Improvement in Metal Immobilization with Biomineralization During Carbonate Precipitation by Poly-Lysine

Microbially induced carbonate precipitation (MICP), a type of urease-based biomineralization, has been a well-researched technique in recent years for heavy metal immobilization; however, the efficiency of the process remains in question. Poly(amino acids) are known to enhance enzymatic activity. Thus, in the present study on carbonate precipitation induced by ureolytic Staphylococcus epidermidis HJ2, poly-Lysine (poly-Lys) was added to obtain higher enzyme activity, and response surface methodology-central composite design was used to identify the optimum conditions for this process. The effect of poly-Lys was investigated in lead (Pb) immobilization in aqueous solution by MICP. The results concluded that the addition of poly-Lys improved the capability of Pb remediation with 92% of the soluble Pb ions immobilized compared to 79% Pb ions in the absence of poly-Lys. The analysis of samples through X-ray diffraction and Fourier transform infrared spectroscopy further indicated that both a greater number and larger calcite crystals were formed during Pb immobilization in the presence of poly-Lys. This study confirms that the addition of poly-Lys is an effective and stable way to enhance MICP efficiency.