Photocatalytic removal of methylene blue using immobilized transition metals doped titanium dioxide on glass and granular activated carbon

Kang, Ling Bao (2009) Photocatalytic removal of methylene blue using immobilized transition metals doped titanium dioxide on glass and granular activated carbon. Masters thesis, Universiti Malaysia Sabah.

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Abstract

Photocatalytic degradation of methylene blue (MB) dye in aqueous solution using metal-doped titania (TiO₂) under UV-A light and in the presence of H2O₂ were investigated The photocatalysts used were single metal-doped TiO₂ (i.e. Cr+ - TiO₂, Cu²⁺-TiO₂, Fe³⁺- TiO₂, MO⁵⁺- TiO₂, and V⁵⁺- TiO₂) and dual metal-doped TiO2 (i.e. Cr+, MO⁵⁺- TiO₂, Cr+, V⁵⁺ - TiO₂,Cu²⁺, MO⁵⁺- TiO₂, Cu²⁺,V⁵⁺- TiO₂ , Fe³⁺,MO⁵⁺- TiO₂ and Fe³⁺, V⁵⁺ - TiO₂) coated on Pyrex-glass tubes, and single metal doped- TiO₂ (i.e. V⁵⁺-TiO2) coated on granular activated carbon (GAC). All the catalysts were prepared in the lab and the doping/coating was done according to sol-gel dip-coating method. For comparison, undoped TiO2 coated on Pyrex-glass tube and GAC were also studied. The reactions were carried out in a photo-reactor. Subsamples of the dye solution was withdrawn at specific time intervals and its absorbance was measured at λmax= 665 nm using a UV-Vis spectrophotometer. The resultant dye degradation was presented as % dye removed and comparisons were made for its values at 120 minutes. The results showed that the degradation of MB using these titania-assisted systems increased with reaction time. Equilibrium, however, was not attained within 120 minutes. Amongst the single metal-doped TiO₂ systems only V⁵⁺-TiO2 produced greater degradation of MB compared with the undoped TiO2. The other single metal-doped TiO₂ systems (MO⁵⁺- TiO₂ > Fe³⁺-TiO2≈ Cr³⁺-TiO2≈ CU²⁺- TiO₂) produced much lower degradation compared to undoped TiO₂. For dual metal-doped TiO2 systems, the degradation efficiency followed the order: Cu²⁺, V⁵⁺ TiO₂ > Fe³⁺, V⁵⁺- TiO₂ > Cr+, V⁵⁺- TiO₂ > Cr+, MO⁵⁺- TiO₂ ≈ Fe³⁺,MO⁵⁺-TiO₂≈ Cu²⁺, MO⁵⁺-TiO₂. Only Cu²⁺,,V⁵⁺-TiO₂ produced greater degradation of MB compared with the undoped TiO₂. However, it's efficiency was lower than V⁵⁺ - TiO₂ but higher than Cu²⁺- TiO₂. Meanwhile the V⁵⁺- doped and undoped TiO₂ catalysts coated on GAC did not exhibit significant photoactivity. The removal of MB from solution by both systems was of similar magnitude to that of due to adsorption by GAC and was about 2x less efficient compared with VS+- TiO₂ and TiO₂ coated on Pyrex-glass tubes. All the above reactions fitted well with pseudo-first-order kinetics according to the Langmuir-Hinshelwood model. Overall, among the systems investigated, photocatalytic degradation of MB is most efficient when V⁵⁺-doped TiO₂ coated on an inert support, namely Pyrex-glass tubes, was used.

Item Type:Thesis (Masters)
Uncontrolled Keywords:methylene blue, photocatalytic degradation, UV-Vis spectrophotometer, granular activated carbon (GAC), sol-gel dip-coating method, Langmuir-Hinshelwood model, Pyrex-glass tube
Subjects:T Technology > TD Environmental technology. Sanitary engineering
Divisions:SCHOOL > School of Science and Technology
ID Code:8913
Deposited By:IR Admin
Deposited On:02 May 2014 10:41
Last Modified:02 May 2014 10:41

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