Facile preparation of core–shell magnetic Fe3O4@ZIF-8-PSS for organic dye adsorption

Abstract

Metal–organic framework (MOF) materials have great potential for solving dye contamination problems due to their excellent organic dye adsorption properties. However, MOF adsorbents present a tremendous drawback of poor separability. Herein, core–shell Fe₃O₄@ZIF-8-PSS with abundant active sites and sensitive magnetic responses was synthesized in one step via simultaneously introducing imidazole ligands and poly(sodium-4-styrenesulfonate) (PSS) modifiers into the dispersion of Fe₃O₄ microspheres. These magnetic Fe₃O₄@ZIF-8-PSS microspheres can be magnetically separated and recovered in only 10 seconds. Moreover, the addition of PSS increases the active sites of Fe₃O₄@ZIF-8-PSS, which is more favorable for the adsorption of organic dyes. The maximum adsorption capacity for crystal violet (CV) can reach 382 mg g⁻¹. The adsorption process was consistent with the Langmuir isotherm and pseudo-second-order kinetic models. The adsorption mechanism of Fe₃O₄@ZIF-8-PSS for CV is mainly attributed to electrostatic interactions and π–π interactions. The effects of solution pH and coexisting ions on the adsorption capacity were adequately discussed. These studies suggest that Fe₃O₄@ZIF-8-PSS not only has efficient adsorption properties but can also be easily separated by external magnetic fields after being used for organic dye wastewater treatment, which may endow it with considerable potential for wastewater treatment.