Reactions: Extracting lithium from fracking wastewater

Letters to the editor

Extracting lithium from fracking wastewater

Please find my comments below on a recent C&EN article “Massive Potential Lithium Source Found in Pennsylvania.”

I am optimistic about the potential application of direct lithium extraction technology on the fracking wastewater from Pennsylvania shale gas wells. Lithium extraction and recovery from complex brines become technically possible with emerging promising technologies such as adsorption by metal oxides and hydroxides, solvent extraction using lithium-selective solvents, sorption using inorganic molecular sieves and ion-exchange sorbents, etc. The brines studied in laboratory research contain lithium concentration as low as 0.12 ppm in the seawater. The lithium contents in oil field water are usually much higher than those in seawater, and therefore it is more realistic for the application of the above technologies. Larger-scale pilot tests and commercial operations have been conducted over the years at numerous geothermal power plants in the US with the proposed process of pretreatment, recovery, and purification of lithium and other valuable materials from geothermal brines. In these complex geothermal brines, lithium is a minor element; the majority is other more abundant elements, including alkali metals, alkaline earth metals, iron and base metals, and metalloids. The lithium content in one of the geothermal brines, the Salton Sea brine in California, is about 200 ppm, which is close to the average lithium concentration of the northeastern Pennsylvania fracking waste brines.

To better understand the economics and environmental sustainability, we need more field studies at larger scales so we can advance commercial-scale lithium extraction and recovery processes. After additional recovery of lithium and any other valuable materials, the remaining contaminant-laced fracking wastewater can be treated under the current injection and disposal practices for fracking wastewater, as there are no radical changes in the waste stream.

Chunli Li
The Woodlands, Texas