Developing nanocomposite PI membranes: Morphology and performance to glycerol removal at the downstream processing of biodiesel production

Nanocomposite solvent resistant (NCSR) membranes were developed and utilized for separation of organic biodiesel rich phase. The modified membranes were fabricated via nonsolvent induced phase separation by addition of different concentrations of functionalized multiwall carbon nanotubes (MWCNTs) in the polyimide (PI) casting solution. The morphological studies, molecular weight cut-off (MWCO), mean pore size, pore size distribution and porosity were evaluated and discussed. The physicochemical properties of the membrane were improved significantly after bulk modification with functionalized MWCNTs. Surface hydrophilicity and roughness were improved with an increase in MWCNTs up to 1 wt%. This was confirmed by fouling analysis where flux recovery (FR) was strongly increased by more than 47% for M2 at the maximum value. To evaluate the performance of modified PI membranes, the crude biodiesel prepared by transesterification reaction of canola oil with an alkaline catalyst was filtered with a dead-end filtration system at 5 bar and 25 °C. The glycerol removal increased with increasing MWCNTs content in the modified PI membranes until it reached to 100% for M3 membrane without any significant changes in methyl ester flux. It may be due to the smaller surface pore size and higher membrane porosity after bulk modification.