Research On Preparation And Properties Of Two Anion Exchange Membranes Based On Diffusion Dialysis

As an important acid recovery technology,diffusion dialysis has been widely used in industrial production activities.However,the design and manufacturing level of the anion exchange membrane directly affects the application potential of the anion exchange membrane as the key component of the acid recovery diffusion dialysis device.In this study,the ion exchange membrane prepared by two kinds of polymers with different hydrophilic properties was studied.It was modified by grafting in a simple and environmentally friendly way to improve the diffusion dialysis application performance of the polymer.The specific research was as follows:In the first part,a series of anion exchange membranes for acid recovery by diffusion dialysis were prepared by Friedel-Crafts reaction using vinyl chloride-vinyl acetate copolymer（P（VC/VAC））and N-methylimidazole（NMI）as raw materials,and their diffusion dialysis performance was characterized by simulated waste acid（1.00 M HCl+0.20 M Fe Cl₂）.The resulting membranes exhibited high dialysis coefficients(U_H⁺;11.60×10^-3m/h-32.50×10^-3m/h)and the separation factors（S）（26.00-36.00）at 25°C.At the same time,standardized techniques were used to evaluate diffusion dialysis-related performance such as ion exchange capacity,water uptake（W_R）,linear expansion rate,elongation at break（E_b）,tensile strength（TS）,initial decomposition temperature and thermal decomposition temperature,etc.Surface morphologies of the prepared anion exchange membranes were determined through scanning electron microscopy analysis（SEM）.Through the proposed method,in this report,toxic reagents（such as methyl iodide）for quaternization are not required to prepare the anion exchange membranes.The experimental work presented here provided the preparation method in this part,which not only was simple and economical but also exhibited excellent membrane performance,suggesting it as one of the promising candidates for diffusion dialysis membranes fabrication.The second part was that we firstly discussed the synthesis of quaternized poly epichlorohydrin（QPECH）by the reaction of poly epichlorohydrin（PECH）with N,N-dimethylethanolamine（DMEA）.After that,different amounts of QPECH were mixed with the polyvinyl alcohol（PVA）and tetraethyl silicate（TEOS）to fabricate a series of anion exchange membranes（AEMs）by sol-gel reaction.The chemical structure of the synthesized QPECH was effectively proved by FTIR and proton nuclear magnetic resonance（¹H NMR）.Hereafter,the composite membrane structure was determined by FTIR,X-ray photoelectron spectroscopy（XPS）and SEM,and the physical and chemical properties such as thermogravimetric analysis（TGA）,W_R,IEC and linear expansion rate（LER）,and diffusion dialysis（DD）were tested.The performance,such as acid recovery and selectivity of PVA/QPECH composite membranes with different QPECH content,was discussed comprehensively.The results showed that the W_Rof the composite membrane was 82.35%-158.54%,the LER was 19.23%-40.74%,and the IEC was from 0.64 mmol/g to 1.76 mmol/g.In the DD test simulating waste acid recovery,the U_H⁺was in the range of11.1×10^-3m/h-30.0×10^-3m/h,and the S was in the range of 24.79-42.24.The U_H⁺and S of the composite membranes were all better than that of commercial membrane DF-120.In conclusion,this study demonstrated that applying PVA/QPECH anion exchange membrane had the potential in acid recovery by DD method.Figure[25]table[9]reference[109]...