Crosslinked aminated lignin hydrogels as functional materials for anionic dye removal

In this study, a crosslinked aminated lignin hydrogel (CALH) was synthesized via the Mannich reaction and evaluated for its potential application in dye removal. The chemical structure of the hydrogel was characterized using Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses, confirming the formation of crosslinking bonds between aminated lignin and poly(ethylene glycol) diglycidyl ether (PEGDGE). The dye adsorption capacity of CALH was assessed using congo red (CR) and methyl orange (MO) as model dyes. The adsorption experiments demonstrated that CALH exhibited strong chemical adsorption through electrostatic interactions and NH–π interactions, facilitated by the introduced amino groups. The adsorption behavior followed a pseudo-second-order kinetic model and was well described by the Langmuir isotherm, indicating monolayer adsorption. The maximum adsorption capacity of CALH for CR and MO was determined to be 170.42 and 195.45 mg·g−1, respectively, highlighting its potential as an efficient adsorbent for dye removal.