Abstract
Recent studies has shown that caffeine, a substance present in beverages such as coffee, in pharmaceuticals products and food, it is present in surface water in several countries. In Brazil, a study conducted in 2014, identified caffeine in public water supply in 22 Brazilian cities including the capital of the Federal District with a 93 % detection rate. The degradation of caffeine in aqueous solution has been studied by different methods. The heterogeneous photocatalysis is highlighted by presenting good results in degradation of emerging pollutants. This study focused on the characterization and evaluation of the photocatalytic activity of ZnO (calcined at 400 °C and noncalcined) for the caffeine degradation. The characterization of materials were perfomed by thermogravimetric analysis, Specific surface area (BET method), pore diameter and pore volume, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and spectroscopy photoacoustic. The analysis results as well the materials characterization indicated that the calcination at 400 °C modified ZnO structure. For the ZnO catalyst (calcined at 400 °C) the photocatalytic activity indicated a caffeine solution degradation of 70 % after around 40 minutes of reaction. On the other hand, for the noncalcined catalyst the degradation, in the same period, was of 40 %. Both catalysts exhibited different kinetic curves, but the calcined ZnO obtained a more sharply response at the beginning of reaction. The reaction was studied in total time of four hours and the results presented a degradation approximately 100 %.
