共查询到19条相似文献，搜索用时 682 毫秒
1.
天然金红石光催化降解藏红T实验研究 总被引：5，自引：0，他引：5
以低压汞灯为光源研究了天然金红石悬浆体系中藏红T的脱色条件及其光催化反应动力学，讨论了溶液初始pH值、催化剂投入量、光强、气流量、催化剂粒径、反应气氛等实验条件对藏红T脱色速率的影响，阐述了实验过程中无机离子的生成情况。结果表明，该反应基本上符合一级反应动力学；在酸性条件下尤其是当溶液初始pH值为2．5时，藏红T的脱色速率要比在碱性和中性条件下快得多；增加光强度能较大地提高反应的降解速率；催化剂最佳投入量为1．3g／L；在氧化气氛下该反应比在非氧化气氛快得多；通入气体的流量在40L／h最合适；反应溶液中有氯离子溶出说明有机物中的含氯部分被降解。本研究为光催化作用降解有机污染物提供了新的途径。 相似文献
2.
在分析化学分寓富集手段中,出现了一种独特的泡塑吸附技术,它已成功地用于各种物料的分析中。1970年,Bowen等首次用泡塑萃取了卤化物中的汞、金、铁、锑、铊、铼和钼离子,以及硝酸溶液中的铀离子。Ross用泡塑作气体色层柱中的捕集剂。有人指出泡塑可捕集水中污染物如 相似文献
3.
在分析化学分离富集手段中,出现了一种独特的泡塑吸附技术,它已成功地用于各种物料的分析中。1970年,Bowen等首次用泡塑萃取了卤化物中的汞、金、铁、锑、铊、铼和钼离子,以及硝酸溶液中的铀离子。Ross用泡塑作气体色层柱中的捕集剂。有人指出泡塑可捕集水中污染物如农药、多氯联苯等。Braun等利用各种萃取剂处理泡塑,研究了镍、铋、钯、铈、钒、铁与钴的分 相似文献
4.
黄铁矿在不同pH值硫酸钠溶液中的电化学腐蚀研究 总被引：1，自引：0，他引：1
溶液的pH值对黄铁矿的电化学腐蚀行为有着重要的影响。本文运用开路电位测量、Tafel扫描、循环伏安扫描以及电化学阻抗谱等电化学测试技术,研究黄铁矿在pH值分别为2.0、6.5、11.0的0.1mol/L Na2SO4溶液中的电化学腐蚀行为。结果表明:溶液中pH值升高时,黄铁矿的开路电位降低,腐蚀电流升高,阻抗谱中圆弧半径减小,这些变化说明了黄铁矿变得更加容易被腐蚀。分析其原因为当溶液中pH值升高时,黄铁矿氧化过程产生的中间产物S2O2-3变得比较稳定,因此,由其分解产生的单质硫的量减少,继而因单质硫在黄铁矿表面吸附造成的钝化作用也随之减弱,黄铁矿的腐蚀速率增加。 相似文献
5.
利用维他命B12进行的全氯乙烯和三氯乙烯还原脱氯与微生物还原脱氯是类似的，并且目前作为一种辅助技术正在应用中。碳同位素分析是在对污染物研究和监测中的一种强大且有效的手段，被用来揭示在实验室微小实验盒中通过全氯乙烯和三氯乙烯的还原脱氯中同位素效果的特性。在实验室试验中，10mg／l的维他命B12降解了大于90％初始的20mg／l的含三氯乙烯的全氯乙烯。64％至72％的全氯乙烯被降解，这是全氯乙烯降解的主要产物。在三氯乙烯试验中，147mg／1的维他命B12降解了大于90％的初始20mg／l的含cDCE的三氯乙烯。30％至35％的三氯乙烯被降解，这是降解的主要产物。在全氯乙烯和三氯乙烯两种反应物中，可以观测到强烈的同位素的裂解。这种降解可以通过全氯乙烯的-16．5‰至-15．8‰浓缩参数和三氯乙烯的一17．2‰至-16．6‰浓缩参数的瑞利模型描述。在所有试验中，裂解都是相似的，平均浓缩参数为-16．5‰土0．6‰。如此显著浓缩参数的产生可以说明同位素分析可以用来监测通过全氯乙烯和三氯乙烯的脱氯和地下水污染物降解。迹象表明，同位素裂解是在氯乙烯与维他命B12发生作用的情况下产生的，正如通过零价铁的还原脱氯已经暗示了的一样。这个反应中e值与氯乙烯厌氧生物降解中e值的差异暗示着在这两种过程中可能存在着速率确定步骤的不同。 相似文献
6.
四氯乙烯在不同地下水环境的生物共代谢降解 总被引：1，自引：0，他引：1
四氯乙烯是地下水中常见的污染物,采用生物方法进行处理的优点是可以实现无害化、无二次污染、处理成本低。四氯乙烯只能在厌氧条件下发生还原脱氯,目前对产甲烷环境下四氯乙烯的降解研究较多,而对较弱还原环境,如反硝化、铁锰还原和硫酸盐还原环境下四氯乙烯的脱氯行为研究甚少。本文采用批实验,研究了在不同地下水环境,包括反硝化、铁还原、硫酸盐还原、混合电子受体和天然地下水环境下四氯乙烯的脱氯性能。结果表明,铁还原环境的四氯乙烯脱氯效果最好,天然地下水环境次之,四氯乙烯的去除率分别达到91.34%和84.71%,四氯乙烯很快转化为三氯乙烯,并可以进一步转化为二氯乙烯,四氯乙烯的降解符合准一级反应动力学方程。在反硝化、硫酸盐还原、混合电子受体环境,四氯乙烯的去除以挥发为主,降解只占很小的比例,且最终的降解产物只有三氯乙烯。地下水中三价铁的存在,对于四氯乙烯脱氯起促进作用;而当地下水中硝酸盐和硫酸盐的浓度较高时,四氯乙烯脱氯受到抑制。 相似文献
7.
纳米零价铁原位注射修复地下水污染是近年发展的新技术,以往研究多侧重于单一目标污染物的去除效果及作用机理,但是地下水多种污染物共存问题不容忽视。本文针对典型污染物三氯乙烯TCE和六价铬Cr(Ⅵ),运用合成的活性高、稳定性强的膨润土负载纳米铁镍(B-Fe/Ni)开展修复实验,研究B-Fe/Ni对TCE和Cr(Ⅵ)共存复合污染的修复效果及其作用机制。通过一步法合成B-Fe/Ni,对TCE和不同浓度Cr(Ⅵ)混合污染的去除进行试验研究,对反应前后的样品B-Fe/Ni进行表征,并跟踪反应过程中TCE和Cr(Ⅵ)的浓度变化。结果表明:B-Fe/Ni同步去除水中TCE和Cr(Ⅵ)快速高效,50 mg/L Cr(Ⅵ)在2 h内能被B-Fe/Ni (1 g/L)完全去除而不受共存TCE(0. 1 mmol/L)的影响,然而TCE降解速率会随共存Cr(Ⅵ)的浓度(0、10、30、50 mg/L)增大而降低。经透射电镜-电子能谱及X射线光电子能谱表征验证,这是由于B-Fe/Ni与Cr(Ⅵ)快速反应,生成部分Fe-Cr共沉淀会覆盖B-Fe/Ni表面的活性位点,抑制了TCE的降解,但通过分析TCE降解产物可知,B-Fe/Ni同样能对TCE完全脱氯。因此,B-Fe/Ni适用于地下水复合污染修复,实际应用时需考虑多种污染物共存的相互影响,选择适宜试剂用量和注射方式,这对纳米零价铁修复技术的发展具有重要理论意义和应用参考价值。 相似文献
8.
《云南地质》2017,(3)
采用强碱性阴离子交换树脂处理水中的邻苯二甲酸酯类有机污染物,根据其理化性质建立高效液相色谱法(HPLC)对邻苯二甲酸酯类物质的含量进行分析检测。根据邻苯二甲酸酯类理化性质考察不同类型的树脂、树脂投加量、溶液初始浓度、溶液反应温度等因素对水中邻苯二甲酸酯类(PAEs)的去除效果的影响。实验表明,在近中性条件下,树脂投加量为0.4g、邻苯二甲酸二甲酯(DMP)初始浓度为21.524mg/L、反应温度30℃、反应5h时,DMP去除率达99%以上。应用强碱性阴离子交换树脂,使邻苯二甲酸酯类有机污染物降解速率得到大幅度提高,并符合经济和环保要求,能够较迅速降解大部分邻苯二甲酸酯,使水中残留邻苯二甲酸酯的含量,达到国标规定以下值。 相似文献
9.
膨润土负载纳米铁去除地下水中六价铬研究 总被引：4，自引：1，他引：3
随着人民生活水平的提高和城市化进程的加快,有机污染物及重金属高强度场地污染对人类健康、生态环境及社会安全构成了严重威胁。地下水中的重金属Cr(Ⅵ)污染逐渐受到重视,纳米零价铁可以有效地将六价铬还原成三价铬,使其沉淀固定下来,从而将污染源区的污染物消减固定,防止其向周围扩散。然而由于纳米铁颗粒微小,易被氧化,极易团聚,自身活性受到限制,因此,纳米铁的分散性、稳定性、良好活性研究至关重要。采用低成本环境友好型粘土矿膨润土作为负载材料制备膨润土负载纳米铁（B-NZVI）,批实验和柱实验研究B NZVI去除模拟地下水中Cr(Ⅵ)。结果表明：(1)自制的膨润土负载纳米铁个体呈球形,呈分散状负载于膨润土;(2)相同铁含量的B-NZVI处理Cr(Ⅵ)的效率远大于纳米铁,还原反应符合伪一级反应动力学模型,表观速率常数K随着B NZVI初始浓度的减小而减小;(3)B NZVI在石英砂柱中基本无迁移,适用于点源污染,Cr(Ⅵ)穿透曲线为B-NZVI的实际应用提供了理论和实验基础。 相似文献
10.
自然界中大多数硫化物矿物都有良好的导电性,具有半导体的性质.当具有不同电极电位的矿物在溶液中接触在一起,就会形成原电池发生电化学腐蚀,其中电极电位低的矿物作为原电池的阳极发生氧化反应,其溶解会加剧,而电极电位高的矿物作为原电池的阴极发生还原反应,其溶解会受到抑制. 相似文献
11.
三氯乙烯（TCE）是一种地下水中常见的有机污染物，传统的地下水循环井修复技术虽然有效但耗时长，且需配套地面处理。文章研发了一种电化学循环井耦合修复体系，以期通过顺序化学氧化 -还原作用高效快速降解地下水中TCE。以地下水循环井为基础，通过抽水井中的地下水电解，原位提供O2和H2，投加Fe（Ⅱ） -EDTA络合物活化O2产生羟基自由基氧化降解TCE，进而利用钯催化剂催化剩余的H2还原降解TCE。在二维砂槽模拟含水层中评价了该体系的运行效果，含水层中初始TCE浓度为7.50 mg/L，经过13天的连续通电处理后，TCE浓度降低到1.65 mg/L，降解率达到78%。处理后Cl-浓度相应增加118.20 μmol/L，接近于TCE降解量（44.50 μmol/L）的3倍，证明TCE近乎完全脱氯。运行过程中，TCE平均降解速率由0~5 d的0.90 mg/(L·d) 降低到9~13 d的0.10 mg/(L·d)，氧化降解主要发生在前期阶段，钯催化还原效率较为稳定，后期两种过程降解效率都逐渐下降，主要原因是溶解态Fe（Ⅱ）浓度减少以及钯催化剂活性降低。该耦合修复体系是基于地下水循环井技术的改进，其氧化 -还原作用机理有望实现地下水中多种不同有机污染物的降解。 相似文献
12.
Denitrification of nitrate-contaminated groundwater using biodegradable snack ware as carbon source under low-temperature condition 总被引：3，自引：1，他引：2
X. M. Wang J. L. Wang 《International Journal of Environmental Science and Technology》2012,9(1):113-118
A considerable increase in nitrate concentration in groundwater has been observed in many countries. This research focuses on nitrate removal using biodegradable snack ware (BSW) as both carbon source and biofilm support for denitrifiers. The denitrification efficiency of a laboratory-scale denitrification reactor packed with BSW was examined in a low-temperature condition. The nitrate removal efficiency supported by BSW decreased to approximately 40% at 12°C from nearly 100% at 25°C with 50?mg/L of nitrate-nitrogen in the influent and 2?h of hydraulic retention time (HRT). The complete nitrate removal was obtained when nitrate-nitrogen concentration was no more than 15?mg/L at 2?h of HRT and at 12°C. If the initial concentration of nitrate-nitrogen was 50?mg/L, 5?h of HRT was needed for the complete nitrate removal. Nitrite concentration in the treated water decreased evidently as HRT was increased from 2 to 5?h, or as nitrate-nitrogen concentration in the influent decreased to 15?mg/L from 50?mg/L. It was observed that varying HRT and nitrate concentration in the influent had no noticeable effect on dissolved organic carbon content in the effluent under the experimental conditions. This study indicated that the complete nitrate removal could be achieved readily even at 12°C using BSW as carbon source by changing HRT or the initial concentration of nitrate in the influent, which has some useful implications in environmental engineering practice. 相似文献
13.
Trichloroethylene (TCE) is one of the most common and persistent groundwater contaminants encountered at hazardous waste sites around the world. A growing body of evidence indicates that iron sulfides play an important role in degrading TCE in natural environments and in engineered systems designed for groundwater cleanup. In this study, we investigate transformation processes of iron sulfides and consequent impacts on TCE degradation using batch experimental techniques, transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS). Our results show that mackinawite is highly reactive toward TCE and no detectable mineralogical changes were detected during the course of reaction. However, freeze-dried FeS transformed to a mixture of mackinawite and greigite during the freeze drying process, with further mineralogical changes during reaction with TCE to lepidocrocite, goethite and pyrite. Newly formed lepidocrocite is a transient phase, with conversion to goethite over time. TCE transformation kinetics show that freeze-dried FeS is 20-50 times less reactive in degrading TCE than non-freeze-dried FeS, and the TCE degradation rate increases with pH (from 5.4 to 8.3), possibly due to an increase of surface deprotonation or electron transfer at higher pH. Results suggest that freeze drying could cause FeS particle aggregation, decreased surface area and availability of reactive sites; it also could change FeS mineralogy and accelerate mineral transformation. These aspects could contribute to the lower reactivity of freeze-dried FeS toward TCE degradation. Modeling results show that FeS transformation in natural environments depends on specific biogeochemical conditions, and natural FeS transformation may affect mineral reactivity in a similar way as compared to the freeze drying process. Rapid transformation of FeS to FeS2 could significantly slow down TCE degradation in both natural and engineered systems. 相似文献
14.
传统原位化学氧化地下水修复技术存在氧化剂迁移距离短和利用率低等问题。本研究在双井循环模式促进传质的基础上,通过注水井中的地下水电解原位提供O2和H2,配合乙二胺四乙酸(ethylenediamine tetraacetic acid,EDTA)络合溶解出含水层Fe(Ⅱ),活化O2产生羟基自由基(•OH),实现地下水三氯乙烯(TCE)的氧化降解。在填充了砂土和黏土互层的二维砂槽中,设置电流为0.2 A、流速为72 cm/d、初始TCE浓度为3 mg/L,经过9 d的连续通电处理后,TCE浓度降低到1 mg/L,降解率达到67%。通电前投加0.5 mmol/L EDTA,经过1 d水流循环后含水层中溶解态Fe(Ⅱ)浓度从02 mg/L增加到414 mg/L,黏土区域较高。通电过程中,循环井促进O2、Fe(Ⅱ)-EDTA和TCE的有效接触与反应,使TCE氧化降解。通电初期,黏土区域Fe(Ⅱ)氧化速率、TCE降解速率较周围慢,后期差异逐渐减小。未通电时加入醋酸钠可促进Fe(Ⅲ)还原,使含水层中铁循环利用。该修复过程通过循环井提升了氧化剂迁移距离,使用源于含水层的Fe(Ⅱ)-EDTA和稳定性较好的O2提高了氧化剂利用率,有望应用于有机污染地下水修复。 相似文献
15.
地下水中三氯乙烯-苯酚的好氧共代谢的实验研究 总被引：4，自引：1，他引：3
以苯酚作为三氯乙烯（TCE）降解的共代谢基质,用瓦勃氏微量呼吸测压仪（简称瓦呼仪）作为测试手段,分析了经苯酚驯化后的混合微生物对苯酚、TCE的降解特性;并讨论了以苯酚作为共代谢基质时TCE降解的可能性。实验结果表明：未驯化的活性污泥不能降解TCE; 经苯酚驯化后的活性污泥,当TCE的质量浓度为50 μg/L时其降解效果较好,TCE的氧化率达3369%;TCE的质量浓度为100 μg/L时其降解效果较差,其氧化率仅为3.2%;苯酚和TCE共代谢降解时,苯酚的存在促进了TCE的降解,当苯酚质量浓度为40 mg/L、TCE质量浓度为50 μg/L时共代谢降解效果最好,TCE的氧化率为79.11%。 相似文献
16.
Degradation of chlorinated ethylenes by Fe0: inhibition processes and mineral precipitation 总被引：2，自引：0，他引：2
17.
Implemented on behalf of the Federal Ministry for Research and Technology (BMFT), a model is developed to trace the nutrient flow of nitrate in the soil and the groundwater on a supraregional scale. Research work is intended to indicate regionally differentiated hazardous potentials and thereby provide a basis for recommending comprehensive measures to protect groundwater in Germany. The adaption of the model to the hydrogeological and agricultural conditions of other states is possible in principle. This article focuses on the hydrogeological model parts. A high nitrate pollution of groundwater can be expected in all regions with intensive agricultural use of the topsoil. In particular, groundwater in solid rock areas is susceptible to nitrate pollution. There a rapid groundwater turnover and thus a short residence time for the groundwater in the aquifer is typical. Oxidizing aquifer conditions usually prevail in solid rock aquifers, preventing nitrate degradation. In many loose rock areas, in contrast, the groundwater has a low flow velocity and a long residence time in the aquifer. Because of a lack of free oxygen, a complete degradation of nitrate can occur, as long as iron sulfide compounds and/or organic carbon are available in the aquifer. A more detailed presentation of the whole research work is given in Wendland et al. (1993). 相似文献
18.
《Geochimica et cosmochimica acta》1999,63(19-20):2919-2928
Construction of the entrance tunnel to the Äspö Hard Rock Laboratory, a prototype repository in Sweden for research into the geological disposal of spent nuclear fuel, has resulted in increased transport of organic carbon from the surface into the groundwater. This increased input of organic matter has induced accelerated oxidation of organic carbon associated with reduction of iron(III) minerals as the terminal electron acceptor in microbial respiration. Hydrochemical modeling of major solute ions at the site indicates an apparent first-order decay constant for organic carbon of 3.7 ± 2.6/yr. This rapid turnover is not accompanied by an equivalent mobilization of ferrous iron. Thermodynamic calculation of iron mineral solubility suggests that ferrous clay minerals may form in hydraulically transmissive fractures. The conditional potentials for the oxidation–reduction of such phases coincide with measured redox potentials at the site. The calculated potential is sufficiently low so that such phases would provide reducing capacity against future intrusion of O2 into the groundwater, thus buffering a repository against oxic corrosion of the engineered barriers. 相似文献
19.
This study was directed toward a preliminary assessment of nitrate degradation in northeast Iowa soils. Soil experimental plots were created with variable combinations of fertilizers, ethanol, irrigation, and plant growth. The maximum average concentration of nitrate was much higher in the chemically fertilized plots (500 mg/km) than those fertilized organically (120 mg/kg). This was attributed to the excessive ammonia volatilization from the applied cow manure. Soil nitrate dropped from 155 to 50 mg/kg in a matter of 3 weeks in the deep samples of the intermittently irrigated plots. This is because higher soil moisture lowered the oxygen level, which favored denitrification. Although ethanol seemed to have restricted the release of nitrate in the manure-treated plots, the data are not conclusive. The highest degradation of soil-nitrate (lowest recovered 38 mg/kg) was observed in the plots that simultaneously grew corn, received cow manure, and were not irrigated. Soils in these plots were depleted of nitrogen by ammonia volatilization from manure, and through the uptake by corn plants. Nitrification of organic nitrogen to nitrate was restricted in plots that were left without irrigation. Rain events helped nitrification on the surface, but promoted denitrification at depth. 相似文献