Integrating Green Chemistry and Analytical Spectroscopy for Brilliant Blue G Removal Using Amberlite XAD7HP Resin

This work presents an integrated green chemistry and analytical approach for the removal of Brilliant Blue G (BBG) using the non-ionic poly(acrylate) resin Amberlite XAD7HP (XAD7HP), emphasizing structure-property-performance relationships relevant to the resin's adsorption behavior. The UV-Vis method used for BBG quantification exhibited excellent linearity in the 10-30 mg/L range (R² = 0.9998). Batch adsorption experiments performed over 15-800 mg/L revealed a well-defined saturation profile, with the Langmuir model providing the best fit (R² = 0.9999) and indicating a monolayer capacity of 117 mg/g and highly favorable adsorption (R_L = 0.001). Kinetic evaluation showed rapid initial uptake followed by intraparticle diffusion, with the pseudo-second-order model offering the highest correlation (R² = 0.9811), while Weber-Morris analysis confirmed the contributions of both film and pore diffusion. FTIR-ATR analysis revealed only minor shifts (<10 cm^-1) in characteristic bands, confirming physisorption driven by hydrogen bonding, π-π interactions, dipole-dipole forces, and hydrophobic effects, without structural modification of the resin. SEM/EDX imaging demonstrated significant morphological changes after adsorption, including partial pore blockage and deposition of dye aggregates within the meso-macroporous network. XRD patterns confirmed the structural stability of the resin, while TG-DSC analysis highlighted its thermal robustness and suitability for reuse. Desorption studies showed that acidic-alcoholic systems (MeOH-HCl, EtOH-HCl) ensured the highest BBG recovery, supporting the regenerability of XAD7HP. Overall, the combined spectroscopic, kinetic, equilibrium, and morphological evidence demonstrates that XAD7HP is a stable, efficient, and reusable resin for BBG removal, offering a sustainable remediation pathway aligned with green analytical chemistry principles.