| Summary: | 碩士 === 弘光科技大學 === 職業安全與防災研究所 === 100 === Semiconductor industry and optoelectronics industry all belong to the core industries in the industrial value heightening plan (i.e., Challenge 2008 - National Development Plan). Organic wastewater accounts for more than 33% of the high-tech manufacturing wastewater. The main components of this organic wastewater are composed of the stripper, polarizing film (PVA), developer and chelating agents. The large amount of organic discharged from industrial effluents is harmful to human health and the environment. The main purpose of this study is to develop a novel electrochemical system containing electrocoagulation and electrooxidation (Electro-Fenton), can effectively treat the organic wastewaters in the high-tech industry (e.g., semiconductor and optoelectronics industry).In the first part, we have developed the electrocoagulation system on treatment of PVA wastewater. For treatment of PVA, several parameters were evaluated to characterize the PVA removal efficiency, such as various current densities and temperatures. The effects of the current density and temperature on the electrical energy consumption were also investigated. The optimum current density and temperature were found to be 5 mA cm-2 and 298 K, respectively. Under these conditions, the PVA and TOC concentration of aqueous PVA solutions decreased by more than 90 % and 80 %, respectively. The experimental data were also compared to different adsorption isotherm models in order to describe the EC process. The adsorption of PVA was best fitted by the Freundlich adsorption isotherm model. Thermodynamic parameters such as the Gibbs free energy, enthalpy, and entropy indicated that the adsorption of PVA on metal hydroxides was feasible, spontaneous and endothermic in the temperature range of 288 to 318 K.
In the second part, the development of the Electro-Fenton system have designed to treat PVA wastewater. For treatment of PVA by Electro-Fenton (Fe oxidation-H2O2), several parameters were evaluated to characterize the PVA removal efficiency in terms of electrical energy consumption, such as initial pH, current densities, and temperatures. The optimum initial pH, current density, and temperature were found to be 3, 7.5 mA cm-2, and 303 K, respectively. In addition, for treatment of PVA by Electro-Fenton (Fe oxidation), the optimum initial pH, H2O2 dosage, current density and temperature were found to be 3, 5 ml, 5 mA cm-2 and 303 K, respectively. Under these conditions, the PVA concentration of PVA aqueous solutions decreased by more than 90 %. A very good agreement with the experimental data was obtained the pseudo-first-order kinetic model, which best described the PVA removal by Electro-Fenton process. Finally, response surface methodology was employed to assess individual and interactive effects of critical process parameters (initial pH, H2O2 dosage; current densities, and temperatures) on treatment performance in terms of PVA removal efficiencies. Optimized reaction conditions of Electro-Fenton (Fe oxidation) system for PVA wastewater were established as initial pH, H2O2 dosage, current densities and temperatures were found to be 2.27, 5.05 ml, 5.57 mA cm-2 and 305.20 K, respectively.
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