Removal of Orange G dye from water by heterogeneous electro Fenton-based processes using Ti4O7 anode and different iron-based catalysts

Abstract Removal of Orange G (OG) dye from water by anodic oxidation (AO), heterogeneous electro Fenton (HEF), and heterogeneous photoelectro-Fenton (HPEF) processes was systematically investigated under different operating conditions. Four distinct heterogeneous catalysts were used in this study: titaniferous sand, pyrite, and sludge derived from electrocoagulation using stainless steel (SS sludge) or iron electrodes (iron sludge); within an electrolytic cell equipped with a Ti 4 O 7 anode and carbon-felt (CF) cathode, a cost-effective configuration for advanced oxidation processes. The optimal operating conditions were chosen based on comparison of total organic carbon (TOC) removal efficiency, mineralization current efficiency (MCE (%)), and energy consumption (EC). A key highlight is the comparison of Ti 4 O 7 /CF and BDD/CF cells, demonstrating that the former cell offers comparable degradation efficiency with significantly improved MCE and low EC values, underscoring its potential as a cost-efficient alternative to traditional AO systems. The used iron-based materials were characterized using SEM–EDS and X-ray diffraction analyses. Besides, reusability runs were performed to demonstrate the sustainability of the most effective catalyst, the SS sludge. Results showed that the most effective treatment of OG solution was achieved using SS sludge, with a stable activity even after five cycles. The HPEF process with Ti 4 O 7 /CF cell exhibited comparable degradation efficiency as the AO process with the BDD/CF cell. Specifically, both the AO process using BDD/CF cell and HPEF with Ti 4 O 7 /CF cell achieved similar mineralization efficiencies, i.e., 84.25% and 82.33%, respectively, while the latter exhibited better MCE and EC values. These findings establish the HPEF process using Ti 4 O 7 /CF cell as an innovative, sustainable, and energy-efficient alternative for dye removal, advancing the application of heterogeneous catalysts in wastewater treatment.