Preparation and characterization of a novel green silica/PVA membrane for water desalination by pervaporation

Abstract

In this study, silica was extracted from rice husk (RH) waste to develop a novel green silica/PVA hybrid membrane for improving the desalination performance by pervaporation. A thermal method with citric acid leaching was applied for the extraction of green silica under different conditions, and the best high-cost purity silica obtained was incorporated into the PVA membrane with loadings of 0%, 10% and 20%. The effect of the green silica content on the membrane characteristics, desalination performance, and pervaporation temperature was investigated. The purest silica (>97 wt%) was obtained for a 5% acid leaching solution, which was used as the filler in the PVA membrane, and at a combustion temperature of 700 °C. The green silica/PVA membrane exhibited a higher roughness and hydrophilicity and a lower crystallinity compared with pure PVA, indicating an enhancement in the permeation flux. The flux of hybrid membranes reached the maximum value of 12.3 kg m−2h−1 at 60 °C for 10% silica loading with a 3.5 wt% NaCl feed concentration. Salt rejection remained higher than 99.9% for all membranes, and the apparent activation energy showed no significant difference between experiments. The results showed that the pervaporation performance was successfully improved by incorporating the RH silica into the PVA membrane.