Abstract:
In this study, silica sodalite (SSOD) nanoparticles were synthesized by topotactic conversion
and functionalized using HNO3/H2SO4 (1:3). The SSOD and functionalized SSOD (fSSOD)
nanoparticles were infused into a Polysulfone (Psf) membrane to produce mixed matrix membranes.
The membranes were fabricated via the phase inversion method. The membranes and the nanoparticles
were characterized using Scanning Electron Microscopy (SEM) to check the morphology of the
nanoparticles and the membranes and Fourier Transform Infrared to check the surface chemistry of
the nanoparticles and the membranes. Thermal stability of the nanoparticles and the membranes
was evaluated using Themogravimetry analysis (TGA) and the degree of hydrophilicity of the membranes
was checked via contact angle measurements. The mechanical strength of the membranes
and their surface nature (roughness) were checked using a nanotensile instrument and Atomic
Force Microscopy (AFM), respectively. The textural property of the nanoparticles were checked by
conducting N2 physisorption experiments on the nanoparticles at 77 K. AMD-treatment performance
of the fabricated membranes was evaluated in a dead-end filtration cell using a synthetic acid mine
drainage (AMD) solution prepared by dissolving a known amount of MgCl2, MnCl2 4H2O, Na2SO4,
Al(NO3)3, Fe(NO3)3 9H2O, and Ca2OH2 in deionized water. Results from the N2 physisorption
experiments on the nanoparticles at 77 K showed a reduction in surface area and increase in pore
diameter of the nanoparticles after functionalization. Performance of the membranes during AMD
treatment shows that, at 4 bar, a 10% fSSOD/Psf membrane displayed improved heavy metal rejection
>50% for all heavy metals considered, expect the SSOD-loaded membrane that showed a
rejection <13% (except for Al3+ 89%). In addition, coating the membranes with a PVA layer improved the antifouling property of the membranes. The effects of multiple PVA coating and behaviour of
the membranes during real AMD are not reported in this study, these should be investigated in a
future study. Therefore, the newly developed functionalized SSOD infused Psf membranes could
find applications in the treatment of AMD or for the removal of heavy metals from wastewater.
