Hydrothermal synthesis of phosphorylated chitosan and its adsorption performance towards Acid Red 88 dye

Phosphorylated chitosan (P-CS) was successfully synthesized using a facile experimental setup of hydrothermal method that was applied to the adsorption of anionic Acid Red 88 (AR88) from aqueous media. The adsorption process obeyed the pseudo-second-order (PSO) kinetic model. In contrast, the adsorption isotherm conformed to the Langmuir model, with the maximum adsorption capacity (qm = 230 mg g−1) at 303 K. Both external and intraparticle diffusion strongly influenced the rate of adsorption. The insights from this study reveal that P-CS could be easily prepared and regenerated for reusability applications. The adsorption mechanism and intermolecular interaction between P-CS and AR 88 were investigated using Fourier transform infrared (FTIR) spectroscopy and calculations via Density Functional Theory (DFT). The key modes of adsorption for the P-CS/AR 88 system are driven by electrostatic attractions, H-bonding, and n-π interactions. The findings herein reveal that P-CS is a promising adsorbent for the removal of anionic dyes such as AR88 or similar pollutants from water. •Phosphorylated chitosan was prepared as an adsorbent.•The adsorbent was characterized by SEM-EDX, ATR-FTIR, BET, and XRD.•Acid Red 88 is adsorbed favorably by the adsorbent at 30 °C (qm = 230 mg g−1).•Pseudo-second order kinetic and Langmuir isotherm adsorption models yield best fits.•The high adsorption uptakes was related to the different modes of adsorption.