Evaluation of a functionalized copolymer as adsorbent on direct dyes removal process: Kinetics and equilibrium studies

Functionalized polymeric microbeads were investigated as adsorbent for the removal of three direct dyes from aqueous solutions. The effects of different experimental parameters, such as initial dye concentration, temperature, and solution pH on the adsorption process were investigated. The adsorption process can be conducted with very good result at normal working conditions: neutral pH and normal temperature. The maximum percentage removal obtained was 99.11% for the symmetrical disazo dye, 90.14% for asymmetrical disazo dye, and 98.53% for trisazo dye. The adsorption kinetics followed the pseudo-second-order equation for all three investigated dyes in all working conditions. The experimental data were fitted to Langmuir, Freundlich, Sips, and RedlichPeterson isotherm models, and the best fit was obtained with Sips model. Thermodynamic parameters (?H degrees, ?S degrees, and ?G degrees) revealed that dye adsorption is an endothermic and spontaneous process. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013