Guidelines for extracting valuable materials from water

Water resource extraction may greatly improve national security and the environment. According to two recent research from Prof. Menachem Elimelech’s group, employing nanofiltration membranes to remove crucial elements from water could have tremendous benefits for national security and the environment. 

The rapid consumption of key goods like water, metals, rare earth elements, nutrients, and medications endangers their supply networks and the ecosystem. To be genuinely effective, Elimelech’s research team encourages their colleagues to customize their efforts to specific materials. In the most current issue of One Earth, they make their case.

The soaring demand for batteries has jeopardized the availability of lithium, a crucial component of low-carbon energy systems. Reducing reliance on mining, single-use consumption, and waste is critical to meet long-term demand.

Critical minerals such as lithium, cobalt, and rare earth elements are critical for national security due to their use in sophisticated technologies such as electric vehicles, renewable energy systems, and defense applications. They must secure their domestic supply to lessen their dependency on foreign sources and preserve competitiveness in important industries. Nanofiltration membranes, which are now used to soften water, remove alcohol from beer, and generate juice concentrate, effectively achieve these aims.

Luis Francisco Villalobos, a postdoctoral researcher, said, “Nanofiltration is used widely at the moment, but we think that there’s still a lot of potential that we cannot untap yet just because we don’t have the right membranes.”

According to the researchers, it is vital to optimize the membrane properties to better distinguish between dissolved components in the feed stream to realize nanofiltration’s environmental benefits fully. The field must improve its comprehension of the underlying concepts of designing and producing single-species selective membranes to develop the next-generation nanofiltration membranes. This would pave the way for solutions that are appropriate for the situation and have clear goals.

The circularity of some crucial materials can be increased if the membranes are better built to separate more complicated solutes that are very similar. For instance, if the pores of a nanofiltration membrane could distinguish between lithium and other ions, the procedure might be used to collect lithium from unusual sources, like the brine produced when oil and other liquids are extracted.

The One Earth study follows the publication of another paper on a similar topic, which emphasized the importance of prioritizing which metals should be recovered from wastewater and brine.

He said. “If you can incorporate such chemistry in these membranes, we can do these things.” 

The researchers prefer to recover metals from industrial effluent, where they are abundant and concentrated, rather than from seawater.

Elimelech said. “The lithium concentration in the ocean is very low, and because it is so low, you need to process millions of gallons of water, and it will be not economical.”

The quantity of lithium in the ocean is relatively low, and treating millions of gallons of water will be prohibitively expensive. DuChanois intends to restrict the list of prioritized metals even lower in the future and to see more significant efforts in creating recovery systems with minimal chemical demand and low energy usage.

Lead author Ryan DuChanois, a postdoctoral research associate at Rice University and former Ph.D. student in Elimelech’s lab, said, “We want to recover some of these metals that are otherwise being wasted because they’re high-value and in potentially short supply, especially as metals are becoming more and more widely used with the energy transition, But because there are so many different metals across the periodic table, we can’t focus on all of them.”

The new study assesses the feasibility of recovering these metals from various water sources by estimating the required operational costs to match market prices and highlights materials and processes that could serve as more sustainable alternatives to metal recovery with further research.

Journal Reference:

1. DuChanois, R.M., Cooper, Lee, B. et al. Prospects of metal recovery from wastewater and brine. Nature Water. DOI: 10.1038/s44221-022-00006-z