Optimization and Modeling of Brilliant Yellow Removal Via Neodymium-Infused Polymeric Hydrogel: A Central Composite Design Study

This study investigates the adsorption performance of a neodymium (III)-reinforced Poly(acrylamide-co-N-vinylimidazole) hydrogel composite [P(AAm-co-NVI)/Nd3+] for the removal of brilliant yellow (BY) dye from aqueous media. The hydrogel structure and metal–polymer interactions were characterized using FT-IR, TGA, SEM, and XRD analyses. The adsorption process was systematically optimized using a central composite design (CCD) approach combined with response surface methodology (RSM). The CCD-RSM second-order model exhibited a good fit to the experimental data (R2 = 0.9350), as supported by ANOVA. Numerical optimization revealed a maximum removal efficiency of 99.13% at a hydrogel dosage of 0.08 g/100 mL, an initial BY concentration of 81.68 mg/L, and a contact time of 61.73 min. Langmuir and the Freundlich isotherms were used in modeling the adsorption data. When the correlation coefficients of both models were compared, it was observed that the Langmuir isotherm provided a better fit for adsorption. The enhanced adsorption performance is attributed to the presence of Nd3+ ions, which promote additional electrostatic interactions and coordination sites between the hydrogel matrix and anionic dye molecules. The results demonstrate that Nd3+-reinforced hydrogels can serve as efficient and tunable adsorbent systems, particularly when process parameters are optimized statistically.