Aplicação de catalisadores na fotodegradação do herbicida Paraquat (1,1'-dimetil-4,4'-bipiridina-dicloreto)

Abstract

In recent years, there has been a growth in the use of herbicides and pesticides with the aim of decrease the time required for harvest and increase the yield of crops. One of the most widely used herbicide is Paraquat (1,1'-dimethyl-4,4'-bipyridine dichloride). A large number of chemicals can not be degraded by conventional methods of water treatment and wastewater. Because of this, it has increased the need for developing new technologies able to degrade these substances, ensuring a low level of contamination and the elimination of toxic compounds. In this context, it highlights the advanced oxidation processes, and among these, heterogeneous photocatalysis because of its potential for application in the degradation of pollutants by use of a semiconductor, usually titanium dioxide, activated by UV radiation. The objective of this study was to use TiO2 catalysts, modified slightly by adding iron in photocatalysis to promote the degradation of Paraquat. a factorial design with central points made to determine the influence of the amount of dopant metal and the calcination temperature of the obtained catalysts was prepared. The catalysts were characterized by determining the specific surface area, specific volume, mean pore diameter and adsorption isotherms by the BET method, scanning electron microscopy (SEM) and photoacoustic spectroscopy. The catalytic tests were conducted with the catalyst in suspension in a jacketed reactor to control reaction temperature and using a 250W mercury halide lamp. Aliquots were withdrawn at certain times to determine the reaction kinetics, and these were analyzed for molecular absorption spectrometry at a wavelength of 263 nm. The catalysts studied showed satisfactory results in the removal of the herbicide, with 90% removal of the pollutant. Statistical data were processed in software Minitab 17. The catalyst that presented the best iron removal percentage was only one who had the calcined titanium dioxide at 500 ° C with removal of 90.2%. However, by factorial design it is possible to optimize experimental parameters in order to obtain the best reaction parameters using a smaller amount of energy for its development.