Taguchi Method-Based Optimisation of Activated Carbon from Couroupita guianensis for Methylene Blue Removal

Introduction: In this study, a natural waste, Couroupita guianensis, is used to produce chemically activated carbon for the removal of methylene blue. Methods: The preparation parameters were studied using the Taguchi method, and the adsorption capacity and rate-limiting mechanisms were determined using the kinetics, equilibrium, and thermodynamic studies. An L16 (4 × 3) orthogonal array was used with activation temperature, activation time, and impregnation ratio as parameters. Analysis of variance was applied to evaluate the interactions and influence of the variables incorporated in the experimental design. Results: Activation temperature had the greatest significance (Factor B = 65.12%). Adsorption kinetics were best described by the diffusion-chemisorption model. BET Type II isotherm best described the equilibrium analysis (R2 = 0.9667). Within the tested concentration range, the highest experimental sorption capacity observed was 183.9 mg/g. The thermodynamic studies showed ΔG° values fell within the 0 to -20 kJ/mol range. Discussion: The BET Type II isotherm suggests multilayer formation on the surface interface. CGF-OC-AC performed well compared to other precursors. ΔG° values implied that physisorption was likely a dominant adsorption mechanism, and a positive (ΔH°) enthalpy change indicated that the process was endothermic. Conclusion: This study shows that the Taguchi method is effective for determining preparation parameters, while ANOVA and regression equations accurately predicted results within standard variations. This research also demonstrates a suitable protocol for the preparation of activated carbon and the ability of CGF-OC-AC in removing methylene blue from aqueous solutions.