Synthesis of nanoiron by microemulsion with Span/Tween as mixed surfactants for reduction of nitrate in water

Denitrification of nitrate in groundwater using iron nanoparticles has received increasing interest in recent years. In order to fabricate iron nanoparticles with homogeneously spherical shape and narrow size distribution, a simple and “green” method was developed to synthesize iron nanoparticles. The conventional microemulsion methods were modified by applying Span 80 and Tween 60 as mixed surfactants. The maximum content of water in the Water-in-oil (W/O) microemulsion and its appropriate forming conditions were found, and then the microemulsion system consisting of saturated Fe²⁺ solution was used to synthesize α-Fe ultrafine particles by redox reaction. The nanoparticles were characterized by using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that the average diameter of the particle is about 80–90 nm. The chemical activity of the obtained iron nanoparticles was studied by the denitrification experiment of nitrate. The results show that under the experimental conditions, iron removed most of the 80 mg/L nitrate within 30 min. The mass balance of nitrate reduction with nanoscale Fe indicates that endproducts are mainly ammonia. Two possible reaction pathways for nitrate reduction by nanoscale iron particles have been proposed in this work. __________ Translated from Chemical Journal of Chinese Universities, 2006, 27(4): 672–675 [译自: 高等学校化学学报]     

Potential and Limitations of Microbial Reductive Dechlorination for Bioremediation Applications

Current knowledge and recent advances in the area of microbial reductive dechlorination of polychlorinated organic compounds are summarized. Factors which may limit the efficacy of the dechlorination process for the in situ bioremediation of contaminated soil and sediment systems are identified. Results of recent studies on the anaerobic biotransformation of soil-sorbed chlorinated ethenes and sediment-sorbed chlorinated benzenes are provided to illustrate how low contaminant bioavailability may control the rate and extent of dechlorination in subsurface systems, especially those with long-term contamination. Use of nonionic, polysorbate surfactants as the sole electron donors of a mixed, methanogenic culture supported the microbial sequential reductive dechlorination of either free or sediment-bound hexachlorobenzene (HCB) to primarily 1,3-dichlorobenzene, but did not enhance the bioavailability of sediment-bound HCB as compared to microcosms, which used glucose. Because current knowledge on the interactions of dechlorinating populations with other microbial populations in the presence of alternative terminal electron acceptors (e.g., nitrate, Fe³⁺ , Mn⁴⁺) is limited, such interactions and their effect on the dechlorination process in subsurface systems need to be further explored to improve our understanding of the reductive dechlorination process in complex environmental systems and lead to the development of more efficient in situ bioremediation technologies and strategies.     

表面活性剂的生态毒理学及其应用研究进展

绝大多数表面活性剂如LAS、AS和AE易被分解,对环境和生物没构成严重的威胁;但部分表面活性剂的降解产物如NP具有潜在的危害,不容忽视。此外,表面活性剂具有增溶和增流作用,能促进疏水性有机污染物的去除,可应用于修复环境污染。     

工业废水处理中应用磁性载体技术的研究

本文介绍了采用磁性载体与A／O联合工艺处理南京金陵石化研究院中试车间产生的含表面活性剂废水技术。采用磁性载体取代一般填料对MBBR工艺进行改良,磁性载体完成挂膜后,微生物的活性明显提高污水处理厂处理能力大幅提升。对比不同工艺处理相同污水时,改良MBBR工艺能保证污水能够平稳达标排放,同时提高了污水处理效率,降低了污水处理厂运行成本,提高了污水处理能力。     

表面活性剂对土壤中重金属清洗及有效态的影响

采用两种常用的表面活性剂-十二烷基苯磺酸钠(阴离子型)、Tween-80(非离子型),对锦州铁合金厂周边Zn、Cd及Pb重金属污染土壤进行化学修复试验,研究两种表面活性剂对重金属Zn、Cd及Pb的去除率及化学形态影响.结果表明,随着表面活性剂浓度的提高,两种表面活性剂对Pb、Cd及Zn的去除作用增强,Tween-80溶液的浓度越高,对重金属的萃取效果越好,对重金属的去除能力大小顺序为Cd>Zn>Pb,最大去除率分别为83.07%、56.78%及42.57%;十二烷基苯磺酸钠在低浓度时对Cd和Pb的去除效果不明显,而对金属Zn的去除效果较好,在0.09 mol.L-1时达到最大值83.86%;与淋溶前土壤中重金属有效态含量相比较,经不同浓度十二烷基苯磺酸钠淋洗后土壤中Cd有效态含量随LAS浓度的升高而先增加后下降,而Pb的有效态含量随十二烷基苯磺酸钠升高而增加;经不同浓度Tween-80淋洗后土壤中Zn及Cd有效态含量都是随Tween-80浓度的升高而先增加后下降,Pb有效态含量随Tween-80升高而下降.     

不同类型表面活性剂对1，2，4-三氯苯的增溶作用

研究了阴离子表面活性剂十二烷基硫酸钠、阳离子表面活性剂十六烷基三甲基溴化铵和非离子表面活性剂脂肪醇聚氧乙烯醚LAE对1,2,4-三氯苯（TCB）的增溶作用。讨论了表面活性剂类型对增溶作用的影响。比较发现,非离子型表面活性剂的增溶能力高于离子型表面活性剂。其原因主要是疏水有机物在非离子表面活性剂胶束中的增溶方式不同造成的。3种表面活性剂对TCB的增溶数据还表明,增港作用不仅在临界胶束浓度（MC）以上发生,而且在表面活性剂浓度低于CMC时亦有明显的增溶作用。     

Controlling microbiological interfacial behaviors of hydrophobic organic compounds by surfactants in biodegradation process

Bioremediation of hydrophobic organic compounds （HOCs） contanlinated soils involves several physicochemical and microbiological interracial processes among the soil-water-microorganism interfaces. The participation of surfactants facilitates the mass transport of HOCs in both the physicochemical and microbiological interfaces by reducing the interfacial tension. The effects and underlying mechanisms of surfactants on the physi-cochemical desorption of soil-sorbed HOCs have been widely studied. This paper reviewed the progress made in understanding the effects of surfactant on microbiological interlhcial transport of HOCs and the underlying mechanisms, which is vital for a better understanding and control of the mass transfer of HOCs in the biodegradation process. In summary, surfactants affect the microbiological interfacial behaviors of HOCs during three consecutive processes： the soil solution-microorganism sorption, the transmembrane process, and the intracellular metabolism. Surfactant could promote cell sorption of HOCs depending on the compatibility of surfactant hydrophile hydrophilic balance （HLB） with cell surface properties; while the dose ratio between surfactant and biologic mass （membrane lipids） determined the transmembrane processes. Although surfactants cannot easily directly affect the intracellular enzymatic metabolism of HOCs due to the steric hindrace, the presence of surfactants can indirectly enhanced the metabolism by increasing the substrate concentrations.     

生物表面活性剂产生菌的筛选及其对土壤重金属铅的活化作用

结合油平板和血平板方法从重金属8处复合污染的土壤样品中筛选出15株能产生物表面活性剂的细菌菌株,其中J119菌株不仅具有良好的产生物表面活性剂的性能,而且能在含铅、镉浓度分别为100～200 mg·L-1、25～100 mg·L-1的平板中生长.同时对J119菌株所产的生物表面活性剂与3种不同类型化学合成表面活性剂活化土壤中铅的效能进行了比较.结果表明,在400 mg·kg-1铅污染土壤中,J119菌株发酵液与化学合成表面活性剂活化土壤中铅的效果相当;与对照相比,在800 mg·kg-1铅污染土壤中,J119菌株发酵液处理使土壤中有效性铅的浓度增加51.1%,而3种化学合成表面活性剂CTAB、SDS、Tween-80处理土壤中有效态铅浓度仅比对照增加28.7%、26.2%和16.0%.另外,J119菌株产生的生物表面活性剂与供试3种化学合成表面活性剂对土壤中铅的活化作用之间存在显著差异.     

表面活性剂在环境中的生物降解

简述表面活性剂对环境的影响,讨论了表面活性剂生物降解性的测试方法、降解过程动力学及其影响因素,并对各类表面活性剂结构与降解能力之间的关系作了评价。     

溴甲酚绿－溴化十六烷基吡啶光度法测定水中阴离子表面活性剂

建立溴甲酚绿（ＢＣＧ）－溴化十六烷基吡啶（ＣＰＢ）光度法测定水中阴离子表面活性剂的方法。实验表明,适合的ＰＨ范围为５．５－９．０,λｍａｘ＝６１４ｎｍ,在８６μｇＣＰＢ存在下,十二烷基苯碘酸钠（ＳＢＳ）和十二烷基硫酸钠（ＳＤＳ）分别在０－８０μｇ／１０ｍｌ和０－７５μｇ／１０ｍｌ范围内符合比耳定律,其表观摩尔吸光系数分别为２．９×１０＾４和３．１×１０＾４Ｌ．ｍｏｌ＾－１．ｃｍ＾－１。用此法测定了