銅綠微囊藻對(duì)混凝除氟的促進(jìn)作用及機(jī)理分析

象 豫,徐 慧,李 昆,王 希,3,吳昊瀾,4,樊 華

銅綠微囊藻對(duì)混凝除氟的促進(jìn)作用及機(jī)理分析

象 豫1,2,徐 慧2,李 昆1*,王 希2,3,吳昊瀾2,4,樊 華1

(1.南昌大學(xué)資源環(huán)境與化工學(xué)院,江西 南昌 330031；2.中國(guó)科學(xué)院生態(tài)環(huán)境研究中心,環(huán)境水質(zhì)學(xué)國(guó)家重點(diǎn)實(shí)驗(yàn)室,北京 100085；3.中國(guó)科學(xué)院大學(xué),北京 100049；4.中國(guó)地質(zhì)大學(xué)(北京)水資源與環(huán)境學(xué)院,北京 100083)

以銅綠微囊藻、氯化鋁(AlCl3·6H2O)為研究對(duì)象,通過三維熒光、場(chǎng)發(fā)射掃描電鏡等表征,探究了藻類對(duì)氟化物混凝去除機(jī)制的影響.結(jié)果表明,在pH值為7.0,8.0,9.0,Al投加量在20.0~80.0mg/L的條件下,銅綠微囊藻對(duì)混凝除氟有明顯的促進(jìn)作用,其促進(jìn)作用主要在于藻絮體對(duì)氟的表面吸附.銅綠微囊藻與氯化鋁水解產(chǎn)物通過吸附架橋和網(wǎng)捕卷掃作用,聚集成較大較多的絮體.絮體粒徑越大,除氟率越高.pH值為7.0,Al投加量為40.0mg/L時(shí),絮體粒徑達(dá)到最大值500μm,此時(shí)氟去除率最高,為77.37%;當(dāng)Al投加量為80.0mg/L時(shí),藻細(xì)胞破損嚴(yán)重,有機(jī)物過多釋放,對(duì)混凝除氟起阻礙作用.絮體破碎吸附實(shí)驗(yàn)結(jié)果表明,對(duì)絮體進(jìn)行一定強(qiáng)度破碎可以增加吸附位點(diǎn),從而提高氟的去除率;但破碎強(qiáng)度過大,絮體粒徑過小,對(duì)氟的吸附效率亦會(huì)降低.

銅綠微囊藻；除氟；混凝；絮體；吸附

氟是人體所必需的微量元素,對(duì)骨骼和牙齒生長(zhǎng)發(fā)育至關(guān)重要,但是長(zhǎng)時(shí)期的過量攝入則會(huì)導(dǎo)致氟中毒[1].天然地質(zhì)條件和以氟為原料的工業(yè)生產(chǎn)過程,如電鍍,陶瓷生產(chǎn),半導(dǎo)體制造以及磚和玻璃生產(chǎn)等,都會(huì)向水環(huán)境中轉(zhuǎn)移氟離子[3].我國(guó)遭受氟超標(biāo)飲用水威脅的人口分布范圍較為廣泛,主要分布區(qū)域是華東,西北,東北,華北等部分省市自治區(qū).我國(guó)農(nóng)村飲用氟離子濃度大于1.5mg/L的飲用水人口達(dá)到5000萬人.

飲用水除氟主要采用混凝沉淀法,吸附法,離子交換法,電滲析,膜分離法等[4-9].相較于其他方法,混凝沉淀法工藝簡(jiǎn)單,處理成本低,水量大且后期維護(hù)少,即使在不發(fā)達(dá)的農(nóng)村地區(qū)也具有很高的可操作性.混凝沉淀法主要是利用混凝劑產(chǎn)生的電性中和、吸附架橋及網(wǎng)捕卷掃等作用.在混凝過程中,鋁鹽水解形成氫氧化鋁絮體,氟化物通過附著在絮體上而被除去.在此過程中涉及到Al-F絡(luò)合,離子交換,電子吸引和物理吸附等多種作用[10].

我國(guó)北方某地區(qū)的地表水氟含量超標(biāo),同時(shí)又伴隨著季節(jié)性水體富營(yíng)養(yǎng)化問題.水體的富營(yíng)養(yǎng)化會(huì)導(dǎo)致水體中藻類的大量生長(zhǎng)繁殖,引起水華的爆發(fā)[11].水華爆發(fā)不僅會(huì)破壞水體的生態(tài)平衡,而且會(huì)嚴(yán)重地干擾水處理過程,藻類的形態(tài)多樣、濃度分布不均、分泌的有機(jī)物量大且種類復(fù)雜,會(huì)對(duì)混凝效果產(chǎn)生較大的影響[12].一般說來,藻類在濃度較低時(shí),對(duì)混凝過程有不同程度的促進(jìn)作用,而在高濃度時(shí),對(duì)混凝過程有不同程度的干擾[13].目前關(guān)于藻類對(duì)混凝除氟影響的研究鮮少,當(dāng)系統(tǒng)中存在氟化物時(shí),藻類細(xì)胞是否會(huì)對(duì)除氟效果產(chǎn)生影響還不清楚.本文以銅綠微囊藻為研究對(duì)象,探究藻類對(duì)氟化物的混凝去除機(jī)制的影響,以及混凝劑、藻類、氟化物三者之間的相互作用、相互影響機(jī)制,以期為水華爆發(fā)階段水體中氟化物的混凝去除實(shí)際應(yīng)用提供參考.

1 材料與方法

1.1 實(shí)驗(yàn)試劑及儀器

NaF,HCl,NaOH,AlCl3·6H2O,NaNO3,NaHCO3等均為分析純?cè)噭?購(gòu)于國(guó)藥化學(xué)試劑有限公司;實(shí)驗(yàn)用水為超純水.

六聯(lián)攪拌儀(MY3000.6G,梅宇,中國(guó));濁度儀(2100N, HACH,美國(guó));pH計(jì)(MP220, Mettler-Toledo,瑞士);紫外分光光度計(jì)(UH5300,Hitachi,日本);馬爾文激光粒度儀(Mastersizer 2000,Malvern,英國(guó));電感耦合等離子體發(fā)射光譜儀(ICPE-9820,島津,日本);離子色譜儀(AQUION,Thermo Fisher Scientific,美國(guó));總有機(jī)碳分析儀(TOC-L,島津,日本);三維熒光光譜儀(F-7000,Hitachi,日本);傅立葉變換紅外光譜儀(Nicolet 8700,Thermo Fisher Scientific,美國(guó));場(chǎng)發(fā)射掃描電子顯微鏡(SU-8020,HITACHI,日本).

1.2 藻種培養(yǎng)及水樣配置

本實(shí)驗(yàn)所用的銅綠微囊藻購(gòu)置于中國(guó)科學(xué)院武漢水生生物研究所,編號(hào)為FACHB-315,采用BG11培養(yǎng)基進(jìn)行培養(yǎng).無菌條件下將藻種接種至玻璃錐形瓶中,放在光照培養(yǎng)箱中進(jìn)行曝氣培養(yǎng),培養(yǎng)條件:溫度(25±1)℃,光照強(qiáng)度2400lux,時(shí)間設(shè)置12h晝/12h夜.藻細(xì)胞對(duì)可見光能產(chǎn)生一定的吸收, 680nm處的光吸收主要是由于藻類細(xì)胞中的葉綠素ａ的存在.本實(shí)驗(yàn)配水中的葉綠素a僅由銅綠微囊藻貢獻(xiàn),因此用680nm處的吸光度(OD680)來間接表示藻細(xì)胞的濃度.

在實(shí)驗(yàn)中,將處于初始穩(wěn)定期的銅綠微囊藻溶液稀釋至680nm吸光度值為0.3,加入5.0mmol/L NaNO3和4.0mmol/L NaHCO3以調(diào)節(jié)離子強(qiáng)度和堿度.在稀釋的藻液中加入NaF,使體系中的氟離子濃度為10.0mg/L.

1.3 實(shí)驗(yàn)方法

1.3.1 混凝實(shí)驗(yàn) 使用1mol/L HCl和0.5mol/L NaOH溶液將水樣分別調(diào)節(jié)pH值為7.0,8.0,9.0,混凝劑為氯化鋁,投加量(以Al計(jì))分別設(shè)置為:1.0,2.0, 5.0,8.0,12.0,15.0,20.0,40.0,60.0,80.0,100.0,120.0mg/L,于六聯(lián)攪拌機(jī)上進(jìn)行混凝實(shí)驗(yàn).混凝程序設(shè)置為: 250r/min轉(zhuǎn)速快速攪拌30s使水質(zhì)混合均勻,投加混凝劑并以200r/min轉(zhuǎn)速快速攪拌90s,以40r/min轉(zhuǎn)速慢速攪拌10min,沉淀30min.每個(gè)樣品做2個(gè)平行實(shí)驗(yàn),混凝結(jié)束后,于上清液下2.0cm處取樣進(jìn)行水質(zhì)分析,取絮體冷凍干燥后進(jìn)行表征.

1.3.2 吸附實(shí)驗(yàn) 在pH值為7.0,Al投加量為40.0mg/L的條件下,對(duì)無NaF的含藻水樣(OD680為0.3)進(jìn)行混凝實(shí)驗(yàn),混凝程序設(shè)置為:250r/min轉(zhuǎn)速快速攪拌30s使水質(zhì)混合均勻,投加混凝劑并以200r/min轉(zhuǎn)速快速攪拌90s,以40r/min轉(zhuǎn)速慢速攪拌10min.再對(duì)已形成的絮體分別以3種攪拌強(qiáng)度(分別為:0,400,800r/min)破碎2min,使其破碎成不同粒徑的絮體,隨后將NaF儲(chǔ)備液投加至破碎后的體系中,使體系的氟離子濃度為10.0mg/L(以F-計(jì)),放于搖床低速震蕩2h,每20min取一次樣進(jìn)行水質(zhì)分析,取絮體冷凍干燥后用于表征.

1.3.3 藻在含氟水體中的培養(yǎng) 將處于初始穩(wěn)定期的銅綠微囊藻溶液稀釋至680nm吸光度值為0.3,加入5.0mmol/L NaNO3和4.0mmol/L NaHCO3以調(diào)節(jié)離子強(qiáng)度和堿度.在稀釋后的藻液中加入NaF,使體系中的氟離子濃度為10.0mg/L,放于搖床低速震蕩2h,定時(shí)取樣檢測(cè)氟離子濃度.

1.4 水質(zhì)分析

水質(zhì)分析主要考察氟離子濃度,藻細(xì)胞濃度以及有機(jī)物種類和濃度.水樣氟離子濃度用離子色譜法測(cè)定;藻細(xì)胞濃度以其懸濁液在680nm處的吸光度值來代表;有機(jī)物的濃度和種類分別用總有機(jī)碳分析儀和三維熒光光譜儀來表征.三維熒光測(cè)定條件設(shè)定為:激發(fā)波長(zhǎng)(X)為220~400nm,發(fā)射波長(zhǎng)(M)為220~ 550nm,狹縫寬度均為5nm;光譜的掃描速度為12000nm/min.將激發(fā)和發(fā)射波長(zhǎng)所形成的熒光區(qū)域進(jìn)行分區(qū),分成代表5種不同類型的有機(jī)物,分別為:芳香蛋白類物質(zhì)Ⅰ(APⅠ),芳香蛋白類物質(zhì)Ⅱ(APⅡ),富里酸類物質(zhì)(FA),溶解性微生物代謝產(chǎn)物(SMP)、腐殖酸類物質(zhì)(HA),各部分分區(qū)范圍如表1所示.通過熒光區(qū)域整合法(FRI),將特定熒光區(qū)域的積分體積進(jìn)行加和,最后以單位濃度(mg/L)溶解有機(jī)碳(DOC)對(duì)其進(jìn)行標(biāo)準(zhǔn)化,得出某一熒光區(qū)域的特定結(jié)構(gòu)有機(jī)物的積分占總積分的比例(,),將樣品的實(shí)測(cè)DOC濃度與(,)相乘,得出各組分濃度[14].

表1 三維熒光光譜5個(gè)積分區(qū)域

1.5 絮體的表征

采用馬爾文激光粒度儀對(duì)絮體的粒徑進(jìn)行實(shí)時(shí)監(jiān)測(cè),場(chǎng)發(fā)射掃描電子顯微鏡對(duì)冷凍干燥后的絮體表面形貌及表面元素成分進(jìn)行點(diǎn)線面觀察和分析.

2 結(jié)果與分析

2.1 銅綠微囊藻對(duì)不同投加量混凝劑除氟的影響

2.1.1 除氟效果 如圖1所示, 隨著混凝劑投量的增加,有藻和無藻體系的氟去除率均呈現(xiàn)出先增加后減小的趨勢(shì).在3個(gè)pH值條件下,當(dāng)Al投加量￡20.0mg/L時(shí),有無銅綠微囊藻對(duì)氟的去除沒有明顯的影響. Al投加量>20.0mg/L時(shí),有藻體系顯示出了更高的去除率.當(dāng)pH=7.0時(shí),銅綠微囊藻對(duì)混凝除氟的促進(jìn)作用最大,無藻體系在Al投加量為20.0mg/L時(shí)達(dá)到最高氟去除率48.11%,這與有藻體系的氟去除率相差無幾;但在Al投加量為40.0mg/L時(shí),有藻體系達(dá)到最高氟去除率73.03%,而此時(shí)無藻體系的氟去除率僅為31.03%,銅綠微囊藻的存在提高了42.00%的氟去除率.

2.1.2 出水pH值 pH值不僅對(duì)鋁鹽的水解和絮凝反應(yīng)速度影響顯著,也會(huì)對(duì)絮凝體的沉降和除氟效果產(chǎn)生明顯影響[15].當(dāng)原水為中性或弱堿性時(shí), Al3+聚合并形成Al2-Al4、Al5-Al12、Al13-Al16等聚合物.這些鋁聚合物可以轉(zhuǎn)化為無定形Al(OH)3或沉淀為不溶性Al-F-OH,兩者都能進(jìn)一步吸附氟化物,除氟效果能得到改善.當(dāng)原水pH值過低時(shí),鋁鹽的水解產(chǎn)物以水合鋁離子為主要形態(tài),對(duì)氟不能進(jìn)行有效的絡(luò)合、沉淀[16].

如圖2所示,在不同的初始pH值條件下,隨著Al投加量增加,兩種體系的pH值變化情況無顯著差異,均呈現(xiàn)緩慢降低的趨勢(shì).Al投加量從0增加到120.0mg/L,平衡pH值均持續(xù)下降到4.5左右,這是由于Al3+水解和OH-的消耗.當(dāng)體系中有銅綠微囊藻存在,Al投加量大于20.0mg/L時(shí),出水pH值的變化幅度明顯較無藻體系小,可見銅綠微囊藻及其有機(jī)物起到了一定程度的緩沖作用[17].

圖2 兩種體系的出水pH值

2.1.3 藻密度 如圖3所示,在pH=7.0,不同Al投加量下混凝出水的濁度和OD680的變化趨勢(shì)顯示出了很高的一致性,均可表征藻的去除效果.Al投加量在0~20.0mg/L范圍內(nèi),OD680快速下降,表明銅綠微囊藻在低的投加量下被大量去除,濁度的快速下降表明體系中已經(jīng)形成了具有一定沉降性的藻絮體.Al投加量在20.0~40.0mg/L時(shí),出水OD680和濁度以緩慢的速度繼續(xù)下降,結(jié)合絮體更加快速生長(zhǎng)的實(shí)驗(yàn)現(xiàn)象以及有藻體系具有高除氟率的實(shí)驗(yàn)結(jié)果,可見有藻體系顯示出的更高的除氟率是由于銅綠微囊藻及其有機(jī)物與混凝劑形成的絮體的作用.藍(lán)藻細(xì)胞的胞外聚合物(EPS)主要由糖類、脂質(zhì)、蛋白質(zhì)類等構(gòu)成,含有羰基、羧基、羥基等豐富的官能團(tuán)[18-20],是復(fù)雜的大分子有機(jī)物,可以提高絮體的初始形成速率,使吸附架橋和網(wǎng)捕卷掃作用增強(qiáng),有助于形成較大粒徑的絮體結(jié)構(gòu)[21],對(duì)氟的吸附作用增強(qiáng)[22].Al>40.0mg/L時(shí),剩余氟離子濃度升高,是由于藻細(xì)胞破損加重,胞內(nèi)有機(jī)物釋放,阻礙了混凝作用.

圖3 Al投加量對(duì)銅綠微囊藻的影響

2.2 三維熒光分析

為探究實(shí)驗(yàn)過程中水樣的有機(jī)物變化,測(cè)量了pH值分別為7.0、8.0、9.0,Al投加量分別為0(原水)、20.0、40.0、80.0mg/L條件下的出水三維熒光.如圖4所示,不同pH值、不同Al投加量的水樣的5種組分的熒光響應(yīng)值和濃度均不同.Al=20.0和40.0mg/L時(shí),各類組分的熒光響應(yīng)值和濃度較原水樣均有一定程度的降低.

圖4 不同條件下的三維熒光圖及各組分濃度

Al投加量為40.0mg/L時(shí),在pH為9.0時(shí),各組分的熒光響應(yīng)值和濃度較20.0mg/L的Al投加量都有上升.但在pH值為7.0和8.0時(shí),芳香蛋白類物質(zhì)和富里酸類物質(zhì)沒有上升.當(dāng)Al投加量增加為80.0mg/L時(shí),3個(gè)pH值條件下,各個(gè)組分的熒光響應(yīng)值和濃度較20.0mg/L的Al投加量均上升.這是因?yàn)楦邼舛鹊慕饘匐x子會(huì)刺激藻細(xì)胞發(fā)生抗氧化反應(yīng)而破壞膜系統(tǒng),胞內(nèi)有機(jī)物流出[23],尤其是腐殖酸的大量溶出,對(duì)混凝起到了干擾[24],從而降低了除氟效果.

2.3 藻絮體的表征

混凝劑投加到水體后,其水解產(chǎn)物與銅綠微囊藻及其EPS發(fā)生吸附架橋和網(wǎng)捕卷掃作用,聚集成較大絮體[25].為探究絮體的粒徑變化,使用馬爾文激光粒度儀對(duì)絮體的粒徑進(jìn)行了實(shí)時(shí)監(jiān)測(cè).在本文中,使用絮體的平均尺寸(50)來代表絮體的實(shí)際尺寸.結(jié)果如圖5,pH值分別為7.0,8.0,9.0時(shí),隨著Al投加量由20.0mg/L增加到80.0mg/L,絮體平衡時(shí)的粒徑呈現(xiàn)出先增大后減小的趨勢(shì),都在40.0mg/L的Al投加量達(dá)到最大平衡粒徑,分別為500.0,350.0和200.0μm,趨勢(shì)與氟去除率相吻合,可見藻類及其有機(jī)物與混凝劑形成的絮體性質(zhì)對(duì)氟的去除起著重要的作用,氟去除率隨絮體粒徑的增大而升高[26].有研究[27]表明絮體的粒徑和分型維數(shù)存在一定聯(lián)系.絮體粒徑越大,分形維數(shù)越小,結(jié)構(gòu)愈松散.絮體粒徑越小,分?jǐn)?shù)維數(shù)越大,結(jié)構(gòu)愈緊實(shí).松散的絮體具有更大的表面積,更有利于吸附.用場(chǎng)發(fā)射掃描電子顯微鏡對(duì)絮體表層進(jìn)行掃描,并利用X射線能譜儀,對(duì)絮體的表層的微區(qū)進(jìn)行F和Al元素的掃描.如圖6所示,可以清楚地看到這兩種元素的面分布情況,F和Al結(jié)合在絮體表層,證明了藻絮體表面Al對(duì)氟的吸附作用.

圖5 不同pH值條件下含藻絮體粒徑隨時(shí)間的變化

圖6 pH=7時(shí)不同Al投加量下含藻絮體FE-SEM圖

2.4 藻絮體破碎后對(duì)氟的吸附作用驗(yàn)證

為了更好的了解混凝過程含藻絮體與氟離子的作用機(jī)理,驗(yàn)證銅綠微囊藻和氯化鋁形成的含藻絮體對(duì)氟的吸附作用,將混凝劑與銅綠微囊藻形成的絮體進(jìn)行不同程度的破碎,用破碎后的絮體進(jìn)行氟的吸附實(shí)驗(yàn).破碎后絮體的粒徑結(jié)果如圖7(a)所示,絮體的粒徑隨破碎強(qiáng)度的增大而減小,平衡時(shí)絮體粒徑分別為200和100μm.吸附后體系中氟的剩余濃度見圖7(b),絮體表面Al與F的分布見圖8,所示結(jié)果驗(yàn)證了含藻絮體對(duì)氟離子的吸附.隨著破碎強(qiáng)度的增大,絮體的粒徑逐漸減小.當(dāng)破碎強(qiáng)度為0r/min時(shí),絮體的粒徑最大.當(dāng)破碎強(qiáng)度為400r/min時(shí),絮體顯示出了更高的吸附效果,是因?yàn)樾躞w破碎程度增大,粒徑減小,表面積增大,暴露出了更多的具有活性的吸附位點(diǎn).破碎強(qiáng)度增加至800r/min時(shí),雖然絮體的粒徑減小,表面積更大,但吸附效果卻下降,這是由于破碎強(qiáng)度太大,減少了具有活性的吸附位點(diǎn)[28],從而降低了氟的吸附效率.

圖7 藻絮體破碎后對(duì)氟的吸附

圖8 pH=7時(shí)不同破碎強(qiáng)度下含藻絮體FE-SEM圖

2.5 銅綠微囊藻對(duì)氟的同化吸收作用

圖9 銅綠微囊藻對(duì)氟離子的同化吸收作用

為了探究銅綠微囊藻對(duì)氟離子的同化吸收作用,將銅綠微囊藻在含氟水體中進(jìn)行培養(yǎng).定時(shí)取樣檢測(cè)體系中氟離子濃度,發(fā)現(xiàn)隨著培養(yǎng)時(shí)間的增加,溶液中氟的濃度僅出現(xiàn)輕微下降.最終測(cè)得氟離子的去除率僅為0.95%,這表明銅綠微囊藻僅能吸收少量的氟，其同化吸收對(duì)氟的去除作用十分微小(圖9).

2.6 促進(jìn)作用機(jī)理

當(dāng)體系中有銅綠微囊藻存在,pH值為7.0,8.0, 9.0時(shí),Al投加量在20.0~80.0mg/L的條件下,銅綠微囊藻對(duì)混凝除氟有明顯的促進(jìn)作用,其促進(jìn)作用機(jī)理如圖10所示,銅綠微囊藻及其有機(jī)物與混凝劑水解產(chǎn)物通過吸附架橋和網(wǎng)捕卷掃作用,聚集成較大較多的絮體.絮體粒徑越大,除氟率越高.當(dāng)Al投加量過高時(shí),藻細(xì)胞破損嚴(yán)重,有機(jī)物過多釋放,對(duì)氟的去除起到了干擾作用.氟的去除作用在有藻體系中一共分為3個(gè)部分,一是非生物沉淀,F與Al轉(zhuǎn)化為不溶性Al-F,Al-F-OH等物質(zhì)[29];二是表面吸附,F吸附在含藻絮體表面;三是被銅綠微囊藻同化吸收.混凝除氟的促進(jìn)作用機(jī)理主要在于含藻絮體的表面吸附,借助銅綠微囊藻增大絮體的粒徑和表面積,通過表面吸附實(shí)現(xiàn)氟的有效去除.

圖10 銅綠微囊藻對(duì)混凝除氟的促進(jìn)作用機(jī)理

3 結(jié)論

3.1 無藻體系在pH=7.0,Al投加量為20.0mg/L條件下達(dá)到最高氟去除率48.11%,此時(shí)有藻體系的氟去除率為49.05%.有藻體系在pH=7.0,Al投加量達(dá)到40.0mg/L條件下達(dá)到最高氟去除率73.03%,此時(shí)無藻體系出水的氟去除率僅為31.03%.Al投加量在20.0~100.0mg/L范圍內(nèi),有藻體系的氟去除率相較于無藻體系明顯更高.

3.2 藻源有機(jī)物對(duì)混凝效果有一定的影響.在Al投加量為20.0和40.0mg/L時(shí),混凝劑對(duì)有機(jī)物有一定的去除.當(dāng)Al投加量為80.0mg/L時(shí),藻細(xì)胞破損加重,胞內(nèi)有機(jī)物釋放,對(duì)混凝起到了干擾作用.

3.3 銅綠微囊藻的存在對(duì)混凝除氟的促進(jìn)作用主要來自于含藻絮體對(duì)氟的表面吸附.銅綠微囊藻及其有機(jī)物與混凝劑水解產(chǎn)物通過吸附架橋和網(wǎng)捕卷掃作用,聚集成較大絮體,Al與F結(jié)合在絮體表面.對(duì)絮體進(jìn)行一定強(qiáng)度破碎可以增加吸附位點(diǎn),從而提高氟的吸附效率.

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Promotion effect ofon defluorination by coagulation and its mechanism analysis.

XIANG Yu1,2, XU Hui2, LI Kun1*, WANG Xi2,3, WU Hao-Lan2,4, FAN Hua1

(1.School of Resources Environment and Chemical Engineering, Nanchang University, Nanchang 330031, China；2.State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China；3.University of Chinese Academy of Sciences, Beijing 100049, China；4.School of Water Resources and Environment Engineering, China University of Geosciences (Beijing), Beijing 100083, China)., 2021,41(4)：1900~1908

and aluminum chloride (AlCl3·6H2O) were chosen to research the effect of algae on the coagulation removal mechanism of fluoride through 3D-EEM, FE-SEM. The results showed thathad an obvious promotion effect on defluorination under the conditions of pH 7.0, 8.0, 9.0 and Al dosage of 20.0~80.0mg/L, which was mainly due to the surface adsorption of fluoride by algal flocs.and the hydrolyzed products of coagulant aggregated into larger flocs by bridging and sweep flocculation. The larger the floc size was, the larger the fluoride removal rate was. When the pH value was 7.0 and the Al dosage was 40.0mg/L, the flocs reached the maximum particle size (500μm), and the fluoride removal rate was the largest (77.37%). When the Al dosage was 80mg/L, the algal cells were seriously damaged and the organic matter was released, which hindered the defluorination process. The results of floc breakage and adsorption experiments showed that certain strength breakage of algae floc could increase the adsorption site and thus improved the removal rate of fluoride. Excessive breakage led to too small particle size of algae flocs, resulting in the reduction of fluoride adsorption efficiency.

；defluorination；coagulation；floc；adsorption

X172

A

1000-6923(2021)04-1900-09

象 豫(1995-),女,河南長(zhǎng)葛人,南昌大學(xué)碩士研究生,研究方向:水質(zhì),水環(huán)境與污染控制.發(fā)表論文3篇.

2020-08-25

國(guó)家科技重大專項(xiàng)(2017ZX07108-002,2017ZX07501-002);國(guó)家自然科學(xué)基金資助項(xiàng)目(51778604);寧夏回族自治區(qū)重大項(xiàng)目(2019BFG02032)

* 責(zé)任作者, 講師, kunli@ncu.edu.cn