Zeolitic imidazolate framework-8/graphene oxide/magnetic chitosan nanocomposites for efficient removal of Congo red from aqueous solution

Abstract

The removal of Congo red (CR) from aqueous solution was reported in this work using a zeolitic imidazolate framework-8/graphene oxide/magnetic chitosan (ZIF-8-GMCS) composite as a novel bio-adsorbent. Such a ZIF-8-GMCS composite consisted of magnetic Fe₃O₄ and ZIF-8 nanoparticles, single-layer graphene oxide (GO) and chitosan (CS), where ZIF-8 nanoparticles with a relatively regular geometry were in situ grown on the surface of the composites. The surface morphology and chemical composition of ZIF-8-GMCS were characterized using various techniques. Herein, the impact of adsorbent dosage, interference of other anionic dyes, initial pH of CR, ionic strength, initial concentration of CR solution, contact time and adsorption temperature on the adsorption performance was systematically explored. The results showed that the adsorption processes follow the Langmuir isotherm model and pseudo-second-order model and the maximum adsorption capacity derived from the Langmuir model is 476.19 mg g⁻¹ at 303.15 K, which is higher than that of most magnetic adsorbents toward CR. Moreover, the adsorption of ZIF-8-GMCS toward CR could be ascribed to the cooperative effect of electrostatic, hydrogen-bonding, coordination and π–π stacking interactions. Our finding demonstrates that ZIF-8-GMCS derived from biomass resources shows potential application prospects in the decontamination of dye wastewater.