Modifying Recycled Graphite with Co₃O₄ Towards a Novel, Efficient Anode for the Electrochemical Treatment of a...

Electrochemical oxidation is an effective method for degrading environmentally harmful textile dyes that are difficult to remove by conventional treatments. The novel graphite-Co₃O₄ anode, prepared by electrochemically modifying recycled graphite tubes for AAS samples and characterized by SEM, EDX, FTIR, XRD, and BET, was used for electrochemical degradation of RB 4 dye in model solutions and textile dyeing effluent. Modification did not disrupt the graphite crystal structure but altered its surface properties, improving its dye degradation performance. It increased the decolorization rate constant of a model solution from 0.0148 min^-1 to 0.0753 min^-1 and maximum COD decay from 59% to 91%, reducing decolorization energy consumption from 3.26 kWh m^-3 to 0.89 kWh m^-3. Degradation at the graphite-Co₃O₄ anode proceeded via ·OH radicals and most likely the Co³⁺/Co²⁺ redox couple. It followed the pseudo-first-order kinetics. Pastel- and dark-shade dyeing textile effluents (containing 53 mg dm^-3 and 159 mg dm^-3 RB 4, respectively) were decolorized in about 70 and 110 min; COD decay reached about 87% and 80% after 180 min of electrolysis, respectively. The corresponding energy consumption was 1.75 kWh m^-3, 2.39 kWh m^-3, 2.97 kWh m^-3, and 2.91 kWh m^-3, respectively. The anode was efficient and stable in the given working conditions.