Effect of heat treatment on pervaporation separation of aqueous salt solution using hybrid PVA/MA/TEOS membrane

Abstract

Heat treatment is believed to be an important step in controlling the morphology and properties of polymer based membranes. In this study, hybrid organic-inorganic membrane based on poly(vinyl alcohol) (PVA), maleic acid (MA) and tetraethyl orthosilicate (TEOS) was synthesised via a sol-gel route. The effects of heating temperature and heating time on pervaporation separation performance of aqueous salt solution were studied in relation to swelling and hydrophilic properties, the free volume, salt transport properties, and water diffusivity of the membrane. The free volume of the hybrid membrane under different heat treatment conditions were well correlated with the pervaporation testing results. With increasing heating temperature or time, the fractional free volume of the hybrid membrane was reduced due to a more compact structure by crosslinking among PVA, MA and TEOS. As a result, the water flux decreased and the salt rejection increased. The salt transport properties followed a similar trend as the water uptake, indicating the hydrated NaCl was solvated by water in the membrane phase.

Poly(ether sulfone) supported hybrid poly(vinyl alcohol)–maleic acid–silicone dioxide membranes for the pervaporation separation of ethanol–water mixtures

“…As the feed volume used in the system was great enough and any feed concentration variation was negligible throughout the experiment, the apparent diffusion coefficient ( D i ) was calculated from the following equation on the basis of Fick's law: where C i is the water concentration on the feed‐side membrane surface.…”

“…We developed a sol–gel derived unsupported PVA–MA–SiO 2 hybrid organic–inorganic membrane for the separation of an aqueous salt solution . The hybrid membrane showed enhancing effects for the diffusion of water molecules through the membrane and the separation of aqueous salt solution, but the J and mechanical strength were still limited by the nature of the unsupported membrane.…”

Comparative study of PVA/SiO2 and PVA/SiO2/glutaraldehyde (GA) nanocomposite membranes prepared by single-step solution casting method

“…Figure 8 shows the effect of temperature on the water uptake properties of the PVA/SiO 2 membranes. Recently, Xie et al [40] reported a significant decrease in the water uptake of PVA/MA/TEOS hybrid membranes from 154 to 43 % when the temperature was raised from 21 to 100°C. However, our PVA/SiO 2 membranes have shown a gradual increase in W u with the increasing temperature, as shown in Fig.…”

Nanoscale homogeneity of silica–poly(vinyl alcohol) membranes by controlled cross-linking via sol–gel reaction in acidified and hydrated ethanol

“…Likewise, preparation of the hybrid membrane using simultaneous cross-linking of poly (vinyl alcohol) with maleic acid and tetraerthoxysilane for pervaporation desalination applications had been reported. [15][16][17] In another studies, poly (vinyl alcohol) blended with poly (ethylene glycol) 18 or a copolymer of poly (vinyl alcoholco-acrylic acid) 19 was cross-linked with tetraethoxysilane to prepare the hybrid membranes. The cross-linking density of the membrane was found to be increased with increase in the tetraethoxysilane content, annealing temperature and time, which resulted in increment of water permselectivity for pervaporation dehydration of ethanol.…”