Photocatalytic degradation of malonic acid in aqueous suspensions of titanium dioxide: An initial kinetic investigation of CO2 photogeneration

The photocatalytic oxidation of malonic acid in aqueous suspensions of TiO2 was investigated by following the formation of CO2. The rate of formation of CO2 is affected by the pH of the aqueous suspension, TiO2 loading, malonic acid concentration, temperature, irradiation time, flow rate and light intensity. The disappearance of malonic acid fits a Langmuir-Hinshelwood kinetic model. Rate constants were calculated by including a correction term alpha(T) to fake into account the decrease in the solubility of CO2 with increasing temperature. The activation energy is 9.99 kJ mol(-1). A quantum yield of 0.26 for CO2 formation was estimated from the proposed mechanism.