Modification of Activated Carbon Electrode for Efficient Electrosorption of Co2+, Mn2+ and Ni2+

Two different modified activated carbon(AC) electrode materials were prepared by modification with H3PO4 and NaOH using commercial AC as raw material. The surface properties and electrochemical properties of the AC before and after modification were investigated using scanning electron microscope(SEM), transmission electron microscope(TEM), Brunauer-Emmett-Teller(BET) test, Fourier transform infrared spectroscopy(FTIR), X-ray photoelectron spectroscopy(XPS) and electrochemical analysis. The results showed that the H3PO4 modification made the pore distribution of AC denser, and the NaOH modification made the pore structure on the surface of AC more clearer and uniform. The specific surface area of the original AC was increased after modification with H3PO4 and NaOH. Moreover, the content of oxygen-containing functional groups of AC was significantly increased by H3PO4 and NaOH modifications. The cyclic voltammetry results showed that both modification treatments improved the specific capacitance of the AC electrode. When the scanning rate was 5 mV/s, the specific capacitances of unmodified, H3PO4 and NaOH modified AC electrodes were 36.51, 77.25 and 85.19 F/g, respectively. The experimental results of electrosorption experiments demonstrate that both modified AC electrodes had excellent removal effects on Co2+, Mn2+ and Ni2+, and the electrosorption processes were more consistent with the Langmuir model. Under the same experimental conditions, the NaOH-modified electrode had higher removal rates and adsorption capacities for Co2+, Mn2+ and Ni2+. The removal rates could reach 96.84%, 94.37% and 96.90%, respectively, and the adsorption capacities were 140.8, 111.4 and 108.5 mg/g, respectively. This work indicates the potential application of modified AC electrodes and electrosorption in the efficient remediation of Co2+, Mn2+ and Ni2+.