Treatment of olive mill effluent by immobilized nano-ZnO-Magnetite

Olive mill wastewater (OMW) contains high concentration of organic matter, acidic pH values, suspended solids and high content of phenols and polyphenols which are toxic substances. The aim of this study is the removals of COD, total phenol, total solid (TS), total nitrogen, total phosphorus and polyphenos (caffeic acid, tyrosol and hydroxytyrosol) in the OMW by Nano-ZnO-Magnetite composite via adsorption and photocatalytic dagradation. The specific objectives of this study are to determine the optimum Nano-ZnO-Magnetite concentration, to evaluate effect of time and pH on the treatment of OMW pollutants for maximum removal of pollutants, and to investigate the recovery of composite. For adsorption mechanism, the optimum concentration of Nano-ZnO-Magnetite, adsorption time and pH was determined as 3 gram per liter, 180 minute and 4, respectively. The maximum removal efficiencies of COD, total phenol, TS, total nitrogen and total phosphorus were found as 12, 9, 10, 7 and 10 percent, respectively. For photocatalytic degradation under UV, the optimum concentration of Nano-ZnO-Magnetite, irradiation time and pH was determined as 3 gram per liter, 30 minute and 4, respectively. The maximum removal efficiencies of COD, total phenol, TS, total nitrogen and total phosphorus were found as 80, 75, 70, 97 and 85 percent, respectively. And also, the maximum removal efficiencies of caffeic acid, tyrosol and hydroxytyrosol were found as 80, 80 and 51 percent, respectively Nano-ZnO-Magnetite concentration: 3 gram per liter, irradiation time: 30 minute, UV power: 300 W). When we used the same Nano-ZnO-Magnetite for fifth times for treatment of OMW , the COD, phenol and TS removal efficiencies decreased from 80 to 52 percent, 75 to 48 percent and 70 to 56 percent, respectively. The cost to treat one liter of OMW is around 500 TL.