Optimum Magnetite–Zeolite Nanoparticles Loading on the Cathode of Microbial Electrochemical–Anaerobic Digestion System for Enhancing Methane Generation

Microbial electrochemical systems (MESs) can enhance methane production in anaerobic digestion, but their performance is hindered by inadequate electron transfer between the cathode and microbes. Magnetite–zeolite (MZ)-based catalysts accelerate electron exchange; however, the optimal loading of MZ is crucial for maximizing MES performance. In this study, different loadings of the MZ catalyst ranging from 0 to 2 mg cm⁻² on the cathode were evaluated to obtain an optimum loading for maximizing methane recovery from MES. Electrochemical analyses demonstrated enhanced electrochemical reduction kinetics of the cathode with increased MZ loading from 0 to 2 mg cm⁻². Among the tested loadings, the MES with 1 mg cm⁻² MZ on the cathode exhibited the highest methane production rate at 548 mL L⁻¹ d⁻¹, surpassing other MES operations with 2 and 0.5 mg cm⁻² (499 and 434 mL L⁻¹ d⁻¹, respectively). Additionally, the MES with 1 mg cm⁻² MZ demonstrated the highest soluble chemical oxygen demand removal efficiency of 87% and total coulomb recovery of 1444.06C ± 42.60C, with the lowest amount of volatile fatty acids accumulation. Consequently, MZ is recommended as a superior catalyst for enhancing MES performance and suggested to utilize 1 mg cm⁻² MZ loading on the cathode to maximize methane production.