Experimental study on comprehensive recovery of acidified sediments from cyanide-containing waste liquid

I. Introduction

Gold producers in acidified waste treatment method in the cyanidation process, accompanied by a large amount of cuprous rhodanide precipitate. In addition to a large amount of copper, these precipitates still need to be comprehensively recovered from gold and silver . A 200t gold concentrate cyanide plant is processed daily, which can produce about 300t of this material in one year, including gold, silver and copper worth nearly 3 million yuan. Most of the companies producing copper thiocyanate precipitates are sold as by-products and are generally not recyclable. Therefore, it is very necessary to research and develop an advanced and reasonable comprehensive extraction technology, and it also meets the requirements of sustainable development of resource-based enterprises.

Second, the nature of the material

The cuprous thiocyanate material is gray or powdery. The results of spectral analysis, multi-element analysis and copper phase analysis of this kind of material in a mine in Shandong are shown in Table 1, Table 2 and Table 3.

Table 1 Material spectral analysis results%

Table 2 Material multi-element analysis results%

*Au, Ag units are g/t

Table 3 Material copper phase analysis results%

From the above analysis, it can be seen that the valuable components recoverable in the material are gold, silver and copper, and the copper is substantially completely produced in the form of cuprous thiocyanate.

Third, test equipment, equipment, reagents and methods

The leaching reaction vessel is a glass beaker; the stirring heating uses a stepless speed regulation magnetic stirring heater; the stirring strength is suitable for the vortex on the surface of the slurry, and the bottom is not deposited; the roasting adopts a muffle furnace, the air is an oxidant, and the material is manually turned; the reagent used It is chemically pure; unless otherwise specified, the calcination temperature is 650 ° C, and the calcination time is 60 min.

Fourth, test results and discussion

(1) Copper recycling

Because the combination of copper and thiocyanate ions in the material is very strong, it is insoluble in dilute sulfuric acid. Therefore, it is necessary to convert the copper in the material into a soluble oxide form before separating the copper.

1. Wet copper immersion exploration test

Are hydrogen peroxide, ferric chloride as the oxidant, potassium permanganate and nitric acid, sulfuric acid as the leaching agent, the test temperatures were room temperature and 85 ℃, to examine the rate of copper leaching. The results show that the above oxidant does not oxidize copper thiocyanate, the total leaching rate of the material is only 10% to 15%, and the amount of copper leaching is extremely small, which is not enough for copper collection.

2. Material roasting test

The results of the calcine test are shown in Table 4.

Table 4 Roasting test results

As the calcination temperature increases, the calcine yield gradually decreases. When the calcination temperature reaches 700 ° C, some sintering of the calcination occurs, which is not conducive to the recovery of gold, silver and copper. Data report: In the case that the calcining does not cause sintering, the greater significance after the temperature increase is that the iron in the calcining can form more magnetic iron oxide. Magnetic iron oxide is a relatively stable oxide. Compared with other structures, iron oxide, sulfuric acid has a small amount of leaching, which can create conditions for the production of qualified copper products in the later stage.

3. Calcine sulfuric acid immersion copper test

The single factor exploration test showed that the preferred operating parameters of the blasted copper were: liquid-solid mass ratio of 3.5:1, sulfuric acid mass fraction of 20%, leaching time of 3 h, and leaching temperature of 85 °C. The test calcine quality was 100 g. The test results are shown in Table 5.

Table 5 Test results of calcined copper sulfate

The higher the calcination temperature, the higher the yield of the leaching slag, but the key is that the iron impurities leached into the solution are low, which is advantageous for the subsequent production of qualified copper sulphate products.

In order to improve the copper recovery rate and further enrich the gold and silver, the 650 ° C produced calcine was subjected to a sulfuric acid dip test, and the operating conditions were the same as above. The test results are as follows: 100 g of a dross is poured, and the amount of slag after the second dipping is 53 g; after the second dipping, the slag yield is: 53% for one dipping, 8.0% for calcining, and 6.1% for raw materials. The main components in the second slag are: gold 767.1g/t, silver 2 236.5g/t, copper 10.22%, and iron 38.63%. The total leaching rate of copper was 98.0%.

4, copper products - biliary production test

There are many solutions for recovering copper products from copper sulfate solutions. This time, the production of cholesteric has been studied. The copper sulfate solution was the solution produced by the 650 ° C calcination leaching in Table 5. The test results are shown in Table 6, and the process flow is shown in Figure 1.

Table 6 Results of crystalline cholesteric test

The test results of copper in the residue after reduction of crystals with iron powder are shown in Table 7.

Table 7 Copper test results in iron powder reduction residue

The copper powder produced is slightly higher than the theoretical amount and is the result of a small amount of copper oxidation gain.

(2) Gold and silver extraction

1. Study on extraction of gold and silver by acid leaching

When leaching silver nitrate, the reaction temperature is 85 ° C, the leaching time is 5 h, 100 g of gold and silver materials are added, 300 ml of water is added, 40 ml of nitric acid is added, and 50 ml of dip is added. The conditions for the immersion of gold in the king are the same as above. The test results are shown in Table 8 and Table 9, respectively, and the process flow is shown in Figure 2.

Table 8 Results of nitrate leaching test

Table 9 Wangshui immersion gold test results

After the end of the Wangshui leaching, the final slag yield of the cuprous thiocyanate material was only 1.4%. The gold leaching rate reached 98.1%, and the index was good.

V. Conclusion

(1) After the oxidizing agent wet oxidation of thiocyanate cyanide, the results of the exploration test of leaching copper by sulfuric acid are not satisfactory, the yield of leaching slag is higher than 85%, and solid-liquid separation is very difficult, which does not reach the separation and extraction of copper. purpose.

(2) The effect of sulfuric acid immersion copper after oxidizing roasting is good, and the copper leaching rate is 98.0%. It is better to use the acid leaching index for the gold and silver in the sulfuric acid leaching residue. The leaching rates were 98.1% for gold and 98.9% for silver, and the final residue was only 1.4% of the original cuprous cyanide material.

(3) The quality of copper products can reach the level of first-class industrial products.