Investigation of color and COD removal from aqueous solutions containing Direct Blue 71 textile dyestuff by electro-Fenton and photoelectro-Fenton methods

Aqueous solutions of textile dyes can cause a wide variety of adverse effects (mutagenic, carcinogenic, etc.) on human and animal health. Therefore, textile industry wastewater must be treated using the most appropriate treatment methods to ensure compliance with permitted discharge limits. Advanced oxidation processes (AOPs) are one of the most commonly used treatment technologies for this purpose. In this study, the effects of some key operating criteria (current density and hydrogen peroxide concentration) on color and COD (Chemical Oxygen Demand) removal from Direct Blue 71 (DB71) textile dye using electro-Fenton (EF) and photoelectro-Fenton (PEF) methods were comparatively investigated. Different current densities (10-30 A/m2) and hydrogen peroxide concentrations (200-1000 mg/L) were tested experimentally. For the EF method, maximum color (97.23%) and COD (92.11%) removal was achieved at a current density of 20 A/m2 and a hydrogen peroxide concentration of 600 mg/L. For the PEF method, maximum color (98.81%) and COD (95.95%) removal was achieved at a current density of 15 A/m2 and a hydrogen peroxide concentration of 400 mg/L. First and second-order experimental kinetic studies were conducted for color and COD removal. Experimental kinetic constants k (min-1) and r2 values were calculated. The total treatment cost for the EF process was found to be $7.574/m³, while for the PEF process it was $5.116/m³.