Synergistic remediation of lead pollution by biochar combined with phosphate solubilizing bacteria

Pb(II) is extreme toxic to biological cells, which limits the restoration of Pb(II) by functional strains. This study examined a Pb(II)-tolerant phosphate solubilizing bacteria(PSB) Ochrobactrum sp. J023 combined with corn stover biochar to enhance the immobilization of Pb(II). The results showed that the removal rate of Pb(II) by biochar combined with phosphate-solubilizing bacteria was as high as 71.30 %. SEM-EDS showed that more disordered crystals appeared on the surface of biochar treated with bacteria. XRD analysis indicated that the mineralization products of Pb(II) in biochar combined strain system were mainly in Pb5(PO4)3OH and Pb5(PO4)3Cl. FT-IR analysis revealed that there were more phosphate groups involved in the mineralization process when biochar was added. XPS verified the formation of PbO or lead-containing precipitates in this system, and the amount of lead precipitates was larger. The mechanism of lead fixation by strain combined with biochar can be regarded that the strain regulates the microenvironment of the biochar surface, enhances the release of phosphate and promotes the generation of stable pyroxite. Moreover, biochar composition and porous structure not only provide nutrient elements for strains, but also protect and promote the metabolism of strains. Biochar adsorption also reduces the loss of available phosphorus, which helps PSB to fix Pb sustainably and effectively. This suggests that the synergistic effect of PSB-biochar can not only effectively reduce the mobility and bioavailability of Pb(II), but also increase the sustainability of remediation. Therefore, the combination of phosphate solubilizing bacteria and biochar is a promising approach to the remediation of heavy metal pollution.