A flow cytometry-based sorting method of many different types of plastic waste
Image credit: J. Nikola
J. NikolaJan 08, 2022
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"Flow plasticometry" device that sorts up to 13 types of plastics by:
aerodynamic focusing of the particles in one-by-one formation
detecting the type of plastics by the hyperspectral camera and dedicated software
sending particles to separate containers ready for further processing and market.
Let's say we want to recycle all the plastic waste and return it to the industry as pure as possible. Now imagine we somehow collected it all. The cigarette buds, coffee cups, straws, bottles, mobile phone masks, packaging, everything is here. Now we shred it on pieces smaller than 0.5 cm in diameter by a huge multi-level shredder. Now we have tons of plastic shreds that are of different shapes, colors, materials, and sizes but don't have the technology that can sort them out.
Recently, these guys used hyperspectral imaging with wavelengths from 955 to 1700 nm on thirteen different plastics and successfully differentiated them. The technology is not new, but they were first to use it in a way to detect which particle is of which plastic material (between 13 of them!) and that's great.
What they didn't find a solution for is how to sort and collect them in a fast and efficient way. The existing technologies of pneumatic ejection units or robotic arms are reliable and fast for separating two types of plastic or other waste. When it comes to simultaneous sorting of more materials, pneumatic ejection units are time-consuming, since the same material needs to be run multiple times, while robotic arms are just not precise enough. That's where I jump in.
How it works?
"Flow plasticometry" scanning and sorting device
The machine should, just like the flow cytometer, have a bottleneck where plastic pieces of shredded size enter one by one.
To ensure regular one-by-one flow of plastics, air could be used (airdynamic focusing). Along with the plastics, air would be blow in the machine (just like the shealth fluid in flow cytometer) and ensure the plastics is propelled inside in a single row while helping the removal of any leftover pieces from the machine.
Once inside the machine in one-by-one order, plastics would pass through a set of hyperspectral cameras that would determine the material (the recent, above-mentioned invention).
Based on the material, plastic particles would then be further propelled by the air and sorted in one of the thirteen containers (one for each type of plastic material). The sorting would be done by the set of valves which would be regulated by the scan reads.
Why is this needed?
simulatenous recycling of all the plastic material, not just the most popular ones
recycling of the sea waste that is often deteriorated and pale (unable to use existing color sorting methods)
high purity of the material --> important because the industry requires recycled resources to be clean enough to ensure consistency and uniformity of the product performance and quality, especially for the food-containing packaging