July 12, 2020

A simple method for determining the difficulty of gold leaching in ore

Gold ore can usually be divided into sulfide ore and oxidized ore. Due to the different mineralization conditions, mineral composition, and gold grain structure of the deposit, the difficulty of gold leaching in the ore is also different. To judge the difficulty of gold leaching in a mine ore and select an appropriate method for gold extraction, not only physical and chemical testing and analysis of the ore, but also multi-programming comparison and test research, time and labor.

After many studies, the Institute of Chemical and Metallurgy of the Chinese Academy of Sciences determined that the oxidant and acid can be consumed according to the leaching process of the ore, and the method of measuring the potential of the slurry at different leaching times by using the saturated potassium oxide calomel electrode is fast, within 24 hours. Economically and easily determine the difficulty of gold leaching in the ore of the deposit, and determine that it is suitable for leaching gold extraction with an acidic medium or an alkaline medium.

The method is to take 10g of a fine grinding ore sample representative of the mine, add 200mL of water to mix, and immerse the mixture for 1 hour at room temperature to measure the potential of the slurry once. Add an appropriate amount of 1:1 HCl to adjust the slurry pH = 1 to 2, and measure the second potential after 0.5h. Then, 2 mL of NaOCl was added, and 1:1 HCl was added to make the slurry pH=1 to 2, and the third potential was measured every 0.5 h. This was done until the potential reached 1.2 V or above and the test was terminated for 12 h. The measured potential values ​​were plotted and the amount of oxidant and acid consumed to stabilize the potential at 1.2 V or above was counted.

Figure 1 is a time-potential diagram of the oxidized ore test of the Zimuyu gold deposit. 10g ore sample only used NaOCl 2mL, HCl 1.7mL, reached 1.2V after 2h potential, and the potential measured in the process of adding oxidant and acid according to time has been stable at 1.2V for more than 12h, indicating that the ore is easy to dip. ore. Figure 2 shows the low-sulfur sulfide ore in the gold mine. Under the same test conditions, 18 mL of NaOCl and 7.7 mL of HCl were shared at 7.5 h. The potential did not reach 1.2 V at one time, and the curve was extremely unstable. . And from the two steps appearing on the curve, it is necessary to use a stronger oxidant for the leaching of the ore. The standard potential (SHE) of the oxidant must be greater than 0.6+0.24=0.84V. To this end, the tester leached the ore sample from the gold mine at 680 ° C and then leached it under the same conditions. The result was 2 h, consumption of NaOCl 2 mL, HCl 1.7 mL potential reached 1.2 V, and continued addition of oxidant and The acid potential has also been stable above 1.2V, and the plotted graph is similar to the time-potential map of the Zimuyu oxidized ore in Figure 1.

Fig.1 Oxidation time-potential diagram of Zimuyu gold ore

Fig. 2 Oxidation time-potential diagram of gold ore

It can be confirmed that when it is difficult to reach and maintain the potential of the dip ore, it is difficult to reach and maintain above 1.2V, and the highest consumption of NaOCl does not need to exceed 20mL. Because 10g of ore sample consumes so much oxidant, it is not economical in industrial production. A suitable method is needed to pre-treat the ore to change the "difficult" nature of the ore.

Experimenter Ya it also refractory ores and other mining carbon, arsenic sulfide-containing ore samples, containing respectively added KMnO4 0.2mol / L in the solution, the solution quickly faded, such fading the solution described ore Has a strong reducing properties. Therefore, the experimenter suggested that these refractory ore (Carlin-type ore) with reduced properties be referred to as "reduced" ore to distinguish between oxidized ore and easily immersed sulfide ore.

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