I had posted my thoughts about this subject on TOB after there had been a number of questions. I'll repost it here, although it's probably prety basic stuff for this esteemed group. Let me know if I get some things wrong; I always like to learn about this stuff.

"There have been several posts recently related to DLE extraction technology and a perceived preference on the part of the current administration for this over other forms of extraction. Some thoughts ….

I’m no expert, but I believe the basics are that lithium is extracted either from liquids (salars or aquifers), or solids (rock or clay). DLE extraction only makes economic sense with liquids. Extraction from rock and clay typically employs a combination of heat and acid, among other steps. 

DLE is generally accepted as being more environmentally friendly because it doesn’t require large evaporation ponds, as traditional brine projects require, nor does it require the type of ground disturbance that traditional mining requires, because DLE infrastructure would consist primarily of limited pipelines and the physical extraction plant. It also requires little or no new, fresh water. The thing is, though, DLE isn’t commercially in use yet. There are a couple of projects in South America that are close, and here in North America SLL is the closest. So several companies have what they consider to be proven DLE processes; they just need to scale it to commercial size. Each DLE company has proprietary technology; there is no manufacturer of generic DLE systems, so each new project comes with process development risk. 

The other issue with DLE is that, remembering it is used with lithium suspended in liquid, there are only a couple of areas in the world where this occurs naturally in volume or concentrations that are marketable. The main area of course is the so-called Lithium Triangle in Argentina, Chile and Bolivia. There is a natural, localized, rich source in the Salton Sea in California as well; this is the project to which the Energy Secretary recently referred during a trip to Nevada, and in which GM just invested. ALB has a modest, 5 ktpa brine project in Silver Peak, Nevada. Another source of lithium in liquid that is currently being exploited is underground aquifers, and more specifically, aquifers that had once held oil but are now exhausted. This is the case for SLL in Arkansas, and for E3 Metals in Alberta, Canada. Projects like these will probably become much more abundant going forward.

While there are many advantages to DLE, the problem is the demand for lithium is far greater than projects using just DLE could satisfy, so traditional lithium mines are here to stay, and grow. Secretary Granholm knows this, and has stated that the administration supports sustainable lithium mining. As far as “traditional” lithium mines go, Thacker Pass is one of the least impactful ones in development. It will be approved."