Flotation, speciation and determination of iron(III) using aluminon in water, real samples and wastes of power stations

Abstract

Aluminon has been investigated for the separation of iron(III) by flotation technique. This reagent formed a 1:1 stable complex in aqueous solution. An intense violet layer is formed after flotation using oleic acid (HOL). A highly selective and sensitive spectrophotometric procedure is proposed for the determination of Fe(III) after overcoming all interferences. Preliminary studies show the possibility of forming a complex with Fe(II) to an extremely low extent. Trials have been carried out to separate Fe(II) and Fe(III) using NH₄SCN or NaF. To prevent the oxidation of Fe(II), NaBH₄ is used.  The separation of Fe(III) and Fe(II) can be achieved using 0.6 mg L^-1 NaBH₄.  The flotation- determination method was carried out at pH 2-3. The formation constant is 1.3×10⁷ L mol^-1 with molar absorptivity of 0.2×10⁵ L mol^-1 cm^-1 and detection limit of 5×10^-6 mol L^-1. The effect of foreign ions is avoided using excess aluminon and 0.5 mg L^-1 NaBH₄. The proposed procedure was applied to synthetic mixtures [Fe(III) + Fe(II)], Fe(III) and some cations, wastes of power stations, simulated samples and real ores.