Photodegradation kinetics of formaldehyde using light sources of UVA, UVC and UVLED in the presence of composed silver titanium oxide photocatalyst

This study investigated the surface modification of photocatalyst and photodecomposition of formaldehyde from indoor pollution source. This study explored the feasibility of the application of the ultraviolet light emitting diode (UVLED) instead of the traditional ultraviolet (UV) lamp to treat the formaldehyde. The photocatalytic decomposition of formaldehyde at various initial concentrations was elucidated according to the Langmuir-Hinshelwood model. The reaction rate constant (k) and adsorption equilibrium constant (K-L) over 0.334 g silver titanium oxide photocatalyst (Ag/TiO2) coated on glass sticks with 254 urn ultraviolet lamp (UVC), 365 nm ultraviolet lamp (UVA), and UVLED are 650 ppmv min(-1) and 2 x 10(-4) ppmv(-1), 500 ppmv min(-1) and 1.04 x 10-4 ppmv(-1), and 600 ppmv min(-1) and 2.52 x 10(-5) ppmv(-1), respectively. A comparison of the simulation results with the experimental data was also made, indicating good agreement. The magnitudes of energy effectiveness (E-e) are in the order of UVLED (0.6942 mg kW(-1)h(-1)) > UVA (0.007 mg kW(-1) h(-1)) > UVC (0.0053 mg kW(-1) h(-1)). The E-e of UVLED is 131 times larger than that of UVC. The UVLED can save a lot of energy in comparison with the traditional UV lamps. Thus, this study showed the feasible and potential use of UVLED in photocatalysis. (c) 2007 Elsevier B.V All rights reserved.