Upgrading of Al 2 O 3 in gibbsite of Sinai (Egypt) shale by sodium dodecyl sulphate

Abstract

The effect of sodium dodecyl sulphate on the flotation of Al₂O₃ from samples of gibbsite of Sinai (Egypt) shale was studied at various operating variables. The assays of the samples are 18·98%Al₂O₃, 15·45%SiO₂, 12·83%Fe₂O₃, 14·87%CaO, 5·74%P₂O₅, 5·34%MnO, 0·86%K₂O, 0·76%Na₂O, 1·50% trace elements and 23·65% loss on ignition. The aim of upgrading Al₂O₃ per cent in the concentrate is to make it suitable for different industrial uses. Sodium dodecyl sulphate (anionic collector) is effective in the acidic pH range. Below the zero charge point of gibbsite where Al₂O₃ is positively charged, the sodium dodecyl sulphate is good at pH 2. Under appropriate conditions [collector dosage, 800 g t⁻¹; pulp density, 300 g L⁻¹; particle size, (−100+80) μm and pH 2], a concentrate containing 39·5%Al₂O₃ at component recovery of 96·9% with mass recovery of 52·8% was obtained. At these conditions, the assays of other ore constituents in the final concentrate were as follows: SiO₂ decreased from 14·2 to 6·4%, CaO decreased from 14·1 to 5·2%, Fe₂O₃ decreased from 13·1 to 5·6%, P₂O₅ decreased from 4·3 to 3·8%, MnO decreased from 4·2 to 3·2%, while K₂O increased from 0·89 to 1·2%, Na₂O increased from 0·69 to 1·1%, traces increased from 1·6 to 2·6% and loss on ignition increased from 25·4 to 31·2%.