The study, published in Communications Earth & Environment, was led by Degao Zhai of the State Key Laboratory of Geological Processes and Mineral Resources at China University of Geosciences in Beijing, together with Gang Zhao, Qingfei Wang and Jiajun Liu from the same institution, and an international team including Anthony E. Williams-Jones of McGill University, Runsheng Yin of the Chinese Academy of Sciences in Guiyang, Ryan Mathur of Juniata College, Manuel Keith of Ludwig-Maximilians-Universität München, Jian-Feng Gao and Di Chen, and Junwei Xu of the Geophysical and Geochemical Survey Institute of Hunan. Their work addresses a stubborn problem in economic geology: for large, low-temperature hydrothermal deposits, direct tracers of metal sources have remained frustratingly limited.

Antimony is far more familiar to most people than they realize. The element is a critical ingredient in flame retardants, lead-acid batteries, semiconductors and a range of military and industrial applications, which is why many governments now classify it as a strategic raw material. China dominates global production, and the South China belt—with world-famous districts such as Xikuangshan—sits at the heart of that dominance. Understanding where its metal comes from is therefore not just an academic puzzle; it directly shapes how exploration geologists decide where to drill next.

The traditional difficulty is that antimony deposits in South China formed from relatively cool hydrothermal fluids, typically far below the temperatures associated with magmatic ore systems. In hotter systems, geochemists can often link ores to specific intrusions or volcanic rocks using a battery of tracers. In these low-temperature systems, however, the fluids traveled long distances, interacted with many different rocks along the way, and left behind few unambiguous fingerprints of their ultimate origin. Competing models have variously invoked the Precambrian basement, sedimentary sequences, or deep crustal and mantle reservoirs, but the evidence has never been decisive.

Zhai and colleagues attacked the problem with a novel strategy: measuring the isotopic compositions of antimony itself, in tandem with mercury, in stibnite—the antimony sulfide mineral that makes up the ores. Isotopes are atoms of the same element with different masses, and their ratios in a mineral act like a chemical passport, recording the reservoir from which the element was derived. Antimony isotope analysis is a young technique, and this study represents one of its most ambitious applications to ore-forming systems. Mercury isotopes, by contrast, are better established, and they bring a special advantage: the mass-independent fractionation signature of mercury, denoted Δ199Hg, is largely unaffected by the ordinary chemical processing that happens as fluids move through the crust, making it an unusually faithful recorder of whether material passed through surface environments or came from the deep Earth.

The results are remarkable for their sheer variability. The measured δ123Sb values of the ores span from −0.64 to +0.69 per mil, the δ202Hg values range from −1.86 to +2.08 per mil, and the Δ199Hg values extend from −0.20 to +0.14 per mil. In isotope geochemistry, such wide spreads are not noise; they are a message. A single, uniform source would produce a narrow cluster of values. Instead, the data point to a mixing relationship between two isotopically distinct reservoirs that contributed metal to the ore-forming fluids in varying proportions across the belt.

The first reservoir is the Precambrian basement, the ancient metamorphic rocks that underlie much of southern China. Metamorphic devolatilization—the process by which heat and pressure drive fluids and volatile elements out of deeply buried rocks—can liberate antimony and mercury from these crustal rocks and release them into circulating hydrothermal systems. The isotopic signatures of the ores that align with this reservoir indicate that the old basement was not a passive bystander but an active supplier of metal to the belt.

The second reservoir is far more dramatic: a deep, recycled mantle-related source. Mercury’s mass-independent signatures in particular carry information about whether the element once cycled through Earth’s surface environment—oceans and atmosphere—before being dragged back into the interior by subduction and later returned through deep fluids. The data support a model in which some of the antimony in the South China belt was ultimately derived from material that had been recycled into the mantle and was released again from depth, a conclusion that connects these shallow, cool ore systems to the planet’s grandest geochemical conveyor belt.

This dual-source picture resolves a long-standing tension in the literature. Earlier debates often treated the question as either-or: either the metal came from the crust or from depth. The coupled isotope approach shows that the answer is both, with the relative contributions varying from deposit to deposit. That insight matters for exploration, because deposits fed predominantly by one reservoir or the other may occur in different structural and geological settings, and the isotopic composition of ore minerals could in principle serve as a vectoring tool, helping geologists assess the character of a system from early-stage samples.

Beyond the immediate implications for antimony, the study demonstrates the broader power of a technique that is only now coming of age. Coupled antimony and mercury isotope analysis offers a potentially powerful tool for identifying metal sources in ore deposits worldwide, the authors argue, and its application may help refine deposit models globally. It also opens a window onto the dynamic interplay between Earth’s interior and crustal metal cycling—the slow, planet-scale circulation that moves elements between the mantle, the crust and the surface over hundreds of millions of years.

For a metal that has become a centerpiece of supply-chain security debates, the new results carry practical weight. If the giant South China belt owes its wealth to a combination of ancient basement rocks and deeply recycled mantle material, then exploration models built on shallow crustal processes alone may be missing part of the story. The isotopic fingerprints locked inside stibnite crystals now suggest that some of the world’s most important antimony ores are, quite literally, gifts from the deep Earth—delivered upward through fluids that connected the planet’s interior to its crust in ways geologists are only beginning to decode.

Subject of Research: Metal sources of the South China antimony belt traced with coupled antimony and mercury isotopes

Article Title: Coupled Sb-Hg isotopes reveal mixed basement and deeply recycled mantle-related metal sources for the South China antimony belt

Article References: Zhai, D., Zhao, G., Williams-Jones, A. E., Yin, R., Mathur, R., Keith, M., Wang, Q., Liu, J., Chen, D., Gao, J.-F., & Xu, J. (2026). Coupled Sb-Hg isotopes reveal mixed basement and deeply recycled mantle-related metal sources for the South China antimony belt. Communications Earth & Environment. https://doi.org/10.1038/s43247-026-04108-4

Image Credits: AI Generated

DOI: 10.1038/s43247-026-04108-4

Keywords: antimony, mercury isotopes, South China, ore deposits, economic geology, geochemistry, Precambrian basement, mantle recycling, stibnite, hydrothermal fluids, metal sources, critical metals

The research team examined thirty dried nodule samples collected during a 1985 cruise using boomerang grabs, from water depths ranging between 4,900 and 5,900 metres. The Central Indian Ocean Basin, a 75,000-square-kilometre exploration area located roughly 864 nautical miles from the southern tip of the Indian Peninsula, has long been the focus of India’s nodule exploration programme. Nodules in the basin range from half a centimetre to 25 centimetres in diameter, though the average is a modest 2 to 4 centimetres. The researchers sorted their specimens into three size classes, small from 0 to 3 centimetres, medium from 3 to 6 centimetres and large above 6 centimetres, and then subjected them to an unusually thorough analytical battery: atomic absorption spectroscopy for major and trace metals, UV-visible spectrophotometry for specific elemental determinations, X-ray diffraction for mineral phases, and both conventional and high-resolution scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy for micro-textures and semi-quantitative chemistry.

The analytical rigour was considerable. Calibration verification standards were run and instruments recalibrated whenever deviations exceeded plus or minus 2 percent, replicate analyses delivered precision better than plus or minus 3 percent for major elements and plus or minus 5 percent for trace elements, and detection limits fell below 1 part per million for trace metals. X-ray diffraction was performed on a Rigaku SmartLab 9 kW instrument with two-theta accuracy maintained within plus or minus 0.02 degrees, while electron microscopy at IIT (BHU) Varanasi resolved features down to 500 nanometres. This combination of bulk chemistry and microscopic observation is what allowed the team to connect what a nodule looks like on the outside with what it is made of, and ultimately with how and where it grew.

On morphology, the nodules proved remarkably varied. Six primary forms emerged from the hand-specimen work: spheroidal, ellipsoidal, discoidal, poly or coalesced forms, biological types containing fragments of tooth, bone or vertebra, and faceted varieties shaped by angular nuclei or fracturing. Spheroidal and ellipsoidal shapes dominate, particularly among small and medium specimens, while larger nodules show increasing irregularity and fragmentation. Surface texture tells its own story: the proportion of rough-surfaced nodules decreases with increasing size, whereas smooth-surfaced nodules become more common in larger classes. Edges are generally rounded, and fractures less than a centimetre wide occur mainly in larger nodules, sometimes filled with sediment or secondary mineral precipitates. The dark brown to black colouration reflects the iron oxyhydroxides and manganese oxides that make up the outer layers, and the overall pattern points to progressive growth by millimetre-scale concentric accretion around a nucleus, with the shape of that nucleus partly steering the final form.

Under the microscope, the nodules revealed a rich mineral inventory. The principal constituents are goethite, lepidocrocite, 7 Å and 10 Å manganates, pyrolusite, quartz and phyllosilicates, with accessory dolomite, calcite, siderite, pyrite, rhodochrosite, marcasite, potassium feldspar, chalcopyrite, zircon, rutile, ilmenite, apatite and chlorite, and traces of gypsum. Iron-manganese oxides and oxyhydroxides constitute more than 70 percent of the nodular mass on average, forming the concentric layers, while silicates and carbonates account for roughly the remaining 30 percent. Intriguingly, the nuclei are composed mainly of zoned carbonates ranging between siderite and rhodochrosite, set in a phyllosilicate-rich matrix containing scattered detrital grains of quartz, feldspar and pyrite. Rhombic carbonate crystals from 2 to 20 micrometres, occasionally reaching 100 micrometres, are commonly associated with goethite, and the matrix of phyllosilicates, manganese oxides and carbonates frequently fills micro-fractures within the nodule interior.

Perhaps the most striking microscopic finding concerns life. Scanning electron microscopy revealed both spherical cocci and elongated rod-shaped microbial forms on nodule surfaces, and the regions enriched in microorganisms were also enriched in manganese, whereas silica dominated areas where microbial structures were absent. The presence of microporous and filamentous structures suggests a possible role for microbial mediation in metal accretion, hinting that nodule growth may begin with the formation of micronodules that later aggregate into larger nodules through continued incorporation of biogenic, detrital and authigenic material. Angular detrital grains embedded in the oxide matrix also point to episodic input of continental material during growth, a reminder that even the most remote abyssal plains receive sediment from distant shores.

The bulk geochemistry delivered the study’s headline result: a systematic inverse relationship between nodule size and metal grade. Larger nodules are comparatively poor in total metal content but enriched in iron, cobalt and moisture, a signature of slow growth under predominantly hydrogenetic conditions, meaning metals scavenged directly from seawater, at greater water depth. Smaller nodules, by contrast, are richer in manganese, zinc and total metal grade, reflecting a stronger diagenetic influence, in which metals are remobilised from suboxic to anoxic sediment layers and diffuse upward through pore waters before re-precipitating around existing nuclei. Under reducing conditions, manganese(IV) oxides dissolve to soluble manganese(II), which migrates into oxic zones and oxidises back onto nodule surfaces, producing higher manganese-to-iron ratios, porous internal textures and faster growth. Medium-sized nodules between 3 and 6 centimetres exhibited the highest metal grades of all, suggesting optimal growth conditions and the greatest economic potential of the three classes.

Correlation analysis sharpened the picture into two contrasting geochemical associations. Manganese clusters strongly and positively with copper, nickel and zinc, an assemblage indicative of diagenetic remobilisation from sediments and pore waters, while iron pairs with cobalt, lead, strontium, calcium oxide, sodium oxide and titanium dioxide, an association suggestive of hydrogenetic precipitation and possible terrigenous input via hydrolytic release of continental material. These two element families are strongly anti-correlated with each other, so a nodule’s chemistry records which of the two metal-supply pathways dominated at any moment. Todorokite, the more crystalline manganese mineral associated with diagenetic formation and greater depths, shows diffraction peaks that generally decrease from small to large nodules, whereas vernadite, the poorly crystalline manganese oxide typical of hydrogenetic growth, remains pervasive. The manganese-to-iron ratio varies from 3.06 in smaller nodules to 2.50 in larger ones, and the combined copper-plus-nickel ratio from 2.05 to 2.22, indicating variation in metal source alongside broadly uniform regional geochemical conditions.

Ternary discrimination diagrams added a genetic verdict. On the classic (Ni + Cu + Co) × 10 – Fe – Mn plot originally proposed by Bonatti, which separates hydrogenetic nodules precipitated from seawater from diagenetic nodules enriched within sediment pore waters, the studied samples plot predominantly within the hydrogenetic field. On the Cu–Ni–Zn diagram they show a strong compositional affinity with Pacific Ocean nodules described by John Mero in his classic 1965 work on marine mineral resources, while the Al–Mn–Fe diagram reveals consistently low aluminium, indicating minimal detrital input and a predominantly authigenic mode of formation. The Si–Mn–Fe diagram places the samples squarely in the oxide-hydroxide domain typical of oceanic nodules. The nodules show moderate enrichment in copper at about 1.10 percent and nickel at about 1.05 percent, comparable to Pacific nodules, cobalt contents of roughly 2,227 parts per million that are relatively lower, and zinc notably enriched relative to typical Pacific values.

One of the most consequential conclusions concerns where the different-sized nodules actually formed. Increasing nucleus size and nucleus-to-nodule ratios with increasing nodule diameter indicate that small and large nodules formed under different environmental conditions and likely at different locations, rather than growing progressively from a common precursor. Because nodules of different sizes occur close together on the seafloor, the authors argue it is not reasonable to suppose the relevant processes operated simultaneously across the area; instead, formation of different-sized nodules took place separately in different regions. They even propose a possible transport scenario: a nucleus initially formed at shallower depth may have been carried downslope by currents to greater depth, where it then grew slowly and hydrogenetically from seawater. For the emerging deep-sea mining industry, the practical message is clear. Hydrogenetic nodules tend to be enriched in cobalt and rare earth elements, whereas diagenetic nodules carry higher nickel-copper grades, and integrating nodule size, internal structure, mineralogy and geochemical proxies is essential both for understanding how these slow-growing archives form and for identifying which fractions of the seafloor hold the most promising metal resources.

Subject of Research: Size-dependent morphology, geochemistry and genesis of ferromanganese nodules in the Central Indian Ocean Basin

Article Title: Morphology, geochemical association and genesis of Fe–Mn nodules from the Central Indian Ocean Basin

Article References: Morphology, geochemical association and genesis of Fe–Mn nodules from the Central Indian Ocean Basin. (n.d.). https://doi.org/10.1007/s44288-026-00661-9

Image Credits: AI Generated

DOI: 10.1007/s44288-026-00661-9

Keywords: ferromanganese nodules, Central Indian Ocean Basin, deep-sea mining, geochemistry, hydrogenetic, diagenetic, manganese, critical metals, X-ray diffraction, scanning electron microscopy, todorokite, vernadite

The stakes are considerable. Granitic pegmatites are increasingly important sources of lithium, caesium, tantalum, beryllium, boron, and a long list of other elements classified as critical raw materials for the green-energy transition. Lithium in particular has become a strategic commodity because of its role in rechargeable batteries for electric vehicles and portable electronics, and this demand has revived interest in pegmatite deposits once considered too low-grade to mine. The difficulty for geologists is that the geochemical processes operating at the magmatic–hydrothermal transition are hard to observe directly. Fluids escape, minerals react, and the record is often incomplete. Quartz, however, grows throughout the entire crystallization sequence of a pegmatite and is stable from the first hydrous granitic melts to the last drops of hydrothermal fluid, making it an ideal witness if its chemistry can be decoded.

Decoding that chemistry is precisely the challenge the Bern team set out to solve. Quartz incorporates only tiny amounts of foreign elements, often below the detection limits of conventional analytical methods, which is why its potential as a tracer of ore-forming fluids has remained underexploited. The researchers focused on free-grown quartz crystals, some longer than ten centimetres, collected from miarolitic cavities, the gas-filled pockets in pegmatites where crystals grow unimpeded into spectacular euhedral forms. Their samples came from two contrasting settings: the Rosina pegmatite on the island of Elba, Italy, a lithium–caesium–tantalum-type pegmatite emplaced into the Miocene Monte Capanne monzogranite, and the Misox pegmatite in the Ticino region of the Swiss Alps, which formed around 23 to 21.5 million years ago during high-temperature metamorphism of the Lepontine dome.

The first step of the multi-method approach was scanning electron microscopy charge contrast imaging, a technique that reveals chemical growth zonation in quartz at a resolution comparable to cathodoluminescence. Uncoated, doubly polished thick sections were imaged with a gaseous scintillation detection system, producing maps in which brighter contrast generally corresponds to higher trace element contents. In the Rosina quartz, the images revealed classic core–rim zonation with brighter cores, suggesting that trace elements were most abundant early in crystal growth. The Misox crystals told a more complicated story: they displayed extensive Dauphiné-law twinning, in which two crystal domains with different crystallographic orientations grew side by side and incorporated different amounts of trace elements, producing contrasting brightness within what is nominally the same growth zone.

Next came Fourier transform infrared spectroscopy, which detects the hydroxyl point defects that tie hydrogen into the nominally anhydrous quartz structure. Each defect species produces a characteristic absorption band: the AlOH defect yields a sharp triplet near 3378, 3310, and 3440 wavenumbers per centimetre, the LiOH defect absorbs near 3480 and 3510, and the BOH defect appears at 3595. By mapping these bands across polished sections in polarized light and applying defect-specific absorption coefficients confirmed by density functional theory calculations, the team converted spectral images into quantitative maps of water coupled to lithium, boron, and aluminium. The results were striking. In Rosina quartz, OH-coupled lithium, boron, and aluminium reached maximum concentrations of 1.9, 3.3, and 8.9 micrograms per gram respectively, dropping by up to an order of magnitude toward the crystal rims. In Misox quartz the pattern reversed, with aluminium defects reaching up to 68 micrograms per gram in the crystal tips.

With the growth architecture mapped, the researchers then navigated laser ablation inductively coupled plasma mass spectrometry spot measurements to specific zones identified in the charge contrast and FTIR images. The LA-ICP-MS data quantified total trace element contents, including titanium, which serves as the basis of the titanium-in-quartz geothermometer. Rosina quartz contained 11 to 450 micrograms per gram of lithium, 43 to 1780 micrograms per gram of aluminium, and up to 12 micrograms per gram of titanium, all highest in the crystal cores. Misox quartz showed the opposite trend, with all measured elements increasing from core to rim. Crucially, lithium and aluminium were linearly correlated in every sample, following an almost perfect one-to-one molar ratio in Rosina quartz, consistent with a coupled substitution in which trivalent aluminium replaces tetravalent silicon and monovalent lithium occupies structural channels to balance the charge.

Titanium-in-quartz thermometry then anchored the chemical zonation to temperature. Assuming a pressure of 2.3 kilobars for Rosina and 5 to 6 kilobars for Misox, and a titanium activity of 0.5 based on the presence of ilmenite in the mineral assemblages, the calculated temperatures decreased smoothly from core to rim in both localities: from about 590 to 330 degrees Celsius in Rosina and from roughly 520 to 300 degrees Celsius in Misox. But the study also exposed a cautionary tale for anyone using this popular thermometer. Because Dauphiné twin domains incorporate different amounts of titanium, identical growth zones in adjacent twin domains yielded apparent temperatures differing by more than 20 degrees Celsius, and in extreme cases up to about 30 degrees. The authors conclude that titanium-in-quartz temperatures cannot realistically be more precise than roughly ten percent, or about 25 degrees Celsius, unless the textural complexity of the crystal is fully characterized first.

The comparison between the two localities produced perhaps the most practically exciting result. When lithium content is plotted against total water content, the Rosina and Misox quartz occupy two distinct compositional fields: for a given water concentration, Rosina quartz carries up to an order of magnitude more lithium. The difference makes geological sense, because the Rosina pegmatite contains lithium micas and lithium tourmalines whereas the Misox pegmatite does not, meaning the Rosina fluids were far more lithium-rich before lithium minerals saturated. This relationship suggests that lithium and water measurements in quartz could serve as a prospecting tool, allowing geologists to identify lithium-rich pegmatite systems even from detrital quartz grains in stream sediments or soils, long before any pegmatite outcrop is found. In an era of surging lithium demand, a cheap mineralogical fingerprint for buried lithium deposits is a prospect with obvious commercial appeal.

Beyond exploration, the study delivers a fundamental insight into how trace elements actually enter the quartz structure. Only a small fraction of total lithium and aluminium, between 5 and 30 percent depending on the element and locality, is incorporated through hydroxyl-coupled defects, yet these defects faithfully record fluid composition because diffusion is too slow at hydrothermal temperatures to erase the sharp zoning. Boron stands out: roughly half of all boron in the studied quartz is associated with hydroxyl defects, and at low concentrations essentially all of it may be. The dominance of the LiOH defect in the Rosina spectra is itself rare, apparently restricted to highly evolved pegmatitic environments. The sharp decrease in lithium, aluminium, and water at the Rosina core–rim transition occurred without any corresponding temperature drop, hinting that factors such as the magmatic–hydrothermal transition itself, or the crystallization of new lithium minerals like lepidolite, controlled the switch in incorporation mechanisms. Each miarolitic cavity, moreover, evolved in isolation at local equilibrium, with different lithium contents but parallel cooling trends. Taken together, the results show that a quartz crystal, interrogated with the right combination of instruments, is not just a pretty specimen but a complete pressure–temperature–composition recorder of the fluids that make ore deposits, and a roadmap for finding the next generation of critical metal resources.

Subject of Research: Trace element and hydroxyl defect zonation in hydrothermal quartz from granitic pegmatites as a recorder of magmatic–hydrothermal fluid evolution and ore formation

Article Title: Hydrothermal quartz genesis revealed by the combination of SEM charge contrast maps, FTIR mapping, and LA-ICP-MS trace element geochemistry

Article References: Bermanec, M., Gies, N. B., Pettke, T., & Hermann, J. (2026). Hydrothermal quartz genesis revealed by the combination of SEM charge contrast maps, FTIR mapping, and LA-ICP-MS trace element geochemistry. European Journal of Mineralogy, 38(4), 397-417. https://doi.org/10.5194/ejm-38-397-2026

Image Credits: AI Generated

DOI: 10.5194/ejm-38-397-2026

Keywords: quartz, pegmatites, hydrothermal fluids, lithium, FTIR spectroscopy, LA-ICP-MS, trace elements, Ti-in-quartz thermometry, ore deposits, critical metals, SEM charge contrast, Elba

The research, led by Thomas Daniel van Gerve, Philippe Muchez, Ted Nuorivaara, and Olivier Namur of KU Leuven and the Geological Survey of Finland, examined magnetite and ilmenite assemblages from drillcore samples taken in the western limb of the Bushveld Complex. The team set out to answer three interconnected questions: what variety of textures exists in the iron-titanium oxide minerals of the ore, how do these textures relate to the chemical composition of the minerals, and what do these relationships mean for the degree of mineral liberation and concentration during industrial processing. Their findings demonstrate that the microstructures formed during slow cooling of the intrusion exert a first-order control on both the vanadium content of the ore minerals and the efficiency of the beneficiation techniques used to concentrate them.

The story begins with the peculiar crystal chemistry of iron-titanium oxides. Magnetite in these ores crystallizes as a solid solution between iron-rich magnetite and titanium-rich ulvöspinel, while ilmenite forms a related series with hematite. At magmatic temperatures these solid solutions are stable, but as the intrusion cools below roughly 600 to 900 degrees Celsius, depending on the components involved, they become unstable and unmix through a process called exsolution. In addition, the ulvöspinel component within magnetite can react with oxygen to produce ilmenite and purified magnetite according to a well-known oxidation reaction. The result is an intricate family of microscopic textures, each recording a different thermal and chemical history and each carrying distinct consequences for how the ore behaves when it is crushed, ground, and separated.

The researchers identified two principal texture types in the Bushveld magnetites. The first, known as cloth texture, consists of a dense three-dimensional network of ulvöspinel lamellae exsolved along the (100), (010), and (001) crystallographic planes of the magnetite host. These lamellae are astonishingly fine, ranging from a few micrometres down to nanometres in thickness, with spacings between roughly 0.1 and 3 micrometres. When cut parallel to the exsolution planes they intersect at right angles, but along other orientations they cross at angles of 60 to 120 degrees, producing the woven appearance that gives the texture its name. Small granular and needle-like aluminum-rich spinel, up to 3 micrometres long, sometimes accompanies these lamellae, although its modal abundance is so low that its impact on processing is expected to be minor.

The second texture family comprises sandwich and trellis textures, characterized by much coarser ilmenite lamellae, roughly 10 to 300 micrometres thick, hosted within magnetite grains and spaced tens to hundreds of micrometres apart. These ilmenite lamellae form through the oxidation of the ulvöspinel component: in sandwich textures the lamellae develop along a single (111) crystallographic plane, while in trellis textures they grow along two or three sets of {111} planes, intersecting at characteristic angles. Notably, the samples with cloth textures all come from stratigraphically lower positions in the intrusion, more than 1,500 metres deep in the studied drillcore, whereas trellis-textured samples occur above 1,300 metres. The presence of residual ulvöspinel cloth in the interstitial magnetite of sandwich-textured grains indicates that these magnetites were never completely oxidized and that the sandwich ilmenite lamellae formed before the cloth texture developed.

The chemical consequences of these textures are profound. Using energy-dispersive X-ray spectroscopy on a field emission gun scanning electron microscope at KU Leuven, the team showed that vanadium is strongly concentrated in magnetite relative to ilmenite. In trellis and sandwich textures, where oxidation has converted all the ulvöspinel to near-endmember phases, ilmenite exsolutions contain 0.27 to 0.46 weight percent V2O5, while the host magnetite carries considerably more, between 0.72 and 1.14 weight percent. This enrichment arises because vanadium is three to four times more compatible in magnetite than in ilmenite, and roughly twice as compatible in endmember magnetite as in ulvöspinel. Every increment of oxidation therefore expels vanadium-poor ilmenite and concentrates the metal into the remaining magnetite, meaning that fully oxidized grains host the highest possible vanadium contents. Titanium behaves in the opposite way, being extracted from the magnetite solid solution into near-stoichiometric ilmenite lamellae with TiO2 contents of 52 to 56 weight percent.

In the cloth-textured grains the analytical picture is different. Because the ulvöspinel lamellae are thinner than the spatial resolution of any current in situ analytical technique, measurements represent mixtures of host and lamellae. These mixed compositions show V2O5 contents rising from about 1.19 weight percent at low magnetite fractions to 2.4 weight percent at higher magnetite fractions, confirming that vanadium preferentially resides in the magnetite component. The researchers attribute the compositional evolution primarily to changes in the parent magma rather than to heterogeneous exsolution, noting that the stratigraphically higher, later-crystallizing trellis samples simply derive from magmas with lower overall vanadium contents. Crucially, however, the pervasive fine intergrowth of the cloth texture means that its degree of mineral liberation, the extent to which individual minerals can be physically separated from one another, is inherently low.

This is where the study connects microscopic mineralogy to industrial economics. Every vanadium processing route begins with crushing and milling followed by magnetic separation, and the efficiency of these steps depends on grain size, intergrowths, microcracks, oxidation states, and surface defects. For sandwich and especially trellis textures, the outlook is comparatively bright. The coarser ilmenite lamellae can be liberated through conventional grinding, and emerging technologies such as high-pressure grinding rolls and microwave treatment, which generate microcracks along grain boundaries, promise to enhance liberation while reducing energy consumption. Once liberated, the larger ilmenite-bearing grains can be separated from vanadium-bearing magnetite by magnetic separation and further enriched by gravity methods or froth flotation, which works best on particles in the 100 to 150 micrometre range. Surface chemistry matters too: the ratio of ferrous to ferric iron on ilmenite surfaces governs the adsorption of anionic collectors such as sodium oleate, and activation with sodium persulfate can further improve flotation performance.

Cloth textures present a far more stubborn challenge. Even a theoretical complete liberation of the cloth structure would require grinding to particle sizes so fine that enrichment becomes nearly impossible, not to mention the immense energy demand such comminution would entail. In the flotation-optimal size range, the ilmenite surface area available to collectors is too small to render particles sufficiently hydrophobic, while at sizes below 20 micrometres gangue minerals form slime coatings that act as depressants and non-selective entrainment carries fine particles into the concentrate. Micro-flotation technologies for fine fractions offer a possible route forward, but they remain under investigation. In any realistic mining scenario, ores containing all texture types cannot be segregated into separate processing streams, so the authors argue that efficient utilization demands carefully planned beneficiation chains combining selective blasting, high-pressure grinding, and a sequence of unit operations designed for different particle size ranges with strategically positioned re-grinding stages.

Ultimately, the study delivers a message that resonates far beyond the Bushveld: the microscopic architecture of ore minerals, forged hundreds of millions of years ago as a magma chamber slowly cooled, dictates the economic viability of critical metal extraction today. Oxidation-driven exsolution simultaneously upgrades the vanadium grade of residual magnetite and purifies titanium into separable ilmenite, but only when the resulting textures are coarse enough to liberate. As global demand for vanadium grows with the expansion of vanadium redox flow batteries and high-strength steels, and as new layered intrusions from Canada to China to Australia are evaluated for exploitation, detailed textural characterization before processing may prove to be one of the cheapest and most powerful tools available for maximizing metal recovery and minimizing wasted energy in the beneficiation of the world’s vanadium-titanium endowment.

Subject of Research: Exsolution textures in Fe–Ti oxide minerals and their control on vanadium and titanium beneficiation in the Bushveld Complex

Article Title: The impact of exsolution textures in Fe–Ti oxide minerals on crushing strategies and vanadium and titanium pre-concentration

Article References: van Gerve, T. D., Muchez, P., Nuorivaara, T., & Namur, O. (2026). The impact of exsolution textures in Fe–Ti oxide minerals on crushing strategies and vanadium and titanium pre-concentration. European Journal of Mineralogy, 38(4), 545-556. https://doi.org/10.5194/ejm-38-545-2026

Image Credits: AI Generated

DOI: 10.5194/ejm-38-545-2026

Keywords: vanadium, titanium, Bushveld Complex, magnetite, ilmenite, exsolution textures, ore beneficiation, mineral processing, layered intrusions, titanomagnetite, froth flotation, critical metals

The challenge that the team set out to solve is deceptively simple to state. Most established separation technologies, including ion exchange and precipitation, were designed and optimized for aqueous solutions. When industrial effluents contain hydrophilic organic solvents such as methanol or N,N-dimethylformamide, the chemistry changes fundamentally. The state of the dissolved metal ions shifts, and the overall properties of the liquid differ from those of an aqueous environment in ways that degrade the performance of conventional approaches. As a result, achieving sufficient separation performance in organic solvent streams has proved difficult, leaving valuable and sometimes hazardous metals locked inside waste liquids that current infrastructure cannot treat effectively.

The new study, published in ACS Applied Materials & Interfaces, centers on a functional sorbent designated DPE6. The material is based on cellulose, an abundant and renewable biopolymer, into which dithiocarbamate groups have been chemically introduced. Dithiocarbamate groups possess a molecular structure that readily binds to metals, and this affinity is the key to the sorbent’s function. By anchoring these metal-binding groups onto a cellulose backbone, the researchers created a solid phase extraction material designed to adsorb metals stably even in organic solvents, a combination of properties that conventional sorbents have not reliably delivered.

To evaluate the material, the scientists, drawn from the College of Science and Engineering and the Nano Life Science Institute at Kanazawa University, the Institute of Environmental Radioactivity at Fukushima University, and Daicel Corporation, investigated the recovery performance for lead and nickel in organic solvents. The results were striking. DPE6 exhibited high sorption performance even in organic media, and the sorption process reached equilibrium within ten minutes, a kinetics profile that matters greatly for any technology intended for practical, high-throughput treatment of industrial waste. The sorbent also demonstrated a high maximum sorption capacity in pure methanol and in pure N,N-dimethylformamide, two solvents that represent particularly challenging environments for metal capture.

Beyond simply demonstrating that the material works, the team systematically investigated how metal sorption varies with the type and properties of the organic solvent, clarifying the impact of solvent choice on metal recovery. This systematic approach is what elevates the work from a single successful demonstration to a transferable technology. Understanding how the surrounding liquid medium influences the binding of metal ions to the solid sorbent provides the foundation for applying the method to real effluents of varying composition, rather than only to idealized laboratory solutions.

The molecular mechanism behind the performance was interrogated with a suite of spectroscopic techniques. Analyses using FT-IR, XPS, and XAS revealed that the sulfur atoms of the dithiocarbamate groups on DPE6 strongly capture metal ions. In other words, the binding event that underpins the entire separation process can be traced to specific sulfur-metal interactions at the surface of the functionalized cellulose. Establishing this mechanism is a key feature of the study, because it not only confirms the functionality of the novel sorbent but also explains why it works in organic solvents, translating molecular insight into a recovery technology applicable to actual organic effluents.

The most compelling test of practicality came from a real industrial waste stream. The research team applied DPE6 to lead-containing organic effluents generated during the recycling of used perovskite solar cells, an emerging photovoltaic technology whose commercial deployment raises questions about end-of-life lead management. In methanol-based effluents, the team succeeded in removing over 99 percent of the lead. In effluents based on N,N-dimethylformamide, a solvent notoriously difficult for conventional sorbents to handle, the removal rate was approximately 91 percent. That second figure is particularly significant: commercially available sorbents have difficulty providing sufficient lead removal performance from DMF-containing effluents, so a cellulose-derived material achieving roughly 91 percent removal in that medium represents a meaningful advance over the existing state of the art.

From an academic standpoint, the significance of the work lies in having systematically elucidated the impact of organic solvent properties on metal sorption by solid phase extraction. This is a domain in which the underlying chemistry has been poorly mapped, precisely because most prior research has focused on aqueous systems. By establishing how solvent identity and properties govern the capture of metal ions by a functionalized solid, the study provides a conceptual framework that other researchers can build upon, extending solid phase extraction into solvent-rich waste streams that were previously considered out of reach.

The applied implications extend well beyond solar cell recycling. The results are expected to be applied to new recycling technologies that recover critical metals from effluents and waste materials containing organic solvents, enabling their reuse as resources. Many industrial processes, from chemical manufacturing to electronics fabrication, generate solvent-containing waste streams in which valuable metals remain dissolved and unrecovered. A sorbent that functions reliably in these environments opens the way to mobilizing unutilized resources, converting waste liabilities into secondary supplies of materials that are otherwise subject to high supply risks and geopolitical concentration.

The broader vision articulated by the researchers is one of resource circulation and sustainability. Finite metal resources cannot be endlessly mined, and the effective use of what has already been extracted is becoming an economic and environmental imperative. Technologies like DPE6, which combine a renewable cellulose base with precisely engineered metal-binding chemistry, point toward a future in which the metals embedded in yesterday’s devices and today’s effluents are recovered, purified, and returned to service. It should be noted that Kanazawa University and Daicel Corporation have jointly filed an international patent application, PCT/JP2021/34658, regarding the technology related to this study, signaling the partners’ intent to move the material from the laboratory toward industrial deployment. The work was supported by JSPS KAKENHI grants JP23K04094, JP25K22855, JP25H01197, and JP24K15337, along with expenses for the joint research with Daicel Corporation borne by the company. If the performance demonstrated with lead and nickel can be extended across the wider family of critical metals, the humble cellulose fiber, decorated with sulfur-rich binding groups, may become an unexpected workhorse of the circular economy.

Subject of Research: Recovery of critical metals from organic solvent effluents using dithiocarbamate-functionalized cellulose sorbents

Article Title: Novel technology for highly efficient recovery of critical metals from organic effluents

Article References: Novel technology for highly efficient recovery of critical metals from organic effluents. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: critical metals, dithiocarbamate, cellulose sorbent, organic effluents, metal recovery, perovskite solar cells, lead removal, nickel, sorption, resource recycling, solid phase extraction, sustainability

Chitosan, derived from chitin in crustacean shells, is one of the most abundant natural biopolymers and carries a dense array of amino and hydroxyl groups along its backbone. These nitrogen- and oxygen-containing functional groups are natural coordination sites for trivalent metal cations, which makes chitosan an attractive scaffold for metal recovery. The catch is that raw chitosan dissolves in acidic media, precisely the environment in which scandium leachates are typically found. The research team, led by Xiaoqi Liu and corresponding author Ting’an Zhang, addressed this weakness by crosslinking the polymer with glutaraldehyde, which locks the chains into an insoluble network while preserving most of the binding sites needed to grab Sc(III) ions from water.

The innovation at the heart of the study, however, lies in a second modification step. Before crosslinking, the researchers incorporated polyethylene glycol with a molecular weight of 200, known as PEG-200, into the chitosan matrix. PEG acts as a pore-forming agent: as the microspheres form, the small polymer molecules occupy space within the gel and later leave behind an open, accessible pore network. This porosity matters enormously in adsorption, because metal ions can only bind to functional groups they can physically reach. By combining PEG-assisted pore formation with glutaraldehyde crosslinking, the team achieved a balance that is difficult to strike: the crosslinks provide acid stability and mechanical integrity, while the PEG template ensures that a large fraction of the binding sites remains accessible to scandium ions in solution.

To verify that the modified material, designated MCS, had actually been fabricated as intended, the researchers subjected it to a battery of characterization techniques. Fourier-transform infrared spectroscopy confirmed the presence of the crosslinking bonds and the N- and O-containing functional groups. Thermogravimetric analysis probed the thermal behavior of the polymer network, while X-ray diffraction revealed changes in crystallinity induced by the modifications. Brunauer-Emmett-Teller measurements quantified the surface area and pore structure, and scanning electron microscopy provided direct images of the microsphere morphology, showing the improved porous architecture relative to the unmodified, glutaraldehyde-crosslinked control material, called GCS. X-ray fluorescence analysis rounded out the picture of the elemental composition. Together, these results confirmed the successful synthesis and the beneficial effect of the PEG-200 pore-forming strategy.

With the material in hand, the team systematically optimized the adsorption conditions. They found that solution pH played a decisive role, with a working pH of 5 delivering the best performance. At lower pH values, protons compete with Sc(III) ions for the amino and hydroxyl sites and can protonate the polymer, suppressing uptake; at pH 5, the balance of electrostatic attraction and coordination chemistry favors binding. The optimal dosage was 50 milligrams of adsorbent, equilibrium was reached within 100 minutes of contact time, and the experiments were carried out at 30 degrees Celsius. These parameters were then fixed for the detailed kinetic, isotherm, and thermodynamic investigations that followed.

The kinetic analysis revealed that Sc(III) adsorption onto MCS follows a pseudo-second-order model, which implies that the rate-limiting step is the chemical interaction between the scandium ions and the binding sites rather than simple diffusion. In practical terms, this means the microspheres are not merely soaking up metal like a sponge but engaging in genuine chemical bonding with the target ions. The equilibrium data, meanwhile, were best described by the Langmuir isotherm, indicating that adsorption proceeds as a monolayer on a finite number of equivalent sites. From the Langmuir fit, the researchers calculated a maximum monolayer adsorption capacity of 55.28 milligrams of scandium per gram of adsorbent at 30 degrees Celsius, a figure that outperformed the non-PEG-modified control and compares favorably with many other adsorbents reported for Sc(III) recovery.

Thermodynamic analysis added further insight into the nature of the process, and the authors concluded that the adsorption mechanism rests on three synergistic interactions. Coordination interactions between Sc(III) and the lone pairs of nitrogen and oxygen atoms in chitosan provide the primary chemical driving force. Electrostatic attraction contributes to the initial approach and attachment of the cations to the polymer surface, and hydrogen bonding involving the hydroxyl-rich matrix helps stabilize the bound species. This multi-mode mechanism is a key reason why the material performs robustly: even if one interaction weakens under changing conditions, the others continue to hold the metal ions in place.

The broader context makes this work particularly timely. Global demand for scandium has been rising with the growth of aerospace manufacturing and clean energy technologies, yet supply chains remain fragile and dominated by a handful of producers. Conventional recovery routes rely on solvent extraction, which requires large volumes of organic solvents and multiple stages of processing, or on specialized ion-exchange resins that can be expensive to synthesize. Adsorption onto biopolymer microspheres offers an alternative that is mechanically simple, potentially regenerable, and built from a renewable raw material. The Chinese team’s approach of using a cheap, low-molecular-weight PEG as a sacrificial pore template is especially appealing because it adds essentially no exotic chemistry to the process while measurably improving performance.

The study also situates itself within a growing body of literature on chitosan-based adsorbents for critical metals. Previous work has shown chitosan composites capturing chromium, copper, lead, and rare earth elements, and other researchers have explored biochar, mesoporous silicon, covalent organic frameworks, and functionalized silica resins for scandium specifically. What distinguishes the new material is the deliberate combination of acid resistance and pore accessibility in a single, easily prepared microsphere. The authors note that the synergistic pairing of PEG-200-assisted pore formation with glutaraldehyde crosslinking is what allows MCS to function in acidic aqueous media, the very condition that defeats many natural polymer adsorbents.

Looking ahead, the findings suggest a practical pathway toward integrating biopolymer adsorbents into hydrometallurgical flowsheets for scandium recovery from red mud leachates and other acidic industrial streams. Questions of selectivity against competing ions, long-term cycling stability, and scale-up of microsphere production will need further study, but the reported capacity, kinetics, and mechanistic understanding provide a solid foundation. As nations race to secure supplies of critical minerals, solutions that marry abundant biological feedstocks with clever polymer engineering may prove to be among the most sustainable tools in the arsenal. This work, supported by the National Natural Science Foundation of China and provincial and university research funds, demonstrates that sometimes the key to unlocking a scarce metal lies in a material as humble as shrimp shell chemistry, refined with a touch of everyday polyethylene glycol.

Subject of Research: PEG-modified crosslinked chitosan microspheres for the adsorptive recovery of scandium(III) ions from aqueous solutions

Article Title: Preparation of modified chitosan microspheres for the removal of Sc(III)

Article References: Liu, X., Zhang, R., Chen, T., Xiang, L., Wang, J., Lv, G., Liu, Y., & Zhang, T. (2026). Preparation of modified chitosan microspheres for the removal of Sc(III). Polymer Bulletin, 83(11), Article 626. https://doi.org/10.1007/s00289-026-06638-5

Image Credits: AI Generated

DOI: 10.1007/s00289-026-06638-5

Keywords: scandium, chitosan, adsorption, PEG-200, glutaraldehyde crosslinking, microspheres, critical metals, rare earth recovery, biopolymer, hydrometallurgy, Langmuir isotherm, water treatment

The research, led by Tanongsak Yingnakorn and Sakhob Khumkoa of Suranaree University of Technology with collaborators including Andrew Abbott of the University of Leicester, tackles a gap that has long frustrated the recycling industry. Conventional recycling routes — pyrometallurgy, which smelts batteries at temperatures up to 1,700 degrees Celsius, and hydrometallurgy, which leaches metals with acids — have been studied extensively. But the upstream stage that feeds them, the mechanical shredding and sorting that concentrates the active electrode materials into black mass, has lacked rigorous paired assessments of cost and environmental impact. Without that baseline, engineers designing full recycling flowsheets have been working partly in the dark.

The team’s approach was refreshingly practical. They obtained donated post-consumer waste: a spent 13-kilogram electric vehicle battery module containing sixteen cells with a nickel-manganese-cobalt cathode, and roughly two kilograms of spent mobile phone batteries with lithium cobalt oxide cathodes. Safety came first. The EV module was discharged electrically, from about 28 volts down to below 0.1 volts, using a custom-built resistor bank. The phone cells, too small to wire individually, were immersed for 24 hours in a 10 percent salt solution — effective, but a choice that would later loom large in the environmental accounting. Electron microscopy and X-ray diffraction confirmed the EV cathode was close to the NMC622 composition, while the phone cells carried the classic cobalt-rich chemistry of consumer electronics.

With the batteries stabilized, the researchers fed them through a custom separation line combining three machines: a shredder that reduced everything to fragments under 10 millimeters, a zigzag air classifier that separates materials by density using a serpentine upward airflow, and a circular vibrating screen with a 500-micron mesh. Two processing routes were tested for each battery type, varying the order of screening and air classification. The verdict was clear. For EV modules, the route that screened first, then air-classified twice at motor frequencies of 23 and 55 hertz, recovered 93.28 percent of the available black mass. For phone cells, the analogous route achieved 75.77 percent. The shredded material was processed under a nitrogen purge to prevent reactions of the thermally unstable lithium hexafluorophosphate electrolyte, which can begin degrading below 40 degrees Celsius when exposed to moisture.

The quality of the recovered powder matters as much as the quantity, and here the results were striking. The EV black mass contained about 3.91 percent lithium, 15.02 percent nickel, 6.01 percent manganese, 7.41 percent cobalt and 53.7 percent carbon, with residual aluminum and copper held below 1 weight percent. The phone-derived powder carried 4.32 percent lithium and 30.95 percent cobalt, with 0.72 percent aluminum and 1.01 percent copper. Both comfortably meet commercial trading specifications, such as Fastmarkets’ thresholds of no more than 2 percent aluminum, copper or fluorine. X-ray diffraction showed the cathode crystal structures survived the mechanical journey intact — no phase transformations, no degradation — a critical point for any downstream process hoping to regenerate rather than merely dissolve the material.

Then came the money. The direct processing cost — electricity, nitrogen gas, and for the phone route, salt, water and hazardous waste disposal — came to just $0.11 per kilogram of EV battery input and $0.53 per kilogram for phone cells. Adding depreciation, labor and a 15 percent management overhead brought the loaded costs to $0.31 and $0.73 per kilogram respectively, far below the $2 to $6 per kilogram typical of pilot-scale processes. Against reference black mass prices of $14.22 per kilogram for NMC622 and $14.05 for lithium cobalt oxide, the baseline net profit was $6.89 per kilogram for EV modules and $8.23 for phone cells, assuming free feedstock. Even when the researchers modeled the realistic scenario of buying scrap on the open market — roughly $2.50 to $2.70 per kilogram in Southeast Asia — both routes remained solidly profitable.

A Monte Carlo simulation across five uncertain variables, from metal prices to plant utilization, reinforced the picture. The median net profit under combined uncertainty was $4.97 per kilogram for the EV route and $6.28 for phones, and the probability of the process losing money was 0.2 percent or less. Feedstock acquisition cost emerged as the dominant driver of profitability, dwarfing electricity prices and separation efficiency. The break-even feedstock price averaged $6.59 per kilogram for EV material — meaning current scrap prices would need to more than double before the flowsheet turned unprofitable. Notably, the phone route earned more per kilogram despite its lower separation efficiency, simply because phone batteries pack a higher proportion of active material and metal foil into every gram.

The life cycle assessment told a more nuanced story. Processing one kilogram of battery waste generated just 0.210 kilograms of carbon dioxide equivalent for the EV route and 0.241 for phones — figures dominated almost entirely by electricity consumption. Because Thailand’s grid draws more than 75 percent of its power from gas and coal, location matters enormously: the researchers calculated that moving the same process to a low-carbon grid would cut the global warming potential by 62.8 percent, from 0.210 to 0.078 kilograms of carbon dioxide equivalent per kilogram of input. The phone route’s Achilles heel was the salt-solution discharge step. When waste treatment was included, its carbon footprint jumped to 2.377 kilograms of carbon dioxide equivalent and its freshwater ecotoxicity soared to nearly 17 CTUe, driven by the incineration of contaminated brine. Reusing the discharge solution for additional batches could cut those impacts by 45 to 60 percent.

The authors are candid about the limits. The runs were single batches of 13 and 2 kilograms on a line designed for 100 kilograms per hour; zigzag classifier efficiency is known to degrade at higher solids loadings, so the figures represent a proof of concept rather than validated industrial performance. The two discharge methods differ between feedstocks, complicating direct comparison, and the life cycle inventory assigns no burden to the 5.5 to 8.3 percent of material lost to dust, volatilized electrolyte and incomplete retrieval — a conservative omission, since that fraction may contain hazardous hydrogen fluoride. Fluorine content could not be quantified with the available instrumentation, and only one cathode chemistry per feedstock was tested.

Still, the study offers something the field has lacked: a fully paired techno-economic and environmental baseline for the same physical flowsheet applied to two structurally distinct battery streams under identical accounting boundaries. Its strategic logic is compelling. Mechanical separation cannot recover individual elements or rebuild cathodes on its own, but as a pre-treatment it delivers a high-grade, low-contamination concentrate at a fraction of the cost of competing routes, feeding hydrometallurgical leaching or direct regeneration with maximum efficiency. As cobalt prices rally and black mass payables hit record highs, and as regulators push extended producer responsibility schemes that pay recyclers to accept spent packs, the humble workhorse of the recycling chain — the shredder, the air classifier, the vibrating screen — may prove to be the quiet engine that makes the battery circular economy finally add up.

Subject of Research: Techno-economic and life cycle assessment of black mass production from spent lithium-ion batteries

Article Title: Baseline techno-economic and life cycle assessment of black mass production

Article References: Yingnakorn, T., Kansomket, C., Longbutsri, C., Scott, S., Patcharawit, T., Yang, J. M., Abbott, A. P., & Khumkoa, S. (2026). Baseline techno-economic and life cycle assessment of black mass production. iScience, 29(10), Article 117729. https://doi.org/10.1016/j.isci.2026.117729

Image Credits: AI Generated

DOI: 10.1016/j.isci.2026.117729

Keywords: lithium-ion battery recycling, black mass, electric vehicles, techno-economic analysis, life cycle assessment, hydrometallurgy, NMC cathode, mechanical separation, circular economy, critical metals, battery discharge, carbon footprint

NCM811, chemically written as LiNi0.8Co0.1Mn0.1O2, belongs to the family of layered oxide cathodes in which nickel, cobalt, and manganese are combined in an 8:1:1 ratio. The high nickel fraction is what gives the material its appeal. Nickel is the workhorse of energy density in these cathodes, and pushing its content toward eighty percent allows battery makers to pack more lithium ions into each cell and therefore more range into each electric vehicle. The trade-off has always been chemistry’s stubborn insistence on purity. Conventional synthesis routes for NCM811 begin with high-purity nickel, cobalt, and manganese salts, because even modest contaminant levels can disrupt the carefully ordered layered crystal structure that lithium ions shuttle between during charging and discharging. Maintaining that structural order is the difference between a cathode that endures thousands of cycles and one that degrades within months.

The problem, as the researchers frame it, is twofold. First, cobalt supply is constrained and geopolitically fragile, with the vast majority of the world’s cobalt mined in a handful of regions and processed through a narrow set of supply chains. Second, the synthesis costs of NCM811 from virgin, reagent-grade salts are high enough to limit its large-scale application despite its performance advantages. Recycling offers an obvious escape route, but the conventional hydrometallurgical recycling of cobalt and manganese from zinc-refining residues runs into its own wall: the multi-step processes required to isolate individual metals from a complex industrial solution are expensive enough to erase the economic advantage of recycling in the first place. Solvent extraction, precipitation, and repeated purification stages each add cost, chemical consumption, and waste.

The new work proposes what the authors call a separation-free strategy, and the name captures its elegance. Rather than purifying the leachate produced by dissolving the high-cobalt zinc residue, the team took that leachate, with its mixture of valuable metals and residual impurities, and used it directly as the feedstock for NCM811 synthesis. The idea inverts the usual logic of hydrometallurgy. Instead of asking how to strip a solution down to individual pure metals, the researchers asked whether the battery cathode itself could tolerate, or even benefit from, the impurity profile that industrial residue carries. If the answer were yes, an entire cascade of separation steps could be deleted from the process chain, along with their associated costs, reagents, and effluents.

The critical question was whether the resulting material would actually behave like real NCM811. Impurities in a leachate can do insidious damage to a cathode. Foreign metal ions can substitute into the layered lattice in ways that block lithium diffusion pathways. Excess sodium, calcium, or other residual elements can form secondary phases that interfere with particle growth during calcination. Any of these effects would show up in the electrochemistry as reduced capacity, poor rate capability, or accelerated fade. So the team ran a direct comparison: they synthesized one batch of NCM811 from their residue-derived leachate and a benchmark batch from high-purity reagents, then examined both materials with the same structural and electrochemical tools.

The structural comparison delivered the study’s first encouraging verdict. According to the abstract, the leachate-derived sample exhibits a crystal structure and micro-morphology similar to those of the sample synthesized from high-purity reagents. In practical terms, that means the layered oxide framework formed properly despite the imperfect feedstock, and the particles developed the morphology that cathode manufacturers look for, the sort of uniform, well-formed secondary particles that support consistent lithium intercalation. For a material as structurally demanding as NCM811, achieving reagent-grade crystallography from an industrial waste stream is the central proof of concept, and the fact that the two samples converged on similar structures suggests the impurities in the zinc residue leachate were either present at tolerable levels or left behind in the solid phases during synthesis.

Structure alone, however, does not make a cathode. The more consequential test was electrochemical, and here too the results were striking. The leachate-derived sample delivered electrochemical performance and reaction kinetics comparable to the reagent-grade benchmark. Reaction kinetics matter because they govern how fast lithium ions can move in and out of the cathode structure, which in turn determines how much capacity a cell can deliver at high charging and discharging rates. A cathode with sluggish kinetics might match a premium material’s capacity at gentle lab currents yet collapse in a fast-charging scenario. By showing that the residue-derived material kept pace with the benchmark on kinetics as well as overall performance, the researchers demonstrated that the separation-free route produced not a degraded approximation of NCM811 but genuine NCM811 quality.

The implications ripple out in several directions at once. For zinc producers, the study transforms a residue stream from a disposal liability into a feedstock for one of the highest-value products in the battery materials market. Zinc purification residue is generated continuously and at scale wherever zinc is refined, and the cobalt content that makes disposal problematic is precisely the cobalt that NCM811 demands. For battery manufacturers, the work suggests a route to low-cost NCM811 fabrication that bypasses the premium pricing of battery-grade cobalt salts. And for the broader circular economy, it exemplifies a philosophy increasingly visible in materials research: rather than recycling waste down into its constituent elements and rebuilding from scratch, upcycle the waste directly into a finished functional material, conserving both the embedded chemical value and the energy that would otherwise be spent on separation.

The approach also carries meaningful sustainability arithmetic. Every purification stage deleted from a hydrometallurgical flowsheet removes not only its operating cost but also its chemical inputs, its water consumption, and its waste outputs. Conventional recycling chains for complex residues can involve dozens of extraction and stripping stages, each with its own organic reagents and raffinate streams. A separation-free strategy collapses that complexity into a single dissolution-and-synthesis pathway. If the economics hold at industrial scale, the study’s claim of a cost-effective pathway for high-value utilization of high-cobalt residue becomes more than a laboratory curiosity; it becomes a template for how critical-metal recovery should be designed, with the end product, not the purity of intermediates, as the organizing goal.

There are, of course, the familiar distances between laboratory demonstration and industrial reality. Real refinery leachates vary in composition from plant to plant and batch to batch, and a process tuned to one residue stream will need robustness across that variability. Scaling the synthesis conditions that produced clean layered oxides on the bench, from co-precipitation through high-temperature calcination, to tonnage quantities is the perennial challenge of cathode manufacturing, one that even established producers navigate with difficulty. The long-term cycling stability of the leachate-derived material over thousands of cycles, and its behavior in full commercial cells rather than laboratory half-cells, remain questions for subsequent work. Yet the core result stands on its own merits. A cathode built from industrial waste performed like one built from laboratory-grade chemicals, which is precisely the kind of result that can redirect both research funding and industrial investment. As demand for nickel-rich cathodes accelerates and cobalt supply tightens, the zinc industry’s forgotten cobalt-rich residue may find itself reclassified from waste product to strategic asset, and the separation-free philosophy behind this work may spread well beyond a single residue stream.

Subject of Research: Upcycling of high-cobalt zinc hydrometallurgy residue into NCM811 lithium-ion battery cathode materials

Article Title: High-value upcycling of high-cobalt zinc hydrometallurgy residue to NCM811 cathode materials via a separation-free strategy

Article References: High-value upcycling of high-cobalt zinc hydrometallurgy residue to NCM811 cathode materials via a separation-free strategy. (n.d.). https://doi.org/10.1007/s11581-026-07499-8

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07499-8

Keywords: NCM811, lithium-ion batteries, cathode materials, cobalt recycling, zinc hydrometallurgy, upcycling, separation-free synthesis, critical metals, energy storage, hydrometallurgical residue, nickel-rich cathodes, circular economy

Oxalic acid is hardly a novelty. The simple dicarboxylic compound has served industries from pharmaceuticals to textiles for generations, and it was first synthesized in 1776 by the Swedish chemist Carl Wilhelm Scheele through the oxidation of sugar with nitric acid. Today it is produced almost exclusively through petrochemical routes that involve volatile intermediates and substantial carbon dioxide emissions. That matters for metal recycling, because oxalic acid’s green credentials collapse when its entire life cycle is considered. A recent assessment found that, weighed against its toxicity and recovery performance, conventionally produced oxalic acid failed to qualify as a green chemical. The paradox is what motivated Aylin Nur Erkmen of FH Münster University of Applied Sciences and her colleagues to ask whether the molecule could instead be brewed by living cells.

Filamentous fungi had long been suspected of doing exactly that. As early as 1893, the microbiologist Carl Wehmer identified Aspergillus niger as an oxalic acid accumulator, distinguishing it from Penicillium species that follow different metabolic fates. Decades later, researchers mapped the underlying biochemistry to a cytoplasmic, tricarboxylic-acid-independent pathway driven by the enzyme oxaloacetate hydrolase, which cleaves oxaloacetate into oxalate. Crucially, that enzyme only operates efficiently when the surrounding pH remains above 4, a detail that turns out to be the linchpin of the entire process. Industrial citric acid fermentation has historically treated oxalic acid as an unwanted by-product to be suppressed; the German team inverted that logic entirely.

The researchers began with a head-to-head comparison of two Aspergillus niger strains in small shake-flask cultures. Over a 240-hour fermentation, the ATCC 1015 strain secreted a mean peak of 71.0 millimolar oxalic acid, clearly outpacing the CECT 2807 strain, which managed only 37.9 millimolar under the same conditions. The difference tracks closely with how fast each strain acidified its environment: ATCC 1015 drove the pH down to about 3.8 within 72 hours, while its competitor hovered near 4.5. Because oxaloacetate hydrolase is suppressed at low pH, the team then intervened, periodically raising the culture pH back toward neutral. The effect was dramatic. Cultures with intermittent pH adjustment on days one, four and seven reached a final titer of 90.4 millimolar, roughly seven times the yield of unregulated cultures by the 168-hour mark. Keeping the medium above the critical pH 4 threshold, the authors conclude, is not merely helpful but essential.

Carbon source selection proved equally consequential. When the fungus was grown on glucose, sucrose or lactose, glucose produced the highest titer, 136.9 millimolar, with a product yield on substrate of about 0.4 grams per gram, outperforming sucrose by a factor of 1.6 and lactose by nearly five. The explanation lies in metabolic plumbing: glucose enters glycolysis directly, channeling carbon efficiently toward oxaloacetate, the immediate precursor of oxalate. More complex sugars like sucrose and lactose require enzymatic breakdown steps first, diverting flux toward other metabolites. Prior work has suggested that glucose can theoretically support yields approaching 75 percent of the maximum, making the monosaccharide the obvious choice for scale-up.

The decisive test came in a 10-liter stirred-tank bioreactor, where the team compared conventional batch fermentation against a fed-batch strategy with pulsed glucose feeding every 72 hours. Batch operation, seeded with a high initial glucose load of 150 grams per liter, struggled through a prolonged lag phase; substantial acid secretion began only after roughly 192 hours, and the culture only hit its stride once residual glucose dipped below about 20 grams per liter, a sign of carbon catabolite repression lifting. Fed-batch operation avoided that pitfall by keeping glucose below the inhibitory threshold throughout, producing a cyclical, sustained surge of acid after each pulse. The result was a peak oxalic acid titer of 260.1 millimolar over 14 days, with a volumetric production rate of 0.061 grams per liter per hour, more than 1.6 times the batch rate.

Yet the scale-up experiments also exposed two stubborn complications. First, the phosphate buffering used to protect against acid-induced product inhibition turned out to be a double-edged sword: excess phosphate fueled exuberant biomass growth at the direct expense of acidogenesis, delaying the onset of exponential oxalate production until roughly 312 hours, when the phosphate surplus had been depleted. The authors interpret this as a metabolic switch consistent with phosphate-starvation-driven acid synthesis and suggest that future work should pinpoint the precise phosphorus threshold that triggers the shift from growth to acid production. Second, operating the bioreactor at pH 6 to favor oxaloacetate hydrolase inadvertently created ideal conditions for glucose oxidase, an enzyme that converts glucose into gluconic acid. The culture accumulated 226.1 millimolar of gluconic acid alongside the oxalate, which does not reduce the final titer but complicates downstream separation of the two organic acids in an industrial setting.

These hurdles did not prevent the team from framing the process as a genuine industrial candidate, and the reasoning is strategic rather than purely about yield. The volumetric product formation rates reported here trail benchmarks from highly specialized fermentation systems, but those systems carry extreme complexity and high capital expenditure. The goal was instead a simplified, robust framework that can reliably supply enough biogenic leaching agent for real-world metal recovery operations without the operational fragility of a bespoke fermentation plant. The authors argue that a consistent supply of oxalic acid matters more for recycling economics than squeezing out the absolute maximum titer, and the fed-batch protocol they describe delivers that consistency at modest technical cost.

The destination for this biologically brewed acid is the gallium locked inside waste light-emitting diodes and other electronic components. Gallium is indispensable for LEDs, smartphones and tablets, and its long-term supply is increasingly viewed as precarious. Oxalic acid is unusually well suited to the task because it performs two jobs at once: it dissolves metal-bearing phases and forms robust octahedral coordination complexes with hard trivalent metals such as aluminum, iron and gallium, while selectively precipitating divalent ions, including rare earth elements. Earlier work by the same group showed that under optimized conditions, oxalic acid could recover up to 37 percent of gallium from waste minerals. Related research has achieved gallium recoveries exceeding 90 percent from waste surface-mounted LEDs at 90 degrees Celsius using 700 millimolar acid.

What makes the study resonate beyond the lab is the broader industrial and political context. The European Union has committed to climate neutrality by 2050 and is pushing to replace fossil feedstocks with sustainable alternatives for material production, while the global demand for oxalic acid stands at roughly 350,000 tons per year. Fermentation based on renewable sugars offers a route to satisfy that demand without petrochemical emissions, and it plugs directly into a circular economy vision in which yesterday’s electronics become tomorrow’s metal mines. Fungal leaching fluids may also carry synergistic secondary metabolites that enhance metal extraction beyond what pure acid alone can achieve, a phenomenon documented in earlier bioleaching studies with other microorganisms. There is still work to do: biological variability inherent to filamentous fungi, visible in the wide error bars across replicates, will demand larger reproducibility studies and possibly morphological stabilization strategies before industrial batches can be standardized. But the trajectory is clear. A mold that chemists once berated for contaminating citric acid fermentations is now being cultivated, carefully and deliberately, as the engine of a greener metallurgy, one whose raw material is glucose and whose product may help defuse the e-waste crisis one fermented liter at a time.

Subject of Research: Fermentation-based biogenic oxalic acid production for sustainable critical metal recovery from electronic waste

Article Title: Fermentation-based oxalic acid production aimed at sustainable critical metal recovery from electronic waste

Article References: Fermentation-based oxalic acid production aimed at sustainable critical metal recovery from electronic waste. (n.d.). https://doi.org/10.1007/s00253-026-14040-4

Image Credits: AI Generated

DOI: 10.1007/s00253-026-14040-4

Keywords: oxalic acid, Aspergillus niger, fermentation, electronic waste, critical metals, gallium, fed-batch, bioleaching, bioprocess engineering, circular economy, rare earth elements, pH control