Optimization of Adsorption of Methylene Blue Dye on Activated Charcoal

By Abigail Seputro

Faculty Mentor: Dr. Leanna Giancarlo


Methylene blue and crystal violet are cationic dyes of high intensity that are commonly discharged in wastewater. The colored compounds in this environment inhibit sunlight penetration in waterways, resulting in the destruction of aquatic ecosystems. Activated carbon offers an attractive option for the efficient removal of dyes from wastewater due its excellent adsorption ability, highly porous structure, and large thermal/chemical stability. This study was conducted in order to investigate the adsorption of methylene blue dye from aqueous solution by various types of activated charcoal using UV-Vis spectroscopy. The effects of temperature and adsorbent quantity were studied to optimize the efficiency of the adsorption process. Crystal violet was an alternate dye used for comparison. Results revealed that a powered activated charcoal with mesh size <80 yielded the greatest adsorption as evidenced by the lowest spectroscopic absorbance. Higher temperature (25 °C vs 35 °C) also yielded greater adsorption. Varying the amount of activated charcoal had minimal effect on the adsorption process. The adsorption process was modeled with Langmuir and Freundlich isotherms. An L-shape curve resulted from the Langmuir model, indicating there were fewer open sites for the methylene blue to fill as the adsorption study progressed. The SEM images of the charcoal samples confirmed the charcoal’s porous structure and supported the adsorption of MB. The Freundlich adsorption isotherm was not applicable with the chosen amounts of adsorbent. In a future study, the concentration of methylene blue can be varied in order to remain within the linear range that the Freundlich isotherm can model.


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