UV/NaClO和UV/過碳酸鈉工藝降解水楊酸的對比

馬曉雁,楊 帆,李青松,楊慶云,陳國元,李國新

UV/NaClO和UV/過碳酸鈉工藝降解水楊酸的對比

馬曉雁1,楊 帆1,李青松2,3*,楊慶云1,陳國元2,李國新2

(1.浙江工業大學土木工程學院,浙江 杭州 310014；2.廈門理工學院水資源環境研究所,福建 廈門 361024；3.廈門理工學院廈門市水資源利用與保護重點實驗室,福建 廈門 361024)

采用UV/NaClO和UV/過碳酸鈉(SPC)工藝降解水中水楊酸(SA),對比考察了氧化劑種類和投加量對SA去除的影響,采用淬滅法和電子順磁共振波譜儀(EPR)鑒定識別了2種工藝中的自由基,通過競爭動力學的方法計算了SA與?OH、CO3?-的二級反應速率常數及反應體系中不同組分的貢獻,從環境水樣模擬、急性毒性和經濟效益等角度比較了SA的去除效果.結果表明,UV/NaClO工藝和UV/SPC工藝降解SA的擬一級動力學常數分別為0.4378,0.3794min-1.UV/NaClO和UV/SPC體系中分別存在?OH、Cl?和O2?-、?OH及CO3?-等自由基.SA與?OH、CO3?-的二級反應速率常數分別為3.97′109,8′107L/(mol×s).UV/NaClO工藝中活性氯自由基(RCS)(79.91%)對SA去除起主導作用;而UV/SPC工藝中O2?-(51.75%)與?OH(41.42%)起主導作用.環境水樣中SA在UV/NaClO和UV/SPC工藝中的降解受到抑制,其反應速率分別平均降低了67%和74%.UV/SPC工藝反應溶液的抑制率(25%)較UV/NaClO工藝反應溶液(63%)低38%.SA降解率達到97.5%以上時UV/SPC工藝的成本[37.1$/(m3×order)]是UV/NaClO工藝成本[4.0$/(m3×order)]的9.3倍,UV/NaClO工藝較UV/SPC工藝具有較高的經濟效益.

UV-AOPs；自由基鑒定；自由基貢獻；急性毒性；經濟效益

近年來藥物和個人護理品(PPCPs)在水體中被頻繁檢出,由于其潛在的危害與風險,水環境中PPCPs的去除對于保障飲水安全具有重要的意義[1-3].目前,基于紫外的高級氧化工藝(UV-AOPs)已廣泛應用于去除水中的PPCPs[4].UV-AOPs常見的氧化劑有雙氧水(H2O2)、次氯酸鈉(NaClO)、臭氧、過硫酸鹽、過碳酸鈉(SPC)等,實際應用中可以根據水質情況采用不同的氧化劑以達到更好的去除效果[4-6].

UV/NaClO工藝能產生將污染物高效去除的?OH和活性氯自由基(RCS,包括Cl?、ClO?、Cl2?-等),且去除富含電子的有機污染物時,RCS比?OH具有更高的二級反應速率常數[7-9].SPC溶于水后經UV照射可產生?OH、O2?-、CO3?-等自由基,且不同pH值條件下主導的自由基不同,這一特點適用于處理不同的目標污染物[10-11].相比于NaClO等液體氧化劑,固體氧化劑SPC具有更好的穩定性、抗爆性和可獲得性[5,12].關于UV/NaClO和UV/SPC工藝去除水中 PPCPs 的研究已有諸多報道,然而2種工藝在相同條件下降解同一污染物時去除效果、機理與經濟效益尚不明確.

水楊酸(SA)是地表水中檢出頻次較高的典型PPCP,地表水中其濃度高達2014.4ng/L,對水生生物構成威脅[2-3].本文采用UV/NaClO和UV/SPC工藝降解水中的SA,從氧化劑投加量、自由基種類與貢獻率、環境水樣應用、急性毒性和經濟效益等角度對比考察2種工藝的差異,以期為去除水中PPCPs工藝選擇提供參考.

1 材料與方法

1.1 實驗材料與儀器

SA(純度99.9%,德國Dr.Ehrenstorfer);硝基苯(NB,AR,阿法埃莎化學有限公司);N,N—二甲基苯胺(DMA,純度399%,上海麥克林生化科技有限公司);三氯甲烷(CF,HPLC,美國Anaqua).過碳酸鈉(SPC, CP)、對氯苯甲酸(pCBA,GC)、5,5-二甲基-1-氧化吡咯啉(DMPO,AR)等購于上海阿拉丁生化科技股份有限公司;五水硫代硫酸鈉(Na2S2O3·5H2O, AR)、叔丁醇(TBA,HPLC)、乙腈(C2H3N,HPLC)、苯酚(PhOH,AR)等購于安譜實驗科技股份有限公司. NaClO、H2O2、NaOH、HCl、NaHCO3、CH3COOH等購于國藥集團化學試劑有限公司,除NaClO為化學純外其余均為分析純.實驗用水為Milli-Q超純水.

高效液相色譜儀(HPLC)(LC-20A,日本Shimadzu)、電子順磁共振波譜儀(EPR) (SN0253,德國Bruker)、便攜式余氯計(CL200,上海三信儀表廠)、pH計(ST2100,常州奧豪斯儀器有限公司)、磁力攪拌器(HJ-6A,江蘇金壇崢嶸儀器)、純水機(Milli-Q,美國Milipore)、發光細菌毒性檢測儀(LumiFox 6800,深圳朗石科學儀器有限公司).

1.2 降解實驗方法

實驗在一個置于磁力攪拌器上的圓柱形容器(容積500mL)中進行,光源為低壓紫外汞燈(0.18mW/cm2,波長254nm),汞燈外套有石英套管.實驗溶液為濃度500μg/L的SA溶液(300mL),實驗前用0.1mol/L的NaOH溶液或0.1mol/L的HCl溶液調節pH值至7.實驗開始時首先投加一定濃度的NaClO或SPC,同時開啟磁力攪拌器與汞燈開始計時,在特定時間取樣經0.22μm濾膜過膜后進行HPLC分析.進樣瓶在實驗開始前先加入10μL濃度為0.01mol/L的Na2S2O3·5H2O以確保完全淬滅剩余氧化劑.所有實驗重復3次并取平均值.

1.3 分析方法

SA的濃度采用HPLC進行檢測.HPLC方法:流動相A:0.1%乙酸溶液;流動相B:乙腈;A:B=65:35;流速為1mL/min;紫外檢測器波長為292nm;柱溫為40℃;進樣體積20μL;

1.4 自由基捕獲實驗方法

鑒定UV/NaClO工藝中Cl?和?OH時,分別調節pH=7和pH=12.5,UV/SPC工藝中?OH和CO3?-鑒定時調節溶液pH=7.由于DMPO-O2?-在水溶液中的存活時間極短,鑒定O2?-在二甲基亞砜溶液中進行[13].降解實驗開始后,在1min時抽取1mL反應液立即與0.1mL 100mmol/L的DMPO溶液混合,迅速用50μL毛細管吸取至一定高度后封口,立即進行EPR檢測.

1.5 急性毒性實驗方法

實驗前混合復蘇稀釋液與發光細菌凍干粉形成細菌液,并活化15min,將空白樣、待測樣與滲透壓調節液以900μL:100μL混合并搖勻.實驗開始時空白樣和待測樣中分別加入50μL細菌液混勻,測量初始發光強度后送入儀器樣本區,培養30min后再進行發光強度檢測.急性毒性的結果可以通過相對抑制率來表示水樣急性毒性強度.

2 結果與討論

2.1 UV/NaClO和UV/SPC工藝對SA的降解

由圖1可知,NaClO與SA的物質的量比從3.7增加至18.5,SA的擬一級動力學常數()由0.0842min-1增加至0.4378min-1,相同反應時間內相應SA的去除從57.3%增加至100%;SPC與SA的物質的量比由7增加至35時,SA的從0.1239min-1增加至0.3794min-1,對應的SA去除率從71.5%提高到97.8%;2種工藝處于同一量級,氧化劑與SA的物質的量比小于14時UV/SPC工藝較大,氧化劑與SA的物質的量比大于14時UV/NaClO工藝較大.SA的與去除率均隨著氧化劑投加量的增大而增加,原因是NaClO的增加可以生成更多的?OH和RCS(式(2～7)),SPC的增加可以生成更多的?OH、O2?-和CO3?-等(式(8～12))[7,10,14].UV/NaClO和UV/SPC工藝氧化劑物質的量投加比增加至5倍時,分別增加至5.2和3.1倍,UV/NaClO工藝的增幅是UV/SPC工藝增幅的1.4倍;當SPC投加的物質的量比超過14時,的增幅變緩,可能原因是溶液中的CO32-和HCO3-會消耗?OH(式(10,13～14))[9],這與Yan等[11]采用Fe2+活化SPC降解磺胺甲惡唑得到的規律相似.

圖1 UV/NaClO和UV/SPC對SA的去除

[SA]0=3.6μmol/L, [NaClO]: [SA]0=3.7、7.4、11.1、14.8、18.5,[SPC] :[SA]0=7、14、21、28、35, pH=(7.0±0.2)

2.2 UV/NaClO和UV/SPC工藝中自由基的鑒定

TBA可用于淬滅?OH和Cl?[15];PhOH可用于淬滅?OH和CO3?-(PhOH-?OH=6×108L/(mol×s),PhOH-CO3?-= 2.2×107L/(mol×s))[12,16];CF可用于淬滅O2?-(CF-O2?-= 3.0×1010L/(mol×s))[10];加入自由基清掃劑TBA、PhOH和CF后2種工藝SA的去除見圖2.

UV/NaClO工藝中SA的去除率隨TBA的增加而減小,表明體系中含有?OH和Cl?.加入過量TBA (20mM)后SA的去除率仍大于單獨NaClO(4.5%)和UV(13%)的去除率,說明體系中存在其他RCS的貢獻.UV/SPC工藝中加入CF、TBA和PhOH后,SA的去除率均不同程度降低,表明體系中含有O2?-、?OH和CO3?-.Yue等[10]用UV/SPC工藝降解辣椒素同樣證明了體系中存在O2?-、?OH和CO3?-.

[SA]0=3.6μmol/L, [NaClO]=40μmol/L,[SPC]=75.6μmol/L,pH=(7.0±0.2)

[NaClO]=40μmol/L, [SPC]=75.6μmol/L, [DMPO]=100mmol/L, 未特殊說明pH=(7.0±0.2)

采用DMPO作為自由基捕獲劑檢測UV/NaClO和UV/SPC工藝中產生的自由基,測定EPR圖譜如圖3.強堿性條件時UV/NaClO體系中?OH(EPR圖譜四線強度比1:2:2:1)更明顯,而弱堿性時DMPO將被氧化為DMPOX(EPR圖譜七線強度比1:2:1:2:1:2:1),其為?OH和Cl?共同氧化的結果[17-18].而UV/SPC體系中檢測到?OH和O2?-(EPR圖譜四線強度比1:1: 1:1)[19].CO3?-作為UV/SPC體系中重要的自由基實驗中未檢測到,這可能是體系中產生的CO3?-量較少,以至EPR無法檢出.

2.3 UV/NaClO和UV/SPC工藝降解SA過程中各組分貢獻

2.3.1 SA與?OH、CO3?-的二級反應速率常數 二級反應速率常數用來描述自由基與化合物之間的反應快慢[16].通過UV/H2O2工藝降解SA與pCBA (pCBA-?OH=5′109L/(mol×s))進行競爭動力學實驗計算SA與?OH的二級反應速率常數(式(15～16))[15](圖4).聯立式(15～16)得式(17),可求出SA與?OH的二級反應速率常數為3.94′109L/(mol×s).該結果略小于Peralta等[20]報道的SA與?OH的二級反應速率常數5′109L/(mol×s),但仍為同一數量級.

圖4 SA和pCBA在UV/H2O2工藝中的降解

[SA]0=[pCBA]0=3.6μmol/L, [H2O2]=60μmol/L, pH=(7.0±0.2)

式中:obs,UV/H2O2,SA和obs,UV/H2O2,pCBA為降解SA、pCBA的擬一級動力學常數;obs,UV,SA和obs,UV,pCBA為單獨UV降解SA、pCBA的擬一級動力學常數;HO?-SA和HO?-pCBA為?OH與SA、pCBA的二級反應速率常數;[HO?]UV/H2O2,SS表示?OH的穩態濃度.

選用TBA與CF分別作為?OH與O2?-的清除劑[10,15],通過SA和PhOH在UV/SPC工藝中的降解求出SA與CO3?-的二級反應速率常數(式(18～ 19))[12],結果見圖5.

據此簡化式(18～19)為式(20～21),聯立式(20～21)得到式(22),可求出SA與CO3?-的二級反應速率常數為1.66′107L/(mol×s).此前Wojnárovits等[16]報道CO3?-與有機分子的二級反應速率常數在102～109L/(mol×s)范圍內,實驗結果與該范圍相符.

圖5 SA和PhOH在UV/SPC工藝中的降解

[SA]0=[PhOH]0=3.6μmol/L, [SPC]=75.6μmol/L, [TBA]=10mmol/L,[CF]=10mmol/L, pH=(7.0±0.2)

式中:T&C表示溶液中加入足量TBA與CF作為自由基淬滅劑;obs,UV/SPC,T&C,SA和obs,UV/SPC,T&C,PhOH為降解SA與PhOH的擬一級動力學常數;obs,UV,T&C,SA和obs,UV,T&C,PhOH為單獨UV降解SA、PhOH的擬一級動力學常數;obs,SPC,T&C,SA和obs,SPC,T&C,PhOH為單獨SPC降解SA、PhOH的擬一級動力學常數;obs,O2?-,T&C,SA和obs,O2?-,T&C,PhOH為O2?-降解SA、PhOH擬一級動力學常數,假定加入的CF完全淬滅O2?-,此處取0;HO?-PhOH為?OH與PhOH的二級反應速率常數;CO3?--SA和CO3?--PhOH為CO3?-與SA、PhOH的二級反應速率常數;[HO?]SS和[CO3?-]SS為該體系下?OH與CO3?-的穩態濃度,設定加入的TBA完全淬滅?OH,此處[HO?]SS取0.

2.3.2 UV/NaClO和UV/SPC不同組分對SA去除的貢獻對比 選用NB、DMA分別作為?OH和CO3?-的探針(NB-?OH=3.9′109L/(mol×s),CO3?--DMA=1.8′109L/(mol×s)),采用探針法通過NB和DMA在UV/ NaClO和UV/SPC工藝中的降解(式(23～25))求出?OH和CO3?-的穩態濃度(圖6)[21-22],進而求出不同組分對SA去除的貢獻.將擬合所得到的擬一級動力學常數代入式(23～25)得出UV/NaClO工藝中?OH的穩態濃度為4.21′10-12mol/L,UV/SPC工藝中?OH和CO3?-的穩態濃度分別為2.72′10-11,8.20′10-11mol/L.

圖6 NB和DMA在UV/NaClO和UV/SPC工藝中的降解

[NB]0=[DMA]0=3.6μmol/L, [NaClO]= 40μmol/L, [SPC]=75.6μmol/L, pH=(7.0±0.2)

式中:obs,UV/NaClO,NB、obs,UV/SPC,NB和obs,UV/SPC,DMA為降解NB、DMA的擬一級動力學常數;obs,UV,NB和obs,UV,DMA分別為單獨UV降解NB、DMA的擬一級動力學常數;HO?-NB和CO3?--DMA分別為NB與?OH、DMA與CO3?-的二級反應速率常數.

由SA與?OH、CO3?-的二級反應速率常數和?OH與CO3?-的穩態濃度,可求得2個工藝下?OH和CO3?-降解SA的擬一級動力學常數(式(26)～(28)).

式中:obs,UV/NaClO,HO?-SA為UV/NaClO工藝下?OH降解SA的擬一級動力學常數;obs,UV/SPC,HO?-SA和obs,UV/SPC,CO3?--SA分別為UV/SPC工藝下?OH、CO3?-降解SA的擬一級動力學常數.

圖7 不同物種在UV/NaClO和UV/SPC工藝中降解SA的貢獻

[SA]0=3.6μmol/L, [NaClO]=40μmol/L,[SPC]=75.6μmol/L,pH=(7.0±0.2)

SA在2種工藝中的降解可表示為式(29～30),由式(29)可求得UV/NaClO工藝中RCS降解SA的擬一級動力學常數為0.1384min-1.由式(30)可求得UV/SPC工藝下O2?-降解SA的擬一級動力學常數為0.1339min-1.

由圖7可知,UV/NaClO工藝中各組分貢獻分別為:RCS(79.91%)＞?OH(9.58%)＞UV(7.85%)＞NaClO(2.66%);UV/SPC工藝中各組分貢獻分別為:O2?-(51.75%)＞?OH(41.42%)＞UV(5.25%)＞SPC(1.04%)＞CO3?-(0.54%).UV/NaClO工藝中占主導的自由基是RCS,其貢獻是?OH的8.3倍,原因是生成的?OH轉化為RCS(式(2～4)),該結果與李博強等[23]研究UV-LED/NaClO去除對乙酰氨基酚所得到的規律一致.而UV/SPC工藝中占主導的自由基是O2?-和?OH,兩者貢獻了SA去除的93.17%,O2?-的貢獻超過50%,造成該結果的原因可能是CO32-的存在促進了O2?-的生成(式(10～12)).實際應用中可以加強自由基的生成與轉化進而增強SA的降解效果.UV對兩種工藝降解SA的貢獻相差不大,這可能是因為2種工藝使用同一光源.?OH在2種工藝中的貢獻率相差31.84%,這是因為UV/SPC工藝中?OH穩態濃度(2.72′10-11mol/L)是UV/NaClO工藝下?OH穩態濃度(4.21′10-12mol/L)的6.5倍.UV/SPC工藝中CO3?-在所有組分中的貢獻最低,該結果為EPR無法檢出CO3?-提供了佐證.原因是?OH與CO32-反應(式(10))的二級反應速率常數為3.9′108L/(mol×s),低于SA與?OH的二級反應速率常數3.94′109L/(mol×s)[9].

2.4 UV/NaClO和UV/SPC工藝環境水樣中SA的降解

考察環境水樣(廈漳地區北溪和江東泵站)、自來水及實驗室超純水(水質參數見表1)中對SA降解的影響,不同水體中SA的降解速率如圖8.

表1 環境水樣的主要水質參數

UV/NaClO和UV/SPC工藝在江東泵站、北溪、超純水和自來水水樣中的反應速率分別為0.0517、0.0253、0.2174、0.1354min-1和0.0452、0.0213、0.2588、0.1383min-1.SA的降解速率為超純水>自來水>江東泵站>北溪,這是因為一方面水樣的濁度不同,影響UV的穿透;另一方面水體由有機物、無機物、浮游生物和微生物等復雜基質構成,這些物質在降解時也參與了反應并消耗了氧化劑及產生的自由基[24-25].Parastoo等[25]應用超聲/臭氧工藝時得出濁度會消耗氧化劑.環境水樣中UV/NaClO工藝降解SA的反應速率平均降低了67%,UV/SPC工藝中SA的反應速率平均降低了74%,UV/SPC工藝較UV/NaClO工藝易受自然水體的抑制,可能的原因是由于?OH的無選擇性幾乎可以與所有有機分子發生反應[6],而UV/SPC工藝中?OH的貢獻率大于UV/NaClO工藝中?OH的貢獻率,故其反應速率受自然水體的抑制更大.

圖8 環境水樣對UV/NaClO和UV/SPC工藝降解SA的影響

[SA]0=3.6μmol/L, [NaClO]=40μmol/L,[SPC]=75.6μmol/L,pH=(7.0±0.2)

2.5 UV/NaClO和UV/SPC工藝降解SA過程中溶液急性毒性變化

圖9 UV/NaClO和UV/SPC工藝降解SA過程中急性毒性變化

[SA]0=3.6μmol/L, [NaClO]=40μmol/L,[SPC]=75.6μmol/L,pH=(7.0±0.2)

本文考察了2種工藝降解純水中SA的溶液急性毒性變化,如圖9,隨著降解進行,UV/NaClO工藝中反應溶液的相對抑制率先增加到100%再降至63%,可能的原因是在產物中發現的典型消毒副產物三氯甲烷導致了反應初期毒性升高,隨著反應的進行有毒產物進一步分解從而相對抑制率逐漸下降[26].而UV/SPC工藝中反應溶液相對抑制率保持在25%左右波動,UV/SPC工藝較UV/NaClO工藝低38%的抑制率、表現出較低的急性毒性.Zupanc等[27]人研究表明SA與?OH會生成PhOH和2,5-二羥基苯甲酸(2,5-DHBA)等產物.通過基于QSAR的ECOSAR軟件模擬評估了這兩種產物的急性毒性[28],結果表明產物急性毒性(PhOHEC50=2.40mg/L, 2,5-DHBAEC50=2.92mg/L,EC50數值越小代表毒性越大)均高于SA(SAEC50=11.35mg/L),故UV/SPC工藝降解SA過程中溶液相對抑制率升高可能是由于生成PhOH和2,5-DHBA造成.推測隨著降解的進行產物將會與生成的自由基進一步發生反應,最終相對抑制率進一步降低.

2.6 UV/NaClO和UV/SPC工藝的經濟效益比較

為從經濟效益角度比較2個工藝,采用單位去除能耗(EE/OUV)表示m3水中降解1個數量級SA所需的電能(式(31)).單個工藝總成本(Cost/Ototal)可表示為電能成本(Cost/OUV)與氧化劑成本(Cost/ Ooxidant)之和(式(32～34)),其中工藝總成本單位為$/ (m3×order),表示m3水中降解1個數量級的SA所需要的成本[26].

式中:表示UV汞燈輸入功率,為2×10-3kW;表示反應時間,h;表示反應溶液的體積,L;obs表示擬一級動力學常數,min-1;0表示SA的初始濃度,為500μg/L;C表示SA在反應時刻的濃度,μg/L; [Oxidant]0表示氧化劑的投加量,mg/L; electricity cost表示電費,這里取0.1$/kWh; price[Ox]表示氧化劑的單價,NaClO為0.13$/kg; SPC為0.3$/kg[12,26].

如圖10所示,單獨UV降解SA的成本為18.9$/(m3×order),UV/NaClO工藝成本隨著投加量的增加呈下降趨勢,從最高8.7$/(m3×order)降至4.0$/ (m3×order).Ox/SA=3.7～7.4時UV/NaClO工藝效益曲線發生了轉折,原因是NaClO投加比較低時整體降解效率隨著投加比的增加提升不明顯,但NaClO增加一倍導致氧化劑成本增加1倍,故表現為Ox/SA= 3.7的總體降解成本低于Ox/SA=7.4時. UV/SPC工藝成本隨著投加量的增加從24.4$/ (m3×order)上升至37.1$/(m3×order),且高于單獨UV降解SA的成本.SA降解率達到97.5%以上時, UV/SPC工藝成本是UV/NaClO工藝的9.3倍.從經濟效益角度UV/NaClO工藝較UV/SPC工藝更節約成本,該結果與Lu等[26]比較UV、UV/NaClO和UV/過硫酸鹽的經濟效益得到的結果相似.

圖10 UV/NaClO和UV/SPC工藝降解SA的經濟效益評價

[SA]0=500μg/L, pH=(7.0±0.2)

3 結論

3.1 兩種工藝對SA均能有效降解,反應速率均隨著NaClO、SPC投加量的增加而增加,氧化劑摩爾投加比超過7.4后UV/NaClO工藝比UV/SPC工藝有更高的反應速率與降解率,UV/NaClO工藝和UV/SPC工藝反應速率最高分別達0.4378, 0.3794min-1.

3.2 UV/NaClO體系存在?OH和Cl?, UV/SPC體系中存在O2?-、?OH和CO3?-.SA與?OH、CO3?-的二級反應速率常數分別為3.97′109,8′107L/(mol×s). UV/ NaClO工藝下?OH的穩態濃度為4.21′10-12mol/ L,UV/SPC工藝下?OH、CO3?-的穩態濃度分別為2.72′10-11,8.20′10-11mol/L.自由基在SA的降解中起主導作用,UV/NaClO工藝中以RCS為主導的各組分貢獻順序為:RCS>?OH>UV>NaClO; UV/SPC工藝中以O2?-和?OH為主導的各組分貢獻順序為:O2?->?OH>UV>SPC>CO3?-.

3.3 兩種工藝在環境水樣中降解SA時反應速率均受到了抑制,UV/SPC工藝較UV/NaClO工藝受自然水體的抑制更明顯.從急性毒性角度,UV/SPC工藝反應溶液較UV/NaClO工藝反應溶液低了38%的抑制率.從經濟效益角度,UV/NaClO工藝較UV/SPC工藝具有較高的經濟效益.

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Comparison of UV/NaClO and UV/ Sodium percarbonate processes for degradation of salicylic acid.

MA Xiao-yan1, YANG Fan1, LI Qing-song2,3*, YANG Qing-yun1, CHEN Guo-yuan2, LI Guo-xin2

(1.College of Civil Engineering, Zhejiang University of Technology, Hangzhou 310014, China；2.Water Resource and Environment Institute, Xiamen University of Technology, Xiamen 361024, China；3.Key Laboratory of Water Resources Utilization and Protectionof Xiamen, Xiamen University of Technology, Xiamen 361024, China)., 2022,42(3)：1182～1190

The degradation of salicylic acid (SA) in aqueous solution by UV/NaClO and UV/SPC processes was investigated. The effects of oxidizer types and dosage on SA removal were compared. The free radicals in the two processes were identified by quenching method and electron paramagnetic resonance(EPR) spectroscopy. The second-order rate constants of ?OH and CO3?-with SA and the contributions of different components in the reaction system were determined by competitive kinetics. The removal of SA was compared in terms of environmental water samples simulation, acute toxicity and economic benefit. The pseudo-first-order kinetic rate constants of UV/NaClO and UV/SPC processes were 0.4378 and 0.3794min-1, respectively. ?OH and Cl? were detected in UV/NaClO process, while O2?-, ?OH and CO3?-were detected in UV/SPC process. The second-order rate constants of ?OH and CO3?-with SA were calculated to be 3.97′109and 8′107L/(mol×s), respectively. Reactive chlorine species (RCS) (79.91%) functioned a dominant role in the removal of SA in UV/NaClO process, while O2?-(51.75%) and ?OH (41.42%) functioned a dominant role in UV/SPC process. The degradation of SA in environmental water samples by UV/NaClO and UV/SPC processes was inhibited, and the removal rates were reduced by 67% and 74%, respectively. The inhibition rate of UV/SPC process (25%) was 38% lower than that of UV/NaClO process(63%). The cost of UV/SPC process[37.1$/(m3×order)] was 9.3 times higher than that of UV/NaClO process[4.0$/(m3×order)] when SA degradation rate was above 97.5%. UV/NaClO process had higher economic benefit than UV/SPC process.

UV-AOPs；radical identify；contribution of free radicals；acute toxicity；economic benefit

X703

A

1000-6923(2022)03-1182-09

馬曉雁(1978-),女,山東萊州人,教授,博士,主要研究方向為飲用水微量有機污染物控制.發表論文30余篇.

2021-08-18

國家自然科學基金資助項目(51878582,51978618);福建省科技計劃引導性資助項目(2021Y0041);福建省自然科學基金資助項目(2020J01256);福建省高校新世紀優秀人才支持計劃項目(JA14227);廈門理工學院科研攀登計劃項目(XPDKT19026)

*責任作者, 研究員, leetsingsong@sina.com