Processing Track: Mineral Processing, Refining and Recycling · Module 2 of 4 · about 15 min
Leaching, electrowinning and lithium
Some ores are processed with chemistry instead of flotation. In leaching, a solution dissolves the metal out of the ore. For many oxide copper ores, dilute sulfuric acid is trickled over heaps of crushed ore, and the copper-bearing solution is collected at the bottom.
The solution then goes through solvent extraction (SX), which pulls copper into an organic liquid and back out into a cleaner, stronger solution, and electrowinning (EW), where electric current plates pure copper onto cathodes. SX-EW makes copper cathode at the mine without a smelter.
Lithium comes from two main sources. Brines are salty underground water, as in Chile's Atacama and at Silver Peak in Nevada, traditionally pumped into evaporation ponds that concentrate the lithium over many months. Hard-rock deposits, mostly the mineral spodumene, are mined, concentrated, roasted and leached, with Australia a major producer according to USGS.
Direct lithium extraction (DLE) is a group of newer methods that pull lithium out of brine with sorbents, ion exchange or membranes instead of ponds. The promise is faster production with less land and water, but each brine is different, so DLE has to prove itself project by project.
Sources
Module quiz
5 questions, 4 correct to pass. You'll see what you missed and why, and you can retake it.