Immobilization and characteristics of potassium magnesium phosphate on copper ions

Abstract

Potassium magnesium phosphate cement (MKPC) can be used in the fields of solidification of heavy metal ions in hazardous waste. Scholars have demonstrated that MKPC has a good curing effect on Cu2+. However, Cu2+ can lead to a significant decrease in the mechanical properties of solidified matrix, resulting in a decrease in compressive strength and even fragility. In view of the existing problems in the current research, a method of MgKPO4·6H2O strengthening MKPC solidifying Cu2+ is proposed to solve the problem of significant mechanical property loss of solidified matrix in the later stage, while also ensuring excellent solidifying effect. The evolution process and morphology of MKPC products after solidifying Cu2+ are studied. In addition, the long-term solidifying effect of MKPC is also tested. The results shows that MKPC with MgKPO4·6H2O has a relatively stable 180d solidifying effect on Cu2+, with a leaching concentration of 7.64 mg/L, which meet the standard requirements. The products of MKPC solidified Cu2+ include Mg.95Cu.05O and Cu3(PO4)2. The process of strengthening and solidifying Cu2+ by MKPC with MgKPO4·6H2O includes adsorption, chemical bond and physical encapsulation. MgKPO4·6H2O provides an auxiliary alkaline environment for the solidification of Cu2+ and has adsorption properties, improving the immobilization effect of Cu2+ and achieving long-term immobilization stability. This study provides a new idea for the solidification of other waste containing divalent heavy metal ions using MKPC with MgKPO4·6H2O.