Heterostructured semiconductors are materials with unique features formed by combination of two or more semiconductors with suitable interface between them. The study of the heterostructures aim the development of physico-chemical and photocatalytic properties higher than their isolated phases, which makes it possible to obtain higher efficiency and lower cost in several technological processes. Recently the heterostructured materials have been extensively used in the development of alternative technologies either for environmental pollution control or for renewable energy production, among other applications. However, the obtaining of a heterostructure with suitable features is not trivial. In this way, this review article presents a broad discussion about methods of obtaining heterostructures formed by semiconductors and their applications in the photochemical processes, mainly in the environmental field. It will be addressed the use of the heterostructures in photocatalytic application for the organic pollutants degradation, heavy metals removal, the inactivation of pathogenic microorganisms, beyond of the volatile organic compounds (VOC’s) photooxidation and the photocatalytic abatement of nitrogen oxide (NOx) in gaseous phase. Finally, a discussion about the carbon dioxide (CO2) photoreduction and hydrogen (H2) production focusing mainly in the chemical energy production will be presented.
In this work, cellulose from beans straw was used to produce a more hydrophobic material (cellulose acetate) for use as oil absorbent. Acetic anhydride was used in the reactions with two catalysts, pyridine (PY) and N-bromosuccinimide (NBS). The materials produced were characterized by infrared spectroscopy, scanning electron microscopy, X-ray diffraction and elemental analysis. NBS proved more efficient than PY, with the resulting materials containing higher number of acetate groups, being more hydrophobic and with higher capacity to absorb soybean oil.
Neste estudo a celulose obtida da palha de feijão foi utilizada para produzir um material hidrofóbico (acetato de celulose) para ser avaliado como absorvente de óleo. Nas reações de acetilação foram utilizados anidrido acético e dois catalisadores, a piridina (PY) e N-bromossuccinimida (NBS). Os materiais produzidos foram caracterizados por espectroscopia na região do infravermelho médio, microscopia eletrônica de varredura, difratometria de raios-X e análise elementar. O NBS mostrou-se mais eficiente que a PY e, seu uso resultou em materiais com maiores quantidades de grupos acetatos, mais hidrofóbicos e com maiores capacidades de absorção de óleo de soja.
In this work synthetic niobia was used to promote the oxidation of methylene blue dye in aqueous medium. The niobia was characterized by N2 adsorption/desorption, XRD and TG measurements. The presence of reactive species on the niobia surface strongly increased the oxidation rate of the methylene blue dye. The reaction mechanism was studied by ESI-MS suggesting that the oxidation of the organic dye involve oxidizing species generated mainly after previous treatment with H2O2. It can be observed that the catalyst is a good material in the activation of gas (atmospheric oxygen) or liquid (hydrogen peroxide) oxidant agent with a total discoloration of the dye solution after only 1 h of reaction.