Advanced statistical and nonlinear modeling approach for dye adsorption onto a sustainable Casuarina-based...

The sustainable microporous adsorbent made from Casuarina equisetifolia cones (CBMA) are examined for the removal of malachite green (MG) dye from wastewater. A high Brunauer-Emmett-Teller (BET) surface area of 736.59 m²/g and many surface functional groups like hydroxyl and carboxyl was revealed by BET, BJH, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and Fourier transform infrared (FTIR) spectroscopy analysis of the CBMA, which was synthesized by thermal carbonization at 400 °C. Nonlinear regression was used to fit isotherm models in order to predict the adsorption process. The Freundlich model was shown to be the greatest fit by statistical ranking using (Akaike information criterion (AIC) = 0.990, Bayesian information criterion (BIC) = 1.384), indicating that MG uptake takes place on a heterogeneous surface with different site energies. According to kinetic study, the pseudo-second-order model (R² = 0.998) best describes the adsorption process. Thermodynamic evaluations established that the adsorption is spontaneous (ΔG° < 0) and endothermic (ΔH° = 16.793 kJ/mol), with a low activation energy (E_a = 15.399 kJ/mol) consistent with a diffusion-controlled process. Response surface methodology (RSM) via a quadratic analysis of variance (ANOVA) model (R² = 0.9913) was utilized to optimize the operational parameters. A contact of 47.14 min, a dose of 0.367 g, and a starting MG concentration of 60.50 mg/L indicated a maximum removal effectiveness of 96.86%.