Pervaporation of ethanol/water mixture by organophilic nano-silica filled PDMS composite membranes

• Organophilic nano-silica filled polydimethylsiloxane membranes are prepared.
• The operation conditions of pervaporation for the ethanol–water mixture were studied.
• These composite membranes exhibit striking performances.

A novel organophilic nano-silica (ONS) filled polydimethylsiloxane (PDMS) composite membrane was prepared and characterized for the pervaporation (PV) of ethanol from water. The sorption and diffusion behaviors of ethanol and water in the composite membranes were investigated. The results showed that with increasing ONS concentration from 0 wt.% to 10 wt.%, the solubility selectivity and the diffusion selectivity increased from 21.87 to 38.85 and from 1.87 to 6.18, respectively. When the temperature ranged from 30 °C to 70 °C, the solubility selectivity increased but the diffusion selectivity first increased and then decreased. The effects of ONS content, feed temperature and permeate-side vacuum on the PV performance of the composite membrane for the pervaporation of 5 wt.% ethanol–water mixture were studied. The examinations showed that the composite membranes exhibited striking advantages in total flux and separation factor as compared with unfilled PDMS membrane. When ONS loading was 5 wt.%, the PDMS composite membrane showed the best PV performances with the permeate flux (J) of 114 g/(m2 · h), the separation factor (α) of 30.1 and permeate separate index (PSI), of 3420, respectively. With an increase of the feed temperature from 30 to 70 °C, the total flux of filled PDMS membrane with 5 wt.% ONS increased apparently from 11.1 to 210 g/(m2 · h), and the maximum separation factor of 30.1 was observed at 60 °C. With an increase of vacuum in permeate-side from 0.075 to 0.100 MPa, both separation factor and total flux increased for filled PDMS membrane with 5 wt.% ONS.