Publication: Nanoporous anodic oxide formation on niobium and niobium-titanium alloys for photoreduction of hexavalent chromium
| datacite.subject.fos | oecd::Engineering and technology::Materials engineering | |
| dc.contributor.author | Nurhaswani Binti Alias | |
| dc.date.accessioned | 2025-04-29T07:12:21Z | |
| dc.date.available | 2025-04-29T07:12:21Z | |
| dc.date.issued | 2023-09-01 | |
| dc.description.abstract | Niobium pentoxide (Nb2O5) nanoparticle, a semiconductor-based compound, has demonstrated significant potential in reducing toxic heavy metal ions such as hexavalent chromium, Cr(VI) to trivalent chromium, Cr(III), comparable to titanium oxide (TiO2). However, the used of this nanoparticle, can create secondary pollutant which is time consuming for the separation step and not economical. The immobilization photocatalyst is one of the best options to address this problem. In this project, the Nb2O5 has been grown on a supported Nb substrate using the anodization procedure and employed right away as a photocatalyst in Cr(VI) solution. The elimination of Cr(VI) from the system is quick and complete when this photocatalyst is used, allowing for repeated uses. The anodization was conducted in fluorinated ethylene glycol (EG) electrolyte at varying anodization parameters included applied voltage, NH4F concentration, anodization time, and electrolyte temperature to optimize the morphology and structural properties of Nb2O5. Anodization of Nb foil at 60 V and 30 min produced weak crystalline orthorhombic Nb2O5 with “pore-in-pore” nanoporous structure. No crystallite Nb2O5 formed when anodization occurred <60 V. Prolonging the anodization time resulted in high dissolution of Nb oxide which are undesirable for the application. The annealing process increased the crystallinity while also influencing the surface and optical properties. When compared to the as-anodized sample, the Nb2O5 annealed sample has a narrow optical band gap, but poor charge separation. As-anodized Nb formed at 60 V and 70 °C electrolyte temperature achieved the highest Cr(VI) reduction (100% reduction within 75 min, surface area: 4 cm2 ) compared to annealed sample (100% reduction within 120 min, surface area: 4 cm2 ), but annealed sample has better cyclability performance (92% of Cr(VI) reduction remained after the fourth cycle). Due to the high recombination rate of photogenerated electron-hole pairs of Nb2O5 and TiO, the TiO2-Nb2O5 mixed oxides were synthesized as well by anodization of TiNb binary alloys in fluorinated EG electrolyte. The TiNb binary alloys was fabricated at different Nb content (wt. %) to evaluate the effect of different composition on morphology and structural properties of mixed oxides TiO2 and Nb2O5 after the anodization. Vertically aligned nanotubular oxide structures were successfully formed on the surface of Ti and TiNb binary alloys pellets as substrate, except on pure Nb, which exhibited the nanopores morphology. The Nb composition in the TiNb binary alloys has an effect on the oxide formation; increasing the Nb content (up to 40 wt.%) resulted in thicker oxide, with sample Ti-40Nb forming the longest nanotubes. Ti-60Nb outperformed all other TiNb binary alloys compositions in photoreduction of Cr(VI) in UV with 100% reduction within 120 minutes (surface area: 1.33 cm2 ). Furthermore, the TiNb mixed oxide exhibits improved photoactivity properties when compared to TiO2 or Nb2O5 alone, owing to excess electrons in TiO2's conduction band that are transferred from Nb2O5 to Cr(VI) | |
| dc.identifier.uri | https://erepo.usm.my/handle/123456789/21470 | |
| dc.language.iso | en | |
| dc.title | Nanoporous anodic oxide formation on niobium and niobium-titanium alloys for photoreduction of hexavalent chromium | |
| dc.type | Resource Types::text::thesis::doctoral thesis | |
| dspace.entity.type | Publication | |
| oairecerif.author.affiliation | Universiti Sains Malaysia |