Biomineralisation for Sustainable Ecotoxic Metal Immobilisation via Enzyme Induced Carbonate Precipitation

Heloisa Dickinson, Jaime Toney, John Murdoch MacDonald

Heavy metal contamination of water presents a critical global challenge driven by the persistence and toxicity of elements such as arsenic, cadmium and lead. Conventional remediation strategies, such as Enzyme-Induced Carbonate Precipitation (EICP), typically rely on commercial urease and a multi-step extraction process, which increases energy demand, generates ammonium byproducts, and requires significant chemical inputs. In this study, we introduce a streamlined EICP approach employing crude soybean urease extract to treat a range of nine ecotoxic metals (As, Cd, Co, Cr, Cu, Li, Ni, Pb, Zn) in aqueous solutions. Crystallographic and morphological analyses revealed calcite as a recurring phase across all treatments, with element-specific carbonate minerals, such as otavite and cerussite, detected in the corresponding systems. The method integrates low-power juicing, single-step filtration, and minimal reagent use, delivering effective removal, while only arsenic and copper exhibited notable enzymatic inhibition. Compared with conventional protocols, the proposed adaptive optimisation workflow lowered energy demand, reduced chemical inputs, and mitigated greenhouse gas emissions. By incorporating waste-derived calcium and urea, the process establishes a closed-loop cycle, offering pathways for application in engineered treatment plants, active dosing systems, or passive remediation schemes. Future work should focus on mixed-metal systems and molecular-scale mechanisms to strengthen the foundation for the field-scale deployment of this sustainable strategy.