Removal of Hexavalent Chromium from Aqueous Solutions by Adsorption on Thermally Modified and Non-Modified Eggshells


Removal of heavy metals from waste water has received a great deal of attention. The compare Cr (VI) adsorption characteristics removing from wastewater by using thermally modified and non-modified eggshells were examined. Adsorption experiments were carried out in a batch process and various experimental Parameters such as effect of pH, adsorbent dosage, contact time, and initial chromium ion concentration on percentage removal have been studied. The modification of eggshells obtained by calcination which was performed in a furnace at 800ᵒC for 2h after crushing of the dried eggshells. The adsorption of chromium ions from solutions containing different initial 〖Cr〗^(+6) concentrations (50,100,150) mg/L. The results show that all factors have a significant effect on the percentage removal of 〖Cr〗^(+6) ions from aqueous solutions and the optimum pH, weight and time of treatment are (8, 5.8), (0.5, 0.01) g and (120 ,60 ) min respectively for non-modify and modify eggshell. The present study was also aimed to evaluate the equilibrium of adsorption process using Langmuir and freundlich isotherms. The Langmuir isotherm was the best for correlation of adsorption data, showing maximum capacities of 16.6 and 159 mg/g for non-modified and modified eggshells, respectively. Meanwhile, the kinetics of (〖Cr〗^(+6)) adsorption on eggshell and modified of eggshells also analyzed using pseudo-first order.