Bromine water + NaCl gold extraction process is a new method of gold cyanide-free extract. The method comprises calcining the gold concentrate to recover sulfur, and then leaching the gold with sodium chloride + bromine water, and the leached noble liquid controls the acidity of the hydrochloric acid to be 10%, and the gold is adsorbed by the foam plastic, and the gold has a gold production for the township enterprise. Very good economic and social benefits.
1) Gold leaching mechanism
The main role of sodium chloride is to provide sufficient chloride ions for the gold dissolution system. The reaction mechanism for dissolving gold using sodium chloride + bromine water system is as follows:
Br 2 +2e - ==== 2Br -
Au+4C1 - ==== AuC1 4 - +3e -
2Au+3Br 2 +8C1 - ==== 2AuC1 4 - +6Br -
2) Process The new process of sodium chloride + bromine water extraction is not suitable for the leaching of gold in sulfur-bearing gold concentrate. Because gold concentrate powder usually contains high sulfur content, gold concentrate must be calcined and pretreated to remove sulfur. The process flow is shown in Figure 1.
figure 1 
[next]
3) Gold concentrate powder roasting is carried out in accordance with a method of preparing sulfuric acid from a sulfur concentrate ore, usually in a special calciner. The calcination temperature is controlled at 600~650 °C, and the calcination time is determined by the amount of sulfur, which is generally 1 h.
4) Immersion gold method 1 direct leaching method. For mineral powder containing gold above 100g/t, it can be directly leached in the leaching tank. The leaching tank is made of hard plastic, and can also be leached by a cement tank. The shape is as shown in Fig. 2, and the size can be determined according to the scale of the design.
figure 2
2 continuous leaching method. For gold concentrate powders having a content of less than 100 g/t, continuous leaching may be employed. In the method, three leaching tanks are connected in series, a certain amount of calcine is added to each tank, and a leaching agent is supplied from the leaching liquid storage tank, so that the leaching agent penetrates into the baking sand layer from top to bottom by pressure. , controlling a certain percolation speed, so that the leachate continuously permeates the calcine in the second and third leaching tanks. The process flow is shown in Figure 3.
image 3 [next]
5) Foaming adsorption and release
The method of dynamic adsorption is to put the foam into a adsorption column of a certain diameter to control a certain flow rate, and the acidified noble liquid flows through the adsorption column, firstly washed with a mass fraction of 2% hydrochloric acid, and then washed with tap water to neutral. Elution was carried out using a mass fraction of 70 to 80 ° C of 0.05% sodium sulfite.
6) Reduction and smelting The eluted noble liquid was transferred to a 5000 mL large flask, placed on an electric furnace and heated to boiling, and a reducing agent A was added for reduction to obtain a sponge gold. After washing the obtained metal sponge, placed in 1% potassium nitrate and 2% borax was added to the graphite crucible by weight, the melting temperature in the furnace of 1250 deg.] C to prepare ingots.
7) Influencing factors 1 The effect of ore roasting on the leaching rate. The gold concentrate with a content of 32.50g/t was selected to test the effect of roasting time on the leaching rate. The results are shown in Table 1.
Table 1 Effect of ore roasting time on leaching rate | |||||
Roasting time / min | 3 | 30 | 60 | 90 | 120 |
Gold leaching rate /% | 0.15 | 0.4 | 98.4 | 99.8 | 99.9 |
It can be seen from Table 1 that the gold concentrate leaching rate is almost zero without calcination, and the leaching rate increases with the calcination time of the calcined ore sample, because the ore sample is calcined to make the ore. The sulfur and organic carbon, graphite and other substances in the sample are removed to expose the gold particles, which is beneficial to the solvent leaching of gold. The calcination and desulfurization operation is simple and rapid, and the calcination temperature in the calcination process is too high or the calcination time is too long, and the ore sample is easily sintered, so that the gold leaching rate is lowered. This is because sodium chloride + bromide water is a neutral solvent. is not easy to make sintered iron oxide is dissolved, hinder leaching for gold extraction, this can be a certain amount of hydrochloric acid added to improve solvency ore pair.
2 The effect of sodium chloride dosage on leaching rate. The relationship between the amount of sodium chloride and the leaching rate is shown in Table 2.
Table 2 Effect of sodium chloride dosage on leaching rate | |||||
Sodium chloride dosage / g | 0.5 | 1 | 3 | 5 | 10 |
Gold leaching rate /% | 93.9 | 99 | 99.1 | 99.3 | 99.2 |
It can be seen from the table that the amount of sodium chloride is 1 g, and the leaching rate of gold is 99.0%. For this experiment, 1 g of sodium chloride is used.
3 The effect of the amount of bromine water on the leaching rate. Bromine water is a strong oxidant. In a neutral solution medium, bromine can oxidize gold (0) to gold (III), and the resulting gold (III) forms a chloroauric acid anion with chloride ions and enters the solution. The effect of the amount of bromine water on the leaching rate is shown in Table 3.
Table 3 Effect of bromine water consumption on leaching rate | ||||
Bromine water concentration /% | 5 | 10 | 20 | 30 |
Gold leaching rate /% | 72.7 | 82.8 | 99.1 | 99.5 |
When the gold is recovered for the foam, the amount of the acid is reduced, and the volume of the fixed leachate is 10 mL. As can be seen from Table 3, the leaching rate of gold increases with the increase of the concentration of bromine water, and when the concentration of bromine water reaches 20%. The leaching rate of gold can reach 99%, so the solution with 20% bromine water concentration is used as the leaching solution. [next]
4 The effect of leaching time on the leaching rate. The impact test results are shown in Table 4.
Table 4 Effect of leaching time on leaching rate | ||||||
Dipping time / h | 2 | 4 | 8 | 12 | 18 | twenty four |
Gold leaching rate /% | 39.7 | 82.2 | 93.8 | 99 | 99.2 | 99.3 |
It can be seen from Table 4 that the leaching rate of gold gradually increases with the leaching time. When the leaching time is 12 h, the leaching rate of gold can reach over 99%.
5 acidity on the impact of foam and activated carbon recovery. In the medium with a mass fraction of 1% to 20% hydrochloric acid, the foam can quantitatively adsorb gold. To this end, a hydrochloric acid dosage test was carried out in a solution of gold leaching, and the results are shown in Table 5.
Table 5 Effect of the amount of hydrochloric acid on the adsorption of gold by plastic foam | ||||
Hydrochloric acid dosage / mL | 0.5 | 1 | 2.5 | 5 |
Gold leaching rate /% | 93.9 | 99 | 99.3 | 99.4 |
It can be seen from the table that in the solution of 10 mL of sodium chloride + bromine water leaching gold, 1 mL of hydrochloric acid (10% hydrochloric acid concentration) is added to the adsorption rate of gold by more than 99%, so it is added to the leachate. 1 ml of hydrochloric acid having a mass fraction of 10% is preferred.
The gold in the leachate can also be recovered by adsorption with activated carbon, but the amount of hydrochloric acid has a great influence on the adsorption rate of gold (see Table 6).
Table 6 Effect of the amount of hydrochloric acid on the adsorption of gold by activated carbon | ||||
Hydrochloric acid dosage / mL | 0.5 | 1 | 2.5 | 5 |
Gold adsorption rate /% | 53.4 | 78.5 | 95 | 99 |
As can be seen from Table 6, 5 mL of hydrochloric acid (33% hydrochloric acid) was added to 10 mL of the leachate, and the adsorption rate of activated carbon to gold was 99% or more.
Compared with the two methods, the use of foam plastic adsorption to recover gold has the following advantages: a) the presence of bromine water is favorable for the adsorption of gold by foaming, the adsorption rate can reach more than 99%; b) the lead which has an influence on the adsorption of gold by activated carbon, Interference ions such as ruthenium , osmium , and tungsten do not affect the adsorption of gold by the foam. Therefore, the selectivity is good and the adaptability to gold extraction is strong; c) the operation is simple and rapid, easy to release, and the ashing method and the sodium sulfite solution can be completely recovered; d) the amount of acid required for foam plastic recovery is small and the cost is low.
6 gold-loaded foam treatment method. The ashing method puts the gold-loaded foam into a 650 ° C high temperature furnace to enter the ashing and burning; the residue contains sponge gold, the gold residue is dissolved in aqua regia, and the mixed reducing agent A is used for reduction to prepare the finished gold. .
The sodium sulfite dissociation method is carried out by rinsing the gold-containing foam with tap water, and then releasing it with 0.05% sodium sulfite at 70-80 ° C, and the gold-containing release liquid is reduced by using a mixed reducing agent A to prepare a finished gold. The foam after release can be used repeatedly.
Acetone dissociation method Gold-loaded foam can be removed by acetone at room temperature, and acetone is recovered by distillation using gold acetone. The residue is gold powder. The foam after release can be used repeatedly.
Lapped Flange,Joint Flange,Lap Joint Flange,LJ Flange
Shandong Zhongnuo Heavy Industry Co.,Ltd. , https://www.zhongnuoflange.com