請用此 Handle URI 來引用此文件: http://hdl.handle.net/11455/5079
標題: 不同操作液對於電動力處理受鎘污染土壤效果之探討
Electrokinetic remediation of cadmium-contaminated soil using different electrolyte solutions
作者: 賴冠君
LAI, KUAN-CHUN
關鍵字: electrokinetic electrokinetic
電動力復育
pH gradient
electrolyte solutions
heavy metals
pH梯度
電解液
重金屬
出版社: 環境工程學系
摘要: 在電動力系統中,正負極會因水電解反應而產生酸鹼梯度而影響去除效果及降低電流效率,故pH值的變化在系統中所造成的影響十分關鍵。因此,本研究利用六種不同之操作液進行電動力實驗,以期能減少或避免電動力反應進行中,酸鹼值梯度的增加,進而提高其去除效率。 本實驗之土樣為高嶺土及石英砂的混合土,將此兩種土樣以含砂量0%、20%和40%混合,並加入500 mg/kg之鎘溶液模擬受污染土樣。實驗之電場強度為1 V/cm,電極為石墨碳棒。反應時間約7天或14天,處理過程中,量測電流變化、操作液pH值和電滲透流,並分析重金屬濃度和其在土中之鍵結型態。 實驗結果顯示,使用自來水當作電解液,在純高嶺土土樣、含砂量20%及含砂量40%之土樣,鎘之去除效率僅為5%、8%和12%。當系統操作液為1M的醋酸時,去除效率分別為60.67%、76.58%和79.35%。因整個土樣都處於低pH值的狀態下,故鎘以離子狀態存在而較易移出。當使用0.1 M EDTA操作液時,三種土樣之去除效率分別為66.43%、71.83%和74.90%。改為鹽類操作液NaCl時,鎘在土中之殘留率是很高的,去除效率分別降為12.37%、27.36%和30.02%。然而,使用氯化鈉操作液,可以有效控制系統中之pH值,使其介於較佳之範圍。吾人使用0.1 M HCl操作液時,去除效率分別為58.75%、62.57%和83.17%,因其為強酸故HCl也能有效的降低土壤試體之pH值。相對地,使用強鹼操作液NaOH時,去除效率分別為27.84%、38.95%和37.51%。其所產生之氫氧根離子會貫穿土壤試體,而使土樣大部分都處於鹼性的範圍,故使重金屬較易產生沉澱而累積在土樣中。使用醋酸與EDTA之去除率最高,HCl之去除率亦相當不錯可高達80.17%。NaCl與NaOH之去除率則在40%以下。而自來水僅達12%。 另外,實驗中鎘的鍵結型態主要是以鍵結能力弱的可交換態、碳酸鹽結合態和鐵錳氧化態存在,有機態及殘留態比例較少。在本研究中,不論使用何種操作液,鍵結能力較弱之前三種型態之去除效果都很好,然而,鍵結能力較強的有機態和殘留態,較不受電動力影響。由此可知,電動力的處理效果主要作用在鍵結能力弱的型態上。
Electrokinetic process is an effective and efficient approach to remove pollutants from a soil. This research is to evaluate different types of operation fluid which will remove the most of cadmium added in kaolinite. An electrokinetic simulator has been designed to conduct the experiments under six electrolytes. By using these electyolytes, we hope that the pH gradient effect will be minimized, and thus an increase in efficiency is predicted. Tests were conducted on a kaolin and two mixtures with sand which were spiked with Cd(II) in concentrations of 500 mg/kg, under the application of a voltage gradient of 1.0 VDC/cm. The distribution of heavy metals in the soils after test will be sectioned, then to be analyzed according to their chemical forms. The electrolyte solutions applied were H2O, 1.0M acetic acid, 0.1M EDTA, 0.1M NaCl, 0.1M HCl, and 0.1M NaOH. The results showed that 5-12% of the Cd(II) was removed from the soils , when the tap water was used. However, the removal was 60.67%, 76.58% and 79.35%, respectively, when using 1.0M acetic acid. When 0.1M EDTA was used as the purging solution in the anode, the removal ratio of cadmium increased to 66.43%, 71.83%, and 74.90%, respectively. But, the removal ratio decreased to 12.37%, 27.36% and 30.02%, respectively, when using 0.1M NaCl. Using 0.1M HCl as the purging solution in the anode, 58.75%, 62.57%, and 83.17% of the initial Cd was removed. When 0.1M NaOH was used as the purging solution in the anode, the removal of cadmium was decreased to 27.84%, 38.95%, and 37.51%, respectively. In conclusion, this research discovered that the six eletrokinetic electrolytes affect the removal efficiency of the designated heavy metals to a large degree. Most of the cadmium removed was in the form of exchangeable, carbonate and Fe-Mn oxides.
URI: http://hdl.handle.net/11455/5079
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