PbCl2 Capture by Kaolin and Metakaolin under Different Influencing Factors of Thermal Treatment

With dramatically increasing emission of heavy metals and chlorinated compounds from thermal treatments of fuels and wastes, kaolin, one of the widely used materials in the industry, was researched to control these pollutants in recent years. To investigate the retention of lead chloride (PbCl2) by kaolin and metakaolin obtained from thermal activation of kaolin, the PbCl2 adsorption experiment in a two-stage furnace was conducted from 600 to 900 degrees C under N-2, H2O, and O-2. Furthermore, the toxicity leaching procedure was also utilized to evaluate the leachability of Pb from used sorbents. The results showed that the capture efficiency of PbCl2 by the sorbents and leachability of Pb from the used sorbents were closely related to the increase of the experimental temperature. The retention of Pb by raw kaolin was superior to that by metakaolin; however, the leachability of Pb from the used metakaolin was totally lower. Adding H2O in the adsorption experiment can obviously increase the retention of Pb by the sorbents and decrease the leachability of Pb from the used sorbents. Besides, the effects of adding O-2 on promoting the retention of Pb by kaolin and reducing the leachability of Pb from used kaolin were also noticeable due to the influence of adding O-2 on enhancing chemical adsorption and melting behavior of kaolin. The maximum capture efficiency of Pb by kaolin and the minimum ratio of leachability from the used kaolin can reach 74.01% and 1.60%, respectively, with the addtion of O-2 in the adsorption experiment at 900 degrees C.