Selective denitrification by peroxidation of 4-nitrophenol using Janus-structured amphiphilic carbon nanotubes

Mestrado de dupla diplomação com a UTFPR - Universidade Tecnológica Federal do ParanáIndustrial pollution has grown a lot in recent times, mostly formed by oily compounds, affecting not only the environmental but also human health. As the concern increases, so does the search for effective treatment, a few years the use of different nanostructure porous carbon materials are being used in catalysis. Therefore, in this work carbon nanotubes (CNTs) were tested as catalysts in the selective denitrification of oily wastewater containing 4-nitrophenol (4-NP) by catalytic wet peroxide oxidation (CWPO). The CNTs were prepared by chemical vapor deposition, feeding sequentially ethylene (E) and/or acetonitrile (A) during different times until 20 min, resulting in samples E20, E15A5, E10A10, E5A15, E1A19 and A20, the number denoting the time feeding of each precursor and the order of appearance of the letter indicating the order of each precursor. The synthesized CNTs were tested in the CWPO of 4-NP in aqueous solutions and in simulated oily wastewater (2,2,4-trimethylpentane and water) at 80 ºC, initial pH = 3.5, C4-NP = 1 g/L, CH2O2 = 3.56 g/L, and Ccatalyst = 2.5 g/L. The catalysts A20, E1A19 and E5A15 promoted a faster decomposition of H2O2 and a lower degradation of 4-NP in the aqueous system, whereas the catalysts E20, E15A5 and E10A10 (more hydrophobic character than previous ones) displayed the opposite trend, since E20 was able to remove 99% of the pollutant and A20 only 69% after 8 h of reaction. E15A5 and E10A10 catalysts were able to remove 100% of 4-NP after 24 h of reaction. In biphasic L-L media all catalysts presented a great conversion of 4-NP after 24 h of reaction. E15A5, E10A10 and E1A19 catalyst allow to completely remove 4-NP and E5A15, A20 and E20 led to obtain a removal of 99%, 99% and 98%, respectively. Besides that, the aromaticity was also measured for comparation of materials. The lower concentration of aromatic intermediates was obtained E15A5 and E10A10 (126.34,249.10 mg/L, respectively), and lower pH (2.42, 2.38, respectively), which supports the formation of carboxylic acids. The highest removals conversions obtained with E15A5 and E10A10 is ascribed to the capacity to stabilize Pickering emulsions by E15A5 and E10A10. The amphiphilic characteristic of this material ensures a closer contact between the liquid phases, allowing higher mass transfer.A poluição industrial cresceu muito nos últimos tempos, em sua maioria essa poluição é formada por compostos oleosos, afetando não apenas o ambiente, mas também a saúde humana. À medida que a preocupação aumenta também aumenta a busca por tratamentos eficientes. Há alguns anos o uso de diferentes matérias de carbono poroso nano estruturados estão sendo utilizados na catálise. Portanto, neste trabalho os nanotubos de carbono foram testados como catalisadores na oxidação seletiva de 4-nitrofenol (4-NP) presente em águas residuais oleosas por oxidação catalítica com peróxido de hidrogénio. Os nanotubos de carbono foram preparados por deposição química em fase vapor, alimentando sequencialmente etileno (E) e/ou acetonitrila (A) durante diferentes tempos até 20 min cada um, resultando nas amostras E20, E15A5, E10A10, E5A15, E1A19 e A20, o número denotando o tempo de alimentação de cada precursor e a ordem de aparecimento da letra indicando a ordem de cada precursor. Os nanotubos de carbono sintetizados foram testados no CWPO do 4-NP em soluções aquosas e em águas residuais oleosas simuladas (2,2,4-trimetilpentano e água) a 80 ºC, pH inicial 3,5, C4-NP = 1 g/L, CH2O2 = 3,56 g/L, e CCatalisador = 2,5 g/L. Os catalisadores A20, E1A19 e E5A15 promoveram uma decomposição mais rápida de H2O2 e uma menor degradação de 4-NP no sistema aquoso, enquanto os catalisadores E20, E15A5 e E10A10 (com um caráter mais hidrofóbico que os anteriores) apresentaram tendência oposta, uma vez que, E20 foi capaz de remover 99% do poluente e A20 apenas 69% após 8 h de reação. Os dois catalisadores capazes de remover 100% de 4-NP após 24 h de reação foram E15A5 e E10A10. Em meio L-L bifásico todos os catalisadores apresentaram uma alta conversão de 4-NP após 24 h de reação, E15A5, E10A10 e E1A19 com 100%, E5A15 e A20 com 99% e E20 com 98%. Além disso, a aromaticidade também foi medida para comparação de materiais. Os catalisadores que apresentaram concentração mais baixa dos intermediários aromáticos foram E15A5 e E10A10 (126,34, 249,10 mg/L, respectivamente), e o pH mais baixo também (2,42, 2,38, respectivamente), isso apoia a ideia da formação de ácidos carboxílicos. Esta tendência de melhores resultados pode ser atribuída à formação de emulsões Pickering pelos materiais E15A5 e E10A10. A característica anfifílica desses materiais garantem um contato mais próximo entre as fases líquidas, permitindo maior transferência de massa

Selective denitrification of lipophilic pollutants from oily wastewater by peroxidation using Janus-structured amphiphilic carbon nanotubes as catalysts

Carbon nanotubes (CNTs) were tested as catalysts in the selective denitrification of 4-nitrophenol (4-NP) from oily wastewater by catalytic wet peroxide oxidation (CWPO). The CNTs were prepared by chemical vapor deposition, feeding sequentially ethylene (E) and/or acetonitrile (A) during different times until 20 min, resulting in samples E20, A20 and E10A10, the number denoting the time feeding of each precursor and the order of appearance of the letter indicating the order of each precursor. The synthesized CNTs were tested in the CWPO of 4-NP in aqueous solutions and in simulated oily wastewater (2,2,4-trimethylpentane and water) at 80 ºC, initial pH 3.5, C4-NP = 1 g L-1, CH2O2 = 3.56 g/L and Ccatalyst = 2.5 g L-1. The catalyst A20 promoted a faster decomposition of H2O2 and a lower degradation of 4-NP in the aqueous system, whereas the catalyst E20 displayed the opposite trend, since E20 was able to remove 99% of the pollutant and A20 only 69% after 8 h of reaction. E10A10 in biphasic L-L media presented the highest conversion of 4-NP after 24 h in the oily phase (51%), followed by A20 (38%) and then E20 (25%). This tendency may be ascribed to the formation of Pickering emulsions by E10A10. The amphiphilic carachteristic of this material ensures a closer contact between the liquid phases, allowing higher mass transfer.This work was financially supported by project "PLASTIC_TO_FUEL&MAT – Upcycling Waste Plastics into Fuel and Carbon Nanomaterials" (PTDC/EQU-EQU/31439/2017), Base Funding - UIDB/50020/2020 of the Associate Laboratory LSRE-LCM - funded by national funds through FCT/MCTES (PIDDAC), and CIMO (UIDB/00690/2020) through FEDER under Program PT2020. Fernanda F. Roman acknowledges the national funding by FCT, Foundation for Science and Technology, and FSE, European Social Fund, through the individual research grant SFRH/BD/143224/2019.info:eu-repo/semantics/publishedVersio

Selective oxidation of 4-nitrophenol with H2O2 in a biphasic system by janus-like carbon nanotubes

The use of petroleum-based products has increased drastically with the increase in population, resulting in the deposition of oily products in aquatic systems. It is estimated that for each ton of petroleum that undergoes refinement processes, between 0.5 and 1 ton of oily wastewaters are generated, bearing an oil concentration that may reach 40 g L-1 [1,2]. Hazardous pollutants dissolved both in oily and aqueous phases may also be found in those oily wastewaters [3], hindering their treatment through conventional processes. Furthermore, the oil phase is, in some cases, an added-value product, and its degradation results in economic losses. Thus, the development of processes that allow the removal of hazardous contaminants from oily and aqueous phases, providing an opportunity for recovering both phases, should be advantageous [3]. This work deals with the selective removal of a hazardous compound (4-nitrophenol, 4-NP) from a simulated oily wastewater (2,2,4-trimethylpentane:water = 10:90 v/v) by an oxidative process considering H2O2 as oxidant and amphiphilic Janus-like carbon nanotubes as catalysts. Amphiphilic catalysts were selected since they should present advantages in this process due to their ability to interact with both aqueous and oily compounds and phases [4]This work was financially supported by project "PLASTIC_TO_FUEL&MAT – Upcycling Waste Plastics into Fuel and Carbon Nanomaterials" (PTDC/EQU-EQU/31439/2017), Base Funding - UIDB/50020/2020 of the Associate Laboratory LSRE-LCM - funded by national funds through FCT/MCTES (PIDDAC), and CIMO (UIDB/00690/2020) through FEDER under Program PT2020. Fernanda F. Roman acknowledges the national funding by FCT, Foundation for Science and Technology, and FSE, European Social Fund, through the individual research grant SFRH/BD/143224/2019.info:eu-repo/semantics/publishedVersio

Amphiphilic carbon nanotubes for catalytic wet peroxide oxidation of 4-nitrophenol

Carbon nanotubes (CNTs) were synthesized via chemical vapor deposition (CVD) over an AlCoFeO4 catalyst by a sequential feed of ethylene (E, as carbon source) and acetonitrile (A, as nitrogen source). The resulting samples were noted E20 (hydrophobic), E10A10 (amphiphilic), and A20 (hydrophilic), the number referring to the feed time (minutes) of each precursor, as reported elsewhere1. These materials were tested in the catalytic wet peroxide oxidation (CWPO) of 4-nitrophenol (4-NP). The reaction was monitored by HPLC (to determine the concentration of 4-NP and respective intermediates), TOC analyzer, and UV-vis spectrophotometry (to quantify H2O2) (Figure 1). After 8 h of reaction, A20 led to the highest consumption of H2O2 (90%), followed by E10A10 (61%) and E20 (52%). On the other hand, the highest degradation of 4-NP was observed with the amphiphilic E10A10 material (98%) followed by E20 (95%), whereas A20 only led to a removal of 69%. Similar behavior was found when analyzing the formation of reaction intermediates (data not shown), i.e., while A20 resulted in the accumulation of 4-nitrocatechol (4-NTC) and hydroquinone (HQ) E10A10 and E20 led to the total conversion of formed 4-NTC and HQ. This resulted in a lower TOC removal for A20 (37%) than to E10A10 and E20 (53%). Therefore, the amphiphilic E10A10 material is a promising catalyst for the CWPO of 4-NP.This work was financially supported by project "PLASTIC_TO_FUEL&MAT – Upcycling Waste Plastics into Fuel and Carbon Nanomaterials" (PTDC/EQU-EQU/31439/2017), Base Funding - UIDB/50020/2020 of the Associate Laboratory LSRE-LCM - funded by national funds through FCT/MCTES (PIDDAC), and CIMO (UIDB/00690/2020) through FEDER under Program PT2020. Fernanda F. Roman acknowledges the funding by FCT, Foundation for Science and Technology, and FSE, European Social Fund, through the individual research grant SFRH/BD/143224/2019info:eu-repo/semantics/publishedVersio

Selective denitrification of a simulated oily wastewater using Janus-structured carbon nanotubes

Carbon nanotubes (CNTs) bearing a Janus-like structure were synthesized by chemical vapor deposition considering ethylene and acetonitrile as carbon and nitrogen sources. The developed materials were applied as catalyst in the oxidation of 4-nitrophenol (4-NP) dissolved in a biphasic medium (water/2,2,4-trimeylpentane) simulating a contaminated oily wastewater. The CNT prepared using both ethylene and acetonitrile precursors shows a Janus-structure, leading to the highest abatement of 4-NP as well as to the highest removal of TOC, proving to be an alternative towards the removal of lipophilic pollutants from oily effluents, allowing to reclaim the oily phase.This work was financially supported by project "PLASTIC_TO_FUEL&MAT – Upcycling Waste Plastics into Fuel and Carbon Nanomaterials" (PTDC/EQU-EQU/31439/2017), Base Funding - UIDB/50020/2020 of the Associate Laboratory LSRE-LCM - funded by national funds through FCT/MCTES (PIDDAC), and CIMO (UIDB/00690/2020) through FEDER under Program PT2020. F. F. Roman acknowledges the national funding by FCT, Foundation for Science and Technology, and FSE, European Social Fund, through the individual research grant SFRH/BD/143224/2019. A. Santos Silva was supported by the doctoral grant SFRH/BD/151346/2021 financed by FCT with funds from NORTE2020, under MIT Portugal Programinfo:eu-repo/semantics/publishedVersio

Effectiveness of plant-derived proanthocyanidins on demineralization on enamel and dentin under artificial cariogenic challenge

Dental caries is considered a disease of high prevalence and a constant problem in public health. Proanthocyanidins (PAs) are substances that have been the target of recent studies aiming to control or treat caries. Objective The aim of this in vitro study was to evaluate the efficacy of a treatment with grape seed extract, under cariogenic challenge, to minimize or even prevent the onset of caries in the enamel and dentin. Material and Methods Blocks of enamel and dentin (6.0x6.0 mm) were obtained from bovine central incisors, polished, and selected by analysis of surface microhardness (SH). The blocks were randomly divided into 3 groups (n=15), according to the following treatments: GC (control), GSE (grape seed extract), GF (fluoride – 1,000 ppm). The blocks were subjected to 6 daily pH cycles for 8 days. Within the daily cycling, the specimens were stored in buffered solution. The blocks were then analyzed for perpendicular and surface hardness and polarized light microscopy. Results The means were subjected to statistical analysis using the ANOVA and Fisher's PLSD tests (p<0.05). For enamel SH, GF showed the highest hardness values. In the dentin, GF was also the one that showed higher hardness values, followed by GSE. Regarding the cross-sectional hardness values, all groups behaved similarly in both the enamel and dentin. The samples that were treated with GSE and fluoride (GF) showed statistically higher values than the control. Conclusion Based on the data obtained in this in vitro study, it is suggested that grape seed extract inhibits demineralization of artificial carious lesions in both the enamel and dentin, but in a different scale in each structure and in a smaller scale when compared to fluoride