Applying microcapsule-based self-healing microbial-induced calcium carbonate materials to remediate lead-containing wastewater in acid environment

Lead (Pb) accumulation can pose serious threats to the environment and cause liver and kidney damage. In recent years, microbial-induced carbonate precipitation (MICP) technology has been widely used for remediating contaminated sites due to its operational efficiency. However, extreme pH conditions can degrade carbonate precipitation, increasing the risk of Pb2+ migration and secondary pollution. This study explores the use of spore-containing microcapsules for Pb immobilization for the first time. The results indicate that during the germination phase, the microcapsules not only shielded the spores from harsh pH conditions but also supplied inosine for their growth and reproduction. The microcapsules promoted spore growth and reproduction through nutrient supplementation, offering additional attachment sites for nucleation with Pb2+ and Ca2+. An immobilization efficiency exceeding 90% was achieved. Cerussite and calcite minerals were observed in scanning electron microscopy (SEM), SEM with energy dispersive X-ray spectroscopy (SEM-EDS), and X-ray diffraction (XRD) analyses, while extracellular polymeric substances (EPS) were detected in both samples in Fourier transform infrared spectrum (FTIR) tests. These findings confirm the role of microcapsules in immobilizing Pb2+.