Capture of volatile hazardous metals using a bed of kaolinite

One of the promising technologies for reducing metals emission from the waste thermal process is the capture of vapor-phase metals through the use of solid sorbents. This study investigated the use of natural kaolinite for the removal of several volatile metals. The capture of cadmium and lead using a packed bed with porous kaolinite of the size range 300-400 Μm was effective. The capturing efficiency increased as the bed temperature increased. The ratio of the sorption reaction rate to the diffusion rate varied on the 10^-2 order of magnitude. This suggests that the resistance of the diffusion within the pores of kaolinite particles is not significant in the selection of sorbent particle size for practice. The capturing mechanism for cadmium chloride is different from that for lead chloride. Cadmium can be reactively scavenged by CdO-Al₂O₃-2SiO₂ as well as metakaolinite, suggesting that a unit mole of metakaolinite can ultimately capture two moles of cadmium.