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  • 學位論文

轉爐石、光化學及電化學方式催化費頓反應以分解水中有機污染物

Application of BOF Slag/Photochemistry/Electrochemistry on the Degradation of Aquatic Organic Pollutants via Fenton Reaction

指導教授 : 張慶源

摘要


過氧化氫與二價鐵離子之混合液稱為Fenton 試劑,過氧化氫藉由二價鐵離子催化後,其所產生的氫氧自由基,具有很強的氧化能力,對有機物的降解及礦化具有良好的效率。本論文擬利用轉爐石、電化學及光化學等三種方式啟動費頓反應,以分別探討其對有機物的分解效率。 轉爐石為煉鋼過程的副產物,其成份組成中,FeO含量達5∼20%,總鐵含量可達15∼30%,若能利用轉爐石中豐富之鐵含量,以應用於催化產生費頓反應來分解有機污染物,可為轉爐石之資源化利用,提供一新的用途。本論文嚐試利用轉爐石所啟動的費頓反應以礦化水溶液中的聚乙烯醇,所得到的結果如下:1. 由轉爐石催化以礦化PEG,主要係藉由轉爐石中溶出之進行同相催化反應造成。2.H2O2、轉爐石添加量分別為3.98 × 10-4 mole min-1 L-1及15 g L-1,在pH = 2時,可對30 g L-1的PEG達到75.5%的最佳礦化效率,在此實驗條件下對Fe2+之莫耳比值為13.5。3. 轉爐石催化以礦化PEG的動力學模式可以1階的動力學方程式加以描述。 光費頓反應為將費頓反應與光化學加以結合,藉由適當波長的紫外光線照射下,水溶液中的可被還原成,故傳統的費頓反應藉由光化學的加入,只需於反應初期添加一定量的鐵離子後,便可藉由光化學反應持續產生亞鐵離子,而且產生過程中亦伴隨著的產生,對費頓反應礦化有機物的效益亦具有提升的效應。本論文嚐試利用光費頓反應以礦化水溶液中的鄰苯二甲酸二丁酯,所得到的結果如下:1. 於波長為312 nm、光強度為120μWcm-2的紫外光照射下,當H2O2添加速率為4.74 × 10-5 mol min-1 L-1,Fe3+的起始加入量為4.50 × 10-4 mol L-1時,所啟動的光費頓反應於水溶液pH值為3時,可達最佳的礦化效率,其於90分鐘的反應時間,可將5 mg L-1 的DBP達到92.4%的礦化效率。2. 本研究中所使用的光費頓反應對DBP的礦化速率可以二階的反應速率式加以描述。 電費頓反應為費頓反應與電化學的反應系統相結合,利用電化學的方式可將水溶液中的溶氧還原成,還原成,及混合後,即可產生費頓反應,所以於反應系統中只要有溶氧及鐵離子,如此便可於反應系統中藉由電化學的反應,持續產生費頓反應所需的亞鐵離子及雙氧水,如此便可於不外加費頓試劑的情況下,達到對反應溶液中的有機污染物持續進行礦化的目的。本論文嚐試利用電費頓反應以礦化水溶液中的RB5,所得到的結果如下:1. 當EWE = -550 mV、[KNO3] ≧ 0.075N、Fe3+ = 20 mg L-1、pH = 3時,對RB5的分解可得較佳的效率。2. 反應溶液之pH值對電費頓反應的效率影響頗大,溶液之pH值若大於4,電費頓反應便幾乎不具任何氧化效率。3. 電費頓反應分解RB5之動力學屬1階反應動力。4. 電費頓反應亦可由銅離子所啟動,且其氧化效率和鐵離子所啟動之電費頓反應相近。 電費頓反應、光費頓反應及轉爐石-費頓反應等方式對目標有機物(RB5)的礦化效率為:光費頓反應>轉爐石-費頓反應>電費頓反應。電費頓反應幾乎不具礦化RB5的能力,其效率僅能將RB5分解而達到脫色的目的;轉爐石-費頓反應與光費頓反應等兩種方法於反應時間為90分鐘時,均可對RB5產生礦化的效果,若以礦化1克RB5所需的加以表示,可發現轉爐石-費頓反應與光費頓反應其礦化1克RB5分別需要101.5及8.2克的,以的應用效率而言,顯然光費頓反應的礦化優於轉爐石-費頓反應。

並列摘要


The application of the Fenton process to decompose organic pollutants has attracted extensive attention due to its satisfactory success. The Fenton reaction reviews that H2O2 reacts with iron salts, which generates strong oxidizing radicals to decompose the organics. Using different types of Fenton reaction to decompose organic target compounds and studying their efficiency is the main purpose of this research. Basic oxygen furnace slag (BOF slag) is one of the solid wastes resulting from the steel making process containing about 12.5 and 4.5 wt.% of FeO and Fe2O3, respectively. Therefore, BOF slag has high potential to be used in the Fenton process as iron source due to the ion abundant iron-containing property, which can thereby achieve the reuse of the wastes and work toward environmental sustainability. This study evaluated the dissolution behavior of basic oxygen furnace slag (BOF slag) and the performance of H2O2 with BOF slag denoted as H2O2/BOF slag process to degrade polyethylene glycol (PEG) in the aqueous solution. A first-order kinetic model with respect to total organic carbon (TOC) was adopted to represent the mineralization of PEG by H2O2/BOF slag process. The experimental results in this study suggested that dosages with 3.98 × 10-4 mole min-1 L-1 H2O2 and 15 g L-1 BOF slag loading in the solution at pH 2 provided the optimal operation conditions for the mineralization of PEG yielding a 75.5% treatment efficiency at 100 min reaction time. The H2O2/Fe2+ ratio was then determined to be 13.5 : 1. Photo-Fenton reaction initiated by the UV irradiation with H2O2/Fe3+, denoted as UV/H2O2/Fe3+, to decompose di-n-butyl phthalate (DBP) in the aqueous solution. The concentration of total organic carbon (TOC) was chosen as a mineralization index of the decomposition of DBP by the UV/H2O2/Fe3+ process. A second-order kinetic model with respect to TOC was adequately adopted to represent the mineralization of DBP by the UV/H2O2/Fe3+ process. The experimental results of this study suggested that the dosages with 4.74 × 10-5 mol min-1 L-1 H2O2 and initial Fe3+ loading concentration of 4.50 × 10-4 mol L-1 in the solution at pH = 3.0 with 120 μWcm-2 UV (312 nm) provided the optimal operation conditions for the mineralization of DBP (5 mg L-1) yielding a 92.4% mineralization efficiency at 90 min reaction time. In an electro-Fenton reactor, oxygen and Fe3+ were reduced into H2O2 and Fe2+ by applying appropriate working electrode voltage in aqueous solution. Reactive black 5 (RB5) dye was chosen as the target compound to evaluate the efficiency of electro-Fenton reaction in this study. The results revealed that an optimal decoloration efficiency of RB5 (ηRB5) was achieved at the working electrode voltage of –550 mV/(Ag/AgCl), and the ionic strengths of KNO3 and of the solution is 0.1 mol L-1 and 20 mg L-1, respectively. Furthermore, when Fe3+ in the reaction solution was substituted by Cu2+, about the same ηRB5 can also be achieved. A first-order kinetic model was adopted to describe the decoloration of RB5 by the electro-Fenton process. The mineralization efficiency of RB5 used the previous three types of Fenton reaction following the sequence: Photo-Fenton > BOF-Fenton > Electro-Fenton. The Electro-Fenton reaction doesn’t possess the ability to mineralize RB5, it just only can decompose RB5 and achieve decoloration. Both of BOF-Fenton and Photo-Fenton can mineralize RB5, in terms of the quantity of H2O2 to mineralize one gram RB5, BOF-Fenton and Photo-Fenton need 101.5 g and 8.2 g H2O2, respectively. The mineralization efficiency of Photo-Fenton is far better than BOF-Fenton.

參考文獻


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