Efficient removal of methylene blue based on activated carbon derived from Pumpkin seed before analysis by UV-Vis spectroscopy

This study explores the utilization of pumpkin seeds as an abundant biomass resource and carbon precursor for the production of activated carbons. The precursor was activated at a 1:1.5 w/w ratio of pumpkin seeds to KOH at 650 °C to produce the activated carbons. SEM-EDX was used to observe the surface morphologies and compositions of the prepared activated carbons, which exhibit a clear porous surface structure and irregularly shaped particles. The activated carbons were used to remove methylene blue dye from aqueous solutions. The methylene blue concentration was determined using a UV-Vis spectrophotometer with a standard curve ranging from 5 to 25 mg L-1, and the limit of detection and limit of quantification were 0.1027 and 0.3424 mg L-1, respectively. A dosage of 0.05 g of activated carbon was sufficient to effectively remove more than 80% of the methylene blue within 5.0 min. The removal of methylene blue increases with contact time, reaching a maximum of 90% at 25 min. The removal of methylene blue is not affected by increasing temperature, but it is influenced by pH, with removal increasing as the medium becomes more alkaline. The adsorption isotherms show that the Freundlich and Temkin isotherms do not apply to the adsorption of the methylene blue onto the activated carbons. Still, the data fit well with the Langmuir isotherm model, which exhibits a high R2 value (0.998).