Search

Process intensification of heterogeneous TiO 2 photocatalysis using a new type of static mixer micro–meso-structured-reactor, based on the NETmix reactor, was evaluated to promote the hexavalent chromium reduction to its trivalent state, in the presence of sacrificial agents. The photocatalytic micro–meso-structured reactor comprises a back acrylic slab where chambers and channels are imprinted and a frontal borosilicate slab with especially high UV transparency, irradiated by simulated solar light. An UV transparent cellulose acetate (CA) sheet coated with TiO 2 -P25 by a simple spray method was assembled between the two slabs of the photoreactor. The reactor geometry provides an efficient exposure of TiO 2 -P25 CA sheets to radiation, with an illuminated surface per unit of volume inside the reactor of 470 m 2 m −3 and 1.36 g TiO 2 per liter of liquid inside the reactor. Beyond that, it provides a good degree of mixing using a laminar flow, maximizing heterogeneous and homogeneous Cr(VI) reduction reactions. Firstly, different organic species were tested as hole scavengers in order to avoid the Cr(III) re-oxidation. The effect of the degree of mixing inside the photoreactor, according to the Reynolds number, on the Cr(VI) photocatalytic reduction was then evaluated. Following, operating conditions such as TiO 2 mass, tartaric acid concentration, pH value, temperature and initial Cr(VI) concentration were analyzed. Results indicate high reduction rates (1 mmol Cr(VI) m −3 illuminated volume s −1 ) and a photonic efficiency of 3.96% for Re = 830, 30 mg TiO 2 and a Cr(VI):tartaric acid molar ratio of 1:90 at pH 3.0 and 25 °C. Finally, the CA sheets coated with thin films of TiO 2 -P25 showed to be suitable for continuous Cr(VI) reduction, without losing efficiency during 3 consecutive photocatalytic cycles.

CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Os vidros borosilicato são obtidos a partir da combinação dióxido de silício (SiO2) com o óxido de boro (B2O3). Onde estes vidros possuem um vasto campo de aplicações na indústria vidreira, indo deste os setores de equipamentos de laboratórios até a criação de sensores ópticos (fibras ópticas). Pois, devido à sua forma estrutural estes vidros possuem uma grande resistência a choques térmicos, uma boa durabilidade química e uma excelente resistividade elétrica se comparados com os demais vidros existentes hoje no mercado. Assim baseando-se nestas características importantes características estruturais, físicas, químicas e também na diversidade de aplicações optou-se nesta pesquisa pela síntese e caracterização dos vidros borosilicatos puros e dopados com íons terras raras de érbio e com nitrato de prata. Com o objetivo de conhecer melhor as principais propriedades destas matrizes vítreas desenvolvidas e de como os íons emissores, as nanopartículas metálicas ou ambos se comportam quando estes se encontram inseridos nelas, ou seja, de comprovar que a inserção dos dopantes nas matrizes vítreas de borosilicato modificam tanto as suas propriedades ópticas quanto as estruturais. Assim foram utilizadas as seguintes técnicas de caracterização: análise térmica diferencial, medida de densidade, índice de refração linear, absorção óptica e microscopia eletrônica de transmissão. Visto que à inserção dos íons de érbio em materiais vítreos oferece grandes possibilidades de aplicações tecnológicas nos setores das telecomunicações, com o objetivo de aumentar a capacidade de transmissão de dados. E quanto a inserção das nanopartículas de prata pode se dizer que a mesma produz efeitos ópticos não lineares de terceira ordem nos compósitos e em comprimentos de onda próximos da característica de ressonância de plasmon superficial dos aglomerados de metal. Logo, a partir dos resultados e das análises obtidas foi possível comprovar que as amostras de vidro borosilicato produzidas nesta pesquisa apresentaram resultados satisfatórios e que são similares aos encontrados nas literaturas pertinentes, mostrando que esse é um material promissor para diversas aplicações tecnológicas na área de materiais e óptica. The borosilicate glasses are obtained from the combination of silicon dioxide (SiO2) with boron oxide (B2O3). Where these glasses have a wide range of applications in the glass industry, the sectors of going this laboratory equipment to the creation of optical (fiber optics). Because, due to its structural form these glasses have a large thermal shock resistance, good chemical durability and excellent electrical resistivity compared with other glasses on the market today. Therefore based on these important structural features, physical, chemical, and also in the variety of applications in this study was chosen for synthesis and characterization of pure borosilicate glass and doped with rare earth ions erbium and silver nitrate. In order to better understand the main properties of these glass matrices developed and how the ion emitters, or both metal nanoparticles behave when they are inserted in them, that , to prove that the insertion of dopants in borosilicate glass matrix changes both their optical and structural properties. We used the following characterization techniques: differential thermal analysis, density measurement, linear refractive index, optical absorption and transmission electron microscopy. Since the insertion of erbium ions in glassy materials has great potential for technological applications in the telecommunications, aiming to increase the capacity of data transmission. And the inclusion of silver nanoparticles nonlinear optical effect of third order in the composites and at wavelengths close to the characteristic surface plasmon resonance of the metal clusters. Thus, from the results and analysis obtained was possible to prove that the samples of borosilicate glass produced in this study showed satisfactory results that are similar to those found in the relevant literature, showing that this is a promising material for technological applications in the area of materials and optics.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:48:24Z No. of bitstreams: 1 S0100-40421998000400025.pdf: 111003 bytes, checksum: ac6cbef5e4ebb3d12463cf5b3360a603 (MD5) Made available in DSpace on 2013-08-22T18:48:24Z (GMT). No. of bitstreams: 1 S0100-40421998000400025.pdf: 111003 bytes, checksum: ac6cbef5e4ebb3d12463cf5b3360a603 (MD5) Previous issue date: 1998-07-01 Made available in DSpace on 2013-09-30T19:38:13Z (GMT). No. of bitstreams: 2 S0100-40421998000400025.pdf: 111003 bytes, checksum: ac6cbef5e4ebb3d12463cf5b3360a603 (MD5) S0100-40421998000400025.pdf.txt: 16210 bytes, checksum: 07252e7b2fd1c233fb11146ab06788a4 (MD5) Previous issue date: 1998-07-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:10:16Z No. of bitstreams: 2 S0100-40421998000400025.pdf: 111003 bytes, checksum: ac6cbef5e4ebb3d12463cf5b3360a603 (MD5) S0100-40421998000400025.pdf.txt: 16210 bytes, checksum: 07252e7b2fd1c233fb11146ab06788a4 (MD5) Made available in DSpace on 2014-05-20T15:10:16Z (GMT). No. of bitstreams: 2 S0100-40421998000400025.pdf: 111003 bytes, checksum: ac6cbef5e4ebb3d12463cf5b3360a603 (MD5) S0100-40421998000400025.pdf.txt: 16210 bytes, checksum: 07252e7b2fd1c233fb11146ab06788a4 (MD5) Previous issue date: 1998-07-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) SnO2 thin layers, prepared from aqueous colloidal suspensions by the sol-gel process, have been dip-coated on commercial borosilicate glasses. The effect of the conditions of deposition on the optical and structural characteristics of the thin layers was analysed by UV-Vis spectroscopy, x-ray reflectometry and electron scanning microscopy. Layers prepared with withdrawal speed in between 0.1 and 10cm/min show thickness smaller than 90nm, roughness of the order of 2nm and transmittance higher than 80%, resulting in good optical quality samples. The roughness increases from 2 to 11nm as the withdrawal speed increases from 10 to 80cm/min, what seems to be associated to the enlargement of the layers thickness (> 90nm). The measurements of mass loss, done after etching with fluoridric acid show that the coated samples are more corrosion resistant than the uncoated borosilicate glass. UNESP Instituto de Química UNESP Instituto de Química