Solidification Mechanism of Cadmium in Clay Sintering.

The effects of chemical composition and sintering temperature on the solidification rate and leaching concentration of Cd in clay sintering material were studied. And the solidification mechanism of Cd during clay sintering was investigated by XRD, SEM, XPS, FTIR and heavy metal speciation analysis. The results show that the increasing content of Fe₂O₃ is beneficial to the formation of hematite, and the residue proportion of Cd sintering at 750 °C is higher than that of other samples. The content of CdAl₂Si₂O₈ increases after increasing the Al/ Si ratio. When the Al/ Si ratio is 0.3 at the sintering temperature of 1050 °C, the solidification rate of Cd can reach 99.64%. When the CaO content increases to 3% (mass fraction), the leaching concentration is lower than 1 mg⋅L^-1. The formation of anorthite increases the pH value of the leaching solution and inhibits the leaching of Cd. The clay can form a denser structure after sintering, which can wrap Cd in the liquid phase. At the same time, Cd²⁺ can replace Ca²⁺ in the crystal to generate stable CdAl₂Si₂O₈, as a result, Cd is fixed in the sintered clay material. [ABSTRACT FROM AUTHOR]