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ABSTRACT: Selectivity for monovalent ions is a very important feature of ion exchange membranes in view of a further expansion of the scope of electrodialysis (ED). An efficient one‐step chemical process to graft a thin polyaniline (PANI) layer on the surface and pores of an ultrafiltration (UF) membrane is reported. The existence of a PANI layer on such modified UF membrane was confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy images. These membranes were extensively characterized by studying their properties such as water uptake, ion‐exchange capacity, contact angle, and performance in diffusion dialysis. ED experiments were conducted by comparing desalting of sodium chloride and magnesium chloride solutions. During the desalting procedure, the driving force has two contributions, the electrical field and the salinity‐gradient. Initially, transport of ions by the electrical field is dominant, while at the end of the experiment, diffusion dialysis by the salinity gradient plays a larger role in ion transport. The presence of PANI can hinder Mg2+ transport from the concentrate to the diluate compartment because of the electrostatic effect, while there is no obvious effect on Na+ ions. The ability of such a surface modification layer to improve the membrane selectivity for Na+/Mg2+ was confirmed by means of ED in a mixed solution. The flux of Na+ was slightly increased to 13.21 × 10−8 mol/L/min while the flux of Mg2+ was reduced to 3.32 × 10−8 mol/L/min, so that the permselectivity is almost doubled. The protonation reaction of the PANI layer creates positive charges, thus leading to an electrical repulsion barrier, which may reduce the penetration of divalent cations with respect to monovalent ions. Polyacrylonitrile‐based UF membranes with different molecular cutoff was used to determine the influence of the permselectivity. Results showed that the membrane permselectivity of smaller molecular cutoff UF membranes is higher. It can be concluded that this method is suitable for preparing membranes based on UF membranes for efficient separation of monovalent ions by electro‐driven separation techniques. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45692. [ABSTRACT FROM AUTHOR]

BACKGROUND Conventional methods for synthesis of quaternary ammonium hydroxides, such as the reaction of quaternary ammonium chloride, ion-exchange and electro-electrodialysis cannot achieve benign production of QAOH without secondary pollution. The objective of the present study was to develop bipolar membrane electrodialysis with a novel stack configuration as an improved method to prepare high purity quaternary ammonium hydroxide from its halide salt. RESULTS To investigate the synthesis of quaternary ammonium hydroxide ( QAOH) with high purity by using electrodialysis with bipolar membranes ( BMED), four different types of quaternary ammonium hydroxides (tetramethylammonium hydroxide, TMAOH; tetrapropylammonium hydroxide, TPAOH; methyltriethylammonium hydroxide, MTAOH; and benzyltrimethylammonium hydroxide, BTAOH) were chosen as the target products. The effect of the molecular structure of four different types of halide salts ( NR4X) on the BMED performance was studied by investigating operating parameters such as current density, feed concentration and feed flow velocity and energy consumption on the basis of ion dimensions and molecular weight, ion electrophoretic mobility and the interaction between ammoniums and membranes. The results indicate that it is feasible to obtain quaternary ammonium hydroxides with high purity (Cl−/Br− content < 500 ppm) by BMED with a novel four-compartment configuration in view of environmental aspects. CONCLUSION For converting higher molecule size halide salts, the process performance was lower, while the energy consumption increased, at similar experimental conditions, which is in line with the theory. © 2014 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Highlights: [•] BMED was adopted for clean post-processing of AMP sulphate. [•] A high AMP recovery and low energy consumption was obtained. [•] An industrial application proved that the BMED process is feasible. [ABSTRACT FROM AUTHOR]

Effective extraction of useful resources from high-salinity textile wastewater is a critical pathway for sustainable wastewater management. In this study, an integrated loose nanofiltration-electrodialysis process was explored for simultaneous recovery of dyes, NaCl and pure water from high-salinity textile wastewater, thus closing the material loop and minimizing waste emission. Specifically, a loose nanofiltration membrane (molecular weight cutoff of ~800 Da) was proposed to fractionate the dye and NaCl in the high-salinity textile wastewater. Through a nanofiltration-diafiltration unit, including a pre-concentration stage and a constant-volume diafiltration stage, the dye could be recovered from the high-salinity textile wastewater, being enriched at a factor of ~9.0, i.e., from 2.01 to 17.9 g·L−1 with 98.4% purity. Assisted with the subsequent implementation of electrodialysis, the NaCl concentrate and pure water were effectively reclaimed from the salt-containing permeate coming from the loose nanofiltration-diafiltration. Simultaneously, the produced pure water was further recycled to the nanofiltration-diafiltration unit. This study shows the potential of the integration of loose nanofiltation-diafiltration with electrodialysis for sufficient resource extraction from high-salinity textile wastewater. [Display omitted] • Integration of loose nanofiltration (NF) with electrodialysis is proposed for textile wastewater treatment. • Loose NF-diafiltration enriches the dye from 2.01 to 17.9 g·L−1 with a purity of 98.4%. • 99.94% of salt is removed by loose NF-diafiltration with 7 diavolumes. • Subsequent electrodialysis effectively recovers water and salt from NF-diafiltration permeate. • No significant fouling of ion exchange membranes is observed in electrodialysis performance. [ABSTRACT FROM AUTHOR]

In the sustainability concept framework, wastewater highly loaded with acid is considered as a valuable resource, rather than a waste. Diffusion dialysis employing anion exchange membranes is a feasible solution to extracting acid from this waste stream. However, conventional anion exchange membranes have dense spatial structures with no observable pores even at nanoscale, which limits the transfer of protons. Porous anion exchange membranes provide a practical avenue to enhance the proton transfer due to their unique spatial structure. In this study, novel porous anion exchange membranes were designed by one-step crosslinking and quaternization of porous brominated poly (phenylene oxide) membrane substrate by 1, 4-diazabicyclo [2.2.2] octane. The resultant porous anion exchange membranes showed a high performance in acid recovery by diffusion dialysis, due to their uniquely tailored microstructures including an extremely thin selective layer and high free space volume. Specifically, the optimal anion exchange membrane possessed an acid dialysis coefficient of 0.066 ± 0.003 m h−1 and an acid/salt separation factor of 96.9 ± 2.5 in the HCl/FeCl 2 mixture solution, outperforming the commercial anion exchange membrane (i.e., DF-120, acid dialysis coefficient of 0.0085 m h−1 and acid/salt separation factor of 18.5). This study demonstrates the great potential in constructing advanced anion exchange membranes at large scale for efficient acid recovery from highly acidic wastewater to support environment sustainability. Image 1 • Novel porous anion exchange membranes (AEMs) are prepared by a facile one-step method. • The tailor-made AEMs show superior performance for acid recovery by diffusion dialysis. • The optimal AEM has an acid dialysis coefficient of 0.066 ± 0.003 m h−1 and an acid/salt separation factor of 96.9 ± 2.5. • Great potential of the porous AEMs in industrial acidic wastewater treatment can be expected. [ABSTRACT FROM AUTHOR]

Post-combustion CO 2 capture by reaction with a strong alkali such as NaOH appears a promising strategy to mitigate CO 2 emission. This study proposes bipolar membrane electrodialysis (BMED) as a technology for the reclamation of NaOH from glyphosate neutralization liquor and its subsequent use as an absorbent for CO 2 capture. The proposed method produces a NaOH solution for further reaction with CO 2 while recovering the glyphosate from the wastewater. A NaOH solution with a concentration of ∼1.45 mol L −1 and purity of ∼96.5% was obtained. Accordingly, a current efficiency of 80.8%, 76.2%, 68.7% and 69.0% at current densities of 30, 40, 50 and 60 mA cm −2 was observed, respectively. In addition, the lowest energy utilization recorded as 2.15 kW h kg −1 was obtained by the BMED process at a low current density of 30 mA cm −2 , resulting in a better performance in view of energy saving. A glyphosate recovery of ca. 98.2% was also achieved. The environmental impact of the BMED process was evaluated in terms of the amount of CO 2 emissions produced and the total amount of CO 2 captured taking into account of the CO 2 production through BMED process. The results demonstrate that a promising CO 2 capture (up to 530.65 g CO 2 kg −1 NaOH) can be only achieved if the electricity resources originate from renewable sources such as wind, hydroelectric, as well as solar photovoltaics or nuclear energy. However, the utilization of non-renewable energy resources for NaOH production by BMED process imposes a risk on producing a significant emission of CO 2 , which makes the application of BMED unviable for a CO 2 capture scenario. [ABSTRACT FROM AUTHOR]

This study aims to investigate the feasibility of an integrated system consisting of a fluidized pellet reactor and bipolar membrane electrodialysis (EDBM) for regeneration of acid and base from wastewater with a high concentration of calcium and nickel ions. The fluidized pellet reactor was used to reduce the potential of scaling on the membranes by crystallization. EDBM was applied to regenerate acid/base from this pretreated wastewater. The results show that calcium and nickel can be removed by the fluidized pellet reactor with sufficient efficiency (74% and 73% without filtration, 74% and 94.4% with filtration, respectively). After pretreatment, it was feasible to regenerate mixed acid and base using EDBM. The current efficiency was 69% for the acid, 80% for the base; the energy consumption was 5.5 kW h/kg acid and 4.8 kW h/kg base at a current density of 60 mA/cm 2 and an initial concentration of 0.2 N. In a long-term experiment, the pretreatment increased cation exchange membrane performance and a high concentration of acid and base up to 1.76 N and 2.41 N was produced with only slight scaling on the cation exchange membrane surface. This integrated process is not only technically but also environmentally feasible, reducing water pollution and yielding valuable products to achieve sustainable development. [ABSTRACT FROM AUTHOR]

Over the last few decades, ion exchange membranes have evolved from a laboratory tool to industrial products with significant technical and commercial impacts. Electrodialysis with bipolar membranes (EDBM) is a technology that can produce acids and bases from the corresponding salt solutions. Bipolar membranes are key factors for splitting water at the interface of a cation and anion exchange layer in an electric field. The ideal bipolar membrane should have a low energy consumption, a high current efficiency and long-term stability. In order to investigate the catalytic effect of a monolayer of MoS 2 , the bipolar membranes were prepared by introducing monolayer MoS 2 to the interface of bipolar membranes. The resulting bipolar membrane was found to have lower potential drop, which clearly demonstrates the applicability of the MoS 2 layer to act as catalyst. Enhanced acid production confirmed this prediction. Furthermore, a bipolar membrane prepared at 90 °C had a low swelling ratio of about 7.5% while maintaining a high water uptake of 71.6%. From the calculation of current efficiency and energy consumption, the bipolar membrane with a monolayer of MoS 2 has a higher current efficiency (45%) and a lower energy consumption (3.6 kW/h·kg) compared to a current efficiency of 24% and an energy consumption of 6.3 kW/h·kg for a bipolar membrane without MoS 2 . This study proves the catalytic function of MoS 2 , which lays a foundation for further research on catalytic bipolar exchange membranes. [ABSTRACT FROM AUTHOR]

Effective fractionation of dyes and salts (NaCl) potentially paves a new path to sustainable treatment of textile wastewater. Herein, a loose nanofiltration (NF) membrane was innovatively used as the anion conductive membrane in electrodialysis (ED) for dye and salt separation. The NF membrane with a molecular weight cut-off of 678 Da showed a sufficient retention for reactive dyes with small molecular weights (<627 Da) predominantly based on synergistic effect of steric repulsion and Donnan repulsion. Simultaneously, the NF membrane had a considerably fast transport for anions (i.e., Cl−), as its loose surface structure created extra nano-channels for ion transfer. The anion conductive loose NF membrane based ED process yielded excellent separation performance in a one-step dye/NaCl fractionation. Specifically, a 98.9% desalination efficiency was obtained by the loose NF-based ED process along with 99.4% dye recovery. Additionally, an extremely low fouling propensity was observed during a 5-cycle ED operation, as the negative surface charge of the loose NF membrane served as an intrinsic barrier to prevent the dye species from entering the membrane pores through electrostatic repulsion. This study demonstrated a desirable potential of loose NF membranes as anion conductive membranes in ED for resource recovery from highly-saline wastewater. Image 1 1. Loose nanofiltration (NF)-based electrodialysis (ED) was used for dye/salt separation 2. Loose NF membrane shows an excellent ion transport as anion conductive membrane 3. Loose NF-based ED yields 98.9% desalination efficiency and 99.4% dye recovery 4. Low fouling propensity is observed for loose NF membrane as anion conductive membrane [ABSTRACT FROM AUTHOR]