土壤芽孢桿菌產(chǎn)胞外聚合物對(duì)Pb2+吸附特性研究

洪 晨,李益飛,司艷曉,邢 奕,4*,王志強(qiáng),張瑩瑩(.北京科技大學(xué)能源與環(huán)境工程學(xué)院,北京0008；2.中國(guó)科學(xué)院生態(tài)環(huán)境研究中心,北京 00085；.清華大學(xué)環(huán)境學(xué)院,北京 00084；4.北京科技大學(xué)工業(yè)典型污染物資源化處理北京市重點(diǎn)實(shí)驗(yàn)室,北京 0008)

土壤芽孢桿菌產(chǎn)胞外聚合物對(duì)Pb2+吸附特性研究

洪 晨1,2,李益飛1,司艷曉3,邢 奕1,4*,王志強(qiáng)1,張瑩瑩1(1.北京科技大學(xué)能源與環(huán)境工程學(xué)院,北京100083；2.中國(guó)科學(xué)院生態(tài)環(huán)境研究中心,北京 100085；3.清華大學(xué)環(huán)境學(xué)院,北京 100084；4.北京科技大學(xué)工業(yè)典型污染物資源化處理北京市重點(diǎn)實(shí)驗(yàn)室,北京 100083)

根據(jù)與細(xì)菌菌體結(jié)合的緊密程度,胞外聚合物(EPS)可以分為粘液層EPS(S-EPS)、松散附著EPS(LB-EPS)、緊密附著EPS(TB-EPS),以土壤芽孢桿菌作為實(shí)驗(yàn)菌株,研究了各層EPS在不同溫度、pH值條件下對(duì)Pb2+的吸附特性,建立了EPS的吸附動(dòng)力學(xué)模型和吸附等溫線模型,并采用掃描電子顯微鏡(SEM)觀察各層EPS吸附Pb2+前后的表觀形態(tài)的變化.當(dāng)吸附溫度為35℃、pH值為5.5時(shí),S-EPS、LB-EPS、TB-EPS對(duì)Pb2+的吸附量分別為91.35、100.61和90.28mg/g,表明LB-EPS對(duì)Pb2+的吸附能力更強(qiáng).各層EPS吸附Pb2+的吸附動(dòng)力學(xué)模型和吸附等溫線模型均符合準(zhǔn)二級(jí)動(dòng)力學(xué)模型和Langmuir等溫吸附模型,表明吸附過程分別受化學(xué)吸附機(jī)理控制和單分子層吸附控制,并通過Langmuir模型計(jì)算得到,S-EPS、LB-EPS、TB-EPS對(duì)Pb2+的最大吸附量分別為124.224、127.389和119.760mg/g.同時(shí),掃描電鏡結(jié)果表明吸附前后各層EPS表觀形態(tài)均差異明顯,其中LB-EPS呈肺泡狀,具有更大的比表面積,因此更多的Pb2+吸附在其表面.

EPS；吸附；Pb2+；動(dòng)力學(xué)；SEM

我國(guó)是礦產(chǎn)資源大國(guó),但長(zhǎng)期以來由于資金與管理等原因,在礦山勘探、開采、選礦及礦物加工等礦區(qū)活動(dòng)對(duì)周圍的環(huán)境,尤其是土壤,造成了嚴(yán)重影響[1-3].重金屬污染[4-5]是礦區(qū)環(huán)境的主要污染問題之一,重金屬在環(huán)境中具有相對(duì)穩(wěn)定性,很難從環(huán)境中徹底清除.

重金屬污染的生物修復(fù)技術(shù)一直是國(guó)內(nèi)外研究的熱點(diǎn)[6-9].微生物修復(fù)法作為一種新興的處理技術(shù),在處理低濃度重金屬污染廢水方面,有著廣闊的應(yīng)用前景[10-11].Guibaud等[12]從活性污泥中提取的胞外聚合物,并采用SMDE極譜法測(cè)量了胞外聚合物與金屬的絡(luò)合電位,結(jié)果表明,SMDE極譜法能夠有效測(cè)定溶液中游離態(tài)金屬的含量.Tunali等[13]研究了葡萄孢菌菌體對(duì)Zn2+的吸附效果,發(fā)現(xiàn)物理化學(xué)預(yù)處理方法均能夠有效提高葡萄孢菌菌體吸附Zn2+的性能.Mesa等[14]發(fā)現(xiàn)植物根際部分的細(xì)菌對(duì)多種重金屬具有抗性,并且這些細(xì)菌能夠有效地促進(jìn)植物的生長(zhǎng).Oves等[15]從工業(yè)污水灌溉的土壤中分離出蘇云金芽孢桿菌菌株,發(fā)現(xiàn)其對(duì)鎘、鉻、銅、鉛和鎳等金屬離子均具有顯著的吸附作用.Guibaud等[16]在研究中發(fā)現(xiàn)從活性污泥中提取的胞外聚合物(EPS)對(duì)于金屬有很強(qiáng)的結(jié)合能力,這種能力有助于保護(hù)細(xì)胞不受到重金屬活性污泥中金屬成分的有害影響.

微生物菌體生長(zhǎng)過程中,隨著新陳代謝的進(jìn)行在菌體表面會(huì)產(chǎn)生主要由多糖、蛋白質(zhì)、核酸、腐殖質(zhì)等物質(zhì)組合團(tuán)聚而成的大分子聚合物[17-19],即胞外聚合物(EPS).根據(jù) EPS與微生物菌體結(jié)合的緊密程度,EPS分為三類:粘液層EPS(S-EPS),松散附著 EPS(LB-EPS),緊密附著EPS(TB-EPS).隨著生物修復(fù)技術(shù)研究的發(fā)展,EPS在生物修復(fù)中的作用也日益受到人們的重視.很多研究表明EPS對(duì)重金屬離子具有吸附效果,Pe′rez等[20]研究了杰米拉類芽孢桿菌的EPS,發(fā)現(xiàn)EPS能夠有效地吸附Pb2+.Wei等[21]研究好氧污泥中 EPS對(duì) Zn(II)的吸附過程,發(fā)現(xiàn)EPS中的蛋白質(zhì)在絡(luò)合 Zn(II)中發(fā)揮了重要作用.Ye等[22]從節(jié)桿菌中提取EPS,研究了EPS對(duì)Cu2+,Pb2+,Cr6+等金屬離子的吸附效果,結(jié)果表明EPS能夠有效地去除廢水中的重金屬離子.已有的研究在 EPS修復(fù)重金屬土壤方面已經(jīng)做了大量的工作,但在不同層組EPS吸附重金屬機(jī)理方面的研究還較少.

本文從鉛鋅礦土壤中提取的抗鉛微生物,研究培養(yǎng)條件對(duì) EPS產(chǎn)量的影響,分析不同層組EPS對(duì) Pb2+的吸附效果.通過吸附動(dòng)力學(xué)模型、吸附等溫線模型、掃描電鏡分析明確不同層組EPS吸附 Pb2+的作用機(jī)理.以期對(duì)于 EPS吸附Pb2+的過程分析提供一定的實(shí)驗(yàn)和理論依據(jù).

1 材料與方法

1.1 樣品采集及處理

1.1.1 微生物 土壤芽孢桿菌提取自江西上饒德興銀山的某鉛鋅礦區(qū)內(nèi)的土壤,是通過對(duì)土壤中微生物進(jìn)行抗鉛的篩選及純化,得到具有抗鉛性的優(yōu)化菌種.

1.1.2 EPS提取 (1)菌種在發(fā)酵培養(yǎng)基(1000mL)中培養(yǎng)1～3d,取400mL在5000r/min條件下離心10min,收獲細(xì)胞.

(2) 將上清液在再生纖維素(RC)透析袋內(nèi)透析得到 S-EPS,轉(zhuǎn)移并保存(-20 ).℃ 試驗(yàn)重復(fù)3次.

(3) 將步驟(1)中沉淀物溶解至超純水中至40mL并在40W下超聲處理1min,再將懸浮液在7000r/min下離心20min.透析得到為L(zhǎng)B-EPS溶液,轉(zhuǎn)移并保存.

(4) 將步驟(3)中沉淀物溶解至超純水中至原體積(10mL),在15000r/min下離心20min.透析得到TB-EPS,轉(zhuǎn)移并保存.將3個(gè)層組的EPS溶液冷凍干燥,制得EPS固體,置于-20℃保存.

1.2 EPS吸附Pb2+試驗(yàn)

向 Pb2+水溶液中分別加入 EPS,進(jìn)行如下 4組實(shí)驗(yàn):(1)溫度對(duì)吸附量的影響實(shí)驗(yàn),Pb2+濃度為150mg/L,EPS投加量為1g/L,pH值為5.5,溫度為25～40 ;(2)pH℃ 值對(duì)吸附量的影響實(shí)驗(yàn),Pb2+濃度為150mg/L,EPS投加量為1g/L,溫度為35 ,pH℃ 值為3～7;(3)吸附時(shí)間對(duì)Pb2+吸附量的影響實(shí)驗(yàn),Pb2+濃度為 150mg/L,EPS投加量為1g/L,pH 值為 5.5,溫度為 35 ;(4)℃ 平衡濃度對(duì)Pb2+吸附量的影響實(shí)驗(yàn),Pb2+濃度為 50mg/L～500mg/L, EPS投加量為1g/L,35℃ , pH 5.5.在恒溫空氣浴振蕩培養(yǎng)箱(一恒科學(xué)儀器有限公司,DHP-9052,中國(guó))中振蕩吸附 120min,將吸附后的溶液通過 0.22μm 的微孔濾膜進(jìn)行過濾,分離出上清液和吸附后的EPS樣品.采用電感耦合等離子體發(fā)射光譜儀(ICP-OES)(Varian,720-ES,美國(guó))測(cè)定上清液中剩余Pb2+的濃度,計(jì)算Pb2+吸附量.

Pb2+吸附量如式(1)

式中:qt為吸附量(mg/g);Co為鉛離子初始濃度(mg/L);Ce為鉛離子最終濃度(mg/L);V為反應(yīng)液的體積,L;M為EPS的質(zhì)量,g.

1.3 SEM測(cè)定

分別準(zhǔn)確稱取兩份各層胞外聚合物 0.1g,其中一份并加入到100mL、150mg/L的硝酸鉛溶液中,調(diào)節(jié)pH值5.5,置于35℃空氣浴震蕩培養(yǎng)箱中震蕩吸附 2小時(shí)后取出,將吸附后的溶液通過0.22μm的微孔濾膜進(jìn)行過濾,分離出上清液和吸附后的EPS樣品.再經(jīng)①漂洗(生理鹽水);②前固定(2,5%戊二醇,4℃冰箱 2h);③漂洗(磷酸緩沖液,5次,每次7min);④后固定(1%鋨酸2h);⑤漂洗(磷酸緩沖液,5次,每次7min);⑥梯度脫水(50%、70%、85%、95%、100%乙醇各一次,每次15min);⑦浸透;⑧純包埋液過夜處理,將制備好的固定樣品送去進(jìn)行 SEM 檢測(cè)[23].采用生物掃描電子顯微鏡(SEM)(卡爾蔡司,ZeissEVO-18,德國(guó))對(duì)吸附前后的各層EPS樣品進(jìn)行觀察.

2 結(jié)果與分析

2.1 EPS產(chǎn)生量分析

培養(yǎng)溫度與pH值是影響微生物生長(zhǎng)存活的重要因素,也同樣影響各層EPS的產(chǎn)量[22,24-26],如圖1所示.在適宜的條件下,微生物生長(zhǎng)迅速,產(chǎn)生的 EPS的量更多.當(dāng)溫度為 35℃、pH值為 5.5時(shí),S-EPS、LB-EPS、TB-EPS產(chǎn)量均達(dá)到最高分別為 762.10mg/L,161.12mg/L,28.61mg/L.三層EPS的所占比例差別明顯,S-EPS比例最高(80.06%)、LB-EPS次之(16.93%)、TB-EPS比例最低(3.01%),Hou等[30]的研究也表明 S-EPS、LB-EPS在EPS總量中占主導(dǎo).

EPS具有抵抗干燥,抵御捕食者以及躲避紫外線等作用,因此EPS大多數(shù)以鞘狀,膠囊狀或粘液狀的形式留在細(xì)胞表面來隔離或固定營(yíng)養(yǎng)物質(zhì)與金屬離子,減少外界環(huán)境的不利影響.環(huán)境溫度在25-35℃或pH值在4.0～5.5范圍內(nèi),溫度較低或 pH值較低時(shí),抑制了細(xì)胞內(nèi)酶的活性,使得EPS產(chǎn)量較低,隨著溫度或pH值的升高,細(xì)胞為了適應(yīng)環(huán)境而使得EPS產(chǎn)量逐漸增大.在溫度為35～40℃或pH值為5.5～6.0時(shí),EPS產(chǎn)量下降.這是因?yàn)榄h(huán)境條件逐漸適于細(xì)胞生長(zhǎng),使得細(xì)胞將營(yíng)養(yǎng)物質(zhì)用于其他代謝物質(zhì)的合成,許多研究也有類似的結(jié)果[27-30].

圖1 EPS產(chǎn)生量(a)溫度影響(培養(yǎng)時(shí)間30h,溫度25～40℃),pH5.5;pH值影響(培養(yǎng)時(shí)間30h,溫度35℃,pH 4～6)Fig.1 Effect of (a) temperature (cultivate time 30h, temperature 25～40℃), (b)pH on yield of EPS (cultivate time 30h, temperature 35℃, pH 4～6)

2.2 EPS吸附Pb2+

S-EPS、LB-EPS、TB-EPS在不同溫度、pH值條件下對(duì)Pb2+的吸附效果如圖2所示.隨著溫度的升高,EPS對(duì)鉛離子的吸附量先增大后減小,如圖2(a)所示.總體而言,各層EPS吸附Pb2+的量隨溫度升高的變化較小,這可能是由于在 25～40℃范圍內(nèi),吸附溫度對(duì)各層 EPS的官能團(tuán)種類、數(shù)量和性質(zhì)的影響較小.

圖2 吸附溫度和pH對(duì)EPS吸附Pb2+效果的影響Fig.2 Effect of temperature and pH on adsorption of Pb2+

pH值對(duì)EPS吸附Pb2+的效果有明顯影響,隨著pH值(3～5.5)升高,各層EPS對(duì)Pb2+的吸附量顯著升高,如圖2(b)所示.這是由于溶液pH值升高過程中,EPS的表面電荷和官能團(tuán)也會(huì)發(fā)生一定的改變[31-32].EPS中蛋白質(zhì)、多糖等有機(jī)物逐漸去質(zhì)子化并且?guī)ж?fù)電,形成-NH-,-COO-, -O-等官能團(tuán)[33].這些官能團(tuán)易與Pb2+絡(luò)合,從而增加吸附量.同時(shí),隨著吸附過程中 PbOH+含量的逐漸增加,促進(jìn)絡(luò)合作用會(huì)進(jìn)一步增強(qiáng).當(dāng) pH值(5.5～7)繼續(xù)升高,Pb2+會(huì)與(OH)2+結(jié)合,發(fā)生羥基化反應(yīng)并形成絡(luò)合物[34].這些絡(luò)合物在形成過程中會(huì)與 EPS中的活性位點(diǎn)發(fā)生競(jìng)爭(zhēng),從而降低EPS的吸附能力,使得EPS對(duì)Pb2+的吸附量下降[35].溫度為 35℃的條件下,S-EPS、LBEPS、TB-EPS對(duì)Pb2+的吸附量在pH=5.5時(shí)達(dá)到最大,分別為 91.35mg/g、100.61mg/g、90.28mg/g.

2.3 EPS吸附動(dòng)力學(xué)

隨著吸附時(shí)間的增加,EPS對(duì) Pb2+的吸附量總體呈現(xiàn)出逐漸增大的變化趨勢(shì).在80min時(shí)達(dá)到吸附平衡,如圖3所示.

圖3 吸附時(shí)間對(duì)Pb2+吸附量的影響Fig.3 Effect of time on adsorption of Pb2+

采用準(zhǔn)一級(jí)和準(zhǔn)二級(jí)模型對(duì) S-EPS、LB-EPS、TB-EPS的吸附動(dòng)力學(xué)進(jìn)行研究,吸附動(dòng)力學(xué)表達(dá)式如式(2)、(3)[34]:

式中:qe(mg/g)和qt(mg/g)是關(guān)于平衡和接觸時(shí)間t (min)的金屬離子吸附量,qe,cal(mg/g)是計(jì)算得到的平衡吸附量,qe,exp(mg/g)是實(shí)驗(yàn)得到的平衡吸附量.K1和K2是準(zhǔn)一級(jí)和準(zhǔn)二級(jí)比例常數(shù).

將S-EPS、LB-EPS、TB-EPS吸附Pb2+的實(shí)驗(yàn)結(jié)果按照上述方程分別進(jìn)行線性回歸運(yùn)算,得到準(zhǔn)一級(jí)和準(zhǔn)二級(jí)動(dòng)力學(xué)模型相關(guān)參數(shù)[36],結(jié)果如表1所示.表1中k1由圖4(a)中l(wèi)n(qe-qt)與t經(jīng)線性擬合得到,k2分別由圖4(b)中t/qt與t經(jīng)線性擬合得到.根據(jù)表 1中的相關(guān)性系數(shù)(R2)可知,準(zhǔn)二級(jí)模型可以更好地描述吸附過程(R2＞0.99),如圖 4(c)所示.S-EPS、LB-EPS、TB-EPS吸附量的計(jì)算值與實(shí)驗(yàn)結(jié)果的吻合度較好(S-EPS、LB-EPS吸附量誤差＜14%,TB-EPS吸附量誤差＜10%).EPS吸附 Pb2+符合準(zhǔn)二級(jí)動(dòng)力學(xué)模型,表明在吸附過程中EPS和Pb2+之間的吸附速率是受化學(xué)吸附機(jī)理控制的,吸附行為是通過EPS與Pb2+共享電子來完成的.

圖4 吸附動(dòng)力學(xué)分析Fig.4 kinetics fit of Pb2+adsorption

表1 EPS對(duì)Pb2+的吸附動(dòng)力學(xué)參數(shù)Table 1 Kinetic parameters for adsorption of Pb2+by EPS

2.4 EPS吸附等溫線

隨著Pb2+平衡濃度增加,EPS對(duì)Pb2+的吸附量呈現(xiàn)出增大的趨勢(shì). Pb2+平衡濃度在0-60mg/L范圍內(nèi),吸附量快速提高;當(dāng) Pb2+平衡濃度＞60mg/L,各層 EPS的吸附量增長(zhǎng)變緩.Pb2+平衡濃 度 為 140.26mg/L(S-EPS),134.09mg/L(LBEPS), 147.71mg/L(TB-EPS)時(shí),三層EPS吸附量達(dá)到最大,分別為 103.74mg/g, 111.91mg/g, 106.29mg/g, 如圖5所示.

圖5 平衡濃度對(duì)Pb2+吸附量的影響Fig.5 Effect of equilibrium concentration on adsorption of Pb2+

EPS對(duì) Pb2+的吸附是一個(gè)動(dòng)態(tài)平衡過程,為了探討 EPS吸附過程的規(guī)律,采用經(jīng)典的Langmuir,Freundlich和Temkin模型對(duì)吸附等溫結(jié)果進(jìn)行分析.Langmuir模型[37-38]假設(shè)吸附的發(fā)生是通過吸附劑表面的單分子層來實(shí)現(xiàn)的,并且沒有吸附質(zhì)間的相互作用[34],如式(4):

式中:Ce(mg/L)是達(dá)到吸附平衡時(shí)的Pb2+濃度; qe(mg/g)是吸附量;qmax(mg/g)是最大吸附量, Keq(L/mg)是Langmuir常數(shù)與吸附自由能相關(guān)[39].

Freundlich模型假設(shè)在吸附劑的不均勻表面上發(fā)生多分子層吸附[40],如式(5)

式中:Kf[mg/g?(L?mg)1/n]是 Freundlich常數(shù)表示吸附質(zhì)的吸附量,nf是不均勻因素,該因素表明了吸附劑的吸附強(qiáng)度.

Temkin模型考慮了吸附質(zhì)間的相互作用,如式(6)

式中:A(L/g)和B(J/mol)是Temkin常數(shù),R是理想氣體常數(shù)8.314J/(mol?K);T(K)是絕對(duì)溫度.

圖6 吸附等溫線分析Fig. 6 Isotherm for adsorption of Pb2+

表2 EPS吸附Pb2+的Langmuir等溫吸附模型參數(shù)Table 2 Langmuir model Isotherm parameters for adsorption of Pb2+by EPS

吸附等溫線參數(shù)如表2～表4所示,相應(yīng)的吸附等溫線模型如圖6所示.表2中keq值由圖6(a)中1/qe與1/ce經(jīng)線性擬合得到,表3中kf值由圖6(b)中l(wèi)nqe與lnce經(jīng)線性擬合得到,表4中A值與B值由圖6(c)中qe與lnce經(jīng)線性擬合得到.從圖 6(d)比較可知,EPS 對(duì) Pb2+的吸附符合Langmuir吸附模型,其中 S-EPS、LB-EPS、TB-EPS的Langmuir吸附模型的相關(guān)性系數(shù)如表2、表3、表4所示,R2分別為0.999、0.998、0.999.吸附等溫線結(jié)果表明,S-EPS、LB-EPS、TB-EPS對(duì) Pb2+的吸附作用均為單分子層吸附,即吸附只發(fā)生在EPS的外表面,相關(guān)研究也得出類似的結(jié)論[41].通過 Langmuir模型計(jì)算得到,S-EPS、LB-EPS、TB-EPS對(duì)Pb2+的最大吸附量分別為124.224, 127.389和119.760mg/g.

表3 EPS吸附Pb2+的Freundlich等溫吸附模型參數(shù)Table 3 Freundlich model Isotherm parameters for adsorption of Pb2+by EPS

表4 EPS吸附Pb2+的Temkin等溫吸附模型參數(shù)Table 4 Temkin model Isotherm parameters for adsorption of Pb2+by EPS

2.5 SEM掃描電鏡分析

采用生物掃描電子顯微鏡(SEM)觀察各層EPS吸附Pb2+前后的表觀形態(tài)的變化,如圖7所示.可以看出各層EPS的形貌特征有較大差別[23].沒有吸附Pb2+的各層EPS中,S-EPS呈現(xiàn)片層狀,表面比較光滑;而LB-EPS表面由很多肺泡狀突起堆疊而成,與 S-EPS相比,LB-EPS的比表面積明顯增大;TB-EPS則呈現(xiàn)絲狀,并纏繞在一起.EPS能夠與Pb2+發(fā)生了離子交換[35],部分基團(tuán)與Pb2+發(fā)生絡(luò)合,并通過表面沉淀作用沉積在 EPS表層[34].吸附后,呈片狀的S-EPS表面附著有大量小的塊狀鉛離子絡(luò)合產(chǎn)物,即大量鉛離子被吸附到 S-EPS表面;肺泡狀的LB-EPS表面團(tuán)聚較多的鉛離子絡(luò)合產(chǎn)物并團(tuán)聚呈球狀,LB-EPS比表面積更大,更多的Pb2+吸附在其表面,這也是LB-EPS對(duì)鉛離子吸附效果優(yōu)于 S-EPS的原因;由于吸附 Pb2+并形成絡(luò)合物,TB-EPS表面也明顯附著有大量塊狀物,絲狀的TB-EPS比表面積最小,因而單位質(zhì)量TB-EPS能夠吸附的Pb2+有限,這也是TB-EPS吸附效果不如LB-EPS、S-EPS的原因.

圖7 各層EPS吸附鉛前后掃描電鏡圖Fig. 7 scanning electron microscope micrographs of EPS before and after Pb2+adsorption

3 結(jié)論

3.1 土壤芽孢桿菌產(chǎn)生的EPS能有效吸附Pb2+,單位吸附量LB-EPS＞S-EPS＞TB-EPS.吸附溫度為35 ,pH℃ 為5.5時(shí),S-EPS、LB-EPS、TB-EPS的吸附量最大,分別為91.35、100.61、90.28mg/g.

3.2 各層EPS對(duì)Pb2+吸附均符合準(zhǔn)二級(jí)動(dòng)力學(xué)模型,吸附速率是受化學(xué)吸附機(jī)理控制;等溫吸附分析結(jié)果表明EPS等溫吸附過程符合Langmuir吸附等溫線模型,各層EPS對(duì)Pb2+的吸附是發(fā)生在EPS表面的單分子層吸附.

3.3 生物掃描電子顯微鏡結(jié)果表明,S-EPS、LB-EPS、TB-EPS的表觀形態(tài)差異明顯,LBEPS呈肺泡狀,比表面積更大,更多的 Pb2+吸附在其表面.

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Pb2+adsorption features of extracellular polymeric substance producted by a Brevibacillus agri strain.

HONG Chen1,2, LI Yi-fei1, SI Yan-xiao3, XING Yi1,4*, WANG Zhi-qiang1, ZHANG Ying-ying1(1.School of Civil and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China；2.Research Center for Eco-Environmental Sciences, Chinese Academy Science, Beijing 100085, China；3.School of Environment, Tsinghua University, Beijing 100084, China；4.Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants, University of Science and Technology Beijing, Beijing 100083, China), China Environmental Science, 2017,37(5)：1805～1813

Extracellular polymeric substances (EPS) were categorized based on the compactness: soluble EPS (S-EPS), loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS). The EPS used for experiment was extracted from Brevibacillus agri strain and the adsorption characteristics of Pb2+onto S-EPS, LB-EPS and TB-EPS were investigated at different temperature and pH. Meanwhile, adsorption kinetics model and adsorption isotherm model were also be established and the change of surface morphology of EPS before and after adsorption were observed by scanning electron microscope (SEM). When temperature was 35 ℃ and pH was 5.5, the Pb2+adsorption capacity of S-EPS, LB-EPS, TB-EPS was 91.35, 100.61, and 90.28mg/g, respectively. The results showed that the Pb2+adsorbability of LB-EPS was better than those of S-EPS and TB-EPS. Additionally, adsorption kinetics and adsorption isotherm of EPS for Pb2+fitted Pseudo second order kinetic model and Langmuir adsorption isotherm model. The results indicated that adsorption process was controlled by chemisorption mechanism and monolayer adsorption, respectively. The largest adsorption capacities calculated by Langmuir adsorption isotherm model of S-EPS, LB-EPS, TB-EPS were 124.224, 127.389 and 119.760mg/g, respectively. Furthermore, SEM analysis confirmed that surface morphology of S-EPS, LB-EPS, and TB-EPS changed significantly before and after adsorption. In which, LB-EPS had the largest adsorption capacity as its pulmonary alveoli structure and large specific surface area.

EPS；adsorption；Pb2+；kinetic；SEM

X703

A

1000-6923(2017)05-1805-09

洪 晨(1984-),男,河北三河人,講師,博士,從事市政污泥處理與資源化方面的研究.發(fā)表論文40篇.

2016-10-10

國(guó)家自然科學(xué)基金資助項(xiàng)目(41273091);科技北京百名領(lǐng)軍人才培養(yǎng)工程資助項(xiàng)目(LJ201620)

* 責(zé)任作者, 教授, xingyi@ustb.edu.cn