Bioremediation of Cd by strain GZ-22 isolated from mine soil based on biosorption and microbially induced carbonate precipitation

Microbially induced carbonate precipitation (MICP) is an emerging and promising bioremediation technology to restore the environment polluted by heavy metals. Carbonate-biomineralization microbe can immobilize heavy metals from mobile species into stable crystals. In the present manuscript, laboratory batch studies were conducted to evaluate the Cd removal ability based on biosorption and MICP, using carbonate-biomineralization microbe GZ-22 isolated from a mine soil. This strain was identified as a Bacillus sp. according to 16S rDNA gene sequence analysis. Results of batch experiments revealed that MICP of the strain GZ-22 showed a greater potential to remove Cd than biomass biosorption under different impact factors such as pH, initial Cd concentration, and contact time. The optimum pH for MICP was 6 (50.34 %), while for biomass biosorption, it was 5 (38.81 %). When the initial concentration of Cd was 10 mg/L, removal efficiency induced by MICP was 53.06 % after 3 h, which was about 11 % greater than the removal efficiency induced by adsorption. The Cd removal efficiency increased as reaction time. The maximum removal efficiency based on MICP can reach 60.72 % at 10 mg/L for 48 h compared with 56.27 % by biosorption. X-ray diffractomer (XRD) revealed that Cd was transformed into CdCO3 by MICP of GZ-22. The present illustrated that the carbonate-biomineralization microbe GZ-22 can offer an effective and eco-friendly approach to immobilize soluble Cd and that MICP may play an important role in heavy metal bioremediation.