Hybrid treatment of olive mill wastewater by iron-catalyzed percarbonate and peroxymonosulfate oxidation followed by electrooxidation

Abstract

In this study, hybrid advanced oxidation processes were applied to effectively treat olive mill wastewater (OMW). In the first stage of the hybrid process, Fe2+-activated peroxymonosulfate (PMS) and percarbonate (PC) oxidation processes were applied. Optimum conditions for maximum chemical oxygen demand (COD), ultraviolet absorbance at 254 nm (UV254), and color removal were determined. Since the difference between the removal efficiencies of the two processes was negligible, the Fe2+-activated PC process was selected. Under optimum conditions (pH: 4, PC dose: 10 g/L, Fe2+ dose: 5 g/L, reaction time: 60 min) with the Fe2+-PC process, 43.3 % COD, 69.4 % UV254, and 88.6 % color removal were obtained. In the second stage, the electrooxidation (EO) process was applied to the effluent of the Fe2+-PC process. Different anode materials were evaluated in EO based on their pollutant removal efficiency, specific energy consumption, anode efficiency, and instantaneous current efficiency, and IrO2-coated Ti (Ti/IrO2) was selected. In the EO process using Ti/IrO2 anode, 1.75 A, pH 3.5, and 120 min, 59.6 % COD, 94.5 % UV254, and 100 % color removal efficiency were achieved. A total of 77.1 % COD, 98.3 % UV254, and 100 % color removal efficiencies were obtained with hybrid processes, and it was seen that hybrid advanced oxidation is an effective application in removing pollutants from OMW.