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Pb sorption on montmorillonite-bacteria composites: A combination study by XAFS, ITC and SCM.
- Source :
-
Chemosphere [Chemosphere] 2018 Jun; Vol. 200, pp. 427-436. Date of Electronic Publication: 2018 Feb 22. - Publication Year :
- 2018
-
Abstract
- Though abundant studies have targeted the characterization of heavy metal adsorption by either clay minerals or bacteria, to date, minimal literature exists which specifically assesses bacteria-clay mineral interactions in the context of metal immobilization. The adsorption of Pb onto montmorillonite, Pseudomonas putida, and their 1:1, 2:1, 6:1 and 12:1 mass ratio composites were investigated by using a combination of atomic force microscope (AFM), X-ray diffraction (XRD), surface complexation modeling (SCM), Pb-L <subscript>III</subscript> edge extended X-ray absorption fine structure (EXAFS) spectroscopy and isothermal titration calorimetry (ITC). The SCM and EXAFS demonstrated that Pb ions coordinate with phosphoryl and carboxyl functional groups on bacteria at low and high concentrations, respectively. The ITC analysis found adverse enthalpy values for Pb adsorption to permanent (-2.91 kJ/mol) and variable charge sites (6.93 kJ/mol) on montmorillonite. The ternary bridging model, EXAFS and ITC provide molecular and thermodynamic evidences for the formation of enthalpy driven (-4.74 kJ/mol) ternary complex (>AlO-Pb-PO <subscript>4</subscript> ) in the composites. The proportion for the bridging structures increased at pH > 5 and high bacterial mass ratios. The formation of ternary complex did not result in the enhanced adsorption of Pb on the composites, but promoted the allocation of Pb on the mineral fraction. The results obtained from SCM, EXAFS and ITC may provide an essential assumption for predicting the speciation and fate of Pb in soils and associated environments.<br /> (Copyright © 2018 Elsevier Ltd. All rights reserved.)
- Subjects :
- Adsorption
Bacterial Adhesion
Bentonite metabolism
Clay
Lead metabolism
Microscopy, Atomic Force methods
Models, Chemical
Pseudomonas putida chemistry
Soil chemistry
Surface Properties
Aluminum Silicates chemistry
Bentonite chemistry
Calorimetry methods
Lead chemistry
Minerals chemistry
Pseudomonas putida physiology
X-Ray Diffraction methods
Subjects
Details
- Language :
- English
- ISSN :
- 1879-1298
- Volume :
- 200
- Database :
- MEDLINE
- Journal :
- Chemosphere
- Publication Type :
- Academic Journal
- Accession number :
- 29501033
- Full Text :
- https://doi.org/10.1016/j.chemosphere.2018.02.136