High-yield production of carbon nanotubes from waste polyethylene and fabrication of graphene-carbon nanotube aerogels with excellent adsorption capacity

Waste plastics recycling and oil/organics remediation are environmental issues of global concern. In this work, a protectant was introduced, for the first time, to make highly efficient catalysts for pyrolysis of waste plastics into carbon nanotubes (CNTs) with high yield. By using waste polyethylene, Co(NO₃)₂ and oleylamine respectively as carbon source, catalyst precursor and protectant, a yield as high as 59.0% was achieved. The CNTs exhibited a high adsorption capacity for methylene blue (up to 107.1 mg/g). Furthermore, by combining the CNTs with graphene oxide, a graphene-CNT aerogel with a low density of 8.2 mg/cm³ and high porosity of 96.0% was successfully prepared. It showed excellent hydrophobicity and mechanical stability, as well as high adsorption capacity of 289–410 g/g oil/organic solvent, which was much higher than most of these achieved by carbon-based three-dimensional materials reported previously, making the as-prepared aerogel a very promising adsorbent for oil/water separation.