Preparation method of an environment-friendly gold extractant

Abstract

The present invention discloses a preparation method of an environmentally friendly gold extraction agent. Cyanate, ferrocene and lead salt are placed in a sealed container and mixed evenly; the mixed materials are calcined; the materials are placed in the air and naturally cooled to room temperature; and then ground into powder to obtain the environmentally friendly gold extraction agent. The present invention can synthesize an environmentally friendly gold extraction agent with the same gold leaching effect as sodium cyanide only by using cyanate, ferrocene and lead salt; the synthesis raw materials are low in price, the synthesis process is simple and convenient, and the synthesized product has the advantages of high gold leaching rate, low toxicity and environmental friendliness, and strong applicability to various gold ores.

Description

Technical Field

[0001] The invention relates to a preparation method of a gold extracting agent. Background Art

[0002] Due to its simple and easy control, high gold leaching rate and low production cost, the cyanide leaching process is still the main method of gold extraction. – ) is highly toxic and can inhibit the activity of respiratory enzymes in organisms, causing cell asphyxiation. It seriously endangers the health of operators and damages the natural ecological environment.

[0003] Therefore, the development and use of low-toxic or non-toxic, efficient gold leaching agents is of great significance to the sustainable development of mining enterprises. Existing low-toxic or non-toxic gold leaching agents can be divided into two categories: cyanide-free gold leaching agents (i.e., non-cyanide gold extraction agents) and cyanide-containing gold leaching agents. Cyanide-free gold leaching agents primarily include thiosulfate, thiourea, lime sulfur, polysulfides, halogens, and their compounds. These agents, which do not produce highly toxic CN-, are the future direction of development. However, due to various factors, such as high reagent costs and complex gold recovery processes in the leachate, they are still limited to laboratory research.

[0004] Cyanide-containing gold leaching agents mainly include thiocyanate, sodium cyanate, sodium dicyanamide, etc. These agents are formed by the bonding of cyanide with hydrocarbon groups or heteroatoms (S, N, etc.). Their cyanide groups and S or N form thiocyanate or cyanamide, which are fixed inside the organic complex ions and are not easy to dissociate into free CN. – , but the lone pair electrons of its active atoms N or S can be combined with gold ions to achieve effective leaching of gold. In addition to the common inorganic gold extracting agents mentioned above, there are also several organic gold extracting agents, such as: (1) Carbonized sodium cyanurate (molecular formula is Na3C6N6H3O3), whose cyanide (-CN) is tightly linked to the organic macromolecular skeleton and is in a stable state in the solution, so it is not easy to dissociate into free CN. –, thus presenting low-toxicity characteristics. The gold leaching reaction equation is: 8Na3C6N6H3O3 + 4Au + O2 + 2H2O → 4Na5Au(C6N6H3O3)2 + 4NaOH; (2) Cyanuric acid (molecular formula: NaC3H2N3O3), which is a polymeric cyanamide organic macromolecule. Its cyano group is relatively more stable when combined with the organic molecular skeleton (the cyano groups are all fixed within a very stable six-membered ring molecular skeleton) and is not easily dissociated into free cyanide ions. The gold leaching reaction equation is: 8NaC3H2N3O3 + 4Au + O2 + 2H2O → 4NaAu(C3H2N3O3)2 + 4NaOH. Therefore, such low-toxic compounds containing cyano groups can also be used in the preparation of gold leaching agents and are expected to completely or partially replace cyanides, reducing the toxicity of the agents while ensuring the leaching effect and alleviating the safety risks brought by cyanides. It is reported that in recent years, low-toxic agents containing cyano groups have achieved some successful industrial applications. For example: The main active ingredient of the Jinchan gold extraction agent of Guangxi Senhe High-tech Co., Ltd. is sodium cyanurate carbide, and the main active ingredient of the Minjie gold extraction agent synthesized by Guangxi Jinzhiyuan Co., Ltd. is sodium polycyanamide. In summary, developing such gold leaching agents at the present stage has very important practical significance.

[0005] For example, the Chinese patent with the authorization announcement number CN103243222B discloses "A modified lime sulfur mixture and its application in the gold leaching process". The modified lime sulfur mixture also contains a stabilizer, an oxidant, and an additive; among them: the stabilizer is sodium hexametaphosphate; the oxidant is composed of calcium peroxide and potassium ferrocyanide; the additive is composed of lead nitrate and soluble bromide. The main defects of this method are: the cost of the potassium ferrocyanide reagent is high, and the gold recovery process in the leaching solution is complex when using the synthesized modified lime sulfur mixture for gold leaching.

[0006] For example, the Chinese patent application with the publication number CN109957664A discloses "An environmentally friendly gold leaching agent and its preparation method". It mixes sodium humate, soda ash, and urea evenly, puts them into a reaction kettle, heats for heat preservation reaction, and after the reaction is completed, cools and adds a gold leaching activator to obtain an environmentally friendly gold leaching agent, where the gold leaching activator is a lead salt or a manganate. The prepared gold leaching agent does not contain cyanide and will not cause cyanide pollution. However, the main defect of this method is that the synthesis raw materials contain urea, and urea will decompose a large amount of ammonia gas when heated, causing environmental pollution.

[0007] The Chinese patent application with the publication number CN116479254A discloses "A Gold and Silver Leaching Agent and Its Preparation Method and Application". It mixes an amide and an inorganic alkaline compound for the first roasting to obtain an intermediate roasted product; mixes the intermediate roasted product and an iron-containing material for the second roasting to obtain a gold and silver leaching agent; where the iron-containing material includes ferrous chloride, potassium ferrocyanide, potassium ferricyanide, ferrous sulfate, hematite, ferrocene, etc. The main defect of this method is that the synthesis process is complex, requiring two roastings and not being able to obtain the gold and silver leaching agent in one step.

[0008] The Chinese patent with the authorization announcement number CN103937986B discloses "A Preparation Method of an Environmentally Friendly Precious Metal Extraction Agent". It mixes sodium cyanate, sodium hydroxide, sodium sulfate, and sodium ferrocyanide in a certain proportion and adds them to a heating crucible until it turns slightly red, heats to 650 - 750 °C to make the material reach a molten state, maintains a high temperature of 750 °C for 30 - 50 minutes and then pours out and cools, and after pulverization, adds bromide and lead salt and stirs and mixes to obtain the environmentally friendly precious metal extraction agent. The main defect of this method is that there are too many types of synthetic raw materials, which may lead to problems such as complex synthetic reaction processes and being difficult to control. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a preparation method of an environmentally friendly gold leaching agent, achieving the gold leaching effect of sodium cyanide, and having the characteristics of fewer types of raw materials, simple production process, low production cost, and low toxicity and environmental friendliness.

[0010] The technical solution of the present invention is as follows:

[0011] A preparation method of an environmentally friendly gold leaching agent is prepared according to the following steps:

[0012] (1) Place cyanate, ferrocene, and lead salt in a sealed container and mix evenly;

[0013] (2) Roast the mixed material;

[0014] (3) Place the material in the air and let it cool naturally to room temperature;

[0015] (4) Grind it into powder to obtain the environmentally friendly gold leaching agent.

[0016] The mass ratio of the cyanate, ferrocene, and lead salt is preferably 60% - 80%, 10% - 30%, and 6% - 10%.

[0017] The mass ratio of the cyanate, ferrocene, and lead salt is further preferably 72%, 20%, and 8%.

[0018] The preferred process conditions for roasting are as follows: air atmosphere, heating rate of 10°C / min to 20°C / min, roasting temperature of 600 to 700°C, and holding time of 20 min to 180 min.

[0019] The roasting temperature is further preferably 630 to 670°C, and the holding time is further preferably 20 to 40 min.

[0020] The cyanate is sodium cyanate or potassium cyanate.

[0021] The lead salt is lead nitrate or lead acetate.

[0022] The mechanism and beneficial effects of the present invention:

[0023] In an environment of ferrous ions, the free oxygen in the gold leaching cyanate solution can combine with ferrous ions alone to form a complex ion. However, since the oxygen content carried by this complex ion is not high, the effect on promoting gold leaching is not obvious. The experimental data of the examples recorded in the specific implementation part of the present invention show that the gold leaching rate of the gold leaching agent synthesized from ferrocene and cyanate is only 51.74%. Similarly, in an environment of lead ions, the free oxygen in the gold leaching cyanate solution can combine with lead ions alone to form a complex ion. However, since the oxygen content carried by this complex ion is also not high, the effect on promoting gold leaching is not obvious. The experimental data of the examples recorded in the specific implementation part of the present invention show that the gold leaching rate of the gold leaching agent synthesized from lead salt and cyanate is only 44.34%.

[0024] Under comparable experimental conditions, the gold leaching rate of the environmentally friendly gold leaching agent synthesized from ferrocene and lead salt together with cyanate is significantly higher than the above combinations, reaching more than 96%. This is because the free oxygen in the solution combines with iron and lead ions to form a complex complex ion. The oxygen content carried by this complex complex ion is much higher, and the solubility and diffusion rate of oxygen in the gold leaching cyanate solution increase significantly, which is more conducive to promoting gold leaching.

[0025] The present invention can synthesize an environmentally friendly gold leaching agent equivalent to sodium cyanide in gold leaching effect only using cyanate, ferrocene and lead salt. It has the characteristics of low cost of synthetic raw materials, simple and convenient synthetic process, high gold leaching rate, low toxicity and environmental protection, and strong applicability to various gold ores. Specific implementation mode

[0026] The following further illustrates the present invention in combination with examples and experimental data.

[0027] The chemical element composition and content of a gold-bearing oxidized ore are shown in Table 1. The gold leaching experiments of Examples 1 to 3 and the comparative example were all carried out using this gold-bearing oxidized ore for experimental research.

[0028] Table 1 Chemical element analysis of gold-bearing oxidized ore

[0029]

[0030] Note: The units of Au and Ag in the table are g / t, and the other components are all in mass percentage.

[0031] Example 1

[0032] (1) Select cyanate, ferrocene, and lead salt as raw materials. Weigh a certain amount of cyanate, ferrocene, and lead salt, and the raw material ratio is shown in Table 2. Put them in a sealed bag and shake well to ensure that the raw materials are fully mixed evenly;

[0033] (2) Place the mixed materials in a porcelain boat and roast them in a muffle furnace; Roasting conditions: air atmosphere, heating rate of 15 °C / min, roasting temperature of 650 °C, and roasting time of 30 min.

[0034] (3) After roasting, place the materials in the air and let them cool naturally to room temperature;

[0035] (4) After complete cooling, grind the product into powder with a mortar to obtain an environmentally friendly gold extraction agent.

[0036] (5) Leaching test: liquid-solid ratio of 4:1; concentration of environmentally friendly gold extraction agent of 0.3 wt.%; pH of 11; rotation speed of 450 rpm; leaching time of 24 h. The gold leaching rates with different raw material ratios are shown in Table 2.

[0037] Table 2 Raw material ratio and its influence on the gold leaching effect of the environmentally friendly gold extraction agent

[0038]

[0039] As can be seen from Table 2, the raw material ratio has a great influence on the gold leaching rate. When the mass ratio of sodium cyanate, ferrocene, and lead nitrate is 9:2.5:1 (test number 5), the gold leaching rate reaches 96.41%.

[0040] Example 2

[0041] (1) Select cyanate, ferrocene, and lead salt as raw materials. Weigh a certain amount of cyanate, ferrocene, and lead salt, and the raw material ratio: the mass ratio of sodium cyanate, ferrocene, and lead nitrate is 9:2.5:1. Put them in a sealed bag and shake well to ensure that the raw materials are fully mixed evenly;

[0042] (2) Place the mixed materials in a porcelain boat and roast them in a muffle furnace; Roasting conditions: air atmosphere, heating rate of 15 °C / min, and roasting time of 30 min. Adjust the roasting temperature according to Table 3.

[0043] (3) After roasting, place the materials in the air and let them cool naturally to room temperature.

[0044] (4) After complete cooling, grind the product into powder with a mortar to obtain the environmentally friendly gold extraction agent.

[0045] (5) Leaching test: liquid-solid ratio 4:1; concentration of gold extraction agent 0.3 wt.%; pH 11; rotation speed 450 rpm; leaching time 24 h. The gold leaching rates at different roasting temperatures are shown in Table 3.

[0046] Table 3 Roasting temperature and its influence on the gold leaching effect of the environmentally friendly gold extraction agent

[0047]

[0048] As can be seen from Table 3, the roasting temperature has a great influence on the gold leaching rate. Too high or too low roasting temperature is not conducive to the synthesis of the gold extraction agent. When the roasting temperature is 650 °C (test number 2), the gold leaching rate reaches 96.41%.

[0049] Example 3

[0050] (1) Select cyanate, ferrocene and lead salt as raw materials. Weigh a certain amount of cyanate, ferrocene and lead salt. The raw material ratio: the mass ratio of sodium cyanate, ferrocene and lead nitrate is 9:2.5:1. Put them in a sealed bag and shake well to ensure that the raw materials are fully mixed evenly;

[0051] (2) Place the mixed material in a porcelain boat and roast it in a muffle furnace; Roasting conditions: air atmosphere, heating rate 15 °C / min, roasting temperature 650 °C. Adjust the roasting time according to Table 4.

[0052] (3) After roasting, place the material in the air and let it cool naturally to room temperature.

[0053] (4) After complete cooling, grind the product into powder with a mortar to obtain the environmentally friendly gold extraction agent.

[0054] (5) Leaching test: liquid-solid ratio 4:1; concentration of gold extraction agent 0.3 wt.%; pH 11; rotation speed 450 rpm; leaching time 24 h. The gold leaching rates at different roasting times are shown in Table 4.

[0055] Table 4 Roasting time and its influence on the gold leaching effect of the environmentally friendly gold extraction agent

[0056]

[0057] As can be seen from Table 4, the roasting time has a great influence on the gold leaching rate. Too long or too short roasting time is not conducive to the synthesis of the gold extraction agent. When the roasting time is 30 min (test number 2), the gold leaching rate reaches 96.41%.

[0058] Comparative example

[0059] Different raw materials: sodium cyanate + ferrocene; sodium cyanate + lead nitrate; sodium cyanate + ferrocene + lead nitrate. The following are the same experimental conditions: air atmosphere, heating rate of 15 °C / min, roasting temperature of 650 °C, roasting time of 30 min. Leaching conditions: liquid-solid ratio of 4:1; concentration of gold extraction agent of 0.3 wt.%; pH of 11; rotation speed of 450 rpm; leaching time of 24 h. The influence of the three groups of raw materials on the gold leaching effect was investigated, and the results are shown in Table 5.

[0060] Table 5 Different Roasted Raw Materials and Their Influence on the Gold Leaching Effect of Environmentally Friendly Gold Extraction Agent

[0061]

[0062] As can be seen from Table 5, the gold leaching rate of the gold extraction agent synthesized from ferrocene and cyanate is only 51.74%, and the gold leaching rate of the gold extraction agent synthesized from lead salt and cyanate is only 44.34%. However, the gold leaching rate of the environmentally friendly gold extraction agent synthesized from ferrocene, lead salt and cyanate reaches 96.41%.

[0063] Example 4

[0064] The chemical composition and content of a gold-bearing sulfide ore are shown in Table 6, and the chemical composition and content of a carbonaceous gold ore are shown in Table 7.

[0065] Table 6 Chemical Composition Analysis of Gold-bearing Sulfide Ore

[0066]

[0067] Note: The units of Au and Ag in the table are g / t, and other components are all mass percentages.

[0068] Table 7 Chemical Composition Analysis of Carbonaceous Gold Ore

[0069]

[0070] Note: The units of Au and Ag in the table are g / t, and other components are all mass percentages.

[0071] (1) Select sodium cyanate, ferrocene and lead salt as raw materials, weigh a certain amount of sodium cyanate, ferrocene and lead salt, and the raw material ratio: the mass ratio of sodium cyanate, ferrocene and lead nitrate is 9:2.5:1. Put them in a sealed bag and shake well to ensure that the raw materials are fully mixed evenly;

[0072] (2) Place the mixed materials in a porcelain boat and roast them in a muffle furnace; Roasting conditions: air atmosphere, heating rate of 15 °C / min, roasting temperature of 650 °C, roasting time of 30 min.

[0073] (3) After roasting, place the materials in the air and let them cool naturally to room temperature;

[0074] (4) After complete cooling, grind the product into powder with a mortar to obtain an environmentally friendly gold extraction agent.

[0075] (5) Leaching test: liquid-solid ratio 4:1; concentration of environmentally friendly gold extraction agent 0.3 wt.%; pH 11; rotation speed 450 rpm; leaching time 24 h.

[0076] Use the environmentally friendly gold extraction agent synthesized in this example to leach the gold-bearing oxide ore in Table 1, the gold-bearing sulfide ore in Table 6, and the carbonaceous gold ore in Table 7 respectively. The results are shown in Table 8.

[0077] Table 8 Comparison of gold leaching effects of environmentally friendly gold extraction agents on different gold ores

[0078]

[0079] As can be seen from Table 8, the synthesized environmentally friendly gold extraction agent has good gold leaching effects on various gold ore types. Therefore, the environmentally friendly gold extraction agent prepared by the present invention has the characteristic of strong applicability to various gold ores.

Claims

1. A preparation method of an environmentally friendly gold extraction agent, characterized in that It is prepared according to the following steps: (1) Place cyanate, ferrocene and lead salt in a sealed container and mix them evenly; (2) Roast the mixed materials; (3) Place the materials in the air and cool them naturally to room temperature; (4) Grind them into powder to obtain an environmentally friendly gold extraction agent; The mass ratios of the cyanate, ferrocene and lead salt are 60% - 80%, 10% - 30% and 6% - 10% respectively.

2. The preparation method of the environmentally friendly gold extraction agent according to claim 1, characterized in that: The mass ratios of the cyanate, ferrocene and lead salt are 72%, 20% and 8% respectively.

3. The preparation method of the environmentally friendly gold extraction agent according to claim 1, characterized in that: In step (2), the process conditions for the roasting are: air atmosphere, heating rate of 10°C / min - 20°C / min, roasting temperature of 600 - 700°C, and heat preservation time of 20 min - 180 min.

4. The preparation method of the environmental protection gold extraction agent according to claim 3, characterized in that: Roasting temperature is 630 - 670°C, and heat preservation time is 20 - 40 min.

5. The preparation method of the environmentally friendly gold extraction agent according to any one of claims 1 to 4, characterized in that: The cyanate is sodium cyanate or potassium cyanate.

6. The preparation method of the environmentally friendly gold extraction agent according to any one of claims 1 to 4, characterized in that: The lead salt is lead nitrate or lead acetate.

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