Enhanced Sodium Alginate Membranes Modified with Metal-Organic Frameworks Based on Zirconium for Energy-Efficient Isopropanol Dehydration by Pervaporation

The zirconium-based metal-organic framework (Zr-MOF) class presents promising modifiers with excellent water stability and adsorption ability for the development of pervaporation mixed matrix membranes (MMMs). Thus, in this study, the effect of the introduction of Zr-MOF MIL-140A with various ligands into sodium alginate (SA) was investigated in order to develop mixed matrix membranes with enhanced characteristics for pervaporation dehydration. The improved SA membrane characteristics were achieved by the variation of MIL-140A concentration (2-5 wt %), different ligands in its structure (MIL-140A-AcOH, MIL-140A-AcOH-EDTA), and CaCl2 cross-linking. The prepared Zr-MOF, composites, and membranes were characterized using attenuated total reflectance-Fourier transform infrared spectroscopy, analysis of low-temperature nitrogen adsorption, scanning electron microscopy, atomic force microscopy, X-ray diffraction analysis, thermogravimetric analysis, and contact angle and liquid uptake measurements. The transport properties of the membranes were tested in the pervaporation dehydration of isopropanol (IPA). The results from quantum chemical computational experiments were employed to explain the observed changes and interactions. It was shown that the modification of the SA matrix with these Zr-MOFs led to the improvement of the pervaporation performance, in particular the permeation flux, due to their unique porous structure, functional groups, and favorable interaction with components of the feed. The SA+MIL-140A(4%) membrane cross-linked with CaCl2 exhibited the best transport characteristics in the pervaporation dehydration of isopropanol (12-70 wt % water): the highest permeation flux of 200-540 g m(-2) h(-1) maintaining 99.99 wt % water content in the permeate.