Two birds, one stone: Simultaneous removal of saccharides and metal ions from ionic liquid solution by selective electrodialysis

Abstract

The efficient and cost-effective elimination of saccharides and metal ions solving in the ionic liquid spinning solution produced in the regenerated cellulose fibers (RCFs) manufacture is highly desirable in view of the RCF quality and IL recycling. Herein, the ‘two birds and one stone’ strategy was proposed for simultaneous removal of saccharides and metal ions solving in [Emim]Dep spinning solution by selective electrodialysis (SED). Benefiting from the electric neutrality of saccharides, the differences of IL and metal ions (Mg2+ and Ca2+) in electrostatic interaction and hydration radius, the permeation ratio of IL (PIL), removal ratios of saccharides (Rs), Mg2+ (RMg2+) and Ca2+ (RCa2+) could reach up to 96.0 %, 94.8 %, 95.0 % and 95.0 %, respectively in the practical ionic liquid spinning solution. The structure of [Emim]Dep after SED process was similar to that of pristine, indicating the stability during the SED process. Interestingly, the presence of saccharides was beneficial to the removal of metal ions because of the complexation. Moreover, the membrane fouling process and mechanism were also investigated by the determination of ion exchange capacity and the characterization of morphology and structure. Along this line, the corresponding cleaning strategy was raised and the performance of the membrane did not change notably within 5-times recycle. Thus, this work put forward a facile and cost-effective method for one-step removal of saccharides and metal ions and the purification of ionic liquids, which could be popularized in the fields of biomass pretreatment and dissolution using ILs.