Cation exchange hybrid membranes prepared from PVA and multisilicon copolymer for application in alkali recovery

Cation exchange multisilicon copolymer with a long main chain and many branched chains as well as high content of cation exchange and -Si(OR)3 groups has been developed from sodium allylsulfonate (SAS) and vinyltrimethoxysilane (VTMS). The corresponding PVA/SiO2 cation exchange hybrid membranes have been prepared via the sol-gel process of the copolymer with poly(vinyl alcohol) (PVA). The hybrid membranes have the water uptake (W-R) 84-106%, ion exchange capacity (IEC) 0.14-0.45 mmol/g, initial decomposition temperature (IDT) 225-233 degrees C and tensile strength (TS) 23.9-44.0 MPa. They are stable in 1 M NaOH solution with a linear expansion ratio (LER) of 17.7-18.3% and a weight loss percent of 4.3-5.5% for 30 days. The diffusion dialysis (DD) process for the alkali mixture indicates that the dialysis coefficients of NaOH (U-OH) are around 0.0065-0.0086 m/h and the separation factors (S) are in the range of 24.4-51.6 for the NaOH/Na2WO4 system and 13.9-9.6 for the NaOH/NaAlO2 system. Hence, the hybrid membranes can be potentially applied in the DD process for the alkali recovery. (c) 2012 Elsevier B.V. All rights reserved.