Magnetically recoverable bagasse-activated carbon composite anodes for sediment microbial fuel cells: enhanced performance in chromium-contaminated soil remediation

Abstract

With the increase in the use of chromium-containing products and the discharge of industrial wastes, the phenomenon of soil chromium pollution is becoming increasingly serious. Sediment microbial fuel cells (SMFCs) can be used for soil remediation In this study, the effect of SMFCs on the remediation of chromium-contaminated soil was studied. Furthermore, in order to improve the repair effect, composite electrodes were investigated as anodes to evaluate their impact on SMFC performance, with graphite felts used as a cathode. The composite electrodes were conductive bagasse-activated carbon (CBAC) composite electrode and magnetized conductive bagasse-activated carbon (MCBAC) composite electrode. An SMFC experimental group (CBAC anode denoted as SMFC-1 and MCBAC anode denoted as SMFC-2) and a control group (graphite felt anode denoted as SMFC-3) were constructed. Results showed that after activation pyrolysis, the material had an obvious pore structure, the specific surface area increased, and the surface functional groups were abundant. However, in order to improve the recovery of electrode materials, magnetization was performed on CBAC. After magnetic modification, the addition of iron oxide (γ-Fe₂O₃) increased the graphitization degree (Raman I_D/I_G = 0.9) and reduced the charge-transfer resistance (7.68 Ω), thereby improving the electrochemical performance of MCBAC. This result was confirmed by CV and EIS results. SMFC-2 exhibited the best electrical performance, and the maximum output voltage of SMFC-2 during the period was 0.58 V, which was better than those of SMFC-1 (0.46 V) and SMFC-3 (0.35 V). Using SMFCs as the power source could effectively drive the removal of chromium from soil, and the maximum removal rate of chromium from soil was as high as 48.86% using SMFC-2. The removal rate of SMFC-1 was 43.53%, which was much higher than that of SMFC-3 (29.97%). Through the analysis of chromium morphology, it could be seen that SMFCs could effectively reduce the effective form of chromium in soil. Compared with the initial form, SMFCs effectively reduced the content of the bioactive form of chromium in soil. In summary, SMFCs can effectively drive the restoration of chromium in soil and provide an intentional reference for the restoration of heavy metals in soil.