Chromium(VI) removal by calcined bauxite

The present paper deals with the efficiency of treated bauxite to remove Cr(VI) from a synthetic solution. It includes adsorption of Cr(VI) as a function of contact time, particle size, adsorbent dosage, temperature and initial concentration of the synthetic solution. The treated bauxite (1 g/25 mL) is found to be capable of removing up to 98% of Cr(VI) from solution having low initial concentration (10 mg/L). The adsorption is highest at 45 °C and rate of adsorption is very slow after 5 min. The adsorption isotherm follows both the Langmuir and Freundlich isotherm. The change in the lattice structure of adsorbent before and after calcinations was analyzed by XRD, FTIR and SEM analysis. The thermodynamic and kinetic parameter such as Gibbs free energy, isosteric heat of adsorption and rate constant were calculated.