Desorption Of Mercuric Chloride from Spent Powdered Activated Carbons via Thermogravimetric Analysis
The objective of this study was to investigate the desorption of mercury chloride (HgCl2) from spent powdered activated carbons (PACs) by thermogravimetric analysis (TGA). Mercury chloride accounts for 60-95% of total mercury emitted from the flue gas of municipal solid waste incinerators (MSWIs), which can be typically removed by injecting PACs into the flue gas. Huge amount of spent PACs are generated as wastes during the HgCl2 adsorption process. Consequently, desorbing HgCl2 from the activated carbons might be an alternative to regenerate the spent activated carbons. However, only a few studies have investigated the mechanisms and kinetics for the desorption of HgCl2 from PACs. In this study, the thermogravimetric analysis (TGA) technology was applied to investigate the desorption mechanisms and kinetic modeling of HgCl2 desorbed from the spent PACs. The experimental parameters investigated in this study included desorption temperature (100, 200, and 300oC), saturated adsorption capacity (0.20~1.8 mg HgCl2/g C), and regeneration cycle (1~10 cycles). Experimental results indicated that the desorption mechanism of HgCl2 from the spent PACs was strongly affected by the desorption temperature and slightly influenced by the saturated adsorption capacity. Both the desorption efficiency and the desorption rate of HgCl2 increased dramatically with the desorption temperature. Moreover, the adsorption capacity of regenerated PACs decreased gradually as the regeneration cycle increased. The fundamental mechanisms and kinetic modeling for the desorption of HgCl2 from the spent PACs were further investigated.