【摘要】：β-N-甲氨基-L-丙氨酸(BMAA)是一種新近發(fā)現(xiàn)的藻毒素,可能是肌萎縮性脊髓側(cè)索硬化癥(ALS)和帕金森癥的重要誘因。有報道稱絕大多數(shù)藍藻能夠分泌該種毒素,并且在世界各地的水體及水產(chǎn)品中均有檢出。當前我國很多地區(qū)水源面臨著嚴重的富營養(yǎng)化問題,其伴生的BMAA問題可能對城鎮(zhèn)居民飲用水安全和身心健康構(gòu)成嚴重的威脅。然而目前有關(guān)BMAA的水處理研究尚鮮見報道,現(xiàn)有水處理工藝能否去除BMAA以及如何安全有效去除BMAA是當前亟待解決的問題,對于提高供水水質(zhì)、保障供水安全有著十分重要的意義。針對上述問題,本研究以凈水廠常規(guī)氧化技術(shù)為基礎(chǔ),研究了典型氧化劑次氯酸鈉和臭氧對于BMAA的氧化效果,考察了氧化劑初始濃度、溫度、pH值等不同條件對BMAA去除效果的影響,同時對次氯酸鈉和臭氧氧化BMAA的氧化產(chǎn)物和氧化路徑進行探究。次氯酸鈉氧化BMAA的研究表明,次氯酸鈉氧化BMAA的反應符合二級反應動力學模型,二級反應動力學常數(shù)為697.6 L·mol-1min-1。溫度越高,次氯酸鈉氧化BMAA反應速率常數(shù)越大,進行Arrhenius和Eyring方程擬合得到反應活化能為16.639kJ/mol,?H*為14.106kJ/mol,?S*為142.250 J/molK。pH值對次氯酸鈉氧化BMAA影響顯著,酸性條件下,次氯酸鈉氧化BMAA的效果最好。臭氧對BMAA的去除主要是臭氧直接氧化作用,反應2分鐘去除率即可達到95%以上。臭氧初始濃度越高,臭氧氧化去除BMAA反應越快,臭氧濃度足夠高時BMAA去除率可達99%,同時一定的臭氧剩余量可保證BMAA的完全去除。不同pH值條件下,臭氧氧化BMAA主要與BMAA在pH值條件下存在形式有關(guān),中性條件下氧化效果最好,反應1分鐘去除率即可達97%。低溫條件有利于臭氧氧化去除BMAA,反應30s低溫條件BMAA去除率比高溫條件高7.3%,側(cè)面驗證臭氧對BMAA的去除主要是臭氧直接氧化作用。次氯酸鈉氧化BMAA過程中,發(fā)現(xiàn)7種氧化產(chǎn)物。他們的質(zhì)核比分別為88(Ⅰ)、153(Ⅰ)、153(Ⅰ)、187(Ⅳ)、187(Ⅴ)、108(Ⅵ)和71(Ⅶ)。次氯酸鈉對BMAA的氧化路徑主要包括(1)氯的取代,產(chǎn)生質(zhì)核比為153(Ⅰ)、153(Ⅰ)、187(Ⅳ)和187(Ⅴ)的氯代物;(2)脫羧基,產(chǎn)生質(zhì)核比為108(Ⅵ)和71(Ⅶ)的產(chǎn)物;(3)N-C鍵氧化斷裂,產(chǎn)生質(zhì)核比為88(Ⅰ)的產(chǎn)物。臭氧氧化BMAA過程中發(fā)現(xiàn)3種產(chǎn)物。他們的質(zhì)核比分別為105(Ⅰ)、91(Ⅱ)、88(Ⅲ),臭氧對BMAA的氧化路徑主要是C-N鍵的氧化斷裂,產(chǎn)生質(zhì)核比為105(Ⅰ)、91(Ⅱ)、88(Ⅲ)的氧化產(chǎn)物。本研究考察了兩種氧化劑在不同條件下對BMAA的去除效能,為飲用水中BMAA的去除提供了理論基礎(chǔ)。綜合對比發(fā)現(xiàn)臭氧對BMAA氧化去除效果明顯優(yōu)于次氯酸鈉,反應迅速、去除效果好且礦化度高,更適用于去除BMAA。
[Abstract]:尾 -N-methylamino-L-alanine (BMAA) is a newly discovered alga toxin, which may be an important cause of (ALS) and Parkinson's disease in amyotrophic lateral sclerosis. Most cyanobacteria are reported to secrete the toxin and are detected in water and aquatic products around the world. At present, many water sources in China are facing serious eutrophication problems, and the associated BMAA problem may pose a serious threat to the safety of drinking water and the physical and mental health of urban residents. However, there are few reports on water treatment of BMAA. Whether the existing water treatment process can remove BMAA and how to remove BMAA safely and effectively is an urgent problem to be solved, and it is necessary to improve the quality of water supply. It is of great significance to ensure the safety of water supply. To solve the above problems, the oxidation effect of typical oxidant sodium hypochlorite and ozone on BMAA was studied on the basis of conventional oxidation technology in water purification plant, and the initial concentration of oxidant was investigated. The effects of temperature and pH value on the removal efficiency of BMAA were investigated. The oxidation products and oxidation paths of BMAA by sodium hypochlorite and ozone oxidation were investigated. The study on the oxidation of BMAA by sodium hypochlorite shows that the reaction of BMAA oxidized by sodium hypochlorite accords with the second-order reaction kinetic model, and the kinetic constant of the second-order reaction is 697.6 L mol -1 min -1. The higher the temperature, the greater the rate constant of BMAA oxidation of sodium hypochlorite. By fitting the Arrhenius and Eyring equation, the activation energy of the reaction is 16.639kJ / mol 路mol ~ (-1) H * = 14.106kJ / mol ~ (-1) S *, and the value of 142.250 J/molK.pH has a significant effect on the oxidation of BMAA by sodium hypochlorite, and the effect of BMAA oxidation by sodium hypochlorite is the best under acidic conditions. The removal of BMAA by ozone was mainly caused by direct ozonation, and the removal rate of BMAA in 2 minutes was over 95%. The higher the initial concentration of ozone, the faster the reaction of BMAA removal by ozone oxidation. When the ozone concentration is high enough, the removal rate of BMAA can reach 99%, and a certain amount of ozone surplus can ensure the complete removal of BMAA. Under different pH conditions, ozone oxidation of BMAA was mainly related to the existence of BMAA at pH value. The oxidation effect was best under neutral conditions, and the removal rate of BMAA reached 97% in 1 minute reaction. The removal rate of BMAA at low temperature for 30s was higher than that at high temperature. It was verified that the removal of BMAA by ozone was mainly direct ozonation. Seven oxidation products were found during the oxidation of BMAA by sodium hypochlorite. Their ratio of plasma to nucleus is 88 (鈪，

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