Preparation and Identification of Optimal Synthesis Conditions for a Novel Alkaline Anion-Exchange Membrane

Aitor Marcos-Madrazo,Laura Simonelli,Víctor Sebastián,Jesús Iniesta,Leticia García-Cruz,María Encabo-Berzosa,Manuel Arruebo,Ángel Irabien,Clara Casado-Coterillo

doi:10.3390/polym10080913

Abstract

The physicochemical and mechanical properties of new alkaline anion-exchange membranes (AAEMs) based on chitosan (CS) and poly(vinyl alcohol) (PVA) polymers doped with unsupported copper nanoparticles (NPs) and copper exchanged over different porous materials were investigated regarding ion-exchange capacity (IEC), OH− conductivity, water uptake (WU), water vapor permeability (WVP), and thermal and mechanical resistance. The influence of the type of filler included in different morphologies and filler loading has been explored using copper exchanged materials such as the layered porous titanosilicate AM-4, layered stannosilicate UZAR-S3, and zeolites Y, MOR, and BEA. Compared to commercially available anion-exchange membranes, the best performing membranes in terms of WU, IEC, OH− conductivity and WVP in this study were those containing 10 wt % of Cu-AM-4 and Cu-UZAR-S3, although 10 wt % Cu-MOR provided better mechanical strength at close values of WVP and anion conductivity. It was also observed that when Cu was exchanged in a porous silicate matrix, its oxidation state was lower than when embedded as unsupported metal NPs. In addition, the statistical analysis of variance determined that the electrochemical properties of the membranes were noticeably affected by both the type and filler loading, and influenced also by the copper oxidation state and content in the membrane, but their hydrophilic properties were more affected by the polymers. The largest significant effects were noticed on the water sorption and transport properties, which gives scope for the design of AAEMs for electrochemical and water treatment applications.

Highlights

Alkaline anion-exchange membranes (AAEMs) are gaining relevance in the electrochemistry field [1], presenting a wide range of sustainable applications
It was remarkable that the two NP loadings studied modified diversely the color of the resulting membrane, being the 5Cu/CS:poly(vinyl) alcohol (PVA)
The copper content was introduced in the polymer CS:PVA blend matrix either as unsupported commercial nanoparticles, or ion-exchanged in various porous supports like AM-4, layered UZAR-S3 stannosilicate, and zeolites

Summary

Introduction

Alkaline anion-exchange membranes (AAEMs) are gaining relevance in the electrochemistry field [1], presenting a wide range of sustainable applications. The major challenges in the development of AAEMs are the improvement in their commonly low. Employing low-cost or renewable polymers, as well as nontoxic inorganic fillers in the synthesis of new membranes is a way of improving the sustainability of the process. To this end, chitosan (CS) and poly(vinyl) alcohol (PVA) constitute some of the renewable or low-cost alternative in AAEMs for electrochemical processes because its high hydrophilicity and ion exchange capacity, controllable permeability, and consequent energy savings [8,9]. Equimolar blends of CS and PVA were previously proposed as alkaline resistant

Methods

Results

Conclusion