The adsorptive capacity of vapor-phase mercury chloride onto powdered activated carbon derived from waste tires.
Injection of powdered activated carbon (PAC) upstream of particulate removal devices (such as electrostatic precipitator and baghouses) has been used effectively to remove hazardous air pollutants, particularly mercury-containing pollutants, emitted from combustors and incinerators. Compared with commercial PACs (CPACs), an alternative PAC derived from waste tires (WPAC) was prepared for this study. The equilibrium adsorptive capacity of mercury chloride (HgCl2) vapor onto the WPAC was further evaluated with a self-designed bench-scale adsorption column system. The adsorption temperatures investigated in the adsorption column were controlled at 25 and 150 degrees C. The superficial velocity and residence time of the flow were 0.01 m/sec and 4 sec, respectively. The adsorption column tests were run under nitrogen gas flow. Experimental results showed that WPAC with higher Brunauer-Emmett-Teller (BET) surface area could adsorb more HgCl2 at room temperature. The equilibrium adsorptive capacity of HgCl2 for WPAC measured in this study was 1.49 x 10(-1) mg HgCl2/g PAC at 25 degrees C with an initial HgCI2 concentration of 25 microg/m3. With the increase of adsorption temperature < or = 150 degrees C, the equilibrium adsorptive capacity of HgCl2 for WPAC was decreased to 1.34 x 10(-1) mg HgCl2/g PAC. Furthermore, WPAC with higher sulfur contents could adsorb even more HgCl2 because of the reactions between sulfur and Hg2+ at 150 degrees C. It was demonstrated that the mechanisms for adsorbing HgCl2 onto WPAC were physical adsorption and chemisorption at 25 and 150 degrees C, respectively. Experimental results also indicated that the apparent overall driving force model appeared to have the good correlation with correlation coefficients (r) > 0.998 for HgCl2 adsorption at 25 and 150 degrees C. Moreover, the equilibrium adsorptive capacity of HgCl2 for virgin WPAC was similar to that for CPAC at 25 degrees C, whereas it was slightly higher for sulfurized WPAC than for CPAC at 150 degrees C.
Lin
Hsun-Yu
HY
Institute of Environmental Engineering, National Sun Yat-Sen University, Taiwan, Republic of China.
Yuan
Chung-Shin
CS
Wu
Chun-Hsin
CH
Hung
Chung-Hsuang
CH
D000327:Adsorption; D000393:Air Pollutants / Q000737:chemistry* / Q000302:isolation & purification; D002244:Carbon / Q000737:chemistry*; D007700:Kinetics; D008627:Mercuric Chloride / Q000737:chemistry* / Q000302:isolation & purification; D008962:Models, Theoretical; D011208:Powders / Q000737:chemistry; D053260:Soot / Q000737:chemistry; D013696:Temperature; D013818:Thermogravimetry / Q000379:methods*; D014835:Volatilization; D018505:Waste Management
D000393:Air Pollutants; D011208:Powders; D053260:Soot; D008627:Mercuric Chloride; D002244:Carbon