Design of self-healable and recyclable multi-network hydrogels for efficient and selective removal of cationic dyes

In this study, a novel multi-network hydrogel with self-healing ability was developed with the aim of addressing the limitations of traditional hydrogels in adsorption processes for organic contaminant removal from water. The hydrogel was designed by incorporating poly(acrylic acid) (PAAc) and poly(vinyl alcohol) (PVA) to create both chemical and physical crosslinked networks, while a dynamic ionically crosslinked network was introduced using Fe3+. A comprehensive range of characterization techniques confirmed the successful formation of the multinetwork hydrogel. Compared to hydrogels with fewer networks, the newly developed PAAc/PVA@Fe3+ hydrogel exhibited significant enhancements in various key aspects. Notably, it demonstrated improved swelling kinetics, mechanical properties including compression strength, Young's modulus, and stretchability, and a remarkable self-healing ability with an efficiency of 88 % at 25 degrees C after an 8 h contact period. In batch experiments, the PAAc/PVA@Fe3+ hydrogel displayed selective adsorption capabilities, particularly for cationic dyes like methylene blue (MB), even in binary dye systems. Moreover, the hydrogel showcased impressive recycling and reusability, maintaining an MB removal efficiency of over 60 % even after undergoing 10 reuse cycles. An essential aspect of its performance was the preservation of its adsorption efficiency even after consecutive selfhealing processes. The unique combination of selective adsorption, self-healing ability, and robust recycling performance positions this hydrogel as a promising candidate for efficient and sustainable water treatment solutions.