Lithium from Spodumene Cost-Efficient Low-Temperature Process for Lithium Extraction

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A research team from MIT and other partners has introduced a process to extract lithium from spodumene with significantly lower energy consumption compared to conventional hard rock processing.

An MIT team describes a process that unlocks spodumene at significantly lower temperatures and almost cyclically recovers lithium salts, alumina, and silica. A corresponding research paper was published in the current issue of the journal Science. According to the researchers, the process aims to make the processing of lithium-bearing hard rock more economical while also reducing waste streams.

Spodumene is considered one of the most important lithium-bearing minerals. Conventional processing typically requires roasting the rock at temperatures above 1,000 degrees Celsius, followed by chemical leaching, often with sulfuric acid. With this established approach, primarily the lithium is further processed. Large quantities of silica-rich residual material remain, in addition to energy-intensive process steps and chemical waste streams.

Lower Temperatures During Processing

The MIT process instead relies on an aqueous solution of ammonium fluoride. This enables the components of spodumene to be chemically processed without first transforming the rock at extremely high temperatures.

A key difference lies in the fact that the process does not first extract the more reactive metals, leaving silica as a residue. The researchers specifically use fluoride chemistry to break the strong silicon-oxygen bonds. From the unlocked material, lithium, aluminum, and silicon compounds can then be separately extracted. For lithium, the team demonstrated pathways to lithium fluoride, lithium carbonate, and lithium hydroxide.

Lithium fluoride is itself a relevant starting material for electrolyte materials. Lithium carbonate and lithium hydroxide are among the established precursors for cathode materials.

By-Products as Part of the Concept

A key feature of the approach is that lithium is not the only target product. Aluminum is also recovered as alumina, and silicon as silicon dioxide. According to the researchers, the alumina is expected to achieve a purity of over 98 percent, making it potentially suitable for applications in the aluminum value chain. Tests have been conducted on the silicon dioxide as an additive for cement.

The process thus follows the goal of converting the largest possible portions of the rock into usable products. The researchers refer to this as a nearly closed material cycle.

The reagent cycle is crucial for this. Ammonium fluoride, ammonia, and hydrogen fluoride compounds are processed and recycled in multiple steps, significantly reducing the need for chemicals according to the study.

Costs, Scaling, and Open Questions

The economic assessment by the researchers concludes that the new process could cost slightly over 5,000 US dollars per usable ton of lithium. For the established hard rock route, they cite nearly 9,000 US dollars. If alumina and silicon dioxide can be sold as by-products, the cost position would improve further. The researchers see the approach as being in a range that could compete with high-quality brine sources.

However, these figures remain model-based estimates. Ore quality, energy prices, chemical losses, local permitting conditions, and investments in new facilities can significantly influence actual profitability. Technically, questions also remain unanswered. While some process steps operate at significantly lower temperatures than traditional roasting, others still require elevated temperatures. Furthermore, handling hydrofluoric compounds necessitates robust safety and plant engineering.

The MIT spin-out Rock Zero was founded for commercialization. According to MIT, the company is working on scaling the process. For the electronics and battery industry, it remains particularly relevant whether the approach can operate outside the laboratory in a stable, safe manner and at the expected costs.