Waste-derived-lignin based hydrogel as a reusable adsorbent for efficient removal of dyes from aqueous solution

for RhB. Isotherm analysis justified that adsorption followed the Freundlich isotherm model, suggesting multilayer adsorption on a heterogeneous surface, while kinetic studies revealed a pseudo-second-order nature. Thermodynamic analysis confirmed that the adsorption process is spontaneous and endothermic. The adsorption mechanism is governed by a combination of electrostatic interactions, hydrogen bonding, and π-π interactions. The hydrogel also demonstrated worthy reusability, maintaining performance over five adsorption-desorption cycles. Therefore, the lignin/PVA hydrogel could be a cost-effective, sustainable, and reusable adsorbent for dye removal from wastewater.