Polydopamine-modification of a magnetic composite constructed from citric acid–cross-linked cyclodextrin and graphene oxide for dye removal from waters

The effect of polydopamine (PDA) modification on aminated Fe 3 O 4 nanoparticles (Fe 3 O 4 -NH 2 )/graphite oxide (GO)/β-cyclodextrin polymer cross-linked by citric acid (CDP-CA) composites were studied for the removal of a cationic dye (methylene blue, MB) and an anionic dye (Congo red, CR) from waters. The micro-structural and magnetic characterizations confirmed the successful preparation of Fe 3 O 4 -NH 2 /GO/CDP-CA and PDA/Fe 3 O 4 -NH 2 /GO/CDP-CA composites. The maximum MB and CR adsorption capacities of Fe 3 O 4 -NH 2 /GO/CDP-CA were 75 mg/g and 104 mg/g, respectively, while the corresponding amounts for PDA/Fe 3 O4-NH 2 /GO/CDP-CA composite were 195 mg/g and 64 mg/g, respectively. The dye sorption behaviors of these two composites were explained by their corresponding surface-charged properties according to the measured zeta potential results. Moreover, the high saturation magnetizations and the stable dye removal rate in the adsorption–desorption cycles indicated the good recyclability and reusability of the fabricated composites. Graphical abstract