PNNL pursues seawater extraction of magnesium and other critical minerals

Researchers at the U.S. Department of Energy's Pacific Northwest National Laboratory are developing three processes to recover critical minerals from seawater or to use seawater-derived chemicals in conventional mining, New Atlas reported. Scientists say 0.1% of the world's seawater contains enough critical elements to power humanity's needs for 50,000 years, and PNNL says it has recovered magnesium, lithium, nickel, platinum-group metals and rare-earth metals using seawater or chemicals generated from it, according to the report. The first process pulls magnesium hydroxide directly from seawater. The second converts concentrated desalination brine into acids and bases for leaching metals from ground ores. The third uses seaweed to gather minerals that are otherwise too dilute to chase. Concentrations remain a barrier. An Olympic-sized pool volume of about 600,000 gallons holds only 0.42 kg of lithium and 0.00095 kg of nickel, but about 2,980 kg of magnesium, New Atlas reported. The United States mined magnesium from seawater for 50 years before switching to imports in the 90s, the article noted. Instead of the multi-stage Dow process that uses lime, PNNL flows seawater alongside a base such as sodium hydroxide in a co-flow reactor so magnesium hydroxide precipitates at the boundary while limiting calcium contamination, according to the report. Project leader Chinmayee Subban said the goal is to maximize dollars per cubic meter of seawater pumped and to scale technologies so they can be economically feasible.