科研之友
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摘要
Non-charged PVA-SiO2 hybrid membranes are prepared through sol-gel process among polyvinyl alcohol.(PVA) and double cross-linking agents, which are selected from four types of alkoxysilanes including tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), gamma-aminopropyl triethoxysilane (APTEOS) and methacryloxypropyl trimethoxy silane (MPS). The double cross-linking agent can combine their advantages including different hydrolysis rates of -OC2H5 and -OCH3 groups, high compatibility of -NH2, and polymerizable C=C bonds. @@@ The -NH2 group from APTEOS can 'enhance membrane homogeneity, thermal stability and flexibility due to its compatibility with PVA-OH groups. The membranes have high selectivity (62-101) but low permeability in diffusion dialysis process for separating NaOH/Na2WO4 solution. Single type of -Si (OCH3) groups produces large silica particles (1.5-5 mu m), which reduce membrane stability but enhance permeability. The membrane has low strength and flexibility, and high swelling degrees in 65 degrees C water (373-408%) and weight loss percentage in 65 degrees C NaOH solution (25.8-28.7%). The permeability can reach up to 0.0076-0.0092 m/h but the selectivity is only 23.7-25.0 at 20-40 degrees C. The combination of -Si(OCH3) and -Si(OC2H5) groups (TEOS and MPS) can obtain high strength and flexibility (20.3 MPa, 571%), acceptable swelling degrees (232-279%) and balanced permeability and selectivity (0.0043-0.0071 m/h, 45110). Hence, double cross-linking agents can be combined to prepare optimized neutral membranes for diffusion dialysis.
