ZIF-8/CS/PVDF Composite membranes: dye separation and self-cleaning properties exploration

With the rapid progress of urbanization and industrialization, water pollution has become an increasingly serious issue, particularly due to dye wastewater, which contains numerous harmful substances and is difficult to treat effectively. Dye wastewater contains many harmful substances and is difficult to treat effectively. Traditional treatment methods are often inefficient and economically unsustainable. In contrast, membrane separation technology offers high separation efficiency and environmental benefits, making it a promising approach for water purification. Therefore, in this paper, the hydrophilic modification of PVDF membranes was carried out by adding ZIF-8 and chitosan(CS), and at the same time, the membranes were endowed with the ability of light self-cleaning. ZIF-8, a metal–organic framework (MOF) material, was synthesized using water as the solvent through the reaction of zinc nitrate with 2-methylimidazole. The PVDF membranes were modified by physical co-mingling, and ZIF-8/CS/PVDF composite membranes with different contents of ZIF-8 and CS were prepared by the submerged precipitation phase transition method. The performance test results demonstrated that the composite membranes doped with ZIF-8 and CS exhibited significant improvements in water contact angle, pure water flux, and dye wastewater treatment performance. Notably, the modified membranes showed exceptional dye removal efficiency and enhanced resistance to membrane fouling. Furthermore, the results of photocatalytic self-cleaning experiments revealed that the modified membranes effectively degraded Congo red and methylene blue dyes under Xenon lamp irradiation, highlighting their excellent photocatalytic self-cleaning capability. These findings suggest that the ZIF-8/CS/PVDF-modified membrane holds great potential for water treatment and self-cleaning applications, achieving up to 93.06% dye rejection and a pure water flux of 95.89 L m⁻² h⁻¹, more than double that of the pristine PVDF membrane.