The process works with single or mixed waste streams, including polypropylene and polyethylene. They are ground into a powder, mixed with potassium acetate and heated at 600 degrees Celsius for 45 minutes, creating particles with pores of 0.7 to 1.4 nanometres. These are capable of holding up to 18% of their own weight in CO2 at room temperature.
According to the researchers, this is a great way to tackle one problem, CO2 emissions, with another, plastic waste. The cost of capturing carbon dioxide from a point source with this method is estimated at $21 per tonne, -much cheaper than the $80 to $160 per tonne for removing CO2 in the traditional, energy-intensive way using amines (nitrogen compounds).
Like the amine-based materials, the sorbent can be reused. By heating it to about 75 degrees Celsius, the retained carbon dioxide is released from the pores, regenerating about 90% of the material’s binding sites. Due to the low temperature, this process can be carried out in PVC vessels, instead of the expensive metal vessels normally required. The researchers also note that the sorbent is expected to have a longer lifetime than liquid amines, reducing downtime due to corrosion and sludge formation.
The findings have been published in the scientific journal ACS Nano.