Produção de nanopartículas monodispersas em aerossóis utilizando separação em campo elétrico

Abstract

The wide range of applications of particulate materials in modern industry, allied with growing concerns about its potential risks to human health and the environment have boosted studies related to the production, control and classification of nanoparticles. Differential Mobility Analyzers (DMAs) are equipment commonly used for the classification of polydisperse nanoparticles in aerosols. The typical geometry of a DMA consists in two concentric cylinders. In the inner cylinder are applied different negative electrical voltages, while the outer cylinder is grounded, generating an electric field between them. Positive nanoparticles are attracted by the inner cylinder, describing different axial trajectories. Those that present a narrow range of electric mobility are collected by a small classification slot, from which the monodisperse aerosol is obtained. Commercial analyzers are equipment that have very high prices in the market, which ends up limiting its use. The aim of this study was to evaluate the performance of a Long Differential Mobility Analyzer (Long-DMA), designed and built at FEQ/UFU, for the classification of polydisperse nanoparticles of available aerosols. The equipment consists of two concentric stainless steel cylinders, so that the inner cylinder was energized by a high voltage source while the outer cylinder was grounded. The polydisperse aerosol used in the experiments was generated by the atomization of the NaCl solution, with concentrations of 0,1; 0,5 and 1 g.L-1. A mobility balance was proposed, based on the Wiedensohler charge distribution, in order to estimate the theoretical distributions of nanoparticles sizes of monodisperse and excess aerosols. With the accomplishment of the experimental procedures it was verified that the Long-DMA was able to produce monodisperse aerosols for all the saline concentrations evaluated, evidencing its potential for the classification of nanoparticles. Comparisons between the experimental and theoretical results showed that the proposed mobility balance was able to describe satisfactorily the distributions related to monodisperse aerosol, especially for the less concentrated solution. It is worth mentioning that the cost of the designed equipment was approximately 10% of the commercial equipment value, which represents a great advantage for its use.