Separation of 3He Isotope from Liquid Helium with the Use of Entropy Filter Composed of Carbon Nanotubes

The 3He isotope finds applications in many areas of science and industry, the most important of which are cryogenics, where 3He allows for achieving millikelvins in dilution refrigerators, and public security with 3He detectors of radioactive materials at airports and important buildings. 3He is also used in medicine for lung tomography. One of the most extraordinary future applications is the use of 3He in fusion reactors for clean energy. 3He is currently very expensive, with prices reaching USD 2750 for 1 liter of gas in normal conditions; thus, more effort is put into finding economically viable methods to acquire this isotope. The article shows research results of acquiring the 3He isotope from liquid helium by a quantum separation method with the use of entropy filters based on new carbon nanomaterials: purified multiwall carbon nanotubes (MWCNTs) and purified multiwall carbon nanotubes decorated with ZrO2 nanoparticles. MWCNTs were bundled and applied in the form of pressed tablets with fixed sizes. The research was conducted at the low-temperature region, where helium exhibits its quantum properties by undergoing a phase transition to the superfluid phase at the lambda temperature: Tλ= 2.18 K. Entropy filters work below this temperature.