Removal of the commercial reactive dye Procion Blue MX-7RX from real textile wastewater using the synthesized Fe₂O₃ nanoparticles at different particle sizes as a source of Fenton's reagent

The aim of the present study was to signify the role of the particle size of an iron source in the photo-Fenton system for textile dyeing wastewater oxidation. In this respect, a facile synthesis of Fe₂O₃ nanoparticles (Fe₂O₃ NPs) <i>via</i> a simple sol-gel route using FeCl₃ with different molarities was investigated. The XRD patterns confirmed the formation of Fe₂O₃ nanoparticles. Furthermore, different molar concentrations of the FeCl₃ precursor significantly influenced the size and shape of the nanoparticles. The treatment of wastewater effluents containing the reactive dye Procion Blue MX-7RX from a real textile dyeing facility, was investigated using the synthesized Fe₂O₃ NPs as a source of the Fenton's reagent photocatalyst. The reaction was initiated and enhanced using an artificial UV source for increasing the ˙OH radical yield. System parameters such as the initial dye load in wastewater, H₂O₂ and Fe₂O₃ NP concentrations, pH and the working temperature were investigated for process optimization. The quality of water in this investigation was examined by making measurements of chemical oxygen demand (COD), total suspended solids (TSS) and dye removal which decreased during the illumination time. The effects of different Fe₂O₃ NPs based on the varying precursor solution molarities namely F1, F3, F5 and F7 on the wastewater remediation were investigated, and the optimum Fe₂O₃ NPs were found to be F1, which exhibited the highest dye removal value of 83% and a chemical oxygen demand (COD) reduction of 88%. Furthermore, the oxidation kinetics of the Procion Blue dye were studied, and the data were well fitted with the second order kinetics. Finally, the thermodynamic parameters including the changes in the Gibbs free energy of activation, entropy of activation and enthalpy of activation for the Procion Blue oxidation with different Fenton's reagent sources under ultraviolet light illustrated that the reaction was non-spontaneous and endothermic.