邰 超,張少棟,陰永光,吳浩賢, ,王 靜

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太陽(yáng)光下水中2, 4, 6-三氯酚的光解機(jī)制研究

邰 超1*,張少棟1,陰永光2,吳浩賢1, 2,王 靜1

(1.河南理工大學(xué)資源環(huán)境學(xué)院,河南 焦作 454000；2.中國(guó)科學(xué)院生態(tài)環(huán)境研究中心,環(huán)境化學(xué)與生態(tài)毒理學(xué)國(guó)家重點(diǎn)實(shí)驗(yàn)室,北京 100085)

對(duì)比研究了太陽(yáng)光下2,4,6-三氯酚(2,4,6-TCP)在純水,可溶性有機(jī)質(zhì)(DOM)溶液和實(shí)際地表水中的光解情況.結(jié)果表明, 2,4,6-TCP在純水中主要為直接光解和自敏化光解,涉及的活性物種為單線(xiàn)態(tài)氧;在DOM水溶液中主要為直接光解和敏化光解,涉及的活性物種為單線(xiàn)態(tài)氧和羥基自由基; 2,4,6-TCP在純水,DOM溶液和實(shí)際地表水中的光解速率均隨溶液含氧量的提高而增加.太陽(yáng)光可見(jiàn)區(qū)對(duì)2,4,6-TCP直接光解沒(méi)有貢獻(xiàn),UVA貢獻(xiàn)為72.60%,而當(dāng)有DOM存在時(shí),可見(jiàn)光區(qū)對(duì)2,4,6-TCP的光解貢獻(xiàn)為12.39%,UVA的貢獻(xiàn)為52.73%.2,4,6-TCP在實(shí)際地表水中的光解與在DOM水溶液中的光解類(lèi)似,都表現(xiàn)為通氮抑制光解,通氧促進(jìn)光解,并且光譜貢獻(xiàn)率也十分接近,表明溶解氧和DOM是2,4,6-TCP在地表水中間接光解的主要影響因素.

2,4,6-三氯酚；光解；太陽(yáng)光；自敏化；可溶性有機(jī)質(zhì)

氯酚類(lèi)化合物(CPs)是一類(lèi)典型的生物難降解有機(jī)污染物,具有良好的殺菌和殺蟲(chóng)功效,廣泛用于除草劑,染料,皮革,殺蟲(chóng)劑和木材防腐劑等方面,造成了CPs在各種環(huán)境介質(zhì)中廣泛存在,濃度水平在0.1~20mg/kg之間[1-2].研究表明,CPs大都具有較強(qiáng)的生物累積性和“三致”效應(yīng),部分還具有明顯的內(nèi)分泌干擾效應(yīng),能夠干擾人體甲狀腺素和腎上腺素的正常分泌和作用[3].因此氯酚類(lèi)污染物受到了高度關(guān)注,其中的2,4,6-三氯酚(2,4,6-TCP),2,4-二氯酚(2,4-DCP)和五氯酚(PCP)已被美國(guó),歐盟和我國(guó)列為優(yōu)先控制污染物.

光解是有機(jī)污染物在自然環(huán)境中降解的重要途徑,直接影響有機(jī)污染物的遷移,轉(zhuǎn)化和歸宿[4-8].對(duì)于CPs而言,由于其具有較強(qiáng)的微生物抑制作用,光解行為的研究就顯得更加重要.CPs在地表太陽(yáng)光譜區(qū)間280~400nm具有較強(qiáng)的光吸收,因此地表水中的CPs在太陽(yáng)光的照射下,可以發(fā)生一系列的直接光解和間接光解過(guò)程,直接影響CPs在地表水中的遷移,轉(zhuǎn)化及毒性[9-11].此前國(guó)內(nèi)外學(xué)者已經(jīng)對(duì)CPs的光轉(zhuǎn)化機(jī)理進(jìn)行了較為深入的研究,主要集中在CPs光解的構(gòu)效關(guān)系[12-13],影響因素[14-15]和降解轉(zhuǎn)化產(chǎn)物[16-17]等,反應(yīng)體系多在純水和模擬光源下進(jìn)行,對(duì)實(shí)際的環(huán)境條件考慮較少,并且對(duì)不同環(huán)境條件下CPs光解所涉及到的活性中間物種認(rèn)識(shí)不足.本文以2,4,6-TCP為研究對(duì)象,對(duì)比研究了太陽(yáng)光下2,4,6-三氯酚在純水,模擬水和實(shí)際地表水中的光化學(xué)轉(zhuǎn)化途徑,考察了羥基自由基和單線(xiàn)態(tài)氧捕獲劑,可溶性有機(jī)質(zhì)(DOM),溶解氧(DO)和太陽(yáng)光譜區(qū)間對(duì)2,4,6-三氯酚光化學(xué)轉(zhuǎn)化的影響,以期進(jìn)一步深化對(duì)2,4,6-三氯酚在水體中光解機(jī)理的認(rèn)識(shí),并為含酚廢水的處理提供基礎(chǔ)數(shù)據(jù)參考.

1 材料與方法

1.1 實(shí)驗(yàn)材料

2,4,6-TCP(98%)購(gòu)自Alfa Aesar公司.DOM標(biāo)準(zhǔn)參考物質(zhì)為SRNOM,購(gòu)自國(guó)際腐植酸物質(zhì)協(xié)會(huì)(IHSS,編號(hào)2R101N),C、H、O、N、S的含量(w/w, %)依次為52.47、4.19、42.69、1.10和0.65.乙腈為色譜純,購(gòu)自美國(guó)Tedia公司.迭氮化鈉、二甲基亞砜(DMSO)均為分析純,購(gòu)自北京國(guó)藥集團(tuán).實(shí)際地表水(采自河南理工大學(xué)馨月湖(35°11'15.9684"N, 113°16'4.1802"E),水樣基本理化參數(shù)為:pH 6.8,TOC 313.33 μmol/L,Cl-3.421mmol/L,Cu 3.90μg/L,Mn 5.76μg/L,(亞)硝酸根和鐵未檢出,采用0.45μm微孔濾膜過(guò)濾后待用.濾光膜采用3M晶銳70濾光膜,拆為兩層,其中一層(B層)只能過(guò)濾UVB,另外一層(A層)UVA和UVB全部過(guò)濾,A層和B層濾光膜的吸收光譜見(jiàn)圖1.所有玻璃或石英器皿經(jīng)王水浸泡過(guò)夜后用乙醇清洗,最后再用超純水沖洗并烘干待用.未加說(shuō)明,所用試劑均為分析純,所用溶液均由Millipore-Q超純水配制.

1.2 儀器

高效液相色譜儀(Agilent 1200)配Zorbax SB-C18色譜柱(150mm×4.6mm,5μm);二極管陣列檢測(cè)器(DAD).Milipore超純水系統(tǒng),出水電阻率大于18.3MΩ.定制250mL圓柱形全石英光化學(xué)反應(yīng)器及斜面支架,斜面傾角45度.浙江托普農(nóng)業(yè)氣象檢測(cè)儀配TP-PH-1光量子計(jì),用于記錄太陽(yáng)光通量.

1.3 光照實(shí)驗(yàn)

向250mL石英光化學(xué)反應(yīng)容器中加入200mL 1mmol/L 2,4,6-TCP溶液,根據(jù)實(shí)驗(yàn)需求,分別加入不同濃度DOM、羥基自由基捕獲劑DMSO、單線(xiàn)態(tài)氧捕獲劑NaN3或者進(jìn)行通氮、通氧處理,混勻后密封,置于支架上于樓頂進(jìn)行光照,支架斜面正對(duì)太陽(yáng)光照方向,同時(shí)進(jìn)行暗反應(yīng)控制實(shí)驗(yàn).在進(jìn)行太陽(yáng)光譜區(qū)間影響實(shí)驗(yàn)時(shí),將石英反應(yīng)器用相應(yīng)的濾光膜包裹,以濾去相應(yīng)區(qū)段的太陽(yáng)光.每次光照分2d進(jìn)行,每天8:00~16:00進(jìn)行光照,連續(xù)取樣16h(光照時(shí)間).同時(shí)每15min采用光量子計(jì)記錄太陽(yáng)有效光通量(PAR,E/m2×s),加和后得到累積光通量(E/m2).

1.4 2,4,6-TCP測(cè)定

從光照開(kāi)始計(jì)時(shí),在0、4、8、12、16h進(jìn)行取樣0.5mL,采用超純水定容至5mL,HPLC測(cè)定,根據(jù)峰面積進(jìn)行定量.DAD檢測(cè)波長(zhǎng)220nm;流動(dòng)相為乙腈-純水(60:40,/,用鹽酸調(diào)pH值為3.5),流速1.0mL/min,進(jìn)樣量25μL.

1.5 2,4,6-TCP光降解速率常數(shù)的計(jì)算

在考慮光通量PAR的情況下,水中污染物的光解符合一級(jí)反應(yīng)動(dòng)力學(xué)方程[18-19](式(1)),對(duì)式(1)進(jìn)行積分并整理后,得到式(2).根據(jù)式(2),測(cè)得2,4,6-TCP在取樣時(shí)刻的濃度C和累積光通量,用對(duì)lnC進(jìn)行線(xiàn)性回歸,即可得到2,4,6-TCP的光解速率常數(shù).

式中:為污染物濃度;為污染物的光降解速率常數(shù),m2/E;PAR為光通量,E/(m2×s);為時(shí)刻為時(shí)的累積光通量,E/m2.

2 結(jié)果與討論

2.1 黑暗對(duì)照實(shí)驗(yàn)

表1 黑暗對(duì)照條件下2,4,6-TCP在3種水中濃度隨時(shí)間變化情況(mmol/L) Table 1 Concentration variation of 2,4,6-TCP over time in three different solutions in dark controlled experiments (mmol/L)

注:a:顯著性,置信區(qū)間95%.

考察了避光條件下2,4,6-TCP在純水、20mg/L DOM溶液和實(shí)際地表水中濃度隨時(shí)間的變化情況,并用SPSS進(jìn)行單樣本和獨(dú)立樣本的t檢驗(yàn),結(jié)果如表1所示.從表1可以看出,黑暗條件下2,4,6-TCP在3種水溶液中濃度隨時(shí)間的變化很小,與開(kāi)始光照時(shí)的濃度1mmol/L相比可以忽略(>0.05),并且3種水溶液之間的2,4,6- TCP濃度變化情況沒(méi)有明顯的差異(>0.05).由此說(shuō)明,光照條件下2,4,6-TCP在3種溶液中的濃度變化,不是由于2,4,6-TCP自身的水解或者微生物降解引起的,而是與光照有關(guān).

2.2 DOM濃度對(duì)2,4,6-TCP光解的影響

考察了2,4,6-TCP在純水和不同濃度的DOM溶液中的光解情況,結(jié)果如圖2所示.從圖2可以看出,2,4,6-TCP的光解符合一級(jí)反應(yīng)動(dòng)力學(xué)方程,用累積光通量對(duì)lnCt進(jìn)行線(xiàn)性回歸,相關(guān)系數(shù)2>0.98,所得直線(xiàn)的斜率即為2,4,6-TCP的光解速率常數(shù)(圖2(a)).不同DOM濃度下2,4, 6-TCP的光解速率常數(shù)具有顯著性差異(t檢驗(yàn),<0.01).低濃度的DOM(小于2mg/L)抑制2,4,6- TCP的光解,而較高濃度時(shí)則促進(jìn)2,4,6-TCP的光解,并且當(dāng)DOM的濃度高于2mg/L時(shí),2,4, 6-TCP的光解速率常數(shù)與DOM濃度呈現(xiàn)良好的線(xiàn)性關(guān)系(圖2(b)).

DOM對(duì)污染物光解的抑制或促進(jìn)的雙重作用在其他研究中也有發(fā)現(xiàn).例如DOM對(duì)熒蒽和芘[20]、苯酚[21]、雙酚A[22]、磺胺甲噁唑[23]以及壬基酚[24]的光解,表現(xiàn)為低濃度下促進(jìn)和高濃度下抑制,而對(duì)磺胺二甲基嘧啶[23]的光解影響則呈現(xiàn)低濃度下抑制和高濃度下促進(jìn).產(chǎn)生這種差異的原因與所用光源的光譜區(qū)間、DOM的競(jìng)爭(zhēng)性光吸收、水體成分以及化合物本身的化學(xué)反應(yīng)活性有關(guān).以上4個(gè)方面因素綜合作用的結(jié)果,造成不同濃度DOM對(duì)不同污染物的光解作用不同.

對(duì)于本研究,2,4,6-TCP和DOM光照前后紫外吸收光譜如圖3所示.從圖3可以看出,光照前后2,4,6-TCP在230nm和310nm 的特征吸收均發(fā)生較大的降低,說(shuō)明2,4,6-TCP發(fā)生了降解,并且DOM存在條件下2,4,6-TCP降解明顯加快.2,4,6-TCP在310nm附近存在較強(qiáng)吸收,能夠吸收太陽(yáng)光中相應(yīng)波段的光輻射,發(fā)生直接光解(反應(yīng)式(1)和式(2)).而DOM在此波段也存在較強(qiáng)光吸收,可以和2,4,6-TCP產(chǎn)生競(jìng)爭(zhēng)性光吸收,從而抑制2,4,6-TCP的光解(反應(yīng)式(3),圖2(b));另一方面,DOM也可以發(fā)生光敏化,產(chǎn)生1O2和·OH(反應(yīng)式(3)~(5))[25],其中1O2的產(chǎn)生速率及其穩(wěn)態(tài)濃度隨DOM濃度的增加而線(xiàn)性增加[26],而單線(xiàn)態(tài)氧與2,4,6-TCP又有較高的反應(yīng)速率常數(shù)(1.67′108mol/L×s)[27],因此,較高濃度的DOM會(huì)促進(jìn)2,4,6-TCP的光解,并在DOM的濃度高于2mg/L時(shí),2,4,6-TCP的光解速率常數(shù)與DOM濃度呈現(xiàn)較好的線(xiàn)性關(guān)系(圖2(b)).

TCP*products (2)

DOM*+ O2DOM +1O2(4)

DOM*+ H2ODOM-H· + ·OH (5)

2.31O2和·OH在2,4,6-TCP光解中的作用

為確定1O2和·OH在2,4,6-TCP光解中所起的作用,用NaN3作為1O2和·OH的清除劑,DMSO作為·OH的清除劑,采用清除劑添加的方法,考察了2,4,6-TCP的光解情況,結(jié)果如圖4所示.

從圖4可以看出,第一,當(dāng)DOM存在時(shí),NaN3和DMSO的加入都會(huì)抑制2,4,6-TCP光解,并且抑制作用高于DOM不存在時(shí)的情況,其原因是NaN3和DMSO的加入清除了DOM光敏化所產(chǎn)生的1O2和·OH,抑制了2,4,6-TCP的間接光解,同時(shí)DOM的濾光作用在清除劑不存在時(shí)進(jìn)一步抑制了2,4,6-TCP的直接光解.第二,當(dāng)DOM不存在時(shí),DMSO的加入對(duì)2,4,6-TCP的光解沒(méi)有明顯影響,而NaN3加入則抑制2,4,6-TCP的光解,說(shuō)明2,4,6-TCP的直接光解過(guò)程中隱含了自敏化光解(式(6),式(7)),自敏化過(guò)程中產(chǎn)生的活性物種為1O2,·OH基本不起作用.

污染物自敏化光解現(xiàn)象在其它研究中也有發(fā)現(xiàn),主要集中在抗生素等藥物分子[28],例如四環(huán)素[29-30]、加替沙星[31]和甲砜霉素[32]等.對(duì)4-氯酚在200~600nm光譜區(qū)間純水中的光解也發(fā)現(xiàn)了自敏化光解,主要通過(guò)·OH途徑完成,并且·OH自敏化光解的貢獻(xiàn)高達(dá)82.8%[33],這與本研究的結(jié)果存在較大差異.參照文獻(xiàn)報(bào)道的方法[23,33],計(jì)算了2,4, 6-TCP在不同條件下直接光解、自敏化光解(式6)、1O2途徑光解(式(7))和·OH途徑光解(式8)的光解速率常數(shù)以及貢獻(xiàn)率,結(jié)果如表2所示.

TCP*+ O2TCP +1O2(6)

1O2+ TCPproducts (7)

表2 直接光解和敏化光解對(duì)2,4,6-TCP在純水和DOM水溶液中光解的貢獻(xiàn) Table 2 Contribution of direct photolysis and sensitized photolysis to the photolysis of 2,4,6-TCP

注:a:含自敏化.

從表2可以看出,純水中2,4,6-TCP在太陽(yáng)光下的自敏化光解中·OH幾乎沒(méi)有貢獻(xiàn),即使DOM存在下·OH途徑光解的貢獻(xiàn)也只有9.60%,要遠(yuǎn)小于文獻(xiàn)報(bào)道的4-氯酚自敏化·OH途徑的貢獻(xiàn)率[33],這可能與化合物自身的性質(zhì)以及光源不同有關(guān),短波長(zhǎng)的光照更有利于溶液中·OH的生成[34].當(dāng)DOM存在時(shí),2,4,6-TCP敏化光解的貢獻(xiàn)率由19.02%提高到33.65%,進(jìn)一步說(shuō)明DOM可以通過(guò)光敏化促進(jìn)2,4,6-TCP光解,涉及到的活性物種主要為·OH和1O2(反應(yīng)式7,8).

2.4 通氮通氧對(duì)2,4,6-TCP光解的影響

水體中光敏化產(chǎn)生的·OH和1O2直接來(lái)源于溶解氧.為進(jìn)一步明確光敏化作用對(duì)2,4,6-TCP光解的貢獻(xiàn),考察了通氮通氧對(duì)2,4,6-TCP光解的影響,結(jié)果如圖5所示.無(wú)論DOM存在與否,通氮抑制2,4,6-TCP的光解,而通氧則促進(jìn)其光解.通氮條件下,DOM的存在會(huì)抑制2,4,6-TCP的光解,原因是DOM與2,4,6-TCP競(jìng)爭(zhēng)性光吸收作用;而通氧條件下DOM存在則促進(jìn)2,4,6-TCP的光解,原因是DOM光敏化產(chǎn)生·OH和1O2,使2,4,6-TCP發(fā)生間接光解.當(dāng)DOM不存在時(shí),通氮條件下2,4,6-TCP光解速率常數(shù)為0.0109m2/E,與DOM不存在加入NaN3時(shí)2,4,6-TCP的光解速率常數(shù)0.0105m2/E (表2)十分接近,原因是通氮和加入NaN3的情況下,2,4,6-TCP只能發(fā)生直接光解.

有關(guān)通氮和通氧對(duì)污染物光解的抑制或促進(jìn)作用,報(bào)道的結(jié)果存在較大差異.例如,萘普生[35]、磺胺二甲基嘧啶[23]、阿替洛爾[36]表現(xiàn)為通氮促進(jìn)而通氧抑制;磺胺甲噁唑[23]、4-氯酚[33]以及本研究則表現(xiàn)為通氮抑制而通氧促進(jìn).產(chǎn)生這種現(xiàn)象的原因和化合物的光化學(xué)性質(zhì)以及與活性氧自由基的反應(yīng)活性有關(guān).盡管自敏化和DOM光敏化可以產(chǎn)生1O2和·OH,但1O2的產(chǎn)生效率要遠(yuǎn)高于·OH[8],因此與1O2的反應(yīng)活性直接決定了化合物的敏化光解對(duì)總光解速率的貢獻(xiàn).如果化合物的敏化光解占主導(dǎo)作用,氧氣的存在會(huì)促進(jìn)化合物光解,反之,氧氣的存在會(huì)抑制化合物光解.而單線(xiàn)態(tài)氧的反應(yīng)具有較高的選擇性,一般對(duì)含有酚羥基、巰基等還原性基團(tuán)的化合物具有較高的反應(yīng)活性,對(duì)其它化合物反應(yīng)活性則較低[37].對(duì)于本研究,2,4,6-TCP的自敏化和DOM自敏化都可產(chǎn)生1O2,并且2,4,6-TCP與1O2具有較高的反應(yīng)速率常數(shù),因此通氧促進(jìn)了2,4,6- TCP的光解,而通氮?jiǎng)t起抑制作用.

2.5 太陽(yáng)光譜區(qū)間對(duì)2,4,6-TCP光解的影響

研究表明,太陽(yáng)光譜區(qū)間對(duì)活性氧自由基的產(chǎn)生具有較大影響[34],可能會(huì)影響2,4,6-TCP光解.進(jìn)一步考察了太陽(yáng)光譜區(qū)間對(duì)2,4,6-TCP光解的影響,結(jié)果如圖6所示.

可以看出,在沒(méi)有DOM存在的情況下,可見(jiàn)光區(qū)不能引起2,4,6-TCP光解,而當(dāng)DOM存在時(shí),可見(jiàn)光區(qū)能夠引起2,4,6-TCP的光解,其原因是DOM在太陽(yáng)光譜區(qū)間大于400nm的光照下能夠產(chǎn)生少量單線(xiàn)態(tài)氧[34].計(jì)算了不同光譜區(qū)間對(duì)2,4,6-TCP的光解的貢獻(xiàn)率,結(jié)果如表3所示.可以看出,在DOM不存在時(shí),UVB對(duì)2,4,6-TCP光解貢獻(xiàn)率為27.4%,而DOM存在時(shí),UVB對(duì)2,4,6-TCP光解貢獻(xiàn)率上升到34.88%,其原因是UVB光敏化DOM產(chǎn)生1O2的能力要比UVA強(qiáng)[34].

表3 太陽(yáng)光譜區(qū)間對(duì)2,4,6-TCP在純水和DOM水溶液中光解的貢獻(xiàn) Table 3 Contribution of different sunlight spectra band to the photolysis of 2,4,6-TCP

2.6 2,4,6-TCP在實(shí)際地表水中的光解

進(jìn)一步考察了2,4,6-TCP在實(shí)際地表水中的光解情況,結(jié)果如圖7和表4所示.可以看出,2,4, 6-TCP在實(shí)際地表水中的光解與在DOM水溶液中的光解類(lèi)似,都表現(xiàn)為通氮抑制光解,通氧促進(jìn)光解.直接光解、間接光解以及不同太陽(yáng)光譜區(qū)間對(duì)2,4,6-TCP的光解貢獻(xiàn)率與2,4,6-TCP在DOM水溶液中的貢獻(xiàn)率十分接近.表明溶解氧和DOM是2,4,6-TCP在實(shí)際地表水中間接光解的主要影響因素.

表4 不同條件下實(shí)際地表水中2,4,6-TCP的光解速率常數(shù)及貢獻(xiàn)比 Table 4 Photolysis rate constants of 2,4,6-TCP under different conditions and their contributuion

3 結(jié)論

3.1 由于競(jìng)爭(zhēng)性光吸收和光敏化活性氧自由基的產(chǎn)生,DOM對(duì)2,4,6-TCP的光解具有雙重作用,表現(xiàn)為濃度較低時(shí)(<2mg/L)抑制2,4,6-TCP的光解,濃度較高時(shí)促進(jìn)2,4,6-TCP的光解.

3.2 2,4,6-TCP在純水中主要為直接光解和自敏化光解,自敏化所產(chǎn)生的活性物種主要為單線(xiàn)態(tài)氧,羥基自由基基本不起作用,在DOM水溶液中主要為直接光解和敏化光解,DOM敏化產(chǎn)生的活性物種為單線(xiàn)態(tài)氧和羥基自由基.

3.3 太陽(yáng)光可見(jiàn)區(qū)對(duì)2,4,6-TCP的直接光解沒(méi)有貢獻(xiàn),UVA(320~400nm)貢獻(xiàn)為72.60%,而當(dāng)有可溶性有機(jī)質(zhì)存在時(shí),可見(jiàn)光區(qū)對(duì)2,4,6-TCP的光解貢獻(xiàn)為12.39%,UVA的貢獻(xiàn)為52.73%.

3.4 太陽(yáng)光譜區(qū)間和溶解氧對(duì)2,4,6-TCP在實(shí)際地表水中光解的影響與2,4,6-TCP在DOM溶液中光解的影響基本類(lèi)似,說(shuō)明實(shí)際地表水中2,4,6-三氯酚間接光解的主要影響因素為溶解氧和DOM.

[1] Xu L, Wang J. Degradation of 2,4,6-trichlorophenol using magnetic nanoscaled Fe3O4/CeO2composite as a heterogeneous Fenton-like catalyst [J]. Separation and Purification Technology, 2015,149:255-264.

[2] Bustos-Ramirez K, Eduardo Barrera-Diaz C, De Icaza-Herrera M, et al. 4-chlorophenol removal from water using graphite and graphene oxides as photocatalysts [J]. Journal of Environmental Health Science and Engineering, 2015,13(1):1-13.

[3] 王兆慧,馬萬(wàn)紅,陳春城,等. TiO2光催化降解氯酚類(lèi)有機(jī)污染物的反應(yīng)機(jī)理 [J]. 中國(guó)科學(xué):化學(xué), 2011,41(8):1286-1297.

[4] Ma D, Liu G, Lv W, et al. Photodegradation of naproxen in water under simulated solar radiation: mechanism, kinetics, and toxicity variation [J]. Environmental Science and Pollution Research, 2014,21(13):7797-7804.

[5] 東 天,馬溪平,王聞燁,等.抗生素光降解研究進(jìn)展 [J]. 環(huán)境科學(xué)與技術(shù), 2014(S1):108-113.

[6] 郭學(xué)濤,楊 琛,曾曉明,等.環(huán)境因素對(duì)針鐵礦光解泰樂(lè)菌素的影響 [J]. 中國(guó)環(huán)境科學(xué), 2014,34(2):364-370.

[7] 劉 萱,王 華,于春艷,等.兩種微藻胞外分泌物與NO2-, NO3-對(duì)2, 4?D光解的影響 [J]. 環(huán)境科學(xué)學(xué)報(bào), 2014,34(4):944-949.

[8] 邰 超,李雁賓,陰永光,等.天然水體中可溶性有機(jī)質(zhì)的自由基光化學(xué)行為 [J]. 化學(xué)進(jìn)展, 2012,24(7):1387-1397.

[9] Li L, Liu W, Zeng H, et al. Photo-induced Metal-Catalyst-Free Aromatic Finkelstein Reaction [J]. Journal of the American Chemical Society, 2015,137(26):8328-8331.

[10] Karci A, Arslan-Alaton I, Olmez-Hanci T, et al. Transformation of 2, 4-dichlorophenol by H2O2/UV-C, Fenton and photo-Fenton processes: oxidation products and toxicity evolution [J]. Journal of Photochemistry and Photobiology A: Chemistry, 2012,230(1): 65-73.

[11] Zhang Y, Pu X, Fang M, et al. 2,4,6-trichlorophenol (TCP) photobiodegradation and its effect on community structure [J]. Biodegradation, 2012,23(4):575-583.

[12] Batoev V B, Matafonova G G, Filippova N I. Direct photolysis of chlorophenols in aqueous solutions by UV radiation from excilamps [J]. Russian Journal of Applied Chemistry, 2011, 84(3):407-411.

[13] Devine A L, Nix M G D, Cronin B, et al. Near-UV photolysis of substituted phenols, I: 4-fluoro-, 4-chloro- and 4-bromophenol [J]. Physical Chemistry Chemical Physics, 2007,9(28):3749- 3762.

[14] Kang C, Gao H, Guo P, et al. Kinetics and mechanism of para-chlorophenol photoconversion with the presence of nitrite in ice [J]. Journal of Hazardous Materials, 2009,170(1):163-168.

[15] Czaplicka M. Photo-degradation of chlorophenols in the aqueous solution [J]. Journal of Hazardous Materials, 2006,134(1-3):45- 59.

[16] Richard C, Krajnik P, Grabner G. Photolysis of 4- chlororesorcinol in water: competitive formation of a singlet ketene and a triplet carbene [J]. Physical Chemistry Chemical Physics, 2010,12(42):14322-14329.

[17] Miller J S. Rose bengal-sensitized photooxidation of 2- chlorophenol in water using solar simulated [J]. Water Research, 2005,39(2/3):412-422.

[18] Li Y B, Mao Y X, Liu G L, et al. Degradation of Methylmercury and Its Effects on Mercury Distribution and Cycling in the Florida Everglades [J]. Environmental Science and Technology, 2010,44(17):6661-6666.

[19] Tai C, Li Y, Yin Y, et al. Methylmercury photodegradation in surface water of the Florida Everglades: Importance of dissolved organic matter-methylmercury complexation [J]. Environmental Science and Technology, 2014,48(13):7333-7340.

[20] Xia X H, Li G C, Yang Z F, et al. Effects of fulvic acid concentration and origin on photodegradation of polycyclic aromatic hydrocarbons in aqueous solution: Importance of active oxygen [J]. Environmental Pollution, 2009,157(4):1352-1359.

[21] Kepczynski M, Czosnyka A, Nowakowska M. Photooxidation of phenol in aqueous nanodispersion of humic acid [J]. Journal Of Photochemistry and Photobiology A-Chemistry, 2007,185(2/3): 198-205.

[22] Liu H, Zhao H M, Quan X, et al. Formation of Chlorinated Intermediate from Bisphenol A in Surface Saline Water under Simulated Solar Light Irradiation [J]. Environmental Science and Technology, 2009,43(20):7712-7717.

[23] 孫興霞,許 毓.水中磺胺類(lèi)抗生素的光降解及富里酸對(duì)其光降解的影響 [J]. 中國(guó)科學(xué)技術(shù)大學(xué)學(xué)報(bào), 2013(8):654-660.

[24] Neamtu M, Frimmel F H. Photodegradation of endocrine disrupting chemical nonylphenol by simulated solar UV- irradiation [J]. Science of the Total Environment, 2006,369(1-3): 295-306.

[25] Vione D, Minella M, Maurino V, et al. Indirect Photochemistry in Sunlit Surface Waters: Photoinduced Production of Reactive Transient Species [J]. Chemistry-A European Journal, 2014, 20(34SI):10590-10606.

[26] Dalrymple R M, Carfagno A K, Sharpless C M. Correlations between Dissolved Organic Matter Optical Properties and Quantum Yields of Singlet Oxygen and Hydrogen Peroxide [J]. Environmental Science and Technology, 2010,44(15):5824-5829.

[27] Tai C, Jiang G, Liu J, et al. Rapid degradation of bisphenol A using air as the oxidant catalyzed by polynuclear phthalocyanine complexes under visible light irradiation [J]. Journal of Photochemistry and Photobiology A: Chemistry, 2005,172(3): 275-282.

[28] 葛林科,張思玉,謝 晴,等.抗生素在水環(huán)境中的光化學(xué)行為 [J]. 中國(guó)科學(xué):化學(xué), 2010(2):124-135.

[29] Werner J J, Arnold W A, Mcneill K. Water Hardness as a Photochemical Parameter: Tetracycline Photolysis as a Function of Calcium Concentration, Magnesium Concentration, and pH [J]. Environmental Science and Technology, 2006,40(23):7236-7241.

[30] Chen Y, Hu C, Qu J, et al. Photodegradation of tetracycline and formation of reactive oxygen species in aqueous tetracycline solution under simulated sunlight irradiation [J]. Journal of Photochemistry and Photobiology A-Chemistry, 2008,197(1):81- 87.

[31] 葛林科,陳景文,張思玉,等.水中氟喹諾酮類(lèi)抗生素加替沙星的光降解 [J]. 科學(xué)通報(bào), 2010(11):996-1001.

[32] Ge L, Chen J, Qiao X, et al. Light-Source-Dependent Effects of Main Water Constituents on Photodegradation of Phenicol Antibiotics: Mechanism and Kinetics [J]. Environmental Science and Technology, 2009,43(9):3101-3107.

[33] Du Y, Fu Q S, Li Y, et al. Photodecomposition of 4-chlorophenol by reactive oxygen species in UV/air system [J]. Journal of Hazardous Materials, 2011,186(1):491-496.

[34] Marchisio A, Minella M, Maurino V, et al. Photogeneration of reactive transient species upon irradiation of natural water samples: Formation quantum yields in different spectral intervals, and implications for the photochemistry of surface waters [J]. Water Research, 2015,73:145-156.

[35] 馬杜娟,劉國(guó)光,呂文英,等.水中萘普生的紫外光降解機(jī)制及其產(chǎn)物毒性研究 [J]. 環(huán)境科學(xué), 2013,34(5):1782-1789.

[36] 季躍飛,曾 超,周 磊,等.阿替洛爾在模擬太陽(yáng)光照射下的光解 [J]. 環(huán)境科學(xué)學(xué)報(bào), 2012,32(6):1357-1363.

[37] Min D B, Boff J M. Chemistry and reaction of singlet oxygen in foods [J]. Comprehensive Reviews In Food Science and Food Safety, 2002,1(2):58-72.

* 責(zé)任作者, 教授, taichao@126.com

Studies on the photodecomposition mechanism of 2,4,6-trichlorophenol in water under sunlight irradiation

TAI Chao1*, ZHANG Shao-dong1, YIN Yong-guang2, WU Hao-xian1,2, WANG Jing1

(1.Institute of Resources and Environment, Henan Polytechnic University, Jiaozuo 454000, China；2.Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, State Key Laboratory of Environmental Chemistry and Ecotoxicology, Beijing 100085, China)., 2016,36(8)：2380~2387

The photodecompositions of 2,4,6-trichlorophenol (2,4,6-TCP) in pure water, dissolved organic matter (DOM) solution, and actual surface water were studied comparatively. The results indicate that there are three pathways in the photodecomposition of 2,4,6-TCP, including direct photolysis, sensitized photolysis, and self-sensitized photolysis. Direct photolysis and self-sensitized are found to be involved in the photolysis of 2,4,6-trichlorophenol in pure water, with singlet oxygen as main active species. Besides direct photolysis, sensitized photolysis of 2,4,6-trichlorophenol is also found in presence of DOM with singlet oxygen and hydroxyl radical as main active species. The degradation rates of 2,4,6-trichlorophenol in pure, DOM-contained and actual surface water all increase with the oxygen content in solution. The visible light has no contribution for the direct photolysis of 2,4,6-TCP, and UVA contribution is 72.60%. While in presence of dissolved organic matter, about 12.39% contribution of visible light is found, and the contribution of UVA is 52.73% in DOM solution. The photolysis of 2,4,6-trichlorophenol in actual surface water is similar to that in DOM solution, in which DO and DOM are the dominant factors in the indirect photolysis of 2,4,6-TCP.

2,4,6-trichlorophenol；photodecomposition；sunlight；self-sensitization；dissolved organic matter

X131

A

1000-6923(2016)08-2380-08

邰 超(1978-),男,河南南陽(yáng)人,教授,博士,主要從事環(huán)境化學(xué)研究.發(fā)表論文40余篇.

2016-01-25

國(guó)家自然科學(xué)基金(21377156);河南省高?？萍紕?chuàng)新團(tuán)隊(duì)項(xiàng)目(16IRTSTHN014);河南理工大學(xué)杰出青年基金(HPUJ2013-04)