利用臭氧與氟化烴溶劑去除水溶液中2,4-二氯酚之研究

Abstract

臭氧因其具有強大的氧化能力,而經常被應用於處理生物難以分解的有機 廢水程序.不過常受限於臭氧於水中的溶解度及製造成本的昂貴而一直無 法廣泛應用於廢水處理程序中.本研究即採用一種新式的二相式反應系統, 其特性為除了一般的水相外,另外提供了一種可以重複使用,具有高臭氧溶 解度且不會與臭氧發生反應的氟化烴溶劑.本二相式反應系統的主要理論 基礎是利用此氟化烴溶劑對有機物的選擇性萃取以及臭氧的氧化作用同時 進行,促使整個反應系統的反應能持續進行.本研究即利用半批式實驗裝 置,對臭氧與2,4-二氯酚在本二相式反應系統中的反應作一初步的研究探 討.實驗過程中採用田口式L18直交表法,推估出本實驗系統分解2,4-二氯 酚的最佳因子組合條件為: 攪拌動力: 1000 rpm, 氣體流率 :800 ml/ min, 臭氧產量: 200 Volt, 氯酚濃度 :100 mg/L,pH 值 :7.5, 離子強 度:0.01M, 溫度:20℃.推定值的有效範圍為(108.93 -67.87)%.同時亦發 現實驗過程中反應的前段應屬於臭氧質傳速率控制,後段則為臭氧反應速 率控制階段.單因子實驗主要是根據前面的L18直交表實驗,獲得對本二相 式反應系統中貢獻率較大的因子如:氣體流率,臭氧量,氯酚濃度等因子為 基礎.探討其個別的反應動力常數值(Kobs),臭氧需求量(O3 m mole 2,4-DCP m mole),二氧化碳生成量,礦化率及氯離子的生成等.實驗結果指 出:於最佳條件下反應動力常數 Kobs=0.145 1/min,氧化mole 之 2,4-二 氯酚所需的臭氧量為 5.24 m mole,二氧化碳生成量為 34.84mg,礦化率 為 21.5%,氯離子生成率為 88%. Ozone, due to its powerful oxidation potential, is considered to be an alternative for the refractory compounds. It has been limited hower, because of ozone's low solubility in water and high charge of equipment, so it can't be extensively in wastewater process. Two-phase ozonation system is a new method for the removel of organic pollutants from wastewater. This system consists of a chemical extraction from the aqueous phase accompanied by oxidation by ozone in both the solvent and aqueous phase. The experiments performed in this study, were preliminary investigations into this semibatch system. In this study a Taguchi Styled design of experiment is selected to identify the significant factors and establish the optimal combination of process parameters of the novel method. The results indicate that the optimal combination represents as follow: agitated level( 1000 rpm), flow rate of the feed gas( 800 ml/min), ozone production rate( 200 Volt), 2,4-dichlorphenol concentraction( 100 mg/L), pH value( 7.5 ), Ion strength( 0.01 M), reaction temperature( 20 ℃). However, it is suggested that at the begin of reaction, the ozone mass- transfer controlled mechanism is predominant, then we find the limit rate mechanism that is changed controll by ozone-reaction- rate . Secondly, under the optimal condition, the pseudo-first order kinetic rate constant is 0.145 l/min, the dosage of ozone for the decomposition of 2,4-dichlorphenol is 5.24 m mole O3/m mole 2,4-dichlorphenol, the mineralization of 2,4-dichlorphenol is about 21.5% and the production of the chlorine ion is 88%.