Activation of persulfate by TiO2-Fe3O4 nanocomposite for reactive red 198 degradation along with modeling and optimization approach

Background: Recently, sulfate radical-based photocatalytic processes have attracted significant interests because of unique advantages in pollutants purification. In this study, TiO2-Fe3O4 nanocomposites in the presence of persulfate and under ultraviolet light-emitting diode (UV-LED) irradiation were applied for reactive red 198 removal with a focus on the main operating parameters such as pH, persulfate molar concentration, irradiation time, and catalyst dosages in different initial concentrations. Methods: The nanoparticles were synthesized by co-precipitation technique. The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR) analysis were used to evaluate TiO2- Fe3O4 nanocomposites. The response surface methodology (RSM) was employed for modeling and optimization. The kinetics and mechanisms of decolorization by sulfate and hydroxyl radicals were investigated. The mineralization of dye was evaluated using total organic carbon (TOC) analysis. Results: Modeling and optimization through RSM showed that the maximum decolorization of reactive red 198 is accursed an initial concentration of 10-50 mg/L was reached under UV-LED irradiation of 62- 85 min, persulfate concentration = 0.8-1 mM, 0.19-0.3 g/L TiO2-Fe3O4 nanocomposites concentration, and pH = 3. The kinetics of process was in agreement with pseudo-first order. The mineralization of reactive red 198 during the optimum conditions was determined at about 61.1% and 49.6%, meanwhile, the decolorization efficiency in the same conditions was approximately 98.1% and 87.6%, respectively. Conclusion: The use of TiO2-Fe3O4 nanocomposites under UV-LED irradiation in the presence of persulfate can be used as an efficient and promising method for dye removal from textile wastewater.