The review focuses on membrane-design approaches rather than reporting a new experiment or clinical study. Its discussion covers substrate regulation, interfacial polymerization and structural optimization of polyamide layers. It highlights emerging membrane concepts, including charged membranes, Janus membranes, biomimetic membranes and membranes containing sub-nanometer channels, which are described as having potential for improved selectivity. The authors also address operating conditions and coexisting ions so that performance considerations reflect realistic brine conditions.

According to the abstract, nanofiltration membranes are presented as promising because they combine low energy consumption with tunable selectivity for Mg²⁺/Li⁺ separation. However, the review does not provide a single quantified separation performance, flux value, energy comparison or durability result in the available summary. Its central contribution is an organized account of separation mechanisms and design strategies reported in recent membrane research.

The authors conclude that important challenges remain in membrane stability, fouling resistance and maintaining performance under high salinity. These limitations bound the current prospects described in the review: improved selectivity in a particular membrane system does not by itself establish reliable performance across complex brines. The review concludes by outlining future-development perspectives for nanofiltration membranes intended for lithium–magnesium separation.

Subject of Research: Review of nanofiltration membrane mechanisms and design strategies for magnesium–lithium separation from brines.

Article Title: Review: nanofiltration membranes for Mg2+/Li+ separation from brines: mechanisms and advanced design strategies

Article References: Yue, T., Li, H., Chen, X., Xiao, S., Wu, Y., & Yu, S. (2026). Review: nanofiltration membranes for Mg2+/Li+ separation from brines: mechanisms and advanced design strategies. Journal of Materials Science, 61(44), 34506-34534. https://doi.org/10.1007/s10853-026-13820-7

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13820-7

Keywords: nanofiltration, magnesium separation, lithium extraction, salt-lake brines, polyamide membranes, size sieving, Donnan exclusion, ion competition, Janus membranes, fouling resistance, Review, membranes

The scale of the challenge is staggering. China alone consumes roughly half of the world’s lithium, driven largely by its dominant position in the electric vehicle market, and has pledged to cut greenhouse gas emissions by 60 to 65 percent by 2030. Meanwhile, mining these metals generates vast quantities of tailings laden with heavy metals and chemicals. When improperly disposed of, these wastes contaminate water supplies, destroy biodiversity, and degrade soil — with acid mine drainage, in which sulfide minerals oxidize to produce extremely acidic runoff, posing the single greatest threat to water quality across large regions. Conventional recycling routes offer little relief: pyrometallurgical smelting is energy-hungry, while hydrometallurgical leaching demands aggressive acids and generates sludge and saline effluents of its own.

Membranes work on an entirely different principle. Instead of burning or dissolving entire waste streams, they act as molecular gatekeepers — semi-permeable barriers that allow some ions to pass while blocking others based on size, electrical charge, or specific chemical interactions. Pressure-driven systems such as ultrafiltration, nanofiltration, and reverse osmosis push liquid through these barriers, while electro-driven systems like electrodialysis use an applied voltage to steer ions toward oppositely charged electrodes. The review categorizes four main feed streams — battery leachates, acid mine drainage, salt-lake brines, and industrial effluents — each with distinct chemistries that demand tailored membrane approaches rather than one-size-fits-all solutions.

The most striking results come from lithium recovery. In acidic sulfate leachates from spent batteries, lithium exists largely as free Li+ ions while cobalt, nickel, and manganese form sulfate complexes. Negatively charged nanofiltration membranes exploit this difference: they repel the multivalent transition metal cations through electrostatic repulsion and size exclusion while allowing the smaller, singly charged lithium ions to permeate. One study cited in the review achieved 99.5 percent pure lithium carbonate after just two nanofiltration passes — approaching battery-grade material without harmful chemical additives. Another research group using polymer inclusion membrane electrodialysis, where selective carriers embedded in a PVDF-HFP polymer matrix bind lithium and cobalt ions, reported recoveries of 99.1 percent for lithium and 99.9 percent for cobalt, with a carbon footprint of just 3.1 kilograms of CO2-equivalent per kilogram of lithium recovered.

Separating lithium from magnesium in brines presents an even tougher puzzle because the two ions have similar ionic radii. Here, the review explains that the key lies in hydration energy: magnesium ions hold water molecules far more tightly than lithium does, giving Mg2+ a bulkier, more strongly bound hydration shell. Negatively charged nanofiltration membranes exploit this by electrostatically repelling the divalent magnesium while the monovalent lithium slips through more easily. Separating cobalt from nickel is harder still — both are divalent with nearly identical hydrated radii — so simple charge exclusion fails. Supported liquid membranes, which impregnate a porous support with a tailored organic extractant that reversibly binds one metal preferentially, offer a way forward, achieving extraction and stripping efficiencies of 85.7 and 83.2 percent for nickel in one reported case.

But the review is refreshingly honest about where membranes struggle. Real battery leachates are not clean laboratory solutions: they are acidic (often below pH 2), highly saline, loaded with organic residues from binders and electrolytes, and contain a shifting cast of competing ions. Under these conditions, membranes fail in chemistry-specific ways. Precipitation is the most common culprit — as pH, temperature, or ionic strength shifts, salts like calcium carbonate, magnesium hydroxide, and gypsum (calcium sulfate dihydrate) become supersaturated and crystallize on membrane surfaces, blocking pores and causing irreversible flux decline. Iron and aluminum hydrolyze into gelatinous hydroxides that clog membranes, while oxidants such as hydrogen peroxide and hypochlorite — often added during leaching — attack polyamide membranes chemically, degrading the polymer itself.

Long-term durability emerges as the review’s central concern. In one particularly revealing study, commercial NF270 and DK nanofiltration membranes were exposed to hydrochloric acid at pH 1 for up to 30 days. Both initially retained divalent ions at 96.5 percent or better, but NF270’s rejection dropped from 99.1 to 84.3 percent over the exposure period — a systematic decline the authors attribute to acid hydrolysis of the polyamide active layer. Another group incorporated sulfonated covalent organic framework nanosheets into a nanofiltration membrane to boost acid resistance; initial lithium rejection was moderate at 43.7 percent while divalent metals exceeded 90 percent, but even this engineered membrane lost significant performance after 7 to 14 days in acid. The lesson, the review argues, is that short-term laboratory tests cannot predict months-long industrial performance.

On economics, the numbers are encouraging but conditional. Membrane processes like electrodialysis and nanofiltration typically consume 0.5 to 5 kWh per cubic meter of treated water — substantially less than conventional thermal or precipitation-based routes, which can exceed 10 kWh per cubic meter when the full water-intensive mining chain is accounted for. Membrane-hybrid systems have demonstrated 50 to 84 percent reductions in total energy demand compared to conventional solvent extraction. Lithium recovered from salt-lake brines costs roughly USD 2 to 3 per kilogram, compared with around USD 80 per kilogram from seawater, while lithium carbonate commands a market price near USD 24 per kilogram — making brine-based membrane recovery economically attractive. Polymeric membranes last 5 to 8 years and ceramic membranes 15 to 20, offering long-term savings through reduced replacement frequency.

Yet the review is careful to position membranes as complementary rather than replacement technology. Nanofiltration achieves lithium selectivity in the 70 to 90 percent range with transition metal rejections typically above 90 percent, but separating chemically similar divalent cations like nickel from cobalt remains limited. Fluxes in concentrated leachates are often constrained to below 10 liters per square meter per hour due to osmotic pressure and fouling. Membranes excel at lithium concentration and acid recovery, but solvent extraction or precipitation is still needed for full transition metal separation. The realistic industrial pathway, the authors suggest, is a hybrid flowsheet: membranes as selective concentration and acid-recycling steps, followed by conventional precipitation to deliver battery-grade products.

The review’s conclusion is both a warning and a roadmap. The principal bottleneck in membrane-based critical material recovery is not initial separation performance — many studies already report 90 to 99 percent recovery — but sustained stability, fouling control, and honest accounting of energy per kilogram of product, membrane lifetime, and cleaning frequency under realistic leachate conditions. Few studies report these parameters, and most rely on simulated rather than real battery-derived streams. Future progress, the authors argue, depends on targeted material innovations such as acid-resistant thin-film composites and crown ether-functionalized ion-exchange membranes, thorough long-term stability testing, and integration into holistic pretreatment and recovery trains. If those gaps close, membranes could shift from promising laboratory curiosities to indispensable components of a circular economy that treats yesterday’s batteries and mine waste as tomorrow’s ore bodies.

Subject of Research: Membrane-based separation technologies for recovering critical metals from spent batteries and mineral wastes

Article Title: Membrane-based extraction of critical materials from spent batteries and other mineral wastes

Article References: Matebese, F., Raseala, M. J., & Moutloali, R. M. (2026). Membrane-based extraction of critical materials from spent batteries and other mineral wastes. Frontiers in Membrane Science and Technology, 5, Article 1766669. https://doi.org/10.3389/frmst.2026.1766669

Image Credits: AI Generated

DOI: 10.3389/frmst.2026.1766669

Keywords: membrane technology, lithium recovery, battery recycling, nanofiltration, electrodialysis, acid mine drainage, critical materials, circular economy, cobalt, nickel, fouling, hydrometallurgy

The scale of the disposal problem is considerable. Coastal discharge can deliver salinity shocks to marine ecosystems, harming corals, seagrasses and shellfish that cannot tolerate hypersaline conditions. Elevated salinity disrupts the osmotic balance of marine organisms, causing dehydration, impaired reproduction and elevated mortality among juvenile fish and larvae. Chemical residues from antiscalants, coagulants and chlorine-based disinfectants add a toxic dimension, while heavy metals such as lead, mercury and chromium, released through pipeline and equipment corrosion, accumulate in marine sediments and can bioaccumulate through the food chain. Thermal desalination plants, which use multi-stage flash and multi-effect distillation, discharge brine at elevated temperatures that can trigger thermal shock in sensitive species and promote algal blooms, whereas reverse osmosis plants produce cooler brine with fewer temperature-related impacts.

Inland disposal carries its own hazards. Deep-well injection risks aquifer salinization if brine migrates through geological formations into freshwater reserves, and poorly lined evaporation ponds can leak salt and contaminants into surrounding soils and groundwater. Regulators have responded with an increasingly complex patchwork of rules. The United Nations Environment Programme recommends limiting discharge salinity to no more than 5 percent above ambient seawater, while the International Maritime Organization’s MARPOL Convention classifies brine as non-harmful only if pre-treated to remove toxic additives. In the United States, the Environmental Protection Agency enforces limits on total dissolved solids and boron under the Clean Water Act, and California’s Carlsbad plant now recovers 98 percent of its brine for industrial salt production. Saudi Arabia mandates offshore diffuser systems, and the United Arab Emirates caps brine temperature at 3 degrees Celsius above ambient seawater.

Yet the same chemistry that makes brine an environmental liability makes it a potential treasure trove. Sodium chloride constitutes roughly 60 to 70 percent of the dissolved solids in brine and can feed the chlor-alkali, Solvay and Hargreaves industrial processes. Magnesium, present at 1350 to 1660 milligrams per cubic decimeter, can be precipitated as magnesium hydroxide and converted into fertilizers or magnesium oxide. Calcium supports the production of gypsum and calcium carbonate, materials consumed at more than 200 million and 100 million tons per year worldwide respectively. Potassium and sulfate are valuable for fertilizers, and trace elements including strontium, boron, rubidium and cesium serve niche markets in drilling fluids, glass and electronics.

The most coveted target is lithium. Although seawater-derived brine contains only about 0.17 milligrams of lithium per cubic decimeter, surging battery demand has strained terrestrial supply chains and focused attention on unconventional sources. Recent pilot projects have achieved lithium concentrations 43,000 times seawater levels through iterative membrane sieving, and electrochemical intercalation and manganese dioxide-based adsorption offer selective extraction routes. Market analyses project that global demand for lithium will rise by 300 percent by 2030, with magnesium demand growing 50 percent, underscoring the strategic value of securing these elements from an existing industrial waste stream rather than opening new mines.

Brine also offers a surprising climate benefit. Its high magnesium and calcium content makes it a potent medium for carbon dioxide mineralization, in which carbonation reactions convert these ions into stable carbonates such as magnesium carbonate and calcium carbonate. The process can sequester up to 2 tons of carbon dioxide per ton of magnesium while producing marketable materials for cement and soil stabilization. A California brackish water treatment plant already produces calcium carbonate pellets that offset 15 percent of its operational emissions, and electrodialysis-coupled carbonation systems have demonstrated feasibility at pilot scale. Advances in pH control and antiscalant-free precipitation are narrowing the gap between laboratory success and commercial deployment.

The salinity gradient between brine and freshwater represents a third avenue of value: renewable energy. Pressure retarded osmosis and reverse electrodialysis harness the chemical potential difference across semi-permeable membranes, and pilot-scale systems have achieved power densities of 2 to 4 watts per square meter. A 240 cubic meter per day pilot plant combining seawater reverse osmosis with pressure retarded osmosis demonstrated a potential 20 percent energy reduction, while hybrid reverse electrodialysis systems integrated with nanofiltration aim to offset desalination energy costs by 20 to 30 percent. Each approach has trade-offs: pressure retarded osmosis delivers higher power density but is more vulnerable to membrane fouling, whereas reverse electrodialysis offers more stable output with lower pretreatment demands.

The technology portfolio for brine valorization is expanding rapidly. Nanofiltration serves as a pretreatment that separates monovalent from divalent ions, generating enriched streams for targeted extraction, while ultra-high pressure reverse osmosis, osmotically assisted reverse osmosis and high-pressure nanofiltration overcome the extreme osmotic pressures of concentrated brines. Electrodialysis with bipolar membranes produces acid and alkaline solutions, and capacitive deionization achieves unprecedented lithium selectivity through electrochemical adsorption. Eutectic freeze crystallization offers an energy-efficient alternative to thermal evaporation for recovering high-purity sodium and potassium chlorides, and membrane distillation-crystallization enables zero-liquid discharge while recovering gypsum and salt. Even biotechnology is entering the field, with halophilic microbes and algal biosorption providing low-energy pathways for metal recovery.

Real-world deployments are beginning to validate the concept. Saudi Arabia’s Water Authority has developed pilot projects recovering magnesium, calcium and sodium chloride from brine, and the Shoaiba nanofiltration facility generates magnesium-enriched streams of up to 1530 milligrams per cubic decimeter for drinking water supplementation and liquid fertilizers. The UAE’s Masdar Initiative has integrated brine management into its sustainability goals, and the EU-funded SEA4VALUE project has demonstrated a modular multimineral recovery process. In the United States and Europe, brine-to-energy pilots are testing osmotic power generation, though scaling these systems remains technically and economically difficult.

Significant barriers persist. Concentrating hypersaline brine can demand 10 to 15 kilowatt-hours per cubic meter, far above the 3 to 4 kilowatt-hours of standard reverse osmosis, and electrochemical lithium extraction currently requires more than 20 kilowatt-hours per kilogram, exceeding terrestrial mining costs by 50 percent. Adsorption systems that perform well in controlled settings lose efficiency in real brine matrices laden with competing ions, and capacitive deionization electrodes degrade during continuous operation. The review’s authors argue that the path forward lies in modular designs, artificial intelligence-driven process optimization, ion-selective membranes including graphene oxide composites, and emerging photoelectrochemical methods that have demonstrated lithium recovery rates of up to 90 percent at around 5 kilowatt-hours per kilogram. Integrated with renewable energy and circular economy frameworks such as the EU’s ZERO BRINE project, brine mining could transform desalination from a water-security measure into a resource-positive industry aligned with the United Nations Sustainable Development Goals on clean water and climate action.

Subject of Research: Recovery of minerals, carbon dioxide sequestration and energy generation from desalination brine

Article Title: Challenges, opportunities, and technological advances in desalination brine mining: a mini review

Article References: Lee, J., & Lee, S. (2025). Challenges, opportunities, and technological advances in desalination brine mining: a mini review. Advances in Industrial and Engineering Chemistry, 1(1), Article 7. https://doi.org/10.1007/s44405-025-00007-y

Image Credits: AI Generated

DOI: 10.1007/s44405-025-00007-y

Keywords: desalination, brine mining, lithium extraction, magnesium recovery, CO2 sequestration, salinity gradient power, reverse osmosis, nanofiltration, electrodialysis, zero liquid discharge, circular economy, water scarcity