Nanoscale homogeneity of silica–poly(vinyl alcohol) membranes by controlled cross-linking via sol–gel reaction in acidified and hydrated ethanol

Abstract

Organic-inorganic hybrid membrane in which nanoscale hybrid domains creating preferential pathways for selective permeation exhibits excellent performance in separation processes. Herein, a synthesis route of sol-gel reaction in acidified and hydrated ethanol to prepare silica-poly (vinyl alcohol) hybrid membrane of nanoscale homogeneity is reported. 29 Si NMR study was performed on the membrane samples to probe the connectivity of SiO4 tetrahedra in the cross-linking hybrid networks while the small-angle scattering study revealed nanostructure of the silica-polymer hybrid. TEM, DSC, IR, TGA, XRD and swelling studies were performed to study other physico-chemical properties of the membrane. The hybrid membrane exhibited superior water permeability 96 L m -2 h -1 µm than the other reported membranes in pervaporation desalination of saline water of 2000 ppm NaCl.

Fabrication of efficient pervaporation desalination membrane by reinforcement of poly(vinyl alcohol)–silica film on porous polysulfone hollow fiber

“…The change in PVA structure after crosslinking with the silanol groups of hydrolyzed TEOS is evident from the characterization results shown in Figure . These characterization results for the PVA‐SiO 2 coating layer were similar to the results for the dense PVA‐SiO 2 film obtained by evaporation of the dilute solution system . Solid PVA granules show the characteristic crystalline peak at 1141 cm −1 and the broad peak in the range of 3200–3650 cm −1 corresponding to inter‐ and intrahydrogen bonding of hydroxyl groups [Figure (a)].…”

“…The coating solution for the PVA‐SiO 2 was a dilute and acidified ethanol–water solution system in which the SiO 2 was crosslinked with PVA chains to form a polymeric hybrid network of low‐dimensional structure. The structural details of the PVA‐SiO 2 hybrid film obtained from such a dilute solution system can be found in our earlier publication . TEOS was hydrolyzed in the presence of a large amount of ethanol and HCl, which prevented a self‐condensation reaction of the silicate groups into a high‐dimensional spherical particle structure so that the hydrolyzed TEOS reacted with the PVA chains to form the coating solution.…”

“…Polymeric materials such as ion‐exchanged polyethylene, co‐polyether ester elastomers, polyether amide, and cellulose acetate have been reported for pervaporation desalination of seawater and brackish water. Organic–inorganic mixed matrix membranes based on poly(vinyl alcohol) (PVA)‐MA‐SiO 2 and PVA‐SiO 2 in a flat sheet geometry were also examined for pervaporation desalination . The preparation of inorganic membranes requires high‐temperature hydrothermal synthesis, costly inorganic supports, and calcination of a structure‐directing agent at high temperature (>800 K).…”

“…The membrane was prepared using an automated dip‐coating method of controlled sorption and evaporation of the coating solution over the support. We have also successfully demonstrated the nanoscale homogeneity of PVA‐SiO 2 membranes by controlled crosslinking of PVA with tetraethylorthosilicate (TEOS) via a sol–gel route using acidified and hydrated ethanol as a solvent . The TEOS ethanol solution was added slowly to a freshly prepared and acidified PVA aqueous solution under stirring conditions at room temperature.…”

Enhanced CO2 separation performance by PVA/PEG/silica mixed matrix membrane

“…It was observed that PVA/PEG membrane exhibited semicrystalline structure with a large peak at 2θ angle of 20°. This is due to the presence of hydroxyl groups in its side chains . It was found that with increase in silica content in the PVA/PEG membrane, crystallinity declined leading to an increase in the amorphous region.…”