Jun 8th 2018
| Resource | Lithium (mg/L) | Dominant Process | Challenges | Opportunities |
|---|---|---|---|---|
| Salars (Lake Brines) | 200-7,000 | Staged evaporation to atmosphere, concentrating and producing lithium. | Large land areas and significant quantities of water used to extract lithium from lake beds. Minimum 18 months from pond start-up to first production due to slow evaporation. |
Massive resource with available natural evaporation energy. Opportunity to hybridize evaporation with concentration and purification technologies. |
| Groundwater Brines | 20-200 | Lithium absorption-desorption on a metal oxide, following by refining. | Tend to be richer in hardness than salars, making processing more challenging. | Vast resources in USA, close to major lithium utilization plays. |
| Oil & Gas Brines | 50-100 | No dominant process established. | Low concentration and extremely large volumes needed, while most produced waters are spread out and smaller volume. | Attractiveness of oil & gas wastewater adding value. |
Roughly half of the world’s commercial lithium is recovered by concentrating naturally occurring lithium brines in evaporation ponds. This practice is low cost and provides ~50% recovery, but is only feasible in arid climates. New technologies are enabling higher recovery of lithium from saline brines without the need for an evaporation pond, opening opportunities in non-desert geographies.
Due to continuing advancements in mobile devices and electric cars, the demand for lithium is outpacing the rate at which lithium is being mined from brines. Lithium is an abundant element, but there are very few commercial resources where lithium is found in concentrations sufficient for producing useful lithium compounds.
The primary sources of lithium are in brines from salars and salt lakes, and lithium-bearing spodumene ores, while geothermal brines represent the second-most productive sources of lithium. Lastly, produced waters from oil & gas fields are an untapped source of lithium that may grow in importance in the future. To ensure the productivity of these lithium resources, it is essential to have lithium recovery technology and processes that are optimized to the characteristics of each individual resource, such as the concentration of lithium, the ratio of lithium to magnesium and calcium ions, and relative concentrations of other ions.
Lithium recovery via conventional chemical precipitation normally starts by subjecting lithium-rich brine to a series of solar pond evaporations. This will precipitate other salts, such as sodium chloride and potassium chloride, while concentrating the lithium. Lime (calcium hydroxide) is then added to the concentrated lithium brine to further remove magnesium as magnesium hydroxide, and sulfate as calcium sulfate. Any calcium in the concentrated brine is removed as calcium carbonate by adding sodium carbonate. The brine that results from these chemical precipitations is then subjected to a carbonation process, where the lithium reacts with sodium carbonate at 80–90°C to produce technical-grade lithium carbonate. This can be further purified to produce battery-grade lithium by re-dissolving the lithium carbonate, and then using an ion exchange process to remove impurities.
To reduce the time that is required for solar-evaporation concentration, lithium will sometimes be precipitated as lithium phosphate, which precipitates more quickly than lithium carbonate due to its roughly 30-fold lower solubility. Lithium phosphate is then converted into battery-grade lithium hydroxide through an electrochemical process.
Lithium-selective ion-exchange sorbents are a promising alternative for extracting lithium from brines. Inorganic ion-exchange sorbents, such as lithium manganese oxides, spinel lithium titanium oxides, and lithium aluminum layered double hydroxide chloride, have been shown to have high capacity for selective lithium uptake. However, the recovery process requires the lithium to be in contact with these sorbents for long periods of time. Additionally, sorbents can be very expensive; they are mostly available as powders that require energy-intensive processes for lithium recovery and can degrade during the acid-driven desorption process.
A novel technique based on an electrolytic cell that contains LiFePO4/FePO4 as an electrode material has been studied to selectively recover lithium. Under an electrochemical process, lithium ions from a lithium-bearing brine are selectively intercalated into a cathode made from FePO4 to form a lithium-saturated LiFePO4. Then, the current is reversed, turning the LiFePO4 into an anode that can be used to recover lithium.
One approach that has been tested to selectively recover lithium from brine involves using an organic phase that comprises kerosene and an extractant, such as tributyl phosphate, trioctylphosphine oxide (TOPO), and beta-diketone compounds. Although these organic phases show very high selectivity toward lithium over sodium and magnesium ions under optimized conditions, the lithium stripping phase uses solvent extraction that can result in costly equipment corrosion. In addition, the residual brine that remains after lithium extraction may require post-treatment to remove the leached solvent before it can safely be sent for disposal.
Reverse osmosis (RO) and nanofiltration (NF) processes have been studied for pre-concentrating or separating lithium from a lithium-bearing brine. A typical lithium brine usually contains high concentrations (e.g. > 5.0 wt%) of salt ions. The maximum salt concentration that an RO/NF process can reach is linked to the osmotic pressure, as well as the membrane’s selectivity and the mechanical stability of any associated equipment. Automated chemical softening systems, such as our BrineRefine system, can help membrane treatment systems reliably reach their treatment limits and improve yield. Conventional NF processes cannot efficiently separate lithium without heavy pre-treatment of the brine, such as diluting the brine with a large amount of fresh water.
Electrodialysis systems, such as our FlexEDR Selective, should be viewed primarily as concentrators and not as refining technology. This is because today’s monovalent EDR systems cannot separate sodium from lithium, and although monovalent electrodialysis may separate monovalent ions from divalent ions, the separation is less effective than chemical methods in the case of lithium, resulting in higher yield losses.
Saltworks Technologies is a leader in the development and delivery of solutions for industrial wastewater treatment and lithium refining. By working with customers to understand their unique challenges and focusing on continuous innovation, Saltworks’ solutions provide best-in-class performance and reliability. From its headquarters in Richmond, BC, Canada, Saltworks’ team designs, builds, and operates full-scale plants, and offers comprehensive onsite and offsite testing services with its fleet of mobile pilots.
Saltworks’ Lithium Test Center combines expertise and industry-leading technology to provide innovative solutions for processing lithium resources into battery-grade outputs. The Center is dedicated to de-risking lithium processing projects and accelerating full-scale implementation.
Saltworks is pleased to announce the production of battery-grade lithium hydroxide from an industrial wastewater. Saltworks’ process harvests lithium hydroxide solids that reach or exceed battery-grade specifications.
This lithium process flow brochure shows how membrane, thermal, and chemical water technologies fit into various stages of lithium production. Learn how to process lithium to battery-grade, downstream of direct lithium extraction.
Saltworks brings water mining expertise and advanced desalination technologies to our lithium clients, offering solutions for concentrating, refining, and converting low-grade lithium sources to battery-grade product. We offer higher purity and lower energy processing technology, that boosts yield, removes unit operations, and reduces cost.
