Lithium is a metal that is widely spread through the Earth’s surface, so much so that it can be harvested to extent to manufacture batteries of millions of cell phones and other battery solutions today. Being a rare Earth metal in comparison to other metals, it does not occur in its elemental form. Instead, it occurs in the form of minerals in igneous rocks and lithium chloride salts found in brine salts . The major suppliers of lithium in the current day Chile and Argentina .
In spite of having a use in manufacturing of the technology that is needed in our daily lives, people face the anxiety of the depletion of lithium reserves. It has been feared that the production of lithium won’t be able to keep pace with its use. With the production levels increased only by 28 % over four years from 2010 to 2014, the production rate seems to be slow. According to experts, it has been predicted that the lithium demand will probably be tripled over the next decade till 2030 .
Solution to the problem: Lithium Extraction from seawater
Apart from the sources like those mentioned earlier, lithium also occurs in seawater. In fact, seawater contains around 230 billion tons of lithium . As mentioned in our earlier article, if we were to combine the lithium extracted from both land and oceans, we would end up with enough lithium to manufacture 14923 billion EVs without recycling .
To support the same, the researchers at Saudi Arabia’s king Abdullah University of Science and Technology (KAUST) have developed technology that can extract lithium from seawater while desalination of seawater. The device employs lithium lanthanum titanium oxide (LLTO) as it’s membrane .
How does it work?
The cell is designed to have three compartments. The first compartment holds sea water, whereas, the second contains a buffer solution and a copper cathode coated with platinum and ruthenium. A LLTO membrane is present in between the first and second compartment. The third compartment holds a solution of sodium chloride and a platinum-ruthenium anode .
Initially, the sea water flows into the first compartment. From there, the positively charged lithium ions pass through the LLTO membrane and enter the second compartment. Simultaneously, negatively charged ions pass an anion exchange membrane and end up in the third compartment of the cell while being attracted to the anode. After a current is passed, the lithium metal is pulled through the LLTO membrane towards the cathode. In this process, we also obtain hydrogen and chlorine as by products .
According to the test results, the concentration of lithium obtained after 5 stages, each of 20 hours, is around 9,000 ppm. This concentration obtained has 99.94 % purity of lithium phosphate. Around 76.3 kWh of electricity is required for the process of making 1 kg of lithium and would be cost around 5 USD. Along with the 1 kg of lithium, the device is also estimated to produce 0.87 kg of hydrogen gas and 31.12 kg of chlorine gas .
Although the device is estimated to produce lithium cheaply, it is yet to be optimized for further use. The tests those were carried out, were on a small scale and the lithium that is produced is not of the purity that can be put to use in manufacturing batteries for EVs .
Still in the developmental process, this technology holds the solution the problem of depleting lithium reserves in the world. Hence, once commercially utilized, it would be used to produce lithium on a large scale that would cater to the production of batteries substantially.
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