As the most important gold extraction method today, the cyanidation process has the advantages of mature process, simple process, high recovery rate, strong adaptability to ore and low cost. However, the cyanidation process also has the disadvantage that the leaching cycle is too long. This is mainly because gold leaching process acts as a leachant CN - O 2 and reaches the diffusion rate from the liquid surface of the gold particles is relatively slow, resulting in slow response speed of the entire process. In recent years, the role of mechanical activation in strengthening hydrometallurgical processes has gradually gained attention. After mechanical activation of the mineral, the reactivity is enhanced, which greatly enhances the leaching process. At the same time, hydrogen peroxide and ammonia as research aids have also been reported at home and abroad. In this study, based on knowledge of the mechanical activation immersion gold process to a flotation gold concentrate containing copper were tested for the study objects, intended to gold leaching process to strengthen measures to carry out some exploration, so as to improve the efficiency of immersion gold Look for some new breakthroughs. First, the nature of raw materials and experimental research methods The cyanide immersion gold sample is a flotation gold concentrate, and the grades of Au and Ag are relatively high. The results of multi-element analysis of flotation gold concentrate are shown in Table 1. In addition, higher levels of pyrrhotite, marcasite and chalcocite, bornite belonging fast soluble iron cyanide and copper cyanide serious harm to the process. Table 1 Multi-element analysis results of copper-bearing gold concentrates (%) element Au Ag Cu Fe S Zn Pb content 57.8g/t 1020g/t 1.05 31.10 38.20 1.37 0.47 The main equipment of this test is XMQ- During the test, 100 g of the raw material was weighed and placed in a ball mill, and an appropriate amount of quicklime (adjusted to a pH of about 1) and a certain amount of sodium cyanide and/or hydrogen peroxide and/or ammonia water were added. Then, according to the test requirements, the mixture is immersed for a certain period of time, filtered after leaching, and the filtrate is subjected to non-toxic treatment, and the filter cake is dried by an electric drying oven. The leaching slag and the filtrate were analyzed by atomic absorption spectroscopy. After confirming the metal balance by calculation, calculate the leaching rate of gold by the following formula: Gold leaching rate (%) = (1 - leaching slag amount × gold grade in slag / original ore weight × grade of gold in raw ore) × 100 Second, the results and discussion (1) Conventional cyanidation immersion gold 100 g of the ore sample was weighed and placed in a ball mill, and 200 mL of water was added to grind fineness to 99.50% to 200 mesh. Then, it is taken out and placed in a stirring tank to be stirred and leached. The leaching conditions are a NaCN concentration of 0.25% and a pH value of about l1. The test results are shown in Figure 1. The conventional leaching gold leaching time is relatively long, the efficiency is relatively low, and the leaching rate reaches 47.74% after stirring for 24 hours. (2) Mechanical activation leaching According to the literature, mechanical activation can enhance the reactivity of minerals and strengthen the leaching process. If mechanical activation is used in cyanide immersion gold, it may solve the problem of long leaching time. Based on this, the author has conducted some research on the mechanical activation and leaching of gold. 1. Reference grinding test The effect of grinding time on mechanically activated immersion gold is shown in Figure 2. As the grinding time increases, the leaching rate of gold increases. The leaching rate of the 3 h gold immersion rate was 53.37%, which was 5.6% higher than the conventional leaching time of 24 h (the leaching rate was 47.74%). This is because the grinding tapered leaching mineral particles, gold particles are fully exposed, increasing the total surface area of gold, and its surface is always kept fresh, eliminating the insoluble impurities or hindered solid reactant film, CN - and O 2 easy Dispersion to the surface of the gold particles reacts with it, greatly enhancing the gold leaching process and improving the leaching efficiency. The effect of slurry concentration on immersion gold is shown in Figure 3. The concentration of pulp has a great influence on immersion gold, and the gold leaching rate increases with the decrease of slurry concentration. This is because the concentration of the solution decreases, the viscosity of the solution decreases, beneficial CN - and O 2 diffusion, gold leaching rate is increased. However, increasing the liquid-solid ratio requires a large-volume leaching device , and liquid-solid separation is difficult. Therefore, the liquid-solid ratio was selected to be 2:1 in the subsequent tests. The relationship between cyanide concentration and gold leaching rate is shown in Figure 4. The increase in sodium cyanide concentration has no significant effect on the gold leaching rate. According to the literature, when the ratio of cyanide concentration to dissolved oxygen concentration in cyanide leaching agent is 4.6-7.4, the dissolution rate of gold reaches a maximum. It can be seen that in the concentration range of sodium cyanide used in the test, the concentration of cyanide is higher than the concentration of oxygen, and the controlling factor is the oxygen concentration. To continue to increase the gold leaching rate, it is necessary to supplement the oxidant. 2. Research on aids In order to speed up the gold leaching rate, the German company Degussa proposed in 1987 a PAL process using H 2 0 2 as a liquid oxidant for cyanide leaching. The test was found by examining the application effect of hydrogen peroxide in the grinding process, as shown in Fig. 5. Adding an appropriate amount of hydrogen peroxide to the slurry can greatly improve the grinding efficiency and shorten the grinding time. However, due to strong oxidizing H 2 0 2, the excess of H 2 0 2 solution will CN - oxidized to cyanate useless, reduced CN - from the concentration of the gold dissolution rate slowed down, and the leaching of gold, There is also a small excess of H 2 O 2 , and these excess H 2 0 2 will destroy Au(CN) 2 - , resulting in a decrease in the amount of gold leaching. It can be seen that how to control the concentration of H 2 O 2 is the key to the assisted dip. Because the ore sample contains a large amount of chalcopyrite, as well as a small amount of porphyrite and chalcopyrite. They are all cyanide-soluble copper. In the process of cyanidation, they consume both cyanide and dissolved oxygen, which reduces the concentration of cyanide and oxygen in the solution, so that the dissolution rate of gold is reduced and the gold leaching rate is also reduced. Research and Practice has proved that: cyano - ammonia systems may be selectively leached from the gold in gold ores containing copper, i.e. copper with aqueous ammonia, cyanide ion and the CN - direct reaction with gold, thereby accelerating the dissolution of gold. The effect of the initial concentration of ammonia in the slurry on the immersion gold is shown in Figure 6. It can be seen from the figure that the addition of an appropriate amount of ammonia water to the slurry can greatly improve the grinding efficiency. This is because NH 3 preferentially complexes with copper, so that cyanide ions directly participate in the gold leaching reaction; coupled with the electrochemical catalysis of Cu(NH 3 ) 4 2+ , the gold leaching rate and gold are improved. Leach rate. However, the ammonia concentration is too high, which causes the pH of the slurry to increase, thereby affecting the leaching of gold. It can be seen from the above test results that the addition of an appropriate amount of ammonia water or hydrogen peroxide is beneficial to the leaching of gold. If the two are added to the cyanide system at the same time, it is possible to simultaneously achieve the assisting effect of the two, further increasing the leaching rate of gold. Figure 7 shows the effect of the initial concentration of sodium cyanide on the cyanidation immersion gold without the addition of a soaking agent, the addition of hydrogen peroxide, and the combined impregnation with aqueous ammonia. When assisted with H 2 O 2 , the concentration of sodium cyanide increases and the leaching rate of gold increases. This shows that after adding H 2 O 2 , the concentration of oxygen is increased, and the diffusion rate is controlled by the cyanide ion concentration, so the leaching rate of gold increases with the increase of sodium cyanide concentration. In the case of joint impregnation, the regularity is basically the same as when no infusion is used, but the leaching rate of gold is about 50% higher. Combined with the change of cyanide concentration under hydrogen peroxide assisted leaching, copper reacts with ammonia to release the cyanide ion consumed by the reaction, and the cyanide concentration is increased accordingly, and the electrochemical catalysis of Cu(NH 3 ) 4 2+ is added . Therefore, the leaching rate of gold is greatly improved. (3) Research on grinding and immersion immersion combined with immersion gold After 2 h of grinding, the grade of gold in the tailings was also higher (10.5 g/t), and about 30% of the gold was not leached. At this time, the leaching rate of gold is further reduced, the leaching rate of gold is relatively small, and the increase of leaching rate is not obvious, and the more refined, the greater the viscosity of the slurry, which makes it difficult to separate the noble liquid from the tail slag. Therefore, the authors proposed a grinding-stirring and immersion combined leaching process. The results of the grinding immersion-stirring immersion gold immersion test are shown in Fig. 8. Comparing the results of immersion for 1 h and grinding for 1 h without leaching agent, the effect of grinding immersion on the immersion-stirring immersion combined with leaching gold is particularly obvious. It is only immersed in the immersion. When the immersion is immersed, the surface of the gold particles loses its mechanical activation, the mineral reactivity decreases drastically, and the kinetic speed of immersion gold is lowered, so the gold leaching rate is low. It can also be seen from the figure that after grinding for 2 h, the stirring leaching rate is the smallest, the grinding immersion is 1 h, and the stirring leaching rate is the largest. This indicates that the grinding is related to the fineness of the ore. When the mineral grain is finer (ie, the longer the grinding time), the gold is fully exposed and the total surface area is increased, the leaching rate is increased; the leaching time is increased, and the corresponding leaching rate is high (as can be seen from the leaching rate with zero stirring time) Therefore, the longer the grinding time, the better. However, when the leaching is stirred, the finer the ore particles, the more the leaching rate and the leaching rate of gold are affected. This is because the longer the immersion time of the grinding, the fine ore particles, the more the impurity ion is also dissolved, with stirring leaching CN - O 2 and the reaction rate of reaction is greatly weakened and gold, and after thinning, the viscosity is increased, Thereby, the diffusion resistance of CN - and O 2 is increased, so the dissolution rate is lowered. Therefore, when using the impregnation-mixing immersion combination, it is necessary to pay attention to the fineness of the grinding to prevent the damage caused by the excessive smelting of the immersion gold. Third, the conclusion (1) The application of mechanical activation technology to cyanide immersion gold enhances the leaching process, thereby increasing the leaching rate and greatly reducing the leaching time. (2) Adding proper amount of hydrogen peroxide and ammonia water to the slurry can increase the leaching rate of gold and enhance the effect of mechanical activation and leaching. (3) The grinding immersion-stirring immersion combined with immersion gold not only eliminates the shortage of mechanical activation immersion time, but also overcomes the shortcoming of stirring immersion time. Greatly improved the efficiency of gold leaching. But be cautious in terms of time matching.
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The reagents used in the test were mainly sodium cyanide, quicklime, hydrogen peroxide and ammonia. Sodium cyanide is a chemically pure reagent and is added to a solution of a certain concentration when used. The quicklime is an analytically pure reagent and is used after grinding in a mortar. Ammonia water is a chemically pure reagent with a NH 3 content of 25% to 28% and a concentration of 0.9 g/mL. Hydrogen peroxide is an analytically pure reagent with a concentration of about 30% and a density of 1.1 g/mL. 
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