Neste trabalho foram testados métodos de obtenção de zeólitas e sílica amorfa a partir das cinzas volantes do carvão utilizado na Usina Termoelétrica Presidente Médici, Candiota, RS, tendo como objetivo principal a transformação de um resíduo sólido de grande impacto ambiental em materiais com maior valor agregado e uma ampla gama de aplicações. As matérias primas, assim como os produtos obtidos foram caracterizados por um conjunto de técnicas, a saber: Difratometria de Raios X(DRX), Fluorescência de Raios X(XFD), CHNS elementar, área superficial específica (BET), Microscopia Eletrônica de Varredura (MEV). Para a síntese das zeólitas foi utilizado o processo em duas etapas que consiste em fusão alcalina seguida de tratamento hidrotérmico. Visando a comparação entre as estruturas formadas, os parâmetros avaliados neste processo foram: natureza da fonte de silício e alumínio, tempo de reação, temperatura de reação e proporção cinza/NaOH. As temperaturas utilizadas foram de 350°C, 600°C e 800°C .em tempos de 3h, 5h e 8h e as proporções cinza/NaOH de 1:1 e 1:2. As análises por difração de raios X dos produtos obtidos por fusão alcalina indicaram estruturas zeolíticas naqueles em que foram usadas as proporções cinza/NaOH de 1:1 em todas as temperaturas utilizadas neste processo variando os tempos de reação. Com a proporção cinza/NaOH de 1:2, não foram obtidas estruturas com características zeolíticas. Para a obtenção da sílica amorfa, as cinzas foram submetidas à fusão alcalina com NaOH seguida de lixiviação com HCl a 25%,sendo obtidos dois produtos:um a partir da fase gel e outro da fase precipitada Os produtos obtidos, analisados por difração de raios X apresentaram valores de 2θ (26,6) característicos da sílica amorfa. Uma avaliação semiquantitativa feita por fluorescência de raios X indica que a sílica amorfa precipitada apresentou pureza acima de 95% e a sílica amorfa obtida a partir do gel, apresentou pureza de 75%. / In this essay, methods of obtaining amorphous silica and zeolites from coal fly ash Presidente Médici Thermoelectric Power Plant have been tested, having as main objective the transformation of a large solid waste environmental impact in high value applicable materials. The raw materials, and the products were characterized by a set of techniques: particle size analysis, X-ray diffraction (XRD), X-Ray Fluorescence (XFD), CHNS elemental (BET) Scanning electron microscopy (SEM), Microscope bench. For the synthesis of zeólitas, the process was done in two steps. It consisted in alkaline fusion followed by hydrothermal treatment. The parameters evaluated in this process were the origin of the source of silicon and aluminum; reaction time, reaction temperature, proportion fly ash/ hydroxide. The temperatures used were 350 °C, 600 °C and 800 °C. To time of 3h, 5h and 8h and cinza/ NaOH proportion of 1:1 and 1:2 . The products obtained by alkaline fusion those in witch were subjected the proportion fly ash /NaOH 1:1 showed zeolitic structures at all temperatures used in this process by varying the reaction time. With the ratio fly ash/NaOH 1:2 not zeolitic structures were obtained.. To obtain amorphous silica, ash was subjected to alkali fusion with NaOH and treated with hydrochloric acid (25%). Two products were obtained: one from the gel phase and other from the the precipitated phase, The x-ray diffraction patterns shows a amorphous band in the 2 θ region in the range between 20° and 40° which is related to the amorphous silica. A semi quantitative evaluation by X-ray fluorescence shows that the amorphous precipitated silica had purity of above 95%, and amorphous silica obtained from gel showed 75% purity.

Neste trabalho foram testados métodos de obtenção de zeólitas e sílica amorfa a partir das cinzas volantes do carvão utilizado na Usina Termoelétrica Presidente Médici, Candiota, RS, tendo como objetivo principal a transformação de um resíduo sólido de grande impacto ambiental em materiais com maior valor agregado e uma ampla gama de aplicações. As matérias primas, assim como os produtos obtidos foram caracterizados por um conjunto de técnicas, a saber: Difratometria de Raios X(DRX), Fluorescência de Raios X(XFD), CHNS elementar, área superficial específica (BET), Microscopia Eletrônica de Varredura (MEV). Para a síntese das zeólitas foi utilizado o processo em duas etapas que consiste em fusão alcalina seguida de tratamento hidrotérmico. Visando a comparação entre as estruturas formadas, os parâmetros avaliados neste processo foram: natureza da fonte de silício e alumínio, tempo de reação, temperatura de reação e proporção cinza/NaOH. As temperaturas utilizadas foram de 350°C, 600°C e 800°C .em tempos de 3h, 5h e 8h e as proporções cinza/NaOH de 1:1 e 1:2. As análises por difração de raios X dos produtos obtidos por fusão alcalina indicaram estruturas zeolíticas naqueles em que foram usadas as proporções cinza/NaOH de 1:1 em todas as temperaturas utilizadas neste processo variando os tempos de reação. Com a proporção cinza/NaOH de 1:2, não foram obtidas estruturas com características zeolíticas. Para a obtenção da sílica amorfa, as cinzas foram submetidas à fusão alcalina com NaOH seguida de lixiviação com HCl a 25%,sendo obtidos dois produtos:um a partir da fase gel e outro da fase precipitada Os produtos obtidos, analisados por difração de raios X apresentaram valores de 2θ (26,6) característicos da sílica amorfa. Uma avaliação semiquantitativa feita por fluorescência de raios X indica que a sílica amorfa precipitada apresentou pureza acima de 95% e a sílica amorfa obtida a partir do gel, apresentou pureza de 75%. / In this essay, methods of obtaining amorphous silica and zeolites from coal fly ash Presidente Médici Thermoelectric Power Plant have been tested, having as main objective the transformation of a large solid waste environmental impact in high value applicable materials. The raw materials, and the products were characterized by a set of techniques: particle size analysis, X-ray diffraction (XRD), X-Ray Fluorescence (XFD), CHNS elemental (BET) Scanning electron microscopy (SEM), Microscope bench. For the synthesis of zeólitas, the process was done in two steps. It consisted in alkaline fusion followed by hydrothermal treatment. The parameters evaluated in this process were the origin of the source of silicon and aluminum; reaction time, reaction temperature, proportion fly ash/ hydroxide. The temperatures used were 350 °C, 600 °C and 800 °C. To time of 3h, 5h and 8h and cinza/ NaOH proportion of 1:1 and 1:2 . The products obtained by alkaline fusion those in witch were subjected the proportion fly ash /NaOH 1:1 showed zeolitic structures at all temperatures used in this process by varying the reaction time. With the ratio fly ash/NaOH 1:2 not zeolitic structures were obtained.. To obtain amorphous silica, ash was subjected to alkali fusion with NaOH and treated with hydrochloric acid (25%). Two products were obtained: one from the gel phase and other from the the precipitated phase, The x-ray diffraction patterns shows a amorphous band in the 2 θ region in the range between 20° and 40° which is related to the amorphous silica. A semi quantitative evaluation by X-ray fluorescence shows that the amorphous precipitated silica had purity of above 95%, and amorphous silica obtained from gel showed 75% purity.

Neste trabalho foram testados métodos de obtenção de zeólitas e sílica amorfa a partir das cinzas volantes do carvão utilizado na Usina Termoelétrica Presidente Médici, Candiota, RS, tendo como objetivo principal a transformação de um resíduo sólido de grande impacto ambiental em materiais com maior valor agregado e uma ampla gama de aplicações. As matérias primas, assim como os produtos obtidos foram caracterizados por um conjunto de técnicas, a saber: Difratometria de Raios X(DRX), Fluorescência de Raios X(XFD), CHNS elementar, área superficial específica (BET), Microscopia Eletrônica de Varredura (MEV). Para a síntese das zeólitas foi utilizado o processo em duas etapas que consiste em fusão alcalina seguida de tratamento hidrotérmico. Visando a comparação entre as estruturas formadas, os parâmetros avaliados neste processo foram: natureza da fonte de silício e alumínio, tempo de reação, temperatura de reação e proporção cinza/NaOH. As temperaturas utilizadas foram de 350°C, 600°C e 800°C .em tempos de 3h, 5h e 8h e as proporções cinza/NaOH de 1:1 e 1:2. As análises por difração de raios X dos produtos obtidos por fusão alcalina indicaram estruturas zeolíticas naqueles em que foram usadas as proporções cinza/NaOH de 1:1 em todas as temperaturas utilizadas neste processo variando os tempos de reação. Com a proporção cinza/NaOH de 1:2, não foram obtidas estruturas com características zeolíticas. Para a obtenção da sílica amorfa, as cinzas foram submetidas à fusão alcalina com NaOH seguida de lixiviação com HCl a 25%,sendo obtidos dois produtos:um a partir da fase gel e outro da fase precipitada Os produtos obtidos, analisados por difração de raios X apresentaram valores de 2θ (26,6) característicos da sílica amorfa. Uma avaliação semiquantitativa feita por fluorescência de raios X indica que a sílica amorfa precipitada apresentou pureza acima de 95% e a sílica amorfa obtida a partir do gel, apresentou pureza de 75%. / In this essay, methods of obtaining amorphous silica and zeolites from coal fly ash Presidente Médici Thermoelectric Power Plant have been tested, having as main objective the transformation of a large solid waste environmental impact in high value applicable materials. The raw materials, and the products were characterized by a set of techniques: particle size analysis, X-ray diffraction (XRD), X-Ray Fluorescence (XFD), CHNS elemental (BET) Scanning electron microscopy (SEM), Microscope bench. For the synthesis of zeólitas, the process was done in two steps. It consisted in alkaline fusion followed by hydrothermal treatment. The parameters evaluated in this process were the origin of the source of silicon and aluminum; reaction time, reaction temperature, proportion fly ash/ hydroxide. The temperatures used were 350 °C, 600 °C and 800 °C. To time of 3h, 5h and 8h and cinza/ NaOH proportion of 1:1 and 1:2 . The products obtained by alkaline fusion those in witch were subjected the proportion fly ash /NaOH 1:1 showed zeolitic structures at all temperatures used in this process by varying the reaction time. With the ratio fly ash/NaOH 1:2 not zeolitic structures were obtained.. To obtain amorphous silica, ash was subjected to alkali fusion with NaOH and treated with hydrochloric acid (25%). Two products were obtained: one from the gel phase and other from the the precipitated phase, The x-ray diffraction patterns shows a amorphous band in the 2 θ region in the range between 20° and 40° which is related to the amorphous silica. A semi quantitative evaluation by X-ray fluorescence shows that the amorphous precipitated silica had purity of above 95%, and amorphous silica obtained from gel showed 75% purity.

Philosophiae Doctor - PhD / Power generation in South Africa depends majorly on the combustion of coal and the increasing demand for energy due to industrialisation and population growth signifies the continuous consumption of coal. During this process, a by-product known as coal fly ash (CFA) is generated which poses several environmental issues. The common management of the waste involves the disposal of CFA in landfills or the direct disposal to open uncultured lands, thus contaminating water bodies by the leaching of constituent CFA metals and salts that render arable land uncultivable.

Zeolites are among the least-known products for environmental pollution control, separation science and technology. Due to their unique porous properties, they are used in various applications in petrochemical cracking, ion-exchange and separation and removal of gases and solvents. The preparation of synthetic zeolites from chemical reagents is expensive. Therefore, in order to reduce costs, zeolite researchers are seeking cheaper aluminosilicate bearing raw materials, such as clay minerals, to produce synthetic zeolites. This research concerns the synthesis of zeolites and zeotypes derived from low-cost materials like kaolinite (KAO), natural clinker (NC) and fly ash (FA). The motivation for using these sources as the starting materials in zeolite synthesis is driven by factors, such as they are cheap and available in bulk quantities, are currently under-utilized, have high workability, and require less water (or solution) for activation. The raw materials were activated by two different routes: (1) classic alkaline hydrothermal synthesis and (2) alkaline fusion prior to hydrothermal synthesis. In the first method, the synthesis of zeolitic materials was carried out generally in alkaline media, although KAO or its calcination product, metakaolinite (MTK), was also activated in the presence or absence of structure directing agents (SDAs) and additional silica (precipitated SiO2), with the last one determining the SiO2/Al2O3 ratio of the reaction mixture and the time given for zeolitization. Synthesis in fluoride- and calcium-bearing media was also used to activate kaolinite. The process of synthesis was optimized by applying a wide range of experimental conditions with a wide range of reaction temperature, time, mineralizer concentration and solid/solution ratio. In the second approach, an alkaline fusion step was conducted prior to hydrothermal treatment, because it plays an important role in enhancing the hydrothermal conditions for zeolite synthesis. On the other hand, this approach was adopted because it can dissolve more aluminosilicates. The main synthesis products obtained after activation of KAO in NaOH solutions included zeolite LTA (LTA), sodalite (SOD), cancrinite (CAN), faujasite (FAU), zeolite Na-P1 (GIS), JBW-type zeolite (JBW), analcime (ANA), whereas the activation of KAO in KOH solutions produced chabazite (CHA), zeolite Barrer-KF, phillipsite (PHI) and K-feldspar. The hydrothermal conversion of kaolinite in fluoride media did not produce successful results, although traces of FAU, GIS, CHA, SOD and CAN crystallized. The activation of KAO in the system CaO-SiO2-Al2O3-H2O promoted the formation of different calcium silicate hydrate (C-S-H) phases, including hydrogarnet (HYD) and tobermorite (TOB). Following the fusion approach, the main zeolitic phases obtained using NaOH as mineralizer were LTA and CAN. The main as-synthesized zeolites obtained from NC by the conventional hydrothermal treatment method include PHI, SOD and CAN. Using the fusion approach, FAU and LTA were obtained with NaOH as an activator, whereas non-zeolitic material crystallized when KOH was used. The main as-synthesized zeolitic materials obtained by hydrothermal reaction of FA include PHI, zeolite Barrer-KF, CHA and SOD with traces of TOB, ANA, zeolite LTF (LTF) and herschelite (HER), appearing occasionally. By the fusion approach, FAU was obtained with NaOH as activator, whereas no zeolitic material crystallized using KOH. Experimental results indicate that the method, mineralizer, concentration and time have strong effects on the type and degree of crystallinity of the synthesis products. On the other hand, the type and chemical composition of the as-synthesized products are strongly dependent on the chemical composition of the starting material. The chemistry of zeolite synthesis was subject to perturbations caused by the presence of impurities in the raw materials, which may remain insoluble during crystallization and cause undesired species to nucleate, developing mixtures of different types of zeolites. However, other physicochemical factors may play a very important role in the thermodynamics and kinetics of zeolite formation. The raw materials have very high contents of SiO2 and Al2O3, with SiO2/Al2O3 ratios appropriate for the synthesis of low-Si zeolitic materials with high crystallinity and cation exchange capacity (CEC). However, although zeolites’ CEC represents a very important characteristic quality in the removal of undesired species from polluted effluents, it is not the deciding factor in determining zeolite performance during ion exchange processes, since numerous other factors also need to be considered. Finally, the potential application of the raw materials and their as-synthesized products as low-cost sorbents in the remediation of metal ions and ammonium from wastewater effluents was investigated. PHI showed a lower efficiency than FAU. Selectivity of FAU for metal removal was, in decreasing order, Fe>As>Pb>Zn>Cu>Ni>Cr. Based on these results, the use of these materials has the potential to provide improved methods for the treatment of contaminated effluents.