Dehydration of glycerin solution using pervaporation: HybSi and polydimethylsiloxane membranes

• Pervaporative dehydration of glycerin solution up to 99 wt% was demonstrated.
• HybSi membrane outperformed PDMS membrane in term of permeate flux.
• Temperature and pressure had significant influence on flux and glycerin retention.
• Molecular movement and transport during pervaporation were postulated.

The dehydration of glycerin solution is an important step in glycerin purification process. In present work, pervaporative dehydration of glycerin solution was studied using HybSi and polydimethylsiloxane (PDMS) pervaporation membranes. The effects of physical property of membrane, operating parameters and glycerin concentrations on the membrane permeate flux and selectivity were examined. The present studies showed that hydrophilic HybSi membrane could provide higher permeate flux as compared to hydrophobic PDMS membrane under an identical operating condition. Remarkable difference in permeate flux was observed when the process was operating at room temperature. The influence of crossflow rate on the permeate flux was relatively low as compared to operating pressure and temperature. Operating temperature was found to possess the greatest influence on permeate flux and selectivity. The speculated molecule movement during pervaporation was discussed based on boundary layer theory and hydrogen bonding theory. The final permeate flux and permeance water content of 13.63 kg/m2 h and 98 wt%, respectively, were achieved by HybSi membrane in the dehydration process of 90 wt% glycerin solution into 99 wt% glycerin solution over a period of ~90 min.