Equilibrium, kinetic and thermodynamic studies of the adsorption of heavy metals from aqueous solution by thermally treated quail eggshell

Abstract

Background and Objective: Nowadays, the contamination of water resources by heavy metals has resulted in serious health issues. The metals in their elemental as well as chemically combined form are toxic, non-degradable and persistence in nature. Thus, there is need to develop a simple, efficient and economical method for removing dissolved heavy metals from water/wastewater. In the present study, it was aimed to prepare a new adsorbent from agricultural waste in order to remove Cu2+ and Zn2+ from aqueous solution. Materials and Methods: Calcium oxide (CaO) based material was prepared from quail eggshell, characterized and used as adsorbent for the removal of Cu2+ and Zn2+ from aqueous solution. Calcined quail eggshell at 900EC was studied and exhibited high adsorption capacity. The effects of variables affecting the adsorption process, contact time, adsorbent dosage, temperature and initial heavy metals concentration were investigated at fixed pH of 4.5. Results: At contact time of 30 min, adsorbent dosage of 1.5 g, temperature of 35°C and initial Cu2+ and Zn2+ concentration of 150 mg L-1, the maximum heavy metals uptake could be achieved. Based on the value of correlation coefficient, the experimental results for Cu2+ best fitted the Langmuir isotherm model with monolayer adsorption capacity of 13.49 mg gG1, while Freundlich isotherm model was best fitted to the experimental results for the Zn2+ adsorption. The kinetics and thermodynamic behaviours of the adsorption process were also investigated. Conclusion: The obtained results showed that the experimental data were in good agreement with pseudo-second-order kinetic model. The results from thermodynamic analysis revealed that the process is spontaneous and endothermic.