Effect of multi-carboxylic functional groups copolymer in blending of chitosan and its performance in pervaporative separation of ethanol/ water mixtures

Biodegradable membranes derived from renewable polymers are gaining attention for sustainable separation processes such as solvent dehydration by membrane pervaporation. In this study, dense chitosan (CS)/poly(malic acid–citric acid) (PMC) blend membranes were fabricated and phosphoric-acid crosslinked for the pervaporation separation of ethanol/water mixtures. The green copolymer PMC was synthesized through bulk-melt condensation of malic acid and citric acid, and subsequently blended with chitosan at different ratios (3:1, 1:1, and 1:3) to develop membranes with improved physicochemical and separation properties. Sorption studies were conducted to evaluate membrane solvent interactions and swelling behavior in ethanol/water mixtures. Structural, thermal, and morphological characteristics of the membranes were examined using Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), tensile testing, and ion exchange capacity (IEC) measurements to understand the effect of blending and crosslinking on membrane performance. The influence of CS/PMC composition on pervaporation performance was investigated for the separation of azeotropic ethanol/water mixtures. Among the prepared membranes, CS/PMC (3:1) and CS/PMC (1:1) exhibited superior performance, achieving flux values of 268.2 and 173.7 g m−2 h−1 with selectivity values of 1214 and 1222, respectively. In addition, the effect of feed water composition on the CS/PMC (1:1) membrane was evaluated, revealing that flux increased linearly with water content, while selectivity decreased. The results demonstrated that the incorporation of PMC and phosphoric acid crosslinking enhances membrane hydrophilicity and structural stability, making the CS/PMC blend membranes promising candidates for efficient ethanol dehydration by pervaporation.