Dye adsorption using low cost carbon adsorbent from agrowaste-pearl millet cob husk

Abstract

Activated carbon (MHAC) has been derived from the millet cob husk in a single step activation at a temperature of 600^oC, impregnation ratio of 2:1 and residence time of 120 min. The Brunauer–Emmett–Teller (BET) surface area of the MHAC is 1342 m²/g and the scanning electron microscopy (SEM) images and Fourier-transform infrared spectroscopy (FT-IR) are similar to commercial activated carbon. The dye removal performance of the generated carbon has been investigated using methylene blue (MB) using following parameters; contact time, initial concentration of MB, pH and temperature. Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D-R) adsorption isotherms and three kinetic models have been studied. The adsorption equilibrium data is best fitted to Langmuir isotherm with R² value of 0.972 .The adsorption kinetics show that pseudo-second-order kinetic model fits better with the experimental data of MB adsorption by MHAC than pseudo-first-order kinetic model. Regeneration of the carbon has been carried out for five cycles and 85.34 % MB could be adsorbed by the spent carbon, after fifth cycle.