A novel technique of COD removal from electroplating wastewater by Fenton-alternating current electrocoagulation

The present study employs a novel technique combining Fenton reaction with sinusoidal alternating current electrocoagulation (FSACEC), which is used to remove chemical oxygen demand (COD) in the simulated electroplating wastewater with the advantages of low energy consumption and small sludge. Fe²⁺, produced from the dissolution of Fe anodes in the FSACEC process, reacts with H₂O₂ to generate more ·OH and forms the iron hydroxide precipitates. The higher efficiency of COD removal is achieved through both effects of the oxidation reaction and the physical adsorption. The scanning electron microscopy (SEM) analysis shows that the particle size of FSACEC products is between 30 and 40 nm, which is less than the Fenton-direct current electrocoagulation products. The effect of the current concentration (I_V), initial pH (pH₀), and the addition of hydrogen peroxide (30% H₂O₂) was discussed on the optimal process parameters. In pH₀ 2.0 wastewater, applying current concentration of 1 A dm^-3, the addition 20 cm³ dm^-3 30% H₂O₂, the removal efficiency of COD reached 94.21% and the residual COD in wastewater was only 60 mg dm^-3 after 90 min of operation. In order to investigate the maximum removal efficiency in a certain period of operation, the larger current concentration is applied to remove COD. The FSACEC process exhibits the higher removal COD efficiency and wider operation range of pH₀ than the single Fenton technique. The FSACEC process is in accordance with the kinetic law of the pseudo-second-order kinetic adsorption model.