Last week, Indian scientists announced that they had successfully extracted uranium from natural seawater. The uranium mined from the earth and used to make nuclear power plant (NPP) fuel is a finite resource, with the World Nuclear Association estimating land-based uranium reserves to be around 5.9 million tonnes. These uranium reserves will be depleted within a century.
Instead, seawater is estimated to contain approximately 4.5 billion tonnes of uranium, though scientists have been grappling with the issue of cost-effective extraction technology. Because the concentration of uranium in seawater is only about 3 micrograms per litre, extracting it is a difficult and expensive task that necessitates the processing of massive amounts of seawater.
Scientists at the Indian Institute of Science Education and Research (IISER) in Pune have been working to extract uranium from seawater, and their findings were recently published in the journal of the Royal Society of Chemistry. Researchers have long struggled to develop an appropriate adsorbent to extract uranium from seawater that combines high capacity, excellent selectivity, and ultra-fast kinetics. This IISER team of scientists created a sponge-like macroporous adsorbent Metal-Organic Framework (MOF) with high uranium extraction capabilities. In comparison to other existing adsorbents, they were able to capture 95 percent of uranium in two hours.
The IISER scientists extracted uranium from seawater in the Arabian Sea off the coast of Mumbai, and the adsorbent achieved a record uranium uptake capacity of 28.2 mg per gramme in only 25 days, “satisfying the remarkable uranium extraction from seawater standard only in 2 days compared to existing adsorbents, including commercially available materials reported so far,” according to their findings.
Lead scientist Sujit K. Ghosh, told reporters that “combined with exceptional selectivity, record capacity, ultrafast kinetics, and long service life, this material could be a potential candidate for the efficient extraction of uranium from natural seawater. The selective ion exchanged harvesting method introduces the concept of extracting uranium from natural seawater, which could lead to an infinite supply of uranium at a low cost.”
The design allows uranium cation to enter and remain inside the natural trap site created inside the MOF (Metal-Organic Framework),” Ghosh added.”With rising global energy demand and environmental concerns associated with fossil fuels, sustainable energy supply to the global community remains a great challenge. “Large-scale uranium extraction from seawater (UES) is widely regarded as a solution to rising global energy demand and the climate change crisis,” the IISER scientists wrote in their paper.
Shilpi Kushwaha, an Indian scientist from the Central Salt and Marine Chemicals Research Institute, received the Young Scientist Award last year for her work in developing a method to extract uranium from secondary sources such as seawater and acidic effluents using crystalline thin films and polymer nanorings.
“We have been able to extract uranium from acidic effluent as well as seawater. In the future, we will try to make it more cost-effective through improvisation so that uranium can be extracted on a larger scale and be commercially viable,” Kushwaha said.
“The demand for energy is growing by the day. Nuclear energy is expected to increase in demand in the near future due to its carbon neutrality. However, uranium reserves are limited, and it is estimated that they will be depleted in more than 100 years,” she said.
“One of the seven chemical separation processes where progress would lead to global gains is uranium extraction from seawater (UES). UES provides additional benefits to any country’s energy security. It is not dependent on terrestrial uranium ore, which reduces environmental concerns associated with land-based mining,” she added.
According to Kushwaha , the heavy metal extracted from seawater is comparable to similar experiments conducted around the world. The US Department of Energy (DOE) noted several years ago that the Japan Atomic Energy Agency pioneered materials that hold uranium as it is stuck, or adsorbed, onto surfaces of the material submerged in seawater in the 1990s.
Following that, the DOE assembled a team of experts from US national laboratories, universities, and research institutes to tackle the challenges of economically extracting uranium from seawater. According to the DOE, the team developed new adsorbents that reduce the cost of extracting uranium from seawater by three to four times. According to the study, one adsorbent material developed could hold 5.2 grammes of uranium per kilogramme of adsorbent after 49 days of natural seawater exposure.
