by Matt Ganser, SVP Sales and Government Affairs

As the world shifts towards electrification, the race for lithium has truly gone global. Enabled by a host of promising Direct Lithium Extraction (DLE) technologies, governments and companies alike have begun to reexamine every brine resource in the hopes of securing local supply or reaping fortunes.

As producers tackle early development challenges, DLE technology selection quickly becomes paramount because of its cascading influence on nearly every facet of the project. Faced with an array of DLE technology choices, producers are quickly finding an Achilles heel in each; speaking generally and reflecting industry sentiment, alumina adsorbents have eluate purity and freshwater usage concerns (eluate = output stream from the DLE process), solvents require a hazardous brew of chemicals (typically a kerosene sort of product), and ion exchange (i.e. Lilac) uses acid.

While it’s challenging to find many industrial scale processes that don’t use acid, its use in IX has led to some concerns about it impacting things like depleted brine, eluate product, and regulatory decisions. Fortunately, we have answers, and we can start to address these concerns not with lab bench hypotheticals, but field data and permits.

Acid is a Feature, Not a Bug

While ion exchange (IX) is not alone in its reagent use in the flowsheet, the volume of acid is higher than some other DLE approaches because it is the primary stripping, or elution, mechanism. In comparison, aluminum adsorbent DLE technologies typically use acid for brine pH adjustment, with freshwater as the primary elution mechanism.

In Lilac’s process, raw brine from a salar, oilfield, geothermal, or other reservoir source passes through our ion exchange media (IXM). The Li+ ions in the feed brine displace the H+ ions bonded to the Lilac IXM. Once the IXM is fully loaded, we strip (or elute) the Li+ ions using a dilute acid, either hydrochloric (HCl) or sulfuric acid (H₂SO₄). To be clear, these are distinct steps; the lithium-depleted brine is reinjected or disposed of without contacting acid.

Figure 1: The basics of the Lilac ion exchange (IX) lithium extraction process.

The result? A highly pure lithium chloride (LiCl) or lithium sulfate (Li₂SO₄) intermediate product, aka eluate stream, regardless of the brine grade or type [Table 1].

Table 1: Lithium and other impurities concentrations of the Lilac eluate with Gen 4 Lilac IX.

Download the full white paper for more data.

We’ll cover more on this on a future blog post, but our view is that an eluate stream like this mitigates the need for exotic (i.e. expensive) downstream purification of magnesium (Mg), calcium (Ca), boron (B), and potassium (K). In brief, we think our eluate stream translates to a higher quality product at a lower overall flowsheet cost. And acid (along with our highly selective extraction media) is the ingredient that makes it possible.

Permits to Prove It

Mining has a checkered history, and permitting authorities understandably care a lot about the flows coming out of any production operation; their primary role is to protect the people and environment.

In DLE, the primary permitting concern is the condition of the lithium-depleted brine, or ‘delithiated’, stream coming out of the DLE unit. Once lithium has been removed from the brine, this stream is typically reinjected into the reservoir, maintaining reservoir pressure while eliminating disposal ponds (a convenient two-for-one deal).

Because we are a new technology that involves acid, we usually get two questions from customers: (1) Is your lithium-depleted brine acidic? (Answer = No) and (2) Can it be permitted? (Answer = Yes).

From a process perspective, the brine does become slightly more acidic as it moves through the IX reactor—we are exchanging Li+ ions for H+ ions in the brine after all—but this is easily fixed with a neutralization step, typically with the addition of something like calcium hydroxide, which is pretty cheap stuff. In doing so, we can tailor the lithium-depleted brine to look nearly identical to the natural brine, sans the lithium, and certainly to whatever pH levels the permitting authorities (or customer) require.

Take the Kachi project [Table 2] as an example. In that case, we used sodium hydroxide for neutralization. This increased the sodium ion levels, but only by a fraction of a percent above the sodium content already naturally present in the brine. And this is what permitting folks have quickly understood in our experience. At the end of the day, although our process uses bases and acids, when one looks at the present ions in the lithium-depleted brine, it closely matches the original brine. We’ve removed lithium, and in its place, there is a tiny bit more sodium (or calcium).

Table 2: Cation concentrations at the Kachi Demo Project with Gen 3 Lilac IX.

The ultimate proof point, frankly, is that authorities who have worked closely with Lilac have already approved permits for the return of lithium-depleted brine to the native resource. At the Great Salt Lake, USA, authorities have granted Lilac a permit to return the lithium-depleted brine from our latest pilot to the lake, for a net non-consumptive use of the lake brine.

Lilac lithium pilot facility on the Great Salt Lake, Utah, USA

A Freshwater Bargain

A key community benefit stemming from our use of acid is that it greatly reduces freshwater consumption. In our IX process, acid, not large volumes of freshwater, is used to strip away the lithium from our beads. We do require water, but its primary use is to dilute our acid and briefly rinse the beads between loading and unloading steps. Most of this water is never mixed with brine and can be easily recovered and recycled. To put this in numbers, our total freshwater use for the Lilac DLE process starts below 20 m3 per t LCE, and with some off-the-shelf recycling technologies, we can cost-effectively reduce this to less than 10 m3 per t LCE.

In contrast, alumina adsorbents rely on freshwater to free lithium and make an eluate stream – it’s the main ‘reagent’ and stripping mechanism – and because there is inherent mixing with brine, it makes it difficult to recycle. Simply put, this approach can use a lot of freshwater.

The Hombre Muerto project in Argentina, one of the most well-known and earliest applications of alumina adsorbent technology, uses 100-120 m3 of freshwater per t LCE to reach an intermediate product¹. Fast forward, the early results from Eramet’s facility, probably the most modern and best example of the potential for DLE (no pre-concentration ponds), are not yet publicly available, but we guess somewhere around 50-100 m3 per t LCE based on our own literature review.

This impact is also felt locally at the project site, as trucking freshwater will almost assuredly be cost prohibitive, straining local freshwater supplies even more.

In short, a small amount of dilute acid effectively replaces a very large amount of freshwater.

Nearing Evaporation Ponds on Costs

Chile and Argentina contain the world’s largest and most well-understood brine resources in massive salars, with high lithium grades and shallow wells that translate to low production costs. If there is a benchmark for OPEX, one of the key metrics for any extraction executive, this is it.

The traditional method involves mixing chemicals and rotating brine through a series of evaporation ponds covering thousands of acres. Essentially, it’s earthworks, pond-liners, chemical addition, and sunlight—literally. This process works, and it’s cheap, but only feasible in a handful of places in the world with those conditions.

While Lilac has not yet been able to match evaporation ponds on an OPEX cash basis, we are close and narrowing the gap with each pilot campaign. In our view, the superior eluate profile enabled by the IX process (and acid) brings us within striking distance.

These all-in costs, based on extensive testwork and third-party FEL engineering, include acid, IXM replacement, power, etc. More to come in a future blog post.

And No, the IXM Doesn’t Degrade Quickly

A familiar question from customers is whether our IXM formulation survives the acidic environment within the IXM reactors (that whole H+ thing). The answer is yes: This is one of our scientific obsessions.

In ion exchange, lithium ions are repeatedly moved in and out of the IXM, similar to ions moving in and out of anodes and cathodes in a battery. This eventually causes wear and degradation over time, impacting overall cycle life and directly translating to OPEX. Ion exchange has historically been seen as a theoretically superior DLE method, but early attempts had issues cycling for longer than a dozen cycles, translating to unacceptably high OPEX.

Solving the issue of durability was of fundamental importance for Lilac and one of our core advancements. By modifying bead formulations, unit operations, reactor design, and more, we have been able to greatly extend cycle life while increasing lithium recovery.

To put this in numbers: In Oakland, we have hit thousands of cycles across a variety of brines, and in a couple of cases, we are on track to exceed 4,000 cycles even on low grade brines. Ultimately, this IXM cycle life translates to practical benefits (higher uptimes) and economic benefits (low OPEX).

Beyond the DLE Block

The need for clean, affordable lithium is a growing problem. As producers review their DLE options, we are encouraging customers to think beyond the DLE block and consider how a technology choice ultimately impacts economics, resource accessibility, compliance, and supply chain security.

We’re biased, but our view is that higher quality eluate and lower freshwater use, enabled by acid, translates into a favorable flowsheet for any brine, anywhere.

Download our White Paper to learn how
Lilac’s IX technology is redefining DLE

¹ Resource and Reserve Report – Pre-Feasibility Study – Salar del Hombre Muerto (Livent, November 2023)