Use of humin as an alternative material for adsorption/desorption of reactive dyes

The objective of this work was to determine the optimum conditions for adsorption/desorption of reactive dyes, using both batch experiments and fixed bed columns with humin immobilized on silica. Results of batch experiments showed that adsorption of Reactive Orange 16 and Reactive Red 120 by humin was most effective at pH 1.0. Adsorption equilibrium was achieved rapidly for all initial dye concentrations employed. Temperature measurements indicated that the process was exothermic, and described by a pseudo-second order kinetic model for both dyes, while the Freundlich and Langmuir isotherms best described the adsorptions of RO 16 and RR 120, respectively. Column experiments showed adsorption efficiencies of 62.1 to 39.6% and 96.2 to 74.8%, and desorption efficiencies of 81.4 to 51.3% and 66.8 to 36.8% for RO 16 and RR 120, respectively, over three cycles. The biosorbent presents excellent performance in removal of reactive dyes, with the advantage that it can be regenerated and reused. (C) 2011 Elsevier B.V. All rights reserved.