Preparation of ultrahigh‐water‐content nanofiber composite hydrogel for Cd 2+ removal

BACKGROUND The rising volumes of industrial wastewater discharge are causing an ecological crisis, which has become a challenge for humans. Herein, a novel ultrahigh‐water‐content nanofiber composite (NC) hydrogel was prepared as an efficient adsorbent for cadmium ion (Cd 2+ ). This hydrogel has a porous and loose 3D cross‐linked structure and the polymer chains are interspersed with titanium dioxide (TiO 2 ) nanofibers, which provide a supporting framework for the NC hydrogel. RESULTS The adsorption of Cd 2+ on the NC hydrogel could rapidly achieve the equilibrium and the maximum adsorption capacity ( q max ) of 76.92 mg g −1 at pH 7 and 293 K. The intraparticle diffusion was the rate‐controlling step in the adsorption process, however, the diffusion coefficient ( D ) was just 2.57 × 10 −10 m 2 s −1 at 298 K, much lower than that of activated carbon. After five adsorption–desorption cycles, the NC hydrogel still maintained a certain adsorption efficiency, obtaining a regenerability close to 95.8%. Simultaneously, results of X‐ray photoelectron spectroscopy analysis revealed that the adsorption was mainly caused by the ion exchange between Cd 2+ and calcium ion (Ca 2+ ), and partly due to the chemisorption of Cd 2+ by hydroxyl groups. CONCLUSION These results suggest that the innovative NC hydrogel can be a potential adsorbent material for removing heavy metal ions from industrial effluent. © 2020 Society of Chemical Industry