Nanoporous activated carbon materials from pomelo peel for efficient adsorption of anionic and cationic dyes

Abstract Activated carbons derived from agricultural wastes, forestry residues, and municipal wastes serve as eco-friendly, low-cost adsorbents and are gaining attention for various environmental applications. Here we report the preparation of nanoporous activated carbon from a novel biomass carbon source, Pomelo peel, by using the phosphoric acid activation method. The phosphoric acid was mixed with Pomelo peel powder at a 1:1 weight ratio and then carbonized at three different temperatures (400, 500, and 600 °C) for three hours in a nitrogen gas atmosphere. Iodine and methylene blue adsorption were used to determine the basic adsorption phenomenon. The result showed the highest iodine number of 868.68 mg/g and methylene blue number of 255.63 mg/g for the sample carbonized at 400 °C (PPC_400). Nitrogen adsorption/desorption measurement showed a high specific surface area of 1424 m2/g and a large pore volume of 1.55 cm3/g. Due to the well-developed porosity, large surface area, and oxygenated surface functional groups, such as hydroxyl, carbonyl, and carboxyl, PPC_400 showed excellent adsorption of anionic dye (Lanasyn-black, LB) and cationic dye (Methylene-blue, MB), and the adsorption phenomena could be described by the Langmuir isotherm model. The adsorption capacity was ca. 232.55 and 217.39 mg/g, respectively. The adsorption kinetics indicated that the adsorption process followed the pseudo-second-order model (R² = 0.99) for both LB and MB dye adsorption on PPC_400.