Low-density polyethylene (LDPE) was used in this work to grow carbon nanotubes (CNTs) by chemical vapor
deposition (CVD) over catalysts based on Ni, Fe and Al, synthesized either by co-precipitation (C) or wet
impregnation (I) methods, with CNT yields in the range of 16–33 %. The morphology of the CNTs was directly
influenced by the route used for the CVD catalyst synthesis, with co-precipitation-derived CVD catalysts resulting
in CNT samples with curly walls. CNTs were purified with H2SO4 (10–50 wt.%) to remove attached metal particles.
All synthesized materials (CVD-catalysts, as-synthesized CNTs, and purified CNTs) were tested as catalysts
in the catalytic wet peroxide oxidation (CWPO) of paracetamol (PCM), chosen as a model pharmaceutical
compound. Removals of 100 % of PCM in 8 h and 71 % of total organic carbon (TOC) in 24 h were achieved, with
an H2O2 consumption efficiency of 76 % in 24 h for purified CNT (CNT@NiFeAl-C-P). The same CVD-catalyst
(NiFeAl-C) was used to grow CNTs using real LDPE waste, and it was tested under the same reaction conditions,
resulting in a PCM and TOC abatement of 90 % and 65 %, respectively. The synthesis of CNTs using LDPE
waste was a good alternative, given the environmental benefits associated with its reintroduction into the
economic cycle as a material with higher value than initially (upcycling).
