Effective treatment of Cu²⁺-containing acid mine drainage with acidic-cupric resistant electroactive biofilms

Currently, whether robust anodic electroactive biofilms (EABs) are obtainable or not and how their electrochemical performances and metal remediation mechanisms during treating acidic mine drainage (AMD) remain largely unknown. Herein, a batch of acidic-cupric dual resistant anodic EABs were first enriched from sediment of AMD under different acidities, and Cu²⁺ removal mechanism during treatment of Cu²⁺-containing AMD in membrane-free microbial fuel cell (MFC) was explored. Results shows that increased acidity inhibited electrochemical performance of anodic EABs. The maximum output voltages of MFC with the EABs enriched at pH7.0, 5.5, 4.5, 3.5, and 3.0 were 505 ± 20 mV, 495 ± 10 mV, 353 ± 21 mV, 305 ± 4 mV, and 206 ± 13 mV respectively with an external resistance of 1000 Ω, which were only slightly inhibited in presence of 50 mg L^-1 Cu²⁺ and recovered immediately after the absence of cupric stress. High power density (97.25 mW m^-2) and high Cu²⁺ removal (92.47%) was achieved for the robust EABs enriched at pH3.0 in presence of 50 mg L^-1 Cu²⁺. Mechanism analyses confirmed that Cu²⁺ was adsorbed by functional groups C-O-C and C-O on the surface of anodic EABs, and the removal of Cu²⁺ was co-precipitated as CuS and Cu₂O. Significant differences on microbial community structure of these robust anodic EABs enriched under different acidities were observed. Alicyclobacillus and Thiomonas were significantly enriched in the robust anodic EABs enriched at pH3.0. This study provided novel insights to enrich robust EABs for developing bioelectrochemical technology for AMD remediation in future.