Document Type : Research Article
Science and Research Branch, Islamic Azad University, Tehran, I.R. IRAN
In this study, processed chicory leaf powder was used as a natural adsorbent to remove cobalt ions from aqueous media. Natural adsorbents was charactrization by several methods include X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform spectroscopy (FTIR), Brunauer-Emmet-Teller (BET) and Particle size analyzer (PSA). A set of experiments was performed to detect the optimal conditions and to investigate the effects of various parameters such as initial concentration, contact time, adsorbent dose, solution pH and temperature on the percentage of removal. The optimal conditions for cobalt removal were: pH = 6-8, contact time 20 min, adsorbent dose 20 mg and initial concentration 15 (mg L-1). Adsorption data showed that the adsorption process is more compatible with Langmuir's isotherm. The kinetic data were consistent with the quasi-second-order model with a valid correlation coefficient. Calculation of thermodynamic values showed that the adsorption process is spontaneous, with decreasing entropy and exothermic. Finally, the introduced sorbent was compared with a strong adsorbent such as carbon nanotubes doped with silver nanoparticles (Ag2O-MWCNT). The optimal conditions for the removal of cobalt ions by the processed synthetic adsorbent were: initial concentration of 10 mg L-1, contact time of 40 min, amount of adsorbent 30 mg and pH = 7. Adsorption data showed that the adsorption process for cobalt ions is compatible with Freundlich's isotherm. The kinetic data were consistent with the quasi-second-order model with a valid correlation coefficient. Calculation of thermodynamic values showed that the adsorption process was spontaneous and exothermic. The results of this comparison show that the introduced natural adsorbent performs even better than the synthetic and expensive adsorbent and provides a promising outlook if further processing and modifications are performed on this adsorbent.