http://nova.newcastle.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:3340 In this paper the problem of calculating the depression of the gas–liquid meniscus by the particle attachment was solved. The analytical approximate equations obtained for small and large radii, rtpc, of the three-phase contact were analyzed and compared to the available numerical results. The Derjaguin equation for small rtpc and the analytical results for large rtpc are accurate for rtpc/L≤0.2 and rtpc/L≥2, respectively, where L is the capillary length. For the meniscus depression with rtpc/L from 0.2 to 2, the empirical equations were obtained based on the asymptotic analysis of the analytical approximate solutions. The empirical numerical constants were obtained by fitting to the exact numerical results. The empirical equations together with the analytical approximate equations provide the accurate predictions for the meniscus depression for the whole range of the radius of the three-phase contact and are expected to be useful for modeling the detachment interaction in the flotation separation processes. 2010-04-27T05:13:04.225Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:3894 Surfactants are used to control the interfacial properties of the gas-liquid and liquid-solid interfaces in flotation. This paper investigates the dynamic adsorption of surfactants at the gas-liquid interface. The dynamic adsorption process was modeled by considering the surfactant mass transfer to the gas-liquid interface by diffusion and the Langmuir and Frumkin adsorption isotherms. The numerical computation was applied to solve the non-linear governing equations. The dynamic adsorption was measured in terms of the dynamic surface tension using the pendant drop method. The theoretical models were compared against the experimental data obtained with non-ionic (Dowfroth 250) and ionic (sodium doderyIbenzene sulfate, SDBS) surfactants. The theoretical results agreed well with the experimental data for SDBS, but not for Dowfrother 250, especially for the initial stage. Reasons for the variation in results are given in the paper. 2010-04-27T05:12:00.425Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:5921 Foam fractionation or ion flotation is a process by which surfactant molecules together with counter-ions are adsorbed onto the gas-liquid interface of rising bubbles within the column. This process results in a foam product known as foamate that is high in surfactant concentration. High extraction rates require a high air injection rate. However, high air injection rates lead to a high rate of concomitant liquid within the foam which results in a relatively low concentration of surfactant in the foamate. Therefore the volume reduction, given by the ratio of the feed flux to foamate flux, should tend to decrease to unsatisfactory levels as the air injection rate increases. Using drift flux theory, an elementary model describing the variation of surfactant recovery with the ratio of the feed to gas flux was developed for a conventional ion flotation system. Incorporated into this model is a simple power law relation for the superficial liquid drainage flux through the foam established by dimensional analysis. Experiments were conducted using a fixed feed to gas flux ratio, the aim being to produce a reasonably constant surfactant recovery. The performance of the process was then assessed in terms of the variation in the volume reduction with the gas flux. The model was found to be consistent with the experimental data. The findings also demonstrated the need to limit the gas flux and hence the feed flux to relatively low values in order to produce satisfactory volume reductions and hence concentration upgrades. 2010-04-27T04:51:13.754Z ]]>