ON THE KINETICS AND EQUILIBRIUM MODELS FOR BIOSORPTION OF NI(II) ONTO A GRAM-POSITIVE BACTERIA STRAIN, RHODOCOCCUS OPACUS, FOR ENVIRONMENTAL APPLICATIONS

摘要

The aim of this fundamental study was to evaluate the biosorption of Ni(II) from aqueous solutionrnstreams onto a Rhodococcus opacus strain through kinetics and equilibrium isotherms studies. Thernbiosorption of nickel achieved its highest value in a pH around 5. The experimental data evaluationrnwas carried out focusing three two-parameter models, as: Langmuir, Freundlich, Dubinin –rnRadushkevich. In order to determine the best isotherm fit, three error analysis methods were used tornassess the data: correlation coefficient (R~2), residual root mean square error (RMSE) and Chi-squarerntest. The error analysis established that the Freundlich model fits better the nickel biosorption data.rnMaximum uptake capacity of nickel reached a value around 7.63 mg.g-1 for R. opacus. The biosorptionrnrate was fast and achieved a removal of around 79 per cent of Ni(II) in the first 5 minutes at roomrntemperature (25 ± 2℃). The experimental kinetics data was evaluated considering two modelsrn(pseudo-second order and pseudo-first order). The error analysis established that the pseudo-secondrnorder model better fits the data.