Non-charged PVA-SiO2 hybrid membranes for potential application in diffusion dialysis

摘要

Non-charged PVA-SiO2 hybrid membranes are prepared from the sol-gel reaction of polyvinyl alcohol (PVA) and methacryloxypropyl trimethoxy silane (γ-MPS) or poly(γ-MPS). As the polymerization degree increases from y-MPS to poly(γ-MPS), the sol-gel solution becomes turbid or generates precipitation, while the formed silica particles in the hybrid membranes become smaller from 1.0-3.4 μm to 0.1-0.2 μm or disappear. The membrane tensile strength (TS) generally increases from 35 MPa to 44 MPa, while the elongation at break (E_b) decreases from 318% to 141%. Three deductions are proposed according to the structure of poly(γ-MPS), membrane swelling behaviors in 65-85 °C water and 65 °C alkaline solution, and the diffusion dialysis (DD) performance. (1) As poly(γ-MPS) contains no ion-exchange groups like the multisilicon copolymer [1], it tends to become inhomogeneous during sol-gel process, which reduces its crosslinking ability. (2) The membrane structure is generally stable in 65 °C water with the swelling degrees of 140-347%, but is damaged in 85 °C water or 65 °C alkaline solution. (3) Non-charged hybrid membranes can be potentially applied in DD process. The dialysis coefficient of NaOH (U_(OH)) is in the range of 0.0069-0.0127 m/h, and the separation factor (S) is in the range of 19-92. The OH" ions may be transferred in the hybrid membranes through PVA OH groups and interstices between organic and inorganic phases, according to the mechanisms of adsorption-desorption and free diffusion, correspondingly.