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Nanotubos de carbono como catalisadores interfaciais na oxidação com peróxido de hidrogénio
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Resumo(s)
Nanotubos de carbono (CNTs) anfifílicos foram testados como emulsionantes Pickering e como catalisadores
interfaciais na remoção de poluentes em sistemas aquosos e bifásicos por oxidação com peróxido de hidrogénio (CWPO). Os materiais foram sintetizados por deposição química em fase vapor num reator de leito fluidizado, alimentando etileno e/ou acetonitrilo. Os CNTs foram testados como catalisadores para a remoção do 2-nitrofenol, usado como poluente lipofílico modelo, em fase aquosa e em mistura bifásica de ciclohexano-água, para simular águas residuais oleosas. O catalisador mais ativo na CWPO em meio aquoso foi CNTs sintetizados com apenas etileno, devido ao seu maior carácter lipofílico. Na CWPO do 2-nitrofenol em mistura bifásica, só os CNTs anfifílicos (contendo uma secção não dopada sintetizada a partir de etileno e outra dopada com N sintetizada a partir de acetonitrilo) mostraram atividade catalítica. Esta atividade foi atribuída à formação de uma emulsão Pickering, que permitiu a decomposição do H2O2 em radicais hidroxilo, na seção hidrofílica do catalisador e a adsorção e posterior reação do 2-nitrofenol com os radicais hidroxilo, na seção lipofílica.
Amphiphilic carbon nanotubes (CNTs) were tested as Pickering emulsifiers and interfacial catalysts in the removal of pollutants from aqueous and biphasic systems by catalytic wet peroxide oxidation (CWPO). The materials were synthesized by catalytic chemical vapour deposition in a fluidized-bed reactor by feeding ethylene and/or acetonitrile. The CNTs were tested as catalysts on the degradation of 2-nitrophenol, used as model lipophilic pollutant, in aqueous phase and in a biphasic mixture of cyclohexane-water to simulate oily wastewaters. The most active catalyst in aqueous CWPO was the CNTs synthesized with ethylene alone, due to its high lipophilic character. In the biphasic CWPO, only the amphiphilic CNTs (containing a lipophilic undoped section synthetized using ethylene and a hydrophilic N-doped section synthetized using acetonitrile) revealed catalytic activity for the removal of 2-nitrophenol. This was ascribed to the formation of Pickering emulsions, which enabled the decomposition of H2O2 into hydroxyl radicals at the hydrophilic section of the catalyst, and the adsorption and further reaction of 2-nitrophenol with the hydroxyl radicals, at the lipophilic section.
Amphiphilic carbon nanotubes (CNTs) were tested as Pickering emulsifiers and interfacial catalysts in the removal of pollutants from aqueous and biphasic systems by catalytic wet peroxide oxidation (CWPO). The materials were synthesized by catalytic chemical vapour deposition in a fluidized-bed reactor by feeding ethylene and/or acetonitrile. The CNTs were tested as catalysts on the degradation of 2-nitrophenol, used as model lipophilic pollutant, in aqueous phase and in a biphasic mixture of cyclohexane-water to simulate oily wastewaters. The most active catalyst in aqueous CWPO was the CNTs synthesized with ethylene alone, due to its high lipophilic character. In the biphasic CWPO, only the amphiphilic CNTs (containing a lipophilic undoped section synthetized using ethylene and a hydrophilic N-doped section synthetized using acetonitrile) revealed catalytic activity for the removal of 2-nitrophenol. This was ascribed to the formation of Pickering emulsions, which enabled the decomposition of H2O2 into hydroxyl radicals at the hydrophilic section of the catalyst, and the adsorption and further reaction of 2-nitrophenol with the hydroxyl radicals, at the lipophilic section.
Descrição
Palavras-chave
Oxidação húmida com peróxido de hidrogénio Nanotubos de carbono Catalisadores anfifílicos Oxidação bifásica
Contexto Educativo
Citação
Díaz de Tuesta, Jose Luis; Machado, Bruno; Serp, Philippe; Silva, Adrián; Faria, Joaquim; Gomes, Helder (2018). Nanotubos de carbono como catalisadores interfaciais na oxidação com peróxido de hidrogénio. In XXVI Congresso Ibero-Americano de Catálise: livro de atas. Coimbra, p. 409-414. ISBN 978-989-8124-23-4