Synthesis, characterization and activity of titanium dioxide based (Ca, Ce, W)-TiO2 photocatalysts for degradation of dye and pesticide
| dc.contributor.author | Uduak, Akpan (George) | |
| dc.date.accessioned | 2015-07-29T06:57:50Z | |
| dc.date.available | 2015-07-29T06:57:50Z | |
| dc.date.issued | 2011 | |
| dc.description.abstract | Global industrialization is not without its attendant challenges. The release of unwanted by-products and pollutants which are carcinogenic and toxic into the environment by textiles, chemicals and processing industries is directly proportional to industrial growth. The environment must be kept safe. Therefore, photocatalysis leading to complete mineralization of pollutant(s) was adopted to treat wastewaters containing dyes (acid red 1, reactive orange 16, reactive blue 19, direct blue 71 and acid blue 25) and a pesticide (2,4-dichlorophenoxyacetic acid; 2,4-D). A composite photocatalyst, electronically stable of the type Ti(l-x-y)Ca(3x-y)Ce(2x-y)W(yt6)02(1-2(y-x)) (at y<2x and x+y<1) with an enhanced photocatalytic activity was developed by doping Ti02 with Ca, Ce and W. The photocatalyst was prepared by sol-gel method, hydrothermally treated and employed in the degradation of the above mentioned pollutants. The effectiveness of the composite photocatalyst was verified by comparing its activity under the same experimental conditions with two commercial photocatalysts; Degussa P25 and Ti~-Sigma product CAS No. 1317-70-0. The developed photocatalyst was better than Ti02-Sigma product in solar photocatalytic degradation of ARl. The reusability test of the developed photocatalyst makes it superior to Degussa P25 (which could not settle out of solution seven months after photocatalytic degradation of 2,4-D), hence rendering it non-reusable. On the other hand, the composite photocatalyst settled out of solution in less than 1 h after irradiation and proved to be as efficient at the fourth cycle as in the first, as it accomplished a complete degradation at the same irradiation time. This advantage of the composite photocatalyst over Degussa P25 limits the number of comparison made between them. Other catalysts were also developed and tested as described in the body of the Thesis. The developed photocatalysts were characterized by X-ray photoelectron spectroscopy (XPS) for the chemical states of the elements in the developed photocatalysts; X-ray diffraction (XRD) and Fourier Transformed Infra Red (FTIR) for structural and functional groups analysis respectively; surface scanning electron microscopy (SEM) for microstructure and morphology; Nitrogenphysisorption for surface area and pore size distributions; and UV-Vis diffused reflectance for band gap evaluations. The doping resulted in a reduction in the band gap of Ti02 from 3.2 eV to 2.94 eV, and hence the photocatalytic reaction was pushed into the visible region. The high resolution XPS analysis revealed that the photocatalysts is stable as its chemical constituents were found to exist in the proposed oxidation states. The photocatalysts have high surface areas available for photocatalysis and are of N2 adsorption.:.desorption isotherms of type IV with type H2 hysteresis loops. V arlo us operational parameters such as initial pollutants concentration, initial pH, calcination/hydrotreatment temperatures and dopant contents were investigated. While pH greatly influenced the photocatalytic process in all cases, initial concentration does not seem to influence the process, except for 2,4-D degradation. The kinetic study revealed that reaction order that best describes the whole process is first order, except for the visible light degradation of ARl where the rate is independent of initial concentration. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/836 | |
| dc.language.iso | en | en_US |
| dc.subject | Titanium dioxide based | en_US |
| dc.title | Synthesis, characterization and activity of titanium dioxide based (Ca, Ce, W)-TiO2 photocatalysts for degradation of dye and pesticide | en_US |
| dc.type | Thesis | en_US |
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