The Eluate Advantage: How DLE Output Drives Project Costs

As the world electrifies and the geopolitics of supply chains unravel, the global race to secure lithium supply is accelerating. Meeting this demand increasingly requires extracting lithium from chemically complex brine resources, including those found in South America, the U.S., and Europe. 

Direct lithium extraction (DLE) has emerged as the enabling technology category to unlock lithium production from these resources, which were previously deemed uneconomic. DLE selectively captures lithium from brine while rejecting impurities, producing a purified intermediate solution – the eluate, the output of the DLE process. This eluate is then refined into saleable lithium products.

Dozens of providers have recently entered the crowded field of DLE, but not all DLE eluates are created equal. Eluate purity, composition, concentration, and consistency directly determine downstream refining costs, capital intensity, and overall project economics. This blog explores the factors that matter most when evaluating eluate streams and how they shape whole-flowsheet economics.

Eluate = the purified, lithium-rich solution produced as the output of the DLE process. 

The Eluate: Keystone of Whole-Flowsheet Economics

Choosing the right DLE technology is essential for optimizing performance and cost for lithium projects. But lithium projects are comprised of an entire flowsheet – starting with the wellfield producing brine all the way through to finished product –, and the DLE portion, or ​‘DLE block,’ is just one segment of that flowsheet. Thus, when evaluating DLE technologies, it is not only important to examine the cost and performance of the DLE block itself, but also its impact on the economics of the rest of the flowsheet.

Costs are distributed across the entire flowsheet, as shown in Exhibits 1 and 2. The DLE block typically accounts for only 20 – 30% of total project CAPEX and 30 – 40% of OPEX of project flowsheet, but has direct impact on the costs for upstream brine pre-treatment and downstream processing & refining. The best fit DLE technology for a given brine resource will therefore produce the eluate profile that delivers lowest overall cost at a flowsheet-level.

Not All Impurities Cost the Same

At its core, DLE is a separation and purification process: lithium is captured while impurities such as sodium, magnesium, calcium, potassium, and boron are rejected. The ​“gold standard” eluate is a highly pure, highly concentrated lithium stream. The purer and more concentrated the eluate, the simpler and cheaper the downstream refining. 

A good DLE may achieve overall 99.9% impurity rejection, but there are important details beyond this headline number. To produce battery-grade lithium, nearly all residual impurities in the eluate must still be removed during refining, and before product crystallization. That’s why it’s essential to look beyond overall rejection rates and look at how specific impurities affect the downstream process and economics.

Boron

Boron (B) is naturally present in many brines and can be a valuable product on its own. However, if it finds its way into the eluate, it adds a costly removal step. For example, take the La Negra lithium plant in Atacama¹ which refines lithium from evaporation ponds. Their boron removal process involves using hydrochloric acid to acidify the brine, mixing that with a solution of boron extractant in an organic solvent, and then separating the boron-lean brine from the organics in a settling tank. The extractant is regenerated with water, producing an additional boron-rich wastewater stream. All these steps increase process complexity, reagent consumption, and cost. 

The high selectivity of Lilac’s ion exchange (IX) technology avoids this problem by rejecting boron outright. In fact, the design for Lilac’s Great Salt Lake Phase 1 commercial facility requires no boron-removal step in refining — lowering both CAPEX and OPEX. This type of B rejection is not generally true of other DLE technologies, where B removal is required even after the DLE process.²

Calcium and Magnesium Hardness

Divalent impurities such as magnesium (Mg) and calcium (Ca), often referred to as hardness, are ubiquitous and inevitably make their way into the eluate. Removing them typically involves chemical softening, treatment with cation exchange resins, or nanofiltration. While these technologies aren’t terribly complicated, they add cost to lithium production, due to the extra reagents required and costs of solid waste disposal, especially in jurisdictions with high waste disposal costs. A high-performance DLE solution ensures that hardness in the eluate is minimized and remains at a consistent level, ensuring efficient operation of the downstream lithium refining equipment.

Lithium-to-Impurity Ratio

While it may seem obvious that lower impurities are better, it is important to understand why it impacts the downstream process. A higher ratio of lithium to impurities increases the lithium concentration at saturation in the crystallizer, leading to better crystallization recovery. It also minimizes the accumulation of impurities in the mother liquor discharged from the crystallizer, allowing a higher portion of it to be recycled for lithium recovery, rather than purged and lost. The net result is higher lithium downstream recovery and better economics.

For project developers competing in a low-price environment, where every percentage of cost savings can be decisive, these impurity factors can make a direct impact on project feasibility and profitability. 

Lilac’s ion exchange (IX) DLE technology consistently delivers high lithium-to-impurity ratios and produces a high purity, high concentration lithium stream, as shown in Exhibit 3.

Higher Lithium Concentration = Lower Costs 

The eluate produced by the DLE process is a salt-containing liquid stream, while the battery-grade lithium carbonate or hydroxide sold to the market is a solid white powder. To get there, nearly all the water in the eluate must be removed before the product can be crystallized. Starting with a higher lithium concentration in the eluate means there is less water to remove and treat, which lowers the costs for pumps, pipes, membranes or evaporation equipment.

The cost impact of producing eluate with a higher lithium concentration is shown in Exhibit 4. A lithium carbonate crystallizer typically requires a feed of >20,000 mg/​L of lithium. If the eluate contains 1,000 mg/​L or less of lithium, as is common with many DLE technologies, a 15 – 30x concentration step is required to reach crystallizer feed. The higher the lithium concentration in the eluate, the lower the required investment to concentrate the eluate. 

By contrast, as shown in Exhibit 3, Lilac’s Gen 5 DLE consistently produces eluate with 4,000+ mg/​L of lithium, regardless of the starting brine grade. At the Great Salt Lake (~70 mg/​L Li), this represents a more than 70x increase from brine to eluate, which reduces the CAPEX for RO concentration by 50 – 80% compared to DLE technologies that produce low (< 1,000 mg/​L) concentration eluates. For projects processing LiCl, this completely eliminates a sea water RO system from the flowsheet, and allows the eluate to be concentrated simply by an evaporator or OARO system.

Consistency: Reliable Eluate Profile, Every Time

Whether it’s dilution, seasonal variation, or changes in well production, brine feed composition will inevitably shift over the 20+ year life of a lithium project due to resource dilution over time from reinjection of de-lithiated brine. A robust DLE technology must handle these variations seamlessly and deliver a consistent eluate profile, so that downstream refining runs smoothly and reliably produces battery-grade product.

Lilac’s IX DLE has demonstrated this across diverse brines, spanning more than two orders of magnitude in lithium and impurity concentrations, as shown in Exhibit 3. Across this spectrum, the eluate consistently contains 4,000+ mg/​L lithium with minimal impurities. This enables a consistent eluate purity to be delivered to downstream refining operations, stabilizing project economics over the project’s entire lifetime.

Better Eluate, Better Economics

For sophisticated developers, unlocking value in DLE projects means optimizing the entire flowsheet, not just the extraction block. By looking beyond headline lithium recovery percentages and impurity rejection rates to more specific impurity content, lithium concentration, and eluate consistency, developers can make smarter technology choices to optimize the whole flowsheet for cost. These properties of the eluate become a lever for lower capital intensity, reduced operating costs, and seamless integration into downstream refining and local manufacturing ecosystems. 

At Lilac, we optimize the eluate properties from the earliest mini-pilot testwork, and carry those insights through FEED and FID. This integrated approach ensures strong, resilient economics — wherever the brine comes from.