Abstract
Microporous organosilica membranes based on 1,2-bis(triethoxylsilyl)ethane (BTESE) were fabricated via an acid-catalyzed sol-gel technique. In the preparation process, the calcination temperature plays a significant role in structural and surface properties of the organosilica networks. With an increase in calcination temperature, the surface hydrophilicity decreased due to the enhanced condensation of Si-OH groups in the networks. N2 adsorption results suggest that the pore structures of BTESE membranes was clearly dependent on the calcination temperature. The pore sizes of the membranes were quantitatively determined by using the Normalized Knudsen-based permeance (NKP) model. In pervaporation tests, the membranes with higher calcination temperatures showed higher salt rejections and lower water permeances, which was attributed to the changes in pore size and surface chemistry of pore walls. The BTESE membranes calcined at 200 °C exhibited superior hydrothermal stability in temperature cycles up to 70 °C and high reproducibility in concentration cycles with NaCl concentrations of 0.2–13 wt%, showing great promise for desalination applications of high-salinity water.
Highlights
The desalination of seawater or brackish water offers a steady supply of clean, fresh water for continuously growing populations
The structural and surface properties of the BTESE networks were finely tailored by changing the calcination temperatures
The surface hydrophilicity of the BTESE networks decreased with an increase in calcination temperature due to the enhanced condensation of Si–OH
Summary
The desalination of seawater or brackish water offers a steady supply of clean, fresh water for continuously growing populations. Compared with the RO process, PV has the advantage of nearly 100% salt rejection and the energy consumption is essentially independent of the feed salinity This feature makes PV suited for desalination of high-salinity water, such as produced water from oil or gas production [10]. Qi et al fabricated BTESE membranes with pore size of 0.362–0.454 nm by firing at 400–600 ◦ C together with a predesigned heating rate and dwelling time [27] These membranes calcined at high temperatures are not appropriate for the applications in water desalination, because the silica networks with small pore size and less silanol groups would hinder the rapid transport of water molecules. BTESE-derived organosilica membranes were fabricated at low calcination temperatures of 100–300 ◦ C and applied to pervaporation of aqueous solutions with varying salinity levels. The desalination performances and transport properties for these membranes with different calcination temperatures were discussed
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