Transforming cerussite to pyromorphite by immobilising Pb(II) using hydroxyapatite and Pseudomonas rhodesiae

Abstract

Lead (Pb) pollution has become one of the most serious environmental problems in recent decades. However, there are few remediation technologies for insoluble cerussite (PbCO₃), which are common in the environment and have high bioavailability. In this study, the immobilisation of Pb(II) released from PbCO₃ by Pseudomonas rhodesiae HP-7 isolated from Pb-contaminated soil was studied. The results showed that hydroxyapatite and PbCO₃ were dissolved by the organic acids secreted by the HP-7 strain, and then the dissolved Pb²⁺ and H₂PO₄^- reacted to form low bioavailable Pb₅(PO₄)₃Cl precipitate. XRD and mass conservation calculations showed that 85.7% of PbCO₃ was transformed to Pb₅(PO₄)₃Cl when P:Pb was 9:5. Our research showed that the HP-7 strain and hydroxyapatite could reduce the bioavailability of Pb(II) in PbCO₃, which could be used for the remediation of Pb-polluted environments.

Keywords: Hydroxyapatite; Pb immobilisation; PbCO(3); Phosphate solubilising bacteria; Pyromorphite.