Adsorption of metal ions in red marine algae Lithothamnium calcareum in the treatment of industrial effluents

Abstract

This study investigated the adsorption capacity of the elements Chromium (Cr), Manganese (Mn) and Zinc (Zn) to marine algae Lithothamnium calcareum by means of adsorption kinetics and batch adsorption tests, with a view to the development of a simple technique for the treatment of effluents that have a high concentration of metal ions. The algae was sieved, washed and subjected to treatment. In the adsorption kinetics, 0.2 g of algae was weighed, an amount transferred to 125 mL Erlenmeyer flasks, to which was added 15 mL of solution with a concentration of 5 mg L-1 of the metal ion. The flasks were stirred at 60 rpm for 240 minutes. In batch adsorption, 0.2 g of algae was weighed, amount transferred to 125 mL Erlenmeyer flasks, to which was added 15 mL of solution with concentrations of 5, 10, 20, 50, 100, 250 e 500 mg L-1 of the metal ion. The flasks were stirred at 60 rpm for 24 hours. In the two tests, the supernatant solutions collected were centrifuged at 2000 rpm for 5 minutes and the equilibrium concentrations of metal ions were determined by atomic absorption spectrometry. It was found that, in 240 minutes of contact, the Lithothamnium calcareum removed 15.5% of Cr, 33.0% of Mn and 8.0% of Zn in solution; and that in 24 hours of contact, at a concentration of 5 mg L-1, it removed 0.4% of Cr, 52.5% of Mn and 92.6% of Zn; and, at a concentration of 500 mg L-1, it removed 20.0% of Cr, 22.6% of Mn and 40.8% of Zn. The results showed that the Lithothamnium calcareum submitted to thermochemical treatment presented potential for use in the adsorption of Cr, Mn and Zn.