Nanosilica reinforced ion-exchange polyHIPE type membrane for removal of nickel ions: Preparation, characterization and adsorption studies

Highly porous styrene/2-ethylhexylacrylate/divinylbenzene polymerized high internal phase emulsion (ST/2EHA/DVB polyHIPE) solid foams reinforced using various amounts of silica nanoparticles (SNPs) were prepared via emulsion templating. The neat and reinforced solid foams were successfully functionalized using sulfuric acid (98%) to introduce the sulfonic groups in the resultant ion-exchange polyHIPE membranes. The effect of SNPs level on the morphology and mechanical properties of the neat and reinforced foams was investigated. The ion-exchange capacity (IEC) of the resulting membranes was measured by titration procedure. The results showed that increasing SNPs level up to 3 wt% enhanced IEC from 3.6 to 3.9 meq g−1 and improved the water uptake (WU) due to increasing SO3H groups inside the polyHIPE type membranes. The efficiency of 3 wt% SNPs reinforced membrane for adsorption of nickel ions was evaluated. The effect of crucial parameters, such as initial nickel concentration, pH of the solution, and membrane contact time, on the removal efficiency was investigated using surface response methodology (SRM) experiment design. Additionally, the adsorption behavior of the membrane was evaluated using different kinetic and isotherm models. The results showed that the adsorption kinetic behavior was in a good agreement with the pseudo-first-order and Elovich model in the low and high nickel concentrations, respectively. Furthermore, the adsorption of nickel ions was fit well on Freundlich adsorption isotherm. The reusability of the reinforced polyHIPE membrane was evaluated for five sorption-desorption cycles.