Biomineralization-Assisted Valorization of Phosphogypsum

The sustainable management of phosphogypsum (PG), a solid waste generated during phosphate fertilizer production via the wet-process phosphoric acid route, remains a major environmental and resource challenge. Transforming this waste stream into functional resources is a key goal in sustainable materials and environmental engineering. PG valorization is constrained by limited Ca2+ availability and the environmental risk of co-occurring leachable impurities. Here, we develop an integrated activation–biomineralization route that (i) mobilizes Ca2+ from PG to substitute for commercial CaCl2 in microbially induced carbonate precipitation (MICP) and (ii) attenuates major co-leached anions and metal impurities. Among the three activators evaluated (NaCl, ammonium acetate, and sodium gluconate), sodium gluconate achieved the highest Ca2+ extraction efficiency (90.96%) via chelation, ion exchange, and limited dissolution of CaSO4·2H2O. At a matched initial Ca2+ concentration (0.3 mol L–1), the gluconate-derived PG calcium source produced a CaCO3 yield comparable to that of the CaCl2 control, with near-complete Ca2+ conversion to solid carbonate. During biomineralization, dissolved F–, SO42–, and PO43– decreased substantially (stabilization efficiencies up to 77.7, 78.9, and 100%, respectively), accompanied by pronounced reductions of Fe, Cd, Pb, and Zn in solution. Mechanistically, impurity attenuation is attributable to cellular uptake, adsorption onto biomass/CaCO3 surfaces, and encapsulation/co-precipitation within calcite. Collectively, this work demonstrates a strategy for Ca-source substitution in MICP while mitigating major dissolved impurities released during PG activation.