We now know how to turn PET plastic into valuable diamonds!
Their production paves the way for a new form of plastics recycling and even has implications for understanding the reactions that take place inside icy planets such as Neptune and Uranus.
What do plastic bottles and planets like Neptune and Uranus have in common? Probably nothing were it not for the reactions that take place inside these ice giants, where conditions are extreme: temperatures reach several thousand degrees Celsius and the pressure is millions of times greater than that of the Earth’s atmosphere.
These conditions can only be simulated for very short periods on Earth, in state-of-the-art laboratories such as the SLAC National Accelerator Laboratory in California: this is where an international team of researchers used the Linac Coherent Light Source (LCLS), a powerful laser based on an accelerator, to confirm their earlier thesis that diamonds rain inside the icy planets.
And to find that, when hitting some plastic samples heated to 6,000 ° C, some of these materials compressed, producing tiny diamonds, known as nanodiamonds. In particular, during the research, the scholars tested what happened by striking polyethylene terephthalate (PET)the plastic that ordinary plastic bottles are made of, highlighting that the balance between carbon, hydrogen, and oxygen of this material may indeed have a lot in common with the interior of frozen planets.
“The effect of oxygen was to accelerate the splitting of carbon and hydrogen and thus encourage the formation of nanodiamonds. – he stated, illustrating the results published in the journal Science Advance, Professor Dominik Kraus, a physicist of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and lecturer at the University of Rostock, Germany -. This means that the carbon atoms can combine more easily and form diamonds”.
The findings of the researchers support the hypothesis that diamonds rain inside the ice giants. In addition to establishing a new method to produce them on Earth as well, paving the way for new forms of recycling of PET plastic which could for example be used to manufacture nanodiamonds that are already used in abrasives and polished agents, and which in the future could be required for the operation of quantum sensors and reaction accelerators to split carbon dioxide.
Because soon we will see more and more plastic bottles with caps that don’t come off
“Until now, diamonds of this type have been mainly produced through explosive reactions– explained Kraus -. With the help of laser flashes, they could instead be produced much cleaner in the future”.
In the scientists’ view, there is the possibility of using high-performance lasers that emit ten flashes per second on a PET film, which is hit by the beam at intervals of one-tenth of a second. The nanodiamonds thus created would come out of the film and would end up in a collection tank full of water where they would be decelerated to be filtered and effectively collected, with the essential advantage, compared to production with explosive methods, that “nanodiamonds can be cut to size in terms of size or even doped with other atoms – emphasized Kraus -. The X-ray laser means we have a laboratory instrument that can precisely control the growth of diamonds”.
Regarding the understanding of the reactions that take place inside the frozen planets, scholars have found a further clue: in combination with diamonds, water could also be produced, but in an unusual variant. “The so-called could form superionic water – Kraus specified -. The oxygen atoms form a crystal lattice in which the hydrogen nuclei move freely“. And because the nuclei are electrically charged, superionic water can conduct electric current and thus help create the magnetic field of the ice giants.
In their experiments, the team has not yet been able to unequivocally prove the existence of superionic water in the mixture with diamonds. However, this research should start closely, in collaboration with the University of Rostock, at the European XFEL in Hamburg, the most powerful X-ray laser in the world.