Optimization of Activated Carbon Production from Coffee Husks Using a Box-behnken Design

Abstract

The constraints of ecological transition require the development of environmentally friendly technologies for industrial wastewater treatment. In this context, this study focuses on the production of activated carbon from coffee husks, an abundant local agricultural waste. The objective is to reduce both environmental impact and production costs while ensuring high adsorption performance for pollution control. The process was optimized using a four-factor Box–Behnken experimental design implemented with Design-Expert software (version 13.0.5.0). The investigated variables included the concentration of the activating agent (orthophosphoric acid), impregnation time, calcination temperature, and calcination time. The iodine number was selected as the response variable. Based on 27 experimental runs, optimal conditions were identified at 15% activating agent, 10 hours of impregnation, and calcination at 400 °C for 120 minutes, yielding an iodine number of 346.367 mg.g⁻¹. The predicted values were in good agreement with the experimental results. Statistical analysis confirmed the adequacy and reliability of the model (R² = 0.9778, predicted R² = 0.8719, Adequacy = 22.96), indicating a strong predictive capability. SEM–EDS analysis and methylene blue adsorption measurements revealed a high mesoporous surface area of 762.74 m².g⁻¹. These findings demonstrate the feasibility of producing eco-efficient activated carbon from coffee husks.