Tumelo Seadira | University of South Africa (original) (raw)
Papers by Tumelo Seadira
Applied Catalysis B: Environmental, 2018
Abstract Nanostructured TiO2 hollow spheres (THS) were prepared via a simple hydrothermal method ... more Abstract Nanostructured TiO2 hollow spheres (THS) were prepared via a simple hydrothermal method with titanium butoxide, ethanol, urea, and ammonium sulphate. The effects of Ti/ethanol, and reflux temperature on the morphological properties of the nanostructured THS were investigated. An impregnation method was subsequently employed to load metals such as Cu, Co, Cr, Ag, and Ni on the optimized THS, followed by calcination in H2/N2 at 450 °C for 4 h. The morphological properties of the prepared samples were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ultraviolet-visible spectroscopy (UV/vis). The SEM and TEM pictures showed that the Ti/ethanol ratio of 1:10 resulted in the formation of uniform hollow spheres. The XRD spectre revealed that phase transformation took place as the reflux temperature was increased, with pure anatase TiO2 hollow spheres being formed at 200 °C. The BET surface areas of the calcined photocatalysts were in the range of 80.6–116 m2/g−1. The UV/vis spectra of the photocatalysts showed that loading of transition metals reduced the band gap of the THS. The activities of the prepared catalysts were tested for hydrogen production via photocatalytic reforming of glycerol under solar irradiation. The improved hydrogen evolution from photocatalytic reforming of glycerol was attributed to: the high surface area which enhanced the adsorption of glycerol onto the surface of photocatalysts; high crystallinity and the reduced band gap which improved the solar light harvesting; the hollow chamber within the TiO2 spheres which produced multiple reflection of the light harvested, thus producing efficient electron/hole pair formation; and the detailed composition of the solids retarded the electron/hole recombination by trapping the electrons generated during the photo excitation of the photocatalysts, and thereby promoted their activity.
Reviews in Chemical Engineering, 2018
The use of biomass to produce transportation and related fuels is of increasing interest. In the ... more The use of biomass to produce transportation and related fuels is of increasing interest. In the traditional approach of converting oils and fats to fuels, transesterification processes yield a very large coproduction of glycerol. Initially, this coproduct was largely ignored and then considered as a useful feedstock for conversion to various chemicals. However, because of the intrinsic large production, any chemical feedstock role would consume only a fraction of the glycerol produced, so other options had to be considered. The reforming of glycerol was examined for syngas production, but more recently the use of photocatalytic decomposition to hydrogen (H2) is of major concern and several approaches have been proposed. The subject of this review is this greener photocatalytic route, especially involving the use of solar energy and visible light. Several different catalyst designs are considered, together with a very wide range of secured rates of H2 production spanning several ord...
Acid mine drainage (AMD) is a serious problem associated with mining activities, and it has the p... more Acid mine drainage (AMD) is a serious problem associated with mining activities, and it has the potential to contaminate surface and ground water. The aim of this study was to evaluate the performance of constructed wetland and photocatalysis in treating AMD. Three identical unvegetated upflow constructed wetlands packed with natural zeolite (clinoptilolite) and coarse silica sand were made of a cylindrical plastic pipe, and the slurry photocatalyst was prepared using quartz material. A hydro-alcohol thermal method was used to prepare an anatase core-void-shell TiO2 photocatalyst. The results showed that the three unvegetated upflow constructed wetlands (CW) had relatively similar percentage removal of heavy metals despite their varying concentrations within the AMD. The removals were: Fe (86.54-90.4%); Cr (56.2-64.5%); Mg (56.2-67.88%); Ca (77.1-100%); and 100% removal was achieved for Be, Zn, Co, Ni, and Mn. The removal of sulphate was also 30%. Heavy metals concentration in CW pa...
M. Tech. (Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Techno... more M. Tech. (Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology
The use of biomass to produce transportation and related fuels is of increasing interest. In the ... more The use of biomass to produce transportation and related fuels is of increasing interest. In the traditional approach of converting oils and fats to fuels, trans-esterification processes yield a very large coproduction of glycerol. Initially, this coproduct was largely ignored and then considered as a useful feedstock for conversion to various chemicals. However, because of the intrinsic large production, any chemical feedstock role would consume only a fraction of the glycerol produced, so other options had to be considered. The reforming of glycerol was examined for syngas production, but more recently the use of photocatalytic decomposition to hydrogen (H 2) is of major concern and several approaches have been proposed. The subject of this review is this greener photocatalytic route, especially involving the use of solar energy and visible light. Several different catalyst designs are considered, together with a very wide range of secured rates of H 2 production spanning several orders of magnitude, depending on the catalytic system and the process conditions employed. H 2 production is especially high when used in glycerol-water mixtures.
Nanostructured TiO 2 hollow spheres (THS) were prepared via a simple hydrothermal method with ti... more Nanostructured TiO 2 hollow spheres (THS) were prepared via a simple hydrothermal method with titanium butoxide, ethanol, urea, and ammonium sulphate. The effects of Ti/ethanol, and reflux temperature on the morphological properties of the nanostructured THS were investigated. An impregnation method was subsequently employed to load metals such as Cu, Co, Cr, Ag, and Ni on the optimized THS, followed by calcination in H 2 /N 2 at 450 °C for 4 h. The morphological properties of the prepared samples were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron mi-croscopy (TEM), and ultraviolet-visible spectroscopy (UV/vis). The SEM and TEM pictures showed that the Ti/ ethanol ratio of 1:10 resulted in the formation of uniform hollow spheres. The XRD spectre revealed that phase transformation took place as the reflux temperature was increased, with pure anatase TiO 2 hollow spheres being formed at 200 °C. The BET surface areas of the calcined photocatalysts were in the range of 80.6–116 m 2 /g −1. The UV/vis spectra of the photocatalysts showed that loading of transition metals reduced the band gap of the THS. The activities of the prepared catalysts were tested for hydrogen production via photocatalytic reforming of glycerol under solar irradiation. The improved hydrogen evolution from photocatalytic reforming of glycerol was attributed to: the high surface area which enhanced the adsorption of glycerol onto the surface of photo-catalysts; high crystallinity and the reduced band gap which improved the solar light harvesting; the hollow chamber within the TiO 2 spheres which produced multiple reflection of the light harvested, thus producing efficient electron/hole pair formation; and the detailed composition of the solids retarded the electron/hole recombination by trapping the electrons generated during the photo excitation of the photocatalysts, and thereby promoted their activity.
Carbon, 2006
The synthesis of platelet carbon nanofibers (PCNFs) on a silicon substrate using chemical vapor d... more The synthesis of platelet carbon nanofibers (PCNFs) on a silicon substrate using chemical vapor deposition method is reported. Scanning electron microscope, high-resolution transmission electron microscopy, and Raman spectroscopy were used to characterize the nanofibers. It is found that these platelet nanofibers are of the order of 10μm long, and most have a nearly rectangular transverse section with several hundreds nm
Applied Catalysis B: Environmental, 2018
Abstract Nanostructured TiO2 hollow spheres (THS) were prepared via a simple hydrothermal method ... more Abstract Nanostructured TiO2 hollow spheres (THS) were prepared via a simple hydrothermal method with titanium butoxide, ethanol, urea, and ammonium sulphate. The effects of Ti/ethanol, and reflux temperature on the morphological properties of the nanostructured THS were investigated. An impregnation method was subsequently employed to load metals such as Cu, Co, Cr, Ag, and Ni on the optimized THS, followed by calcination in H2/N2 at 450 °C for 4 h. The morphological properties of the prepared samples were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ultraviolet-visible spectroscopy (UV/vis). The SEM and TEM pictures showed that the Ti/ethanol ratio of 1:10 resulted in the formation of uniform hollow spheres. The XRD spectre revealed that phase transformation took place as the reflux temperature was increased, with pure anatase TiO2 hollow spheres being formed at 200 °C. The BET surface areas of the calcined photocatalysts were in the range of 80.6–116 m2/g−1. The UV/vis spectra of the photocatalysts showed that loading of transition metals reduced the band gap of the THS. The activities of the prepared catalysts were tested for hydrogen production via photocatalytic reforming of glycerol under solar irradiation. The improved hydrogen evolution from photocatalytic reforming of glycerol was attributed to: the high surface area which enhanced the adsorption of glycerol onto the surface of photocatalysts; high crystallinity and the reduced band gap which improved the solar light harvesting; the hollow chamber within the TiO2 spheres which produced multiple reflection of the light harvested, thus producing efficient electron/hole pair formation; and the detailed composition of the solids retarded the electron/hole recombination by trapping the electrons generated during the photo excitation of the photocatalysts, and thereby promoted their activity.
Reviews in Chemical Engineering, 2018
The use of biomass to produce transportation and related fuels is of increasing interest. In the ... more The use of biomass to produce transportation and related fuels is of increasing interest. In the traditional approach of converting oils and fats to fuels, transesterification processes yield a very large coproduction of glycerol. Initially, this coproduct was largely ignored and then considered as a useful feedstock for conversion to various chemicals. However, because of the intrinsic large production, any chemical feedstock role would consume only a fraction of the glycerol produced, so other options had to be considered. The reforming of glycerol was examined for syngas production, but more recently the use of photocatalytic decomposition to hydrogen (H2) is of major concern and several approaches have been proposed. The subject of this review is this greener photocatalytic route, especially involving the use of solar energy and visible light. Several different catalyst designs are considered, together with a very wide range of secured rates of H2 production spanning several ord...
Acid mine drainage (AMD) is a serious problem associated with mining activities, and it has the p... more Acid mine drainage (AMD) is a serious problem associated with mining activities, and it has the potential to contaminate surface and ground water. The aim of this study was to evaluate the performance of constructed wetland and photocatalysis in treating AMD. Three identical unvegetated upflow constructed wetlands packed with natural zeolite (clinoptilolite) and coarse silica sand were made of a cylindrical plastic pipe, and the slurry photocatalyst was prepared using quartz material. A hydro-alcohol thermal method was used to prepare an anatase core-void-shell TiO2 photocatalyst. The results showed that the three unvegetated upflow constructed wetlands (CW) had relatively similar percentage removal of heavy metals despite their varying concentrations within the AMD. The removals were: Fe (86.54-90.4%); Cr (56.2-64.5%); Mg (56.2-67.88%); Ca (77.1-100%); and 100% removal was achieved for Be, Zn, Co, Ni, and Mn. The removal of sulphate was also 30%. Heavy metals concentration in CW pa...
M. Tech. (Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Techno... more M. Tech. (Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology
The use of biomass to produce transportation and related fuels is of increasing interest. In the ... more The use of biomass to produce transportation and related fuels is of increasing interest. In the traditional approach of converting oils and fats to fuels, trans-esterification processes yield a very large coproduction of glycerol. Initially, this coproduct was largely ignored and then considered as a useful feedstock for conversion to various chemicals. However, because of the intrinsic large production, any chemical feedstock role would consume only a fraction of the glycerol produced, so other options had to be considered. The reforming of glycerol was examined for syngas production, but more recently the use of photocatalytic decomposition to hydrogen (H 2) is of major concern and several approaches have been proposed. The subject of this review is this greener photocatalytic route, especially involving the use of solar energy and visible light. Several different catalyst designs are considered, together with a very wide range of secured rates of H 2 production spanning several orders of magnitude, depending on the catalytic system and the process conditions employed. H 2 production is especially high when used in glycerol-water mixtures.
Nanostructured TiO 2 hollow spheres (THS) were prepared via a simple hydrothermal method with ti... more Nanostructured TiO 2 hollow spheres (THS) were prepared via a simple hydrothermal method with titanium butoxide, ethanol, urea, and ammonium sulphate. The effects of Ti/ethanol, and reflux temperature on the morphological properties of the nanostructured THS were investigated. An impregnation method was subsequently employed to load metals such as Cu, Co, Cr, Ag, and Ni on the optimized THS, followed by calcination in H 2 /N 2 at 450 °C for 4 h. The morphological properties of the prepared samples were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron mi-croscopy (TEM), and ultraviolet-visible spectroscopy (UV/vis). The SEM and TEM pictures showed that the Ti/ ethanol ratio of 1:10 resulted in the formation of uniform hollow spheres. The XRD spectre revealed that phase transformation took place as the reflux temperature was increased, with pure anatase TiO 2 hollow spheres being formed at 200 °C. The BET surface areas of the calcined photocatalysts were in the range of 80.6–116 m 2 /g −1. The UV/vis spectra of the photocatalysts showed that loading of transition metals reduced the band gap of the THS. The activities of the prepared catalysts were tested for hydrogen production via photocatalytic reforming of glycerol under solar irradiation. The improved hydrogen evolution from photocatalytic reforming of glycerol was attributed to: the high surface area which enhanced the adsorption of glycerol onto the surface of photo-catalysts; high crystallinity and the reduced band gap which improved the solar light harvesting; the hollow chamber within the TiO 2 spheres which produced multiple reflection of the light harvested, thus producing efficient electron/hole pair formation; and the detailed composition of the solids retarded the electron/hole recombination by trapping the electrons generated during the photo excitation of the photocatalysts, and thereby promoted their activity.
Carbon, 2006
The synthesis of platelet carbon nanofibers (PCNFs) on a silicon substrate using chemical vapor d... more The synthesis of platelet carbon nanofibers (PCNFs) on a silicon substrate using chemical vapor deposition method is reported. Scanning electron microscope, high-resolution transmission electron microscopy, and Raman spectroscopy were used to characterize the nanofibers. It is found that these platelet nanofibers are of the order of 10μm long, and most have a nearly rectangular transverse section with several hundreds nm