EFFECT OF SULFUR IMPREGNATION METHOD ON ACTIVATED CARBON UPTAKE OF GAS-PHASE MERCURY

The dynamics of granular activated carbon (GAG) adsorbers for the upta ke of gas-phase mercury was evaluated as a function of temperature, in fluent mercury concentration, and empty bed contact time. Sulfur-impre gnated carbons exhibited enhanced mercury removal efficiency over virg in carbon due to the formation of mercuric sulfide on the carbon surfa ce. The effect of the sulfur impregnation method on mercury removal ef ficiency was examined through experiments conducted on commercially av ailable sulfur-impregnated carbon (HGR) and carbon impregnated with su lfur in our laboratory (BPL-S). Although HGR and BPL-S possess similar sulfur contents, BPL-S is impregnated at a higher temperature, which promotes a more uniform distribution of sulfur in the GAC pore structu re. At low influent mercury concentrations and low temperatures, HGR a nd BPL-S performed similarly in the removal of mercury gas. However, a s the temperature was increased above the melting point of sulfur, the performance of HGR deteriorated significantly, while the performance of BPL-S slightly improved. At high influent mercury concentrations, H GR performed better than BPL-S, regardless of temperature. For both HG R and BPL-S, the observed dynamic mercury adsorptive capacities were f ar below the capacities predicted by the stoichiometry of mercuric sul fide formation. In HGR carbon the sulfur is very accessible, but agglo meration that occurs at high temperatures causes the sulfur to be rela tively unreactive. In BPL-S carbon, on the other hand, the sulfur rema ins in a highly reactive form, but its location deep in the internal p ores makes it relatively inaccessible and prone to blockage by HSS for mation.