Chinese scientists extract lithium from seawater, holding promise for new energy tech

Chinese scientists extract lithium from seawater, holding promise for new energy tech

Chinese scientists say they have discovered a promising and sustainable method for extracting lithium from seawater, offering an efficient alternative amid increasing demand for the key battery metal in renewable energy technologies while minimising the environmental impact.

The surge in production of new energy vehicles and energy storage devices has led to a robust demand for lithium. But for now, lithium is mainly sourced from hard rock ores, such as spodumene, or from natural brines, both of which involve energy-intensive and environmentally costly processes.

A study published on Friday in the peer-reviewed journal Science presents a novel seawater lithium extraction technique using solar energy.

Led by Zhu Jia, of Nanjing University, and Mi Baoxia, from the University of California, Berkeley, the research team proposed a solar transpiration-powered lithium extraction and storage (STLES) device that uses sunlight to extract and store lithium from brine.

The device consists of a solar transpirational evaporator, a lithium storage layer and a nanofiltration membrane. It uses solar energy to generate high capillary pressure within the evaporator, which drives lithium through the membrane and into the storage layer.

Lithium extraction from seawater has been an area of potential but has many challenges. There are around 230 billion tonnes of lithium in the world’s seawater, about 16,000 times the reserves of the metal that can be exploited now.

The presence of abundant magnesium, calcium, sodium, potassium and lithium in seawater complicates the separation process.

According to a report last year from the Shanghai-based news outlet The Paper, industry insiders noted that the low concentration of lithium in seawater typically required desalination before extraction, making the overall cost of this method more than 10 times higher than other techniques.

Due to these costs and technical challenges, seawater lithium extraction has not yet become a mainstream source of the metal. However, recent research may change that.

Zhu’s team designed an aluminium oxide membrane modified with aluminium nanoparticles. As water vaporises under solar transpiration and moves through the channels in the membrane, lithium ions (Li+) are extracted and separated from divalent ions such as magnesium (Mg2+) and calcium (Ca2+).

According to the paper, a porous silica frit, or porous ceramic material, above the membrane captures the separated lithium salts. Lithium recovery from the silica frit is achieved with a simple water rinse, which can be performed at night when salt production is lower.

Zhu said in the paper.

Long-term experiments, various membrane tests and different size assessments demonstrate the stability, compatibility and scalability of the STLES,

The STLES device operates passively – without the need for extra energy – making it cost-effective and environmentally friendly. It can also be integrated with existing evaporation ponds, helping to cut installation costs, and has the potential to treat hypersaline brines with high osmotic pressures.

In the same issue of Science, another study conducted by Chinese researchers at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia reported success in extracting lithium from Dead Sea brine using electrochemical cells.

In pilot tests involving simulated brine with less than 0.1 per cent lithium chloride, the researchers achieved lithium recovery rates exceeding 80 per cent, marking a significant step towards real-world feasibility.

Although these technologies have shown promise in the laboratory and at the preliminary pilot scale, the economics and environmental impact in commercial-scale applications require further evaluation.

Scientist Seth Darling from the University of Chicago noted in a perspective article in the same issue.

A key challenge that remains is optimising extraction efficiency while minimising environmental impacts, particularly in terms of water usage and land disruption,

He said,

The economic viability of these new methods is still uncertain. The materials used in these processes, such as aluminium nanoparticles and anodic aluminium oxide membranes, are generally costly and may need to be replaced with more affordable alternatives that maintain comparable performance,

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