| 摘要: | 甲苯 （Toluene）的毒害性為急毒性，對人體有著相當高的危害性，且汽油中也含有甲苯的成分，因儲油槽漏油事件汙染土壤，因此對汙染物的去除為刻不容緩的。本實驗係以臭氧處理砂中的甲苯，藉以比較與氮氣去除的效果。實驗設計是利用管柱砂實驗來模擬不飽和層土壤，通以氮氣及氧氣，並以不同的氣體流量（200 ml/min、100 ml/minr及50 ml/min）以及不同含水率的砂（4%及8%）、添加入濃度為99.7%的甲苯，劑量分別為（0.5 ml、1 ml、2 ml及4 ml）、不同的砂粒徑（0.125~0.375 mm及0.475~1 mm），對臭氧處理甲苯的效率做討論之。在氮氣與臭氧的200 ml/min流量實驗組中，以臭氧通入氣體的實驗組，管柱口甲苯濃度可由在90 PV時測得的18 ppm下降到200 PV時測到的1 ppm以下的濃度，甚至無法檢出；反觀以氮氣通入氣體的實驗組，管柱口甲苯的濃度只能由在90 PV測得的22 ppm下降到200 PV測得的7 ppm。故臭氧進行處理甲苯的實驗是比用氮氣更為快速有效率的。其中PV（Pore Volumes）又稱孔隙體積，一個PV代表氣體在管柱中置換一次。
而在通以不同流量的臭氧氣體實驗組中，管柱口甲苯濃度在分別由80 PV左右時18 ppm、21 ppm及17 ppm降至在200 PV時的無法檢出(N.D.)、1.5 ppm及4 ppm，可得知流量較大可以使管柱口之甲苯濃度最快降低至無法檢出(N.D.)。而在通以200 ml/min流量的臭氧，以不同砂粒徑實驗組中，管柱出口濃度分別由在50 PV測得的6 ppm、18 ppm下降至在200 PV的2.4 ppm、無法檢出(N.D.)，可得知以粒徑較大可以使管柱口之甲苯濃度最快降低至無法檢出(N.D.)。而在砂含水率實驗組中，8%含水率實驗組管柱出口濃度在100 PV時測得為18 ppm而在200 PV時下降為無法檢出(N.D.)，但4%含水率實驗組管柱出口濃度在250 PV時測得為14 ppm而在800 PV時下降為4 ppm，可得知含水率較高可以使管柱口之甲苯濃度最快降低至無法檢出(N.D.)。
關鍵詞：甲苯、臭氧、不飽和層土壤、孔隙體積
Toluene, a major constituent in gasoline, is toxic and harmful to human. It could contaminate soils when gasoline leaks from its storage tank. The objective of this research is to evaluate the removal efficiency of ozone venting in treating toluene-contaminated soils. Experiments were conducted at three different flow rates (i.e., 200 ml/min, 100 ml/min, 50 ml/min), tow different water saturations (i.e., 4%, 8%), three different toluene volumes (i.e., 0.5 ml, 1 ml, 2 ml, 4 ml) , and two different soil particle sizes ( 0.125~0.375 mm, 0.475~1 mm). When nitrogen gas was controlled at 200 mL/min, toluene concentration dropped to 18 ppm within 90 pore volumes to 1 ppm within 200 pore volumes. On the other hand, when ozone gas was controlled at 200 mL/min, toluene concentration dropped from 7 ppm within 200 pore volumes to 22 ppm within 90 pore volumes. This proves that ozone gas is more efficient than nitrogen gas in removing toluene. As different flow rates (i.e., 200 ml/min, 100 ml/min, 50 ml/min) of ozone were applied, it was found that the flow rate of 200 mL/min has the highest removal efficiency. Also it was found that at the particle size range of 0.475~1 mm, its removal efficiency is better than at 0.125~0.375 mm. Finally, it was found that at a higher saturation of 8% the removal efficiency was greater than at a lower saturation of 4%.
Keyword: Toluene, Ozone, unsaturated layer of soil, PV |
