Enhanced adsorption of Cr (VI) from aqueous solution by zirconium impregnated chitosan microspheres: mechanism and equilibrium

Abstract

ABSTRACT The present paper reports a novel adsorbent that is synthesized with chitosan and zirconium ions through a simple method, for the removal of Cr (VI) ions from solutions. In this study, the effects of solution pH, absorbent dosage, contact time, and initial concentration were evaluated through a series of experiments. The modified chitosan was also characterized by SEM-EDS, FTIR, TG, and XPS. It is found that the Cr (VI) adsorption capacity by Zr-CS of 230.41 mg/g, was achieved at pH 4.5. The adsorption results indicated that the adsorption process was in line with Langmuir isotherm at 25°C. At the same time, the kinetic studies indicated that the adsorption process followed a pseudo-second-order model. Therefore, Zr-CS is a very promising adsorbent for the treatment of chromium-containing wastewater. XPS and element spectrum images, however, showed the difference between the adsorbent before and after Cr (VI) adsorption. According to the data, the adsorption should include electrostatic interaction between protonated amino and Cr (VI) as well as complexation of Zr with Cr (VI). According to the experimental data, it is believed that zirconium-modified chitosan adsorbent is an effective adsorbent for removing chromium ions in the solution.