Sequential leaching for the recovery of alumina from a Canadian clay

Clays are abundant minerals containing from 15 to 40% w/w of alumina that can be extracted using various processes. Laboratory tests were conducted to verify if alumina can be produced from a Canadian illite/chlorite type clay. Results show that smelter grade alumina can be produced, although with low alumina recoveries, using a standard sulphuric acid processing flow sheet that requires clay to be initially heat treated. The application of a sequential sulphuric/hydrochloric leach to the clay increases alumina recovery by more than 10% and can be almost equivalently applied to heat treated or crude clay.