Investigating and comparing chemical, electrochemical, and photo-electrochemical processes in decreasing dissolved iron from oily wastewaters using steel slag

The disposal of petroleum wastewater is one of the important environmental concerns. Therefore, the present study aimed to investigate and compare the Performance of Fenton, Photo-Fenton (PF), Electro-Fenton (EF), and Photo-Electro-Fenton (PEF) processes in decreasing iron dissolved desalination unit effluent using steel slag as catalyst, cathode and, anode. Experimental variables in this study include pH (3, 5, and 7), hydrogen peroxide concentration (5, 10, and 15 mM/L), reaction time (30, 60, and 90 min), catalyst (5, 7.5, and 10 g/L), radiation intensities (16, 24, and 32 W), and voltages (5, 15, and 30 V). Also, the Taguchi experimental design with 9, 9, 9, and 27 experimental runs was established to determine the level of process parameters for processes of Fenton, EF, PF, and PEF, respectively. For this purpose, a pilot was made to perform the experiments using UV-C lamps (200–280 nm) with a power of 8 W (32 W in total) and an AC power supply of 0–30 V in the range of 0–2 A. Results showed that the maximum removal percentage of dissolved iron 98.72% was obtained for the PEF process under conditions of pH = 7, H 2 O 2 concentration of 10 mM/L, a catalyst mass of 5 g/L, radiation intensity of 32 W, and output voltage of 15 V within 90 min. In general, our findings showed that EF, PF, and Fenton processes had the highest abilities to decrease dissolved iron using steel slag following the PEF process, respectively.