Plastic shopping bags might have a valuable future, first blasted in a furnace at more than 800 degrees Celsius and then possibly turned into materials able to deliver targeted cancer treatments, among other things.
Researchers at the University of Adelaide have found a way to recycle non-biodegradable bags into a material with such tiny particles they can only be seen under a microscope.
Professor Dusan Locic from the School of Chemical Engineering says the carbon nanotubes had valuable properties.
“They are hundreds of times stronger than steel, they have excellent electrical properties,” he said.
“They can be used for new electronic devices, they can be used for solar cells, for batteries.
“They’re also used for making new tennis racquets.”
The tiny tubes each are one nanometre in diameter, about one-10,000th the width of a human hair.
The new approach to making carbon nanotubes was the idea of Professor Locic’s PhD student Tariq Altalhi.
Professor Locic said not only was the method a good way of recycling, it also was more environmentally friendly than other methods.
“Most current methods they’re using carbon sources like methane, propane and some organic solvent and my student came up with the idea of using simple plastic bags,” he said.
“All previous methods use a catalyst and that catalyst is found to be toxic.”
Potential targeting of cancer cells
“For example, for drug delivery they cannot be used because they have toxic catalysts,” he said.
“Our method doesn’t use any catalysts.
“We’re looking to develop a new approach to put the drug inside this carbon nanotube and modify the special antibodies, so when they’re injected into the body they can find the cancer cell, come into the cell and the drug can be delivered.”
Another PhD student who worked on the project, Tarush Kumeria said the transformation from shopping bag to nanotube was relatively simple.
“We just take a normal plastic bag and we make small pieces, a few milligrams,” he said.
“We put it in the furnace along with our membrane, that is alumina (aluminium oxide) and then we heat it up to 800 degrees.
“When we heat plastic it melts and breaks in to carbon molecules. When they go inside those alumina membranes they form tubes.”
Limited waste from processing
The process also is considered swift.
“After 15 minutes [of heating] we leave it for cooling down for a day,” Mr Kumeria said.
“At the end of the day, we get those membranes with carbon nanotubes. In one membrane, there are a few million, their diameter is very small, so in one centimetre of area there are millions of tubes there.”
He said there was limited waste from the process.
“The efficiency, we concluded, is about 90 per cent,” he said.
Professor Locic said the production process could be customised.
“We can control the size of these tubes – the size, the shape, the length,” he said.
But he warned it should not be seen as a way to stop plastic bags ending up in landfill.
“By this technology we can produce much larger quantities of carbon nanotubes by using actually free waste material such as grocery plastic bags. We cannot recycle millions of tonnes but … we are using this base material and making new, very valuable nano material that can be used for many applications,” he said.
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