Concentration effect of chromic acid solutions on the enrichment of Cr(VI)in droplets from bursting bubbles

The effect of electrolyte concentration on the enrichment of Cr(VI) in drop lets generated from bubbles bursting on the surface of chromic acid solutio n was investigated,vith an experimental bubbling system for CrO3 concentrat ions in the range of 31.25-375 g/L in the bulk solution with a gas flow rat e of 4 L/min. A cascade impactor collected droplet samples on polyvinyl chl oride filters for chemical analysis. A laser aerosol spectrometer and an ae rodynamic particle sizer were employed simultaneously to measure the number concentration and size distribution of the droplets. For the 5 electrolyte concentrations studied, the measured droplet size distributions had count median diameters (CMDs) in the range of 0.15-0.18 mu m. The droplet volume distributions calculated from droplet number concentration data were bimoda l, indicating the presence of both film and jet droplets which had a mode a t 3-4 mu m and over 10 mu m, respectively. As the CrO3 concentration in the bulk solution increased, the mode of the volume distribution of film dropl ets tended to shift toward smaller sizes, whereas that of jet droplets tend ed to shift toward larger sizes. The concentration ratio, defined as the ra tio of the Cr(VI) concentration in droplets to that of the bulk solution, w as found to decline sharply with increasing electrolyte concentration in th e bulk solution.