Adsorption Behavior and Mechanism of Methylene Blue by AA / AMPS / NVP Hydrogel

ABSTRACT Dye pollution in aquatic environments poses severe threats to ecological systems and human health. Hydrogels, featuring abundant functional groups and large specific surface area, are promising dye adsorbents. We aimed to develop a facile, rapid synthesis strategy for hydrogels with superior swelling performance and high cationic dye adsorption capacity. This was achieved via free radical copolymerization of AA, AMPS, and NVP. The synthesized hydrogel AA/AMPS/NVP exhibits a remarkable swelling ratio of 1202 g·g −1 in deionized water and 175 g·g −1 in 0.9% NaCl solution. Adsorption experiments reveal that the methylene blue (MB) adsorption capacity of the hydrogel is influenced by contact time, initial MB concentration, temperature, and solution pH. Kinetic analysis shows that the adsorption process is fitted by the pseudo‐second‐order model. Isotherm study indicates that MB adsorption follows the Langmuir model, with a maximum adsorption capacity of 1290.54 mg·g −1 . After 5 adsorption–desorption cycles, the MB removal efficiency remains at 58.38%. FT‐IR analysis shows that chemical adsorption dominates the interaction between MB molecules and the hydrogel, involving electrostatic attraction and hydrogen bonding between MB cations and functional groups (COOH, SO 3 H) of the hydrogel. Collectively, AA/AMPS/NVP exhibits great potential as an efficient and reusable adsorbent for the remediation of wastewater.