Mineral particle

Prior to about 1920, flotation procedures were rather crude and rested primarily on the observation that copper and lead-zinc ore pulps (crushed ore mixed with water) could be benefacted (improved in mineral content) by treatment with large amounts of fatty and oily materials. The mineral particles collected in the oily layer and thus could be separated from the gangue and the water. Since then, oil flotation has been largely replaced by froth or foam flotation. Here, only minor amounts of oil or surfactant are used and a froth is formed by agitating or bubbling air through the suspension. The oily froth or foam is concentrated in mineral particles and can be skimmed off as shown schematically in Fig. XIII-4. 

The importance of the thin film between the mineral particle and the air bubble has been discussed in a review by Pugh and Manev [74]. In this paper, modem studies of thin films via SFA and interferometry are discussed. These film effects come into play in the stability of foams and froths. Johansson and Pugh have studied the stability of a froth with particles. Small (30-/ m), moderately hydrophobic 6c = 65°) quartz particles stabilized a froth, while more hydrophobic particles destabilized it and larger particles had less influence [75]. 

The flotation process is based on the exploitation of wettabiUty differences of particles to be separated. Differences of wettabiUty among soHd (mineral) particles can be natural, or can be induced by the use of chemical adsorbates. Because the largest segment of industrial appHcations is conducted in water, with air, the following discussion is confined mainly to these fluids. 

The ore is ordinarily ground to pass through a ca 1.2-mm (14-mesh) screen, mixed with 8—10 wt % NaCl and other reactants that may be needed, and roasted under oxidising conditions in a multiple-hearth furnace or rotary kiln at 800—850°C for 1—2 h. Temperature control is critical because conversion of vanadium to vanadates slows markedly at ca 800°C, and the formation of Hquid phases at ca 850°C interferes with access of air to the mineral particles. During roasting, a reaction of sodium chloride with hydrous siUcates, which often are present in the ore feed, yields HCl gas. This is scmbbed from the roaster off-gas and neutralized for pollution control, or used in acid-leaching processes at the mill site. 

Figure 18-82 illustrates the relationship between solids concentration, iuterparticle cohesiveuess, and the type of sedimentation that may exist. Totally discrete particles include many mineral particles (usually greater in diameter than 20 Im), salt crystals, and similar substances that have httle tendency to cohere. Floccnleut particles generally will include those smaller than 20 [Lm (unless present in a dispersed state owing to surface charges), metal hydroxides, many chemical precipitates, and most organic substances other than true colloids. 

In the D-R Denver machine (Fig, 19-7,5), the pulp enters the top oF the recirculation well A, while the low-pressure air enters through the air passage B. Pulp and air are intimately mixed and thrown outward bv the rotating impeller C through the stationaiv diFFiiser D. The collector-coated mineral particles adhere to be removed in the Froth product. 

Nitric oxide may induce deleterious effects when airway epithelial or immunological cells are exposed to mineral particles (asbestos, quartz). These particles also stimulate cells to produce NO in large quantities, but pulmonary cells are unable to destroy these particles, and a non-physiologically excess production of NO results, perhaps causing tissue damage due to a reaction of NO with cellular macromolecules. 

These experimental data may, presumably, be attributed to the fact that the so-called juvenile surfaces are formed as a result of filler breaking. In the review [22] it is noted that juvenile surfaces enhance the filler-polymer interactions even to the latter s grafting to the mineral particle surfaces. 

A chemical agent having the ability to lift, separate, and maintain in suspension a variety of mineral particles for a limited period. 

The amount of particulate matter varies from very high values in silt carrying rivers (the Mississippi River carries an average of 2600 mg/liter at flood time) to practically zero (0.05 mg/liter ref. 17) in the ocean. A typical value may be 1-10 mg/liter. The mineral particles often consist of clay with ion exchange properties. 

In the flotation process, surfactant-coated mineral particles float to the surface of the mixture, where they become trapped in the froth. The gangue settles to the bottom. 

A few studies on grain size of minerals in midoceanic ridge chimneys have been published. Feely et al. (1987) described the grain size of mineral particles in the smoke and sediment samples from southern Juan de Fuca Ridge. They report the following grain sizes sphalerite 0.3-100 p.m in diameter (usually less than 20 p.m) pyrite 0.1-10 p.m Fe-Si, Ca-Si phases 5-150 p.m. Converse et al. (1984) reported the grain size... 

It is worth elucidating mineral particle behavior in hydrothermal plumes in order to consider the formation mechanism of chimney and massive ores on the seafloor. Using the grain size data on sulfides and sulfates, the density of the fluids and of the minerals, the relationship between vertical settling rate and grain size of sulfides and sulfates can be derived based on the following Stokes equation ... 

The above summarized mineralogical and geochemical studies on Kuroko and Mariana chimneys (Shikazono and Kusakabe, 1999), and previous studies on midoceanic ridge chimneys, combined with the studies of mineral particle behaviors in the plumbing system, are used to develop the following plausible model for the growth history of sulfate-sulfide chimneys on the seafloor (Shikazono and Kusakabe, 1999). 

The development of specific and reliable analytical procedures for the detection, location, and quantification of mineral particles in biological tissues (Henderson and Barr, 1988) has provided both the experimental techniques and additional evidence for detecting aluminosilicates in Alzheimer brains (Singhrao et al., 1990). The association of asbestos-related disease with severe... 

Sedimentary rocks have formed as a result of accumulation and compaction of mineral particles derived from pre-existing rocks, transported from their original places of occurrence and deposited in new environments. The essential ingredients for the formation of sedimentary rocks are (i) source materials, (ii) mechanical and chemical disintegration of these source materials, (iii) transportation of the released materials either in a clastic form... 

---