Biossorção do cromo trivalente e hexavalente proveniente do curtume utilizando a microalga Scenedesmus sp.

Abstract

The incorrect disposal of residues containing heavy metals presents serious risks to the environment and to the living beings, tannery effluents if they are not treated correctly can harm the environment, in this way the biosorption method can be presented as a low cost alternative and efficient. The objective of this work was to analyze the effect of chromium III and VI on the growth of the microalga and the capacity of removal of these ions by the microalga. For the experimental tests a synthetic solution of potassium dichromate for chromium VI that was complexed with 1,5 diphenylcarbazide and chromium-based sulfate for chromium III which was complexed with ethylenediamine tetraacetic acid (EDTA), both for analysis in Uv-vis spectrometry. The concentrations used for testing the effect of chromium in the microalgae were 1,0 mg L-1 to 500,0 mg L-1 for chromium III and from 0,1 mg L-1 to 10,0 mg L-1 for chromium VI. The tests performed verified the effect of chromium on microalgae growth, adsorption kinetics, adsorption isotherm and adsorption capacity of chromium III and VI metal. The inhibitory effect on the growth of Scenedesmus sp microalgae was found, reaching 100% inhibition for the concentration of 500,0 mg L-1 of chromium III and 91,53% with respect to chromium VI. The results obtained using the chromium III solution with concentrations of 100 mg L-1 to 500 mg L-1 achieved removal rates of more than 50%, reaching 100% at certain concentrations in the tests using the synthetic solution chromium VI removal percentage was above 25% and reaching 100% removal at some concentrations, the concentrations tested for chromium VI ranged from 1 mg L-1 to 50 mg L-1. It was observed that the removal capacity of chromium III per gram of dry biomass versus living biomass are not statistically different and for chromium VI they are statistically different. The results were efficient in the biosorption of the chromium metal by the Scenedesmus sp microalgae, the application of the biosorption is promising, especially in concentrations close to the limit allowed by the National Council of the Environment (CONAMA), indicating potential of use in the treatment of liquid effluents.