氧化石墨烯/聚偏氟乙烯复合膜的制备及抗污染性能

采用改进的Hummers法制备出具有"二维结构"的氧化石墨烯(graphene oxide,GO),以聚偏氟乙烯(PVDF)为高分子聚合物,聚乙烯吡咯烷酮(PVP)为制孔剂,采用浸没沉淀相转化法制备得到GO/PVP/PVDF复合超滤膜。测定了复合超滤膜的纯水通量、接触角、污染物截留、膜片SEM和AFM图像、膜面Zeta电位以及复合膜与牛血清蛋白(BSA)之间的微观作用力等参数。结果表明,随着GO含量的增加,膜表面亲水性官能团的含量显著增加,复合膜的接触角从74.61°(M0)减小到66.39°(M2),纯水通量增加了33%;SEM和AFM的结果表明,复合膜的膜孔有所拓宽,表面粗糙度由23.79(M0)降低为20.2(M3),表面更加平滑。而GO的加入使得复合膜与BSA之间的微观作用力也从2.47 m N·m-1降至0.13 m N·m-1,说明GO/PVP/PVDF复合超滤膜较传统PVDF超滤膜具有较优越的抗污染性能。     

远程氨等离子体表面改性聚偏氟乙烯超滤膜的效果分析

采用远程氨等离子体对聚偏氟乙烯(PVDF)超滤膜进行了表面改性实验,通过水接触角表征了改性前后PVDF超滤膜表面的亲水性能,利用扫描电镜(SEM)和X-射线光电子能谱(XPS)表征了改性前后PVDF超滤膜表面的形貌、化学成分变化,通过牛血清白蛋白(BSA)过滤实验评价了改性前后PVDF超滤膜的过滤性能及抗污染性能。结果表明,远程氨等离子体改性的最佳条件为射频功率为40 W,处理时间为45 s,气体流量为20 cm~3·min~(-1);远程氨等离子体通过将含氧、含氮官能团引入PVDF超滤膜表面,使其表面亲水性官能团增多,表面的亲水性能得到提高,水接触角从95.63°降至52.79°,同时降低了对材料表面的刻蚀作用;通过BSA溶液过滤实验,改性后PVDF超滤膜具有良好的过滤性能和抗污染性能,其水通量、 BSA通量分别从87.42、48.00 L·(m~2·h)~(-1)增至129.36、79.98 L·(m~2·h)~(-1),截留率从81.43%增至87.70%,总污染率从70.25%降至45.96%。综合上述结果,经过远程氨等离子体改性后,PVDF超滤膜的亲水性能、过滤性能及抗污染性能均得到改善。     

溶液对蛋白质污染膜的清洗效果分析

采用牛血清蛋白(BSA)代表有机物,自行开发了聚偏氟乙烯(PVDF)膜片,结合耗散型石英晶体微天平(QCM-D),考察不同NaCl浓度条件下BSA在PVDF膜面的微观解吸行为及吸附层结构特征;并使用原子力显微镜测定相应离子条件下与膜污染行为相关的微观作用力大小,综合膜性能恢复实验,解析NaCl溶液对有机物污染膜的清洗机理.结果表明:随着NaCl离子浓度的从1增加到300 mmol·L~(-1),PVDF与羧基官能团之间的相互作用力逐渐减小,BSA污染层松散度逐渐增大;同时引入大量的水合Na~+离子进入BSA污染层内部,破坏BSA污染层内部的静电吸引力和氢键,进而破坏吸附层结构,伴随着BSA污染膜的通量恢复率随着NaCl离子浓度的增加而大幅度提高。     

用微观作用力解析无机离子对腐殖酸的膜污染行为影响

基于Na+、Ca2+离子在天然水体中的普遍存在及对超滤膜有机污染行为的影响,本研究主要考察了不同离子条件下腐殖酸(HA)对PVDF超滤膜污染行为的影响机理。使用原子力显微镜结合自制的膜材料及污染物探针定量测定了不同离子条件下PVDF-HA及HA-HA之间的相互作用力,同时进行了相应的膜污染实验及定量研究腐殖酸的去除效果。结果表明,PVDF-HA及HA-HA之间的相互作用力大小与膜污染速率及污染幅度呈正相关关系。一价Na+离子通过电荷屏蔽可降低HA表面的带电量,对HA膜污染行为及PVDF-HA及HA-HA之间作用力的影响并不明显。二价Ca2+离子通过电荷中和作用大幅度降低了HA表面的有效带电量,使得PVDF-HA及HA-HA之间的粘附力增大,加剧了膜污染速率。而过多的Ca2+离子会加剧HA之间的聚合,降低了HA进入膜孔内的机率,虽然会短暂的增加腐殖酸的去除效率但无法从根本减轻膜污染。     

亲疏水性溶解性有机物对聚偏氟乙烯超滤膜污染行为

选用模拟亲疏水性有机物及实际二级处理水中的亲疏水性有机物,分别进行了聚偏氟乙烯(PVDF)超滤膜污染实验.并测定了不同污染物与膜及污染物间的作用力,分析亲/疏水性有机物对PVDF超滤膜的污染行为.结果表明,膜-污染物及污染物间相互作用力是控制膜污染行为的主导因素.亲水性有机物与PVDF超滤膜之间的相互亲和力较强,致使运行初期膜通量的大幅度下降,是PVDF膜的优势污染物.但是,针对实际污染物,运行后期,疏水性有机物之间较强的相互作用力使得其取代了亲水性有机物,成为膜的优势污染物.此外,模拟亲疏水性有机物的膜污染变化规律与实际亲疏水性有机物相似,表明使用模拟污染物可一定程度上预测实际废水中相应性能污染物的膜污染行为.     

表面改性GOT/PVDF超滤膜的制备及对水中微污染物的去除

以氧化石墨烯-二氧化钛(GOT)纳米复合物作为亲水化改性剂,通过动态过滤法对聚偏氟乙烯(PVDF)超滤膜进行改性,得到GOT/PVDF改性膜。分别选用腐殖酸(HA)、磺胺嘧啶(SDZ)作为水中微污染物的代表物质,研究了改性膜在不同光照条件下对HA及SDZ的去除行为,同时考察了膜表面GOT的稳定性。结果表明:GOT/PVDF改性膜能提高对水中天然有机物的去除并控制膜污染;在光催化条件下,GOT/PVDF膜能够去除98.3%的SDZ,远高于黑暗条件下31.8%的去除率。     

铋改性沸石粉强化超滤膜性能的研究

为进一步提高超滤工艺对废水深度处理效果、减缓超滤膜污染,研究提出铋改性沸石粉强化超滤(Bi-Z-UF),并对铋改性沸石粉投加量、粒径和反冲洗频率进行优化以获得高效的强化效果。结果表明:(1)相比直接超滤和天然沸石粉强化超滤,Bi-Z-UF更能有效减缓膜通量下降速率,经过3个过滤周期,膜反冲洗后几乎能恢复到初始膜通量。(2)Bi-Z-UF对污水处理厂二级出水中COD、254nm处吸光度(UV_(254))和TN的去除率最高分别可达26%、23%和16%。(3)铋改性增加了沸石的吸附活性中心,在超滤膜表面形成了疏松有孔的"保护层",能减少污染物与超滤膜直接接触,有利于减缓膜通量下降速率,并促进对污染物的吸附、截留与去除,强化了超滤膜性能。     

PVDF/PMMA与PVDF/TPU共混膜抗污染性能研究及应用

观察新型五孔PVDF共混改性纤维膜SEM形貌特征,采用逐级通量法测定PVDF/PMMA和PVDF/TPU共混改性膜的临界通量,研究在次临界和超临界通量下A(PVDF/PMMA)与B(PVDF/TPU)2种管式膜组件的过滤和抗污染性能,并在次临界通量下处理地表水。结果表明,PVDF共混改性膜具有优良的微观结构,且膜B性能较好;膜A、B的临界通量分别为12 L/(m2.h)和10 L/(m2.h);膜组件B比膜组件A抗污染性能好。次临界通量下膜组件的运行比超临界通量下的稳定。与采用单独超滤处理某市地表水相比,2种膜组件采用混凝+超滤工艺的运行处理效果更好,且膜组件B比膜组件A处理效果佳。     

CNT-PVDF复合中空纤维膜的制备及其电辅助抗膜污染性能

电辅助膜过滤是减缓膜污染的有效方法,但是受限于缺乏稳定性好、机械强度高、制备工艺简单的导电膜。通过在PVDF膜表面真空抽滤CNT制备得到了导电的碳纳米管-聚偏氟乙烯(CNT-PVDF)复合中空纤维膜,然后利用酸化CNT表面羧基与聚乙烯醇的羟基发生交联反应来固定CNT,以提高导电功能层的稳定性。抗污染实验结果表明:单纯膜过滤在5个运行周期内的膜通量衰减72%,反冲洗再生后膜通量为初始通量的58%;而在电辅助下(2 V电压,膜作为阴极),静电排斥作用可以有效降低膜通量衰减速度,减缓膜污染程度,5个运行周期内的膜通量衰减均小于10%,反冲洗再生时能完全恢复膜初始通量。以上研究结果可为推进电辅助缓解膜污染技术的实际应用提供参考。     

氧化石墨烯改性PVDF/PET复合膜的制备及其抗污染性能

采用PET编织管作为复合膜的结构层,将PVP和氧化石墨烯(GO)分别作为制孔剂和改性剂与PVDF基材混合,通过涂覆-浸没凝胶相转化法制备得到具有亲水性的高强度PVDF/PET编织管复合膜。观察复合膜的断面结构和表面形貌,测定其纯水通量、表面基团以及接触角等性能参数,并将不同浓度GO改性复合膜应用于序批式膜生物反应器(SMBR)中。利用原子力显微镜(AFM)及自制的污染物胶体探针测定了溶解性微生物产物(SMP)与膜面之间的微观作用力,考察改性复合膜的抗污染特性。在40 d的反应器运行实验中,GO改性复合膜的清洗周期较改性前延长了20%~40%,该结果说明改性复合膜能够有效抑制膜面对污染物的吸附,且GO质量分数为0.5%时清洗周期最长。AFM测试结果显示,复合膜中GO质量分数为0.5%时,SMP与膜面之间的黏附力最小,抗污染能力最强。     

Use of diffuse reflectance spectrometry in spot test reactions for quantitative determination of cations in water

Diffuse reflectance spectroscopy can be successfully used for the quantitative determination of small amounts of pollutants like metals. The remission function was found to be linearly proportional to the concentration, when we applied the Kubelka–Munk equation. The color reactions of Cu(II), Co(II), and Ni(II) with dithiooxamide, were realised on filter paper. Reaction between Fe(III) and ammonium thiocyanate was realized on filter paper and gelatine matrix. All measurements were accomplished with a laboratory-constructed reflectometer. We have obtained a calibration curve by plotting the optical density of reflectance A_R vs log of the mol l⁻¹ concentration. Limits of detection at the 10⁻⁴ M level were estimated for all the compounds. Linear dynamic range extend over one order of magnitude and shows the potential of device for the quantitative analysis of environmental pollutants.     

Distribution and sources of polyfluoroalkyl substances (PFAS) in the River Rhine watershed

The concentration profile of 40 polyfluoroalkyl substances (PFAS) in surface water along the River Rhine watershed from the Lake Constance to the North Sea was investigated. The aim of the study was to investigate the influence of point as well as diffuse sources, to estimate fluxes of PFAS into the North Sea and to identify replacement compounds of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). In addition, an interlaboratory comparison of the method performance was conducted. The PFAS pattern was dominated by perfluorobutane sulfonate (PFBS) and perfluorobutanoic acid (PFBA) with concentrations up to 181 ng/L and 335 ng/L, respectively, which originated from industrial point sources. Fluxes of ΣPFAS were estimated to be ∼6 tonnes/year which is much higher than previous estimations. Both, the River Rhine and the River Scheldt, seem to act as important sources of PFAS into the North Sea.     

Polychlorinated dibenzo-p-dioxins and related compounds: the blood levels of young Japanese women.

We investigated PCDDs and related compounds in the blood of young Japanese women, approximately 20 years of age, who had not yet had children, and discussed how the TEQ level of PCDDs and related compounds in their blood may affect the next generation. Means of total TEQ levels were 0.063 pg/g for whole blood basis and 21 pg/g for lipid basis. TEQ of PCDDs, PCDFs and coplanar PCBs accounted for about 43, 34 and 23% of the total TEQ in the whole blood basis, respectively. In the lipid basis, their values were about 44, 34 and 22%, respectively. Previously, we investigated PCDDs and related compounds levels in mother's breast milk, lymphocyte subpopulation and thyroid function of their children, and found negative correlations between the TEQ level of PCDDs and related compounds and CD4+/CD8+, and/or the TEQ level of PCDDs and related compounds and the T₄ level in 36 mothers and children. Of these cases, the average age was approximately 28 years. PCDDs and related compounds may be related to immunopathy, such as atopic dermatitis. The effects of PCDDs and related compounds on babies of young Japanese women are important and must be further evaluated.     

Effect of vegetation in pilot-scale horizontal subsurface flow constructed wetlands treating sulphate rich groundwater contaminated with a low and high chlorinated hydrocarbon

In order to characterize the effect of vegetation on performance of constructed wetlands (CWs) treating low and high chlorinated hydrocarbon, two pilot-scale horizontal subsurface flow (HSSF) CWs (planted with Phragmites australis and unplanted) treating sulphate rich groundwater contaminated with MCB (monochlorobenzene, as a low chlorinated hydrocarbon), (about 10 mg L⁻¹), and PCE (perchloroethylene, as a high chlorinated hydrocarbon), (about 2 mg L⁻¹), were examined. With mean MCB inflow load of 299 mg m⁻² d⁻¹, the removal rate was 58 and 208 mg m⁻² d⁻¹ in the unplanted and planted wetland, respectively, after 4 m from the inlet. PCE was almost completely removed in both wetlands with mean inflow load of 49 mg m⁻² d⁻¹. However, toxic metabolites cis-1,2-DCE (dichloroethene) and VC (vinyl chloride) accumulated in the unplanted wetland; up to 70% and 25% of PCE was dechlorinated to cis-1,2-DCE and VC after 4 m from the inlet, respectively. Because of high sulphate concentration (around 850 mg L⁻¹) in the groundwater, the plant derived organic carbon caused sulphide formation (up to 15 mg L⁻¹) in the planted wetland, which impaired the MCB removal but not statistically significant. The results showed significant enhancement of vegetation on the removal of the low chlorinated hydrocarbon MCB, which is probably due to the fact that aerobic MCB degraders are benefited from the oxygen released by plant roots. Vegetation also stimulated completely dechlorination of PCE due to plant derived organic carbon, which is potentially to provide electron donor for dechlorination process. The plant derived organic carbon also stimulated dissimilatory sulphate reduction, which subsequently have negative effect on MCB removal.     

BAT and BEP as instruments for reducing emissions of unintentionally produced POPs and development of guidelines under the stockholm convention

The 6th Intergovernmental Negotiating Committee (INC 6), under the Stockholm Convention on POPs, gave an expert group the mandate to develop guidelines for the application and implementation of best available techniques (BAT) and best environmental practices (BEP) for the prevention and reduction of unintentionally produced and emitted POPs, including polychlorinated dibenzodioxins/-furans (PCDD/Fs), polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB). Measures to reduce or eliminate the release of these POPs to the environment can be found in Article 5 of the Convention. BAT and BEP are already being applied as emission reduction instruments in a number of industrialised countries and are elements of other major international treaties, e.g. the UN ECE Protocol on POPs and the Marine Convention's OSPAR and HELCOM, and of the EU Directive for Integrated Pollution Prevention and Control (IPPC Directive). Existing concepts are presented and compared with the requirements of the Stockholm Convention. Consequences, perspectives and questions for the future intersessional work of the above-mentioned Expert Group are discussed.     

Natural attenuation of trichloroethene and its degradation products at a lake-shore site

Subsurface contamination by trichloroethene (TCE) was detected at a Michigan National Priorities List (NPL) site in 1982. The TCE plume resulted from the disposal of spent solvent and other chemicals at an industrial facility located in the eastern shore of Lake Michigan. TCE degradation products of three dichloroethene (DCE) isomers, vinyl chloride (VC) and ethene were present. The plume was depleted of oxygen and methanogenic at certain depths. Transects of the plume were sampled by slotted auger borings the year after the TCE plume was first discovered. Water samples were also taken from lake sediments to a depth of 12 m about 100 m offshore. Later samples were taken along the shoreline of the lake with a hand-driven probe. Later in 1998 water was taken from sediments about 3-m from the shoreline. The average concentration of each chemical and net apparent base coefficient between appropriate pairs of transects between the lower site and lakeshore were calculated. Loss rates were then calculated from an analytical solution of the two-dimensional advective-dispersive-reactive transport equation. Net apparent rate coefficients and a set of coupled reaction rate equations were used to extract the apparent loss coefficients. This study showed the field evidence for natural attenuation of TCE.     

Reduction in uptake by rice and soybean of aromatic arsenicals from diphenylarsinic acid contaminated soil amended with activated charcoal

Activated charcoal (AC) amendment has been suggested as a promising method to immobilize organic contaminants in soil. We performed pot experiments with rice and soybean grown in agricultural soil polluted by aromatic arsenicals (AAs). The most abundant AA in rice grains and soybean seeds was methylphenylarsinic acid (MPAA). MPAA concentration in rice grains was significantly reduced to 2% and 3% in 0.2% AC treated soil compared to untreated soil in the first year of rice cultivation. In the second year, MPAA concentration in rice grains was significantly reduced to 15% in 0.2% AC treated soil compared to untreated soil. MPAA concentration in soybean seeds was significantly reduced to 44% in 0.2% AC treated soil compared to untreated soil. AC amendment was effective in reducing AAs in rice and soybean.     

Using a Set of Strategic Indicator Systems as a Decision-making Support Implement for Establishing a Recycling-oriented Society - A Taiwanese Case Study (16 pp)

Background Scope and Aims. To realize the vision of sustainable development (SD) originating from the ‘only one earth’ philosophy, and to integrate the conceptions of ecology and sustainability into the planning and decision-making criteria of urban growth management, the establishment of a recycling-oriented society (ROS) is essential. However, before the above intention can be achieved, it is indispensable to develop a system of strategic indicators for supporting a radical reformation of the urban development plan. Therefore, this study, based on the conception of the new urban development pattern ROS, attempted to carefully choose a sample city in Taiwan for launching a preliminary case study, and furthermore designed and proposed a concise and strategy-oriented assessment indicator system termed ROSAIS. ROSAIS, on the one hand, can act as a compass for understanding resource using efficiency and recycling status during city development and, on the other hand, can serve as an implement supporting decision-making for ROS construction.Methods According to the definition and spirit of ROS, the structure of ROSAIS should clearly represent the relationship between resources and environment in human activities. The eco-efficiency indicator system (EEIS) and environmental symbiosis indicator system (ESIS) can be considered two key sub-indicator systems, and are the necessary components of ROSAIS. EEIS chooses the dominant production sectors in urban economic activities to calculate their eco-efficiency (EE). Separately, for obtaining a consensus regarding the framework of ESIS, the questionnaire approaches and expert consultation, together with the research experience and foundation of current relevant studies and indicator systems, are applied when crucial resource and environmental issues and respective indicators are selected.Results and Discussion The calculation results of EEIS in this case study indicated that among the three dominant production activities (agricultural, fishery, and animal husbandry sector) the fishery sector has the highest EE, which indicates that the fishery activities and resources significantly influence the sustainability of the economic-environmental system of the sample city. Furthermore, according to a consensus achieved in ESIS, local green spaces, resource recovery, energy consumption pattern change, freshwater conservation and greenhouse effect abatement were considered as the five crucial issues influencing how the case study city can develop into an ES-city. The rate of local green spaces, resource recycling, freshwater conservation and the rate of reduction of nonrenewable energy use as well as carbon dioxide (CO2) emissions were used to evaluate the above five issues.Conclusion This case study is unparalleled in Taiwan. Even in Japan, where ROS legislation has been implemented, this kind of study remains in the preliminary stages. Furthermore, when communicating the indicator results, it is essential to provide the context and countermeasures of the crucial issues that are faced. The two sub-indicator systems proposed in this case study could comply completely with the above-mentioned requirements. For example, the EEIS provides information for achieving a balance between environmental burden and economic benefits among dominant production sectors; the ESIS provides information for setting strategies for overcoming the crucial issues faced. Recommendation and Outlook This study recommends that urban planers should consider the construction of the corresponding strategic indicator system to be indispensable, and makes further use of the indicator results related to the environmental education of residents for identifying and promoting participation with ROS, and turning them into implements for supporting urban SD decision-making. Furthermore, a successful indicator system depends on data availability and quality. This study recommends that urban planers should pay considerable attention to constructing relevant data collection channels, databases and the data quality.     

Emissions from soil fumigation in two raised bed production systems tarped with low permeability films

Raised beds are used to produce some high-value annual fruit and vegetable crops such as strawberry in California (CA) and tomato in Florida (FL), USA. Pre-plant soil fumigation is an important tool to control soil-borne pests in the raised beds. However, fumigant emissions have detrimental environmental consequences. Field trials were conducted to evaluate emissions of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) in two different production systems with raised beds covered by different tarps. In the CA trial, InLine (60.8% 1,3-D and 33.3% CP) was drip-applied at 340 kg ha⁻¹ to 5 cm deep in the beds (30 cm high and 107 cm wide) tarped with polyethylene (PE) or virtually impermeable film (VIF). In the FL trial, carbonated Telone C35 (63.4% 1,3-D and 34.7% CP) was shank-applied at 151 kg ha⁻¹ to 20 cm deep in the beds (22 cm high and 76 cm wide) tarped with totally impermeable film (TIF). Emissions from tarped beds relative to furrows were contrary between the two trials. For the CA trial, the emission was 47% of applied 1,3-D and 27% of applied CP from PE tarped beds and 31% of applied 1,3-D and 15% of applied CP from VIF tarped beds, while that from uncovered furrows was <0.4% for both chemicals in both fields. In the FL trial, only 0.1% 1,3-D was emitted from the TIF tarped beds, but 27% was measured from the uncovered furrows. Factors contributing to the differences in emissions were chiefly raised-bed configuration, tarp permeability, fumigant application method, soil properties, soil water content, and fumigant carbonation. The results indicate that strategies for emission reduction must consider the differences in agronomic production systems. Modifying raised bed configuration and fumigant application technique in coarse textured soils with TIF tarping can maximize fumigation efficiency and emission reduction.     

机动车尾气中氮氧化物的分析检测技术

为了分析机动车尾气氮氧化物净化催化剂的催化性能 ,建立了一套尾气模拟评价体系 ,分别使用电化学法、化学发光法和比色法 3种氮氧化物分析手段进行检测。结果表明 ,3种方法都能在一定精度范围内测量机动车尾气中的氮氧化物 ,化学发光法测量精度高 ,响应时间短 ,能够及时地反映发动机运转过程中的氮氧化物浓度变化情况 ,是一种较好的分析手段。电化学法随着使用时间推移 ,响应时间变长 ,灵敏度降低 ,需要及时更换传感器。比色法通过化学吸收可以测定氮氧化物的浓度 ,不能实现连续在线分析 ,只能采样测量。在分析中 ,还尝试利用一些辅助设备 ,将尾气中的NO和NO2转化后再通入测量仪器 ,实现测量总氮氧化物或其中某一气体的功能