Synthesis of mesoporous carbon–silica nanocomposite water-treatment membranes using a triconstituent co-assembly method

Abstract

A direct synthesis method is introduced to prepare mesoporous carbon-silica nanocomposite (CSN) membranes for water-treatment applications. Unlike the intricate and expensive nanocasting method, this triconstituent co-assembly method is a one-pot synthesis method using Pluronic F127 as templating agent with a hybrid organic-inorganic matrix formed by tetraethylorthosilicate (TEOS), resorcinol and formaldehyde. The silica content is varied in the polymer solution to investigate the material properties, stability of the nanocomposite mesostructured and membrane performance in vacuum membrane distillation (VMD). The CSN materials are carbonised under nitrogen at temperatures of 600-900 °C without any significant lattice shrinkage, demonstrating excellent stability. They possess a highly ordered pore structure with moderate BET surface area (430-550 m 2 g -1 ) and narrow pore size distribution at around 5.5-7.6 nm. Based on the FTIR and NMR analyses, there is no covalent bond between the carbon and silica networks, but the carbon compound was found to affect the condensation degree of the silica. Raising the temperature from 700 to 900 °C leads to further condensation of the carbon network, which in turn releases hydroxyl or water groups that can attack adjacent siloxane bonds. The CSN membranes performed well in VMD with water permeation flux up to 12 L m -2 h -1 and salt rejection > 99 %. This work shows that a different strategy of modifying silica-based membrane can be successfully applied for the desalination of saline waters through VMD.

Analytical Understanding of the Materials Design with Well‐Described Shrinkages on Multiscale

“…In case of carbon‐silica nanocomposite, unique shrinkage behavior is occurred because of the rigidity of silica inside flexible polymer. Such carbon–silica nanocomposites can be synthesized from tetraethylorthosilicate (TEOS), resorcinol and formaldehyde using Pluronic F127 . Condensation of polymeric frameworks can be understood by tracing the change of the FTIR spectra during carbonization.…”

“…Such carbon-silica nanocomposites can be synthesized from tetraethylorthosilicate (TEOS), resorcinol andf ormaldehyde using Pluronic F127. [4] Condensation of polymeric frameworks can be understood by tracing the change of the FTIR spectra during carbonization. In addition, removal of Pluronic F127 is also confirmed by FTIR;p eaks at 2882 and 1345 cm À1 corresponds to Pluronic F127 disappeared after carbonization ath ight emperature.…”

“…Enormous efforts have been devoted to distinguish such shrinking behaviors and their mechanisms. After the systematic analysis is carried out, a lot of evidence based on experimental results shows that the inductive factors of shrinkages consist of a capillary force at drying process, molecular‐level condensation, template removal (especially for porous materials), phase transition at high temperature, changing in bond length, and so on . So far, various analytical tools and methods have been facilitated for observing the variations in the structure of materials from molecular scale to micro‐ and macroscales.…”

“…After the systematica nalysisi sc arriedo ut,alot of evidence based on experimental results shows that the inductive factorso fs hrinkages consist of ac apillary force at drying process, molecular-level condensation, template removal (especially for porous materials), phase transition ath igh temperature, changing in bond length, and so on. [2][3][4][5][6][7] So far,v ariousa nalytical tools and methods have been facilitated for observing the variations in the structureo fm aterials from molecular scale to micro-and macroscales. Precise measurement and in situ observation are beneficial for developinge fficient and innovative synthetic routes.…”

Structural evolution of nickel oxide silica sol-gel for the preparation of interlayer-free membranes

“…As a result, the silica membranes become unstable when exposed to water, rendering the membranes ineffective for desalination applications as demonstrated by Elma et al [16]. To address this problem, hybrid silica membranes were prepared with carbon templates such as surfactants [17,18] and triblock co-polymers [19], where the organic template was carbonised into carbon moieties inside the silica matrix, or using organo-silica precursors [20,21] to introduce non-hydrophilic C\ \C bridges between silicon atoms in order to reduce propensity of water hydrolysis.…”