改性凹凸棒土/納米鐵復(fù)合材料去除地下水的研究

董 磊,龔 磊,林 莉,馮 雪,李青云

(1.長(zhǎng)江水利委員會(huì)長(zhǎng)江科學(xué)院流域水環(huán)境研究所,湖北 武漢 430010; 2.長(zhǎng)江水利委員會(huì)長(zhǎng)江科學(xué)院流域水資源與生態(tài)環(huán)境科學(xué)湖北省重點(diǎn)實(shí)驗(yàn)室,湖北 武漢 430010;3.長(zhǎng)江水利委員會(huì)長(zhǎng)江科學(xué)院黨群辦公室,湖北 武漢 430010)

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董 磊1,2,龔 磊3,林 莉1,2,馮 雪1,2,李青云1,2

(1.長(zhǎng)江水利委員會(huì)長(zhǎng)江科學(xué)院流域水環(huán)境研究所,湖北 武漢 430010; 2.長(zhǎng)江水利委員會(huì)長(zhǎng)江科學(xué)院流域水資源與生態(tài)環(huán)境科學(xué)湖北省重點(diǎn)實(shí)驗(yàn)室,湖北 武漢 430010;3.長(zhǎng)江水利委員會(huì)長(zhǎng)江科學(xué)院黨群辦公室,湖北 武漢 430010)

凹凸棒土理想結(jié)構(gòu)式是[Mg5][Si8O20](OH)2(OH2)4·4H2O,屬于含水富鎂鋁硅酸鹽纖維狀黏土礦物[13],直徑一般為20～50 nm,長(zhǎng)幾百納米至幾微米,是天然的納米材料。凹凸棒土內(nèi)部具有發(fā)育的微孔孔道,其成分、形態(tài)、結(jié)構(gòu)、物理化學(xué)性質(zhì)都比較特殊。凹凸棒土的吸附性與比表面積成正相關(guān),將其進(jìn)行酸改性或熱活化均可增大比表面積。酸改性可使凹凸棒土的八面體層不斷溶解,進(jìn)而提高礦物的微孔隙及微孔比表面積,增強(qiáng)凹凸棒土的吸附性能[14]。熱改性可使凹凸棒土內(nèi)部的有機(jī)質(zhì)及其部分礦物質(zhì)分解,孔道變得疏松,孔隙容積和比表面積增加,其吸附性隨之增強(qiáng)[15]。

基于對(duì)凹凸棒土的獨(dú)特結(jié)構(gòu)和吸附性能的認(rèn)識(shí),許多學(xué)者將凹凸棒土作為吸附劑進(jìn)行了深入的研究[16-19]。王金明等[16-17]分別用酸、微波加熱等方法對(duì)凹凸棒土進(jìn)行改性,用于吸附核素Sr2+、苯酚。Sanchez等[18-19]對(duì)凹凸棒土進(jìn)行改性,并對(duì)改性后的吸附性能進(jìn)行研究。總體而言,凹凸棒土具有結(jié)構(gòu)獨(dú)特和吸附性能良好的優(yōu)點(diǎn),已經(jīng)取得的成果表明凹凸棒土是一種優(yōu)良的水處理吸附劑,特別是經(jīng)過(guò)改性后的凹凸棒土吸附性能更佳。

1 試驗(yàn)材料與儀器

1.1 試驗(yàn)材料

實(shí)驗(yàn)所用凹凸棒土由江蘇玖川納米材料科技發(fā)展有限公司提供。硝酸鉀、亞硝酸鈉、氫氧化鈉、硫酸鋅、碘化鉀、碘化汞、酒石酸鉀鈉、硼氫化鈉、無(wú)水乙醇、氨基磺酸、4-氨基苯磺酸胺、N-(1-萘基)-乙二胺二鹽酸鹽、六水合氯化鐵、六偏磷酸鈉等均為分析純,實(shí)驗(yàn)用水為脫氧去離子水。

1.2 試驗(yàn)儀器

萬(wàn)分之一電子天平(美國(guó)DENVER,TP-21);低速臺(tái)式離心機(jī)(上海安亭科學(xué),TDL-40B);紫外可見(jiàn)分光光度計(jì)(日本島津,UV2600);電熱鼓風(fēng)干燥箱(上海博迅實(shí)業(yè),BGZ-240);多參數(shù)分析儀(上海雷磁,DZB-718);水浴恒溫振蕩器(江蘇金壇普天,SHY-2A);冷凍干燥機(jī)(美國(guó) GOLD SIM,FD5-3B)。

1.3 改性凹凸棒土、納米鐵和復(fù)合材料的制備方法

1.3.1 凹凸棒土的提純

凹凸棒土研磨過(guò)200目篩后,將凹凸棒土配成懸浮液,在懸浮液中加入六偏磷酸鈉作為分散劑[20-21],磁力攪拌,50℃下超聲波處理后靜置,取上層乳白色懸浮液離心處理,將離心后的沉淀物在105℃條件下干燥6 h后研磨過(guò)200目篩,得到提純后凹凸棒土。

1.3.2 凹凸棒土的酸改性

相關(guān)研究采用不同濃度的鹽酸對(duì)凹凸棒土進(jìn)行酸處理[22-23]。本試驗(yàn)優(yōu)化后采用濃度為1 mol/L的鹽酸對(duì)提純后凹凸棒土酸改性,凹凸棒土與鹽酸的固液比為1∶10。磁力攪拌,50℃超聲波處理,離心過(guò)濾,離心后的沉淀物采用去離子水洗滌,洗滌至中性,然后將所得沉淀物在105℃條件下干燥并過(guò)200目篩,得到粒徑不大于200目的酸改性凹凸棒土。

1.3.3 凹凸棒土的熱改性

相關(guān)研究表明對(duì)凹凸棒土進(jìn)行熱活化改性時(shí)不宜超過(guò)500℃,且活化時(shí)間3 h較為合適[24-25]。因此,本試驗(yàn)對(duì)提純后的凹凸棒土進(jìn)行熱改性時(shí),焙燒溫度設(shè)置為100～500℃,焙燒時(shí)間3 h,冷卻后,過(guò)200目篩,得到粒徑不大于200目的熱改性凹凸棒土。

1.3.4 復(fù)合材料和納米鐵的制備

復(fù)合材料和納米鐵均采用液相還原法制備,參考相關(guān)文獻(xiàn)[26-27],稱(chēng)取2 g純化改性凹凸棒土,用50 mL的去離子水和乙醇混合溶液(體積比4∶1)溶解,按質(zhì)量比為1∶10、1∶5、1∶3、1∶2、1∶1加入六水合氯化鐵,攪拌2 h;并向其中滴加100 mL一定濃度的KBH4溶液,滴加速度控制在0.2 mL/s左右,反應(yīng)完畢后繼續(xù)攪拌1 h,保證KBH4與Fe3+充分反應(yīng),反應(yīng)見(jiàn)式(1),整個(gè)試驗(yàn)過(guò)程均在氬氣保護(hù)下進(jìn)行。

12H++6H2

(1)

反應(yīng)結(jié)束后,離心過(guò)濾,所得沉淀物用乙醇洗滌3～4次,再真空過(guò)濾干燥。納米鐵在相同條件下制備,但不加純化改性的凹凸棒土。復(fù)合材料和納米鐵均儲(chǔ)存于密封棕色玻璃瓶(通氬氣除氧)。

1.4 試驗(yàn)方法

試驗(yàn)中用錫紙包覆反應(yīng)離心管,避免光照,以模擬地下水的黑暗環(huán)境;向反應(yīng)溶液中通氬氣,去除反應(yīng)溶液中的DO以模擬地下水DO環(huán)境。

1.4.1 改性凹凸棒土選擇試驗(yàn)

1.4.2 復(fù)合材料制備試驗(yàn)

2 結(jié)果與討論

2.1 復(fù)合材料的制備及性能

2.1.1 凹凸棒土改性條件的確定

圖1 3種改性條件下凹凸棒土對(duì)去除率

圖2 不同焙燒溫度下凹凸棒土對(duì)的吸附性能

圖3 4種改性條件下凹凸棒土對(duì)去除率

綜上,本研究選用的凹凸棒土采用先提純,后熱活化的方式進(jìn)行改性,熱活化條件:焙燒溫度270℃,焙燒時(shí)間3 h。

2.1.2 復(fù)合材料制備方案的確定

圖4 不同質(zhì)量比下復(fù)合材料對(duì)去除率

圖5 不同材料下“三氮”變化情況

圖6 反應(yīng)過(guò)程中溶液pH值變化

圖7 DO對(duì)去除率及其還原產(chǎn)物生成率的影響

圖8 光照對(duì)去除率及其還原產(chǎn)物生成率的影響

(2)

(3)

(4)

2 Fe0+2H2O+O2→2Fe(OH)2

(5)

4Fe(OH)2+O2+2H2O→4Fe(OH)3

(6)

圖9 溫度對(duì)去除率及其還原產(chǎn)物生成率的影響

Fe0+2H2O→Fe2++H2+2OH-

(7)

(8)

(9)

3 結(jié) 論

a. 確立凹凸棒土改性條件、凹凸棒土與六水合氯化鐵最佳質(zhì)量比等關(guān)鍵試驗(yàn)參數(shù),優(yōu)化了復(fù)合材料制備方案;復(fù)合材料較單獨(dú)納米鐵穩(wěn)定性好,不易凝聚成團(tuán),不容易被氧化。

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Study of removal of nitrate nitrogen from groundwater using modified attapulgite-Fe nano composite material

DONG Lei1,2, GONG Lei3, LIN Li1,2, FENG Xue1,2, LI Qingyun1,2

(1.BasinWaterEnvironmentalResearchDepartment,ChangjiangRiverScientificResearchInstitute,ChangjiangWaterResourcesCommission,Wuhan430010,China; 2.KeyLabofBasinWaterResourceandEco-EnvironmentalScienceinHubeiProvince,ChangjiangRiverScientificResearchInstitute,ChangjiangWaterResourcesCommission,Wuhan430010,China; 3.PartyandMassLineOffice,ChangjiangRiverScientificResearchInstitute,ChangjiangWaterResourcesCommission,Wuhan430010,China)

In this study, we synthesized modified attapulgite-Fe nano composite material (A-NZVI) using the liquid-phase reduction method, and investigated the stability of A-NZVI and changes of three kinds of nitrogen (NO3--N, NH4+-N, and NO2--N) in the reaction process. We also analyzed the effects of groundwater environmental factors (dissolved oxygen, temperature, and light) on the removal of NO3--N with A-NZVI. In the simulation of groundwater environment, the three kinds of materials were ranked in the following descending order according to their reactivity in removing NO3--N: A-NZVI, nanoscale zero-valent iron, and modified attapulgite. The conversion rate of NH4+-N was low, with nearly no NO2--N generated, when using A-NZVI. Dissolved oxygen and temperature had significant influence on the removal of NO3--N from groundwater with A-NZVI. When in the light and dark environment, the removal rate of NO3--N and the amounts of generated NH4+-N and NO2--N had no significant difference. The findings of the study provided a theoretical basis and technical support for restoration projects for groundwater with NO3--N pollution.

groundwater; nitrate nitrogen; modified attapulgite-Fe nano composite material; environmental factor

10.3880/j.issn.1004-6933.2017.01.014

國(guó)家自然科學(xué)基金(41302204);中央級(jí)公益性科研院所基本科研業(yè)務(wù)費(fèi)項(xiàng)目(CKSF2014029/SH)

董磊(1987—),男，工程師，碩士,主要從事水環(huán)境治理。E-mail: dongleigushi@163.com

X523

A

1004-6933(2017)01-0067-08

2016-04-23 編輯：王 芳)