A comparative sorption study of Cr³⁺ and Cr⁶⁺ using mango peels: Kinetic, equilibrium and thermodynamic

The present study investigates a comparative study of the sorption of Cr³⁺ and Cr⁶⁺ from water using an agricultural by-product; mango peels in batch system under the effect of initial metal ion concentrations, solution pH, temperature, sorbent dose and contact time. Characterization of the mango peels was done before and after sorption of Cr³⁺ and Cr⁶⁺ using scanning electron microscopy, surface area pore size analyzer and FTIR spectroscopy. The pH study revealed that that maximum removal of Cr³⁺ and Cr⁶⁺ was obtained at pH 5.0 and 7.0 respectively. Among various kinetic models, pseudo-2^nd order well explained the data owing to the higher values of R² and the nearness between the values of experimental and calculated sorption capacities. The isotherms study revealed that Freundlich is the suitable isotherm for explanation of the equilibrium data due to higher R² values. The monolayer sorption capacity of mango peels was found to be 98.039 mg g^-1 for Cr³⁺ and 66.666 mg g^-1 for Cr⁶⁺. The spontaneity and exothermic nature of the sorption process of Cr³⁺ and Cr⁶⁺ using mango peels was reflected from thermodynamic study.