Self-assembled hydrogels constructed via host-guest polymers with highly efficient dye removal capability for wastewater treatment

In this study, new self-assembled hydrogels constructed by cyclodextrin polymer (P-CD)/ferrocene-modified poly acrylic acid (PAA-Fc) were designed and prepared via host-guest interactions. These obtained hydrogels were characterized by different methods such as Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric (TG) and specific surface area tests. SEM images confirmed that the prepared hydrogels had a three-dimensional (3D) porous network structure with pore size ranging from several hundred nanometers to several tens of micrometers. The network structure of the hydrogels could be adjusted by varying the concentrations of P-CD. In addition, the gel-sol transition process would occur when the gel has redox stimulation. In particular, the prepared hydrogels have different adsorption mechanisms in the adsorption of poisonous organic molecules, including bisphenol A (BPA) and methylene blue (MB). It was found that the adsorption process had high pH dependence. The adsorption data for BPA and MB were found to be consistent with the pseudo-first-order model and the pseudo-second-order model, respectively. The maximum adsorption capacity of the hydrogel material reached 23.61 mg/g for BPA and 24.64 mg/g for MB. Present hydrogels removed BPA mainly via host-guest interaction and removed MB by hydrogen bonding and electrostatic interaction. Present obtained hydrogels provided new clues for the design of environmentally friendly hydrogel adsorbents.