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

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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.