Itaconate-functionalized hydrochar derived from co-hydrothermal carbonization of PVC and bamboo for the methylene blue adsorption

To develop an efficient and green adsorbent for cationic dye removal, a one-step method was developed to prepare the IFPHC adsorbent, involving the solvent-free radical copolymerization of itaconic acid with a bamboo/PVC co-hydrothermal carbon. The reaction was initiated by ammonium persulfate under alkaline conditions. The performance of the resulting IFPHC was assessed for its efficacy in removing methylene blue (MB) from water, demonstrating a high adsorption capacity. Characterization results from Zeta potential, BET, FTIR, XPS, and SEM demonstrated a high density of carboxylate functional groups on the material, accounting for its high affinity for cationic pollutants. As determined by the Langmuir model, IFPHC exhibited a maximum MB adsorption capacity of 613.94 mg·g⁻¹ at 298 K. The adsorption behavior was accurately captured by the Langmuir isotherm and pseudo-second-order kinetics, suggesting a monolayer chemisorption process. Combined characterization analysis confirmed that electrostatic attraction and hydrogen bonding were the primary mechanisms. The former occurred between IFPHC's anionic groups and MB's cationic –N(CH₃)₂⁺ moiety, while the latter involved IFPHC's C–OH/carboxylate groups and the N atom in MB's phenothiazine ring. Therefore, this work demonstrates that solvent-free radical copolymerization provides a green and practical alternative to conventional solvent-based methods for fabricating functional hydrochar. It simultaneously addresses the valorization of PVC-containing waste and the remediation of dye-laden wastewater, presenting a novel strategy that fills the gap for scalable and sustainable adsorbent synthesis. • Itaconate-functionalized co-hydrothermal carbon adsorbent was prepared by solvent-free radical copolymerization. • IFPHC shows superior adsorption performance than IFHC due to its surface hydroxyl and carboxylate functional groups. • The main adsorption mechanism was electrostatic attraction, π-π interactions, ion exchange and hydrogen bonding. • Solvent-free radical copolymerization is an environmentally friendly method for fabricating efficient functional sorbents.