Extraction of lithium from micaceous waste from china clay production

Abstract The granites of South-West England are a potential source of lithium which is generally found within the mica mineral, zinnwaldite. It is mainly found in the central and western end of the St. Austell granite. When kaolin extraction occurs in these areas a mica-rich waste product is produced which is currently disposed of in tailings storage facilities. In this study a tailings sample containing 0.84% Li 2 O was upgraded by a combination of froth flotation, using dodecylamine as the collector, and wet high intensity magnetic separation (WHIMS) to 2.07% Li 2 O. The concentrate was then roasted with various additives, including limestone, gypsum and sodium sulphate, over a range of temperatures. The resulting products were then pulverised before being leached with water at 85 °C. Analysis of these products by XRD revealed that the water-soluble sulphates, KLiSO 4 and Li 2 KNa(SO 4 ) 2 , were produced under specific conditions. A maximum lithium extraction of approximately 84% was obtained using gypsum at 1050 °C. Sodium sulphate produced a superior lithium extraction of up to 97% at 850 °C. In all cases iron extraction was very low. Preliminary tests on the leach solution obtained by using sodium sulphate as an additive have shown that a Li 2 CO 3 product with a purity of >90% could be produced by precipitation with sodium carbonate although more work is required to reach the industrial target of >99%.