Automação de um sistema de direcionamento de luz no processo de degradação fotocatalítica de efluentes por irradiação solar

Abstract

Photocatalytic reactions that use sunlight face problems throughout the day due to periodicity, affecting the yield of the reaction. The problem was solved by creating a prototype based on a model created in CAD software from which it moves radially to where there is a greater incidence of light through the interaction of LDR resistors and Arduino microcontroller sensors. Three photocatalysis experiments were carried out. In the first two trials, the treatment of 100 mL and 250 mL, respectively, of the methylene blue dye solution at a concentration of 50 mg L-1 at initial pH 7.0 was performed. In the third experiment, the solution of 50 g L-1 reactive blue 5G dye solution with initial pH 2.0 was used. In the three cases, the dosage of 1 g L-1 of the catalyst was used, with titanium dioxide being the first test and zinc oxide in the other two tests. The experimental procedure consisted of adding the catalyst to the volume of dye solution to be treated, the mixture being kept in the dark for 15 minutes, and hydrogen peroxide was added at a rate of 100 μL per 100 mL of solution. After this the reactor was exposed to sunlight under constant magnetic stirring and the concentration variation was measured by the absorbances obtained with respect to time. All the tests were carried out in the conventional photocatalytic reactor and in the solar light directing prototype, in order to compare the efficiency of the dye degradation in the two systems. The results indicated that the processes performed in the prototype allowed the establishment of equilibrium in advance, compared to the conventional system in which only a fixed magnetic stirrer is used. In addition the efficiency in the degradation of the dye using the prototype was slightly superior in all tests. For the first experiment the efficiencies were very close with 98.57% degradation for prototype and 98.55% for the fixed agitator. In experiment 2, there was slight favoring of the degradation of the dye with the experiment conducted the prototype (63, 84%), when compared to the System with fixed shaking (62.63%). For these experiments, evaporation rates and mean operating temperature were 0.035 mm min-1 and 21.45 ° C in experiment 1 and 0.05 mm min-1 and 18.59 ° C in experiment 2. For the third experiment, the efficiencies were 98.48% for the prototype and 86.39% for the fixed agitator, and the process favoring the Solar Light Steering System was observed, possibly due to the higher radiation incidence. The evaporation rate and the average temperature of the prototype in the experiment were 0.03 mm.min-1 and 21.03º C. In general, it is possible to verify the satisfactory nature of the prototype built in the efficiency improvement of the process of solar photocatalysis by the search automated lighting, as well as the possibility of monitoring operating conditions such as evaporation rate and temperature autonomously.