【摘要】：飲用水水體或水源中存在一類高氧化態(tài)且毒性較強(qiáng)的微量污染物,它們難以被現(xiàn)有的常規(guī)處理或深度處理工藝去除,零價鐵還原是潛在去除技術(shù)之一。本文研究了金屬鐵對四氯化碳(CCl4)、鹵乙酸(HAA9)與溴酸鹽(Br O3-)三類微量污染物的去除特性、影響因素與反應(yīng)機(jī)理,為相關(guān)污染物的去除提供理論依據(jù)及解決方案。填充柱實驗表明,在空床接觸時間(EBCT)為2.5-10 min,反應(yīng)溫度為5-35oC范圍內(nèi),金屬鐵對一氯乙酸(MCAA)的去除率為16.4-81.3%;對CCl4、HAA8和BrO3-的去除率基本接近100%。CCl4、MCAA與二氯乙酸(DCAA)去除過程中鹵素質(zhì)量不守恒,推測是溶解氧(DO)的存在導(dǎo)致金屬鐵對污染物的去除機(jī)制發(fā)生改變。搖瓶實驗表明,當(dāng)溫度為25oC,反應(yīng)時間為2 h時,隨著DO濃度從0增加到12 mg/L,金屬鐵對BrO3-的去除效果不斷下降;對CCl4、MCAA、DCAA與三氯乙酸(TCAA)的去除效果先上升后下降,最佳的DO濃度分別為1.27、1.52、1.52與0.75 mg/L。CCl4、MCAA、DCAA、TCAA與BrO3-的去除率分別為12.1-45.8%、1.25-27.5%、22.4-68.1%、26.0-80.5%與52.5-100%;偽一級反應(yīng)速率常數(shù)分別為0.08-0.29、0.0002-0.16、0.12-0.53、0.18-0.73與0.41-3.91 h-1。金屬鐵去除污染物的步驟包括遷移、擴(kuò)散、吸附與還原過程。金屬鐵顆粒表面的腐蝕產(chǎn)物從外到內(nèi)依次為纖鐵礦、綠鐵銹、磁鐵礦與氧化亞鐵,污染物經(jīng)非導(dǎo)電層(纖鐵礦)擴(kuò)散到導(dǎo)電層內(nèi),隨后被還原。金屬鐵去除CCl4與MCAA的限速步驟為還原過程;去除DCAA與TCAA的限速步驟在DO濃度低于2.59 mg/L時為還原過程,較高時為擴(kuò)散過程;去除Br O3-的限速步驟為傳質(zhì)過程。當(dāng)污染物氧化能力大于氧時,DO的存在對污染物的去除產(chǎn)生抑制作用;反之,在一個較低的DO區(qū)間(0-2 mg/L)內(nèi)可強(qiáng)化污染物的去除效果�；诮饘勹F去除污染物的機(jī)理,本文提出針對不同微量污染物的金屬鐵及其組合去除工藝。金屬鐵填充柱(EBCT為10 min)對Br O3-的去除率基本接近100%;吹脫與金屬鐵組合工藝(氣水比為2、曝氣時間為10 min、EBCT為2.5 min)對CCl4的去除率達(dá)98%;金屬鐵與生物活性炭組合工藝(EBCT分別為2.5與10 min)對HAA9的去除率達(dá)99%。
[Abstract]:There are a class of highly oxidized and highly toxic trace pollutants in drinking water or water source which are difficult to be removed by conventional or advanced treatment processes. Zero valent iron reduction is one of the potential removal techniques. In this paper, the removal characteristics, influencing factors and reaction mechanism of three kinds of trace pollutants of carbon tetrachloride (CCl4), haloacetic acid (HAA9) and bromate (Br O 3-) by metal iron were studied, which provided theoretical basis and solution for the removal of related pollutants. The packed column experiment showed that the removal rate of (MCAA) by metal iron was 16.4-81.3 when the empty bed contact time (EBCT) was 2.5-10 min, and the reaction temperature was 5-35oC. The removal rate of CCl4,HAA8 and BrO3- is close to 100%. The mass of halogen is not conserved during the removal of CCl4MCAA and dichloroacetic acid (DCAA). It is inferred that the existence of dissolved oxygen (DO) leads to the change of the removal mechanism of pollutants by iron metal. The results of shaking flask test showed that when the temperature was 25oC and the reaction time was 2 h, the removal efficiency of BrO3- was decreased with the increase of DO concentration from 0 to 12 mg/L,. The removal efficiency of CCl4,MCAA,DCAA and trichloroacetate (TCAA) increased first and then decreased. The best DO concentration was 1.27o1.52 mg/L.CCl4,MCAA,DCAA,TCAA and 0.75 mg/L.CCl4,MCAA,DCAA,TCAA and BrO3- removal efficiency were 12.1-45.8, respectively. 1.25-27.5: 22.4-68.1% 26.0-80.5% and 52.5-100%; The pseudo-first-order reaction rate constants are 0.08-0.29, 0.0002-0.16, 0.12-0.53, 0.18-0.73 and 0.41-3.91 h-1, respectively. Removal of contaminants by metal iron involves migration, diffusion, adsorption and reduction. The corrosion products on the surface of metallic iron particles are followed by fiberite, green rust, magnetite and ferrous oxide, and the contaminants are diffused through the non-conductive layer (pyrite) into the conductive layer, and then reduced. The limiting step of removing CCl4 and MCAA is reduction process, the limiting step of removing DCAA and TCAA is reduction process when the concentration of DO is lower than 2.59 mg/L, and the limiting step of removing Br O _ 3- is mass transfer process when the concentration of DO is lower than 2.59 mg/L. When the oxidation capacity of pollutants is greater than that of oxygen, the presence of DO can inhibit the removal of pollutants, whereas in a lower DO range (0-2 mg/L), the removal efficiency of pollutants can be enhanced. Based on the mechanism of removal of pollutants by metal iron, the removal process of metal iron and its combination for different trace pollutants is proposed in this paper. The removal rate of Br O _ 3- by metal iron filled column (EBCT = 10 min) was close to 100, and the removal rate of CCl4 by blowing off with metal iron (air-water ratio was 2, aeration time was 10 min,EBCT, 2.5 min) was 98%. The removal rate of HAA9 by the combined process of metal iron and biological activated carbon (EBCT = 2. 5 and 10 min) was 99%.
【學(xué)位授予單位】：清華大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TU991.2

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