利用觸媒提昇電動力法處理受BTEX污染土壤效率之研究

Using Catalyst to Improve Electrokinetic Efficiency in Soil BTEX Remediation

薩支高(Jy-Gau Sah) ； 蔡在唐(Tzai-Tang Tsai)

《臺灣農業化學與食品科學》 43卷4期 (2005/08) Pp. 304-312

https://doi.org/10.6578/TJACFS.2005.039

摘要

台灣地區儲油槽總數已逾五千座，部分油槽站齡達20年，若地下油槽鏽蝕使油品外洩可能會污染土壤。電動力法處理有機污染場址是經濟及技術可行之現地整治技術之一。BTEX（苯、甲苯、乙苯及二甲苯）則是土壤汽油污染重要監測指標項目之一。本研究選用觸媒為鈦棒及鐵網電極在不同電解液中腐蝕形成之二氧化鈦及無定形鐵，配合焦耳效應熱脫附現象提昇電動力法復育受汽油污染紅壤之處理效率。結果發現，經電壓40V通電21天後土壤中BTEX殘留率可減低至10% C/Co以下，BTEX實際累積削減率約50至60%（包括焦耳效應及觸媒作用影響，不含自然衰減率37.7%），其效果依序為鈦棒電極組（以0.1M NaCl為電解液）＞鐵網電極組（以0.1 M NaCl為電解液）＞鈦棒電極組（以蒸餾水為電解液）＞鐵網電極組（以蒸餾水為電解液）。經與石墨棒電極對照組比較發現，鈦棒及鐵網腐蝕產生之觸媒經通電21天後，分別可使土壤BTEX累積削減率升高8.85%及4.87%。印證試驗發現鈦棒在土壤中腐蝕產生之白色粉末經X-ray鑑定下確為二氧化鈦；另添加2.5%高純度二氧化鈦及鐵粉在通電13天(40V)後即能提昇BTEX削減效率約15.3%及12.7%，且由照光試驗也證實激發二氧化鈦表面進行催化效應能量主要來自電能而非光能。受到反應時間限制在通電後並未發現有中間分解產物，但因水反應形成之OH理論上應可與供電子官能基進行鄰位(ortho)及對位(para)取代反應，而使BTEX降解成醇類甚至為二氧化碳，故焦耳效應熱脫附現象及取代降解反應對BTEX累積削減率影響皆應是存在的。

關鍵字

觸媒 ； 電動力法 ； BTEX苯、甲苯、乙苯及二甲苯 ； 土壤污染

並列摘要

There are more than five thousand oil tanks in Taiwan and some of them had been used for more than 20 years. Oil leaks from rusted underground tanks may pollute soil and groundwater. BTEX is an important pollution indexes selected to identify gasoline pollution in soil and water. The electrokinetic (EK) process is developed as a highly cost-effective and feasible in-situ technology for soil remediation. We selected TiO2 and iron as catalysts that may release from Ti rods and iron web electrodes during the soil EK process. Accompany with Joule thermal desorption effect, such catalysts were found to improve the efficiency on soil's gasoline EK remediation. After 21 days of EK process with 40 V DC, remaining BTEX in soils were found low to less than 10% C/Co (including 37.7% of natural degradation). The complete degradation rates of BTEX in different experiment sets were listed as follows : using Ti rods as electrodes and 0.1 M NaCl as conductor ＞ using iron web as electrodes and 0.1 M NaCl as conductor ＞ using Ti rods as electrodes and distilled water as conductor ＞ using iron web as electrodes and distilled water as conductor Comparing with the contrast set using graphite as electrode, soil BTEX degradation rates of using Ti electrode or iron web as electrodes were 8.85% or 4.87% higher X-ray detection had confirmed the white power appeared in soil after EK process is TiO2 that was released from Ti electrode. Experiment sets that spiking pure TiO2 or iron powder into soil will raise 15.3 or 12.7% of the EK efficiencies related to the contrast. A lighting experiment also confirmed that lighting did not induce the surface catalyst reaction. Electricity supplies the energy to raise EK efficiency. Although other side-products were not detected in soil in this short time experiment, ortho-and para-replacement might occurred during a longer EK process as our previously soil diesel EK study had found. Both of the Joule thermal effect and catalyst replacement reaction may have contributed to EK degradation of BTEX in soil.

並列關鍵字

Catalyst ； Electrokinetic ； BTEX Benzene, Toluene, Ethylbenzene and Xylenes ； Soil contamination