Dual-Stage Response Surface Methodology Optimization of Sugarcane Bagasse Biochar Production and Methylene Blue Adsorption

Agricultural waste valorization into functional carbonaceous materials addresses critical challenges in waste management and water pollution remediation.This study developed an integrated dual response surface methodology framework for optimizing sugarcane bagasse biochar production and methylene blue (MB) adsorption.Pyrolysis optimization via face-centered Central Composite Design (RSM-CCD) evaluated temperature and residence time effects on biochar yield and carbon content.Analysis of variance confirmed highly significant quadratic models with excellent predictive capabilities for both responses.Optimal pyrolysis conditions of 500 °C and 75 min produced biochar with 31.4% yield and 82.3% carbon content, achieving an effective balance between carbonization extent and material recovery.Subsequent adsorption optimization using Box-Behnken Design (RSM-BBD) systematically investigated initial dye concentration, temperature, and contact time at fixed pH and biochar dosage.The adsorption capacity model exhibited exceptional fit statistics, with initial concentration identified as the dominant influencing factor.Optimum adsorption conditions of 50 mg/L MB, 38.1 °C, and 65.1 min achieved 99.1% removal efficiency with 4.91 mg/g adsorption capacity.FTIR, XPS, and SEM characterization revealed abundant oxygen-containing functional groups, aromatic carbon structures, and hierarchical pore networks that facilitate dye adsorption through electrostatic interactions, π-π stacking, and hydrogen bonding mechanisms.