Catalytic nitrate removal from water, past, present and future perspectives

Barrabés, Noelia; Sá, Jacinto

doi:10.1016/j.apcatb.2011.03.011

Cited by 251 publications

(172 citation statements)

References 95 publications

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“…ions to diffuse into the SnO 2 matrix. As mentioned before, such close proximity plays a crucial role in stabilization of lower oxidation state of promoter in case of bimetallic Pd-Sn catalyst (Barrabes and Sá 2011). Recently a peculiar behavior of Pd/SnO 2 has been reported by means of Pd particle intrusion into the support upon reduction (Kamiuchi et al 2010).…”

Section: Structure-reactivity Relationshipsmentioning

confidence: 99%

“…At the moment the mechanism of water denitration in the presence of H 2 on noble metal-supported catalyst is still not completely understood (Barrabes and Sá 2011). Traditional mechanism advocates occurrence of consecutive reaction steps at different entities of bimetallic catalysts, i.e.…”

Section: Structure-reactivity Relationshipsmentioning

confidence: 99%

“…In contrast, Pd particles of sample 2 exposed to H 2 demonstrate further Pd-O charge transfer as characteristic of Pd-SnO 2 interaction, due to Pd position remaining deeply embedded in the SnO 2 matrix. As pointed by Barrabes and Sá (2011) for conventional supported Pd-Sn catalyst, close proximity between noble metal and promoter is essential to stabilize the later in its lower oxidation state which is the active phase.…”

Section: Structural Investigationmentioning

confidence: 99%

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Strong metal–support interaction as activity requirement of palladium-supported tin oxide sol–gel catalyst for water denitration

Bošković

Kovacevic

Kiss

et al. 2012

Int. J. Environ. Sci. Technol.

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Two nanocrystalline palladium-supported tin oxide catalysts for water denitration were synthesized by a modified sol-gel technique using appropriate chloride precursors for both support and active phases, and citric acid to tune the rate of hydrolysis and condensation. The difference among sample preparation procedures refers to the moment of the noble metal loading to the support, as well as to the calcination temperature altitude followed. Thus, mesoporous tin oxide was synthesized by a sol-gel method following calcination at 700°C. The palladium active phase was introduced afterwards by means of palladium chloride solution impregnation, followed by calcination at 400°C (sample 1). Alternatively, simultaneous complexation of both metal and support precursors followed by single calcination at 700°C was applied for preparation of sample 2. The former sample showed higher activity and selectivity in hydro-denitration of water model system initially containing 100 ppm of nitrates. This was explained by preferential textural, morphological and structural properties accomplished by early contact of metal and support nanoparticles, while achieved by calcination at high single temperature forcing diffusion of palladium ions into the tin oxide matrix. The outcome is very well distribution of palladium and strong metal-support interaction leading to multivalent tin. This indicates partly reduced tin oxide formation in the course of its reduction in hydrogen, which may act as active site in denitration reaction.

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Section: Structure-reactivity Relationshipsmentioning

confidence: 99%

Section: Structure-reactivity Relationshipsmentioning

confidence: 99%

Section: Structural Investigationmentioning

confidence: 99%

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Strong metal–support interaction as activity requirement of palladium-supported tin oxide sol–gel catalyst for water denitration

Bošković

Kovacevic

Kiss

et al. 2012

Int. J. Environ. Sci. Technol.

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“…Além disso, o seu manejo é mais complexo que os outros tipos de tratamentos existentes, pois seu sucesso depende de um controle rígido do pH, da temperatura e da quantidade de nutrientes do meio onde se encontram os micro-organismos. 2 A catálise heterogênea é um dos caminhos para que se consiga a degradação de nitrato e nitrito à nitrogênio molecular com produção de baixas quantidades de subprodutos. Diversos estudos exploram a redução catalítica como uma forma de degradação de NO 3 -utilizando como redutor o hidrogênio (H 2 ), contudo a formação de quantidade considerável de amônio como subproduto é uma das desvantagens deste tipo de tratamento.…”

Section: Introductionunclassified

“…Diversos estudos exploram a redução catalítica como uma forma de degradação de NO 3 -utilizando como redutor o hidrogênio (H 2 ), contudo a formação de quantidade considerável de amônio como subproduto é uma das desvantagens deste tipo de tratamento. [2][3][4][5][6] Nos últimos anos vêm se desenvolvendo a técnica de redução fotocatalítica para a degradação de nitrato com o fim de se obterem menores concentrações finais de subprodutos e para a diminuição dos custos operacionais que na redução catalítica convencional são altos devido a necessidade de injeção de H 2 no sistema. [7][8][9][10][11][12] Os melhores resultados descritos na literatura utilizando a redução fotocatalítica são obtidos com o uso de pequenas moléculas de ácidos carboxílicos como redutores, que fornecem à solução reacional dióxido de carbono (CO 2 ) e hidrogênio importantes para a redução de NO 3 -e para pequena formação de subprodutos indesejáveis.…”

Section: Introductionunclassified

Nitrate Photocatalytic Reduction Using Mono and Bimetallic Catalysts Supported on Titanium Dioxide Nanowires and Nitrogen, Carbon Codoped Titanium Dioxide

Souza¹,

Oliveira²,

Barbosa³

2018

Rev. Virtual Quim.

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Abstract:Nitrate is one of the compounds most commonly found in natural water sources due to the infinity and diversity of sources, natural and anthropogenic. Its excess can lead to various damages to health and the environment, however cheap and efficient ways of nitrate contaminated water treatment are not yet a reality. The photocatalysis is one of the ways of nitrate and/or nitrite contaminated aquifer or drinking water sources treatment, which aggregate low cost and efficiency, using ultraviolet (UV) or visible radiation as energy source. Focusing on this form of treatment, new photocatalysts for the reduction nitrogen species such as nitrate and nitrite to molecular nitrogen were synthesized. Titanium dioxide nanowires (Nwires) and titanium dioxide doped with nitrogen and carbon (NCTiO2) were used to support the mono-and bimetallic catalysts. The metals were deposited on the supports surface using the impregnation method. Silver (Ag) and palladium (Pd) were used to produce the monometallic catalysts. The bimetallic catalysts were obtained by deposition of copper (Cu) and tin (Sn) in the priors. The photocatalytic tests were performed with potassium nitrate and formic acid (electron donor) solution prepared in the laboratory, under nitrogen flow, controlled temperature, and using UV radiation source. Both Nwires support as monoand bimetallic catalysts supported on it, did not obtain comparable results to its precursor P25, the deposition of metals practically not improved the photocatalytic activity of the material. The support NCTiO2 proved very effective in the nitrate photocatalytic reduction, with results similar to those of its precursor (Degussa P25, 80% anatase, 20% rutile). The metal deposition 5 % Pd and 2 % Sn, relative to the total weight, in the support NCTiO2 led the complete reduction of the initial nitrate three hours before the best result found with the P25, and 97 % selectivity to N2, the highest among the catalysts studied. The influence of the concentration of the reaction formic acid (electron donor), of the radiation source and the importance of activation of the catalyst with H2 before the test were observed. The reconstitution ability of active sites reducing nitrate and nitrite catalyst was also evaluated, which remained active and with high selectivity to N2 after being reused five times.Keywords: Nitrate; photocatalysis; bimetallic catalysts. ResumoO nitrato é um dos compostos mais comumente encontrado em cursos d'água devido à infinidade e diversidade de fontes existentes, sejam naturais ou antrópicas. Seu excesso pode levar a diversos prejuízos a saúde e ao meio ambiente, contudo formas baratas e eficientes de tratamento de águas contaminadas com nitrato ainda não são uma realidade. Uma das formas de remediação de aquíferos ou fontes de água contaminadas com nitrato ou nitrito, que pode agregar baixo custo e eficiência, é a utilização da fotocatálise, a qual usa radiação ultravioleta (UV) ou visível como fonte energética para a degradação de nitrato e também de nitrito. Focando ...

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