Plastic waste-derived carbon nanotubes: Influence of growth catalyst and catalytic activity in CWPO
Fernanda F. Roman, Adriano S. Silva, José L. Diaz de Tuesta, Arthur P. Baldo, Jessica Lopes, Giane Gonçalves, Ana I. Pereira, Paulo Praça, Adrián M.T. Silva, Joaquim L. Faria, Manuel Bañobre‐López, Hélder Gomes
Abstract
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 H 2 SO 4 (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 H 2 O 2 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). • CNTs were synthesized from LDPE considering distinct CVD catalysts. • CNTs were applied as catalysts in the wet peroxide oxidation (CWPO) of paracetamol. • H 2 SO 4 -washed CNTs display slower H 2 O 2 decomposition but higher CWPO efficiencies. • H 2 SO 4 -washing with concentrations over 30 % removes metals and reduces leaching. • CNTs obtained from pure LDPE and LDPE plastic waste behave similarly in CWPO.