| Summary: | 碩士 === 國立雲林科技大學 === 環境與安全工程系碩士班 === 94 === This study was to investigate the removal efficiency and the feasibility of volatility organic compounds (VOCs) using laboratory-scale photo electrochemical oxidation scrubber (PEOS). The key study of this stage is to conduct the performance of oxidation reactor for removing toluene. The results of study on toluene treatment shows that the initial toluene concentration of 2000 ppm is effectively decomposed to attain 90% conversion after 50 minutes in the following conditions: current density 1 mA/cm2; pH 2; a distance of 1 cm between anode and cathode; a ferrous ion dosage of 15 mg/L, an UV radiation wavelength of 254 nm. The reaction rate constant t is 2.9 hr-1 is more than 13 times of other advanced oxidation process , such as UV/H2O2 etc., the reaction of PEOS is differs from conventional Fenton’s method due to not adding ferrous ion(Fe2+) and H2O2 during the treatment process. Thus, the ferrous ion sludge production of PEOS would be less than Fenton’s process.
Therefore, the study developed a set of new air pollution control equipment for photo-electrochemical oxidation combine chemical scrubber technology removing volatile organic compounds. It is based on the electrochemical principle to generate H2O2 from the cathode reduction of oxygen and to add suitable ferrous ion, followed by the generation of hydroxyl radicals (•OH) from H2O2 by a Fenton-like reaction involving a catalyst of UV radiation. The reaction process is different from traditional Fenton method due to don’t need to add ferrous ion and H2O2 , besides sludge from the Photo-electrochemical oxidation would be less. However, the oxidation agent can be recycled, not only decreasing second pollutants but also removing volatile organic compounds from this equipment.
The results of experiments on toluene treatment efficiency by PEOS showed that the average concentration of toluene was approximately 200 ppm, it was effectively decomposed to attain 60% conversion after 180 minutes in the following conditions: current density 1.25 mA/cm2；pH 2; a ferrous ion dosage of 15 mg/L; add inorganic anions, and a UV radiation wavelength of 254 nm.
The results of the practical effect estimation, by using an above-mentioned operation condition to remove toluene for eight hours, it can still maintain average effectively is 51%. Therefore, it proves that is an applied potential equipment. Besides, by measuring to obtain PEOS does generates •OH. With the batch operation system, the •OH production in the UV/H2O2 is more than 1.25 times of this method after 15 seconds, and both produce •OH is almost consistent after 600 seconds. But, UV/H2O2 must add Fe2+ and H2O2 contiguously, just maintain the oxidizing ability, however this method only needs to supply electric current contiguously to keep it on.
In addition to removing efficiency, the study also analyzes the intermediate of toluene. The results detection responds 30 minutes appears that it include butane, ethyl benzene, o-xylene, p-xylene, cyclopropane and phenol etc., among p-xylene is the most. However, respond to 60 minutes almost have not other intermediates and already transfer the CO2 or H2O. Therefore, it shows that the PEOS does reduce the toxicity of the pollutants. This method didn''t add Fe2+ and H2O2 contiguously, so that mainly operation cost are electricity charges, the operation cost were NT$ 8/(Kg waste gas). It has competitive advantages and operates convenient than other air pollution control equipments.
The study developed a set of practical and operated convenient of pollution control equipment. After trying to increase oxidizing ability and feasibility. The result of the study will provide design and operational parameters to the industrial for removing VOCs and odors.
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