The research team, led by doctoral student Toranosuke Horikawa of the School of Engineering and Associate Professor Masatoshi Kondo of the Laboratory for Zero-Carbon Energy, has been developing what they call an alternative approach to resource extraction based on liquid tin. Their earlier work established the core principle: when desalination brine is brought into direct contact with hot liquid tin, water evaporates and can be collected as distilled water, while dissolved elements such as magnesium, sodium, calcium, and potassium are absorbed into the liquid metal. In effect, the molten tin acts as both a heat-transfer medium and a chemical sponge, separating the valuable components of brine in a single integrated operation.

But the earlier experiments left a critical problem unresolved. Alongside the useful metals, chlorine and sulfur from the brine were also incorporated into the liquid tin. These nonmetallic contaminants react with magnesium to form compounds such as magnesium sulfate, which would sharply limit the industrial usefulness of any recovered material. Magnesium is a strategically important element, used in automobiles, aerospace components, batteries, cement, and refractory materials, and conventional recovery methods typically demand large quantities of chemicals or electricity while generating secondary waste. A product contaminated with sulfur and chlorine would undermine the entire premise of the process.

The team’s solution was to add a vacuum-degassing step before magnesium recovery. In the experiments, approximately 8 grams of tin was melted and held at temperatures between 573 and 673 kelvin, roughly 300 to 400 degrees Celsius. Artificial brine, prepared with heavy water to enable isotope tracing during gas analysis, was supplied onto the liquid surface at a rate of 0.1 milliliters per minute. The water evaporated and was collected separately as distilled product, while magnesium, sodium, chlorine, sulfur, and other brine-derived components were taken up into the liquid metal below.

The brine-loaded tin was then heated under a high vacuum of about 10 to the power of minus 3 pascals, ramping from 573 or 673 kelvin up to 973 kelvin, approximately 700 degrees Celsius, at a controlled rate of 2.5 kelvin per minute, and held at the peak temperature for roughly ten minutes. Gas analysis revealed that the unwanted chlorine- and sulfur-containing species were released as volatile gases, including hydrogen chloride, deuterium chloride, molecular chlorine, sulfur dioxide, and hydrogen sulfide. By measuring the change in the mass of the liquid tin before and after treatment, the researchers estimated that about 59 to 67 percent of the brine-derived gaseous components had been removed from the metal.

With the contaminants largely stripped away, the next stage exploited a simple thermodynamic principle: the solubility of dissolved elements in liquid tin falls as the temperature drops. After degassing, the tin was slowly cooled while the vacuum was maintained, and as the solubility declined, dissolved elements precipitated out of the metal in a process the researchers describe as recovery by cooling, or solubility-driven precipitation. Microscopic observations showed that magnesium-rich and sodium-rich regions formed at different locations within the solidified tin, indicating that the elements could be spatially separated from one another during the cooling process itself.

The quantitative results were striking. When 20 milliliters of brine was processed at 673 kelvin, the magnesium concentration in the recovered precipitate reached up to about 280 times that of the original brine, and the ratio of magnesium to sodium increased by roughly a factor of 5,300. The amount of magnesium recovered was estimated to be equivalent to more than 99 percent of the magnesium that had been absorbed into the liquid tin. Electron microscopy and electron backscatter diffraction analysis further confirmed that the major crystalline phase in the magnesium-rich precipitate was magnesium oxide, MgO, a chemically simple and industrially relevant compound rather than a complex contaminated salt.

One of the most significant advantages of the approach is what it avoids. Because the process separates and concentrates magnesium without relying on large additions of alkaline chemicals, it may substantially reduce chemical consumption and the secondary waste streams associated with conventional precipitation methods. The thermal energy required to keep the tin molten could, in principle, be supplied by concentrated solar thermal energy or by high-temperature industrial waste heat, opening a pathway to low-carbon operation. A conceptual design developed by the team estimated that, under idealized conditions, the electricity required for the vacuum-degassing step could be as low as about 1.7 kilowatt-hours per kilogram of magnesium recovered.

To illustrate the potential scale, the researchers modeled a solar-driven module designed for a sunny, water-stressed region such as Egypt. In this scenario, a solar concentrator with a diameter of 15 meters was estimated to have the potential to produce about 970 kilograms of freshwater and recover approximately 2.8 kilograms of magnesium per day. While these figures come from an idealized design study rather than an operating plant, they sketch the outline of a technology that could turn the economics of desalination on its head, converting the largest liability of the industry into a co-product revenue stream while easing the environmental burden of brine discharge.

The researchers describe the broader concept as mining without digging: obtaining valuable resources not from newly excavated ores, but from water streams that are currently treated as waste. The vision is compelling, but the path from laboratory demonstration to practical deployment still requires substantial engineering. The next step, according to the team, is to develop a continuous system in which liquid tin circulates through the full cycle of freshwater production, vacuum degassing, magnesium precipitation and recovery, and tin reuse. Long-term stability of the molten metal, compatibility with structural materials at operating temperatures, purification of the recovered magnesium product, overall energy consumption, and economic feasibility will all need careful evaluation. If those hurdles can be cleared, the humble brine pipe at the back of a desalination plant may one day rank among the world’s more sustainable magnesium mines.

Subject of Research: Magnesium recovery from seawater desalination brine using liquid tin direct-contact distillation and vacuum degassing

Article Title: Mining without digging: liquid metal tin turns desalination brine into a magnesium resource

Article References: Mining without digging: liquid metal tin turns desalination brine into a magnesium resource. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: desalination, brine, magnesium recovery, liquid tin, vacuum degassing, magnesium oxide, water scarcity, solubility-driven precipitation, solar thermal energy, resource recovery, Science Tokyo, Distalination journal

The central concept in the review is bioavailability, defined as the proportion of ingested magnesium that is absorbed and utilized by the body. This is where the science becomes technically interesting, because the number printed on a supplement label reflects only the total elemental magnesium content of the compound, not how much of it will survive the journey through the gastrointestinal tract and into circulation. Magnesium oxide, one of the cheapest and most common forms on the market, delivers a high elemental load but dissolves poorly in intestinal fluids, and comparative studies have repeatedly shown that more soluble salts outperform it. In a randomized cross-over study, magnesium citrate produced higher urinary excretion and serum levels than magnesium oxide after single-dose administration, and earlier work comparing the two salts reached similar conclusions.

The review organizes supplement forms into a hierarchy of chemical classes: inorganic salts such as oxide and chloride, organic salts such as citrate, lactate, and aspartate, chelated forms in which magnesium is bound to amino acids, and advanced formulations that use encapsulation or controlled-release technology. Organic salts and chelates generally offer better solubility, gastrointestinal tolerability, and bioavailability than magnesium oxide, although the authors caution that outcomes vary with the specific formulation, the dose, the food matrix consumed alongside it, and individual physiological characteristics. In other words, there is no single universal winner; the performance of a magnesium product emerges from an interaction between chemistry and context.

Understanding how the intestine absorbs magnesium helps explain these differences. Absorption occurs along the small intestine and, to a lesser extent, the colon through two mechanistically distinct pathways. At low luminal concentrations, magnesium crosses the epithelium via saturable, transcellular channels, a process that can be regulated according to the body’s magnesium status. When luminal concentrations rise, a second, paracellular pathway allows magnesium to flow between cells down its electrochemical gradient in a non-saturable manner. This dual system has a practical consequence that many consumers miss: very large doses do not proportionally increase absorption, because the saturable pathway becomes overwhelmed and the passive pathway captures only a fraction of the remaining load. Splitting a dose or choosing a form that dissolves efficiently can therefore matter more than simply taking more milligrams.

Dietary context exerts a powerful influence on how much magnesium the gut actually takes up, and the review details both the enhancers and the saboteurs. On the positive side, fermentable fibers such as inulin, fructo-oligosaccharides, galactooligosaccharides, resistant starch, and resistant maltodextrin stimulate microbial fermentation in the colon, lowering pH and promoting mineral solubility and absorption. Human studies have shown that five weeks of short-chain fructo-oligosaccharide intake increased intestinal magnesium absorption and status in postmenopausal women, and similar benefits have been documented in adolescent girls. Proteins and medium-chain triglycerides also support absorption; medium-chain fatty acids improved calcium and magnesium uptake in patients with intestinal resections, and medium-chain triglyceride feeding enhanced mineral absorption in premature infants.

On the inhibitory side of the ledger sit phytate, oxalic acid, and certain polyphenols, all of which form poorly soluble complexes with magnesium ions in the gut lumen. Phytic acid added to white wheat bread significantly reduced fractional apparent magnesium absorption in human subjects, and spinach, a vegetable rich in both magnesium and oxalate, delivered less absorbable magnesium than kale, which has a low oxalate content despite comparable mineral content on paper. These findings carry a counterintuitive message: a food can be chemically rich in magnesium yet nutritionally poor as a source of it. Food processing can shift the balance, however, because sourdough fermentation activates endogenous phytase enzymes and a moderate pH decrease is sufficient to degrade much of the phytate in whole wheat flour, restoring the bioavailability of the grain’s minerals.

The review also highlights how formulation technology is reshaping the supplement landscape. Microencapsulated magnesium products, in which the mineral is wrapped in protective coatings, have shown improved absorption and fewer gastrointestinal side effects in comparative clinical studies. Sucrosomial magnesium, a formulation in which the mineral is carried inside phospholipid vesicles, demonstrated favorable bioavailability in both ex vivo work and a double-blinded cross-over study in healthy subjects. Extended-release matrices offer a different strategy: a magnesium lactate dihydrate extended-release caplet showed measurable absolute bioavailability in healthy volunteers, with the slow release designed to avoid saturating the intestinal transport pathways. These advanced systems reflect a growing recognition that the delivery vehicle is as important as the salt itself.

Measuring bioavailability remains a methodological challenge, and the review surveys the tools researchers use to compare forms. Stable isotope techniques allow true fractional absorption to be tracked from a labeled dose, while urinary excretion after single doses or in magnesium-saturated subjects provides a practical proxy. Serum and circulating ionized magnesium, intracellular magnesium in leukocytes measured by X-ray dispersion analysis, and in vitro models such as Caco-2 intestinal barrier cell cultures each add complementary evidence, though animal studies, including rat work comparing ten organic and inorganic magnesium salts, sometimes show smaller differences between forms than human trials, particularly when diets are high in phytic acid. The authors argue that supplementation should be assessed beyond elemental content alone, considering absorption, retention, and ultimately tissue utilization.

For the growing population of consumers reaching for magnesium to support sleep, muscle recovery, or cardiovascular health, the practical takeaway is nuanced. The form matters, with citrate, organic salts, and chelates generally outperforming oxide; the dose and timing matter, because absorption efficiency declines as dose rises; and the meal matters, because phytate-rich and oxalate-rich foods can bind magnesium while fermentable fibers, adequate protein, and medium-chain triglycerides can enhance its uptake. Individual factors, including age-related changes in gut function and the presence of intestinal disease or resection, further modulate how much of any given dose the body retains. As the review concludes, evaluating a magnesium supplement requires looking past the label’s elemental magnesium number to the chemistry of the salt, the sophistication of the formulation, and the dietary environment in which it is taken, a framing that may finally bring rigor to one of the supplement industry’s most crowded categories.

Subject of Research: Magnesium bioavailability, intestinal absorption mechanisms, and comparative performance of dietary supplement forms

Article Title: Advances in magnesium bioavailability: dietary factors, absorption mechanisms, and comparative performance of supplement forms

Article References: Gultekin, S., & Tomas, M. (2026). Advances in magnesium bioavailability: dietary factors, absorption mechanisms, and comparative performance of supplement forms. Food Science and Biotechnology. https://doi.org/10.1007/s10068-026-02319-1

Image Credits: AI Generated

DOI: 10.1007/s10068-026-02319-1

Keywords: magnesium, bioavailability, intestinal absorption, dietary supplements, magnesium citrate, magnesium oxide, phytate, oxalate, prebiotics, microencapsulation, chelated minerals, nutritional deficiency

Mayenite owes much of its chemical personality to its architecture. It crystallizes in a cubic structure with space group I-43d, and its unit cell can be described as a positively charged framework of twelve cage-like units, [Ca24Al28O64]4+, in which two negatively charged free oxygen ions wander randomly among the cages. Because it costs only about one-third as much energy to pull one of these cage oxygens out of mayenite as it does from plain lime, the oxygen behaves almost as if it were free. Water molecules can slip through inter-cage channels into the interior of the structure, meet these quasi-free O2− ions and form hydroxyl groups — a mechanism that explains why C12A7 dissolves nearly instantaneously on contact with water. Even a dose of roughly nine percent can dramatically accelerate the setting and hardening of Portland cement, which is why mayenite sits at the heart of set regulators and spray-applied concrete accelerators.

The classic picture of mayenite hydration, established decades ago, is straightforward but troublesome. Below about 20 °C, C12A7 hydrates into metastable hexagonal phases — platy CAH10 and C2AH8. With time or heat, these convert into the thermodynamically stable cubic hydrogarnet C3AH6, releasing amorphous aluminum hydroxide. The conversion shrinks volume and raises density, enlarging the porosity of the hardened paste and degrading late-age strength. In recent years, researchers have sought to steer this pathway by doping the clinker with foreign ions. Magnesium is an obvious candidate: it enters clinker naturally from limestone raw materials, substitutes for calcium in aluminate lattices during sintering, and during hydration shifts the chemical equilibrium toward hydrotalcite, a layered double hydroxide, and magnesium-modified calcium silicate hydrate. What remained unclear was precisely how temperature modulates this magnesium intervention in mayenite.

To find out, Hu Yaru, Yang Jiahui, Wang Kai, Peng Lingwei, Song Qiang, Cheng Fuan, Chen Yanxin and Pan Zhigang synthesized magnesium-containing C12A7 from analytical-grade calcium carbonate, alumina and basic magnesium carbonate. The magnesium precursor was calcined at 900 °C into MgO powder, all raw materials were sieved to 75 micrometers, and 40 grams of MgO were added per 100 grams of C12A7, achieving a molar magnesium-to-aluminum ratio of one. Pellets were fired to 1450 °C, held for three hours and rapidly air-cooled. X-ray fluorescence showed the resulting clinker contained 43.15 percent MgO, 27.33 percent CaO and 28.86 percent Al2O3. Ground clinker was then hydrated at a water-to-solid ratio of 10:1 in nitrogen-purged sealed bottles, cured at room temperature, 50 °C or 80 °C, and halted at ages from three to twenty-eight days for XRD, FT-IR, TG-DTG and SEM-EDS analysis.

The clinker itself told the first story. Diffraction revealed two phases, C12A7 and periclase (MgO), with no free lime. Backscattered electron imaging showed clean phase separation: black granular MgO grains dispersed in a grey mayenite matrix, with trace C3A inclusions too small for diffraction to detect. Crucially, energy-dispersive spectroscopy showed the mayenite lattice had absorbed a small amount of magnesium — about 0.85 percent of calcium sites were occupied by Mg2+, nudging the Ca/Al ratio slightly below its theoretical value. Line scans across phase boundaries recorded a sharp magnesium rise within about 2.5 micrometers of the interface, evidence of genuine lattice substitution rather than mere mechanical mixing.

At room temperature, hydration followed the textbook route with a twist. After three days, the dominant product was metastable C2AH8, accompanied by traces of hydrotalcite and a diffuse halo of amorphous aluminum hydroxide. Notably, no CAH10 appeared during the first fourteen days, when laboratory temperatures averaged 30 °C — warm enough, it seems, to suppress its formation — but CAH10 precipitated between fifteen and twenty-eight days as the ambient temperature dropped to an average of 25.89 °C. This brackets the stability window of CAH10 in magnesium-bearing systems below 30 °C. Cubic C3AH6 emerged at seven days and grew steadily through the conversion reaction in which three molecules of C2AH8 yield two of C3AH6 plus aluminum hydroxide and water. The metastable hexagonal hydrates, under electron microscopy, appeared as large platy crystals, bent sheets squeezed by neighboring crystals, and multilayer stacks tens of nanometers thick.

Raising the cure to 50 °C changed the cast entirely. From day three, the products were stable C3AH6, amorphous aluminum hydroxide and hydrotalcite, with no CAH10 whatsoever. Thermogravimetric curves lost the low-temperature peaks associated with the metastable phases and gained a new peak near 229 °C, the fingerprint of water leaving hydrotalcite interlayers. By twenty-eight days, hydrotalcite accounted for 34.9 percent of the sample — a striking yield driven by the accelerating dissolution of MgO. Electron microscopy showed polyhedral hydrogarnet grains and spherical periclase particles wrapped in flaky agglomerates whose magnesium-to-aluminum ratio of about two confirmed hydrotalcite; at late ages, hydrotalcite sheets were found embedded within individual C3AH6 crystals, hinting at a direct transformation route. The analysis also revealed ternary calcium–magnesium–aluminum hydrates with an approximate stoichiometry of CaMgAl2(OH)10, an intermediate stage on the way to magnesium dominance.

At 80 °C the transformation became aggressive and visually dramatic. Hydrotalcite reached nearly a quarter of the solid mass within three days, and residual periclase was almost completely consumed by fourteen days. Because C3AH6 does not decompose below 282 °C and no CAH10 was present to feed aluminum, the observed decline of hydrogarnet could only mean one thing: magnesium ions dissolved from MgO were eroding C3AH6 itself, harvesting its aluminum to build hydrotalcite. Electron micrographs captured the aftermath — tiny hydrotalcite flakes nucleating on hydrogarnet surfaces, hollowed-out grains retaining only their outer contours like fossil shells, and finally rose-petaled hydrotalcite aggregates. The driving force is thermodynamic: hydrotalcite carries a smaller solubility product and a lower Gibbs free energy of formation than C3AH6. Broadened diffraction peaks with low-angle shoulders suggested a richer hydrotalcite family at this temperature, including compositions approximating Mg6Al2(OH)18·4.5H2O and Mg2Al(OH)7.

Synthesizing the data, the team proposes a unified pathway. Magnesium-containing mayenite first dissolves to metastable CAH10 and C2AH8, which convert with time and temperature into C3AH6. Meanwhile MgO hydrolyzes slowly, releasing Mg2+ that first reacts with calcium aluminate hydrates to form ternary Ca–Mg–Al intermediates and then fully replaces calcium to yield low-calcium hydrotalcite. Heat accelerates every step: the conversion of metastable phases, the dissolution of MgO, and the erosion of hydrogarnet. For engineers, the message is that temperature is a dial controlling not just the speed but the very destination of mayenite hydration — and that endogenous magnesium, often treated as a clinker nuisance, can be enlisted to steer cement chemistry toward thermodynamically robust, potentially more durable products.

Subject of Research: Hydration characteristics of magnesium-containing mayenite (C12A7) cured at room temperature, 50 °C and 80 °C

Article Title: Hydration characteristics of magnesium-containing C 12 A 7 cured at room temperature, 50 ℃ and 80 ℃

Article References: Hydration characteristics of magnesium-containing C 12 A 7 cured at room temperature, 50 ℃ and 80 ℃. (n.d.). https://doi.org/10.1016/j.cscm.2026.e06495

Image Credits: AI Generated

DOI: 10.1016/j.cscm.2026.e06495

Keywords: mayenite, C12A7, calcium aluminate cement, hydrotalcite, magnesium oxide, hydration, curing temperature, C3AH6, CAH10, C2AH8, XRD, SEM-EDS