Adsorption of hexavalent chromium ions from aqueous solutions using nano-chitin: kinetic, isotherms and thermodynamic studies

Abstract

Treatment of the industrial wastewater before discharging into aquatic ecosystems using a new technology such as nanotechnology seems necessary. There are different methods for the removal of the heavy metals in the wastewater. In this study, nano-chitin was purchased from the Nano-Novin Polymer Company and used as an adsorbent for the removal of chromium (VI) ions from aqueous solution in a batch system. The effects of pH, temperature, contact time, concentration, and adsorbent dose were investigated. According to the results, the optimum conditions of adsorption occurred at pH = 6, temperature = 25 °C, 60 minutes contact time, and 0.6 g·L−1 adsorbent dose. Investigation of equilibrium isotherms showed that the isotherm fitted the Freundlich model with a correlation coefficient of R2 = 0.9689. The pseudo second-order model with the larger correlation coefficient had a greater fitness against experimental data in the kinetic studies. Thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy were calculated, which indicated spontaneous, endothermic, and random processes, respectively. Given the good results of this project, nano-chitin can be suggested as a novel adsorbent which is highly capable of adsorbing hexavalent chromium from aqueous solutions. Highlights Nano-chitin was purchased from the Nano-Novin Polymer Company.; Nano-chitin as a novel adsorbent is highly capable of adsorbing chromium from aqueous solutions.; The results showed that pH = 6, adsorbent dose of 0.1 g/L, 25 °C and 60-minute contact time were the optimum adsorption values in this research.; The results showed the data better fitted the Freundlich isotherm model and kinetic pseudo-second-order model.;

Keywords

• adsorption
• cr (vi)
• isotherm
• nano-chitin
• nanotechnology