Instrumental analysis study of iron species biosorption by Sargassum biomass

The mechanism of iron uptake by the dry biomass of the brown seaweed Sargassum fluitans was investigated at the molecular level using different instrumental techniques. Transmission electron microscopy (TEM) and the chemical microanalysis by electron dispersive spectroscopy (EDS) of the biomass exposed to iron solutions confirmed the deposition of the metal mainly in the cell wall. The analysis of the Fe(II)-exposed biomass by X-ray photoelectron spectroscopy (XPS) indicated the presence of Fe in two states of oxidation in the biomass exposed to ferrous iron solution, whereas only Fe(III) was present in ferric iron-exposed biomass, suggesting a partial oxidation of Fe(II) when in contact with the biomass. In both Fe(II)- and Fe(III)exposed samples, XPS indicated iron complexation with sulfate groups in the biomass. The FTIR analysis of metal-loaded biomass samples revealed the chelating character of the ion complexation to carboxyl groups as well as the complexation of Fe(III) with sulfur of sulfonate groups in the biomass. This work confirmed the participation of carboxyl groups in the uptake of both Fe(II) and Fe(III), and of sulfonate groups in the uptake of Fe(III) by S. fluitans biomass.