Investigation of the competitive adsorption mechanism between typical volatile organic compounds (VOCs) and water vapor in waste gas emissions from the fermentation industry

The fermentation waste gas, characterized by high humidity and diverse volatile organic compounds (VOCs), poses challenges for adsorption in activated carbon devices. In this study, starch-based activated carbon was used as an adsorbent, targeting typical VOCs from fermentation industries-methyl mercaptan, toluene, and n-hexane. The adsorption behavior of water vapor and VOCs on the carbon interface was analyzed through adsorption experiments, structure characterization, and molecular simulations. Results showed that at 70% RH, the adsorption capacities of toluene and n-hexane experienced a reduction of 42.15% and 59.24% respectively compared to their respective capacities without water vapor at the breakthrough moment, while methyl mercaptan's capacity increased by 32.29% due to dissolution in condensed water within micropores. Water displaced all three VOCs during multicomponent adsorption. Reducing surface carboxyl groups, pyrrolic-N, and pyridinic-N enhances selective adsorption of VOCs. Among the VOCs, toluene shows the strongest interaction with activated carbon, followed by n-hexane and then methyl mercaptan. However, a water film under high humidity hinders the adsorption of n-hexane and toluene, reducing selectivity. These research findings will contribute to a comprehensive understanding of the mechanisms underlying the absorption of VOCs in high humidity environments by activated carbon.