Currently, the world's gold reserves in more than 213 difficult process ore, gold production 1/3 from refractory ore. With the depletion of easily leached gold ore resources, the development and utilization of refractory gold ore with fine granules and high sulphur and high arsenic has become a major trend.
The high sulfur and high arsenic gold concentrate mineral composition is very complicated, gold is often wrapped in other minerals, and the gold leaching rate is very low. In order to develop such resources, it is necessary to carry out process mineralogical research. For the analysis of refractory gold mineral phases, the predecessors have done a lot of work, but more focused on a certain research method, such as X-ray diffraction analysis. These methods are able to determine the phase composition of the ore, but cannot observe the state of the mutual wrapping. In this paper, X-ray diffraction analysis, mineral dissociation analysis and scanning electron microscopy and energy spectrum analysis are used to determine the phase composition of high sulfur and high arsenic refractory gold concentrate, and to observe various phases. The state of occurrence, in order to provide guidance for exploring the gold extraction process of high-sulfur and high-arsenic refractory metallurgical concentrates.
First, the experiment
(1) Source of raw materials
The gold concentrate used in the experiment was taken from a gold smelter in Henan. The sample was further pulverized to 50 to 335 μm using a small pulverizer (FW-400A type, Beijing Zhongxing Weiye Instrument Co., Ltd.). The cyanide leaching rate of gold was found to be 26.95%. According to the grade of the gold mine, it is a refractory gold concentrate. In this paper, chemical minerals analysis, X-ray diffraction analysis, mineral dissociation analysis, scanning electron microscopy and energy spectroscopy are carried out to study the process mineralogy.
(two) test method
1. X-ray diffraction analysis (XRD)
The gold fine mineral phase composition was measured by a D/max-rB type X-ray diffractometer (Japanese physics).
2. Mineral Dissociation Analysis (MLA)
The mineral structure and composition of gold concentrates were studied using a mineral dissociation analyzer (FEI.Quanta 600. JKtech MLA suite 2008).
3. Scanning electron microscopy-energy spectroscopy (SEM-EDS)
X-ray scanning micro-analysis of gold concentrates was performed using a JSM-5600 LV scanning electron microscope (Japan Electronics) and an IE 300 X EDS spectrometer (Oxford, UK).
Second, the results and discussion
(1) Analysis of chemical composition
The chemical composition (mass fraction) of gold concentrate was determined by flame atomic absorption spectrophotometry (atomic absorption spectrophotometer, AA320 type), as shown in Table 1. The gold concentrate contains 13.91% S, containing 16.6% of Fe and 7.54% of As. It is a typical high-sulfur and high-arsenic gold concentrate.
Table 1 Gold concentrate elemental composition
Remark: Au and Ag units are g·t -1 .
(2) Mineral phase composition
1, XRD analysis
The phase composition of the sample was determined by X-ray diffraction. Figure 1 shows the XRD pattern of the gold concentrate. As can be seen from Figure 1, gold concentrate containing quartz, pyrite, arsenopyrite, white mica, chlorite, and calcite, the main phases of arsenopyrite, pyrite, quartz and muscovite.
Figure 1 Gold concentrate XRD pattern
2, MLA analysis
Figure 2 is an MLA diagram of gold concentrate particles. Table 2 shows the particle size distribution characteristics of gold concentrate. It is known from Table 2 and Figure 2 that the main metal minerals are arsenopyrite and pyrite, and the gangue minerals are mainly quartz and muscovite. Figure 2 shows that gold-independent particles cannot be observed, and gold can be leached by cyanidation experiments, indicating that gold is present in gold-bearing minerals in invisible gold states such as submicroscopic gold and ultramicroscopic gold. Such ore cannot be exposed to gold particles even if it is extremely fine. At the time of cyanidation, the gold particles cannot be exposed to the cyanide-containing solution, and the gold cannot be dissolved. It can also be seen from Fig. 2 that in the refractory gold concentrate, the distribution of various minerals is uneven, and the typical features are that the poisonous sand and the pyrite are intertwined, and the gangue such as quartz also wraps other minerals. Therefore, the pretreatment method must be carefully designed to destroy the gold-bearing minerals and expose the gold to maximize the gold leaching rate.
Figure 2 MLA diagram of gold concentrate particles
(a-pyrite; b-toxic sand; c-quartz; d-black mica; e- muscovite)
Table 2 Mineral size distribution characteristics of gold concentrate /%
3. SEM-EDS analysis
Scanning electron microscopy and spectrometers combine the selection and measurement of microdomains. Figure 3 shows the secondary electron map (SE) of the surface morphology of the gold concentrate and the position of the line scan from which the line scan distance can be estimated to be approximately 10 μm. As can be seen from Figure 3, the distribution of silicon and oxygen, sulfur and iron, arsenic sulfur and iron in the gold concentrate is closely related on the scan line, but gold independent particles are still not observed. This is consistent with the previous XRD test results and MLA analysis, further proof that the main components of the mine are pyrite, arsenopyrite and quartz, and gold is present in the gold-bearing minerals in an invisible gold state.
Figure 3 The surface morphology of the gold concentrate, the secondary electron map and the position of the scan line
Third, the conclusion
Through the elemental analysis, XRD analysis, MLA analysis and SEM-EDS analysis of high sulfur and high arsenic gold concentrate, the following conclusions are drawn:
(1) The gold content of gold concentrate is 47.5g·t -1 , Ag 8.46g·t -1 , S 13.91% (mass fraction), As 7.54% (mass fraction), and the gold leaching rate is only 26.95%. Typical high sulfur and high arsenic refractory gold concentrate.
(2) The main metal minerals in gold concentrates are arsenopyrite and pyrite. The gangue minerals are mainly quartz and muscovite. In gold concentrates, the harmful components are mainly arsenic, and the arsenic-containing minerals are in the form of arsenopyrite. Gold is present in gold-bearing minerals in the form of invisible gold.
(3) A variety of minerals are wrapped with each other. Pretreatment methods must be carefully designed to destroy the gold-bearing minerals and expose the gold to maximize the gold leaching rate.
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