Study on solidification behaviors of chemically bonded phosphate ceramics for lead ion

Abstract

Chemically bonded phosphate ceramics (CBPC) as a novel matrix was developed for the treatment of Pb2+ in hazardous waste. However, it is difficult to analyze and study the early solidifying behaviors of CBPC due to its rapid condensation. In order to study the early solidifying behaviors of CBPC solidifying Pb2+, CBPC suspension and paste were selected to systematically study the pH value, conductivity, ion concentration, hydration heat release, leaching toxicity, coagulation time, mechanical properties and other solidifying behaviors of CBPC solidifying Pb2+. The product evolution process of CBPC solidifying Pb2+ and the occurrence mode of Pb2+ in CBPC were studied and improved. The results showed that Pb2+ delayed the reaction of CBPC, the total amount of hydration heat in CBPC suspension decreased and the total amount of hydration heat in CBPC paste increased gradually in the later stage. After solidifying Pb2+ with CBPC, the content of K-struvite decreased, a large number of coarse pores appeared in the microscopic morphology and the structure was loose. The product of CBPC solidifying Pb2+ was Pb3(PO4)2 with low solubility. The properties of the products were stable. The solidifying methods of CBPC to Pb2+ included adsorption, physical coating, ion exchange, chemical bonding and many ways of synergy. The efficient solidification of Pb2+ by CBPC can promote the sustainability of environmental protection.