Reduction of Fe2O3 content of foyaite by flotation and magnetic separation for ceramics production

Abstract

Feldspars are used as a fluxing agent in ceramics and glass production. However, the presence of iron-bearing minerals reduces whiteness of the ceramics. The objective of this work was to decrease the Fe2O3 content of a foyaite to <1% by flotation and magnetic separation, individually or combined, to make the sample suitable for white ceramics manufacture. The sample was prepared regarding its particle size distribution, characterised, and submitted to concentration experiments. Flotation was arried out to investigate promising anionic collectors and the most suitable conditions of dosage and pH. Wet magnetic separation was used in several stages, increasing the magnetic field. Lastly, magnetic separation was applied to the concentrate of the most efficient flotation test. Technological characterisation showed that the foyaite sample displays 3.2% Fe2O3 from pyroxene/amphibole. The most efficient flotation condition was the reverse flotation of iron-bearing minerals with alkyl sulphate as collector under 400 g t−1 at pH 4. The desired specification was reached after three cleaner stages, yielding a concentrate with 0.92% Fe2O3 and 74.6 wt.% recovery. By magnetic separation, the Fe2O3 content was reduced to 0.8% with 70.6 wt.% recovery, after five stages of concentration with the magnetic field varying from 0.78 to 1.12 T. The most efficient combined circuit comprised three stages of flotation followed by one stage of magnetic separation at 0.78 T. The concentrate presented 0.55% Fe2O3 and 71.2 wt.% recovery. Keywords: Flotation, Foyaite, Magnetic separation, White ceramic