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In an effort to combat global climate change, scientists are inventively competing to design ever more efficient carbon dioxide capture systems to reduce atmospheric concentrations. In a joint effort, manufacturers are starting to equip themselves with air handling centers, especially so-called DAC (direct air capture) systems, to reduce their CO2 footprint. The latter, however, remains quite limited in terms of capacity. Operating costs are also a brake because the chemical reactions are very energy intensive. A new Japanese carbon capture system aims to overcome these obstacles by using “liquid-solid phase separation” technology, which directly removes CO2 from the atmosphere. 99% efficient with low CO2 concentrations and twice as fast as current DACs, this new system would be the fastest in the world.
Many researchers believe that the effects of climate change have already reached a point of no return. These consequences are already being felt in many countries around the world, where the damage is dramatic. Countries like India and Pakistan, for example, have recently made headlines with extreme and unusual temperature rises. In other lands, thousands of acres of forest are disappearing to give way to deserts. Without lasting solutions, this kind of disaster risks hitting even more countries.
In an effort to curb these harmful impacts, technologies are being developed to reduce carbon emissions (one of the most important man-made factors in climate change). In addition to reducing atmospheric carbon, researchers see opportunities to recycle captured CO2. Current technologies make it possible to capture, store and convert CO2 into other industrially recyclable chemical compounds.
However, several obstacles still need to be overcome before current DAC technologies (such as those using potassium hydroxide and calcium hydroxide) can be used on a large scale. One of the challenges is efficiency, as the CO2 concentrations in the air only allow very slow chemical reactions with the trapping substances. In addition, the captured CO2 is difficult to extract and recycle, insofar as the chemical reactions that enable desorption are very energy-intensive.
A new study led by Tokyo Metropolitan University concerns liquid-solid phase separation system DACs. Normally, this kind of separation should work on the basis of the precipitation principle, that is to say that in a liquid-solid mixture the densest bodies gather at the bottom of the container, through the influence of gravity. However, in a liquid-solid separation that works continuously, the solid particles fail to sediment completely and the liquid therefore remains charged with solids at the outlet of the system.
On the other hand, most DACs pass air through a liquid, where a chemical reaction takes place between the liquid and CO2. As the reaction progresses, the more reaction product accumulates in the liquid, making subsequent reactions slower and slower.
The new liquid-solid separation system, presented in the study published in the journal ACS Publications, allows the insoluble and solid reaction product to come out of solution. Therefore, there is no accumulation of solid particles in the liquid and the reaction rate does not decrease.
In their new carbon capture system, the researchers modified the structure of liquid amine compounds to optimize the rate and efficiency of the chemical reaction with a wide range of CO2 concentrations in the air (up to about 400 ppm).
They then discovered that one of their aqueous solutions, especially isophorone diamine (IPDA), can capture and convert 99% of CO2 from the air into a solid precipitate of carbamic acid. In addition, it is sufficient to heat the solid dispersed in solution to 60 ° C to reverse the reaction and thus release CO2 again while recovering the original liquid.
In addition, the CO2 removal rate was at least twice as high as for conventional laboratory DAC systems, making it the fastest of its kind in the world, even at low CO2 concentrations.
The Japanese team also believes that its new process will eventually be applicable on a large scale. The use of the captured carbon for industries and the manufacture of household products will also be investigated, making this new collection system a versatile solution.