β-cyclodextrin and magnetic graphene oxide modified porous composite hydrogel as a superabsorbent for adsorption cationic dyes: Adsorption performance, adsorption mechanism and hydrogel column process investigates

The β-cyclodextrin/magnetic graphene oxide (β-CD/MGO) functionalized polyacrylic acid-based porous superabsorbent composite hydrogel adsorbent (β-CD/MGO/PAA) was prepared via simple one-pot polymerization. Fourier transform infrared spectra (FT-IR), Raman spectra (Raman), scanning electron microscopy (SEM), The thermogravimetric analysis (TGA) and vibrating sample magnetometry (VSM) confirmed the successfully synthesized of β-CD/MGO/PAA hydrogel. This hydrogel as-prepared combined the advantages of β-cyclodextrin, magnetic graphene oxide and polyacrylic acid, owned exceedingly plentiful carboxyl and hydroxyl groups, and provide a large number of adsorption active sites. β-CD/MGO/PAA hydrogel adsorption performance test showed excellent removal efficiency for 50 mg/L of methylene blue (MB), safranine T (ST), rhodamine B (RhB) and malachite green (MG), which were 99.1%, 98.5%, 97.1% and 95.0%, respectively. Furthermore, batch and filtration adsorption experiments towards MB and ST were carried out to investigate the adsorption capacity and mechanisms in detail. Pseudo-first-order, Pseudo-second-order, Intra-particle diffusion and Liquid film diffusion models were used to evaluate the adsorption kinetic data while Langmuir isotherm, Freundlich isotherm and Temkin isotherm models were used to evaluate adsorption equilibrium data. The adsorption capacity of MB and ST at 298 K were as high as 2802.67 mg/g and 1470.33 mg/g, respectively. Meanwhile, β-CD/MGO/PAA hydrogel can effective selectively adsorbed cationic dyes in cationic/anionic mixture dyes solution, and can quickly separate from the aqueous solution under the action of an external magnetic field. Moreover, removal efficiency of MB and ST still were reached 95.0% and 85.0% after eight adsorption–desorption cycles. We found that electrostatic interactions, hydrogen bond interactions, π-π conjugate interactions and host–guest supramolecular interactions existed between β-CD/MGO/PAA hydrogel and cation dyes molecules in adsorption process. Finally, it was demonstrated that the β-CD/MGO/PAA hydrogel was suitable for used as adsorption column packing to rapidly purify wastewater by filtration.