Copper miners

Both sodium sulfide and the bisulfide are used in the flotation process for copper minerals and as a depilatory for animal liides (see Copper Copper ALLOYS Leather). Also, sodium polysulfide can be produced from Na2S, and elemental sulfur can be produced if H2S is generated as an intemiediate. 

Copper ore minerals maybe classified as primary, secondary, oxidized, and native copper. Primaryrninerals were concentrated in ore bodies by hydrothermal processes secondary minerals formed when copper sulfide deposits exposed at the surface were leached by weathering and groundwater, and the copper reprecipitated near the water table (see Metallurgy, extractive). The important copper minerals are Hsted in Table 1. Of the sulfide ores, bornite, chalcopyrite, and tetrahedrite—teimantite are primary minerals and coveUite, chalcocite, and digenite are more commonly secondary minerals. The oxide minerals, such as chrysocoUa, malachite, and azurite, were formed by oxidation of surface sulfides. Native copper is usually found in the oxidized zone. However, the principal native copper deposits in Michigan are considered primary (5). 

The economics of some mines frequentiy depend heavily on the revenues derived from leaching the waste to recover additional copper. This waste material, which has to be removed to uncover the ore, may be hauled to specially constmeted dumps, where the sulfides, the most common form of copper mineral, are oxidized and the leach solution can contact the waste material uniformly. Economics sometimes precludes optimization of dumps for leaching operations because of such factors as compaction, size distribution, and terrain (16). 

Flotation reagents are selected to produce a stable froth and adjust the affinity of target minerals to collect in the froth. Other reagents depress the collection of minerals in the froth. The froth containing the copper minerals overflows into collection launders. 

Copper exists in crustal rocks at concentrations ranging from about 10 to a few hundred ppm, with 70 ppm being about average. In addition, at least 20 copper minerals have been identified, containing copper in the 0, +1, or -i-II oxidation state. These are primarily sulfides, hydroxides, and carbonates, of which chalcopyrite (CuFeS2), is most common. Copper is also foimd in relatively high concentrations in deep-sea ferromanganese nodules, in many cases at concentrations... 

Several copper minerals, containing copper in the divalent state, are completely soluble in sulfuric acid according to the following reactions ... 

CuFeS2 (chalcopyrite) is one of the most important copper minerals. Red /3-Cu2HgI4 and yellow )3-Ag2HgI4 (CdGa2S4 type) are thermochromic they transform at 70 °C and 51 °C, respectively, to modifications having different colors (black and orange) in these the atoms and the vacancies have a disordered distribution. 

A variety of mineral ores, mostly copper minerals such as malachite and chrysocolla, were probably the most used green pigments in the past. Various green minerals derived from metals other than copper, such as green earth (see below) were used in confined regions. 

The presence of various types of clay slimes also has a significant effect on flotation properties of oxide copper minerals [2],... 

In most cases, oxide copper ores contain more than one copper oxide mineral, and also contain mixtures of sulphide and oxide copper minerals. From a processing point of view, the oxide copper ores can be divided into the following five groups ... 

Copper oxide mixed ore - Type 1. The main copper minerals found in these ores include malachite, pseudo-malachite, chrysocolla and some tenorite. These ores also may contain mainly siliceous gangue minerals, including spherocobaltite as the main cobalt minerals. The carbonaceous types also contain an appreciable amount of clay slime minerals. 

Mixed copper sulphide oxide ores. These contain varieties of both sulphide and oxide minerals, and are the most complex copper-bearing ores from a beneficiation point of view. The major copper minerals present in this ore type include bomite, chalcocite, covellite, malachite, cuprite and chrysocolla. In some cases, significant amounts of cobalt minerals are also present in this ore. 

Flotation Properties of the Individual Copper Minerals and Mixtures... 

The flotation characteristics of the oxide copper minerals from natural ore are dependent on several main factors, some of which include the following ... 

Chemical composition and physical structure of the oxide copper minerals and the ionic composition of the slurry phase play important roles in the floatability of various oxide minerals. The oxide copper minerals are often porous, and in some cases, water soluble. Some of the oxide minerals tend to slime during grinding, and flotation of fine oxide minerals is rather difficult. 

The gangue constituents and their nature are sometimes determining factors in selection of a treatment process for beneficiation of oxide copper ores. Highly weathered ores usually contain a fairly large amount of slimes, which has a negative effect on the floatability of oxide copper minerals. Also, there is an appreciable difference in floatability between oxide minerals from carbonaceous and siliceous ores. 

The mechanical strength of the surface layers of many of the oxide copper minerals is weak. Therefore, flotation of oxide copper ores using sulphidization method, can improve by reducing turbulence and attrition within the flotation cell [3],... 

Floatability of malachite is one of the most important oxide copper minerals for production of copper from oxide ores using flotation. Extensive research has been carried out by a number of researchers [4-7] in which various flotation methods were examined. 

In the deposits where oxide cobalt is present, it is common to have oxide copper minerals. The cobalt is, therefore, recovered in a bulk copper-cobalt concentrate that is processed using a hydrometallurgical technique to produce separate copper and cobalt metals. Oxide... 

Flotation Practice in Beneficiation of Oxide Copper Minerals... 

The most preferred sulphidizer used in flotation of oxide copper minerals is Na2S 9H20. Other sulphidizers used in operating plants include NaHS and (NH4)2S. Actually, the selection of a sulphidizer is based on the consumption required for flotation of oxide copper from particular ore types. For example, in some cases the consumption requirement of NaHS is much higher than for Na2S. Figure 19.5 shows the effect of different levels of sulphidizer on the recovery of malachite using xanthate collector. 

As mentioned earlier in this chapter, the choice of collector is very much dependent on the type of copper minerals, as well as the type of gangue minerals present in the natural ore. If the ore contains siliceous gangue minerals, then various fatty acid modifications can be used as the principal collector in plant practice. Ores containing carbonaceous and dolo-mitic gangue minerals, where sulphidization method is used, xanthate collector is used as... 

The mixed sulphide oxide ores usually contain two or more oxide minerals, including cuprite, malachite and tenanntite. The sulphide copper minerals are represented by covellite and bomite. Examples of this type of operation are located in the former Republic of Zaire (Komoto, Dima 1 and 2 plants), and the Nchanga open pit plant in Zambia. 

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