| Summary: | 碩士 === 國立屏東科技大學 === 環境工程與科學系 === 91 === Thermal treatments always play an important role in off-site soil remediation technologies, especially for the volatile and semi-volatile organic contaminants high concentration in localized pollution. However, there are still several restrictions in thermal treatment in practice. Microwave heating treatment not only has advantages of saving energy, saving time, and being environmentally friendly, but solving the problems that traditional thermal treatment meets. It is expectable microwave would be a powerful technique in the future.
Glyphosate, (N-(phosphonomethyl) glycine) is the widely used herbicide we use today. This paper shows the result of different ten soil series heated by microwave and trying to find out the reasons influence the heating temperature. Afterwards, we added glyphosate into soils to imitate the contamination in high concentration and heated by microwave. Afetr shaking extraction of samples, use GC-MSD to analyze and get the removal efficiency. Finally we used solvent to absorb the exhaust gas for residue glyphosate or other toxic derivatives in it. The result shows there are two types of heating cuves: Soil series of Wukueiliao, Erhshui, Changbin, Taikang, Xiuyou can be heating over 1000℃ easily by microwave power without adding active carbon. Soil series of Erhshui, Taikang, Xiuyou can reach 1000℃ within 5 minutes rapidly and show much better efficiency than the traditional heating. Other soil series such as Chnagchung, Hsiachung, Tunghaifeng, Fangliao, Laopi can be heated slowly and reach the temperature from 200℃ to 600℃ and get over 1000℃ when the volume ratio of soil to the adding carbon is 80 to 20. Except for Hsiuyou series, the content of crystalline iron oxide of soil series heated easily are all over 15g/kg while the content of quartz of them are the least, so it is possible there is some connection between the heating temperature and content of quartz and crystalline iron. However Hsiuyou series is an exception and it could be the reason Hsiuyou series is the clay or the heterogeneity of the soil.
The DREs (Destruction and removal efficiency) of glyphosate of all soil series for microwave 40 minutes exceed 99 % except for 96.9 % of Erhshui Series, 98.2 % of Tunghaifeng series and 98.6 % of Hsiachung Series. The DRE of Laopi and Fangliao series could even reach 100 % and exhibited the treatment of microwave heating is fast and powerful.
There is no any contaminant in the exhaust gas observed in methyl alcohol absorbent after microwave, the possible reason is glyphosate was decomposed in to other metabolites directly in soil matrix and not desorbed into the air. There are less di-(2-ethyl hexyl)phthalate (DEHP) in the blanks and exhaust gas of samples absorbed by water, so it is not necessary to dispose the exhaust gas in further application.
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