李 偉,王華偉*,孟祥宇,楊樂巍,丁浩然,李書鵬,劉淵文,孫英杰,劉 鵬,王亞楠

表面活性劑淋溶-化學(xué)氧化處理焦化場(chǎng)地高環(huán)多環(huán)芳烴污染土壤

李 偉1,王華偉1*,孟祥宇1,楊樂巍2,3,丁浩然2,3,李書鵬2,3,劉淵文2,3,孫英杰1,劉 鵬2,3,王亞楠1

(1.青島理工大學(xué)環(huán)境與市政工程學(xué)院,山東 青島 266520；2.北京建工環(huán)境修復(fù)股份有限公司,北京 100015；3.污染場(chǎng)地安全修復(fù)國(guó)家工程實(shí)驗(yàn)室,北京 100015)

為了探究表面活性劑淋溶-化學(xué)氧化技術(shù)對(duì)焦化場(chǎng)地有機(jī)污染土壤的修復(fù)效能,以安徽某焦化場(chǎng)地多環(huán)芳烴(PAHs)污染土壤為實(shí)驗(yàn)對(duì)象,分析了表面活性劑濃度、液固比、淋溶時(shí)間和淋溶次數(shù)等工藝參數(shù)對(duì)淋溶效果的影響,在優(yōu)化工藝參數(shù)的基礎(chǔ)上,進(jìn)一步研究了化學(xué)氧化對(duì)PAHs的去除效能.結(jié)果表明:1)吐溫80(TW80)對(duì)PAHs污染土壤的淋溶效果優(yōu)于曲拉通和鼠李糖脂,用于后續(xù)實(shí)驗(yàn); 2)當(dāng)TW80濃度為6g/L,液固比為10:1,淋溶時(shí)間為4h時(shí)為最佳工藝參數(shù),此時(shí)ΣPAHs的淋溶效率為43.5%; 3)多次淋溶有助于提高PAHs的淋溶效率,連續(xù)淋溶3次后ΣPAHs的淋溶效率為63.3%,淋溶5次時(shí)淋溶率升高至72.1%; 4)TW80淋溶5次,采用10%的H2O2氧化處理后ΣPAHs去除率為79.4%,而采用10% KMnO4氧化處理后ΣPAHs去除率為81.2%,其中苯并[a]芘去除率為98.3%;5) TW80淋溶處理后,H2O2或KMnO4氧化處理均能提高PAHs的去除效率,淋溶5次+1% H2O2和淋溶3次+1% KMnO4處理后苯并[a]芘含量分別為0.39和0.46mg/kg,均滿足《土壤環(huán)境質(zhì)量建設(shè)用地土壤污染風(fēng)險(xiǎn)管控標(biāo)準(zhǔn)(試行)》(GB 36600-2018) 第一類用地篩選值要求; 6)表面活性劑淋溶+化學(xué)氧化技術(shù)對(duì)PAHs去除效果良好,該技術(shù)在PAHs污染土壤修復(fù)具有潛在的應(yīng)用前景.

焦化場(chǎng)地；多環(huán)芳烴(PAHs)；表面活性劑；化學(xué)氧化；修復(fù)技術(shù)；土壤

多環(huán)芳烴(PAHs)是焦化場(chǎng)地污染土壤中典型污染物之一,具有環(huán)境持久性、生物蓄積性、遠(yuǎn)距離遷移性以及“三致”等特性[1].PAHs是指含兩個(gè)或兩個(gè)以上苯環(huán)以稠環(huán)型和非稠環(huán)型連接起來的芳烴[2],其具有較高的辛醇-水分配系數(shù)和親脂疏水性,隨著苯環(huán)數(shù)量的增加而逐漸升高,使PAHs的水溶性降低[3-4],化學(xué)穩(wěn)定性、毒性和生物累積性顯著增加,且極易吸附在土壤有機(jī)質(zhì)表面,增加其環(huán)境風(fēng)險(xiǎn)[5-6].陳倩等[7]研究發(fā)現(xiàn),一些重工業(yè)城市及周邊土壤中PAHs污染嚴(yán)重，其中苯并[a]芘超標(biāo)嚴(yán)重.Zhang等[8]研究也表明,焦化場(chǎng)地污染土壤中高環(huán)PAHs組分含量較高,可在環(huán)境中長(zhǎng)期累積,對(duì)周邊環(huán)境造成嚴(yán)重的威脅[9].研究表明,高環(huán)PAHs會(huì)通過皮膚、呼吸道和食物鏈等方式進(jìn)入人體,危害人體健康[10-11].因此,高環(huán)PAHs是焦化場(chǎng)地污染土壤修復(fù)治理的難點(diǎn)和痛點(diǎn),開發(fā)高環(huán)PAHs的修復(fù)技術(shù)已迫在眉睫.

目前,PAHs污染土壤的修復(fù)技術(shù)有淋溶、熱脫附、化學(xué)氧化和生物修復(fù)等[12].表面活性劑淋溶修復(fù)技術(shù)原理在于利用表面活性劑形成以疏水性的非極性親油基為內(nèi)核的膠團(tuán)分子,改變液體界面張力,降低PAHs的有機(jī)質(zhì)-水分配系數(shù)(oc)以提高PAHs的水溶性,使更多的PAHs溶解在液相中,以達(dá)到修復(fù)的目的[13-15].其主要過程是通過分散、聚集和增溶作用,提高PAHs在土壤顆?？讖街械倪w移能力,促進(jìn)疏水性有機(jī)污染物在固態(tài)顆粒上的解吸,使其溶解到溶液中[16-18].PAHs淋溶效果受表面活性劑種類、工藝參數(shù)(濃度、液固比、淋溶時(shí)間等)、污染物含量及土壤類型等多種因素影響.熱脫附技術(shù)是通過直接或間接加熱,將污染土壤加熱至目標(biāo)污染物的沸點(diǎn)以上,通過控制系統(tǒng)溫度和物料停留時(shí)間有選擇地促使污染物氣化揮發(fā),使目標(biāo)污染物與土壤顆粒分離、去除[19-20].但其存在脫附時(shí)間長(zhǎng)、尾氣處理工藝不完善且缺乏相應(yīng)的工程設(shè)計(jì)參數(shù)與運(yùn)行經(jīng)驗(yàn),高環(huán)PAHs處理成本高等問題[21-22].化學(xué)氧化技術(shù)是利用氧化劑的氧化作用將土壤中有機(jī)污染物轉(zhuǎn)化為毒性更小或無毒的物質(zhì).雖然化學(xué)氧化技術(shù)相對(duì)其他技術(shù)效果更理想,但在實(shí)際修復(fù)中發(fā)現(xiàn)對(duì)高環(huán)PAHs的修復(fù)效果差別較大,部分氧化劑僅在高劑量時(shí)才能滿足修復(fù)目標(biāo),但這樣不僅會(huì)造成處理成本遞增,也會(huì)引發(fā)其他問題[23].研究表明[24],單獨(dú)使用KMnO4氧化處理時(shí)會(huì)降低土壤的滲透性,進(jìn)而使土壤質(zhì)量退化.此外,生物修復(fù)技術(shù)(如微生物修復(fù)),具有成本低、環(huán)境擾動(dòng)小和可就地處理等優(yōu)點(diǎn),但其單獨(dú)處理時(shí)修復(fù)周期長(zhǎng),且不能用于高污染PAHs污染土壤修復(fù).

鑒于上述修復(fù)技術(shù)單一應(yīng)用時(shí)成本高、不理想、無法滿足修復(fù)要求等問題,有科研人員采用多種技術(shù)聯(lián)合的修復(fù)方式,起到“1+1>2”的效果.Derudi等[25]在生物處理后利用臭氧進(jìn)行化學(xué)氧化,以增強(qiáng)PAHs的降解效率.研究發(fā)現(xiàn),該方法可以有效去除工業(yè)場(chǎng)地老化土壤中的PAHs,其中低環(huán)PAHs的去除率達(dá)到90%以上.Gou等[26]研究了過硫酸鹽化學(xué)氧化聯(lián)合土著微生物對(duì)老化土壤中PAHs的去除效能,土著微生物的存在提高了PAHs的去除效能.然而,大多數(shù)研究并未針對(duì)高環(huán)PAHs污染土壤,且微生物修復(fù)期較長(zhǎng),無法用于城市工業(yè)污染土壤修復(fù).因此,針對(duì)高環(huán)PAHs污染土壤的修復(fù)技術(shù)和去除性能仍需深入研究.

本文以安徽某焦化場(chǎng)地高環(huán)PAHs污染土壤為研究對(duì)象,選取吐溫80(TW80)、曲拉通-100(TX-100)和鼠李糖脂等表面活性劑為淋溶劑,研究了淋溶劑種類、濃度、液固比、淋溶時(shí)間和淋溶次數(shù)對(duì)PAHs淋溶效率的影響,在優(yōu)化上述工藝參數(shù)的基礎(chǔ)上,進(jìn)一步研究化學(xué)氧化技術(shù)對(duì)殘余PAHs的去除效率,綜合評(píng)價(jià)表面活性劑淋溶-化學(xué)氧化技術(shù)對(duì)污染土壤PAHs的去除效果,以期為焦化場(chǎng)地PAHs污染土壤的修復(fù)提供數(shù)據(jù)支撐.

1 材料與方法

1.1 供試藥劑

吐溫80(TW-80)、曲拉通 (TX-100)(分析純)購(gòu)買于上海麥克林生化科技有限公司.鼠李糖酯、二氯甲烷和正己烷(分析純) 購(gòu)買于上海默克化工技術(shù)有限公司.乙腈、甲醇(色譜純) 購(gòu)買于上海默克化工技術(shù)有限公司).

1.2 供試土壤

土壤樣品取自安徽合肥某焦化廠污染場(chǎng)地.土壤經(jīng)去除雜質(zhì)混合均勻風(fēng)干保存.污染土壤基本理化性質(zhì):含水率為8.8%,pH值為8.4,有機(jī)質(zhì)為78.4g/ kg,電導(dǎo)率為645.5μS/cm,Mn為581.0mg/kg, Fe為39.6g/kg.污染土壤16種PAHs含量見表1.該污染土壤ΣPAHs含量為300.1mg/kg,根據(jù)第一類用地篩選值要求[27],該污染土壤中苯并[a]蒽、苯并[b]熒蒽、苯并[a]芘、茚并[1,2,3-cd]芘、二苯并[a,h]蒽含量超出標(biāo)準(zhǔn)限值,其超標(biāo)倍數(shù)分別為5.4, 7.9, 49.3, 3.4和9.8倍.對(duì)比分析可知,該污染土壤主要以高環(huán)PAHs為主.

表1 污染土壤中16種PAHs含量

注: *選自《土壤環(huán)境質(zhì)量建設(shè)用地土壤污染風(fēng)險(xiǎn)管控標(biāo)準(zhǔn)(試行)》(GB 36600—2018)第一類用地篩選值[27].

1.3 實(shí)驗(yàn)設(shè)計(jì)

1.3.1 表面活性劑淋溶對(duì)污染土壤PAHs的淋溶效果 分析了表面活性劑種類對(duì)PAHs淋溶效果的影響.結(jié)合相關(guān)研究報(bào)道[28-30],選取吐溫80(TW80)、曲拉通(TX-100)和鼠李糖脂[31]等3種表面活性劑進(jìn)行淋溶實(shí)驗(yàn).取3.00g污染土壤于50mL離心管中,按液固比為10:1加入濃度為6g/L的TW80、TX-100和鼠李糖脂溶液,置于翻轉(zhuǎn)振蕩60r/min 振蕩6h.反應(yīng)結(jié)束后將離心管至于5000r/min離心10min,實(shí)現(xiàn)固液分析,測(cè)定土壤中PAHs含量,計(jì)算PAHs淋溶效率.此外,選取上述淋溶效果好的表面活性劑,進(jìn)一步探究表面活性劑濃度、液固比、淋溶時(shí)間和淋溶次數(shù)對(duì)PAHs淋溶效果的影響.分別調(diào)節(jié)表面活性劑濃度為4, 6, 8g/L,液固比為5:1, 10:1, 20:1,淋溶時(shí)間為2, 4, 6, 8h,淋溶次數(shù)為1, 2, 3, 4, 5次,其余操作步驟上同,定期取樣,測(cè)定土壤中PAHs含量.

1.3.2 化學(xué)氧化技術(shù)對(duì)污染土壤PAHs的去除效果 在優(yōu)化淋溶工藝參數(shù)的基礎(chǔ)上,進(jìn)一步分析化學(xué)氧化技術(shù)對(duì)殘留PAHs的去除效果.根據(jù)文獻(xiàn)報(bào)道[10],選取H2O2和KMnO4氧化劑,氧化劑添加濃度為1%、3%、6%和10%(質(zhì)量比),調(diào)節(jié)液固比1.5:1,攪拌均勻后靜置反應(yīng)24h,測(cè)定土壤中PAHs含量,計(jì)算其去除效率.

1.4 分析方法

土壤樣品中PAHs含量測(cè)定采用高效液相色譜法(HPLC).首先,取冷凍干燥后土壤樣品(3.00g)于50mL比色管中,按液固比10:1加入二氯甲烷:正己烷= 1:1的混合溶劑,250W超聲提取30min,重復(fù)3次.隨后,以5000r/min離心10min,實(shí)現(xiàn)固液分離.取10mL上清液過無水硫酸鈉小柱,再經(jīng)旋轉(zhuǎn)蒸發(fā)儀濃縮至1mL.通過硅膠小柱凈化,再氮吹至近干,乙腈定容至1mL.16種PAHs含量采用HPLC測(cè)定.色譜條件:色譜柱為Sunniest C18,柱長(zhǎng)250mm,內(nèi)徑4.6mm,粒徑5μm;流動(dòng)相為水和乙腈(體積比為7:3);流速1.2mL/min;進(jìn)樣量10μL. PAHs的定量方法為采用外標(biāo)法,標(biāo)線范圍為1～10mg/L.

pH值用PHS-3C pH計(jì)測(cè)定;EC值用DDS- 307A電導(dǎo)率儀測(cè)定;有機(jī)質(zhì)用灼燒法測(cè)定[30]. Fe、Mn采用石墨爐消解儀進(jìn)行前處理待測(cè).

1.5 統(tǒng)計(jì)分析

本實(shí)驗(yàn)所有實(shí)驗(yàn)組均設(shè)置3組平行,使用Origin 2021進(jìn)行作圖.數(shù)據(jù)統(tǒng)計(jì)分析采用SPSS 20.0單因素方差分析(LSD事后多重比較法)進(jìn)行多樣本組間差異性分析,不同大小寫字母代表不同處理間差異顯著(<0.05).

2 結(jié)果與討論

2.1 表面活性劑淋溶對(duì)土壤PAHs修復(fù)效果

2.1.1 不同表面活性劑對(duì)PAHs的淋溶效果 不同類型表面活性劑理化性質(zhì)有所差異,會(huì)影響其對(duì)PAHs的淋溶效果.TW80、TX-100等非離子表面活性劑在水中以非離子分子或膠束狀態(tài)存在,是應(yīng)用較多的高效非離子表面活性劑.鼠李糖脂是目前研究最廣泛的生物表面活性劑之一,由銅綠假單胞菌經(jīng)發(fā)酵而產(chǎn)生,屬于糖脂類陰離子型表面活性劑.

由圖1可知,3種表面活性劑對(duì)PAHs均有一定的淋溶效果,但不同的表面活性劑對(duì)ΣPAHs的淋溶效果差異較大,其中TW80的淋溶效率最高.當(dāng)表面活性劑濃度為6g/L、液固比為10:1、淋溶時(shí)間為6h時(shí),TW80對(duì)ΣPAHs的淋溶效率為42.3%,其次為TX-100(26.2%),鼠李糖脂最低,淋溶效率僅為9.8%.伴隨表面活性劑的加入,PAHs有機(jī)質(zhì)-水分配系數(shù) (oc)降低,促進(jìn)了PAHs的解吸和溶解[32],使更多的PAHs溶解進(jìn)入液相.3種表面活性劑對(duì)PAHs的淋溶效果差異較大,可能是因?yàn)橄嗤瑵舛缺砻婊钚詣┰谖廴就寥乐械钠胶鉂舛却笾孪嗤琜33],而土壤對(duì)TW80的飽和吸附量遠(yuǎn)低于TX-100和鼠李糖脂,會(huì)使更多的TX-100和鼠李糖脂被緊密吸附在土壤顆粒中,難以有效參與PAHs的淋溶.此外,與TX-100和鼠李糖脂相比,TW80的疏水基碳鏈數(shù)量最多[34],導(dǎo)致其親水親油系數(shù)最低,增加其對(duì)PAHs的淋溶效果[35].袁笑等[29]研究也發(fā)現(xiàn),TW-80對(duì)模擬土壤ΣPAHs的淋溶效率要優(yōu)于鼠李糖脂.肖鵬飛等[36]研究也發(fā)現(xiàn),吐溫系列表面活性劑對(duì)土壤PAHs淋溶效果較好,淋溶效率最高可達(dá)79.2%.因此,選擇TW-80用于后續(xù)實(shí)驗(yàn),進(jìn)一步優(yōu)化其工藝參數(shù).

圖1 不同表面活性劑對(duì)污染土壤PAHs的淋溶效率

不同小寫字母代表處理間差異達(dá)到顯著水平(<0.05),相同字母表示處理間不顯著(<0.05),下同

2.1.2 TW80對(duì)污染土壤PAHs的淋溶效果 研究表明,表面活性劑濃度、液固比、淋溶時(shí)間、淋溶次數(shù)等工藝參數(shù)會(huì)影響TW-80對(duì)土壤中PAHs的淋溶效果[37].因此,進(jìn)一步研究了上述參數(shù)對(duì)PAHs 的淋溶效果,并進(jìn)行了工藝參數(shù)優(yōu)化,結(jié)果見圖2.

由圖2可知,當(dāng)TW80濃度由4g/L增加至8g/L時(shí),PAHs的淋溶效率呈現(xiàn)先上升后下降的趨勢(shì).當(dāng)TW80濃度為4g/L時(shí),其對(duì)ΣPAHs的淋溶效率25.5%,當(dāng)濃度提高到6g/L時(shí),其對(duì)ΣPAHs的淋溶效率最高,為43.2%,而TW80濃度在8g/L時(shí)僅為21.4%.與此同時(shí),苯并[a]蒽、苯并[b]熒蒽及苯并[a]芘等也呈類似趨勢(shì),均在6g/L淋溶效率最高,其淋溶效率分別為41.3%、40.6%和44.4%.可能是因?yàn)楦邼舛鹊腡W80會(huì)堵塞土壤顆粒之間的孔隙,無法實(shí)現(xiàn)土壤顆粒內(nèi)部PAHs解吸.此外,與模擬土壤相比,實(shí)際土壤化學(xué)組成更加復(fù)雜,PAHs與土壤顆粒之間的結(jié)合能力更強(qiáng),很難從土壤顆粒完全解吸[38].袁笑等[29]研究表明,TW80濃度為5g/L時(shí),PAHs的淋溶效率較好,在60%左右.吉紅軍等[18]研究發(fā)現(xiàn),在一定范圍內(nèi)PAHs的淋溶效率與TW80濃度呈正相關(guān)性,當(dāng)TW80濃度為7.5%、10%時(shí),ΣPAHs的淋溶效率分別為24.3%和37.8%.綜合分析,TW80濃度為6g/L時(shí)是較優(yōu)的濃度選擇,用于后續(xù)實(shí)驗(yàn).

圖2 不同濃度、液固比和淋溶時(shí)間下TW80對(duì)PAHs的淋溶效率

液固比也是影響污染土壤PAHs淋溶效果的重要因素之一.當(dāng)液固比在5:1至20:1時(shí),PAHs的淋溶效率隨液固比的增加而增大.液固比為5:1、10:1和20:1時(shí)ΣPAHs的淋溶效率分別為36.2%、43.0%和51.3%.苯并[a]蒽、苯并[b]熒蒽、苯并[a]芘、二苯并[a,h]蒽和茚并[1,2,3-cd]芘等規(guī)律一致,當(dāng)液固比為20∶1時(shí)其淋溶效率分別為53.6%、48.4%、59.5%、49.2%和47.1%.研究表明,隨著液固比增加,參與反應(yīng)的TW80增多,PAHs與TW80接觸次數(shù)增加,促進(jìn)了PAHs的淋溶效果[29].雖然PAHs的淋溶效率隨液固比呈正相關(guān)性,但液固比過高時(shí)可操作性不強(qiáng),產(chǎn)生的廢液處理成本遞增.因此,考慮到實(shí)際施工和綜合經(jīng)濟(jì)效益,液固比10:1是一個(gè)相對(duì)經(jīng)濟(jì)有效且符合實(shí)際操作的選擇.

此外,淋溶時(shí)間也會(huì)影響污染土壤PAHs的淋溶效果.隨著淋溶時(shí)間的延長(zhǎng),PAHs的淋溶效率呈遞增趨勢(shì).當(dāng)淋溶時(shí)間為2h時(shí),ΣPAHs的淋溶效率為35.5%,淋溶時(shí)間延長(zhǎng)到4h時(shí),ΣPAHs的淋溶效率增加為43.5%,繼續(xù)延長(zhǎng)到8h時(shí),ΣPAHs的淋溶效率僅為48.7%.在淋溶時(shí)間為4h 時(shí),苯并[a]蒽、苯并[b]熒蒽、苯并[a]芘、二苯并[a,h]蒽和茚并[1,2,3-cd]芘的淋溶效率分別為46.1%、37.3%、52.1%、42.5%和34.8%.總體而言,淋溶時(shí)間為4h時(shí),PAHs淋溶效率已達(dá)到平衡,隨淋溶時(shí)間的延長(zhǎng),PAHs的淋溶效果未得到顯著提升.李爽等[39]研究發(fā)現(xiàn),PAHs淋溶效率會(huì)隨反應(yīng)時(shí)間的延長(zhǎng)而增大.鐘金魁等[40]的研究結(jié)果表明,污染物的表觀溶解度會(huì)隨著淋溶時(shí)間的延長(zhǎng)而增大,并在一定時(shí)間內(nèi)達(dá)到峰值;當(dāng)淋溶時(shí)間繼續(xù)增加時(shí),污染物再次返回到固相中與土壤顆粒形成強(qiáng)結(jié)合態(tài),使其更難以被淋溶.

圖3 不同淋溶次數(shù)下TW80對(duì)PAHs的淋溶效率

在上述實(shí)驗(yàn)結(jié)果表明,TW80淋溶的最佳工藝參數(shù)為:TW80濃度為6g/L,液固比為10:1,淋溶時(shí)間為4h.在此基礎(chǔ)上,進(jìn)一步研究了淋溶次數(shù)對(duì)PAHs淋溶效率的影響(圖3).結(jié)果表明,隨著淋溶次數(shù)增加,PAHs的淋溶效率也逐漸增加.淋溶3次后ΣPAHs的淋溶效率為63.3%,相較于2次和1次淋溶的淋溶效率提高了8.4%和16.9%.此時(shí)苯并[a]蒽、苯并[b]熒蒽、苯并[a]芘、二苯并[a,h]蒽和茚并[1,2,3-cd]芘的淋溶效率為61.2%、69.0%、63.8%、39.8%和42.8%.然而,繼續(xù)增加淋溶次數(shù)時(shí),PAHs的淋溶效率增加不明顯,5次淋溶時(shí)ΣPAHs的淋溶效率僅增加了8.8%.這可能是實(shí)驗(yàn)土壤經(jīng)過了長(zhǎng)時(shí)間的老化,PAHs已滲透到土壤黏土顆粒微孔中,形成強(qiáng)結(jié)合態(tài)的PAHs,難于溶解釋放[18].

2.2 化學(xué)氧化技術(shù)對(duì)PAHs的去除效果

H2O2和KMnO4氧化處理時(shí)PAHs去除率如圖4和5所示.從圖4中可以看出,ΣPAHs的去除率隨氧化劑濃度的升高而增加,當(dāng)淋溶1次、3次、5次后,添加10% H2O2時(shí)ΣPAHs的去除率最高,分別為53.6%、69.1%和79.4%.此外,淋溶次數(shù)越多,高環(huán)PAHs去除效率也越高,苯并[a]蒽和苯并[b]熒蒽的去除率呈顯著上升趨勢(shì),當(dāng)淋溶5次時(shí),苯并[a]芘的去除率在98.0%以上,苯并[a]蒽和苯并[b]熒蒽的去除率在80%左右,而更高環(huán)的二苯并[a,h]蒽和茚并[1,2,3-cd]芘均則在60%左右.

圖4 TW80多次淋溶+H2O2氧化對(duì)PAHs去除效率

由圖5可知,與H2O2處理相同,KMnO4氧化處理對(duì)ΣPAHs的去除率隨氧化劑濃度的升高而升高,但淋洗次數(shù)增加至5次時(shí), KMnO4氧化劑量為1%、3%、6%時(shí),ΣPAHs的去除率分別為66.7%、78.3%和81.2%.值得注意的是,在淋溶次數(shù)為3次時(shí),不同劑量KMnO4氧化處理對(duì)苯并[a]芘具有較高的去除率,接近100%.隨著淋溶次數(shù)的增加,部分高環(huán)PAHs的去除效率仍呈上升趨勢(shì),但增幅不明顯.

圖5 TW80多次淋溶+ KMnO4氧化對(duì)PAHs去除效率

對(duì)比發(fā)現(xiàn),不論H2O2還是KMnO4,其氧化處理后PAHs去除率有所提升,且ΣPAHs的去除率與氧化劑濃度呈正相關(guān)性[41],即氧化劑濃度越高,PAHs的去除效率也越高.但氧化劑對(duì)PAHs的降解作用的提升作用十分有限,其原因可能包括2方面: 1)TW80會(huì)與土壤中PAHs結(jié)合成黏性物質(zhì),進(jìn)而堵塞土壤之間的空隙,氧化劑無法接觸到深層次的PAHs[18]; 2)土壤中殘留的TW80會(huì)消耗大量的氧化劑,造成PAHs未能與氧化劑充分反應(yīng),進(jìn)而影響了PAHs去除速率[42].

2.3 表面活性劑淋溶-化學(xué)氧化技術(shù)處理PAHs效果分析

如表2所示, 5種高環(huán)PAHs的原始含量均高于篩選值,其中苯并[a]芘超標(biāo)倍數(shù)最大,達(dá)到了49.3倍.經(jīng)過TW80淋溶后,高環(huán)PAHs含量顯著降低,多次淋溶(3或5次)時(shí)仍未達(dá)到標(biāo)準(zhǔn)限制要求.5次淋溶后苯并[a]芘含量降至7.67mg/kg,含量仍較高.從不同淋溶次數(shù)+化學(xué)氧化處理結(jié)果可知,淋溶5次+1% H2O2和淋溶3次+1% KMnO4處理后苯并[a]芘含量分別為0.39和0.46mg/kg,均滿足篩選值的0.55mg/kg,同時(shí),當(dāng)淋溶5次+10% KMnO4處理后苯并[a]蒽含量低于篩選值的5.50mg/kg.然而,其他高環(huán)PAHs含量仍高于篩選值,后續(xù)仍需進(jìn)一步優(yōu)化工藝參數(shù),以提高高環(huán)PAHs的去除效率.

表2 表面活性劑淋溶-化學(xué)氧化技術(shù)處理后PAHs含量變化(mg/kg)

表3 主要處理技術(shù)對(duì)PAHs的去除效果對(duì)比分析

對(duì)比分析了幾種典型技術(shù)對(duì)PAHs的處理效率,結(jié)果見表3.Gou等[41]在使用10%的H2O2預(yù)處理廢棄鋼廠老化污染土壤中PAHs時(shí)發(fā)現(xiàn),ΣPAHs的去除率為61.7%,處理后ΣPAHs含量高達(dá)134.0mg/kg,但高環(huán)PAHs去除率較低,僅為43.5%～54.7%.袁笑等[29]制備模擬PAHs污染土壤,研究了表面活性劑淋溶對(duì)PAHs去除效率,其發(fā)現(xiàn)TX-100對(duì)ΣPAHs和苯并[a]芘的淋溶效率為60%左右.Li等[42]也研究了表面活性劑淋溶對(duì)PAHs的淋溶效率,與袁笑等[29]效果相近.此外,Liao等[43]研究了化學(xué)氧化技術(shù)對(duì)PAHs的去除效能,當(dāng)0.4mol/L KMnO4和30%H2O2+0.5mol/L FeSO4處理時(shí),ΣPAHs的去除效率分別為92.4%和54.1%.Gou等[26]研究了化學(xué)氧化聯(lián)合生物刺激對(duì)PAHs的去除效果,其發(fā)現(xiàn)苯并[a]芘的去除率在70%左右.當(dāng)采用表面活性劑淋溶+化學(xué)氧化技術(shù)處理時(shí),ΣPAHs去除效率達(dá)到81.2%,其中苯并[a]芘的去除可到達(dá)98.3%.對(duì)比分析可知,表面活性劑淋溶+化學(xué)氧化技術(shù)對(duì)PAHs去除效率較佳,該技術(shù)具有良好的應(yīng)用前景.

3 結(jié)論

3.1 TW80對(duì)土壤中PAHs的淋溶效果優(yōu)于TX- 100和鼠李糖脂,對(duì)ΣPAHs的淋溶效率為42.3%,用于后續(xù)實(shí)驗(yàn).

3.2 以TW80為淋溶劑時(shí),發(fā)現(xiàn)其濃度為6g/L,液固比為10:1,淋溶時(shí)間為4h時(shí)淋溶效果最好,達(dá)到了43.5%.

3.3 多次淋溶有助于提高PAHs的淋溶效率,淋溶3次后ΣPAHs的淋溶效率為63.3%,淋溶5次時(shí)淋溶率升高至72.1%.

3.4 TW80淋溶處理后,H2O2或KMnO4氧化處理均能提高PAHs的去除效率,淋溶5次+1% H2O2和淋溶3次+1% KMnO4處理后苯并[a]芘含量分別為0.39和0.46mg/kg,均滿足《土壤環(huán)境質(zhì)量建設(shè)用地土壤污染風(fēng)險(xiǎn)管控標(biāo)準(zhǔn)(試行)》(GB 36600—2018)第一類用地篩選值要求.表面活性劑淋溶+化學(xué)氧化技術(shù)對(duì)PAHs去除效果良好,該技術(shù)具有潛在的應(yīng)用前景.

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Research on the efficiency of surfactant leaching coupled with chemical oxidation on high rings polycyclic aromatic hydrocarbons removal from coking contaminated soil.

Li Wei1,Wang Hua-wei1*, Meng Xiang-yu1, Yang Yue-wei2,3, DING Hao-ran2,3, Li Shu-peng2,3, Liu Yuan-wen2,3, Sun Ying-jie1, Liu Peng2,3, Wang Ya-nan1

(1.School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao 266520, China；2.Beijing Construction Engineering Environmental Remediation Co., Ltd., Beijing 100015, China；3.National Engineering Laboratory for Safety Remediation of Contaminated Sites, Beijing 100015, China)., 2023,43(12)：6474～6481

In order to explorthe remediation efficiency of surfactant leaching combined with chemical oxidation technology on the treatment of organic polluted soil in coking sites, the polycyclic aromatic hydrocarbons (PAHs) contaminated soil in a coking site in Anhui Province was taken as the experimental object, and the effect of process parameters such as surfactant concentration, liquid-solid ratio, leaching time and number of leaching on the leaching efficiency was analyzed. On the basis of optimizing the process parameters, the efficiency of chemical oxidation on the removal of PAHs was further investigated. The results showed that: 1) Tween 80 (TW80) was more effective than Triton and rhamnolipid in leaching PAHs from soil, which was used for subsequent experiments; 2) The removal efficiency of ΣPAHs was 43.5% when the concentration of TW80was 6g/L, the liquid-solid ratio was 10:1and the leaching time was 4h; 3) Multiple leaching was helpful for improving the leaching efficiency of PAHs, and the leaching efficiencies of ΣPAHs were 63.3% and 72.1% after three and five times leaching, respectively; 4) The removal efficiency of ΣPAHs increased to 79.4% after TW80 leaching five times combined with the oxidation of 10% H2O2, while the ΣPAHs removal efficiency increased to 81.2% after oxidation treatment with 10% KMnO4, in which the benzo[a]pyrene removal efficiency was 98.3%; 5) After TW80 leaching treatment, the combination of H2O2or KMnO4oxidation treatment can improve the removal efficiency of PAHs, the content of benzo[a]pyrene was 0.39mg/kg and 0.46mg/kg after five times leaching combined with 1% H2O2and three times leaching combined with 1% KMnO4, respectively, which can met the screening value requirement of soil environmental quality risk control standard for soil contamination of development land (GB36600-2018); 6) The combination of surfactant leaching with chemical oxidation technology has a good efficiency on PAHs removal. This technology has a potential application prospect on the remediation of PAHs contaminated soil.

coking site；polycyclic aromatic hydrocarbons (PAHs)；surfactant；chemical oxidant；remediation technology；soil

X53

A

1000-6923(2023)12-6474-08

李 偉,王華偉,孟祥宇,等.表面活性劑淋溶-化學(xué)氧化處理焦化場(chǎng)地高環(huán)多環(huán)芳烴污染土壤 [J]. 中國(guó)環(huán)境科學(xué), 2023,43(12):6474-6481.

Li W, Wang H W, Meng X Y, et al. Research on the efficiency of surfactant leaching coupled with chemical oxidation on high rings polycyclic aromatic hydrocarbons removal from coking contaminated soil [J]. China Environmental Science, 2023,43(12):6474-6481.

2023-05-16

國(guó)家重點(diǎn)研發(fā)計(jì)劃(2020YFC1807905);東營(yíng)市科技計(jì)劃項(xiàng)目(2022ZD20);國(guó)家自然科學(xué)基金資助項(xiàng)目(52370173)

* 責(zé)任作者, 副教授, wanghuawei210@163.com

李 偉(1995-),男,內(nèi)蒙古錫林郭勒盟人,青島理工大學(xué)碩士研究生,主要研究方向?yàn)槲廴緢?chǎng)地修復(fù).liwei19952022@163.com.