Scalable Antifouling Reverse Osmosis Membranes Utilizing Perfluorophenyl Azide Photochemistry

We present a method to produce anti‐fouling reverse osmosis (RO) membranes that maintains the process and scalability of current RO membrane manufacturing. Utilizing perfluorophenyl azide (PFPA) photochemistry, commercial reverse osmosis membranes were dipped into an aqueous solution containing PFPA‐terminated poly(ethyleneglycol) species and then exposed to ultraviolet light under ambient conditions, a process that can easily be adapted to a roll‐to‐roll process. Successful covalent modification of commercial reverse osmosis membranes was confirmed with attenuated total reflectance infrared spectroscopy and contact angle measurements. By employing X‐ray photoelectron spectroscopy, it was determined that PFPAs undergo UV‐generated nitrene addition and bind to the membrane through an aziridine linkage. After modification with the PFPA‐PEG derivatives, the reverse osmosis membranes exhibit high fouling‐resistance.

     

Bipolar reverse osmosis membrane for separating mono-and divalent ions

Bipolar reverse osmosis membranes that have both negatively and positively charged layers have been prepared to enhance the selectivity towards mono- and divalent ions in respect of both cations and anions. Positively charged layers are formed on low pressure reverse osmosis membranes having negative charge (NTR-7410 and 7450) by an adsorption method using polyethyleneimine (PEI) or a quaternary ammonium polyelectrolyte (QAP). These layers attach to the membrane's dense layer, which is made of sulfonated polyether sulfone. The selectivity of mono- and divalent ions is proven by experimental results for single electrolytes (NaCl, Na₂SO₄ and MgCl₂). Although negatively charged membranes repulse divalent anions more strongly than cations and monovalent anions, bipolar reverse osmosis membranes reject both divalent cations and divalent anions better than monovalent ions. An optimal preparation method for bipolar membranes showing selectivity towards mono- and divalent ions were developed. The bipolar membranes showed good ion selectivity for artificial sea water.     

海水淡化原理及方法综述

介绍了海水淡化的原理和多级闪蒸、反渗透2种常用的海水淡化方法,并且简要回顾了我国海水淡化的研究和技术应用情况。     

Electrodialysis with Bipolar Membranes for Valorization of Brines

Several industrial processes, such as desalination or neutralization, generate brines defined as concentrated solutions of salts in water, usually NaCl, typically discharged in the vicinities of the desalination plant or factory. To reduce the environmental impact and promote the valorization of the wasted resources, alternatives must be sought. Among sustainable alternatives for the recovery of brines, the possibility of using Electrodialysis with Bipolar Membranes (EDBM) is of interest, because it allows recovering brines as useful acids and bases. This review focuses on the discussion of the technical aspects of the EDBM as a means to treat streams rich in NaCl from reverse osmosis desalination and industrial processes in order to complete the direct delivery of chemicals for self-supply. The main environmental issues associated with desalination brine disposal are presented. The state-of-the-art of valorization of brines by EDBM to acids and bases is completed. This work concludes with an in-depth discussion of the technical, techno-economic and economic barriers that prevent the widespread use of EDBM technology.     

Transport of Na2SO4 and MgSO4 solutions through a composite membrane

Retention curves with a composite membrane (HR 95) have been measured for different solutions of Na₂SO₄ and MgSO₄. Salt permeabilities in the skin and the porous layer of the composite membrane have been calculated. The results show that the salt permeability in the skin layer is 15% of that corresponding to the porous layer. Electrical resistances for the composite membrane and another membrane similar to the supported membrane (without skin layer) have been measured using both direct and alternating current. From the a.c. values, assuming that no concentration polarization exists at the skin-porous layer interface, the electrical resistance for the skin layer at different concentrations was estimated. The membrane resistance values were also determined by impedance spectroscopy measurements, and the results agree with those previously found by a.c. measurements.     

From capacitive deionization to desalination batteries and desalination fuel cells

The considerable growth of the world population, concomitant with an increase in environmental pollution, aggravates the antinomy between supply and demand for drinking water. Various desalination technologies have been developed to address this issue, allowing for abundant saltwater as a source for drinking water. Electrochemical desalination attracts more and more attention due to its high energy efficiency, facile operation, and low cost. Especially within the last decade, tremendous scientific progress on electrochemical desalination technologies has been made. This article reviews the development of electrochemical desalination technologies and introduces a facile classification into three generations based on the different working principles. The cell architecture, metrics, advantages, and disadvantages of other electrochemical desalination technologies are introduced and compared.     

A Polyoxometalate-Based Binder-Free Capacitive Deionization Electrode for Highly Efficient Sea Water Desalination

Capacitive deionization is a promising technique in sea water desalination. Compared with common electrodes, mixed capacitive-deionization electrodes exhibit better performance in sea water desalination because they integrate pseudocapacitance and electric double-layer capacitance in one system. Herein, a 3D binder-free mixed capacitive-deionization electrode was fabricated by direct electrodeposition of SiW₁₂O₄₀⁴⁻ and polyaniline on a 3D exfoliated graphite carrier. In this electrode, SiW₁₂O₄₀⁴⁻/polyaniline composite particles with a size of about 100–120 nm are dispersed homogenously on the 3D exfoliated graphite carrier. Its specific capacitance reaches 352 F g⁻¹ at 1 A g⁻¹. With increasing current from 1 to 20 A g⁻¹, the specific capacitance only decays by 32 %. When employed in sea water desalination, the performance of this mixed capacitive-deionization electrode is also excellent. At 1.2 V, the salt adsorption capacity of this mixed electrode reaches 23.1 mg g⁻¹ with a salt adsorption rate of 1.38 mg g⁻¹ min⁻¹ in 500 mg L⁻¹ NaCl. The performance of this electrode is well retained after 30 cycles. The excellent sea water desalination performance originates from the synergistic effect between SiW₁₂O₄₀⁴⁻ and polyaniline. This work has developed polyoxometalate as a new material for capacitive-deionization electrodes.     

羟丙基醋酸纤维素的合成及其膜的反渗透性

研究了羟丙基纤维素和羟丙基醋酸纤维素的合成。制备羟丙基纤维素的较佳反应温度为40℃左右和2小时或稍长,羟丙基含量随环氧丙烷浓度的增加而增加。在制备羟丙基醋酸纤维素时,随羟丙基含量的增加,所需醋化和水解的时间减少。以甘油-正丙醇或磷酸为添加剂,丙酮为溶剂经30～60s蒸发后制得了羟丙基醋酸纤维素反渗透膜。后者在20kg/cm~2下对氯化钠脱盐率可达95～98％,水通量1.0～2.1mL/cm~2·h,其使用温度上限比醋酸纤维素反渗透膜提高10℃以上。     

Influence of Substitutional Defects in ZIF-8 Membranes on Reverse Osmosis Desalination: A Molecular Dynamics Study

In this study, molecular dynamics simulation is used to investigate the effects of water-based substitutional defects in zeolitic imidazolate frameworks (ZIF)-8 membranes on their reverse osmosis (RO) desalination performance. ZIF-8 unit cells containing up to three defect sites are used to construct the membranes. These substitutional defects can either be Zn defects or linker defects. The RO desalination performance of the membranes is assessed in terms of the water flux and ion rejection rate. The effects of defects on the interactions between the ZIF-8 membranes and NaCl are investigated and explained with respect to the radial distribution function (RDF) and ion density distribution. The results show that ion adsorption on the membranes occurs at either the nitrogen atoms or the defect sites. Complete NaCl rejection can be achieved by introducing defects to change the size of the pores. It has also been discovered that the presence of linker defects increases membrane hydrophilicity. Overall, molecular dynamics simulations have been used in this study to show that water-based substitutional defects in a ZIF-8 structure reduce the water flux and influence its hydrophilicity and ion adsorption performance, which is useful in predicting the type and number of defect sites per unit cell required for RO applications. Of the seven ZIF-8 structures tested, pristine ZIF-8 exhibits the best RO desalination performance.     

Swelling of ultrathin crosslinked polyamide water desalination membranes

We study the water swelling behavior of semiaromatic crosslinked polyamide (PA) ultrathin films to characterize the network properties of the polymer. Specifically, we use X-ray reflectivity to measure film thickness increase and polymer density decrease of the PA films due to swelling. With the aid of a modified Flory–Rehner theory used to describe the constrained swelling behavior of polymer networks, we are able to extract the Flory interaction parameter and the monomer units between crosslinks by performing the swelling experiments at different levels of hydration. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

应用于土遗址文物脱盐的高分子材料

运用吸附脱盐法除去土遗址中的可溶盐,所用的吸附材料是脱盐的关键要素之一。本文介绍了用于土遗址脱盐的吸附材料发展历程及其现状,重点介绍了耐盐性高分子吸水材料用于土遗址基体中盐类脱除的机理、存在的问题及发展方向,文中还对高分子吸水材料可能取得的进展和前景进行了展望。     

高回收率膜法苦咸水淡化工艺的应用研究进展

膜法苦咸水淡化过程中,符合环境保护要求的浓排水处理方法成本高昂,所以只有当回收率达到较高值时,在实际运行中才具有经济可行性。目前,在不加剧膜污染的条件下进一步提高苦咸水淡化系统回收率的方法已成为该领域研究热点。本文详细综述了高回收率膜法苦咸水淡化工艺的应用研究进展,包括基于反渗透、纳滤、正渗透、膜蒸馏、电渗析和电容去离子化淡化工艺过程,以及这些过程面临的热点问题,并对此提出了建议。     

Geminal poly(silyl ester)s: Highly labile degradable polymers

Geminal silyl ester linkages were used for the backbone construction of linear polymers, which exhibit rapid cleavage in the presence of atmospheric water. A series of poly(gem-silyl ester)s with two ester groups flanking each silicon atom were synthesized, in order to probe the effects of different silyl-substituted side-chain groups upon the physical and chemical properties. The transsilylation condensation reaction of bis(trimethylsilyl) terephthalate with dichlorodiisopropylsilane, dichlorodicyclohexylsilane, dichloromethyl-n-octadecylsilane, and dichloromethyl-4-methylphenethylsilane gave the four poly(gem-silyl ester)s with two isopropyl, two cyclohexyl, one methyl plus one octadecyl, and one methyl plus one 4-methyl-phenethyl side-chain groups per silicon, respectively. The polymers were characterized by NMR (¹H, ¹³C, and ²⁹Si), infrared spectroscopy (IR), size-exclusion chromatography (SEC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Hydrolytic degradation studies of the polymers solvated in tetrahydrofuran and as bulk samples in the solid state were performed in the presence of atmospheric water as the nucleophilic cleavage agent, and the molecular weight loss was monitored by SEC. Poly(diisopropylsilyl terephthalate) (1a) and poly(dicyclohexylsilyl terephthalate) (1b) were found to be more stable towards nucleophilic degradation in comparison to poly(methyl-n-octadecylsilyl terephthalate) (1c) and poly(methyl-4-methylphenethylsilyl terephthalate) (1d), due to the presence of sterically bulky isopropyl or cyclohexyl groups attached to the silicon atoms. All of the polymers degraded into small molecules upon hydrolysis, with the exception that the degradation products of 1c and 1d self-condensed in the solid state to form the respective polysiloxanes. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3606–3613, 1999     

Antimicrobial polymers containing melamine derivatives. II. Biocidal polymers derived from 2‐vinyl‐4,6‐diamino‐1,3,5‐triazine

Poly(2‐vinyl‐4,6‐diamino‐1,3,5‐triazine) (PVDAT) and a series of poly(styrene‐co‐2‐vinyl‐4,6‐diamino‐1,3,5‐triazine) (PS‐co‐VDAT) copolymers were synthesized via conventional free‐radical polymerizations. The polymer structures were confirmed by Fourier transform infrared, NMR, and elemental analysis. The molecular weights were determined by gel permeation chromatography studies, and the thermal properties were characterized by differential scanning calorimetry and thermogravimetric analysis. After treatment with chlorine bleach, PVDAT and PS‐co‐VDAT provided potent antimicrobial functions against multidrug‐resistant Gram‐negative and Gram‐positive bacteria. The antimicrobial functions were durable for longer than 3 months and rechargeable for more than 50 times. The structure–property relationship of the polymers was further discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4089–4098, 2005     

Synthesis and gas transport properties of new aromatic 3F polymers

New aromatic 3F polymers were obtained from condensations of 2,2,2-trifluoroacetophenone (1) with biphenyl (a), terphenyl (b), a mixture of biphenyl with terphenyl (ab), phenyl ether (c) and diphenoxybenzophenone (d). The reactions were performed at room temperature in the Brønsted superacid trifluoromethanesulfonic acid (TFSA) and in a mixture of TFSA with dichloromethane. The polymers show high glass transition temperatures >170 °C, excellent thermal stability (decomposition temperatures ≥475 °C) and good solubility in chlorinated solvents and strong acids. The 3F polymer structures based on biphenyl and terphenyl show attractive permeability coefficients for CO₂ (∼200 Barrers) and H₂ (∼120 Barrers), whereas the 3F polymers that contain ether linkages have permeability coefficients in the typical range of regular polysulfone and polycarbonate. However, in sharp contrast to polysulfone and polycarbonate families, new 3F polymers possess high chemical stability and they have advantages since their reactions, based on commercially available monomers, can be carried out in one-pot at room temperature and offer a large variety of structures not possible to prepare by other synthetic methods.     

Synthesis of ionic block polymers for desalination membranes

Copolymer containing 2-vinylpyridine–trimethylsilyl methacrylate, styrene–2-vinylpyridine, and styrene–trimethylsilyl methacrylate blocks as well as terpolymers containing the styrene2–vinylpyridine–trimethylsilyl methacrylate blocks were synthesized by initiation of the appropriate monomers sequentially both with butyllithium and sodium. These polymers were subjected to hydrolysis by which the acrylate ester segment is converted to the free acid and to the reaction with methyl iodide, which quaternizes the pyridine segment; finally the hydrolyzed and quaternized polymers were subjected to dehydrohalogenation with external base. The properties of these block polymers and blends of the styrene-containing block copolymers were examined, especially in regard to their suitability as reverse osmosis desalination membranes.     

Highly alkaline stable anion exchange membranes from nonplanar polybenzimidazole with steric hindrance backbone

The anion exchange membranes (AEMs) with both high ionic conductivity and alkali stability are always the research focus of the AEM fuel cells. Here, a novel nonplanar polymer for AEMs manufacture, mPBI‐TP‐x‐R, with excellent hydroxide stability and satisfactory processability is reported for the first time. The serial mPBI‐TP‐x resins with steric hindrance were prepared by copolymerization among 3,3′,4,4′‐tetraaminobiphenyl, isophthalic acid and tetraphenyl‐terephthalic acid (TP) in different ratios under microwave condensation. The copolymers mPBI‐TP‐x were quaternized at N1/N3‐sites of benzimidazole unit in backbone with alkyl groups (R?CH₃, C₂H₅, n‐C₃H₇, or n‐C₄H₉) to prepare soluble ionomers, and the corresponding membranes in hydroxyl ion form were prepared by a solution casting method and subsequent ion‐exchange process. The chemical structure of all membranes was characterized using FTIR and ¹H NMR spectroscopy. The properties of ion exchange capacity, water uptake, swelling ratio, tensile strength, ionic conductivity, and alkaline stability were measured. Among the prepared membranes, the mPBI‐TP‐15%‐(n‐Bu) exhibited the excellent alkaline stability (only degradation ca. 5% under 1M NaOH aqueous solution at 60 °C for 800 h) and satisfactory OH^? conductivity (46.66 mS/cm at 80 °C). The current research provides a useful exploration to commercial application of alkaline fuel cell. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1087–1096     

苦咸水反渗透淡化中膜面结垢预测及防垢进展

苦咸水反渗透（BWRO）中的防垢过程,首先取决于给水水质,而根据水质条件和垢在膜面的形成机理采取相应的防垢措施是非常重要的。 显然,有效地管控膜面无机结垢及抑制膜面污染需要开展无机结垢趋势的预测、防垢措施和非破坏性无机垢监控等方面的技术研究。 一系列传统和新兴的分析技术,包括摩尔比率法、直接目测法和光谱法等已应用于BWRO过程中膜面防垢研究。 本文详细综述了该过程中无机结垢趋势的预测、防垢方法和非破坏性无机垢监控技术等方面的研究进展。 此外,针对目前的研究方向提出了建议。     

Living polymers and polymer solutions: a misleading analogy

 Experimental results from colloidal suspensions of worm-like micelles are currently interpreted in terms of close analogies between this kind of systems and polymeric solutions. In particular, it was hypothesized that the viscoelastic properties of dense systems of giant flexible cylindrical micelles can be rationalized in terms of an entangled network of worm-like aggregates, very similar to a neutral random polymeric network. Such an idea is strongly supported by theoretical results that, in a mean-field appro ximation, suggests for an unlimited growth process of the micellar contour length with concentration. The mean-field theory indicates for an exponentially shaped length distribution function, with mean <L> depending on concentration, φ, in agreement with a scaling law <L>∝φ^α (α=0.5 in the simpler approach). A number of experimental results seem to be successfully interpretable within this framework. Aim of this work is to show that the agreement between theory and experiment is just an accident, being the mean-field approach, in principle, inadequate in describing systems dense enough to show a concen tration dependence of the mean micellar size. It will be unambiguously shown that there is no way to describe semi-diluted micellar solutions through a mean-field approximation and that there does not exist any scaling law of the kind <L>∝φ^α. Furthermore, it will be shown that the shape of the size distribution function is markedly different from the exponential one. The basis for a more realistic approach for the growth process of micellar aggregates is also presented and some pre liminary indications are success fully compared with experimental results. Received: 24 February 1997 Accepted: 22 April 1997     

Proton conducting polymers containing 1H‐1,2,3‐triazole moieties

Polyacrylates containing a different number of 1H‐1,2,3‐triazole groups per repeat unit have been synthesized via conventional free radical polymerization. These polymers were characterized by nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Proton conductivity measurements were made using impedance spectroscopy. Introduction of more than one triazole per repeat unit did not result in an increase in conductivity as there was an accompanying increase in glass transition temperature (T_g). A maximum conductivity of 17.5 μS/cm was obtained at 200 °C under anhydrous condition. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 188–196, 2009