Lead Biosorption in 'Arribadas' Algal Biomass

摘要

The "Arribadas" algae represent a mixture of brown, red and green nonliving marine algae collected at Jaguaribe beach, Itamaraca - PE, Brazilian northeast. Equilibrium experiments were conducted and results compared to the values obtained for Sargassum sp. Maximum lead uptake capacities of 294.1, 138.9 and 95.2 mg/g were obtained for Sargassum at pH 4, and for "Arribadas" at pH 4 and 3 respectively. Kinetics of Pb was very fast achieving 85% of total uptake in 15 min. Ion exchange seems to be the principal mechanism involved during the process. Light metal ions were released, especially Ca and Mg, while Na and K were released in very little amount. Uptake of Pb and H were considered. Therefore, the ion exchange mechanism was chosen to model the isotherm. Equilibrium constants of 14.8 and 30.8 were obtained at pH 4 for "Arribadas" and Sargassum sp., respectively. The effect of particle size distribution on the kinetics of lead was not significant between the ranges 0.149-0.297 and 0.297-0.590 mm. Total amount of ions removed from solution, H~+ and Pb~(2+), almost matched the total released ions, Ca~(2+) and Mg~(2+), at pH 4. However, at pH 3, more ions were released than removed. Bigger pH variation was noticed with solutions that do not contain lead and with higher pH, indicating a possible competition between these two ions, Pb~(2+) and H~+.