Ureidoarene–heteropolysiloxane as alkali transport promoter within hybrid membranes for diffusion dialysis

Abstract

Alkali transport promoter is designed from 3-(ureidoarene)propyltriethoxysilane (UPTS), which takes sol–gel process to form ureidoarene–heteropolysiloxane (UHPS) within polyvinyl alcohol (PVA). Hence PVA-based hybrid membranes are obtained for diffusion dialysis (DD) application. Besides, sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) is used as reference to compare the formation of alkali transport promoter within different polymer matrix.The micro-aggregation of UHPS within PVA leads to loose structure, while within SPPO leads to plenty of clusters within 0.1–0.5μm. The membrane swelling resistance is improved but the alkaline stability is reduced in the presence of UHPS. The PVA-based membranes have the tensile strength (TS) of 19–52MPa, and the elongation at break (Eb) of 343–534%. DD results show that the dialysis coefficients of OH− (UOH) are in the range of 0.01–0.022m/h in the presence of UHPS, which are about 2–5times higher than the blank PVA or SPPO membranes. The separation factors (S) are in the range of 26–32, which are also higher than the blank membranes. Hence, UHPS can act as alkali transport promoter for DD process. The effect of UHPS is affected by the membrane matrix and micro-aggregation degree.