Dechlorination of chlorinated hydrocarbons by bimetallic Ni/Fe immobilized on polyethylene glycol-grafted microfiltration membranes under anoxic conditions

In this study, the dechlorination of chlorinated hydrocarbons including trichloroethylene (TCE), tetrachloroethylene (PCE) and carbon tetrachloride (CT) by bimetallic Ni/Fe nanoparticles immobilized on four different membranes was investigated under anoxic conditions. Effects of several parameters including the nature of membrane, initial concentration, pH value, and reaction temperature on the dechlorination efficiency were examined. The scanning electron microscopic images showed that the Ni/Fe nanoparticles were successfully immobilized inside the four membranes using polyethylene glycol as the cross-linker. The agglomeration of Ni/Fe were observed in poly(vinylidene fluoride), Millex GS and mixed cellulose ester membranes, while a relatively uniform distribution of Ni/Fe was found in nylon-66 membrane because of its hydrophilic nature. The immobilized Ni/Fe nanoparticles exhibited good reactivity towards the dechlorination of chlorinated hydrocarbons, and the pseudo-first-order rate constant for TCE dechlorination by Ni/Fe in nylon-66 were 3.7-11.7 times higher than those in other membranes. In addition, the dechlorination efficiency of chlorinated hydrocarbons followed the order TCE > PCE > CT. Ethane was the only end product for TCE and PCE dechlorination, while dichloromethane and methane were found to be the major products for CT dechlorination, clearly indicating the involvement of reactive hydrogen species in dechlorination. In addition, the initial rate constant for TCE dechlorination increased upon increasing initial TCE concentrations and the activation energy for TCE dechlorination by immobilized Ni/Fe was 34.9 kJ mol⁻¹, showing that the dechlorination of TCE by membrane-supported Ni/Fe nanoparticles is a surface-mediated reaction.     

减压膜蒸馏法处理石煤提钒废水

利用减压膜蒸馏设备处理石煤提钒废水，分别比较了废水经预处理前后，料液温度、流量、渗透侧真空度等操作条件对膜通量和截留率的影响。测定了不同浓缩倍数情况下膜通量的变化。实验表明，进料温度升高会使膜通量增加，温度为65℃时，热效率最高为70．1％。提高料液流量或真空度都会使膜通量增加。废水经VMD处理产出的淡水电导率均在10μS／cm以下，脱盐率可达99．98％以上。在温度为70％、流量为60L／h、真空度为0．095MPa时，石煤提钒废水经预处理后的废水膜通量为11．359kg／（m^2·h），浓缩10倍时，膜通量仍有3．185kg／（m^2·h）。     

超滤膜技术在环境工程水处理中的应用

随着我国经济水平的不断提高,也给我国环境带来了巨大的影响。与此同时,科技水平的不断发展,也使我国水处理技术日臻完善。目前,在环境工程水处理的过程中不仅可以通过物理、化学方法,还可以通过超滤膜技术来对环境工程水处理的质量进行监控,其是以传统水处理工艺为基础,通过全面的改革及调整,形成的一种新型的处理技术,能够确保水环境具备理想的可行性和适宜性,从而提升水处理效果。     

湿法再生吸附剂制备及用于大气CO2的直接捕集

基于湿法再生吸附技术，利用强碱性季铵盐树脂材料制备了异相吸附剂薄膜，应用于大气中极低CO2的直接分离，以对抗全球变暖。通过滴定法分析吸附剂材料的电荷密度和吸附容量，利用SEM分析不同工况下制备出来的膜材料的表观结构，并对膜材料进行CO2吸附性能的测试。结果发现，热处理能够明显提高膜材料的吸附性能，还研究吸附剂制备对吸附速率，吸附量和机械强度等性能的影响，发现粒径小于43μm的树脂粉末，按60％质量分数制成的500μm厚膜材料具有较优的综合性能。     

好氧颗粒污泥对膜生物反应器污泥性能的影响

采用膜生物反应器进行含酚废水的处理,探讨投加好氧颗粒污泥对反应器中污泥性能的影响。结果表明,在膜生物反应器中投加好氧颗粒污泥能有效改善污泥性能,提高处理效果。从采用絮状污泥到逐渐增加好氧颗粒污泥投加量为100%的过程中,反应器中污泥浓度明显提高,MLSS由5 582 mg/L增加到8 168 mg/L;沉降性能得到改善,SVI由135.85 mL/g下降到29.36 mL/g;疏水性增强,Zeta电位由-20.302 mV升高到-4.325 mV;对含酚废水中COD、NH3-N的降解能力明显提高,COD、NH3-N、NO3-N去除率分别由87.3%、83.2%、55.3%增加到99.2%、94.9%、66.3%。改善了膜污染现象,膜通量衰减率由63.3%降低到42.8%。用二元多项式三维回归分析,得到污染物去除率关于好氧颗粒污泥投加量和反应器运行时间的二元方程,对指导好氧颗粒污泥膜生物反应器的连续运行具有重要意义。     

膜吸收法净化低浓度甲醛和氨气

基于膜吸收技术自制双层平板式膜吸收器，搭建净化低浓度甲醛和氨气污染模拟系统，考察不同膜结构参数、进气流量、吸收剂流量等因素对其净化效果的影响。结果表明，聚偏氟乙烯PVDF对低浓度甲醛和氨气的净化效率高于聚四氟乙烯PTFE。对同一材质膜，随着膜孔隙率的增大，甲醛和氨气的净化率呈上升趋势。随着进气流量的增加。甲醛和氨气的净化效率降低；而吸收剂流量对其净化效率影响不大。对于所有实验条件，平均膜孔径为0．22μm的PVDF4#在进气流量ug=120L／h时，甲醛和氨气的净化效率最高，分别达94．7％和96．3％。     

盐类对模拟胞外聚合物(EPS)膜污染的影响

实验旨在研究盐类对模拟胞外聚合物(EPS)溶液在超滤和微滤过程中膜污染影响,通过添加与无添加盐类的模拟溶液的比较,研究盐类对EPS膜过滤在死端过滤过程的影响。实验考察了不同模拟溶液的膜通量衰减情况和滤饼比阻,并利用Hermia模型对实验数据进行拟合分析验证膜污染机理。实验结果表明,在超滤过程中,Ca2+和Al3+能在一定程度上提高膜通量,降低滤饼比阻,延缓膜污染;在微滤过程中,两者的添加反而降低了初始通量,添加Ca2+后滤饼比阻值反而有所增大;Na+对超/微滤过程影响很小。通过Hermia模型拟合分析发现,在超滤过程中,添加盐和无添加的溶液均以滤饼堵塞机理为主,而在微滤过程中则是以中间堵塞和滤饼堵塞机理为主。     

盐度对序批式反应器与间歇曝气膜生物反应器污水处理效果的影响

采用序批式反应器(SBR)与间歇曝气膜生物反应器(IAMBR)处理模拟生活污水,考察了进水盐度对两反应器污水处理效果的影响。研究表明,当进水盐度为0g/L(以NaCl质量浓度计,下同)时,SBR和IAMBR对总有机碳(TOC)、NH4+-N及TN的去除能力相当,IAMBR未表现出明显的优势;当进水盐度为10g/L时,SBR和IAMBR对TOC、NH4+-N及TN的去除产生明显的差异。IAMBR因为膜的截留与微生物富集作用,对污染物的去除无明显变化,依然保持了较高的污染物去除率,而SBR受盐度冲击影响较大,TOC、NH4+-N及TN的去除率均大幅降低,说明IAMBR具有较高的抗盐度冲击性能。     

A/O-MBR中MLSS浓度对污泥性能及膜通量的影响

采用国产聚丙烯中空纤维帘式膜组件,进行了A/O-MBR系统处理生活污水的实验研究,主要探讨了系统中污泥浓度(MLSS)与膜通量变化过程的关系。实验结果表明,MLSS由3 805 mg/L升高到6 912 mg/L时,污泥混合液胞外聚合物(EPS)由43 mg/g VSS增加到81 mg/g VSS,EPS中多糖与蛋白质的比例从0.87增加到1.08。同时,污泥相对疏水性(RH)的降低与Zeta电位的升高也在一定程度上共同促进了膜污染速率的上升。实验条件下,当运行时间为60 d左右,MLSS升高至6 200 mg/L时,跨膜压差上升迅速,膜组件清洗周期由初始的22 d缩短为11 d。A/O-MBR中由于MLSS浓度变化而导致的活性污泥混合液特性的变化,是影响膜通量变化的重要原因。     

Pervaporation of ethanol produced from banana waste

Banana waste has the potential to produce ethanol with a low-cost and sustainable production method. The present work seeks to evaluate the separation of ethanol produced from banana waste (rejected fruit) using pervaporation with different operating conditions. Tests were carried out with model solutions and broth with commercial hollow hydrophobic polydimethylsiloxane membranes. It was observed that pervaporation performance for ethanol/water binary mixtures was strongly dependent on the feed concentration and operating temperature with ethanol concentrations of 1–10%; that an increase of feed flow rate can enhance the permeation rate of ethanol with the water remaining at almost the same value; that water and ethanol fluxes was increased with the temperature increase; and that the higher effect in flux increase was observed when the vapor pressure in the permeate stream was close to the ethanol vapor pressure. Better results were obtained with fermentation broth than with model solutions, indicated by the permeance and membrane selectivity. This could be attributed to by-products present in the multicomponent mixtures, facilitating the ethanol permeability. By-products analyses show that the presence of lactic acid increased the hydrophilicity of the membrane. Based on this, we believe that pervaporation with hollow membrane of ethanol produced from banana waste is indeed a technology with the potential to be applied.