Photocatalytic Degradation of Formaldehyde in Gas Phase on TiO2 Films: A Kinetic Study

Abstract

The kinetic modeling of the photocatalytic degradation of formaldehyde — a major indoor pollutant — in air using an experimental catalytic wall continuous reactor is addressed. A stainless steel flat plate coated with titanium dioxide was placed within the reactor, over which flows an air stream with a known concentration of formaldehyde. The energy source for the ultraviolet radiation that initiates the degradation reactions is provided by a group of five black light lamps next to the reactor window. An analytical expression for the photocatalytic degradation of formaldehyde in air is proposed, based on published literature on accepted reaction mechanisms. Once the kinetic control regime for the reactor was determined, experiments were conducted by the variation of the three operating variables that influence the reaction rate: the inlet formaldehyde concentration, the relative humidity and the level of radiation. A non-linear expression resulting from the combination of a mass balance for formaldehyde and the rate expression were used to estimate the kinetic parameters. The photocatalytic oxidation process for the removal of formaldehyde in air proved to be feasible and efficient under the operating conditions analyzed.