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Wei Y, Yuan C, Xu X, Chen X, Ren Z, Gui X, Zhao L, Qiu H, Cao X. Colloid formation and facilitated chromium transport in the coastal area soil induced by freshwater and seawater alternating fluctuations. WATER RESEARCH 2022; 218:118456. [PMID: 35447418 DOI: 10.1016/j.watres.2022.118456] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 04/09/2022] [Accepted: 04/12/2022] [Indexed: 06/14/2023]
Abstract
Seawater seasonal fluctuation results in its close interaction with freshwater in the coastal area, which may affect behavior of contaminants there. This study was conducted to explore the transport and transformation of soil colloid and associated Cr during freshwater and seawater alternating fluctuations by laboratory experiment and numerical simulation. Such a fluctuation brought downward migration of Cr from upper contaminated soil and induced reduction of Cr(VI) into Cr(III). An obvious increase of retained Cr(III) was observed at the lower layers of soil due to the reducing environment. More importantly, the colloids with average sizes between 800-1500 nm was formed during the fluctuation and mainly composed of microcline and Fe/Mn oxides minerals, which determined the Cr transport. Compared with the previous freshwater fluctuation, seawater fluctuations generated more and larger-sized colloids due to its high ionic strength. These colloids carried over 94% Cr in the effluent and Cr(III) accounted for over 95% of total Cr. A colloid-facilitated Cr transport modeling showed that the soil retained Cr decreased by about 14% after eight rounds of fluctuation on an actual soil-contaminated site scale. Our study provides insight for the understanding of geochemical process of Cr in the coastal area under freshwater and seawater fluctuation conditions.
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Affiliation(s)
- Yaqiang Wei
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Chengpeng Yuan
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xiaoyun Xu
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
| | - Xiang Chen
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Zhefan Ren
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xiangyang Gui
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Ling Zhao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Hao Qiu
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xinde Cao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China; Shanghai Engineering Research Center of Solid Waste Treatment and Resource Recovery, Shanghai Jiao Tong University, Shanghai 200240, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China.
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2
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Yang B, Qiu H, Zhang P, He E, Xia B, Liu Y, Zhao L, Xu X, Cao X. Modeling and visualizing the transport and retention of cationic and oxyanionic metals (Cd and Cr) in saturated soil under various hydrochemical and hydrodynamic conditions. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 812:151467. [PMID: 34742969 DOI: 10.1016/j.scitotenv.2021.151467] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 11/01/2021] [Accepted: 11/01/2021] [Indexed: 06/13/2023]
Abstract
Cationic and oxyanionic metals are widely existed in the aquatic and soil environment with the process of industrialization and they may behave different transport properties in aquifer systems due to the opposite charges. In this study, the comparative transport behaviors of Cd2+ and CrO42- in water-saturated soil columns were investigated under a variety of hydrochemical and hydraulic conditions such as pH, ionic strength (IS), and flow rate. The transport mechanisms of Cd(II) and Cr(VI) were explored by fitting the breakthrough curves with a two-site non-equilibrium transport model. Results indicated that high solution pH inhibited the transport of Cd(II) due to the enhanced electrostatic interaction. In contrast, the migration of Cr(VI) was promoted with the least amount of Cr(VI) (1.23 mg) being retained in soil at high pH, ascribing to the stronger electrostatic repulsion between anions and soil surface. Meanwhile, high pH conditions were not favorable for the participation of reduced iron in the reduction process of Cr(VI), resulting in the least amount of Cr(III) detected (22%). The increase in ionic strength decreased the negativity of the potential at the adsorption plane, which enhanced the transport of cationic Cd(II) and the retardation of anionic Cr(VI). In addition, the increase in flow rate facilitated the transport of Cd(II) and Cr(VI), mainly due to the decreasing contacting with porous media and enhanced dispersion effect. These findings demonstrated that the fate and environmental behavior of metal cations and anions differed with the change of hydrochemical and hydrodynamic properties, which should be considered for the risk assessment and remediation of metal contaminated sites.
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Affiliation(s)
- Bin Yang
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Hao Qiu
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
| | - Peihua Zhang
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Erkai He
- School of Geographic Sciences, East China Normal University, Shanghai 200241, China
| | - Bing Xia
- Anhui Academy of Environmental Science Research, Hefei 230051, China
| | - Yang Liu
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China
| | - Ling Zhao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xiaoyun Xu
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xinde Cao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
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Cai M, Zhao X, Wang X, Shi G, Hu C. Se changed the component of organic chemicals and Cr bioavailability in pak choi rhizosphere soil. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2021; 28:67331-67342. [PMID: 34245415 DOI: 10.1007/s11356-021-13465-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Accepted: 03/11/2021] [Indexed: 06/13/2023]
Abstract
Rhizosphere organic chemicals response and its role on Cr/Se adsorption are of great importance to understand Cr/Se bioavailability in Cr-contaminated soil with the application of Se. In the current work, the processes were carried out using rhizobox experiment (Brassica campestris L. ssp. chinensis Makino). The results showed that in soil contaminated by 200 mg kg-1 Cr(III), Se(IV) complexed with Cr(III) and carboxylic acid (cis-9,10-Epoxystearic acid, hexadecanedioic acid) reduced Cr(VI) to Cr(III), thus increasing of Cr adsorption, furtherly decreasing Cr bioavailability. While in soil contaminated by 120 mg kg-1 Cr(VI), Se(VI) competed for adsorption sites with Cr(VI) and salicylic acid activated insoluble Cr(III), thus decreasing Cr adsorption, finally increasing Cr bioavailability. Moreover, with Cr contamination, Se bioavailability in soil was enhanced by the secretion of carboxylic acid, which can reduce Se to lower valent state and compete the adsorption sites and complex with Se oxyanion. These results yielded a better understanding of rhizosphere dynamics regulating by Se application in Cr-contaminated soil. Moreover, the current study supplemented the theoretical basis for beneficial elements application as an environment-friendly resource to facilitate cleaner production in heavy metal contaminated soil.
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Affiliation(s)
- Miaomiao Cai
- College of Resources and Environment, Huazhong Agricultural University/Hubei Provincial Engineering Laboratory for New-Type Fertilizer/Research Center of Trace Elements/Hubei Key Laboratory of Soil Environment and Pollution Remediation, Wuhan, 430070, China
| | - Xiaohu Zhao
- College of Resources and Environment, Huazhong Agricultural University/Hubei Provincial Engineering Laboratory for New-Type Fertilizer/Research Center of Trace Elements/Hubei Key Laboratory of Soil Environment and Pollution Remediation, Wuhan, 430070, China
| | - Xu Wang
- Institute of Quality Standard and Monitoring Technology for Agro-products of Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China
| | - Guangyu Shi
- College of Environment Science and Engineering, Suzhou University of Science and Technology, Suzhou, 215009, China
| | - Chengxiao Hu
- College of Resources and Environment, Huazhong Agricultural University/Hubei Provincial Engineering Laboratory for New-Type Fertilizer/Research Center of Trace Elements/Hubei Key Laboratory of Soil Environment and Pollution Remediation, Wuhan, 430070, China.
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Wei Y, Xu X, Zhao L, Chen X, Qiu H, Gao B, Cao X. Migration and transformation of chromium in unsaturated soil during groundwater table fluctuations induced by rainfall. JOURNAL OF HAZARDOUS MATERIALS 2021; 416:126229. [PMID: 34492983 DOI: 10.1016/j.jhazmat.2021.126229] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 04/01/2021] [Accepted: 04/18/2021] [Indexed: 06/13/2023]
Abstract
The groundwater table fluctuation zone is the main interface for contaminants to transport between the unsaturated soil and saturated aquifers which still lacks of concern. In this study, we explored the interactions of Cr(VI) in this specific zone during water table fluctuation through laboratory experiment and numerical modeling. The higher reduction of Cr(VI) was found in the lower soil layer due to the lower Eh at the bottom layer of the unsaturated zone and the Cr(III) concentration increased with rise in water level and fluctuation amplitudes. After twice water fluctuation, nevertheless, there was still about 42.2% Cr retained in the soil and dominantly present as Cr(III) form. The model coupling reaction network with hydrodynamic field showed the cumulative Cr(III) in the unsaturated soil zone had a faster increase at the higher water level rise speed compared with lower rise speed. The cumulative Cr(VI) decreases over time in the saturated aquifers, whereas the cumulative Cr(III) increased with the increase of fluctuation amplitude. Reduction of Cr(VI) into Cr(III) was accompanied with Fe(II) and organic carbon oxidation. The results indicate that the hydrodynamic conditions have impacts on the redox environment of soil which could further affect the transformation and transport of Cr.
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Affiliation(s)
- Yaqiang Wei
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xiaoyun Xu
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
| | - Ling Zhao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xiang Chen
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Hao Qiu
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Bin Gao
- Department of Agricultural and Biological Engineering, University of Florida, Gainesville, FL 32611, USA
| | - Xinde Cao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China; Shanghai Engineering Research Center of Solid Waste Treatment and Resource Recovery, Shanghai Jiao Tong University, Shanghai 200240, China
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Hua H, Zhao Z, Xu R, Chang E, Fang D, Dong Y, Hong Z, Shi R, Jiang J. Effect of ferrolysis and organic matter accumulation on chromate adsorption characteristics of an Oxisol-derived paddy soil. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 744:140868. [PMID: 32717467 DOI: 10.1016/j.scitotenv.2020.140868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Revised: 06/14/2020] [Accepted: 07/08/2020] [Indexed: 06/11/2023]
Abstract
How paddy cultivation influences the adsorption isotherms, envelopes, and the kinetics of hexavalent chromate (Cr(VI)) on Fe (hydro)oxide-rich paddy soil, as well as the mechanisms involved, remain largely unaddressed. To this end, the Cr(VI) adsorption characteristics on a paddy soil, in comparison with its parent upland Oxisol, were studied. The results showed that Cr(VI) adsorption capacities (Qmad) were higher in the surface Oxisol than in the same layer of paddy soil. The Qmad increased by 18.0% and 41.3% after removal of soil organic matter (SOM) from the surface Oxisol and paddy soil layers, respectively, indicating that Cr(VI) adsorption was considerably inhibited by SOM. The adsorption and desorption isotherms demonstrated that non-electrostatic adsorption was mainly responsible for Cr(VI) adsorption, accounting for 59.37%-83.42% of Cr(VI) adsorption capacities. The negative shift of the zeta potential-pH curves with Cr(VI) loading further corroborated the finding that non-electrostatic adsorption is largely responsible for Cr(VI) retention. Cr(VI) adsorption at equilibrium, obtained by the stirred flow chamber technique, and the free Fe (hydro)oxides (Fed) contents were in the same order, suggesting that Fed are the main adsorbents for Cr(VI). Therefore, paddy cultivation has had a profound impact on the electrochemical properties of the Oxisol and on subsequent Cr(VI) adsorption characteristics.
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Affiliation(s)
- Hui Hua
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, P. O. Box, 821, Nanjing, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Zhenjie Zhao
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, P. O. Box, 821, Nanjing, China
| | - Renkou Xu
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, P. O. Box, 821, Nanjing, China
| | - E Chang
- Institute of Information Science and Technology, Southeast University, Nanjing 210096, China
| | - Di Fang
- College of Resources and Environmental Sciences, Nanjing Agriculture University, Nanjing, 210095, China
| | - Ying Dong
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, P. O. Box, 821, Nanjing, China
| | - Zhineng Hong
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, P. O. Box, 821, Nanjing, China
| | - Renyong Shi
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, P. O. Box, 821, Nanjing, China
| | - Jun Jiang
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, P. O. Box, 821, Nanjing, China.
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Islam MA, Angove MJ, Morton DW. Recent innovative research on chromium (VI) adsorption mechanism. ACTA ACUST UNITED AC 2019. [DOI: 10.1016/j.enmm.2019.100267] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Veselská V, Šillerová H, Göttlicher J, Michálková Z, Siddique JA, Číhalová S, Chrastný V, Steininger R, Mangold S, Komárek M. The role of soil components in synthetic mixtures during the adsorption and speciation changes of Cr(VI): Conjunction of the modeling approach with spectroscopic and isotopic investigations. ENVIRONMENT INTERNATIONAL 2019; 127:848-857. [PMID: 31075676 DOI: 10.1016/j.envint.2019.03.066] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 02/26/2019] [Accepted: 03/27/2019] [Indexed: 06/09/2023]
Abstract
This study investigates redox transitions associated with the adsorption of Cr(VI) on commonly occurring soil components (silicates, oxides and humic acids) and their synthetic mixtures by coupling the mechanistic surface complexation modeling with spectroscopic and isotopic analyses. The mixtures of soil components were prepared to reflect the composition of the real anthroposol sample, determined by X-ray Powder Diffraction (XRD), total organic carbon (TOC) measurement and extraction methods. The effect of different initial Cr(VI) concentrations (2×10-2, 5×10-4, 10-4, 10-5, and 10-6M), background electrolyte (10-3, 10-2, and 10-1M KNO3), pH values (3-9), and sorbate/sorbent ratios (2g/L - 20g/L) were investigated. Maghemite and ferrihydrite were confirmed to be the main phases controlling Cr(VI) adsorption with increasing Cr(VI) concentration. Humic acids were primarily responsible for Cr(VI) reduction, especially at low pH values. The reduction of Cr(VI) was also proved in case of illite and kaolinite by XAS and isotopic analyses. Illite revealed higher reduction capacity in comparison with kaolinite based on XAS measurements. Chromium isotopic fractionation, resulting from Cr(VI) reduction, was the highest in the case of humic acids, followed by kaolinite and illite. However, a dissolution of intrinsic Cr originally present within kaolinite and illite might affect the final Cr isotopic composition of the supernatants due to its different Cr isotopic signature. In general, the combination of three different approaches was confirmed to offer more comprehensive information about Cr(VI) adsorption and/or reduction in soils. Detailed studies using soil mixtures can help to predict how the soil components affect Cr(VI) behavior in natural soils and possibly could improve the environmental remediation processes.
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Affiliation(s)
- Veronika Veselská
- Department of Environmental Geosciences, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, CZ-16500 Prague, Czech Republic.
| | - Hana Šillerová
- Department of Environmental Geosciences, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, CZ-16500 Prague, Czech Republic
| | - Jörg Göttlicher
- Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, DE-76344 Eggenstein-Leopoldshafen, Germany
| | - Zuzana Michálková
- Department of Environmental Geosciences, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, CZ-16500 Prague, Czech Republic
| | - Jamal A Siddique
- Department of Environmental Geosciences, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, CZ-16500 Prague, Czech Republic
| | - Sylva Číhalová
- Department of Environmental Geosciences, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, CZ-16500 Prague, Czech Republic
| | - Vladislav Chrastný
- Department of Environmental Geosciences, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, CZ-16500 Prague, Czech Republic
| | - Ralph Steininger
- Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, DE-76344 Eggenstein-Leopoldshafen, Germany
| | - Stefan Mangold
- Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, DE-76344 Eggenstein-Leopoldshafen, Germany
| | - Michael Komárek
- Department of Environmental Geosciences, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, CZ-16500 Prague, Czech Republic
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Zhou L, Ye B, Xia S. Structural characteristics of cake layer in membrane bioreactor with chromate exposure. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2019; 169:583-589. [PMID: 30476820 DOI: 10.1016/j.ecoenv.2018.11.056] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 11/01/2018] [Accepted: 11/14/2018] [Indexed: 06/09/2023]
Abstract
Chromate (CrO42-) exposure, especially high concentration (mg/L), still probably occurs in the industrial and mining area due to industrial accidents or even illegal discharge, though CrO42- has been restricted to be discharged into wastewater treatment system (WWTS). Therefore, this study was applied to better understand the structural characteristics of cake layer in membrane bioreactor (MBR), which is one of best alternative for WWTS of industrial or mining area, with CrO42- exposure. Three submerged MBRs with CrO42- exposure (10 mg/L was normal high concentration CrO42-; 50 mg/L as extreme level for better identification; 0 mg/L as control condition) were applied in this study. Results showed that CrO42- exposure caused an obvious variation of cake layer structure. Because of organic component variation, cake layer structure with CrO42- exposure was re-constructed into loose and porous with biomicromolecules, and resulted in the rapid cake layer thickness increase, finally leading to severe membrane biofouling. Additionally, CrO42- distributed evenly along the cross-sectional cake layer. CrO42- only induced the inorganic structure variations of cake layer, but without any obvious effects on the other inorganic elements structure. CrO42- exposure induced the bacterial community structure variation and led to tolerated-CrO42- microorganisms as the majority in cake layer community, but had no obvious effects on the population diversity.
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Affiliation(s)
- Lijie Zhou
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, PR China.
| | - Biao Ye
- State Key Laboratory of Pollution Control and Resource Reuse, Shanghai Institute of Pollution Control and Ecological Security, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, PR China
| | - Siqing Xia
- State Key Laboratory of Pollution Control and Resource Reuse, Shanghai Institute of Pollution Control and Ecological Security, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, PR China.
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Zhang X, Tong J, Hu BX, Wei W. Adsorption and desorption for dynamics transport of hexavalent chromium (Cr(VI)) in soil column. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2018; 25:459-468. [PMID: 29043590 DOI: 10.1007/s11356-017-0263-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 09/19/2017] [Indexed: 06/07/2023]
Abstract
Batch experiments have been carried out to study the adsorption of heavy metals in soils, and the migration and transformation of hexavalent chromium (Cr(VI)) in the soil of a vegetable base were studied by dynamic adsorption and desorption soil column experiments. The aim of this study was to investigate the effect of initial concentration and pH value on the adsorption process of Cr(VI). Breakthrough curve were used to evaluate the capacity of Cr(VI) adsorption in soil columns. The results show that the higher the initial concentration, the worse the adsorption capacity of Cr(VI). The adsorption of Cr(VI) was strongly sensitive to pH value. The capacity of Cr(VI) adsorption is maximized at very low pH value. This may be due to changes in pH that cause a series of complex reactions in Cr(VI). In a strongly acidic environment, the reaction of Cr(VI) with hydrogen ions is accompanied by the formation of Cr3+, which reacts with the soil free iron-aluminum oxide to produce hydroxide in the soil. The results of the desorption experiments indicate that Cr(VI) is more likely to leach from this soil, but if the eluent is a strong acid solution, the leaching process will be slow and persistent. During the experiment, the pH value of the effluent was in the range of 7-8.5, which tends to the original pH value of the soil. It is indicating that the soil has a strong buffer on the acid liquid. The program CXTFIT was used to fit the breakthrough curve to estimate parameters. The results of the calculation of the dispersion coefficient (D) can be obtained by this program. The two-site model fit the breakthrough curve data of Cr(VI) well, and the parameters calculated by the CXTFIT can be used to explain the behavior of Cr(VI) migration and transformation in soil columns. When pH = 2, the retardation factor (R) reach at 79.71 while the value of the R is generally around 10 in other experiments. The partitioning coefficient β shows that more than half of the adsorption sites are instantaneous in this adsorption process and non-equilibrium affects the Cr(VI) transport process in this soil.
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Affiliation(s)
- Xiaowei Zhang
- School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, People's Republic of China
- Key Laboratory of Groundwater Circulation and Evolution, China University of Geosciences (Beijing), Ministry of Education, Beijing, 100083, People's Republic of China
| | - Juxiu Tong
- School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, People's Republic of China.
- Key Laboratory of Groundwater Circulation and Evolution, China University of Geosciences (Beijing), Ministry of Education, Beijing, 100083, People's Republic of China.
| | - Bill X Hu
- School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, People's Republic of China
- Key Laboratory of Groundwater Circulation and Evolution, China University of Geosciences (Beijing), Ministry of Education, Beijing, 100083, People's Republic of China
| | - Wenshuo Wei
- School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, People's Republic of China
- Key Laboratory of Groundwater Circulation and Evolution, China University of Geosciences (Beijing), Ministry of Education, Beijing, 100083, People's Republic of China
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