Treatment of plastic recycling plant wastewater with hybrid electrochemical process

In this thesis, treatment of plastic recycling plant wastewater by hybrid electrochemical process was studied. Simultaneous hybrid, sequential hybrid and integrated/combined hybrid processes, which are hybrid utilization types of electrochemical processes, were applied in the experimental studies. The effect of operating parameters such as pH, current density, electrolysis time and stirring speed on the removal efficiency was investigated. Aluminum (Al), stainless steel (SS), lead oxide (PbO2), mixed metal oxide (Pt-IrO2) and boron doped diamond (BDD) electrodes were used in the experiments. As a result of the experimental studies, it was seen that plastic recycling plant wastewater can be treated in all hybrid processes. Among the hybrid processes, the lowest removal efficiency was obtained in the simultaneous hybrid process, while the highest removal efficiency was obtained in the integrated/combined hybrid electrochemical process. The highest Total Organic Carbon (TOC) removal efficiencies obtained by simultaneous, sequential and integrated/combined hybrid electrochemical processes were 24.1%, 54.5% and 89.2%, respectively. Chemical Oxygen Demand (COD) removal rate was calculated as 94% for the process with the highest TOC removal efficiency. The highest removal efficiencies were obtained at pH, electrolysis time and current density of 6, 90 minutes and 2 A, respectively. In addition, in the experimental studies in which the effect of mixing speed on removal efficiency was examined, while doubling the mixing speed increased the removal efficiency by 2% under the same experimental conditions, quadrupling the mixing speed increased the removal efficiency by 3.2%. It was observed that the TOC removal efficiency will reach 92.4% and higher levels by increasing the mixing speed. In all experimental studies, the highest removal efficiency was achieved in the experimental set with the BDD electrode. Parameters such as energy consumption and current efficiency are some of the important parameters of electrochemical processes. For this reason, the energy data of the electrodes were also analyzed in this study. In terms of specific energy consumption values, the BDD electrode was found to be more efficient than the other electrodes. The study also examined parameters such as Average Oxidation State (AOS) and Carbon Oxidation State (COS) to determine its biodegradability. Cost analysis was also performed for the process where the optimum removal efficiency was obtained and it was determined as 9.34 m3/USD.