An efficient reusable perylene hydrogel for removing some toxic dyes from contaminated water

The synthesis of adsorbents that meet the need for large‐scale production at relatively low cost that are capable of removing anionic and cationic toxic dyes from aqueous solutions, with high sorption capacity and reusability, is urgently needed from an environmental and industrial viewpoint. In this context the identification of hydrogels that remove dyes efficiently under ambient conditions and at near‐neutral pH, without the necessity pre‐treatment is an imperative. In this study we report the preparation of two hydrogels using the redox polymerization of acrylamide, hydroxyethyl methacrylate (HEMA) and N‐isoporpylacrylamide, H1 and acrylamide, HEMA, N‐isoporpylacrylamide and perylene‐5‐ylpent‐3‐yne‐2‐methylprop‐2‐enoate‐co‐2‐methyl‐2‐(prop‐2‐enoylamino) propane‐1‐sulfonic acid (PePnUMA‐Co‐AMPS), H2. These hydrogels proved to be effective for the removal of methylene blue (MB), fuchsin acid (FA) and congo red (CR) from aqueous solution at near‐neutral pH where their adsorption behaviour was in keeping with the Langmuir model having qmax values of 769.2 mg g−1 (MB), 1666.7 mg g−1 (FA) and 2358.2 mg g−1 (CR) respectively. Adsorption of MB and FA by these hydrogels follows pseudo‐first‐order kinetic, whilst the adsorption of CR follows pseudo‐second‐order kinetics. Detailed hermodynamic analysis indicated that the dye–adsorbent interaction as primarily one of physisorption in nature. Finally, desorption studies carried out in 1.0 M NaClO4 indicated that these adsorbents could be recycled at least four times using a variety of dyes while maintaining their mechanical properties.