System for Characterizing Aerosols from Bubbling Liquids

Abstract

The transfer of materials from the liquid phase to the gaseous phase by the bursting of gas bubbles at the liquid surface is of concern in many industrial and environmental applications, e.g., microorganism generation from wastewater treatment plants and health club whirlpools. Most previous studies have focused on single-bubble bursting, which is rarely found in actual situations. An experimental system has been developed that is large enough to accommodate multiple-bubble bursting and overcomes the difficulties of sampling and analysis of liquid droplets above the surface of a bubbling liquid. The system uses dynamic aerosol spectrometers to provide real-time information on the concentrations and size distributions of the liquid droplets generated and of the materials contained in the liquid droplets after their evaporation. Specially designed impactors are used to size classify the droplets so that the content of the droplets of various size ranges can be evaluated. Examples of measured droplet distributions show that the system is independent of the distance above the liquid surface at which the sample is taken. The geometric mean diameter of the droplets generated from 2.57-mm bubbles was found to be 2.0 μm with ag = 1.96. In one experiment with a suspension of 0.56-μm diameter latex spheres at a concentration of 109/cm3 in distilled water, 61% of the measured droplets contained latex particles. This represented a several hundredfold enrichment over the bulk concentration of particles.