Semiconductor-assisted photodegradation of lignin, dye, and kraft effluent by Ag-doped ZnO

Gouvêa, Carlos Alberto Klimeck; Wypych, Fernando; Moraes, Sandra Gomes de; Durán, Nélson; Peralta‐Zamora, Patricio

doi:10.1016/s0045-6535(99)00312-4

Cited by 165 publications

(77 citation statements)

References 24 publications

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“…Essa última poderá catalisar reações de fotólise da água ou fotodegradação de moléculas contaminantes de águas, procedimento que poderá ser adotado em processos de remediação de efluentes. Processos semelhantes são utilizados como semicondutores tradicionais como TiO 2 e ZnO 80,81 . Recentemente reportou-se a síntese 26,79 e utilização de nanopartículas de dissulfeto de molibdênio na fotooxidação de moléculas orgânicas 79 .…”

Section: Outras Aplicaçõesunclassified

Dissulfeto de molibdênio, um material multifuncional e surpreendente

Wypych

2002

Quím. Nova

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Recebido em 6/10/00; aceito em 4/4/01 MOLYBDENUM DISULFIDE, A MULTIFUNCTIONAL AND REMARKABLE MATERIAL. The aim of this work is to review the chemical and physical properties of layered molybdenum disulfide. The three polymorphic/polytypic modifications of the compound were found, the polytypes 2H (molybdenite) and 3R are semiconductors while the polymorph 1T is an electronic conductor. 2H-MoS 2 has several important industrial applications as hydrotreatment catalysts, energy storage devices, solar cells, solid lubricants, among others. When intercalated, the 2H phase changes to a distorted 1T phase, producing unstable intercalation compounds that can be exfoliated in solution, producing single layers and consequently nanocomposites. The direct synthesis of the 1T phase produces stable intercalation compounds. Recently molybdenum disulfide was prepared as nanotubes and fulerenelike structures that bring new insights in the investigation of this important material.Keywords: molybdenum disulfide; intercalation; layered materials. INTRODUÇÃOO dissulfeto de molibdênio pertence a uma classe de materiais conhecidos como compostos lamelares e ocorre em três modificações polimórficas/politípicas 1,2 . A fase mais comum (2H) ocorre na natureza na forma de molibdenita. Nas modificações 2H e 3R, áto-mos de molibdênio estão ligados covalentemente à átomos de enxofre numa geometria trigonal prismática regular (Figura 1). Os prismas trigonais estão ligados entre si pelas arestas, produzindo unidades bidimensionais conhecidas como lamelas. Essas lamelas que, estão conectadas por forças fracas do tipo Van der Waals, podem se ordenar de maneira diferente originando os dois politipos. Na fase 1T a forma ondulada se deve à distorção da esfera de coordenação octaédrica do centro metálico 2 . A forma do politipo 1T não distorcida está representada na Figura 1. Figura 1. Representação esquemática das estrutura das fases 2H, 3R e 1T (não distorcida), do dissulfeto de molibdênio.As propriedades dos politipos são diferentes. A fase 1T é condutora 2 enquanto que as fases 2H e 3R são diamagnéticas e semicondutoras 3. Além das três formas conhecidas de hábito cristalino, o dissulfeto de molibdênio se apresenta na forma amorfa 4,5 , como nanotubos 6,7 e esferas de dimensões nanoscópicas 7,8 semelhantes as estruturas dos fulerenos.As aplicações do dissulfeto de molibdênio vão desde baterias no estado sólido que utilizam meio não aquoso e íons lítio intercaláveis [9][10][11] , células solares 12 , como lubrificantes sólidos 13 , catalisadores [14][15][16][17][18] , onde desempenha um papel de importância fundamental, além de outras.Um dos processos de síntese do dissulfeto de molibdênio nas fases polimórficas 2H e 3R é a reação térmica direta entre o molibdênio metálico e enxofre elementar em ampolas de quartzo. Quando cristais grandes forem necessários utiliza-se o método de transporte de vapor químico com um halogeneto como o iodo como agente transportante 19 (Eq.1).Mo + 2 S ® MoS 2 + 2 I 2 « MoI 4 + S 2Nesse procedimento, quantidades estequ...

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Section: Outras Aplicaçõesunclassified

Dissulfeto de molibdênio, um material multifuncional e surpreendente

Wypych

2002

Quím. Nova

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“…22 The photocatalytic activity of ZnO has been widely explored and reported. 14,23 In terms of studying the mechanism of photocatalysis, facilitates a study of the recombination of electron-hole pairs and hence a suitable probe in the study of highly active photocatalysts. The emission properties have also been used to sense the presence of organic molecules in its immediate vicinity.…”

Section: Introductionmentioning

confidence: 99%

A Highly Efficient Ag-ZnO Photocatalyst: Synthesis, Properties, and Mechanism

2008

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Highly photocatalytically active silver-modified ZnO has been prepared and the effect of silver modification was studied. The structural and optical properties were characterized by X-ray diffraction, Fourier transform IR, differential scanning calorimetry, BET surface area, Raman, UV-vis, and photoluminescence spectroscopy. The photocatalytic activity of these materials was studied by analyzing the degradation of an organic dye, rhodamine 6G (R6G), and it is found that 3 mol % silver-modified ZnO at 400 °C shows approximately four times higher rate of degradation than that of unmodified ZnO and a three times higher rate than that of commercial TiO 2 photocatalyst Degussa P-25. It was also noted that the photocatalytic activity for the modified ZnO sample was five times higher than the unmodified sample using sunlight. The effect of silver in enhancing the photocatalytic activity has been studied by analyzing the emission properties of both ZnO and silvermodified ZnO in the presence (emission increases) and absence (emission decreases) of R6G. We attribute these observations to the extent of valence band hole production and the role of silver in trapping the conduction band (CB) electrons in the absence of R6G. In the presence of R6G, the dye preserves the CB electron population in the metal oxide, thus preserving and enhancing emission intensity. The sensitizing property of the dye and electron scavenging ability of silver together constitute to the interfacial charge transfer process in such a way to utilize the photoexcited electrons.

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“…The first one showed little effect on color and COD removals, whereas the second one induced modifications in the kinetic profile of color reduction (Table 4). In addition, Gouvea et al (2000) reported the semiconductorassisted photochemical degradation of lignin, dye, and kraft effluent using an Ag-doped ZnO catalyst. Results addressed that lignin color progressively decreased up to a 50% after 15 minutes of treatment; whereas it was almost total (99%) after 60 minutes.…”

Section: Semi-conductor Photocatalytic Processesmentioning

confidence: 99%

“…80% TOC removal) by applying this treatment at basic pH to a biologically pretreated pulp and paper mill effluent, using 0.75 g·L -1 of TiO 2 at pH = 11 during 60 minutes (Table 4); working at a neutral pH produced better treatment efficiencies purifying effluents in a newsprint paper mill (Merayo et al 2013), as well as it also yielded an almost complete decolorization of a kraft pulp mill effluent (Gouvea et al 2000). A lower competition of anions and cations for the reactive sites of TiO 2 particles may be responsible for treatment improvement at neutral pH values.…”

Section: Semi-conductor Photocatalytic Processesmentioning

confidence: 99%

The application of advanced oxidation technologies to the treatment of effluents from the pulp and paper industry: a review

Hermosilla

Merayo

Gascó

et al. 2014

Environ Sci Pollut Res

159

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Paper industry is adopting zero liquid effluent technologies to reduce fresh water use and meet environmental regulations, which implies water circuits closure and the progressive accumulation of pollutants that must be removed before water re-use and final wastewater discharge. The traditional water treatment technologies that are used in paper mills (such as dissolve air flotation or biological treatment) are not able to remove recalcitrant contaminants. Therefore, advanced water treatment technologies, such as advanced oxidation processes (AOPs), are being included in industrial wastewater treatment chains aiming to either improve water biodegradability or its final quality. A deep review of the current state of the art regarding the use of AOPs for the treatment of the organic load of effluents from the paper industry is herein addressed considering mature and emerging treatments for a sustainable water use in this sector. Wastewater composition, which is highly dependent of the raw materials being used in the mills, the selected AOP itself, and its combination with other technologies, will determine the viability of the treatment. In general, all AOPs have been reported to achieve good organics removal efficiencies (COD removal >40%; and about an extra 20% if AOPs are combined with biological stages). Particularly, ozonation has been the most extensively reported and successfully implemented AOP at an industrial scale for effluent treatment or reuse within pulp and paper mills; although Fenton processes (photo-Fenton particularly) have actually addressed better oxidative results (COD removal ≈65-75%) at lab scale, but still need further development at large scale.

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Semiconductor-assisted photodegradation of lignin, dye, and kraft effluent by Ag-doped ZnO

Cited by 165 publications

References 24 publications

Dissulfeto de molibdênio, um material multifuncional e surpreendente

Dissulfeto de molibdênio, um material multifuncional e surpreendente

A Highly Efficient Ag-ZnO Photocatalyst: Synthesis, Properties, and Mechanism

The application of advanced oxidation technologies to the treatment of effluents from the pulp and paper industry: a review

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