UV/PS降解水中2,4-二氯苯酚及毒性評(píng)價(jià)研究

陳菊香,高乃云,魯 仙,王超慧,古振川,江 闖,楊 靜(.新疆大學(xué)建筑工程學(xué)院,新疆 烏魯木齊 80047；.同濟(jì)大學(xué),污染控制與資源化研究國(guó)家重點(diǎn)實(shí)驗(yàn)室,上海 0009；.內(nèi)蒙古科技大學(xué)能源與環(huán)境學(xué)院,內(nèi)蒙古 包頭 0400)

UV/PS降解水中2,4-二氯苯酚及毒性評(píng)價(jià)研究

陳菊香1,2,高乃云2*,魯 仙2,王超慧3,古振川2,江 闖2,楊 靜1(1.新疆大學(xué)建筑工程學(xué)院,新疆 烏魯木齊 830047；2.同濟(jì)大學(xué),污染控制與資源化研究國(guó)家重點(diǎn)實(shí)驗(yàn)室,上海 200092；3.內(nèi)蒙古科技大學(xué)能源與環(huán)境學(xué)院,內(nèi)蒙古 包頭 014010)

比較采用PS,UV/PS 2種工藝降解2,4-DCP的去除效果、一級(jí)反應(yīng)動(dòng)力學(xué);考察不同氧化劑(PS)劑量、不同初始濃度的2,4-DCP、腐殖酸條件對(duì)該光解反應(yīng)速率常數(shù)的影響以及采用發(fā)光菌青海弧菌–Q67來(lái)評(píng)價(jià)2,4-DCP和光解過(guò)程中間產(chǎn)物溶液對(duì)生態(tài)環(huán)境的毒性評(píng)價(jià).實(shí)驗(yàn)結(jié)果表明,單獨(dú)PS工藝光解2,4-DCP去除率僅有4%,而UV/PS光解2,4-DCP去除率高達(dá)96.4%,充分說(shuō)明UV/PS工藝可高效去除2,4-DCP,且其反應(yīng)基本遵循擬一級(jí)反應(yīng)動(dòng)力學(xué),一級(jí)反應(yīng)動(dòng)力學(xué)常數(shù)為35.1×10-3min-1.UV/PS降解2,4-DCP的降解率和反應(yīng)速率常數(shù)隨著氧化劑(PS)的增加而增大,隨著 2,4-DCP初始濃度增大而降低.隨著腐殖酸初始濃度的增大,有先增大后變小的過(guò)程.毒性評(píng)價(jià)實(shí)驗(yàn)中,隨著2,4-DCP光解45min,發(fā)光菌抑制率降低,溶液對(duì)環(huán)境毒性在降低,且從長(zhǎng)期時(shí)間規(guī)律來(lái)看,同一氧化時(shí)間溶液對(duì)發(fā)光菌相對(duì)抑制率與發(fā)光菌接觸時(shí)間沒(méi)有關(guān)系.

2,4-二氯苯酚；UV/PS；動(dòng)力學(xué)；擬一級(jí)；毒性評(píng)價(jià)

氯酚類(lèi)化合物(CPs)是產(chǎn)量高,用途廣,毒性大,難降解的一類(lèi)芳香族化合物,目前已被廣泛用作防腐劑,殺菌劑,殺蟲(chóng)劑和藥物等[1-2].

2,4-二氯苯酚(2,4-DCP) 等多種氯酚已被中國(guó),美國(guó)等多個(gè)國(guó)家列入優(yōu)先控制污染物名單

[3-4]. 2,4-DCP對(duì)生態(tài)環(huán)境的危害受到高度重視,各國(guó)研究者已經(jīng)從其環(huán)境分布,降解方法,中間產(chǎn)物,生態(tài)毒性等方面開(kāi)展了大量研究工作

[5-8].近幾年研究表明,紫外(UV)系統(tǒng)可以有效活化過(guò)硫酸鹽或過(guò)硫酸氫鹽等氧化劑[9-14],激發(fā)生成強(qiáng)氧化性羥基自由基和硫酸根自由基來(lái)降解水中親水性難降解的持久性有機(jī)物.該光氧化工藝具有氧化還原電位高等特點(diǎn),但具有一定的選擇性,故此需對(duì) 2,4-DCP的降解效果,動(dòng)力學(xué),影響因素,生態(tài)毒性評(píng)價(jià)等方面展開(kāi)研究.

本研究采用紫外激活過(guò)硫酸鈉溶液生成OH?和SO4?-的方法對(duì)2,4-DCP進(jìn)行去除,比較了PS,UV/PS 2種工藝分別降解2,4-DCP的效果,考察投加不同氧化劑劑量,不同初始濃度的目標(biāo)污染物,腐殖酸濃度等影響因素對(duì) UV/PS降解2,4-DCP的效果影響.并采用發(fā)光菌青海弧菌sp.-Q67發(fā)光菌抑制率及相對(duì)抑制率來(lái)評(píng)價(jià)2,4-DCP及光解過(guò)程中溶液對(duì)環(huán)境的毒性.

1 材料與方法

1.1 試驗(yàn)材料

2,4-二氯苯酚(色譜純)購(gòu)自阿拉丁(上海)貿(mào)易有限公司,過(guò)硫酸鈉,乙醇(ETOH, ≥99.7%),叔丁醇(TBA,≥99.5%) ,磷酸氫二鈉、磷酸二氫鈉、腐殖酸等試劑均購(gòu)自國(guó)藥集團(tuán)化學(xué)試驗(yàn)有限公司.甲醇(色譜純)購(gòu)自西格瑪奧德里奇(上海)貿(mào)易有限公司.

紫外光照實(shí)驗(yàn)裝置采用準(zhǔn)平行光束儀,該裝置根據(jù)國(guó)際紫外協(xié)會(huì)的標(biāo)準(zhǔn)進(jìn)行設(shè)計(jì)自制,低壓汞燈(75W,天津新景有限公司).2,4-DCP濃度檢測(cè)采用高效液相色譜儀(HPLC2010)(日本島津),配有C18色譜( 250mm×4.62mm×5μm, Waters).

毒性評(píng)價(jià)實(shí)驗(yàn)用菌種為青海弧菌(Vibrio qinghaiensis sp.-Q67,簡(jiǎn)稱Q67),購(gòu)自北京濱松光子技術(shù)股份有限公司;發(fā)光菌抑制率數(shù)據(jù)檢測(cè)采用酶標(biāo)儀(美國(guó)BioTek儀器有限公司).

1.2 實(shí)驗(yàn)方法

實(shí)驗(yàn)室條件下,用去離子水配制溶液,在200mL結(jié)晶皿中加入含目標(biāo)污染物 2,4-DCP的溶液100mL(已采用磷酸鹽緩沖溶液將pH調(diào)至 7.0),加入按規(guī)定的物質(zhì)的量比配好的過(guò)硫酸鈉溶液作氧化劑,隨后將結(jié)晶皿放置在紫外光照儀器試驗(yàn)臺(tái)上,同時(shí)開(kāi)始計(jì)時(shí),且控制好室內(nèi)反應(yīng)溫度,分別在時(shí)間點(diǎn)0, 5, 10, 20, 30, 45, 60min采用移液槍取樣,每次取 0.8mL樣品于預(yù)先放置了足量淬滅劑甲醇的棕色液相小瓶中,以保證氧化反應(yīng)在取樣點(diǎn)時(shí)終止.實(shí)驗(yàn)進(jìn)行3次取平均值.

毒性實(shí)驗(yàn)過(guò)程中污染物按稀釋因子設(shè)計(jì) 12個(gè)濃度梯度,各濃度3個(gè)平行,與24個(gè)空白一起安排在標(biāo)準(zhǔn)的白色不透明 96孔板上,試液體積為100μL,總體積為200μL.

1.3 分析方法

2,4-DCP采用高效液相色譜儀(島津 LC-2030)配備 UV/Vis 紫外可見(jiàn)光檢測(cè)器進(jìn)行檢測(cè),色譜柱型號(hào)為VP-ODS C18,流動(dòng)相為乙腈和甲酸(1/1000),V(乙腈):V(甲酸)=70:30,流速為1mL/min,柱溫為30℃,檢測(cè)波長(zhǎng)為230nm,檢測(cè)時(shí)間為8.0min.

毒性實(shí)驗(yàn)采用長(zhǎng)期微板毒性分析法(L-MTA)[15-16],通過(guò)Power Wave微孔板分光光度計(jì)(美國(guó) BioTek儀器有限公司)測(cè)得數(shù)據(jù),并用APTox軟件進(jìn)行數(shù)據(jù)處理.污染物毒性表達(dá)為發(fā)光菌抑制率,單位為百分抑制率.

2 結(jié)果與討論

2.1 不同氧化工藝(PS,UV/PS)降解2,4-DCP

圖1描述了不同氧化工藝在(25±2)℃,pH值為7.0, 2mmol/L緩沖溶液條件下光解6 μmol/L的 2,4-DCP的光解效果及對(duì)光解數(shù)據(jù)進(jìn)行一級(jí)反應(yīng)動(dòng)力學(xué)模型擬合曲線.由圖 1(a)可知,分別采用PS單獨(dú)降解2,4-DCP45min降解率達(dá)4%,降解效果幾乎可被忽略.采用 UV/PS工藝光解2,4-DCP同樣的反應(yīng)條件,同樣的反應(yīng)時(shí)間,降解速率迅速增大,降解率可達(dá) 96.4%.說(shuō)明 PS在紫外光照后加快了2,4-DCP的降解速率,進(jìn)而證明了紫外激發(fā) PS溶液生成大量的 OH? 或SO4?-[17-18].分別將 PS,UV/PS的光解數(shù)據(jù)進(jìn)行擬一級(jí)反應(yīng)動(dòng)力學(xué)擬合,擬合線性相關(guān)系數(shù) R2= 0.99,符合擬一級(jí)反應(yīng)動(dòng)力學(xué)模型. PS, UV/PS兩種方法降解的反應(yīng)速率常數(shù)分別是 0.4×10-3和35.1×10-3min-1.

圖1 (a)45min PS、UV/PS工藝降解2,4-DCP效果 (b)擬一級(jí)動(dòng)力學(xué)線性擬合Fig.1 (a)Degradation of 2,4-DCP under PS,UV/PS in 45min(b)Pseudo first order kinetic linear fitting

2.2 PS不同初始濃度的影響

由2.1已證明紫外激發(fā)過(guò)硫酸鈉鹽溶液可生成OH?或SO4?-,則過(guò)硫酸鈉的量決定了溶液中被激發(fā)生成的OH?或SO4?-的量,試驗(yàn)在2,4-DCP初始濃度為 6μmol/L,紫外光強(qiáng)度為 410mJ/cm2,初始pH值為7.0,則該研究分別選用100, 300, 500, 700, 900μmol/L的PS加入溶液中、,不同氧化劑投加量對(duì)降解效果的影響.結(jié)果如圖 2所示在45min反應(yīng)時(shí)間內(nèi),隨著氧化劑投加量從 100分別增加至 300, 500, 700, 900μmol/L對(duì)應(yīng)的UV/PS系統(tǒng)中去除率分別從37.7%增加至67.3%, 79.8%, 90.4%和 96.4%,整體趨勢(shì)表現(xiàn)出氧化劑投加量越大,2,4-DCP去除率越高.從圖2(a)可知2,4-DCP在不同的PS濃度值下的降解數(shù)值符合擬一級(jí)反應(yīng)動(dòng)力學(xué),線性較好R2=0.99.將不同PS濃度下2,4-DCP光解kobs常數(shù)再進(jìn)行擬合,發(fā)現(xiàn)兩者呈現(xiàn)線性關(guān)系,如式(1):

UV/PS:kobs= 0.039[PS]0+0.1863, R2=0.999 (1)

圖2 (a)不同初始濃度PS下光解一級(jí)擬合曲線(b)不同PS劑量與反應(yīng)速率常數(shù)線性擬合Fig.2 (a)First order reaction kinetics under different initial concentrations of PS by UV/PS ; (b)Linear fitting of different PS dose and corresponding reaction rate constant

2.3 2,4-DCP不同初始濃度的影響

在氧化劑PS物質(zhì)的量投加量為900 μmol/L,紫外光強(qiáng)度為410mJ/cm2,初始pH值為7.0的條件下,試驗(yàn)配置初始濃度分別為 6, 12, 24和 48 μmol/L的2,4-DCP溶液.

由圖3所示, 2,4-DCP的降解均符合擬一級(jí)動(dòng)力學(xué)模型(R2≥0.99).根據(jù)擬一級(jí)動(dòng)力學(xué)模型可以將2,4-DCP的物質(zhì)的量濃度變化用表達(dá)式(2):

-d[2,4-DCP]t/dt= kobs[2,4-DCP]0(2)式中:[2,4-DCP]0和[2,4-DCP]t分別代表在反應(yīng)初始時(shí)刻和反應(yīng)t時(shí)刻2,4-DCP的物質(zhì)的量濃度(μmol/L).從圖3中可以看出,在UV/PS工藝系統(tǒng)中,隨著2,4-DCP初始濃度的增加, 2,4-DCP的去除率降低,對(duì)應(yīng)的 kobs也降低.UV/PS工藝中, 2,4-DCP的去除率從 96.4%分別下降至 91.6%, 88.2%和79.3%.

圖3 不同初始濃度2,4-DCP對(duì)光解2,4-DCP的影響Fig.3 Effects of different initial concentration of 2, 4-DCP on the photolysis of 2, 4-DCP

2.4 腐殖酸的影響

在2,4-DCP初始濃度為6μmol/L,氧化劑PS物質(zhì)的量投加量分別為 1mmol/L,初始 pH值為7.0,紫外光輻照強(qiáng)度為410mJ/cm2的條件下,向系統(tǒng)中投加不同濃度腐殖酸(0～10.0mg/L)來(lái)考察腐殖酸對(duì)2,4-DCP降解效果的影響(腐殖酸做為天然水體水質(zhì)背景).單獨(dú)UV系統(tǒng)中,投加不同濃度的腐殖酸對(duì)2,4-DPC降解速率常數(shù)影響不大, kobs值變化幅度小于10%.而對(duì)UV/PS系統(tǒng)而言,系統(tǒng)表現(xiàn)出低濃度腐殖酸條件下 kobs值大,而高濃度腐殖酸條件下kobs值小的規(guī)律.在UV/PS工藝?yán)?隨著腐殖酸初始濃度從 0增加到 2.5和5.0mg/L時(shí), kobs值從 2.8×10-3增加至 3.34× 10-3min-1.而當(dāng)腐殖酸濃度繼續(xù)增加至 7.5和10.0mg/L時(shí), kobs值則分別為2.73×10-3和2.62× 10-3min-1.

腐殖酸的存在對(duì) 2,4-DCP的降解產(chǎn)生明顯影響的主要原因可能為:低濃度腐殖酸中存在的?OH等化學(xué)鍵能夠激發(fā)產(chǎn)生更多的自由基,促進(jìn)對(duì)目標(biāo)污染物2,4-DCP的降解;而達(dá)到一定濃度之后的高濃度腐殖酸對(duì)自由基的競(jìng)爭(zhēng)作用太過(guò)于明顯,抑制了自由基與2,4-DCP目標(biāo)污染物的反應(yīng).

圖4 不同初始濃度腐殖酸對(duì)光解2,4-DCP的影響Fig.4 Effect of different initial concentration of humic acid on photolysis of 2, 4-DCP

2.5 生態(tài)毒性評(píng)價(jià)

圖5 生態(tài)毒性評(píng)價(jià)Fig.5 Toxicity evaluation of photolysis process

本次實(shí)驗(yàn)采用發(fā)光菌青海弧菌-Q67的發(fā)光抑制率及相對(duì)抑制率來(lái)評(píng)價(jià) 2,4-DCP及UV/PS光解2,4-DCP過(guò)程生態(tài)環(huán)境的毒性.本次實(shí)驗(yàn)選用氧化時(shí)間分別是0, 15, 30, 45min溶液依次與發(fā)光菌分別接觸0.25, 0.5, 1, 2, 3h.由圖5可知,光解氧化 2,4-DCP45min過(guò)程中隨著2,4-DCP濃度的降低,中間產(chǎn)物的增多,發(fā)光菌抑制率在下降.說(shuō)明中間產(chǎn)物的毒性在降低.光氧化45min溶液與發(fā)光菌接觸0.25, 0.5, 1,2, 3h的抑制率分別從94%, 96%, 96.3%, 97%, 98%降到9%, 7%, 7.8%, 9%, 10%,通過(guò)計(jì)算相對(duì)抑制率分別是90%, 92%, 92%, 91%, 90%.我們可以發(fā)現(xiàn)氧化45min取樣溶液與發(fā)光菌不同接觸時(shí)間內(nèi)的相對(duì)抑制率幾乎是一樣的,這說(shuō)明毒性評(píng)價(jià)從長(zhǎng)期時(shí)間規(guī)律上來(lái)說(shuō),接觸時(shí)間對(duì)毒性大小影響基本無(wú)關(guān).

3 結(jié)論

3.1 UV/PS工藝可高效去除2,4-DCP,去除率可高達(dá)96.4%.UV/PS光解2,4-DCP基本遵循擬一級(jí)反應(yīng)動(dòng)力學(xué),反應(yīng)動(dòng)力學(xué)常數(shù)是 35.1× 10-3min-1.

3.2 不同PS劑量下,UV/PS光解2,4-DCP的反應(yīng)降解率及速率常數(shù)隨著 PS劑量增多而增大,不同劑量與其對(duì)應(yīng)的反應(yīng)速率常數(shù)擬合呈線性關(guān)系.

3.3 UV/PS光解 2,4-DCP的反應(yīng)降解率及速率常數(shù)隨 2,4-DCP初始濃度增大而降低;隨腐殖酸初始濃度的增大,光解反應(yīng)速率常數(shù)先增大后降低.

3.4 UV/PS光解 2,4-DCP45min,隨 2,4-DCP濃度的降低,中間產(chǎn)物的增多,發(fā)光菌抑制率降低,溶液對(duì)環(huán)境的毒性在降低.從長(zhǎng)期實(shí)驗(yàn)規(guī)律來(lái)講同一氧化時(shí)間,與發(fā)光菌不同接觸時(shí)間的溶液對(duì)發(fā)光菌的相對(duì)抑制率幾乎是相同的,即從長(zhǎng)期實(shí)驗(yàn)規(guī)律來(lái)講接觸時(shí)間對(duì)毒性大小沒(méi)有影響.

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Degradation of 2, 4-dichlorophenol in aqueous solution using UV/PS and toxicity evaluation investigation.

CHEN Ju-xiang1,2, GAO Nai-yun2*, LU Xian2, WANG Chao-hui3, GU Zhen-chuan2, JIANG Chuang2, YANG Jing1
(1.College of Architecture and Civil Engineering, Xinjiang University, Urumqi 830047, China；2.State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092, China；3.School of Energy and Environment, Inner Mongolia University of Science and Technology, Baotou 014010, China). China Environmental Science, 2017,37(1)：162～166

The removal effects and the first order reaction kinetics of 2, 4-DCP with PS and UV/PS were compared, respectively. The effect of oxidant (PS) dosage, different initial 2, 4-DCP concentration and humic acid on the photolysis reaction were investigated. The vibrio-qinghaiensis sp.–Q67 was applied to evaluate the environmental toxicity of 2, 4-DCP solution and successive transformation products during UV/PS process. The results showed that the removal percentage of 2, 4-DCP was only 4% for the only PS process, while the degradation percentage reached higher 96.4% with UV/PS process, which showed the 2, 4-DCP was effectively degraded by UV/PS process compared with the PS alone. Meanwhile the pseudo-first-order reaction equation could well describe the 2, 4-DCP degradation behavior and the kobs(reaction rate constant) was 35.1×10-3min-1in UV/PS process. The degradation efficiency and rate constant rate increased with the increasing of the oxidant (PS) dosage, decreased with the increase of initial 2, 4-DCP concentration. The coexisting HA promoted the 2, 4-DCP degradation at the beginning and then gradually inhibited the degradation. For toxicity evaluation experiment, Luminescent bacteria inhibition rate decreased with the decrease of concentration of 2, 4-DCP and the increase of intermediate products, which indicated the reduction of environmental toxicity of the reaction system. According to the multiple experimental results, the relative inhibition rate of luminescent bacteria had no relation with exposure time of luminescent bacteria under the same oxidation time.

2, 4-DCP；UV/PS；kinetics；pseudo first-order；toxicity evaluation

X703

A

1000-6923(2017)01-0162-05

陳菊香(1979-),女,重慶大足人,副教授,主要從事水處理理論與技術(shù).發(fā)表論文20余篇.

2016-05-10

國(guó)家科技重大項(xiàng)目(2012ZX07403-001);國(guó)家自然科學(xué)基金資助項(xiàng)目(51178321);新疆大學(xué)大學(xué)生創(chuàng)新訓(xùn)練計(jì)劃項(xiàng)目(201610755018)

* 責(zé)任作者, 教授, gaonaiyun@126.com