Most salt-lake brines in China are of the magnesium sulfate subtype and the ratio of Mg/Li can be as high as 500. The chemical precipitation approach that has been successfully applied to low calcium and magnesium brines (such as those from Zabuye and Jezecaka Lake) consumes a large quantity of chemicals and generates a huge amount of solid waste.
In addition, lithium loss due to co-precipitation and adsorption to calcium/magnesium precipitate is also significant. The technologies to extract lithium from brine with a high Mg/Li ratio include calcination, adsorption, extraction and membrane separation. These technologies have been explored for potential large-scale production. Some of these technologies have achieved significant progressed over the last few years and one of which is the adsorption method using lithium-ion sieves.
Adsorption using lithium-ion selective sieve was claimed by Lanke Lithium (蓝科), a subsidiary of Qinghai Salt Lakes Holding Co Ltd (SZSE: 000792) to reach commercialisation. Lanke has a project in the Qarhan Salt Lakes with a capacity of 10,000 tons per year, and are due to start commissioning their second plant with a capacity of 20,000 tons per year by mid 2019.
The lithium-ion sieve is a specific absorbent with a high selectivity for lithium ions. Li–Mn–O ternary oxides have been used to prepare ion sieves for lithium recovery from salt-lake brines because the Li–Mn–O framework can maintain a cubic spinel structure during the Li+ insertion and extraction process. These oxides contain a series of chemicals, such as the spinel manganese oxides, and nanostructure MnO2. Inspired by the lithium ion sieve, titanium lithium ionic and lithium iron phosphate (LiFePO4) sieves have also been investigated. These absorbents have been tested for recovery of lithium from brine from Qarhan saline lake.
Challenges for ionic sieves include:
Hence, to improve the performance, Lanke have invested in research to improve the granulation and regeneration of lithium sieves.
Lanke expands on the back of successful commercialisation of its extraction technology
The 20,000-ton battery-grade lithium carbonate expansion project of Lanke Lithium Industry will be completed and put into operation in the second half of 2019, and the target of annual production of 30,000 tons of lithium carbonate will be achieved by 2020. As of mid-May 2018, the output of lithium carbonate in Lanke Lithium Industry has exceeded 3,000 tons, of which more than 100 tons are battery-grade products, which is higher than the same period in 201. Lanke's annual output has reached 10,000 tons in 2018, compared with 8,000 tons in 2017.
In addition, the preliminary work of BYD's 30,000 ton battery-grade lithium carbonate project in Qinghai Salt Lake is steadily progressing. If the projects of Lanke Lithium Industry and BYD are put into operation smoothly, the total production capacity of lithium carbonate will reach 60,000 tons, with an output value of 4.5 billion yuan. In 2016, more than 100 salt lake areas in Qinghai have proven lithium reserves of 17.24 million tons, accounting for 83% of China's total lithium resources and one third of the world's brine lithium reserves. The salt lake of Lanke Lithium Industry is Qarhan Salt Lake, located in the western part of Qinghai Province. Its reserves reaches 7 million tons and brine production reaches 200,000 tons per year. But its grade is low, lithium content is only 0.01%. The ratio of magnesium to lithium in raw brine is as high at up to 1,800 times, while that in older brines is about 450 times of lithium, so it is difficult to extract lithium.
A spokesman for Lanke lithium industry told InProved that there are no problems with technology and products. Lithium carbonate products meet national standards and Lanke are improving products according to downstream demand. On the issue of low lithium content in the Qarhan Salt Lakes, the company uses the Russian-invented lithium-ion sieve adsorption method to extract lithium, which has a high yield and minimal pollution to the environment. On the issue of boron removal, which is unique to the Qinghai Salt Lake, the company will bid for a boron removal device in the near future, docking the existing 10,000-ton device, and is expected to run in a complete set at the end of August 2019 to further improve product quality.
It is understood that in order to better protect intellectual property rights of the lithium extraction technology in salt lakes, Lanke Lithium Industry is expected to apply for 5-8 invention patents and 2-3 other patents in the lithium salt extraction field in 2019.
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