The acid extraction of lithium from the granites of South West England

Abstract

The current main sources for lithium consist of the mineral spodumene and a number of other complex silicates. Process routes to lithium from these silicates often involve thermal pretreatment to assist dissolution of the values. In this work some lithium containing materials including granites and pegmatites which occur in South West England have been examined by acid leaching for the dissolution of lithium values.

Leaching with sulphuric acid was carried out in an autoclave at up to 533 K and with hydrochloric acid in closed vessels up to 363 K. Sulphuric acid was shown to be the more selective reagent for lithium dissolution and led up to 70% of the lithium content being dissolved to produce final liquors containing up to 3 g l⁻¹ in the case of a St. Austell pegmatic sample. Hydrochloric acid led to significant codissolution of other elements such as iron, aluminium, calcium and magnesium, which would have undesirable effects in solution purification and concentration processes.

It would appear that the amblygonite content of the material is possibly readily dissolved by both acids but the lithium in other silicates was more resistant to dissolution. Nevertheless such materials deserve consideration as lithium resources.