Thermodynamic properties of dye removal from colored textile wastewater by poly(propylene imine) dendrimer

In this paper, the thermodynamic properties of textile dye removal from aqueous solutions using poly(propylene imine) (PPI) dendrimer were studied. Direct Red 80 (DR80) and Acid Green 25 (AG25) were used as model dyes. The surface coverage of dendrimer was obtained to investigate the adsorbent characteristics. The effect of temperature on dye removal has been studied at different dye concentrations. The adsorption isotherms (Langmuir and Freundlich) and kinetics (pseudo-first-order and pseudo-second-order) were studied in various temperatures. Thermodynamic parameters such as free energy of adsorption (Delta G), enthalpy (Delta H), and entropy (Delta S) changes were calculated to predict the nature of the adsorption. It was found that the isotherm data of DR80 and AG25 followed Langmuir model at different temperatures. Adsorption kinetics of dyes was found to conform to pseudo-second-order with a good correlation coefficient. The estimated values for G showed that the adsorption process was spontaneous. Based on the data of the present study, it can be concluded that PPI dendrimer, as an eco-friendly material, is a suitable adsorbent for the elimination of dyes from colored textile wastewater at different temperatures.