Immobilization Of Pb In A Geopolymer Matrix

In a geopolymer matrix prepared by mixing a metakaolinite precursor with a solution of potassium hydroxide and silicate, 1 wt% Pb as the nitrate has been immobilized. Under the US Environmental Protection Agency test protocol, the Pb release was less that 5ppm, the acceptable limit for landfills in the USA. Electron microscopy showed Pb was present in the major amorphous phase and a minor Ca-rich potassium silicate phase. Heating cured samples to several hundred degrees Centigrade was not significantly advantageous for immobilizing Pb.