Mineralized polyacrylonitrile-based ultrafiltration membranes with improved water flux and rejection towards dye
2013
Chen, Xiao-Na | Wan, Ling-Shu | Wu, Qing-Yun | Zhi, Suo-Hong | Xu, Zhi-Kang
In this work, we employed CaCO₃ mineralization to greatly improve the water flux and dye rejection of polyacrylonitrile-based (PAN) ultrafiltration membranes. PAN-based membranes were prepared with 1.0–5.0wt% of poly(acrylic acid) (PAA) as a matrix for mineralization. These membranes were subsequently mineralized with CaCO₃ by an alternate soaking process (ASP). The optimized mineralization condition was 10 cycles of ASP with 100mM CaCl₂ and Na₂CO₃ 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 CaCO₃ 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 1.0wt%, 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 Ca²⁺ in the mineralization of CaCO₃ as well as the enhanced hydrophilicity by CaCO₃. The mineralized membranes even showed a high rejection of Congo red, which makes them potential in nanofiltration for dye-polluted wastewater.
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