Response Surface Modeling and Optimization of Microwave‐Activated Persulfate Oxidation of Olive Oil Mill Wastewater

Abstract

Olive oil mill wastewater (OMW) is environmentally hazardous not only because it contains high recalcitrant and toxic compounds, but also due to its high organic load and turbidity. In this study, oxidation of OMW by microwave (MW)‐activated persulfate is investigated. Box–Behnken design is applied to investigate the effects of operating conditions on operating cost, organic matter, and color removal. Multi response optimization is performed according to minimum operating cost, maximum organic matter and color removal efficiencies. At optimum conditions (persulfate anion dose of 266 g L−1, oxidation duration of 23.58 min, MW power of 567 W, and initial pH 2), chemical oxygen demand (COD) removal of 63.38%, color removal of 94.85%, and operating cost of 0.0633 Euro/g total organic carbon (TOC) removal are found. The biochemical oxygen demand (BOD5)/COD ratio is increased from 0.144 to 0.285. Results of Pareto analysis show individual effect of MW power is 92.81% for TOC removal, 15.52% for color removal, 68.99% for operating cost, respectively. According to the results, it is not recommended to use this process as an ultimate treatment unit due to the high amount of oxidizing agent consumed. Instead, it is recommended to be used as a pre‐ or post‐treatment step.

Effect of storage time on the biodegradability of olive oil mill wastewater from the cold extraction of olive oil system

“…The major waste product from the extraction of olive oil in heavily polluted acidic liquid form is OMW. Because of the presence of tannins and phenolic compounds of low molecular weight (6,7), it has an extreme purple-brown or brown-red to black appearance and an olive oil odor. Its composition is variable and complex, primarily consisting of sugars, lipids, polyalcohols, proteins, organic acids and polyphenols (8).…”

Thermal and Radiation Based Catalytic Activation of Persulfate Systems in the Removal of Micropollutants: A Review

“…The interaction of microwave radiation with various substances occurs via the three steps of penetration, reflection, and absorption, which result in direct internal heating. , About 85% of the electrical energy is converted to heat energy . The various advantages offered by microwave radiation include minimal energy requirement and activation energy, shorter reaction time, higher selectivity in terms of reaction, energy of high utilization efficiency, comparatively high power density, intensive molecular level heating, homogeneous environment, and an eco-friendly and cost-effective process. ,− In recent decades, microwave irradiation has received extensive research attention, as energy is transformed by irradiation, resulting in the rotation of dipolar molecules (i.e., dielectric material/water molecules) . As these dipolar molecules try to align themselves at a rate of 2.45 billion times s –1 in the alternating electric field and magnetic field, friction is caused between the dipolar molecules, thus producing heat, and this is known to increase the rate or speed of the reaction .…”

“…Temperature is an essential parameter for the generation of sulfate radicals from persulfate through the activation of microwave radiation. It has been proposed that microwave heating provides faster and low activation energy to activate the persulfate resulting in an increased rate of degradation compared to conventional heating methods . In general, persulfate (the oxidant) has a high dielectric loss factor (ε″) value and is also known to exhibit ultrafast realignment rates, thereby rapidly increasing the temperature .…”

Persulfate Process Activated by Homogeneous and Heterogeneous Catalysts for Synthetic Olive Mill Wastewater Treatment

“…The sulfate radicals (SO 4 2− ) bind with the pollutants by removing hydrogen from the saturated carbon and adding it in the double bonds or by electron transfer, causing partial or total mineralization of the organic matter [10].…”