Potentiality of waste human hair towards removal of chromium(VI) from solution: kinetic and equilibrium studies

Abstract

Abstract Industrial and agricultural activities discharges huge amount of hazardous pollutants that lead to massive environmental pollution and health hazards. Keratin is a fascinating protein and useful biopolymer, which is usually found in wool, human hair, nails, feathers, etc. The present research deals with the potentiality of human hair towards removal of hexavalent chromium from aqueous solution through batch mode. The adsorbent was characterized by pHZPC and SEM study. The Cr(VI) adsorption was studied with the help of different process parameters, viz. initial concentration, contact time, adsorbent dose, pH, and temperature. Results revealed that Cr(VI) adsorption by human hair was highly pH sensitive. Maximum Cr(VI) was adsorbed from water at pH 1.0. Study of temperature effect on chromium adsorption confirmed the endothermic behaviour of the process. On the other hand, thermodynamic properties were also calculated and found that physisorption was dominant with activation energy of 0.385 kJ mol−1. Kinetic study revealed that pseudo-second-order model was followed by the adsorption process. Adsorption equilibrium was analysed with Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models. Results showed that the adsorption system followed both Langmuir and Freundlich isotherms with Langmuir adsorption capacity of 9.852 mg g−1, which was compared with other adsorbents and observed that the performance of the present adsorbent is better than others. Finally, it can be concluded that human hair could be an alternative chief low-cost waste material for decontamination of heavy metals from an aqueous medium.

Keywords

• Human hair
• Hexavalent chromium
• Adsorption
• Isotherm
• Keratin
• Kinetics