J. Membr. Sci. 2017, 537, Pages 111–118 (1 September 2017)
By Hui-Fang Xiao, Qing Chen, Huan Cheng, Xiu-Min Li, Wen-Meng Qin, Bao-Sheng Chen, Dong Xiao, Wei-Ming Zhang*
j.memsci.2017.05.009, fulltext mmc1.xlsx

Zinc metal is mainly produced by a hydrometallurgical process, in which zinc electrolyte is recirculated, and impurities especially halides are accumulated then, which have dreadful impacts on the process and product. Until now numerous efforts have been made to remove halides from the electrolyte, but none of them are fully satisfying, and it is still a big issue for the industry. As a conventional membrane technology, diffusion dialysis (DD) is originally designed to recover free acid from acid-salt mixture by concentration gradient. In this work, we proposed a novel process to selectively remove these halide impurities from the spent zinc electrolyte by DD directly. Significant Cl- and F- permselectivities over HSO4- are observed in this process. The removal efficiencies are as high as 50–70% and 30–42% for chloride and fluoride, respectively, while the zinc loss is less than 1%. The flow intensity in the current work is much higher than that in conventional DD, which reduces the overall cost immensely. The mechanism of this selective mass transfer is also studied intensively to understand influence of flow intensity, charge number and hydrated radii of ions on the permselectivity. The results here are not confined to provide a superior method to remove halide impurities for the zinc industry, but also extend new applications and deepen understandings for the well-established DD process in selective ion separation. This capability is very likely to become a new growth point and future direction for the DD process besides acid/alkali recovery.

J. Membr. Sci. 2017, 525, Pages 229–239 (1 March 2017)
By Zijun Xia, Libin Ying, Jianhua Fang*, Yu-Yu Du, Wei-Ming Zhang*, Xiaoxia Guo, Jie Yin
j.memsci.2016.10.050, local fulltext

A series of polybenzimidazole copolymers with varied content of pendant amino groups have been synthesized by condensation polymerization of 4,4′-dicarboxydiphenyl ether (DCDPE), 5-aminoisophthalic acid (APTA) and 3,3′-diaminobenzidine (DAB) in polyphosphoric acid at 190 °C for 20 h. The resulting copolymers undergo post-sulfonatation in fuming sulfuric acid at 100 °C yielded the highly sulfonated polybenzimidazoles (SOPBI-NH2(x/y), ‘x/y’ refers to the monomer molar ratio of DCDPE to APTA). A series of covalently cross-linked membranes (CSOPBI-NH2(x/y)) with good mechanical properties are fabricated by solution cast technique using bisphenol A epoxy resin as a cross-linker. The CSOPBI membranes show 3–4 orders of magnitude lower VO2+ permeability and 6–30 times higher ion diffusion selectivity (proton vs. VO2+) than Nafion117. The charge-discharge behaviors of the vanadium redox flow batteries (VRBs) assembled with the CSOPBI-NH2(x/y) membranes and Nafion 117 are investigated and compared. The VRBs assembled with the CSOPBI membranes exhibit significantly higher columbic efficiency and lower self-discharge rate than that assembled with Nafion 117 owing to the extremely lower vanadium cations crossover of the former. The VRB assembled with the CSOPBI-NH2(9/1) membrane exhibits fairly high energy efficiency (~85% at 60 mA cm−2) and little decay in performance is observed after 300 charge-discharge cycles.

J. Membr. Sci. 2015, 493, pp 28–36 (29 June, 2015)
By Chang Xue, Qing Chen, Yuan-Yuan Liu, Yu-Ling Yang, Dan Xu, Lixin Xue and Wei-Ming Zhang*
10.1016/j.memsci.2015.06.027, local fulltext

Currently nanofiltration predominates the membrane application of dye desalting and purification, and it is very effective to produce low-salt dye from raw dye with high inorganic salt impurities. However it is difficult and costly to produce dye products with ultralow impurities, because the desalting performance decreases proportionally as the concentration of salt impurity decreases. Here in this study, an optimized electrodialysis desalting process was proposed to fill the gap. The dye–membrane interactions, fouling mechanism and abatement strategy were carefully investigated and well understood. Long term system performance stability and reasonable process cost are achieved. Nearly all SO42− in the feed dye can be removed, and residual [Cl−] is only 130 mg/L (~96% removal) in the final aqueous dye product (~200 g/L). The overall purification cost is $0.097/kg as dye solids, which is very economically competitive. The electrodialysis desalting process proposed here provides another feasible and competitive approach for dye desalting and purification other than nanofiltration.

J. Membr. Sci., 2013, 432, pp 90–96 (1 April, 2013)
By Jin-Xia Zhuang, Qing Chen, Shun Wang, Wei-Ming Zhang*, Wei-Guo Song*, Li-Jun Wan, Kun-Song Ma, Chun-Nian Zhang
10.1016/j.memsci.2013.01.016 local fulltext

A zero discharge process was proposed to totally recover both acid and aluminum resource from the waste acid in foil industry. Diffusion dialysis (DD) was coupled with electrodialysis with bipolar membranes (EDBM) in this process, in which most of the free acid was first recovered by DD; and the resulting waste dialysate was further basified by EDBM, recovering aluminum resource and the rest of free acid. Through this process, all components in waste acid were recovered as valuable chemicals, resulting in zero discharge of dangerous effluents. This process is profitable in terms of cost analysis and significantly reduces the environmental burden of foil industry, enabling the foil industry to be more cost-effective, more environmental friendly and more sustainable.