Effect of biopolymer chitosan on manganese immobilization improvement by microbial‑induced carbonate precipitation

Microbially induced carbonate precipitation (MICP), as an eco-friendly and promising technology that can transform free metal ions into stable precipitation, has been extensively used in remediation of heavy metal contamination. However, its depressed efficiency of heavy metal elimination remains in question due to the inhibition effect of heavy metal toxicity on bacterial activity. In this work, an efficient, low-cost manganese (Mn) elimination strategy by coupling MICP with chitosan biopolymer as an additive with reduced treatment time was suggested, optimized, and implemented. The influences of chitosan at different concentrations (0.01, 0.05, 0.10, 0.15 and 0.30 %, w/v) on bacterial growth, enzyme activity, Mn removal efficiency and microstructure properties of the resulting precipitation were investigated. Results showed that Mn content was reduced by 94.5 % within 12 h with 0.15 % chitosan addition through adsorption and biomineralization as MnCO