Pb is a toxic heavy metal in contaminated soil and water, resulted from industrial activities, mine exploration, etc. Phosphate solubilizing bacteria are able to secrete organic acids and further to enhance the solubility of phosphates. Enterobacter. sp and geological fluorapatite (FAp) were applied to investigate the biotransformation of Pb2+ in solution with SO42-, PO43-, and Cl- species by ICP-OES, ATR-IR, XRD, and SEM. Enterobacter. sp can lower pH of the medium to ∼4. Meanwhile, >90% mobile Pb (declining from 1000 to 30 ppm) was immobilized via the combination of Enterobacter. sp and FAp. With the addition of FAp and Pb, pyromorphite was precipitated, but with relatively low content. In contrast, abundant anglesite mineral was formed in such weakly acidic system. These anglesite crystals can even absorb phosphates particles onto their surface. Additionally, geochemical modeling confirms the formation of anglesite and cerussite under weekly acidic and alkalic condition respectively, especially when H2PO4- concentration <10-8 mM. Furthermore, the presence of Cl- in solution leads to the formation of chloropyromorphite when H2PO4- concentration >10-12 mM, especially under neutral environment. This study explored the biotransformation of Pb in SO4-PO4-Cl aqueous system and hence provided guidance on bioremediation of Pb by bacteria and FAp.
Keywords: Anglesite; Chloride; Lead; Modeling; Phosphate; Phosphate-solubilizing bacteria.
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