Abstract
This work reports on the potential of waste material of coffee grounds to produce an activated carbon as an adsorbent for methyl orange (MO) adsorption. The coffee grounds material was activated by HNO3 and 500 °C of conventional thermal process. The coffee grounds activeated carbon (CGAC) was characterized by SEM, FT-IR and pHzpc properties. Batches of tests were conducted to investigate the MO molecule removal efficiency at different pH values, contact time, adsorbent dosage, and temperatures. The concentrations of MO were analyzed using an UV-Vis spectroscopy. The maximum adsorption capacity at equilibrium (q) of MO was 658 mg/g when pH, initial concentration, contact time and temperature of MO solution are 3, 300 mg/L, 90 min and 30 ºC, respectively and the dose of CGAC was 0.05 g. The Langmuir, Freundlich and Dubinin–Radushkevich isotherms were used to analyze the experimental equilibrium data. The best fit of the experimental data was obtained by the Freundlich isotherm, having an R2 value of 0.9536, indicating the heterogeneity of the CGAC and multi-layer coverage of MO onto the CGAC adsorbent. The reaction was exothermic and the ∆G values were negative, indicating the feasibility and spontaneous nature of adsorption.
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