Optimization of waste paper pretreatment using response surface methodology for enhanced cellulose recovery efficiency

Abstract

This study focuses on optimizing the pretreatment process of waste cardboard using sodium hydroxide (NaOH) to recover high-purity cellulose for biological and industrial applications. Response Surface Methodology (RSM) combined with Central Composite Design (CCD) was used to investigate and optimize technological parameters, including NaOH concentration, temperature, treatment time, and the NaOH-to-paper ratio. A bleaching step using sodium hypochlorite (NaClO) was subsequently applied to improve cellulose purity. The optimal conditions were found at a temperature of 100°C, treatment time of 3.5 hours, 2.5% NaOH concentration, and a NaOH-to-paper ratio of 70/1 mL/g, resulting in a maximum impurity removal efficiency of 40.347%. The treated samples were characterized by field-emission scanning electron microscopy (FE-SEM) to observe surface morphology and Fourier-transform infrared spectroscopy (FTIR) to identify changes in chemical functional groups. This study contributes to enhancing paper recycling efficiency, minimizing solid waste, and promoting environmentally friendly and sustainable paper production processes. Recovered cellulose can be applied in the production of biofilms, biomedical materials, composite materials, or bio-adsorbent products, thereby increasing the utilization value of recycled materials and advancing the circular economy model.