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Barreto MSC, Elzinga EJ, Kubicki JD, Sparks DL. A multi-scale assessment of the impact of salinity on the desorption of chromate from hematite: Sea level rise implications. JOURNAL OF HAZARDOUS MATERIALS 2024; 465:133041. [PMID: 38043423 DOI: 10.1016/j.jhazmat.2023.133041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 11/08/2023] [Accepted: 11/17/2023] [Indexed: 12/05/2023]
Abstract
The solubility and transport of Cr(VI) is primarily controlled by adsorption-desorption reactions at the surfaces of soil minerals such as iron oxides. Environmental properties such as pH, ionic strength, and ion competition are expected to affect the mobility and fate of Cr(VI). Sea level rise (SLR), and consequent seawater intrusion, is creating a new biogeochemical soil environment at coastal margins, potentially impacting Cr(VI) retention at contaminated sites. We employed in-situ ATR-FTIR spectroscopy and DFT calculations to investigate at the molecular level the adsorption of Cr(VI) on the hematite surface and its desorption by sulfate, as a function of pH and ionic strength. We further used a batch experiment to assess Cr(VI) desorption at varying artificial seawater (ASW) concentrations. IR results demonstrate the complexity of Cr(VI) adsorption, showing a combination of monodentate inner-sphere complexation at high pH and dichromate outer-sphere (∼75%) at low pH. The Cr(VI)-complexes exhibited desorption induced by increasing pH values (58% of desorption) and sulfate competition (∼40% desorption). ASW desorbed ∼20% more Cr(VI), even at just 1% concentration. Our findings provide insight into Cr(VI)-adsorption complexation that controls the retention and remobilization of Cr(VI) on Fe-oxide minerals. The results point to an elevated risk of Cr(VI) mobilization in contaminated soils affected by SLR.
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Affiliation(s)
| | - Evert J Elzinga
- Department of Earth & Environmental Sciences, Rutgers University, Newark, NJ, USA
| | - James D Kubicki
- Department of Earth, Environmental & Resource Sciences, The University of Texas at El Paso, El Paso, TX, USA
| | - Donald L Sparks
- Department of Plant & Soil Sciences, University of Delaware, Newark, DE, USA
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2
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Chen W, Li B, Yin W, Zeng W, Li P, Wu J. Promoted iron corrosion and subsequent hexavalent chromium removal in zero-valent iron systems by oxidant activation. CHEMOSPHERE 2024; 352:141391. [PMID: 38325615 DOI: 10.1016/j.chemosphere.2024.141391] [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: 11/14/2023] [Revised: 01/24/2024] [Accepted: 02/03/2024] [Indexed: 02/09/2024]
Abstract
Zero-valent iron (ZVI), as an effective medium, is widely used to eliminate heavy metal ions in filter tanks. However, it will react with Cr(VI) to generate Fe-Cr precipitates with low conductivity on its surface, resulting in slow iron corrosion and low Cr(VI) removal efficiency. In this study, three oxidants (KMnO4, NaClO, and Na2S2O8) were employed to promote iron corrosion in ZVI systems for enhanced Cr(VI) removal at a concentration of 5 mg/L through batch tests and column experiments. The ZVI/KMnO4, ZVI/NaClO, and ZVI/Na2S2O8 systems achieved significantly higher Cr(VI) removal rates of 31.5%, 52.8%, and 65.9% than the ZVI system (9.8%). Solid phase characterization confirmed that these improvements were attributed to promoted iron corrosion and secondary mineral formation (e.g., lepidocrocite, ferrihydrite, and magnetite) by oxidants. Those minerals offered more reaction sites for Cr(VI) reduction, adsorption, and sequestration. Cycle experiments indicated that ZVI/oxidant systems could stably remove Cr(VI). In long-term column experiment, the ZVI/NaClO column showed a much longer life-span and exhibited a 34.8 times higher Cr(VI) removal capacity than that of the ZVI column. These findings demonstrated that ZVI in combination with a reasonable amount of oxidants was a promising method for removing Cr(VI) in practical filter tanks and provided a new insight to enhance Cr(VI) removal.
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Affiliation(s)
- Weiting Chen
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China
| | - Bing Li
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China
| | - Weizhao Yin
- School of Environment, Jinan University, Guangzhou, 510632, China
| | - Weilong Zeng
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China
| | - Ping Li
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China
| | - Jinhua Wu
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China; The Key Laboratory of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou, 510006, China; The Key Laboratory of Environmental Protection and Eco-Remediation of Guangdong Regular Higher Education Institutions, Guangzhou, 510006, China; Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Recycling, Guangzhou, 510006, China.
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3
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Li W, Feng Z, Zhu X, Gong W. Efficient removal of Cr (VI) from coal gangue by indigenous bacteria-YZ1 bacteria: Adsorption mechanism and reduction characteristics of extracellular polymer. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2024; 272:116047. [PMID: 38301582 DOI: 10.1016/j.ecoenv.2024.116047] [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: 09/17/2023] [Revised: 01/02/2024] [Accepted: 01/27/2024] [Indexed: 02/03/2024]
Abstract
The existence of heavy metals (especially Cr (VI)) in coal gangue has brought great safety risks to the environment. The indigenous bacteria (YZ1 bacteria) were separated and applied for removing Cr (VI) from the coal gangue, in which its tolerance to Cr (VI) was explored. The removal mechanism of Cr (VI) was investigated with pyrite in coal gangue, metabolite organic acids and extracellular polymer of YZ1 bacteria. The concentration of Cr (VI) could be stabilized around 0.012 mg/L by the treatment with YZ1 bacteria. The Cr (VI) tolerance of YZ1 bacteria reached 60 mg/L, and the removal efficiency of Cr (VI) was more than 95% by using YZ1 bacteria combined with pyrite. The organic acids had a certain reducing ability to Cr (VI) (removal efficiency of less than 10%). The extracellular polymers (EPS) were protective for the YZ1 bacteria resisting to Cr (VI). The polysaccharides and Humic-like substances in the soluble extracellular polymers (S-EPS) had strong adsorption and reduction effect on Cr (VI), in which the tryptophan and tyrosine proteins in the bound extracellular polymers (LB-EPS and TB-EPS) could effectively promote the reduction of Cr (VI). YZ1 bacteria could obviously reduce the damage of Cr (VI) from coal gangue to the environment.
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Affiliation(s)
- Wang Li
- College of Chemistry and Chemical Engineering, Henan Polytechnic University, Jiaozuo, Henan 454000, China; Henan Key Laboratory of Coal Green Conversion, Henan Polytechnic University, China
| | - Zhaoxiang Feng
- College of Chemistry and Chemical Engineering, Henan Polytechnic University, Jiaozuo, Henan 454000, China; Henan Key Laboratory of Coal Green Conversion, Henan Polytechnic University, China
| | - Xiaobo Zhu
- College of Chemistry and Chemical Engineering, Henan Polytechnic University, Jiaozuo, Henan 454000, China; Henan Key Laboratory of Coal Green Conversion, Henan Polytechnic University, China.
| | - Wenhui Gong
- College of Chemistry and Chemical Engineering, Henan Polytechnic University, Jiaozuo, Henan 454000, China
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4
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Huang X, Yang G. Enhanced immobilization of Arsenic(III) and Auto-oxidation to Arsenic(V) by titanium oxide (TiO 2), due to Single-Atom vacancies and oxyanion formation. J Colloid Interface Sci 2023; 650:1327-1338. [PMID: 37478750 DOI: 10.1016/j.jcis.2023.07.103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Revised: 06/28/2023] [Accepted: 07/16/2023] [Indexed: 07/23/2023]
Abstract
Pollution control of As(III), a naturally occurring carcinogen, has recently gained a global attention, while due to the dominance of neutral H3AsO3 over a wide pH range, As(III) immobilization by most minerals is not efficient as As(V) immobilization. TiO2 shows promise for controlling As(III) pollution, and herein, a comprehensive study about As(III) adsorption by TiO2 and oxyanion formation is conducted by means of DFT + D3 methods. Both anatase and rutile are effective for As(III) adsorption, while As(III) adsorption affinities differ significantly and are -1.48 and -3.79 eV for pristine surfaces, ascend to -3.85 and -5.08 eV for O vacancies, and further to -5.37 and -5.26 eV for Ti vacancies, respectively. The bidentate binuclear complexes dominate for pristine surfaces, and O vacancies prefer OAs insertion into TiO2 lattice, while for Ti vacancies, all As(III) centers are auto-oxidized to As(V). Ti-3d, O-2p or/and As-4p rather than other orbitals contribute significantly to As adsorption, and O and Ti vacancies promote adsorption through stronger orbital hybridization. The superior adsorption for Ti vacancies originates from As(V) formation instead of bonding interactions. The formation of As oxyanions, which may occur spontaneously at pristine surfaces and is greatly promoted by O and Ti vacancies, enhances As(III) adsorption pronouncedly and becomes a viable strategy for As(III) immobilization. H2AsO3- and HAsO32- dominate for pristine surfaces and O vacancies, and for Ti vacancies, H2AsO4- and HAsO42- dominate over anatase whereas AsO43- also makes an important contribution over rutile. Results rationalize experimental observations available, and provide significantly new insights about the migration, bioavailability and fate of As(III) over TiO2 surfaces that facilitate the exploration of scavengers for As and other pollutants.
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Affiliation(s)
- Xiaoxiao Huang
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Gang Yang
- College of Resources and Environment, Southwest University, Chongqing 400715, China.
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5
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He Q, He Y, Zhang Z, Ou GZ, Zhu KF, Lou W, Zhang KN, Chen YG, Ye WM. Spatiotemporal distribution and pollution control of pollutants in a Cr(VI)-contaminated site located in Southern China. CHEMOSPHERE 2023; 340:139897. [PMID: 37604342 DOI: 10.1016/j.chemosphere.2023.139897] [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: 12/07/2022] [Revised: 08/15/2023] [Accepted: 08/18/2023] [Indexed: 08/23/2023]
Abstract
Soil and groundwater Cr(VI) pollution resulting from improper disposal and accidental spills is a critical problem worldwide. In this study, a comprehensive study was conducted to assess the hydrogeological conditions of a contaminated site, obtain spatiotemporal distribution and trend forecasts of pollutant Cr(VI), and determine the feasibility of applying clayey engineered barriers for pollution control. The results showed that the hydraulic conductivity (K) of the clayey barrier (1.56E-5 m/d) is several orders of magnitude lower than that of the stratum beneath the contaminated site, with K values ranging from 0.0014 to 4.76 m/d. Cr(VI) exhibits high mobility and a much higher concentration in the vadose zone, with maximum values of 6100 mg/kg in topsoil and 2090 mg/L in the perched aquifer. The simulation results indicated that the groundwater in the vicinity of the contaminated site, as well as downstream of the Lianshui River, is seriously threatened by Cr(VI). Notably, the pollution plume could occur downstream of the Lianshui River after 8 years. The retention efficiency of clayey engineered barriers will decrease over time, at 61.6% after 8 years and 33% after 20 years. This work contributes to an in-depth understanding of Cr(VI) migration at contaminated sites.
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Affiliation(s)
- Qi He
- Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring (Central South University), Ministry of Education, Changsha, 410083, PR China; School of Geosciences and Info-Physics, Central South University, Changsha, 410083, China; School of Chemistry and Chemical Engineering, Central South University, Changsha, 410083, China
| | - Yong He
- Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring (Central South University), Ministry of Education, Changsha, 410083, PR China; School of Geosciences and Info-Physics, Central South University, Changsha, 410083, China.
| | - Zhao Zhang
- Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring (Central South University), Ministry of Education, Changsha, 410083, PR China; School of Geosciences and Info-Physics, Central South University, Changsha, 410083, China
| | - Ge-Zhi Ou
- Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring (Central South University), Ministry of Education, Changsha, 410083, PR China; School of Geosciences and Info-Physics, Central South University, Changsha, 410083, China
| | - Kao-Fei Zhu
- Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring (Central South University), Ministry of Education, Changsha, 410083, PR China; School of Geosciences and Info-Physics, Central South University, Changsha, 410083, China
| | - Wei Lou
- Hunan HIKEE Environmental Technology CO., Ltd., Changsha, 410221, China
| | - Ke-Neng Zhang
- Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring (Central South University), Ministry of Education, Changsha, 410083, PR China; School of Geosciences and Info-Physics, Central South University, Changsha, 410083, China
| | - Yong-Gui Chen
- Key Laboratory of Geotechnical & Underground Engineering of Ministry of Education and Department of Geotechnical Engineering, Tongji University, Shanghai, 200092, PR China
| | - Wei-Min Ye
- Key Laboratory of Geotechnical & Underground Engineering of Ministry of Education and Department of Geotechnical Engineering, Tongji University, Shanghai, 200092, PR China
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Sun P, Liu Y, Wang R, Zhu Z, Wu J, Zhou J, Zhang Y, Jia H, Wang T. In-situ CO2−/ OH redox induced by degradation intermediate organic acids realized simultaneously Cu-EDTA decomplexation and Cr(VI) reduction in a plasma process. Sep Purif Technol 2023. [DOI: 10.1016/j.seppur.2023.123705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
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7
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He Q, He Y, Hu HP, Lou W, Zhang Z, Zhang KN, Chen YG, Ye WM, Sun J. Laboratory investigation on the retention performance of a soil-bentonite mixture used as an engineered barrier: insight into the effects of ionic strength and associated heavy metal ions. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:50162-50173. [PMID: 36790709 DOI: 10.1007/s11356-023-25780-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 02/03/2023] [Indexed: 04/16/2023]
Abstract
Soil-bentonite (S-B) materials are promising backfill materials for use as engineered barriers in heavy metal-contaminated sites. The effects of contaminant exposure on the retention performance of the S-B barrier remain unrevealed. In this study, based on the pollution status of an abandoned ferroalloy factory located in southern China, the retention performance of the S-B mixture toward Cr(VI) and Zn(II) was studied through adsorption and diffusion experiments sequentially; the separate effect of ionic strength (binary solution) and the combined effect of ionic strength and associated heavy metal ion (ternary solution) were discussed. In NaCl-Cr(VI)/Zn(II) binary solutions, the adsorption of Zn(II) onto the S-B mixture is larger than that of Cr(VI). Kd, Qmax, and ɛacc (accessible porosity) of Cr(VI) increase through increasing ionic strength, while Zn(II) shows the opposite trend; De (effective diffusion coefficient) values for both Cr(VI) and Zn(II) increased with increasing ionic strength and follow a sequence of Cr(VI) > Zn(II), indicating a better retention performance of the S-B mixture to Zn(II). For a given ionic strength, the adsorption of Zn(II) was larger than that of Cr(VI), which can be attributed to the retention specificity of the S-B mixture to anion and cation. In Cr(VI)-Zn(II)-NaCl ternary solutions, the adsorptions of Cr(VI) and Zn(II) are enhanced in varying degrees when compared with their binary solution, which probably could be attributed to the ion bridge role of Cr(VI)/Zn(II) to connect each other that relatively increased the adsorption capacity of S-B material. This work will contribute to an in-depth understanding of the retention performance of the S-B mixture in complicated chemical environments and facilitate the selection of future remediation strategies.
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Affiliation(s)
- Qi He
- Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring (Central South University), Ministry of Education, Changsha, People's Republic of China
- School of Geosciences and Info-Physics, Central South University, Changsha, 410083, China
- School of Chemistry and Chemical Engineering, Central South University, Changsha, 410083, China
| | - Yong He
- Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring (Central South University), Ministry of Education, Changsha, People's Republic of China.
- School of Geosciences and Info-Physics, Central South University, Changsha, 410083, China.
| | - Hui-Ping Hu
- School of Chemistry and Chemical Engineering, Central South University, Changsha, 410083, China
| | - Wei Lou
- Hunan HIKEE Environmental Technology CO., LTD, Changsha, 410221, China
| | - Zhao Zhang
- Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring (Central South University), Ministry of Education, Changsha, People's Republic of China
- School of Geosciences and Info-Physics, Central South University, Changsha, 410083, China
| | - Ke-Neng Zhang
- Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring (Central South University), Ministry of Education, Changsha, People's Republic of China
- School of Geosciences and Info-Physics, Central South University, Changsha, 410083, China
| | - Yong-Gui Chen
- Key Laboratory of Geotechnical & Underground Engineering of Ministry of Education and Department of Geotechnical Engineering, Tongji University, Shanghai, 200092, People's Republic of China
| | - Wei-Min Ye
- Key Laboratory of Geotechnical & Underground Engineering of Ministry of Education and Department of Geotechnical Engineering, Tongji University, Shanghai, 200092, People's Republic of China
| | - Jing Sun
- State Key Laboratory of Environmental Geochemistry, Guiyang, 550081, People's Republic of China
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8
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Zhu L, Hong C, Zhang J, Qiu Y. Long-distance mobilization of chromium(III) in soil associated with submicron Cr 2O 3. JOURNAL OF HAZARDOUS MATERIALS 2023; 445:130519. [PMID: 36493648 DOI: 10.1016/j.jhazmat.2022.130519] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 11/26/2022] [Accepted: 11/27/2022] [Indexed: 06/17/2023]
Abstract
Trivalent chromium is generally assumed to form insoluble species, resulting in low mobility of Cr(III) in soils. Here, we report continuous distributions (0-19 m) of a high concentration of Cr(III) in the alkaline soils of a historically industrial site for producing Na2Cr2O7, CrO3, and Cr2O3, which challenges this abovementioned conventional wisdom. The thermodynamic equilibrium model showed the low possibility of Cr(III) originating from Cr(VI) reduction under the redox conditions of this study. The AF4-MALLS-ICP-MS and μ-XRF-XANES were used to identify the particle size distribution of Cr(III)-containing colloids and Cr(III) species in mobile colloids. In any soil layer, Cr(III) accounts for 71.1-94.3% of the total Cr in submicron soil colloids and is composed of submicron intrinsic Cr2O3 (55.2%-63.8%), Cr(OH)3 (0-33.0%), and Cr(III) adsorbed by ferrihydrite (0-19.0%) and clay montmorillonite (11.1%-21.1%) colloid. On the contrary, Cr(VI) was mainly distributed in bulk soil (> 2 µm) except for the topsoil, accounting for 62.6-90.0% of total Cr(VI). Organic matter content and soil texture are the most critical factors driving the mobilization of submicron colloids in soils by principal component analysis. Humic acid (HA) formed HA-corona on Cr2O3 surface and enhanced colloidal dispersion, thereby accelerating the long-distance mobilization of submicron Cr2O3 colloids in alkaline soil layers, whereas the heteroaggregation of clay colloid with Cr2O3 was only favorable for short-distance mobilization. Our findings help to re-recognize the potential migration risks of insoluble heavy metals in soils.
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Affiliation(s)
- Ling Zhu
- Department of Environmental Science, College of Environmental Science and Engineering, Tongji University; State Key Laboratory of Pollution Control and Resources Reuse, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Chengyi Hong
- Department of Environmental Science, College of Environmental Science and Engineering, Tongji University; State Key Laboratory of Pollution Control and Resources Reuse, Shanghai 200092, China
| | - Jichen Zhang
- Department of Environmental Science, College of Environmental Science and Engineering, Tongji University; State Key Laboratory of Pollution Control and Resources Reuse, Shanghai 200092, China
| | - Yuping Qiu
- Department of Environmental Science, College of Environmental Science and Engineering, Tongji University; State Key Laboratory of Pollution Control and Resources Reuse, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China.
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9
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Huang X, Li T, Yang G. Immobilization of As(III) by gibbsite and catalytic oxidation to As(V): Profound impacts of doping and unraveling of associated mechanisms. CHEMOSPHERE 2023; 313:137583. [PMID: 36529173 DOI: 10.1016/j.chemosphere.2022.137583] [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: 06/12/2022] [Revised: 12/12/2022] [Accepted: 12/14/2022] [Indexed: 06/17/2023]
Abstract
As(III) is highly toxic, and its adsorption and oxidation to As(V) by minerals represent two effective approaches to remediate As(III)-contaminated sites. Gibbsite, one of the most abundant natural minerals, shows decent adsorption for As(III), and in this study, mechanisms of As(III) immobilization and oxidation by gibbsite with different dopants (M = Fe(III), Mn(III), Mn(IV)) are addressed by periodic DFT calculations. Influences of Fe(III) content and Mn oxidation state are also inspected. Although a majority remain structurally similar to those of pristine gibbsite, new adsorption configurations emerge due to doping: Inner-sphere complexes with M - As bonds for all doping, bidentate binuclear complexes for double Fe(III) doping, and physisorption with weak OMn-As interactions for Mn(IV) doping. As(III) adsorption affinities are significantly altered by doping and rely on dopants, while inner-sphere complexes with M-OAs bonds are always lowest-energy except doping Mn(III) that prefers trigonal bipyramidal coordination and impedes As(III) chemisorption. Doping causes strong M-3d and OAs-2p orbital interactions that facilitate As(III) adsorption whereas disappear for pristine gibbsite. Double Fe(III)- and Mn(IV)-doped gibbsite materials are effective for As(III) oxidation to As(V), and mechanisms differ significantly although all are characterized by dual electron transfers. Activation barriers for the most favorable reaction paths amount to 1.02 and 1.26-1.31 eV, respectively. Physisorbed and outer-sphere As(III) complexes exhibit comparable reactivities as chemisorbed complexes that become focus of literature reports, and may also be involved during interfacial and environmental reactions. Results rationalize experimental observations available, and provide significantly new insights that conduce to manage As-associated pollution and design efficient As(III) scavengers and oxidation catalysts.
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Affiliation(s)
- Xiaoxiao Huang
- College of Resources and Environment, Southwest University, Chongqing, 400715, China
| | - Tingting Li
- College of Resources and Environment, Southwest University, Chongqing, 400715, China
| | - Gang Yang
- College of Resources and Environment, Southwest University, Chongqing, 400715, China.
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10
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Wang K, Ma Y, Sun B, Yang Y, Zhang Y, Zhu L. Transport of silver nanoparticles coated with polyvinylpyrrolidone of various molecular sizes in porous media: Interplay of polymeric coatings and chemically heterogeneous surfaces. JOURNAL OF HAZARDOUS MATERIALS 2022; 429:128247. [PMID: 35065312 DOI: 10.1016/j.jhazmat.2022.128247] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 12/19/2021] [Accepted: 01/06/2022] [Indexed: 06/14/2023]
Abstract
Silver nanoparticles (AgNPs) are usually capped with stabilizing agents to protect their activities and improve stability. Polyvinylpyrrolidone (PVP) is one of the most used capping agents of AgNPs, and may affect the transport of AgNPs in porous media. The transport and retention of AgNPs capped with PVPs of different molecular weights (PVP10-AgNP, PVP40-AgNP and PVP360-AgNP) in uncoated, and humic acid (HA)-, kaolinite (KL)- and ferrihydrite (FH)-coated sand porous media were investigated. Among the three AgNPs, PVP360-AgNP exhibited the highest mobility and eluted from all types of porous media. This is because PVPs of higher molecular weight provided stronger steric effect and electrostatic repulsive forces among PVP-AgNPs, inducing stronger blocking and shadow effects. The transport of the PVP-AgNPs increased in the HA-Sand columns, while decreased in the KL- and FH-Sand columns, especially for PVP10-AgNP and PVP40-AgNP. The simulation results using one-site kinetic model indicated that HA-Sand reduced the maximum retention capacity (Smax), while KL- and FH-Sand increased the Smax as well as the first-order attachment rate coefficients (katt), particularly at high ionic strength. The results shed light on the interplay of the capping agents of AgNPs and the surface heterogeneity on the transport of AgNPs in porous media.
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Affiliation(s)
- Kunkun Wang
- Key Laboratory of Pollution Processes and Environmental Criteria, Ministry of Education, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, PR China
| | - Yi Ma
- Key Laboratory of Pollution Processes and Environmental Criteria, Ministry of Education, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, PR China
| | - Binbin Sun
- Key Laboratory of Pollution Processes and Environmental Criteria, Ministry of Education, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, PR China
| | - Yi Yang
- Key Laboratory of Pollution Processes and Environmental Criteria, Ministry of Education, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, PR China
| | - Yinqing Zhang
- Key Laboratory of Pollution Processes and Environmental Criteria, Ministry of Education, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, PR China
| | - Lingyan Zhu
- Key Laboratory of Pollution Processes and Environmental Criteria, Ministry of Education, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, PR China.
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11
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Zhu C, Huang X, Li T, Wang Q, Yang G. Mechanisms for Cr(VI) reduction by alcohols over clay edges: Reactive differences between ethanol and ethanediol, and selective conversions to Cr(IV), Cr(III) and Cr(II) species. J Colloid Interface Sci 2021; 603:37-47. [PMID: 34186408 DOI: 10.1016/j.jcis.2021.06.123] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 06/19/2021] [Accepted: 06/21/2021] [Indexed: 11/30/2022]
Abstract
Catalytic reduction by alcohols over clay minerals works efficiently under a wide range of pH and represents an emerging approach to control Cr(VI) contamination. Herein, mechanisms for Cr(VI) adsorption and reduction at clay edges are addressed by dispersion-corrected periodic DFT calculations, considering different active sites, and types (monohydric and polyhydric) and coverage of alcohols. Cr(VI) adsorbs favorably at clay edges, forming direct bonds and strong H-bonds. Mechanisms for Cr(VI) reduction by alcohols are largely determined by π-conjugation development, and efficient conversion conduces to Cr(VI) removal. Cr(II), Cr(III) and Cr(IV) are useful for different purposes, and high selectivity towards these products is realized through rational catalysts design: 1) Cr(IV) dominates at Al3+ site with all ethanol coverage, Al3+ site with high-coverage ethanediol, and Mg2+ site with low-coverage ethanol; 2) Cr(III) dominates at Al3+ and Mg2+ sites with low-coverage ethanediol; 3) Cr(II) dominates at Mg2+ site with high-coverage ethanol or ethanediol. Results agree finely with experimental observations available, and significant new insights have been provided for Cr management and recycling. Detailed electronic structure and vibrational analyses, which can also guide future experimental studies, manifest that Cr(VI) reduction progresses are effectively monitored by ESR and FT-IR techniques.
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Affiliation(s)
- Chang Zhu
- College of Resources and Environments & Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, Southwest University, Chongqing 400715, China
| | - Xiaoxiao Huang
- College of Resources and Environments & Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, Southwest University, Chongqing 400715, China
| | - Tingting Li
- College of Resources and Environments & Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, Southwest University, Chongqing 400715, China
| | - Qian Wang
- College of Resources and Environments & Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, Southwest University, Chongqing 400715, China
| | - Gang Yang
- College of Resources and Environments & Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, Southwest University, Chongqing 400715, China.
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