Binding of Sb(III) by Sb-tolerant Bacillus cereus cell and cell-goethite composite: implications for Sb mobility and fate in soils and sediments
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Adsorption onto mineral and bacterial surfaces can profoundly affect the mobility and fate of dissolved ions in soils; however, currently, there is a poor understanding of antimony (Sb) adsorption onto mixture of these two sorbents. This study aims at investigating the adsorption of Sb(III) to an antimony-tolerant soil bacterium Bacillus cereus and cell-goethite binary composite under anaerobic condition.
Materials and methods
Adsorption isotherms and adsorption edges (pH 3–10) were conducted to explore the adsorption capacity of Sb(III) to goethite, bacteria, and the cell-goethite composite. X-ray photoelectron spectroscopy (XPS) was applied to determine the surface functional groups that are responsible for Sb adsorption.
Results and discussion
Scanning electron microscope shows that nano-particulate goethite is strongly adsorbed onto the cell surfaces to give a mineral film. The cell-goethite composite displays an additive Sb adsorption behavior, i.e., composite adsorptivity is the sum of the individual end-member metal adsorptivities (i.e., the additivity rule). Sb(III) adsorption to goethite, Bacillus cereus cells, and the cell-goethite composite is independent of pH. Using high-resolution XPS spectra, we identify the ferric hydroxyl functional groups of goethite and the carboxyl and amino/amide groups of bacteria responsible for Sb binding to the binary solid products. Moreover, the molecular binding mechanisms are very similar between the composite and the isolated end-member bacteria and mineral phases.
Sb(III) adsorption to the bacteria-goethite conforms to a component-additive rule. Goethite component plays a more important role in Sb binding to the bacteria-mineral composite. New findings of this research suggest that it should be careful to use the universal adsorption rule for cations as previously suggested, to simulate anion adsorption to organo-iron oxide composite.
KeywordsAdsorption Antimony Component additivity Goethite Organo-mineral association
This study was financially supported by the National Science Foundation of China (41671475), Environmental Protection Department of Hunan Province (Xiangcai jianzhi 2016, 59), the Education Department of Hunan Foundation (16C0225), Hunan Provincial Natural Science Foundation of China (2018JJ3239), National Key R&D Program of China (2017YFD0801505), and Science Foundation for Young Scholars of Hunan Agricultural University (No: 17QN37).