Mechanical enrichment of converted spodumene by selective sieving

• Particle size separation was effective for the enrichment of spodumene concentrate.
• Almost pure spodumene concentrates were obtained by selective sieving.
• Waste rock originated impurities were removed almost completely.
• The method required light grinding prior to sieving.

Spodumene ore can be concentrated in large particle size of 1–6 mm by a dense media separation (DMS) process. The concentrate typically contains relatively large amounts of impurities due to the incomplete liberation of spodumene and the quite narrow density difference between spodumene and gangue minerals. The extraction of lithium from spodumene requires the phase transformation of spodumene from α- to β-form which takes place at 1100 °C. After heat treatment the Li2O content of spodumene concentrate can be improved by particle size separation. In this work the technical and economical possibilities of producing first low grade concentrates by DMS method and increasing the grade afterwards by particle size separation were studied. Various DMS spodumene concentrates were mechanically enriched after heat treatment by selective sieving. Autogenous and ball mill grinding were used to increase the separation efficiency between the spodumene and the gangue minerals. The Li2O contents of the concentrates were increased from 5.1%, 3.6%, 3.1% and 1.4% to 6.8%, 5.8%, 5.9% and 5.0%, respectively. The energy economy of the sieving method was evaluated from the perspective of increased energy consumption in the heat treatment process.

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