Effect of calcination time of a quadruple-element doped titania nanoparticles in the photodegradation of gaseous formaldehyde under blue light irradiation

The photocatalytic degradation of gaseous formaldehyde using Ag/F/N/W-doped titanium dioxide was examined. The photocatalytic reaction was conducted using photocatalysts immobilized on glass tubular reactors illuminated under blue LED lights. Factors affecting gaseous formaldehyde degradation such as photocatalyst's calcination time and dosage, initial formaldehyde concentration, light intensity and operating temperature were studied. Results show that the photocatalytic degradation rate increases with pollutant concentration indicating no mass transfer limitations within the formaldehyde concentration range used. The photodegradation of the formaldehyde using catalyst calcined for 5 h reached ∼88%. The photocatalyst concentration giving the highest degradation rate is found to be 0.10 gL^-1. Which means that upon increasing the concentration of the immobilized photocatalysts will increase its thickness and it may not increase the number of the photo-induced particles. On the other hand, increasing light intensity and operating temperature increased the photocatalytic degradation of gaseous formaldehyde. The maximum light intensity and operating temperature were measured at 25 Wm^-2 and 40 °C, respectively. Langmuir-Hinshelwood kinetic type model was used to describe the photocatalytic reaction. The photocatalytic degradation behavior of gaseous formaldehyde on the modified photocatalyst follows a pseudo-first order rate equation based on a Langmuir-Hinshelwood kinetic type model.

Effect of catalyst calcination temperature in the visible light photocatalytic oxidation of gaseous formaldehyde by multi-element doped titanium dioxide

The present study investigates the influence of calcination temperature on the properties and photoactivity of multi-element doped TiO₂. The photocatalysts were prepared by incorporating silver (Ag), fluorine (F), nitrogen (N), and tungsten (W) into the TiO₂ structure via the sol-gel method. Spectroscopic techniques were used to elucidate the correlation between the structural and optical properties of the doped photocatalyst and its photoactivity. XRD results showed that the mean crystallite size increased for undoped photocatalysts and decreased for the doped photocatalysts when calcination was done at higher temperatures. UV-Vis spectra showed that the absorption cut-off wavelength shifted towards the visible light region for the as-synthesized photocatalysts and band gap narrowing was attributed to multi-element doping and calcination. FTIR spectra results showed the shifting of OH-bending absorption bands towards increasing wave numbers. The activity of the photocatalysts was evaluated in terms of gaseous formaldehyde removal under visible light irradiation. The highest photocatalytic removal of gaseous formaldehyde was found at 88%. The study confirms the effectiveness of multi-element doped TiO₂ to remove gaseous formaldehyde in air by visible light photocatalysis and the results have a lot of potential to extend the application to other organic air contaminants.

Degradation of gaseous formaldehyde via visible light photocatalysis using multi-element doped titania nanoparticles

This study developed a modified titanium dioxide photocatalyst doped with multi-element synthesized via sol-gel process to productize a novel photocatalyst. The study includes degradation of gaseous formaldehyde under visible light using the synthesized novel titanium dioxide photocatalyst. Varying molar ratios from 0 to 2 percent (%_mole in titanium dioxide) of ammonium fluoride, silver nitrate and sodium tungstate as dopant precursors for nitrogen, fluorine, silver and tungsten were used. Photodegradation of gaseous formaldehyde was examined on glass tubular reactors illuminated with blue light emitting diodes (LEDs) using immobilized photocatalyst. The photocatalytic yield is analyzed based on the photocatalyst surface chemical properties via X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FTIR) Spectrophotometry, Brunauer-Emmett-Teller (BET) and X-ray Diffraction (XRD) characterization results. The applied modifications enhanced the visible light capability of the catalyst in comparison to the undoped catalyst and commercially available Degussa P-25, such that it photocatalytically degrades 88.1% of formaldehyde in 120 min. Synthesized titanium dioxide photocatalyst exhibits a unique spin orbital at 532.07 eV and 533.27 eV that came from the hybridization of unoccupied Ti d(t_2g) levels.