Kinetics flotation

Flotation reagents are used in the froth flotation process to (/) enhance hydrophobicity, (2) control selectivity, (J) enhance recovery and grade, and (4) affect the velocity (kinetics) of the separation process. These chemicals are classified based on utili2ation collector, frother, auxiUary reagent, or based on reagent chemistry polar, nonpolar, and anionic, cationic, nonionic, and amphoteric. The active groups of the reagent molecules are typically carboxylates, xanthates, sulfates or sulfonates, and ammonium salts. 

Flotation process kinetics determine the residence time, the average time a given particle stays in the flotation pulp from the instant it enters the ceU until it exits. One way to study flotation kinetics is to record flotation recoveries as a function of time under a given set of conditions such as pulp pH, coUector concentration, particle size, etc. The data allow the derivation of an expression that describes the rate of the process. 

First-order kinetics (ie, n = 1) is frequently assumed and seems adequate to describe the kinetics of most flotation processes. However, highly hydrophobic particles float faster and very fine particles or coarse ones outside the optimal flotation size range (see Fig. 1) take longer to coUect in the froth layer. ExceUent reviews of the subject are available in the Hterature (27). 

The study of flotation kinetics relates to a number of mass transfer processes and these are listed in Table 2.8. The term, entrainment which figures in the mass transfer process statements made in Table 2.8 may be elaborated. It is the process by which particles enter the base of a flotation froth and are transferred up and out of the flotation cell suspended in the water between bubbles. Entrainment should be distinguished from true flotation, whereby particles come out of the cell attached to bubble surfaces. True flotation is chemically selective, while the entrainment process recovers both gangue and valuable minerals alike. Entrainment harms the product grade since recovery of the more abundant gangue mineral reduces the quality of the concentrate. This is especially true in the processing of fine ores. Much flotation research has dealt with reducing entrainment in order to improve... 

Kinetics and Case Histories of Activated Sludge Secondary Flotation Systems... 

Specific Kinetics of the Improved Activated Sludge Process Using Secondary Flotation... 

Finkelstein, N. P., 1999. Addendum to The activation of sulphide minerals for flotation a review. Inter. J. Miner. Process, 55(4) 283 - 286 Fomasiero, D., Montalti, M., Ralston, J., 1995. Kinetics of adsorption of ethyl xanthate on pyrrhotite in situ UV and infiared spectroscopic studies. Langmuir, 11 467 - 478 Forssberg, K. S. E., Antti, B. M., Palsson, B., 1984. Computer-assisted calculations of thermodynamic equilibria in the chalcopyrite-ethyl xanthate system. In M. J. Jones and R. Oblatt (eds.). Reagents in the Minerals Industry. IMM, Rome, Italy, 251 - 264 Fuerstenau, M. C., Kuhn, M. C., Elgillani, D. A., 1968. The role of dixanthogen in xaomthate flotation ofpyrite. Trans. AIME, 241 437 Fuerstenau, M. C. and Sabacky, B. J., 1981. Inter. J. Miner. Process, 8 79 - 84 Fuerstenau, M. C., Misra, M., Palmer, B. R., Xanthate adsorption on selected sulphides in the presence of oxygen. Inter. J. Miner. Process... 

Pozzo, R. L., Malicsi, A. S., Iwasaki, L, 1988. Pyrite-pryyhotite-grinding media contact and its effect on flotation. Minerals Metallurgical Processing, 5(1) 16-21 Pozzo, R. L., Malicsi, A. S., Iwasaki, I., 1990. Pyrite-pyrrhotite-grinding media contact and its effect on flotation. Minerals Metallurgical Processing, 7(1) 16 - 21 Prestidge, C. A., Thiel, A. G., Ralston, J., Smart, R. S. C., 1994. The interaction of ethyl xanthate with copper (II)—activated zinc sulphide kinetic effects. Colloids Surfece, A. Physicochem. Eng. Aspects, 85 51 - 68... 

Miner. Process Extra. Metall. Rev., 11 187-210 Yarar, B., Haydon, B. C., Kitchener, J. A., 1969. Electrochemistry of the galena-diethyldithio carbamate-oxygen flotation system. Trans. Instn. Min. Metall. Sec.C, 78 C181 - C184 Yekeler Meftuni, Sonmez Ibrahim, 1997. Effect of the hydrophobic fraction and particle size in the collectorless column flotation kinetics. Colloids and Surfaces A Physicochemical and Engineering, 121(1) 9-13... 

A decrease in flotability is characterized by an increase in polarity of the adsorption layer of both surfactants due to the formation of a second adsorption layer with polar groups of the surfactant orientated toward the bulk phase, up to the CMC. The analysis of the flotation measurements was carried out on the basis of kinetic data for the shortest constant... 

Mr. Campbell Anthracite lithotypes were investigated for their electro-kinetic characteristics to establish a basis for separation, utilizing froth flotation methods. The electrokinetic characteristics of macerals were not investigated. However, results from the lithotype work does imply that macerals have different electrokinetic characteristics. I believe electrophoretic methods could be used effectively to separate macerals for laboratory purposes. 

Loveday, B. K., Analysis of Froth Flotation Kinetics, Inst. Min. MetalL Trans., CIS, 219 (1966). 

The study of adsorption kinetics of a surfactant on the mineral surface can help to clarify the adsorption mechanism in a number of cases. In the literature we found few communications of this kind though the adsorption kinetics has an important role in flotation. Somasundaran et al.133,134 found that the adsorption of Na dodecylsulfonate on alumina and of K oleate on hematite at pH 8.0 is relatively fast (the adsorption equilibrium is reached within a few minutes) as expected for physical adsorption of minerals with PDI H+ and OH". However, the system K oleate-hematite exhibits a markedly different type of kinetics at pH 4.8 where the equilibrium is not reached even after several hours of adsorption. Similarly, the effect of temperature on adsorption density varies. The adsorption density of K oleate at pH 8 and 25 °C is greater than at 75 °C whereas the opposite is true at pH 4.8. Evidently the adsorption of oleic acid on hematite involves a mechanism that is different from that of oleate or acid soaps. 

This example is divided into three parts. In (a), the development of a new, selfaspirating and radially discharging funnel-shaped nozzle is presented. In (b), a flotation cell with two spatially separated spaces is described. The inner chamber is used for contacting gas bubbles with flocks and the annular ring around it is needed for the tranquilization of liquid throughput. This facilitates the complete separation of the flocks from the biologically purified waste water. It is shown how the flotation kinetics can be determined in this continuously run cell and how this knowledge is used to scale-up a full-scale flotation plant. On the contrary, in (c), data from batch-wise performed experiments are used to evaluate the flotation kinetics and to scale-up continuously run full-scale flotation cells. 

If we assume that the current in the annulus is not back-mixed, then it has a residence time characteristic of an ideal plug flow. Due to the fact that flotation is a depletion process which obeys the 1st order time law, the flotation kinetics is given by the correlation... 

Fig. 59 Flotation kinetics in the material system activated siudge/biologically purified waste water from [84], Parameter gas throughput, qG.

The structure electrical double layer at the silica-aqueous electrolyte interface was one of the earlier examined of the oxide systems. At the beginning the investigations were performed with application of electrokinetic methods next, with potentiometric titrations. The properties of this system were very important for flotation in mineral processing. Measurements proved that pHpZC and pHiep are equal to 3, but presence of some alkaline or acidic contaminants may change the position of these points on pH scale. Few examples, concerning edl parameters are shown in Table 3. Presented data concern a group of systems of different composition of the liquid phase and solid of a different origin. The latest measurements of this system takes into account the kinetics of the silica dissolution [152], and at zeta measurements, also the porosity of dispersed solid [155]. 

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