Optimisation of activated carbon from fruit stones and shells derived via molten salt activation for dye removal

Abstract

Recent advancements in activated carbon production involve molten salt activation using a eutectic mixture of ZnCl₂-NaCl-KCl. This study explores the production of activated carbon from fruit waste, specifically walnut shells, using a 60:20:20 mol % eutectic mixture. Optimal conditions were identified through response surface methodology, with 400 °C and a salt-to-biomass ratio of 10 g/g, yielding a surface area of 276 m²/g. These conditions were applied to cherry, olive, and plum stones, with plum stones achieving the highest surface area of 351 m²/g. Characterization was performed through elemental and proximate analysis, gas adsorption (N₂, CO₂), and chemical adsorption of iodine and dyes. Despite some substandard qualities, the study highlights a unique mesoporous pore size distribution, with all samples exhibiting a distinct peak around 22 nm, a characteristic feature of the eutectic salt mixture used.