At present, the gold mining industry sector still lacks in-depth research on gold- cobalt - arsenic concentrates. The authors studied the results of the gold-drill-arsenic flotation concentrate using the pyro-hydrometallurgical process. The process includes: two-stage calcination of the flotation concentrate (the first stage-decomposition roasting, the second stage-sulfation roasting), and the slag after the sulphation roasting is subjected to leaching and cyanidation of the leaching residue.
The basis for the treatment of such concentrates by the pyro-metallurgical process is that, in practice, it is most common to treat refractory gold-arsenic concentrates with this process, and for cobalt-containing arsenic sulfide products. Processing also has great practical significance.
However, in practice, arsenic removal is often used to remove arsenic from the original material prior to sulfation roasting. The biggest disadvantage is the ability to form a handsome acid salt, thereby reducing the processing efficiency of the next process. In addition, a large amount of arsenic-containing sulfur dioxide will be produced. To make full use of this part of sulfur dioxide, it will cost a lot.
The use of decomposing roasting without air is a promising method to improve the treatment effect of multi-metallic mineral raw materials, comprehensive utilization and reduce environmental pollution.
The flotation concentrate obtained from the selection of gold-drill-arsenic ore was studied under semi-industrial conditions. Chemical composition of concentrate, %: 9.3Si0 2 ; 1.2Al 2 O 3 ; 24.0Fe total ; 2.94 MSO; 4.66CaO; 1.02Cu; 32.0As; 1.13Co, 0.43Bi; 0.05Ni; 15.5S total, 1.58C organic . Concentrate grinding fineness is 92%-0.074 mm. Mineral analysis showed concentrate mainly pyrite and arsenic brass pyrite, magnetite, galena, covellite, sphalerite, pyrrhotite individual particulate form is present.
According to the analysis results of the micro X-ray spectroscopy analyzer, the main metal mineral - arsenic pyrite - is a variant of cobalt (including cobalt arsenite pyrite) with inhomogeneous cobalt isomorphous impurities, and the cobalt content fluctuates at 4.36~ Within the range of 7.41%. Studies by thermal graphic methods have shown that such ore-bearing variants of arsenopyrite are more difficult to oxidize than cobalt-free arsenopyrite. Therefore, it is difficult to completely remove arsenic from the concentrate during oxidative baking.
The calcination temperature is in the range of 490~730C, which can oxidize the concentrate most strongly. The carbonaceous material present in this concentrate has been shown to be capable of adsorbing active graphite . The phase analysis proves that 73.2% of the gold in the concentrate (present in the continuous and free state) can be dissolved by cyanide, and 24.96% of the gold is symbiotic with the sulfide (mainly arsenic pyrite), 1.84% gold. Associated with gangue.
Gold, cobalt and silver are industrially valuable components in flotation concentrates. The ratio of gold and silver in the concentrate is 1:1.2. Due to the complex composition of the concentrate, the presence of fine-grained gold (0.001~0.008 mm) and the presence of cobalt isomorphous impurities in arsenic pyrite and the high arsenic content (32%), such concentrates are extremely difficult to handle, Not suitable for processing in the conventional way.
The decomposition roasting of concentrates was investigated in a special laboratory setup (Fig. 1). The original concentrate 1 was placed in a quartz ampoules 2. Place the flask in the heating section 3 of the sublimator. The second part of the sublimator, the unheated half 4, is used to condense arsenic trioxide, which is the product of As vapors which are separated from the concentrate when oxidized by air. The isothermal device is heated by the nickel- chromium alloy resistance wire 6, and the degree of heating is adjusted by the varistor 8. A special device is used to cause the sublimator to perform a 360° C continuous reversible rotation in one direction and the other direction, thereby continuously mixing the concentrate.
The results of the study prove that the recovery of arsenic during the decomposition roasting process depends on the temperature, the sublimation time and the discharge value in the system. The optimum conditions for decomposition and calcination were determined as follows: the temperature in the sublimator was 760-780 ° C; the calcination time was 2 hours, and the negative pressure in the system was 0.1 × 10 5 Pa. The air consumed by arsenic vapor oxidation is 3 to 4 liters / minute.
The slag obtained at this time contains 2.82 to 3.37 As and 19 to 21.9 S. The recovery rates of arsenic and sulfur from concentrate to sublimate were 94.06~92.8% and 6.83~14.6%, respectively. The content of arsenic trioxide in the dissimilar materials was 99.21%.
The mineral analysis of the slag showed that the sulfur in the slag was monoclinic pyrrhotite (sulfur content 51.7~55.27 atomic %) and contained 0.37~3.45% impurities and 0.15~ arsenic impurities. 1.72%.
The reason for the incomplete sublimation of arsenic is the formation of orthorhombic arsenic in pyrrhotite. It is an iron arsenide (which contains 7.0 to 10.0% of cobalt) which is neither volatilized nor decomposed during decomposition and calcination. Sulfur in the form of sulfide (19~21.98%) is present in the slag. This eliminates the need for special sulfating agents in the next stage of roasting.
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