Here’s another thing to do with that mountain of used plastic: get it to absorb excess carbon dioxide.
What seems like a win-win for a few pressing environmental issues, describes a Rice University laboratory’s newly discovered chemical technique for transforming waste plastics into efficient carbon dioxide (CO2) sorbent for industry.
Risk chemist James Tour and co-lead authors Rice alumnus Wala Algozeeb, graduate student Paul Savas and postdoc researcher Zhe Yuan reported in the journal American Chemical Society ACS Nano that heating plastic waste in the presence of potassium acetate produced particles with nanometer-scale pores that capture carbon dioxide molecules.
These particles can be used to remove CO2 from flue gas streams, they reported.
“Point sources for CO2 emissions such as exhaust pipes from power plants can be equipped with this waste plastic material to remove huge amounts of CO2 it would normally fill the atmosphere, “said Tour.” It’s a great way to have a problem, plastic waste, solve another problem, CO2 emissions. “
A current process to pyrolyze plastics known as chemical recycling produces oils, gases and waxes, but the carbon by-product is almost useless, he said. However, pyrolysis of plastics in the presence of potassium acetate produces porous particles capable of holding up to 18% of their own weight in CO2 at room temperature.
In addition, typical chemical recycling does not work for low carbon polymer waste to generate CO2 sorbent, including polypropylene and high and low density polyethylene, the main constituents of municipal waste, these plastics work particularly well to capture CO2 by treatment with potassium acetate.
The laboratory estimates that the cost of carbon dioxide collection from a point source such as post-combustion flue gas will be $ 21 per liter. tons, far cheaper than the energy-intensive, amine-based process commonly used to extract carbon dioxide from natural gas inputs, which costs $ 80- $ 160 per tonne. ton.
As amine-based materials, the sorbent can be recycled. Heating to about 75 degrees Celsius (167 degrees Fahrenheit) releases trapped carbon dioxide from the pores and regenerates about 90% of the material’s binding sites.
Because it cycles at 75 degrees Celsius, polyvinyl chloride containers are sufficient to replace the expensive metal containers normally required. The researchers noted that the sorbent is expected to have a longer life than liquid amines, reducing downtime due to corrosion and sludge formation.
To make the material, waste plastics are converted to powder, mixed with potassium acetate and heated at 600 C (1,112 F) for 45 minutes to optimize the pores, most of which are about 0.7 nanometers wide. Higher temperatures led to wider pores. The process also produces a wax by-product that can be recycled into detergents or lubricants, the researchers said.
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Wala A. Algozeeb et al., Plastic Waste Product Captures Carbon Dioxide in Nanometer Pores, ACS Nano (2022). DOI: 10.1021 / acsnano.2c00955
Provided by Rice University
Citation: Lab turns hard to treat plastic waste into carbon-capture master (2022, April 5) retrieved April 6, 2022 from https://phys.org/news/2022-04-lab-hard-to-process-plastic- carbon -capture-master.html
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