The present study explores the process of adsorption by Nutraceutical Industrial Fennel Seed Spent (NIFSS), a byproduct of Nutraceutical Industry, for the removal of Malachite Green (MG), a toxic cationic dye. In this process, the effect of various factors like initial dye concentration, adsorbent dosage, temperature, pH and particle size were studied. The experimental equilibrium data were analyzed using Langmuir, Freundlich and Tempkinisotherms. The adsorption kinetics of pseudo-first order, pseudo-second order models were used for the kinetic studies. The value of maximum adsorption capacity (qm = 103.09 mg/g) was close to the experimental value (qe = 98.0mg/g), and correlation coefficient (R2 ) of0.964. The experimental data fitted very well to pseudo-second order kinetic model. The values of thermodynamic parameters like ΔG0 , ΔH0 and ΔS0 indicated that adsorption was almost spontaneous and endothermic in nature. The low value of ΔH0 suggests that the process is predominantly a physical one. From the Fourier-transform Infrared Spectroscopy (FTIR) spectra and scanning electron microscopy (SEM) images, it was apparent that MG is adsorbed onto NIFSS. Possible mechanisms of interaction that occur in MG-NIFSS system are discussed. Experimental results suggest that NIFSS is a fast and effective adsorbent for removing MG from aqueous solutions.
