Single and Dual Adsorption of Vapor-Phase Hg0 and/or HgCl2 by Innovative Composite Activated Carbons Impregnated with both S0 and Na2S

[[abstract]]This study investigated the single and dual adsorption of vapor-phase Hg0 and/or HgCl2 using an innovative composite sulfurized activated carbon prepared by combining two sulfur impregnation methods. Thermogravimetric analysis (TGA) technology was applied to determine the saturated adsorptive capacity of Hg0 and/or HgCl2. Experimental results indicated that the saturated adsorptive capacity of Hg0 and/or HgCl2 increased with both the concentration and adsorption temperature. This suggests that the adsorption of Hg0 and/or HgCl2 on the composite sulfurized PACs follows a process of chemisorptions, with adsorption being favored at elevated temperatures. Additionally, when the adsorption occurred at 200–300°C, the saturated adsorptive capacity of Hg0 on the composite sulfurized PACs was higher than that of HgCl2. Using coal-fired power plants as an example, the saturated adsorptive capacity of single Hg0 or HgCl2 was always higher than that of dual Hg0 and HgCl2 when the molar ratio of influent HgCl2 to Hg0 was 5:5. In addition, the breakthrough time became shorter and the saturated adsorptive capacity decreased significantly, suggesting that competitive adsorption of Hg0 and HgCl2 occurred on the activated sites. Using municipal solid waste incinerators (MSWIs) as an example, where the molar ratio of influent HgCl2 to Hg0 was 6:4, the saturated adsorptive capacity of HgCl2 and/or Hg0 at the coal-fired power plants was significantly lower than that of the MSWIs at the adsorption temperatures of 150, 200, and 300°C. This shows that HgCl2 is a more competitive adsorbate than Hg0, which could tentatively be replaced by HgCl2 on the adsorptive sites. The experimental results indicate that the molar ratio of influent HgCl2 to Hg0 affected the viscosity of these two mercury species, as well as the saturated adsorptive capacity of dual Hg0 and HgCl2. The saturated adsorptive capacities of Hg0/HgCl2 found in this study were approximately 2.9–61.4 and 8.4–251.1 times higher than those in previous studies

Adsorption of vapor-phase elemental mercury (Hg0) and mercury chloride (HgCl2) with innovative composite activated carbons impregnated with Na2S and S0 in different sequences

[[abstract]]As powdered activated carbon (PAC) is being widely used for mercury adsorption, its efficiency can be enhanced by sulfur impregnation. In this study, innovative composite PACs impregnated with two sulfur species, vapor-phase elemental sulfur (S0) and aqueous-phase sodium sulfide (Na2S), in different sequences were developed for investigating the removal of gaseous elemental mercury (Hg0) or mercury chloride (HgCl2) with respect to the adsorptive capacities and adsorption rates at different influent Hg0 or HgCl2 concentrations and different adsorption temperatures. The effects of sulfur impregnation on the physicochemical characteristics of the PACs, including specific surface area, volumes of various pore sizes, and sulfur content, were also examined. In the results, the PACs impregnated with aqueous Na2S, followed by the subsequent gaseous Hg0 impregnation exhibited higher adsorptive capacities of both mercury species. At elevated adsorption temperatures (200 and 300 ?C), the adsorption of Hg0 is more effective onto the surface of the composite sulfur-impregnated PACs, whereas the composite PACs provided elevated capacities for HgCl2 at a lower adsorption temperature (150 ?C), suggesting possible variation of mercury control strategies under different circumstances. These findings provide insight into the application of this innovative composite PACs for the removal of gaseous Hg0 or HgCl2. Higher adsorptive capacities of Hg0 or HgCl2 compared to those of previous studies were achieved by using the innovative composite sulfur-impregnated activated carbons

Enhancing the adsorption of vapor-phase mercury chloride with an innovative composite sulfur-impregnated activated carbon

[[abstract]]Mercury chloride (HgCl2) is the major mercury derivate emitted from municipal solid waste incinerators, which has high risk to the environment and human health. This study investigated the adsorption of vapor-phase HgCl2 with an innovative composite sulfurized activated carbon (AC), which was derived from the pyrolysis, activation, and sulfurization of waste tires. The composite sulfur-impregnation process impregnated activated carbon with aqueous-phase sodium sulfide (Na2S) and followed with vapor-phase elemental sulfur (S0). Thermogravimetric analysis (TGA) was applied to investigate the adsorptive capacity of vapor-phase HgCl2 using the composite sulfurized AC. The operating parameters included the types of composite sulfurized AC, the adsorption temperature, and the influent HgCl2 concentration. Experimental results indicated that the sulfur-impregnation process could increase the sulfur content of the sulfurized AC, but decreased its specific surface area. This study further revealed that the composite sulfurized AC impregnated with aqueous-phase Na2S and followed with vapor-phase S0 (Na2S + S0 AC) had much higher saturated adsorptive capacity of HgCl2 than AC impregnated in the reverse sequence (S0 + Na2S AC). A maximum saturated adsorptive capacity of HgCl2 up to 5236 μg-HgCl2/g-C was observed for the composite Na2S + S0 AC, which was approximately 2.00 and 3.17 times higher than those for the single Na2S and S0 ACs, respectively

Source Allocation of Long-Range Asian Dusts Transportation across the Taiwan Strait by Innovative Chemical-Assisted Identification Methods

This study used the backward trajectory calculation to obtain the transportation routes of Asian dusts and further combined the chemical composition with the enrichment factor (EF) and the grey relational analysis (GR) to identify the potential sources of eighteen Asian dust storm (ADS) events. The results showed that the chemical compositions of atmospheric particles sampled at the Pescadores Islands were very similar to source soils fugitively emitted from Inner Mongolia, which could assist in identifying the source regions of Asian dusts. This study further compared the source allocation of Asian dusts obtained from EF, GR, and backward trajectory, which showed that the source regions of Asian dusts obtained from these three methods were quite similar. The similarity of backward trajectory and GR reached as high as 83.3%. Moreover, the similarity of backward trajectory calculation and EF or GR was up to 77.8% while that of the GR and EF was up to 83.3%. Overall, these three methods can successfully allocate the source regions of Asian dusts by 66.7%. Moreover, these innovative chemical-assisted methods can be successfully applied to identify the source regions of Asian dusts for 18 ADS events