Determination of the Adsorptive Capacity and Adsorption Isotherm of Vapor-Phase Mercury Chloride on Powdered Activated Carbon Using Thermogravimetric Analysis

摘要

This study investigated the use of thermogravimetric analysis (TGA) to determine the adsorptive capacity and adsorption isotherm of vapor-phase mercury chloride on powdered activated carbon (PAC). The technique is commonly applied to remove mercury-containing air pollutants from gas streams emitted from municipal solid waste incinerators. An alternative form of powdered activated carbon derived from a pyrolyzed tire char was prepared for use herein. The capacity of waste tire-derived PAC to adsorb vapor-phase HgCl_2 was successfully measured using a self-designed TGA adsorption system. Experimental results showed that the maximum adsorptive capacities of HgCl_2 were 1.75, 0.688, and 0.230 mg of HgCl_2 per gram of powdered activated carbon derived from carbon black at 30, 70, and 150℃ for 500 μg/m~3 of HgCl_2, respectively. Four adsorption isotherms obtained using the Langmuir, Freundlich, Redlich-Peterson, and Brunauer-Emmett-Teller (BET) models were used to simulate the adsorption of HgCl_2. The comparison of experimental data associated with the four adsorption isotherms indicated that BET fit the experimental results better than did the other isotherms at 30℃, whereas the Freundlich isotherm fit the experimental results better at 70 and 150℃. Furthermore, the calculations of the parameters associated with Langmuir and Freundlich isotherms revealed that the adsorption of HgCl_2 by PAC-derived carbon black favored adsorption at various HgCl_2 concentrations and temperatures.