Salt lake lithium extraction is evolving from a single “liquid-phase separation” approach toward more diversified process pathways. Traditional solar evaporation methods rely on long-term evaporation concentration and staged crystallization to enrich lithium, while direct lithium extraction (DLE) technologies use adsorption, ion exchange, membrane separation, and other approaches to extract lithium directly from brine. Although these two routes differ in efficiency and process design, both ultimately address the challenge of separating lithium from coexisting elements such as sodium, potassium, magnesium, and boron. As salt lake resource development increasingly expands into low-grade, high-impurity, and severely water-constrained regions, reducing freshwater consumption, managing complex impurities, and improving resource utilization efficiency are becoming critical factors in technology selection. Against this backdrop, a new approach different from conventional liquid-phase lithium extraction has attracted attention: allowing salts in brine to precipitate first, followed by selective lithium extraction from solid salts. The Solar-Driven Selective Dissolution (SSD)process proposed by a research team from Monash University in Australia represents a notable exploration in this direction.
The fundamental innovation of SSD lies in transforming crystallization from merely a concentration step into a separation method. The basic process uses solar evaporation to gradually precipitate salts from brine and form solid salts, followed by selective separation based on the differences in solubility among various salts in organic solvents. Research indicates that lithium chloride can preferentially dissolve into the liquid phase, while sodium chloride, potassium chloride, and certain impurities such as boron and sulfate remain largely in the solid phase. Magnesium and other components can be further separated through subsequent solvent systems. In other words, SSD does not attempt to directly “find lithium” within highly complex brine. Instead, it first changes the composition of the material system through salt precipitation and then reduces separation difficulty by leveraging solubility differences. This “solidification first, extraction second” logic provides an alternative process configuration for traditional salt lake lithium extraction.
Water consumption is one of the key reasons why this technological approach deserves attention. Many salt lake projects worldwide are located in arid regions, where freshwater availability directly affects production costs, environmental impact, and long-term operational sustainability. Although traditional evaporation methods utilize solar energy, they generally require long processing cycles. DLE technologies can shorten processing flows, but they do not necessarily eliminate overall process water requirements. SSD attempts to use solar energy for front-end concentration and salt precipitation, followed by lithium selective dissolution through anhydrous organic solvents, thereby reducing dependence on freshwater. The research team conducted experiments using actual salt samples from the Uyuni and Hombre Muerto salt lakes, achieving lithium recovery rates exceeding 90%, with the highest recovery approaching 95%, while also demonstrating effective removal of certain impurities. If this performance can be further validated through larger-scale continuous operation, SSD could present significant application potential in water-limited salt lake regions.
However, transitioning SSD from laboratory results to industrial-scale production still requires addressing several challenges. The first concerns the safety and recycling of organic solvents. Solvents such as ethanol and acetone are volatile and flammable, meaning large-scale deployment would require supporting systems including closed-loop operation, explosion protection, condensation recovery, and VOC control. The relatively high solvent recovery rates achieved under laboratory conditions also require validation through long-term continuous operation. The second challenge involves the management of large quantities of by-product salts generated after precipitation. If solid sodium chloride, potassium chloride, and other products can be effectively separated and utilized, they could further improve project economics. Conversely, if these materials require disposal as waste, downstream costs may offset the technology’s advantages. Therefore, the commercial value of a new technology should not be evaluated solely based on lithium recovery rates, but should also consider energy consumption, solvent losses, by-product utilization, equipment investment, safety, environmental compliance, and long-term operating costs.
More importantly, the insights brought by SSD extend beyond the technology itself. The differences among salt lakes in lithium concentration, magnesium-to-lithium ratio, boron content, sulfate levels, climate conditions, and water availability mean that no universal process can be applied to all projects. Future salt lake lithium extraction is more likely to evolve toward the integration of multiple unit technologies: evaporation and crystallization may serve as front-end concentration and impurity removal steps, while DLE, membrane separation, ion exchange, or electrodialysis technologies may enable high-selectivity lithium recovery in subsequent stages. For resources with high magnesium content, high boron levels, or severe water constraints, modifying brine composition through upstream salt precipitation, concentration, or impurity removal may be more meaningful than simply improving the performance of a single lithium extraction unit. In other words, crystallization may no longer be viewed merely as an intermediate stage in traditional evaporation-based processes, but rather as a new resource pretreatment approach.
BICHEM believes that SSD and DLE are not simple alternatives to each other; more importantly, they encourage the industry to rethink the boundaries of salt lake lithium extraction processes. As a DLE technology company, BICHEM does not focus on replicating a single technology across all salt lakes, but instead combines suitable separation units based on specific brine conditions to achieve a balance among recovery rate, water consumption, energy efficiency, and operational stability. For certain salt lakes characterized by high impurities, low lithium grades, or severe water scarcity, reasonable front-end salt precipitation, concentration, or impurity removal may create synergies with DLE, membrane separation, and other technologies. In the future, the most competitive salt lake lithium extraction solutions may not be those with the highest performance metrics from a single technology, but those capable of transforming complex salt lake resources into stable lithium supplies through lower water consumption, higher resource utilization efficiency, and more controllable lifecycle costs.
