Nanyang technological university pioneered plastic degradation methods

- Dec 13, 2019-

Scientists at nanyang technological university in Singapore have come up with a new way to degrade plastic waste.

The new chemical treatment method is the first of its kind reported.

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In simple terms, the process is largely chemical, with the help of two main substances, sunlight and vanadium.

Scientists added a metal called vanadium to the plastic as a catalyst, then exposed it to sunlight, where the plastic molecules were dissolved to produce a chemical called formic acid.

Formic acid is a versatile natural chemical that can be used as a food preservative, antibacterial cleaner or hydrogen fuel cell.

And the current market demand for formic acid is strong, the market size of millions of tons every year.

The catalyst used in the process is a metal called vanadium, which is biocompatible and low toxic and is often used as an alloy for cars or aircraft.

In response, scientists at nanyang technological university believe the method could use visible light and metal-free catalysts to completely break down non-biodegradable plastics, such as polyethylene, and would treat plastic waste in an environmentally sustainable way.

The findings were first reported in the journal Advanced Science in October.

What's the principle?

Most plastics do not break down easily at high temperatures because they contain special, inert chemical bonds called carbon-carbon bonds.

In addition, most reactions have energy barriers, and the addition of a vanadium catalyst (technically known as a photocatalyst) helps lower the energy barrier, thereby reducing the heat required to drive the reaction.

The process begins by dissolving vanadium into plastic products -- such as polythene cup fire bags -- and then exposing it to the sun.

To make sense of the analogy, the carbon-carbon bond can be likened to a zipper, in which vanadium ACTS as the handle, unzipping the zipper when the pressure (in this case, sunlight) increases.

The same goes for dissolving plastic.

In addition, this chemical process produces not only formic acid but also carbon dioxide.

Scientists at nanyang technological university say there are many ways to capture the gas.

In existing industrial processes, for example, carbon dioxide can be converted to carbon monoxide, which in turn can be combined with hydrogen to form syngas - mainly used for chemical and biological processing and for the production of methanol.

While this method currently dissolves polyethylene plastics, it doesn't work with another type of plastic called polyethylene terephthalate (PET).

The technology is not yet commercially viable and could take another five years of work.

It is urgent to alleviate the plastic crisis

Our world is facing the threat of plastic.

Of the plastic we use, 58% will end up in landfills or rivers and lakes, while only 18% will be recycled for processing.

Among them, Marine plastic rubbish is more shocking.

According to a report last year, the amount of plastic dumped into the Pacific Ocean is larger than the area of France, Germany and Spain combined.

The biggest concern is that the plastic does not break down, but breaks down over time into tiny pieces of plastic that are then eaten by Marine life and eventually made its way into the body.

A study by the World Wide Fund for Nature estimated that the average person eats about the size of a credit card every week.