PNNL

As technology evolves, the demand for domestic critical materials—such as nickel—continues to increase beyond what can be practically sourced using traditional mining methods. Researchers are exploring alternative, previously unconsidered nickel sources, such as the mineral olivine, that have lower concentrations of the critical element but are widely available across the United States.

Scientists from the Non-Equilibrium Transport Driven Separations (NETS) Initiative are identifying ways to leverage unconventional resources to develop robust, secure domestic supply chains for critical minerals. In research published in RSC Sustainability, NETS researchers found that waste acid enabled more efficient extraction of nickel from the common mineral olivine than commercial hydrochloric acid. A preliminary economic analysis of the team’s approach showed that combining waste product from a marine process with nickel recovery from olivine results in an additional $24 per ton of ore sold, leading to a net positive price compared to previous studies showing a net negative. 

“I think there’s something powerful about utilizing materials we would typically either ignore or consider as waste,” said Chinmayee Subban, the corresponding author of the study and a leader in the NETS Initiative. “In order to meet the growing demand for critical minerals, we have to be creative about our resources. Using waste to act as a reagent helps us lower costs and be more efficient in our overall approach.”

The team coupled critical mineral extraction to a marine-based process that generates both acidic and basic streams from seawater. In an initial step, they combined olivine rock with the waste acid at room temperature to leach the nickel. A second step uses a small amount of the basic product to remove other undesirable elements while leaving nickel and magnesium in solution. The nickel-rich solution is then electroplated to form a valuable nickel-iron alloy suitable for use in stainless steel production. The magnesium remaining in solution is returned to the ocean. While this approach couples the two processes for efficiency, they remain modular—deployable individually or in concert with other systems.

On the economics side, the integrated process offers cost reduction in two ways. First, using the acid waste product in the nickel extraction process means it is no longer necessary to dispose of the acid, which saves costs. Second, enhanced olivine leaching with waste acid increases overall nickel yield, improving process efficiency while producing a critical material. “Generating multiple value streams is central to enabling the use of lower-grade ores and alternate feedstocks,” said Subban. “The electrochemical process can be easily scaled-up or down, and performed anywhere with access to seawater, which also offers abundant untapped marine energy resources, making it potentially field-deployable in remote locations.”  

This approach is part of a larger research effort to reimagine mining on land and at sea. Researchers across Pacific Northwest National Laboratory are developing new methods to extract critical minerals with less infrastructure overhead, from more challenging-to-access resources, and using unconventional sources previously deemed economically unviable. This research was funded by the NETS Initiative and the Hydropower and Hydrokinetic Office (H2O).