Optimization of the integral valorization process for orange peel waste using a design of experiments approach: Production of high-quality pectin and activated carbon

The aim of this study was to optimize the integral valorization of orange peel waste by obtaining activated carbon after a process of pectin recovery in recycling of orange peel by transformation to value-added products of pectin extraction and activated carbon preparation. The study was supported by statistical analysis, and the significant factors and optimal conditions were obtained from the statistical analysis. Using a representative sample of orange peel waste, a yield of 29.37% pectin was recovered at the optimal operating conditions (phosphoric acid as the extraction agent, 95 °C as the impregnation temperature and a 2-hour extraction time). Activated carbon (AC) was prepared from the remaining solid residue. The conditions that improve the resulting material quality were H₃PO₄ [0.6 M] used as the activating agent, an impregnation temperature of 95 °C, a carbonization temperature of 400 °C and 1 h of carbonization time. The obtained AC showed a sorption capacity of 2342.91 mg g^-1, a value higher than that reported for commercial activated carbon. Using a model dye chemical, the sorption kinetics and thermodynamics of AC were found to follow a pseudo-second-order rate and the Freundlich models, respectively. Using the process conditions obtained in this study, it was possible to optimize the yield and also obtain good-quality products from valorization of orange peel.