Precipitation flotation

The slowly rising foam in a tall column can Be employed as the sorbent for continuous chromatographic separations [Talman and Rubin, Sep. Sci., 11, 509 (1976)]. Low gas rates are also employed in short columns to produce the scumlike froth of batch-operated ion flotation, microflotation, and precipitate flotation. 

Overflow at the rate of 2700 m (713,000 gal) per day from a zinc-concentrate thickener is treated by ion flotation, precipitate flotation, and untrafine-particle flotation [Nagahama, Can. Min. Metall. Bull., 67, 79 (1974)]. In precipitate flotation only the surface of the particles need be coated with collector. Therefore, in principle less collector is required than for the equivalent removal of ions by foam fractionation or ion flotation. 

Medina, B.Y., Torem, M.L., and De Mesquita, L.M.S., Removal of chromium III from liquid effluent streams by precipitate flotation, in Waste Treatment, and Clean Technology, The Global Symposium on Recycling, REWAS 04, Vol. II, Gaballah, I., Mishra, B., Solosabal, R., and Tanaka, M., Eds., Madrid, Spain, September 26-29, 2004. 

In addition to these three treatments, there are several alternative treatment technologies applicable to the treatment of common metals wastes. These technologies include electrolytic recovery, electrodialysis, reverse osmosis, peat adsorption, insoluble starch xanthate treatment, sulfide precipitation, flotation, and membrane filtration.1516... 

Wang, M.H.S., Granstrom, M.L., Wilson, T.E., and Wang, L.K., Removal of lignin from water by precipitate flotation, Journal of Environmental Engineering Division, Proceedings of the ASCE, 100 (EE3), 629-640, 1974. 

Liquid-solid distributions are involved in ion-exchange and other adsorption-based separation processes, separation processes based on crystallization or precipitation, flotation processes for ore dressing, and smelting processes. 

The objective of the work is to present an experiment-founded adsorption model for precipitate flotation. Batch precipitate flotation of CufOH) with dodecylbenzene sulphonate (DBS) as collector, was carried out both with dissolved (DAF) and dispersed (DIS) air. The processes were considered as a succession of the dynamic equilibria taking place at the gasliquid and solidliquid interfaces. Both flotation processes were expressed quantitatively in terms of surface concentrations of Cu(OH)2 and DBS per unit surface area of the air buble, as well as the ratio of the numbers of air bubbles and solid particles (B /P ). Also the maximal concentrations of both DBS and Cu(OH)2, recoverable under the given conditions were calculated. All these values were determined by following the Cu(OH)2 and DBS recovery. The 2 flotation techniques were compared in regard to their efficiency and mechanism. Finally, the results obtained were discussed in terms of the other models for the colloid particle adsorption at the air-water interface. 

The aim of this investigation has been to set-up a real model for precipitate flotation which would comprise adsorption processes at both the aicdiquid and liquid-solid interfaces, as well as some elements of fluid mechanics. All the parameters in the model have been determined experimentally. The initial concentrations of both DBS and Cu(0H)2 in the experiment have been varied in parallel. Recoveries of the Rotated species have been determined in order to calculate their real and maximal (theoretical) values for the surface concentrations. Formation of the particle-bubble aggregates has been monitored by determining the number and diameter of both the particles and air bubbles. The collector adsorption in the flotation systems has been studied via recovery of DBS itself on air bubbles, as well as in the presence of Cu(0H)2. 

Batch precipitate flotation with dispersed [10, 11] and dissolved [12 ]air has been carried out on a conventional laboratory set-up microflotation, adopting the procedures described earlier. The air flow rate in the flotation with dispersed air was 3 dm /h... 

The dependence of the values for surface concentrations of DBS in the presence > " in the absence ( dbS Cu(OH)2, on the initial DBS concentrations is depicted in Fig. 3. The figure actually shows the DBS separation in precipitate flotation in the presence of Cu(OH)2, as well as its recovery in the foam flotation. Surface concentrations of DBS obtained in the DAF system in the presence of Cu(0H)9 are about 10—30 times higher if compared to the DIS system. This is again the consequence of a smaller amount of air involved in the DAF system, which causes the total bubble surface to be lower. It is evident that the Tjjgg values in both systems are about 2—10 times lower from same time the recoveries of pure DBS are lower and... 

Flotation is the term used to describe a process in which the species being separated from the bulk liquid media are insoluble particulates. Froth flotation is another one of the two foam separation processes. It also involves the production of foam in a heterogeneous aqueous system, and has a great deal of potential for the water and wastewater treatment. Froth flotation can be subdivided into at least seven categories (42,43,84), including precipitate flotation, ion flotation, molecular flotation, microflotafion, adsorption flotation, ore flotation, macroflotation, and adsorbing colloid flotation. They are described separately below. 

One of the most important adsorptive bubble separation processes is nonfoaming flotation. The process is termed flotation because the species being separated from the bulk media are mainly or partially insoluble particulates, such as sludges or agglomerates. It is a nonfoaming process system in which no production of foam is involved. 3.2.3.I. Nonfoaming Precipitate Flotation... 

Potable water clarification and tertiary wastewater treatment (4—9) by dissolved air flotation cells are typical examples of nonfoaming precipitate flotation in which the... 

Type of flow pattern(s) involved in an adsorptive bubble separation system depends on the type of process used. For example, bubble fractionation involves two-phase (gas-phase and liquid-phase) bubble flow, while solvent sublation involves multiphase bubble flow in their vertical bubble cells. Foam fractionation involves a two-phase bubble flow in the bottom bubble cell, and a two-phase froth flow in the top foam cell. However, all froth flotation processes (i.e., precipitate flotation, ion flotation, molecular flotation, ore flotation, microflotation, adsorption flotation, macroflotation, and adsorbing colloid flotation) involve multiphase bubble flow and multiphase froth flow. 

E. J. Hahne and T. A. Pinfold, Precipitate flotation flotation of silver, uranium and gold, J. Appl.Chem. 19, 57-59 (1969). 

J. A. Lusher and F. Sebba, Separation of aluminum from beryllium in aqueous solutions by precipitate flotation, J. Appl. Chem. 16, 129-132 (1966). 

Ion flotation is a process in which metal ions are removed from dilute, aqueous solutions by interaction with dissolved, surface active organic collectors. The metal-collector complexes or ion pairs adsorb preferentially at solution-air interfaces, and hence can be removed by sparging air through the solution and separating the resulting loam." Precipitate flotation is a related technique in which an insoluble compound that is hydrophobic, or can be rendered so using... 

K. Sreenivasarao, Removal of Toxic Metals from Dilute Synthetic Solutions by lon-and Precipitate-flotation, Ph.D. dissertation. University of California at Berkeley, 1996. K. Sreenivasarao and F. M. Doyle, Decomposition of Heavy Metal-dodecylsulfate Complexes, Treatment and Minimization of Heavy Metal-Containing Wastes, J. P. Hagar, B. Mishra, C. F. Davidson and I. L. Litz (eds.), TMS, Warrendale, PA., 1995 pp. 3-14. 

Ions of precipitate particles are adsorbed or attached at the surface of bubbles rising through a liquid, and are thereby separated. A substance which is not surface-active itself can be made so through union with, or adherence to, a surface-active agent (surfactant). Froth flotation involves separation (pre-concentration) by frothing. If an insoluble product is formed in interaction between the ion to be separated and a surfactant, the process is called ion flotation. If the ion is first precipitated and the precipitate is then floated with or without the addition of a surfactant, the process is called precipitate flotation. Flotation is accomplished in a special cylindrical vessel provided with a sintered glass disk at the bottom to break the gas (nitrogen, air) stream into small bubbles [92]. 

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