Degradation of organic pollutants in photocatalytic reactors

Titanium dioxide-mediated photocatalytic mineralization of oxalic acid and formic acid as model compounds were studied in a laboratory-scale reactor and in a pilot equipment to promote the development of procedures for wastewater treatment. Experimental results obtained by using various TiO2 catalysts indicate that the adsorption of the pollutant substrates on the surface of the semiconductor particles is not directly correlated with the specific surface area of the adsorbent. The initial rate of the photocatalytic degradation of the model compounds is enhanced by increasing the adsorption capability of the titanium dioxide applied, but the overall mineralization efficiency is jointly determined by several factors such as the crystal structure, the mean value and the distribution of the particle size, as well as the number of the hydroxyl groups on the particle surface. The VP P90 TiO2 proved to be the most efficient photocatalyst for degradation of both model compounds studied. Application of static mixer in the pilot equipment enhanced the rate of the photocatalytic mineralization of formic acid by about 27%. This effect can be attributed to the increased interfacial mass transfer facilitating the movement of photogenerated HO● radicals from the catalyst surface or the boundary layer to the bulk solution.