Abstract:
This work investigates hybrid silica membranes by mixing tetraethyl orthosilicate
(TEOS) and triethoxy vinyl silane (TEVS) by employing K2S2O8 (KPS) as initiator.
KPS aims to provide radical polymerization to create C - C bonds linkage as a
secondary network and then generates more spaces in silica network. Then free
radical polymerization formed by KPS affects the oriented growth of particles. In
order to avoid the decomposition of C - C groups within the silica matrices, it was
found that the calcination temperature of xerogels recommends up to 350°C.
Densification was formed when TEVS composition ratio is greater than TEOS
composition. Therefore, the TEVS:TEOS molar ratio was set as 10:90 whilst
microporosity was attained. This indicates that pure TEVS is not suitable to
produce amorphous silica due to the functional groups formed block pores. The
water fluxes found (< 2 kg m-2 h-1), however, the water fluxes for the hybrid
organo-silica membranes reduced slightly only as a function of the salt content in
the saline water, contrary to pure silica. This strongly suggests that the salt
concentration polarisation was greatly reduced by having carbon moieties
embedded into silica matrices. The water fluxes increased significantly from 4 to
21-24 kg m-2 h-1 as the temperature was raised from 40 to 60 °C whilst
maintaining salt rejections in excess of 99%. This was mainly attributed to the
linear organic C-C chains embedded in the silica matrices. In conclusion, the
incorporation between organic-inorganic network enhance the hydrophobic
properties of silica matrices.
