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Lithium can be extracted from geothermal waste

14 December 2009 No Comment

Technology.am (Dec. 14, 2009) — A practice developed by a Californian company, Simbol Mining, will allow the valuable mineral lithium, broadly used in high-density batteries, to be reclaimed from the hot waste water generated by a geothermal power plant in California.

lithiumThe utilization of lithium has been ever-increasing internationally, and is predicted to triple by 2020 as lithium battery use increases, electric cars become more prevalent, and as more batteries are used to stock up electricity produced by solar and wind sources.

The conventional sources of lithium are soil and brine dried in salt ponds, particularly in Chile and Bolivia, however the waste water produced at the geothermal power plant, which can be millions of gallons a day, is uniformly rich in lithium. Extracting the lithium from geothermal waste water is easier than extracting from brine, and less water-intensive than extracting from soil, and the process has a smaller atmosphere footprint because the water has by now been extracted to produce electricity.

The geothermal plant is built on top of the San Andreas Fault at the Salton Sea in southeastern California, in the region of 80 miles east of San Diego. The plant is one of a cluster of geothermal plants that draw hot water at up to 360C from underground to the surface to generate the steam that drives electricity-generating turbines. The hot waste water formed in the procedure is salty and rich in silicates and minerals such as lithium.

The existence of silicates presented problems in the removal because they have to be inclined to clog equipment; however Simbol currently uses a technique developed in the Lawrence Livermore National Laboratory in Livermore, California to get rid of the silicates from the waste by precipitation and filtration. The filtered water is then passed over a chemical resin that draws lithium ions from the solution to form lithium chloride, and then the residual solution is returned to the ground. Lithium chloride is not an appropriate form for shipping, so sodium carbonate is added, and the mixture forms lithium carbonate, which is easier to convey.

The extraction process is to some extent driven by the heat of the waste water, which means the environmental impacts are comparatively minimal, according to geologist Michael McKibben of the University of California at Riverside.

Simbol Mining has tested the procedure completely and is now constructing a pilot plant, which is anticipated to generate around a tonne of lithium for every month. If the pilot is flourishing, more motivated plants will be built. Chief Executive Officer of Simbol, Luka Erceg, said he too expects the technique to be used to extract other minerals such as manganese and zinc, since the Salton Sea is rich in minerals having, as Erceg said, “half the periodic table” in the water.

Simbol Mining’s project has been aided by $6.7 million in funding from Firelake Capital and Mohr Davidow Ventures.

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