Dye removal by adsorption on KOH-modified activated carbon obtained from biomass

This study explores the potential of plant-derived waste as a precursor for activated carbon production for dye removal from aqueous media. Activated carbon was synthesized from apricot kernel shells through carbonization at 300 °C followed by chemical activation using potassium hydroxide (KOH). The resulting materials were characterized using SEM, EDX, and TG–DTG analysis. Surface acidity has been found to reduce the oxidation of carboxylic groups after the primary treatment. The adsorption performance for methyl orange (MO) and methylene blue (MB) has been investigated using UV–Vis spectroscopy to determine removal efficiency (R) and specific surface area (SSA). The maximum equilibrium adsorption capacity (qe) for MO was 345 mg/g when the solution temperature, contact time and initial concentration were 25 °C, 30 min, and 75 mg/L, correspondingly, with an AC/KOH ratio of 1:2. For MB, the maximum qe was 290 mg/g at a ratio of 1:1. The best fit for the experimental data has been achieved using the Langmuir isotherms. Moreover, chemisorption has been identified as the rate-limiting step of the removal process, and the high correlation coefficient (R2 = 0.989–0.991) for both dyes indicates a monolayer adsorption mechanism by the activated carbon surface.