Repurposing Plastic Waste Into Chemically Activated Carbon as Functional Adsorbents: Kinetic Analysis for Phenol Degradation and Methylene Blue Adsorption

This study explores the conversion of plastic into NaOH and HNO₃ activated carbon (NHAC and HNAC) and ceria-impregnated activated carbon prepared using microwave and hydrothermal methods (Ce-M + AC and Ce-H + AC) for environmental applications. The focus is on the catalytic oxidation of phenolic compounds and adsorption of methylene blue dye. FTIR analysis confirmed the presence of functional groups critical for adsorption. SEM and BET analyses revealed that HNAC had the lowest surface area (0.735 m²/g) and largest particle size (88.64 μm), and Ce-H + AC shows the highest surface area (442.71 m²/g) and smallest particle size (14.73 μm). In catalytic wet oxidation of phenol, Ce-H + AC achieved a degradation efficiency of 99.6% due to better surface properties and metal functionality; however, HNAC (97.65%) was less effective due to its limited surface properties. In the case of methylene blue adsorption, Ce-H + AC shows again the highest performance with 99.92% adsorption, and HNAC shows the lowest adsorption performance with 14.54% adsorption. Adsorption kinetics followed the pseudo–second-order model, with most samples showing high R² values, except the HNAC sample. This research highlights the potential of repurposing plastic waste into effective adsorbents for environmental remediation.