Pretreatments for seawater desalination by pervaporation using the developed green silica/PVA membrane

Abstract

In this study, different pretreatments were evaluated for the desalination of seawater by pervaporation using the green silica/PVA membrane. The quality of water samples treated by sand filtration, coagulation, coagulation + sand filtration and microfiltration was analyzed in terms of turbidity, total suspended solids (TSS), conductivity, pH and biochemical oxygen demand (BOD). The most viable pretreatment, based on the effluent quality and process simplicity, was chosen for the desalination process. The green silica/PVA membrane was fabricated with rice husk silica and used in pervaporation at different temperatures, comparing raw and pretreated seawater as feed streams. There was no significant difference (p > 0.05) in the water quality results for the effluents from the different pretreatments, probably due to low concentration of suspended solids in the raw seawater used. Sand filtration was chosen as a pretreatment for desalination due to its simplicity, low cost and high effluent quality. Pervaporation desalination with the effluent of sand filtration (EFS) as the feed stream achieved a permeate flux of 10.6 kg m−2 h−1 at 60 °C, while with the use of raw seawater (RS) the permeate flux values were 50% lower for all temperatures studied. Total ion rejection was greater than 99.9% at all temperatures, using EFS or RS as feed streams. This study showed that sand filtration was the most appropriate seawater pretreatment of those studied for desalination via pervaporation using the novel green silica/PVA membrane.