富里酸在聚苯乙烯微塑料上的吸附行為

孫 璇,俞安琪,王學(xué)松,林陸健,湯 帥,李夢(mèng)瑤

富里酸在聚苯乙烯微塑料上的吸附行為

孫 璇,俞安琪,王學(xué)松*,林陸健,湯 帥,李夢(mèng)瑤

(江蘇海洋大學(xué)環(huán)境與化學(xué)工程學(xué)院,江蘇 連云港 222000)

主要探究富里酸(FA)在聚苯乙烯(PS)和HBCD-PS復(fù)合物(HBCD-PS)微塑料上的吸附特性與作用機(jī)制.結(jié)果表明,PS對(duì)FA幾乎沒(méi)有吸附效果,然而HBCD的存在顯著地促進(jìn)了FA在HBCD-PS上的吸附行為.W-M顆粒內(nèi)擴(kuò)散和Boyd擴(kuò)散模型證實(shí)了HBCD-PS對(duì)FA的吸附過(guò)程主要受顆粒內(nèi)擴(kuò)散控制.HBCD-PS對(duì)FA的吸附過(guò)程更加符合準(zhǔn)二級(jí)動(dòng)力學(xué)和Freundlich模型.溶液pH值和NaCl含量顯著地影響HBCD-PS對(duì)FA的吸附量. HBCD-PS主要通過(guò)疏水和靜電相互作用與FA結(jié)合.此外,重金屬離子(Cu(Ⅱ)、Pb(Ⅱ)、Zn(Ⅱ)和Cd(Ⅱ))的存在促進(jìn)了FA在HBCD-PS上的吸附,這與它們之間的絡(luò)合能力呈正相關(guān).

微塑料；六溴環(huán)十二烷；富里酸；吸附機(jī)理；金屬離子

近年來(lái),由于塑料制品產(chǎn)量的迅速增加和處置不當(dāng),導(dǎo)致大量的塑料碎片進(jìn)入水生環(huán)境中.這些塑料碎片經(jīng)過(guò)風(fēng)化、侵蝕磨損和光氧化等過(guò)程最終降解為尺寸較小的塑料碎片,其中,微型塑料碎片(微塑料,有效直徑小于5mm[1])被認(rèn)為是水生生態(tài)系統(tǒng)中的一個(gè)嚴(yán)重新風(fēng)險(xiǎn)[2-3].由于微塑料具有體積小、比表面積大、疏水性強(qiáng)等物理化學(xué)性質(zhì)[4],使得其可通過(guò)聚集或吸附在生物體細(xì)胞膜的表面上從而對(duì)水生生物構(gòu)成潛在的威脅[5].此外,微塑料可能會(huì)吸附一些污染物并通過(guò)食物網(wǎng)將它們轉(zhuǎn)移到生物體中,這就造成了更為嚴(yán)重的毒性效應(yīng)[2].因此,探究微塑料富集污染物的行為和作用機(jī)制可以為環(huán)境中微塑料風(fēng)險(xiǎn)的評(píng)估提供一定的理論依據(jù).

目前,許多研究表明微塑料可作為一些污染物的載體,如重金屬[6-7]、抗生素[8]、多氯聯(lián)苯[9]、多環(huán)芳烴[10]等.其中,Fang等[11]發(fā)現(xiàn)己唑醇、腈菌唑和三唑醇在聚苯乙烯(PS)微塑料上的吸附主要由靜電和疏水相互作用所控制.一些藥物(如三氯生[12]和土霉素[13])在微塑料上的吸附也展現(xiàn)出類(lèi)似的作用機(jī)制.Lin等[8]探究四環(huán)素在聚酰胺(PA)微塑料上的吸附行為,發(fā)現(xiàn)疏水分配作用是該過(guò)程的主要作用機(jī)制.在自然水環(huán)境中,溶解性有機(jī)碳(DOC)的濃度范圍為0.5～10mg/L;濕地系統(tǒng)中DOC的平均含量在15～30mg/L[14].其中,富里酸(FA)是一種廣泛存在于天然水體中的常見(jiàn)溶解性有機(jī)物(DOM),其含有大量羧基、羥基和酚類(lèi)等活性官能團(tuán)[15].FA的存在對(duì)有機(jī)污染物和重金屬離子等污染物的遷移、轉(zhuǎn)化和毒性有重要的調(diào)控作用[16-18].最近研究報(bào)道FA的存在能夠顯著地影響一些污染物在微塑料上的界面行為[19-21].然而,關(guān)于FA在微塑料上吸附行為的研究較為匱乏.因此,探究FA與微塑料之間的相互作用機(jī)制對(duì)評(píng)價(jià)微塑料在環(huán)境中生態(tài)風(fēng)險(xiǎn)的評(píng)估具有重要意義.

1 材料和方法

1.1 材料與試劑

富里酸(FA)、氯化鈉(NaCl)、氫氧化鈉(NaOH)、硝酸銅(Cu(NO3)2·3H2O)、硝酸鋅(Zn(NO3)2·6H2O)、硝酸鉛(Pb(NO3)2)、硝酸鎘(Cd(NO3)2·4H2O)均購(gòu)自中國(guó)上海阿拉丁試劑有限公司,硝酸(HNO3)購(gòu)自中國(guó)南京化學(xué)試劑有限公司,所有實(shí)驗(yàn)所用的化學(xué)試劑均為分析純.實(shí)驗(yàn)材料包括六溴環(huán)十二烷(HBCD)粉末、聚苯乙烯(PS)微塑料、PS摻雜HBCD的復(fù)合物微塑料(HBCD-PS,HBCD的含量約2%(質(zhì)量分?jǐn)?shù)))均購(gòu)自中國(guó)連云港啟航阻燃材料有限公司.其中,采用粉碎機(jī)將微塑料顆粒制備成尺寸分別為30～50, 150～200, 300～350目的顆粒.

1.2 實(shí)驗(yàn)方法

溶解一定量固體于超純水中制備了FA儲(chǔ)備液(1g/L)和4種金屬離子(Zn(Ⅱ)、Cd(Ⅱ)、Pb(Ⅱ)、Cu(Ⅱ))儲(chǔ)備液(10mmol/L).其中,加入10mL HNO3(1%)于金屬離子儲(chǔ)備液,以防止形成金屬氧化物沉淀.所有吸附實(shí)驗(yàn)均在黑暗條件下的恒溫振蕩器中進(jìn)行,其轉(zhuǎn)速為190r/min. 采用HNO3和NaOH調(diào)節(jié)溶液pH值. 所有實(shí)驗(yàn)3組平行,同時(shí)進(jìn)行空白實(shí)驗(yàn).

1.2.1 吸附動(dòng)力學(xué) 分別稱(chēng)取0.3g的HBCD-PS、PS微塑料(150～200目)于150mL錐形瓶中,隨后加入100mL濃度為10mg/L、pH值為6的FA溶液,在恒溫振蕩器中設(shè)置溫度分別為15, 25和40℃進(jìn)行振蕩直至吸附平衡.按照時(shí)間間隔(0.25, 0.5, 1, 2, 4, 6, 12, 24, 36, 48和60h)取樣,將取樣樣品放入轉(zhuǎn)速為4000r/min的離心機(jī)內(nèi)離心5min,并于黑暗中存儲(chǔ).

1.2.2 吸附等溫線(xiàn) 將FA母液分別稀釋成濃度為1, 2, 5, 10, 20, 30和50mg/L, 3種HBCD-PS微塑料尺寸(30～50, 150～200, 300～350目)以探究微塑料尺寸對(duì)吸附性能的影響,溫度設(shè)置為25℃.其余所有實(shí)驗(yàn)條件及操作均與吸附動(dòng)力學(xué)實(shí)驗(yàn)中相同.

1.2.3 pH值、鹽度和重金屬離子的影響 采用HNO3和NaOH溶液調(diào)節(jié)FA溶液的pH值(3～10).用一系列不同濃度的NaCl溶液(0%～3.5%)模擬鹽度對(duì)其吸附的影響.Zn(Ⅱ)、Cd(Ⅱ)、Pb(Ⅱ)、Cu(Ⅱ)母液分別稀釋為0.005, 0.01, 0.02, 0.03和0.05mmol/L.溫度設(shè)置在25℃.其余所有實(shí)驗(yàn)條件均與動(dòng)力學(xué)實(shí)驗(yàn)中相同.

1.3 表征及測(cè)定方法

采用掃描電鏡(SEM, MERLIN Compact型,德國(guó))表征微塑料表面特征, 傅里葉紅外光譜儀(ATR- FTIR,Thermo Nicolet iS50型,美國(guó))辨識(shí)材料表面的官能團(tuán),電位分析儀(Malvern Zetasizer Nano ZS90型,英國(guó))測(cè)定微塑料表面的電荷.采用X射線(xiàn)光電子能譜(XPS,Thermo Scientific K-Alpha型,英國(guó))表征吸附FA前后微塑料的表面元素組成和化學(xué)狀態(tài).

采用紫外-可見(jiàn)光分光光度計(jì)(UV-5100B型,中國(guó))在波長(zhǎng)254nm處測(cè)定FA的吸光度.

1.4 數(shù)據(jù)處理及吸附模型

根據(jù)初始濃度與剩余濃度之間的質(zhì)量差計(jì)算吸附量(Q),見(jiàn)式(1):

錫是我國(guó)優(yōu)勢(shì)金屬資源，錫石多金屬硫化礦是我國(guó)特色錫礦資源。由于錫石性脆，在選礦生產(chǎn)中存在錫石過(guò)磨和硫化礦欠磨的突出矛盾，影響錫的金屬回收率和硫化礦精礦質(zhì)量?？紤]到該類(lèi)礦石的礦物組成復(fù)雜，涉及硫化礦、氧化礦和脈石等眾多礦物成分，且不同礦物成分存在較大的吸波特性差異，因此，本文從利用微波選擇性加熱潛力出發(fā)，研究傳統(tǒng)加熱與微波加熱預(yù)處理對(duì)錫石多金屬硫化礦助磨的差異，旨在探索錫石多金屬硫化礦的微波加熱輔助磨礦新途徑。

式中:Q(mg/g)和C(mg/L)分別為(h)時(shí)刻的吸附量和吸附質(zhì)濃度;0(mg/L)為吸附質(zhì)的初始濃度;為微塑料的質(zhì)量,g;為溶液的體積,L.

采用準(zhǔn)一級(jí)動(dòng)力學(xué)、準(zhǔn)二級(jí)動(dòng)力學(xué)、W-M顆粒內(nèi)擴(kuò)散和Boyd擴(kuò)散動(dòng)力學(xué)模型擬合實(shí)驗(yàn)數(shù)據(jù).

2 結(jié)果和討論

2.1 表征

由圖1可知,HBCD-PS微塑料為不規(guī)則顆粒,表面呈現(xiàn)出許多褶皺、孔隙等.這些不規(guī)則的結(jié)構(gòu)可能為HBCD-PS微塑料吸附FA提供了吸附的位點(diǎn).吸附FA后,HBCD-PS表面許多孔隙的消失,表明HBCD-PS對(duì)FA的吸附過(guò)程可能存在著微孔填充的機(jī)制[28].此外,這兩種微塑料的一些表征如SEM- EDS, BET, XRD, TGA見(jiàn)文獻(xiàn)[6].總體來(lái)說(shuō),HBCD的加入改變了PS微塑料表面的物理、化學(xué)性能,這主要是由生產(chǎn)工藝引起的.

采用FTIR和XPS表征來(lái)分析HBCD-PS微塑料與FA之間的作用機(jī)制.HBCD-PS及其吸附FA后的FTIR光譜圖如圖2所示.大約在2930cm-1的峰是脂肪族結(jié)構(gòu)(–CH、–CH2和–CH3)中的C–H伸縮振動(dòng)所致[29].大約在1450cm-1處的峰由C–C振動(dòng)引起[30].在691cm-1的峰可能是由于C–Br伸縮振動(dòng)導(dǎo)致[6].HBCD-PS吸附FA后,1450cm-1處的峰偏移至1455cm-1,說(shuō)明了HBCD-PS對(duì)FA的吸附過(guò)程中可能存在著疏水相互作用[31].沒(méi)有新峰的出現(xiàn)及原峰的消失,說(shuō)明該吸附過(guò)程主要以物理作用為主[32].

圖1 100～150目HBCD-PS微塑料的照片和SEM圖

(a,b,c,d) HBCD-PS微塑料;(e,f)吸附FA后的HBCD-PS

圖2 HBCD-PS微塑料及其負(fù)載FA后的FTIR光譜圖

由圖3a可知, HBCD-PS微塑料表面存在著C1s、O1s和Br3d峰,其原子百分比含量分別為82.35%、9.19%和7.06%. HBCD-PS吸附FA后,其O1s的含量顯著地增長(zhǎng)至15.28%,證實(shí)了FA吸附在HBCD-PS表面上.在C1s精細(xì)譜中(圖3b), HBCD-PS微塑料呈現(xiàn)出C—H/C—C(284.8eV)、C-Br (286.2eV)和π-π*(291.5eV)化學(xué)鍵.吸附FA后, HBCD-PS的C1s精細(xì)譜中新增加O=C-O (289.1eV)再一次證實(shí)了FA確實(shí)吸附在HBCD-PS微塑料表面上.FA的分子中含有O=C-O官能團(tuán),因此,FA的吸附使HBCD-PS表面呈現(xiàn)出O=C-O官能團(tuán).

(a)全譜圖;(b) C1s的精細(xì)譜圖

2.2 吸附動(dòng)力學(xué)

圖4 不同溫度下PS和HBCD-PS微塑料對(duì)FA的吸附動(dòng)力學(xué)

由圖4可知,PS對(duì)FA幾乎沒(méi)有吸附效果,然而HBCD的存在顯著地促進(jìn)了FA在HBCD-PS上的吸附行為.其中,隨著溫度的升高,HBCD-PS對(duì)FA的吸附量增加.這表明了高溫有利于HBCD-PS對(duì)FA的吸附,該過(guò)程主要為吸熱反應(yīng).采用準(zhǔn)一級(jí)動(dòng)力學(xué)和準(zhǔn)二級(jí)動(dòng)力學(xué)模型對(duì)吸附數(shù)據(jù)進(jìn)行擬合,擬合的結(jié)果如表1所示.較大的2值以及較小的RMSE值說(shuō)明了HBCD-PS對(duì)FA的吸附過(guò)程更加符合準(zhǔn)二級(jí)動(dòng)力學(xué)模型,這表明吸附過(guò)程是多個(gè)吸附階段共同作用的結(jié)果[29].

表1 FA在HBCD-PS微塑料上的吸附動(dòng)力學(xué)模型擬合參數(shù)

注:1和2分別為準(zhǔn)一級(jí)和準(zhǔn)二級(jí)動(dòng)力學(xué)的平衡速率常數(shù);e為平衡時(shí)的吸附量;2為相關(guān)系數(shù); RMSE為殘差均方根誤差.

表2 HBCD-PS微塑料吸附FA的顆粒內(nèi)擴(kuò)散模型擬合參數(shù)

注:為內(nèi)擴(kuò)散模型的速率常數(shù);與擴(kuò)散邊界層相關(guān).

通常來(lái)說(shuō),吸附過(guò)程分為4個(gè)過(guò)程,即傳質(zhì)、膜擴(kuò)散、顆粒內(nèi)擴(kuò)散和吸附[29,33].本研究采用膜擴(kuò)散和顆粒內(nèi)擴(kuò)散模型來(lái)探究FA在HBCD-PS上吸附過(guò)程的速率限速步驟.圖5a為3種溫度下HBCD-PS對(duì)FA的吸附顆粒內(nèi)擴(kuò)散模型擬合圖,其相關(guān)擬合參數(shù)如表2所示.從中可以得出,FA在HBCD-PS上的吸附過(guò)程主要涉及到3個(gè)階段,第一階段代表FA在HBCD-PS表面上的膜擴(kuò)散;第二階段與顆粒內(nèi)擴(kuò)散有關(guān);第三階段主要為FA在HBCD-PS上的吸附/解析動(dòng)態(tài)平衡控制.其中,所有的C值(邊界層厚度)均不為0,表明FA的整個(gè)吸附過(guò)程不僅受顆粒內(nèi)擴(kuò)散所控制,還受膜擴(kuò)散與吸附/解析動(dòng)態(tài)平衡的影響[34].圖5b為3種溫度下HBCD-PS對(duì)FA的吸附過(guò)程的Boyd擬合圖.如果圖中Bt與的曲線(xiàn)是線(xiàn)性的,并且通過(guò)原點(diǎn),則吸附過(guò)程中的速率控制步驟主要為顆粒內(nèi)擴(kuò)散;反之,膜擴(kuò)散為速率控制步驟.由圖5b可知,所有溫度下的曲線(xiàn)呈線(xiàn)性并且通過(guò)原點(diǎn),這暗示著FA在HBCD-PS上的吸附過(guò)程主要受顆粒內(nèi)擴(kuò)散所控制[28].綜上所述,HBCD-PS對(duì)FA的吸附涉及到多個(gè)吸附步驟,其中顆粒內(nèi)擴(kuò)散是該過(guò)程的主要速率限速步驟.

(a)顆粒擴(kuò)散模型;(b)內(nèi)擴(kuò)散(Boyd)模型,B為Boyd常數(shù)

2.3 吸附等溫線(xiàn)

由圖6可知,HBCD-PS的尺寸越小,其對(duì)FA的吸附量越大.這主要是由于微塑料尺寸越小,其比表面積越大,可提供給FA的吸附位點(diǎn)也隨著增加.Lin等[8]探究四環(huán)素在尼龍微塑料上的吸附行為也得出了相似的結(jié)論.隨著FA濃度的升高,吸附量逐漸呈非線(xiàn)性增長(zhǎng).因此,采用Freundlich和Langmuir等溫線(xiàn)模型對(duì)吸附數(shù)據(jù)進(jìn)行擬合,擬合結(jié)果見(jiàn)表3.相比于Langmuir模型,Freundlich模型中的2值均更接近于1以及RMSE值均較小,說(shuō)明了HBCD-PS對(duì)FA的吸附主要為表面不均勻吸附.陳守益等[35]探究PE和PVC微塑料對(duì)泰樂(lè)菌素的吸附也得出了類(lèi)似的結(jié)論. 3種尺寸HBCD-PS對(duì)FA的最大吸附量(m)遵循著:1.868mg/g (300～350目) > 0.597mg/g (150～ 200目) > 0.254mg/g (30～50目).此外,f和m值隨著HBCD-PS尺寸的減小而增加,也說(shuō)明了微塑料尺寸越小,其對(duì)FA的吸附能力越強(qiáng).Freundlich模型中的f值大于1,說(shuō)明了HBCD-PS對(duì)FA的可用吸附位點(diǎn)是有限的.

圖6 FA在HBCD-PS微塑料上的吸附等溫線(xiàn)

表3 3種尺寸的HBCD-PS微塑料吸附FA的擬合等溫線(xiàn)模型參數(shù)

注:m為最大吸附量;L為L(zhǎng)angmuir方程的常數(shù);F和f為Freundlich方程的常數(shù).

2.4 pH值和鹽度的影響

如圖7a所示,在溶液pH值為4～10之間時(shí), HBCD-PS對(duì)FA的吸附幾乎不受溶液pH值的影響,這表明疏水相互作用可能是該過(guò)程的主要作用機(jī)制.值得注意的是,在pH值3～4之間,吸附量隨著溶液pH值的減小顯著地下降.根據(jù)Zeta電位分析儀可知,HBCD-PS微塑料的pHZPC為3.71(圖7a).因此,HBCD-PS表面在pH值小于3.71時(shí)攜帶大量正電荷.當(dāng)pH值高于pHZPC時(shí),HBCD-PS表面的負(fù)電荷數(shù)隨著溶液pH值的增加而增加.對(duì)于FA而言,羧基和酚基官能團(tuán)中間pH值的范圍分別為2～3.8和7.2～10.9[36].因此,在實(shí)驗(yàn)pH值下,FA主要以分子或者陰離子形式存在.此外,在pH值3～9時(shí),FA的zeta電位為負(fù)值[37].這說(shuō)明在低pH值條件下,靜電吸引在HBCD-PS與FA的吸附過(guò)程中起關(guān)鍵作用.其中, HBCD中由于Br原子電負(fù)性較強(qiáng),使得C原子上的電子云偏向于Br原子上,導(dǎo)致Br原子上帶有負(fù)電荷而C原子上帶正電荷.因此,FA可能通過(guò)靜電引力吸附在HBCD上的帶正電荷C原子上(圖8).但隨著pH值的增加,兩種帶負(fù)電荷的物種之間的相互排斥逐漸增強(qiáng).另一個(gè)原因是,隨著pH值的增加,FA的羥基、羧基等含氧官能團(tuán)會(huì)不斷地脫質(zhì)子,這不僅使FA的負(fù)電荷增加,而且使FA的H鍵供體減少,FA的溶解度增加[37-38].因此,較高的pH值導(dǎo)致HBCD-PS對(duì)FA的吸附能力急劇下降. HBCD-PS對(duì)FA的吸附具有明顯的pH值依賴(lài)性,這與Engel等[39]通過(guò)對(duì)DOM的吸附進(jìn)行研究得到的結(jié)果一致.

采用一系列的NaCl濃度來(lái)探究鹽度對(duì)HBCD-PS吸附FA過(guò)程的影響.通常來(lái)說(shuō),FA會(huì)在低pH值或高離子強(qiáng)度下凝聚或沉淀[39-40],這意味著空間位阻的減小會(huì)促進(jìn)對(duì)FA的吸附.因此,疏水相互作用可以根據(jù)溶液pH值和鹽度對(duì)FA吸附行為的影響來(lái)判別.從圖7b可以清楚地看出,FA的吸附量在高鹽度時(shí)明顯增加,而在低鹽度時(shí)則輕微地受到影響.這主要是因?yàn)楦啕}度會(huì)導(dǎo)致FA分子的鹽析效應(yīng)和構(gòu)像變化[41-42].此外,陽(yáng)離子的存在可能會(huì)壓縮微塑料的靜電雙層[43],以及中和表面的負(fù)電荷,從而減弱HBCD-PS與FA之間的靜電排斥的作用.當(dāng)陽(yáng)離子濃度較高時(shí),FA分子與陽(yáng)離子之間可能會(huì)形成陽(yáng)離子橋,這也有助于HBCD- PS對(duì)FA的吸附[44].綜上所述,疏水和靜電相互作用可能是HBCD-PS微塑料對(duì)FA的吸附過(guò)程的主要作用機(jī)制.

圖8 HBCD-PS微塑料與FA之間靜電引力示意

2.5 重金屬離子的影響

如圖9所示,Cu(Ⅱ)和Pb(Ⅱ)的加入顯著地促進(jìn)FA在HBCD-PS上的吸附量,然而Zn(Ⅱ)和Cd(Ⅱ)的加入對(duì)FA的吸附量只起到輕微的促進(jìn)作用.這現(xiàn)象主要?dú)w因于這些二價(jià)金屬離子可以作為FA與HBCD-PS之間的“橋梁”[41].因此,FA可以通過(guò)與Cu(Ⅱ)、Pb(Ⅱ)、Zn(Ⅱ)和Cd(Ⅱ)絡(luò)合從而促進(jìn)在HBCD-PS上的吸附.此外,對(duì)HBCD-PS吸附FA的促進(jìn)量與金屬離子和FA的絡(luò)合能力有關(guān).先前的文章中,Kinniburgh等[45]報(bào)道了FA與金屬離子的絡(luò)合能力遵循著: Pb(Ⅱ) > Cu(Ⅱ) > Cd(Ⅱ) (對(duì)于羧基型位點(diǎn))和Cu(Ⅱ) > Pb(Ⅱ) > Cd(Ⅱ) (對(duì)于酚基型位點(diǎn)). Guthrie 等[46]調(diào)查FA與Cu(Ⅱ)、Zn(Ⅱ)和 Cd(Ⅱ)的絡(luò)合能力,也提出了在這些金屬離子中,Cu(Ⅱ)與FA的絡(luò)合能力最強(qiáng).總而言之,這4種金屬離子的存在能夠促進(jìn)FA在HBCD-PS微塑料表面上的吸附行為;其中,Cu(Ⅱ)和Pb(Ⅱ)對(duì)HBCD-PS吸附FA的促進(jìn)影響顯著高于Zn(Ⅱ)和Cd(Ⅱ).

圖9 Cu(Ⅱ)、Pb(Ⅱ)、Zn(Ⅱ)和Cd(Ⅱ)離子濃度對(duì)HBCD-PS微塑料吸附FA的影響

3 結(jié)論

3.1 PS微塑料對(duì)FA幾乎沒(méi)有吸附效果,然而HBCD的存在顯著地促進(jìn)了FA在HBCD-PS微塑料上的吸附行為.HBCD-PS微塑料的尺寸越小呈現(xiàn)出對(duì)FA的吸附量越大;高溫有利于HBCD-PS對(duì)FA的吸附.

3.2 HBCD-PS對(duì)FA的吸附過(guò)程主要受顆粒內(nèi)擴(kuò)散控制,該吸附過(guò)程更加符合準(zhǔn)二級(jí)動(dòng)力學(xué)和Freundlich模型.

3.3 疏水和靜電相互作用為HBCD-PS對(duì)FA吸附過(guò)程的主要作用機(jī)制.

3.4 金屬離子(Cu(Ⅱ)、Pb(Ⅱ)、Zn(Ⅱ)和Cd(Ⅱ))的存在促進(jìn)了FA在HBCD-PS上的吸附行為,這與它們之間的絡(luò)合能力呈正相關(guān).其中,Cu(Ⅱ)和Pb(Ⅱ)對(duì)HBCD-PS吸附FA的促進(jìn)影響顯著高于Zn(Ⅱ)和Cd(Ⅱ).

[1] Bakir A, Rowland S J, Thompson R C. Competitive sorption of persistent organic pollutants onto microplastics in the marine environment [J]. Marine Pollution Bulletin, 2012,64(12):2782–2789.

[2] Wei H, Bsa B, Jie L, et al. Microplastics and associated contaminants in the aquatic environment: A review on their ecotoxicological effects, trophic transfer, and potential impacts to human health [J]. Journal of Hazardous Materials, 2020,405:124187.

[3] Cole M, Lindeque P, Halsband C, et al. Microplastics as contaminants in the marine environment: A review [J]. Marine Pollution Bulletin, 2011,62(12):2588–2597.

[4] Engler R E. The complex interaction between marine debris and toxic chemicals in the ocean [J]. Environmental Science and Technology, 2012,46(22):12302–12315.

[5] Liu P, Qian L, Wang H, et al. New insights into the aging behavior of microplastics accelerated by advanced oxidation processes [J]. Environmental Science and Technology, 2019,53(7):3579–3588.

[6] Lin L, Tang S, Wang X, et al. Hexabromocyclododecane alters malachite green and lead(II) adsorption behaviors onto polystyrene microplastics: Interaction mechanism and competitive effect [J]. Chemosphere, 2020,265:129079.

[7] 范秀磊,常卓恒,鄒曄鋒,等.可降解微塑料對(duì)銅和鋅離子的吸附解吸特性 [J].中國(guó)環(huán)境科學(xué),2021,41(5):2141-2150.

Fan X L, Chang Z H, Zou Y F, et al. Adsorption and desorption properties of degradable microplastic for Cu2+and Zn2+[J]. China Environmental Science, 2021,41(5):2141-2150.

[8] Lin L, Tang S, Wang X S, et al. Accumulation mechanism of tetracycline hydrochloride from aqueous solutions by nylon microplastics [J]. Environmental Technology and Innovation, 2020,18(1):100750.

[9] Velzeboer I, Kwadijk C J A F, Koelmans A A. Strong sorption of PCBs to NP, MP, carbon nanotubes and fullerenes [J]. Environmental Science and Technology, 2014,48:4869–4876.

[10] Fries E, Zarfl C. Sorption of polycyclic aromatic hydrocarbons (PAHs) to low and high density polyethylene (PE) [J]. Environmental Science and Pollution Research, 2012,19(4):1296–1304.

[11] Fang S, Yu W, Li C, et al. Adsorption behavior of three triazole fungicides on polystyrene microplastics [J]. Science of the Total Environment, 2019,691:1119–1126.

[12] Ma J, Zhao J, Zhu Z, et al. Effect of microplastic size on the adsorption behavior and mechanism of triclosan on polyvinyl chloride [J]. Environmental Pollution, 2019,254:113104.

[13] Zhang H, Wang J, Zhou B, et al. Enhanced adsorption of oxytetracycline to weathered microplastic polystyrene: Kinetics, isotherms and influencing factors [J]. Environmental Pollution, 2018,243:1550–1557.

[14] Tang S, Lin L, Wang X, et al. Adsorption of fulvic acid onto polyamide 6microplastics: Influencing factors, kinetics modeling, site energy distribution and interaction mechanisms [J]. Chemosphere, 2021,272:129638.

[15] Islam A, Morton D W, Johnson B B, et al. Adsorption of humic and fulvic acids onto a range of adsorbents in aqueous systems, and their effect on the adsorption of other species: A review [J]. Separation and Purification Technology, 2020,247:116949.

[16] Tang W, Zeng G, Gong J, et al. Impact of humic/fulvic acid on the removal of heavy metals from aqueous solutions using nanomaterials: A review [J]. Science of the Total Environment, 2014,468–469:1014–1027.

[17] Wu C, Lin C, Ma H, et al. Effect of fulvic acid on the sorption of Cu and Pb onto γ-Al2O3[J]. Water Research. 2003,37:743–752.

[18] Zhang H, Wen J, Fang Y, et al. Influence of fulvic acid on Pb(II) removal from water using a post-synthetically modified MIL-100(Fe) [J]. Journal of Colloid And Interface Science, 2019,551:155–163.

[19] Zhang H, Jiaqing W, Zhou B, et al. Enhanced adsorption of oxytetracycline to weathered microplastic polystyrene: Kinetics, isotherms and influencing factors [J]. Environmental Pollution, 2018,243:1550–1557.

[20] Xu B, Liu F, Brookes P C, et al. Microplastics play a minor role in tetracycline sorption in the presence of dissolved organic matter [J]. Environmental Pollution, 2018,240:87–94.

[21] Yu F, Li Y, Huang G, et al. Adsorption behavior of the antibiotic levofloxacin on microplastics in the presence of different heavy metals in an aqueous solution [J]. Chemosphere, 2020,260:127650.

[22] Turner A. Polystyrene foam as a source and sink of chemicals in the marine environment: An XRF study [J]. Chemosphere, 2020,263:128087.

[23] Duan H, Yu D, Zuo J, et al. Characterization of brominated flame retardants in construction and demolition waste components: HBCD and PBDEs [J]. Science of the Total Environment, 2016,572:77–85.

[24] Thaysen C, Sorais M, Verreault J, et al. Bidirectional transfer of halogenated flame retardants between the gastrointestinal tract and ingested plastics in urban-adapted ring- billed gulls [J]. Science of the Total Environment, 2020,730:138887.

[25] Liu X, Zheng M, Wang L, et al. Hexabromocyclododecanes on polypropylene microplastics [J]. Marine Pollution Bulletin, 2018,135:581–586.

[26] Sun R, Luo X, Zheng X,et al. Hexabromocyclododecanes ( HBCDs ) in fish: Evidence of recent HBCD input into the coastal environment [J]. Marine Pollution Bulletin, 2018,126:357–362.

[27] Jang M, Shim W J, Han G M, et al. Widespread detection of a brominated flame retardant, hexabromocyclododecane, in expanded polystyrene marine debris and microplastics from South Korea and the Asia-Paci fic coastal [J]. Environmental Pollution, 2020,231:785–794.

[28] Wang Y, Wang X, Li Y, et al. Biofilm alters tetracycline and copper adsorption behaviors onto polyethylene microplastics [J]. Chemical Engineering Journal, 2020,392:123808.

[29] 張瑞昌,李澤林,魏學(xué)鋒,等.模擬環(huán)境老化對(duì)PE微塑料吸附Zn(Ⅱ)的影響 [J].中國(guó)環(huán)境科學(xué),2020,40(7):3135-3142.

Zhang R C, Li Z L, Wei X F, et al. Effects of simulated environmental aging on the adsorption of Zn(II) onto PE microplastics [J]. China Environmental Science, 2020,40(7):3135-3142.

[30] Chang P H, Jean J S, Jiang W T, et al. Mechanism of tetracycline sorption on rectorite [J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2009,339(1–3):94–99.

[31] Schmidt P, Dybal J, Trchová M. Investigations of the hydrophobic and hydrophilic interactions in polymer-water systems by ATR FTIR and Raman spectroscopy [J]. Vibrational Spectroscopy, 2006,42(2):278–283.

[32] Lin L, Tang S, Wang X, et al. Sorption of tetracycline onto hexabromocyclododecane/polystyrene composite and polystyrene microplastics: Statistical physics models, influencing factors, and interaction mechanisms [J]. Environmental Pollution, 2021,284:117164.

[33] Ho Y S, Mckay G, Hong T, et al. Kinetics of pollutant sorption by biosorbents: Review [J]. Separation and Purification Methods, 2000,29:189–232.

[34] Wu P, Cai Z, Jin H, et al. Adsorption mechanisms of five bisphenol analogues on PVC microplastics [J]. Science of the Total Environment, 2019,650:671–678.

[35] 陳守益,郭學(xué)濤,龐敬文.微塑料對(duì)泰樂(lè)菌素的吸附動(dòng)力學(xué)與熱力學(xué) [J].中國(guó)環(huán)境科學(xué),2018,38(5):1905-1912.

Chen S Y, Guo X T, Pang J W. Sorption kinetics and thermodynamics study of tylosin by microplastics [J]. China Environmental Science, 2018,38(5):1905-1912.

[36] Dryer D J, Fabbricino M. In situ examination of the protonation behavior of fulvic acids using differential absorbance spectroscopy [J]. 2008,42(17):6644–6649.

[37] Yang K, Xing B. Adsorption of fulvic acid by carbon nanotubes from water [J]. Environmental Pollution, 2009,157(4):1095–1100.

[38] Huang G, Xiao H, Chi J, et al. Effects of pH on the aqueous solubility of selected chlorinated phenols [J]. Journal of Chemical & EngineeringData, 2000,45:411–414.

[39] Engel M, Chefetz B. Adsorption and desorption of dissolved organic matter by carbon nanotubes: Effects of solution chemistry [J]. Environmental Pollution, 2016,213:90–98.

[40] Abdurahman A, Cui K, Wu J, et al. Adsorption of dissolved organic matter (DOM) on polystyrene microplastics in aquatic environments: Kinetic, isotherm and site energy distribution analysis [J]. Ecotoxicology and Environmental Safety, 2020,198:110658.

[41] Erhayem M, Sohn M. Stability studies for titanium dioxide nanoparticles upon adsorption of Suwannee River humic and fulvic acids and natural organic matter [J]. Science of the Total Environment, 2014,468–469:249–257.

[42] Hyung H, Kim J. Natural organic matter (NOM) adsorption to multi-walled carbon nanotubes: Effect of NOM characteristics and water quality parameters [J]. 2008,42(12):4416–4421.

[43] Wu X, Liu P, Huang H, et al. Adsorption of triclosan onto different aged polypropylene microplastics: Critical effect of cations [J]. Science of the Total Environment, 2020,717:137033.

[44] Liang L, Luo L, Zhang S. Adsorption and desorption of humic and fulvic acids on SiO2particles at nano-and micro-scales [J]. Colloids and Surfaces A Physicochemical and Engineering Aspects, 2011,384(1–3):126–130.

[45] Kinniburgh D G, Milne C J, Benedetti M F, et al. Metal ion binding by humic acid: Application of the NICA-Donnanmodel [J]. Environmental Science & Technology, 1996,30(5):1687–1698.

[46] Guthrie J W, Hassan N M, Salam M S A, et al. Complexation of Ni , Cu , Zn , and Cd by DOC in some metal-impacted freshwater lakes: A comparison of approaches using electrochemical determination of free-metal-ion and labile complexes and a computer speciation model, WHAM V and VI [J]. Analytica Chimica Acta, 2005,528:205–218.

Adsorption behaviors of fulvic acid onto polystyrene microplastics.

SUN Xuan, YU An-qi, WANG Xue-song*, LIN Lu-jian, TANG Shuai, LI Meng-yao

(School of Environmental and Chemical Engineering, Jiangsu Ocean University, Lianyungang 222000, China)., 2022,42(1)：285～292

Adsorption properties and interaction mechanisms of fulvic acid (FA) onto polystyrene (PS) and HBCD-PS composites (HBCD-PS) microplastics were investigated. Results show that the adsorption amounts of FA onto PS microplastics were negligible, while the presence of HBCD significantly enhanced the adsorption of FA onto HBCD-PS microplastics which, as confirmed by W-M intra particles and Boyd diffusion models, was mainly dominated by intra-particle diffusion. The FA adsorption onto HBCD-PS closely conformed to the pseudo-second-order and the Freundlich models. The solution pH and NaCl contents significantly affected the adsorption amounts of FA onto HBCD-PS. Overall, HBCD-PS mainly combined with FA through hydrophobic and electrostatic interactions. Besides, the presence of heavy metal ions (Cu(Ⅱ), Pb(Ⅱ), Zn(Ⅱ) and Cd(Ⅱ)) enhanced the adsorption capacities of FA onto HBCD-PS, which was positively correlated with their complexation ability.

microplastics；hexabromocyclododecane；fulvic acid；adsorption mechanisms；metal ions

X131

A

1000-6923(2022)01-0285-08

孫 璇(1996-),女,江蘇徐州人,江蘇海洋大學(xué)碩士研究生,主要從事環(huán)境中微塑料與污染物的界面行為與作用機(jī)制研究.

2021-06-07

江蘇省高等學(xué)校自然科學(xué)重點(diǎn)基金項(xiàng)目(19KJA430009);江蘇省研究生科研與實(shí)踐創(chuàng)新計(jì)劃項(xiàng)目(KYCX20-2957)

* 責(zé)任作者, 教授, snowpine1969@126.com