The Adsorptive Capacity of Vapor-Phase Mercury Chloride onto Powdered Activated Carbon Derived from Waste Tires

Abstract

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 mercurycontaining 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 (HgCl 2 ) 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°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 HgCl 2 at room temperature. The equilibrium adsorptive capacity of HgCl 2 for WPAC measured in this study was 1.49 ϫ 10 Ϫ1 mg HgCl 2 /g PAC at 25°C with an initial HgCl 2 concentration of 25 g/m 3 . With the increase of adsorption temperature Յ150°C, the equilibrium adsorptive capacity of HgCl 2 for WPAC was decreased to 1.34 ϫ 10 Ϫ1 mg HgCl 2 /g PAC. Furthermore, WPAC with higher sulfur contents could adsorb even more HgCl 2 because of the reactions between sulfur and Hg 2ϩ at 150°C. It was demonstrated that the mechanisms for adsorbing HgCl 2 onto WPAC were physical adsorption and chemisorption at 25 and 150°C, respectively. Experimental results also indicated that the apparent overall driving force model appeared to have the good correlation with correlation coefficients (r) Ͼ0.998 for HgCl 2 adsorption at 25 and 150°C. Moreover, the equilibrium adsorptive capacity of HgCl 2 for virgin WPAC was similar to that for CPAC at 25°C, whereas it was slightly higher for sulfurized WPAC than for CPAC at 150°C.

Removal and recovery of gas-phase element mercury by metal oxide-loaded activated carbon

“…The spent sorbents were placed in an open platinum pan and the experiments conducted in N 2 at a flow rate of 50 mL min −1 . Different from the work of Lin which kept the temperature at certain degree [12], nominal heating rate of 20 K min −1 was employed to increase the desorption temperature from 293 K to 1073 K and continuous records of temperature and sorbent weight were taken. The vapor-phase Hg 0 concentrations were analyzed continuously using a SG-921 cold vapor atomic absorption spectroscopy (CVAAS).…”

“…Lin et al used TGA to determine the adsorptive capacity and adsorption isotherm of vapor-phase mercury chloride on powdered activated carbon [11,12]. In this study, we used TGA to analyze the adsorbed mercury species of spent sorbents.…”

“…Virgin activated carbon (AC) showed less Hg 0 capture ability, especially at high temperatures [11,12]. For this reason, chemically treated AC, such as sulfur (S), chlorine (Cl) and iodine (I) impregnated AC [13][14][15], were applied for the mercury emission control.…”

Enhanced mercuric chloride adsorption onto sulfur-modified activated carbons derived from waste tires

“…The capabilities of the elemental sulfur diffusing into the mesopores and macropores of the activated carbons were significantly different at temperatures of 400 and 650 C, resulting in a clear dissimilarity in the sulfur content of the activated carbons. Moreover, some studies have reported a mass ratio of carbon and sulfur of 1:4 (Hladíková et al, 2001); however, the aforementioned research showed that the adsorptive capacity of sulfur-impregnated activated carbons produced at the carbon-to-sulfur mass ratio of 1:3 was superior to 1:0.5, 1:1, 1:2, and 1:4 (Lin et al, 2006). Thus, the experiments conducted in this study used sulfur-impregnated activated carbons produced at the carbon-to-sulfur mass ratio of 1:3.…”

Removal of mercury (II), elemental mercury and arsenic from simulated flue gas by ammonium sulphide

“…reacted with sulfide ions (S 2-) to generate stable mercuric sulfide precipitate under the condition of weak alkaline,[46] and the Hg 2+ removal principle can be fully explained by the equation(7).…”