METAL OXIDE HETEROSTRUCTURES FOR EFFICIENT PHOTOCATALYSTS

Photocatalytic processes over semiconducting oxide surfaces have attracted worldwide attention as potentially efficient, environmentally friendly and low cost methods for water/air purification as well as for renewable hydrogen production. However, some limitations to achieve high photocatalytic efficiencies have been found due to the fast recombination of the charge carriers. Development of heterostucture photocatalysts by depositing metals on the surface of semiconductors or by coupling two semiconductors with suitable band edge position can reduce recombination phenomena by vectorial transfer of charge carriers. To draw new prospects in this domain, three different kinds of heterostructures such as n-type/n-type semiconductor (SnO2/ZnO), metal/n-type semiconductor (RuO2/TiO2 and RuO2/ZnO) and p-type/n-type semiconductor (NiO/TiO2) heterojunction nanomaterials were successfully prepared by solution process. Their composition, texture, structure and morphology were thoroughly characterized by FTIR, X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM) and N2 sorption measurements. On the other hand, a suitable combination of UV–visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS) data provided the energy band diagram for each system. The as-prepared heterojunction photocatalysts showed higher photocatalytic efficiency than P25 TiO2 for the degradation of organic dyes (i.e. methylene blue and methyl orange) and the production of hydrogen. Particularly, heterostructure RuO2/TiO2 and NiO/TiO2 nanocomposites with optimum loading of RuO2 (5 wt %) and NiO (1 wt %), respectively, yielded the highest photocatalytic activities for the production of hydrogen. These enhanced performances were rationalized in terms of suitable band alignment as evidenced by XPS/UPS measurements along with their good textural and structural properties. This concept of semiconducting heterojunction nanocatalysts with high photocatlytic activity should find industrial application in the future to remove undesirable organics from the environment and to produce renewable hydrogen

Hydrothermal synthesis of mesoporous TiO2 nanoparticles for enhanced photocatalytic degradation of organic dye

In this work, mesoporous TiO2 nanoparticle photocatalyst has been prepared by hydrothermal method using titanium tetrachloride as precursor. The resulting photocatalysts have been characterized using X-ray diffraction (XRD), nitrogen adsorption-desorption analyses, RAMAN spectroscopy, Transmission Electron Microscopy (TEM) and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The results showed that the synthesized 2 OiT was anatase phase and mesoporous with specific surface 133.45 m2/g. The decomposition of methylene blue dye under the influence of ultraviolet light was used to test the photocatalytic performance of the produced TiO2 photocatalyst. The photocatalytic activity of the TiO2 photocatalyst for the breakdown of methylene blue dye was significantly higher than that of the commercial TiO2 P25 used as a reference. Moreover, the prepared photocatalyst was stable and reusable. The larger surface area of hydrothermally produced TiO2 was the reason for this enhanced photocatalytic activity. As a result, it is expected that this approach of photocatalytically active semiconducting nanocatalysts will be used in industry to eliminate undesired organics from the environment

METAL OXIDE HETEROSTRUCTURES FOR EFFICIENT PHOTOCATALYSTS

Photocatalytic processes over semiconducting oxide surfaces have attracted worldwide attention as potentially efficient, environmentally friendly and low cost methods for water/air purification as well as for renewable hydrogen production. However, some limitations to achieve high photocatalytic efficiencies have been found due to the fast recombination of the charge carriers. Development of heterostucture photocatalysts by depositing metals on the surface of semiconductors or by coupling two semiconductors with suitable band edge position can reduce recombination phenomena by vectorial transfer of charge carriers. To draw new prospects in this domain, three different kinds of heterostructures such as n-type/n-type semiconductor (SnO2/ZnO), metal/n-type semiconductor (RuO2/TiO2 and RuO2/ZnO) and p-type/n-type semiconductor (NiO/TiO2) heterojunction nanomaterials were successfully prepared by solution process. Their composition, texture, structure and morphology were thoroughly characterized by FTIR, X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM) and N2 sorption measurements. On the other hand, a suitable combination of UV–visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS) data provided the energy band diagram for each system. The as-prepared heterojunction photocatalysts showed higher photocatalytic efficiency than P25 TiO2 for the degradation of organic dyes (i.e. methylene blue and methyl orange) and the production of hydrogen. Particularly, heterostructure RuO2/TiO2 and NiO/TiO2 nanocomposites with optimum loading of RuO2 (5 wt %) and NiO (1 wt %), respectively, yielded the highest photocatalytic activities for the production of hydrogen. These enhanced performances were rationalized in terms of suitable band alignment as evidenced by XPS/UPS measurements along with their good textural and structural properties. This concept of semiconducting heterojunction nanocatalysts with high photocatlytic activity should find industrial application in the future to remove undesirable organics from the environment and to produce renewable hydrogen

Hétérostuctures à base d'oxydes métalliques semi-conducteurs pour de nouveaux photocatalyseurs performants

Photocatalytic processes over semiconducting oxide surfaces have attracted worldwide attention aspotentially efficient, environmentally friendly and low cost methods for water/air purification as well as forrenewable hydrogen production. However, some limitations to achieve high photocatalytic efficiencies havebeen found due to the fast recombination of the charge carriers. Development of heterostucture photocatalystsby depositing metals on the surface of semiconductors or by coupling two semiconductors with suitable bandedge position can reduce recombination phenomena by vectorial transfer of charge carriers. To draw newprospects in this domain, three different kinds of heterostructures such as n-type/n-type semiconductor(SnO2/ZnO), metal/n-type semiconductor (RuO2/TiO2 and RuO2/ZnO) and p-type/n-type semiconductor(NiO/TiO2) heterojunction nanomaterials were successfully prepared by solution process. Their composition,texture, structure and morphology were thoroughly characterized by FTIR, X-ray diffraction (XRD), Ramanspectroscopy, transmission electron microscopy (TEM) and N2 sorption measurements. On the other hand, asuitable combination of UV–visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy(XPS) and ultraviolet photoemission spectroscopy (UPS) data provided the energy band diagram for eachsystem. The as-prepared heterojunction photocatalysts showed higher photocatalytic efficiency than P25 TiO2for the degradation of organic dyes (i.e. methylene blue and methyl orange) and the production of hydrogen.Particularly, heterostructure RuO2/TiO2 and NiO/TiO2 nanocomposites with optimum loading of RuO2 (5 wt %)and NiO (1 wt %), respectively, yielded the highest photocatalytic activities for the production of hydrogen.These enhanced performances were rationalized in terms of suitable band alignment as evidenced by XPS/UPSmeasurements along with their good textural and structural properties. This concept of semiconductingheterojunction nanocatalysts with high photocatlytic activity should find industrial application in the future toremove undesirable organics from the environment and to produce renewable hydrogen.Les processus photocatalytiques à la surface d’oxydes métalliques semi-conducteurs font l’objet d’intensesrecherches au niveau mondial car ils constituent des alternatives efficaces, respectueuses de l’environnement etpeu coûteuses aux méthodes conventionnelles dans les domaines de la purification de l’eau et de l’air, et de laproduction « verte » d’hydrogène. Cependant, certaines limitations pour atteindre des efficacitésphotocatalytiques élevées ont été mises en évidence avec les matériaux semiconducteurs classiques du fait de larecombinaison rapide des porteurs de charge générés par illumination. Le développement de photocatalyseurs àbase d’héterostuctures obtenues par dépôt de métaux à la surface de matériaux semiconducteurs ou parassociation de deux semiconducteurs possédant des bandes d’énergie bien positionnées devrait permettre delimiter ces phénomènes de recombinaison via un transfert de charge vectoriel. Dans ce contexte, trois typesd’hétérostructures telles que des nanomatériaux à base d’hétérojonction semiconducteur n/semiconducteur n(SnO2/ZnO), metal/semiconducteur n (RuO2/TiO2 and RuO2/ZnO) et semiconducteur p/semiconducteur n(NiO/TiO2) ont été synthétisées avec succès par différentes voies liquides. Leur composition, leur texture, leurstructure et leur morphologie ont été caractérisées par spectroscopies FTIR et Raman, par diffraction des rayonsX, microscopie électronique en transmission (MET) et porosimétrie de sorption d’azote. Par ailleurs, unecombinaison judicieuse des données issues de mesures effectuées par spectroscopie UV-visible en réflexiondiffuse (DRS) et par spectroscopies de photoélectrons X (XPS) et UV (UPS) a permis de déterminer lediagramme d’énergie des bandes pour chaque système étudié. Les catalyseurs ainsi obtenus ont conduit à desefficacités photocatalytiques plus élevées qu’avec le dioxyde de titane P25 pour la dégradation de colorantsorganiques (bleu de méthylène, l’orangé de méthyle) et la production d’hydrogène. En particulier, lesnanocomposites RuO2/TiO2 et NiO/TiO2 contenant une quantité optimale de RuO2 (5 % en masse) et de NiO(1% en masse), respectivement, ont conduit aux efficacités photocatalytiques les plus importantes pour laproduction d’hydrogène. Ces excellentes performances photocatalytiques ont été interprétées en termesd’alignement adéquat des bandes d’énergies des matériaux associé à des propriétés texturales et structuralesfavorables. Ce concept de photocatalyseurs à base d’hétérojonctions semiconductrices d’activité élevée devrait àl’avenir trouver des débouchés industriels dans les domaines de l’élimination de l’environnement de composésorganiques indésirables et de la production « verte » d’hydrogène

Metal oxide heterostructures for efficient photocatalysts

Les processus photocatalytiques à la surface d’oxydes métalliques semi-conducteurs font l’objet d’intensesrecherches au niveau mondial car ils constituent des alternatives efficaces, respectueuses de l’environnement etpeu coûteuses aux méthodes conventionnelles dans les domaines de la purification de l’eau et de l’air, et de laproduction « verte » d’hydrogène. Cependant, certaines limitations pour atteindre des efficacitésphotocatalytiques élevées ont été mises en évidence avec les matériaux semiconducteurs classiques du fait de larecombinaison rapide des porteurs de charge générés par illumination. Le développement de photocatalyseurs àbase d’héterostuctures obtenues par dépôt de métaux à la surface de matériaux semiconducteurs ou parassociation de deux semiconducteurs possédant des bandes d’énergie bien positionnées devrait permettre delimiter ces phénomènes de recombinaison via un transfert de charge vectoriel. Dans ce contexte, trois typesd’hétérostructures telles que des nanomatériaux à base d’hétérojonction semiconducteur n/semiconducteur n(SnO2/ZnO), metal/semiconducteur n (RuO2/TiO2 and RuO2/ZnO) et semiconducteur p/semiconducteur n(NiO/TiO2) ont été synthétisées avec succès par différentes voies liquides. Leur composition, leur texture, leurstructure et leur morphologie ont été caractérisées par spectroscopies FTIR et Raman, par diffraction des rayonsX, microscopie électronique en transmission (MET) et porosimétrie de sorption d’azote. Par ailleurs, unecombinaison judicieuse des données issues de mesures effectuées par spectroscopie UV-visible en réflexiondiffuse (DRS) et par spectroscopies de photoélectrons X (XPS) et UV (UPS) a permis de déterminer lediagramme d’énergie des bandes pour chaque système étudié. Les catalyseurs ainsi obtenus ont conduit à desefficacités photocatalytiques plus élevées qu’avec le dioxyde de titane P25 pour la dégradation de colorantsorganiques (bleu de méthylène, l’orangé de méthyle) et la production d’hydrogène. En particulier, lesnanocomposites RuO2/TiO2 et NiO/TiO2 contenant une quantité optimale de RuO2 (5 % en masse) et de NiO(1% en masse), respectivement, ont conduit aux efficacités photocatalytiques les plus importantes pour laproduction d’hydrogène. Ces excellentes performances photocatalytiques ont été interprétées en termesd’alignement adéquat des bandes d’énergies des matériaux associé à des propriétés texturales et structuralesfavorables. Ce concept de photocatalyseurs à base d’hétérojonctions semiconductrices d’activité élevée devrait àl’avenir trouver des débouchés industriels dans les domaines de l’élimination de l’environnement de composésorganiques indésirables et de la production « verte » d’hydrogène.Photocatalytic processes over semiconducting oxide surfaces have attracted worldwide attention aspotentially efficient, environmentally friendly and low cost methods for water/air purification as well as forrenewable hydrogen production. However, some limitations to achieve high photocatalytic efficiencies havebeen found due to the fast recombination of the charge carriers. Development of heterostucture photocatalystsby depositing metals on the surface of semiconductors or by coupling two semiconductors with suitable bandedge position can reduce recombination phenomena by vectorial transfer of charge carriers. To draw newprospects in this domain, three different kinds of heterostructures such as n-type/n-type semiconductor(SnO2/ZnO), metal/n-type semiconductor (RuO2/TiO2 and RuO2/ZnO) and p-type/n-type semiconductor(NiO/TiO2) heterojunction nanomaterials were successfully prepared by solution process. Their composition,texture, structure and morphology were thoroughly characterized by FTIR, X-ray diffraction (XRD), Ramanspectroscopy, transmission electron microscopy (TEM) and N2 sorption measurements. On the other hand, asuitable combination of UV–visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy(XPS) and ultraviolet photoemission spectroscopy (UPS) data provided the energy band diagram for eachsystem. The as-prepared heterojunction photocatalysts showed higher photocatalytic efficiency than P25 TiO2for the degradation of organic dyes (i.e. methylene blue and methyl orange) and the production of hydrogen.Particularly, heterostructure RuO2/TiO2 and NiO/TiO2 nanocomposites with optimum loading of RuO2 (5 wt %)and NiO (1 wt %), respectively, yielded the highest photocatalytic activities for the production of hydrogen.These enhanced performances were rationalized in terms of suitable band alignment as evidenced by XPS/UPSmeasurements along with their good textural and structural properties. This concept of semiconductingheterojunction nanocatalysts with high photocatlytic activity should find industrial application in the future toremove undesirable organics from the environment and to produce renewable hydrogen

Hétérostuctures à base d'oxydes métalliques semi-conducteurs pour de nouveaux photocatalyseurs performants

Les processus photocatalytiques à la surface d oxydes métalliques semi-conducteurs font l objet d intensesrecherches au niveau mondial car ils constituent des alternatives efficaces, respectueuses de l environnement etpeu coûteuses aux méthodes conventionnelles dans les domaines de la purification de l eau et de l air, et de laproduction verte d hydrogène. Cependant, certaines limitations pour atteindre des efficacitésphotocatalytiques élevées ont été mises en évidence avec les matériaux semiconducteurs classiques du fait de larecombinaison rapide des porteurs de charge générés par illumination. Le développement de photocatalyseurs àbase d héterostuctures obtenues par dépôt de métaux à la surface de matériaux semiconducteurs ou parassociation de deux semiconducteurs possédant des bandes d énergie bien positionnées devrait permettre delimiter ces phénomènes de recombinaison via un transfert de charge vectoriel. Dans ce contexte, trois typesd hétérostructures telles que des nanomatériaux à base d hétérojonction semiconducteur n/semiconducteur n(SnO2/ZnO), metal/semiconducteur n (RuO2/TiO2 and RuO2/ZnO) et semiconducteur p/semiconducteur n(NiO/TiO2) ont été synthétisées avec succès par différentes voies liquides. Leur composition, leur texture, leurstructure et leur morphologie ont été caractérisées par spectroscopies FTIR et Raman, par diffraction des rayonsX, microscopie électronique en transmission (MET) et porosimétrie de sorption d azote. Par ailleurs, unecombinaison judicieuse des données issues de mesures effectuées par spectroscopie UV-visible en réflexiondiffuse (DRS) et par spectroscopies de photoélectrons X (XPS) et UV (UPS) a permis de déterminer lediagramme d énergie des bandes pour chaque système étudié. Les catalyseurs ainsi obtenus ont conduit à desefficacités photocatalytiques plus élevées qu avec le dioxyde de titane P25 pour la dégradation de colorantsorganiques (bleu de méthylène, l orangé de méthyle) et la production d hydrogène. En particulier, lesnanocomposites RuO2/TiO2 et NiO/TiO2 contenant une quantité optimale de RuO2 (5 % en masse) et de NiO(1% en masse), respectivement, ont conduit aux efficacités photocatalytiques les plus importantes pour laproduction d hydrogène. Ces excellentes performances photocatalytiques ont été interprétées en termesd alignement adéquat des bandes d énergies des matériaux associé à des propriétés texturales et structuralesfavorables. Ce concept de photocatalyseurs à base d hétérojonctions semiconductrices d activité élevée devrait àl avenir trouver des débouchés industriels dans les domaines de l élimination de l environnement de composésorganiques indésirables et de la production verte d hydrogène.Photocatalytic processes over semiconducting oxide surfaces have attracted worldwide attention aspotentially efficient, environmentally friendly and low cost methods for water/air purification as well as forrenewable hydrogen production. However, some limitations to achieve high photocatalytic efficiencies havebeen found due to the fast recombination of the charge carriers. Development of heterostucture photocatalystsby depositing metals on the surface of semiconductors or by coupling two semiconductors with suitable bandedge position can reduce recombination phenomena by vectorial transfer of charge carriers. To draw newprospects in this domain, three different kinds of heterostructures such as n-type/n-type semiconductor(SnO2/ZnO), metal/n-type semiconductor (RuO2/TiO2 and RuO2/ZnO) and p-type/n-type semiconductor(NiO/TiO2) heterojunction nanomaterials were successfully prepared by solution process. Their composition,texture, structure and morphology were thoroughly characterized by FTIR, X-ray diffraction (XRD), Ramanspectroscopy, transmission electron microscopy (TEM) and N2 sorption measurements. On the other hand, asuitable combination of UV visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy(XPS) and ultraviolet photoemission spectroscopy (UPS) data provided the energy band diagram for eachsystem. The as-prepared heterojunction photocatalysts showed higher photocatalytic efficiency than P25 TiO2for the degradation of organic dyes (i.e. methylene blue and methyl orange) and the production of hydrogen.Particularly, heterostructure RuO2/TiO2 and NiO/TiO2 nanocomposites with optimum loading of RuO2 (5 wt %)and NiO (1 wt %), respectively, yielded the highest photocatalytic activities for the production of hydrogen.These enhanced performances were rationalized in terms of suitable band alignment as evidenced by XPS/UPSmeasurements along with their good textural and structural properties. This concept of semiconductingheterojunction nanocatalysts with high photocatlytic activity should find industrial application in the future toremove undesirable organics from the environment and to produce renewable hydrogen.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Jackfruit (<i>Artocarpus heterophyllus</i>) leaf powder: An effective adsorbent for removal of methylene blue from aqueous solutions

142-149Batch sorption experiments were carried out using jackfruit leaf powder (JLP), for the removal of methylene blue (MB) from aqueous solutions. Effects of process parameters pH, adsorbent mass, concentration and contact time were studied. The amount of MB adsorbed per unit weight of the adsorbent increased with the increase of pH, concentration and contact time. The pH at the point of zero charge (pHPZC) of the adsorbent was found to be 3.9. Adsorption of MB was found highly pH dependent. The FTIR of the adsorbent was done to find the potential adsorption sites for interaction with the cationic MB dye. Equilibrium data were fitted to Langmuir and Freundlich isotherms. The equilibrium data were best represented by both the isotherms. Maximum dye uptake was found to be 326.32 mg/g, indicating that JLP can be used as an excellent low-cost adsorbent for removal of MB dye. From experimental data it was found that adsorption of MB onto JLP followed pseudo second order kinetics. The desorption studies showed that most of the MB can be recovered by decreasing the pH of the solution. The experimental result inferred that electrostatic attraction between the surface and the dye is one of the major adsorption mechanisms for binding MB to JLP surface

Textile Effluent Treatment Plant Sludge: Characterization and Utilization in Building Materials

The main objective of this study is to characterize and find a potential use of textile effluent treatment plant (ETP) sludge produced in Bangladesh. Textile ETP sludge collected from the local textile industries have been characterized in the laboratory. The physicochemical and engineering properties of the sludge have been studied. Collected ETP sludge has been processed to get cement-like fine powder that has been used for partial replacement of Portland cement/sand in the composition of the mortar and concrete specimens. Different mechanical (compressive and flexural strength), physical (water absorption) and morphological (porosity) properties of the test specimens have been evaluated. The test result shows that the addition of sludge in the mortar and concrete composition as a substitution of Portland cement or sand decreases the compressive strength and flexural strength, and increases the water absorption and porosity of the mortar and concrete specimens. Leaching study, conducted for the sludge-based mortar and concrete specimens following tank leaching test procedure, reveals that the concentration of leached metals is quite low than the limits specified by the Department of Environment in Bangladesh. These results amply demonstrate that textile ETP sludge can be utilized for making non-structural building components where lower strength is justified

Arsenic removal by conventional and membrane technology: An overview

441-450Presently used arsenic removal technology has been reviewed, pointing especially to the promise of membrane technologies as a practical means of purification. The membrane technologies include reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF) and microfiltration (MF). Among them, the applications of the first two have proved to be reliable in removing arsenic from water. The influence of membrane materials, membrane type, operating conditions such as temperature, pressure, pH of the feed solution and feed concentration on arsenic removal efficiency by membrane technologies are discussed. This paper also provides a comparison between conventional technologies and membrane technologies for arsenic removal and concludes that membrane technology is preferred for water treatments to meet the maximum contaminant limit (MCL) standard

Hydrothermal synthesis of mesoporous TiO2 nanoparticles for enhanced photocatalytic degradation of organic dye

320-330In this work, mesoporous TiO2 nanoparticle photocatalyst has been prepared by hydrothermal method using titanium tetrachloride as precursor. The resulting photocatalysts have been characterized using X-ray diffraction (XRD), nitrogen adsorption-desorption analyses, RAMAN spectroscopy, Transmission Electron Microscopy (TEM) and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The results showed that the synthesized 2 OiT was anatase phase and mesoporous with specific surface 133.45 m2/g. The decomposition of methylene blue dye under the influence of ultraviolet light was used to test the photocatalytic performance of the produced TiO2 photocatalyst. The photocatalytic activity of the TiO2 photocatalyst for the breakdown of methylene blue dye was significantly higher than that of the commercial TiO2 P25 used as a reference. Moreover, the prepared photocatalyst was stable and reusable. The larger surface area of hydrothermally produced TiO2 was the reason for this enhanced photocatalytic activity. As a result, it is expected that this approach of photocatalytically active semiconducting nanocatalysts will be used in industry to eliminate undesired organics from the environment