UV/VIS Photocatalytic Degradation Of Formaldehyde By Bamboo Activated Carbon Supported Catalyst

Adsorption and photocatalytic oxidation have shown advantages in wastewater treatment, but they have shortcomings. In this thesis, the adsorption of bamboo activated carbon (BAC) and the photocatalysis of titanium dioxide (TiO₂) act synergistically in the treatment of formaldehyde aqueous solution. On the basis of review of domestic and international research, composites of TiO₂ and BAC (TiO₂/BAC) were developed through sol-gel method. Mean while, elements of Pt and N were doped in the composite to produce Pt/N/TiO₂/BAC. The photocatalysis under UV/Vis light was investigated. Main contents and results are summarized as follows:1, Preparation and charactorizition of BAC and TiO₂/BAC Activated carbons were produced from bamboo cane through phosphoric acid activation. Supported TiO₂ catalyst was prepared by sol-gel method. Performance of composite catalyst was discussed according to the degradation rate of formaldehyde aqueous solution. The results showed that TiO₂/BAC can remove formaldehyde distinctly and its degradation rate is more than that of BAC, TiO₂ and even the mixture of BAC and TiO₂ . N2 adsorption analysis showed that the catalysts had lower BET surface area and lower pore volume after loading. SEM analysis showed TiO₂ particles dispersed irregularly on the surface of BAC. XRD analysis showed BAC was helpful to decrease the size of microcrystal, and the crystal form is anatase. FT-IR result showed TiO₂ was supported through chemical band Ti-O-C.2, Photocatalysis of TiO₂/BAC Effects of BAC, light, pre-absorbing time, catalyst dosage, initial concentration and pH on photocatalysis were investigated. Results showed that BAC, which owned high surface area and proper pore size distribution, as loader was helpful for photocatalysis; TiO₂ can show catalysis only when the UV light was on, and the degradation rate rose when the light intensity was higher; Proper pre-absorbing time contributed to increase degradation rate and made the reaction more efficient. Both rising and falling of pH did good to the formaldehyde degradation. The maxmum of formaldehyde degradation rate was up to more than 95 %, when catalyst dosage is 1.0 g, initial concentration is 5 mg·L^-1, loading time is 2 and the reaction continued 480 min. The photocatalysts prepared kept high performance after 4 reusing times and can be separated easily. The reaction can be well fitted using Langmuir-Hinshelwood kinetic equation.3, Preparation and charactorizition of Pt/N/TiO₂/BAC SEM analysis showed that Pt, N co-doping is helpful for the scattering of TiO₂ particles on the BAC surface; XRD analysis showed that the co-doping can not change the crystal type, N inhibited anatase changing to tutile and lessened agglomeration. FT-IR result showed chemical band Ti-O-C was produced. XPS result showed N entered into the TiO₂ lattice, Pt made more active sites and there were oxygen vacancies on the catalyst surface. UV-Vis analysis showed N widened light abstraction width and Pt enhanced photocatalysis.4, Photocatalysis of Pt/N/TiO₂/BAC under visible light Effect of doping on adsorption and effects of calcination temperature and Pt doping quantity on photocatalysis were investigated. The results showed that doping reduce adsorption and co-doping of Pt and N can not only widened the light abstraction width but also enhanced photocatalysis. When calcination temperature was 500℃, Pt content was 1.0 %and reaction continued 315min, formaldehyde degradation rate was up to 64.01 %, which was 2.6 times of TiO₂/BAC with similar conditions. The photocatalysts prepared was prone to separation.