Chlorination gold extraction production practice

I plant using an aqueous solution of chloride purification of gold two years of production proved from electrolytic silver anode mud, the process design is successful, the actual situation of our plant, our plant will help improve economic efficiency.

First, the process

(1) Raw material requirements: After the silver electrolysis anode mud is sieved and sorted out, the hot residue is washed to neutral with hot water. The chemical composition is (%): Au 51.29, Ag 51.29, Ag 31.27, Cu 1.69, Pb 1.87, Bi 7.63.

(2) The process flow is shown on the right.

Silver anode mud chlorination gold extraction process diagram

Second, production practice

(1) Aqueous solution chlorination: The silver anode mud is slurried in a chlorination tank according to a liquid-solid ratio of 6 to 10:1, the slurry contains hydrochloric acid 3 mol/L, and the anode mud is added to a weight of 10% to 15% NaCl. Before preparing the slurry, the stirring should be started first, and steam is heated at the same time. When the temperature reaches 80 °C, the chlorine gas is passed, and the chlorine gas process temperature is controlled by 80 to 90 °C. After 24h, the slag sample was observed. If the slag completely turned white, it indicated that the chlorination had reached the end point, stopped the chlorine, and then chlorinated for 8 hours, then stood still for 8 hours, naturally filtered, and the filter residue was washed with 3 mol/L hydrochloric acid until colorless. The filter residue and wash water are pumped to the high level tank using a vacuum pump. Gold is introduced into the solution in the form of tetrachloroauric acid by the chlorination process, and silver forms silver chloride into the slag, thereby achieving separation of gold and silver. Chlorochlorinated liquid component (g/L): Au 49.13, Ag 0.088 g, Cu 1.73, Pb 1.96, Bi 7.75. Chlorine slag component (%): Au 2.48, Ag 69.89, Cu none, Pb 0.025, Bi 0.021.

(2) Neutralization: Put the chlorinated liquid into the neutral tank from the high level tank, start stirring, and simultaneously heat the steam. When the temperature reaches 70-80 °C, slowly add saturated sodium hydroxide solution for about 2h. When the pH reached 2, the addition was stopped and stirring was continued for 1 h. After the neutralization, the liquid was naturally filtered overnight, and the residue was washed with dilute hydrochloric acid of pH 2.0 until the washing liquid was colorless, and the filtrate and the washing liquid were pumped to the high tank by a vacuum pump. The composition of the liquid after neutralization (g/L): Au 43.76, Ag 0.01, Cu 1.06, Pb 0.95, Bi0.01. Neutralization slag composition (%): Au 0.94, Ag 0.004, Cu 0.28, Pb 5.34, Bi 35.51.

(3) Reduction of oxalic acid: The neutralized liquid is placed in a reduction tank and heated by steam. When the temperature reaches 80-90 ° C, oxalic acid is added in batches. The amount of oxalic acid added is 2.5 to 3 times the amount of gold in the solution. After the addition of oxalic acid, the mixture was kept warm for 1 hour, and then settled statically for 2 to 3 hours. The supernatant is aspirated, the gold powder is washed with water, and the combined solution and the washing water are combined to recover gold, platinum and palladium . After the reduction, the liquid component (g/L): Au 1.12, Ag 0.01, Cu 0.051, Pb 0.90, Bi 0.01.

(4) Gold powder washing

1. Hydrochloric acid washing: Put the gold powder into the reaction tank, add 6mol/L analytical pure HCl according to the solid-liquid ratio 1:3~5, heat it by 80°C or more, and wash it for 2~3h under manual stirring. The supernatant was scooped out, washed with distilled water to neutral powder, washing lotions and replacing the recovery of gold with zinc powder, powder feed nitric acid wash. Washing liquid component (g/L): Au 0.122, Ag 0.044, Cu 1.58, Pb 0.115, Bi 0.003.

2. Nitric acid washing: Put the gold powder into the reaction tank, add 10mol/L analytical pure HNO3 solution according to the solid-liquid ratio 1:3~5, heat it by 80°C or more, and wash it for 2~3h under manual stirring. The supernatant is decanted, washed with distilled water until neutral, and the washing liquid and washing water are replaced with zinc powder to recover gold, and the gold powder is sent to ammonia washing. Washing liquid component (g/L): Au 0.219, Ag 0.0003, Cu 1.32, Pb 0.005, Bi 0.001.

3. Ammonia water washing: Put the gold powder into the reaction tank, add concentrated analytical ammonia water according to the solid-liquid ratio 1:3~5, stir at room temperature for 2~3h, and remove the supernatant. The filtrate contains Au<0.0004g/L. Discard. The gold powder is washed with distilled water until neutral, washed and discarded, and the gold powder is steam-dried in the reaction tank for 1 to 2 hours, placed in a porcelain plate, and sent to dryness. Washing liquid component (g/L): Au 0.0001, Ag 0.006, Cu 3.3, Pb 0.0003, Bi 0.003. Gold ingot composition (%): Au 99.7, Ag 0.002, Cu 0.02, Pb 0.001, Bi 0.0005, Fe 0.005, Sb 0.001.

Third, economic and technical indicators

The main indicators are as follows:

Chlorinated slag contains Au<2.5%

Gold recovery rate of 99.8%

Material consumption (kg/kgAu):

Chlorine 2 analytical pure HCl 1.5

Caustic 3 Analytically pure HNO ₃ 1.5

Industrial hydrochloric acid 10 Analytically pure NH ₃ ·H ₂ O 1.5

Oxalic acid 3

(1) Copper is the main factor affecting the quality of gold powder

During the reduction of oxalic acid, copper precipitates in the form of copper oxalate, which seriously affects the quality of the gold powder. Although the gold powder is washed with water, pickled and washed with ammonia, the gold powder formed during the reduction of oxalic acid often aggregates a large amount of copper impurities and is not easily broken, which causes great trouble for washing. Therefore, starting from the silver electrolytic anode mud washing, the copper is reduced to the left and right, reducing the copper contained in the raw material entering the chlorination system, so that the amount of copper oxalate precipitated during the reduction of oxalic acid is greatly reduced, and the quality of the gold powder is ensured.

(2) Gold powder washing costs are high

The chlorination and gold extraction process of the ice solution, the processing cost of the gold powder is about the yuan salt, and the gold powder washing cost is about. Chemical purity or industrial purity should be used instead of analytical purity, and unnecessary washing procedures should be appropriately removed.

(3) Treatment of chlorinated slag and neutralized slag

Our factory returns the chlorinated slag and neutralized slag to the silver furnace for smelting, and the loss of gold and silver is relatively large. There are two ways to reduce the loss of gold and silver: one is to replace the chlorinated slag and the neutralized slag with iron in a hydrochloric acid medium, so that the silver chloride becomes crude silver powder and then returns to the silver furnace; the second is to chlorinate And the neutralization slag is alkali-converted to convert silver chloride into silver oxide, then washed with water until no Cl ^- , then dissolved with nitric acid, the solution is returned to silver electrolysis, and the slag is returned to chlorination.

(4) The gold content in the slag is high

After the anode mud is chlorinated, the gold content of the slag is generally above, which affects the direct yield of gold. The reason for the high gold content is that the strength of the stirring in the chlorination process is not enough, so that the large particle material is deposited on the bottom of the cylinder; the second is insufficient artificial stirring force, the washing water temperature is low, and the washing time is small.

V. Conclusion

1. The investment in the aqueous solution chlorination method is small, and the precious metal has a small backlog. After the reduction liquid is replaced by the zinc powder, the tail liquid contains gold to a pressure of 0.0004 g/L, which can be discharged.

2, a simple method is an aqueous solution of chloride, technical conditions easy to control, can be stably produced 1 ^# 2 ^# gold gold.

3. The use of aqueous chlorination instead of traditional gold electrolysis can revitalize a large number of assets and improve economic efficiency.

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