Removal of cationic methylene blue and malachite green dyes from aqueous solution by waste materials of Daucus carota

In present study adsorption capacity of waste materials of Daucus carota plant (carrot stem powder: CSP and carrot leaves powder: CLP) was explored for the removal of methylene blue (MB) malachite green (MG) dye from water. The morphology and functional groups present were investigated by scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectroscopy. The operating variables studied were pH, adsorbent dose, ionic strength, initial dye concentration, contact time and temperature. Equilibrium data were analysed using Langmuir and Freundlich isotherm models and monolayer adsorption capacity of adsorbents were calculated. Kinetic data were studied using pseudo-first and pseudo-second order kinetic models and the mechanism of adsorption was described by intraparticle diffusion model. Various thermodynamic parameters such as enthalpy of adsorption Delta H degrees, free energy change Delta G degrees and entropy Delta S degrees were estimated. Negative value of Delta H degrees and negative values of Delta G degrees showed that the adsorption process was exothermic and spontaneous. Negative value of entropy AS showed the decreased randomness at the solid liquid interface during the adsorption of MB and MG onto CSP and CLP. (C) 2011 King Saud University. Production and hosting by Elsevier B.V. All rights reserved.