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Chen DT, Roy A, Bogush A, Stegemann JA. Speciation of toxic metals in metal finishing filter cake by X-ray absorption spectroscopy. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2024; 360:120994. [PMID: 38749132 DOI: 10.1016/j.jenvman.2024.120994] [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: 01/18/2024] [Revised: 03/15/2024] [Accepted: 04/20/2024] [Indexed: 06/05/2024]
Abstract
The speciation of Cr, Zn, Cu and Pb in two metal finishing filter cakes (TX and ST) was investigated by X-ray absorption spectroscopy (XAS) complemented by X-ray fluorescence (XRF) and X-ray diffraction (XRD). XRF showed that concentrations of Cr, Zn, Cu and Pb were 1.4%, 0.19%, 0.20% and 0.01%, respectively, in TX, and 12.6%, 3.3%, 1.3% and 0.21% in ST. No crystalline phases were detected in TX by XRD whereas ST was dominated by calcite. Cr and Fe K edge XAS showed Cr to be trivalent and octahedrally coordinated, co-precipitated with Fe as CrxFe1-x-(oxy)hydroxides in both filter cakes. Zn, P and Ca K edge XAS showed that 2ZnCO3∙3Zn(OH)2 and Zn3(PO4)2 were the dominant zinc-containing phases, with combined tetrahedral and octahedral coordination; Zn phases were slightly more crystalline in TX than ST. Pb L3 edge X-ray absorption near edge spectroscopy (XANES) found that Pb was likely adsorbed on amorphous SiO2. Cu, Si and S K edge XAS showed that all Cu was divalent, and the dominant copper phases were found to be Cu2Cl(OH)3, Cu(OH)2 and CuSO4·5H2O for ST, whereas Cu appeared to adsorb to amorphous SiO2 for TX, which contained much less Pb. Cr is thus immobilized in the filter cakes in a phase with low solubility at environmentally feasible pH values, whereas Zn, Cu and Pb could be released when the pH decreases below 8 or above 11. These findings are significant for the development of waste management regulations and/or metal recovery methods (e.g., hydro/pyrometallurgy).
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Affiliation(s)
- Dan Ting Chen
- Department of Civil, Environmental and Geomatic Engineering (CEGE), University College London (UCL), Chadwick Building, Gower Street, London, WC1E 6BT, UK
| | - Amitava Roy
- Louisiana State University Center for Advanced Microstructures and Devices, Baton Rouge, LA, 70806, USA
| | - Anna Bogush
- Department of Civil, Environmental and Geomatic Engineering (CEGE), University College London (UCL), Chadwick Building, Gower Street, London, WC1E 6BT, UK
| | - Julia A Stegemann
- Department of Civil, Environmental and Geomatic Engineering (CEGE), University College London (UCL), Chadwick Building, Gower Street, London, WC1E 6BT, UK.
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Raji F, Nguyen CV, Nguyen NN, Nguyen TAH, Nguyen AV. Probing interfacial water structure induced by charge reversal and hydrophobicity of silica surface in the presence of divalent heavy metal ions using sum frequency generation spectroscopy. J Colloid Interface Sci 2023; 647:152-162. [PMID: 37247479 DOI: 10.1016/j.jcis.2023.05.125] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 05/12/2023] [Accepted: 05/17/2023] [Indexed: 05/31/2023]
Abstract
HYPOTHESIS Adsorption of divalent heavy metal ions (DHMIs) at the mineral-water interfaces changes interfacial chemical species and charges, interfacial water structure, Stern (SL), and diffuse (DL) layers. These molecular changes can be detected by probing changing orientation and hydrogen-bond network of interfacial water molecules in response to changing local charges and hydrophobicity. EXPERIMENTS Sum-frequency generation (SFG) spectroscopy was used to probe changes in vibrational resonances of interfacial OH vs. DHMI concentration and pH. SFG spectra were deconvoluted using the measured surface potential and maximum entropy method in conjunction with the electrical double-layer theory for the SL and DL structures and correlated by hydrophobicity. FINDINGS Three surface charge reversals (CRs) were detected at low (CR1), medium (CR2), and high (CR3) pHs. Unlike CR1, SFG signals were minimized at CR2 and CR3 for DHMIs-silica systems highlighting considerable alterations in the structure of interfacial waters due to the inner-sphere sorption of metal hydroxo complexes. SFG results showed "hydrophobic-like" stretching modes at > 3600 cm-1 for Pb-, Cu-, and Zn-treated silica. However, contact angle measurements revealed the hydrophobization of silica only in the presence of Pb(II), as confirmed by an in-depth SFG analysis of the hydrogen-bond network of the interfacial water molecules in the SL.
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Affiliation(s)
- Foad Raji
- School of Chemical Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Cuong V Nguyen
- School of Chemical Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Ngoc N Nguyen
- School of Chemical Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Tuan A H Nguyen
- Sustainable Minerals Institute, The University of Queensland, QLD 4072, Australia
| | - Anh V Nguyen
- School of Chemical Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia.
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Zhang Y, Cao B, Yin H, Meng L, Jin W, Wang F, Xu J, Al-Tabbaa A. Application of zeolites in permeable reactive barriers (PRBs) for in-situ groundwater remediation: A critical review. CHEMOSPHERE 2022; 308:136290. [PMID: 36058373 DOI: 10.1016/j.chemosphere.2022.136290] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 08/25/2022] [Accepted: 08/28/2022] [Indexed: 06/15/2023]
Abstract
Permeable reactive barrier (PRB) is one of the most promising in-situ groundwater remediation technologies due to its low costs and wide immobilization suitability for multiple contaminants. Reactive medium is a key component of PRBs and their selection needs to consider removal effectiveness as well as permeability. Zeolites have been extensively reported as reactive media owing to their high adsorption capacity, diverse pore structure and high stability. Moreover, the application of zeolites can reduce the PRBs fouling and clogging compared to reductants like zero-valence iron (ZVI) due to no formation of secondary precipitates, such as iron monosulfide, in spite of their reactivity to remove organics. This study gives a detailed review of lab-scale applications of zeolites in PRBs in terms of sorption characteristics, mechanisms, column performance and desorption features, as well as their field-scale applications to point out their application tendency in PRBs for contaminated groundwater remediation. On this basis, future prospects and suggestions for using zeolites in PRBs for groundwater remediation were put forward. This study provides a comprehensive and critical review of the lab-scale and field-scale applications of zeolites in PRBs and is expected to guide the future design and applications of adsorbents-based PRBs for groundwater remediation.
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Affiliation(s)
- Yunhui Zhang
- College of Environmental Science and Engineering, Key Laboratory of Yangtze River Water Environment, Ministry of Education, Tongji University, Shanghai, 200092, China; Department of Engineering, University of Cambridge, Cambridge, CB2 1PZ, United Kingdom.
| | - Benyi Cao
- Department of Civil and Environmental Engineering, University of Surrey, Guildford, GU2 7XH, United Kingdom.
| | - Hailong Yin
- College of Environmental Science and Engineering, Key Laboratory of Yangtze River Water Environment, Ministry of Education, Tongji University, Shanghai, 200092, China.
| | - Lite Meng
- College of Environmental Science and Engineering, Key Laboratory of Yangtze River Water Environment, Ministry of Education, Tongji University, Shanghai, 200092, China.
| | - Wei Jin
- College of Environmental Science and Engineering, Key Laboratory of Yangtze River Water Environment, Ministry of Education, Tongji University, Shanghai, 200092, China.
| | - Fei Wang
- Institute of Geotechnical Engineering, School of Transportation, Southeast University, Nanjing, 210096, China.
| | - Jian Xu
- State Environmental Protection Key Laboratory of Soil Environmental Management and Pollution Control, Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment of China, Nanjing, 210042, China.
| | - Abir Al-Tabbaa
- Department of Engineering, University of Cambridge, Cambridge, CB2 1PZ, United Kingdom.
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Alby D, Charnay C, Heran M, Prelot B, Zajac J. Recent developments in nanostructured inorganic materials for sorption of cesium and strontium: Synthesis and shaping, sorption capacity, mechanisms, and selectivity-A review. JOURNAL OF HAZARDOUS MATERIALS 2018; 344:511-530. [PMID: 29100131 DOI: 10.1016/j.jhazmat.2017.10.047] [Citation(s) in RCA: 122] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Revised: 10/19/2017] [Accepted: 10/22/2017] [Indexed: 06/07/2023]
Abstract
Liquid wastes containing non-ferrous heavy metal ions and some radionuclides, 137Cs and 90Sr in particular, represent one of the most dangerous sources of environmental contamination. The remediation of wastewater containing such pollutants continue to be among the biggest challenges of Sustainable Development and Environmental Safety. Sorption-based technologies have proven their efficiency also in reducing the radionuclide content in aqueous streams to low-level residual activity, with the concomitant decrease in the amount of ultimate solid waste generated. Although sorption of cesium and strontium by resins, clays, and zeolites has been investigated intensively and even used in real applications, there is still considerable scope for improvement in terms of retention capacity and selectivity. Recent progress in design and preparation of nanostructured inorganic materials has attracted growing interest based on the potential for improving the retention performance when coupling such functionalities as ion exchange capacity, structural flexibility that may result in steric retention effects, as well as the propensity to interact specifically with the target metal cations. Titanate, vanadate, and tungsten based materials, manganese oxides, hexacyanoferrates, metal sulfides, ammonium molybdophosphates, or hydroxyapatite, characterized by various structures and morphologies, are reviewed with the emphasis being put on synthesis and shaping of such materials, their structure in relationship with the capacity and selectivity of trapping cesium and strontium from either single or multi-component aqueous solutions, as well as the possible retention mechanism. The potential candidates for remediation uses are selected with regard to their sorption capacity and distribution coefficient towards target cations, and also the pH window for an optimum cation capture.
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Affiliation(s)
- Delhia Alby
- Institut Charles Gerhardt, UMR-5253 CNRS-UM-ENSCM, Université de Montpellier, Place E. Bataillon, F-34095 Montpellier cedex 5, France
| | - Clarence Charnay
- Institut Charles Gerhardt, UMR-5253 CNRS-UM-ENSCM, Université de Montpellier, Place E. Bataillon, F-34095 Montpellier cedex 5, France
| | - Marc Heran
- Institut Européen des Membranes, UMR5635 CNRS-UM-ENSCM, Université de Montpellier, Place E. Bataillon, F-34095 Montpellier cedex 5, France
| | - Bénédicte Prelot
- Institut Charles Gerhardt, UMR-5253 CNRS-UM-ENSCM, Université de Montpellier, Place E. Bataillon, F-34095 Montpellier cedex 5, France
| | - Jerzy Zajac
- Institut Charles Gerhardt, UMR-5253 CNRS-UM-ENSCM, Université de Montpellier, Place E. Bataillon, F-34095 Montpellier cedex 5, France.
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Zhang C, Sale PWG, Tang C. Cadmium uptake by Carpobrotus rossii (Haw.) Schwantes under different saline conditions. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2016; 23:13480-13488. [PMID: 27025219 DOI: 10.1007/s11356-016-6508-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Accepted: 03/17/2016] [Indexed: 06/05/2023]
Abstract
Plants used for phytoextraction of heavy metals from contaminated soils with high levels of salinity should be able to accumulate heavy metals and also be tolerant to salinity. Australian native halophyte species Carpobrotus rossii has recently been shown to tolerate and accumulate multiple heavy metals, especially cadmium (Cd). This study examined the effects of salt type and concentration on phytoextraction of Cd in C. rossii. Plants were grown in contaminated soil for 63 days. The addition of salts increased plant growth and enhanced the accumulation of Cd in shoots up to 162 mg kg(-1) which almost doubled the Cd concentration (87 mg kg(-1)) in plants without salt addition. The increased Cd accumulation was ascribed mainly to increased ionic strength in soils due to the addition of salts and resultantly increased the mobility of Cd. In comparison, the addition of Cl(-) resulted in 8-60 % increase in Cd accumulation in shoots than the addition of SO4 (2-) and NO3 (-). The findings suggest that C. rossii is a promising candidate in phytoextraction of Cd-polluted soils with high salinity levels.
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Affiliation(s)
- Chengjun Zhang
- Department of Animal, Plant and Soil Sciences, Centre for AgriBioscience, La Trobe University, Melbourne Campus, Bundoora, VIC, 3086, Australia
| | - Peter W G Sale
- Department of Animal, Plant and Soil Sciences, Centre for AgriBioscience, La Trobe University, Melbourne Campus, Bundoora, VIC, 3086, Australia
| | - Caixian Tang
- Department of Animal, Plant and Soil Sciences, Centre for AgriBioscience, La Trobe University, Melbourne Campus, Bundoora, VIC, 3086, Australia.
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Butkus MA, Riegner DE, Olind J. Immobilization of lead by phosphate amended Polonite. CHEMOSPHERE 2016; 151:310-317. [PMID: 26950021 DOI: 10.1016/j.chemosphere.2016.02.066] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 01/29/2016] [Accepted: 02/16/2016] [Indexed: 06/05/2023]
Abstract
Polonite is an alkaline material that is used to remove nutrients from domestic wastewater and it has been evaluated as a fertilizer. Stabilization of Pb by Polonite and Polonite amended with orthophosphate, PO4, (Polonite-P) was studied. Octacalcium phosphate (Ca8H2(PO4)6·5H2O) was a primary species of PO4 formed on the surface of Polonite-P. Lead was found to be associated with pozzolanic reaction products in Pb treated Polonite and Pb treated Polonite-P samples. Formation of Pb oxides, as precipitates or surface complexes, were substantial constituents of Pb treated Polonite. Dissolution of Ca8H2(PO4)6·5H2O followed by formation of Pb4O(PO4)2 was a probable mechanism of Pb removal by Polonite-P. Polonite-P could be a suitable replacement for current PO4 sources as a Pb stabilization agent. Finally, LDI-TOF was an effective technique for evaluating forms of Pb on Polonite and Polonite-P.
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Affiliation(s)
- Michael A Butkus
- Environmental Engineering Program, Department of Geography and Environmental Engineering, U.S. Military Academy, West Point, NY 10996, USA.
| | - Dawn E Riegner
- Chemistry Program, Department of Chemistry and Life Science, U.S. Military Academy, West Point, NY 10996, USA
| | - Johannes Olind
- Environmental Engineering Program, Department of Geography and Environmental Engineering, U.S. Military Academy, West Point, NY 10996, USA
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7
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Li L, Scheckel KG, Zheng L, Liu G, Xing W, Xiang G. Immobilization of lead in soil influenced by soluble phosphate and calcium: lead speciation evidence. JOURNAL OF ENVIRONMENTAL QUALITY 2014; 43:468-474. [PMID: 25602648 DOI: 10.2134/jeq2013.07.0272] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We investigated the effect of soluble Ca on the speciation of Pb in phosphate-amended soils. A calcareous soil was amended in sequence with soluble phosphate (0 and 299 mg kg P), calcium nitrate (0, 200, and 400 mg kg Ca), and/or lead nitrate (0 and 1000 mg kg Pb) and incubated for 50 d. Extractable Ca was relatively similar across all samples, with a minor reduction in Ca release for treatments amended with P possibly from the formation of Ca-phosphate minerals. Olsen-P extractability from P-added treatments was highest in the non-Pb-amended soils and was about 40% lower when Pb was added as a result of Pb-phosphate formation. In the absence of P, diethylene triamine pentaacetic acid (DTPA)-Pb extractability increased with increasing Ca amendment; however, in the P-amended treatments, DTPA-Pb decreased with increasing Ca addition. X-ray absorption spectroscopy results of the Pb spiked soils indicate that adsorbed Pb is the primary phase (up to 92%) in non-P-amended soils with minor distribution to hydrocerussite and Pb-phosphate phases. In the P-amended treatments, Pb speciation shifted to Pb-phosphate [chloropyromorphite and Pb(PO)] (42-48%) and adsorbed Pb (44-50%). As Ca concentration increased in the P-amended soils, Pb-phosphate speciation moved from combined chloropyromorphite and Pb(PO) (0 mg kg Ca) to exclusively chloropyromorphite. The study demonstrates that soluble Ca enhances Pb immobilization with P amendments.
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8
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Ren X, Yang S, Hu F, He B, Xu J, Tan X, Wang X. Microscopic level investigation of Ni(II) sorption on Na-rectorite by EXAFS technique combined with statistical F-tests. JOURNAL OF HAZARDOUS MATERIALS 2013; 252-253:2-10. [PMID: 23500786 DOI: 10.1016/j.jhazmat.2013.02.033] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 02/16/2013] [Accepted: 02/20/2013] [Indexed: 06/01/2023]
Abstract
Extended X-ray absorption fine structure (EXAFS) spectroscopy combined with statistical F-tests is used to investigate the local atomic structures of Ni(II) adsorbed on Na-rectorite. The EXAFS analysis results of Ni(II) sorption samples indicate that the first coordination shell consists of ~6 O at the Ni-O interatomic distance (R) of ~2.04 Å. The presence of Ni backscattering at R(Ni-Ni) = 3.06 Å in the second coordination shell suggests the formation of Ni(II) precipitate. The results of F-tests show that the Ni(II) precipitate is Ni-Al layered double hydroxide (LDH). Our results demonstrate that Ni(II) ions are retained via different mechanisms depending on solution conditions. At low pH, Ni retention is controlled mainly by the outer-sphere surface complexation. With increasing pH, outer-sphere and inner-sphere surface complexation dominate Ni uptake. Furthermore, Ni surface loading increases with temperature increasing at pH 6.5 due to the formation of inner-sphere surface complexes and Ni-Al LDH. The formation of Ni-Al LDH becomes the dominate mechanism at the elevated pH and temperature. In the presence of humic substances, the sorption of Ni(II) on Na-rectorite is dominated by the formation of ternary surface complexes. These results are important to understand the physicochemical behavior of Ni(II) in the natural environment.
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Affiliation(s)
- Xuemei Ren
- School of Chemistry and Environment, North China Electric Power University, Beijing 102206, China
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9
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Sandhu NK, Axe L, Jahan K, Ramanujachary KV, Coolahan K. Environmental impact of metal and metalloid leaching from highway marking glass beads. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:4383-4391. [PMID: 23586397 DOI: 10.1021/es3027264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Recently, metals and metalloids have been observed at elevated concentrations in glass beads imported to the US. Average total concentrations in imported batches ranged from 103 to 683 mg kg(-1) for As, 62 to 187 mg kg(-1) for Sb, and 23 to 179 mg kg(-1) for Pb. The labile fraction associated with the glass beads resulted in leached concentrations as great as 538 μg L(-1) for As, 1092 μg L(-1) for Pb, and 160 μg L(-1) for Sb. Sequential extraction was conducted as well to better understand the form of metals and metalloids associated with the glass beads. Only 0.23% of As, 3.40% of Pb, 2.37% of Ba, and 1.92% of Mn were extracted in the exchangeable (As, Mn, and Ba) and the oxidizable forms (Pb), whereas greater than 97% of metals and metalloids present were associated with the glass matrix. Nonparametric statistics were applied to test total concentrations that resulted in exceedances in the groundwater quality criteria. Results demonstrated that the As, Pb, and Sb limits were exceeded for 98%, 58%, and 15% of the samples tested respectively suggesting a potential environmental impact to groundwater used as a drinking water source.
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Affiliation(s)
- Nimrat K Sandhu
- Department of Civil & Environmental Engineering, New Jersey Institute of Technology, Newark, New Jersey 07102, USA
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Struis RPWJ, Pasquali M, Borgese L, Gianoncelli A, Gelfi M, Colombi P, Thiaudière D, Depero LE, Rizzo G, Bontempi E. Inertisation of heavy metals in municipal solid waste incineration fly ash by means of colloidal silica – a synchrotron X-ray diffraction and absorption study. RSC Adv 2013. [DOI: 10.1039/c3ra41792a] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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11
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Prelot B, Einhorn V, Marchandeau F, Douillard JM, Zajac J. Bulk hydrolysis and solid-liquid sorption of heavy metals in multi-component aqueous suspensions containing porous inorganic solids: are these mechanisms competitive or cooperative? J Colloid Interface Sci 2012; 386:300-6. [PMID: 22889625 DOI: 10.1016/j.jcis.2012.07.045] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 07/10/2012] [Accepted: 07/12/2012] [Indexed: 11/18/2022]
Abstract
Fundamental aspects of the removal of heavy metals from aqueous streams under conditions of competition among the various species have been studied between pH 3 and 9 on Spherosil XO75LS, ordered mesoporous MCM-41 and MCF silicas, as well as a MCF sample grafted with (3-aminopropyl)methoxydimethylsilane (AMPS-MCF). Cd(II), Co(II), Pb(II), or Sr(II) nitrate solutions were used to determine the percentage of metal uptake by each solid at 298 K as a function of the pH of the equilibrium solution, at an initial metal concentration of 0.0001 mol L(-1) and the ionic strength being fixed with 0.01 mol L(-1) NaNO(3). Almost complete retention of the heavy metals on the four solid samples was observed, with the process beginning at pH values smaller than those marking the onset of "bulk" precipitation of a given metal in "free" solution. The heavy metal-uptake mechanism was regarded as hydrolysis-like phenomenon in metal-containing solid suspensions. Weak adsorption of metal species from slightly acidic and neutral solutions was a kind of nucleation step. Adding cadmium to an equimolar solution containing cobalt, lead, or strontium showed no significant effect on the retention of the main metal component. This indicated the great independence of the retention mechanisms.
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Affiliation(s)
- Benedicte Prelot
- Institut Charles Gerhardt Montpellier, UMR 5253 CNRS-UM2-ENSCM-UM1, Agrégats, Interfaces et Matériaux pour l'Energie, Montpellier, France.
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Voglar D, Lestan D. Pilot-scale washing of metal contaminated garden soil using EDTA. JOURNAL OF HAZARDOUS MATERIALS 2012; 215-216:32-39. [PMID: 22410723 DOI: 10.1016/j.jhazmat.2012.02.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Revised: 01/28/2012] [Accepted: 02/08/2012] [Indexed: 05/31/2023]
Abstract
Ten batches (75kg each) of garden soil with >50% of silt and clay and average 1935mgkg(-1) Pb, 800mgkg(-1) Zn, 10mgkg(-1) Cd and 120mgkg(-1) As were remediated in a pilot-scale chemical extraction plant. Washing with 60mmol ethylenediaminetetraacetic acid (EDTA) per kg of soil on average removed 79, 38, 70, and 80% of Pb, Zn, Cd and As, respectively, and significantly reduced the leachability, phyto-accessibility and oral-availability of residual toxic metals, as assessed using deionised water, toxicity characteristic leaching procedure (TCLP), diethylenetriamine pentaacetic acid extraction (DTPA) and physiologically based extraction test (PBET) tests. The used soil washing solution was treated before discharge using an electrochemical advanced oxidation process with graphite anode: EDTA was removed by degradation and toxic metals were electro-precipitated onto a stainless steel cathode. The novelty of the remediation technique is separation of the soil from the washing solution and soil rinsing (removal of mobilized contaminants) carried out in the same process step. Another novelty is the reuse of the soil rinsing solution from the previous batch for cleansing the soil sand, soil rinsing and for preparation of the washing solution in subsequent batches. The cost of energy and material expenses and disposal of waste products amounted to approximately 75€ton(-1) of soil.
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Affiliation(s)
- David Voglar
- Agronomy Department, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia
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Copper release kinetics from a long-term contaminated acid soil using a stirred flow chamber: Effect of ionic strength and pH. J Colloid Interface Sci 2012; 367:422-8. [DOI: 10.1016/j.jcis.2011.09.057] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 09/19/2011] [Accepted: 09/23/2011] [Indexed: 11/21/2022]
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14
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Venäläinen SH. Apatite ore mine tailings as an amendment for remediation of a lead-contaminated shooting range soil. THE SCIENCE OF THE TOTAL ENVIRONMENT 2011; 409:4628-4634. [PMID: 21871651 DOI: 10.1016/j.scitotenv.2011.08.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Revised: 08/02/2011] [Accepted: 08/02/2011] [Indexed: 05/31/2023]
Abstract
This study investigated the use of tailings from apatite ore beneficiation in the remediation of a heavily contaminated shooting range soil. The tailings originating in Siilinjärvi carbonatite complex, Finland, consist of apatite residues accompanied by phlogopite and calcite. In a pot experiment, organic top layer of a boreal forest soil predisposed to pellet-derived lead (Pb) was amended with tailings of various particle-sizes (Ø>0.2mm, Ø<0.2mm and unsieved material) differing in their mineralogical composition. After 9-, 10-, 14- and 21-month incubation, the samples were monitored for tailings-induced changes in the different Pb pools by means of sequential fractionation. Following the incubation, the samples were extracted with water and the extracts were analyzed for Pb species distribution by means of a cation exchange resin. The results revealed that Pb was continuously released from the shotgun pellet fragments due to weathering. However, the apatite and calcite compartments in the tailings counteracted the mobility of the released Pb through the formation of sparingly soluble fluorpyromorphite and cerussite. Furthermore, the tailings efficiently reduced the bioavailability of Pb by transferring it from the water-soluble and exchangeable pools into the organic one. The material also increased the proportion of the less toxic non-cationic Pb to the total dissolved Pb from the initial level of 5% to 9-12%. The results suggest that the tailings-induced stabilization of Pb may be an environmentally sound remediation technique at polluted sites.
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Affiliation(s)
- Salla H Venäläinen
- University of Helsinki, P.O. Box 27, 00014 University of Helsinki, Finland.
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MacLean LCW, Beauchemin S, Rasmussen PE. Lead speciation in house dust from Canadian urban homes using EXAFS, micro-XRF, and micro-XRD. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2011; 45:5491-5497. [PMID: 21591711 DOI: 10.1021/es2001503] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
X-ray absorption fine-structure (XAFS) spectroscopy, micro-X-ray fluorescence (μXRF), and micro-X-ray diffraction (μXRD) were used to determine the speciation of Pb in house dust samples from four Canadian urban homes having elevated Pb concentrations (>1000 mg Pb kg(-1)). Linear combination fitting of the XAFS data, supported by μXRF and μXRD, shows that Pb is complexed in a variety of molecular environments, associated with both the inorganic and organic fractions of the dust samples. The inorganic species of lead identified were as follows: Pb metal, Pb carbonate, Pb hydroxyl carbonate, Pb oxide, and Pb adsorbed to iron oxyhydroxides. Pb carbonate and/or Pb hydroxyl carbonate occurred in all four dust samples and accounted for 28 to 75% of total Pb. Pb citrate and Pb bound to humate were the organic species identified. The results of this study demonstrate the ability of XAFS to identify Pb speciation in house dust and show the potential to identify Pb sources from new homes versus older homes. Understanding Pb speciation and how it influences bioaccessibility is important for human health risk assessment and risk management decisions which aim to improve indoor environmental health.
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Affiliation(s)
- Lachlan C W MacLean
- Health Canada, Environmental Health Science and Research Bureau, Ottawa, Canada
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Goveia D, Pinheiro JP, Milkova V, Rosa AH, van Leeuwen HP. Dynamics and heterogeneity of Pb(II) binding by SiO2 nanoparticles in an aqueous dispersion. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:7877-7883. [PMID: 21612251 DOI: 10.1021/la2008182] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Pb(II) binding by SiO(2) nanoparticles in an aqueous dispersion was investigated under conditions where the concentrations of Pb(2+) ions and nanoparticles are of similar magnitude. Conditional stability constants (log K) obtained at different values of pH and ionic strength varied from 4.4 at pH 5.5 and I = 0.1 M to 6.4 at pH 6.5 and I = 0.0015 M. In the range of metal to nanoparticle ratios from 1.6 to 0.3, log K strongly increases, which is shown to be due to heterogeneity in Pb(II) binding. For an ionic strength of 0.1 M the Pb(2+)/SiO(2) nanoparticle system is labile, whereas for lower ionic strengths there is loss of lability with increasing pH and decreasing ionic strength. Theoretical calculations on the basis of Eigen-type complex formation kinetics seem to support the loss of lability. This is related to the nanoparticulate nature of the system, where complexation rate constants become increasingly diffusion controlled. The ion binding heterogeneity and chemodynamics of oxidic nanoparticles clearly need further detailed research.
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Butkus MA, Johnson MC. Influence of phosphate on the transport properties of lead in sand. JOURNAL OF HAZARDOUS MATERIALS 2011; 185:275-280. [PMID: 20934809 DOI: 10.1016/j.jhazmat.2010.09.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Revised: 08/10/2010] [Accepted: 09/06/2010] [Indexed: 05/30/2023]
Abstract
Temporal moment analysis was used to examine the transport of lead species in sand columns. The influence of sodium phosphate (PO(4(aq))) and hydroxyapatite (HA) on lead transport was also evaluated. Transport properties of lead microparticles (diameter>0.45 μm) were a function of electrophoretic mobility: those particles with electrophoretic mobility less than -1 × 10(-8)m(2)/Vs exhibited significantly lower dimensionless first temporal moment (θ) and second temporal moment (σ(θ)(2)). The forms of lead investigated in this work had a tendency to move in sand over a wide pH range. Although the PO(4(aq)) amendment substantially reduced lead mass recoveries in the sand column effluent, lead microparticles were formed that had a tendency to move rapidly and with minimal dispersion when compared with controls. Treatments with HA provided limited reduction in lead mass recovery and minimal changes in lead transport properties. A colloid stability model was used to predict attachment of lead particles in sand.
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Affiliation(s)
- Michael A Butkus
- Department of Geography and Environmental Engineering, US Military Academy, West Point, NY 10996, United States.
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Yip TCM, Tsang DCW, Lo IMC. Interactions of chelating agents with Pb-goethite at the solid-liquid interface: Pb extraction and re-adsorption. CHEMOSPHERE 2010; 81:415-421. [PMID: 20643473 DOI: 10.1016/j.chemosphere.2010.06.069] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2010] [Revised: 06/23/2010] [Accepted: 06/29/2010] [Indexed: 05/29/2023]
Abstract
The use of ethylenediaminetetraacetic acid (EDTA) for soil remediation is under concern due to its non-biodegradability and toxicity; thus, its biodegradable structural isomer, [S,S]-ethylenediamine disuccinate ([S,S]-EDDS), has been proposed as an emerging substitute. In this study, batch experiments were performed to quantify the Pb extraction from goethite by EDTA and EDDS, respectively, and attenuated total reflectance-Fourier transform infrared (ATR/FT-IR) spectroscopy was used to investigate the corresponding mechanisms at the solid-liquid interface at different pH and reaction times. The Pb extraction was pH-dependent for both chelating agents; mildly alkaline condition was favorable for EDDS, while mildly acidic condition for EDTA. The discrepancy between two structural isomers might be caused by their pH-dependent zwitterionic structures. The ATR/FT-IR results revealed that under acidic conditions, hydrogen-bonded carboxyl groups were present in both zwitterionic EDDS and EDTA. However, ring structure of zwitterionic EDDS formed with stable intramolecular hydrogen bond might limit the availability for EDDS to extract Pb from goethite. On the other hand, each protonated amine of zwitterionic EDTA could form hydrogen bonds with two neighbouring carboxyl groups, intensifying the negative charge of carboxyl groups and enhancing the Pb extraction efficiency. However, there was a higher amount of re-adsorption of PbEDTA than PbEDDS, because zwitterionic EDTA resulted in a greater Pb extraction and facilitated iron dissolution which significantly altered the goethite morphology, particle size, and surface area. These results suggested that, despite being structural isomers, EDDS and EDTA resulted in varying extents of Pb extraction and re-adsorption due to their different zwitterionic properties.
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Affiliation(s)
- Theo C M Yip
- Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Hong Kong, China.
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Goh KH, Lim TT, Banas A, Dong Z. Sorption characteristics and mechanisms of oxyanions and oxyhalides having different molecular properties on Mg/Al layered double hydroxide nanoparticles. JOURNAL OF HAZARDOUS MATERIALS 2010; 179:818-827. [PMID: 20399010 DOI: 10.1016/j.jhazmat.2010.03.077] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Revised: 03/15/2010] [Accepted: 03/16/2010] [Indexed: 05/29/2023]
Abstract
The sorption ability of fast-coprecipitated and hydrothermally-treated Mg/Al layered double hydroxide nanoparticles (FCHT-LDH) for various oxyhalides and oxyanions was evaluated. Interactions of oxyhalide such as monovalent bromate or oxyanions such as divalent chromate and divalent vanadate with FCHT-LDH were investigated using a combination of macroscopic (batch sorption/desorption studies and electrophoretic mobility (EM) measurements) and microscopic techniques (CHNS/O, XRD, FTIR, XPS, and EXAFS analyses). The sorption studies on various oxyanions and oxyhalides suggested that their sorption characteristics on FCHT-LDH were largely governed by their ionic potentials and molecular structures. Oxyanions which have ionic potentials higher than 7 nm(-1) were found to be more readily sorbed by FCHT-LDH than oxyhalides with ionic potentials lower than 5 nm(-1). The results obtained also demonstrated that trigonal pyramid oxyhalides showed a lower degree of specificity for FCHT-LDH than the tetrahedral coordinated oxyanions. From the macroscopic and microscopic studies, monovalent oxyhalide sorption on FCHT-LDH was postulated to occur mainly via anion exchange mechanism with subsequent formation of outer-sphere surface complexes. For polyvalent oxyanion sorption on FCHT-LDH, the mechanisms were possibly associated with both anion exchange and ligand exchange reactions, resulting in the coexistence of outer-sphere and inner-sphere surface complexes.
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Affiliation(s)
- Kok-Hui Goh
- School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Republic of Singapore.
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Elmanfe G, Stephan L, Olier R, Privat M. Enhanced metal adsorption on solid suspensions by organic molecules. J Colloid Interface Sci 2010; 345:496-504. [DOI: 10.1016/j.jcis.2010.01.090] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2009] [Revised: 01/29/2010] [Accepted: 01/31/2010] [Indexed: 11/17/2022]
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Macroscopic and spectroscopic characterization of selenate, selenite, and chromate adsorption at the solid–water interface of γ-Al2O3. J Colloid Interface Sci 2009; 340:153-9. [DOI: 10.1016/j.jcis.2009.08.033] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Accepted: 08/12/2009] [Indexed: 11/22/2022]
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Pingitore NE, Clague JW, Amaya MA, Maciejewska B, Reynoso JJ. Urban airborne lead: X-ray absorption spectroscopy establishes soil as dominant source. PLoS One 2009; 4:e5019. [PMID: 19340295 PMCID: PMC2659775 DOI: 10.1371/journal.pone.0005019] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2008] [Accepted: 02/09/2009] [Indexed: 11/19/2022] Open
Abstract
Background Despite the dramatic decrease in airborne lead over the past three decades, there are calls for regulatory limits on this potent pediatric neurotoxin lower even than the new (2008) US Environmental Protection Agency standard. To achieve further decreases in airborne lead, what sources would need to be decreased and what costs would ensue? Our aim was to identify and, if possible, quantify the major species (compounds) of lead in recent ambient airborne particulate matter collected in El Paso, TX, USA. Methodology/Principal Findings We used synchrotron-based XAFS (x-ray absorption fine structure) to identify and quantify the major Pb species. XAFS provides molecular-level structural information about a specific element in a bulk sample. Pb-humate is the dominant form of lead in contemporary El Paso air. Pb-humate is a stable, sorbed complex produced exclusively in the humus fraction of Pb-contaminated soils; it also is the major lead species in El Paso soils. Thus such soil must be the dominant source, and its resuspension into the air, the transfer process, providing lead particles to the local air. Conclusions/Significance Current industrial and commercial activity apparently is not a major source of airborne lead in El Paso, and presumably other locales that have eliminated such traditional sources as leaded gasoline. Instead, local contaminated soil, legacy of earlier anthropogenic Pb releases, serves as a long-term reservoir that gradually leaks particulate lead to the atmosphere. Given the difficulty and expense of large-scale soil remediation or removal, fugitive soil likely constrains a lower limit for airborne lead levels in many urban settings.
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Affiliation(s)
- Nicholas E Pingitore
- Department of Geological Sciences, The University of Texas at El Paso, El Paso, TX, USA.
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Kumar R, Mishra P. Main group metal – organic frameworks of Bi(V) and Pb(II) derived from 2-[4,6-diamino-3-[3-amino-6-(1-methyamino-ethyl) tetrahydropyran-2-yl] oxy-2-hydroxy-cyclohexoxy]-5-methyl-4-methylamino-tetrahydropyran-3,5-diol and their molecular modeling. MAIN GROUP CHEMISTRY 2007. [DOI: 10.1080/10241220701687941] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Xie L, Giammar DE. Chapter 13 Influence of Phosphate on Adsorption and Surface Precipitation of Lead on Iron Oxide Surfaces. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/s1571-9197(07)07013-9] [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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Xu Y, Boonfueng T, Axe L, Maeng S, Tyson T. Surface complexation of Pb(II) on amorphous iron oxide and manganese oxide: Spectroscopic and time studies. J Colloid Interface Sci 2006; 299:28-40. [PMID: 16483594 DOI: 10.1016/j.jcis.2006.01.041] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2005] [Revised: 01/19/2006] [Accepted: 01/19/2006] [Indexed: 10/25/2022]
Abstract
Hydrous Fe and Mn oxides (HFO and HMO) are important sinks for heavy metals and Pb(II) is one of the more prevalent metal contaminants in the environment. In this work, Pb(II) sorption to HFO (Fe(2)O(3) x nH(2)O, n=1-3) and HMO (MnO(2)) surfaces has been studied with EXAFS: mononuclear bidentate surface complexes were observed on FeO(6) (MnO(6)) octahedra with PbO distance of 2.25-2.35 Angstrom and PbFe(Mn) distances of 3.29-3.36 (3.65-3.76) Angstrom. These surface complexes were invariant of pH 5 and 6, ionic strength 2.8 x 10(-3) to 1.5 x 10(-2), loading 2.03 x 10(-4) to 9.1 x 10(-3) mol Pb/g, and reaction time up to 21 months. EXAFS data at the Fe K-edge revealed that freshly precipitated HFO exhibits short-range order; the sorbed Pb(II) ions do not substitute for Fe but may inhibit crystallization of HFO. Pb(II) sorbed to HFO through a rapid initial uptake ( approximately 77%) followed by a slow intraparticle diffusion step ( approximately 23%) resulting in a surface diffusivity of 2.5 x 10(-15) cm(2)/s. Results from this study suggest that mechanistic investigations provide a solid basis for successful adsorption modeling and that inclusion of intraparticle surface diffusion may lead to improved geochemical transport depiction.
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Affiliation(s)
- Ying Xu
- Department of Civil and Environmental Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA
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Arai Y, Sparks DL, Davis JA. Arsenate adsorption mechanisms at the allophane-water interface. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2005; 39:2537-44. [PMID: 15884346 DOI: 10.1021/es0486770] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
We investigated arsenate (As(V)) reactivity and surface speciation on amorphous aluminosilicate mineral (synthetic allophane) surfaces using batch adsorption experiments, powder X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS). The adsorption isotherm experiments indicated that As(V) uptake increased with increasing [As-(V)]0 from 50 to 1000 microM (i.e., Langmuir type adsorption isotherm) and that the total As adsorption slightly decreased with increasing NaCl concentrations from 0.01 to 0.1 M. Arsenate adsorption was initially (0-10 h) rapid followed by a slow continuum uptake, and the adsorption processes reached the steady state after 720 h. X-ray absorption spectroscopic analyses suggest that As(V) predominantly forms bidentate binuclear surface species on aluminum octahedral structures, and these species are stable up to 11 months. Solubility calculations and powder XRD analyses indicate no evidence of crystalline Al-As(V) precipitates in the experimental systems. Overall, macroscopic and spectroscopic evidence suggest that the As(V) adsorption mechanisms at the allophane-water interface are attributable to ligand exchange reactions between As-(V) and surface-coordinated water molecules and hydroxyl and silicate ions. The research findings imply that dissolved tetrahedral oxyanions (e.g., H2PO42- and H2AsO4(2-)) are readily retained on amorphous aluminosilicate minerals in aquifer and soils at near neutral pH. The inner-sphere adsorption mechanisms might be important in controlling dissolved arsenate and phosphate in amorphous aluminosilicate-rich low-temperature geochemical environments.
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Affiliation(s)
- Yuji Arai
- United States Geological Survey, Menlo Park, California 94025, USA.
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Scheckel KG, Impellitteri CA, Ryan JA. Lead sorption on ruthenium oxide: a macroscopic and spectroscopic study. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2004; 38:2836-2842. [PMID: 15212257 DOI: 10.1021/es035212l] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The sorption and desorption of Pb on RuO2.xH2O were examined kinetically and thermodynamically via spectroscopic and macroscopic investigations. X-ray absorption spectroscopy (XAS) was employed to determine the sorption mechanism with regard to identity and interaction of nearest atomic neighbors, bond distances (R), and coordination numbers (N). The kinetics of the Pb-Ru-oxide sorption reaction are rapid with the equilibrium loading of Pb on the surface achieving approximately 1:1 wt/wt (129 micromol m(-2)). XAS data indicate that Pb adsorbed as bidentate innersphere complexes with first shell Pb-O parameters of RPb-O = 2.27 A and NPb-O = 2.1-2.5. Pb-Ru interatomic associations suggest two distinct bidentate surface coordinations of Pb to edges (RPb-RuI approximately 3.38 A, NPb-RuI approximately 1.0) and shared corners (RPb-RuII approximately 4.19 A, NPb-RuII approximately 0.8) on RuO2 octahedra (cassiterite-like structure), and an additional second neighbor backscattering of Pb indicates the formation of Pb-Pb dimers (RPb-Pb degrees 3.89 A, NPb-Pb approximately 0.9). Desorption studies as a function of aging time (1 h to 1 year) using a continuous stirred-flow reactor with a background electrolyte (0.01 M NaNO3, pH 6) demonstrated that Pb was tightly bound (99.7-99.9% retained). The Pb sorption capacity and retention on RuO2.xH2O is greater than that of other metal oxides examined in the literature. The results of this study imply that RuO2.xH2O may serve as a high capacity remediation treatment media.
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Affiliation(s)
- Kirk G Scheckel
- United States Environmental Protection Agency, ORD, NRMRL, LRPCD, MB, 5995 Center Hill Avenue, Cincinnati, Ohio 45224, USA.
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Rouff AA, Elzinga EJ, Reeder RJ, Fisher NS. X-ray absorption spectroscopic evidence for the formation of Pb(II) inner-sphere adsorption complexes and precipitates at the calcite-water interface. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2004; 38:1700-1707. [PMID: 15074678 DOI: 10.1021/es0345625] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Combined batch sorption and in situ X-ray absorption spectroscopy provide direct assessment of the mechanisms for Pb(II) sorption atthe calcite--water interface under low-temperature conditions. At low metal concentration, 1 microM initial Pb, X-ray absorption fine structure data indicate the formation of Pb mononuclear inner-sphere complexes at the surface. A first-shell Pb-O bond length of 2.34 A is consistent with nearest oxygen neighbors in 3- or 4-fold coordination with a distorted trigonal pyramidal or square pyramidal geometry with a stereochemically active electron lone pair. For high initial Pb concentrations, 20 and 60 microM Pb, precipitation of hydrocerussite and cerussite secondary phases dominates Pb partitioning. At 5 and 10 microM initial Pb, the sorption mechanism is dual in nature with persistence of the mononuclear adsorption complex combined with precipitation of a cerussite phase occurring prior to saturation of theoretically available surface sites. The formation of inner-sphere complexes implies strong metal interactions with the surface-the mechanistic reason for the affinity of Pb for calcite as observed in macroscopic studies. The geometry of the adsorbed complex can influence Pb coprecipitation, as a change to octahedral coordination is required for incorporation into calcite. The results provide the basis for predictions of Pb sequestration by calcite in natural systems.
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Affiliation(s)
- Ashaki A Rouff
- Department of Geosciences, Center for Environmental Molecular Science, State University of New York at Stony Brook, Stony Brook, New York 11794, USA.
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