Equilibrium, Kinetics and Thermodynamics Studies on the Bisorption of Textile Dyes onto Polyamidoamine Dendrimer Functionalized Soy Hull

In this work, the soy hull has been modified with polyamdioamine dendrimer to prepare a kind of new adsorbents possessing abundant nitrogen functional groups. The adsorption behaviors of the modified soy hull for methyl blue (MB), acid fuchsine (AF), and malachite green (MG) were studied. The removal efficiency of the three organic dyes was in the order of AF>MB>MG, and its values increased with increasing contact time. The adsorption kinetics was studied by pseudo-first-order and pseudo-second-order kinetics models, and the adsorption isotherms were studied by Langmuir and Freundlich isotherm. The pseudo-second-order model and Freundlich isotherm were found to fit well the adsorption processes of the modified soy hull. Thermodynamic data of the adsorption processes were also calculated according to the adsorption thermo-chemistry between the modified soy hull and organic dyes molecules. The values of △G (for MB, AF and MG) are negative, which shows that the adsorption process is spontaneous. The positive value of △H indicates that the adsorption is endothermic and higher temperature makes the adsorption easier. The positive value of △S indicated that the randomness is increased at the solid-solution interface during adsorption process.