

Muller, I.

1997-01-01

Over the past 18 years a large inventory of glasses which have undergone leach testing has been built up at the Vitreous State Laboratory of The Catholic University of America. These glasses include a very wide range of compositions, most from actual mixed wastes and many natural analogs. A variety in the test protocol have been used, including PCT, ANSI, TCLP, IAEA, Flow, Soxhlet, MCC1, MCC3, and DIN. Many of these tests have been conducted for over a decade and are still ongoing. The progress of the tests is monitored by periodic sampling with fluid replacement. Twenty different leachants (including groundwaters, humic acid and pH buffers) have been employed. Occasionally, some of the glass is removed from the leaching vessels to observe the altered layers forming on the glass and to identify reaction products. Slight variations in the composition of the glass, subjected to PCT leaching, exhibit widely differing leaching behaviors. The evolution of leachate composition over time often shows a basically stable leach rate followed by a dramatic increase, with times of onset varying considerably, primarily as a function of glass composition. The same rapid rise in leachate has also been observe for a given glass composition studied at different S/V ratio. The study of such non-linearity in glass leaching is the subject of this review. (author)

Speciation of arsenic and selenium during leaching of fly ash

NARCIS (Netherlands)

Hoek, E.E. van der

1995-01-01

The leaching (release) of large amounts of oxyanions, such as those of arsenic and selenium, is an major environmental problem when it comes to the disposal or use of coal fly ash. To predict environmentally safe conditions for the disposal or use of fly ash in, for example,

Comparison of leaching tests and study of leaching mechanisms

International Nuclear Information System (INIS)

Amarantos, S.G.; Papadokostaki, K.G.; Petropoulos, J.H.

1985-10-01

The present work is concerned first with the study of certain aspects of the leaching kinetics of Cs + and Sr ++ embedded in cement, as Cs 2 SO 4 and SrSO 4 , and in particular: (a) the comparative evaluation of leaching in (i) stagnant, (ii) stirred and (iii) continuously flowing (modified Soxhlet) water, (b) the effect of atmospheric CO 2 on elution, (c) the effect of temperature changes during leaching. Secondly, model kinetic studies were carried out using cellulose acetate incorporating SrSO 4 , CaSO 4 or NaCl. The main results obtained were: (1) Cs leaching rates were not significantly affected by the leaching method or by the presence of atmospheric CO 2 . The embedded Cs exists in relatively easily leachable and less rapidly leachable (most probably located within the gel regions) forms. (2) Elution of Sr is retarded by stagnant and infrequently renewed leachant (method (i)) and by the presence of atmospheric CO 2 ; leaching method (iii), which tends to minimize both of these effects, gave the highest elution rates. (3) The observed elution kinetics in the case of cellulose acetate-CaSO 4 or SrSO 4 conform to the Higuchi model, but a more elaborate theory is needed for the cellulose acetate-NaCl system. (author)

Carbonate heap leach of uranium-contaminated soils

International Nuclear Information System (INIS)

Turney, W.R.; Mason, C.F.V.; Longmire, P.

1994-01-01

A new approach to removal of uranium from soils based on existing heap leach mining technologies proved highly effective for remediation of soils from the Fernald Environmental Management Project (FEMP) near Cincinnati, Ohio. In laboratory tests, remediation of uranium-contaminated soils by heap leaching with carbonate salt solutions was demonstrated in column experiments. An understanding of the chemical processes that occur during carbonate leach of uranium from soils may lead to enhancement of uranium removal. Carbonate leaching requires the use of an integrated and closed circuit process, wherein the leach solutions are recycled and the reagents are reused, resulting in a minimum secondary waste stream. Carbonate salt leach solution has two important roles. Primarily, the formation of highly soluble anionic carbonate uranyl species, including uranyl dicarbonate (UO 2 CO 32 = ) and uranyl tricarbonate (UO 2 CO 33 4- ), allows for high concentration of uranium in a leachate solution. Secondly, carbonate salts are nearly selective for dissolution of uranium from uranium contaminated soils. Other advantages of the carbonate leaching process include (1) the high solubility, (2) the selectivity, (3) the purity of the solution produced, (4) the relative ease with which a uranium product can be precipitated directly from the leachate solution, and (5) the relatively non-corrosive and safe handling characteristics of carbonate solutions. Experiments conducted in the laboratory have demonstrated the effectiveness of carbonate leach. Efficiencies of uranium removal from the soils have been as high as 92 percent. Higher molar strength carbonate solutions (∼0.5M) proved more effective than lower molar strength solutions (∼ 0.1M). Uranium removal is also a function of lixiviant loading rate. Furthermore, agglomeration of the soils with cement resulted in less effective uranium removal

Accelerated Leach Test(s) Program. Annual report

International Nuclear Information System (INIS)

Dougherty, D.R.; Fuhrmann, M.; Colombo, P.

1985-09-01

This report summarizes the work performed for the Accelerated Leach Test(s) Program at Brookhaven National Laboratory in Fiscal Year 1985 under the sponsorship of the US Department of Energy's Low-Level Waste Management Program (LLWMP). Programmatic activities were concentrated in three areas, as listed and described in the following paragraphs. (1) A literature survey of reported leaching mechanisms, available mathematical models and factors that affect leaching of LLW forms has been compiled. Mechanisms which have been identified include diffusion, dissolution, ion exchange, corrosion and surface effects. Available mathematical models are based on diffusion as the predominant mechanism. Although numerous factors that affect leaching have been identified, they have been conveniently categorized as factors related to the entire leaching system, to the leachant or to the waste form. A report has been published on the results of this literature survey. (2) A computerized data base of LLW leaching data and mathematical models is being developed. The data are being used for model evaluation by curve fitting and statistical analysis according to standard procedures of statistical quality control. (3) Long-term tests on portland cement, bitumen and vinyl ester-styrene (VES) polymer waste forms are underway which are designed to identify and evaluate factors that accelerate leaching without changing the mechanisms. Results on the effect of temperature on leachability indicate that the leach rates of cement and VES waste forms increase with increasing temperature, whereas, the leach rate of bitumen is little affected

Leaching Test Relationships, Laboratory-to-Field Comparisons and Recommendations for Leaching Evaluation using the Leaching Environmental Assessment Framework (LEAF)

Science.gov (United States)

This report presents examples of the relationships between the results of laboratory leaching tests, as defined by the Leaching Environmental Assessment Framework (LEAF) or analogous international test methods, and leaching of constituents from a broad range of materials under di...

Selection of a leaching test method for waste product conformity verification

Energy Technology Data Exchange (ETDEWEB)

Lopes, Isabel Sofia R.F.S.; Tello, Clédola Cássia O.; Haucz, Maria Judite A., E-mail: isabel.lopes@cdtn.br, E-mail: tellocc@cdtn.br, E-mail: hauczmj@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

2017-07-01

A study on the waste acceptance criteria (WAC) for disposal in a near-surface repository is being implemented by CDTN / CNEN. The acceptance criteria are used to ensure the safety in the repository facility in order to protect the employees, the public and the environment from some possible harmful and dangerous effects of the ionizing radiation. A near-surface repository is intended to be built for disposal of the Brazilian low- and intermediate level wastes. Leaching was the criterion chosen to be studied in this research. It is extremely important for the safety assessment to evaluate the waste form in relation to the radionuclides release, to predict the repository performance in the long term. As in the Brazilian WAC the test to measure the radionuclides leaching is not defined yet, two leaching tests were selected to be performed, the ISO 6961 and the ASTM C1308. The results will be analyzed in order to verify their similarities and differences and also their advantages and disadvantages. Inactive tracers cesium and lead were used as tracers to follow the leaching in both procedures. (author)

Selection of a leaching test method for waste product conformity verification

International Nuclear Information System (INIS)

Lopes, Isabel Sofia R.F.S.; Tello, Clédola Cássia O.; Haucz, Maria Judite A.

2017-01-01

A study on the waste acceptance criteria (WAC) for disposal in a near-surface repository is being implemented by CDTN / CNEN. The acceptance criteria are used to ensure the safety in the repository facility in order to protect the employees, the public and the environment from some possible harmful and dangerous effects of the ionizing radiation. A near-surface repository is intended to be built for disposal of the Brazilian low- and intermediate level wastes. Leaching was the criterion chosen to be studied in this research. It is extremely important for the safety assessment to evaluate the waste form in relation to the radionuclides release, to predict the repository performance in the long term. As in the Brazilian WAC the test to measure the radionuclides leaching is not defined yet, two leaching tests were selected to be performed, the ISO 6961 and the ASTM C1308. The results will be analyzed in order to verify their similarities and differences and also their advantages and disadvantages. Inactive tracers cesium and lead were used as tracers to follow the leaching in both procedures. (author)

Carboxymethyl starch/montmorillonite composite microparticles: Properties and controlled release of isoproturon.

Science.gov (United States)

Wilpiszewska, Katarzyna; Spychaj, Tadeusz; Paździoch, Waldemar

2016-01-20

Preparation of novel high substituted carboxymethyl starch-based microparticles containing sodium montmorillonite (MMT) by crosslinking with Al(3+) was described. For preparing nanocomposite granules carboxymethyl starch (CMS) from native potato starch as well as CMS from amylopectin has been used. The hydrophilic CMS/MMT composite systems were used for herbicide, i.e. isoproturon encapsulation (ca. 75% encapsulation efficiency). The herbicide release rate from CMS/MMT composites in water was significantly reduced when compared to commercial isoproturon: 95% released after ca. 700 h and ca. 24h, respectively. Leaching in soil from composite systems was relatively slower than release in water. After a series of eight irrigations leached about 10% of isoproturon loaded. The CMS/MMT carriers could reduce the potential leaching of herbicide and beneficially reduce pollution of the environment. Copyright © 2015 Elsevier Ltd. All rights reserved.

Modeling long-term leaching experiments of full scale cemented wastes: effect of solution composition on diffusion

International Nuclear Information System (INIS)

Borkel, C.; Montoya, V.; Kienzler, B.

2015-01-01

The code PHREECQ V3.1 has been used to simulate leaching experiments performed with cemented simulated waste products in tap water for more than 30 years. In this work the main focus is related with the leaching of Cs explained by diffusion processes. A simplifying model using the code PHREECQ V3.1 was used to investigate the influence of different parameters on the release of Cs from the cement solid to the leaching solution. The model setup bases on four main assumptions: a) the solid as well as the distribution of Cs is homogeneous and of isotropic texture, b) there is no preferential direction regarding cement degradation or water intrusion into the solid, c) the pore space is entirely connected and d) Cs adsorption to the cement or container is negligible. In the modeling the constraint of charge balance was stressed. Effective diffusion coefficients (D e ) were obtained analytically and from modeling the diffusive release of Cs from cemented waste simulates. The obtained values D e for Cs leaching are in perfect agreement with the values published in literature. Contradictory results to diffusive release were obtained from XRD analysis of the solids, suggesting that water may not have penetrated the cement monoliths entirely, but only to some centimeters depth. XRD analysis have been done to determine the solid phases present in cement and are used to help outlining strength and weaknesses of the different models

Single-pass continuous-flow leach test of PNL 76-68 glass: some selected Bead Leach I results

International Nuclear Information System (INIS)

Coles, D.G.

1981-01-01

A single-pass continuous-flow leach test of PNL 76-68 glass beads (7 mm dia) was concluded after 420 days of uninterrupted operation. Variables included in the experimental matrix were flow-rate, leachant composition, and temperature. Analysis was conducted on all leachate samples for 237 Np and 239 Pu as well as a number of nonradioactive elements. Results indicated that flow-rate and leachant systematically affected the leach rate, but only slightly. Temperature effects were significant. Plutonium leach rate was lower at higher temperature suggesting that Pu sorption onto the beads was enhanced at the higher temperature. The range of leach rates for all analyzed elements (except Pu), at both temperature, at all three flow rates, and with all three leachant compositions varied only three orders of magnitude. The range of variables used in this experiment covered those expected in many proposed repository environments. The preliminary interpretation of the results also indicated that matrix dissolution may be the dominant leaching mechanism, at least for Np in bicarbonate leachant. Regardless of the leaching mechanism the importance of this study is that it bounds the effects of repository environments when the ground water is oxidizing and when it doesn't reach the waste form until the waste has cooled to ambient rock temperature

Assessment of weathering and leaching rates of Thule hot particles

Energy Technology Data Exchange (ETDEWEB)

Roos, P. (Technical Univ. of Denmark, Risoe National Laboratory for Sustainable Energy, Roskilde (Denmark)); Outola, I. (STUK-Radiation and Nuclear Safety Authority (Finland)); Nygren, U.; Ramebaeck, H. (FOI CBRN Defence and Security (Sweden)); Sidhu, R. (Institute of Energy Technology, Environmental Monitoring Section, Health and Safety Dept. (Norway))

2010-03-15

Within the current project a methodology for separating actinide particles originating from the Thule 1968 accident has been developed. Particles were completely isolated in water using visual and radiometric methods. The particles were attached electrostatic to a plastic support and could easily be moved to any container for leaching studies or other type of studies. Leaching and dissolution studies performed within the project indicate that some particles are relatively easily destroyed or leached while others are more refractory. The results shows that even though the oxide particles are hard to completely dissolve they release material even when exposed to weak solvents like water and salt solutions. Exposures to lung simulant fluids show relatively slow dissolution rates comparable to what is found using only water. Sequential extraction of particles shows that variation between particles is very large; some dissolve easily while some does not. Of radiological importance is the disruption of particles when exposed to dissolution. (author)

Assessment of weathering and leaching rates of Thule hot particles

International Nuclear Information System (INIS)

Roos, P.; Outola, I.; Nygren, U.; Ramebaeck, H.; Sidhu, R.

2010-03-01

Within the current project a methodology for separating actinide particles originating from the Thule 1968 accident has been developed. Particles were completely isolated in water using visual and radiometric methods. The particles were attached electrostatic to a plastic support and could easily be moved to any container for leaching studies or other type of studies. Leaching and dissolution studies performed within the project indicate that some particles are relatively easily destroyed or leached while others are more refractory. The results shows that even though the oxide particles are hard to completely dissolve they release material even when exposed to weak solvents like water and salt solutions. Exposures to lung simulant fluids show relatively slow dissolution rates comparable to what is found using only water. Sequential extraction of particles shows that variation between particles is very large; some dissolve easily while some does not. Of radiological importance is the disruption of particles when exposed to dissolution. (author)

Leaching of the simulated borosilicate waste glasses and spent nuclear fuel under a repository condition

International Nuclear Information System (INIS)

Kim, Seung Soo; Chun, Kwan Sik; Kang, Chul Hyung; Suh, Hang Suk

2002-12-01

Leaching behaviors of simulated waste glass and spent fuel, contacted on bentonite blocks, in synthetic granitic groundwater were investigated in this study. The leach rate of boron from borosilicate waste glass between the compacted bentonite blocks reached about 0.03 gm-2day-1 at 1500 days, like as that of molybdenum. However, the concentration of uranium in leachate pass through bentonite blocks was less than their detection limits of 2 μg/L and whose yellow amorphous compound was found on the surface of glass contacted with the bentonite blocks. The leaching mechanism of waste glasses differed with their composition. The release rate of cesium from PWR spent fuel in the simulated granitic water without bentonite was leas than $1.0x10 -5 fraction/day after 300 days. The retardation factor of cesium by a 10 -mm thickness of bentonite block was more than 100 for 4-years leaching time. The cumulative release fraction of uranium for 954 days was 0.016% (1.7x10 -7 fraction/day) in granitic water without bentonite. The gap inventory of cesium for spent fuel G23-J11 was 0.15∼0.2%. However, the release of cesium from C15-I08 was 0.9% until 60 days and has being continued after that. Gap inventories of strontium and iodine in G23-J11 were 0.033% and below 0.2%, respectively. The sum of fraction of cesium in gap and grain boundary of G23-J11 was suggested below 3% and less

The effects of temperature on the leaching behavior of cement waste forms: The cement/sodium sulfate system

International Nuclear Information System (INIS)

Fuhrmann, M.; Pietrzak, R.; Heiser, J.; Franz, E.M.; Colombo, P.

1989-10-01

The leaching mechanisms of simulated low-level radioactive waste forms are being determined as support for development of an accelerated leach test. Two approaches are being used: (1) comparisons of leaching data with results of a model that describes diffusion from a finite cylinder, and (2) observation of the leaching process at temperatures between 20 degree C and 65 degree C. To provide results that can be used for modeling, leaching at elevated temperatures must change neither the leaching mechanism nor the structural controls of leaching such as the porosity. Releases of 137 Cs, 85 Sr, calcium, sodium and potassium from portland cement containing sodium sulfate, as a simulated evaporator sludge, have been determined under a variety of experimental conditions. Data from the leach tests were compared to model results for diffusion from the finite cylinder. While most leaching appears to be diffusion controlled, notable exceptions occur. For all samples activation energies ranging between 6 and 11 Kcal/mole have been calculated from the relationship of the effective diffusion coefficient to increasing temperature, close to the expected value of 5 Kcal/mole for diffusion. 11 refs., 4 figs., 2 tabs

Leaching properties of solidified TRU waste forms

International Nuclear Information System (INIS)

Colombo, P.; Neilson, R.M. Jr.

1979-01-01

Safety analysis of waste forms requires an estimate of the ability of these forms to retain activity in the disposal environment. This program of leaching tests will determine the leaching properties of TRU contaminated incinerator ash waste forms using hydraulic cement, urea--formaldehyde, bitumen, and vinyl ester--styrene as solidification agents. Three types of leaching tests will be conducted, including both static and flow rate. Five generic groundwaters will be used. Equipment and procedures are described. Experiments have been conducted to determine plate out of 239 Pu, counter efficiency, and stability of counting samples

Leaching behavior of U, Mn, Sr, and Pb from different particle-size fractions of uranium mill tailings.

Science.gov (United States)

Liu, Bo; Peng, Tongjiang; Sun, Hongjuan

2017-06-01

Pollution by the release of heavy metals from tailings constitutes a potential threat to the environment. To characterize the processes governing the release of Mn, Sr, Pb, and U from the uranium mill tailings, a dynamic leaching test was applied for different size of uranium mill tailings samples. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS) were performed to determine the content of Mn, Sr, Pb, and U in the leachates. The release of mobile Mn, Sr, Pb, and U fraction was slow, being faster in the initial stage and then attained a near steady-state condition. The experimental results demonstrate that the release of Mn, Sr, Pb, and U from uranium mill tailings with different size fractions is controlled by a variety of mechanisms. Surface wash-off is the release mechanism for Mn. The main release mechanism of Sr and Pb is the dissolution in the initial leaching stage. For U, a mixed process of wash-off and diffusion is the controlling mechanism.

To accelerate technology of in situ leaching and heap leaching for mining mineral resources of China

International Nuclear Information System (INIS)

Luo Mei

1999-01-01

Recently, in situ leaching and heap leaching are the most advanced technology for mining low-grade mineral resources in the world. The author briefly expounds the basic concept and advantages of in situ leaching and heap leaching and deals with the main research content of the hydrometallurgical technology of in situ leaching and heap leaching, its development and present application at home and abroad. Having expounded the gap existing between China's technology of in situ leaching and heap leaching and the foreign technology, the author forecasts the prospects of accelerating the mining of China's mineral resources by using the technology of in situ leaching and heap leaching

Uranium in situ leach mining in the United States. Information circular

International Nuclear Information System (INIS)

Larson, W.C.

1978-01-01

This report discusses uranium in situ leach mining in the United States; the purpose of which is to acquaint the reader with an overview of this emerging mining technology. This report is not a technical discussion of the subject matter, but rather should be used as a reference source for information on in situ leaching. An in situ leaching bibliography is included as well as engineering data tables for almost all of the active pilot-scale and commercial uranium in situ leaching operators. These tables represent a first attempt at consolidating operational data in one source, on a regional scale. Additional information is given which discusses the current Bureau of Mines uranium in situ leaching research program. Also included is a listing of various State and Federal permitting agencies, and a summary of the current uranium in situ leaching operators. Finally, a glossary of terms has been added, listing some of the more common terms used in uranium in situ leach mining

In-situ uranium leaching

International Nuclear Information System (INIS)

Dotson, B.J.

1986-01-01

This invention provides a method for improving the recovery of mineral values from ore bodies subjected to in-situ leaching by controlling the flow behaviour of the leaching solution. In particular, the invention relates to an in-situ leaching operation employing a foam for mobility control of the leaching solution. A foam bank is either introduced into the ore bed or developed in-situ in the ore bed. The foam then becomes a diverting agent forcing the leaching fluid through the previously non-contacted regions of the deposit

Study on Leaching of Hexavalent Chromium from Hardened Concretes Using Tank Leaching Test

OpenAIRE

Takahashi, Shigeru; Sakai, Etsuo; Sugiyama, Takafumi

2007-01-01

Tank leaching tests were carried out to investigate the behavior of leaching trace elements from monolith samples. This study consists of two series, and the trace element used was hexavalent chromium. In Series I, the influence of the leachant/surface area of the specimen (L/S ratio) on the leaching amount was investigated. The leaching amount was found to increase with the amount of worked water. This shows that any L/S ratio can be selected in the tank leaching test. In Series II, th...

Laboratory study on leaching of a sandstone-type uranium deposit for acid in-situ leaching

International Nuclear Information System (INIS)

Wen Zhenqian; Yao Yixuan; Zheng Jianping; Jiang Yan; Cui Xin; Xing Yongguo; Hao Jinting; Tang Huazhang

2013-01-01

Ore samples were took from in-situ leaching experiment boreholes in a sandstone-type uranium deposit. Technological mineralogy study, agitating leaching and column leaching experiments were carried. The results show that the content of minerals consuming acid and deoxidized minerals is low. When sulfuric acid concentration was 1O g/L, initial uranium content was 0.0224%, and liquid-to-solid ratio was l.91, leaching rate of column leaching experiments is 89.19%, acid consumption is 8.2 kg/t ore, acid consumption is 41.88 t/tU. Acid leaching, technology is recommend for field in-situ leaching experiment, sulfuric acid concentration in confecting solution is 10 g/L, and oxidizing agent is needless during leaching process. (authors)

Leaching TC-99 from DWPF glass in simulated geologic repository groundwaters

International Nuclear Information System (INIS)

Bibler, N.E.; Jurgensen, A.R.

1986-01-01

The purpose was to determine if DWPF glass in geologic groundwaters would immobilize Tc-99 as well as it does other elements. A previous study (using a borosilicate glass of a very different composition from DWPF glass) indicated that Tc-99 leached rapidly from the glass suggesting that glass may not be a good matrix for immobilizing Tc-99. It was suggested that the Tc-99 had migrated to vesicles in the glass while the glass was still molten. To determine if borosilicate glass was a good immobilizing matrix for Tc-99, this study was performed using DWPF glass. The leaching of Tc-99 was compared to other elements in the glass. It was shown that rapid leaching will not occur with SRP glass. The leach rate for Tc-99 was nearly identical to that for B, a matrix element in the glass. Another objective was to compare the release of Tc-99 under oxidizing and reducing conditions with other elements in the glass. In the tests described here, even though the glass was dissolving more under reducing conditions as a result of abnormally high pH values, less Tc-99 appeared in solution

Mechanical properties and leaching modeling of activated incinerator bottom ash in Portland cement blends.

Science.gov (United States)

Onori, Roberta; Polettini, Alessandra; Pomi, Raffaella

2011-02-01

In the present study the evolution of mechanical strength and the leaching behavior of major and trace elements from activated incinerator bottom ash/Portland cement mixtures were investigated. Chemical and mechanical activation were applied with the purpose of improving the reactivity of bottom ash in cement blends. Chemical activation made use of NaOH, KOH, CaCl(2) or CaSO(4), which were selected for the experimental campaign on the basis of the results from previous studies. The results indicated that CaCl(2) exhibited by far the best effects on the evolution of the hydration process in the mixtures; a positive effect on mechanical strength was also observed when CaSO(4) was used as the activator, while the gain in strength produced by KOH and NaOH was irrelevant. Geochemical modeling of the leaching solutions provided information on the mineral phases responsible for the release of major elements from the hardened materials and also indicated the important role played by surface sorption onto amorphous Fe and Al minerals in dictating the leaching of Pb. The leaching of the other trace metal cations investigated (Cu, Ni and Zn) could not be explained by any pure mineral included in the thermodynamic database used, suggesting they were present in the materials in the form of complex minerals or phase assemblages for which no consistent thermodynamic data are presently available in the literature. Copyright © 2010 Elsevier Ltd. All rights reserved.

Leaching studies of heavy concrete material for nuclear fuel waste immobilization containers

International Nuclear Information System (INIS)

Onofrei, M.; Raine, D.; Brown, L.; Hooton, R.D.

1989-08-01

The leaching behaviour of a high-density concrete was studied as part of a program to evaluate its potential use as a container material for nuclear fuel waste under conditions of deep geologic disposal. Samples of concrete material were leached in deionized distilled water, Standard Canadian Shield Saline Solution (SCSSS), SCSSS plus 20% Na-bentonite, and SCSSS plus granite and 20% Na-bentonite under static conditions at 100 degrees celsius for periods up to 365 days. The results of these leaching experiments suggest that the stability of concrete depends on the possible internal structural changes due to hydration reactions of unhydrated components, leading to the formation of C-S-H gel plus portlandite (Ca(OH) 2 ). The factors controlling the concrete leaching process were the composition of the leachant and the concentration of elements in solution capable of forming precipitates on the concrete surface, e.g., silicon, Mg 2+ and Ca 2+ . The main effect observed during leaching was an increase in groundwater pH (from 7 to 9). However, the addition of Na-bentonite suppressed the normal tendency of the pH of the groundwater in contact with concrete to rise rapidly. It was shown that the solution concentration of elements released from the concrete, particularly potassium, increased in the presence of Na-bentonite

Heap leaching for uranium

International Nuclear Information System (INIS)

1988-01-01

Denison Mines Ltd. is using two bacterial leaching processes to combat the high cost of extracting uranium from low grade ore in thin reefs. Both processes use thiobacillus ferro-oxidans, a bacterium that employs the oxidation of ferrous iron and sulphur as its source of energy for growth. The first method is flood leaching, in which ore is subjected to successive flood, drain and rest cycles. The second, trickle leaching, uses sprinklers to douse the broken muck continuously with leaching solution. In areas where grades are too low to justify the expense of hauling the ore to the surface, the company is using this biological process underground to recover uranium. In 1987 Denison recovered 840 000 lb of uranium through bacterial heap leaching. It plans to have biological in-place leaching contribute 25% of the total uranium production by 1990. (fig.)

Data report on leach tests of Pu-doped UO2 in PBB1 brine: Salt Repository Project

International Nuclear Information System (INIS)

Gray, W.J.

1987-10-01

This report provides results from a series of leach tests conducted using nonirradiated uranium dioxide (UO 2 ) doped with plutonium (Pu) to simulate the alpha activity of spent fuel specimens used in recent spent fuel leach tests. The purpose was to determine whether alpha radiation from the spent fuel could be responsible for uranium release values in spent fuel leach tests in salt brine that were at least 100 times greater than from similar tests with nonirradiated UO 2 pellets. The data in this data report are preliminary; they have been neither analyzed nor evaluated. 2 refs., 2 figs., 8 tabs

Mechanisms of Vanadium Recovery from Stone Coal by Novel BaCO3/CaO Composite Additive Roasting and Acid Leaching Technology

Directory of Open Access Journals (Sweden)

Zhenlei Cai

2016-03-01

Full Text Available In this report, the vanadium recovery mechanisms by novel BaCO3/CaO composite additive roasting and acid leaching technology, including the phase transformations and the vanadium leaching kinetics, were studied. The purpose of this manuscript is to realize and improve the vanadium recovery from stone coal using BaCO3/CaO as the composite additive. The results indicated that during the composite additive BaCO3/CaO roasting process, the monoclinic crystalline structure of muscovite (K(Al,V2[Si3AlO10](OH2 was converted into the hexagonal crystalline structure of BaSi4O9 and the tetragonal crystalline structure of Gehlenite (Ca2Al2SiO7, which could, therefore, facilitate the release and extraction of vanadium. Vanadium in leaching residue was probably in the form of vanadate or pyrovanadate of barium and calcium, which were hardly extracted during the sulfuric acid leaching process. The vanadium leaching kinetic analysis indicated that the leaching process was controlled by the diffusion through a product layer. The apparent activation energy could be achieved as 46.51 kJ/mol. The reaction order with respect to the sulfuric acid concentration was 1.1059. The kinetic model of vanadium recovery from stone coal using novel composite additive BaCO3/CaO could be finally established.

Microbial ecology of Rum Jungle, III. Leaching behaviour of sulphidic waste material under controlled conditions

International Nuclear Information System (INIS)

Babij, T.; Goodman, A.; Khalid, A.M.; Ralph, B.J.

1981-12-01

The discharge, into river systems, of acid and heavy metals generated by leaching of sulphidic waste materials at the abandoned opencut uranium mine at Rum Jungle, Northern Territory, is causing continuing pollution of the surrounding environment. The maximum effects of acid and microorganisms on samples from the overburden dump material, under defined and controlled environmental conditions, were assessed using reactor systems. These samples came from the overburden dump resulting from the mining of White's orebody. Similarly, the stability of tailings material under conditions of flooding and increasing acidity was determined. At ph 2.5, metals in White's dump material were solubilised by acid attack only, whereas at pH 3.5, bacterial activity (principally that of Thiobacillus ferrooxidans) generated acidity and contributed significantly to metal release. Under microaerophilic conditions Thiobacillus ferrooxidans continued to effect metal release from the ore, but did not produce further acidity. If White's overburden is returned to the acidic, flooded opencuts, complete solubilisation of the material will occur. The exclusion of oxygen from the dump will not necessarily stop bacterially catalysed leaching processes. Under highly aerated and agitated flooded conditions the tailings material was not active, except for copper release of about 2 g kg -1 ore at pH 4.0. The only deleterious element released by increasing acidity was copper, which was 100 per cent solubilised at pH 2.5. Uranium was always lss than 3 μg kg -1 ore, and lead was detected only at pH 2.5. Indigenous leaching bacteria did not develop

Laboratory leach tests of phosphate/sulfate waste grout and leachate adsorption tests using Hanford sediment

Energy Technology Data Exchange (ETDEWEB)

Serne, R.J.; Martin, W.J.; McLaurine, S.B.; Airhart, S.P.; LeGore, V.L.; Treat, R.L.

1987-12-01

An assessment of the long-term risks posed by grout disposal at Hanford requires data on the ability of grout to resist leaching of waste species contained in the grout via contact with water that percolates through the ground. Additionally, data are needed on the ability of Hanford sediment (soil) surrounding the grout and concrete vault to retard migration of any wastes released from the grout. This report describes specific laboratory experiments that are producing empirical leach rate data and leachate-sediment adsorption data for Phosphate-Sulfate Waste (PSW) grout. The leach rate and adsorption values serve as inputs to computer codes used to forecast potential risk resulting from the use of ground water containing leached species. In addition, the report discusses other chemical analyses and geochemical computer code calculations that were used to identify mechanisms that control leach rates and adsorption potential. Knowledge of the controlling chemical and physical processes provides technical defensibility for using the empirical laboratory data to extrapolate the performance of the actual grout disposal system to the long time periods of interest. 59 refs., 83 figs., 18 tabs.

Laboratory leach tests of phosphate/sulfate waste grout and leachate adsorption tests using Hanford sediment

International Nuclear Information System (INIS)

Serne, R.J.; Martin, W.J.; McLaurine, S.B.; Airhart, S.P.; LeGore, V.L.; Treat, R.L.

1987-12-01

An assessment of the long-term risks posed by grout disposal at Hanford requires data on the ability of grout to resist leaching of waste species contained in the grout via contact with water that percolates through the ground. Additionally, data are needed on the ability of Hanford sediment (soil) surrounding the grout and concrete vault to retard migration of any wastes released from the grout. This report describes specific laboratory experiments that are producing empirical leach rate data and leachate-sediment adsorption data for Phosphate-Sulfate Waste (PSW) grout. The leach rate and adsorption values serve as inputs to computer codes used to forecast potential risk resulting from the use of ground water containing leached species. In addition, the report discusses other chemical analyses and geochemical computer code calculations that were used to identify mechanisms that control leach rates and adsorption potential. Knowledge of the controlling chemical and physical processes provides technical defensibility for using the empirical laboratory data to extrapolate the performance of the actual grout disposal system to the long time periods of interest. 59 refs., 83 figs., 18 tabs

Leaching Mechanisms Program. Annual report

International Nuclear Information System (INIS)

Dougherty, D.; Colombo, P.; Doty, R.; Fuhrmann, M.

1984-09-01

The primary goal of this work is to determine the leaching mechanisms of a variety of matrix materials either in use or being considered for the solidification of low-level radioactive wastes by defense and commercial waste generators. Since this program is new and did not formally begin until May of FY 84, the results reported here are few and preliminary. Efforts were concentrated in the following activities: (1) The literature search for leaching data and proposed leaching models and mechanisms for low-level waste. (2) Data base development for leaching data being compiled from the literature and from the leaching experiments in this program. (3) The selection of solidification agents for the experimental part of the program. (4) Fabrication of leach samples and initiation of leach testing. 28 references, 9 figures, 4 tables

Implementation of the Leaching Environmental Assessment ...

Science.gov (United States)

LEAF provides a uniform and integrated approach for evaluating leaching from solid materials (e.g., waste, treated wastes such as by solidification/stabilization, secondary materials such as blast furnace slags, energy residuals such as coal fly ash, soil, sediments, mining and mineral processing wastes). Assessment using LEAF applies a stepwise approach that considers the leaching behavior of COPCs in response to chemical and physical factors that control and material properties across a range of plausible field conditions (US EPA, 2010). The framework provides the flexibility to tailor testing to site conditions and select the extent of testing based on assessment objectives and the level of detailed information needed to support decision-making. The main focus will be to discuss the implementation of LEAF in the US and the How to Guide that has recently been completed. To present the How To Guide for the implementation of the leaching environmental assessment framework to an international audience already familiar with comparable leaching tests in use in Europe. Will be meeting with European colleagues on their interest in expanding methods to include organics.

Potential for leaching of arsenic from excavated rock after different drying treatments.

Science.gov (United States)

Li, Jining; Kosugi, Tomoya; Riya, Shohei; Hashimoto, Yohey; Hou, Hong; Terada, Akihiko; Hosomi, Masaaki

2016-07-01

Leaching of arsenic (As) from excavated rock subjected to different drying methods is compared using sequential leaching tests and rapid small-scale column tests combined with a sequential extraction procedure. Although the total As content in the rock was low (8.81 mg kg(-1)), its resulting concentration in the leachate when leached at a liquid-to-solid ratio of 10 L kg(-1) exceeded the environmental standard (10 μg L(-1)). As existed mainly in dissolved forms in the leachates. All of the drying procedures applied in this study increased the leaching of As, with freeze-drying leading to the largest increase. Water extraction of As using the two tests showed different leaching behaviors as a function of the liquid-to-solid ratio, and achieved average extractions of up to 35.7% and 25.8% total As, respectively. Dissolution of As from the mineral surfaces and subsequent re-adsorption controlled the short-term release of As; dissolution of Fe, Al, and dissolved organic carbon played important roles in long-term As leaching. Results of the sequential extraction procedure showed that use of 0.05 M (NH4)2SO4 underestimates the readily soluble As. Long-term water extraction removed almost all of the non-specifically sorbed As and most of the specifically sorbed As. The concept of pollution potential indices, which are easily determined by the sequential leaching test, is proposed in this study and is considered for possible use in assessing efficacy of treatment of excavated rocks. Copyright © 2016 Elsevier Ltd. All rights reserved.

In-situ leaching of crownpoint, NM, uranium ore: Part 7 - Laboratory study of chemical agents for molybdenum restoration

International Nuclear Information System (INIS)

Strom, E.T.; Vogt, T.C.

1987-01-01

One possible drawback to the use of an in-situ leaching to recover uranium is the potential release of previously insoluble chemical species into the formation water. Before a pilot test of in-situ uranium leaching at Crownpoint, NM, was begun, extensive laboratory studies were undertaken to develop chemical methods for treating one possible contaminant, molybdenum (Mo). New Mexico regulations restrict the amount of Mo permissable in formation waters after leaching to less than 1 ppm. Two techniques to restore Mo after leaching were studied with core and pack tests. These studies suggest that if Mo restoration problems occur in the field, the use of precipitating agents such as Ca/sup 2+/ or reducing agents such as Fe/sup 2+/ may be helpful in ameliorating such problems

Single-pass continuous-flow leach test of PNL 76-68 glass: some selected Bead Leach I results

International Nuclear Information System (INIS)

Coles, D.G.

1981-01-01

A single-pass continuous-flow leach test of PNL 76-68 glass beads (7 mm dia) was concluded after 420 days of uninterrupted operation. Variables included in the experimental matrix were flow-rate, leachant composition, and temperature. Analysis was conducted on all leachate samples for 237 Np and 239 Pu as well as a number of nonradioactive elements. Results indicated that flow-rate and leachant systematically affected the leach rate, but only slightly. Temperature effects were significant. Plutonium leach rate was lower at higher temperature suggesting that Pu sorption onto the beads was enhanced at the higher temperature. The range of leach rates for all analyzed elements (except Pu), at both temperatures, at all three flow rates, and with all three leachant compositions varied over only three orders of magnitude. The range of variables used in this experiment covered those expected in many proposed repository environments. The preliminary interpretation of the results aPPh 3 also reacted with Mn 2 (CO) 10 and Cp 2 Mo 2 (CO) 6 to give a variety of products at room temperature. A radical mechanism was suggested

Fouling Release Coatings Based on Polydimethylsiloxane with the Incorporation of Phenylmethylsilicone Oil

Directory of Open Access Journals (Sweden)

Miao Ba

2018-04-01

Full Text Available In this study, phenylmethylsilicone oil (PSO with different viscosity was used for research in fouling release coatings based on polydimethylsiloxane (PDMS. The surface properties and mechanical properties of the coatings were investigated, while the leaching behavior of PSO from the coatings was studied. Subsequently, the antifouling performance of the coatings was investigated by the benthic diatom adhesion test. The results showed that the coatings with high-viscosity PSO exhibited high levels of hydrophobicity and PSO leaching, while the high PSO content significantly decreased the elastic modulus of the coatings and prolonged the release time of PSO. The antifouling results indicated that the incorporation of PSO into coatings enhanced the antifouling performance of the coating by improving the coating hydrophobicity and decreasing the coating elastic modulus, while the leaching of PSO from the coatings improved the fouling removal rate of the coating. This suggests a double enhancement effect on the antifouling performance of fouling release coatings based on PDMS with PSO incorporated.

Leaching characteristics of vanadium in mine tailings and soils near a vanadium titanomagnetite mining site

Energy Technology Data Exchange (ETDEWEB)

Yang, Jinyan; Tang, Ya; Yang, Kai [College of Architecture and Environment, Sichuan University, Chengdu 610065 (China); Rouff, Ashaki A. [School of Earth and Environmental Sciences, Queens College City University of New York, 65-30 Kissena Boulevard, Flushing, NY 11367 (United States); Elzinga, Evert J. [Department of Earth and Environmental Sciences, Rutgers University, Newark, NJ (United States); Huang, Jen-How, E-mail: jen-how.huang@unibas.ch [Institute of Environmental Geosciences, University of Basel, CH-4056 Basel (Switzerland)

2014-01-15

Highlights: • Vanadium in the soil and mine tailings has low solubility. • The leachability of vanadium in the mine tailings is lower than in the soil. • Low risk of vanadium migrating from the soil and mine tailings into the surrounding environment. • Drought and rewetting increase vanadium release from the soil and mine tailings. • Soil leaching processes control vanadium transport in soils overlain with mine tailings. -- Abstract: A series of column leaching experiments were performed to understand the leaching behaviour and the potential environmental risk of vanadium in a Panzhihua soil and vanadium titanomagnetite mine tailings. Results from sequential extraction experiments indicated that the mobility of vanadium in both the soil and the mine tailings was low, with <1% of the total vanadium readily mobilised. Column experiments revealed that only <0.1% of vanadium in the soil and mine tailing was leachable. The vanadium concentrations in the soil leachates did not vary considerably, but decreased with the leachate volume in the mine tailing leachates. This suggests that there was a smaller pool of leachable vanadium in the mine tailings compared to that in the soil. Drought and rewetting increased the vanadium concentrations in the soil and mine tailing leachates from 20 μg L{sup −1} to 50–90 μg L{sup −1}, indicating the potential for high vanadium release following periods of drought. Experiments with soil columns overlain with 4, 8 and 20% volume mine tailings/volume soil exhibited very similar vanadium leaching behaviour. These results suggest that the transport of vanadium to the subsurface is controlled primarily by the leaching processes occurring in soils.

Thermal treatment and leaching of biochar alleviates plant growth inhibition from mobile organic compounds

Directory of Open Access Journals (Sweden)

Nigel V. Gale

2016-08-01

Full Text Available Recent meta-analyses of plant responses to biochar boast positive average effects of between 10 and 40%. Plant responses, however, vary greatly across systems, and null or negative biochar effects are increasingly reported. The mechanisms responsible for such responses remain unclear. In a glasshouse experiment we tested the effects of three forestry residue wood biochars, applied at five dosages (0, 5, 10, 20, and 50 t/ha to a temperate forest drystic cambisol as direct surface applications and as complete soil mixes on the herbaceous pioneers Lolium multiflorum and Trifolium repens. Null and negative effects of biochar on growth were found in most cases. One potential cause for null and negative plant responses to biochar is plant exposure to mobile compounds produced during pyrolysis that leach or evolve following additions of biochars to soil. In a second glasshouse experiment we examined the effects of simple leaching and heating techniques to ameliorate potentially phytotoxic effects of volatile and leachable compounds released from biochar. We used Solid Phase Microextraction (SPME–gas chromatography–mass spectrometry (GC-MS to qualitatively describe organic compounds in both biochar (through headspace extraction, and in the water leachates (through direct injection. Convection heating and water leaching of biochar prior to application alleviated growth inhibition. Additionally, growth was inhibited when filtrate from water-leached biochar was applied following germination. SPME-GC-MS detected primarily short-chained carboxylic acids and phenolics in both the leachates and solid chars, with relatively high concentrations of several known phytotoxic compounds including acetic acid, butyric acid, 2,4-di-tert-butylphenol and benzoic acid. We speculate that variable plant responses to phytotoxic organic compounds leached from biochars may largely explain negative plant growth responses and also account for strongly species

Leaching behaviour of hazardous waste under the impact of different ambient conditions.

Science.gov (United States)

Pecorini, Isabella; Baldi, Francesco; Bacchi, Donata; Carnevale, Ennio Antonio; Corti, Andrea

2017-05-01

The overall objective of this study is to provide an improved basis for the assessment of the leaching behaviour of waste marked as hazardous partly stabilised (European waste catalogue code 19 03 04 ∗ ). Four samples of hazardous partly stabilised waste were subjected to two leaching tests: up-flow column tests and batch equilibrium tests. The research was carried out in two directions: the first aims at comparing the results of the two experimental setups while the second aims at assessing the impact of different ambient conditions on the leaching behaviour of waste. Concerning this latter objective the effect of mesophilic temperature, mechanical constraints and acid environment were tested through column percolation tests. Results showed no significant differences between batch and column leaching test outcomes when comparing average concentrations calculated at a liquid to solid ratio of 10:1 l kg -1  TS. Among the tested ambient conditions, the presence of an acid environment (pH=4.5) accelerated the leaching process resulting in a higher cumulative released quantity measured on the majority of the investigated polluting substances. On the contrary, the effect of temperature and mechanical constraints seemed to not affect the process showing final contents even lower than values found for the standard test. This result was furthermore confirmed by the application of the principal component analysis. Copyright © 2016 Elsevier Ltd. All rights reserved.

Long-term lessons on pesticide leaching obtained via the Danish Pesticide Leaching Assessment Programme

DEFF Research Database (Denmark)

Rosenbom, Anette E.; Olsen, Preben; Plauborg, Finn

To avoid any unacceptable influence on the environment posed by pesticides and their degradation products, all pesticides used in the European Union needs authorization. The authorization procedure includes assessing the leaching risk of both pesticides and their degradation products...

EFFECTS OF LEACHING MEDIUM ON LEACHABILITY OF WOOD PRESERVING N'N-HYDROXYNAPTHALIMIDE (NHA)

OpenAIRE

Evren Terzi,; Dilek Dogu,; Feyza Kurt,; S. Nami Kartal,; Frederick Green

2012-01-01

Laboratory leaching test procedures usually call for the use of distilled or deionized water; however, treated wood is generally exposed to different types of water, soil, and weather conditions. Thus, factors such as salinity, hardness, pH, temperature etc. might be important in the release of different amounts of biocide compounds. This study evaluates the release of the sodium salt of the calcium precipitating and wood preserving agent N’N-hydroxynapthalimide (NHA) from treated wood specim...

Densification of salt-occluded zeolite a powders to a leach-resistant monolith

International Nuclear Information System (INIS)

Lewis, M.A.; Fischer, D.F.; Murhpy, C.D.

1993-01-01

Pyrochemical processing of spent fuel from the Integral Fast Reactor (IFR) yields a salt waste of LiCl-KCl that contains approximately 6 wt% fission products, primarily as CsCl and SrCl 2 . Past work has shown that zeolite A will preferentially sorb cesium and strontium and will encapsulate the salt waste in a leach-resistant, radiation-resistant aluminosilicate matrix. However, a method is sill needed to convert the salt-occluded zeolite powders into a form suitable for geologic disposal. We are thus investigating a method that forms bonded zeolite by hot pressing a mixture of glass frit and salt-occluded zeolite powders at 990 K (717 degree C) and 28 MPa. The leach resistance of the bonded zeolite was measured in static leach tests run for 28 days in 363 K (90 degree C) deionized water. Normalized release rates of all elements in the bonded zeolite were low, 2 d. Thus, the bonded zeolite may be a suitable waste form for IFR salt waste

The role of nano-perovskite in the negligible thorium release in seawater from Greek bauxite residue (red mud)

DEFF Research Database (Denmark)

Gkamaletsos, Platon; Godelitsas, Athanasios; Kasama, Takeshi

2016-01-01

-ICP-MS, using Mediterranean seawater from Greece, indicated significant release of V, depending on S/L ratio, and negligible release of Th at least after 12 months leaching. STEM-EDS/EELS & HR-STEM-HAADF study of the leached BR at the nanoscale revealed that the significant immobility of Th4+ is due to its...

Bacterial leaching of waste uranium materials.

Science.gov (United States)

Barbic, F F; Bracilović, D M; Krajincanić, B V; Lucić, J L

1976-01-01

The effect of ferrobacteria and thiobacteria on the leaching of waste uranium materials from which 70-80% of uranium was previously leached by classical chemical hydrometallurgical procedure has been investigated. The bacteria used are found in the ore and the mine water of Zletovska River locality, Yugoslavia. Parameters of biological leaching were examined in the laboratory. Leaching conditions were changed with the aim of increasing the amount of uranium leached. The effect of pyrite added to the waste materials before the beginning of leaching has also been examined. Uranium leaching is directly proportional to the composition and number of ferrobacteria and thiobacteria, and increased by almost twice the value obtained from the same starting materials without using bacteria. Increased sulphuric acid concentrations stimulate considerably the rate of leaching. Uranium leaching is increased up to 20% while sulphuric acid consumption is simultaneously decreased by the addition of pyrite. Uranium concentrations in starting waste materials used for leaching were extremely low (0.0278 and 0.372% U) but about 60% recovery of uranium was obtained, with relatively low consumption of sulphuric acid.

Bacterial leaching of waste uranium materials

International Nuclear Information System (INIS)

Barbic, F.F.; Bracilovic, D.M.; Krajincanic, B.V.; Lucic, J.L.

1976-01-01

The effect of ferrobacteria and thiobacteria on the leaching of waste uranium materials from which 70-80% of uranium was previously leached by classical chemical hydrometallurgical procedure has been investigated. The bacteria used are found in the ore and the mine water of Zletovska River locality, Yugoslavia. Parameters of biological leaching were examined in the laboratory. Leaching conditions were changed with the aim of increasing the amount of uranium leached. The effect of pyrite added to the waste materials before the beginning of leaching has also been examined. Uranium leaching is directly proportional to the composition and number of ferrobacteria and thiobacteria, and increased by almost twice the value obtained from the same starting materials without using bacteria. Increased sulphuric acid concentrations stimulate considerably the rate of leaching. Uranium leaching is increased up to 20% while sulphuric acid consumption is simultaneously decreased by the addition of pyrite. Uranium concentrations in starting waste materials used for leaching were extremely low (0.0278 and 0.0372% U) but about 60% recovery of uranium was obtained, with relatively low consumption of sulphuric acid. (author)

In situ leaching of uranium

International Nuclear Information System (INIS)

Martin, B.

1980-01-01

A process is described for the in-situ leaching of uranium-containing ores employing an acidic leach liquor containing peroxymonosulphuric acid. Preferably, additionally, sulphuric acid is present in the leach liquor. (author)

Study of the sulfuric acid leaching and bacterial leaching of low grade uranium ore by orbital shaker experiment

International Nuclear Information System (INIS)

Li Guangyue; Liu Yulong; Wang Yongdong; Ding Dexin

2009-01-01

The sulphuric acid leaching and bacteria leaching by orbital shaker experiments were conducted for the low grade uranium ore from a uranium mine in Guangdong Province. The results show that, when the concentration of sulphuric acid and that of slurry were 30 g/L and 25%, respectively, the conditions were most favourable for sulphuric acid leaching and the rate of leaching reached 92.92%, that, when pH value was 1.5, inoculation amount, 10%, concentration of slurry, 10%, the conditions were most favourable for bacteria leaching and the rate of leaching reached 95.93%, that, compared with sulphuric acid leaching, bacteria leaching decreased sulphuric acid consumption by 17.2% and increased the rate of leaching by 3%, and that, under the most favourable conditions for suphuric acid leaching, if 1% natrium chlorate was added, the rate of leaching increased to 96.46%, but 10 kg of natrium chlorate was consumed for 1 ton of uranium ore. (authors)

Development of an accelerated leach test(s) for low-level waste forms

International Nuclear Information System (INIS)

Dougherty, D.R.; Fuhrmann, M.; Colombo, P.

1986-01-01

An accelerated leach test(s) is being developed to predict long-term leaching behavior of low-level radioactive waste (LLW) forms in their disposal environments. As necessary background, a literature survey of reported leaching mechanisms, available mathematical models and factors that affect leaching of LLW forms has been compiled. Mechanisms which have been identified include diffusion, dissolution, ion exchange, corrosion and surface effects. A computerized data base of LLW leaching data and mathematical models is being developed. The data is being used for model evaluation by curve fitting and statistical analysis according to standard procedures of statistical quality control. Long-term leach tests on portland cement, bitumen and vinyl ester-styrene (VES) polymer waste forms are underway which are designed to identify and evaluate factors that accelerate leaching without changing the mechanisms. Initial results on the effect of temperature on leachability indicate that the leach rates of cement and VES waste forms increase with increasing temperature, whereas, the leach rate of bitumen is little affected

A mechanistic model for leaching from low-level radioactive waste packages

International Nuclear Information System (INIS)

Kempf, C.R.

1988-01-01

The development of a waste leaching model to predict radionuclide releases from porous wastes in corrodible outer containers in unsaturated conditions and/or conditions of intermittent water flow is summarized in this paper. Three major processes have been conceptualized as necessarily participating in waste leaching: infiltration of water to the waste package; interaction of this water with the waste; and exit of radionuclide-laden water from the waste package. Through the exit point, the main features of the whole leaching process ware held in common. The departure occurs in two main ways: 1) the method of entrance of the radionuclides to leachant (i.e. part of the waste-water interaction phase outlined earlier); and 2) the mode of exit from waste form/waste package (i.e., the exit of radionuclide-laden water phase). The first branching point, which occurs in relation to 1), leads to either readily soluble species directly entering leachant on contact, or to other processes - mainly expected to be diffusion, dissolution or ion exchange, or some combination thereof

Chlorination leaching of cadmium

International Nuclear Information System (INIS)

Lach, E.; Pajak, I.; Bojanowska, A.

1978-01-01

The results of the investigations on chlorination leaching of cadmium from dust coming from dry dust collector of sinter belt, that is leaching with water saturated with gaseous chlorine and leaching with solutions of ammonium chloride and sodium chloride were given. The optimum conditions for these processes were established. It was found, that the method of leaching in the presence of gaseous chlorine is more effective, as it allows to report into the solution over 90% cadmium contained in dust. Owing to technical difficulties, environmental protection and safety conditions more advantageous seems to be the use as leaching agent of the ammonium chloride solutions. When applying 20% NH 4 Cl and temperature of 60 0 C, the time of 2 hours and the ratio of solid to liquid of 1:5, 70% cadmium contained in the dust can be reported into the solution. (auth.)

Eh and fission product solubilities: two factors in the leaching of UO2

International Nuclear Information System (INIS)

Ogard, A.E.; Duffy, C.J.

1981-01-01

Eh was found to have a large effect on the dissolution of UO 2 in water at pH 4. As was estimated from thermodynamic data, the solubility was found to decrease as the oxygen fugacity, and therefore the Eh of the water, was decreased. Some of the rare earths and other actinides such as europium, cerium, americium, and plutonium released during the leaching of a spent fuel element behaved differently. These elements were not affected to any large extent by the variation in Eh of these experiments. It has been postulated that these elements reached their solubility limits and precipitated as the spent fuel was leached. 2 figures, 2 tables

Extraction of nickel from Ramu laterite by sulphation roasting-water leaching

Science.gov (United States)

Wang, Weiwei; Du, Shangchao; Liu, Guo; Tang, Jianwen; Lu, Yeda; Lv, Dong

2017-08-01

Recovery of nickel from a PNG nickel laterite with high content of iron by a sulphation roasting-water leaching has been studied. The influences of sulfuric acid/ore ratio, temperature of roasting and water on recovery efficiency were investigated. The effective separation of nickel over the co-existed elements including iron was achieved by the process with mixing, curing, roasting and leaching stages. Near 100% of nickel was leached from the roasted laterite by water at 80°C in an atmospheric air, while co-leaching of about 2% of iron, under the optimal pre-treatment conditions with the ratio of acid: ore around 0.45:1 and the roasting temperature about 650°C. The advantages and disadvantages of sulphation atmospheric leaching are compared with pressure acid leaching with engineering consideration.

Leaching of Titanium and Silicon from Low-Grade Titanium Slag Using Hydrochloric Acid Leaching

Science.gov (United States)

Zhao, Longsheng; Wang, Lina; Qi, Tao; Chen, Desheng; Zhao, Hongxin; Liu, Yahui; Wang, Weijing

2018-05-01

Acid-leaching behaviors of the titanium slag obtained by selective reduction of vanadium-bearing titanomagnetite concentrates were investigated. It was found that the optimal leaching of titanium and silicon were 0.7% and 1.5%, respectively. The titanium and silicon in the titanium slag were firstly dissolved in the acidic solution to form TiO2+ and silica sol, and then rapidly reprecipitated, forming hydrochloric acid (HCl) leach residue. Most of the silicon presented in the HCl leach residue as floccules-like silica gel, while most of the titanium was distributed in the nano-sized rod-like clusters with crystallite refinement and intracrystalline defects, and, as such, 94.3% of the silicon was leached from the HCl leach residue by alkaline desilication, and 96.5% of the titanium in the titanium-rich material with some rutile structure was then digested by the concentrated sulfuric acid. This provides an alternative route for the comprehensive utilization of titanium and silicon in titanium slag.

Immobilized waste leaching

International Nuclear Information System (INIS)

Suarez, A.A.

1989-01-01

The main mechanism by which the immobilized radioactive materials can return to biosphere is the leaching due to the intrusion of water into the repositories. Some mathematical models and experiments utilized to evaluate the leaching rates in different immobilization matrices are described. (author) [pt

Heavy Metal Pollution Potential of Zinc Leach Residues Discarded in çinkur Plant

OpenAIRE

ALTUNDOĞAN, H. Soner; ERDEM, Mehmet; ORHAN, Ramazan

1998-01-01

In this paper, results of the study on heavy metals solubility behaviour of filter cakes from leaching of clinkerized Waelz oxide and flue dust collected during clinkerization in çinkur plant are given. The release of heavy metals into water was investigated by subjecting the cakes to solubility tests systematically. The effect of contact time, pH, liquid/solid ratio and successive extractions on the releasing of heavy metals (Cd, Pb, Mn and Zn) into water was examined and their conc...

COMPILATION OF LABORATORY SCALE ALUMINUM WASH AND LEACH REPORT RESULTS

International Nuclear Information System (INIS)

Harrington, S.J.

2011-01-01

This report compiles and analyzes all known wash and caustic leach laboratory studies. As further data is produced, this report will be updated. Included are aluminum mineralogical analysis results as well as a summation of the wash and leach procedures and results. Of the 177 underground storage tanks at Hanford, information was only available for five individual double-shell tanks, forty-one individual single-shell tanks (e.g. thirty-nine 100 series and two 200 series tanks), and twelve grouped tank wastes. Seven of the individual single-shell tank studies provided data for the percent of aluminum removal as a function of time for various caustic concentrations and leaching temperatures. It was determined that in most cases increased leaching temperature, caustic concentration, and leaching time leads to increased dissolution of leachable aluminum solids.

COMPILATION OF LABORATORY SCALE ALUMINUM WASH AND LEACH REPORT RESULTS

Energy Technology Data Exchange (ETDEWEB)

HARRINGTON SJ

2011-01-06

This report compiles and analyzes all known wash and caustic leach laboratory studies. As further data is produced, this report will be updated. Included are aluminum mineralogical analysis results as well as a summation of the wash and leach procedures and results. Of the 177 underground storage tanks at Hanford, information was only available for five individual double-shell tanks, forty-one individual single-shell tanks (e.g. thirty-nine 100 series and two 200 series tanks), and twelve grouped tank wastes. Seven of the individual single-shell tank studies provided data for the percent of aluminum removal as a function of time for various caustic concentrations and leaching temperatures. It was determined that in most cases increased leaching temperature, caustic concentration, and leaching time leads to increased dissolution of leachable aluminum solids.

BLT-EC (Breach, Leach Transport, and Equilibrium Chemistry), a finite-element model for assessing the release of radionuclides from low-level waste disposal units: Background, theory, and model description

International Nuclear Information System (INIS)

MacKinnon, R.J.; Sullivan, T.M.; Simonson, S.A.; Suen, C.J.

1995-08-01

Performance assessment models typically account for the processes of sorption and dissolution-precipitation by using an empirical distribution coefficient, commonly referred to as K d that combines the effects of all chemical reactions between solid and aqueous phases. In recent years, however, there has been an increasing awareness that performance assessments based solely on empirically based K d models may be incomplete, particularly for applications involving radionuclides having sorption and solubility properties that are sensitive to variations in the in-situ chemical environment. To accommodate variations in the in-situ chemical environment, and to assess its impact on radionuclide mobility, it is necessary to model radionuclide release, transport, and chemical processes in a coupled fashion. This modeling has been done and incorporated into the two-dimensional, finite-element, computer code BLT-EC (Breach, Leach, Transport, Equilibrium Chemistry). BLT-EC is capable of predicting container degradation, waste-form leaching, and advective-dispersive, multispecies, solute transport. BLT-EC accounts for retardation directly by modeling the chemical processes of complexation, sorption, dissolution-precipitation, ion-exchange, and oxidation-reduction reactions. In this report we: (1) present a detailed description of the various physical and chemical processes that control the release and migration of radionuclides from shallow land LLW disposal facilities; (2) formulate the mathematical models that represent these processes; (3) outline how these models are incorporated and implemented in BLT-EC; and (4) demonstrate the application of BLT-EC on a set of example problems

Enhancement of gold grade through arsenic removal in the gold concentrate using sulfuric acid baking and hot water leaching

Science.gov (United States)

On, Hyun-sung; Lim, Dae-hack; Myung, Eun-ji; Kim, Hyun-soo; Park, Cheon-young

2017-04-01

In order to improve gold recovery, in general, the roasting process is carried out on gold concentrate. However in this process, Arsenic(As) is released from the gold concentrate and valuable elements such as Fe, Cu, Zn and Pb are converted into oxides. This causes air pollution through the release of As and loss of valuable elements by discarding the oxide minerals in the tailings. In order to prevent the release of As and the loss of valuable metals, an acid baking experiment was carried out on the gold concentrate with the addition of an H2SO4 solution. The baking effect, H2SO4 concentration effect and the effects of changing the baking time were examined using an electric furnace. In experimental results, soluble metal sulfates such as Rhomboclase and Mikasite were formed in the baked samples as seen through XRD analysis. In hot(70 degree Celsius) water leaching of the roast and baked samples, As the contents leached were 60 times more in the baked sample than the roast sample, and the Fe, Cu, Zn and Pb contents were 17, 10, 14, 13 times in the baked sample than in the roast sample, respectively. In the water leached solid-residues, the maximum gold grade was upgraded by 33% due to the acid baking effect. It is confirmed that acid baking with H2SO4 prevented As release into the air and the recovery of valuable metals through hot water leaching such as Fe, Cu, Zn and Pb which were formerly discarded in the tailings. Acknowledgment : This work was supported by the Energy and Resources Engineering Program Grant funded by the Ministry of Trade, Industry and Energy, Korea

Nitrate Leaching Management

Science.gov (United States)

Nitrate (NO3) leaching is a significant nitrogen (N) loss process for agriculture that must be managed to minimize NO3 enrichment of groundwater and surface waters. Managing NO3 leaching should involve the application of basic principles of understanding the site’s hydrologic cycle, avoiding excess ...

Nitrate leaching index

Science.gov (United States)

The Nitrate Leaching Index is a rapid assessment tool that evaluates nitrate (NO3) leaching potential based on basic soil and climate information. It is the basis for many nutrient management planning efforts, but it has considerable limitations because of : 1) an oversimplification of the processes...

Leaching of actinides from nuclear waste glass: French experience

International Nuclear Information System (INIS)

Vernaz, E.Y.; Godon, N.

1991-01-01

The activity concentration versus time of a typical LWR glass shows that after 300 years most of the activity is attributable to three actinides (Np, Pu and Am) and to 99 Tc. This activity decreases slowly, and some 50.000 years are necessary before the activity concentration drops to the level of the richest natural ores. This paper reviews the current state of knowledge concerning the kinetics of actinide release from glass subjected to aqueous leaching

The leaching of lead from lead-based paint in landfill environments.

Science.gov (United States)

Wadanambi, Lakmini; Dubey, Brajesh; Townsend, Timothy

2008-08-30

Lead leaching from lead-based paint (LBP) was examined using standardized laboratory protocols and tests with leachate from actual and simulated landfill environments. Two different LBP samples were tested; leaching solutions included leachates from three municipal solid waste (MSW) landfills and three construction and demolition (C&D) debris landfills. The toxicity characteristic leaching procedure (TCLP) and the synthetic precipitation leaching procedure (SPLP) were also performed. Lead concentrations were many times higher using the TCLP compared to the SPLP and the landfill leachates. No significant difference (alpha=0.05) was observed in leached lead concentrations from the MSW landfill and C&D debris landfill leachates. The impact of other building materials present in LBP debris on lead leaching was examined by testing mixtures of LBP (2%) and different building materials (98%; steel, wood, drywall, concrete). The type of substrate present impacted lead leaching results, with concrete demonstrating the most dramatic impact; the lowest lead concentrations were measured in the presence of concrete under both TCLP and SPLP extractions.

Long-term leaching of nutrients and contaminants from wood combustion ashes

DEFF Research Database (Denmark)

Maresca, Alberto; Hyks, J.; Astrup, Thomas Fruergaard

2018-01-01

With increasing amounts of woody biomass being combusted for energy purposes worldwide, more wood ash is being generated and needs management. As an alternative to landfilling, residues may be utilised for liming and fertilising purposes on forest soils. Comprehensive evaluations of long-term lea......With increasing amounts of woody biomass being combusted for energy purposes worldwide, more wood ash is being generated and needs management. As an alternative to landfilling, residues may be utilised for liming and fertilising purposes on forest soils. Comprehensive evaluations of long......-term leaching from these residues are needed in order to assess potential environmental impacts associated with their utilisation. Two Danish wood ash samples, one fly ash and one mixed ash (a combination of fly ash and bottom ash), were evaluated in long-term percolation column tests (up to L/S ∼2000 L....../kg), in order to quantify the release of major, minor and trace metal(loid)s. While columns of three different lengths were used, the leaching of individual elements could be described as a function of the L/S ratio – irrespective of the column length. At L/S 1000 L/kg, the cumulative releases of K, S, Na, Ca...

Strontium and cesium release mechanisms during unsaturated flow through waste-weathered Hanford sediments

International Nuclear Information System (INIS)

Chang, Hyun-Shik; Um, Wooyong; Rod, Kenton A.; Serne, R. Jeffrey; Thompson, Aaron; Perdrial, Nicolas; Steefel, Carl I.; Chorover, Jon

2011-01-01

Leaching behavior of Sr and Cs in the vadose zone of Hanford site (WA, USA) was studied with laboratory-weathered sediments mimicking realistic conditions beneath the leaking radioactive waste storage tanks. Unsaturated column leaching experiments were conducted using background Hanford pore water focused on first 200 pore volumes. The weathered sediments were prepared by 6 months reaction with a synthetic Hanford tank waste leachate containing Sr and Cs (10-5 and 10-3 molal representative of LO- and HI-sediment, respectively) as surrogates for 90Sr and 137Cs. The mineral composition of the weathered sediments showed that zeolite (chabazite-type) and feldspathoid (sodalite-type) were the major byproducts but different contents depending on the weathering conditions. Reactive transport modeling indicated that Cs leaching was controlled by ion-exchange, while Sr release was affected primarily by dissolution of the secondary minerals. The later release of K, Al, and Si from the HI-column indicated the additional dissolution of a more crystalline mineral (cancrinite-type). A two-site ion-exchange model successfully simulated the Cs release from the LO-column. However, a three-site ion-exchange model was needed for the HI-column. The study implied that the weathering conditions greatly impact the speciation of the secondary minerals and leaching behavior of sequestrated Sr and Cs.

Analysis of chromium and sulphate origins in construction recycled materials based on leaching test results.

Science.gov (United States)

Del Rey, I; Ayuso, J; Galvín, A P; Jiménez, J R; López, M; García-Garrido, M L

2015-12-01

Twenty samples of recycled aggregates from construction and demolition waste (CDW) with different compositions collected at six recycling plants in the Andalusia region (south of Spain) were characterised according to the Landfill Directive criteria. Chromium and sulphate were identified as the most critical compounds in the leachates. To detect the sources of these two pollutant constituents in recycled aggregate, environmental assessments were performed on eight construction materials (five unused ceramic materials, two old crushed concretes and one new mortar manufactured in the laboratory). The results confirmed that leached sulphate and Cr were mainly released by the ceramic materials (bricks and tiles). To predict the toxicological consequences, the oxidation states of Cr (III) and Cr (VI) were measured in the leachates of recycled aggregates and ceramic materials classified as non-hazardous. The bricks and tiles mainly released total Cr as Cr (III). However, the recycled aggregates classified as non-hazardous according to the Landfill Directive criteria mainly released Cr (VI), which is highly leachable and extremely toxic. The obtained results highlight the need for legislation that distinguishes the oxidative state in which chromium is released into the environment. Leaching level regulations must not be based solely on total Cr, which can lead to inaccurate predictions. Copyright © 2015 Elsevier Ltd. All rights reserved.

Leaching of FGD Byproducts Using a CSTX

Energy Technology Data Exchange (ETDEWEB)

Kairies, C.L.; Schroeder, K.T.; Cardone, C.R.

2005-09-01

Leaching studies of coal utilization byproducts (CUB) are often performed to determine the compatibility of the material in a particular end-use or disposal environment. Typically, these studies are conducted using either a batch or a fixed-bed column technique. Fixed-bed columns offer the advantage of a continuous flow of effluent that provides elution profiles with changing elution volume and pH. Unfortunately, clogs can form in fixed-bed leaching columns, either because of cementitious properties of the material itself, such as is seen for fluidized bed combustion (FBC) fly ash, or because of precipitate formation, such as can occur when a high-calcium ash is subjected to sulfate-containing leachates. Also, very fine-grained materials, such as gypsum, do not provide sufficient permeability for study in a fixed-bed column. A continuous, stirred-tank extractor (CSTX) is being used as an alternative technique that can provide the elution profile of column leaching but without the low permeability problems. The CSTX has been successfully employed in the leaching of flue gas desulfurization products that would not be sufficiently permeable under traditional column leaching conditions. The results indicate that the leaching behavior depends on a number of factors, including (but not limited to) solubility and neutralization capacity of the mineral phases present, sorption properties of these phases, behavior of the solubilized material in the tank, and the type of species in solution. In addition, leaching to near-exhaustion of a wallboard produced from FGD gypsum has allowed the isolation of a highly adsorptive phase. This phase appears to be present in at least some FGD gypsums and accounts for the immobilization of trace metals such as arsenic, cobalt, lead, and mercury.

Modelling of Pb release during Portland cement alteration

Energy Technology Data Exchange (ETDEWEB)

Benard, A. [INERIS Mediterrannee, F-13545 Aix En Provence 04 (France); Rose, J.; Borschneck, D.; Bottero, J.Y. [Univ Paul Cezanne, CNRS, UMR 6635, CEREGE, IFR PMSE 112, F-13545 Aix En Provence, (France); Hazemann, J.L. [CNRS, Cristallog Lab, F-38042 Grenoble 09 (France); Proux, O. [Univ Grenoble 1, CNRS, UMR, LGIT, F-38400 St Martin Dheres (France); Trotignon, L. [CEA Cadarache, DTN, SMTM, Lab Modelisat Transferts Environm, 13 - Saint Paul lez Durance (France); Nonat, A. [Univ Bourgogne, CNRS, UMR 5613, Fac Sci Mirande, Lab Rech Reactivite Solides, F-21078 Dijon (France); Chateau, L. [ADEME, F-49004 Angers (France)

2009-07-01

Complex cementitious matrices undergo weathering with environmental exchange and can release metallic pollutants during alteration. The molecular mechanisms responsible for metal release are difficult to identify, though this is necessary if such processes are to be controlled. The present study determines and models the molecular mechanisms of Pb release during Portland cement leaching. As Pb release is strongly related to its speciation (i.e. atomic environment and the nature of bearing phases), the first objective of the present study was to investigate the evolution of Pb retention sites together with the evolution of the cement mineralogy during leaching. Complementary and efficient investigation tools were used, namely X-ray diffraction, micro-X-ray fluorescence and X-ray absorption fine structures. The second objective was to reproduce our results with a reactive transport code (CHESS/HYTEC) in order to test the proposed speciation model of Pb. Combined results indicate that in both the unaltered core and the altered layer of the leached cement, Pb(II) would be retained through C-S-H 'nano-structure', probably linked to a Q(1) or Q(2P) silicate tetrahedra. Moreover in the altered layer, the presence of Fe atoms in the atomic environment of Pb is highly probable. Unfortunately little is known about Fe phases in cement, which makes the interpretation difficult. Can Fe-substituted hydrogranet (C(3)AH(6)) be responsible for Pb retention? Modelling results were consistent with Pb retention through C-S-H in layers and also in an additional, possibly Fe-containing, Pb-retention phase in the altered layer. (authors)

Development of an accelerated leach test(s) for low-level waste forms

International Nuclear Information System (INIS)

Dougherty, D.R.; Fuhrmann, M.; Colombo, P.

1985-01-01

An accelerated leach test(s) is being developed to predict long-term leaching behavior of low-level radioactive waste (LLW) forms in their disposal environments. As necessary background, a literature survey of reported leaching mechanisms, available mathematical models and factors that affect leaching of LLW forms has been compiled. Mechanisms which have been identified include diffusion, dissolution, ion exchange, corrosion and surface effects. A computerized data base of LLW leaching data and mathematical models is being developed. The data is being used for model evaluation by curve fitting and statistical analysis according to standard procedures of statistical quality control. Long-term leach tests on portland cement, bitumen and vinyl ester-styrene (VES) polymer waste forms are underway which are designed to identify and evaluate factors that accelerate leaching without changing the mechanisms. Initial results on the effect of temperature on leachability indicate that the leach rates of cement and VES waste forms increase with increasing temperature, whereas, the leach rate of bitumen is little affected. 10 refs., 5 figs

Leaching Behavior of Heavy Metals from Cement Pastes Using a Modified Toxicity Characteristic Leaching Procedure (TCLP).

Science.gov (United States)

Huang, Minrui; Feng, Huajun; Shen, Dongsheng; Li, Na; Chen, Yingqiang; Shentu, Jiali

2016-03-01

As the standard toxicity characteristic leaching procedure (TCLP) can not exhaust the acid neutralizing capacity of the cement rotary kiln co-processing solid wastes products which is particularly important for the assessment of the leaching concentrations of heavy metals. A modified TCLP was proposed. The extent of leaching of heavy metals is low using the TCLP and the leaching performance of the different metals can not be differentiated. Using the modified TCLP, however, Zn leaching was negligible during the first 180 h and then sharply increased (2.86 ± 0.18 to 3.54 ± 0.26 mg/L) as the acidity increased (pH leaching is enhanced using the modified TCLP. While Pb leached readily during the first 126 h and then leachate concentrations decreased to below the analytical detection limit. To conclude, this modified TCLP is a more suitable method for these cement rotary kiln co-processing products.

Leaching of CCA-treated wood: implications for waste disposal

International Nuclear Information System (INIS)

Townsend, Timothy; Tolaymat, Thabet; Solo-Gabriele, Helena; Dubey, Brajesh; Stook, Kristin; Wadanambi, Lakmini

2004-01-01

Leaching of arsenic, chromium, and copper from chromated copper arsenate (CCA)-treated wood poses possible environmental risk when disposed. Samples of un-weathered CCA-treated wood were tested using a variety of the US regulatory leaching procedures, including the toxicity characteristic leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP), extraction procedure toxicity method (EPTOX), waste extraction test (WET), multiple extraction procedure (MEP), and modifications of these procedures which utilized actual MSW landfill leachates, a construction and demolition (C and D) debris leachate, and a concrete enhanced leachate. Additional experiments were conducted to assess factors affecting leaching, such as particle size, pH, and leaching contact time. Results from the regulatory leaching tests provided similar results with the exception of the WET, which extracted greater quantities of metals. Experiments conducted using actual MSW leachate, C and D debris leachate, and concrete enhanced leachate provided results that were within the same order of magnitude as results obtained from TCLP, SPLP, and EPTOX. Eleven of 13 samples of CCA-treated dimensional lumber exceeded the US EPA's toxicity characteristic (TC) threshold for arsenic (5 mg/L). If un-weathered arsenic-treated wood were not otherwise excluded from the definition of hazardous waste, it frequently would require management as such. When extracted with simulated rainwater (SPLP), 9 of the 13 samples leached arsenic at concentrations above 5 mg/L. Metal leachability tended to increase with decreasing particle size and at pH extremes. All three metals leached above the drinking water standards thus possibly posing a potential risk to groundwater. Arsenic is a major concern from a disposal point of view with respect to ground water quality

Manual of acid in situ leach uranium mining technology

International Nuclear Information System (INIS)

2001-08-01

In situ leaching (ISL) technology recovers uranium using two alternative chemical leaching systems - acid and alkaline. This report brings together information from several technical disciplines that are an essential part of ISL technology. They include uranium geology, geohydrology, chemistry as well as reservoir engineering and process engineering. This report provides an extensive description of acid ISL uranium mining technology

Manual of acid in situ leach uranium mining technology

Energy Technology Data Exchange (ETDEWEB)

NONE

2001-08-01

In situ leaching (ISL) technology recovers uranium using two alternative chemical leaching systems - acid and alkaline. This report brings together information from several technical disciplines that are an essential part of ISL technology. They include uranium geology, geohydrology, chemistry as well as reservoir engineering and process engineering. This report provides an extensive description of acid ISL uranium mining technology.

Demonstration Of LEACHXS(trademark)/Orchestra Capabilities By Simulating Constituent Release From A Cementitious Waste Form In A Reinforced Concrete Vault

International Nuclear Information System (INIS)

Langton, C.; Meeussen, J.; Sloot, H.

2010-01-01

The objective of the work described in this report is to demonstrate the capabilities of the current version of LeachXS(trademark)/ORCHESTRA for simulating chemical behavior and constituent release processes in a range of applications that are relevant to the CBP. This report illustrates the use of LeachXS(trademark)/ORCHESTRA for the following applications: (1) Comparing model and experimental results for leaching tests for a range of cementitious materials including cement mortars, grout, stabilized waste, and concrete. The leaching test data includes liquid-solid partitioning as a function of pH and release rates based on laboratory column, monolith, and field testing. (2) Modeling chemical speciation of constituents in cementitious materials, including liquid-solid partitioning and release rates. (3) Evaluating uncertainty in model predictions based on uncertainty in underlying composition, thermodynamic, and transport characteristics. (4) Generating predominance diagrams to evaluate predicted chemical changes as a result of material aging using the example of exposure to atmospheric conditions. (5) Modeling coupled geochemical speciation and diffusion in a three layer system consisting of a layer of Saltstone, a concrete barrier, and a layer of soil in contact with air. The simulations show developing concentration fronts over a time period of 1000 years. (6) Modeling sulfate attack and cracking due to ettringite formation. A detailed example for this case is provided in a separate article by the authors (Sarkar et al. 2010). Finally, based on the computed results, the sensitive input parameters for this type of modeling are identified and discussed. The chemical speciation behavior of substances is calculated for a batch system and also in combination with transport and within a three layer system. This includes release from a barrier to the surrounding soil as a function of time. As input for the simulations, the physical and chemical properties of the

The fate of cyanide in leach wastes at gold mines: An environmental perspective

International Nuclear Information System (INIS)

Johnson, Craig A.

2015-01-01

Highlights: • This paper reviews the fate of cyanide in mineral processing wastes at gold mines. • Ore leaching produces numerous cyanide-containing species besides the gold complex. • Many cyanide species are eliminated or sequestered naturally over time. • Sequestered cyanide can be remobilized if conditions change. • Toxicity of released solutions can be reduced by photolytic reactions or offgassing. - Abstract: This paper reviews the basic chemistry of cyanide, methods by which cyanide can be analyzed, and aspects of cyanide behavior that are most relevant to environmental considerations at mineral processing operations associated with gold mines. The emphasis is on research results reported since 1999 and on data gathered for a series of U.S. Geological Survey studies that began in the late 1990s. Cyanide is added to process solutions as the CN − anion, but ore leaching produces numerous other cyanide-containing and cyanide-related species in addition to the desired cyanocomplex of gold. These can include hydrogen cyanide (HCN); cyanometallic complexes of iron, copper, zinc, nickel, and many other metals; cyanate (CNO − ); and thiocyanate (SCN − ). The fate of these species in solid wastes and residual process solutions that remain once gold recovery activities are terminated and in any water that moves beyond the ore processing facility dictates the degree to which cyanide poses a risk to aquatic organisms and aquatic-dependent organisms in the local environment. Cyanide-containing and cyanide-related species are subject to attenuation mechanisms that lead to dispersal to the atmosphere, chemical transformation to other carbon and nitrogen species, or sequestration as cyanometallic precipitates or adsorbed species on mineral surfaces. Dispersal to the atmosphere and chemical transformation amount to permanent elimination of cyanide, whereas sequestration amounts to storage of cyanide in locations from which it can potentially be remobilized by

PEP Run Report for Integrated Test A, Caustic Leaching in UFP-VSL-T01A, Oxidative Leaching in UFP-VSL-T02A

International Nuclear Information System (INIS)

Guzman-Leong, Consuelo E.; Bredt, Ofelia P.; Burns, Carolyn A.; Daniel, Richard C.; Su, Yin-Fong; Geeting, John G.H.; Golovich, Elizabeth C.; Josephson, Gary B.; Kurath, Dean E.; Sevigny, Gary J.; Smith, Dennese M.; Valdez, Patrick L.J.; Yokuda, Satoru T.; Young, Joan K.

2009-01-01

Pacific Northwest National Laboratory (PNNL) was tasked by Bechtel National Inc. (BNI) on the River Protection Project-Hanford Tank Waste Treatment and Immobilization Plant (RPP-WTP) project to perform research and development activities to resolve technical issues identified for the Pretreatment Facility (PTF). The Pretreatment Engineering Platform (PEP) was designed and constructed and operated as part of a plan to respond to issue M12, 'Undemonstrated Leaching Processes.'(a) The PEP, located in the Process Engineering Laboratory-West (PDLW) located in Richland, Washington, is a 1/4.5-scale test platform designed to simulate the WTP pretreatment caustic leaching, oxidative leaching, ultrafiltration solids concentration, and slurry washing processes. The PEP replicates the WTP leaching processes using prototypic equipment and control strategies. The PEP also includes non-prototypic ancillary equipment to support the core processing.

The leaching characteristics of vitrified slag

International Nuclear Information System (INIS)

Zhang, Jinlong; Li, Yaojian; Tian, Junguo; Sheng, Hongzhi; Xu, Yongxiang

2010-01-01

Full Text: Plasma-arc technology was developed to fix the heavy metal of flying ash by the Institute of Mechanics, Chinese Academy of Sciences (CAS-IMECH). A direct current (DC) experimental facility of 30 kW with plasma-arc technology was setup to form vitrified slag. The additives (CaO, SiO 2 ) were added into the reactor to form vitrified slag and fix the heavy metal (Cr, Pb), under dissimilar condition (long and short heating-up time, natural and water cooling). Vitrified slag was broken into different particle size, from 0.1 mm to 1 cm. The particles with different specific surface area were used to study the leaching of heavy metals in vitrified slag rate of speed. The pH value of leaching solution are from 2 to 12, the experiment was kept at different external temperature, from 4 degree Celsius to 70 degree celsius, for 1 week to 1 month. Heavy metal leaching concentration was used to measure the chemical stability of vitrified slag. The results show that the higher specific surface area, the higher heavy metal leaching concentration, but when the specific surface area reaches a certain value, little change in leaching concentration. The impact of temperature on leaching concentration was not significant, from 4 degree Celsius to 70 degree Celsius. The leaching concentration increases with decreasing of the pH value of leaching solution when the pH value of leaching solution less than 7, and little change in concentration increases with pH value when the pH value of leaching solution more than 7. Compared with the leaching concentration after 1 month, the leaching concentration after 1 week has not changed significantly. (Author)

Rates of leaching of radium from contaminated soils: an experimental investigation of radium bearing soils from Port Hope, Ontario

International Nuclear Information System (INIS)

Nathwani, J.S.; Phillips, C.R.

1978-01-01

The leachability of Ra-226 from soil at Port Hope, Ontario contaminated by waste from a long established U refinery is described here. A small-scale static leach test was devised to provide information to permit an assessment of hazard due to leaching in the environment. Two different leaching solutions were prepared to simulate a range of infiltrating water quality in disposal environments: one by bubbling CO 2 into distilled water to pH 5.5, and another by bubbling SO 2 into water to pH 3.5. Narrow-range size fractions of the soils (i.e. 0.250 to 0.105 mm) were leached for 30 to 45 days (equivalent rainfall of 2 to 3 yr). It was found that leaching is significantly affected by soil texture, total amounts leached and the maximum concentrations reached being much greater for coarser, and intermediate size fractions than for fine soil fractions. Also, leachant acidity significantly increased leaching rates and resulted in enhanced mobility in soils. A straight line for the plot of Q/Q 0 (cumulative fraction released) vs. Tsup(1/2) (T is leaching time in days) indicated that leaching could be considered to be a diffusion phenomenon in accordance with Fick's law. Diffusion coefficients ranging from 5 X 10 -11 to 2 X 10 -13 cm 2 day -1 were found. These coefficients provide a basis for estimating the fraction that would be leached over longer periods. (Auth.)

Spent UO{sub 2} TRISO coated particles. Instant release fraction and microstructure evolution

Energy Technology Data Exchange (ETDEWEB)

Curtius, Hildegard; Kaiser, Gabriele; Lieck, Norman; Guengoer, Murat; Klinkenberg, Martina; Bosbach, Dirk [Research Center Juelich (Germany). Inst. of Energy and Climate Research IEK-6: Nuclear Waste Management and Reactor Safety

2015-09-01

The impact of burn-up on the instant release fraction (IRF) from spent fuel was studied using very high burn-up UO{sub 2} fuel (∝ 100 GWd/t) from a prototype high temperature reactor (HTR). TRISO (TRi-structural-ISO-tropic) particles from the spherical fuel elements contain UO{sub 2} fuel kernels (500 μm diameter) which are coated by three tight layers ensuring the encapsulation of fission products during reactor operation. After cracking of the tight coatings {sup 85}Kr and {sup 14}C as {sup 14}CO{sub 2} were detected in the gas fraction. Xe was not detected in the gas fraction, although ESEM (Environmental Scanning Electron Microscope) investigations revealed an accumulation in the buffer. UO{sub 2} fuel kernels were exposed to synthetic groundwater under oxic and anoxic/reducing conditions. U concentration in the leachate was below the detection limit, indicating an extremely low matrix dissolution. Within the leach period of 276 d {sup 90}Sr and {sup 134/137}Cs fractions located at grain boundaries were released and contribution to IRF up to max. 0.2% respectively 8%. Depending on the environmental conditions, different release functions were observed. Second relevant release steps occurred in air after ∝ 120 d, indicating the formation of new accessible leaching sites. ESEM investigations were performed to study the impact of leaching on the microstructure. In oxic environment, numerous intragranular open pores acting as new accessible leaching sites were formed and white spherical spots containing Mo and Zr were identified. Under anoxic/reducing conditions numerous metallic precipitates (Mo, Tc and Ru) filling the intragranular pores and white spherical spots containing Mo and Zr, were detected. In conclusion, leaching in different geochemical environments influenced the speciation of radionuclides and in consequence the stability of neoformed phases, which has an impact on IRF.

Release of segregated nuclides from spent fuel

Energy Technology Data Exchange (ETDEWEB)

Johnson, L.H.; Tait, J.C. [Atomic Energy Canada Ltd., Pinawa, MB (Canada). Whiteshell Laboratories

1997-10-01

The potential release of fission and activation products from spent nuclear fuel into groundwater after container failure in the Swedish deep repository is discussed. Data from studies of fission gas release from representative Swedish BWR fuel are used to estimate the average fission gas release for the spent fuel population. Information from a variety of leaching studies on LWR and CANDU fuel are then reviewed as a basis for estimating the fraction of the inventory of key radionuclides that could be released preferentially (the Instant Release Fraction of IRF) upon failure of the fuel cladding. The uncertainties associated with these estimates are discussed. 33 refs, 6 figs, 3 tabs.

Modeling of facade leaching in urban catchments

Science.gov (United States)

Coutu, S.; Del Giudice, D.; Rossi, L.; Barry, D. A.

2012-12-01

Building facades are protected from microbial attack by incorporation of biocides within them. Flow over facades leaches these biocides and transports them to the urban environment. A parsimonious water quantity/quality model applicable for engineered urban watersheds was developed to compute biocide release from facades and their transport at the urban basin scale. The model couples two lumped submodels applicable at the basin scale, and a local model of biocide leaching at the facade scale. For the facade leaching, an existing model applicable at the individual wall scale was utilized. The two lumped models describe urban hydrodynamics and leachate transport. The integrated model allows prediction of biocide concentrations in urban rivers. It was applied to a 15 km2urban hydrosystem in western Switzerland, the Vuachère river basin, to study three facade biocides (terbutryn, carbendazim, diuron). The water quality simulated by the model matched well most of the pollutographs at the outlet of the Vuachère watershed. The model was then used to estimate possible ecotoxicological impacts of facade leachates. To this end, exceedance probabilities and cumulative pollutant loads from the catchment were estimated. Results showed that the considered biocides rarely exceeded the relevant predicted no-effect concentrations for the riverine system. Despite the heterogeneities and complexity of (engineered) urban catchments, the model application demonstrated that a computationally "light" model can be employed to simulate the hydrograph and pollutograph response within them. It thus allows catchment-scale assessment of the potential ecotoxicological impact of biocides on receiving waters.

Statistical tests applied as quality control measures to leaching of nuclear waste glasses and in the evaluation of the leach vessel

International Nuclear Information System (INIS)

Bokelund, H.; Deelstra, K.

1988-01-01

Simple statistical tests, such as regression analysis and analysis of variance, have been applied to data obtained from leaching experiments carried out under various conditions of time and temperature. The precision and the accuracy of the overall leaching procedure were evaluated considering the short term within laboratory effects. The data originated from determinations of the mass losses of leached glass specimens and from measurements of the electrical conductivity and the pH of the leachants. The solution conductivity correlates highly with the normalized mass loss; hence it provides a consistency check on the measurements of the latter parameter. The overall relative precision of the leaching test method was found to be 5-12%, including the effects caused by inhomogeneity of the glass specimens. The conditions for the application of the teflon inserts often used in leaching devices have been investigated; a modified cleaning procedure is proposed to ascertain the absence of systematic errors by their repeated utilization (quality control). The operational limit of 190 0 C, as specified by the Materials Characterization Center, Richland, USA was confirmed experimentally. 8 refs.; 1 figure; 8 tabs

Bottle roll leach test for Temrezli uranium ore

International Nuclear Information System (INIS)

Çetin, K.; Bayrak, M.; Turan, A. İsbir; Üçgül, E.

2014-01-01

The bottle roll leach test is one of the dynamic leaching procedure which can meet in-situ mining needs for determining suitable working conditions and helps to simulate one of the important parameter; injection well design. In this test, the most important parameters are pulp density, acidic or basic concentration of leach solution, time and temperature. In recent years, bottle roll test is used not only for uranium but also gold, silver, copper and nickel metals where in situ leach (ISL) mining is going to be applied. For this purpose for gold and silver metal cyanide bottle roll tests and for uranium metal; acidic and basic bottle roll tests could be applied. The new leach test procedure which is held in General Directorate of Mineral Research and Exploration (MTA) of Turkey is mostly suitable for determining metal extraction conditions and recovery values in uranium containing ore bodies. The tests were conducted with samples taken from Temrezli Uranium Ore located in approximately 200 km east of Turkey’s capital, Ankara. Mining rights of Temrezli Ore is controlled 100% by Anatolia Energy Ltd. The resource estimate includes an indicated mineral resource of 10.827 Mlbs U_3O_8 [~4160 t U] at an average grade of 1426 ppm [~1210 ppm U] and an additional inferred resource of 6.587 Mlbs of U_3O_8 [~2530 t U] at an average grade of 904 ppm [~767 ppm U]. In accordance with the demand from Anatolia Energy bottle roll leach tests have been initiated in MTA laboratories to investigate the recovery values of low-grade uranium ore under in-situ leach conditions. Bottle roll leaching tests are performed on pulverized samples with representative lixiviant solution at ambient pressure and provide an initial evaluation of ore leachability with a rough estimate of recovery value. At the end of the tests by using 2 g/L NaHCO_3 and 0.2 g/L H_2O_2 more than 90% of uranium can pass into leach solution in 12 days. (author)

Defining Effective Salt Leaching Regions Between Drains

OpenAIRE

ANAPALI, Ömer; ŞAHİN, Üstün; ÖZTAŞ, Taşkın; HANAY, Abdurrahman

2014-01-01

The application of sufficient amounts of leaching water by means of an effective method is very important in the management and reclamation of saline and sodic soils. Reclamation cannot be achieved with insufficient leaching water application, while excess water application may cause severe problems in soil. Knowledge of the leaching regions and intensities may help to control the amounts of leaching water through effective leaching methods in areas of limited leaching. This study was und...

Leaching From Biomass Gasification Residues

DEFF Research Database (Denmark)

Allegrini, Elisa; Boldrin, Alessio; Polletini, A.

2011-01-01

The aim of the present work is to attain an overall characterization of solid residues from biomass gasification. Besides the determination of chemical and physical properties, the work was focused on the study of leaching behaviour. Compliance and pH-dependence leaching tests coupled with geoche......The aim of the present work is to attain an overall characterization of solid residues from biomass gasification. Besides the determination of chemical and physical properties, the work was focused on the study of leaching behaviour. Compliance and pH-dependence leaching tests coupled...

Measurement of leach rates: a review

International Nuclear Information System (INIS)

Mendel, J.E.

1982-01-01

A historical perspective of the techniques that can be used to measure the leach rate of radioactive waste forms is presented. The achievement of leach rates that are as low as possible has been an important goal ever since the development of solidification processes for liquid radioactive wastes began in the 1950's. Leach tests can be divided into two major categories, dynamic and static, based on whether or not the leachant in contact with the test specimen is changed during the course of the test. Both types of tests have been used extensively. The results of leach tests can be used to compare waste forms, and that has been a major purpose of leach data heretofore; increasingly, however, the data now are needed for predicting long-term leaching behavior during geologic disposal. This requirement is introducing new complexities into leach testing methodology. 3 figures, 2 tables

Statistical Evaluation and Optimization of Factors Affecting the Leaching Performance of Copper Flotation Waste

OpenAIRE

Çoruh, Semra; Elevli, Sermin; Geyikçi, Feza

2012-01-01

Copper flotation waste is an industrial by-product material produced from the process of manufacturing copper. The main concern with respect to landfilling of copper flotation waste is the release of elements (e.g., salts and heavy metals) when in contact with water, that is, leaching. Copper flotation waste generally contains a significant amount of Cu together with trace elements of other toxic metals, such as Zn, Co, and Pb. The release of heavy metals into the environment has resulted in ...

Predicting Mineral N Release during Decomposition of Organic Wastes in Soil by Use of the SOILNNO Model

International Nuclear Information System (INIS)

Sogn, T.A.; Haugen, L.E.

2011-01-01

In order to predict the mineral N release associated with the use of organic waste as fertilizer in agricultural plant production, the adequacy of the SOILN N O model has been evaluated. The original thought was that the model calibrated to data from simple incubation experiments could predict the mineral N release from organic waste products used as N fertilizer on agricultural land. First, the model was calibrated to mineral N data achieved in a laboratory experiment where different organic wastes were added to soil and incubated at 15 degree C for 8 weeks. Secondly, the calibrated model was tested by use of NO 3 -leaching data from soil columns with barley growing in 4 different soil types, added organic waste and exposed to natural climatic conditions during three growing seasons. The SOILN N O model reproduced relatively well the NO 3 -leaching from some of the soils included in the outdoor experiment, but failed to reproduce others. Use of the calibrated model often induced underestimation of the observed NO 3 -leaching. To achieve a satisfactory simulation of the NO 3 -leaching, recalibration of the model had to be carried out. Thus, SOILN N O calibrated to data from simple incubation experiments in the laboratory could not directly be used as a tool to predict the N-leaching following organic waste application in more natural agronomic plant production systems. The results emphasised the need for site- and system-specific data for model calibration before using a model for predictive purposes related to fertilizer N value of organic wastes applied to agricultural land.

Effects of manganese oxide on arsenic reduction and leaching from contaminated floodplain soil

DEFF Research Database (Denmark)

Ehlert, Katrin; Mikutta, Christian; Kretzschmar, Ruben

2016-01-01

Reductive release of the potentially toxic metalloid As from Fe(III) (oxyhydr)oxides has been identified as an important process leading to elevated As porewater concentrations in soils and sediments. Despite the ubiquitous presence of Mn oxides in soils and their oxidizing power toward As.......7) on As speciation and release from an As-contaminated floodplain soil (214 mg As/kg) under anoxic conditions. Our results show that birnessite additions significantly decreased As leaching. The reduction of both As and Fe was delayed, and As(III) accumulated in birnessite-rich column parts, indicating...

Mechanisms of leaching and corrosions of vitrified radioactive waste forms

International Nuclear Information System (INIS)

Lanza, F.; Conradt, R.; Hall, A.R.; Malow, G.; Trocellier, P.; Van Iseghem, P.

1985-01-01

The estimation of the risk connected with the storage of radioactive waste in geological formations asks for reliable extrapolation of the data for leaching and corrosion of glasses to very long times. As a consequence the knowledge of the physico-chemical mechanisms which dominate the leaching phenomena can be very useful. In the corrosion due to aqueous solution three main mechanisms can be identified: ion exchange, matrix dissolution and formation of a surface layer. The work performed in the different laboratories has allowed to evaluate the relative importance of the various mechanism. The alkali ion exchange does not seems to be predominant in defining the release of the various elements, the matrix dissolution being the most important. The surface composition is important as the compounds present could dominate the matrix dissolution kinetic. Besides the surface layer could form an impervious layer, which, if stable in time, could protect effectively the glass

PEP Run Report for Integrated Test A, Caustic Leaching in UFP-VSL-T01A, Oxidative Leaching in UFP-VSL-T02A

Energy Technology Data Exchange (ETDEWEB)

Guzman-Leong, Consuelo E.; Bredt, Ofelia P.; Burns, Carolyn A.; Daniel, Richard C.; Su, Yin-Fong; Geeting, John GH; Golovich, Elizabeth C.; Josephson, Gary B.; Kurath, Dean E.; Sevigny, Gary J.; Smith, Dennese M.; Valdez, Patrick LJ; Yokuda, Satoru T.; Young, Joan K.

2009-12-04

Pacific Northwest National Laboratory (PNNL) was tasked by Bechtel National Inc. (BNI) on the River Protection Project-Hanford Tank Waste Treatment and Immobilization Plant (RPP-WTP) project to perform research and development activities to resolve technical issues identified for the Pretreatment Facility (PTF). The Pretreatment Engineering Platform (PEP) was designed and constructed and operated as part of a plan to respond to issue M12, “Undemonstrated Leaching Processes.”(a) The PEP, located in the Process Engineering Laboratory-West (PDLW) located in Richland, Washington, is a 1/4.5-scale test platform designed to simulate the WTP pretreatment caustic leaching, oxidative leaching, ultrafiltration solids concentration, and slurry washing processes. The PEP replicates the WTP leaching processes using prototypic equipment and control strategies. The PEP also includes non-prototypic ancillary equipment to support the core processing.

XPS and ion beam scattering studies of leaching in simulated waste glass containing uranium

International Nuclear Information System (INIS)

Karim, D.P.; Pronko, P.P.; Marcuso, T.L.M.; Lam, D.J.; Paulikas, A.P.

1980-01-01

Glass samples (consisting of 2 mole % UO 3 dissolved in a number of complex borosilicate simulated waste glasses including Battelle 76-68) were leached for varying times in distilled water at 75 0 C. The glass surfaces were examined before and after leaching using x-ray photoemission spectroscopy and back-scattered ion beam profiling. Leached samples showed enhanced surface layer concentrations of several elements including uranium, titanium, zinc, iron and rare earths. An experiment involving the leaching of two glasses in the same vessel showed that the uranium surface enhancement is probably not due to redeposition from solution

Pesticide leaching through sandy and loamy fields e Long-term lessons learnt from the Danish Pesticide Leaching Assessment Programme

DEFF Research Database (Denmark)

Rosenbom, Annette Elisabeth; Olsen, Preben; Plauborg, Finn

2015-01-01

The European Union authorization procedure for pesticides includes assessment of the leaching risk posed by pesticides and their degradation products aimed at avoiding any unacceptable influence on the environment, in particular contamination of water, including drinking water and groundwater...

Effect of weathering on chromated copper arsenate (CCA) treated wood : leaching of metal salts and change in water repellency

Science.gov (United States)

R. Sam Williams; Stan Lebow; Patricia Lebow

2003-01-01

Wood pressure-treated with chromated copper arsenate (CCA) wood preservative is commonly used for outdoor construction. Oxides of arsenic, copper, and chromium are bound in the wood by a complex series of chemical reactions, but a small percentage of these compounds are gradually released by leaching and weathering. Recent studies suggest that the release of these...

The Danish Pesticide Leaching Assessment Programme

DEFF Research Database (Denmark)

Rosenbom, Annette Elisabeth; Brüsch, Walter Michael; Juhler, Rene K.

In 1998, the Danish Parliament initiated the Pesticide Leaching Assessment Programme (PLAP), an intensive monitoring programme aimed at evaluating the leaching risk of pesticides under field conditions. The objective of the PLAP is to improve the scientific foundation for decision......-making in the Danish regulation of pesticides. The specific aim is to analyse whether pesticides applied in accordance with current regulations leach to groundwater in unacceptable concentrations. The programme currently evaluates the leaching risk of 41 pesticides and 40 degradation products at five agricultural......, thiamethoxam, tribenuronmethyl, and triasulfuron) did not leach during the 1999-2009 monitoring period. 13 of the applied pesticides exhibited pronounced leaching of the pesticide and/or their degradation product(-s) 1 m b.g.s. in yearly average concentrations exceeding 0.1 μg/l (maximum allowable...

Application of percolation leaching in Fuzhou uranium mine

International Nuclear Information System (INIS)

Jiang Lang; Wang Haita; He Jiangming

2006-01-01

In order to solve these problems such as high cost by conventional agitation leaching, low permeability and low leaching rate by heap leach, a percolation leaching method was developed. Two-year's production results show that leaching rate of uranium is up to 90% by this method. Compared with conventional agitation leaching, the power, sulfuric acid and lime consumption by the percolation leaching decreased by 60%, 27% and 77% respectively. (authors)

Development of a computerized data base for low-level waste leaching data

International Nuclear Information System (INIS)

Dougherty, D.R.; Colombo, P.

1987-01-01

A computerized data base (db) of low-level waste (LLW) leaching data is being compiled by Brookhaven National Laboratory under contract to the DOE Low-Level Waste Management Program. Although this db is being compiled as part of an effort to develop accelerated leach test procedures for LLW forms, other involved in LLW management may find it useful. The db is implemented on an IBM PC XT and is self-contained in that its data manipulation and analysis programs are not proprietary (i.e., need not be purchased). The db includes data from the Accelerated Leach Test(s) Program plus selected literature data, which have been selected based on criteria that include completeness of the experimental description and elucidation of leaching mechanisms. 6 references, 5 figures, 3 tables

Effect of different glass and zeolite A compositions on the leach resistance of ceramic waste forms

International Nuclear Information System (INIS)

Lewis, M.A.; Hash, M.; Glandorf, D.

1996-01-01

A ceramic waste form is being developed for waste generated during electrometallurgical treatment of spent nuclear fuel. The waste is generated when fission products are removed from the electrolyte, LiCl-KCl eutectic. The waste form is a composite fabricated by hot isostatic pressing a mixture of glass frit and zeolite occluded with fission products and salt. Normalized release rate is less than 1 g/m 2 d for all elements in MCC-1 leach test run for 28 days in deionized water at 90 C. This leach resistance is comparable to that of early Savannah River glasses. We are investigating how leach resistance is affected by changes in cationic form of zeolite and in glass composition. Composites were made with 3 forms of zeolite A and 6 glasses. We used 3-day ASTM C1220-92 (formerly MCC-1) leach tests to screen samples for development purposes only. The leach test results show that the glass composites of zeolites 5A and 4A retain fission products equally well. Loss of Cs is small (0.1-0.5 wt%), while the loss of divalent and trivalent fission products is one or more orders of magnitude smaller. Composites of 5A retain chloride ion better in these short-term screens than 4A and 3A. The more leach resistant composites were made with durable glasses rich in silica and poor in alkaline earth oxides. XRD show that a salt phase was absent in the leach resistant composites of 5A and the better glasses but was present in the other composites with poorer leach performance. Thus, absence of salt phase corresponds to improved leach resistance. Interactions between zeolite and glass depend on composition of both

Mechanisms of iodine release from iodoapatite in aqueous solution

Science.gov (United States)

Zhang, Z.; Wang, J.

2017-12-01

Immobilization of iodine-129 with waste forms in geological setting is challenging due to its extremely long half-life and high volatility in the environment. To evaluate the long-term performance of waste form, it is imperative to determine the release mechanism of iodine hosted in the waste form materials. This study investigated the iodine released from apatite structured waste form Pb9.85 (VO4)6 I1.7 to understand how diffusion and dissolution control the durability of apatite waste form. A standard semi-dynamic leach test was adopted in this study. Samples were exposed in fresh leachant periodically and the leachant was replaced after each interval. Each experiment was carried out in cap-sealed Teflon vessels under constant temperature (e.g. 90 °C). ICP-MS analysis on the reacted leachates shows that Pb and V were released constantly and congruently with the stoichiometric ratio of Pb/V. However, iodine release is incongruent and time dependent. The iodine release rate starts significantly higher than the corresponding stoichiometric value and gradually decreases, approaching the stoichiometric value. Therefore, a dual-mode mechanism is proposed to account for the iodine release from apatite, which is dominated by short-term diffusion and long-term dissolution processes. Additional tests show that the element release rates depend on a number of test parameters, including sample surface to solution volume ratio (m-1), interval (day), temperature (°C), and solution pH. This study provides a quantitative characterization of iodine release mechanism. The activation energy of iodine leaching 21±1.6 kJ/mol was obtained by varying the test temperature. At the test conditions of to neutral pH and 90 °C, the long-term iodine release rate 3.3 mg/(m2 • day) is projected by normalizing sample surface area to solution volume ratio (S/V) to 1.0 m-1 and interval to 1 day. These findings demonstrate i) the feasibility of our approach to quantify the release mechanism

Leaching of heavy metals from steelmaking slags

Directory of Open Access Journals (Sweden)

Gomes, J. F. P

2006-12-01

Full Text Available Leaching tests with EAF and Ladle slags were performed, using a flow through test and the standard batch test DIN 38414-S4. The previous method was used to simulate the leaching behaviour of steel slags under landfill. The chemical analysis of the leachates during this period shows, in general, for both types of slag, an increase of heavy metal releases with ageing. Standard test method DIN 38414-S4 was used to evaluate leachability of heavy metals by water in unprocessed slags. After more than one year of trials, slag samples submitted to these trials presented very low total leaching levels. The most extracted elements are calcium and magnesium. Nevertheless, in flow-through test, calcium and magnesium leached from solid slags are below 0.5% and all other metals below 0.1%. Leachates obtained with DIN 38414-S4 present, as expected, higher leaching values; however, these are inferior to 5 % (Ca and 1% (other elements.

Este articulo contiene los resultados obtenidos en ensayos de lixiviación de escorias de acero (horno electrico y cuchara ejecutados siguiendo la metodologia de flujo dinámico así como el ensayo normalizado DIN 38414-S4. El primer ensayo intenta simular el comportamiento de lixiviación de las escorias en vertedero. Para las escorias ensayadas se han complementado los ensayos con el análisis químico de los lixiviados y se ha verificado un aumento de la liberación de metales pesados. El ensayo DIN 38414-S4 se ha utilizado para evaluar la lixiviación por agua de metales pesados, en muestras de escorias originales. Despues de un año de ensayos, se han observado niveles muy bajos de lixiviación. Los elementos mas lixiviados han sido calcio y magnesio. No obstante, en los ensayos de flujo dinámico, el calcio y el magnesio lixiviados de las escorias sólidas era menor de 0,5% y el resto de los otros metales era inferior a 0,1%. Los lixiviados obtenidos con el ensayo DIN 38414-S4 presentan, como era de esperar, valores

Sustainable Soil Washing: Shredded Card Filtration of Potentially Toxic Elements after Leaching from Soil Using Organic Acid Solutions.

Directory of Open Access Journals (Sweden)

Christopher Ash

Full Text Available Shredded card (SC was assessed for use as a sorbent of potentially toxic elements (PTE carried from contaminated soil in various leachates (oxalic acid, formic acid, CaCl2, water. We further assessed SC for retention of PTE, using acidified water (pH 3.4. Vertical columns and a peristaltic pump were used to leach PTE from soils (O and A/B horizons before passing through SC. Sorption onto SC was studied by comparing leachates, and by monitoring total PTE contents on SC before and after leaching. SC buffers against acidic soil conditions that promote metals solubility; considerable increases in solution pH (+4.49 were observed. Greatest differences in solution PTE content after leaching with/without SC occurred for Pb. In oxalic acid, As, Cd, Pb showed a high level of sorption (25, 15, and 58x more of the respective PTE in leachates without SC. In formic acid, Pb sorption was highly efficient (219x more Pb in leachate without SC. In water, only Pb showed high sorption (191x more Pb in leachate without SC. In desorption experiments, release of PTE from SC varied according to the source of PTE (organic/mineral soil, and type of solvent used. Arsenic was the PTE most readily leached in desorption experiments. Low As sorption from water was followed by fast release (70% As released from SC. A high rate of Cd sorption from organic acid solutions was followed by strong retention (~12% Cd desorption. SC also retained Pb after sorption from water, with subsequent losses of ≤8.5% of total bound Pb. The proposed use of this material is for the filtration of PTE from extract solution following soil washing. Low-molecular-mass organic acids offer a less destructive, biodegradable alternative to strong inorganic acids for soil washing.

Sustainable Soil Washing: Shredded Card Filtration of Potentially Toxic Elements after Leaching from Soil Using Organic Acid Solutions

Science.gov (United States)

Ash, Christopher; Drábek, Ondřej; Tejnecký, Václav; Jehlička, Jan; Michon, Ninon; Borůvka, Luboš

2016-01-01

Shredded card (SC) was assessed for use as a sorbent of potentially toxic elements (PTE) carried from contaminated soil in various leachates (oxalic acid, formic acid, CaCl2, water). We further assessed SC for retention of PTE, using acidified water (pH 3.4). Vertical columns and a peristaltic pump were used to leach PTE from soils (O and A/B horizons) before passing through SC. Sorption onto SC was studied by comparing leachates, and by monitoring total PTE contents on SC before and after leaching. SC buffers against acidic soil conditions that promote metals solubility; considerable increases in solution pH (+4.49) were observed. Greatest differences in solution PTE content after leaching with/without SC occurred for Pb. In oxalic acid, As, Cd, Pb showed a high level of sorption (25, 15, and 58x more of the respective PTE in leachates without SC). In formic acid, Pb sorption was highly efficient (219x more Pb in leachate without SC). In water, only Pb showed high sorption (191x more Pb in leachate without SC). In desorption experiments, release of PTE from SC varied according to the source of PTE (organic/mineral soil), and type of solvent used. Arsenic was the PTE most readily leached in desorption experiments. Low As sorption from water was followed by fast release (70% As released from SC). A high rate of Cd sorption from organic acid solutions was followed by strong retention (~12% Cd desorption). SC also retained Pb after sorption from water, with subsequent losses of ≤8.5% of total bound Pb. The proposed use of this material is for the filtration of PTE from extract solution following soil washing. Low-molecular-mass organic acids offer a less destructive, biodegradable alternative to strong inorganic acids for soil washing. PMID:26900684

Pressure leaching of chalcopyrite concentrate

Science.gov (United States)

Aleksei, Kritskii; Kirill, Karimov; Stanislav, Naboichenko

2018-05-01

The results of chalcopyrite concentrate processing using low-temperature and high-temperature sulfuric acid pressure leaching are presented. A material of the following composition was used, 21.5 Cu, 0.1 Zn, 0.05 Pb, 0.04 Ni, 26.59 S, 24.52 Fe, 16.28 SiO2 (in wt.%). The influence of technological parameters on the degree of copper and iron extraction into the leach solution was studied in the wide range of values. The following conditions were suggested as the optimal for the high-temperature pressure leaching: t = 190 °C, PO2 = 0.5 MPa, CH2SO4 = 15 g/L, L:S = 6:1. At the mentioned parameters, it is possible to extract at least 98% Cu from concentrate into the leaching solution during 100 minutes. The following conditions were suggested as optimal for the low-temperature pressure leaching: t = 105 °C, PO2 = 1.3-1.5 MPa, CH2SO4 = 90 g/L, L:S = 10:1. At the mentioned parameters, it is possible to extract up to 83% Cu from the concentrate into the leach solution during 300-360 minutes.

Selective Leaching of Dissolved Organic Matter From Alpine Permafrost Soils on the Qinghai-Tibetan Plateau

Science.gov (United States)

Wang, Yinghui; Xu, Yunping; Spencer, Robert G. M.; Zito, Phoebe; Kellerman, Anne; Podgorski, David; Xiao, Wenjie; Wei, Dandan; Rashid, Harunur; Yang, Yuanhe

2018-03-01

Ongoing global temperature rise has caused significant thaw and degradation of permafrost soils on the Qinghai-Tibetan Plateau (QTP). Leaching of organic matter from permafrost soils to aquatic systems is highly complex and difficult to reproduce in a laboratory setting. We collected samples from natural seeps of active and permafrost layers in an alpine swamp meadow on the QTP to shed light on the composition of mobilized dissolved organic matter (DOM) by combining optical measurements, ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry, radiocarbon (14C), and solid-state 13C nuclear magnetic resonance spectroscopy. Our results show that even though the active layer soils contain large amounts of proteins and carbohydrates, there is a selective release of aromatic components, whereas in the deep permafrost layer, carbohydrate and protein components are preferentially leached during the thawing process. Given these different chemical characteristics of mobilized DOM, we hypothesize that photomineralization contributes significantly to the loss of DOM that is leached from the seasonally thawed surface layer. However, with continued warming, biodegradation will become more important since biolabile materials such as protein and carbohydrate are preferentially released from deep-layer permafrost soils. This transition in DOM leachate source and associated chemical composition has ramifications for downstream fluvial networks on the QTP particularly in terms of processing of carbon and associated fluxes.

Estimated water requirements for gold heap-leach operations

Science.gov (United States)

Bleiwas, Donald I.

2012-01-01

This report provides a perspective on the amount of water necessary for conventional gold heap-leach operations. Water is required for drilling and dust suppression during mining, for agglomeration and as leachate during ore processing, to support the workforce (requires water in potable form and for sanitation), for minesite reclamation, and to compensate for water lost to evaporation and leakage. Maintaining an adequate water balance is especially critical in areas where surface and groundwater are difficult to acquire because of unfavorable climatic conditions [arid conditions and (or) a high evaporation rate]; where there is competition with other uses, such as for agriculture, industry, and use by municipalities; and where compliance with regulatory requirements may restrict water usage. Estimating the water consumption of heap-leach operations requires an understanding of the heap-leach process itself. The task is fairly complex because, although they all share some common features, each gold heap-leach operation is unique. Also, estimating the water consumption requires a synthesis of several fields of science, including chemistry, ecology, geology, hydrology, and meteorology, as well as consideration of economic factors.

Construction and demolition waste: Comparison of standard up-flow column and down-flow lysimeter leaching tests.

Science.gov (United States)

Butera, Stefania; Hyks, Jiri; Christensen, Thomas H; Astrup, Thomas F

2015-09-01

Five samples of construction and demolition waste (C&DW) were investigated in order to quantify leaching of inorganic elements under percolation conditions according to two different experimental setups: standardised up-flow saturated columns (<4mm particle size) and unsaturated, intermittent down-flow lysimeters (<40mm particle size). While standardised column tests are meant primarily to provide basic information on characteristic leaching properties and mechanisms and not to reproduce field conditions, the lysimeters were intended to mimic the actual leaching conditions when C&DW is used in unbound geotechnical layers. In practice, results from standardised percolation tests are often interpreted as estimations of actual release from solid materials in percolation scenarios. In general, the two tests yielded fairly similar results in terms of cumulative release at liquid-to-solid ratio (L/S) 10l·kgTS; however, significant differences were observed for P, Pb, Ba, Mg and Zn. Further differences emerged in terms of concentration in the early eluates (L/S<5l·kg(-1)TS) for Al, As, Ba, Cd, Cu, DOC, Mg, Mn, Ni, P, Pb, Sb, Se, Si, Zn. Observed differences between tests are likely to be due to differences in pH related to crushing and exposure of fresh particle surfaces, as well as in equilibrium conditions. In the case of C&DW, the standardised column tests, which are more practical, are considered to acceptably describe cumulative releases at L/S 10l·kg(-1)TS in percolation scenarios. However, when the focus is on estimation of initial concentrations for (for example) risk assessment, data from standardised column tests may not be fully applicable, and data from lysimeters may be used for validation purposes. Se, Cr and, to a lesser extent, SO4 and Sb were leaching from C&DW in critical amounts compared with existing limit values. Copyright © 2015 Elsevier Ltd. All rights reserved.

A study on dissolution and leaching behaviour of spent nuclear fuels

International Nuclear Information System (INIS)

Lee, Chang Heon; Im, Hee Jung; Kim, Jong Gu; Park, Yang Soon; Ha, Yeong Keong

2010-12-01

This state of the art report describes a leaching behaviour of spent nuclear fuels which should be considered for safety assessment of spent nuclear fuel disposal in a deep geological repository. A decisive factor of a dissolution of UO 2 , a matrix of the fuel, is chemical characters (redox potential, pH, concentration of inorganic anions, water radiolysis subsequent by radiation field of the fuels) of ground water expected to be in contact with the fuels after the container has failed due to corrosion as well as atmosphere condition of a deep geological repository, which can change the oxidation state of UO 2 . The release rates of radionuclides from UO 2 matrix depend largely on their location within the fuels, that is, the radionuclides fixed in the fuel/cladding gap and grain boundaries are rapidly released. However, the radionuclides within the grains of the fuel are slowly released, and then their release rate is governed by a dissolution behaviour of UO 2

Leaching of cadmium and tellurium from cadmium telluride (CdTe) thin-film solar panels under simulated landfill conditions.

Science.gov (United States)

Ramos-Ruiz, Adriana; Wilkening, Jean V; Field, James A; Sierra-Alvarez, Reyes

2017-08-15

A crushed non-encapsulated CdTe thin-film solar cell was subjected to two standardized batch leaching tests (i.e., Toxicity Characteristic Leaching Procedure (TCLP) and California Waste Extraction Test (WET)) and to a continuous-flow column test to assess cadmium (Cd) and tellurium (Te) dissolution under conditions simulating the acidic- and the methanogenic phases of municipal solid waste landfills. Low levels of Cd and Te were solubilized in both batch leaching tests (<8.2% and <3.6% of added Cd and Te, respectively). On the other hand, over the course of 30days, 73% of the Cd and 21% of the Te were released to the synthetic leachate of a continuous-flow column simulating the acidic landfill phase. The dissolved Cd concentration was 3.24-fold higher than the TCLP limit (1mgL -1 ), and 650-fold higher than the maximum contaminant level established by the US-EPA for this metal in drinking water (0.005mgL -1 ). In contrast, the release of Cd and Te to the effluent of the continuous-flow column simulating the methanogenic phase of a landfill was negligible. The remarkable difference in the leaching behavior of CdTe in the columns is related to different aqueous pH and redox conditions promoted by the microbial communities in the columns, and is in agreement with thermodynamic predictions. Copyright © 2017 Elsevier B.V. All rights reserved.

Nitrate leaching in an Andisol treated with different types of fertilizers

International Nuclear Information System (INIS)

Maeda, Morihiro; Zhao Bingzi; Ozaki, Yasuo; Yoneyama, Tadakatsu

2003-01-01

Nitrate leaching in upland fields under Japanese conditions may be reduced by substituting compost or slow-release fertilizer for readily available chemical fertilizer. - Nitrate (NO 3 ) leaching was studied in an Andisol treated with four N fertilizers (SC: swine compost, CU: coated urea, AN: ammonium N, or NF: no fertilizer) for 7 years. Sweet corn (Zea mays L.) was grown in summer, followed by Chinese cabbage (Brassica rapa L. var. amplexicaulis) or cabbage (Brassica oleracea L. var. capitata) in autumn each year. In chemical fertilizer plots treated with AN or CU, NO 3 -N concentrations in soil water at 1-m depth increased markedly in the summer of the second year and fluctuated between 30 and 60 mg l -1 . In the SC plot, NO 3 -N concentration started increasing in the fourth year, reaching the same level as in the AN and CU plots in the late period of the experiment. In the NF plot, NO 3 -N concentration was about 10 mg l -1 for the first 4 years and decreased to 5 mg l -1 . The potential NO 3 -N concentrations by an N and water balance equation satisfactorily predicted NO 3 -N concentration in the AN and CU plots, but substantially overestimated that in the SC plot, presumably because a large portion of N from SC first accumulated in soil in the organic form. Our results indicate that, under the Japanese climate (Asian monsoon), excessive N from chemical fertilizers applied to Andisols can cause substantial NO 3 leaching, while compost application is promising to establish high yields and low N leaching during a few years but would cause the same level of NO 3 leaching as in chemically fertilized plots over longer periods

Product consistency leach tests of Savannah River Site radioactive waste glasses

International Nuclear Information System (INIS)

Bibler, N.E.; Bates, J.K.

1990-01-01

The product consistency test (PCT) is a glass leach test developed at the Savannah River Site (SRS) to confirm the durability of radioactive nuclear waste glasses that will be produced in the Defense Waste Processing Facility. The PCT is a seven day, crushed glass leach test in deionized water at 90C. Final leachates are filtered and acidified prior to analysis. To demonstrate the reproducibility of the PCT when performed remotely, SRS and Argonne National Laboratory have performed the PCT on samples of two radioactive glasses. The tests were also performed to compare the releases of the radionuclides with the major nonradioactive glass components and to determine if radiation from the glass was affecting the results of the PCT. The test was performed in triplicate at each laboratory. For the major soluble elements, B, Li, Na, and Si, in the glass, each investigator obtained relative precisions in the range 2-5% in the triplicate tests. This range indicates good precision for the PCT when performed remotely with master slave manipulators in a shielded cell environment. When the results of the two laboratories were compared to each other, the agreement was within 20%. Normalized concentrations for the nonradioactive and radioactive elements in the PCT leachates measured at both facilities indicated that the radionuclides were released from the glass slower than the major soluble elements in the glass. For both laboratories, the normalized releases for both glasses were in the general order Li ∼ B ∼ Na > Si > Cs - 137 > Sb - 125 < Sr - 90. The normalized releases for the major soluble elements and the final pH values in the tests with radioactive glass are consistent with those for nonradioactive glasses with similar compositions. This indicates that there was no significant effect of radiation on the results of the PCT

Vanadium Extraction from Shale via Sulfuric Acid Baking and Leaching

Science.gov (United States)

Shi, Qihua; Zhang, Yimin; Liu, Tao; Huang, Jing

2018-01-01

Fluorides are widely used to improve vanadium extraction from shale in China. Sulfuric acid baking-leaching (SABL) was investigated as a means of recovering vanadium which does not require the use of fluorides and avoids the productions of harmful fluoride-containing wastewater. Various effective factors were systematically studied and the experimental results showed that 90.1% vanadium could be leached from the shale. On the basis of phase transformations and structural changes after baking the shale, a mechanism of vanadium extraction from shale via SABL was proposed. The mechanism can be described as: (1) sulfuric acid diffusion into particles; (2) the formation of concentrated sulfuric acid media in the particles after water evaporation; (3) hydroxyl groups in the muscovite were removed and transient state [SO4 2-] was generated; and (4) the metals in the muscovite were sulfated by active [SO4 2-] and the vanadium was released. Thermodynamics modeling confirmed this mechanism.

Heap leaching procedure for the Uranium extraction

International Nuclear Information System (INIS)

Shishahbore, M. R.

2002-01-01

Heap leaching of Uranium ores is currently in use in several countries. Before taking any decision for construction of heap in industrial scale, it is necessary to obtain the main factors that influence the heap leaching process, such as acid construction, acid solution flowrate, temperature of reaction, or size, ration of liquid to solid, permeability and suitable oxidant. To achieve the above parameters, small scale column leaching is usually recommended. In this project column leaching were carried out in 6 plexiglass column with 43.5 cm an height and 7.4 cm inner diameter. In each column closely 2.00 kg Uranium ore were leached by sulfuric acid. Leaching operation on Iranian ores from two different anomalies from the same area were investigated. In this project, six column were leached at different flowrate of eluent and effect of oxidant were investigated. Acid consumption were in the range of 60 - 144 kg per ton ore and recovery between 73.07% - 99.97%. Finally according to the results obtained, investigated that over are suitable to heap leaching technique. Al tough, to enforce of heap leaching project need to more experiments

Process for controlling calcium in a leach operation

International Nuclear Information System (INIS)

Habib, E.J.

1982-01-01

A method for controlling calcium, e.g. calcite, build-up in the leach solution of a uranium and/or related values recovery operation wherein the leach solution is flowed through a value bearing ore to dissolve the desired values. A soluble fluoride, e.g. sodium fluoride, is added to the leach solution after it has passed through the ore to thereby precipitate calcium fluoride from the leach solution and lower the calcium content of the leach solution. The soluble fluoride may be added to the leach solution before the leach solution passes through the process equipment which is used to remove the values from the leach solution or the soluble fluoride may be added after the leach solution passes through the process equipment. If added before, it is preferable to also add a carbonate/bicarbonate solution along with the soluble fluoride to prevent coprecipitation of uranyl/desired value fluoride or to redissolve coprecipitated fluoride back into the leach solution

Bacteria heap leaching test of a uranium ore

International Nuclear Information System (INIS)

Liu Hui; Liu Jinhui; Wu Weirong; Han Wei

2008-01-01

Column bioleaching test of a uranium ore was carried out. The optimum acidity, spraying intensity, spray-pause time ratio were determined. The potential, Fe and U concentrations in the leaching process were investigated. The effect of bacteria column leaching was compared with that of acid column leaching. The results show that bacteria column leaching can shorten leaching cycle, and the leaching rate of uranium increases by 9.7%. (authors)

Life cycle assessment and residue leaching: The importance of parameter, scenario and leaching data selection

DEFF Research Database (Denmark)

Allegrini, Elisa; Butera, Stefania; Kosson, D.S.

2015-01-01

of systems and products and can be applied to waste management systems to identify environmental benefits and critical aspects thereof. From an LCA perspective, residue utilisation provides benefits such as avoiding the production and depletion of primary materials, but it can lead to environmental burdens......Residues from industrial processes and waste management systems (WMSs) have been increasingly reutilised, leading to landfilling rate reductions and the optimisation of mineral resource utilisation in society. Life cycle assessment (LCA) is a holistic methodology allowing for the analysis......, due to the potential leaching of toxic substances. In waste LCA studies where residue utilisation is included, leaching has generally been neglected. In this study, municipal solid waste incineration bottom ash (MSWI BA) was used as a case study into three LCA scenarios having different system...

Leaching of hydrophobic Cu and Zn from discarded marine antifouling paint residues: Evidence for transchelation of metal pyrithiones

International Nuclear Information System (INIS)

Holmes, Luke; Turner, Andrew

2009-01-01

Leaching of Cu and Zn from a composite of discarded antifouling paint residues ([Cu] = 288 mg g -1 ; [Zn] = 96 mg g -1 ) into natural sea water has been studied over a period of 75 h. Total Cu and Zn were released according to a pseudo first-order reaction, with rate constants on the order of 0.3 and 2.5 (mg L -1 ) -1 h -1 , respectively, and final concentrations equivalent to the dissolution of about 8 and 2% of respective concentrations in the composite. Time-distributions of hydrophobic metals, determined by solid phase extraction-methanol elution, were more complex. Net release of hydrophobic Cu was greater in the absence of light than under a sequence of light-dark cycles; however, hydrophobic Zn release was not detected under the former conditions but contributed up to 50% of total aqueous Zn when light was present. These observations are interpreted in terms of the relative thermodynamic and photolytic stabilities of biocidal pyrithione complexes. - Hydrophobic Cu and Zn leached from antifouling paint particles into sea water appear to be pyrithione complexes.

Experimental Study and Reactive Transport Modeling of Boric Acid Leaching of Concrete

Directory of Open Access Journals (Sweden)

Chiang K.-T. K.

2013-07-01

Full Text Available Borated water leakage through spent fuel pools (SFPs at pressurized water reactors is a concern because it could cause corrosion of reinforcement steel in the concrete structure, compromise the integrity of the structure, or cause unmonitored releases of contaminated water to the environment. Experimental data indicate that pH is a critical parameter that determines the corrosion susceptibility of rebar in borated water and the degree of concrete degradation by boric acid leaching. In this study, reactive transport modeling of concrete leaching by borated water was performed to provide information on the solution pH in the concrete crack or matrix and the degree of concrete degradation at different locations of an SFP concrete structure exposed to borated water. Simulations up to 100 years were performed using different boric acid concentrations, crack apertures, and solution flow rates. Concrete cylinders were immersed in boric acid solutions for several months and the mineralogical changes and boric acid penetration in the concrete cylinder were evaluated as a function of time. The depths of concrete leaching by boric acid solution derived from the reactive transport simulations were compared with the measured boric acid penetration depth.

Health risk assessments of DEHP released from chemical protective gloves.

Science.gov (United States)

Chao, Keh-Ping; Huang, Chan-Sheng; Wei, Chung-Ying

2015-01-01

The substance di-2-ethylhexyl phthalate (DEHP) is widely used as a plasticizer in chemical protective gloves to improve their flexibility and workability. However, it is possible that workers using protective gloves to handle various solvents may be exposed to DEHP leached by the solvents. Using an ASTM F739 permeation cell, it was found that BTEX solvents permeating through the glove samples dissolved DEHP from the gloves. Even without continuously contacting the permeant, DEHP was released from the contaminated glove samples during the desorption experiments. The DEHP leaching amounts were found to be inversely correlated to the permeability coefficients of BTEX in the glove samples. This result implied that the larger the amount of DEHP released from the glove samples, the higher the permeation resistance of gloves. Although chemical protective gloves provide adequate skin exposure protection to workers, the dermal exposure model developed herein indicates that leaching of DEHP from the glove samples may pose a potential health risk to the workers who handle BTEX. This study suggests that the selection of protective gloves should not only be concerned with the chemical resistance of the gloves but also the health risk associated with leaching of chemicals, such as DEHP, used in the manufacturing of the gloves. Copyright © 2014 Elsevier B.V. All rights reserved.

Comparative characterization of sewage sludge compost and soil: Heavy metal leaching characteristics.

Science.gov (United States)

Fang, Wen; Wei, Yonghong; Liu, Jianguo

2016-06-05

The leaching and accumulation of heavy metals are major concerns following the land application of sewage sludge compost (SSC). We comparatively characterized SSC, the reference soil, and the SSC amended soil to investigate their similarities and differences regarding heavy metal leaching behavior and then to evaluate the effect of SSC land application on the leaching behavior of soil. Results showed that organic matter, including both of particulate organic matter (POM) and dissolved organic matter (DOM), were critical factors influencing heavy metal leaching from both of SSC and the soil. When SSC was applied to soil at the application rate of 48t/ha, the increase of DOM content slightly enhanced heavy metal leaching from the amended soil over the applicable pH domain (6leaching behavior of heavy metals. The geochemical speciation modeling revealed that heavy metal speciation in the solid phase were similar between the reference soil and the amended soil. Copyright © 2016 Elsevier B.V. All rights reserved.

Impact of Leaching Conditions on Constituents Release from Flue Gas Desulfurization Gypsum (FGDG) and FGDG-Soil Mixture

Science.gov (United States)

The interest in using Flue Gas Desulfurization Gypsum(FGDG) has increased recently. This study evaluates the leaching characteristics of trace elements in "modern" FGDG (produced after fly ash removal) and FGDG-mixed soil (SF) under different environmental conditions using rece...

Behaviour Test with the Leaching of a Waste package

International Nuclear Information System (INIS)

Fischer, G.R

1999-01-01

The radioactive wastes are classified, in low, intermediate and high level wastes, according to the characteristics of the radionuclides in, its specific activity and half-life.Those are the three parameters that indicate how long the radioactive waste will be keep confined, in safe conditions before its contaminants go into the environment or before the institutional controls on the final disposal installations are removed.The confinement time can be estimated in ten half-lives, because since that moment its activity has decayed at one thousandth from the original .In low level wastes the confinement periods are nearly fifty years while in intermediate level, the periods can be until three hundreds years.These times are normally controlled by government institutions that are in charge of looking after people about the no-liberation of toxic elements at the environment.Therefore the wastes can be confined in a motionless matrix so that they can be placed in shallow land burials.On the other hand, the high level wastes which confinement times are estimated in ten or so thousand years, must be disposed in deep underground geological repositories.Obviously, there are no state controls for them.There are several matrices or different ways of stabilizing a waste, that will be introduced in this essay.It is also important to take account into the factors that degrade those matrices and speed up the released time of the radionuclides into the environment.There have been analyzed too, the radionuclides transport process that go through the matrix and the factors that affect the aforesaid process.Moreover, the diffusion was studied in a such detailed way, assuming that it is the most important mass transport process, in agreement with other studies made before.The leach rates and the diffusion coefficients have been calculated and determinated by means of measurements in a full scale leaching test.Those coefficients were compared with small-scale laboratory and

Statistical comparison of leaching behavior of incineration bottom ash using seawater and deionized water: Significant findings based on several leaching methods.

Science.gov (United States)

Yin, Ke; Dou, Xiaomin; Ren, Fei; Chan, Wei-Ping; Chang, Victor Wei-Chung

2018-02-15

Bottom ashes generated from municipal solid waste incineration have gained increasing popularity as alternative construction materials, however, they contains elevated heavy metals posing a challenge for its free usage. Different leaching methods are developed to quantify leaching potential of incineration bottom ashes meanwhile guide its environmentally friendly application. Yet, there are diverse IBA applications while the in situ environment is always complicated, challenging its legislation. In this study, leaching tests were conveyed using batch and column leaching methods with seawater as opposed to deionized water, to unveil the metal leaching potential of IBA subjected to salty environment, which is commonly encountered when using IBA in land reclamation yet not well understood. Statistical analysis for different leaching methods suggested disparate performance between seawater and deionized water primarily ascribed to ionic strength. Impacts of leachant are metal-specific dependent on leaching methods and have a function of intrinsic characteristics of incineration bottom ashes. Leaching performances were further compared on additional perspectives, e.g. leaching approach and liquid to solid ratio, indicating sophisticated leaching potentials dominated by combined geochemistry. It is necessary to develop application-oriented leaching methods with corresponding leaching criteria to preclude discriminations between different applications, e.g., terrestrial applications vs. land reclamation. Copyright © 2017 Elsevier B.V. All rights reserved.

Equilibrium leaching of toxic elements from cement stabilized soil.

Science.gov (United States)

Voglar, Grega E; Leštan, Domen

2013-02-15

The toxicity characteristics leaching procedure (TCLP) is commonly used to assess the efficiency of solidification/stabilization (S/S) of pollutants in wastes, despite recent objections to this method. In this study, formulations of 7, 10, 15 and 20% (w/w) of calcium aluminate cement (CAC) and sulfate resistant Portland cement (SRC) were used for S/S of soil from brownfield contaminated with 43,149, 10,115, 7631, 6130, 90, 82 mg kg(-1) of Zn, Pb, Cu, As, Cd and Ni, respectively. CAC produced S/S soil monoliths of higher mechanical strength (up to 7.65 N mm(-2)). Mass-transfer analysis indicated surface wash-off as a mechanism of toxic elements release, and equilibrium leaching as a crucial parameter of S/S efficiency assessment. In the expected range of field soil pH after S/S (pH 7-9), the TCLP gave markedly different results than the multi-point pH equilibrium leaching method (using nine targeted pH values): up to 2953-, 94-, 483-, 1.3-, 27- and 1.5-times more Zn, Pb, Cu, As, Cd and Ni, respectively, was determined in the TCLP leachate. S/S with CAC reduced leachability of toxic elements more effectively than SRC. Our results indicate that, under given field conditions, the TCLP significantly underrates the efficiency of S/S of contaminated soil with cementitious binders. Copyright © 2012 Elsevier B.V. All rights reserved.

Gold Leaching Characteristics and Intensification of a High S and As-Bearing Gold Concentrate

Science.gov (United States)

Yang, Yong-bin; Liu, Xiao-liang; Jiang, Tao; Li, Qian; Xu, Bin; Zhang, Yan

Some high sulfur and arsenic-bearing gold concentrate has a gold leaching rate less than 80% by oxidation roasting-pickling-cyanidation process. The characteristics and intensification of gold leaching were studied systemically. By combining chemical composition and phase analysis, the low gold leaching rate was found to lie in the capsulation of gold by iron-containing phases including iron oxides, arsenopyrite and pyrite. 96.66% of gold in the industrial leaching residue was capsulated and 95.88% of the capsulated turned out to be in the iron-containing phases. The results of laboratory pickling-cyanidation experiments on the calcine and industrial leaching residue presented further demonstration for the fact that gold capsulated in the iron-containing phases was hard to be leached. However, the gold cyanide leaching rate of calcine could be raised over 95% by a reduction roasting-pickling pretreatment which played such a significant role in exposing the capsulated gold that gold leaching was intensified remarkably.

Contaminant Leach Testing of Hanford Tank 241-C-104 Residual Waste

Energy Technology Data Exchange (ETDEWEB)

Cantrell, Kirk J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Snyder, Michelle M.V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wang, Guohui [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Buck, Edgar C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2015-07-01

Leach testing of Tank C-104 residual waste was completed using batch and column experiments. Tank C-104 residual waste contains exceptionally high concentrations of uranium (i.e., as high as 115 mg/g or 11.5 wt.%). This study was conducted to provide data to develop contaminant release models for Tank C-104 residual waste and Tank C-104 residual waste that has been treated with lime to transform uranium in the waste to a highly insoluble calcium uranate (CaUO4) or similar phase. Three column leaching cases were investigated. In the first case, C-104 residual waste was leached with deionized water. In the second case, crushed grout was added to the column so that deionized water contacted the grout prior to contacting the waste. In the third case, lime was mixed in with the grout. Results of the column experiments demonstrate that addition of lime dramatically reduces the leachability of uranium from Tank C-104 residual waste. Initial indications suggest that CaUO4 or a similar highly insoluble calcium rich uranium phase forms as a result of the lime addition. Additional work is needed to definitively identify the uranium phases that occur in the as received waste and the waste after the lime treatment.

Speciation of heavy metals in garden soils. Evidences from selective and sequential chemical leaching

Energy Technology Data Exchange (ETDEWEB)

Cheng, Zhongqi; Lee, Leda; Dayan, Sara; Grinshtein, Michael [Brooklyn College of The City Univ. of New York, Brooklyn, NY (United States). Environmental Sciences Analytical Cnter; Shaw, Richard [USDA-NRCS NYC Soil Survey, Staten Island, NY (United States)

2011-06-15

Purpose: Gardening (especially food growing) in urban areas is becoming popular, but urban soils are often very contaminated for historical reasons. There is lack of sufficient information as to the bioavailability of soil heavy metals to plants and human in urban environments. This study examines the relative leachability of Cr, Ni, As, Cd, Zn, and Pb for soils with varying characteristics. The speciation and mobility of these metals can be qualitatively inferred from the leaching experiments. The goal is to use the data to shed some light on their bioavailability to plant and human, as well as the basis for soil remediation. Materials and methods: Selective and sequential chemical leaching methods were both used to evaluate the speciation of Cr, Ni, As, Cd, Zn, and Pb in soil samples collected from New York City residential and community gardens. The sequential leaching experiment followed a standard BCR four-step procedure, while selective leaching involved seven different chemical extractants. Results and discussion: The results from selective and sequential leaching methods are consistent. In general, very little of the heavy metals were found in the easily soluble or exchangeable fractions. Larger fractions of Cd and Zn can be leached out than other metals. Lead appears predominantly in the organic or carbonate fractions, of which {proportional_to} 30-60% is in the easily soluble organic fraction. Most As cannot be leached out by any of the extractants used, but it could have been complicated by the ineffective dissolution of oxides by ammonium hydroxylamine. Ni and Cr were mostly in the residual fractions but some released in the oxidizable fractions. Therefore, the leachability of metals follow the order Cd/Zn > Pb > Ni/Cr. Conclusions: Despite of the controversy and inaccuracy surrounding chemical leaching methods for the speciation of metals, chemical leaching data provide important, general, and easy-to-access information on the mobility of heavy metals

Uranium potential of southwestern New Mexico (southern Hidalgo County), including observations on crystallization history of lavas and ash tuffs and the release of uranium from them. Final report

International Nuclear Information System (INIS)

Walton, A.W.; Salter, T.L.; Zetterlund, D.

1980-08-01

Geological environments present in southwestern New Mexico include thick sequences of sedimentary rock including limestone, conglomerates, sandstone, and shale: igneous intrusions with associated metal deposits; caldera centers, margins, and outflow facies; and basins with marginal faults and thick late Cenozoic sedimentary fillings. Predominant rock types are Paleozoic carbonates, Mesozoic terrigeneous rocks and carbonates, and Cenozoic volcanic rocks and basin-filling terrigeneous rocks. Consideration of information available in Preliminary Reconnaissance Reports and in Hydrogeochemical and Stream Reconnaissance Reports together with 347 new whole rock chemical analyses points to three areas of anomalous uranium abundance in Hidalgo County, New Mexico. The area has experienced three major periods of igneous activity in Phanerozoic time: one associated with the Laramide cycle of the Late Cretaceous and early Tertiary, mid-Tertiary cycle of silicic volcanism with abundant calderas, and a late Tertiary cycle of mafic volcanism. Silicic volcanic rocks are the most common exposed rock type in the area, and the most enriched in uranium (range, 0.4 to 19 ppM). The most likely source for any uranium ore-forming solutions lies with this cycle of volcanism. Solutions might have been introduced during volcanism or formed later by groundwater leaching of cooled volcanic rocks. Results indicate that groundwater leaching of cooled volcanic rocks was not an effective means of mobilizing uranium in the area. Study of several rhyolite lava flows indicates that they were emplaced in supercooled condition and may have crystallized completely at temperatures well below their liquids, or they may have warmed as crystallization released latent heat. Statistical comparison of the uranium concentration revealed no differences between vitrophyres and associated felsites

Uranium potential of southwestern New Mexico (southern Hidalgo County), including observations on crystallization history of lavas and ash tuffs and the release of uranium from them. Final report

Energy Technology Data Exchange (ETDEWEB)

Walton, A.W.; Salter, T.L.; Zetterlund, D.

1980-08-01

Geological environments present in southwestern New Mexico include thick sequences of sedimentary rock including limestone, conglomerates, sandstone, and shale: igneous intrusions with associated metal deposits; caldera centers, margins, and outflow facies; and basins with marginal faults and thick late Cenozoic sedimentary fillings. Predominant rock types are Paleozoic carbonates, Mesozoic terrigeneous rocks and carbonates, and Cenozoic volcanic rocks and basin-filling terrigeneous rocks. Consideration of information available in Preliminary Reconnaissance Reports and in Hydrogeochemical and Stream Reconnaissance Reports together with 347 new whole rock chemical analyses points to three areas of anomalous uranium abundance in Hidalgo County, New Mexico. The area has experienced three major periods of igneous activity in Phanerozoic time: one associated with the Laramide cycle of the Late Cretaceous and early Tertiary, mid-Tertiary cycle of silicic volcanism with abundant calderas, and a late Tertiary cycle of mafic volcanism. Silicic volcanic rocks are the most common exposed rock type in the area, and the most enriched in uranium (range, 0.4 to 19 ppM). The most likely source for any uranium ore-forming solutions lies with this cycle of volcanism. Solutions might have been introduced during volcanism or formed later by groundwater leaching of cooled volcanic rocks. Results indicate that groundwater leaching of cooled volcanic rocks was not an effective means of mobilizing uranium in the area. Study of several rhyolite lava flows indicates that they were emplaced in supercooled condition and may have crystallized completely at temperatures well below their liquids, or they may have warmed as crystallization released latent heat. Statistical comparison of the uranium concentration revealed no differences between vitrophyres and associated felsites.

Long-term leaching from MSWI air-pollution-control residues: Leaching characterization and modeling

DEFF Research Database (Denmark)

Hyks, Jiri; Astrup, Thomas; Christensen, Thomas Højlund

2009-01-01

Long-term leaching of Ca, Fe, Mg, K, Na, S, Al, As, Ba, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Zn, Mo, Sb, Si, Sri, Sr, Ti, V, P, Cl, and dissolved organic carbon from two different municipal solid waste incineration (MSWI) air-pollution-control residues was monitored during 24 months of column percolat......Long-term leaching of Ca, Fe, Mg, K, Na, S, Al, As, Ba, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Zn, Mo, Sb, Si, Sri, Sr, Ti, V, P, Cl, and dissolved organic carbon from two different municipal solid waste incineration (MSWI) air-pollution-control residues was monitored during 24 months of column...... percolation experiments; liquid-to-solid (L/S) ratios of 200-250 L/kg corresponding to more than 10,000 years in a conventional landfill were reached. Less than 2% of the initially present As, Cu, Pb, Zn, Cr, and Sb had leached during the Course of the experiments. Concentrations of Cd, Fe, Mg, Hg, Mn, Ni, Co......, Sn, Ti, and P were generally bellow 1 mu g/L; overall less than 1% of their mass leached. Column leaching data were further used in a two-step geochemical modeling in PHREEQC in order to (i) identify solubility controlling minerals and (ii) evaluate their interactions in a water-percolated column...

Composition and leaching of construction and demolition waste: Inorganic elements and organic compounds

DEFF Research Database (Denmark)

Butera, Stefania; Christensen, Thomas Højlund; Astrup, Thomas Fruergaard

2014-01-01

Thirty-three samples of construction and demolition waste collected at 11 recycling facilities in Denmark were characterised in terms of total content and leaching of inorganic elements and presence of the persistent organic pollutants PCBs and PAHs. Samples included (i) "clean" (i.e. unmixed...... for leaching, was observed indicating that the number of analysed samples may be critical in relation to decisions regarding management and utilisation of the materials. Higher leaching of chromium, sulphate and chloride were observed for masonry-containing and partly carbonated samples, indicating that source...... segregation and management practices may be important. Generally, leaching was in compliance with available leaching limits, except for selenium, and in some cases chromium, sulphate and antimony. © 2014 Elsevier B.V....

Certain aspects of leaching kinetics of solidified ''radioactive wastes'' - Laboratory studies

International Nuclear Information System (INIS)

Amarantos, S.G.; Petropoulos, J.H.

1981-01-01

A laboratory study of the kinetics of leaching of Cs + and Sr ++ incorporated as sulphates in cement (Portland type) or base asphalt with distilled water as leachant is reported. The comparison of different leaching methods (including stagnant or stirred leachant with periodic renewal and a new method of ''continuous leachant renewal'') and the study of the effect of temperature were among the particular objectives of this work. The results for the cemented salts indicate that the new method of ''continuous leachant renewal'' is more efficient than the others. Is has been also found that the other leaching methods, including the widely used stagnant, periodically renewed leachant, can be seriously affected in certain circumstances by factors which have hitherto been left uncontrolled. An observed sharp diminution in the elution rate of Sr ++ from cement samples appears to be attributable to the action of atmospheric CO 2 . It has been observed that temperature affects the acceleration in the earlier and later stages of cement-Cs 2 SO 4 leaching. (T.A.)

Pretreatment of Tc-Containing Waste and Its Effect on Tc-99 Leaching From Grouts

International Nuclear Information System (INIS)

Aloy, Albert; Kovarskaya, Elena N.; Harbour, John R.; Langton, Christine A.; Holtzscheiter, E. William

2007-01-01

A salt solution (doped with Tc-99), that simulates the salt waste stream to be processed at the Saltstone Production Facility, was immobilized in grout waste forms with and without (1) ground granulated blast furnace slag and (2) pretreatment with iron salts. The degree of immobilization of Tc-99 was measured through monolithic and crushed grout leaching tests. Although Fe (+2) was shown to be effective in reducing Tc-99 to the +4 state, the strong reducing nature of the blast furnace slag present in the grout formulation dominated the reduction of Tc-99 in the cured grouts. An effective diffusion coefficient of 4.75 x 10 -12 (Leach Index of 11.4) was measured using the ANSI/ANS-16.1 protocol. The leaching results show that, even in the presence of a concentrated salt solution, blast furnace slag can effectively reduce pertechnetate to the immobile +4 oxidation state. The measured diffusivity was introduced into a flow and transport model (PORFLOW) to calculate the release of Tc-99 from a Saltstone Vault as a function of hydraulic conductivity of the matrix. (authors)

Minimizing lead release levels in secondary smelters slags

International Nuclear Information System (INIS)

Shenkler, E.S.; Graham, S.; Ghosh, R.; Greenhut, V.A.

1991-01-01

Five lead-containing slags and four mattes were analyzed to reveal microstructure, semi-quantitative microchemistry, and phases present. To determine if the slags could be incorporated as a glass so that lead release levels could be stabilized, glass batches were formulated based on slag compositions. Leaching tests showed that all materials that were fritted in a glass batch had lower lead release levels than non-adjusted materials, and all could satisfy EPA test requirements. The mole ratio of glass modifiers to glass formers played an important role in the extent of lead release. Small additions of phosphate to a batch had a significant effect on lowering lead release levels

Radionuclide release from PWR spent fuel specimens with induced cladding defects

International Nuclear Information System (INIS)

Wilson, C.N.; Oversby, V.M.

1984-03-01

Radionuclide releases from pressurized water reactor (PWR) spent fuel rod specimens containing various artificially induced cladding defects were compared by leach testing. The study was conducted in support of the Nevada Nuclear Waste Storage Investigations (NNWSI) Waste Package Task to evaluate the effectiveness of failed cladding as a barrier to radionuclide release. Test description and results are presented

Effects of aged sorption on pesticide leaching to groundwater simulated with PEARL

NARCIS (Netherlands)

Boesten, Jos J.T.I.

2017-01-01

Leaching to groundwater is an important element of the regulatory risk assessment of pesticides in western countries. Including aged sorption in this assessment is relevant because there is ample evidence of this process and because it leads to a decrease in simulated leaching. This work assesses

Effects of Pregnant Leach Solution Temperature on the Permeability of Gravelly Drainage Layer of Heap Leaching Structures

Directory of Open Access Journals (Sweden)

mehdi amini

2013-12-01

Full Text Available In copper heap leaching structures, the ore is leached by an acidic solution. After dissolving the ore mineral, the heap is drained off in the acidic solution using a drainage system (consisting of a network of perforated polyethylene pipes and gravelly drainage layers and is, then, transferred to the leaching plant for copper extraction where the copper is extracted and the remaining solution is dripped over the ore heap for re-leaching. In this process, the reaction between the acidic solution and copper oxide ore is exothermal and the pregnant leach solution (PLS, which is drained off the leaching heap, has a higher temperature than the dripped acidic solution. The PLS temperature variations cause some changes in the viscosity and density which affect the gravelly drainage layer's permeability. In this research, a special permeability measuring system was devised for determining the effects of the PLS temperature variations on the permeability coefficient of the gravelly drainage layer of heap leaching structures. The system, consisting of a thermal acid resistant element and a thermocouple, controls the PLS temperature, which helps measure the permeability coefficient of the gravelly drainage layer. The PLS and gravelly drainage layer of Sarcheshmeh copper mine heap leaching structure No. 1 were used in this study. The permeability coefficient of the gravelly soil was measured against the PLS and pure water at temperatures varying between 3°C to 60°C. Also, the viscosity and density of the PLS and pure water were measured at these temperatures and, using existing theoretical relations, the permeability coefficient of the gravel was computed. A comparison between the experimental and theoretical results revealed a good conformity between the two sets of results. Finally, a case (Taft heap leaching structure, Yazd, Iran was studied and its gravelly drainage layer was designed based on the results of the present research.

Uranium extraction history using pressure leaching

International Nuclear Information System (INIS)

Fraser, K.S.; Thomas, K.G.

2010-01-01

Over the past 60 years of uranium process development only a few commercial uranium plants have adopted a pressure leaching process in their flowsheet. The selection of acid versus alkaline pressure leaching is related to the uranium and gangue mineralogy. Tetravalent (U"+"4) uranium has to be oxidized to hexavalent (U"+"6) uranium to be soluble. Refractory tetravalent uranium requires higher temperature and pressure, as practised in pressure leaching, for conversation to soluble hexavalent uranium. This paper chronicles the history of these uranium pressure leaching facilities over the past 60 years, with specific details of each design and operation. (author)

A new Leaching System, Sheta Extractor

International Nuclear Information System (INIS)

Sheta, M.E.

2008-01-01

Moving of crushed solid ores against leaching solution in a continuous countercurrent arises a true technical problem. This invented system introduces a practical solution for such problem. Inside the system, the crushed ore is driving against gravity, whereas the leaching solution moves in the opposite direction. Contact between the two phases occurs with gentle stirring. After contact, discharging of the processed phases takes place automatically out the system. The system was investigated for uranium leaching from a coarse grained fraction (+2 --- -- -30 mm) of uranium mineralized granite sample. Uranium leaching percent reached to nearly 50% using sulfuric acid

Using polymer-coated controlled-release fertilizers in the nursery and after outplanting

Science.gov (United States)

Thomas D. Landis; R. Kasten Dumroese

2009-01-01

Controlled-release fertilizers (CRF) are the newest and most technically advanced way of supplying mineral nutrients to nursery crops. Compared to conventional fertilizers, their gradual pattern of nutrient release better meets plant needs, minimizes leaching, and therefore improves fertilizer use efficiency. In our review of the literature, we found many terms used...

A simple method using on-line continuous leaching and ion exchange chromatography coupled to inductively coupled plasma mass spectrometry for the speciation analysis of bio-accessible arsenic in rice.

Science.gov (United States)

Horner, Nolan S; Beauchemin, Diane

2012-03-02

A simple method for the speciation analysis of bio-accessible arsenic (As) in rice was developed using a continuous on-line leaching method to release the bio-accessible fraction. The continuous on-line leaching method has several advantages over commonly used batch methods including quicker and easier sample preparation, reduced risk of contamination and access to real time leaching data. The bio-accessibility of As in the samples was monitored using inductively coupled plasma mass spectrometry (ICP-MS). Results from a certified reference material as well as cooked and uncooked white rice showed that the majority of As was leached by saliva. Results obtained using the continuous on-line leaching method were comparable to those obtained using a batch method. Speciation analysis of the saliva leachate was performed using ion exchange chromatography coupled to ICP-MS. The four most toxic forms of As (As(III), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and As(V)) were clearly separated within 5 min in a single chromatographic run. Over 92% of bio-accessible As in the certified reference material and uncooked white rice sample was in the form of DMA and As(V), whereas it was present as DMA and As(III) in the cooked white rice. Copyright © 2011 Elsevier B.V. All rights reserved.

Microbial leaching of low grade sandstone uranium ores: column leaching studies

International Nuclear Information System (INIS)

Bhatti, T.M.; Malik, K.A.; Khalid, A.M.

1991-01-01

Microbial leaching studies on a low-grade sandstone uranium ore from Baghalchur Ore Deposits, D. G. Khan, Pakistan, containing 0.027 % U/sub 3/O/sub 8/ for extraction of uranium, were conducted in columns. Baghalchur sandstone uranium ore which is alkaline in nature, contained 5.0% calcite [CaCo/sub 3/], 2-3 % Fe/sub 2/O/sub 3/ and pyrite [FeS/sub 2/] less than 0.1 %. The ore amended with sulfur and/or sulfur slag as external energy source was found to leach with indigenous microflora mostly belonging to the genus Thiobacillus which are present in the uranium mine water. Column leaching studies revealed that when the ore was amended with elemental sulfur and irrigated with mine water (pH 3.5) 53 % U/sub 3/O/sub 8/ could be solubilized from it. However, when the natural mine water was used as such (pH 7.4) the solubilization of uranium was decreased to 41 % U/sub 3/O/sub 8/ in 90 days under similar conditions of percolation rate and temperature. The addition of (NH/sub 4/)/sub 2/SO/sub 4/ (3.0 g/L) in mine water was found to enhance the uranium leaching to 70 % U/sub 3/O/sub 8/ from the columns containing ore amended with sulfur slag. (author)

Leaching behavior of simulated high-level waste glass

International Nuclear Information System (INIS)

Kamizono, Hiroshi

1987-03-01

The author's work in the study on the leaching behavior of simulated high-level waste (HLW) glass were summarized. The subjects described are (1) leach rates at high temperatures, (2) effects of cracks on leach rates, (3) effects of flow rate on leach rates, and (4) an in-situ burial test in natural groundwater. In the following section, the leach rates obtained by various experiments were summarized and discussed. (author)

PRESERVATIVE LEACHING FROM WEATHERED CCA-TREATED WOOD

Science.gov (United States)

Disposal of discarded CCA-treated wood in landfills raises concerns with respect to leaching of preservative compounds. When unweathered CCA-treated wood is leached using the toxicity characteristic leaching procedure (TCLP), arsenic concentrations exceed the toxicity characteris...

Effects of aerobic and anaerobic biological processes on leaching of heavy metals from soil amended with sewage sludge compost.

Science.gov (United States)

Fang, Wen; Wei, Yonghong; Liu, Jianguo; Kosson, David S; van der Sloot, Hans A; Zhang, Peng

2016-12-01

The risk from leaching of heavy metals is a major factor hindering land application of sewage sludge compost (SSC). Understanding the change in heavy metal leaching resulting from soil biological processes provides important information for assessing long-term behavior of heavy metals in the compost amended soil. In this paper, 180days aerobic incubation and 240days anaerobic incubation were conducted to investigate the effects of the aerobic and anaerobic biological processes on heavy metal leaching from soil amended with SSC, combined with chemical speciation modeling. Results showed that leaching concentrations of heavy metals at natural pH were similar before and after biological process. However, the major processes controlling heavy metals were influenced by the decrease of DOC with organic matter mineralization during biological processes. Mineralization of organic matter lowered the contribution of DOC-complexation to Ni and Zn leaching. Besides, the reducing condition produced by biological processes, particularly by the anaerobic biological process, resulted in the loss of sorption sites for As on Fe hydroxide, which increased the potential risk of As release at alkaline pH. Copyright © 2016 Elsevier Ltd. All rights reserved.

Nitrate leaching beneath a containerized nursery crop receiving trickle or overhead irrigation.

Science.gov (United States)

Colangelo, D J; Brand, M H

2001-01-01

Container production of nursery crops is intensive and a potential source of nitrogen release to the environment. This study was conducted to determine if trickle irrigation could be used by container nursery producers as an alternative to standard overhead irrigation to reduce nitrogen release into the environment. The effect of overhead irrigation and trickle irrigation on leachate nitrate N concentration, flow-weighted nitrate N concentration, leachate volume, and plant growth was investigated using containerized rhododendron (Rhododendron catawbiense Michx. 'Album') supplied with a controlled-release fertilizer and grown outdoors on top of soil-monolith lysimeters. Leachate was collected over two growing seasons and overwinter periods, and natural precipitation was allowed as a component of the system. Precipitation accounted for 69% of the water entering the overhead-irrigated system and 80% of the water entering the trickle-irrigated system. Leachate from fertilized plants exceeded the USEPA limit of 10 mg L(-1) at several times and reached a maximum of 26 mg L(-1) with trickle irrigation. Average annual loss of nitrate N in leachate for fertilized treatments was 51.8 and 60.5 kg ha(-1) for the overhead and trickle treatments, respectively. Average annual flow-weighted concentration of nitrate N in leachate of fertilized plants was 7.2 mg L(-1) for overhead irrigation and 12.7 mg L(-1) for trickle irrigation. Trickle irrigation did not reduce the amount of nitrate N leached from nursery containers when compared with overhead irrigation because precipitation nullified the potential benefits of reduced leaching fractions and irrigation inputs provided under trickle irrigation.

Developments of bacteria leaching technologies in uranium and gold ores at home and abroad

International Nuclear Information System (INIS)

Gao Renxi; Guan Zibin; Tian Shengjun

2000-01-01

The present development, including development of new leaching processes and equipment and soon, in bacteria leaching of uranium and gold ores at home and abroad are described. Opinions and advices are presented

Analysis of factors affecting the effect of stope leaching

International Nuclear Information System (INIS)

Xie Wangnan; Dong Chunming

2014-01-01

The industrial test and industrial trial production of stope leaching were carried out at Taoshan orefield of Dabu deposit. The results of test and trial production showed obvious differences in leaching rate and leaching time. Compared with industrial trial production of stope leaching, the leaching rate of industrial test was higher, and leaching time was shorter. It was considered that the blasting method and liquid arrangement were the main factors affecting the leaching rate and leaching time according to analysis. So we put forward the following suggestions: the technique of deep hole slicing tight-face blasting was used to reduce the yield of lump ores, the effective liquid arrangement methods were adopted to make the lixiviant infiltrating throughout whole ore heap, and bacterial leaching was introduced. (authors)

Long-term leaching behavior of vitrified high-level wastes

International Nuclear Information System (INIS)

Ishiguro, Katsuhiko; Sonobe, Hitoshi; Sasaki, Noriaki; Kashihara, Hidechiyo

1985-01-01

A long-term Soxhlet leaching test, long-term static leaching test, solubility evaluation test and actual-scale glass solid leaching test were carried out for simulated vitrified wastes. Under high flow-rate leachate conditions, the leaching of high-solubility substances such as B and Na increases almost linearly with time while that of Fe, Ni and rare earth metals strongly depends on their solubility. The overall leaching rate changes (tends to decrease) with time under static conditions. The elution or diffusion is the rate determining step in the earlier region of the leaching process while the solubilities of major components have greater effects in the latter region. The change of the dominant leaching mechanism is delayed more largely as the surface-area to leachate-volume (SA/V) ratio decreases. Actual-scale glass specimens showed almost the same leaching behaviors as small-scale ones. If cracks exist in glass solid, the leaching in them is slow causing little effects on the overall leaching rate. This may be due to the fact that solubility-dependent leaching is occuring in the cracks. The long-term static leaching observations were not satisfactorily explained by the MCC-3 type solubility test results. It is important to clarify the solubility-dependent leaching behaviors at large SA/V ratios. (Nogami, K.)

Development of a computerized data base for low-level radioactive waste leaching data: Topical report

International Nuclear Information System (INIS)

Dougherty, D.R.; Colombo, P.

1986-09-01

This report documents the development of a computerized data base (db) of leaching data for solidified low-level radioactive waste (LLW) forms. Brookhaven National Lab performed this work under contract with the US Department of Energy's Low-Level Waste Management Program as part of an effort to develop an accelerated leach test(s) that can be used to predict leachabilities of LLW forms over long time periods, i.e., hundreds of years. The accelerated leach test(s) is (are) to be developed based on knowledge of leaching mechanisms and factors that affect leaching. Although developed specifically for the Accelerated Leach Test(s) Program, this db may be useful to others concerned with the management of low-level waste. The db is being developed to provide efficient data compilation and analysis capabilities. The data compiled in the db, which include data from the Accelerated Leach Test(s) Program and selected data from the literature, have been selected to elucidate leaching mechanisms and factors that affect leaching and are not meant to be a comprehensive compilation of leaching data. This report presents the data compilation aspect of the db. It does not present the programmatic results obtained from analysis of the data regarding leaching mechanisms and factors that affect leaching, which will be presented in reports from the Accelerated Leach Test(s) Program. 6 refs

Release rates of soluble species at Yucca Mountain

International Nuclear Information System (INIS)

Lee, W.W.-L.; Pigford, T.H.

1989-02-01

Experimental leaching of spent fuel shows that some fission product species are preferentially released upon contact with water. We analyze the conservative case of bare spent fuel in contact with saturated tuff using diffusional mass transfer analysis. For the parameter values used, the USNRC release rate limit is not exceeded, except for 99 Tc. The presence of a container and the distribution of water contact over time will assist in meeting this criterion. 6 figs., 2 tabs

Effect of preconditioning on silver leaching and bromide removal properties of silver-impregnated activated carbon (SIAC).

Science.gov (United States)

Rajaeian, Babak; Allard, Sébastien; Joll, Cynthia; Heitz, Anna

2018-07-01

Silver impregnated activated carbon (SIAC) has been found to be effective in mitigating the formation of brominated-disinfection by products during drinking water treatment. However, there are still uncertainties regarding its silver leaching properties, and strategies for the prevention of silver leaching have remained elusive. This study focused on the evaluation of one type of commercially available SIAC for its ability to remove bromide while minimising silver leaching from the material. Both synthetic and real water matrices were tested. Depending on solution pH, it was found that changing the surface charge properties of SIAC, as measured by the point of zero charge pH, can result in additional bromide removal while minimising the extent of silver leaching. To better understand the mechanism of silver leaching from the SIAC, eight preconditioning environments, i.e. variable pH and ionic strength were tested for a fixed amount of SIAC and two preconditioning environments were selected for a more detailed investigation. Experiments carried out in synthetic water showed that preconditioning at pH 10.4 did not deteriorate the capacity of SIAC to remove bromide, but significantly decreased the release of silver in the form of ionic silver (Ag + ), silver bromide (AgBr) and silver chloride (AgCl) from 40% for the pristine to 3% for the treated SIAC. This was confirmed using a groundwater sample. These results suggest that preconditioned SIAC has the potential to be an effective method for bromide removal with minimised silver leaching in a long-term field application for drinking water production. Copyright © 2018 Elsevier Ltd. All rights reserved.

Synergistic Effect of Nanosilica Aerogel with Phosphorus Flame Retardants on Improving Flame Retardancy and Leaching Resistance of Wood

Directory of Open Access Journals (Sweden)

Xiaodan Zhu

2014-01-01

Full Text Available Nanosilica (Nano-SiO2 sol fabricated by a sol-gel process was introduced into wood modification with phosphorus flame retardants to improve the flame retardancy and leaching resistance of wood. The obtained materials were characterized by scanning electron microscopy and energy dispersive spectrometer (SEM-EDS, thermogravimetric analysis (TGA, cone calorimetric (CONE, and infrared spectroscopy (FT-IR. The residual rate of flame retardants before and after leaching was determinated by a leaching resistance. The results showed that the phosphorus flame retardants and SiO2 sol could reside in the poplar wood and are widely distributed in the vessels, pits, wood timber, and the spaces between wood cells of poplar substrate. TGA and CONE results indicated that the introduction of nano-SiO2 aerogel with phosphorus flame retardants had a significantly synergistic effect on improving the flame retardancy and inhibiting the release of smoke and toxic gases. In addition, the leaching resistance test, combined with infrared analysis and EDS analysis, confirmed that the phosphorus flame retardants were able to be fixed by SiO2 aerogel in the wood.

Bicarbonate leaching of uranium

International Nuclear Information System (INIS)

Mason, C.

1998-01-01

The alkaline leach process for extracting uranium from uranium ores is reviewed. This process is dependent on the chemistry of uranium and so is independent on the type of mining system (conventional, heap or in-situ) used. Particular reference is made to the geochemical conditions at Crownpoint. Some supporting data from studies using alkaline leach for remediation of uranium-contaminated sites is presented

Bicarbonate leaching of uranium

Energy Technology Data Exchange (ETDEWEB)

Mason, C.

1998-12-31

The alkaline leach process for extracting uranium from uranium ores is reviewed. This process is dependent on the chemistry of uranium and so is independent on the type of mining system (conventional, heap or in-situ) used. Particular reference is made to the geochemical conditions at Crownpoint. Some supporting data from studies using alkaline leach for remediation of uranium-contaminated sites is presented.

Use of fly ash, phosphogypsum and red mud as a liner material for the disposal of hazardous zinc leach residue waste.

Science.gov (United States)

Coruh, Semra; Ergun, Osman Nuri

2010-01-15

Increasing amounts of residues and waste materials coming from industrial activities in different processes have become an increasingly urgent problem for the future. The release of large quantities of heavy metals into the environment has resulted in a number of environmental problems. The present study investigated the safe disposal of the zinc leach residue waste using industrial residues such as fly ash, phosphogypsum and red mud. In the study, leachability of heavy metals from the zinc leach residue has been evaluated by mine water leaching procedure (MWLP) and toxicity characteristic leaching procedure (TCLP). Zinc removal from leachate was studied using fly ash, phosphogypsum and red mud. The adsorption capacities and adsorption efficiencies were determined. The adsorption rate data was analyzed according to the pseudo-second-order kinetic, Elovich kinetic and intra-particle diffusion kinetic models. The pseudo-second-order kinetic was the best fit kinetic model for the experimental data. The results show that addition of fly ash, phosphogypsum and red mud to the zinc leach residue drastically reduces the heavy metal content in the leachate and could be used as liner materials.

Main ways and suitable technologies of improving economic benefits for uranium ore heap leaching in China (the end)

International Nuclear Information System (INIS)

Guan Zibin

2001-01-01

Combining with practice of China's uranium ore heap leaching, the author proposes main ways and suitable technologies in the fields of emphasizing feasibility research, adopting strengthened technologies, improving equipment level, optimizing control technological factors and developing application range and so on, which include adopting acid-currying and ferric sulphate-trickle leaching process, bacteria heap leaching, countercurrent heap leaching, selecting advanced material of heap bottom, developing large mechanized heap construction equipment and methods, popularizing drip irrigation distributing solution, optimizing heap leaching process parameters, as well as developing recovery equipment suited to heap leaching, etc, in order to increase leaching rate, reduce heap leaching period and achieve more economic benefits

Release and transport of fission product cesium in the TMI-2 accident

International Nuclear Information System (INIS)

Lorenz, R.A.; Collins, J.L.

1986-01-01

Approximately 50% of the fission product cesium was released from the overheated UO 2 fuel in the TMI-2 accident. Steam that boiled away from a water pool in the bottom of the reactor vessel transported the released fission products throughout the reactor coolant system (RCS). Some fission products passed directly through a leaking valve with steam and water into the containment structure, but most deposited on dry surfaces inside of the RCS before being dissolved or resuspended when the RCS was refilled with water. A cesium transport model was developed that extended measured cesium in the RCS back to the first day of the accident. The model revealed that ∼62% of the released 137 Cs deposited on dry surfaces inside of the RCS before being slowly leached and transported out of the RCS in leaked or letdown water. The leach rates from the model agreed reasonably well with those measured in the laboratory. The chemical behavior of cesium in the TMI-2 accident agreed with that observed in fission product release tests at Oak Ridge National Laboratory (ORNL)

Effects of tuff waste package components on release from 76-68 simulated waste glass: Final report

International Nuclear Information System (INIS)

McVay, G.L.; Robinson, G.R.

1984-04-01

An experimental matrix has been conducted that will allow evaluation of the effects of waste package constituents on the waste form release behavior in a tuff repository environment. Tuff rock and groundwater were used along with 304L, 316, and 1020M ferrous metals to evaluate release from uranium-doped MCC 76-68 simulated waste glass. One of the major findings was that in the absence of 1020M mild steel, tuff rock powder dominates the system. However, when 1020M mild steel is present, it appears to dominate the system. The rock-dominated system results in suppressed glass-water reaction and leaching while the 1020M-dominated system results in enhanced leaching - but the metal effectively scavenges uranium from solution. The 300-series stainless steels play no significant role in affecting glass leaching characteristics. 6 refs., 28 figs., 5 tabs

Leaching characteristics of rare metal elements and chlorine in fly ash from ash melting plants for metal recovery.

Science.gov (United States)

Jung, Chang-Hwan; Osako, Masahiro

2009-05-01

In terms of resource recovery and environmental impact, melting furnace fly ash (MFA) is attracting much attention in Japan due to its high metal content. The study aims to obtain fundamental information on using a water extraction method not only to concentrate valuable rare metals but also to remove undesirable substances such as chlorine for their recovery from MFA. The composition and leaching characteristics of MFA was investigated. The results revealed that the metal content in MFA is nearly equal to raw ore quality. The content of Ag, In, Pd, Pb, and Zn is, in fact, higher than the content of raw ore. As for leaching behavior, Ag, Bi, In, Ga, Ge, Sb, Sn, and Te showed the lowest release at a neutral pH range. Pd was leached constantly regardless of pH, but its concentration was quite low. On the other hand, most of the Tl was easily leached, revealing that water extraction is not appropriate for Tl recovery from MFA. Major elements Cl, Ca, Na, and K, occupying about 70% of MFA, were mostly leached regardless of pH. Base metal elements Cu, Pb, and Zn showed minimum solubility at a neutral pH. The leaching ratio of target rare metal elements and base metal elements suggests that the optimal pH for water extraction is 8-10, at which the leaching concentration is minimized. The water extraction process removed most of the Cl, Ca, Na, and K, and the concentration of rare metals and base metals increased by four or five times.

Chlorine-assisted leaching of Key Lake uranium ore

International Nuclear Information System (INIS)

Haque, K.E.

1981-04-01

Bench-scale chlorine-assisted leach tests were conducted on the Key Lake uranium ore. Leach tests conducted at 80 0 C on a slurry containing 50% solids during 10 hours of agitation gave the maximum extraction of uranium - 96% and radium-226 - 91%. Chlorine was added at 23.0 Kg Cl 2 /tonne of ore to maintain the leach slurry pH in the range of 1.5-1.0. To obtain residue almost free of radionuclides, hydrochloric acid leaches were conducted on the first stage leach residues. The second stage leach residue still was found to contain uranium - 0.0076% and radium-226 - 200 pCi/g of solids

Radionuclide release from PWR spent fuel specimens with induced cladding defects

International Nuclear Information System (INIS)

Wilson, C.N.; Oversby, V.M.

1984-03-01

Radionuclide releases from pressurized water reactor (PWR) spent fuel rod specimens containing various artificially induced cladding defects were compared by leach testing. The study was conducted in support of the Nevada Nuclear Waste Storage Investigations (NNWSI) Waste Package Task to evaluate the effectiveness of failed cladding as a barrier to radionuclide release. Test description and results are presented. 6 references, 4 figures

Chemicals having estrogenic activity can be released from some bisphenol A-free, hard and clear, thermoplastic resins.

Science.gov (United States)

Bittner, George D; Denison, Michael S; Yang, Chun Z; Stoner, Matthew A; He, Guochun

2014-12-04

Chemicals that have estrogenic activity (EA) can potentially cause adverse health effects in mammals including humans, sometimes at low doses in fetal through juvenile stages with effects detected in adults. Polycarbonate (PC) thermoplastic resins made from bisphenol A (BPA), a chemical that has EA, are now often avoided in products used by babies. Other BPA-free thermoplastic resins, some hypothesized or advertised to be EA-free, are replacing PC resins used to make reusable hard and clear thermoplastic products such as baby bottles. We used two very sensitive and accurate in vitro assays (MCF-7 and BG1Luc human cell lines) to quantify the EA of chemicals leached into ethanol or water/saline extracts of fourteen unstressed or stressed (autoclaving, microwaving, UV radiation) thermoplastic resins. Estrogen receptor (ER)-dependent agonist responses were confirmed by their inhibition with the ER antagonist ICI 182,780. Our data showed that some (4/14) unstressed and stressed BPA-free thermoplastic resins leached chemicals having significant levels of EA, including one polystyrene (PS), and three Tritan™ resins, the latter reportedly EA-free. Exposure to UV radiation in natural sunlight resulted in an increased release of EA from Tritan™ resins. Triphenyl-phosphate (TPP), an additive used to manufacture some thermoplastic resins such as Tritan™, exhibited EA in both MCF-7 and BG1Luc assays. Ten unstressed or stressed glycol-modified polyethylene terephthalate (PETG), cyclic olefin polymer (COP) or copolymer (COC) thermoplastic resins did not release chemicals with detectable EA under any test condition. This hazard survey study assessed the release of chemicals exhibiting EA as detected by two sensitive, widely used and accepted, human cell line in vitro assays. Four PC replacement resins (Tritan™ and PS) released chemicals having EA. However, ten other PC-replacement resins did not leach chemicals having EA (EA-free-resins). These results indicate that PC

Leaching of hydrophobic Cu and Zn from discarded marine antifouling paint residues: Evidence for transchelation of metal pyrithiones

Energy Technology Data Exchange (ETDEWEB)

Holmes, Luke [School of Earth, Ocean and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom); Turner, Andrew, E-mail: aturner@plymouth.ac.u [School of Earth, Ocean and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom)

2009-12-15

Leaching of Cu and Zn from a composite of discarded antifouling paint residues ([Cu] = 288 mg g{sup -1}; [Zn] = 96 mg g{sup -1}) into natural sea water has been studied over a period of 75 h. Total Cu and Zn were released according to a pseudo first-order reaction, with rate constants on the order of 0.3 and 2.5 (mg L{sup -1}){sup -1} h{sup -1}, respectively, and final concentrations equivalent to the dissolution of about 8 and 2% of respective concentrations in the composite. Time-distributions of hydrophobic metals, determined by solid phase extraction-methanol elution, were more complex. Net release of hydrophobic Cu was greater in the absence of light than under a sequence of light-dark cycles; however, hydrophobic Zn release was not detected under the former conditions but contributed up to 50% of total aqueous Zn when light was present. These observations are interpreted in terms of the relative thermodynamic and photolytic stabilities of biocidal pyrithione complexes. - Hydrophobic Cu and Zn leached from antifouling paint particles into sea water appear to be pyrithione complexes.

Implementation of the Leaching Environmental Assessment Framework

Science.gov (United States)

New leaching tests are available in the U.S. for developing more accurate source terms for use in fate and transport models. For beneficial use or disposal, the use of the leaching environmental assessment framework (LEAF) will provide leaching results that reflect field condit...

Leaching materials from cavities

International Nuclear Information System (INIS)

Hodgson, T.D.; Jordan, T.W.J.

1980-01-01

A material is leached from a cavity by contacting the material with a liquid and subjecting the liquid to a number of pressure cycles, each pressure cycle involving a decrease in pressure to cause boiling of the liquid, followed by a rise in pressure to inhibit the boiling. The method may include the step of heating the liquid to a temperature near to its boiling point. The material may be nuclear fuel pellets or calcium carbonate pellets. (author)

Leaching methods for conditioned radioactive waste

International Nuclear Information System (INIS)

Carpentiero, R.; Bienvenu, P.; Huebra, A. G. de la; Dale, C.; Grec, D.; Gallego, C.; Rodriguez, M.; Vanderlinden, F.; Voors, P. I.; Welbergen, J.; May, R.; Fays, J.

2005-01-01

The physico-chemical characterization of solidified, real or simulated, radioactive waste is essential in determining their long-term stability in conditions close to that which could be encountered during disposal. The evaluation or prediction of the performance of conditioned waste passes through many suitable studies and experiments, according to a documented qualification programme. In this respect the leaching test is among the first important techniques to evaluate the feasibility of a waste form and for comparing and selecting the best waste form. So the leaching behaviour of an immobilized radioactive waste is a relevant property to be studied. The objective of the present report is to collect and describe the most representative leaching methods used in international laboratories, mainly at European level, whether standard or standard-derived. In this instance the work is a summary of the Network knowledge and applications on leaching processes in order to exchange information and scientific and technical experiences in this respect. The focus is to express all the relevant parameters of the test and its field of application. all this background is the needed starting point to clarify the similarities and shortcomings of the methods used in the EN-TRAP laboratories and, subsequently, the possible equalities or differences which can be attributed to the characteristic parameters of the different type of wastes treated. In order to comprise the significance and the effects of the parameters involved in leaching phenomena, an initial discussion on leaching mechanisms and on achievable results is made in this document. The international standardised methods are summarised as being the origin for all the network leaching procedures. This work in a preliminary way represents a comparative review ordered to introduce an unique leaching procedure to be tested in an interlaboratory comparative exercise. Further the unique method would be a quick internal reference

Transuranium elements leaching from simulated HLW glasses in synthetic interstitial claywater

International Nuclear Information System (INIS)

Wang, L.

1992-08-01

The main objective of this Master Thesis is to measure the steady-state concentrations of Pu, Np, and Am upon the leaching of High-Level Waste Glass in two types of synthetic claywater: humic acid free and humic acid containing synthetic claywater. The synthetic claywater has a composition that is representative for the in-situ interstitial groundwater of the Boom clay formation, a potential geological repository of radioactive waste in Belgium. The steady-state concentrations of transuranium elements were measured by leaching experiments with a typical duration of 400 days. Five main conclusions are drawn from the experimental data. (1) The transuranium elements that are released from simulated High Level Waste Glass are dominantly present in the synthetic claywater solutions as colloids. These colloids are smaller than 2 nm in absence of humic acids. In the presence of humic acids however, the colloids interact with actinides (adsorb or coagulate) and form particles larger than 2 nm. Np and Am are associated with inorganic and organic colloids in the synthetic interstitial claywater solution whereas Pu forms only inorganic colloids. (2) The steady-state concentration of Pu is in good agreement with the solubility of the Pu compound PuO 2 .xH 2 O. It is therefore concluded that PuO 2 .xH 2 O is the solubility controlling phase. (3) The Pu(IV)-species are dominant in the leaching solutions. Carbonate and humic acid complexes are negligible. (4) The steady-state concentrations of Np and Am in leaching solutions were much lower than the values calculated on the basis of known thermodynamic data. This indicates that the solubility controlling phases for Np and Am were not correctly identified or that the measured Np and Am concentrations were not steady-state values. (5) Non-active glass leaching tests have indicated that no organic colloids were formed as a result of glass dissolution. (A.S.)

Stainless Steel Leaches Nickel and Chromium into Foods During Cooking

OpenAIRE

Kamerud, Kristin L.; Hobbie, Kevin A.; Anderson, Kim A.

2013-01-01

Toxicological studies show that oral doses of nickel and chromium can cause cutaneous adverse reactions such as dermatitis. Additional dietary sources, such as leaching from stainless steel cookware during food preparation, are not well characterized. This study examined stainless steel grades, cooking time, repetitive cooking cycles, and multiple types of tomato sauces for their effects on nickel and chromium leaching. Trials included three types of stainless steels and a stainless steel sau...

Groundwater restoration with in situ uranium leach mining

International Nuclear Information System (INIS)

Charbeneau, R.J.

1984-01-01

In situ leach mining of uranium has developed into a major mining technology. Since 1975, when the first commercial mine was licensed in the United States, the percentage or uranium produced by in situ mining has steadily grown from 0.6 to 10 percent in 1980. Part of the reason for this growth is that in situ mining offers less initial capital investment, shorter start-up times, greater safety, and less labor than conventional mining methods. There is little disturbance of the surface terrain or surface waters, no mill tailings piles, and no large open pits, but in situ leaching mining does have environmental disadvantages. During the mining, large amounts of ground water are cirulated and there is some withdrawal from an area where aquifers constitute a major portion of the water supply for other purposes. When an ammonia-based leach system is used, the ammonium ion is introduced into an area where cation exchange on clays (and some production of nitrate) may occur. Also, injection of an oxidant with the leach solution causes valence and phase changes of indigenous elements such as As, Cu, Fe, Mo, Se, S, and V as well as U. Furthermore, the surrounding ground water can become contaminated by escape of the leach solution from the mining zone. This chapter presents an overview of the in situ mining technology, including uranium deposition, mining techniques, and ground water restoration alternatives. The latter part of the chapter covers the situation in South Texas. Economics and development of the industry, groundwater resources, regulation, and restoration activities are also reviewed

Application of XPS and nuclear technique to the study of the gel layers formed under different redex conditions on leached glasses

International Nuclear Information System (INIS)

Manara, A.; Lanza, F.; Ceccone, G.; Della Mea, G.; Salvagno, G.

1984-01-01

Surface analysis has been conducted on samples leached in a Soxhlet apparatus at 100 0 C in presence and in absence of air. The XPS and RBS techniques were applied to analyse the content of the silicon, iron and uranium while the nuclear reaction method was utilized to analyse the hydrogen content. The anoxic environment favors the release of iron while decreasing the dissolution of uranium. Hydrogen content is always higher in samples leached in presence of air. Silicon depletion is evident in all cases. The diffusion process seems to regulate the growth of the layer on the glass surface. After long leaching time a detachment, at least partial, of this layer is observed. 14 refs., 9 figs., 1 tab

Continuous-flow leaching studies of crushed and cored SYNROC

International Nuclear Information System (INIS)

Coles, D.G.; Bazan, F.

1982-01-01

Both crushed (150- to 300- μm) and cored (1,8- mm-diam) samples of SYNROC have been leached with single-pass continuous-flow leaching equipment. Crushed samples of cesium-hollandite were also leached in a similar experiment. Temperatures used were 25 0 and 75 0 C and leachates were 0.03 N NaHCO 3 and distilled water. Leaching rates from SYNROC-C were ranked cesium > strontium greater than or equal to calcium > barium > zirconium. A comparison of leaching rates is made between crushed SYNROC, cored SYNROC, and Pacific Northwest Laboratory 76-68 glass beads. This comparison depends on how the surface areas are determined for each sample. Based on geometric surface areas for SYNROC cores and glass beads, cesium leach rates from SYNROC compare well with both sodium and neptunium leached from the glass. The other elements leached from SYNROC are lower than sodium and neptunium leached from glass. They also vary for each element, while glass shows nearly the same leach rate for both sodium and neptunium

Continuous-flow leaching studies of crushed and cored SYNROC

International Nuclear Information System (INIS)

Coles, D.G.; Bazan, F.

1981-01-01

Both crushed (150 to 300 μm) and cored (1.8 mm diameter) samples of SYNROC have been leached with the single-pass continuous-flow leaching equipment. Crushed samples of Cs-hollandite were also leached in a similar experiment. Temperatures used were 25 and 75 0 C and leachates were 0.03 N NaHCO 3 and distilled water. Leaching rates from SYNROC C were ranked Cs > Sr greater than or equal to Ca > Ba > Zr. A comparison of leaching rates is made between crushed SYNROC, cored SYNROC, and PNL 76-68 glass beads. This comparison depends on how the surface areas are determined for each sample. Based on geometric surface areas for SYNROC cores and glass beads Cs leach rates from SYNROC compare well with both Na and Np leached from the glass. The other elements leached from SYNROC are lower than Na and Np leached from glass. They also vary for each element while glass shows nearly the same leach rate for both Na and Np

Simfuel dissolution studies in granitic groundwater leaching experiments at VTT

International Nuclear Information System (INIS)

Ollila, K.

1992-12-01

The dissolution behaviour of an irradiated analogue of spent nuclear fuel, SIMFUEL, was studied in synthetic granitic groundwater. The release of uranium and the minor components was monitored during static (bach) leaching experiments in oxic and anoxic (N 2 ) atmosphere at 25 deg C. Molybdenum, ruthenium, barium and zirconium showed a trend to congruent dissolution behaviour with UO 2 matrix towards the end of the experimental time (540 days) under anoxic conditions. Under oxic conditions, molybdenum and strontium had higher release rates relative to the matrix (the exp. time of 220 days). The presence of particulate material in the leachates in anoxic atmosphere was shown by SEM/EDX and XRD analyses. The material retained on membrane after filtration consisted of Ca-rich and U-rich particles in addition to finely divided material. Calcite (CaCO 3 ) and uranium oxide were identified. (orig.)

Mechanisms that control aqueous leaching of nuclear waste glass

International Nuclear Information System (INIS)

Simmons, J.H.; Barkatt, A.; Macedo, P.B.

1982-01-01

The development of predictive models and risk calculations for the time evolution of radioactive isotope leaching from fixation solids depends on many factors, including measurement accuracy, measurement relevance, a complete understanding of possible dissolution mechanisms, and the ability to project worst case conditions for all appropriate mechanisms. Some of the mechanisms observed and understood at present are the mechanisms of dissolution of glasses in neutral unbuffered water, the effects of structural disintegration of the glass protective layer, the effects of slowly flowing bath waters and possibly, the mechanisms of leach-rate reduction by solution saturation. The mechanisms that control radiation and temperature effects including alpha particle emission and nuclear transmutations are as yet little understood or investigated

Leaching of Cu, Cd, Pb, and phosphorus and their availability in the phosphate-amended contaminated soils under simulated acid rain.

Science.gov (United States)

Cui, Hongbiao; Zhang, Shiwen; Li, Ruyan; Yi, Qitao; Zheng, Xuebo; Hu, Youbiao; Zhou, Jing

2017-09-01

Phosphate amendments have been used to immobilize heavy metal-contaminated soils. However, phosphate amendments contain large amounts of phosphorus, which could leach out to potentially contaminate groundwater and surface water. A laboratory column leaching experiment was designed to study the effects of simulated acid rain (SAR) on the potential release of copper (Cu), lead (Pb), cadmium (Cd), and phosphorus (P), and their availability after immobilizing with hydroxyapatite (HAP) and potassium dihydrogen phosphate (PDP). The application of HAP and PDP enhanced the leachate electrical conductivity, total organic carbon, and pH. Higher P was found in the PDP- (>4.29 mg L -1 ) and HAP-treated (>1.69 mg L -1 ) columns than that in untreated (phosphate amendments might promote the leaching of some metals while immobilizing others.

Antimony smelting process generating solid wastes and dust: characterization and leaching behaviors.

Science.gov (United States)

Guo, Xuejun; Wang, Kunpeng; He, Mengchang; Liu, Ziwei; Yang, Hailin; Li, Sisi

2014-07-01

A large amount of solid waste has been produced by the antimony smelting process in the "World Capital of Antimony", Xikuangshan area in China. This study comprehensively investigated the physical and chemical characteristics of the various solid wastes, as well as the leaching behavior of the solid wastes, which included water-quenched slag, arsenic-alkali residue, desulfurized slag and blast furnace dust. These four types of waste were enriched in a variety of heavy metals and metalloids and more specifically with As and Sb levels up to 8.6 × 10⁴ and 3.16×10⁵ mg/kg, respectively, in arsenic-alkali residue. For desulfurized slag and water-quenched slag, the leaching concentration of Sb significantly exceeded the acceptable limits during the leaching tests using the toxicity characteristic leaching procedure and the synthetic precipitation leaching procedure. In addition, As leaching in arsenic-alkali residue was extraordinarily hazardous, being three orders of magnitude higher than the regulatory level of As. According to the results of the extraction tests, all the tested wastes were classified as hazardous waste. Copyright © 2014. Published by Elsevier B.V.

In-situ leaching of Crownpoint, New Mexico, uranium ore: Part 7 - laboratory study of chemical agents for molybdenum restoration

International Nuclear Information System (INIS)

Strom, E.T.; Vogt, T.C.

1985-01-01

While in-situ leaching has significant advantages over conventional uranium recovery methods, one possible drawback to its use is the potential release of previously insoluble chemical species into the formation water. Before Mobil began a pilot test of in-situ uranium leaching at Crownpoint, New Mexico, extensive laboratory studies were undertaken to develop chemical methods for treating one possible contaminant, molybdenum (Mo). In-situ production of uranium entails oxidizing uranium from the insoluble +4 oxidation state to the soluble, readily complexed +6 state. However, this process also transforms insoluble Mo +4 compounds such as molybdenite or jordesite, MoS 2 , into the soluble T6 form, molybdate, Mo0 4 2- . New Mexico regulations restrict the amount of Mo permissible in formation waters after leaching to less than one ppm. Conceptually, Mo restoration after leaching can be dealt with in one of two ways. (1) The oxidizing environment can be left unchanged with something added to render the molybdate ion insoluble or (2) the environment can be changed to a reducing one, converting the Mo back to the less soluble +4 oxidation state

Leaching studies on SYNROC at 950C and 2000C

International Nuclear Information System (INIS)

Oversby, V.M.; Ringwood, A.E.

1982-01-01

Crushed samples of SYNROC containing 9%, 16% and 20% of simulated high-level nuclear waste were tested for leaching behavior in distilled water at 95 0 C and 200 0 . Leach solutions were analyzed for Cs, Ca, Ba, Sr, Ti, Zr, Nd and U. Results showed that leach rates based on these elements did not change significantly as the waste loading was increased from 9 to 20%. At both temperatures, leach rates showed a decrease as leaching progressed until a plateau level was reached. Plateau leach rates, which were between 10 and 100 times lower than initial leach rates, reflect the expected long term leaching behaviour of the samples. Plateau values of leach rates for SYNROC depend on the element being leached. Highest values are found for Cs and Ba (1 to 2 x 10 -7 g/cm 2 d at 95 0 C) and lowest values for U (5 x 10 -10 g/cm 2 d at 95 0 C). Increasing leaching temperature to 200 0 C produces higher leach rates for all elements except Nd. Comparison of SYNROC leach rate data with that for PNL 76-68 glass shows that at 200 0 C the leach rate for U from SYNROC is 3000 times less than that from glass. (Auth.)

Alternative leaching processes for uranium ores

International Nuclear Information System (INIS)

Ring, R.J.

1979-01-01

Laboratory studies have been carried out to compare the extraction of uranium from Australian ores by conventional leaching in sulphuric acid with that obtained using hydrochloric acid and acidified ferric sulphate solutions. Leaching with hydrochloric acid achieved higher extractions of radium-226 but the extraction of uranium was reduced considerably. The use of acidified ferric sulphate solution reduced acid consumption by 20-40% without any detrimental effect on uranium extraction. The ferric ion, which is reduced during leaching, can be reoxidized and recycled after the addition of acid makeup. Hydrogen peroxide was found to be an effective oxidant in conventional sulphuric acid leaching. It is more expensive than alternative oxidants, but it is non-polluting, lesser quantities are required and acid consumption is reduced

Leaching behaviour of strontium-90 in cement composites

International Nuclear Information System (INIS)

Matsuzuru, H.; Ito, A.

1977-01-01

The leaching of 90 Sr from a cement composite into an aqueous phase has been studied by the method recommended by IAEA. The amount leached was measured as functions of waste to cement ratio (Wa/C), salt content of waste, temperature of leachant and curing time of specimens. The leach coefficient of 90 Sr varies from ca. 6 x 10 -8 to 4 x 10 -7 cm 2 /day depending on the composition of specimen and the leaching conditions. The leachability depends on such factors as Wa/C, temperature of leachant and curing time. The Portland cement composite gives a higher leaching fraction than the slag cement one. Additives used have no significant effect on the leachability. The amount leached in deionized water as a leachant is higher than in synthetic sea water. On the basis of the results obtained, the amount of 90 Sr leached from a composite of 200 1 drum size for an extended period was estimated. (author)

Aqueous-chlorine leaching of typical Canadian uranium ores

International Nuclear Information System (INIS)

Haque, K.E.

1982-01-01

Laboratory-scale aqueous-chlorine leaches were conducted on quartz-pebble conglomerates, pegmatite and vein-type ores. Optimum leach temperatures, pulp density and retention times were determined. Uranium extraction of 98 per cent was obtained from the Elliot Lake, Madawaska Mines of Bancroft and Rabbit Lake ores, 96 per cent from the Key Lake ore and 86 per cent from the Agnew Lake ore. However, tailings containing 15-20 pCi g -1 of radium-226 were obtained only from the Elliot Lake and Agnew lake quartz-pebble conglomerates and Bancroft pegmatite-type ores by second-stage leaches with HCl. The second-stage leach results indicate that multistage (3 or 4) acid-chloride or salt-chloride leaches might be effective to obtain tailings containing 15-20 pCi 226 Ra g -1 from the high-grade vein-type ores. Comparative reagent-cost estimates show that the sulphuric-acid leach process is far less expensive than aqueous chlorine leaching. Nevertheless, only the aqueous chlorine and acid-chloride leaches in stages are effective in producing tailings containing 15-20 pCi 226 Ra g -1 from the typical Canadian uranium ores. (Auth.)

A review of mathematical modeling and simulation of controlled-release fertilizers.

Science.gov (United States)

Irfan, Sayed Ameenuddin; Razali, Radzuan; KuShaari, KuZilati; Mansor, Nurlidia; Azeem, Babar; Ford Versypt, Ashlee N

2018-02-10

Nutrients released into soils from uncoated fertilizer granules are lost continuously due to volatilization, leaching, denitrification, and surface run-off. These issues have caused economic loss due to low nutrient absorption efficiency and environmental pollution due to hazardous emissions and water eutrophication. Controlled-release fertilizers (CRFs) can change the release kinetics of the fertilizer nutrients through an abatement strategy to offset these issues by providing the fertilizer content in synchrony with the metabolic needs of the plants. Parametric analysis of release characteristics of CRFs is of paramount importance for the design and development of new CRFs. However, the experimental approaches are not only time consuming, but they are also cumbersome and expensive. Scientists have introduced mathematical modeling techniques to predict the release of nutrients from the CRFs to elucidate fundamental understanding of the dynamics of the release processes and to design new CRFs in a shorter time and with relatively lower cost. This paper reviews and critically analyzes the latest developments in the mathematical modeling and simulation techniques that have been reported for the characteristics and mechanisms of nutrient release from CRFs. The scope of this review includes the modeling and simulations techniques used for coated, controlled-release fertilizers. Copyright © 2017 Elsevier B.V. All rights reserved.

Bacterial Leaching

Indian Academy of Sciences (India)

and studies microbial biotechnology and ... foundation for subsequent research into the role of microorgan- ... are more readily accesible, for example those in solution, rather .... Vat leaching as currently applied to oxide ores involves the.

Leaching behavior of solidified plastics radioactive wastes

International Nuclear Information System (INIS)

Yook, Chong Chul; Lee, Byung Hun; Jae, Won Mok; Kim, Kyung Eung

1986-01-01

It is highly needed to develope the solidification process to dispose safely the radioactive wastes increasing with the growth of the nuclear industry. The leaching mechanisms of the solidified plastic wastes were investigated and the leaching rates of the plastic wastes were also measured among the many solidification processes. In addition, the transport equation based on the diffusion or the diffusion-dissolution was compared with the empirical equation derived from the experimental data by graphical method. Consequently, leaching process of the solidified plastic wastes is quite well agreed with the mass transport theory, but it may be difficult to simulate leaching process by diffusion dissolution mechanism. But the theoretical equation could be applicable to the cumulative amount of radionuclides leached form the plastic wastes disposed into the environment. (Author)

Leaching of tritium from a cement composite

International Nuclear Information System (INIS)

Matsuzuru, Hideo; Ito, Akihiko

1978-10-01

Leaching of tritium from cement composites into an aqueous phase has been studied to evaluate the safety of incorporation of the tritiated liquid waste into cement. Leaching tests were performed by the method recommended by the International Atomic Energy Agency. The Leaching fraction was measured as functions of waste-cement ratio (Wa/C), temperature of leachant and curing time. The tritium leachability of cement in the long term test follows the order: alumina cement portland cement slag cement. The fraction of tritium leached increases with increasing Wa/C and temperature and decreasing curing period. A deionized water as a leachant gives a slightly higher leachability than synthetic sea water. The amount leached of tritium from a 200 l drum size specimen was estimated on the basis of the above results. (author)

Waste water treatment of CO2+O2 in-situ leaching uranium

International Nuclear Information System (INIS)

Xu Lechang; Liu Naizhong; Du Zhiming; Wang Hongying

2012-01-01

An in-situ leaching uranium mine located in Northern China uses CO 2 +O 2 leaching process to leach uranium. The consumption of industrial reagent and water, and generation and discharge of waste water are minimized by comprehensive waste water treatment technology with process water recycle, reverse osmosis and natural evaporation. The process water of the mine that can be recycled and reused includes barren fluid, solution washing loaded resin, precipitating mother solution and filtered liquor of yellow cake. Solution regenerating barren resin is treated by reverse osmosis. Concentrated water from reverse osmosis and solution washing barren resin are naturally evaporated. (authors)

Small-scale and large-scale testing of photo-electrochemically activated leaching technology in Aprelkovo and Delmachik Mines

Science.gov (United States)

Sekisov, AG; Lavrov, AYu; Rubtsov, YuI

2017-02-01

The paper gives a description of tests and trials of the technology of heap gold leaching from rebellious ore in Aprelkovo and Delmachik Mines. Efficiency of leaching flowsheets with the stage-wise use of activated solutions of different reagents, including active forms of oxygen, is evaluated. Carbonate-peroxide solutions are used at the first stage of leaching to oxidize sulfide and sulfide-arsenide ore minerals to recover iron and copper from them. The second stage leaching uses active cyanide solutions to leach encapsulated and disperse gold and silver.

Leaching behavior of lanthanum, nickel and iron from spent catalyst using inorganic acids

Science.gov (United States)

Astuti, W.; Prilitasari, N. M.; Iskandar, Y.; Bratakusuma, D.; Petrus, H. T. B. M.

2018-01-01

Highly technological applications of rare earth metals (REs) and scarcity of supply have become an incentive torecover the REs from various resources, which include high grade and low grade ores, as well as recycledwaste materials. Spent hydrocracking catalyst contain lanthanum and a variety of valuable metals such as nickel and iron. This study investigated the recovery of lanthanum, nickel and iron from spent hydrocracking catalyst by leaching using various inorganic acid (sulfuric acid, hydrochloric acid, and nitric acid). The effect of acid concentration, type of acid and leaching temperature was conducted to study the leaching behavior of each valuable metal from spent-catalyst. It has been shown that it is possible to recover more than 90% of lanthanum, however the leaching efficiency of nickel and iron in this process was very low. It can be concluded that the leaching process is selective for lanthanum recovery from hydrocracking spent-catalyst.

Comparing soil carbon loss through respiration and leaching under extreme precipitation events in arid and semiarid grasslands

Science.gov (United States)

Liu, Ting; Wang, Liang; Feng, Xiaojuan; Zhang, Jinbo; Ma, Tian; Wang, Xin; Liu, Zongguang

2018-03-01

Respiration and leaching are two main processes responsible for soil carbon loss. While the former has received considerable research attention, studies examining leaching processes are limited, especially in semiarid grasslands due to low precipitation. Climate change may increase the extreme precipitation event (EPE) frequency in arid and semiarid regions, potentially enhancing soil carbon loss through leaching and respiration. Here we incubated soil columns of three typical grassland soils from Inner Mongolia and the Qinghai-Tibetan Plateau and examined the effect of simulated EPEs on soil carbon loss through respiration and leaching. EPEs induced a transient increase in CO2 release through soil respiration, equivalent to 32 and 72 % of the net ecosystem productivity (NEP) in the temperate grasslands (Xilinhot and Keqi) and 7 % of NEP in the alpine grasslands (Gangcha). By comparison, leaching loss of soil carbon accounted for 290, 120, and 15 % of NEP at the corresponding sites, respectively, with dissolved inorganic carbon (DIC, biogenic DIC + lithogenic DIC) as the main form of carbon loss in the alkaline soils. Moreover, DIC loss increased with recurring EPEs in the soil with the highest pH due to an elevated contribution of dissolved CO2 from organic carbon degradation (indicated by DIC-δ13C). These results highlight the fact that leaching loss of soil carbon (particularly in the form of DIC) is important in the regional carbon budget of arid and semiarid grasslands and also imply that SOC mineralization in alkaline soils might be underestimated if only measured as CO2 emission from soils into the atmosphere. With a projected increase in EPEs under climate change, soil carbon leaching processes and the influencing factors warrant a better understanding and should be incorporated into soil carbon models when estimating carbon balance in grassland ecosystems.

Comparing soil carbon loss through respiration and leaching under extreme precipitation events in arid and semiarid grasslands

Directory of Open Access Journals (Sweden)

T. Liu

2018-03-01

Full Text Available Respiration and leaching are two main processes responsible for soil carbon loss. While the former has received considerable research attention, studies examining leaching processes are limited, especially in semiarid grasslands due to low precipitation. Climate change may increase the extreme precipitation event (EPE frequency in arid and semiarid regions, potentially enhancing soil carbon loss through leaching and respiration. Here we incubated soil columns of three typical grassland soils from Inner Mongolia and the Qinghai–Tibetan Plateau and examined the effect of simulated EPEs on soil carbon loss through respiration and leaching. EPEs induced a transient increase in CO2 release through soil respiration, equivalent to 32 and 72 % of the net ecosystem productivity (NEP in the temperate grasslands (Xilinhot and Keqi and 7 % of NEP in the alpine grasslands (Gangcha. By comparison, leaching loss of soil carbon accounted for 290, 120, and 15 % of NEP at the corresponding sites, respectively, with dissolved inorganic carbon (DIC, biogenic DIC + lithogenic DIC as the main form of carbon loss in the alkaline soils. Moreover, DIC loss increased with recurring EPEs in the soil with the highest pH due to an elevated contribution of dissolved CO2 from organic carbon degradation (indicated by DIC-δ13C. These results highlight the fact that leaching loss of soil carbon (particularly in the form of DIC is important in the regional carbon budget of arid and semiarid grasslands and also imply that SOC mineralization in alkaline soils might be underestimated if only measured as CO2 emission from soils into the atmosphere. With a projected increase in EPEs under climate change, soil carbon leaching processes and the influencing factors warrant a better understanding and should be incorporated into soil carbon models when estimating carbon balance in grassland ecosystems.

Leaching Behavior of Heavy Metals and Transformation of Their Speciation in Polluted Soil Receiving Simulated Acid Rain

Science.gov (United States)

Zheng, Shun-an; Zheng, Xiangqun; Chen, Chun

2012-01-01

Heavy metals that leach from contaminated soils under acid rain are of increasing concern. In this study, simulated acid rain (SAR) was pumped through columns of artificially contaminated purple soil. Column leaching tests and sequential extraction were conducted for the heavy metals Cu, Pb, Cd, and Zn to determine the extent of their leaching as well as to examine the transformation of their speciation in the artificially contaminated soil columns. Results showed that the maximum leachate concentrations of Cu, Pb, Cd, and Zn were less than those specified in the Chinese Quality Standards for Groundwater (Grade IV), thereby suggesting that the heavy metals that leached from the polluted purple soil receiving acid rain may not pose as risks to water quality. Most of the Pb and Cd leachate concentrations were below their detection limits. By contrast, higher Cu and Zn leachate concentrations were found because they were released by the soil in larger amounts as compared with those of Pb and Cd. The differences in the Cu and Zn leachate concentrations between the controls (SAR at pH 5.6) and the treatments (SAR at pH 3.0 and 4.5) were significant. Similar trends were observed in the total leached amounts of Cu and Zn. The proportions of Cu, Pb, Cd, and Zn in the EXC and OX fractions were generally increased after the leaching experiment at three pH levels, whereas those of the RES, OM, and CAR fractions were slightly decreased. Acid rain favors the leaching of heavy metals from the contaminated purple soil and makes the heavy metal fractions become more labile. Moreover, a pH decrease from 5.6 to 3.0 significantly enhanced such effects. PMID:23185399

DEVELOPMENT OF PASSIVE DETOXIFICATION TECHNOLOGY FOR GOLD HEAP LEACH STOCKPILED WASTES

OpenAIRE

M.P. Belykh; A.Yu. Chikin; S.V. Petrov; N.L. Belkova

2017-01-01

Purpose. The processes of biopassive detoxication are of special interest for the solution of environmental issues of detoxification of gold heap leach cyanide-bearing wastes whose detoxification period is unlimited. These processes are based on spontaneous degradation of cyanides under the influence of natural factors including the action of autochthonous bacterial community. The purpose of the work is to develop a biopassive detoxification technology of heap leach stockpiled wastes. Methods...

Water leaching of borosilicate glasses: experiments, modeling and Monte Carlo simulations

International Nuclear Information System (INIS)

Ledieu, A.

2004-10-01

This work is concerned with the corrosion of borosilicate glasses with variable oxide contents. The originality of this study is the complementary use of experiments and numerical simulations. This study is expected to contribute to a better understanding of the corrosion of nuclear waste confinement glasses. First, the corrosion of glasses containing only silicon, boron and sodium oxides has been studied. The kinetics of leaching show that the rate of leaching and the final degree of corrosion sharply depend on the boron content through a percolation mechanism. For some glass contents and some conditions of leaching, the layer which appears at the glass surface stops the release of soluble species (boron and sodium). This altered layer (also called the gel layer) has been characterized with nuclear magnetic resonance (NMR) and small angle X-ray scattering (SAXS) techniques. Second, additional elements have been included in the glass composition. It appears that calcium, zirconium or aluminum oxides strongly modify the final degree of corrosion so that the percolation properties of the boron sub-network is no more a sufficient explanation to account for the behavior of these glasses. Meanwhile, we have developed a theoretical model, based on the dissolution and the reprecipitation of the silicon. Kinetic Monte Carlo simulations have been used in order to test several concepts such as the boron percolation, the local reactivity of weakly soluble elements and the restructuring of the gel layer. This model has been fully validated by comparison with the results on the three oxide glasses. Then, it has been used as a comprehensive tool to investigate the paradoxical behavior of the aluminum and zirconium glasses: although these elements slow down the corrosion kinetics, they lead to a deeper final degree of corrosion. The main contribution of this work is that the final degree of corrosion of borosilicate glasses results from the competition of two opposite mechanisms

Long-term elevated temperature leaching of solid waste forms

International Nuclear Information System (INIS)

Kenna, B.T.; Murphy, K.D.; Levine, H.S.

1978-01-01

Long-term soxhlet leaching of simulated waste glass and ceramic materials was initiated to elucidate leaching behavior of complex wasteforms. A cyclic leaching pattern was found in all systems over a 20 month period. Maxima and minima were observed in the leaching rates of all components studied with the minima coinciding. The data suggested several mechanistic features which are described, but they did not conform with reported simple leaching mechanisms

Investigation of Released Cadmium and Lead from Different Colors of Over Glaze Designs to Food Stuff in Different Conditions

Directory of Open Access Journals (Sweden)

H. Hashemi-Moghaddam

2012-03-01

Full Text Available In this paper, leaching of lead and cadmium was investigated from porcelain over glaze designs between different colors.  Also the effect of microwave heating was considered on leaching of lead and cadmium.  Dishes were selected with a decor with the dominant color of gray, red, yellow, blue, and dark blue. Amounts of cadmium and lead which leached from the container by acetic acid and orange juice were measured according to the standard ASTM C738.  The results showed that especially in the red and dark blue colors cadmium and lead could be released easily by either acetic acid or orange juice, and these amounts were much higher than the permissible standard amount. Also microwave heating could enhance releasing of lead and cadmium from decorated dinnerware. 

Chemical characterization, leach, and adsorption studies of solidified low-level wastes

International Nuclear Information System (INIS)

Walter, M.B.; Serne, R.J.; Jones, T.L.; McLaurine, S.B.

1986-12-01

Laboratory and field leaching experiments are beig conducted by Pacific Northwest Laboratory (PNL) to investigate the performance of solidified low-level nuclear waste in a typical, arid, near-surface disposal site. Under PNL's Special Waste Form Lysimeters-Arid Program, a field test facility was constructed to monitor the leaching of commercial solidified waste. Laboratory experiments were conducted to investigate the leaching and adsorption characteristics of the waste forms in contact with soil. Liquid radioactive wastes solidified in cement, vinyl ester-styrene, and bitumen were obtained from commercial boiling water and pressurized water reactors, and buried in a field leaching facility on the Hanford site in southeastern Washington State. Batch leaching, soil column adsorption, and soil/waste form column experiments were conducted in the laboratory, using small-scale cement waste forms and Hanford site ground water. The purpose of these experiments is to evaluate the ability of laboratory leaching tests to predict leaching under actual field conditions and to determine which mechanisms (i.e., diffusion, solubility, adsorption) actually control the concentration of radionuclides in the soil surrounding the waste form. Chemical and radionuclide analyses performed on samples collected from the field and laboratory experiments indicate strong adsorption of /sup 134,137/Cs and 85 Sr onto the Hanford site sediment. Small amounts of 60 Co are leached from the waste forms as very mobile species. Some 60 Co migrated through the soil at the same rate as water. Chemical constituents present in the reactor waste streams also found at elevated levels in the field and laboratory leachates include sodium, sulfate, magnesium, and nitrate. Plausible solid phases that could be controlling some of the chemical and radionuclide concentrations in the leachate were identified using the MINTEQ geochemical computer code

Leaching of gallium from gaiter granite, eastern desert, Egypt

International Nuclear Information System (INIS)

Zahran, M.A.; Mahmoud, KH.F.; Mahdy, M.A.; Abd El-Hamid, A.M.

2006-01-01

Preliminary leaching tests of gallium from some Egyptian granite rocks such as those of Gabal Gattar area was investigated by using 8 M HCl acid and sodium perchlorate as oxidant. To achieve the optimum leaching conditions, the factors affecting the leaching efficiency as the acid type and concentration, oxidant type and amount, leaching temperature, agitation time, solid / liquid ratio and the effect of grain size were studied. The complete chemical analysis of the collected samples was firstly carried out to determine the chemical features of the Gattarian granite. More than 97% of gallium content was leached when applying these optimum leaching conditions

Hydration of dicalcium silicate and diffusion through neo-formed calcium-silicate-hydrates at weathered surfaces control the long-term leaching behaviour of basic oxygen furnace (BOF) steelmaking slag.

Science.gov (United States)

Stewart, Douglas I; Bray, Andrew W; Udoma, Gideon; Hobson, Andrew J; Mayes, William M; Rogerson, Mike; Burke, Ian T

2018-04-01

Alkalinity generation and toxic trace metal (such as vanadium) leaching from basic oxygen furnace (BOF) steel slag particles must be properly understood and managed by pre-conditioning if beneficial reuse of slag is to be maximised. Water leaching under aerated conditions was investigated using fresh BOF slag at three different particle sizes (0.5-1.0, 2-5 and 10 × 10 × 20 mm blocks) and a 6-month pre-weathered block. There were several distinct leaching stages observed over time associated with different phases controlling the solution chemistry: (1) free-lime (CaO) dissolution (days 0-2); (2) dicalcium silicate (Ca 2 SiO 4 ) dissolution (days 2-14) and (3) Ca-Si-H and CaCO 3 formation and subsequent dissolution (days 14-73). Experiments with the smallest size fraction resulted in the highest Ca, Si and V concentrations, highlighting the role of surface area in controlling initial leaching. After ~2 weeks, the solution Ca/Si ratio (0.7-0.9) evolved to equal those found within a Ca-Si-H phase that replaced dicalcium silicate and free-lime phases in a 30- to 150-μm altered surface region. V release was a two-stage process; initially, V was released by dicalcium silicate dissolution, but V also isomorphically substituted for Si into the neo-formed Ca-Si-H in the alteration zone. Therefore, on longer timescales, the release of V to solution was primarily controlled by considerably slower Ca-Si-H dissolution rates, which decreased the rate of V release by an order of magnitude. Overall, the results indicate that the BOF slag leaching mechanism evolves from a situation initially dominated by rapid hydration and dissolution of primary dicalcium silicate/free-lime phases, to a slow diffusion limited process controlled by the solubility of secondary Ca-Si-H and CaCO 3 phases that replace and cover more reactive primary slag phases at particle surfaces.

The role of drainage ditches in greenhouse gas emissions and surface leaching losses from a cutaway peatland cultivated with a perennial bioenergy crop

Energy Technology Data Exchange (ETDEWEB)

Hyvonen, N.P.; Huttunen, J.T.; Shurpali, N.J.; Lind, S.E.; Marushchak, M.E.; Martikainen, P.J. [University of Eastern Finland, Kuopio (Finland). Dept. of Environmental Science], E-mail: niina.hyvonen@uef.fi; Heitto, L. [Environmental Research of Savo-Karjala Ltd, Kuopio (Finland)

2013-06-01

We studied greenhouse gas (GHG) emissions from drainage ditches and leaching losses in a boreal cutaway peatland cultivated with reed canary grass (Phalaris arundinacea) for bioenergy. The objectives of the study were to assess to what extent GHG emissions from drainage ditches and leaching of carbon and nutrients via surface drainage contribute to the total losses of carbon and nitrogen from the site. The emissions of CH{sub 4}, N{sub 2}O and CO{sub 2} were measured with static chamber methods for three years and leaching losses for seven years. On average, the drainage ditches (covering 6% of the study site area) released 10% of the total CH{sub 4} emission (0.33 g m{sup -2} a{sup -1}), and 1% and 5% of the total N{sub 2}O and CO{sub 2} emissions, respectively. Leaching of total nitrogen and phosphorous were 0.31 and 0.03 g m{sup -2} a{sup -1}, respectively. Leaching values were lower than those reported for agricultural catchments in general. (orig.)

Microbial leaching of iron from pyrite by moderate thermophile chemolithotropic bacteria

International Nuclear Information System (INIS)

Ilyas, S.; Niazi, S.B.

2007-01-01

The present work was aimed at studying the bioleachability of iron from pyrite by the selected moderately thermophilic strains of acidophilic chemolithotrophic and acidophilic heterotrophic bacteria. These included Sulfobacillus thermosulfidooxidans (chemolithotroph) and an un-identified strain of acidophilic heterotroph (code 6A1TSB) isolated from local environments. As compared to inoculated flasks, dissolution of metal (due to acid leaching) was significantly low in the un-inoculated control flasks in all the experiments in ore. A decrease in the bioleaching activity was observed at the later stages of bioleaching of metal from ore. Among the strategies adopted to enhance the metal leaching rates, a mixed consortium of the metal adapted cultures of the above-mentioned bacteria was found to exhibit the maximum metal leaching efficiency. In all the flasks where high metal leaching rates were observed, concomitantly biomass production rates were also high indicating high growth rates. It showed that the metal bioleaching capability of the bacteria was associated with their growth. Pyrite contained 42% iron. (author)

Composition and leaching of construction and demolition waste: inorganic elements and organic compounds.

Science.gov (United States)

Butera, Stefania; Christensen, Thomas H; Astrup, Thomas F

2014-07-15

Thirty-three samples of construction and demolition waste collected at 11 recycling facilities in Denmark were characterised in terms of total content and leaching of inorganic elements and presence of the persistent organic pollutants PCBs and PAHs. Samples included (i) "clean" (i.e. unmixed) concrete waste, (ii) mixed masonry and concrete, (iii) asphalt and (iv) freshly cast concrete cores; both old and newly generated construction and demolition waste was included. PCBs and PAHs were detected in all samples, generally in non-critical concentrations. Overall, PAHs were comparable to background levels in urban environments. "Old" and "new" concrete samples indicated different PCB congener profiles and the presence of PCB even in new concrete suggested that background levels in raw materials may be an issue. Significant variability in total content of trace elements, even more pronounced for leaching, was observed indicating that the number of analysed samples may be critical in relation to decisions regarding management and utilisation of the materials. Higher leaching of chromium, sulphate and chloride were observed for masonry-containing and partly carbonated samples, indicating that source segregation and management practices may be important. Generally, leaching was in compliance with available leaching limits, except for selenium, and in some cases chromium, sulphate and antimony. Copyright © 2014 Elsevier B.V. All rights reserved.

Released fraction of polychlorinated biphenyls from soil-biosolid system using a leaching procedure and its comparison with bioavailable fraction determined by wheat plant uptake.

Science.gov (United States)

Jachero, Lourdes; Leiva, Claudio; Ahumada, Inés; Richter, Pablo

2017-11-01

The bioavailability of polychlorinated biphenyls (PCBs) in soils amended with biosolids was estimated using an aqueous leaching process of the compounds combined with rotating disk sorptive extraction (RDSE), and compared with bioavailability determined through of PCB absorption in wheat plants growing in the same soil-biosolid matrix. The matrices consisted of soil amended with biosolids at doses of 30, 90, and 200 Mg/ha, which increase concomitantly the organic matter content of the matrix. Considering that PCBs were natively absent in both the biosolids and soil used, the compounds were spiked in the biosolids and aged for 10 days. For each biosolid dose, the aqueous leaching profile was studied and equilibrium time was calculated to be 33 h. The leaching fractions determined by RDSE, considering total PCBs studied, were 12, 7, and 6% and the bioavailable fractions absorbed by the wheat root were found to be 0.5, 0.3, and 0.2% for 30, 90, and 200 Mg/ha doses, respectively. Both fractions leachable and bioavailable decrease with both increasing hydrophobicity of the compound (Kow) and increasing in the biosolid dose. It was found that both fractions (leaching and bioavailable) correlated according to the bivariate least squares regression, represented by a coefficient of correlation of 0.86. Therefore, the application of the chemical method involving a leaching procedure is an alternative to estimate the bioavailable fraction of PCBs in wheat plants in a simpler and in a shorter time.

Measurement of leached hulls

International Nuclear Information System (INIS)

Reilly, T.D.

1979-07-01

Leached hulls are the short lengths of fuel rod cladding and fuel element hardware which constitute a major waste product of a reprocessing plant employing a chop-and-leach head-end process. The small, undissolved fuel residue (0.1 to 1.0% of original fuel content) which is discarded with this waste must be measured for safeguards, material accountability, and process control reasons. This report gives a critical analysis of hull measurement techniques involving the analysis of fission product gamma rays, spontaneous fission neutrons from curium, and delayed neutron activation. Major emphasis is given to the measurement of 2186-keV gamma rays from 144 Ce-- 144 Pr. A detailed description of typical leached hull characteristics is presented at the beginning of the report. An extensive review of experience gained from existing hull measurement systems in the United Kingdom, France, Japan, Germany, Italy, and the United States is presented

Partitioning of elements during coal combustion and leaching experiments

Energy Technology Data Exchange (ETDEWEB)

Wang Wen-feng; Qin Yong; Song Dang-yu; Wang Jun-yi [China University of Mining & Technology, Xuzhou (China). School of Resources and Earth Science

2009-04-15

The mineral component and content of sulfur and 42 major and trace elements of the feed coal, fly and bottom ashes collected from Shizuishan coal-fired power plant, Ningxia, China were analyzed using AFS, INAA, ICP-MS, ICP-AES, XRD. Based on the coal combustion and leaching experiments, the partitioning of these elements during coal combustion and the leaching behavior of the 11 potentially hazardous elements, including As, Cd, Co, Cr, Hg, Mo, Ni, Pb, Se, Th and U were investigated. The results show that the distribution of elements in the fly and bottom ashes is controlled by their volatilities and modes of occurrence in the coal. The degree of volatilization of elements may be mainly associated with boiling/melting points of these elements and their compounds. The elements easily volatilized, organically bound or associated with sub-micrometer and nano minerals (e.g. Al and Na) tend to be enriched in the fine fractions of fly ash, and most elements do not vaporize which are approximately equally partitioned in the fly and bottom ashes. The emission rates of As, Cr, K, Mg, Mn, Mo, Pb, Sb, and Zn are notably influenced by the temperature ranging from 877 to 1300{sup o}C. The leaching behavior of elements depend significantly on their geochemical properties and modes of occurrence. The elements with a low degree of volatilization are not easily leached, while volatile elements easily leached under the acid conditions. Arsenic, B Br, Cd, Cu, Hg, Pb, S, Sb and Se show a higher emission rate during coal combustion, and the leached concentrations of Cd, Co, Mo, Ni and U in the acid media exceed their limited concentrations recommended in relevant environment quality standards for water, which will harm the environment. 32 refs., 4 figs., 4 tabs.

Implementation Guidance for the Next Generation Leaching Tests

Science.gov (United States)

Poster provides an overview of the purpose and utility of this research, highlights of the research to support the Leaching Environmental Assessment Framework (LEAF), application and translation (including data management and analysis software), intended end users, and lessons le...

Product consistency leach tests of Savannah River Site radioactive waste glasses

International Nuclear Information System (INIS)

Bibler, N.E.; Bates, J.K.

1989-01-01

The Product Consistency Test (PCT) is a glass leach test that was developed at the Savannah River Site (SRS) to routinely confirm the durability of nuclear waste glasses that will be produced in the Defense Waste Processing Facility. The PCT is a 7 day, crushed glass leach test in deionized water at 90 degree C. Final leachates are filtered and acidified prior to analysis. To demonstrate the reproducibility of the PCT when performed remotely, SRS and Argonne National Laboratory have performed the PCT on samples of two radioactive glasses. The tests were also performed to compare the releases of the radionuclides with the major nonradioactive glass components and to determine if radiation from the glass was affecting the results of the PCT. The test was performed in triplicate at each laboratory. For the major soluble elements, B, Li, Na, and Si, in the glass, each investigator obtained relative precisions in the range 2--5% in the triplicate tests. This range indicates good precision for the PCT when performed remotely with master slave manipulators in a shielded cell environment

Disposal of leached residual in heap leaching by neutralization

International Nuclear Information System (INIS)

Wang Jingmin

1993-01-01

The disposal results of leached residual with lime are described. Using the ratio of residual to lime being 100 : 1 the ideal disposal results were obtained with the effluent of the neutralized residual close to neutral

Zinc Leaching from Tire Crumb Rubber

Science.gov (United States)

Rhodes, E. P.; Ren, J.; Mays, D. C.

2010-12-01

Recent estimates indicate that more than 2 billion scrap tires are currently stockpiled in the United States and approximately 280 million more tires are added annually. Various engineering applications utilize recycled tires in the form of shredded tire crumb rubber. However, the use of tire crumb rubber may have negative environmental impacts, especially when the rubber comes into contact with water. A review of the literature indicates that leaching of zinc from tire crumb rubber is the most significant water quality concern associated with using this material. Zinc is generally used in tire manufacturing, representing approximately 1.3% of the final product by mass. This study will report results from the U.S. Environmental Protection Agency’s (EPA’s) Synthetic Precipitation Leaching Procedure, batch leaching tests, and column leaching tests performed to quantify the process by which zinc leaches from tire crumb rubber into water. Results are interpreted with a first-order kinetic attachment/detachment model, implemented with the U.S. Agricultural Research Service software HYDRUS-1D, in order to determine the circumstances when zinc leaching from tire crumb rubber would be expected to comply with the applicable discharge limits. One potential application for recycled tires is replacing sand with tire crumb rubber in granular media filters used for stormwater pollution control. For this to be a viable application, the total zinc in the stormwater discharge must be below the EPA’s benchmark value of 0.117 mg/L.

Continuous-flow leaching studies of crushed and cored SYNROC

International Nuclear Information System (INIS)

Coles, D.G.; Bazan, F.

1980-01-01

Both crushed (150 to 300 μm) and cored 1.8 mm diameter) samples of SYNROC have been leached with the single-pass continuous-flow leaching equipment. Crushed samples of Cs-hollandite were also leached in a similar experiment. Temperatures used were 25 0 C and 75 0 C and leachates were 0.03 N NaHCO 3 and distilled water. Leaching rates from SYNROC C were ranked Cs > Sr greater than or equal to Ca > Ba > Zr. A comparison of leaching rates is made between crushed SYNROC, cored SYNROC, and PNL 76-68 glass beads. Problems encountered when comparing the leaching rates of different waste forms are discussed

Quantitative characterization of TiO2 nanoparticle release from textiles by conventional and single particle ICP-MS

Science.gov (United States)

Mackevica, Aiga; Olsson, Mikael Emil; Hansen, Steffen Foss

2018-01-01

TiO2 is ubiquitously present in a wide range of everyday items, both as an intentionally incorporated additive and naturally occurring constituent. It can be found in a wide range of consumer products, including personal care products, food contact materials, and textiles. Normal use of these products may lead to consumer and/or environmental exposure to TiO2, possibly in form of nanoparticles. The aim of this study is to perform a leaching test and apply state-of-the-art methods to investigate nano-TiO2 and total Ti release from five types of commercially available conventional textiles: table placemats, wet wipes, microfiber cloths, and two types of baby bodysuits, with Ti contents ranging from 2.63 to 1448 μg/g. Released particle analysis was performed using conventional and single particle inductively coupled plasma mass spectrometry (ICP-MS and spICP-MS), in conjunction with transmission electron microscopy (TEM), to measure total and particulate TiO2 release by mass and particle number, as well as size distribution. Less than 1% of the initial Ti content was released over 24 h of leaching, with the highest releases reaching 3.13 μg/g. The fraction of nano-TiO2 released varied among fabric types and represented 0-80% of total TiO2 release. Particle mode sizes were 50-75 nm, and TEM imaging revealed particles in sizes of 80-200 nm. This study highlights the importance of using a multi-method approach to obtain quantitative release data that is able to provide an indication regarding particle number, size distribution, and mass concentration, all of which can help in understanding the fate and exposure of nanoparticles.

Method of continuous pressure leaching of ores

International Nuclear Information System (INIS)

Fiala, P.; Baloun, S.; Polansky, M.

1987-01-01

Ore leaching, especially suspensions of ground ore or fine ore fractions from physical treatment was divided into two operations. The former, i.e., ore mixing with technical grade concentrated sulfuric acid proceeded in a separate mixer. The mixture was then transported into an autoclave where the actual leaching proceeded for 2 to 4 hours. The extracted mixture was discharged through the autoclave bottom. The leaching autoclave used can be without any inner structures. The separation of mixing from the actual leaching allows processing ores with high levels of clay components, increasing operating reliability of the facility, reducing consumption of special structural materials and energy, and increasing process efficiency. (E.S.)

COPPER LEACHING FROM WASTE ELECTRIC CABLES BY BIOHYDROMETALLURGY

OpenAIRE

Lambert, Fanny; Bastin, David; Gaydardzhiev, Stoyan; Léonard, Grégoire

2015-01-01

This study examines the leaching of copper from waste electric cables by chemical leaching and leaching catalysed by Acidithiobacillus ferrooxidans in terms of leaching kinetics and reagents consumption. Operational parameters such as the nature of the oxidant (Fe3+, O2), the initial ferric iron concentration (0-10 g/L) and the temperature (21-50°C) were identified to have an important influence on the degree of copper solubilisation. At optimal process conditions, copper extraction above 90%...

Radiocesium leaching from contaminated litter in forest streams

International Nuclear Information System (INIS)

Sakai, Masaru; Gomi, Takashi; Naito, Risa S.; Negishi, Junjiro N.; Sasaki, Michiko; Toda, Hiroto; Nunokawa, Masanori; Murase, Kaori

2015-01-01

In Japanese forests suffering from the Fukushima Daiichi Nuclear Power Plant accident, litter fall provides a large amount of radiocesium from forests to streams. Submerged litter is processed to become a vital food resource for various stream organisms through initial leaching and subsequent decomposition. Although leaching from litter can detach radiocesium similarly to potassium, radiocesium leaching and its migration are poorly understood. We examined both radiocesium and potassium leaching to the water column and radiocesium allocation to minerals (glass beads, silica sand, and vermiculite) in the laboratory using soaked litter with and without minerals on a water column. The mineral types did not affect radiocesium leaching from litter, but soaking in water for 1, 7, and 30 days decreased the radiocesium concentration in litter by ×0.71, ×0.66, and ×0.56, respectively. Meanwhile, the 1-, 7-, and 30-day experiments decreased potassium concentration in litter by ×0.17, ×0.11, and ×0.09, respectively. Leached radiocesium remained in a dissolved form when there was no mineral phases present in the water, whereas there was sorption onto the minerals when they were present. In particular, vermiculite adsorbed radiocesium by two to three orders of magnitude more effectively than the other minerals. Because radiocesium forms (such as that dissolved or adsorbed to organic matter or minerals) can further mobilize to ecosystems, our findings will increase our understanding regarding the dynamics of radiocesium in stream ecosystems. - Highlights: • Radiocesium in contaminated litter was leached when soaked in water. • Radiocesium in litter leached slowly compared to potassium. • Minerals adsorbed dissolved radiocesium that was leached from litter. • Vermiculite effectively adsorbed radiocesium leached from litter

Slow diuron release formulations based on clay-phosphatidylcholine complexes

Czech Academy of Sciences Publication Activity Database

Undabeytia, T.; Recio, E.; Maqueda, C.; Sanchez-Verdejo, T.; Balek, Vladimír

2012-01-01

Roč. 55, JAN (2012), s. 53-61 ISSN 0169-1317 R&D Projects: GA MŠk(CZ) LC523 Institutional support: RVO:61388980 Keywords : Diuron * Phosphatidylcholine * Clay mineral * Leaching * Bioactivity * Slow release Subject RIV: CA - Inorganic Chemistry OBOR OECD: Inorganic and nuclear chemistry Impact factor: 2.342, year: 2012

Precipitation of uranium peroxide from the leach liquor of uranium ores

International Nuclear Information System (INIS)

Gao Xizhen; Lin Sirong; Guo Erhua; Lu Shijie

1995-06-01

A chemical precipitation process of recovering uranium from the leach liquor of uranium ores was investigated. The process primarily includes the precipitation of iron with lime, the preprocessing of the slurry of iron hydroxides and the precipitation of uranium with H 2 O 2 . The leach liquor is neutralized by lime milk to pH 3.7 to precipitate the iron hydroxides which after flocculation and settle is separated out and preprocessed at 170 degree C in an autoclave. H 2 O 2 is then used to precipitate uranium in the leach liquor free of iron, and the pH of process for uranium precipitation adjusted by adding MgO slurry to 3.5. The barren solution can be used to wash the filter cakes of leach tailing. The precipitated slurry of iron hydroxides after being preprocessed is recycled to leaching processes for recovering uranium in it. This treatment can not only avoid the filtering of the slurry of iron hydroxides, but also prevent the iron precipitate from redissolving and consequently the increase of iron concentration in the leach liquor. The results of the investigation indicate that lime, H 2 O 2 and MgO are the main chemical reagents used to obtain the uranium peroxide product containing over 65% uranium from the leach liquor, and they also do not cause environmental pollution. In accordance with the uranium content in the liquor, the consumption of chemical reagent for H 2 O 2 (30%) and MgO are 0.95 kg/kgU and 0.169 kg/kgU, respectively. (1 fig., 8 tabs., 7 refs.)

Recycling of spent lithium-ion battery cathode materials by ammoniacal leaching

International Nuclear Information System (INIS)

Ku, Heesuk; Jung, Yeojin; Jo, Minsang; Park, Sanghyuk; Kim, Sookyung; Yang, Donghyo; Rhee, Kangin; An, Eung-Mo; Sohn, Jeongsoo; Kwon, Kyungjung

2016-01-01

Highlights: • Ammoniacal leaching is used to recover spent Li-ion battery cathode materials. • Leaching agents consist of ammonia, ammonium sulfite and ammonium carbonate. • Ammonium sulfite is a reductant and ammonium carbonate acts as pH buffer. • Co and Cu can be fully leached while Mn and Al are not leached. • Co recovery via ammoniacal leaching is economical compared to acid leaching. - Abstract: As the production and consumption of lithium ion batteries (LIBs) increase, the recycling of spent LIBs appears inevitable from an environmental, economic and health viewpoint. The leaching behavior of Ni, Mn, Co, Al and Cu from treated cathode active materials, which are separated from a commercial LIB pack in hybrid electric vehicles, is investigated with ammoniacal leaching agents based on ammonia, ammonium carbonate and ammonium sulfite. Ammonium sulfite as a reductant is necessary to enhance leaching kinetics particularly in the ammoniacal leaching of Ni and Co. Ammonium carbonate can act as a pH buffer so that the pH of leaching solution changes little during leaching. Co and Cu can be fully leached out whereas Mn and Al are hardly leached and Ni shows a moderate leaching efficiency. It is confirmed that the cathode active materials are a composite of LiMn_2O_4, LiCo_xMn_yNi_zO_2_, Al_2O_3 and C while the leach residue is composed of LiNi_xMn_yCo_zO_2, LiMn_2O_4, Al_2O_3, MnCO_3 and Mn oxides. Co recovery via the ammoniacal leaching is believed to gain a competitive edge on convenitonal acid leaching both by reducing the sodium hydroxide expense for increasing the pH of leaching solution and by removing the separation steps of Mn and Al.

EFRT M-12 Issue Resolution: Caustic-Leach Rate Constants from PEP and Laboratory-Scale Tests

Energy Technology Data Exchange (ETDEWEB)

Mahoney, Lenna A.; Rassat, Scot D.; Eslinger, Paul W.; Aaberg, Rosanne L.; Aker, Pamela M.; Golovich, Elizabeth C.; Hanson, Brady D.; Hausmann, Tom S.; Huckaby, James L.; Kurath, Dean E.; Minette, Michael J.; Sundaram, S. K.; Yokuda, Satoru T.

2010-01-01

Pacific Northwest National Laboratory (PNNL) has been tasked by Bechtel National Inc. (BNI) on the River Protection Project-Hanford Tank Waste Treatment and Immobilization Plant (RPP-WTP) project to perform research and development activities to resolve technical issues identified for the Pretreatment Facility (PTF). The Pretreatment Engineering Platform (PEP) was designed, constructed and operated as part of a plan to respond to issue M12, “Undemonstrated Leaching Processes” of the External Flowsheet Review Team (EFRT) issue response plan.( ) The PEP is a 1/4.5-scale test platform designed to simulate the WTP pretreatment caustic leaching, oxidative leaching, ultrafiltration solids concentration, and slurry washing processes. The PEP replicates the WTP leaching processes using prototypic equipment and control strategies. The PEP also includes non-prototypic ancillary equipment to support the core processing. The work described in this report addresses caustic leaching under WTP conditions, based on tests performed with a Hanford waste simulant. Because gibbsite leaching kinetics are rapid (gibbsite is expected to be dissolved by the time the final leach temperature is reached), boehmite leach kinetics are the main focus of the caustic-leach tests. The tests were completed at the laboratory-scale and in the PEP, which is a 1/4.5-scale mock-up of key PTF process equipment. Two laboratory-scale caustic-leach tests were performed for each of the PEP runs. For each PEP run, unleached slurry was taken from the PEP caustic-leach vessel for one batch and used as feed for both of the corresponding laboratory-scale tests.

Development of an accelerated leaching method for incineration bottom ash correlated to toxicity characteristic leaching protocol.

Science.gov (United States)

Lin, Shengxuan; Zhou, Xuedong; Ge, Liya; Ng, Sum Huan; Zhou, Xiaodong; Chang, Victor Wei-Chung

2016-10-01

Heavy metals and some metalloids are the most significant inorganic contaminants specified in toxicity characteristic leaching procedure (TCLP) in determining the safety of landfills or further utilization. As a consequence, a great deal of efforts had been made on the development of miniaturized analytical devices, such as Microchip Electrophoresis (ME) and μTAS for on-site testing of heavy metals and metalloids to prevent spreading of those pollutants or decrease the reutilization period of waste materials such as incineration bottom ash. However, the bottleneck lied in the long and tedious conventional TCLP that requires 18 h of leaching. Without accelerating the TCLP process, the on-site testing of the waste material leachates was impossible. In this study, therefore, a new accelerated leaching method (ALM) combining ultrasonic assisted leaching with tumbling was developed to reduce the total leaching time from 18 h to 30 min. After leaching, the concentrations of heavy metals and metalloids were determined with ICP-MS or ICP-optical emission spectroscopy. No statistical significance between ALM and TCLP was observed for most heavy metals (i.e., cobalt, manganese, mercury, molybdenum, nickel, silver, strontium, and tin) and metalloids (i.e., arsenic and selenium). For the heavy metals with statistical significance, correlation factors derived between ALM and TCLP were 0.56, 0.20, 0.037, and 0.019 for barium, cadmium, chromium, and lead, respectively. Combined with appropriate analytical techniques (e.g., ME), the ALM can be applied to rapidly prepare the incineration bottom ash samples as well as other environmental samples for on-site determination of heavy metals and metalloids. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An evaluation of arsenic release from monolithic solids using a modified semi-dynamic leaching test

International Nuclear Information System (INIS)

Dermatas, Dimitris; Moon, Deok Hyun; Menounou, Nektaria; Meng, Xiaoguang; Hires, Richard

2004-01-01

Quicklime and quicklime-fly ash-based stabilization/solidification (S/S) effectiveness was evaluated by performing semi-dynamic leaching tests (American Nuclear Society 16.1). Artificial soil samples, contaminated with arsenic trioxide (As 2 O 3 ) as well as field soil samples contaminated with arsenic (As) were tested. The artificial soils were prepared by mixing amounts of kaolinite or montmorillonite with fine quartz sand. The S/S effectiveness was evaluated by measuring effective diffusion coefficients (D e ) and leachability indices (LX). Treatment was most effective in kaolinite-based artificial soils treated with quicklime and in quicklime-fly ash treated field soils. The experimental results indicate that D e values were lowered as a result of S/S treatment. Upon treatment LX values were higher than 9, suggesting that S/S treated soils are acceptable for 'controlled utilization'. Based on a model developed by de Groot and van der Sloot [G.J. de Groot, H.A. van der Sloot, in: T.M. Gilliam, C.C. Wiles (Eds.), Stabilization and Solidification of Hazardous, Radioactive, and Mixed Wastes, vol. 2, ASTM STP 1123, ASTM, PA, 1992, p. 149], the leaching mechanism for all of the treated soils was found to be controlled by diffusion. The effect of soluble silica (Si) on As leachability was also evaluated. When soluble Si concentration was less than 1 ppm, As leachability was the lowest. The controlling mechanism of As immobilization whether sorption, precipitation, or inclusion was also evaluated. It was determined that precipitation was the dominant mechanism

EFRT M12 Issue Resolution: Comparison of PEP and Bench-Scale Oxidative Leaching Results

Energy Technology Data Exchange (ETDEWEB)

Rapko, Brian M.; Brown, Christopher F.; Eslinger, Paul W.; Fountain, Matthew S.; Hausmann, Tom S.; Huckaby, James L.; Hanson, Brady D.; Kurath, Dean E.; Minette, Michael J.

2009-08-14

Pacific Northwest National Laboratory (PNNL) has been tasked by Bechtel National Inc. (BNI) on the River Protection Project-Hanford Tank Waste Treatment and Immobilization Plant (RPP-WTP) project to perform research and development activities to resolve technical issues identified for the Pretreatment Facility (PTF). The Pretreatment Engineering Platform (PEP) was designed and constructed and is to be operated as part of a plan to respond to issue M12, “Undemonstrated Leaching Processes.” The PEP is a 1/4.5-scale test platform designed to simulate the WTP pretreatment caustic leaching, oxidative leaching, ultrafiltration solids concentration, and slurry washing processes. The PEP replicates the WTP leaching processes using prototypic equipment and control strategies. The PEP also includes non-prototypic ancillary equipment to support the core processing. Two operating scenarios are currently being evaluated for the ultrafiltration process (UFP) and leaching operations. The first scenario has caustic leaching performed in the UFP-2 ultrafiltration feed vessels (i.e., vessel UFP-VSL-T02A in the PEP; and vessels UFP-VSL-00002A and B in the WTP PTF). The second scenario has caustic leaching conducted in the UFP-1 ultrafiltration feed preparation vessels (i.e., vessels UFP-VSL-T01A and B in the PEP; vessels UFP-VSL-00001A and B in the WTP PTF). In both scenarios, 19-M sodium hydroxide solution (NaOH, caustic) is added to the waste slurry in the vessels to dissolve solid aluminum compounds (e.g., gibbsite, boehmite). Caustic addition is followed by a heating step that uses direct steam injection to accelerate the leaching process. Following the caustic leach, the vessel contents are cooled using vessel cooling jackets and/or external heat exchangers. The main difference between the two scenarios is that for leaching in UFP1, the 19-M NaOH is added to un-concentrated waste slurry (3 to 8 wt% solids), while for leaching in UFP2, the slurry is concentrated to nominally

Leaching process

International Nuclear Information System (INIS)

Heinen, H.J.; McClelland, G.E.; Lindstrom, R.E.

1982-01-01

A gold and uranium ore is heap leached in accordance with the process comprising initial agglomeration of fines in the feed by means of a binding agent and cyanide solution. The lixiviant comprises a compatible mixture of sodium cyanide and sodium bicarbonate

Leaching process

Energy Technology Data Exchange (ETDEWEB)

Heinen, H J; McClelland, G E; Lindstrom, R E

1982-10-18

A gold and uranium ore is heap leached in accordance with the process comprising initial agglomeration of fines in the feed by means of a binding agent and cyanide solution. The lixiviant comprises a compatible mixture of sodium cyanide and sodium bicarbonate.

Leaching of potassium in a lysimeter experiment

International Nuclear Information System (INIS)

Gerzabek, M.H.

1996-11-01

Leaching of potassium was studied in the lysimeter plant in Seibersdorf/Austria (Pannonian climate). Averaged over three years, gravitational water amounted to 15.7% of the sum of precipitation (mean 485 mm) and irrigation (mean 138 mm). Differences between the four soils with respect to drainage were explained by the specific percentage of the soil skeleton. The average yearly potassium leaching ranged from 3.64 kg K/ha·yr (Dystric-Cambisol) to 22.7 kg K/ha·yr (drained Gleysol). Correlation between gravitational water volume and potassium leaching were only significant for one out of four soil types. No correlation was observed between extractable potassium in the soil profiles and potassium leaching. (author)

Acidic leaching of potentially toxic metals cadmium, cobalt, chromium, copper, nickel, lead, and zinc from two Zn smelting slag materials incubated in an acidic soil.

Science.gov (United States)

Liu, Taoze; Li, Feili; Jin, Zhisheng; Yang, Yuangen

2018-07-01

A column leaching study, coupled with acid deposition simulation, was conducted to investigate the leaching of potentially toxic metals (PTM) from zinc smelting slag materials (SSM) after being incubated in an acid Alfisol for 120 days at room temperature. Two SSMs (SSM-A: acidic, 10 yrs exposure with moderate high PTM concentrations versus SSM-B: alkaline, 2 yrs exposure with extremely high PTM concentrations), were used for the incubation at 0.5, 1, 2.5, 5 wt% amendment ratios in triplicate. Five leaching events were conducted at day 1, 3, 7, 14, and 28, and the leaching of PTMs mainly occurred in the first three leaching events, with the highest PTM concentrations in leachate measured from 5 wt% SSM amendments. After leaching, 2.5, 12, 5.5, 14, 11, and 9 wt% of M3 extractable Pb, Zn, Cd, Co, Cr, and Ni could be released from 5 wt% SSM-A amended soils, being respectively 25, 12, 4, 2, 2, and 2 times more than those from 5 wt% SSM-B amended soils. In the leachates, the concentrations of PTMs were mostly affected by leachant pH and were closely correlated to the concentrations of Fe, Al, Ca, Mg and P with Cd, Pb, and Zn showing the most environmental concern. Visual MINTEQ 3.1 modeling suggested metallic ions and sulfate forms as the common chemical species of PTMs in the leachates; whereas, organic bound species showed importance for Cd, Pb, Cu, and Ni, and CdCl + was observed for Cd. Aluminum hydroxy, phosphate, and sulfate minerals prevailed as the saturated minerals, followed by chloropyromorphite (Pb 5 (PO 4 ) 3 Cl) and plumbogummite (PbAl 3 (PO 4 ) 2 (OH) 5 ·H 2 O) in the leachates. This study suggested that incubation of SSMs in acidic soil for a long term can enhance the release of PTMs as the forms of metallic ions and sulfate when subjected to acid deposition leaching. Copyright © 2018 Elsevier Ltd. All rights reserved.

Recovery of Iron from Pyrolusite Leaching Slag by a Lab-Scale Circulation Process of Oxalic Acid Leaching and Ultraviolet Irradiation

Directory of Open Access Journals (Sweden)

Biao Deng

2017-12-01

Full Text Available Pyrolusite leaching slag is a Fe-containing slag generated from pyrolusite leaching process with SO2. Recovery of iron from the slag not only has economic benefit, but also prevents the secondary pollution to the environment. A novel lab-scale cyclic process for recovering iron from pyrolusite leaching slag was introduced. The process contains two steps: (1 iron was leached with oxalic acid and [Fe(C2O4n](3−2n+ solution was generated; (2 the [Fe(C2O4n](3−2n+ solution was irradiated by ultraviolet and ferrous oxalate precipitation were obtained. The effect of operation parameter on leaching and irradiation process were studied separately. In the leaching process, the optimal solid/liquid ratio, oxalic acid concentration, leaching temperature, stirring rate, and leaching time are 1:50, 0.40 mol/L, 95 °C, 300 r/min, and 3 h, respectively. In the irradiation process, the best irradiation wavelength, Fe/oxalic acid molar ratio and irradiation time are 254 nm, 1:4, and 30 min. Besides, a test of 9 continuous cycles was carried out and the performance and material balance of the combined process were investigated. The results showed that the cyclic process is entirely feasible and prove to be stable producing, and ferrous oxalate of 99.32% purity. Material balance indicated that 95.17% of iron was recovered in the form of FeC2O4·2H2O, and the recovery efficiency of oxalic acid was 58.52%.

Experiment on bio-leaching of associated molybdenum and uranium ore

International Nuclear Information System (INIS)

Zheng Ying; Fan Baotuan; Liu Jian; Meng Yunsheng; Liu Chao

2007-01-01

Column leaching experiment results on associated molybdenum uranium ore by bacteria (T. f) are introduced. The ore are leached for 210 days using bacteria domesticated to tolerate molybdenum, the leaching of uranium is of 98% and leaching of molybdenum is of 41%. Sulphuric acid produced by bio-oxidation of sulfides in ore can meet the demand of ore leaching. (authors)

ESCA studies on leached glass forms

International Nuclear Information System (INIS)

Dawkins, B.G.

1979-01-01

Electron Spectroscopy for Chemical Analysis (ESCA) results for frit, obsidian, NBS standard, and Savannah River Laboratory (SRL) glass forms that have been subjected to cumulative water leachings of 36 hours show that [Na] exhibits the largest and fastest change of all the elements observed. Leaching of surface Na occurred within minutes. Surface Na depletion increased with leach time. Continuous x-ray irradiation and argon ion milling induced Na mobility, precluding semiquantitative ESCA analysis at normal operating temperatures. However, the sample stage has been equipped with a liquid nitrogen supply and alkali mobility should be eliminated in future work

Nanostructured Diclofenac Sodium Releasing Material

Science.gov (United States)

Nikkola, L.; Vapalahti, K.; Harlin, A.; Seppälä, J.; Ashammakhi, N.

2008-02-01

Various techniques have been developed to produce second generation biomaterials for tissue repair. These include extrusion, molding, salt leaching, spinning etc, but success in regenerating tissues has been limited. It is important to develop porous material, yet with a fibrous structure for it to be biomimetic. To mimic biological tissues, the extra-cellular matrix usually contains fibers in nano scale. To produce nanostructures, self-assembly or electrospinning can be used. Adding a drug release function to such a material may advance applications further for use in controlled tissue repair. This turns the resulting device into a multifunctional porous, fibrous structure to support cells and drug releasing properties in order to control tissue reactions. A bioabsorbable poly(ɛ-caprolactone-co-D,L lactide) 95/5 (PCL) was made into diluted solution using a solvent, to which was added 2w-% of diclofenac sodium (DS). Nano-fibers were made by electrospinning onto substrate. Microstructure of the resulting nanomat was studied using SEM and drug release profiles with UV/VIS spectroscopy. Thickness of the electrospun nanomat was about 2 mm. SEM analysis showed that polymeric nano-fibers containing drug particles form a highly interconnected porous nano structure. Average diameter of the nano-fibers was 130 nm. There was a high burst peak in drug release, which decreased to low levels after one day. The used polymer has slow a degradation rate and though the nanomat was highly porous with a large surface area, drug release rate is slow. It is feasible to develop a nano-fibrous porous structure of bioabsorbable polymer, which is loaded with test drug. Drug release is targeted at improving the properties of biomaterial for use in controlled tissue repair and regeneration.

Leaching behaviour of incineration bottom ash in a reuse scenario: 12years-field data vs. lab test results.

Science.gov (United States)

Di Gianfilippo, Martina; Hyks, Jiri; Verginelli, Iason; Costa, Giulia; Hjelmar, Ole; Lombardi, Francesco

2018-03-01

Several types of standardized laboratory leaching tests have been developed during the past few decades to evaluate the leaching behaviour of waste materials as a function of different parameters, such as the pH of the eluate and the liquid to solid ratio. However, the link between the results of these tests and leaching data collected from the field (e.g. in disposal or reuse scenarios) is not always straightforward. In this work, we compare data obtained from an on-going large scale field trial, in which municipal solid waste incineration bottom ash is being tested as road sub-base material, with the results obtained from percolation column and pH-dependence laboratory leaching tests carried out on the bottom ash at the beginning of the test. The comparisons reported in this paper show that for soluble substances (e.g. Cl, K and SO 4 ), percolation column tests can provide a good indication of the release expected in the field with deviations usually within a factor of 3. For metals characterized by a solubility-controlled release, i.e. that depends more on eluate pH than the liquid to solid ratio applied, the results of pH-dependence tests describe more accurately the eluate concentration trends observed in the field with deviations that in most cases (around 80%) are within one order of magnitude (see e.g. Al and Cd). The differences between field and lab-scale data might be in part ascribed to the occurrence in the field of weathering reactions (e.g. carbonation) but also to microbial decomposition of organic matter that modifying leachate pH affect the solubility of several constituents (e.g. Ca, Ba and Cr). Besides, weathering reactions can result in enhanced adsorption of fulvic acids to iron/aluminum (hydr)oxides, leading to a decrease in the leaching of fulvic acids and hence of elements such as Cu, Ni and Pb that strongly depend on DOC leaching. Overall, this comparison shows that percolation column tests and pH-dependence tests can represent a reliable

Laboratory studies on leaching of low grade uranium ores and treatment of low level liquid waste generated by leaching experiments

International Nuclear Information System (INIS)

Palabrica, O.T.; Antonino, E.J.; Caluag, L.A.; Villamater, D.

1980-07-01

Acid leaching experiments of preconcentrated uranium ore were carried out at a pulp density of 50% solids, using sulfuric acid with sodium chlorate as oxidant. The different leaching parameters considered in this work were temperature, oxidant level and leaching time. In the experimental procedure, the concentration of oxidant and the temperature were varied to determine how they affect the leaching process. Experimental results are illustrated in tabulated form for better interpretation. Uranium analyses were done by fluorimetric and delayed-neutron activation analysis. An anion exchange method using Dowex 1 x 8, 200-400 mesh (Cl - ) was used in treating the low-level liquid waste generated by leaching experiments. The purpose of this treatment was to minimize radioactive contamination in the waste materials and also to recover some of the uranium left in the liquid waste. (author)

Spent LWR fuel leach tests: Waste Isolation Safety Assessment program

International Nuclear Information System (INIS)

Katayama, Y.B.

1979-04-01

Spent light-water-reactor (LWR) fuels with burnups of 54.5, 28 and 9 MWd/kgU were leach-tested in deionized water at 25 0 C. Fuel burnup has no apparent effect on the calculated leach rates based upon the behavior of 137 Cs and 239+240 Pu. A leach test of 54.5 MWd/kgU spent fuel in synthetic sea brine showed that the cesium-based leach rate is lower in sea brine than in deionized water. A rise in the leach rate was observed after approximately 600 d of cumulative leaching. During the rise, the leach rate for all the measured radionuclides become nearly equal. Evidence suggests that exposure of new surfaces to the leachant may cause the increase. As a result, experimental work to study leaching mechanisms of spent fuel has been initiated. 22 figures

Analysis of SPR salt cavern remedial leach program 2013.

Energy Technology Data Exchange (ETDEWEB)

Weber, Paula D.; Gutierrez, Karen A.; Lord, David L.; Rudeen, David Keith

2013-09-01

The storage caverns of the US Strategic Petroleum Reserve (SPR) exhibit creep behavior resulting in reduction of storage capacity over time. Maintenance of oil storage capacity requires periodic controlled leaching named remedial leach. The 30 MMB sale in summer 2011 provided space available to facilitate leaching operations. The objective of this report is to present the results and analyses of remedial leach activity at the SPR following the 2011 sale until mid-January 2013. This report focuses on caverns BH101, BH104, WH105 and WH106. Three of the four hanging strings were damaged resulting in deviations from normal leach patterns; however, the deviations did not affect the immediate geomechanical stability of the caverns. Significant leaching occurred in the toes of the caverns likely decreasing the number of available drawdowns until P/D ratio criteria are met. SANSMIC shows good agreement with sonar data and reasonably predicted the location and size of the enhanced leaching region resulting from string breakage.

Leaching of wood ash - Laboratory and field studies; Lakning av vedaska - Laboratorie- och faeltstudier

Energy Technology Data Exchange (ETDEWEB)

Larsson, Per-Erik

2012-02-15

High forest production leads to diminishing amounts of base cations and micro nutrients in forest soils. This is due to uptake in, and harvest of, the trees. Losses can be compensated for by spreading stabilized wood ash on the forest ground, which means recycling of base cations and micro nutrients. Chemical composition of wood ash can easily be described by standard methods in the laboratory. However, this does not include the process of leaching in nature, such as which components and leaching rate for different compounds. During field conditions several factors are added, which are not available in the laboratory. After almost 10 years in the forest soils there still remains large quantities of the original product. Only 10-30 % of the wood ash products and 5 % of the lime product has been leached. In the laboratory study the leached amount was slightly larger, at the most 35 % for wood ash and 20 % for lime. Both studies indicate long time for weathering of the products in forest soils. Slower leaching rate from pellets of wood ash compared to leaching rate from crushed wood ash in the laboratory study is not verified by the field study. This indicates limited possibilities to control rates of leaching in the environment

Recycling of spent lithium-ion battery cathode materials by ammoniacal leaching

Energy Technology Data Exchange (ETDEWEB)

Ku, Heesuk; Jung, Yeojin; Jo, Minsang; Park, Sanghyuk [Department of Energy & Mineral Resources Engineering, Sejong University, Seoul 05006 (Korea, Republic of); Kim, Sookyung [Urban Mine Department, Korea Institute of Geoscience and Mineral Resources, 124 Gwahang-no, Yuseong-gu, Daejeon (Korea, Republic of); Yang, Donghyo, E-mail: ydh@kigam.re.kr [Urban Mine Department, Korea Institute of Geoscience and Mineral Resources, 124 Gwahang-no, Yuseong-gu, Daejeon (Korea, Republic of); Rhee, Kangin; An, Eung-Mo; Sohn, Jeongsoo [Urban Mine Department, Korea Institute of Geoscience and Mineral Resources, 124 Gwahang-no, Yuseong-gu, Daejeon (Korea, Republic of); Kwon, Kyungjung, E-mail: kfromberk@gmail.com [Department of Energy & Mineral Resources Engineering, Sejong University, Seoul 05006 (Korea, Republic of)

2016-08-05

Highlights: • Ammoniacal leaching is used to recover spent Li-ion battery cathode materials. • Leaching agents consist of ammonia, ammonium sulfite and ammonium carbonate. • Ammonium sulfite is a reductant and ammonium carbonate acts as pH buffer. • Co and Cu can be fully leached while Mn and Al are not leached. • Co recovery via ammoniacal leaching is economical compared to acid leaching. - Abstract: As the production and consumption of lithium ion batteries (LIBs) increase, the recycling of spent LIBs appears inevitable from an environmental, economic and health viewpoint. The leaching behavior of Ni, Mn, Co, Al and Cu from treated cathode active materials, which are separated from a commercial LIB pack in hybrid electric vehicles, is investigated with ammoniacal leaching agents based on ammonia, ammonium carbonate and ammonium sulfite. Ammonium sulfite as a reductant is necessary to enhance leaching kinetics particularly in the ammoniacal leaching of Ni and Co. Ammonium carbonate can act as a pH buffer so that the pH of leaching solution changes little during leaching. Co and Cu can be fully leached out whereas Mn and Al are hardly leached and Ni shows a moderate leaching efficiency. It is confirmed that the cathode active materials are a composite of LiMn{sub 2}O{sub 4}, LiCo{sub x}Mn{sub y}Ni{sub z}O{sub 2,} Al{sub 2}O{sub 3} and C while the leach residue is composed of LiNi{sub x}Mn{sub y}Co{sub z}O{sub 2}, LiMn{sub 2}O{sub 4}, Al{sub 2}O{sub 3}, MnCO{sub 3} and Mn oxides. Co recovery via the ammoniacal leaching is believed to gain a competitive edge on convenitonal acid leaching both by reducing the sodium hydroxide expense for increasing the pH of leaching solution and by removing the separation steps of Mn and Al.

Numerical simulation of vertical infiltration for leaching fluid in situ

International Nuclear Information System (INIS)

Li Jinxuan; Shi Weijun; Zhang Weimin

1998-01-01

Based on the analysis of movement law of leaching fluid in breaking and leaching experiment in situ, the movement of leaching fluid can be divided into two main stages in the leaching process in situ: Vertical Infiltration in unsaturation zone and horizontal runoff in saturation zone. The corresponding mathematics models are sep up, and the process of vertical infiltration of leaching fluid is numerically simulated

Assessment of heavy metals leaching from (biochar obtained from industrial sewage sludge

Directory of Open Access Journals (Sweden)

Julija Pečkytė

2015-10-01

Full Text Available Biochar can be produced from many various feedstock including biomass residues such as straw, branches, sawdust and other agricultural and forestry waste. One of the alternatives is to obtain biochar from industrial sewage sludge, however, the use of such a product could be limited due to high quantities of heavy metals in the biochar as a product. Total concentration of heavy metals provides only limited information on the behavior of heavy metals, therefore, batch leaching and up-flow percolation leaching tests were applied to study the leaching of heavy metals (Cd, Pb, Cr, Ni, Zn, Cu from (biochar produced from two types of sewage sludge: from paper mill and leather industries.

Role of construction debris in release of copper, chromium, and arsenic from treated wood structures

Science.gov (United States)

Stan T. Lebow; Steven A. Halverson; Jeffrey J. Morrell; John. Simonsen

Recent research on the release of wood preservatives from treated wood used in sensitive environments has not considered the potential contribution from construction residues. This study sought to develop leaching rate data for small construction debris and compare those to the release rate from treated wood itself. Western hemlock boards were pressure treated with...

Stainless steel leaches nickel and chromium into foods during cooking.

Science.gov (United States)

Kamerud, Kristin L; Hobbie, Kevin A; Anderson, Kim A

2013-10-02

Toxicological studies show that oral doses of nickel and chromium can cause cutaneous adverse reactions such as dermatitis. Additional dietary sources, such as leaching from stainless steel cookware during food preparation, are not well characterized. This study examined stainless steel grades, cooking time, repetitive cooking cycles, and multiple types of tomato sauces for their effects on nickel and chromium leaching. Trials included three types of stainless steels and a stainless steel saucepan, cooking times of 2-20 h, 10 consecutive cooking cycles, and four commercial tomato sauces. After a simulated cooking process, samples were analyzed by ICP-MS for Ni and Cr. After 6 h of cooking, Ni and Cr concentrations in tomato sauce increased up to 26- and 7-fold, respectively, depending on the grade of stainless steel. Longer cooking durations resulted in additional increases in metal leaching, where Ni concentrations increased 34-fold and Cr increased approximately 35-fold from sauces cooked without stainless steel. Cooking with new stainless steel resulted in the largest increases. Metal leaching decreases with sequential cooking cycles and stabilized after the sixth cooking cycle, although significant metal contributions to foods were still observed. The tenth cooking cycle resulted in an average of 88 μg of Ni and 86 μg of Cr leached per 126 g serving of tomato sauce. Stainless steel cookware can be an overlooked source of nickel and chromium, where the contribution is dependent on stainless steel grade, cooking time, and cookware usage.

Stainless Steel Leaches Nickel and Chromium into Foods During Cooking

Science.gov (United States)

Kamerud, Kristin L.; Hobbie, Kevin A.; Anderson, Kim A.

2014-01-01

Toxicological studies show that oral doses of nickel and chromium can cause cutaneous adverse reactions such as dermatitis. Additional dietary sources, such as leaching from stainless steel cookware during food preparation, are not well characterized. This study examined stainless steel grades, cooking time, repetitive cooking cycles, and multiple types of tomato sauces for their effects on nickel and chromium leaching. Trials included three types of stainless steels and a stainless steel saucepan; cooking times of 2 to 20 hours, ten consecutive cooking cycles, and four commercial tomato sauces. After a simulated cooking process, samples were analyzed by ICP-MS for Ni and Cr. After six hours of cooking, Ni and Cr concentrations in tomato sauce increased up to 26- and 7-fold respectively, depending on the grade of stainless steel. Longer cooking durations resulted in additional increases in metal leaching, where Ni concentrations increased 34 fold and Cr increased approximately 35 fold from sauces cooked without stainless steel. Cooking with new stainless steel resulted in the largest increases. Metal leaching decreases with sequential cooking cycles and stabilized after the sixth cooking cycle, though significant metal contributions to foods were still observed. The tenth cooking cycle, resulted in an average of 88 μg of Ni and 86 μg of Cr leached per 126 g serving of tomato sauce. Stainless steel cookware can be an overlooked source of nickel and chromium, where the contribution is dependent on stainless steel grade, cooking time, and cookware usage. PMID:23984718

In situ leaching of uranium: Technical, environmental and economic aspects

International Nuclear Information System (INIS)

1989-01-01

Within the framework of its activities in nuclear raw materials the International Atomic Energy Agency has convened a series of meetings to discuss various aspects of uranium ore processing technology, recovery of uranium from non-conventional resources and development of projects for the production of uranium concentrates including economic aspects. As part of this continuing effort to discuss and document important aspects of uranium production the IAEA convened a Technical Committee Meeting on Technical, Economic and Environmental Aspects of In-Situ Leaching. Although the use of this technique is limited by geological and economic constraints, it has a significant potential to produce uranium at competitive prices. This is especially important in the current uranium market which is mainly characterised by large inventories, excess production capability and low prices. This situation is not expected to last indefinitely but it is unlikely to change drastically in the next ten years or so. This Technical Committee Meeting was held in Vienna from 3 to 6 November 1987 with the attendance of 24 participants from 12 countries. Eight papers were presented. Technical sessions covered in-situ mining research, environmental and licensing aspects and restoration of leached orebodies; the technological status of in-situ leaching, the current status and future prospects of in-situ leaching of uranium in Member States, general aspects of planning and implementation of in-situ projects and the economics of in-situ leaching. Refs, figs and tabs

Leaching of cyanogenic glucosides and cyanide from white clover green manure

DEFF Research Database (Denmark)

Bjarnholt, Nanna; Lægdsmand, Mette; Hansen, Hans Chr. Bruun

2008-01-01

Use of crops for green manure as a substitute for chemical fertilizers and pesticides is an important approach towards more sustainable agricultural practices. Green manure from white clover is rich in nitrogen but white clover also produces the cyanogenic glucosides (CGs) linamarin...... and lotaustralin; CGs release toxic hydrogen cyanide (HCN) upon hydrolysis which may be utilized for pest control. We demonstrate that applying CGs in the form of a liquid extract of white clover to large columns of intact agricultural soils can result in leaching of toxic cyanide species to a depth of at least 1...

Leaching of TCIPP from furniture foam is rapid and substantial.

Science.gov (United States)

Stubbings, William A; Harrad, Stuart

2018-02-01

A series of laboratory experiments were conducted, in which waste furniture polyurethane foam samples containing tris (1-chloro-2-propyl) phosphate (TCIPP) were contacted with a range of leaching fluids, formulated to simulate the composition of landfill leachate. Leaching was examined under a number of different scenarios, such as: dissolved humic matter concentration, pH, and temperature, as well as the effect of agitation, and waste:leaching fluid contact duration. In addition to single batch (no replenishment of leaching fluid), serial batch (draining of leachate and replenishment with fresh leaching fluid at various time intervals) experiments were conducted. Leaching of TCIPP from PUF appears to be a first order process. Concentrations of TCIPP in leachate generated by the experiments in this study ranged from 13 mg L -1 to 130 mg L -1 . In serial batch leaching experiments, >95% of TCIPP was depleted from PUF after 168 h total contact with leaching fluid. Our experiments indicate leaching is potentially a very significant pathway of TCIPP emissions to the environment. Copyright © 2017. Published by Elsevier Ltd.

Remediation of hazardous waste sites by heap leaching

International Nuclear Information System (INIS)

Samani, Z.; Hanson, A.; Dwyer, B.

1994-01-01

Efforts are being made to devise technologies and treatment systems to remediate contaminated soil-on site without generating significant wastes for off-site disposal. Heap leaching, a technique used extensively in the mining industry, has been investigated as a method for remediation of hazardous chemical contamination of the vadose zone. In the mining industry, metal-bearing ore is excavated and mounded on a pad. The metals are removed by passing a special leaching solution through the ore. In this study, the removal of chromium(VI) from the New Mexico soils (sand, sandy loam, and clay) using heap leaching was evaluated at a column scale. The heap leaching study demonstrated greater than 99% removal of Cr(VI) from all three soils using tap water as the leaching agent. (author) 13 figs., 5 tabs., 21 refs

Comparison of oxidants in alkaline leaching of uranium ore

International Nuclear Information System (INIS)

Sreenivas, T.; Rajan, K.C.; Srinivas, K.; Anand Rao, K.; Manmadha Rao, M.; Venkatakrishnan, R.R.; Padmanabhan, N.P.H.

2007-01-01

The uranium minerals occurring in various ore deposits consists of predominantly uranous ion (U +4 ), necessitating use of an oxidant and other lixiviants for efficient dissolution during leaching. Unlike acid leaching route, where uranium minerals dissolution could be achieved efficiently with cheaper lixiviants, processing of ores by alkaline leaching route involve expensive lixiviants and drastic leaching conditions. Alkaline leaching of uranium ores becomes economical only upon using cheaper and efficient oxidants and conservation of other reagents by their recycle. The present paper gives efficacy of various oxidants - KMnO 4 , NaOCl, Cu - NH 3 , air and oxygen, in the leaching of uranium from a low-grade dolostone hosted uranium ore of India. A comparison based on technical merits and cost of the oxidant chemicals is discussed. (author)

Leach behavior of hydrofracture grout incorporating radioactive wastes

International Nuclear Information System (INIS)

Moore, J.G.; Godbee, H.W.; Kibbey, A.H.

1976-01-01

Rates at which Sr, Cs, Pu, and Cm are leached from hydrofracture grout were measured. The fraction of an isotope leached varied with the square root of time if the leachant was replaced more frequently than once per day, but was inhibited or depressed if replacement was made less often. The amount of Sr or Cs leached from the grout varied directly with the degree of drying during curing and inversely with the time of curing. Of the clay additives studied for enhancing cesium retention, Grundite, while satisfactory, was the least effective. In general, the isotope leach rate followed the order: Cs greater than Sr greater than Cm greater than Pu. The amount leached as a function of the leachant varied in the order: distilled water greater than tap water greater than grout water. Concentrating the waste by a factor of up to 4 before grouting had little effect on the leach rate. Comparison with results for other products indicates that the grout can provide leach rates comparable to those for wastes incorporated into borosilicate glass. Theoretical relationships that consider diffusion and instantaneous reaction (an equilibrium or time-dependent relationship between mobile and immobile forms of a species) were in good agreement with the data for the 28-day-cured grout when the leachant was initially replaced twice per day. The credibility of laboratory results with simulated waste was substantiated by a short-term continuous leach test made on a fragment of a core sample of actual hydrofracture grout. The modified effective diffusivities (10 -11 to 10 -10 cm 2 /s, equivalent to a leach rate of the order of 10 -7 g cm -2 day -1 ) for Sr and Cs calculated from these data are comparable to laboratory values. 17 figures, 5 tables

Pilot test of bacterial percolation leaching at Fuzhou uranium mine

International Nuclear Information System (INIS)

Fan Baotuan; Liu Jian; Jiang Yngqiong; Cai Chunhui; Jiang Lang; Zhou Renhua; Tong Changning; Zhang Hongli

2006-01-01

Total 18 t uranium ores of Fuzhou Uranium Mine packed in three or four columns in series were leached by bacterial percolation. The results show that without adding any other chemical oxidant such as sodium chlorate, the leaching rate measured by residue is 91.45%-94.48%, leaching time is 50-60 d, acid consumption is 6.17%-7.75%, and residue grade is 0.0149%-0.0208%. Compared with conventional percolation leaching process, the leaching rate is improved by 3%, leaching time is shorted by 26%, and acid consumption is saved by 34%. Accumulation pattern of ΣFe and F - in the process of leaching is discussed. Influence of F - on bacterial growth, regeneration of barren solution as well as correlative techniques are reviewed. (authors)

Percolation leaching and uranium recovery of El erediya granitic rocks, eastern desert, Egypt

International Nuclear Information System (INIS)

Abdel Monem, H.M.; Ali, M.M.; Hassan, M.A.

1998-01-01

El erediya uranium occurrence is located in the vicinity of qena-safaga road, central eastern desert. A bulk head sample of about 50 kg was prepared for this study. mineralogically, uranophane is the essential uranium mineral identified in the studied bulk head sample. It occurs as yellow flakes and acicular grains filling fractures, whereas the gangue minerals are mainly composed of quartz, altered potash feldspar, and minor plagioclase. The head sample assays as 74.36% SiO 2 , 13.81% Al 2 O 3 and 0.091% U. Percolation leaching utilizing H 2 SO 4 was performed at a fairly low Ph value. The examined factors include Ph of the leach solution, the grain size beside the duration time. More than 97% leaching of the uranium was reported after percolating the leach solution for 6 weeks at ph 1.4. Thus it could be possible to produce a pregnant leach solution assaying more than 1.2 g U/L by using a multi-stage leaching system. For recovering uranium, tri-octyl-phosphine oxide (TOPO) in kerosene was found to be the most powerful U-extractant. Good U-distribution coefficient (E) of 103 has been obtained with 0.1 M TOPO in the presence of 0.1 M HNO 3

Roasting and leaching behaviors of vanadium and chromium in calcification roasting-acid leaching of high-chromium vanadium slag

Science.gov (United States)

Wen, Jing; Jiang, Tao; Zhou, Mi; Gao, Hui-yang; Liu, Jia-yi; Xue, Xiang-xin

2018-05-01

Calcification roasting-acid leaching of high-chromium vanadium slag (HCVS) was conducted to elucidate the roasting and leaching behaviors of vanadium and chromium. The effects of the purity of CaO, molar ratio between CaO and V2O5 ( n(CaO)/ n(V2O5)), roasting temperature, holding time, and the heating rate used in the oxidation-calcification processes were investigated. The roasting process and mechanism were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetry-differential scanning calorimetry (TG-DSC). The results show that most of vanadium reacted with CaO to generate calcium vanadates and transferred into the leaching liquid, whereas almost all of the chromium remained in the leaching residue in the form of (Fe0.6Cr0.4)2O3. Variation trends of the vanadium and chromium leaching ratios were always opposite because of the competitive reactions of oxidation and calcification between vanadium and chromium with CaO. Moreover, CaO was more likely to combine with vanadium, as further confirmed by thermodynamic analysis. When the HCVS with CaO added in an n(CaO)/ n(V2O5) ratio of 0.5 was roasted in an air atmosphere at a heating rate of 10°C/min from room temperature to 950°C and maintained at this temperature for 60 min, the leaching ratios of vanadium and chromium reached 91.14% and 0.49%, respectively; thus, efficient extraction of vanadium from HCVS was achieved and the leaching residue could be used as a new raw material for the extraction of chromium. Furthermore, the oxidation and calcification reactions of the spinel phases occurred at 592 and 630°C for n(CaO)/ n(V2O5) ratios of 0.5 and 5, respectively.

Hydrochloric acid leaching of uranium, thorium, radium and rare-earth elements, from an Elliot lake radioactive ore

International Nuclear Information System (INIS)

Mahdy, M.A.

1988-01-01

Extraction of uranium by commercial methods using sulphuric acid developed a lot of environmental problems. To avoid such problems, other uranium extraction techniques have been adopted including fluorination, chlorination, chlorine assisted leaching, hydrochloric acid leaching, etc. This work is oriented towards the study of the factors controlling the hydrochloric acid leaching. The target of the study is to extract the total amount of U, Th, Ra-226 and rare earth elements. By using a suitable combination of the leaching factors, it was possible to achieve the designed target

Acid agglomeration heap leaching: present status, principle and applications

International Nuclear Information System (INIS)

Zeng Yijun

2004-01-01

For extracting valuable metal from clay-bearing acidic ores of poor permeability, agglomerated acid heap leaching appears to be the most effective method, whereas conventional leaching and general heap leaching bring about unsatisfactory recovery and poor economic returns. The present state of research work on acid agglomeration worldwide and its basic principle are discussed. The first commercial application employing acid agglomeration-heap leaching in China is also introduced

Introduction to in situ leaching technique and facility at Smith Ranch uranium project in USA

International Nuclear Information System (INIS)

Xu Lechang; Wang Delin; Sun Xianrong; Gao Shangxiong

2005-01-01

The history of in situ leaching of uranium in USA is reviewed. Some techniques and parameters of alkaline in situ leach at Smith Ranch uranium project are introduced, including well field, sorption, elution, precipitation, filter and drying, automatic control, radiation protection, safety and environmental protection. (authors)

Sustained release of radioprotective agents

International Nuclear Information System (INIS)

Shani, J.

1980-11-01

New pharmaceutical formulations for the sustained release into the G.I. tract of radioprotective agents have been developed by the authors. The experimental method initially consisted in the production of methylcellulose microcapsules. This method failed apparently because of the premature ''explosion'' of the microcapsules and the consequent premature release of massive amounts of the drug. A new method has been developed which consists in drying and pulverising cysteamine and cysteine preparations, mixing them in various proportions with stearic acid and ethylcellulose as carriers. The mixture is then compressed into cylindrical tablets at several pressure values and the leaching rate of the radioprotective agents is then measured by spectrophotometry. The relation between the concentration of the active drug and its rate of release, and the effect on the release rate of the pressure applied to the tablet during its formation were also investigated. Results indicating that the release rate was linearly related to the square root of ''t'' seem to be in agreement with what is predictable, according to Higuchi's equation, save for the very initial and terminal phases. A clear correlation was also established between the stearic acid/ethylcellulose ratios and the release of 20% cysteine, namely a marked decrease in the rate of cysteine release was observed with increasing concentrations of stearic acid. Finally, it was observed that a higher formation pressure results in quicker release of the drug

ALKALINE CARBONATE LEACHING PROCESS FOR URANIUM EXTRACTION

Science.gov (United States)

Thunaes, A.; Brown, E.A.; Rabbitts, A.T.

1957-11-12

A process for the leaching of uranium from high carbonate ores is presented. According to the process, the ore is leached at a temperature of about 200 deg C and a pressure of about 200 p.s.i.g. with a solution containing alkali carbonate, alkali permanganate, and bicarbonate ion, the bicarbonate ion functionlng to prevent premature formation of alkali hydroxide and consequent precipitation of a diuranate. After the leaching is complete, the uranium present is recovered by precipitation with NaOH.

Urban trees reduce nutrient leaching to groundwater.

Science.gov (United States)

Nidzgorski, Daniel A; Hobbie, Sarah E

2016-07-01

Many urban waterways suffer from excess nitrogen (N) and phosphorus (P), feeding algal blooms, which cause lower water clarity and oxygen levels, bad odor and taste, and the loss of desirable species. Nutrient movement from land to water is likely to be influenced by urban vegetation, but there are few empirical studies addressing this. In this study, we examined whether or not urban trees can reduce nutrient leaching to groundwater, an important nutrient export pathway that has received less attention than stormwater. We characterized leaching beneath 33 trees of 14 species, and seven open turfgrass areas, across three city parks in Saint Paul, Minnesota, USA. We installed lysimeters at 60 cm depth to collect soil water approximately biweekly from July 2011 through October 2013, except during winter and drought periods, measured dissolved organic carbon (C), N, and P in soil water, and modeled water fluxes using the BROOK90 hydrologic model. We also measured soil nutrient pools (bulk C and N, KCl-extractable inorganic N, Brays-P), tree tissue nutrient concentrations (C, N, and P of green leaves, leaf litter, and roots), and canopy size parameters (leaf biomass, leaf area index) to explore correlations with nutrient leaching. Trees had similar or lower N leaching than turfgrass in 2012 but higher N leaching in 2013; trees reduced P leaching compared with turfgrass in both 2012 and 2013, with lower leaching under deciduous than evergreen trees. Scaling up our measurements to an urban subwatershed of the Mississippi River (~17 400 ha, containing ~1.5 million trees), we estimated that trees reduced P leaching to groundwater by 533 kg in 2012 (0.031 kg/ha or 3.1 kg/km 2 ) and 1201 kg in 2013 (0.069 kg/ha or 6.9 kg/km 2 ). Removing these same amounts of P using stormwater infrastructure would cost $2.2 million and $5.0 million per year (2012 and 2013 removal amounts, respectively). © 2016 by the Ecological Society of America.

HYDRAULIC AND LEACHING BEHAVIOUR OF BELITE CEMENTS PRODUCED WITH ELECTRIC ARC FURNACE STEEL SLAG AS RAW MATERIAL

Directory of Open Access Journals (Sweden)

Iacobescu R. I.

2013-06-01

Full Text Available Three belite-rich cements consisting of a clinker made with 0 (BC, 5 (BC5 and 10 wt. % (BC10 electric arc furnace steel slag (EAFS as raw material, were studied for their hydraulic and leaching behaviour. Hydration behaviour was studied by FTIR, TG/DTG and SEM analyses. The cements with EAFS resulted in a higher C2S/C3S and C4AF/C3A ratio compared to the reference body. As a result, the rate of hydration was low at early days whereas the structure was porous with scattered AFm and C–S–H crystals. At 28 days, a comparable dense microstructure consisting largely of C–S–H is observed in all mortars. Leaching was studied for V and Cr by means of tank test according to standard NEN 7345. The results showed V release below 2 μg/l. Chromium release calculated per 24 h was 1.4 μg/l in BC5 and 2.4 μg/l in BC10, which is much lower than the parametric value of 50 μg/l specified by the European Directive for drinking water (98/83/EC.

Technique for in situ leach simulation of uranium ores

International Nuclear Information System (INIS)

Grant, D.C.; Seidel, D.C.; Nichols, I.L.

1985-01-01

In situ uranium mining offers the advantages of minimal environmental disturbance, low capital and operating costs, and reduced mining development time. It is becoming an increasingly attractive mining method for the recovery of uranium from secondary ore deposits. In order to better understand the process, a laboratory technique was developed and used to study and simulate both the chemical and physical phenomena occurring in ore bodies during in situ leaching. The laboratory simulation technique has been used to determine effects of leaching variables on permeability, uranium recovery, and post-leach aquifer restoration. This report describes the simulation system and testing procedure in sufficient detail to allow the construction of the system, and to perform the desired leaching tests. With construction of such a system, in situ leaching of a given ore using various leach conditions can be evaluated relatively rapidly in the laboratory. Not only could optimum leach conditions be selected for existing ore bodies, but also exploitation of new ore bodies could be accelerated. 8 references, 8 figures, 2 tables

Leach testing of waste glasses under near-saturation conditions

International Nuclear Information System (INIS)

Strachan, D.M.; Grambow, B.

1983-11-01

Two waste glasses, MCC 76 to 68 and C31 to 3, were leached in deionized water and 0.001 M MgCl 2 for periods up to 158 days. At 57 days the gel layer was removed from some of the specimens and leaching continued for up to 100 days. Results from leaching in deionized water showed that the gel layer was not protective. Results from leaching in 0.001 M MgCl 2 are in good agreement with the predicted results obtained from the use of the PHREEQE geochemical code and with sepiolite [Mg 2 Si 3 O 6 (OH) 4 ] as the Mg-bearing precipitate. Both B and Si were predicted and observed to increase with increasing glass dissolution while maintaining sepiolite solubility. Both MCC 76 to 68 and C31 to 3 glasses showed increased leaching in 0.001 M MgCl 2 upon removal of the layer. This suggests a leaching mechanism whereby leaching is driven by the formation of an alteration product

Defense High-Level Waste Leaching Mechanisms Program. Final report

Energy Technology Data Exchange (ETDEWEB)

Mendel, J.E. (compiler)

1984-08-01

The Defense High-Level Waste Leaching Mechanisms Program brought six major US laboratories together for three years of cooperative research. The participants reached a consensus that solubility of the leached glass species, particularly solubility in the altered surface layer, is the dominant factor controlling the leaching behavior of defense waste glass in a system in which the flow of leachant is constrained, as it will be in a deep geologic repository. Also, once the surface of waste glass is contacted by ground water, the kinetics of establishing solubility control are relatively rapid. The concentrations of leached species reach saturation, or steady-state concentrations, within a few months to a year at 70 to 90/sup 0/C. Thus, reaction kinetics, which were the main subject of earlier leaching mechanisms studies, are now shown to assume much less importance. The dominance of solubility means that the leach rate is, in fact, directly proportional to ground water flow rate. Doubling the flow rate doubles the effective leach rate. This relationship is expected to obtain in most, if not all, repository situations.

Defense High-Level Waste Leaching Mechanisms Program. Final report

International Nuclear Information System (INIS)

Mendel, J.E.

1984-08-01

The Defense High-Level Waste Leaching Mechanisms Program brought six major US laboratories together for three years of cooperative research. The participants reached a consensus that solubility of the leached glass species, particularly solubility in the altered surface layer, is the dominant factor controlling the leaching behavior of defense waste glass in a system in which the flow of leachant is constrained, as it will be in a deep geologic repository. Also, once the surface of waste glass is contacted by ground water, the kinetics of establishing solubility control are relatively rapid. The concentrations of leached species reach saturation, or steady-state concentrations, within a few months to a year at 70 to 90 0 C. Thus, reaction kinetics, which were the main subject of earlier leaching mechanisms studies, are now shown to assume much less importance. The dominance of solubility means that the leach rate is, in fact, directly proportional to ground water flow rate. Doubling the flow rate doubles the effective leach rate. This relationship is expected to obtain in most, if not all, repository situations

Hydrochloric acid leach of Agnew Lake uranium concentrate

International Nuclear Information System (INIS)

Haque, K.E.; Ipekoglue, B.

1981-10-01

Hydrochloric acid leaching was conducted on the radioactive mineral concentrate separated from the Agenw Lake uranium ore. Leach tests conducted at the optimum conditions (75 0 C; 36 hours; 66.0 Kg HCl/tonne; solid:liquid -1:1) resulted in the extraction of 87% uranium and 84% radium. The radionuclide level of the residue was U-0.016%, Th-0.24% and Ra-65 pCi/g solids. However to obtain a residue almost free of radium (i.e., Ra level at the detection limit: 4-6 pCi/g solids), the first stage leach residue was further treated with hydrochloric acid. The radium level in the best second stage leach residue was also above the target level. Therefore, multistage (3 or 4) hydrochloric acid and/or neutral chloride leaching is recommended to obtain tailings almost free of radionuclide

Bioleaching combined brine leaching of heavy metals from lead-zinc mine tailings: Transformations during the leaching process.

Science.gov (United States)

Ye, Maoyou; Yan, Pingfang; Sun, Shuiyu; Han, Dajian; Xiao, Xiao; Zheng, Li; Huang, Shaosong; Chen, Yun; Zhuang, Shengwei

2017-02-01

During the process of bioleaching, lead (Pb) recovery is low. This low recovery is caused by a problem with the bioleaching technique. This research investigated the bioleaching combination of bioleaching with brine leaching to remove heavy metals from lead-zinc mine tailings. The impact of different parameters were studied, including the effects of initial pH (1.5-3.0) and solid concentration (5-20%) for bioleaching, and the effects of sodium chloride (NaCl) concentration (10-200 g/L) and temperature (25 and 50 °C) for brine leaching. Complementary characterization experiments (Sequential extraction, X-ray diffractometer (XRD), scanning electronic microscope (SEM)) were also conducted to explore the transformation of tailings during the leaching process. The results showed that bioleaching efficiency was significantly influenced by initial pH and solid concentration. Approximately 85.45% of iron (Fe), 4.12% of Pb, and 97.85% of zinc (Zn) were recovered through bioleaching in optimum conditions. Increasing the brine concentration and temperature promoted lead recovery. Lead was recovered from the bioleaching residues at a rate of 94.70% at 25 °C and at a rate of 99.46% at 50 °C when the NaCl concentration was 150 g/L. The study showed that bioleaching significantly changed the speciation of heavy metals and the formation and surface morphology of tailings. The metals were mainly bound in stable fractions after bioleaching. Copyright © 2016 Elsevier Ltd. All rights reserved.

Thiosulfate leaching of gold from waste mobile phones.

Science.gov (United States)

Ha, Vinh Hung; Lee, Jae-chun; Jeong, Jinki; Hai, Huynh Trung; Jha, Manis K

2010-06-15

The present communication deals with the leaching of gold from the printed circuit boards (PCBs) of waste mobile phones using an effective and less hazardous system, i.e., a copper-ammonia-thiosulfate solution, as an alternative to the conventional and toxic cyanide leaching of gold. The influence of thiosulfate, ammonia and copper sulfate concentrations on the leaching of gold from PCBs of waste mobile phones was investigated. Gold extraction was found to be enhanced with solutions containing 15-20 mM cupric, 0.1-0.14 M thiosulfate, and 0.2-0.3 M ammonia. Similar trends were obtained for the leaching of gold from two different types of scraps and PCBs of waste mobile phones. From the scrap samples, 98% of the gold was leached out using a solution containing 20 mM copper, 0.12 M thiosulfate and 0.2 M ammonia. Similarly, the leaching of gold from the PCBs samples was also found to be good, but it was lower than that of scrap samples in similar experimental conditions. In this case, only 90% of the gold was leached, even with a contact time of 10h. The obtained data will be useful for the development of processes for the recycling of gold from waste mobile phones. Copyright 2010 Elsevier B.V. All rights reserved.

Leaching of Antimony (Sb)from Municipal Solid Waste Incineration (MSWI) Residues

Energy Technology Data Exchange (ETDEWEB)

Herrmann, Inga

2004-07-01

The mobility of antimony (Sb) in municipal solid waste incineration (MSWI) residues often exceeds the limit values stipulated by the European Union. As an ash treatment by washing is conceivable, this work investigated the Sb release from Swedish bottom ash and fly ash when mixed with water. The leaching experiments revealed the factors significantly (a = 0.05) affecting Sb release from the ashes. The following factors were investigated: Liquid to solid ratio (L/S), time, pH, carbonation (treatment with CO{sub 2}), ultrasonics and temperature. The data were evaluated using multiple linear regression (MLR). The impact of the factors could be quantified. The maximum Sb release calculated was 13 mg/kg DM for bottom ash and 51 mg/kg DM for fly ash. The derived models explained the observed data well. Nevertheless, the calculated values were subject to a high uncertainty. For bottom ash, a lowering of the Sb total content of approximately 22% could be achieved. If this also involves a sufficient lowering of the Sb mobility to meet EU limit values could not yet be assessed. Chemical equilibrium calculations were performed to explain the empirical results. However, no solid phases controlling Sb release from the ashes could be identified.

EFRT M-12 Issue Resolution: Comparison of PEP and Bench-Scale Oxidative Leaching Results

Energy Technology Data Exchange (ETDEWEB)

Rapko, Brian M.; Schonewill, Philip P.; Brown, Christopher F.; Eslinger, Paul W.; Fountain, Matthew S.; Hausmann, Tom S.; Huckaby, James L.; Hanson, Brady D.; Kurath, Dean E.; Minette, Michael J.

2010-01-01

Pacific Northwest National Laboratory (PNNL) has been tasked by Bechtel National Inc. (BNI) on the River Protection Project-Hanford Tank Waste Treatment and Immobilization Plant (RPP-WTP) project to perform research and development activities to resolve technical issues identified for the Pretreatment Facility (PTF). The Pretreatment Engineering Platform (PEP) was designed, constructed, and operated as part of a plan to respond to issue M12, “Undemonstrated Leaching Processes” of the External Flowsheet Review Team (EFRT) issue response plan.( ) The PEP is a 1/4.5-scale test platform designed to simulate the WTP pretreatment caustic leaching, oxidative leaching, ultrafiltration solids concentration, and slurry washing processes. The PEP replicates the WTP leaching processes using prototypic equipment and control strategies. The PEP also includes non-prototypic ancillary equipment to support the core processing.

EFRT M-12 Issue Resolution: Comparison of PEP and Bench-Scale Oxidative Leaching Results

International Nuclear Information System (INIS)

Rapko, Brian M.; Schonewill, Philip P.; Brown, Christopher F.; Eslinger, Paul W.; Fountain, Matthew S.; Hausmann, Tom S.; Huckaby, James L.; Hanson, Brady D.; Kurath, Dean E.; Minette, Michael J.

2010-01-01

Pacific Northwest National Laboratory (PNNL) has been tasked by Bechtel National Inc. (BNI) on the River Protection Project-Hanford Tank Waste Treatment and Immobilization Plant (RPP-WTP) project to perform research and development activities to resolve technical issues identified for the Pretreatment Facility (PTF). The Pretreatment Engineering Platform (PEP) was designed, constructed, and operated as part of a plan to respond to issue M12, 'Undemonstrated Leaching Processes' of the External Flowsheet Review Team (EFRT) issue response plan. The PEP is a 1/4.5-scale test platform designed to simulate the WTP pretreatment caustic leaching, oxidative leaching, ultrafiltration solids concentration, and slurry washing processes. The PEP replicates the WTP leaching processes using prototypic equipment and control strategies. The PEP also includes non-prototypic ancillary equipment to support the core processing.

Release of silver nanoparticles from outdoor facades

International Nuclear Information System (INIS)

Kaegi, Ralf; Sinnet, Brian; Zuleeg, Steffen; Hagendorfer, Harald; Mueller, Elisabeth; Vonbank, Roger; Boller, Markus; Burkhardt, Michael

2010-01-01

In this study we investigate the release of metallic silver nanoparticles (Ag-NP) from paints used for outdoor applications. A facade panel mounted on a model house was exposed to ambient weather conditions over a period of one year. The runoff volume of individual rain events was determined and the silver and titanium concentrations of 36 out of 65 runoff events were measured. Selected samples were prepared for electron microscopic analysis. A strong leaching of the Ag-NP was observed during the initial runoff events with a maximum concentration of 145 μ Ag/l. After a period of one year, more than 30% of the Ag-NP were released to the environment. Particles were mostly 2 S. - We provide direct evidence for the release of silver nanoparticles from exterior paints to the aquatic environment.

Recycling of spent lithium-ion battery cathode materials by ammoniacal leaching.

Science.gov (United States)

Ku, Heesuk; Jung, Yeojin; Jo, Minsang; Park, Sanghyuk; Kim, Sookyung; Yang, Donghyo; Rhee, Kangin; An, Eung-Mo; Sohn, Jeongsoo; Kwon, Kyungjung

2016-08-05

As the production and consumption of lithium ion batteries (LIBs) increase, the recycling of spent LIBs appears inevitable from an environmental, economic and health viewpoint. The leaching behavior of Ni, Mn, Co, Al and Cu from treated cathode active materials, which are separated from a commercial LIB pack in hybrid electric vehicles, is investigated with ammoniacal leaching agents based on ammonia, ammonium carbonate and ammonium sulfite. Ammonium sulfite as a reductant is necessary to enhance leaching kinetics particularly in the ammoniacal leaching of Ni and Co. Ammonium carbonate can act as a pH buffer so that the pH of leaching solution changes little during leaching. Co and Cu can be fully leached out whereas Mn and Al are hardly leached and Ni shows a moderate leaching efficiency. It is confirmed that the cathode active materials are a composite of LiMn2O4, LiCoxMnyNizO2, Al2O3 and C while the leach residue is composed of LiNixMnyCozO2, LiMn2O4, Al2O3, MnCO3 and Mn oxides. Co recovery via the ammoniacal leaching is believed to gain a competitive edge on convenitonal acid leaching both by reducing the sodium hydroxide expense for increasing the pH of leaching solution and by removing the separation steps of Mn and Al. Copyright © 2016 Elsevier B.V. All rights reserved.

Long-term leaching behavior of simulated Savannah River Plant waste glass: Part 1, MCC-1 leachability results, four-year leaching data

International Nuclear Information System (INIS)

Wicks, G.G.; Stone, J.A.; Chandler, G.T.; Williams, S.

1986-08-01

Long-term leaching data were obtained on SRP 131/TDS waste glass using MCC-1 or slightly modified MCC-1 standard leaching tests. Experiments were conducted out to four years at 40 0 C and 3-1/2 years at 90 0 C. These experiments have produced the longest standardized leaching data currently available in the waste management community. Long-term leaching data provide important input to modeling of waste glass behavior and ultimate prediction of waste glass performance. In this study, the leaching behavior of SRP waste glass was found to be excellent; leachates based on a variety of elements were not only very low, but also improved with increasing time. In addition to these data, results are also reported from another independent Savannah River study. Leaching behavior at 40 0 C and 90 0 C was assessed not only for a similar SRP 131 waste glass composition, but also for extreme waste glass compositions involving high-iron and high-aluminum waste. In addition, these experiments were performed using not only a standard deionized water leachant, but also simplified brine and silicate groundwater simulations. These two large data bases will be summarized and correlated along with some of the more interesting results recently reported in another study, a two-year leaching program performed on a similar SRP waste glass composition at Battelle Pacific Northwest Laboratories

Apparatus for leaching core material from clad nuclear fuel pin segments

International Nuclear Information System (INIS)

Yarbro, O.O.

1980-01-01

This invention relates to improved apparatus for countercurrently contacting liquids and solids to dissolve, or leach, a selected component of the solids while minimizing back-mixing of the liquid phase. The apparatus includes an elongated drum which is rotatable about its longitudinal axis in either direction and is partitioned radially into a solids-inlet/liquid-outlet compartment at one end, a solids-outlet/liquid-inlet compartment at its other end, and leaching compartments therebetween. The drum is designed to operate with its acid-inlet end elevated and with the longitudinal axis of the drum at an angle in the range of from about 3* to 14* to the horizontal. Each leaching compartment contains a chute assembly for advancing solids into the next compartment in the direction of solids flow when the drum is rotated in a selected direction. The chute assembly includes a solids-transfer baffle and a chute in the form of a slotted, skewed, conical frustum portion. When the drum is rotated in the direction opposite to that effecting solids transfer, the solids-transfer baffles continually separate and re -mix the solids and liquids in their respective compartments. The partitions defining the leaching compartments are formed with corresponding outer, annular, imperforate regions, each region extending inwardly from the partition rim to an annular array of perforations concentric with the rim. In each leaching compartment, the spacing between the rim and the perforations determines the depth of liquid at the liquid-outlet end of the compartment. The liquid input to the drum assembly flows continuously through the compartments, preventing back-mixing due to density differences, whereas backflow due to waves generated by the solids-transfer baffles is virtually eliminated because of the tilted orientation of the drum assembly

Experimental methodology for assessing the environmental fate of organic chemicals in polymer matrices using column leaching studies and OECD 308 water/sediment systems: Application to tire and road wear particles.

Science.gov (United States)

Unice, Kenneth M; Bare, Jennifer L; Kreider, Marisa L; Panko, Julie M

2015-11-15

Automobile tires require functional rubber additives including curing agents and antioxidants, which are potentially environmentally available from tire and road wear particles (TRWP) deposited in soil and sediment. A novel methodology was employed to evaluate the environmental fate of three commonly-used tire chemicals (N-cyclohexylbenzothiazole-2-sulfenamide (CBS), N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine (6-PPD) and 1,3-diphenylguanidine (DPG)), using a road simulator, an artificial weathering chamber, column leaching tests, and OECD 308 sediment/water incubator studies. Environmental release factors were quantified for curing (f(C)), tire wear (f(W)), terrestrial weathering (f(S)), leaching from TRWP (f(L)), and environmental availability from TRWP (f(A)) by liquid chromatography-tandem mass spectroscopy (LC/MS/MS) analyses. Cumulative fractions representing total environmental availability (F(T)) and release to water (FR) were calculated for the tire chemicals and 13 transformation products. F(T) for CBS, DPG and 6-PPD inclusive of transformation products for an accelerated terrestrial aging time in soil of 0.1 years was 0.08, 0.1, and 0.06, respectively (equivalent to 6 to 10% of formulated mass). In contrast, a wider range of 5.5×10(-4) (6-PPD) to 0.06 (CBS) was observed for F(R) at an accelerated age of 0.1 years, reflecting the importance of hydrophobicity and solubility for determining the release to the water phase. Significant differences (p<0.05) in the weathering factor, f(S), were observed when chemicals were categorized by boiling point or hydrolysis rate constant. A significant difference in the leaching factor, f(L), and environmental availability factor, f(A), was also observed when chemicals were categorized by log K(ow). Our methodology should be useful for lifecycle analysis of other functional polymer chemicals. Copyright © 2015 Elsevier B.V. All rights reserved.

Cement based grouts - longevity laboratory studies: leaching behaviour

International Nuclear Information System (INIS)

Onofrei, M.; Gray, M.; Roe, L.

1991-12-01

This report describes a series of laboratory tests carried out to determine the possible leaching behaviour of cement-based grouts in repository environments. A reference high-performance cement-based grout, comprised of Canadian Type 50 (U.S. Type V) Sulphate Resisting Portland Cement, silica fume, potable water and superplasticizer, and a commercially available cement grout were subjected to leaching in distilled water and three simulated groundwaters of different ionic strength. Hardened, monolithic specimens of the grout were leached in static, pulsed-flow and continuous flow conditions at temperatures from 10 degrees C to 150 degrees C for periods of up to 56 days. The changes in concentration of ions in the leachants with time were determined and the changes in the morphology of the surfaces of the grout specimens were examined using electron microscopy. After a review of possible mechanisms of degradation of cement-based materials, the data from these experiments are presented. The data show that the grouts will leach when in contact with water through dissolution of more soluble phases. Comparison of the leaching performance of the two grouts indicates that, while there are some minor differences, they behaved quite similarly. The rate of the leaching processes were found to tend to decrease with time and to be accompanied by precipitation and/or growth of an assemblage of secondary alteration phases (i.e., CaCO 3 , Mg(OH) 2 ). The mechanisms of leaching depended on the environmental conditions of temperature, groundwater composition and water flow rate. Matrix dissolution occurred. However, in many of the tests leaching was shown to be limited by the precipitated/reaction layers which acted as protective surface coatings. (37 refs.) (au)

Enhancements of LEACH Algorithm for Wireless Networks: A Review

Directory of Open Access Journals (Sweden)

M. Madheswaran

2013-12-01

Full Text Available Low Energy Adaptive Clustering Hierarchy (LEACH protocol is the first hierarchical cluster based routing protocol successfully used in the Wireless Sensor Networks (WSN. In this paper, various enhancements used in the original LEACH protocol are examined. The basic operations, advantages and limitations of the modified LEACH algorithms are compared to identify the research issues to be solved and to give the suggestions for the future proposed routing algorithms of wireless networks based on LEACH routing algorithm.

Molybdenum isotope fractionation during acid leaching of a granitic uranium ore

Science.gov (United States)

Migeon, Valérie; Bourdon, Bernard; Pili, Eric; Fitoussi, Caroline

2018-06-01

As an attempt to prevent illicit trafficking of nuclear materials, it is critical to identify the origin and transformation of uranium materials from the nuclear fuel cycle based on chemical and isotope tracers. The potential of molybdenum (Mo) isotopes as tracers is considered in this study. We focused on leaching, the first industrial process used to release uranium from ores, which is also known to extract Mo depending on chemical conditions. Batch experiments were performed in the laboratory with pH ranging from 0.3 to 5.5 in sulfuric acid. In order to span a large range in uranium and molybdenum yields, oxidizers such as nitric acid, hydrogen peroxide and manganese dioxide were also added. An enrichment in heavy Mo isotopes is produced in the solution during leaching of a granitic uranium ore, when Mo recovery is not quantitative. At least two Mo reservoirs were identified in the ore: ∼40% as Mo oxides soluble in water or sulfuric acid, and ∼40% of Mo hosted in sulfides soluble in nitric acid or hydrogen peroxide. At pH > 1.8, adsorption and/or precipitation processes induce a decrease in Mo yields with time correlated with large Mo isotope fractionations. Quantitative models were used to evaluate the relative importance of the processes involved in Mo isotope fractionation: dissolution, adsorption, desorption, precipitation, polymerization and depolymerization. Model best fits are obtained when combining the effects of dissolution/precipitation, and adsorption/desorption onto secondary minerals. These processes are inferred to produce an equilibrium isotope fractionation, with an enrichment in heavy Mo isotopes in the liquid phase and in light isotopes in the solid phase. Quantification of Mo isotope fractionation resulting from uranium leaching is thus a promising tool to trace the origin and transformation of nuclear materials. Our observations of Mo leaching are also consistent with observations of natural Mo isotope fractionation taking place during

Method of repair of short circuits for in-situ leaching

International Nuclear Information System (INIS)

Baughman, D.R.; Bergeson, J.R.

1984-01-01

In an acidic in-situ leaching system, a short circuit passage through a subterranean formation between a fracture associated with an injection well and a fracture associated with a production well can be plugged by introducing a non-acidic liquid for displacing acidic leach liquid from the short circuit passage, introducing into the injection well a basic composition including a sealing material that gels under acidic conditions, and introducing sufficient liquid into the injection well to displace at least a portion of the basic composition containing sealing material from the injection well into the short circuit passage. Liquid flow between the injection well and the production well is then discontinued for a sufficient time for residual acid in the subterranean formation surrounding the short circuit passage to contact the sealing material and cause gelation of the sealing material in the short circuit passage. The introduction of acidic leach liquid to the formation can then continue. The sealing material may be a polymer or a water soluble silicate

The enhancing of Au-Ag-Te content in tellurium-bearing ore mineral by bio-oxidation-leaching

Science.gov (United States)

Kim, PyeongMan; Kim, HyunSoo; Myung, EunJi; Kim, YoonJung; Lee, YongBum; Park*, CheonYoung

2015-04-01

The purpose of this study is to enhance the content of valuable metals such as Au-Ag-Te in tellurium-bearing minerals by bio-oxidation-leaching. It was confirmed that pyrite, chalcopyrite, sphalerite and galena were produced together with tellurium-bearing minerals including hessite, sylvanite and tellurobismuthite from ore minerals and concentrates through microscopic observation and SEM/EDS analysis. In a bio-oxidation-leaching experiment, with regard to Au, Ag, Te, Cu and Fe, the changes in the amount of leaching and the content of leaching residues were compared and analyzed with each other depending on the adaptation of an indigenous microbe identified as Acidithiobacillus ferrooxidans. As a result of the experiment, the Au-Ag-Te content in tellurium-bearing ore mineral was enhanced in the order of physical oxidation leaching, physical/non-adaptive bio-oxidation-leaching and physical/adaptive biological leaching. It suggests that the bio-oxidation-leaching using microbes adapted in tellurium-bearing ore mineral can be used as a pre-treatment and a main process in a recovery process of valuable metals. "This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education(NRF-2013R1A1A2004898)"

Characterizing the Leaching Behavior of Coal Combustion Residues using the Leaching Environmental Assessment Framework (LEAF) to Inform Future Management Decisions

Science.gov (United States)

Abstract for presentation on Characterizing the Leaching Behavior of Coal Combustion Residues using the Leaching Environmental Assessment Framework (LEAF) to Inform Future Management Decisions. The abstract is attached.

Leaching of RA-226 contaminated gravel using different aqueous treatments

Energy Technology Data Exchange (ETDEWEB)

Mamoon, A; Abulfaraj, W H; Sohsah, M A [King Abdulaziz University, Jeddah, Saudi Arbabia (Saudi Arabia)

1997-12-31

Investigation of the efficiencies of different aqueous leaching treatments was carried out on gravel artificially contaminated with Ra-226. The extent of leaching efficiency was determined in terms of Ra-226 and its daughter Rn-222. Liquid scintillation counting using high efficiency mineral oil based liquid scintillator was the technique adopted for measuring Ra-226 and Rn-222 leached off the contaminated gravel. Water, dilute solutions of barium chloride and HCl were used as leachants. Different masses of gravel were leached with 200 mL of leachant for various contact time periods. The leached Rn-222 activity measured was plotted vs the decay factor e; from which Rn-222 and Ra-226 originally present in the sample were determined. Several leaching parameters were tested; namely type of leachant, leachant volume/gravel mass ratio, leachant contact time, effect of varying Ba Cl{sub 2} concentration, and successive leaching. Optimization of the leaching parameters for desorption of Ra-226 off the contaminated gravel under laboratory conditions may help determine the ideal conditions for remediating soil contaminated with radium or chemically similar radionuclides. 7 figs.

Optimization of the factors that accelerate leaching

International Nuclear Information System (INIS)

Fuhrmann, M.; Pietrzak, R.F.; Franz, E.M.; Heiser, J.H. III; Colombo, P.

1989-03-01

The prediction of long-term leachability of low-level radioactive waste forms is an essential element of disposal-site performance assessment. This report describes experiments and modeling techniques used to develop an accelerated leach test that meets this need. The acceleration in leaching rates caused by the combinations of two or more factors were experimentally determined. These factors were identified earlier as being able to individually accelerate leaching. They are: elevated temperature, the size of the waste form, the ratio of the volume of leachant to the surface area of the waste form, and the frequency of replacement of the leachant. The solidification agents employed were ones that are currently used to treat low-level radioactive wastes, namely portland type I cement, bitumen, and vinyl ester-styrene. The simulated wastes, sodium sulfate, sodium tetraborate, and incinerator ash, are simplified representatives of typical low-level waste streams. Experiments determined the leaching behavior of the radionuclides of cesium (Cs-137), strontium (Sr-85), and cobalt (Co-60 or Co-57) from several different formulations of solidification agents and waste types. Leaching results were based upon radiochemical and elemental analyses of aliquots of the leachate, and on its total alkalinity and pH at various times during the experiment (up to 120 days). Solid phase analyses were carried out by Scanning/Electron Microscopy and Energy Dispersive Spectroscopy on the waste forms before and after some leaching experiments. 43 refs., 96 figs., 16 tabs

LEACHING BOUNDARY IN CEMENT-BASED WASTE FORMS

Science.gov (United States)

Cement-based fixation systems are among the most commonly employed stabilization/solidification techniques. These cement haste mixtures, however, are vulnerable to ardic leaching solutions. Leaching of cement-based waste forms in acetic acid solutions with different acidic streng...

Kinetics of acid leaching of ilmenite decomposed by KOH part 1: decomposition by KOH and leaching by HCl

International Nuclear Information System (INIS)

Nayl, A.A; Aly, H.F.

2010-01-01

Decomposition of ilmenite by KOH solutions, to convert titanium to potassium titanate, was first studied . This was followed by leaching titanium from the ilmenite paste using HCl solutions in the temperature range 50-150 degree C for different periods up to 3 hr. The significant factors affecting the leaching process were studied. The experimental data of the decomposition rate of ilmenite by KOH and of the formed KOH paste by HCl under the relevant operating variables were interpreted with the shrinking core model under chemically controlled process. The apparent activation energy for leaching of titanium in both cases bas been evaluated and discussed.

Leach testing of Idaho Chemical Processing Plant final waste forms

International Nuclear Information System (INIS)

Schuman, R.P.

1980-01-01

A number of pellets and highly durable glasses prepared from nonradioactive-simulated high-level wasste calcines have been leach tested. The leach tests are patterned on the IAEA standard test and the proposed Materials Characterization Center tests. Most tests are made with static distilled water at 25, 70, 95, 250, and 350 0 C and in refluxing distilled water, Soxhlet, at 95 0 C. Leach rates are determined by analyzing the leachate by instrumental activation analysis or spectrochemical analysis and from weight loss. Leaches are run on glass using cast and core drilled cylinders, broken pieces and coarse ground material. Sample form has a considerable effect on leach rates; solid pieces gave higher leach rates than ground glass when expressed in g/cm 2 /day. Cesium, molybdenum and weight loss leach rates of cast glass cylinders in distilled water varied from -7 g/cm 7 /day at 25 0 C to approx. 10 -3 g/cm 2 /day at 250 0 C. The leach rates in static distilled water at 95 0 C were considerably lower than those in refluxing distilled water, Soxhlet, at the same temperature. Even at 25 0 C, sodium, cesium, and molybdenum readily leached from the porous pellets, but the pellets showed no visible attack, even at 250 0 C

Leaching of spent fuel in the presence of environmental material

International Nuclear Information System (INIS)

Le Lous, Karine

1997-01-01

The aim of this work is the study of the alteration kinetics of spent fuels and the making of a status of the radioactivity released by spent fuels in conditions of direct disposal in deep underground. A system has been fitted inside a shielded cell to study the leaching by synthetic groundwater of fuel powder irradiated at 60 GWJ.tU -1 in the presence of environmental material (clay or granite) at 40 bars and 90 deg. C. This system allows to reach and keep reductive conditions characteristic of the redox conditions of a deep geological repository. The preparation of calibrated spent fuel powders and the recovery of the activity fixed by the environmental materials has required the implementation of specific procedures. Similar experiments have been performed in parallel with Simfuel in a controlled area. A first series of experiments has been carried out in 4 environments for each fuel. Important sorption phenomena take place in the environmental materials and the actinide concentrations stabilize rapidly at low values: 10 -8 mol/l for U, 10 -12 mol/l for Pu and 10 -13 -10 -14 mol/l for Cm. The activity released by 90 Sr at the end of each experiment is about two times higher in the presence of clay than in the presence of granite. The average alteration rates are of about 0.2 mg.m -2 /day in the presence of granite and 0.4 to 0.6 mg.m -2 /day in the presence of clay. They are comparable to those reported in the literature for reducing conditions. Such tests are necessary to determine the leaching rate of spent fuels in reducing conditions and in the absence of environmental materials in order to show the possible effects of these materials. (J.S.)

Leaching of Electronic Waste Using Biometabolised Acids

Institute of Scientific and Technical Information of China (English)

M. Saidan; B. Brown; M. Valix

2012-01-01

The revolution in information and communication technology has brought huge technical benefits and wealth, but has created a major global problem： the generation of vast amounts of electronic waste, or e-waste through product obsolesce. The challenge in managing e-waste will be in developing sustainable recycling tech- nologies that are able to address the volume and complexity of this waste using cost effective and ecologically sen-sitive methods. In this study, the capability or microorganism metabolic acids in dissolving the metallic tractions from waste printed circuit boards was examined. Several factors were considered in the examination of the activityof the acids-including secondary reactions, solution pH, temperature and the nature of ligands in solutions （or bioacid constituents）. The leaching tests were cgnducted ex-situ, using synthetic organic acids. Leaching was performed for periods of up to 6 hat 70-90 ℃ and 1000 r-min-1.

pH triggered controlled drug delivery from contact lenses: Addressing the challenges of drug leaching during sterilization and storage.

Science.gov (United States)

Maulvi, Furqan A; Choksi, Harsh H; Desai, Ankita R; Patel, Akanksha S; Ranch, Ketan M; Vyas, Bhavin A; Shah, Dinesh O

2017-09-01

In the present work a novel cyclosporine-loaded Eudragit S100 (pH-sensitive) nanoparticles-laden contact lenses were designed to provide sustained release of cyclosporine at therapeutic rates, without leaching of drug during sterilization and storage period (shelf life). The nanoparticles were prepared by Quasi-emulsion solvent diffusion technique using different weight ratios of cyclosporine to Eudragit S100. The contact lenses with direct drug entrapment were also fabricated (DL-50) for comparison. The percentage swelling and optical transparency of nanoparticles-laden contact lenses were improved in comparison to DL-50 lenses. The nanoparticles-laden contact lenses showed sustained drug release profiles, with inverse relationship to the amount of nanoparticles loaded in the contact lenses. It was interesting to note that nanoparticles form nanochannels/cavities after dissolution of Eudragit S 100 in tear fluid pH=7.4 (in vitro release study). This followed the precipitation of drug in hydrogel matrix of contact lenses. As the amount of nanoparticles loading increased, more number of cavities were formed, which caused the formation of large cavities in contact lens matrix. This in turn precipitated the drug. The nanoparticles-laden contact lenses with 1:1 (drug: Eudragit) weight ratio showed the most promising results of sustaining the drug release up to 156h, without affecting optical and physical properties of contact lenses. Packaging study confirmed that the drug was not leached in packaging solution (buffer, pH=6.5) from nanoparticles-laden lenses during shelf life period. In-vivo study in rabbit tear fluid showed sustained release up to 14days. The study revealed the application of pH-sensitive nanoparticles-laden contact lenses for controlled release of cyclosporine without altering the optical and physical properties of lens material. Copyright © 2017 Elsevier B.V. All rights reserved.

A new wall function boundary condition including heat release effect for supersonic combustion flows

International Nuclear Information System (INIS)

Gao, Zhen-Xun; Jiang, Chong-Wen; Lee, Chun-Hian

2016-01-01

Highlights: • A new wall function including heat release effect is theoretically derived. • The new wall function is a unified form holding for flows with/without combustion. • The new wall function shows good results for a supersonic combustion case. - Abstract: A new wall function boundary condition considering combustion heat release effect (denoted as CWFBC) is proposed, for efficient predictions of skin friction and heat transfer in supersonic combustion flows. Based on a standard flow model including boundary-layer combustion, the Shvab–Zeldovich coupling parameters are introduced to derive a new velocity law-of-the-wall including the influence of combustion. For the temperature law-of-the-wall, it is proposed to use the enthalpy–velocity relation, instead of the Crocco–Busemann equation, to eliminate explicit influence of chemical reactions. The obtained velocity and temperature law-of-the-walls constitute the CWFBC, which is a unified form simultaneously holding for single-species, multi-species mixing and multi-species reactive flows. The subsequent numerical simulations using this CWFBC on an experimental case indicate that the CWFBC could accurately reflect the influences on the skin friction and heat transfer by the chemical reactions and heat release, and show large improvements compared to previous WFBC. Moreover, the CWFBC can give accurate skin friction and heat flux for a coarse mesh with y"+ up to 200 for the experimental case, except for slightly larger discrepancy of the wall heat flux around ignition position.

Method for evaluating leaching from LSA-III material

International Nuclear Information System (INIS)

Abe, H.; Satoh, K.; Ozaki, S.; Watabe, N.; Iida, T.; Akamatsu, H.

1989-01-01

The IAEA transport regulations are scheduled to be introduced in Japan. New regulations are supposed to be set forth for low specific activity (LSA) material and industrial packaging (IP) as solidified concentrated waste water should correspond to the LSA material. Solidified concentrated waste water should be transported in accordance with the new transport regulations which reflect the IAEA transport regulations. As one of the regulations for LSA material, the leaching test for LSA-III materials states that the radioactive loss due to leaching without the packaging should not exceed 0.1 A 2 when left in the water for 7 days. This test method is called Transport regulations hereafter. Since the test had not been conducted in Japan before now, there was no available data. Consequently, it is necessary to make an assessment on whether the current solidified concentrated waste water can satisfy the leaching amount of radioactive nuclide specified in the IAEA transport regulations. If the test is performed in accordance with the IAEA transport regulations, however, it is necessary to measure the amount of radioactive nuclide actually leached from the solidified concentrated waste water. Since the solidified concentrated waste water is put in a drum cam, it is necessary to prepare large-scale hot test equipment. In this study, therefore, the leaching test was conducted on the solidified concentrated waste water to propose the means of a leaching assessment which can be conducted with ordinary equipment to evaluate the leaching for assessment of the adaptability to IAEA transport regulations. In addition, the leaching test was performed in accordance with the IAEA method to examine the co-relation between the transport regulations and the IAEA method. Many test results have been reported for the IAEA method in Japan, which will be detailed later on

Oxidative Pressure Leaching of Silver from Flotation Concentrates with Ammonium Thiocyanate Solution

Science.gov (United States)

Yang, Sheng-Hai; Yang, Jian-Guang; Liu, Wei; Chen, Geng-Tao; Tang, Mo-Tang; Qiu, Guan-Zhou

2010-02-01

The thermodynamics and technologies of the selective pressure leaching of silver from flotation concentrates were investigated in an ammonium thiocyanate medium. Thermodynamic analyses, which include silver solubility in NH4SCN solution and Eh-pH diagrams of the Me-MeS-NH4SCN-H2O system at 25 °C, were discussed. The effects of several factors, such as temperature, leaching time, oxidant, pH value, flotation concentrates concentration, surfactant concentration, and so on, on the extraction percentages of silver and zinc were investigated. The following optimal leaching conditions were obtained: NH4SCN concentration 1.5 M, lignin concentration 0.5 g/L, Fe3+ concentration 2 g/L, flotation concentrates addition 200 g/L, and oxygen pressure 1.2 MPa at 130 °C for 3 hours. Under these optimum conditions, the average extraction percentage of silver exceeded 94 pct, whereas the average extraction percentage of zinc was less than 3 pct. Only 7 pct of ammonium thiocyanate was consumed after 4 cycles, which indicated that ammonium thiocyanate hardly was oxidized under these oxidative pressure leaching conditions.

The leaching kinetics of cadmium from hazardous Cu-Cd zinc plant residues.

Science.gov (United States)

Li, Meng; Zheng, Shili; Liu, Biao; Du, Hao; Dreisinger, David Bruce; Tafaghodi, Leili; Zhang, Yi

2017-07-01

A large amount of Cu-Cd zinc plant residues (CZPR) are produced from the hydrometallurgical zinc plant operations. Since these residues contain substantial amount of heavy metals including Cd, Zn and Cu, therefore, they are considered as hazardous wastes. In order to realize decontamination treatment and efficient extraction of the valuable metals from the CZPR, a comprehensive recovery process using sulfuric acid as the leaching reagent and air as the oxidizing reagent has been proposed. The effect of temperature, sulfuric acid concentration, particle size, solid/liquid ratio and stirring speed on the cadmium extraction efficiency was investigated. The leaching kinetics of cadmium was also studied. It was concluded that the cadmium leaching process was controlled by the solid film diffusion process. Moreover, the order of the reaction rate constant versus H 2 SO 4 concentration, particle size, solid/liquid ratio and stirring speed was calculated. The XRD and SEM-EDS analysis results showed that the main phases of the secondary sulfuric acid leaching residues were lead sulfate and calcium sulfate. Copyright © 2017 Elsevier Ltd. All rights reserved.

Accelerated leach testing of radionuclides from solidified low-level waste

International Nuclear Information System (INIS)

Pietrzak, R.F.; Fuhrmann, M.; Franz, E.M.; Heiser, J. III; Colombo, P.

1989-01-01

This paper describes some of the work performed to develop an accelerated leach test designed to provide data that show long-term leaching behavior of solidified waste in a relatively short period of testing (1,2). The need for an accelerated leach test stems from the fact that the response of an effectively solidified waste form to the leaching process is so slow that a very long time is required to complete a test which shows the long-term leaching behavior of a waste form. Because of time limitations, as well as economic considerations, most studies have been limited to the early stages of the leaching process which is predominantly controlled by diffusion, although acknowledged to be due to also dissolution, corrosion or ion-exchange

Organic reductants based leaching: A sustainable process for the recovery of valuable metals from spent lithium ion batteries.

Science.gov (United States)

Chen, Xiangping; Guo, Chunxiu; Ma, Hongrui; Li, Jiazhu; Zhou, Tao; Cao, Ling; Kang, Duozhi

2018-05-01

It is significant to recover metal values from spent lithium ion batteries (LIBs) for the alleviation or prevention of potential risks towards environmental pollution and public health, as well as for the conservation of valuable metals. Herein a hydrometallurgical process was proposed to explore the possibility for the leaching of different metals from waste cathodic materials (LiCoO 2 ) of spent LIBs using organics as reductant in sulfuric acid medium. According to the leaching results, about 98% Co and 96% Li can be leached under the optimal experimental conditions of reaction temperature - 95 °C, reaction time - 120 min, reductive agent dosage - 0.4 g/g, slurry density - 25 g/L, concentration of sulfuric acid-3 mol/L in H 2 SO 4  + glucose leaching system. Similar results (96% Co and 100% Li) can be obtained in H 2 SO 4  + sucrose leaching system under optimized leaching conditions. Despite a complete leaching of Li (∼100%), only 54% Co can be dissolved in the H 2 SO 4  + cellulose leaching system under optimized leaching conditions. Finally, different characterization methods, including UV-Vis, FT-IR, SEM and XRD, were employed for the tentative exploration of reductive leaching reactions using organic as reductant in sulfuric acid medium. All the leaching and characterization results confirm that both glucose and sucrose are effective reductants during leaching, while cellulose should be further degraded to organics with low molecular weights to achieve a satisfactory leaching performance. Copyright © 2018 Elsevier Ltd. All rights reserved.

Study of radionuclide leaching from the residues of K Basin sludge dissolution

International Nuclear Information System (INIS)

Bechtold, D.B.

1998-01-01

The sludges remaining in the K Basins after removal of the spent N Reactor nuclear fuel will be conditioned for disposal. After conditioning, an acid-insoluble residue will remain that may require further leaching to properly condition it for disposal. This document presents a literature study to identify and recommend one or more chemical leaching treatments for laboratory testing, based on the likely compositions of the residues. The processes identified are a nitric acid cerate leach, a silver-catalyzed persulfate leach, a nitric hydrofluoric acid leach, an oxalic citric acid reactor decontamination leach, a nitric hydrochloric acid leach, a ammonium fluoride nitrate leach, and a HEOPA formate dehydesulfoxylate leach. All processes except the last two are recommended for testing in that order

Effect of Medicinal Plants Cultivation on the Physicochemical Properties of Leached Chernozem

Science.gov (United States)

Svistova, I. D.; Stekol'nikov, K. E.; Paramonov, A. Yu.; Kuvshinova, N. M.

2016-02-01

For the first time, a nonspecific neutralizing effect of rhizodeposits of medicinal plants has been found in a leached chernozem. The neutralization of actual, exchangeable, and total acidity of the soil takes place against the background of a decrease in the activity of calcium ions in the soil solution. It can be supposed that this effect is due to the release of secondary metabolites of phenol nature in the rhizodeposits. These substances can change the anionic composition of the soil adsorption complex. Plant species with the maximum effect on the composition of the soil adsorption complex have been identified.

A two-step leaching method designed based on chemical fraction distribution of the heavy metals for selective leaching of Cd, Zn, Cu, and Pb from metallurgical sludge.

Science.gov (United States)

Wang, Fen; Yu, Junxia; Xiong, Wanli; Xu, Yuanlai; Chi, Ru-An

2018-01-01

For selective leaching and highly effective recovery of heavy metals from a metallurgical sludge, a two-step leaching method was designed based on the distribution analysis of the chemical fractions of the loaded heavy metal. Hydrochloric acid (HCl) was used as a leaching agent in the first step to leach the relatively labile heavy metals and then ethylenediamine tetraacetic acid (EDTA) was applied to leach the residual metals according to their different fractional distribution. Using the two-step leaching method, 82.89% of Cd, 55.73% of Zn, 10.85% of Cu, and 0.25% of Pb were leached in the first step by 0.7 M HCl at a contact time of 240 min, and the leaching efficiencies for Cd, Zn, Cu, and Pb were elevated up to 99.76, 91.41, 71.85, and 94.06%, by subsequent treatment with 0.2 M EDTA at 480 min, respectively. Furthermore, HCl leaching induced fractional redistribution, which might increase the mobility of the remaining metals and then facilitate the following metal removal by EDTA. The facilitation was further confirmed by the comparison to the one-step leaching method with single HCl or single EDTA, respectively. These results suggested that the designed two-step leaching method by HCl and EDTA could be used for selective leaching and effective recovery of heavy metals from the metallurgical sludge or heavy metal-contaminated solid media.

ALUMINUM AND CHROMIUM LEACHING WORKSHOP WHITEPAPER

International Nuclear Information System (INIS)

McCabe, D; Jeff Pike, J; Bill Wilmarth, B