Metallurgical waste, mainly composed of magnetite (Fe3O4) with low particle size, was used as non-conventional adsorber to fix and remove toxic organic compounds from aqueous solutions. Previous studies indicated that magnetite used in acidic solutions under continuous stirring could have some desagregation and dissolution processes. This effect was considered undesirable on adsorption processes because it represents the reduction of the adsorption capacity and another source of iron for environmental contamination. Solutions of sodium metasilicate, iron sulfate and sodium hydroxide were used, trying to improve the chemical stability of the magnetite granulometric fractions to be applied as adsorbers in acid solutions. The experimental results allow to conclude that the treatment with sodium metasilicate results on better adsorption properties, in spite of the reduction of the removal percentage of the organic compound in 1% (from 98% without treatment to 97% with sodium metasilicate) and the reduction on the adsorption velocity (from 30.10-3 mg.g-1.min-1 to 10.10-3 mg.g-1.min-1). The magnetite fraction treated with metasilicate shows enhancement on chemical stability with the reduction of weight loss, desegregation and dissolution processes (46%); in the analysis of the isotherm curves obtained for #30 treated fraction and #30 fraction without treatment, the treated fraction shows lower interference of the dissolution and desagregation processes and better correspondence with the Freundlich adsorption model.
magnetite; residues; waste; metallurgy; adsorber; adsorption; heavy metals
