A popular article over last few days is one about crystalline salt that can uptake and store oxygen in high concentration. It was published in Chemical Science by Jonas Sundberg and coauthors from University of Southern Denmark.1 The article describes a synthetized crystalline containing cobalt combined with an organic compound, which has some properties of biological carriers of oxygen like iron-based hemoglobin in mammals or similar copper-based carriers in other animals.
The most significant property of this crystalline is that it binds oxygen reversibly – it can uptake oxygen and release it – and that this process may be controlled. Professor Christine McKenzie, the leader of the team that synthetized the crystalline, told the Science Daily2 that among other applications: “When the material is saturated with oxygen, it can be compared to an oxygen tank containing pure oxygen under pressure – the difference is that this material can hold three times as much oxygen. This could be valuable for lung patients who today must carry heavy oxygen tanks with them. But also divers may one day be able to leave the oxygen tanks at home and instead get oxygen from this material as it “filters” and concentrates oxygen from surrounding air or water. A few grains contain enough oxygen for one breath, and as the material can absorb oxygen from the water around the diver and supply the diver with it, the diver will not need to bring more than these few grains.”
Many divers around the world have expressed hopeful interest that soon they may be able to swim underwater like a fish without cumbersome scuba equipment. Unfortunately, that reality is not yet attainable, because in addition to a supply of oxygen, divers must have two additional needs met: wash out of carbon dioxide from the lungs and removal of carbon dioxide from the breathing gas.
The simplest case is diving with a closed-circuit breathing apparatus on pure oxygen. Using the new crystalline to supply oxygen in this type of scuba apparatus could make the tank of compressed oxygen unnecessary, but this is the smaller part of the breathing apparatus. The unit would still need to contain a scrubber for CO2 removal and a breathing bag or counterlung to enable breathing. Even in the case that a similar crystalline for CO2 removal would be available, the breathing bag would still be needed because the CO2 has to be washed out from the lungs. However, breathing pure oxygen limits diving to a shallow depth because of oxygen toxicity.
For diving in a typical recreational scuba range, the oxygen in breathing gas must be diluted with nitrogen to keep oxygen below toxic limits. This is achieved by using compressed air, which contains 78% nitrogen. Only 21% of the gas supply is comprised of oxygen, and about three-quarters of it is wasted when breathing on open circuit. Application of crystalline would make open-circuit diving outdated, but divers would have to switch to closed-circuit rebreathers (CCR).
CCR class of breathing gear is quite bulky, and the tank supplying the oxygen is rather small, because nothing is wasted. This tank could be replaced by a device containing crystalline. The rest of the parts that add up to 30 to 45 pounds of the CCR mass would still have to be there: tanks providing inert gas for oxygen dilution, scrubber containing chemical material for removal of carbon dioxide, and counterlungs enabling pulmonary ventilation. Of course, all other gas conduits, sensors and electronic components would still be needed.
Thus, while this invention may prove very useful in many areas, its application in scuba diving is not imminent and will not reduce scuba to a pocket-size gadget.
- Jonas Sundberg, Lisa J. Cameron, Peter D. Southon, Cameron J. Kepert, Christine J. McKenzie. Oxygen chemisorption/desorption in a reversible single-crystal-to-single-crystal transformation. Chemical Science, 2014; 5 (10): 4017
- New material steals oxygen from air. Science Daily
Post written by: Petar Denoble, MD, D.Sc.
3/4 of O2 is wasted when breathing open circuit on the surface, but at depth the waste is greater. E.g. at 10m it would be 7/8, and 30m 15/16, and at 70m 31/32 (about 97%). That’s why CCR is so efficient at depth. It sounds like getting the big benefits will have to wait until there are similar breakthroughs for diluent and scrubber.