Integrated salt and energy recovery from dyeing wastewater via fenton and photo-fenton oxidation: Industrial approach

This study investigates the treatment of textile dyeing wastewater using Fenton and photo-Fenton oxidation processes, achieving high chemical oxygen demand (COD) and color removal efficiencies alongside significant salt and energy recovery. Optimal conditions for Fenton oxidation were determined as 0.5 g/L FeSO4, 2.7 g/L H2O2, and a reaction time of 30 minutes, resulting in COD and color removal efficiencies of 93 % and 69 %, respectively. Similar conditions were employed for photo-Fenton oxidation while exposing the system to UV radiation using the Solar Atlas Suntest, achieving 95 % COD removal and 99 % color removal. The study employed a central composite design (CCD) for process modeling, and an analysis of variance (ANOVA) was conducted to assess variable effects. The R2 values for Fenton oxidation were found to be 0.9957 for COD removal and 0.9838 for color removal, while those for photo-Fenton oxidation were 0.9971 and 0.9877, respectively, indicating excellent model accuracy. Among the investigated parameters, H2O2 concentration was identified as the most influential factor for color removal, while temperature and reaction time were critical for COD removal. Additionally, the process facilitated 70 % salt recovery, enabling the reuse of treated saline water in industrial applications without operational issues, thereby demonstrating its feasibility for real-scale implementation. A detailed cost analysis revealed that treating 1 m3 of wastewater using photo-Fenton oxidation costs $6.8, underscoring its economic viability. Furthermore, approximately 29.07 kWh of energy was recovered using the residual heat from treated water at an initial temperature of 25 degrees C.