Immobilization of lead by phosphate amended Polonite

• The ability of Polonite & PO4 amended Polonite (Polonite-P) to bind Pb was studied.
• Both formed Pb-cementitious hydrate products – desirable forms of stabilized Pb.
• Polonite-P released PO4 to form desirable low solubility Pb–PO4 precipitates.
• Polonite-P could be a suitable replacement for other PO4 sources to immobilize Pb.

Polonite is an alkaline material that is used to remove nutrients from domestic wastewater and it has been evaluated as a fertilizer. Stabilization of Pb by Polonite and Polonite amended with orthophosphate, PO4, (Polonite-P) was studied. Octacalcium phosphate (Ca8H2(PO4)6·5H2O) was a primary species of PO4 formed on the surface of Polonite-P. Lead was found to be associated with pozzolanic reaction products in Pb treated Polonite and Pb treated Polonite-P samples. Formation of Pb oxides, as precipitates or surface complexes, were substantial constituents of Pb treated Polonite. Dissolution of Ca8H2(PO4)6·5H2O followed by formation of Pb4O(PO4)2 was a probable mechanism of Pb removal by Polonite-P. Polonite-P could be a suitable replacement for current PO4 sources as a Pb stabilization agent. Finally, LDI-TOF was an effective technique for evaluating forms of Pb on Polonite and Polonite-P.