| Summary: |
The objective of this project is the development of an innovative process to eliminate simultaneously organic and inorganic pollutants from water and wastewater. Inorganic species are usually formed during oxidation of organic compounds and different technologies are required for the removal of organic and inorganic compounds. For that purpose, integrated ozonation and reduction technologies in the presence of highly stable and selective catalysts in the structured form are considered. Particular attention will be addressed to organic pollutants, as model pollutants, which oxidation leads to the formation of undesirable inorganic species in solution, namely bromate and nitrate ions. The proposing team has proven expertise in this area, with several scientific articles published in ISI journals and participations in European and national funding projects (MONACAT, CLEANWATER, FREECATS, NANO/NTecCA/0122/2007, NEPCAT). The development of nanostructured carbon materials as carbon nanotubes, graphene oxide and mesoporous carbons with tailored surface and textural properties to act as support or as catalyst on their own, mainly in powder form, for water purification and wastewater treatment by advanced oxidation processes has been extensively studied by the research team. However, for industrial applications, it is necessary to incorporate the catalyst on macroscopic host structures to ensure the environmental safety and the easy reutilization of the catalysts. The advantage of using immobilized catalysts is evident in flow reactors, since problems related to pressure drop, plugging and flow misdistribution can be avoided. Therefore, as a prospective solution for practical application in water treatment facilities, the main objective of this project is transpose the potential of the most promising catalysts (selected according to our extensive knowledge and results obtained in the last years) onto a macrostructured support, such as monoliths, to be assessed in catalyti  |
Summary
The objective of this project is the development of an innovative process to eliminate simultaneously organic and inorganic pollutants from water and wastewater. Inorganic species are usually formed during oxidation of organic compounds and different technologies are required for the removal of organic and inorganic compounds. For that purpose, integrated ozonation and reduction technologies in the presence of highly stable and selective catalysts in the structured form are considered. Particular attention will be addressed to organic pollutants, as model pollutants, which oxidation leads to the formation of undesirable inorganic species in solution, namely bromate and nitrate ions. The proposing team has proven expertise in this area, with several scientific articles published in ISI journals and participations in European and national funding projects (MONACAT, CLEANWATER, FREECATS, NANO/NTecCA/0122/2007, NEPCAT). The development of nanostructured carbon materials as carbon nanotubes, graphene oxide and mesoporous carbons with tailored surface and textural properties to act as support or as catalyst on their own, mainly in powder form, for water purification and wastewater treatment by advanced oxidation processes has been extensively studied by the research team. However, for industrial applications, it is necessary to incorporate the catalyst on macroscopic host structures to ensure the environmental safety and the easy reutilization of the catalysts. The advantage of using immobilized catalysts is evident in flow reactors, since problems related to pressure drop, plugging and flow misdistribution can be avoided. Therefore, as a prospective solution for practical application in water treatment facilities, the main objective of this project is transpose the potential of the most promising catalysts (selected according to our extensive knowledge and results obtained in the last years) onto a macrostructured support, such as monoliths, to be assessed in catalytic oxidation and reduction under continuous operation. Several strategies for immobilization will be considered with the aim of developing novel structured catalysts that can enhance catalytic conversions, selectivities and catalyst lifetime. The deposition of an active phase on a structured support allows the introduction of engineering concepts in catalyst design, and although the general bases for the preparation of structured catalysts is well established, there are still many aspects to improve, making this an exciting field of research. The degradation of selected organic pollutants by catalytic ozonation and removal of nitrate and bromate by catalytic reduction in the presence of structured catalysts will be individually considered in flow reactors. After selection of the best experimental conditions for the oxidation and reduction reactors, the final target is to integrate both reactors simultaneously removing organic and inorganic pollutants in the same continuous process. |
| Results: |
O processo mecânico no moinho de bolas levou a um aumento da área superficial dos catalisadores em forma de pó (nanotubos de carbono - CNT).
Conseguiu-se um revestimento homogéneo com uma camada de espessura controlada nos catalisadores estruturados sob a forma de monólitos de cordierite revestidos por materiais à base de CNT utilizando-se o processo de revestimento por dip-coating.
Nos ensaios preliminares de ozonização, os catalisadores estruturados na forma moída com tamanho de partícula controlado apresentaram performances catalíticas pelo menos semelhantes aos catalisadores preparados pelo método mais comum (deposição química de vapor - CVD).
A performance dos catalisadores estruturados nos ensaios preliminares na forma moída está relacionada principalmente com a quantidade de carbono depositada nos suportes estruturados, sendo que esta depende do método de processamento e das propriedades morfológicas e texturais dos CNT.
O controlo da morfologia e propriedades superficiais dos CNT permitiu atingir excelente adesão dos materiais de carbono aos suportes estruturados.
Nos ensaios preliminares de redução do ião bromato, os catalisadores com suportes modificados através de tratamento mecânico apresentam atividade catalítica superior.
Nos ensaios preliminares de redução do ião perclorato verificou-se que a estrutura microporosa dos carvões activados promove a sua impregnação com óxido de rénio, o que não acontece quando os CNT foram usados como suporte para esta fase, resultando assim numa perda da atividade.
A atividade dos catalisadores testados durante a redução do ião nitrato diminui na presença de compostos orgânicos, estando em estudo os respectivos mecanismos de desativação. |