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Wu M, Bi E, Li B. Cotransport of nano-hydroxyapatite and different Cd(II) forms influenced by fulvic acid and montmorillonite colloids. WATER RESEARCH 2022; 218:118511. [PMID: 35512536 DOI: 10.1016/j.watres.2022.118511] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 04/09/2022] [Accepted: 04/23/2022] [Indexed: 06/14/2023]
Abstract
Soil colloids can affect the cotransport of nanoparticles and pollutants. In this study, the influencing mechanisms of organic fulvic acid (FA) and inorganic montmorillonite colloid (MONT) on the cotransport of nHAP and Cd(II) were investigated. Column experiments combined with Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, attachment efficiency calculation and two-site kinetic retention model were applied to study the mechanisms. Results showed that the co-existence of FA or MONT made the transport of nHAP improved by 58-75% and 33-59%, respectively. Both of them could improve the stability of nHAP particles and enhance electrostatic repulsion between nHAP particles and sand. Retention of nHAP in the sand was mainly caused by secondary energy minimum and physical straining. The co-existence of FA or MONT changed the amount of adsorbed species of Cd(II) and decreased the retardation effect of nHAP on Cd(II) transport. With increasing FA concentration, soluble FA·Cd and suspended nHAP·FA·Cd complexes in the system increased. Transport of soluble Cd(II) and total Cd(II) were strengthened due to the concentration effect of FA and the improved stability of nHAP particles. With increasing MONT concentration, the amount of soluble Cd(II) decreased, but that of colloidal Cd(II) (nHAP·Cd and MONT·Cd) increased. Due to the stronger effect of colloidal Cd(II) change than that of the soluble Cd(II) change, the transport of total Cd(II) was improved by 34-57%. The findings of this study can help to understand the fate of nanoparticles and Cd(II) in natural water and soil.
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Affiliation(s)
- Mengmeng Wu
- School of Water Resources and Environment, Beijing Key Laboratory of Water Resources and Environmental Engineering, and MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing 100083, PR China; China National Environmental Monitoring Centre, Beijing 100012, PR China
| | - Erping Bi
- School of Water Resources and Environment, Beijing Key Laboratory of Water Resources and Environmental Engineering, and MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing 100083, PR China.
| | - Binghua Li
- Department of Water Resources, Beijing Water Science and Technology Institute, Beijing 100048, PR China
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2
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Chen Z, Wang S, Hou H, Chen K, Gao P, Zhang Z, Jin Q, Pan D, Guo Z, Wu W. China's progress in radionuclide migration study over the past decade (2010-2021): Sorption, transport and radioactive colloid. CHINESE CHEM LETT 2022. [DOI: 10.1016/j.cclet.2022.02.054] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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3
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Dang H, Yi X, Zhang Z, Zhang H, Lin J, Zhang W, Zhai S, Zhang J, Bai T, Zhang X, Liang J, Wang W. The level, distribution and source of artificial radionuclides in surface soil from Inner Mongolia, China. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2021; 233:106614. [PMID: 33901800 DOI: 10.1016/j.jenvrad.2021.106614] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Revised: 03/29/2021] [Accepted: 04/04/2021] [Indexed: 06/12/2023]
Abstract
Mid- and long-half-life artificial radioisotopes in the earth's surface environment are of great concern to the environmental radiation risk assessment. As nuclear fuel and fission products, 239Pu, 240Pu, 241Am, 90Sr and 137Cs in soils from Inner Mongolia of China were analyzed with a modified systematic separation procedure combined with ICP-MS and LSC measurements, to study the level, distribution and source of artificial radionuclides in the region. The radioactivity and inventory of 137Cs (0.26-28.3 Bq/kg, 0.5-5.4 kBq/m2), 239+240Pu (0.05-1.26 Bq/kg, 20-229 Bq/m2), 241Am (0.036-0.35 Bq/kg, 11-81 Bq/m2) and 90Sr (1.2-7.6 Bq/kg, 0.39-1.7 kBq/m2) all lie in the range of the global fallout. Vertical distributions of these radionuclides were examined for two soil core samples SC14025 and SC14038, and great differences were observed between these two sample locations. For SC14025 where little human disturbance to soil occurred, both 137Cs and 239+240Pu have a subsurface activity maximum followed by an exponential decay. Fittings base on CDE model gives a small downward migration velocity of about 0.097 cm/y for both Pu and 137Cs. Source identification for SC14025 and SC14038 soil cores with 240Pu/239Pu (average of 0.180 ± 0.017 and 0.164 ± 0.035, respectively), 137Cs/239+240Pu (average of 25.3 ± 0.6 and 25.6 ± 3.0, respectively) and 241Am/239+240Pu (average of 0.56 ± 0.08 and 0.60 ± 0.09, respectively) ratios consistently indicated that anthropogenic radionuclides in Xilingol region are mostly from the global fallout of atmospheric nuclear weapons tests in the last century. According to the geographical distribution of the radioactivity level, the high radioactivity level in the east of Inner Mongolia probably results from enhanced deposition by the blocking of the Great Khingan Range.
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Affiliation(s)
- Haijun Dang
- Northwest Institute of Nuclear Technology, Xian, 710024, China
| | - Xiaowei Yi
- Northwest Institute of Nuclear Technology, Xian, 710024, China
| | - Zilu Zhang
- Northwest Institute of Nuclear Technology, Xian, 710024, China
| | - Haitao Zhang
- Northwest Institute of Nuclear Technology, Xian, 710024, China.
| | - Jianfeng Lin
- Northwest Institute of Nuclear Technology, Xian, 710024, China
| | - Weichao Zhang
- Northwest Institute of Nuclear Technology, Xian, 710024, China
| | - Shaojing Zhai
- Northwest Institute of Nuclear Technology, Xian, 710024, China
| | - Jiamei Zhang
- Northwest Institute of Nuclear Technology, Xian, 710024, China
| | - Tao Bai
- Northwest Institute of Nuclear Technology, Xian, 710024, China
| | - Xiaolin Zhang
- Northwest Institute of Nuclear Technology, Xian, 710024, China
| | - Jianfeng Liang
- Northwest Institute of Nuclear Technology, Xian, 710024, China
| | - Wei Wang
- Northwest Institute of Nuclear Technology, Xian, 710024, China
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Yosri A, Siam A, El-Dakhakhni W, Dickson-Anderson S. A Genetic Programming-Based Model for Colloid Retention in Fractures. GROUND WATER 2019; 57:693-703. [PMID: 30653668 DOI: 10.1111/gwat.12860] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 01/08/2019] [Accepted: 01/12/2019] [Indexed: 06/09/2023]
Abstract
Understanding the behavior of colloids in groundwater is critical as some are pathogenic while others may facilitate or inhibit the transport of dissolved contaminants. Colloid behavior in saturated fractured aquifers is governed by the physical and chemical properties of the groundwater-particle-fracture system. The interaction between these properties is nonlinear, and there is a need for a mathematical model describing the relationship between them to advance the mechanistic understanding of colloid transport in fractures and facilitate modeling in fractured environments. This paper coupled genetic programming and linear regression within a multigene genetic programming framework to develop a robust mathematical model describing the relationship between colloid retention in fractures and the physical and chemical parameters that describe the system. The data employed for model development and validation were collected from a series of 75 laboratory-scale colloid tracer experiments conducted under a range of conditions in three laboratory-induced discrete dolomite fractures and their epoxy replicas. The model sufficiently reproduced the observed data with coefficients of determination (R2 ) of 0.92 and 0.80 for model development and validation, respectively. A cross-validation demonstrated the model generality to 86% of the observed data. A variance-based global sensitivity analysis confirmed that attachment is the primary retention mechanism in the systems employed in this work. The model developed in this study provides a tool describing colloid retention in factures, which furthers the understanding of groundwater-particle-fracture system conditions contributing to the retention of colloids and can aid in the design of groundwater remediation strategies and development of groundwater management plans.
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Affiliation(s)
- Ahmed Yosri
- Department of Civil Engineering, McMaster University, Hamilton, Ontario L8S4L7, Canada
| | - Ahmad Siam
- Department of Civil Engineering, McMaster University, Hamilton, Ontario L8S4L7, Canada
| | - Wael El-Dakhakhni
- Department of Civil Engineering, McMaster University, Hamilton, Ontario L8S4L7, Canada
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Chen Y, Ma J, Li Y, Weng L. Enhanced cadmium immobilization in saturated media by gradual stabilization of goethite in the presence of humic acid with increasing pH. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 648:358-366. [PMID: 30121035 DOI: 10.1016/j.scitotenv.2018.08.086] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 07/27/2018] [Accepted: 08/06/2018] [Indexed: 05/20/2023]
Abstract
Goethite (Gt) and humic acid (HA) are important components of soil that significantly affect Cd mobility. In this study, the co-transport of Cd2+ and Gt with/without HA in saturated sand columns was investigated by monitoring the breakthrough curves at different pH values. A solute transport model was used to study Cd2+ transport and retention in the saturated sand in the presence of Gt and HA, and a colloid transport model was used to describe the Gt colloid (GtC) transport in the columns. Our results showed that the transport behaviors of Cd2+ and Gt colloids/aggregates were regulated by pH. Cadmium transport was significantly inhibited at high pH due to its adsorption on the sand and Gt. Moreover, Gt retention was gradually stabilized with increasing pH regardless of its forms, i.e., individual colloids (GtC) or larger assemblages of particles due to aggregation (GtA). This retention was obviously enhanced in the presence of HA. Thus, the superposition of increased Cd2+ adsorption on Gt and Gt retention (stabilization) enhanced the immobilization of Cd2+ at high pH. In addition to stabilizing Gt, HA further enhance Cd2+ adsorption on Gt, thus promoting Cd2+ immobilization. However, only a small amount of organic-matter-bound Cd2+ was observed in the columns with injected HA. The major fractions of retained Cd2+ were exchangeable Cd2+ and Fe-oxide-bound Cd2+. Our results provide new insights into the roles of Gt and HA in the transport and mobilization of Cd2+ in soil-groundwater systems.
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Affiliation(s)
- Yali Chen
- Agro-Environmental Protection Institute, Ministry of Agriculture, Tianjin 300191, China
| | - Jie Ma
- Agro-Environmental Protection Institute, Ministry of Agriculture, Tianjin 300191, China; College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, China.
| | - Yongtao Li
- Agro-Environmental Protection Institute, Ministry of Agriculture, Tianjin 300191, China; College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, China
| | - Liping Weng
- Agro-Environmental Protection Institute, Ministry of Agriculture, Tianjin 300191, China.
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Li X, Zhang W, Qin Y, Ma T, Zhou J, Du S. Fe-colloid cotransport through saturated porous media under different hydrochemical and hydrodynamic conditions. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 647:494-506. [PMID: 30086501 DOI: 10.1016/j.scitotenv.2018.08.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 07/13/2018] [Accepted: 08/02/2018] [Indexed: 06/08/2023]
Abstract
To investigate the effect of different colloids on Fe migration in saturated porous media under different hydrochemical and hydrodynamic conditions, experiments were performed using colloidal silicon (inorganic) and colloidal humic acid (HA, organic), which are representative of the colloids in groundwater. Transport of Fe with and without colloid was investigated by column experiments using various porous media, colloid concentrations, ionic strengths (ISs), cation valences, and flow rates. The results show that colloidal silicon promotes and colloidal HA inhibits Fe transport, which is mainly because of their different bonding ratio, bonding modes with Fe and opposite surface charges between Fe-colloidal silicon and Fe-colloidal HA. Almost 100% of HA binds to Fe through the deprotonated functional groups, whereas only 13.3% of colloidal silicon binds to Fe, which is by electrostatic forces. Cotransport is also dependent on the hydrochemical and hydrodynamic conditions. For the Fe-colloidal silicon system, increasing the colloid concentration and flow rate, and decreasing the IS enhances Fe transport. Compared with colloidal silicon concentration = 10 mg/L, flow rate = 0.25 mL/min, and IS = 0.05 with CaCl2, a higher colloidal silicon concentration (20 mg/L), a higher flow rate (0.50 mL/min), and a lower IS (<0.0005 M) increase Fe recovery by 1.69%, 94.49% and 38.92%, respectively. Fe migration is also different in different porous media. For the Fe-colloidal HA system, Fe recovery decreases by 81.46% as the colloidal HA concentration increases from 0 to 20 mg/L. The type of porous medium and flow rate conditions have the same effects on Fe-colloidal HA transport as for colloidal silicon, although the electrical conditions have the opposite effect. With increasing IS, Fe-colloidal HA transport is enhanced because of competitive adsorption of the cations and Fe to colloidal HA and the porous medium.
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Affiliation(s)
- Xiaofei Li
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021, China; College of New Energy and Environment, Jilin University, Changchun 130021, China
| | - Wenjing Zhang
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021, China; College of New Energy and Environment, Jilin University, Changchun 130021, China.
| | - Yunqi Qin
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021, China; College of New Energy and Environment, Jilin University, Changchun 130021, China
| | - Tianyi Ma
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021, China; College of New Energy and Environment, Jilin University, Changchun 130021, China
| | - Jingjing Zhou
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021, China; College of New Energy and Environment, Jilin University, Changchun 130021, China
| | - Shanghai Du
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021, China; College of New Energy and Environment, Jilin University, Changchun 130021, China
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Ge M, Wang D, Yang J, Jin Q, Chen Z, Wu W, Guo Z. Co-transport of U(VI) and akaganéite colloids in water-saturated porous media: Role of U(VI) concentration, pH and ionic strength. WATER RESEARCH 2018; 147:350-361. [PMID: 30321825 DOI: 10.1016/j.watres.2018.10.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 09/27/2018] [Accepted: 10/02/2018] [Indexed: 05/13/2023]
Abstract
Remediating uranium contamination becomes a worldwide interest because of increasing uranium release from mining activities. Due to ubiquitous presence of pyrite and the application of iron-based technology, colloidal iron oxy-hydroxides such as akaganéite colloid (AKC) extensively exist in uranium polluted water at uranium tailing sites. In this context, we studied individual and co-transport of U(VI) and AKC in water-saturated sand columns at 50 mg/L AKC and environmentally relevant U(VI) concentrations (5.0 × 10-7 ∼ 5.0 × 10-5 M). It was found that, in addition to the impact of pH and ionic strength, whether AKC facilitated U(VI) transport depended on U(VI) concentration as well. The presence of AKC facilitated U(VI) transport at relatively low U(VI) concentration (5.0 × 10-7 ∼ 5.0 × 10-6 M), which was due to the strong adsorption of U(VI) on AKC and faster transport of AKC than that U(VI) as observed in their individual transport experiments. At relatively high U(VI) concentrations (5.0 × 10-5 M), however, AKC impeded U(VI) transport because U(VI) of high concentration decreased AKC colloidal stability and increased AKC aggregation and attachment. Thus, U(VI) and AKC co-transport was even blocked completely at relatively high pH and ionic strength. The mechanisms behind the co-transport of U(VI) and AKC were also confirmed by assessing the evolutions of aqueous pH and AKC zeta potential and particle size distribution in the column effluents. A two-site non-equilibrium model and a two-site kinetic attachment/detachment model well-described the breakthrough curves of U(VI) and AKC, respectively. Knowledge generated from this study provides a thorough understanding of uranium transport in the absence/presence of AKC, and brings new insights into the influence of contaminant concentration on co-transport in the presence of colloids.
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Affiliation(s)
- Mengtuan Ge
- Radiochemistry Laboratory, School of Nuclear Science and Technology, Lanzhou University, 730000, Lanzhou, China
| | - Dengjun Wang
- National Research Council Resident Research Associate at the U.S. Environmental Protection Agency, 919 Kerr Research Drive, Ada, OK, 74820, USA
| | - Junwei Yang
- Radiochemistry Laboratory, School of Nuclear Science and Technology, Lanzhou University, 730000, Lanzhou, China
| | - Qiang Jin
- Radiochemistry Laboratory, School of Nuclear Science and Technology, Lanzhou University, 730000, Lanzhou, China
| | - Zongyuan Chen
- Radiochemistry Laboratory, School of Nuclear Science and Technology, Lanzhou University, 730000, Lanzhou, China; The Key Laboratory of Special Function Materials and Structure Design, Ministry of Education, Lanzhou University, 730000 Lanzhou, China.
| | - Wangsuo Wu
- Radiochemistry Laboratory, School of Nuclear Science and Technology, Lanzhou University, 730000, Lanzhou, China; The Key Laboratory of Special Function Materials and Structure Design, Ministry of Education, Lanzhou University, 730000 Lanzhou, China
| | - Zhijun Guo
- Radiochemistry Laboratory, School of Nuclear Science and Technology, Lanzhou University, 730000, Lanzhou, China; The Key Laboratory of Special Function Materials and Structure Design, Ministry of Education, Lanzhou University, 730000 Lanzhou, China.
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Agresti F, Zin V, Barison S, Sani E, Meucci M, Mercatelli L, Nodari L, Rossi S, Bobbo S, Fabrizio M. NIR transmittance tuneability under a magnetic field of colloidal suspensions of goethite (α-FeOOH) nanorods. RSC Adv 2017. [DOI: 10.1039/c7ra00721c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Goethite (α-FeOOH) nanorods were synthesized and their size and shape were controlled by synthesis parameters. Stable colloidal suspensions were prepared and their transmittance in NIR range was tuned by modifying magnetic field direction and strength.
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Affiliation(s)
- F. Agresti
- Institute of Condensed Matter Chemistry and Technologies for Energy (ICMATE)
- National Research Council of Italy (CNR)
- 35127 Padova
- Italy
| | - V. Zin
- Institute of Condensed Matter Chemistry and Technologies for Energy (ICMATE)
- National Research Council of Italy (CNR)
- 35127 Padova
- Italy
| | - S. Barison
- Institute of Condensed Matter Chemistry and Technologies for Energy (ICMATE)
- National Research Council of Italy (CNR)
- 35127 Padova
- Italy
| | - E. Sani
- National Institute of Optics (INO)
- National Research Council of Italy (CNR)
- 50125 Firenze
- Italy
| | - M. Meucci
- National Institute of Optics (INO)
- National Research Council of Italy (CNR)
- 50125 Firenze
- Italy
| | - L. Mercatelli
- National Institute of Optics (INO)
- National Research Council of Italy (CNR)
- 50125 Firenze
- Italy
| | - L. Nodari
- Institute of Condensed Matter Chemistry and Technologies for Energy (ICMATE)
- National Research Council of Italy (CNR)
- 35127 Padova
- Italy
| | - S. Rossi
- Institute of Construction Technologies (ITC)
- National Research Council of Italy (CNR)
- 35127 Padova
- Italy
| | - S. Bobbo
- Institute of Construction Technologies (ITC)
- National Research Council of Italy (CNR)
- 35127 Padova
- Italy
| | - M. Fabrizio
- Institute of Condensed Matter Chemistry and Technologies for Energy (ICMATE)
- National Research Council of Italy (CNR)
- 35127 Padova
- Italy
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Liao P, Yuan S, Wang D. Impact of Redox Reactions on Colloid Transport in Saturated Porous Media: An Example of Ferrihydrite Colloids Transport in the Presence of Sulfide. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:10968-10977. [PMID: 27654458 DOI: 10.1021/acs.est.6b02542] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Transport of colloids in the subsurface is an important environmental process with most research interests centered on the transport in chemically stable conditions. While colloids can be formed under dynamic redox conditions, the impact of redox reactions on their transport is largely overlooked. Taking the redox reactions between ferrihydrite colloids and sulfide as an example, we investigated how and to what extent the redox reactions modulated the transport of ferrihydrite colloids in anoxic sand columns over a range of environmentally relevant conditions. Our results reveal that the presence of sulfide (7.8-46.9 μM) significantly decreased the breakthrough of ferrihydrite colloids in the sand column. The estimated travel distance of ferrihydrite colloids in the absence of sulfide was nearly 7-fold larger than that in the presence of 46.9 μM sulfide. The reduced breakthrough was primarily attributed to the reductive dissolution of ferrihydrite colloids by sulfide in parallel with formation of elemental sulfur (S(0)) particles from sulfide oxidation. Reductive dissolution decreased the total mass of ferrihydrite colloids, while the negatively charged S(0) decreased the overall zeta potential of ferrihydrite colloids by attaching onto their surfaces and thus enhanced their retention in the sand. Our findings provide novel insights into the critical role of redox reactions on the transport of redox-sensitive colloids in saturated porous media.
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Affiliation(s)
- Peng Liao
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences , 388 Lumo Road, Wuhan 430074, P. R. China
| | - Songhu Yuan
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences , 388 Lumo Road, Wuhan 430074, P. R. China
| | - Dengjun Wang
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences , 71 East Beijing Road, Nanjing 210008, P. R. China
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Lin J, Dang H, Xie J, Zhou G, Li M, Zhang J. Plutonium partitioning in water-granite and water-α-FeOOH systems: from a viewpoint of a three-phase system. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2015; 17:1672-1679. [PMID: 26244590 DOI: 10.1039/c5em00041f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Traditional sorption experiments commonly treat the colloidal species of low-solubility contaminants as immobile species when separated by centrifugation or ultrafiltration. This study shows that, from a viewpoint of a three-phase system, the mobile Pu species, especially the colloidal species, play an important role in Pu partitioning in water-granite and water-α-FeOOH systems. A new distribution coefficient term Ks/(d+c) was defined to take the mobile colloidal species into consideration, and it differs to the traditional distribution coefficient Ks/d by orders of magnitude in the water-granite and water-α-FeOOH systems. This term, Ks/(d+c), can quantitatively describe Pu partitioning in the suspension, in particular the fraction of mobile species that dominate Pu migration in the environment. The effects of ionic strength (I) and pH on the Pu partitioning in water-granite and water-α-FeOOH systems are well interpreted with respect to the zeta potential change of granite grains, α-FeOOH colloid particles and polymeric Pu. It is concluded that the presence of the α-FeOOH colloid with a low concentration (<10 mg L(-1)) is favorable for the stability of colloidal Pu and leads to large proportion of mobile Pu, especially colloid-associated Pu, which will migrate much faster than dissolved Pu in groundwater.
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Affiliation(s)
- Jianfeng Lin
- Northwest Institute of Nuclear Technology, Xi'an 710024, Shaanxi, China.
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