Effect of surface tension and brine concentration on mass transfer in micro-bubble aeration

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references: p.75-80.Issued also on microfiche from Lange Micrographics.This study shows that brine concentration and dynamic surface tension (DST) affect bubble size. The surface tension of a bubble increases as the diameter of a bubble decreases due to the non-coalescing effects of an increased electrolyte concentration. An increase in surface tension increases the resistance to mass transfer across the bubble interface. By using the American Society of Civil Engineers' (ASCE) reaeration technique, the mass transfer coefficient is determined as a function of bubble size and brine concentration. The DST is measured with a SensaDyne PC9000 differential pressure tensiometer as a function of bubble frequency and brine concentration. The bubble sizes produced by the tensiometer are calculated from the measured bubble frequencies, and the bubble sizes in the mass transfer column are statistically measured using a digital video camera and an imaging program called SigmaScanTm. The resulting statistical correlation allows the mass transfer coefficient of a brine solution to be predicted by a correlation dependent solely on the DST of bubbles in the system. This is possible because both DST and the mass transfer coefficient are functions of brine concentration and bubble size. Currently, the correlation for DST is valid for deionized water up to 8 % by weight brine solutions and bubble sizes from 0.26 mm to 0.66 mm. The mass transfer data should be extended to larger bubble sizes in high concentrations of brine to complete the mass transfer characterization. In addition, these methods should be extended to different column configurations so an additional variable for mixing effects can be accounted for in a generalized model