Adsorption behavior of herbicide paraquat from aqueous solutions using starfish particles: kinetic, isotherm, and thermodynamic studies

The adsorption of paraquat (PQ) on starfish particles was investigated to calculate the kinetic, isotherm, and thermodynamic parameters. The experiments were carried out as a function of particle size of adsorbent, adsorbent dosage, contact time, initial PQ concentration, stirring speed, and temperature. The kinetic data followed the pseudo-second-order kinetic model, and the equilibrium data were well fitted by the Langmuir isotherm model with the maximum adsorption amount of 10.235mgg(-1) at 288K. Thermodynamic parameters, including standard Gibbs free energy changes (G(0)), standard entropy changes (S-0), and standard enthalpy changes (H-0) were also calculated. The results demonstrated that PQ was adsorbed onto starfish particles spontaneously and exothermically in nature. The adsorption process followed a physisorption mechanism. In addition, the starfish particles were successfully utilized to real sample. Hence, starfish particles are eligible for treating the wastewater containing PQ as an effective and low-cost adsorbent. (c) 2015 Curtin University of Technology and John Wiley & Sons, Ltd.