Recycling of PVC could become possible
PVC recycling could become possible
Scientists from the University of Michigan develop a safe way to recycle it
Polyvinyl chloride, or what is known for short asPVCis one of the most produced types of plastic in the United States, and the third highest in the world in terms of volume.
PVC constitutes a huge amount of the plastic materials that we use daily. Much of the plastic used in hospital equipment – tubes, blood bags, masks, etc. – is made ofPVC, as is the case With most of the pipes used in modern plumbing, window frames, floors, etc., which are made entirely or contain varying percentages of PVC, it is also used in insulating materials for electrical wires and in the manufacture of materials such as curtains, tents, fabrics and clothing, but there is a problem: PVC has Zero recycling rates; Due to a number of reasons related to its chemical composition.
The obstacles behind the difficulty of recycling PVC
University of Michigan researchers, led by first study author Danielle Vagnani and lead researcher Anne McNeil, have discovered a way to chemically recyclePVC into a usable material. The researchers were able to find a way to use the phthalate compound, which It is found in plasticizers – one of the most harmful components of PVC – as an intermediate for the chemical reaction of recycling, and the results of the research were published in the journal Nature Chemistry.
While Vagnani, who completed her work as a postdoctoral researcher in the university’s Department of Chemistry, said: “PVC is a type ofplasticthat no one wants to deal with; Because it has its own unique set of problems, as polyvinyl chloride usually contains a lot of plasticizers that are used to transform PVC from a hard, hard plastic into a soft and flexible material, but it causes significant contamination of everything around it in the recycling stages, and usually It is highly toxic, and it releases hydrochloric acid very quickly when exposed to some heat.”
Plastic is recycledUsually by melting it and reshaping it into lower quality materials in a process called mechanical recycling, but when heat is applied to PVC, one of its basic components, known as plasticizers, It seeps easily from plastic and is then transferred to other plastics in the recycling stream. In addition, hydrochloric acid is easily released when exposed to heat, which can lead to corrosion of recycling equipment, in addition to causing chemical burns to the skin and eyes. For workers in the recycling plant.
What’s more, phthalate, a common plasticizer in PVC, is a highly toxic endocrine disruptor; Which means it can interfere with thyroid hormone, growth hormones and hormones related to reproduction in mammals, including humans.
To find a wayto recycle PVCwithout using heat, Vagnani began exploring electrochemistry, and she and a collaborating team found that plasticizers, one of the major recycling difficulties, could facilitate chemical breakdown For PVC waste, these plasticizers improve the efficiency of the new method, and electrochemistry can control hydrochloric acid emissions.
“What we found is that the new method still releases hydrochloric acid, but at a much slower and more controlled rate compared to before,” Vagnani said. She added: “PVC is a polymer with a backbone consisting of carbon and hydrogen, and the carbon atoms are connected to each other by Through single covalent bonds, another chlorine group is attached to each carbon group, but under thermal activation, hydrochloric acid quickly decomposes from this system. Which leads to the formation of a carbon double bond along the polymer backbone.”
The solution in electrochemistry
The research team realized that it was not possible to use heat in the recycling process, and instead resorted to electrochemistry. To introduce a free electron into the structure of PVC; Which causes the structure to have a negative charge, which breaks the bond between chlorine and carbon. This results in a negatively charged chloride ion. Because researchers use electrochemistry, they can control the rate at which electrons are introduced into the system, which controls how quickly hydrochloric acid is produced.
The resulting acid can then be used in industries as a reagent for other chemical reactions, and chloride ions can also be used in a range of other chemical uses, including pharmaceutical and agricultural ingredients. The study shows how scientists can think about chemical recycling of otherwise difficult materials that for years have been classified as “non-recyclable.”
To put things in a clearer context, we find that in the United States, the plastic recycling rate is still stuck at 9%, as only a few types of plastic are recycled, and even for the plastic that we recycle, it results in low-quality polymers, which then end up in landfills. Waste.
In conclusion, there is no doubt that the development of humanity in recent decades has relied heavily on plastic products in general and PVC in particular. Behind these amazing materials are innovative technologies that have improved our lives in many ways. However, short-sightedness in the process of… Production in how to deal with the waste resulting from these products led to a delay in finding appropriate solutions for recycling.
