Crosslinked 4,4'-methylenediphenyl diisocyanate/aminated graphene oxide/gelatin terpolymer composite as a reusable...

In this investigation, a crosslinked MDI/Am-GO/Gel terpolymer composite was engineered through the chemical terpolymerization of 4,4'-methylenediphenyl diisocyanate, gelatin, and aminated graphene oxide as a reusable bio-macromolecular adsorbent for the preferential removal of methylene blue (MB) from aqueous media. The chemical and physical properties of the MDI/Am-GO/Gel composite were analyzed using FTIR, XRD, SEM, XPS, and zeta potential measurements to identify its morphology, composition, surface charge, and crystallographic features. The composite exhibited the highest MB removal efficiency of 99.27% under neutral pH and room temperature within 60 min. The adsorption data were interpreted using kinetic and isotherm models, revealing that combined physical and chemical interactions governed the removal process. The Freundlich model best fitted the equilibrium data, while the Langmuir model estimated a maximum adsorption capacity of 322.58 mg/g. The kinetic data were better represented by the pseudo-second-order model, suggesting the contribution of chemical interactions during MB uptake. Single-solute comparative adsorption tests indicated a preferential adsorption behavior toward cationic dyes, especially MB. The recycling of MDI/Am-GO/Gel for six successive MB adsorption runs demonstrated stable adsorption performance, with a total removal decline of 10.91% after the sixth cycle. The mechanistic insight suggested that MB adsorption onto MDI/Am-GO/Gel proceeded through H-bonding, Coulombic attraction, n-π interactions, and π-π interactions. Overall, the crosslinked MDI/Am-GO/Gel composite can be considered a promising reusable adsorbent for cationic dye removal from contaminated water.