Immobilization of cadmium in river sediment using phosphate solubilizing bacteria coupled with biochar-supported nano-hydroxyapatite

Cadmium pollution in river sediment is serious and single remediation method is difficult to deal with. Thus, it is extremely urgent to remediate Cd contaminated river sediments. A new remediation system with phosphate solubilizing bacteria (PSBs) and biochar supported nano-hydroxyapatite (nHAP@BC) was provided to enhance the immobilization efficiency of Cd in this research. The passivation effect of PSB + nHAP@BC under different conditions and its mechanism were investigated. The results showed that the highest Cd 2+ immobilization efficiency could reach 90% in the liquid medium when using PSB cooperated with 5:1 nHAP@BC in the condition of temperature 15–37 °C, pH = 7, initial Cd 2+ concentration less than 0.5 mM. Meanwhile, the characterization results of XRD and FT-IR showed that Cd might exist in the form of Cd-HAP containing CdPO 4 . Furthermore, the simulated sediment remediation experiment indicated that the acid soluble fraction of Cd was reduced by 28% and transferred to the residual fraction. This work demonstrated that PSBs cooperated with nHAP@BC was an excellent candidate of passivation material for sediment Cd and could be considered as an effective way for immobilizing Cd in the future.