Adsorption kinetics and thermodynamics of methylene blue by HKUST-1

Abstract

The removal of Methylene Blue (MB) from water samples was successfully achieved with high efficiency of 94.2% at 298 K after 60 min using Basolite C300 (or HKUST-1) as a new class of emerging adsorbent called metal organic frameworks. The effect of different experimental parameters, namely dye concentration (50, 150, 200, and 300 mg/L), adsorbent dosage (50, 100, and 150 mg), and temperature (298, 313, and 323 K) was investigated. The adsorption of MB onto HKUST-1 was confirmed using several characterization tests including X-ray diffraction, scanning electron microscope, energy dispersive X-Ray analyzer, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The Langmuir and Freundlich isotherm models were applied to correlate the adsorption isotherms. Although the experimental data fit both models, the Langmuir model is more suitable for higher adsorbent dosage while the Freundlich model is better for lower adsorbent dosage. Based on the Langmuir isotherm, the maximum adsorption capacity of MB onto HKUST-1 reached 250 mg/g. Furthermore, the adsorption kinetic studies showed that the pseudo-second-order kinetic model yields the best fit for the kinetic data with a regression constant, R 2 , of (0.9916 to 0.9998). The thermodynamic studies revealed that the process is exothermic (ΔH° = –112.172 kJ/mol) and spontaneous (ΔG° negative) in nature.