Plastik geri dönüşüm tesisi atıksularının Fenton ve Elektro-Fenton prosesleri ile arıtımı

With increased level of welfare and industrial development, plastic materials are taken places in almost every area of production of various goods in our lives. However, as a result of increasing usage of plastic materials, amount of plastic wastes are augmented continuously. Recycling of plastic wastes is important from the economic point of the waste recycling as well as reducing the amount of waste on the environment and nature. In our country, especially the number of plastic recycling facilities is increasing every year. In the recycling of plastic materials, wastewater is arisen from washing the plastic burrs. The main pollutants in this type of wastewaters are chemical oxygen demand (COD) together with suspended solids and color. Fenton process is one of the most powerful and known advanced oxidation processes. It is based on the production of hydroxyl radicals (OH●) as a result of the reaction between H2O2 and catalyst ferrous ion (Fe2+) under acidic conditions. When compared with the other advanced oxidation processes, while its main advantage is its simple and cheap application, the most important disadvantage of Fenton process is that the catalyst Fe2+ is rapidly converted to Fe3+ which reacts with H2O2 much more slowly, and changed slowly into Fe2+ in the oxidation reaction. Therefore, the rate of Fenton reaction slows down, as the amount of catalyst Fe2+ decreases. On the other hand, the amount of chemical treatment sludge can increase as a result of the usage of the excess amount of ferrous iron. There are several modifications of Fenton process. A combination of Fenton process with electrochemical process is named as electro-Fenton process and this combination enhances oxidation efficiency of the Fenton process. When sacrificial iron electrodes are utilized in electro-Fenton process, the H2O2 is externally added. Sacrificial iron anode is utilized as a ferrous ion source in this electrochemical process. The treatment of various industrial wastewaters via Fenton and electro- Fenton processes has been extensively investigated. Up to the date, the author could not find any study about the treatment of plastic recycling industry effluents by the Fenton and electro-Fenton processes. Therefore, the authors aimed to provide more insight to the feasible treatment of plastic recycling wastewaters by two different applications of Fenton process in this work. The effects of the main operating parameters (reaction time, pH, electrical current, ferrous ion dosage and H2O2 dosage) of the process on the efficiencies of COD removal, which is the target parameter, were investigated. Moreover, kinetic analysis for COD removal was also performed under the optimum conditions predetermined in this study. All experiments were performed using real wastewater supplied from the plastic recycling facility in Nevsehir. In the experimental studies, while the optimized conditions were found as pH = 3, [Fe2+] = 250 mg/L and [H2O2] = 250 mg/L for Fenton process and pH = 3, electricity current = 1,25 A ve [H2O2] = 200 mg/L for electro – Fenton process. Under these circumstances, COD removal efficiencies for Fenton and electro-Fenton processes were % 79,6 and % 81,2, respectively. On the other hand, it was determined that the COD removal in Fenton process was occurred much faster than that of electro- Fenton process. In this case, it was because of the reagents added in the dissolved form in Fenton process. But, electro-Fenton process was more effective even at less H2O2 dosage because of its electro-chemical H2O2 production ability. According to the results of kinetic studies, COD removal via the electro-Fenton and Fenton both processes was fitted well the second-order kinetics. As a result, both of processes has been determined to be effective processes for the treatment of plastic recycling facility wastewater.