ORC-GAC-Fe0 system for the remediation of trichloroethylene and monochlorobenzene contaminated aquifer: 1. Adsorption and degradation

Activities at a former Chemistry Triangle in Bitterfeld, Germany, resulted in contamination of groundwater with a mixture of tdchloroethylene(TCE) and monochlorobenzene(MCB). The objective of this study was to develop a barrier system,which includes an ORC(oxygen release compounds) and GAC(granular activated carbon) layer for adsorption of MCB and bioregeneration of GAC, a Fe^0 layer for chemical reductive dechlorination of TCE and other chlorinated hydrocarbon in situ. A laboratory-scale column experiment was conducted to evaluate the feasibility of this proposed system. This experiment was performed using a series of continuous flow Teflon columns including an ORC column, a GAC column, and a Fe^0 column. Simulated MCB and TCE contaminated groundwater was pumped upflow into this system at a flow rate of 1.1 ml/min. Results showed that 17%-50% of TCE and 28%-50% of MCB were dissipated in ORC column. Chloride ion, however, was not released, which suggest the dechlorination do not happen in ORC column. In GAC column, the adsorption of contaminants on activated carbon and their induced degradation by adapted microorganisms attached to the carbon surface were observed. Due to competitive exchange processes, TCE can be desorbed by MCB in GAC column and further degraded in iron column. The completely dechlorination rate of TCE was 0.16-0.18 cm^-1, 1-4 magnitudes more than the formation rate of three dichloroethene isomers. Cis-DCE is the main chlorinated product, which can be cumulated in the system, not only depending on the formation rate and its decaying rate, but also the initial concentration of TCE.     

微电流对零价铁还原Cr(Ⅵ)过程中去钝化作用研究

为解决零价铁(ZVI)作为渗透反应格栅(PRB)反应介质处理六价铬〔Cr(Ⅵ)〕时产生钝化导致处理效率低的问题,提出了在反应介质上施加低直流电压,产生微电流去钝化的措施。通过PRB柱流动模拟试验,以粒径为0.15~0.35 mm的工业铁粉为反应介质,施加不同低电压,分析ZVI去除Cr(Ⅵ)的效果。结果表明:当Cr(Ⅵ)去除率达到60%时,施加1、3、7 V电压的试验组对应的出水体积分别是对照组的1.42、1.88和2.75倍;微电流可以在一定程度上解决ZVI的钝化问题,提高ZVI的利用效率,施加电压增大,ZVI的利用效率逐渐增高;施加电压产生的微电流对Cr(Ⅲ)沉淀影响不大,会对Fe(Ⅱ)或Fe(Ⅲ)的沉淀物产生影响。     

蔗糖改性纳米铁原位反应带对硝基苯污染的模拟修复研究

在一维模拟装置中创建改性纳米铁原位反应带,研究反应带对硝基苯污染的修复情况,并通过反应带渗透性变化对其可持续修复能力进行评估.模拟试验结果表明:不同条件下硝基苯的去除率为45%~80%;反应带渗透性变化过程按时间分为3个阶段,分别是0~10d的快速下降期、10~30d的缓慢下降期和30~60d的稳定期,平均下降了53.2%,堵塞现象未发生,反应带可持续修复能力较好.较大的介质粒径和浆液浓度使污染物降解效率增加,硝基苯去除率可分别提高23.7%和13.7%;较高的地下水流速和污染物浓度不利于污染物的去除,硝基苯去除率均下降约46.8%.各反应带中实际参与反应的铁与硝基苯的物质的量比值分别为11.2、17.9、12.6、3.3和25.7,改性纳米铁颗粒的实际利用率较低,实际应用中浆液需要过量注入.     

Quantification of changes in zero valent iron morphology using X-ray computed tomography

Morphological changes within the porous architecture of laboratory scale zero valent iron （ZVI） permeable reactive barriers （PRBs）, after exposure to different groundwater conditions, have been quantified experimentally for different ZVI/sand ratios （10%, 50% and 100%, W/W） with the aim of inferring porosity changes in field barriers. Column studies were conducted to simulate interaction with different water chemistries, a synthetic groundwater, acidic drainage and deionised （DI） water as control. Morphological changes, in terms of pore size and distribution, were measured using X-ray computed tomography （CT）. CT image analysis revealed significant morphological changes in columns treated with different water chemistries. For example, 100% ZVI （W/W） columns had a higher frequency of small pores （0.6 mm） was observed in ZVI grains reacted with typical groundwater, resulting in a porosity of 27%, compared to 32% when exposed to DI water. In comparison, ZVI grains treated with the acidic drainage had higher porosity （44%） and larger average pore size （2.8 mm）. 10% ZVI PRB barrier material had the highest mean porosity （56%） after exposure to any water chemistry whilst 100% ZVI （W/W） columns always had the lowest （34%） with the 50% ZVI （W/W） in between （40%）. These results agree with previously published PRB field data and simultaneously conducted geochemical monitoring and mass balance calculation, indicating that both the geochemical and hydraulic environment of the PRB play an important role in determining barrier lifespan. This study suggests that X-ray CT image analysis is a powerful tool for studying the detailed inter pores between ZVI grains within PRBs.     

零价铁PRB修复2,4-DNT污染地下水模拟研究

研究了零价铁(Fe0)作为PRB墙体介质材料去除地下水环境中2,4-二硝基甲苯(2,4-DNT)可行性.通过室内试验研究地下水环境中Fe0去除水相2,4-DNT效果以及降解动力学参数,并结合一假设地下水受2,4-DNT污染的场地,采用Visual Modflow模拟Fe0墙体材料PRB(Fe0-PRB)修复地下水中2,4-DNT降解效果并评价其可行性.结果表明:在模拟过程中,PRB能有效控制并减少污染羽面积,降低污染浓度;污染4a后,污染地下水的2,4-DNT总质量约1.46×104kg,可推知PRB修复达标耗用Fe0材料为8.76×104kg;渗透系数增大导致地下水速率增大,2,4-DNT与墙体Fe0材料接触时间不充分,污染物污染下游地下水,同时也加速PRB上游污染羽面积减少.因此,结合数值模拟是有效的评价PRB介质材料修复地下水污染效果及确定PRB参数的重要手段之一.     

地下水中阴离子对球磨零价铁除砷影响

研究了不同浓度下几种阴离子（NO₃^-、SO₄^2-、H₂PO₄^-、SiO₃^2-）对球磨零价铁（BZVI）除砷规律的影响,探讨了上述阴离子对BZVI氧化As（Ⅲ）能力的影响,三价砷及五价砷的转化机制,及BZVI腐蚀产物.研究证实,不同浓度的NO₃^-和SO₄^2-对砷去除效率影响不显著,但是随着H₂PO₄^-和SiO₃^2-浓度升高,溶液中As（V）分别由25.1%上升到83.6%和下降到3.8%;通过SEM和拉曼光谱分析发现,H₂PO₄^-促进BZVI的腐蚀,导致As（Ⅲ）氧化能力增强;而铁表面形成二氧化硅聚合物或非晶固相则是SiO₃^2-降低BZVI对砷氧化和吸附能力的主要机制.     

用双层PRB技术处理垃圾填埋场地下水污染的可行性研究

设计了双层结构可渗透反应屏障(PRB),对渗滤液污染地下水原位处理的可行性进行实验研究.其中,第一反应器主要填充了零价铁,对复杂的不可生物降解和难生物降解的卤代烃等有机物进行分解;第二反应器主要填充了释氧剂(ORC),对有机物进行彻底的处理.实验结果表明:经过第一反应器后BOD5 COD值由0 32升高至0 75,铵离子和硝酸根离子的去除率分别达到85%和80%;ORC反应器最大释氧量为7 64mg·L-1.采用双层PRB结构治理渗滤液污染地下水是可行的.     

Arsenic and chromate removal from water by iron chips-Effects of anions

The purpose of this study is to estimate the removal efficiency of As and Cr (VI) by one kind of industrial waste — iron chips, as well as to estimate the effects of typical inorganic anions (sulfate, phosphate, and nitrate), and typical organic anions (citrate, oxalate, and humate) on As or Cr (VI) removal. The results showed that 98% of As (V) and 92% of As (III) could be removed from aqueous phase by the iron chips within 60 min. Compared with As species, Cr (VI) was removed much more rapidly and efficiently with 97% of Cr (VI) being removed within 25 min. The removal efficiency for arsenic was in the order: As (III) (sulfate), As (III) (nitrate) or As (III), As (III) (humate), As (III) (oxalate), As (III) (citrate), As (III) (phosphate), and for chromate was in the order: Cr (VI) (sulfate), Cr (VI) (phosphate) or Cr (VI) (nitrate) or Cr (VI) (oxalate), Cr (VI), Cr (VI) (citrate), Cr (VI) (humate). In all the treatments, pH level increased with time except for As (III), the removal of which was either without anions or in the presence of humate or nitrate.     

Dechlorination of chlorophenols by zero valent iron impregnated silica

Laboratory studies were conducted to find out the efficacy of uniquely prepared zero valent iron impregnated silica in transforming xenobiotic chlorophenols namely 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol. Continuous mode column experiments were performed to investigate the transformation of chlorophenols by varying pH, column height, flow rate and initial chlorophenol concentration. Reusability study of the zero valent iron impregnated silica was studied as well as the morphological changes and the chemical composition of the catalyst medium were also investigated. Dechlorination kinetic studies were conducted and the order of dechlorination of chlorophenols was found to be 2,4,6-trichlorophenol > 2,4-dichlorophenol > 4-chlorophenol. The optimum pH, column height and flow rate were found to be 7, 20 cm and 0.75 L/hr respectively for all chlorophenols in the reaction duration of 4 hr. Intermediates formed during dechlorination study were identified by gas chromatography-mass spectroscopy analysis. This method was applied to real pulp and paper wastewater and was found satisfactory.     

制备斜发沸石和零价铁复合材料处理水中的六价铬污染

为了更好地降低我国地下水中六价铬污染给公众的健康带来的危害,本研究以渗透反应墙为处理地下水六价铬污染的主要方法,沸石和零价铁为反应材料,结合沸石虽价格低廉,但经长时间运行后吸附的六价铬有可能发生解吸,零价铁虽能完全去除六价铬但成本很高的特点,研发出了斜发沸石和零价铁的复合材料,以作为渗透反应墙的填充材料.研发主要分三个步骤:1)遴选出吸附效果较好的斜发沸石;2)确定最优表面活性剂及最优施用浓度;3)确定沸石与零价铁的复合工艺方法.最终方案为斜发沸石、六烷基三甲基溴化铵、还原铁粉、斜发沸石粉和超纯水按比例均匀混合后加热至90℃.由此制得的复合材料,具有良好的反应性能和便于装填的形状,生产成本也比较低廉,可以作为修复六价铬污染的反应墙填充材料.     

泡沫强化多孔介质中纳米零价铁迁移试验

通过批量模拟试验考察了纳米零价铁(NZVI)在水、十二烷基硫酸钠(SDS)溶液与SDS泡沫3种流体中的沉降性能,以及3种流体输送作用下NZVI在多孔介质中的迁移分布特性.结果表明:NZVI在SDS溶液中的稳定性远大于其在水中的稳定性;搅拌速度为3000r/ min时,NZVI在泡沫中的分布较均匀且泡沫对NZVI携带量较大;NZVI对泡沫稳定性影响不大.水、SDS溶液、SDS泡沫分别作为输送流体时,NZVI迁移的最大距离分别为0.8m,7.9m和2.1m,SDS溶液和泡沫均显著促进了其在多孔介质中的运移.当NZVI由SDS溶液和泡沫输送时,其在介质中的分布范围(33.5%和42.5%)大于水(12.8%);由于重力作用,SDS溶液携带NZVI的迁移主要集中在垂向上,水平迁移能力有限;而泡沫受重力影响较小,其携带的NZVI在水平和垂直方向上的分布更为均匀.可见泡沫作为NZVI的输送流体具有明显优势.     

Reductive transformation and detoxification mechanism of 2,4-dinitrochlorobenzene in combined zero valent iron and anaerobic-aerobic process

A combined zero valent iron (ZVI) and anaerobic-aerobic process was adopted for the treatment of 2,4-dinitrochlorobenzene (DNCB)-containing wastewater. The transformation pathway, reduction of acute toxicity and enhancement of biodegradability were investigated. After pretreatment by ZVI, DNCB in wastewater could be completely converted into 2,4-diaminochlorobenzene (DACB). The ratio of BOD₅/COD increased from 0.005 ± 0.001 to 0.168 ± 0.007, while EC_{50, 48 hr} (V/V) increased from 0.65% to 5.20%, indicating the enhancement of biodegradability and reduction of acute toxicity with the pretreatment by ZVI. DACB was further dechlorinated to m-phenylenediamine during the anaerobic process using methanol as electron donor, with EC_{50, 48 hr} increasing from 5.20% to 48.2%. After the subsequent anaerobic-aerobic process, m-phenylenediamine was degraded completely, with effluent COD of 67.5 ± 10.8 mg/L. This effluent of the subsequent anaerobic-aerobic process was not toxic to zebrafish. The combined ZVI and anaerobic-aerobic process offers bright prospects for the treatment of chlorinated nitroaromatic compound-containing wastewater.     

剩余污泥微波-淘洗及零价铁强化发酵性能

为解决微波预处理高含固率污泥存在碳源溶出率低和释放的碳源有效性低的问题,本文选用淘洗的方法,同时将零价铁(ZVI)添加到淘洗污泥的混合液和上清液中进行厌氧发酵以强化碳源的有效性.结果表明,淘洗显著提升了微波预处理高含固率(TS=11％～17％)污泥的碳溶出率,水淘和碱淘较未淘洗时碳源溶出率分别提高了13％～68％、14...     

硅藻泥包埋纳米零价铁处理含铬废水的研究

采用环境友好型矿物材料硅藻泥(Diatom Mud)包埋纳米零价铁(nZVI)得到复合材料(D-nZVI),分别用XRD、SEM和TEM对样品分析表征.同时,通过考察D-nZVI中硅藻泥的用量、投加量、含Cr(VI)废水浓度、p H值、处理时间等对Cr(VI)去除率的影响,进一步研究了反应动力学等.结果表明,在25℃的条件下,D-nZVI中硅藻泥的用量为20%时,D-nZVI对Cr(VI)的去除效率要高于nZVI.p H值较低时D-nZVI的处理效果更好,并且含Cr(VI)废水的浓度越高,去除率越低,投加量增多和反应时间越长,Cr(VI)的去除率越高.当D-nZVI的用量为16 g·L-1,Cr(VI)废水浓度为10 mg·L-1,p H=3时,Cr(VI)的去除率达99%.从SEM和TEM样品分析结果可以看出,硅藻泥表面有很多小而均匀的小孔,较好地包埋或附着在纳米零价铁的表面上,起到了很好的抗氧化作用,为D-nZVI吸附、还原和共沉淀降解Cr(VI)提供了有力依据.     

氧化石墨烯负载零价纳米铁吸附水中环丙沙星的研究

通过溶液还原法制备了氧化石墨烯负载零价纳米铁NZVI16-GO1(F16G1),并将其用于水中环丙沙星的去除.同时,采用X射线衍射仪(XRD)、场发射扫描电镜(FE-SEM)、能谱仪(EDS)和热重分析仪(TG)等手段表征了F16G1的结构、化学组成和微观形貌.结果发现,F16G1对水中环丙沙星具有良好的吸附性能;氧化石墨烯的引入可以有效降低零价纳米铁的自身团聚;F16G1与环丙沙星的吸附作用很大程度上受静电引力的影响.实验同时考察了p H值、反应时间、初始浓度、投加量等因素对F16G1吸附环丙沙星的影响.结果表明,在p H=4~5之间,溶液的p H值对吸附量没有明显影响;F16G1对环丙沙星的最大吸附量是656.66 mg·g-1;Langmuir等温吸附模型可以用来描述吸附平衡过程.零价纳米铁的磁性使复合材料便于回收.     

两种修复模式下CAHs污染地下水的原位对照

为探究氯代脂肪烃（CAHs）污染地下水原位修复的长效性及环境的长期响应,选择华北某废弃化工厂污染区,开展了生物刺激、零价铁（ZVI）-生物刺激耦合中试对照试验,系统对比了2种修复模式下CAHs的降解效率及地下水生物化学参数的动态变化规律.结果表明,修复后长达4~5a内总CAHs含量均降至50 μg/L以下,耦合修复策略提高了CAHs的整体降解效率且未出现浓度反弹,同时可更快速地改善地下环境,为潜在降解菌的生长提供有利条件.两种修复方式对地下水细菌多样性的长期影响基本一致,均有利于向脱硫菌门Desulfobacterota和绿弯菌门Chloroflexi演化.最终生物刺激区总细菌数量高于耦合修复区约1个数量级,但后者地下水中的脱卤球菌属Dehalococcoidia数量（2.1~35）×10³copies/mL反而高于前者（8.3~9.1）×10³copies/mL,这更有利于CAHs的彻底脱氯.     

高岭土负载纳米铁在含水层的运移行为及重金属污染修复效能研究

为克服重金属污染物修复过程中纳米零价铁易氧化、团聚等缺陷,本研究将其负载于高岭土表面合成负载型纳米零价铁复合材料（K-nZVI）,并利用批次试验、沉降试验及模拟柱试验研究了K-nZVI在含水层中的运移行为及其对地下水重金属污染的修复效能.结果表明,K-nZVI对Pb、Cu、Cd均有很好的去除效果,去除率随着初始浓度的增加、反应温度的升高、反应时间的延长而升高,且在弱碱性条件下修复效果最好.此外,K-nZVI在含水层中表现出较好的分散和稳定性能,运移行为可通过一维对流-弥散-沉积模型描述,其运移能力随着初始浓度的增加、砂颗粒粒径的减小、地下水流速的降低和离子浓度的升高而逐渐减弱.     

不同载体携带纳米零价铁在多孔介质中的迁移特性

批次试验和模拟柱试验探讨了NZVI在3种载体(水、十二烷基硫酸钠(SDS)溶液和SDS泡沫)中的稳定性以及在3种载体携带作用下NZVI在多孔介质(0.25~0.5mm, 0.5~0.9mm, 0.9~1.4mm)中的迁移特性.由实验可知,对于NZVI悬浊液,在0.9~1.4mm,0.5~0.9mm和0.25~0.5mm介质中,NZVI从模拟柱中的溢出率分别为20.9%,17.4%和6.5%,NZVI在介质中分布的均匀性关系为0.9~1.4mm>0.5~0.9mm>0.25~0.5mm;对于SDS-NZVI悬浊液,NZVI在0.9~1.4mm 和0.5~0.9mm介质中的迁移性较0.25~0.5mm介质远远增强,NZVI在介质中分布均匀性关系为0.5~0.9mm>0.9~1.4mm>0.25~0.5mm;对于NZVI负载泡沫,NZVI在0.5~0.9mm与0.25~0.5mm介质中的迁移性较NZVI悬浊液和SDS-NZVI悬浊液增强,NZVI在0.5~0.9mm介质中分布均匀性较好,0.25~0.5mm其次,0.9~1.4mm均匀性最差.研究结果表明,SDS溶液和SDS泡沫与水相比较均有效促进了NZVI在3种介质中的运移,然而对于0.9~1.4mm介质,SDS溶液对NZVI迁移的促进作用较SDS泡沫更明显,对于0.25~0.5mm介质,SDS泡沫对NZVI迁移的促进作用较SDS溶液更大.     

A review： Advances in microbial remediation of trichloroethylene （TCE）

Research works in the recent past have revealed three major biodegradation processes leading to the degradation of trichloroethylene. Reductive dechlorination is an anaerobic process in which chlorinated ethenes are used as electron acceptors. On the other hand, cometabolism requires oxygen for enzymatic degradation of chlorinated ethenes, which however yields no benefit for the bacteria involved. The third process is direct oxidation under aerobic conditions whereby chlorinated ethenes are directly used as...     

微生物降解污染地下水中三氯乙烯的微宇宙试验研究

三氯乙烯(TCT)是我国地下水中一类检出率极高的挥发性氯代烃有机物,为丰富国内氯代烃污染地下水生物修复的理论支持,从北京市某氯代烃实际污染场地采集含水层沉积物及地下水,利用微宇宙试验体系,在厌氧条件下分别研究了添加不同浓度的醋酸钠、乳酸钠、乳酸对地下水中TCE去除效果的影响,结合各厌氧体系内中间产物的分析和微生物多样性的变化对反应机理进行阐述。结果表明:厌氧条件下,添加1.0 g/L醋酸钠的反应体系中TCE的去除率最高,可达94.5%,且添加醋酸钠的反应体系可长时间维持中性pH及较低的氧化还原电位。在对厌氧反应降解中间产物的分析中,反应第30天中间产物只检测到了顺式1,2-二氯乙烯,推测本试验厌氧条件下TCE生物降解主要机制为氢解反应;微宇宙体系内,各样品的优势菌门均含有Proteobacteria(变形菌门)、Firmicutes(厚壁菌门),且均为氯代烃的潜在高效降解菌;基因定量分析显示,各反应体系中细菌总量显著增长,且各样品均检测到较高水平的功能基因tceA(水样中拷贝数可达10⁶~10⁷ L^-1),推测TCE的降解可能是在功能基因tceA的作用下而发生氢解反应。