Comparison of Pb(II) immobilized by bone char meal and phosphate rock: characterization and kinetic study.

Adsorption isotherms and kinetics of aqueous Pb(II) by bone char meal (BM) and phosphate rock (PR) were investigated using batch experiments. Pb removal was characterized and effects of pH and reaction time on Pb removal efficiency by BM/PR were also investigated. Results indicated that Pb removal efficiency by BM and PR is mainly controlled by dissolution of phosphatic components associated with apatite, followed by subsequent precipitation of geochemically stable pyromorphite [Pb10(PO4)6(OH,Cl)2]. Sorption kinetics results indicated that Pb sorption onto BM or PR was generally biphasic, with initially fast reactions followed by slow and continuous reactions. Pb removal efficiency by BM and PR increased with increasing pH except at a pH higher than 6.15. Sorption isotherms showed that BM has a much higher Pb removal rate than PR in solution; the greater capability of BM than of PR to remove aqueous Pb indicates its potential as another promising way to remediate Pb-contaminated media.