Why you might watn to make deuterium is your business, but this article describes what it is and how it is made in concept.
Water is normally a collection of interacting molecules of H2O, that is, two atoms of hydrogen bound to one atom of oxygen. An atom of hydrogen is normally just one proton surrounded by one electron, but since it is number of protons in the nucleus defines the element, hydrogen with a neutron added is still hydrogen (because it still has one proton) but it is called deuterium for clarity. The difference in the number of neutrons is called an isotope. Thus, one proton, one neutron and one electron makes heavy hydrogen. Some isotopes are stable and some are radioactive. Heavy hydrogen is not radioactive.
The natural abundance of deuterium in water is close to 0.015% or 150 ppm, and the ratio of approximately 1 deuterium atom for every 6,600 hydrogen atoms is a reasonable approximation, though some sources suggest it might be slightly more frequent (closer to 1 in 6,420 or 6,500). To make heavy water (deuterium oxide, D2O), you need to separate deuterium from regular hydrogen in water. Here are the main methods used to produce heavy water:
1. Distillation
Distillation exploits the slight difference in boiling points between regular water (H2O) and heavy water (D2O). By repeatedly distilling water, you can gradually increase the concentration of heavy water. This method requires a large number of distillation stages to achieve significant enrichment, making it energy-intensive and less efficient for large-scale production[1].
2. Electrolysis
Electrolysis involves passing an electric current through water to separate it into hydrogen and oxygen. Since deuterium (D) and hydrogen (H) have slightly different electrochemical properties, deuterium can be enriched in the remaining water. This process requires a substantial amount of water and electricity. Using iron or steel cathodes can improve the separation efficiency between hydrogen and deuterium[1][2].
- Setup: Prepare an electrolysis cell with a steel cathode and a nickel anode. Fill the cell with distilled water mixed with a small amount of sodium hydroxide (NaOH) to improve conductivity.
- Electrolysis Process: Pass an electric current through the water. Deuterium has a slightly higher electrochemical potential than hydrogen, so it will concentrate in the remaining water as hydrogen is preferentially released as gas.
- Concentration: Continue the electrolysis process until the volume of water is significantly reduced. This will concentrate the deuterium in the remaining water. For example, electrolyzing 20 liters of water down to a few milliliters can significantly increase the deuterium concentration.
3. Chemical Exchange Processes
The Girdler sulfide process is the most efficient and widely used method for producing heavy water on an industrial scale. This dual-temperature exchange process exploits the temperature-dependent equilibrium of deuterium exchange between water and hydrogen sulfide (H2S) gas[6][9]. The process utilizes two columns: a “cold tower” at 30°C and a “hot tower” at 130°C[6].
In the cold tower, deuterium preferentially migrates from H2S to water, creating enriched heavy water. This enriched water then enters the hot tower, where deuterium transfers back to H2S gas. The enriched H2S is cycled back to the cold tower, establishing a cascade system that progressively concentrates deuterium[6][9].
While highly effective, the Girdler sulfide process has drawbacks, including the use of large quantities of toxic H2S gas and potential corrosion issues[9]. Despite these challenges, it remains the primary method for bulk heavy water production due to its efficiency and scalability[6][7]. The process typically enriches water to 15-20% deuterium oxide, with further concentration achieved through additional methods like vacuum distillation[9].
4. Laser-Based Methods
An alternative method involves using lasers to selectively dissociate deuterated hydrofluorocarbons, forming deuterium fluoride, which can then be separated by physical means. While this method consumes less energy than the Girdler sulfide process, it is currently uneconomical due to the high cost of the necessary hydrofluorocarbons[1].
Summary
While there are several methods to produce heavy water, the Girdler sulfide process is the most cost-effective for large-scale production. For small-scale or experimental purposes, electrolysis and distillation are more feasible, though they require significant time and resources to achieve high concentrations of heavy water.
More Reading
[1] https://en.wikipedia.org/wiki/Heavy_water
[2] https://www.youtube.com/watch?v=rDMKRRTSjow
[3] https://www.scienceforums.net/topic/26125-making-heavy-water/
[4] https://www.aphelper.doe.gov/help/AP_Help/a2-6-Deuterium_Systems.htm
[5] https://www.chemicalforums.com/index.php?topic=27129.0
[6] https://energyeducation.ca/encyclopedia/Heavy_water
[7] https://www.globallcadataaccess.org/heavy-water-production-upr-ecoinvent-36-consequential
[8] https://www.researchgate.net/figure/Production-of-Heavy-Water-using-distillation-by-the-Hydrogen-sulfide-process_fig5_242126786
[9] http://nationalregister.sc.gov/SurveyReports/HC02002.pdf
[10] https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Map:_Inorganic_Chemistry_%28Housecroft%29/10:_Hydrogen/10.03:_Isotopes_of_Hydrogen/10.3C:_Deuterated_Compounds