Browsing by Author "Silva, Fernando Alves"
Now showing 1 - 5 of 5
Results Per Page
Sort Options
- Degradation of paracetamol by wet peroxide oxidation using carbon nanotubes synthesized from plastic solid wastePublication . Sanches, Lucas Fenato; Silva, Adriano S.; Roman, Fernanda; Díaz de Tuesta, Jose Luis; Silva, Fernando Alves; Pereira, Ana I.; Silva, Adrián; Gomes, HelderWithin increased production and economic/social dependence of plastic utilization, an environmental problem has also emerged. In this scenario, plastic solid waste (PSW) recycling/management/recovery has become a problem of public concern, with a global generation estimated at 150 million tonnes per year. Materials produced from PSW can be classified as primary (performance/characteristics equivalent to virgin plastic), secondary (performance’s requirement lower than the original application), tertiary (PSW used as feedstock for the generation of chemicals and fuels), and quaternary (energy recovery via incineration) recycled materials [1]. For instance, pyrolysis of PSW has been extensively used for the thermochemical conversion of useless PSW into oil, gas, and carbon materials, thus classified as terciary recycled material.
- Magnetic carbon nanotubes obtained from plastic as catalysts for wet peroxide oxidation of paracetamolPublication . Sanches, Lucas Fenato; Silva, Adriano S.; Roman, Fernanda; Díaz de Tuesta, Jose Luis; Silva, Fernando Alves; Silva, Adrián; Gomes, HelderMagnetic carbon nanotubes (MCNTs) were prepared by catalytic chemical vapour deposition (CCVD) and tested as catalysts for catalytic wet peroxide oxidation (CWPO) of paracetamol (PCM). For the synthesis of the MCNTs, low-density polypropylene (LDPE) and high-density polypropylene (HDPE) were used as model carbon precursors present in urban plastic solid waste (Aboul-Enein, 2018). The catalyst employed in CCVD was magnetite supported on alumina prepared by a sol-gel process. The CWPO runs were conducted with the stoichiometric concentration of H2O2 needed for the full mineralization of 100 ppm of PCM, at 80 °C and initial pH 3.5, following experimental methods described elsewhere (Silva, 2019). The catalyst prepared from LDPE, LDPE_MCNTW, was able to completely degrade the pollutant within 6 h of reaction, while HDPE_MCNTW took 8 h to achieve the same removal. Iron measurement in the final reaction solutions showed the absence of possible additional pollution coming from iron leaching of the catalysts.
- Magnetic carbon nanotubes prepared from LDPE, HDPE and PPPublication . Sanches, Lucas Fenato; Silva, Adriano S.; Roman, Fernanda; Silva, Ana P. F.; Díaz de Tuesta, Jose Luis; Silva, Fernando Alves; Silva, Adrián; Faria, Joaquim; Gomes, HelderPlastics are among the most generated solid wastes, predominantly composed by polymers, as low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP).1 This work deals with the preparation of magnetic carbon nanotubes (CNTs) by catalytic chemical vapor deposition (CCVD) at 850 ºC, considering LDPE, HDPE and PP as carbon precursors representative of urban plastic solid waste in a perspective of circular economy.1 Magnetite supported in alumina nanoparticles previously synthesized by sol-gel were used as catalysts in the CCVD process. Afterward, each synthesized CNT was washed with 50% H2SO4 at 140 °C during 3 h to remove the remaining magnetite, following methods previously described.2 The successful removal of the magnetite particles was assessed measuring the ashes content of the CNTs, removals higher than 83% being achieved (ashes content of final CNT products ranging from 4.2 to 7.9%). The remaining catalyst was located inside the CNTs, conferring magnetic properties to the materials even after washing (Figure 1). BET specific surface areas of 94, 75, and 66 m2 g-1 were found for CNT_LDPE, CNT_HDPE and CNT_PP, respectively, and a slight increase of 1-5 m2 g-1 was observed after washing the materials with acid.
- Polyolefin-derived carbon nanotubes as magnetic catalysts for wet peroxide oxidation of paracetamol in aqueous solutionsPublication . Díaz de Tuesta, Jose Luis; Silva, Adriano S.; Roman, Fernanda; Sanches, Lucas Fenato; Silva, Fernando Alves; Pereira, Ana I.; Silva, Adrián; Faria, Joaquim; Gomes, HelderThis work deals with developing feasible valorization technologies to prepare carbon nanotubes (CNTs) from plastic solid waste and demonstrate their application in catalytic wet peroxide oxidation (CWPO). CNTs were synthesized by catalytic chemical vapor deposition (CCVD) at 850 oC, considering low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP) as carbon precursors representative of urban plastic solid waste. Iron oxide nanoparticles supported in alumina, previously synthesized by sol-gel, were used as catalysts in the CCVD process. TEM micrographs allow us to determine 41 nm as the average outer diameter of the CNTs and to visualize magnetic iron nanoparticles (ca. 10 nm) embedded inside the CNTs (ca. 6.4 % of content measured as ashes). These magnetic nanoparticles were kept in the CNT structure even after the puri-fication of the CNTs with sulphuric acid, allowing to obtain magnetic CNTs. All purified and non-purified CNTs prepared from the polyolefins were assessed as catalysts in CWPO of paracetamol (PCM), used as a model pharmaceutical contaminant in water at CPCM,0 = 100 mu g mL-1 (CH2O2,0 = 472 mu g mL-1, CCNT = 2.5 g L-1, pH0 = 3.5 and T = 80 degrees C). The concentrations of PCM, H2O2, aromatic and total phenolic compounds were monitored for 24 h. All CNTs showed catalytic activity, allowing the complete degradation of PCM at 6 h of reaction time. The stability and reusability of materials are tested and proved in CWPO.
- Valorisation of polyolefins into magnetic carbon nanotubes: application as catalysts in wet peroxide oxidation of paracetamolPublication . Sanches, Lucas Fenato; Silva, Adriano S.; Roman, Fernanda; Díaz de Tuesta, Jose Luis; Silva, Fernando Alves; Gomes, HelderThis work deals with the application of magnetic carbon nanotubes (MCNTs) in the catalytic wet peroxide oxidation (CWPO) of paracetamol (PCM), a pharmaceutical compound selected as model contaminant of emerging concern (CEC). MCNTs were synthetized by catalytic chemical vapor deposition (CCVD) at 850 ºC, considering low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP) as carbon precursors representative of urban plastic solid waste. Magnetite supported in alumina (Fe3O4@Al2O3) nanoparticles previously synthesized by sol-gel were used as catalysts in the CCVD process. The synthesized MCNTs were tested in the CWPO of PCM at 80 ºC, monitoring during 24 h the concentration of H2O2, PCM, Total Organic Carbon (TOC) and aromatic compounds. All MCNT catalysts show activity allowing to decompose completely the pharmaceutical in aqueous solutions after 360 min. In particular, the MCNTs synthesized from HDPE lead to complete removal of the pollutant after 30 min of reaction. By TOC analysis, it was observed that the CNTs led to obtain mineralization degrees higher than 38% of the pollutant after 24 h. Aromaticity test indicated that the catalyst prepared from HDPE promotes more degradation of the intermediates than the catalyst prepared from LDPE and PP.