基于XRD和SEM的含碳微细粒金矿氧化焙烧机理研究

doi:10.3964/j.issn.1000-0593(2018)05-1592-07

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Abstract The carbonaceous fine-grained gold ore is one of the main types of refractory gold deposits in the world with huge reserves. The organic carbon and graphite in the ore can adsorb the cyanide complex in the solution, so the carbon-bearing gold ore needs to be pre-treated before leaching. Oxidation roasting is the best pretreatment process with the longest application time, the best reliability and the adaptability. It has been successfully used in the production practice. Traditional oxidation roasting method has the disadvantages of high production cost, complicated dust collecting system and so on. In recent years, domestic and foreign scholars have done a lot of research work on roasting process and equipment, and achieved fruitful research results, which has injected new vitality into the development of oxidation roasting technology. However, there are few researches on the theory of roasting and the research methods are relatively simple. Especially, the relevant theory of roasting process is relatively weak, which affects the development of roasting technology to a certain extent. Roasting time is the key factor that affects roasting, which determines the progress of chemical reaction and the degree of phase change. In this study, under different time conditions (roasting temperature 650 ℃), the carbon-containing fine-grained gold ores were roasted and leached. For the first time, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy spectrum analysis (EDS) and pore structure analysis were used to analyze and characterize the gold. Then the mechanism of the oxidation of carbonaceous material, the change of crystal structure and the change of phase on the gold leaching during the oxidation roasting process were also revealed. Process mineralogy study showed that the main minerals are quartz, dolomite, calcite, sericite, kaolinite, pyrite and graphite; The native gold in the ore is fine with the grain size of 5～10 μm, which is wrapped by quartz and carbonaceous debris. Carbonaceous (organic carbon and graphite carbon) has high content and fine grain size, and is closely associated with gangue minerals. The result of roasting-leaching experiment shows that the leaching rate of gold was only 12.50% when the raw ore was directly leached, and the role of “carbonaceous robbery gold” was significant. With the increase of roasting time, the leaching rate of gold first increased and then changed smoothly. When the roasting time was 2 h, the leaching rate of gold was the highest. When roasting time was 1 h, the reaction of dehydroxylation was occurred on sericite, kaolinite was decomposed into montmorillonite, the pyrite was oxidized to hematite, and carbonaceous (organic carbon and graphitic carbon) was oxidized and produced CO₂ but was not fully oxidized. At this moment, the d100 and d101 values and the average pore size of quartz were small, which was unfavorable to the diffusion of leaching agent, resulting in the gold leaching rate at only 58.09%. When the roasting time was 1.5 h, the dolomite began to decompose; the carbonaceous material has completely burned. CO₂ produced increased the number of micropores, which was conducive to the proliferation of leaching agent, so the gold leaching rate increased to 73.34%. When roasting time was 2 h, dolomite decomposed completely, and MgO was formed. The d₁₀₁ value of quartz reached the maximum (4.255 03 nm), the calcareous bulk density became higher; Furthermore, the pore volume and average pore diameter reached the maximum, which were respectively 0.009 954 cm³·g^-1 and 6.640 80 nm. The most pores produced in calcine increased the diffusion channel of leaching agent, which was beneficial to the gold leaching. The gold leaching rate also reached the maximum (91.28%). When the roasting time was 3 h, the surface of sample produced Ca₂SiO₄, CaSO₄ and so on which were easy to form low melting point material at high temperature, so weak sintering occurred. The micropores inside the particles were filled and closed, the micropores, the pore volume and the average pore size reduced. The internal structure became dense, which was not conducive to the proliferation of leaching agent, causing the decrease of the gold leaching rate.

Key words：Carbonaceous fine-grained gold ores; Oxidation roasting; Crystal structure; X-ray diffraction analysis(XRD); Scanning electron microscope (SEM)

Received: 2017-12-27 Accepted: 2018-03-12

ZTFLH:

TD953

Corresponding Authors: JIN Jian-ping E-mail: 117964815@qq.com; 276728309@qq.com

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2018)05-1592-07 OR https://www.gpxygpfx.com/EN/Y2018/V38/I05/1592

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