earth science

Hydrotalcite

Hydrotalcite is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Hydrotalcite rather than just read about it. In short: Hydrotalcite, or formerly also völknerite, is a layered double hydroxide (LDH) of general formula Mg6Al2CO3(OH)16·4H2O, whose name is derived from its resemblance with talc and its high water content. Multiple structures containing loosely bound carbonate (CO2−3) ions exist.

Key takeaways

Hydrotalcite belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Hydrotalcite to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Hydrotalcite from memory before moving on to harder problems.

Reference excerpt

Hydrotalcite, or formerly also völknerite, is a layered double hydroxide (LDH) of general formula Mg6Al2CO3(OH)16·4H2O, whose name is derived from its resemblance with talc and its high water content. Multiple structures containing loosely bound carbonate (CO2−3) ions exist. The easily exchangeable carbonates enable applications of the mineral in wastewater treatment and the immobilisation of radioactive waste after nuclear fuel reprocessing.

Structure and discovery It was first described in 1842 for an occurrence in a serpentine–magnesite deposit in Snarum, Modum, Buskerud, Norway. It occurs as an alteration mineral in serpentinite in association with serpentine, dolomite and hematite. The layers of the structure stack in multiple ways, to produce a 3-layer rhombohedral structure (3R polytype), or a 2-layer hexagonal structure (2H polytype) formerly known as manasseite. The two polytypes are often intergrown.

Applications

Anion exchange Layered double hydroxides (LDH) are well known for their anion exchange properties.

Wastewater treatment Treating mining and other wastewater by producing hydrotalcite often produces substantially less sludge than lime. In one test, final sludge reductions reached up to 90 percent. This alters the concentration of magnesium and aluminum and raises the pH of water. As the crystals form, they trap other waste substances including radium, rare earths, anions and transition metals. The resulting mixture can be removed via settling, centrifuging, or other mechanical means.

Anion getter for nuclear waste disposal Hydrotalcite has been studied as potential getter for iodide to scavenge the long-lived 129I (T1/2 = 15.7 million years) and also other fission products such as 79Se (T1/2 = 327,000 years) and 99Tc, (T1/2 = 211,000 years) present in spent nuclear fuel to be disposed under oxidising conditions in volcanic tuff at the Yucca Mountain nuclear waste repository. However, carbonate anions easily replace iodide anions in its interlayer and therefore the selectivity coefficient for the anion exchange is not favorable. Another difficulty arising in the quest for an iodide getter for radioactive waste is the long-term stability of the sequestrant that must survive over geological time scales.

Medical Hydrotalcite is also used as an antacid, such as Maalox (magnesium-aluminium oxide).

See also Barbertonite Brucite, Mg(OH)2 Fougerite Layered double hydroxide (LDH) Magnesium hydroxide Stichtite

References

Douglas, G., Shackleton, M. and Woods, P. (2014). Hydrotalcite formation facilitates effective contaminant and radionuclide removal from acidic uranium mine barren lixiviant. Applied Geochemistry, 42, 27–37. Douglas, G.B. (2014). Contaminant removal from Baal Gammon acidic mine pit water via in situ hydrotalcite formation. Applied Geochemistry, 51, 15–22.

Further reading Jow, H. N.; R. C. Moore; K. B. Helean; S. Mattigod; M. Hochella; A. R. Felmy; J. Liu; K. Rosso; G. Fryxell; J. Krumhansl (2005). Yucca Mountain Project-Science & Technology Radionuclide Absorbers Development Program Overview. Yucca Mountain Project, Las Vegas, Nevada (US). Jow, H. N.; R. C. Moore; K. B. Helean; J. Liu; J. Krumhansl; Y. Wang; S. Mattigod; A. R. Felmy; K. Rosso; G. Fryxell (February 2005). Radionuclide absorbers development program overview. Office of Civilian Radioactive Waste Management (OCRWM), Science and Technology Program (Report). pp. 13 of view graphs. Jow, Hong-Nian (2005-02-01). "Radionuclide absorbers development program overview". INIS – International Nuclear Information System. Retrieved 2025-06-12. Kaufhold, S.; M. Pohlmann-Lortz; R. Dohrmann; R. Nüesch (2007). "About the possible upgrade of bentonite with respect to iodide retention capacity". Applied Clay Science. 35 (1–2): 39–46. doi:10.1016/j.clay.2006.08.001. Krumhansl, J. L.; P. Zhang; H. R. Westrich; C. R. Bryan; M. A. Molecke (2000). "Technetium getters in the near surface environment". Migration Conference. 99. Krumhansl, J. L.; J. D. Pless; J. B. Chwirka; K. C. Holt (2006). Yucca Mountain Project getter program results (Year 1) I-I29 and other anions of concern. SAND2006-3869, Yucca Mountain Project, Las Vegas, Nevada. Mattigod, S. V.; G. E. Fryxell; R. J. Serne; K. E. Parker (2003). "Evaluation of novel getters for adsorption of radioiodine from groundwater and waste glass leachates". Radiochimica Acta. 91 (9): 539–546. doi:10.1524/ract.91.9.539.20001. S2CID 97175034. Mattigod, S. V.; R. J. Serne; G. E. Fryxell (2003). Selection and testing of getters for adsorption of iodine-129 and technetium-99: a review. PNNL-14208, Pacific Northwest National Lab., Richland, WA (US). Moore, R. C.; W. W. Lukens (2006). Workshop on development of radionuclide getters for the Yucca Mountain waste repository: proceedings. SAND2006-0947, Sandia National Laboratories. Pless, J. D.; J. Benjamin Chwirka; J. L. Krumhansl (2007). "Iodine sequestration using delafossites and layered hydroxides". Environmental Chemistry Letters. 5 (2): 85–89. doi:10.1007/s10311-006-0084-8. S2CID 98329183. Stucky, G.; H. M. Jennings; S. K. Hodson (1992). Engineered cementitious contaminant barriers and their method of manufacture. Google Patents.

Illustrations

Worked examples

Example 1 — a first encounter with Hydrotalcite

Start with the simplest possible case. Write down what Hydrotalcite claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Hydrotalcite before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Hydrotalcite ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Hydrotalcite

In research: Hydrotalcite appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Hydrotalcite in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Hydrotalcite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aluminium minerals, Carbonate minerals, Hydroxide minerals, so understanding it makes those chapters shorter.
In everyday life: Look for Hydrotalcite outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Hydrotalcite in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hydrotalcite means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Hydrotalcite out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hydrotalcite in simple terms?

Why does Hydrotalcite matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Hydrotalcite?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Hydrotalcite.