The changes in the indicators for the performance of 3D-MFC system during the acclimation of inoculum are shown in Fig. 2a–d. The electrogenic acclimation tests were conducted to guarantee the biofilm formation, the reproduction of the electroactive microorganisms, and the bio-oxidation of acetate before the Co(II)-removal process [43], [44]. The sulfuric acid solution with the initial pH of 4 and AC particles prepared at 300 °C was adopted as the catholyte and the cathodic stacking material,
