Improved photocatalytic activity of d-FeOOH by using H2O2 as an electron acceptor.

In this work, d-FeOOH nanoparticles were synthesized by a simple co-precipitation method and used as a photocatalyst in the presence of H2O2 for the oxidation of Rhodamine B (RhB) dye under artificial light. The d-FeOOH was characterized by powder X-ray diffraction, 57Fe M?ssbauer spectroscopy, N2 adsorption/desorption and UV?vis diffuse reflectance measurements. The d-FeOOH nanoparticles have high specific surface area (101 m2 g 1) and optical bandgap energy of 2.02 eV. Under artificial light, only 59% of RhB (100 mL; 20 mg L 1) was photocatalytically degraded by d-FeOOH in 60 min reaction. However, after adding H2O2, the photocatalytic activity of d-FeOOH was significantly improved, reaching 87% of dye removal. Tests using scavengers of reactive species and EPR analysis revealed that h+ and OH are the main species in this system. Based on the experimental results, the mechanism of RhB photodegradation in the presence of d-FeOOH and H2O2 was proposed. By this mechanism, the OH can be formed by direct water oxidation or by H2O2 reduction, as the electron transfer from the conduction band of d-FeOOH to H2O2 is thermodynamically favorable. Moreover, the H2O2 retards the electron-hole recombination in d-FeOOH, thus increasing its photocatalytic activity. Given its high efficiency for degrading RhB in water, d-FeOOH revealed to be a promising photocatalyst to be tested in the oxidation of emerging pollutants for the environmental decontamination

Processo para obten??o e estabiliza??o de nanopart?culas de Magnetita, produtos e uso

"A presente inven??o descreve o processo de obten??o e estabiliza??o de nanoparticulas de magnetita (Fe304), com tamanho e formato controlados, atrav?s do aquecimento de amostras sint?ticas ou naturais, de ?xidos ou oxidr?xidos de ferro (III), como hematita (a-Fe203), maghemita (y-Fe203 ), lepidocrocita (y-FeOOH), goethita (a-FeOOH), akaganeita (13-FeOOH), feroxita (S-FeOOH), com sacarose ou outros hidratos de carbono com f?rmula C,,(H2O)n , como glicose, frutose, lactose, maltose, celobiose, amido, glicog?nio, celulose, todos os componentes no estado s?lido. O carv?o produzido pela queima do hidrato de carbono forma uma pel?cula na superf?cie da magnetita, consequentemente prevenindo sua oxida??o a hematita. Essa camada de carbono pode ser removida posteriormente de forma simples para uso em processos que exijam a superf?cie exposta da magnetita. As nanoparticulas de magnetita obtidas podem ser utilizadas em processos catal?ticos que exijam pequenos tamanhos de part?culas ou em processos de hipertermia magn?tica, como carreadores de f?rmacos em sistemas de libera??o controlada e como agentes de contraste em imagens de resson?ncia magn?tica.

Novel protocol for the solid-state synthesis of magnetite for medical practices.

It is reported a novel approach to prepare nanoparticles of magnetite (Fe3O4) by heating a mixture of synthetic commercial maghemite (? Fe2O3) with sucrose. This solidstate reaction leads to the chemical reduction of part of the Fe3+ of the precursor oxide to render Fe2+ and Fe3+ in octahedral and Fe3+ in tetrahedral sites of the Fe-O coordination framework. Powder X-ray diffraction patterns, FTIR and 298 K M?ossbauer spectra confirm the conversion of maghemite into magnetite. Based on these results, the optimal sucrose:maghemite rate was found to be 4

Preparation and characterization of Fe3O4-Pt nanoparticles.

Pt and Pt-based nanomaterials are active anticancer drugs for their ability to inhibit the division of living cells. Nanoparticles of magnetite containing variable proportions of platinum were prepared in the laboratory. The magnetite nanoparticles with platinum (Pt-Fe3O4) were obtained by reducing the Fe3+ of the maghemite (? Fe2O3) mixed with platinum (II) acetylacetonate and sucrose in two inversely coupled ceramic crucibles and heated in a furnace at 400 ?C for 20 min. The formed carbon during this preparation acts to chemically reduce the ferric iron in maghemite. Moreover, its residual layer on the particle surface prevents the forming magnetite from oxidizing in air and helps retain the platinum in the solid mixture. The produced Pt-magnetite samples were characterized by 57Fe-M?ossbauer spectroscopy, powder X-ray diffraction, scanning electron microscopy, and magnetization measurements.Measurements of AC magnetic-field-induced heating properties of the obtained nanocomposites, in aqueous solution, showed that they are suitable as a hyperthermia agent for biological applications

Ni?bio : um elemento qu?mico estrat?gico para o Brasil.

Niobium, in fact, is an essential element for Brazil. Their applications are so many and so special that they put it as one of the subjects treated by the wikiLeaks site as strategic and that it should be treated in the USA. It is one of the elements most exported by Brazil and is mainly used in the production of special alloys for use in gas pipelines, air turbines, among other applications. It is believed that niobium-based materials can be obtained for applications with higher added value and in equally strategic areas. Research to obtain active and selective drugs, materials to maximize the use of renewable energy, and new nanostructured materials to improve the performance of different components are ongoing and promise a revolution for the next few years

Room temperature selective conversion of aniline to azoxybenzene over an amorphous niobium oxyhydroxide supported on ?-FeOOH.

In this work, catalysts for the oxidation of aniline into azoxybenzene were prepared by combining ?-FeOOH nanoparticles with 0, 2.5, 5, and 10 wt.% niobium oxyhydroxides by a simple co-precipitation method. The niobium oxyhydroxide actively changed the chemical and textural properties of ?-FeOOH, as verified by XRD, M?ssbauer spectroscopy, N2 adsorption-desorption measurements, and TEM images. Therefore, the catalytic performance of ?-FeOOH to convert aniline into azoxybenzene in the presence of hydrogen peroxide was significantly improved. The catalytic activity and selectivity changed with the Nb content in the composite. The effect of different reaction parameters like solvent type, H2O2 volume, and reaction time has been studied in detail. The catalyst with 10 wt.% Nb was the most efficient among the evaluated catalysts, showing 100% conversion of aniline with 80.2% selectivity to azoxybenzene when propanol was used as solvent at 25 ?C. Moreover, the catalyst 10 wt.% Nb exhibited good stability and could be reused for various cycles without significant loss of catalytic activity

Processo para remo??o de As(V) de ?guas contaminadas e sua utiliza??o como precursor na fabrica??o de materiais fotocal?ticos ativos

A tecnologia consiste no processo para purifica??o de ?guas contaminadas com As(V) e no reaproveitamento do As(V) como um precursor para a fabrica??o de materiais fotocatal?ticos que podem ser aplicados em processos de remedia??o ambiental de sistemas aquosos contaminados com poluentes org?nicos ou inorg?nicos. O processo pode ser entendido em 3 etapas: (i) o As(V) presente em sistemas aquosos contaminados ? adsorvido na superf?cie de ?xidos ou oxidr?xidos de ferro. Posteriormente, o adsorvente contendo As(V) ? separado da solu??o aquosa, por atra??o magn?tica, centrifuga??o ou filtra??o, produzindo ?gua sem As(V); (ii) o adsorvente contendo As(V) ? submetido a tratamento com solu??o extratora "A" a fim de remover o As(V) do adsorvente para a solu??o. O adsorvente pode ser recuperado e estocado para posterior uso em novos ciclos de adsor??o. (iii) A solu??o resultante contendo o As(V) dessorvido ? submetida a tratamento com uma solu??o coletora "B". Ap?s o tratamento, um composto s?lido de cor castanho-avermelhado ? formado. A suspens?o ? centrifugada e o s?lido resultante ? base de As(V) ? lavado v?rias vezes com ?gua destilada e seco a temperatura ambiente. O Material formado apresenta alta atividade fotocatal?tica sendo aplic?vel na descontamina??o ambiental de sistemas aquosos

Processo qu?mico de oxida??o do grafite para obten??o de ?xido de grafite, ?xido de grafeno e grafeno: uso do sistema Fenton como oxidante

Grafite foi oxidado pelo sistema Fenton (uma mistura de Fe2 eH202) para produzir ?xido de grafite. Este sistema ? ambientalmente mais favor?vel que os sistemas convencionais existentes, devido a rea??o de Fenton ocorrer ? temperatura ambiente e press?o atmosf?rica, como tamb?m por n?o haver libera??o de gases durante o processo de oxida??o do grafite. Uma vez formado o ?xido de grafite por este m?todo verde, a esfolia??o do mesmo em ultrassom de banho leva ? forma??o de ?xido de grafeno que pode posteriormente ser reduzido atrav?s de um agente redutor, para ent?o formar o grafeno, um material que tem ampla aplica??o em nanoeletr?nica, sensores,supercapacitores e cat?lise. O m?todo de oxida??o de grafite descrito aqui pode ser aplicado em qualquer processo qu?mico de produ??o de ?xido de grafite, ?xido de grafeno ou grafeno

Processo catal?tico de determina??o da demanda qu?mica de oxig?nio usando nanopart?culas de ?xidos de ferro magn?ticas

Um novo m?todo de determina??o da demanda qu?mica de oxig?nio foi desenvolvido. O m?todo baseia-se no uso de nanopart?culas magn?ticas do tipo "core-shell" de ?xidos e/ou oxidr?xidos de ferro como catalisadores que s?o capazes de ativar a mol?cula de H202 para produzir radicais hidroxila que s?o esp?cies altamente reativas e n?o seletivas capazes de oxidar completamente compostos org?nicos em meio aquoso. O m?todo apresenta v?rias vantagens em rela??o aos existentes, uma vez que n?o utiliza reagentes t?xicos, a rea??o de oxida??o da mat?ria org?nica pode ser realizada a temperatura ambiente e press?o atmosf?rica, n?o utiliza radia??o UV e n?o necessita de potencial externo para que a rea??o ocorra. Trata-se, pois, de um m?todo simples, barato, ambientalmente e energeticamente favor?vel. O limite de detec??o do m?todo foi de 2,00 mg L- 1 de DQO, no entanto foi observado sinal anal?tico para 0,5 mg L- 1 de DQO. O m?todo desenvolvido ? r(...