An adsorbent for Cs removal from contaminated water based on phosphotungstic acid (PTA) embedded in SiO 2 network was synthesized and granulated with γ-Al 2 O 3 . PTA/SiO 2 had a high adsorption capacity towards Cs while the binder provided excellent mechanical characteristics of the material. It was shown that small particles of PTA/SiO 2 with the sizes of 0.1–1 µm occupied space between larger particles of the binder (up to 5 µm). Chemical interaction between PTA and γ-Al 2 O 3 during the adsorbent preparation also took place. The obtained porous material with the specific surface area of 286.9 m 2 /g contained 4.73% of PTA. Presence of Keggin units in the structure was confirmed by solid state NMR spectroscopy. Study of the adsorbent in Cs + adsorption from solutions demonstrated its high adsorption capacity. The concentrations of Cs + in the solutions after the column tests decreased by 3.3–5.2 times. The presence of Na + and K + as competing ions did not affect the adsorption. The material was tested in clean-up of radioactive water from the shelter of Chernobyl nuclear power plant (Ukraine). A significant decrease of 137 Cs radioactivity was detected in all samples of radioactive water, especially in acidic solutions. Thus the adsorbent can be used for water treatment after incidents resulting in release of radioactive isotopes 134 Cs and 137 Cs.

The adsorption of cesium on mesoporous silica materials containing embedded phosphotungstic acid (PTA) was studied. The materials contained active adsorbent and binders: γ-Al2O3, kaolin, or charcoal. The presence of Keggin units of PTA in the bound materials was confirmed by FT-IR spectroscopy. Among all materials, the formulation with γ-Al2O3 demonstrated the highest porosity and effectiveness in adsorption. Pure PTA/SiO2 contained a significant fraction of small particles between 100 and 300 nm. However, in the alumina-bound material, they were not detected. SEM imaging showed that these particles occupied interparticle space between larger γ-Al2O3 particles. The material was stable up to 540 °C. In most materials, the adsorption of cesium decreased with increase of the binder contents but not proportionally. The adsorption capacity of all materials depended on the concentration of cesium in the solutions. Maximum adsorption was achieved after 1 h. The adsorption of cesium is controlled by intraparticle diffusion while its rate can be described by the pseudo-second-order model.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-03-23T18:44:54Z No. of bitstreams: 1 JANAINA RAFAELLA SCHEIBLER - DISSERTAÇÃO PPGEQ 2015..pdf: 2465420 bytes, checksum: cbecc726b67d3d76a334570b655735eb (MD5) / Made available in DSpace on 2018-03-23T18:44:54Z (GMT). No. of bitstreams: 1 JANAINA RAFAELLA SCHEIBLER - DISSERTAÇÃO PPGEQ 2015..pdf: 2465420 bytes, checksum: cbecc726b67d3d76a334570b655735eb (MD5) Previous issue date: 2015 / Entre as membranas inorgânicas microporosas, as membranas zeolíticas constituem uma tecnologia promissora, devido às suas potenciais aplicações normalmente na desidratação do álcool, separação de moléculas de gás, separação de isômeros ou em processos químicos, incluindo reações de esterificação. Sob este aspecto, torna-se imprescindível o estudo das rotas de preparação desses materiais, visando desenvolver produtos com qualidade e a baixo custo. Portanto, a inovação deste estudo se dá na síntese de membranas zeolíticas via método de síntese poreplugging visando a utilização das membranas inorgânicas para permeação gasosa de N2. Neste trabalho foram desenvolvidos os seguintes materiais: zeólita ZSM-5, membranas cerâmicas (γ-alumina e α-alumina) e as membranas zeolíticas (ZSM5/γ-alumina e ZSM-5/α-alumina). A zeólita ZSM-5 foi sintetizada por meio do método hidrotérmico. As membranas cerâmicas (γ-alumina e α-alumina) foram preparadas a partir da técnica de conformação de pós cerâmicos e posteriormente submetidas à sinterização a uma temperatura de 1000 ºC/1h e 1200 ºC/1h respectivamente. A preparação das membranas zeolíticas (ZSM-5/γ-alumina e ZSM-5/α-alumina) foi realizada com base no método pore in plugging. As amostras foram caracterizadas a partir das técnicas de difração de raios X e Microscopia Eletrônica de Varredura. Os resultados experimentais permitem diversas conclusões acerca do desenvolvimento dos materiais: zeólita ZSM-5, membranas cerâmicas (γ-alumina e α-alumina) e membranas zeolíticas (ZSM-5/γ-alumina e ZSM-5/α-alumina). A partir da difração de raios X, foi possível verificar que o método de síntese empregado, foi efetivo na obtenção da zeólita ZSM-5. O difratograma apresentou picos característicos de uma zeólita ZSM-5 quando comparada ao padrão. Os resultados obtidos por DRX para as membranas cerâmicas (γ-alumina e α-alumina) demonstraram a formação de picos característicos do óxido de alumínio, os materiais são cristalinos e puros. Para o método pore-plugging pode se dizer que é um método promissor, pois mostrou uma formação satisfatória da camada zeolítica no resultado do DRX de ambas as membranas zeolíticas (ZSM-5/γ-alumina e ZSM-5/α-alumina). / Among the microporous inorganic membranes, zeolite membranes are a promising technology due to their potential applications normally in alcohol dehydration, separation of gas molecules, separation of isomers or chemical processes, including esterification reactions. In this regard, it is essential to study the preparation of these materials routes in order to develop products with quality and low cost. Therefore, innovation of this study gives the synthesis of zeolite membranes via pore-plugging synthesis method aimed at the use of inorganic membranes for gas permeation N2. In this work the following materials were developed: ZSM-5 zeolite, ceramic membranes (γ-alumina and α-alumina) and zeolitic membranes (ZSM-5/γ-alumina and ZSM-5/α-alumina). Zeolite ZSM-5 was synthesized by the hydrothermal method. Ceramic membranes (γ-alumina and α-alumina) were prepared from the ceramic powder forming technique, and subsequently subjected to a sintering temperature of 1000 °C/1h and 1200 °C/1h respectively. The preparation of zeolite membranes (ZSM-5/γ-alumina and ZSM-5/α-alumina) was carried out based on the method in pore plugging. The samples were characterized from the techniques of X diffraction and scanning electron microscopy rays. The experimental results allow several conclusions about the development of materials: zeolite ZSM-5, ceramic membranes (γ-alumina and α-alumina) and zeolite membranes (ZSM-5/γ-alumina and ZSM-5/αalumina). From the X-ray diffraction, it found that the method of synthesis used was effective in obtaining the zeolite ZSM-5. The XRD pattern showed peaks characteristic of ZSM-5 compared to the standard. The results obtained by XRD ceramic membranes (γ-alumina and α-alumina) showed the formation of peaks characteristic of aluminum oxide, the materials are crystalline and pure. For the poreplugging method can be said to be a promising method because it showed a satisfactory formation of the zeolite layer on the result of XRD both zeolite membranes (ZSM-5/γ-alumina and ZSM-5/α-alumina).