Study on the mechanism and stability of microbially induced struvite precipitation (MISP) for enhanced immobilization of uranium

The microbial induced carbonate precipitation (MICP) technique has been shown to immobilize a wide range of heavy metals. However, the MICP process for removing uranium-dominated composite heavy metals ignores the formation of substances such as uranyl carbonate, which can easily lead to uranium migration. Furthermore, the by-product ammonia is one of the bottlenecks limiting the application of MICP. In this work, the microbially induced struvite precipitation (MISP) method was used to enhance U immobilization while reducing by-product contamination. The results showed that the optimal uranium removal rate of the MISP process was increased by 82.98% compared to the MICP. Characterization results confirmed the co-precipitation of U with NH4+ in the form of uramphite and struvite, while the participation of U changed the mineral crystal shape. Stability experiments showed that the maximum release of U from struvite was only 1.27%, which is much lower than the minimum release of U from CaCO3. As a result, the MISP process both enhanced uranium immobilization efficiency, decreased the risk of uranium migration-release, and reduced the environmental impact of the by-product ammonia. These results provided a new perspective for studying U contamination remediation and its co-precipitation behavior in microbial mineralization.