Iron removal by fixed-bed adsorption with thermochemically treated Lithothamnium calcareum algae

Abstract

Difficulty in removing metallic ions from water has led to the development of new technologies. This work aims to investigate the removal of Fe2+ from water by a fixedbed column filled with bioclastic granules of the algae Lithothamnium calcareum. The bioclastic granules were thermo-chemically treated in order to unblock the existent pores and improve the sorption capacity. The column was constructed in an acrylic tube with height of 14.9 cm and diameter of 4.58 cm filled with the earlier prepared Lithothamnium calcareum. Then a solution of Iron Sulfate in the concentration of 500 mg L−1 of Fe2+ was applied in hydraulic loads of 2, 4, 6, 8 and 10 cm and the hydraulic conductivity was determined. The miscible displacement was evaluated by the construction of breakthrough curves for each load, considering the mass flux and diffusive–dispersive flux and only the diffusive–dispersive flux. Peclet number, diffusion coefficient and dispersivity of the porous medium were also determined. Evaluation of the mass balance of the bioclastic granules column experiment was performed through sigmoidal models. The column showed removal efficiency of Fe2+ around 50% and high values of retardation factor (2.410 < R < 4.092) indicating the high interaction between Lithothamnium calcareum and the solute. The dispersive flux was predominant according to the miscible displacement and sigmoidal models evaluated. Thus, the use of Lithothamnium calcareum is an interesting alternative to remove excess of iron from consumption water, protecting from changes in color, turbidity and flavor of the water, and from pipe obstructions.