The Competitive Adsorption of Heavy Metals under Various Incineration Conditions.

Abstract

The main objective of this study is to investigate the competitive adsorption behavior of multiple components on sorbents (silica sand with limestone) at different operating conditions (temperature, additives of chloride, operating time). Moreover, the Toxicity Characteristic Leaching Process (TCLP) analyzed the leaching rates of metals from the spent sorbents.The results show that the adsorption capacities of Pb and Cd are better among those four metals on the sorbents. At 850°C, the adsorption of Pb and Cd can reach the adsorption saturation points. However, the adsorption amounts on the sorbents will increase as the operating temperature increases. X-ray powder diffract meter (XRD) analysis revealed the adsorption components on the sorbents had metal fusion formations. The TCLP tests show that the leaching rate of metals are significantly lower at 600°C, however, as the operating temperature increases (700°C and 850°C), the sorbents became more stable. At the same temperature, increasing the operating time on the incinerator shows a decreasing leaching rate on the sorbent. Adding PVC or NaCl will decrease the adsorption amounts of Pb and Cd, but increase the leaching rates of all metals on the sorbent. Competitive effects were analyzed by comparing single-component adsorption and multiple-component adsorption cases. The result shows that a multiple-component case has a better adsorption capacity than that of a single-component case.