Influence Of Coupling Agents On Pervaporation Performances Of Silica/PDMS Composite Membranes

In this dissertation, the composite polydimethylsiloxane (PDMS) membranes supported by cellulose acetate (CA) microfiltration membrane were successfully prepared by adding nano-fumed silica particles modified with silane coupling reagent, NH2-C3H6-Si(OC2H5)3(AMES). Response surface methodology (RSM) was used to optimize the PDMS membrane preparation conditions. The effects of silica content, AMES/silica weight ratio, and PDMS concentration on the pervaporation performances of the nano-composite PDMS membranes were investigated for recovering ethanol from aqueous solution by pervaporation. According to the regression equations with a statistical software Design-Expert7.1.4., the maximum permeation flux of239.1g·m-2·h-1could be obtained, and the corresponding selectivity was6.09in10wt%ethanol aqueous solution. The preparation conditions of the composite membrane with the above separation performances were:8.36wt%silica loading,0.16AMES/silica weight ratio and6.64wt%PDMS concentration. The effects of the preparation conditions on the pervaporation performances of the composite membranes were obtained. The preparation conditions used in next studies with different coupling agent were established.Modified nano-fumed silica with silane coupling was used as filler to prepare PDMS membranes supported by CA microfiltration membranes. The effects of the type of silane coupling agents NH2-C3H6-Si(OC2H5)3(AMES), CH3C(CH2)COO(CH2)3Si(OCH3)3(MEMS) and CH3(CH2)15Si(OCH3)3)(HEMS) on the pervaporation performances of the nano-composite PDMS membranes were also investigated.Nano-composite PDMS membranes were used to separate ethanol from aqueous solution by pervaporation. It was found that the addition of the three kinds of modified silica particles could all significantly improve the pervaporation performances of the composite membranes. With the increase of the three kinds of modified silica content in the membranes, the flux all increase significantly and then maintains within a certain range, while the separation factors first increase and then decrease for all silica-PDMS composite membranes. The effects of the three kinds of silane coupling agents on the permeation flux are as followed: HEMS>MEMS>AMES. The separation factor of silica-PDMS composite membranes modified by MEMS is similar to AEMS, while HEMS is far less than the other two. When the added content of silica modified with MEMS was4wt%, the separation factor reached the maximum value of11.17and the permeation flux maintained about216.1g·m-2·h-1in10wt%ethanol/water solution at40℃.