Interactions of PbCl2 capture and CdCl2 capture by kaolin in the high-temperature PbCl2-CdCl2-Kaolin reaction system.

• Interactions of multiple-metals with kaolin were studied in two-stage fixed bed. • PbCl 2 vapor in flue gas promoted CdCl 2 capture by kaolin. • CdCl 2 vapor in flue gas promoted PbCl 2 capture by kaolin. • PbCl 2 or adsorption products inhibited CdCl 2 desorption rate to capture more CdCl 2. • Eutectic melting led to new active sites in internal layer to boost Pb and Cd capture. Using kaolin for capturing hazardous metals is an effective and promising technology. However, interactions of multiple-metals with kaolin are not been clearly understood. Interactions of PbCl 2 capture and CdCl 2 capture by kaolin in high-temperature PbCl 2 -CdCl 2 -Kaolin reaction system were investigated in a two-stage fixed bed at 800 °C. Capture efficiency considering kaolin dihydroxylation and Pb/Al or Cd/Al were used to evaluate capture performance of kaolin. The results showed that kaolin captured more PbCl 2 or CdCl 2 in the cases that kaolin captured PbCl 2 and CdCl 2 at the same time, kaolin captured CdCl 2 after its first capture of PbCl 2 and kaolin captured PbCl 2 after its first capture of CdCl 2 than in the case that kaolin only captured PbCl 2 or kaolin only captured CdCl 2. PbCl 2 vapor promoted absorption of kaolin for CdCl 2 , and CdCl 2 vapor also promoted adsorption of kaolin for PbCl 2. Heavy metal capture effects were controlled by chemical kinetics due to small particle size of kaolin and short contract time between heavy metal chloride and kaolin. PbCl 2 vapor or adsorption products on kaolin surface promoted capture effect of CdCl 2 through inhibiting desorption rate of CdCl 2. Adsorption products promoted eutectic melting of kaolin surface, and slightly melted kaolin surface exposed new layers with more active sites to continue reactions of kaolin with PbCl 2 and CdCl 2. Therefore, PbCl 2 vapor in the gas flow promoted absorption of kaolin for CdCl 2 , and CdCl 2 vapor also promoted adsorption of kaolin for PbCl 2. The results can provide an important reference for Pb and Cd capture during MSW incineration. [ABSTRACT FROM AUTHOR]