Aplicação de técnicas fototérmicas no estudo de materiais de interesse tecnológico e ambiental

Abstract

Air pollution is currently one of the most serious environmental problems. The use of fossil fuels (oil, coal, and natural gas) has produced considerable amounts of greenhouse gases, which consequently causes climate change. The transport sector is considered one of the main polluters of the environment worldwide, due to the intensive use of fossil fuels from the industrial revolution. Therefore, the role of the use of biofuels (biodiesel and ethanol) in the transport sector has been discussed in Brazil in order to minimize the risks caused to the global environment. In this way, the study of gases from the combustion of diesel/biodiesel blends engines is extremely important to evaluate the environmental sustainability of these fuels in the country. Therefore, this research has the objective of evaluating the emission of pollutant gases (N2O, CO2, CO, NOx and NO) from the combustion in bench engine diesel. This engine is supplied with binary blends of diesel/biodiesel from bovine tallow for different volumetric concentrations B7, B15, B20, B25, B35 and B50. For the characterization and detection of gaseous emissions, the photoacoustic spectroscopy and electrochemical sensors were used. In addition, the thermal diffusivity properties of these binary mixtures were obtained by thermal lens technique. Also, was used thermal lens technique optimized mode, which is a variant of the conventional technique, but with greater sensitivity. This technique was used during the internship abroad to perform measurements of different solutions of gold nanoparticles. The study of nanoparticles has scientific and commercial interest to a wide variety of applications in biomedicine, chemical and biological detection sensors, photothermal therapies in cancer and pharmaceutical applications, and also used in biodiesel studies. The results obtained for the emissions of pollutant gases showed that there was emission of N2O in all the samples for the two modes of rotation. Mixture B15 showed the lowest emission with a value of 5.3 ppmv, in low spin mode. While the B7 mixture had the highest emission of this gas in the value of 7.4 ppmv, for high rotation. On the other hand, the levels of CO2 concentration in low rotation varied between the minimum and maximum values of 2.1 to 2.4%, and high rotation, ranging from 2.2 to 2.5%. For CO emissions, with the engine in the low speed mode, it obtained minimum and maximum values of 866.7 to 1333.3 ppmv, and in high rotation, ranging from 666.7 to 1000.0 ppm, respectively. The NOx concentrations of the samples in the low-rotation mode varied from 87.0 to 114.5 ppmv and for high rotation were 85.7 to 103.7 ppmv, respectively. The NO emissions of the samples in the low rotation mode obtained a variation from 83.0 to 109.5 ppm and for high rotation were from 81.7 to 98.7 ppm, respectively. The results of thermal diffusivity for the different mixtures presented values ranging from (1.03 ± 0.03)x10-3cm-2/s and (0.87 ± 0.06)x10-3cm-2/s With the optimized thermal lens mode optimized different concentrations gold nanoparticles were studied, which when adding 1 μL of the solution 1.95x10-4 mg/ml of 50 nm NPsAu in a 0.1 cm cuvette with 0.24 ml of deionized water, 1 Au NP was detected, thus demonstrating the strong sensitivity of this thermal lens technique in the optimized mode.