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 (RL = 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.