Continuous and efficient immobilization of heavy metals by phosphate-mineralized bacterial consortium

Traditional sewage treatment technology cannot remove heavy metals, which needs to be improved urgently. Lysinibacillus with the function of bio-mineralization was screened and loaded on granular sludge to form a phosphate-mineralized bacterial consortium, which demonstrated the ability of self-regulating pH and automatic solid-liquid separation. Heavy metals could be fixed on the bacterial consortium to produce stable and harmless phosphate minerals. The highest removal efficiency of Pb(II), Cd(II), and Ni(II) were 97.9%, 70%, and 40%, respectively. Organic matter and other metal ions in actual polluted water had little effect on the Pb(II) removal efficiency. Mechanism analysis was conducted through 3D-EEM, XRD, SEM-EDS, XPS, FTIR, and high-throughput sequencing analyses. The bacterial consortium was a multi-species coexistence system, but Lysinibacillus played a major role in removing Pb(II). C-O and O-H bonds of tyrosine and phosphorous organics were broken by enzyme catalysis and the metal-oxygen bond (Pb-O) was formed. Mineral crystals in the reactor accumulated, transforming from the initial phase non-crystalline structure to the metaphase Pb-3(PO4)(2) and eventually to the Pb-5(PO4)(3)OH. This research obtained a promising technique for immobilizing Pb(II) or other hazardous metals continuously and efficiently.

Automated summary

Lysinibacillus can immobilize heavy metals to form stable phosphate minerals; the bacterial consortium has the ability of self-regulating pH and automatic solid-liquid separation; mechanism analysis through various analytical methods revealed the removal process of Pb(II).