Determinação de frequências ultrassônicas para dessalinização de águas salobras.

Abstract

Water is an indispensable asset for human life, but over the years it has become increasingly scarce. Add to this the fact that most of the water in the world is not drinkable, that is, with a large presence of salts. Thus, desalination emerges as an alternative for generating water for human consumption. Although there are different desalination methods, most of them are economically unfeasible or have problems with the maintenance of their systems. After the identification of the use of high-frequency ultrasound (HFUS), to evaporate brackish water, a bench prototype was built to carry out ultrasonic desalination experiments. In the first chamber of this prototype, the sonicated brackish water vapor is entrained by air heated by the very thermal inertia of the sonication stage, with the separation of water-salts in a posterior chamber. In the last chamber, the water vapor is recovered by condensation and the air is released through a porous seal. As independent variables, the flow rate of the entrained air of the sonicated water vapor and the temperature of the water-salt mixing and separation chamber were established. The response variables responsible for the analysis of the operational conditions of the desalinator were the desalination efficiencies and the percentage reduction in the conductivity of the water produced. The results show that the rational use of all energy used for the production of 1.7 MHz sound waves, associated with the production of compressed air, was necessary for the production of 0.025 L.(kW.h)-1 of freshwater. They also showed that even with low salinity water (2.2 x 10-7 ppm) it was possible to achieve a salt removal rate of 85%, demonstrating good effectiveness of the US as an individual technique. It is expected that, based on the results presented here, further studies will be carried out using new variables such as the salinity of the incoming water and the performance of prototype tests involving serial desalination chambers.