Valorization of phosphogypsum into carbon-neutral lime for soil lead immobilization

Conventional hydrated lime (Ca(OH) 2 ) is widely applied to immobilize heavy metals in soils but is associated with substantial CO 2 emissions during limestone calcination. This study presents a carbon-neutral waste valorization technology that converts phosphogypsum waste into hydrated lime (HLPG) via alkaline conversion without CO 2 release. The synthesized HLPG was fully transformed into Ca(OH) 2 and exhibited physicochemical properties comparable to commercial hydrated lime (CHL). In aqueous systems, HLPG achieved >95% Pb 2+ removal at pH ≥3, matching CHL performance. In Pb-contaminated soil, HLPG increased soil pH from 5.6 to 9.4, reduced phytoavailable Pb by up to 99.6%, enhanced microbial activity by 40%, decreased Pb uptake by lettuce by 82%, and increased plant biomass by 17% at optimal application rates. By integrating waste valorization, carbon-neutral lime production, and effective soil remediation , this technology offers a scalable and sustainable solution for managing Pb-contaminated soils while mitigating greenhouse gas emissions.