Gaseous hydrophilic/hydrophobic volatile organic compound removal and power production by bioelectrochemical systems comprising agro-waste-based biochar-optimized proton exchange membranes

The co-existence of hydrophilic and hydrophobic volatile organic compounds (VOCs) in industrial environments poses a challenge for bioelectrochemical systems (BES). To enhance the efficacy of BES in treating both hydrophilic and hydrophobic VOCs, this study focused on optimizing the proton exchange membrane (PEM). The diffusion of VOCs through PEMs produced from four types of agricultural wastes demonstrated that PEMs made from walnut husk (WH) and cork biochar provided excellent diffusion of hydrophobic and hydrophilic VOCs, respectively. A composite desirability coefficient of 0.885 for the PEM_Cork/WH membrane, fabricated by combining walnut husk and cork using the response surface methodology (RSM) under optimized fabrication conditions, indicated that PEMs with low oxygen diffusivity, high proton transfer rates, and excellent electrical conductivity were successfully developed in this study. BES using PEM_Cork/WH demonstrated an impressively high VOC removal efficiency, eliminating 98.7 % and 71.4 % of gaseous acetone and toluene, respectively. Compared with PEMs made from conductive carbon black (PEM_CCB), BES using PEM_Cork/WH reduced the total internal resistance, boosting the voltage output and power density by 1.37 and 2.28 times, respectively. The PEM_Cork/WH developed in this study significantly improves the performance of BES in treating hydrophilic and hydrophobic VOCs and can potentially promote renewable energy applications.