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Essential oils (EO) obtained from plants have proven industrial applications in the manufacturing of perfumes and cosmetics, in the production and flavoring of foods and beverages, as therapeutic agents in aromatherapy, and as the active principles or excipients of medicines and pharmaceutics due to their olfactory, physical-chemical, and biological characteristics. On behalf of the new paradigm of a more natural and sustainable lifestyle, EO are rather appealing due to their physical, chemical, and physiological actions in human beings. However, EO are unstable and susceptible to degradation or loss. To tackle this aspect, the encapsulation of EO in microporous structures as zeolites is an attractive solution, since these host materials are cheap and non-toxic to biological environments. This overview provides basic information regarding essential oils, including their recognized benefits and functional properties. Current progress regarding EO encapsulation in zeolite structures is also discussed, highlighting some representative examples of essential oil delivery systems (EODS) based on zeolites for healthcare applications or aromatherapy., The authors are grateful for the national funds provided by the FCT (Foundation for Science and Technology, Portugal) under the projects UIDB/04050/2020 (CBMA) and PTDC/AAGTEC/5269/2014 (FEDER, European Fund for Regional Development)/COM PETE/POCI—Operational Competitiveness and Internationalization Programme under the project POCI-01-0145-FEDER-006958. They are grateful for the financial support provided by the Research Centers CQ/UM through UID/QUI/0686/2020 and Project BioTecNorte (operation NORTE-01-0145-FEDER-000004), supported by the Northern Portugal Regional Operational Programme (NORTE 2020) under the Portugal 2020 Partnership Agreement through the European Regional Development Fund., info:eu-repo/semantics/publishedVersion

Tese de doutoramento em Química Aplicada, A qualidade da água, através de contaminações de poluentes orgânicos, onde se incluem os corantes azo, tem impacto na saúde humana e no meio ambiente. O trabalho apresentado nesta dissertação teve como objetivo a preparação e a caracterização de catalisadores heterogéneos funcionalizados com metais de transição, utilizando como suportes os zeólitos e a sua aplicação na catálise oxidativa usando a reação de Fenton, perspetivando a mineralização dos corantes azo selecionados, Procion Yellow e Tartrazina. Utilizaram-se duas estruturas zeolíticas, FAU (zeólito Y) e MFI (zeólito ZSM5), para preparar os catalisadores heterogéneos a estudar na degradação de poluentes através da reação de Fenton em fase aquosa, recorrendo ao método de troca iónica. O método escolhido foi bastante eficaz na preparação dos catalisadores heterogéneos monometálicos e bimetálicos, através da via sequêncial, com Fe, Cu e Mn nos zeólitos ZSM5 e Y. Os catalisadores heterogéneos bimetálicos preparados pela via simultânea com Fe, Cu, Mn, Co, Ni e Zn foram obtidos com o zeólito NaY. Os catalisadores heterogéneos foram caracterizados por diferentes técnicas de análise: espectroscopia de emissão atómica com plasma induzido, microscopia eletrónica de varrimento, espectroscopia fotoelectrónica de raios-X, difração de raios-X, espectroscopias de infravermelho (FTIR) e ultravioleta/visível, voltametria cíclica e isotérmicas de adsorção de azoto. As técnicas de caracterização mostraram que os catalisadores heterogéneos foram obtidos com sucesso. A atividade catalítica dos diferentes catalisadores heterogéneos foi estudada na oxidação dos corantes azo presentes em efluentes usando a reação de Fenton, tendo-se verificado que estes catalisadores são eficientes, especialmente os catalisadores preparados com a estrutura FAU. A presença de dois metais no zeólito é essencial a fim de aumentar a atividade catalítica, observando-se um efeito de sinergia entre o Fe e o outro metal, utilizando as condições experimentais estabelecidas neste trabalho. Os estudos de reutilização dos catalisadores mostraram que não ocorreu perda das suas propriedades catalíticas e estruturais., Water quality, through contamination of organic pollutants, where azo dyes are included, has an impact on human health and the environment. The work presented in this dissertation aimed the preparation and characterization of heterogeneous catalysts functionalized with transition metals, using zeolites as supports and their application in oxidative catalysis by the Fenton reaction, aiming the mineralization of the selected azo dyes, Procion yellow and tartrazine. Two zeolitic structures, FAU (zeolite Y) and MFI (zeolite ZSM5) were used to prepare heterogeneous catalysts in the degradation of pollutants through the aqueous phase Fenton reaction, using the ion exchange method. The chosen method was quite effective in preparing the monometallic and bimetallic heterogeneous catalysts with Fe, Cu and Mn on ZSM5 and Y zeolites through the sequential route. The bimetallic heterogeneous catalysts prepared by the simultaneous route with Fe, Cu, Mn, Co, Ni and Zn were obtained with the NaY zeolite. The heterogeneous catalysts were characterized by different analysis techniques: induced plasma atomic emission spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, spectroscopies of infrared (FTIR) and ultraviolet/visible, cyclic voltammetry and nitrogen adsorption isotherms. The characterization techniques showed that the heterogeneous catalysts were successfully obtained. The catalytic activity of the different heterogeneous catalysts was studied in the oxidation of azo dyes present in effluents using the Fenton reaction, and it was found that these catalysts are efficient, especially the catalysts prepared with the FAU structure. The presence of two metals in the zeolite is essential in order to increase the catalytic activity, and a synergistic effect between Fe and the other metal was observed using the experimental conditions established in this work. The reuse studies showed that no loss of its catalytic and structural properties occurred.