Preparation and properties of polyvinyl alcohol (PVA)/amino-modified mesoporous silica (AMMS) composite membranes for diffusion dialysis

It is a plaguing problem of obtaining high ion flux while maintaining high selectivity during the diffusion dialysis (DD) process. However, functionalized mesoporous silica-based composite membrane is considered to be one of the effective candidates to solve it. Here, we report amino-modified mesoporous silica (AMMS) blended with pre-crosslinked polyvinyl alcohol (PVA) solution, after which a series of composite membranes were obtained to maintain high ion flux and selectivity. The fundamental properties of as-prepared membranes were tested, including water uptake (WR), alkali resistance, mechanical and thermal properties. The results of WR (181.7%–289.7%), alkali resistance (with swelling degree in the range of 250%–471% and mass loss in the range of 27.6%–35.3%), mechanical (with tensile strength (TS) in the range of 29.9–41.8 MPa and elongation at break (Eb) in the range of 135.3%–180.4%), and thermal (degradation temperature was higher than 200 °C) properties demonstrated that the as-prepared membranes possess higher water uptake and moderate alkali resistance and can be potentially applied in alkaline DD process. Further, microscopic morphologies of as-prepared membranes confirmed well dispersion of AMMS in PVA matrix and good compatibility between the two phases, which could be attributed to the hydrogen bonding between –NH2 of AMMS and –OH of PVA molecular. NaOH/Na2WO4 system was introduced to evaluate separation performance of as-prepared membranes via DD process and the effect of AMMS was detected preliminarily. The results indicated that amino-modified mesoporous silica (AMMS) blended with pre-crosslinked polyvinyl alcohol (PVA) membrane possessed high ion flux and selectivity simultaneously, and had strong practical application prospects. The mesopores and –NH2 groups of AMMS promoted the transport of OH− via hydrogen bonds synergistically. [Display omitted] •PVA/AMMS composite membranes were prepared by blending PVA and AMMS.•The composite membranes were used for alkali recovery via diffusion dialysis process.•UOH and S of composite membranes improved simultaneously with suitable dosage of AMMS.