Comparison between different keratin-composed biosorbents for the removal of heavy metal ions from aqueous solutions

This study examined and compared the ability of chicken feathers, human hair and animal horns, as keratin-composed biosorbents, for the removal of Zn²⁺ and Cu²⁺ ions from single metal ion aqueous solutions under different operating conditions. The three biosorbents investigated in this study were all capable of adsorbing Zn²⁺ and Cu²⁺ ions from aqueous solutions. The biosorbent showing the highest uptake of Zn²⁺ and Cu²⁺ ions was animal horns. Chicken feathers showed a higher Cu²⁺ ion uptake and a lower Zn²⁺ ion compared to human hair. Increasing the initial concentration of Zn²⁺ or Cu²⁺ ions, or increasing the initial pH value, increased the metal ion uptake. Such uptake decreased when the temperature was raised from 25°C to 50°C for all adsorbent/metal ion combinations except for Zn²⁺ ion/human hair where the uptake increased with temperature. It was demonstrated that the addition of NaCl salt to the metal ion solution depressed the metal ion uptake. The Freundlich isotherm model was found to be applicable to the adsorption data for Cu²⁺ and Zn²⁺ ions.