Self‐Assembled Asymmetric Block Copolymer Membranes: Bridging the Gap from Ultra‐ to Nanofiltration

The self‐assembly of block copolymers is an emerging strategy to produce isoporous ultrafiltration membranes. However, thus far, it has not been possible to bridge the gap from ultra‐ to nanofiltration and decrease the pore size of self‐assembled block copolymer membranes to below 5 nm without post‐treatment. It is now reported that the self‐assembly of blends of two chemically interacting copolymers can lead to highly porous membranes with pore diameters as small as 1.5 nm. The membrane containing an ultraporous, 60 nm thin separation layer can fully reject solutes with molecular weights of 600 g mol^?1 in aqueous solutions with a water flux that is more than one order of magnitude higher than the permeance of commercial nanofiltration membranes. Simulations of the membrane formation process by dissipative particle dynamics (DPD) were used to explain the dramatic observed pore size reduction combined with an increase in water flux.     

高分子膜错流纳滤的多场耦合有限元分析

纳滤膜的应用日益广泛, 但其传质机理和优化设计的研究还有待深入. 本文首先描述了表征高分子膜纳滤的道南-位阻孔模型(Donnan Steric Pore Model, DSPM), 进而描述了在DSPM模型基础上发展起来的表征错流纳滤的孔-极化输运模型(Pores and Polarization Transport Model, PPTM). 针对在PPTM模型中用经验模型描述膜上方溶液速度场的不足, 用Navier-Stokes方程和连续性方程来描述溶液在膜上方自由空间内的流动, 并用有限元方法模拟膜上方的溶液错流速度场, 从而实现了膜内传质的DSPM模型、膜上方离子浓度场、膜上方自由空间流场的多场耦合有限元分析. 通过与实验结果以及传统PPTM结果的对比可以发现, 该修正方法能反映膜上方自由空间中的溶液速度场和离子浓度场的变化趋势并且在数值上也更为逼近实验值. 改进后的模型将为高分子膜错流纳滤过程的优化设计提供更可靠的理论依据.     

Nanomaterials and Water Purification: Opportunities and Challenges

Advances in nanoscale science and engineering suggest that many of the current problems involving water quality could be resolved or greatly ameliorated using nanosorbents, nanocatalysts, bioactive nanoparticles, nanostructured catalytic membranes and nanoparticle enhanced filtration among other products and processes resulting from the development of nanotechnology. Innovations in the development of novel technologies to desalinate water are among the most exciting and promising. Additionally, nanotechnology-derived products that reduce the concentrations of toxic compounds to sub-ppb levels can assist in the attainment of water quality standards and health advisories. This article gives an overview of the use of nanomaterials in water purification. We highlight recent advances on the development of novel nanoscale materials and processes for treatment of surface water, groundwater and industrial wastewater contaminated by toxic metal ions, radionuclides, organic and inorganic solutes, bacteria and viruses. In addition, we discuss some challenges associated with the development of cost effective and environmentally acceptable functional nanomaterials for water purification.     

聚电解质层层自组装纳滤膜*

层层自组装技术能够方便地对膜的微观结构和组成进行调控,已在制备复合型纳滤膜方面取得了迅速的发展。本文综述了近年来用于聚电解质层层自组装纳滤膜的制备方法,种类以及影响因素。介绍了静态层层交替沉积、压力驱动自组装和电场强化自组装等三种制备方法;归纳了均聚型、共聚型和有机/无机杂化型等三类用于层层自组装纳滤膜的聚电解质的特点;讨论了聚电解质的荷电性、电荷密度和电离程度等因素对其自组装膜分离性能的影响。总结了聚电解质自组装纳滤膜在水处理和有机溶剂中物质的分离等方面的应用。同时,对提高聚电解质自组装纳滤膜的组装效率,分离性能和发展方向提出了设想和建议。     

Aroma Profile and Chemical Composition of Reverse Osmosis and Nanofiltration Concentrates of Red Wine Cabernet Sauvignon

Wine aroma represents one of the main properties that determines the consumer acceptance of the wine. It is different for each wine variety and depends on a large number of various chemical compounds. The aim of this study was to prepare red wine concentrates with enriched aroma compounds and chemical composition. For that purpose, Cabernet Sauvignon red wine variety was concentrated by reverse osmosis (RO) and nanofiltration (NF) processes under different operating conditions. Different pressures (2.5, 3.5, 4.5 and 5.5 MPa) and temperature regimes (with and without cooling) were applied on Alfa Laval LabUnit M20 equipped with six composite polyamide RO98pHt M20 or NF M20 membranes. Higher pressure increased the retention of sugars, SO₂, total and volatile acids and ethanol, but the temperature increment had opposite effect. Both membranes were permeable for water, ethanol, acetic acid, 4-ethylphenol and 4-ethylguaiacol and their concentration decreased after wine filtration. RO98pHt membranes retained higher concentrations of total aroma compounds than NF membranes, but both processes, reverse osmosis and nanofiltration, resulted in retentates with different aroma profiles comparing to the initial wine. The retention of individual compounds depended on several factors (chemical structure, stability, polarity, applied processing parameters, etc.).     

Influence of diazonium-induced surface grafting on PES NF membrane fouling reduction in algal-rich water treatment

The algae bloom phenomenon incurs a major challenge to conventional drinking water treatment processes due to the discharges of a large amount of intracellular pollutant and odor compounds in the water sources. Membrane processes have been considered as promising technologies to treatment of algal-rich water due to complete algal cell rejection however, its application has been limited by membrane fouling. In this work, the high-performance loose antifouling PES NF membranes were fabricated using diazonium-induced grafting and applied for treating real algal effluent. The modified membranes exhibited complete algal dye removal and turbidity removal throughout the long-term filtration. Also, the coupling and radically modified membranes can be able to removed COD by up to 90% and 88%, respectively, while a removal efficiency of 24% was observed for bare membrane. It is worth noting that, a relative smooth behavior in permeate flux by loose modified membranes during prolonged algal dye filtration, demonstrating exceptional anti-fouling property of membranes. In addition, the fouled modified membranes were effectively recovered by water flushing. Both loose modified membranes exhibited excellent resistance in the strongly acidic environment. These high performance antifouling NF membranes affords an innovative methodology toward the treatment of algal-rich water.     

Polydopamine Bilayer Nanofiltration Membranes with Excellent Resistance to Delamination

Abstract

Bilayer nanofiltration (NF) membranes tend to delaminate and have poor stability when applied in organic solvents due to their bi-layered structure. In this study we prepared two types of polydopamine (PDOPA) modified NF membranes including PDOPA-TMC (trimesoyl chloride)/PSF and PDOPA/PIP(Piperazine)-TMC/PSF NF membranes on polysulfone (PSF) ultrafiltration membranes via interfacial polymerization based on PDOPA’s specialized molecular structure and high adhesion property. The separation performance and stability of the NF membranes were investigated. Both the polyester bonds of the PDOPA bilayer membranes and the bioadhesion of the PDOPA were simultaneously beneficial to improving the structure and chemical stabilities of the bilayer membranes. After soaking both the PDOPA-TMC/PSF and PDOPA/PIP-TMC/PSF NF membranes in ethanol solvent for 12?days, the rejection of Congo red only decreased by 1.8% (original, 99.9%) and 1.2% (original, 99.9%), respectively. For the PDOPA/PIP-TMC/PSF NF membrane, the rejection of Na₂SO₄ was only reduced by 1.6% (original, 98.5%). Moreover, the separation performances of both the PDOPA-TMC/PSF and PDOPA/PIP-TMC/PSF NF membranes were still excellent after soaking in a sodium hypochlorite solution (50?ppm) for 240?h (12,000?ppm·hours). The NF membranes thus exhibited long-term structural stability in ethanol and excellent chemical stability in the sodium hypochlorite solution. In particular, no delamination was observed in the above experiments, which is significant for their use in the wastewater treatment field.     

耐溶剂纳滤膜

纳膜分离过程是一种选择性高、操作简单、能耗低的分离技术,已在各工业领域和科学研究中得到广泛的应用。纳滤过程的诸多优点,使其在石油化工、医药、食品等领域的非水溶液体系中具有极大的潜在应用价值,而传统的纳滤膜难以拓宽到非水溶液体系中使用,为此进一步研究和发展耐溶剂纳滤膜,对于拓宽纳滤过程的应用极其重要。目前,耐溶剂纳滤膜已成为膜分离科学领域的研究热点,在现有报道的文献基础上,本文综述了有关在非水溶液体系中使用的耐溶剂纳滤膜制备的研究进展,并对将来的发展方向提出了建议。     

有机-无机杂化膜的研究进展

有机-无机杂化膜由于具备了无机膜和有机膜各自的特点,具有良好的分离特性和物化稳定性,因而成为当前膜技术领域新型膜材料研究的热点.本文主要介绍了近年来国内外有机-无机杂化膜的研究现状、杂化膜的制备方法、结构和应用.