Flotation

It is generally accepted that the collector, potassium ethyl xanthate, will not float sphalerite. However, Gaudin showed that sphalerite readily floats if activated with certain metal cations before exposure to xanthate. Ralston and Hunter found that copper sulfate, is the best activator for sphalerite.

In recent years flotation reaction products formed on mineral surfaces have been analyzed by infrared techniques. Peck used the potassium bromide pellet technique to study oleic acid and sodium oleate adsorption on fluorite, barite, and calcite. Poling and Leja used the differential reflectance technique for studying the adsorption of xanthate on nickel surfaces. The Bureau of Mines used the internal reflection technique in conjunction with solvent extraction procedures to study the reaction of aqueous potassium ethyl xanthate on galena surfaces. In the internal reflection technique described by Harrick, a sample that selectively absorbs infrared radiation, when placed in contact with a reflecting prism, will produce an absorption spectrum that is characteristic of the material.

The objective of the research described in this paper was to determine the relationship between values of the pH of the collector solution and the amounts of the reaction products, cuprous ethyl xanthate and ethyl dixanthogen, adsorbed on sphalerite surfaces.

Experimental Materials and

The present investigation set out to study the individual flotation behavior of leached quartz, unleached hematite, and unleached calcite with anionic and cationic collectors. The flotation response of mixtures of the minerals taken two at a time was then determined, and finally the experiments were repeated for mixtures of all three. Obviously there exists in nature no other quartz-calcite-hematite mixture like it so that, even if the authors could explain the behavior of their artificial system, it would be of little avail. The investigation did, however, produce some interesting and controversial results.

Materials and Experimental Procedure

Quartz, from the Hardin Mine, Dixon, New Mexico, was leached in concentrated HCl for 48 hours and then washed thoroughly with distilled water. Oolitic hematite, from Clinton, New York, containing Al, Mn, Mg, and Ca as its chief contaminants, and calcite, from Magdalena, New Mexico, containing Al, Fe, Mn, and Mg as prime impurities, were used without leaching.

All minerals were wet ground in a pebble mill and screened to give a minus 65, plus 150 mesh fraction for flotation tests and a minus 150 mesh fraction for electrokinetic studies. After drying at room temperature, magnetic material was removed and samples were stored dry in

This article discusses the effect of physical and chemical modifications of starches on the anionic and cationic flotation of silica from oxidized iron ores and magnetite-taconite concentrates, and the results of the interaction of starch, pH, and calcium ions on the flocculation, clarification, and filtration of iron ore slimes and magnetite- taconite tailings. Starches, particularly when anionically modified, were found to be effective depressants in anionic silica flotation. British gums and dextrins were beneficial for oxidized iron ores, but none of the starches or starch derivatives appeared to have any effect on magnetite-taconite concentrates.

Anionic Silica Flotation

In the soap flotation of activated silica from iron ores a critical amount of starch addition exists beyond which flotation performance stabilizes. This critical amount of starch is dependent on the degree of grind and hence on the amount of slimes contained in the ore. With an ore sample essentially minus 325 mesh and containing approximately 50 to 55 percent iron, the critical amount of starch is about 4 lb per ton. This starch requirement contributes to a large portion of the total reagent cost, and it becomes of great interest to decrease this amount either through physical or chemical modification of the

Oxidation potentials have been measured in the presence of various concentrations of cyanide, ferrocyanide, and ferricyanide and ethyl xanthate at various values of pH and related to flotation response. Eh-pH diagrams are constructed and show that the formation of surface ferric ferrocyanide is probably responsible for depression when cyanide is added.

Experimental Materials and Techniques

Pure potassium ethyl xanthate was used as collector, and reagent grade potassium cyanide, potassium ferrocyanide, potassium ferricyanide were used as depressants. Reagent grade HCl and KOH were added for pH adjustment. Conductivity water, made by passing distilled water through an ion exchange column, was used in all of the experimental work.

Two pure samples of pyrite were used in the investigation. Sample preparation for flotation involved dry-grinding with a mortar and pestle and sizing the product to 100 x 200 mesh. Prior to flotation, a 0.75-gram sample of the mineral was added to a solution containing a known amount of depressant at the desired pH value, and the system was conditioned for four minutes. Following this, a known amount of collector was added and the system was conditioned for another four minutes. The pH was measured, termed flotation pH; the pulp was transferred to a Hallimond

The zero-points-of-charge of apatite, calcite, and fluorite are pH 6.4, 10.8, and 10.0, respectively. Scheelite is negatively charged above at least pH 3. Flotation responses of these minerals in the presence of potassium oleate and sodium silicate are presented and compared with electrokinetic data. Colloidal silica appears to be the species principally responsible for calcite depression, while silicate anion is the species responsible for fluorite depression. Additions as high as 1 x 10-³ mole/liter silicate have no effect on the flotation responses of apatite and scheelite.

Selective flotation of nonmetallic minerals is difficult to achieve with fatty acids or soaps by themselves. As a result, specific reagents are added to aid these separations, and one of the reagents commonly employed for this purpose is sodium silicate. Flotation separations of various calcium-bearing minerals such as fluorite from calcite and scheelite from calcite and apatite almost always involve the use of sodium silicate, for example.

Pure samples of apatite (Durango), calcite (Icelandspar), fluorite, and scheelite were used in this investigation. Pure potassium oleate was used as collector, while reagent-grade HCl and KOH were employed for pH adjustment.

The first series of experiments involved flotation of scheelite in the absence and presence of sodium silicate. Flotation

A fully-instrumented driving mechanism has been constructed to study the power, aerating and solid suspension characteristics of several laboratory flotation machines.

Machines operating over normal flotation speed ranges give constant power numbers in liquid systems indicating that they operate under fully baffled turbulent flow conditions. Owing to lack of geometrical scaling, power numbers for different sizes of cells of the same make are different. Even larger differences occur between cells of different manufactures. For a given impeller, varying the tank size did not significantly affect the power consumption. Tank geometry and baffling has a slight effect on power consumption with shrouded impellers.

Apparatus and Experimental Details

The driving mechanism was equipped with adapters for interchanging impellers and shroudings and several tank designs and sizes were available so that this unit could be converted from a simple agitator to any kind of laboratory flotation machine (Table 1). A strain gauge torque measuring device and a phototachometer were built into the driving mechanism, and speed variation was obtained by means of a DC motor with a rectifier and voltage regulator. These experimental facilities represented a considerable improvement over previous work in which power and speed were measured by means of a watt meter

The ores used in the investigation were obtained from the Aluminum Silicates, Inc., Washington, Ga., and the Commercialores, Inc., Clover, S. C.

The sample from Georgia contained kyanite and quartz with clay pyrophyllite, limonite, pyrite, and rutile. Petrographic examination showed that the kyanite was essentially; liberated between -35 and 48 mesh. In the screen sizes between 48 and 100 mesh a few of the, kyanite grains had small attachments of quartz.

The mineral constituents of the sample from South Carolina were kyanite, quartz, mica, clay, pyrite, limonite, and rutile. The kyanite was essentially liberated at 65 mesh. In the screen sizes between 65 and 200 mesh, a few of the kyanite grains had small attachments of quartz.

Petrographic analyses of the two samples are, given in table 1.

Experimental Results

Laboratory Batch Tests

Preliminary batch flotation tests were made of the two ores to determine the optimum conditions for separating the kyanite from the gangue minerals. The use of varying quantities and types of collectors and depressants, conditioning at different time and pulp solids, and varying the pH of the pulp were investigated. Results of preliminary tests led to adoption of

The gradual depletion of high-grade sulphide mineral deposits has turned the attention of the mineral industry to the recovery of metals from the oxides and silicates. Anionic (fatty acid) and cationic collectors have in some cases made flotation of non-sulphides possible, although in general, flotation of oxide ores is not as yet an economic process.

Sulphidization of Metal Oxides and Silicates

Sulphidization with hydrogen sulphide gas was carried out in a horizontal tube furnace (Fig. I). The temperature of the furnace was regulated by means of a Variac and determined with a chromel-alumel thermocouple. The constant temperature zone in the furnace was about 6″ in length, and it was within this zone that the experiments were carried out.

Samples of reagents or minerals, placed in a 3″ alundum boat, were inserted within the constant temperature zone of the furnace. Nitrogen gas (6 ppm O2 content) was passed through the tubes at room temperature to remove air in the tube, and continued to pass whilst the furnace was heating up. When the required temperature was reached, hydrogen sulphide was allowed to enter the tube and the supply of nitrogen was shut off.

Experimental Results

When H2S, either alone or with nitrogen, is

Because of the extensive surface area of oil droplets in emulsions, emulsion flotation offers possibilities for the recovery of finely divided mineral particles. Surfactants must stabilize the emulsion and possess an affinity for the desired minerals. Other important factors are the nature of the emulsion ingredients, the relative volumes of the continuous and discontinuous phases, the charge sign borne by the droplets of the oil phase, the zeta potential of the desired mineral, the soluble salt content the water-pulped and ground ores. At or near the isoelectric point or ZPC, the double layer about, the mineral-laden oil droplets is reduced in thickness and the droplets will coalesce and continue to aggregate into agglomerates. Inversion from O/W to W/O can occur depending upon a number of interrelated factors. Electrokinetic Instrumentation to measure, the ZPC, electrophoretic mobility, zeta potential and streaming current are invaluable in the application of emulsion flotation to metallic and no metallic minerals.

Background

In mineral separation, an emulsion is a mixture of two immiscible or partially miscible liquids and one or more surface active agents, one of which may or may not be a collector. When the continuous phase is water and the dispersed phase is a ‘neutral oil’ (petroleum