Volatile organic compounds (VOCs) recovery from aqueous solutions via pervaporation with vinyltriethoxysilane-grafted-silicalite-1/polydimethylsiloxane mixed matrix membrane

Abstract

Recovery of volatile organic compounds (VOCs) from industrial wastewaters is important for the prevention of environmental pollution. This study investigated pervaporative recovery of VOCs by vinyltriethoxysilane (VTES)-grafted-silicalite-1/PDMS mixed matrix membrane (MMM) from the methanol-containing binary, ternary and quaternary wastewater solutions. The separation of methanol/water binary mixtures was first conducted. The influence of feed concentration and temperature on the membrane performance, such as permeation fluxes and VOC/water separation factor, was investigated. It was observed that with the increase of VOC concentration in the feed, the total permeation flux increased and the selectivity changed slightly first, then decreased. At a feed methanol concentration of 10.51wt% at 65°C, the maximum PSI of 5346g/m2h with a separation factor of over 10 were obtained with the VTES-g-silicalite-1/PDMS MMM, which makes it among the best in the literature and is very competitive for methanol recovery from aqueous solutions. The apparent activation energies of water and VOC during the pervaporation process was calculated based on Arrhenius equation. Then the mixed matrix membrane was applied to ternary and quaternary wastewater model solutions. Compared with binary methanol/water mixture, the addition of ethanol and/or acetone led to a decrease of the total flux, methanol flux, and methanol/water separation factor, but increased the total VOCs flux and the permeate VOCs concentration. Separation factors of individual VOC towards water follow the order of acetone>ethanol>methanol, which is consistent with those in binary aqueous mixtures.