Preparation of novel composite membranes for the pervaporation separation of water–acetic acid mixtures

Novel composite membranes were prepared involving “class I” and “class II” hybrid materials. The membranes obtained were characterized by Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Membranes exhibited a remarkable increase in degree of swelling with increasing zeolite loading in “class II” hybrid material. The pervaporation performance of these membranes for the separation of water–acetic acid mixtures was investigated in terms of feed composition and zeolite loading. Both the permeation flux and selectivity increased simultaneously with increasing zeolite content in the membrane matrix. This was explained on the basis of enhancement of hydrophilicity, selective adsorption and the establishment of molecular sieving action. While assessing the membranes’ efficiency, it was noticed that both total flux and flux of water are overlapping each other, signifying that the membranes developed in the present study involving “class I” and “class II” are highly selective towards water. Among the membranes developed, the membrane containing 15 mass% of zeolite exhibited the highest separation selectivity of 2423 with a flux of 8.35 × 10−2 kg/m2 h for 10 mass% of water in the feed at 30 °C. Comparison was also made to justify the efficiency of the developed membranes with respect to efficiency of the membranes reported in the literature. From the temperature dependent diffusion and permeation values, the Arrhenius activation parameters were estimated. The resulting activation energy values obtained for water diffusion being lower than those of acetic acid diffusion values, suggest that the composite membranes exhibit higher separation efficiency. The negative heat of sorption values (ΔHs) obtained for all the membranes, suggesting that Langmuir's type of sorption is predominant in the process.