低揮發性化合物亨利常數量測方法之研究; A method to measure Henry’s law constants of low volatile compounds

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题名:	低揮發性化合物亨利常數量測方法之研究;A method to measure Henry’s law constants of low volatile compounds
作者:	陳俊成;Chun-Cheng Chen
贡献者:	環境工程研究所
关键词:	揮發;亨利常數;表面損失揮發模式;擾流;風速;surface depletion rate-limiting model;volatilization;liquid stirring;wind speed;Henry’s law constant
日期:	2005-07-04
上传时间:	2009-09-21 12:16:33 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	本研究主要內容在於建立新的量測方法，用以估算低揮發性化合物之亨利常數值。傳統上測量低揮發性化合物之亨利常數值常使用氣提法或者是密閉系統法，然而在使用上述方法估算亨利常數時，會有化合物吸附、平衡時間過長和實驗設備要求高等問題存在。為了克服上述問題，本研究以半密閉系統之模廠，在不同擾流條件下，測量低揮發性有機化合物揮發速率常數，最後利用表面損失揮發模式(surface depletion rate-limiting, SDRL)，在氣相參數β已知與擾流常數α假設為一的情形下，求得低揮發性化合物之亨利常數值。藉由文獻值與以模式預測獲得到之亨利常數值來驗證本研究發展之方法所求得亨利常數的準確性。由實驗結果顯示，所選擇有機化合物均能利用一階反應方程式求得揮發速率常數值，所計算之亨利常數值亦都在文獻值的範圍內，且相對於傳統密閉系統來說，本研究所使用的時間較短且容易控制，不過所使用的化合物亨利常數值愈高，高擾流條件的效率愈差。至於本研究求得之結果與蒸氣壓/水溶解度、官能基與鍵結貢獻模式等預測模式推估之值有所差距的原因，應是本研究選用低水溶解度與化學結構式複雜的化合物所導致。與傳統二層膜理論計算之亨利常數值相比較，表面損失揮發模式所求得的亨利常數值相對較低，其原因可能在於質量傳送假設與參考化合物不同所造成。由各模式相互比較之後，以本研究之表面損失揮發模式計算的亨利常數值較具準確性。 The lack of accurate Henry's law constants (H) is one of the major problems on determining fates of organic compounds in the environment. Methods of experimentally determine H can be roughly divided into kinetic and static thermodynamic measurement. It takes more than half month for the traditional static methods to experimentally determining the Henry’s law constants of low volatility organic compounds. Thus, a new approach in this study has been developed to measure the H of low volatility organic compounds（dimensionless < 10-4）. According to the traditional concepts, the volatilization rate constants of low H compounds in aqueous solution have a good correlation with their H values. Thus, the H values of low H compounds （dimensionless < 10-4） were considerably obtained from the kinetic method based on the loss rate of a substance from water. In our previous investigation, the surface depletion rate-limiting model (SDRL) for calculating volatilization rates of low H compounds under gas and liquid turbulence was developed. As a result, the H values of the low H compounds under the gas and liquid turbulence were estimated with the SDRL model. The obtained H values were compared with other approaches including traditional two film theory, vapor pressure /aqueous solubility, bond contribution method and group contribution method. As the H values obtained form the above-mentioned method was compared the literature values, SDRL model shows more accuracy than the other method. It can be concluded that the presented approach is a good way on determining the H values for the low H compounds.
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