Biocomposite efficiency for Cr(VI) adsorption: Kinetic, equilibrium and thermodynamics studies

Abstract

Bio-composite of mango (Mangifera indica) was prepared and employed for Cr(VI) adsorption from aqueous media. The effect of various process variables i.e., pH, Cr(VI) ions initial concentration, adsorbent dosage, contact time and temperature were optimized. The optimum levels of pH, adsorbent dose, contact time, initial Cr(VI) ions concentration and temperature were 3, 0.05g, 30min, 200mg/L and 33°C, respectively for maximum Cr(VI) adsorption on to bio-composite. Isotherms (Langmuir, Freundlich and Harkins-Jura) and kinetic models (pseudo-first-order and pseudo-second–order) and intraparticle diffusion model were applied to understand the adsorption mechanism of Cr(VI). Pseudo-second-order kinetic model and Langmuir isotherm fitted well to the Cr(VI) adsorption data. Composite pre-treatment with surfactants and co-metal ions (Na+, K+, Ca2+, Cu2+, Al3+ and Fe3+) affected the Cr(VI) adsorption slightly. Thermodynamic parameters (ΔG0, ΔH0 and ΔS0) revealed that the Cr(VI) adsorption process was spontaneous and exothermic in nature. Cr(VI) desorption was achieved using NaOH solution efficiently, which revealed the recycling possibility of prepared composite. From results, it can be concluded that bio-composite is efficient for Cr(VI) adsorption and could be employed for Cr(VI) removal from industrial effluents.