Mineralized polyacrylonitrile-based ultrafiltration membranes with improved water flux and rejection towards dye

In this work, we employed CaCO 3 mineralization to greatly improve the water flux and dye rejection of polyacrylonitrile-based (PAN) ultrafiltration membranes. PAN-based membranes were prepared with 1.0–5.0   wt% of poly(acrylic acid) (PAA) as a matrix for mineralization. These membranes were subsequently mineralized with CaCO 3 by an alternate soaking process (ASP). The optimized mineralization condition was 10 cycles of ASP with 100   mM CaCl 2 and Na 2 CO 3 solutions. The resulted membranes were characterized with field emission scanning electron microscopy , X-ray diffraction, and energy dispersion X-ray analysis combined with elemental distribution mapping. The mineralized CaCO 3 particles were found to be deposited throughout the membranes. Results also indicated that the pure water flux of PAN-based membranes decreased with PAA if the content was larger than 1.0   wt%, which was due to the stretching of PAA chains deriving from the electrostatic repulsion of COO − groups. In contrast, the mineralized membranes showed a dramatic increase of water flux owing to the chain collapse of PAA caused by the formation of complexes with Ca 2+ in the mineralization of CaCO 3 as well as the enhanced hydrophilicity by CaCO 3 . The mineralized membranes even showed a high rejection of Congo red, which makes them potential in nanofiltration for dye-polluted wastewater.