•Anion-exchange membrane with reduced proton leakage is developed successfully.•It is possible to simultaneously improve conductivity and acid block property of membranes.•Acid block property is strengthened via construction of microphase separation morphology.Nowadays, excess quantities of industrial waste acid with low concentration have become not only a serious threat to environment but also a huge resource waste. Electrodialysis (ED) should have played important roles therein. However, the substantial proton leakage of anion exchange membrane (AEM) seriously deteriorates its work performances. In this report, the water uptake of AEM is controlled for alleviating the problem by material selection, for example, hydrophobic skeleton and weakly basic anion exchange groups. Of note, two kinds of membrane structures are designed and investigated. One is the semi-interpenetrating network which is achieved by blending PVDF with DMAEMA and DVB copolymer, the other is a so-called microphase-separated structure which is driven by the polarity difference of segments of the side-chain-type membrane material, PVDF-g-PDMAEMA. Series of electrodialysis experiments confirm that the as-prepared AEMs do exhibit remarkable acid block property. In particular, PVDF-g-PDMAEMA AEM displays more outstanding comprehensive properties, such as area electrical resistance, anti-swelling and limiting current densities. Based on comparison of results achieved in electrochemical characterizations, morphology observations and measurements of water uptake and acid adsorption, it is concluded that the microphase separation of the hydrophilic and hydrophobic segments contributes to the formation of ion nanochannels and then induces some consequential confinement effects.

•The universality and influence factors of ion substitution electrodialysis were investigated.•The ion substitution electrodialysis was further modified for improving its work performance.•The reclamation of waste acid and conversion of organic acid were carried out simultaneously.In view of some inherent problems, such as the high mobility of protons and low dissociation degrees of organic acid, the conventional electrodialysis technology must be improved before being applied widely in the related fields. In this work, a win-win strategy for simultaneously reclaiming industrial waste acid and producing organic acid by ion substitution electrodialysis (ISED) was put forward. Above all, the ISED technology was further investigated, including its universality and work performance influenced by the membrane selection. Subsequently, a modified ISED was developed and applied in the conversion of acetic acid using the simulated waste acid effluent as proton source. The experiments indicated that a much better work performance, including improved current efficiency and conversion rate and reduced energy consumption, can be achieved when compared to the conventional technology. Especially, it was observed that the content of electro-migrated metal ions in the produced organic acid was so low that a high purity organic acid product can be easily obtained after a simple post-treatment.

•Membrane was modified by covalent bonding layer-by-layer assembly.•Surface homogeneity of heterogeneous membrane was improved by the modification.•Endowment of permselectivity between anions was attempted by surface modification.In this work, glutaraldehyde-induced poly(ethyleneimine) (PEI) multilayer deposition was attempted with the aim to improve the electrodialytic transport properties of a heterogeneous anion exchange membrane (AEM), including selective separation between specific anions and amelioration of concentration polarization. Firstly, the change of surface hydrophilicity and morphology after modification were investigated by contact angle measurement and scanning probe microscope observation. Then, the electrodialytic transport properties were comprehensively evaluated by the measurements of salt permeability coefficient, permselectivity of counter-ions, membrane electrical resistance and limiting current density. Especially, in order to simulate the possible applications in the seawater utilization and groundwater purification, two kinds of systems such as Cl−/SO42 − system and F−/Cl− system were chosen to estimate and compare the selective separation properties of the membranes. Furthermore, the alteration of surface heterogeneity after modification was understood by chronopotentiometric and current–voltage curves. The experimental results showed that PEI multilayers formed by covalent layer-by-layer assembly can effectively adjust the surface hydrophilicity and improve the surface homogeneity of heterogeneous AEM at a slight sacrifice of membrane conductance. Thereupon, the selective separation between the anions with different hydration energy can be achieved. The improvement of surface homogeneity can contribute to the amelioration of the concentration polarization during a electrodialysis process.

•Cation exchangers with small size and narrow size distribution were fabricated.•Charged microspheres were used as additives for preparing heterogeneous membranes.•A method for improving heterogeneous membrane properties was proposed.In this study, the sulfonated polystyrene microspheres (MPs) which embraced much smaller particle size and narrower size distribution than those of conventional resin powders (RPs) were synthesized and employed as ion-exchangers exclusively or additives to prepare heterogeneous cation exchange membrane (CEM). Thereupon the effects of the incorporation of the charged MPs on the properties of heterogeneous CEM were investigated. Firstly, the morphologies of the synthesized MPs and the corresponding CEMs were examined by SEM observation. Then, the membrane properties were comprehensively evaluated by the measurements of ion exchange capacity, water uptake, transport number, salt permeability coefficient, membrane resistance, limiting current density and so on. Moreover, surface homogeneity was explored by means of the chronopotentiometric analyses. The experimental results showed that the required amount of RPs can be reduced significantly by adding moderate MPs while achieving the similar or even higher membrane conductivity at almost no sacrifice of other membrane properties. Moreover, the surface homogeneity was also enhanced, which can effectively alleviate the concentration polarization behavior at the membrane/solution interface. All these experimental results indicated that the added MPs can make good connections among the conductive regions both in membrane body and at membrane surface and then facilitate ion transport.