Fabrication of a novel “loose” nanofiltration membrane by facile blending with Chitosan–Montmorillonite nanosheets for dyes purification

The novel hybrid material, clay/polymer nanocomposite has represented a desired alternative for designing the mixed matrix membranes (MMMs) due to their excellent overall performance, such as good hydrophilic nature, high mechanical strength, enhanced thermal stability, etc. In this study, we report a feasible method to fabricate a novel “loose” nanofiltration membrane by blending with Chitosan–Montmorillonite (CS–MMT) nanosheets via phase inversion method. The results of FT-IR, XRD and TEM showed that CS–MMT nanosheets were successfully fabricated. It was found that the hydrophilicity and water flux of hybrid membranes greatly improved after adding CS–MMT nanosheets. Meanwhile, the hybrid membranes exhibited a preferable antifouling property, that is, high flux recovery ratio (ca. 92%) and low total flux decline ratio (ca. 0.26) when CS–MMT content was only 1.0 wt.%. Additionally, CS–MMT nanosheets provided an enhanced mechanical property, thus giving rise to significant promotion in both tensile strength and elongation at break of the hybrid membranes. More importantly, the “loose” nanofiltration membrane showed higher rejection for Reactive Black 5 and Reactive Red 49, and lower rejection for bivalent salts unlike the conventional nanofiltration membranes. Therefore, the “loose” nanofiltration membrane could be used for dyes purification with low pressure and high efficiency.