TiO2 Synthesis and Photocatalytic Experiments for the Determination of Photonic and Quantum Efficiencies

CARNELLI, PATRICIO FRANCISCO FLORENCIO; THOMAS, CECILIA; ALFANO, ORLANDO MARIO; CANDAL, ROBERTO JORGE

San Martín, Buenos Aires

Simposio; The Fifth International Symposium on Environmental Biotechnology and Engineering; 2016

Instituto de Investigación e Ingeniería Ambiental, UNSAM

Titanium dioxide (TiO2) is the most used photocatalyst for non-biodegradable water contaminants. At least in the last 20 years it has been exhaustively studied, but it is difficult to compare the existing works regarding the properties and mechanisms affecting the TiO2 quantum efficiency, one of the most significant parameters affecting the photocatalytic activity of a material.In this work, we made use of the sol-gel method to synthesize TiO2 nanoparticle powders with different mass ratios between crystal phases and different morphologies. These characteristics were controlled through the synthesis parameters and the calcination temperature. By this procedure we want to compare the obtained catalysts and try to identify the characteristics that are of most relevance for the photocatalysis reaction.The obtained powders were characterized by means of x-ray diffraction (XRD), scanning electron microscopy (SEM), and the BET method for specific surface area determination. With these measurements we corroborated that we can effectively control the catalysts properties: we obtained pure anatase or rutile powders, and we also obtained samples with anatase/rutile percentages of 80/20 or 40/60, to give some examples. We also have powders with particle sizes ranging from 15 to 100 nm and surface areas varying from 20 to 90 m2/g.We performed photocatalytic experiments using a slurry reactor with formic acid as a test contaminant. In this case we achieved, for some powders, degradation rates similar to those corresponding to the commercial catalyst Aeroxide TiO2 P25.With the results of the photocatalytic experiments we determined the photonic efficiencies of our photocatalysts, ranging from 0,06% to 0,55%, while we obtained a value of 0,67% for P25 in the same reactor conditions.Finally, we measured the relevant optical properties (absorbance, diffusereflectance, and diffuse transmittance) of our synthesized samples. These properties were used in a Monte Carlo model to solve the radiative transference equation (RTE) and to obtain the quantum efficiency. Once again, we obtained a wide range of values, from 0.05% to 0.42%, being the best close to the one from P25 (0.51%).So far we have obtained satisfactory results. This work is still ongoing and we are planning to synthesize new catalysts to further correlate our efficiency results with the synthesis parameters.