Enterobacter sp. SX4 Shows Breakthrough in Cleaning Cadmium and Nickel from Polluted Soils via Eco-friendly MICP Technology

Researchers Dejun Yang, Shengnan Bei, and Yong Yang from China University of Mining and Technology and Nanjing Agricultural University have identified the crucial role of urea concentration in improving Microbiologically Induced Calcite Precipitation (MICP) for heavy-metal soil cleanup. Using an efficient urease-producing strain SX4 (Enterobacter sp.) isolated from mining areas, the team systematically tested urea concentrations (0–40 g·L⁻¹) to remove cadmium (Cd) and nickel (Ni) from single- and co-polluted soils.

The study found 20 g·L⁻¹ urea to be optimal, achieving the highest metal removal rates—45.71% for Cd and 43.34% for Ni in single-metal soils, and 32.44% and 38.75% respectively under co-polluted conditions. Lower or higher urea concentrations reduced remediation efficiency due to either insufficient carbonate generation or ammonia toxicity.

Microscopic and XRD analyses confirmed that SX4 induced stable calcite precipitation, which immobilized Cd and Ni by co-precipitation within the crystal lattice. This biomineralization process offers a low-cost, eco-friendly solution for soil restoration. The research underscores that fine-tuning urea levels is vital to balancing microbial activity and environmental safety for real-world applications of MICP in heavy-metal-contaminated sites.

Reference

Yang, D., Bei, S., & Yang, Y. (2025). Effect of urea concentration on the combined pollution of Cd and Ni in microbiologically induced calcite precipitation (MICP) treatment. Biodegradation, 36(6), 107. https://doi.org/10.1007/s10532-025-10204-7