Adsorptive uptake of basic dyes from aqueous solution by novel brown linseed deoiled cake activated carbon: Equilibrium isotherms and dynamics

In present work, various process parameters for the adsorptive removal of acridine orange and azure B onto a novel activated carbon prepared from brown linseed (Linum usitatissimum L.) deoiled cake with phosphoric acid activation were optimized. The activated carbon was characterized using FTIR, surface area (adsorption desorption isotherm), field emission-scanning electron microscopy, and X-ray diffraction studies. Isotherm data were modeled using non-linear Langmuir, Freundlich, Temkin and D-R equations. Freundlich isotherm model best fitted the data with good correlation coefficient, suggesting heterogenous distribution of adsorption sites. The adsorbent demonstrated high Langmuir monolayer saturation capacity (Q(m)) of 213.57 for acridine orange and 136.58 mg/g for azure B. Pseudosecond-order kinetic model followed the kinetic data, with liquid-film diffusion controlling the overall adsorption rate. The negative Delta G degrees values (5.92-13.15 kJ/mol for AO and 10.21-20.98 kJ/mol for AzB) confirmed the feasibility and spontaneity of the process. The positive values of Delta H degrees (17.16-75.48 kJ/mol) indicated endothermic adsorption. (C) 2016 Elsevier Ltd. All rights reserved.