Biomineralization of lead in wastewater: Bacterial reutilization and metal recovery

Biomineralization has not been widely applied due to the lack of bacterial reusability, which needs to be investigated urgently. In this study, we found Lysinibacillus could immobilize Pb²⁺ at initial pH ≥ 2.0. Lead ion recovery and cell reutilization could be achieved efficiently at pH = 1.0 (c_(HNO3) = 0.1 mol/L). Besides, the strong chelating agent EDTA-2Na (c_(EDTA-2Na)= 0.1 mol/L) was used for comparison. The oxidative damaging effect of cells could be reduced by both eluents. Mechanism analysis was conducted through zeta potential measurement, 3D-EEM, cyclic voltammetry, FE-EPMA, XRD, FTIR, and XPS. After the cells were eluted by HNO₃, the enzyme activity enhanced and the removal efficiency increased continuously. Cells were used to remove Pb²⁺ repeatedly, and regular-shaped Pb₃(PO₄)₂ crystals were always formed. After the cells were eluted by EDTA-2Na, cells were more prone to redox reaction and were induced to produce mercaptan (R-SH). The active hydrogen in R-SH could react with peroxide free radicals. New free radicals were formed after the R-SH was stripped of hydrogen, and finally, PbS stable mineral was formed. This research provides a new strategy to realize bacterial reutilization, which is a breakthrough in the field of biomineralization.