Chinese researchers have developed an environmentally friendly method to extract caesium from brine, a process they say could boost China’s supply of the strategic resource.

Caesium, a rare metal, is a critical strategic resource used in satellite atomic clocks, missile thermal imaging sensors and advanced speciality glass. China and the United States are the top consumers of caesium, yet both rely heavily on imports.

It is primarily found in the Earth’s crustal ores as well as salt lake brines and seawater. Known commercial deposits include the Tanco mine in Canada, the Bikita mine in Zimbabwe, the Karibib project in Namibia and the Sinclair deposit in Australia.

China’s state-owned Sinomine Resources controls the Tanco and Bikita operations but domestic caesium reserves – while considerable – are mostly locked in brine that is difficult to process. Only a fraction exist as caesium ores, and most are low-grade associated minerals.

The caesium present in salt lake brine poses two major challenges: its concentration is relatively low, and the brine contains high levels of sodium, potassium, magnesium, calcium and rubidium ions, which interfere with caesium separation.