楊 柳,劉 丹,劉世昂,吳西林,陳建榮

多活性位點(diǎn)的磁性氮摻雜石墨烯活化過一硫酸鹽研究

楊 柳,劉 丹,劉世昂,吳西林*,陳建榮

(浙江師范大學(xué)地理與環(huán)境科學(xué)學(xué)院,浙江 金華 321004)

通過簡(jiǎn)單的一鍋法制備Fe2O3、Fe3N、單原子Fe(SA-Fe)和N摻雜的磁性石墨烯材料(Fe-MNG)應(yīng)用于催化活化過一硫酸鹽(PMS). 結(jié)果表明,Fe-MNG/PMS體系可在寬的pH范圍(3-10)氧化降解磺胺異惡唑(SIZ),降解率均達(dá)到99%以上. 經(jīng)過五次循環(huán)使用其對(duì)SIZ的降解率仍保持在95%以上. Fe-MNG中的SA-Fe、N等活性位點(diǎn)可高效催化活化PMS產(chǎn)生各種活性氧物種(ROS). 淬滅實(shí)驗(yàn)和電子順磁共振波譜分析表明Fe-MNG/PMS體系中產(chǎn)生多種ROS,包括硫酸根自由基(SO4?–)、羥基自由基(HO?)和單線態(tài)氧(1O2),證明存在自由基和非自由基兩種氧化過程. 此外,Fe-MNG具有大的比表面積(446.18m2/g),能將水中有機(jī)微污染物吸附富集到材料表面,同時(shí)在Fe-MNG表面催化PMS產(chǎn)生大量ROS,實(shí)現(xiàn)對(duì)有機(jī)微污染物的原位、高效氧化去除. Fe-MNG還具有磁性,易于分離和回收,具有潛在的應(yīng)用前景.

高級(jí)氧化；過一硫酸鹽；石墨烯；吸附；單原子催化

磺胺類抗生素是一大類抗菌藥物和生長(zhǎng)促進(jìn)劑[1].磺胺呈弱酸性,溶于水,不能被人和動(dòng)物完全代謝,也不能在常規(guī)污水處理廠中有效去除[2].因此,磺胺很容易排放到地表水中,并轉(zhuǎn)移到水生環(huán)境中[3-4].磺胺的使用量很大,2016年美國(guó)對(duì)磺胺類抗生素的使用量為369t/a,2013年中國(guó)的使用量為7890t/a)[5].大量的研究表明,磺胺類藥物已經(jīng)廣泛存在于各種環(huán)境介質(zhì),包括地表水[6],地下水[7]和沉積物[8]中. 磺胺類藥物在環(huán)境中累積將導(dǎo)致抗生素的耐藥性增加,誘導(dǎo)產(chǎn)生“超級(jí)細(xì)菌”,將對(duì)生態(tài)系統(tǒng)和人類健康構(gòu)成巨大威脅.因此,高效去除水中的磺胺類抗生素具有重要的意義[9].

近年來,基于過硫酸鹽的高級(jí)氧化工藝(AOPs),由于其強(qiáng)的氧化能力和綠色、無污染等優(yōu)點(diǎn),被廣泛的研究應(yīng)用于有機(jī)污染物的降解[10-13].與HO?相比,SO4?–具有更強(qiáng)的氧化性、更長(zhǎng)的半衰期(30～ 40μs)[14].盡管過渡金屬離子(Mn2+、Fe2+、Co2+、Ni2+和Cu2+等)能有效地活化過硫酸鹽產(chǎn)生SO4?–[15-16],但使用過渡金屬離子易造成二次環(huán)境污染且消耗大量的金屬催化劑[17].因此,研究開發(fā)具有高催化活性、高穩(wěn)定性、環(huán)境友好、易于固液分離和重復(fù)使用的催化材料[18],具有重要的應(yīng)用價(jià)值.

納米催化劑具有大比表面積、高催化活性和易于調(diào)控等優(yōu)點(diǎn),被廣泛的應(yīng)用于非均相催化領(lǐng)域.納米材料催化的非均相高級(jí)氧化技術(shù)具有催化效率較高和環(huán)境友好等優(yōu)點(diǎn)[19].過渡金屬氧化物納米粒子能高效地活化過一硫酸鹽(PMS)降解水中的有機(jī)污染物[20-21].在各種過渡金屬氧化物中,鐵氧化物如Fe2O3、Fe3O4具有較好的生物相容性、較低的毒性和磁性等優(yōu)點(diǎn)[22],在環(huán)境催化領(lǐng)域具有潛在的應(yīng)用價(jià)值.此外,負(fù)載型金屬催化材料也被廣泛研究應(yīng)用于環(huán)境催化.例如,鈷酞菁負(fù)載的還原氧化石墨烯、CuFe2O4納米顆粒負(fù)載的氮摻雜氧化石墨烯等均能有效催化活化PMS[20,23-24].石墨烯負(fù)載的金屬催化劑具有金屬催化和石墨烯吸附雙重優(yōu)勢(shì),有望實(shí)現(xiàn)對(duì)水中有機(jī)污染物的高效吸附富集和催化降解.然而,上述石墨烯基催化材料仍存在制備方法復(fù)雜、難以回收利用和穩(wěn)定性較差等缺點(diǎn).

為了解決上述問題,本文采用簡(jiǎn)單的一鍋法制備了具有多活性位點(diǎn)的Fe2O3、Fe3N和單元子Fe負(fù)載的氮摻雜磁性石墨烯(Fe-MNG),并成功應(yīng)用于高效催化活化PMS.本研究包括以下幾個(gè)部分:1)探究初始pH、催化劑用量和PMS用量等對(duì)Fe-MNG/PMS體系降解磺胺異噁唑(SIZ)的影響;2)研究Fe-MNG的穩(wěn)定性和循環(huán)使用性能;3)通過各種表征手段探明Fe-MNG催化PMS的活性位點(diǎn),識(shí)別活性氧(ROS)物種,推測(cè)Fe-MNG/ PMS體系中ROS產(chǎn)生機(jī)理.

1 實(shí)驗(yàn)部分

1.1 試劑與儀器

三聚氰胺(M)由鼎盛鑫化學(xué)工業(yè)有限公司(中國(guó)天津)提供.美羅培南(MEM)、糠醇(FFA)、氯化血紅素(Hemin)和聚乙烯亞胺(PEI)購(gòu)自阿拉丁試劑公司(中國(guó)).磺胺異惡唑(SIZ),磺胺甲惡唑(SMX)購(gòu)自東京化學(xué)工業(yè)有限公司(日本東京).三聚氰酸(CA)購(gòu)自阿法埃莎公司(中國(guó)).過一硫酸鹽(PMS)、鹽酸(HCl)、氫氧化鈉(NaOH)、甲醇(CH3OH)、異丙醇((CH3)2CHOH)購(gòu)自國(guó)藥化學(xué)試劑有限公司(中國(guó)).實(shí)驗(yàn)用0.45μm水系聚醚砜過濾膜購(gòu)于天津津騰實(shí)驗(yàn)設(shè)備有限公司.

用透射電子顯微鏡(TEM,JEM-2100,日本)、X射線光電子能譜(XPS,Thermo Escalab 250,美國(guó))、X射線衍射儀(XRD,Shimadzu XRD-6000,日本)、激光拉曼光譜儀(Raman, Horiba Jobin Yvon LabRam,法國(guó))對(duì)材料進(jìn)行表征.使用比表面分析儀(Quantachrome Instruments version 11.03)測(cè)試材料的比表面積和孔徑.采用總有機(jī)碳(TOC)分析儀(Elementar,Liqui TOC II,德國(guó))測(cè)定反應(yīng)溶液中有機(jī)物總量.電子順磁共振(EPR,JES-FA200,Japan)測(cè)定體系中的活性氧物種.溶液中的有機(jī)物含量由高效液相色譜儀測(cè)定(HPLC,Agilent 1200Infinity).

1.2 Fe-MNG的制備

前驅(qū)體由0.32g(2.5mmol)的三聚氰胺(M)、0.52g(4mmol)的三聚氰酸(CA)和0.50g的聚乙烯亞胺(PEI)在20mL去離子水中自組裝得到.將得到的乳狀膠體用0.45μm濾膜過濾,在60℃下真空干燥10h,即得到PEI-MCA前驅(qū)體.將血紅素(0.05g)溶于5.0mL乙醇中并與1.25g PEI-MCA前驅(qū)體充分研磨.將得到的混合物置于管式煅燒爐中,在550℃、氮?dú)鈿夥罩徐褵?h,后升溫至800℃煅燒2h.待管式爐冷卻至室溫,即得到Fe-MNG材料.

1.3 催化降解實(shí)驗(yàn)

將3.0mg催化劑粉末超聲分散到30mL的SIZ溶液(20mg/L)中,攪拌60min達(dá)到吸附平衡.接著在懸浮液中加入3.0mg的PMS引發(fā)氧化降解反應(yīng).在一定的時(shí)間間隔,吸取0.5mL反應(yīng)溶液加入到0.5mL甲醇中淬滅反應(yīng),并立即用0.45μm的過濾膜分離催化劑.溶液中的SIZ濃度通過高效液相色譜 (HPLC)測(cè)定.HPLC檢測(cè)器為紫外檢測(cè)器,檢測(cè)波長(zhǎng)為270nm.流動(dòng)相的組成為乙腈:水(含0.15%三氟乙酸(TFA))=55:45,流速為0.7mL/min,進(jìn)樣量為20μL.循環(huán)實(shí)驗(yàn)保持上述所有條件不變,每次降解實(shí)驗(yàn)后,將Fe-MNG催化劑分離,用乙醇和去離子水分別清洗3次后真空干燥,再進(jìn)行下一次循環(huán).

2 結(jié)果與討論

2.1 材料表征

透射電子顯微鏡(TEM)圖片中[圖1(a)],Fe納米顆粒分布在在褶皺的石墨烯薄片上.高分辨TEM (HRTEM)圖像[圖1(b)]顯示Fe納米粒子的晶格條紋間距均為0.23nm,對(duì)應(yīng)于Fe2O3的(104)晶面[25].由圖1c的TEM圖片和圖1d～1f的能量色散X射線能譜(EDX)分析,可以看出,C、N元素均勻分布在石墨烯片的整個(gè)范圍內(nèi),而Fe顆粒分散在石墨碳基質(zhì)中.Fe-MNG和石墨烯(graphene)的X-射線衍射(XRD) [圖1(g)]顯示在20°～30°之間存在一個(gè)寬峰,對(duì)應(yīng)于石墨烯中石墨碳的特征峰[26].而Fe-MNG的XRD圖譜中大多數(shù)的特征峰屬于Fe2O3(JCPDS 16-0653)22和Fe3N(JCPDS 49-1664).圖1h中,Fe-MNG的拉曼光譜中存在G帶和D帶[27]. G帶(1580cm–1)由sp2碳的振動(dòng)形成,D帶(1350cm–1)由無序碳產(chǎn)生[28].D帶與G帶的強(qiáng)度比為1.37[29].表明該氮摻雜的石墨烯中存在大量的缺陷,從而提供額外的活性位點(diǎn).

圖1 樣品的TEM圖、能譜mapping圖像、XRD譜圖和Raman光譜圖

圖2 刻蝕后Fe-MNG的TEM、XRD和HAADF-STEM圖片

Fe-MNG中除了存在Fe2O3和Fe3N外,還存在大量的單原子Fe(SA-Fe)分散在石墨烯載體中.為證明單原子Fe(SA-Fe)的存在,通過酸刻蝕后,Fe-MNG中的鐵氧化合物以及鐵氮化合物均被去除,僅檢測(cè)到一個(gè)石墨稀的寬峰.由圖2(a)中的TEM和HRTEM圖片,以及圖2(b)中的XRD譜圖可以證明鐵顆粒被去除.球差矯正高角環(huán)形暗場(chǎng)像掃描透射電子顯微鏡(HAADF-STEM)圖片[圖2(c)、2(d)]顯示存在大量的金屬原子亮點(diǎn)(白色虛線圓圈標(biāo)注),說明存在SA-Fe活性位點(diǎn).進(jìn)一步證明Fe2O3、Fe3N、單原子Fe(SA-Fe)和N摻雜的磁性石墨烯材料(Fe-MNG)被成功制備.

圖3 Fe-MNG的N2吸附—脫附及XPS譜圖

圖4 pH值、PMS和Fe-MNG用量對(duì)SIZ降解的影響

[SIZ]=20mg/L,[PMS]=0.1g/L,[Fe-MNG]=[FeSO4]=0.1g/L,pH=3.0,=303K

如圖3a所示,圖中吸附等溫線在相對(duì)高壓力區(qū)域(/0>0.5)呈現(xiàn)出閉合的回滯環(huán),證明存在大量的介孔.圖3a中孔徑分布也證明了介孔的存在[30].根據(jù)Brunauer-Emmett-Teller(BET)分析, Fe-MNG的比表面積為446.18m2/g,說明其比表面積巨大.該材料的多孔性質(zhì)和大的比表面積賦予其大量的離子、分子傳輸通道和暴露更多的催化活性位點(diǎn),從而極大提升非均相催化的效率[31-32].圖3(b)為Fe-MNG和石墨烯的X-射線光電子能譜(XPS)圖,可以看出Fe-MNG中存在C,N,O和Fe元素.其中N的峰最強(qiáng),說明其中大量的N摻雜.這些N摻雜在石墨烯載體中提供了豐富的缺陷位點(diǎn),同時(shí)為固定金屬Fe原子提供優(yōu)良的配位環(huán)境.Fe-MNG的高分辨N 1s XPS譜圖在398.2, 399.6,400.6和404.0eV處的峰,分別對(duì)應(yīng)于吡啶N(63.2%)、吡咯N(17.3%)、石墨N(19.5%)和氧化N[圖3(c)][33-34].大量存在的吡啶N和吡咯N為Fe單原子提供錨定位點(diǎn).此外,吡啶N和吡咯N上的孤對(duì)電子與石墨烯π電子耦合,極大促進(jìn)了催化過程中石墨烯載體與金屬活性位點(diǎn)之間的電子轉(zhuǎn)移.高分辨Fe 2p XPS光譜中[圖3(d)]存在4個(gè)峰,其中710.9和724.5eV對(duì)應(yīng)于Fe2+,712.9和729.0eV處對(duì)應(yīng)于Fe3+[35-36].Fe3+主要來源于Fe2O3,而Fe2+主要來源于單原子Fe,進(jìn)一步證明Fe-MNG中存在多種Fe活性位點(diǎn)[37].

2.2 吸附、催化性能研究

對(duì)Fe-MNG催化活化過一硫酸鹽(PMS)降解磺胺異惡唑(SIZ)的性能進(jìn)行了研究.如圖4(a)所示,在60min吸附過程,大約10-20%的SIZ被吸附.在寬的pH值范圍 (pH 3.0～10.0),Fe-MNG/PMS體系中SIZ(20mg/L)的降解率均達(dá)到98%以上.在pH11.0時(shí),SIZ的降解率下降到65%,說明在強(qiáng)堿性條件下Fe-MNG/PMS體系的氧化性能降低.在堿性條件下PMS易失去質(zhì)子生成SO52?(式(1)),并進(jìn)一步消耗PMS反應(yīng)生成1O2(式(2)).

HSO5?- H+→ SO52?(1)

HSO5?+ SO52?→HSO4?+ SO42?+1O2(2)

SO4?–+ OH?→SO42?+ HO?(3)

盡管堿可以活化PMS,但是強(qiáng)堿性條件不利于SO4?–的生成(式(3)),導(dǎo)致在pH11時(shí)氧化效果變差.此外,在堿性條件下HO?自由基的氧化還原電位下降,導(dǎo)致其氧化性能下降.圖4(b)展示了Fe-MNG/ PMS體系反應(yīng)過程中的pH值變化,可以發(fā)現(xiàn)體系的pH值略有下降,說明加入了少量的PMS(0.1g/L)對(duì)體系的pH值略有影響.采用ICP-MS檢測(cè)了不同pH值條件下鐵離子的浸出,測(cè)得的鐵離子濃度均小于0.1mg/L,說明該材料具有優(yōu)異的穩(wěn)定性,證明炭包裹可以減少金屬的浸出.圖4(c)和圖4(d)表明在較低的Fe-MNG(0.05g/L)和PMS(0.05g/L)用量下,SIZ的降解率均能達(dá)到99%,說明該體系具有高的催化氧化效率,可以極大減少催化劑和氧化劑的用量.本文還比較了基于PMS的非均相催化氧化體系與均相催化氧化體系降解SIZ的效果,從圖4(e)可以看出Fe-MNG/PMS比Fe2+/PMS能更好地降解SIZ,這可能由于Fe-MNG催化劑中有更多的催化活性位點(diǎn)且提高了PMS的利用率.此外,在均相體系中Fe2+逐漸被氧化為Fe3+且不易再生,使得其催化性能下降.污染物的礦化程度也是衡量高級(jí)氧化體系的重要指標(biāo).如圖4(f)所示,在140min內(nèi),Fe-MNG/PMS降解SIZ體系的總有機(jī)碳(TOC)去除率達(dá)到90%,表明大量的中間產(chǎn)物降解為小分子H2O和CO2[38-39],證明Fe-MNG/PMS高級(jí)氧化體系具有優(yōu)異的氧化能力,對(duì)污染物的礦化程度較高.

循環(huán)使用性能是衡量催化劑實(shí)用性的一項(xiàng)重要指標(biāo).如圖5a所示,在Fe-MNG/PMS體系中,五次循環(huán)降解SIZ的去除率分別達(dá)到99.9%, 99.8%, 99.0%,98.0%和96.0%,表明該催化劑具有良好的循環(huán)使用性能.研究了Fe-MNG對(duì)SIZ的吸附性能(圖5b).SIZ在Fe-MNG上的吸附等溫線分別用Langmuir和Freundlich等溫線模型進(jìn)行擬合[40-41]. Langmuir模型數(shù)學(xué)公式如下:

式中:e(mg/g)為平衡條件下單位質(zhì)量Fe-MNG對(duì)SIZ的吸附量,e(mg/L)是吸附平衡時(shí)溶液中SIZ的濃度,max(mg/g)為計(jì)算得到的SIZ在Fe-MNG上的最大吸附量,而(L/g)為L(zhǎng)angmuir模型的吸附常數(shù)[42].Freundlich模型的數(shù)學(xué)公式如下:

e=e1/n(5)

Freundlich常數(shù)和分別代表了吸附能力和吸附強(qiáng)度.表1為對(duì)應(yīng)的擬合參數(shù).結(jié)果表明Langmuir模型能更好的擬合實(shí)驗(yàn)數(shù)據(jù),說明SIZ在Fe-MNG上的吸附屬于單層吸附[43].SIZ在Fe-MNG上的最大吸附量達(dá)到263.27mg/g,表面該材料具有較大的吸附容量.此外,Fe-MNG易于在外加磁場(chǎng)下分離、回收和重復(fù)使用(圖5b).

圖5 Fe-MNG催化降解及吸附試驗(yàn)

[SMX]=[SIZ]=[MEM]=20mg/L,[PMS]=0.1g/L,[Fe-MNG]=0.1g/L,pH=7.0,=303K,=24h

表1 Langmuir和Freundlich模型擬合吸附等溫線參數(shù)

在制藥廠污水處理廠出水中添加SIZ(20mg/L)模擬真實(shí)廢水,進(jìn)一步探究Fe-MNG催化活化PMS對(duì)實(shí)際廢水的處理效果.結(jié)果表明[圖5(c)],在10min內(nèi)超過94%的SIZ被氧化去除.此外,Fe-MNG/PMS體系還能高效去除其它抗生素類有機(jī)微污染物[圖5(d)],如磺胺甲惡唑(去除率88.7%)和美洛培南(去除率90.0%).上述結(jié)果表明,具有多催化活性位點(diǎn)的Fe-MNG材料能高效活化PMS;同時(shí)大比表面積的石墨烯載體賦予其優(yōu)異的吸附性能,能有效富集水中低濃度的有機(jī)微污染物;通過吸附富集和催化氧化協(xié)同作用實(shí)現(xiàn)水中抗生素類有機(jī)微污染物的快速高效去除.此外, Fe-MNG還具有磁性和優(yōu)異的循環(huán)使用性能,易于回收和重復(fù)使用,具有潛在的應(yīng)用前景.

2.3 催化機(jī)理探究

猝滅實(shí)驗(yàn)可探究Fe-MNG/PMS體系中產(chǎn)生的活性物種.采用異丙醇(IPA)淬滅羥基自由基(HO?),甲醇(MeOH)淬滅HO?和硫酸根自由基(SO4?–),糠醇(FFA)淬滅單線態(tài)氧(1O2).如圖6(a)所示,加入FFA、IPA和MeOH后,SIZ的降解率分別為29%、88%和58%,表明1O2、SO4?–和HO?均起到氧化降解SIZ的作用.因此,Fe-MNG對(duì)SIZ優(yōu)異的降解效果歸因于自由基(SO4?–,HO?)與非自由基(1O2)的共同作用.

圖6 猝滅實(shí)驗(yàn)、EPR譜圖和Fe-MNG/PMS體系降解SIZ示意

電子順磁共振 (EPR)實(shí)驗(yàn)使用5,5-二甲基-1-吡咯啉N-氧化物(DMPO)作為SO4?–和HO?捕獲劑,2,2,6,6-四甲基-4-哌啶醇(TEMP)作為1O2捕獲劑.如圖6(b)所示,在Fe-MNG/PMS體系中觀察到相同強(qiáng)度的三重峰,對(duì)應(yīng)于TEMP-1O2信號(hào),表明在Fe-MNG/PMS體系中產(chǎn)生1O2物種[17,44].類似地, Fe-MNG/PMS體系中探測(cè)到DMPO-HO?(1:2:2:1四重峰)和DMPO-SO4?–(1:1:1:1:1:1六重峰)的信號(hào)[圖6(c)],表明Fe-MNG可以有效活化 PMS產(chǎn)生活性自由基.上述結(jié)果進(jìn)一步證明SO4?–,HO?與1O2共存于Fe-MNG/PMS體系中.

首先,活性Fe物種可以催化活化PMS產(chǎn)生自由基.其中,單元子Fe物種(≡Fe2+)可催化PMS產(chǎn)生SO4?–(反應(yīng)式(6)和(7)).此外,產(chǎn)生的SO4?–可進(jìn)一步生成HO?(反應(yīng)式(8))[45].

HSO5–+ ≡Fe2+→ SO4?–+ ≡Fe3++ OH–(6)

≡Fe3++ HSO5–→ SO5?–+ Fe2++ H+(7)

SO4?–+ H2O→ SO42–+ HO?(8)

其次,豐富的N活性位點(diǎn)也可通過電子轉(zhuǎn)移活化PMS(反應(yīng)式(9)和(10)),產(chǎn)生SO4?–和HO?自由基[46].

HSO5–+ e–→ SO42–+ HO?(9)

HSO5–+ e–→ OH–+ SO4?–(10)

在Fe-MNG作用下,PMS產(chǎn)生大量的1O2(反應(yīng)式(11)).上述結(jié)果表明,Fe-MNG可以顯著活化PMS產(chǎn)生大量ROS(反應(yīng)式(12)).最終,表面吸附的SIZ可以上述原位產(chǎn)生的ROS降解為小分子中間產(chǎn)物,并逐漸礦化為H2O和CO2[圖6(d)].

2SO5??+ H2O → 2HSO4?+1.51O2(11)

SO4??+?OH +1O2+ SIZ → degraded products(12)

3 結(jié)論

采用簡(jiǎn)單的一鍋法,合成出具有Fe2O3、Fe3N、SA-Fe和N摻雜的Fe-MNG材料.Fe-MNG復(fù)合材料兼具優(yōu)異的吸附性能和催化效果,通過高效吸附富集和快速氧化降解,實(shí)現(xiàn)抗生素類有機(jī)微污染物如SMX、SIZ和MEM的高效去除.Fe-MNG活化PMS氧化過程包括自由基和非自由基兩種途徑,產(chǎn)生的SO4??、?OH 和1O2多種ROS共同起到高效氧化和礦化有機(jī)污染物的作用.此外,Fe-MNG還具有磁性和優(yōu)良的循環(huán)使用性能,易于回收和重復(fù)使用.本研究提供了一種廉價(jià)制備具有多活性中心的新型石墨烯復(fù)合材料的方法,將極大推動(dòng)非均相類芬頓氧化技術(shù)的實(shí)際應(yīng)用.

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Magnetic N-doped graphene with multiple catalytic sites for efficient activiation of peroxymonosulfate.

YANG liu, LIU Dan, LIU Shi-ang, WU Xi-lin*, CHEN Jian-rong

(College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China)., 2021,41(9)：4127～4134

The Fe2O3, Fe3N, single-atom Fe (SA-Fe) and N-doped magnetic graphene (Fe-MNG) were prepared by a facile one-pot method and applied for the activation of perpxymonosulfate (PMS). The results show that Fe-MNG/PMS system was efficient for the oxidative degradation of sulfisoxazole (SIZ) over a wide pH range (3～10) with the removal percentages over 99%. After five cycles, degradation percentages of SIZ maintain over 95% by using the recycled Fe-MNG catalyst. The multiple catalytic sites such as SA-Fe and N of Fe-MNG can effectively activate PMS for the generation of various reactive oxygen species (ROS). Quenching experiment and electron paramagnetic resonance spectroscopy showed that SO4?–, HO? and1O2were produced in the Fe-MNG/PMS system, demonstrating the co-existence of free radicals and non-radicals processes. In addition, the Fe-MNG possesses large surface area (446.18m2/g), which can pre-concentrate organic micropollutants onto its surface by adsorption, simultaneously producing a large amount of ROS via PMS activation, leading to the in-situ and high-efficiency oxidation and removal of organic micropollutants. The Fe-MNG also possesses magnetic properties which can be easily recycled, indicating its great application potential.

advanced oxidation process；peroxymonosulfate；graphene；adsorption；single-atom catalysis

X703.5

A

1000-6923(2021)09-4127-08

楊 柳(1995-),女,新疆五家渠人,浙江師范大學(xué)碩士研究生,主要研究方向?yàn)楦呒?jí)氧化技術(shù).

2021-02-02

浙江省自然科學(xué)基金(LGF19B070006);浙江省重點(diǎn)研發(fā)計(jì)劃(2021C03163)

* 責(zé)任作者, 副教授, dbwxl@zjnu.cn