Contents lists available at ScienceDirect Journal of Membrane Science journal homepage: www.elsevier.com/locate/memsci Proton blockage membrane with tertiary amine groups for concentration of sulfonic acid in electrodialysis Liang Wang a, ⁎ , Zhenxing Li a , Zhaozan Xu b , Fan Zhang a , Johnson E. Efome c, ⁎ , Nanwen Li b, ⁎ a State Key Laboratory of Separation Membranes and Membrane Processes, and School of Environmental and Chemical Engineering, Tianjin Polytechnic University, Tianjin 300387, PR China b State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, PR China c Industrial Membrane Research Institute, Department of Chemical and Biochemical Engineering, University of Ottawa, 161 Louis Pasteur, Ottawa, ON, Canada K1N 6N5 ARTICLE INFO Keywords: Anion exchange membrane Proton blockage membrane Acid recovery Concentration Electrodialysis Ion exchange capacity ABSTRACT The weak base of tertiary amine groups was introduced into poly (2, 6-dimethyl-1, 4-phenylene oxide) (PPO) anion exchange membranes (AEMs) by Cu(I)-catalyzed “click chemistry” in order to fabricate proton blockage membranes for sulfonic acid concentration in electrodialysis (ED). The degree of functionalization has been confirmed quantitatively by 1 H NMR spectroscopy. Fourier transform infrared spectroscopy (FTIR) was also used to confirm the functional groups in the membranes matrix. The prepared proton blockage membrane with tertiary ammonium groups showed lesser swelling and water uptake ratios than the typical AEMs with strong organic base of quaternary ammonium groups. It is believed that the strong organic base of quaternary am- monium has a stronger hydration effect on water than that of tertiary amine groups. Interestingly, the con- centration limitation of membranes with tertiary amine groups was higher than that of the membrane with quaternary ammonium groups, indicative of the proton blocking capabilities of the AEMs as a result of the weak base introduced into the matrix. Moreover, it was found that the concentration limitation of tertiary amine based AEMs was also influenced by the weight-based ion exchange capacities (IEC w ), essentially the water uptake and swelling ratios of the membranes. The highest concentration limitation of AEMs with tertiary ammonium groups for H + was 3.02 mmol/L with IEC w value of 1.67 mmol/g, which is slightly higher than the 3.00 mol/L reported for the commercial AEM (Neosepta ACM). Therefore, AEMs containing weak base groups are potential candi- dates for proton blockage membrane for acid recovery applications by ED process. 1. Introduction Sulfonic acids are widely used as cleaning agents for metal surfaces, catalysts in organic reactions and electrolytes in storage batteries among other applications [1–4]. Treatment of waste acid solutions is a challenging process across the globe. In an attempt to resolve the issue, Electrodialysis (ED) which uses charged ion exchange membranes with an electrical potential as driving force for proton enrichment is an ef- ficient technology that has been employed [5–7]. ED is an electro- membrane driven process for selective separation and recovery of ions from the waste solution. In this process, ions are transferred from a dilute compartment to a concentrated compartment through ion ex- change membranes under an electric field [8]. The research into ion exchange membranes have expanded beyond the academic realm into industrial research and development because of its outstanding se- lectivity properties to fulfill specific requirements [9–13]. However, in the acid concentration process, the proton leakage of normal anion exchange membranes (AEMs) having quaternary ammonium groups have pose serious challenges including low concentration limitation which impedes the ED development advancements. Therefore, it is expected that preparing cost effective anion exchange membranes, e.g. proton blockage membrane (PBM) with high permeability of anions and low proton leakage of proton will go a long way in bringing enhancing ED. At the same time, while hoping that achieving the goal of primary performance including high limiting current density at low membrane area resistance is achievable [14]. Generally, polymers with tethered organic cations have been com- monly employed in preparing anion exchange membranes for electro- dialysis. These anion conductive organic cations have been obtained by introducing quaternary ammonium using chloromethylation of aro- matic rings or bromination on the benzylic methyl groups of the polymers, followed by the Menshutkin reaction with a tertiary amine. Various polymer backbones have been investigated for AEMs including polyaromatics [15,16], polyolefins [17,18], polystyrene [19–23], https://doi.org/10.1016/j.memsci.2018.03.011 Received 8 February 2018; Received in revised form 3 March 2018; Accepted 7 March 2018 ⁎ Corresponding author. E-mail addresses: mashi7822@163.com (L. Wang), jefom061@uottawa.ca (J.E. Efome), linanwen@sxicc.ac.cn (N. Li). Journal of Membrane Science 555 (2018) 78–87 Available online 17 March 2018 0376-7388/ © 2018 Elsevier B.V. All rights reserved. T