Removal of lead from acidic wastewater by bio-mineralized bacteria with pH self-regulation.

Microorganisms with the function of bio-mineralization were isolated from a soil. They were identified as urease-producing bacteria and phosphate-solubilizing bacteria. These two kinds of bacteria belong to the eosinophilic bacteria, which regulated the pH of solution and removed Pb2+ the best at the initial solution pH of 4. The Pb2+ removal mechanism was further explored using various techniques including zeta potential measurement, three-dimensional fluorescence, FTIR, XRD, and TEM-EDS. The results showed that extracellular adsorption, intracellular accumulation and bio-mineralization occurred at the same time and converted to each other. The extracellular adsorption of urease-producing bacteria was through electrostatic adsorption and gradually decomposed urea to produce PbCO3 minerals. The extracellular adsorption of phosphate-solubilizing bacteria was controlled by extracellular polymeric substances (EPS) and rapidly formation of Pb3(PO4)2 stable minerals. In addition, the stabilities of Lead minerals of the two strains were compared. The results showed that the precipitates of phosphate-solubilizing bacteria were more stable. While phosphate-solubilizing bacteria have some advantages, both strains can play important roles in bio-mineralization of HMs in acidic wastewater.