A method for reducing mercury content in precious liquid of gold smelting

Abstract

The present invention belongs to the technical field of gold smelting, and proposes a method for reducing the mercury content in the precious liquid of gold smelting. First, the mercury content in the precious liquid of gold smelting to be treated is determined, and then sodium diethyldithiocarbamate and a composite sulfur slow-release agent are added to the precious liquid in sequence, and the reaction temperature is controlled to be 25°C to 35°C, and the stirring speed is 150 rpm to 250 rpm to react for 2 hours to 4 hours; the composite sulfur slow-release agent is prepared from calcium sulfoaluminate, modified silica gel and nano-carbon tubes; finally, the precious liquid is filtered and separated. The present invention adopts a new composite sulfur slow-release agent, which can intelligently regulate the release rate of sulfur ions according to the ion concentration environment in the precious liquid, and at the same time add a specific ion selective promoter to accurately guide the sulfur ions to preferentially combine with mercury for precipitation, thereby effectively reducing the mercury content without affecting the gold and silver extraction rates in the precious liquid.

Description

Technical Field

[0001] The invention belongs to the field of gold smelting, and relates to a method for efficiently reducing the mercury content in precious liquid of a gold smelting water system. Background Art

[0002] In the gold smelting process, ore generally contains impurities such as mercury. After leaching and other processes, mercury enters the precious liquid. The presence of mercury in the precious liquid brings many challenges to the subsequent extraction of gold and silver. On the one hand, mercury is prone to react undesirably with the reagents used to extract gold and silver, reducing the extraction rate of gold and silver; on the other hand, mercury-containing precious liquid will cause environmental risks during subsequent treatment and pollute the soil and water after discharge.

[0003] At present, there are many shortcomings in the methods of reducing the mercury content in precious liquid. Some methods will still affect the extraction rate of gold and silver while removing mercury. Some methods also have disadvantages such as complex operation and high cost. The Chinese invention patent application with publication number CN109154033A discloses a "method for separating mercury from ore leachate". Its main technical measures are: adding a precipitant to the ore leachate, the precipitant includes a dithiocarbamate / salt polymer, a thiocarbamate / salt compound or a mixture thereof; adding a coagulant to the ore leachate to form a distributed composition, the coagulant includes Fe 3+ 、Al 3+ or a mixture thereof; and the mercury-containing precipitate is separated from the distributed composition to form the treated ore leachate. Its main disadvantages are: (1) The synergistic effect of the precipitant and the coagulant is poor: although the precipitant and coagulant added in this method can separate mercury, the synergistic effect of the two in practical applications is not ideal. The process of precipitation of the precipitant dithiocarbamate / salt polymer, thiocarbamate / salt compound and mercury is easily interfered by other impurity ions in the precious solution, and the Fe contained in the coagulant 3+ 、Al 3 + In the process of promoting precipitation and coagulation, side reactions will occur with some components in the precious liquid, affecting the overall mercury removal effect and resulting in unstable mercury removal rate. (2) High risk of gold and silver loss: Since the selectivity of the precipitant and coagulant for mercury is not strong enough, it is easy to react or co-precipitate with precious metals such as gold and silver during the precipitation of mercury. This not only reduces the extraction rate of gold and silver, but also increases the difficulty and cost of subsequent gold and silver recovery, resulting in waste of resources. (3) High subsequent treatment cost: After the formed mercury-containing precipitate is separated from the distributed composition, the treatment of the mercury-containing precipitate is difficult and prone to secondary pollution. At the same time, the separation process may require the use of specific equipment and processes, which increases equipment investment and operating costs. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for reducing the mercury content in the precious liquid of gold smelting, further reducing the mercury content in the precious liquid, reducing the influence of mercury on the extraction rate of gold and silver, improving the efficiency and quality of gold smelting, and reducing environmental pollution.

[0005] The technical solution of the present invention is as follows:

[0006] A method for reducing the mercury content in gold smelting precious liquid comprises the following steps:

[0007] (1) Determine the mercury content in the gold smelting precious liquid to be treated;

[0008] (2) adding sodium diethyldithiocarbamate and a composite sulfur slow-release agent to the precious liquid in sequence, controlling the reaction temperature to be 25°C to 35°C, and stirring at a speed of 150 rpm to 250 rpm for a reaction time of 2 to 4 hours; wherein the mass of sodium diethyldithiocarbamate added is 25% to 45% of the mass of mercury in the gold smelting precious liquid to be treated; wherein the composite sulfur slow-release agent is prepared from calcium sulfoaluminate, modified silica gel and carbon nanotubes in a mass ratio of (2.5 to 3.5): (1.5 to 2.5): 1; and the mass of the composite sulfur slow-release agent added is 90% to 110% of the mass of mercury in the gold smelting precious liquid to be treated;

[0009] (3) Filter and separate the precious liquid after completing the reaction in step (2).

[0010] Preferably, the preparation method of the composite sulfur slow-release agent is: firstly, calcium sulfoaluminate and modified silica gel are mixed and stirred at 55-65° C. for 30-90 minutes, and then nano carbon tubes are added and stirred and reacted for 90-150 minutes.

[0011] Preferably, the added mass of the sodium diethyldithiocarbamate is 38% to 40% of the mass of mercury in the gold smelting precious liquid to be treated.

[0012] Preferably, the preparation method of the composite sulfur slow-release agent is as follows: the amount of the composite sulfur slow-release agent used is 97% to 98% of the mass of mercury in the gold smelting precious liquid to be treated.

[0013] Preferably, the composite sulfur slow-release agent is prepared from calcium sulfoaluminate, modified silica gel and carbon nanotubes in a mass ratio of 3:2:1.

[0014] Preferably, the modified silica gel is a modified silica gel containing mercapto groups on the surface.

[0015] Further preferably, the modified silica gel containing mercapto groups on the surface is prepared according to the following method: first, anhydrous ethanol and γ-mercaptopropyltrimethoxysilane are added to a container, and acetic acid is added after stirring to adjust the pH value to 4-5, and the dried silica gel is added to the container, and refluxed at 70°C-80°C for 3-5 hours; then filtered, washed with anhydrous ethanol to remove the unreacted modifier on the surface; finally dried to obtain the modified silica gel containing mercapto groups on the surface; the mass ratio of the silica gel and γ-mercaptopropyltrimethoxysilane used is 100: (8-12).

[0016] The beneficial effects of the present invention are as follows:

[0017] First, the new composite sulfur slow-release agent used in the present invention intelligently regulates the sulfur ion release rate according to the ion concentration environment in the precious liquid. Under the action of the ion selective promoter, the sulfur ions preferentially combine with mercury to form mercuric sulfide precipitation. Since the ability of sulfur ions to combine with gold is relatively weak, they basically do not combine with gold under this condition, and their ability to combine with silver is relatively weak relative to mercury, so they will only combine with silver after the mercury is basically precipitated completely. Therefore, the present invention can further reduce the mercury content in the precious liquid, reduce the impact of mercury on the extraction rate of gold and silver, improve the efficiency and quality of gold smelting, and reduce environmental pollution.

[0018] Second, compared with the Chinese invention patent application with publication number CN109154033A, a method for separating mercury from ore leachate (hereinafter referred to as the reference patent), the present invention has the following technical advantages: (1) Higher selectivity for mercury removal: The new composite sulfur slow-release agent used in the present invention can intelligently control the release rate of sulfur ions according to the ion concentration environment in the precious liquid, and at the same time add a specific ion selective promoter to accurately guide the sulfur ions to preferentially combine with mercury for precipitation. In contrast, the precipitant and coagulant in the reference patent have poor selectivity for mercury and are prone to cause gold and silver losses. The present invention effectively reduces the mercury content without affecting the gold and silver content in the precious liquid, greatly improving the recovery rate of gold and silver. (2) Easier to control the reaction conditions: The present invention only needs to control the reaction temperature at 25℃-35℃, the stirring speed at 150 rpm-250 rpm, and the reaction time for 2-4 hours. It is simple to operate, the reaction conditions are mild, and it is easy to implement in industrial production. The reference patent has a complicated operation process, strict requirements on the amount of reagents added and the reaction conditions, and is difficult to promote and apply on a large scale. (3) Lower cost: The raw materials for preparing the novel composite sulfur slow-release agent of the present invention, calcium sulfoaluminate, modified silica gel and carbon nanotubes, are all easily available and of low cost. In addition, the present invention does not require the use of complex equipment and cumbersome operating procedures, thereby reducing equipment investment and operating costs. In comparison, the reference patent may not only have higher reagent costs, but also higher costs for subsequent treatment of mercury-containing precipitates. (4) Better environmental performance: During the mercury removal process, the present invention effectively reduces the impact on precious metals such as gold and silver, reduces resource waste, and reduces environmental pollution. At the same time, the generated mercuric sulfide precipitate is relatively stable, which is convenient for subsequent treatment and reduces the risk of secondary pollution. In the reference patent, improper treatment of mercury-containing precipitates can easily cause secondary pollution. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with embodiments and experimental data.

[0020] Preparation Example 1 of Composite Sulfur Slow-Release Agent

[0021] First, 50 g of calcium sulfoaluminate and 33.3 g of modified silica gel were mixed and stirred at 60° C. for 1 hour, and then 16.7 g of carbon nanotubes were added and stirred and reacted for 2 hours to obtain a composite sulfur slow-release agent.

[0022] Preparation Example 2 of Composite Sulfur Slow-Release Agent

[0023] First, 250 g of calcium sulfoaluminate and 250 g of modified silica gel were mixed and stirred at 55° C. for 30 minutes, and then 100 g of carbon nanotubes were added and stirred and reacted for 90 minutes to obtain a composite sulfur slow-release agent.

[0024] Preparation Example 3 of Composite Sulfur Slow-Release Agent

[0025] First, 350 g of calcium sulfoaluminate and 150 g of modified silica gel were mixed and stirred at 65° C. for 90 minutes, and then 100 g of carbon nanotubes were added and the mixture was stirred and reacted for 150 minutes to obtain a composite sulfur slow-release agent.

[0026] The modified silica gel used in the above embodiment is a modified silica gel containing mercapto groups on the surface, and the specific preparation method is as follows:

[0027] (1) Prepare raw materials: Select ordinary silica gel with appropriate particle size, clean it and dry it for later use. Prepare γ-mercaptopropyltrimethoxysilane as a modifier, anhydrous ethanol as a solvent, and acetic acid as a catalyst and pH regulator.

[0028] (2) Modification treatment: Add 200 ml of anhydrous ethanol to a three-necked flask, then add 2 g of γ-mercaptopropyltrimethoxysilane, stir evenly, and add acetic acid to adjust the pH value to 4-5. Add 20 g of dried silica gel to the three-necked flask and reflux at 75°C for 4 hours.

[0029] (3) Post-treatment: After the reaction is completed, the silica gel is filtered out and repeatedly washed with anhydrous ethanol to remove the unreacted modifier on the surface. It is then dried at 110°C for 3 hours to obtain a modified silica gel containing mercapto groups on the surface.

[0030] Example 1 of reducing the mercury content of precious liquid

[0031] Step 1: Take 1000ml of precious liquid from the gold smelting water system and determine the contents of mercury, gold and silver, which are 56.4mg / L, 1.23mg / L and 4.68mg / L respectively.

[0032] Step 2: First, add 18.8 mg of sodium diethyldithiocarbamate as an ion-selective promoter to the precious solution, and then add 60 mg of the composite sulfur slow-release agent prepared in Preparation Example 1 to the precious solution, control the reaction temperature to 25°C, and react at a stirring speed of 150 rpm for 2 hours.

[0033] Step 3: After the reaction is completed, a microporous filter membrane with a pore size of 0.5 μm is used to filter and separate the precious liquid that has completed the second step reaction.

[0034] Step 4: The contents of mercury, gold and silver in the precious liquid after separation were measured to be 2.46 mg / L, 1.24 mg / L and 4.59 mg / L respectively. The results showed that the mercury content was reduced by 95.64%, while the gold and silver contents remained basically unchanged. The gold content was slightly higher than that before the reaction in the second step, which may be due to detection errors.

[0035] Example 2 of reducing the mercury content of precious liquid

[0036] The first step of this embodiment is the same as the first step of the first embodiment of reducing the mercury content in the precious liquid.

[0037] The second step of this embodiment is different from the second step of the embodiment 1 for reducing the mercury content in the noble liquid in that the reaction temperature is adjusted from 25° C. to 35° C., the reaction time is adjusted from 2 hours to 4 hours, and the stirring speed is adjusted from 150 rpm to 250 rpm.

[0038] The third step of this embodiment is different from the third step of the first embodiment for reducing the mercury content in the precious liquid in that the precious liquid after the second step reaction is centrifuged at a rotation speed of 4500 rpm instead of being filtered through a filter membrane.

[0039] The contents of mercury, gold and silver in the precious liquid after separation were measured to be 2.23 mg / L, 1.23 mg / L and 4.68 mg / L respectively. The results showed that the mercury content was reduced by 96.05%, while the gold and silver contents remained basically unchanged.

[0040] Example 3 of reducing the mercury content of precious liquid

[0041] The first step of this embodiment is the same as the first step of the first embodiment of reducing the mercury content in the precious liquid.

[0042] The second step of this embodiment is different from the second step of the first embodiment for reducing the mercury content in the precious liquid only in that the added mass of the sodium diethyldithiocarbamate is 14.2 mg.

[0043] The third step of this embodiment is the same as the third step of the first embodiment for reducing the mercury content in the precious liquid.

[0044] The mercury, gold and silver contents in the precious liquid after separation were measured, and the mercury content, gold content and silver content were 3.1mg / L, 1.22mg / L and 4.65mg / L respectively. The results showed that the mercury content was reduced by 94.5%, and the gold and silver contents were reduced by 0.81% and 0.64% respectively.

[0045] Example 4 of reducing the mercury content of precious liquid

[0046] The first step of this embodiment is the same as the first step of the first embodiment of reducing the mercury content in the precious liquid.

[0047] The second step of this embodiment is different from the second step of the first embodiment for reducing the mercury content in the precious liquid only in that the added mass of the sodium diethyldithiocarbamate is 22.5 mg.

[0048] The third step of this embodiment is the same as the third step of the first embodiment for reducing the mercury content in the precious liquid.

[0049] The contents of mercury, gold and silver in the precious liquid after separation were measured, and the mercury content, gold content and silver content were 2.1mg / L, 1.23mg / L and 4.66mg / L respectively. The results showed that the mercury content was reduced by 96.3%, and the gold and silver contents were reduced by 0% and 0.43% respectively.

[0050] Example 5 of Reducing Mercury Content in Precious Liquid

[0051] The first step of this embodiment is the same as the first step of the first embodiment of reducing the mercury content in the precious liquid.

[0052] The second step of this embodiment is different from the second step of the embodiment 1 for reducing the mercury content in the precious liquid in that 55 mg (instead of 60 mg) of the composite sulfur sustained-release agent prepared in the preparation example 1 is added.

[0053] The third step of this embodiment is the same as the third step of the first embodiment for reducing the mercury content in the precious liquid.

[0054] The contents of mercury, gold and silver in the precious liquid after separation were measured, and the mercury content, gold content and silver content were 2.2mg / L, 1.23mg / L and 4.67mg / L respectively. The results showed that the mercury content decreased by 96.1%, the gold content remained basically unchanged, and the silver content decreased by 0.21%.

[0055] Example 6 of Reducing Mercury Content in Precious Liquid

[0056] The first step of this embodiment is the same as the first step of the first embodiment of reducing the mercury content in the precious liquid.

[0057] The second step of this embodiment is different from the second step of the embodiment 1 for reducing the mercury content in the precious liquid in that 50 mg (instead of 60 mg) of the composite sulfur sustained-release agent prepared in the preparation example 1 is added.

[0058] The third step of this embodiment is the same as the third step of the first embodiment for reducing the mercury content in the precious liquid.

[0059] The contents of mercury, gold and silver in the precious liquid after separation were measured, and the mercury content, gold content and silver content were 2.3mg / L, 1.24mg / L and 4.67mg / L respectively. The results showed that the mercury content decreased by 95.9%, the gold content increased slightly and could be regarded as basically unchanged, and the silver content decreased by 0.21%.

[0060] Comparative analysis of reducing mercury content in precious liquid

[0061] The sodium sulfide precipitation method was used to treat the same 1000 ml precious liquid sample as in Example 1 for reducing the mercury content in the precious liquid. Based on relevant research and previous experimental foundations, the amount of sodium sulfide added is 1.2 times the theoretical amount required for complete reaction with mercury (taking into account the incompleteness of the reaction). In this experiment, the mercury content of the precious liquid is 56.4 mg / L, that is, the mass of mercury in 1000 ml of precious liquid is 56.4 mg. According to the chemical reaction formula Hg 2+ + S 2- = HgS↓, the molar ratio of mercury to sodium sulfide (Na2S) is 1:1, the molar mass of mercury is about 200.6g / mol, and the molar mass of sodium sulfide is about 78g / mol. According to calculations, theoretically, about 21.7mg of sodium sulfide is required to completely react with 56.4mg of mercury. Therefore, the actual mass of sodium sulfide added is 21.7mg×1.2 ≈ 26.0mg.

[0062] The control process parameters were as follows: the reaction temperature was controlled at 25 °C, the stirring speed was set at 200 rpm, and the reaction time was 2 h.

[0063] After the reaction is completed, the precious liquid that has completed the second step reaction is filtered and separated using a microporous filter membrane with a pore size of 0.5 μm.

[0064] The contents of mercury, gold and silver in the precious liquid after separation were measured, and the mercury content, gold content and silver content were 15.0 mg / L, 1.05 mg / L and 4.00 mg / L respectively. The results showed that the mercury content was reduced by 73.4%, and the gold and silver contents were reduced by 14.6% and 14.5% respectively. By comparison, it was found that the sodium sulfide precipitation method, as a traditional method, not only had a poor mercury removal effect, but also had a significant decrease in gold and silver contents, while the method of the present invention can effectively reduce the mercury content and the gold and silver contents are basically unaffected.

[0065] It can be seen from the above examples and comparative experiments that the method of the present invention can effectively reduce the mercury content in the precious liquid and has little effect on the gold and silver contents, which has significant advantages.

Claims

1. A method for reducing the mercury content in gold smelting precious liquid, characterized in that The following steps are involved: (1) Determine the mercury content in the gold smelting precious liquid to be treated; (2) adding sodium diethyldithiocarbamate and a composite sulfur slow-release agent to the precious liquid in sequence, controlling the reaction temperature to be 25°C to 35°C, and stirring at a speed of 150 rpm to 250 rpm for a reaction time of 2 to 4 hours; wherein the mass of sodium diethyldithiocarbamate added is 25% to 45% of the mass of mercury in the gold smelting precious liquid to be treated; wherein the composite sulfur slow-release agent is prepared from calcium sulfoaluminate, modified silica gel and carbon nanotubes in a mass ratio of (2.5 to 3.5): (1.5 to 2.5): 1; and the mass of the composite sulfur slow-release agent added is 90% to 110% of the mass of mercury in the gold smelting precious liquid to be treated; The modified silica gel is a modified silica gel containing mercapto groups on the surface; (3) Filter and separate the precious liquid after completing the reaction in step (2).

2. The method for reducing the mercury content in gold smelting precious liquid according to claim 1, characterized in that The preparation method of the composite sulfur slow-release agent is as follows: firstly, calcium sulfoaluminate and modified silica gel are mixed and stirred at 55-65° C. for 30-90 minutes, and then nano carbon tubes are added and stirred and reacted for 90-150 minutes.

3. The method for reducing the mercury content in gold smelting precious liquid according to claim 1 or 2, characterized in that The added mass of the sodium diethyldithiocarbamate is 38% to 40% of the mass of mercury in the gold smelting precious liquid to be treated.

4. The method for reducing the mercury content in gold smelting precious liquid according to claim 1 or 2, characterized in that The added mass of the composite sulfur slow-release agent is 97% to 98% of the mass of mercury in the gold smelting precious liquid to be treated.

5. The method for reducing the mercury content in gold smelting precious liquid according to claim 1 or 2, characterized in that: The composite sulfur slow-release agent is prepared from calcium sulfoaluminate, modified silica gel and carbon nanotubes in a mass ratio of 3:2:

1.

6. The method for reducing the mercury content in gold smelting precious liquid according to claim 1, characterized in that The modified silica gel containing mercapto groups on the surface is prepared according to the following method: first, anhydrous ethanol and γ-mercaptopropyltrimethoxysilane are added to a container, and acetic acid is added after stirring to adjust the pH value to 4-5, and the dried silica gel is added to the container, and refluxed at 70°C-80°C for 3-5 hours; then filtered, washed with anhydrous ethanol to remove the unreacted modifier on the surface; finally dried to obtain the modified silica gel containing mercapto groups on the surface; the mass ratio of the silica gel and γ-mercaptopropyltrimethoxysilane used is 100: (8-12).