Browsing by Author "Dias, Arnaldo"
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- Hybrid magnetic nanoparticles for wet peroxide oxidation of paracetamolPublication . Dias, Arnaldo; Silva, Adriano S.; Roman, Fernanda; Silva, Ana P. F.; Díaz de Tuesta, Jose Luis; Lima, Ana Maria; Gomes, HelderA performance de nanopartículas de ferrite de cobalto, ferrite de cobalto recoberta por carbono preparada por uma metodologia tradicional e ferrite de cobalto preparada por metodologia verde foi avaliada na remoção de paracetamol (PCM), escolhido como poluente modelo, por um processo de oxidação húmida com peróxido de hidrogénio (CWPO). O núcelo magnético foi sintetizado por sol-gel, e na metodologia tradicional de recobrimento de carbono foi considerado resorcinol/formaldeído como precursores de carbono, enquanto que na metodologia verde foi considerado phloroglucinol/ácido glioxílico. Todas as nanopartículas magnéticas (NPMs) apresentaram atividade na remoção de PCM por CWPO. Ambas as NPMs recobertas com carbono apresentaram resultados melhores que o núcleo não recoberto, devido à presença da camada de carbono à volta do núcleo, que também tem atividade pelas propriedades eletrónicas do recobrimento de carbono. O catalisador recoberto pela metodologia verde possui uma decomposição de peróxido de hidrogénio mais controlada. O teste de reutilização do catalisador mostrou a estabilidade do material, com perfis de concentração similares e uma remoção de PCM mais rápida que na primeira utilização
- Hybrid multi-core shell magnetic nanoparticles for wet peroxide oxidation of paracetamol: application in synthetic and real matricesPublication . Silva, Adriano S.; Roman, Fernanda; Dias, Arnaldo; Díaz de Tuesta, Jose Luis; Narcizo, Alexandre; Silva, Ana P. F.; Çaha, Ihsan; Deepak, Francis Leonard; Bañobre-López, Manuel; Ferrari, Ana M.; Gomes, HelderClean water availability is becoming a matter of global concern in the last decades. The responsible entities for wastewater treatment do not have the proper facilities to deal with a wide range of pollutants. Special attention should be given to emerging contaminants, whose presence in water bodies may cause adverse effects on the aquatic ecosystem and human health. Most studies in the literature do not consider the development of their solution in real matrices, which can hinder the applicability of the explored alternative in the real scenario. Therefore, in this work, we demonstrate the applicability of hybrid magnetic nanoparticles for removing paracetamol (PCM) from simulated and real matrices by catalytic wet peroxide oxidation (CWPO). To achieve carbon coating, the nanoparticles were prepared via the traditional route (resorcinol/formaldehyde, CoFe@CRF). A new methodology was also considered for synthesizing thin-layered carbon-coated magnetic nanoparticles (phloroglucinol/ glyoxalic acid, CoFe@CPG). TEM images revealed a multi-core shell structure formation, with an average carbon layer size of 7.8 ± 0.5 and 3.2 ± 0.3 nm for resorcinol/formaldehyde and phloroglucinol/ glyoxalic acid methodology, respectively. Screening the materials’ activity for PCM oxidation by CWPO revealed that the nanoparticle prepared by phloroglucinol/glyoxalic acid methodology has higher performance for the degradation of PCM, achieving 63.5% mineralization after 24 h of reaction, with similar results for more complex matrices. Iron leaching measured at the end of all reactions has proven that the carbon layer protects the core against leaching.
- Simultaneous removal of o-and p-nitrophenol from contaminated water by wet peroxide oxidation using carbon-coated magnetic ferrite as catalystPublication . Dias, Arnaldo; Silva, Adriano S.; Silva, Ana P. F.; Roman, Fernanda; Díaz de Tuesta, Jose Luis; Oliveira, Jéssica; Ferrari, Ana M.; Lenzi, Giane G.; Gomes, Helder; Oliveira, JessícaGroundwater is the most common source of drinking water worldwide and is currently facing contamination problems with the discharge of pollutants into aquatic systems through different means, namely through municipal, industrial and agricultural activities. Contaminants, such as herbicides, pharmaceuticals, phenolic compounds and personal care products are not removed by conventional treatments from wastewater treatment plants, leading to their accumulation in the environment. In this regard, o-nitrophenol (o-NP) and p-nitrophenol (p-NP), commonly used as raw materials in chemical and pharmaceutical engineering, represent a severe risk to humans and aquatic life, leading to the necessity to properly treat wastewaters containing these contaminants before discharge into the aquatic environment. Catalytic wet peroxide oxidation (CWPO) showed promising results for removing nitrophenols from wastewater in previous works. In this technology, H2O2 is used as an oxidant, and its interaction with a suitable catalyst leads to the formation of hydroxyl radicals under determined conditions already established in literature (pH and temperature have a strong influence) [1]. Typical catalysts employed have a transition metal in its structure. Carbon-based catalysts also have activity in this technology, mostly ascribed to the electronic properties of the carbonaceous surface. Furthermore, carbon-coated metal oxide materials (hybrid) have also demonstrated potential applications in CWPO. Those structures combine carbon and metal activities with the advantage of protecting the metal core from leaching, increasing the efficiency and stability of the catalysts.
- Wet peroxide oxidation of paracetamol using carbon-coated spinel ferrite nanoparticles as catalystPublication . Gomes, Helder; Dias, Arnaldo; Silva, Adriano S.; Roman, Fernanda; Silva, Ana P. F.; Lima, Ana M.F.; Díaz de Tuesta, Jose LuisIn this study, carbon-based magnetic nanoparticles (MNPs) have been prepared by sucessive sol-gel method for core bare preparation and carbon coated through polymerization of phloroglucinol/glyoxylic acid, which are greener carbon precursors than the conventional method of resorcinol/formaldehyde (R/F), since formaldehyde is known to be a carcinogenic reagent. The bare core (CoFe2O4) and the carbon-coated MNPs (CoFe2O4@C) were tested as catalysts in the removal of paracetamol (PCM) from an aqueous solution by catalytic wet peroxide oxidation under optimum operational conditions, pH 3.5 and 80 °C. Values of paracetamol abatment between 33.0 and 100% were achieved after 6 h of reaction for the bare core and the carbon-based MNPs, respectively.