水中金屬離子對紫外光催化二氧化鈦分解氯酚類有機物之影響

Abstract

近年來運用高級氧化處理技術，去除水中危害性有機物的研究逐漸盛行，主要是著眼點於傳統的生物處理法，對於具有生物毒性的有機物處理效率甚低，或者會導致處理系統破壞而失常。因此對於有害性的毒性物質皆以物化處理之效率較佳，近年來國內外對於廢水物化處理的研究相當多，其中運用紫外光催化二氧化鈦處理廢水的研究也不少，並且因催化劑可回收再利用或可使用太陽能而具有發展性。 本研究之目的，於金屬離子可能對於光催化二氧化鈦分解有機物的影響加以探討。討論因子為曝氣量、金屬離子濃度、pH值及溫度等，背景因子探討。研究結果顯示錳、鈷離子存在時單氯酚之分解速率趨勢為2-CP>4-CP>3-CP，鎳離子存在時反應分解速率為4-CP>2-CP>3-CP，銅離子存在時有機物的反應分解速率則為3-CP>4-CP>2-CP。依據文獻中所顯示，金屬離子對於光催化二氧化鈦分解有機物所產生之影響，與金屬之氧化還原電位及其吸附特性有關，本研究依此推測，銅離子與鎳離子於反應中對單氯酚的吸附特性與錳、鈷之特性不同，而單氯酚與金屬離子的錯合作用導致反應速率的改變。研究中各種金屬離子對於分解總有機碳的影響，於所試驗的各種單氯酚中均以2-CP的礦化效率較佳， 3-CP與4-C則與存在的金屬種類有關。 光催化二氧化鈦分解2-CP作用中，四種金屬離子所產生的反應，可以用一次方程式表示。除此之外，我們的研究顯示反應速率與金屬離子並沒有明顯的相關，反而是與起始的有機物濃度有密切關聯。在L-H模式及其衍生模式的基礎下，本研究修正了因為有機化合物濃度變化及中間產物所造成的誤差。並且預測出在催化作用的表面反應速率與金屬離子的氧化還原反應有關。

Since conventional biological technologies can only have low treatment efficiencies toward bio-toxic organic wastewater, and sometimes cause the disorder of the treatment system. Studies to using on advanced oxidation processes for removing hazardous organic compounds from wastewaters have become more and more popular. Thus, chemical treatment is generally considered to be one of the highly efficient technologies for treating the hazardous wastewaters. Recently, a large number of studies have focused on employing the chemical processes for wastewater treatment. Among all of these studies, a lot of articles focused on applying UV-illuminated TiO2 suspensions for wastewater treatment. Because the catalyst is recyclable, and also available for existing nature light, this technology has a great potential in the removal of organic pollutants. The main purpose of this study was to investigate the effect of metal ions on the oxidation of organic compounds in a suspended TiO2 system. The studied factors included dissolved oxygen, concentration of metal ions, pH and temperature. Results showed that the degradation rate for 2-CP is higher than that for 4-CP, and 4-CP is higher than 3-CP in the presence of Mn(II) or Co(II). While the degradation rate for 4-CP is higher than 2-CP, and 2-CP is higher than 3-CP in the presence of Ni(II). Degradation rate for 3-CP is higher than 4-CP, and 4-CP is higher than 2-CP in the presence of Cu(II). Several studies have demonstrated that the influence of metal ions in the suspended TiO2 system depended on the redox potentials and adsorption characteristics of the metal ions. This study also revealed that 2-CP was mineralized more completely than other types of monochlorophenols. Moreover, the mineralization efficiencies for 3-CP and 4-CP were dependent of the species of metal ions.