Browsing by Author "Faria, Joaquim L."
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- Plastic waste-derived carbon nanotubes: Influence of growth catalyst and catalytic activity in CWPOPublication . Roman, Fernanda; Silva, Adriano S.; Tuesta, Jose L. Diaz de; Baldo, Arthur P.; Lopes, Jessica P.M.; Gonçalves, Giane; Pereira, Ana I.; Praça, Paulo; Silva, Adrián M.T.; Faria, Joaquim L.; Bañobre-López, Manuel; Gomes, HelderLow-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 LDP 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).
- Polyolefin and Polystyrene‐Derived Carbon Nanotubes: Catalysts for Oxidative Desulfurization Under a Biphasic SystemPublication . Roman, Fernanda; Batista, Maria C.; Silva, Adriano S.; Bezerra, Ana Júlia Briganti; Tuesta, Jose L. de Diaz de; Mambrini, Raquel V.; Silva, Adrián M. T.; Faria, Joaquim L.; Gomes, HelderThe conversion of plastic solid waste into carbon nanotubes (CNTs) via chemical vapor deposition (CVD) and the effectiveness of these CNTs as catalysts for oxidative desulfurization (ODS) of a simulated fuel were investigated. The primary focus is on the use of CNTs synthesized from various polymer sources, including polyolefins and polystyrene (PS), to remove sulfur compounds using hydrogen peroxide (H 2 O2 ) as an oxidant. The surface modification of CNTs by using acids (H2 SO4 or HNO3 ), the influence of the carbon feedstock (polyolefins vs PS), the use of co-catalysts, and the effect of the extractant phase were all evaluated on the oxidative removal of dibenzothiophene from a simulated fuel. Results revealed that CNTs derived from polyolefins displayed higher desulfurization efficiency (up to 77% in 8 h), with nitric acid-treated CNTs showing the best performance under oil-water biphasic systems. Replacing water with acetonitrile and adding a co-catalyst (formic acid) resulted in a desulfurization of 91% in 2 h of reaction. Under certain conditions, C─S bond cleav-age was observed. This research contributes to the valorization of plastic solid waste and the reduction of atmospheric pollution, promoting circular economy practices and environmental sustainability.