Investigation of adsorption performance of chitosan for the removal of hexavalent chromium from aqueous solutions

Abstract

Hexavalent chromium is a highly toxic pollutant that exists in industrial wastewater effluents. The efficient removal of Cr(VI) from these effluents before their discharging into the environment is of great importance. Biopolymer chitosan was used as an adsorbent for the removal of Cr(VI) ions from aqueous solutions. The adsorbent characterization was carried out by scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Batch adsorption experiments were conducted to evaluate the effects of different parameters, such as contact time, solution pH, adsorbent dose, initial Cr(VI) concentration and ionic strength, on Cr(VI) removal. The obtained results revealed that the adsorption equilibrium was accomplished within 60 min. The adsorption was highly dependent on the solution pH and the maximum removal of Cr(VI) occured in the pH range 2.0-3.5. Analysis of kinetic parameters of Cr(VI) adsorption showed that pseudo-second order model described the kinetics for the investigated system. The data were fitted using two equilibrium adsorption models-Langmuir and Freundlich isotherm. The adsorption equilibrium data fit the Langmuir equation and the maximum adsorption capacity was found to be 91.4 mg g-1. The presence of co-existing anions at higher concentrations significantly reduced the removal of Cr(VI) by chitosan. According to the presented results, it can be concluded that biopolymer chitosan has a great potential for application in the treatment of chromium contaminated wastewaters.