Adsorption of Volatile Organic Compounds at Medium-High Temperature Conditions by Activated Carbons

Abstract

Activated carbon (AC) adsorption is an effective method for abatement of volatile organic compounds (VOCs) in coal-fired power plants. The adsorption behaviors of VOCs (toluene and chlorobenzene) for ACs (coconut shell-based AC (CSAC) and wood-based AC (WAC)) under medium-high temperature (MHT: 90–150 °C) conditions were investigated in a fixed-bed reactor. The results indicated that the adsorption capacity of VOCs was reduced with increasing temperature. CSAC had a higher adsorption capacity and adsorption rate for the two VOCs than WAC at the same adsorption temperature. The adsorption capacity of toluene was within the range of 13.9–49.9 mg/g, while that for chlorobenzene was 26–80.3 mg/g. The content of oxygen-containing groups on the AC surface was increased with acid modification and decreased with alkali modification. The adsorption capacity of AC was improved to varying degrees after chemical modification. Adsorption was mainly controlled by physical adsorption, whereas the effects of chemisorption became evident with increasing temperature. The interactions between oxygen-containing groups and VOCs were more beneficial for improving adsorption capacity than π–π interactions. The pseudofirst-order kinetic model better described the adsorption of VOCs by ACs. The MHT conditions promoted the intraparticle diffusion; lower VOC concentration resulted in the external mass transfer of AC becoming the adsorption rate-limiting step. Increasing the external surface area and micropore volume of AC and enriching the content of surface oxygen-containing groups were useful in enhancing the VOC removal efficiency.

MOF@PVA beads for dynamic and low concentration VOC capture

“…Dynamic toluene adsorption. The dynamic adsorption of toluene was evaluated following the procedures in the literature 25,26 with minor modifications as follows: a schematic representation of the flow system employed is presented in Scheme 1, consisting of the toluene VOC generator, U-tube to hold the MOF@PVA beads, and the detection device, which is the FTIR. The total flow rate was kept at 1 L min À1 with the concentration of toluene controlled at 200 ppm toluene in N 2 .…”

“…where k i (g mg À1 min À1/2 ) is the intraparticle diffusion rate constant and C i is the constant. 26 Scheme 1 Diagram for dynamic toluene adsorption.…”

“…The experimental data were more suitably fitted for the pseudo-second-order model as compared to the pseudo-first-order model (correlation coefficient R 2 = 0.99847, 0.99976), and the q e was close to the experimental value (Table 2), suggesting that it is influenced by chemisorption. 26 Furthermore, in order to shed more light toward understanding the adsorption process, the intraparticle diffusion model was utilized to determine the diffusion mechanism for toluene. Fig.…”

The adsorption properties of microporous activated carbon prepared from pistachio nut shell for low-concentration VOCs under low-medium temperatures

“…According to the IUPAC classification, the isotherms are type I physical adsorption isotherm (Ma et al, 2020), suggesting that PSAC-1 and PSAC-2 are microporous materials (micro porosity: 94.41 % for PSAC-1, 92.41 % for PSAC-2). CAC nitrogen adsorption-desorption isotherms belongs to type Ⅰ and type Ⅳ mixture physical adsorption isotherm (Gao et al, 2013).…”

Adsorption of 1,2-Dichlorobenzene from the Aqueous Phase onto Activated Carbons and Modified Carbon Nanotubes

“…Then adsorbate forms a molecular film on the adsorbent’s surface. In addition, it is a non-destructive technique [ 1 , 2 ]. Throughout adsorption, various types of organic compounds are removed from aqueous solutions, e.g., chloroderivatives, such as 1,2—dichlorobenzene, dyes such as methylene blue, and numerous volatile organic compounds [ 3 , 4 , 5 , 6 ].…”