| Summary: | 碩士 === 國立高雄第一科技大學 === 環境與安全衛生工程所 === 98 === The annual production of ethylene reaches 110-120 million tons in recent years, making it the major petrochemical product in the whole world. Ethylene is the raw material for plastic production when chlorine is added to form 1,2-dichloroethane and then vinyl chloride monomer (VCM) that has an annual production of 25-30 million tons. During the VCM manufacturing process, the contamination of chloroehanes and chloroethylenes are commonly detected, and due to its massive production such contamination has a great impact to the adjacent areas as well as the environment.
Cleanup alternatives of chlorinated ethanes and ethylenes include chemical oxidation, biological treatment, and iron reduction means. In our previous patent awarded studies, the results showed that bio-mimicked organo-metallic catalysts degraded many cyclic, toxic chemicals, and it was interesting to know whether those catalysts degraded non-cyclic chemicals like chlorinated ethanes and ethylenes, too. Thus, the objectives of this study include: (1) to determine the most applicable metallic catalyst(s) in treating the target compounds in soil and in liquid, (2) to explore the optimal dosages of oxidant and catalyst(s) and its degradation kinetics of target compounds, and (3) to investigate the feasibility of using a two-stage treatment (i.e., chemical followed by biological mean) while remedying the target compounds. Artificial prepared 1,000 ppm contaminated liquid and soil were treated by various metallic complexes as catalyst and peroxide as oxidant to conclude the objectives.
After screening 6 metal ions, 3 chetaltors and a total of 20 metallic complexes, EDTA and Fe2+ were deemed as feasible chetaltors and metallic ion, respectively, for treating chloroethanes- and chloroethylenes-contaninated media. In soil, uses of 54.1 μmole EDTA and 54.0 μmole Fe2+ per 2-gram soil, along with 4.41mmole H2O2, resulted in average 46% chloroethanes and 32% of chloroethylenes degradation. In liquid, uses of 9.0 mM EDTA and 9.0 mM Fe2+, along with 0.49 mM H2O2, resulted in average 32% chloroethanes and 58% of chloroethylenes degradation. Oxidation of chloroethanes and chloroethylenes was limited at certain extent. Raise initial H2O2 dose higher than 1.47 mmole per 2-gram soil and 0.74 mM in treating soil and liquid respectively, showed little improvement in pollutants degradation. The soil/liquid degradation coefficients (θ1) were generally much larger, the degraded pollutants (θ2) much more, and the remained pollutants (θ3) much smaller than the blank ones. These results of parameter estimation agreed with the observations. Yet, due to the high volatilization of the most pollutants, the model failed to fit the tail-end observations. The %pollutant degradation data depicted that most oxidation occurred with 4 hours of reaction. The studied treatment alternative degraded rather efficient while treating the target pollutants, yet some reactions stopped without complete degradation and the reason remained unclear. In the two stage treatment of chloroethane and chloroethylenes over time, the results of both soil and liquid treatments looked similar. In the aerobic treatment, volatilization was the dominant factor that resulted in the disappearance of targeted pollutants. In the anaerobic treatment, biodegradation of the target pollutants observed, yet the extent of degradation was limited.
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