Separation of thiophene/n-heptane mixtures using PEBAX/PVDF-composited membranes via pervaporation

Composited membranes made of poly (ether-block-amide)/polyvinylidene difluoride (PEBAX 2533/PVDF) were prepared for separation of thiophene/n-heptane mixtures via pervaporation. PEBAX 2533 was selected based on its solubility parameter calculated by the group contribution method. The membranes' sorption properties were studied in swelling experiments. The suitability of the membranes for the separation of mixtures was explored via pervaporation experiments. Swelling experiments showed that the degree of swelling increased with increasing temperature and thiophene concentration. The effects of thiophene feed concentration and operation temperature on pervaporation performance were investigated. Experimental results showed that increases in the thiophene concentration and system temperature both not only led to significant increase in total flux, but also caused decrease in separation factor. This result also showed that PEBAX/PVDF-composited membranes are more selective to thiophene than to n-heptane. When feed thiophene concentration was 1000 μg/g and feed temperature was 40 °C, total flux and separation factor were 3.8 kg/(m2 h) and 4.0, respectively. Elemental analysis (CHNS-O) was performed to determine the molar ratio of polyether and polyamide in PEBAX 2533. The results showed that this molar ratio was 10:1. The membranes were characterized by scanning electron microscopy (SEM) to study surface and cross-sectional morphologies. SEM images showed that there is an interface between the PEBAX 2533 separation layer and the PVDF support layer. The surface of the PEBAX 2533 separation layer was dense and had no obvious defects. The activity energy was calculated according to the Arrhenius equation. Pervaporation results were compared with those reported in the literatures. This work may provide useful insights into the viability of the removal of sulfur compounds from gasoline via pervaporation.