Effects of Electrode Materials on the Degradation of Sulfamethoxazole in Biofilm Electrode Systems

Abstract

Sulfamethoxazole (SMX) is frequently detected in water, which can cause bacterial resistance and spread resistance genes. Activated carbon, graphite rods, and carbon fiber were used as electrodes to construct biofilm electrode systems for the removal of SMX in water. According to the SMX removal efficiency during three experimental batches, the carbon brush electrodes (CB) had the best removal efficiency; the removal rate of SMX reached 98.23% within 192 h at Cycle 3. However, the removal efficiencies of activated carbon (AC) electrodes and graphite rod (GR) electrodes were only 88.31% and 16.80%. The properties of different electrodes, including specific surface area, contact angle, and resistivity, were the crucial factors affecting the electrode’s biocompatibility and electron-transfer properties. The 16S ribosomal ribonucleic acid (rRNA) gene sequencing results revealed that the richness and diversity of the microbial community on CB electrodes were higher than those of the other electrodes. The linear discriminant analysis effect size (LEfSe), analysis showed that the dominant functional bacteria were enriched on the CB electrodes. The phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) analysis results further demonstrated that the CB electrodes could utilize their unique properties to enhance the relative abundance of cellular process functions, thus promoting the degradation of SMX in the biofilm electrode systems. This study explained the mechanism of different electrode materials in affecting the SMX removal efficiency in the biofilm electrode systems. It provides a reference and theoretical basis for selecting electrode materials in bioelectrochemical systems.