Sol–gel derived poly(vinyl alcohol)/maleic acid/silica hybrid membrane for desalination by pervaporation

Abstract

Highly dispersed homogeneous hybrid polymer-inorganic membranes based on poly(vinyl alcohol) (PVA), maleic acid (MA) and inorganic silica were synthesized via a sol-gel method. Tetraethoxy-silane (TEOS) was used as the silica precursor with MA as an additional crosslinking agent. A range of techniques such as FTIR, SEM, TGA, XRD and DSC were used to characterise the nanostructure and properties of hybrid membranes. Results revealed silica nanoparticles (<10 nm) were well dispersed in the polymer matrix with chemical bonding between the organic and inorganic phases. Thermal properties of the hybrid membranes were significantly enhanced when compared with pure PVA membranes, and swelling of PVA based hybrid membranes was greatly suppressed.The chemically crosslinked PVA with maleic acid and silica resulted in the formation of new hybrid membranes with improved pervaporation properties for desalination application. The pervaporation separation performance of aqueous salt solution was found to be directly related to the diffusion coefficient of water through hybrid PVA/MA/silica membranes. Introduction of MA and silica at given amounts into the polymer chain increased the amorphous region of the membrane and favoured the diffusion of water molecules through the membrane. A water flux of 6.93 kg/m 2 ·hr with salt rejection of >99.5% was achieved at a 6 Torr vacuum and 22°C.

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

“…The kinetic desorption method is well established for characterising the salt transport properties of polymer membranes [12,13,14,15]. A typical NaCl desorption curve from the kinetic desorption experiments in this study is shown in Figure 3.…”

“…Without heat treatment, the crosslinking reactions among PVA, MA and TEOS, and also the polycondensation of TEOS are most likely incomplete. Especially, the esterification reactions between PVA and MA in the aqueous phase, since they are generally favoured by heating [12]. As a result, the unheated membranes tended to swell due to their less compact structure and consequently, hydrated NaCl was solvated by the water in the membrane and the salt rejection was lower.…”

“…In our previous work [11,12], we have demonstrated that a new type of hybrid organic-inorganic membrane could be fabricated via a sol-gel route based on PVA, MA and TEOS. The hybrid membrane has shown significantly improved swelling and thermal properties.…”

Separation of aqueous salt solution by pervaporation through hybrid organic–inorganic membrane: Effect of operating conditions

“…In our recent work, the pervaporation separation of aqueous salt solution was carried out to evaluate the pervaporation performance of hybrid organic-inorganic membranes based on PVA, maleic acid (MA) and silica [13]. We found that the hybrid PVA/MA/silica membrane showed superior performance with a high water flux (up to 5.5 kg/m 2 .hr) and a very high salt rejection (up to 99.9%).…”

Suppressing Salt Transport through Composite Pervaporation Membranes for Brine Desalination

“…GO: graphene oxide. The freestanding films' swelling properties were also studied as it is closely related to the membrane's cross-linking density and free volume [12]. The equilibrium water content (EWC) values of freestanding films (Table 3) in both Mill-Q water and 100 g/L NaCl aqueous solution were investigated.…”