Preparation method and application of low-toxicity efficient gold leaching agent

Abstract

The invention discloses a preparation method and application of a low-toxicity efficient gold leaching agent, and belongs to the technical field of hydrometallurgy. The preparation method comprises the following steps: uniformly mixing sodium cyanate and manganese dioxide, roasting, and mixing the roasted product with sodium citrate to obtain the polymeric cyanamide low-toxicity high-efficiency gold leaching agent. The adopted raw materials are simple in variety, non-toxic and low in price, the synthesis process is simple and easy to control, and the prepared gold leaching agent has the advantages of being low in toxicity, good in gold leaching effect, low in agent dosage and the like and has wide application prospects.

Description

Technical Field

[0001] The present invention relates to a method for preparing a gold leaching agent, in particular to a method for preparing a low-toxic and high-efficiency gold leaching agent, and also to the application of the prepared gold leaching agent, belonging to the technical field of hydrometallurgy. Background Art

[0002] Gold is a strategic metal with both commodity and currency attributes, and plays an irreplaceable role in ensuring national economic security. Due to its advantages such as simple process, low production cost, and high gold leaching rate, the cyanidation method has long dominated the gold extraction industry. However, cyanide is a highly toxic substance, and there are many restrictions in various links such as transportation, storage, and use. Therefore, the use of non-toxic or low-toxic agents instead of sodium cyanide for gold extraction has become an urgent need in the gold industry. There are literature reports that thiosulfate, thiourea, thiocyanate, etc. are used as non-toxic gold leaching agents. However, due to the high cost of gold extraction, the complex gold recovery process in the leaching solution, and the difficulty in circulating the gold extraction solution, these non-toxic gold leaching agents have not yet been widely promoted and applied.

[0003] In recent years, some new gold leaching agents have appeared in the Chinese market. These new gold leaching agents are mainly obtained by high-temperature roasting of various chemical reagents. Their toxicity is lower than that of sodium cyanide. Some of them have been industrially applied at home and abroad, but the specific formula and synthesis conditions are rarely disclosed.

[0004] In addition, several domestic invention patents have reported on the synthesis and application of some new gold leaching agent products. For example, the patent application with publication number CN108441648A discloses "an environmentally friendly gold leaching agent and its preparation method", which uses 20-50% sodium carbonate, 10-50% urea, 1-10% sodium chloride, 1-5% sodium sulfide, 1-5% iodine, 1-5% potassium ferrocyanide, 1-5% sodium thiocyanate, 1-5% sodium bromide and 1-5% sodium thiosulfate as raw materials, and heats to 700-800 ° C in a closed container and keeps warm for 1-5 hours to obtain a gold leaching agent. The main defects of this method are: too many types of synthetic raw materials, resulting in a complex synthesis reaction process and difficulty in regulation, and high synthesis temperature and long insulation time, resulting in excessively high synthesis costs.

[0005] For another example, the patent application with publication number CN116640922A discloses “an improved powdered gold leaching agent and its preparation method”, which uses urea, sodium carbonate, sodium sulfate, activated carbon, iron catalyst, sodium tetrapolyphosphate, sodium citrate and sodium lignin sulfonate as raw materials. First, urea and sodium carbonate are mixed and added to the reactor, and then the temperature is raised to 120°C and activated carbon and iron catalyst are added. After reacting for 20 to 30 minutes, the temperature is raised to 150 to 200°C and the reaction is continued for 20 to 30 minutes to obtain an intermediate product; then, sodium sulfate is added to the intermediate product after keeping it warm for 30-50 minutes, and after mixing evenly, the temperature is raised to 300 to 350°C and kept warm for 0.5 to 1 hour to obtain a first-order reactant; then, the first-order reactant is heated to 450 to 500°C and kept warm for 1 to 1.5 hours to obtain a second-order reactant; then, the second-order reactant is cooled to 200°C and kept warm for 20 to 30 minutes. min, add sodium tetrapolyphosphate and sodium citrate, mix evenly, and cool to room temperature to obtain a semi-finished product; finally, crush the semi-finished product into powder, add sodium lignin sulfonate and mix evenly to obtain a gold leaching agent. It can be seen that this method not only has too many types of synthetic raw materials, but also requires five-stage roasting, and the synthesis process is very complicated, which is difficult to promote and apply.

[0006] For example, the patent application with publication number CN106399712A discloses "a low-toxic and environmentally friendly gold dressing agent and its preparation method", which uses urea, sodium carbonate, ferrous salt, catalyst (activated carbon, nickel catalyst, iron catalyst), sodium cyanate, sodium bicarbonate, sodium citrate, thiourea and sodium thiosulfate as raw materials. First, urea, sodium carbonate, ferrous salt, catalyst and sodium cyanate are mixed and added to the reaction container. After the temperature is raised to the melting of all the materials in the reaction container, sodium cyanate is added and kept at 700-850°C for 3-5 hours. Then, the step roasting product is filtered to remove impurities, introduced into the receiving plate, cooled, and then sodium bicarbonate, sodium citrate, thiourea and sodium thiosulfate are added to obtain the gold leaching agent. The method has complex types of synthetic raw materials, which makes the roasting process difficult to control, and the insulation temperature is high and the time is long, so the synthesis cost is too high. In addition, the amount of the gold leaching agent used for stirring and leaching of gold concentrate reaches 3-5 kg / t.

[0007] For example, the patent application with publication number CN102121067A discloses a "harmless mineral processing additive and its preparation method and application", which uses sodium hydroxide, sodium carbonate, urea, and ferroxanthate as raw materials, and heats at 600-1000 ° C for 1-2 hours to obtain the gold leaching agent. The raw materials and synthesis process used in this method are relatively simple, but the ferroxanthate in the raw material is expensive, and it will decompose to produce highly toxic sodium cyanide at the heat preservation temperature, resulting in the prepared gold leaching agent with high toxicity. In addition, the roasting temperature can reach up to 1000 ° C, so the synthesis cost is relatively high. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a preparation method and application of a low-toxic and high-efficiency gold leaching agent. The raw materials for preparing the gold leaching agent are non-toxic and simple in type, the synthesis process is simple, the cost is low, and no toxic gas is generated during the production process, and it is easy to industrialize the production. The synthesized gold leaching agent has low toxicity, and the gold leaching process does not need to change the original cyanide gold leaching process, and the dosage of the agent is small, the leaching speed is fast, and the gold leaching rate is high.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for preparing a low-toxic and high-efficiency gold leaching agent is prepared according to the following steps: (1) Raw material mixing: Mix the raw materials sodium cyanate and manganese dioxide evenly under sealed conditions; (2) Calcination: The mixed material is placed in a high-temperature heating container and calcined under a controlled atmosphere to obtain a calcined product; (3) Preparation of gold leaching agent: Mix the roasted product with sodium citrate to obtain a low-toxic and high-efficiency gold leaching agent.

[0010] Preferably, in step (1), the mass ratio of the raw materials sodium cyanate and manganese dioxide is 4:(0.5-1.5). The mass ratio of the raw materials sodium cyanate and manganese dioxide is more preferably 4:1.

[0011] Preferably, in step (2), the process conditions for calcination are: the mixed raw material is heated with the furnace, the heating rate is 5-20°C / min, the holding temperature is 450-550°C, the volume ratio of N2: O2 in the calcination atmosphere is 4:1-8:1, and the holding time is greater than 20 min. The heating rate is more preferably 10°C / min; the holding temperature is more preferably 500°C; the calcination atmosphere is more preferably N2: O2 in the volume ratio is 6:1-8:1; the holding time is more preferably 20-60 min.

[0012] Preferably, in step (3), the mass ratio of the calcined product to sodium citrate is 100:(1-10), and more preferably 100:(3-10).

[0013] The low-toxic and high-efficiency gold leaching agent prepared by the preparation method is used for leaching gold from gold-containing raw materials including gold ore, anode mud and electronic waste.

[0014] Mechanism of the present invention: With sodium cyanate as the ligand source and manganese dioxide as the catalyst, under high temperature conditions, both raw materials are in a molten state, sodium cyanate undergoes a polymerization reaction, and manganese dioxide promotes the polymerization of sodium cyanate, and finally forms a polycyanamide gold leaching agent with a triazine structure. Since the cyanide group is fixed in a stable six-membered ring molecular skeleton, it is not easy to dissociate into free cyanide ions, so its toxicity is very low. The lone pair of electrons of the active atom N in the cyanide group on the skeleton can form a bond with the gold ion, thereby achieving effective leaching of gold. Sodium citrate can react with the dissolved Cu in the leaching process. 2＋ 、Zn 2＋ , Ca 2＋ Mg 2＋ Harmful impurity metal ions react to form chelates, which disperse the gangue minerals and reduce their consumption of oxygen in the solution, thereby increasing the "effective active oxygen" content in the ore pulp, reducing the consumption of gold leaching agents and improving the gold leaching effect.

[0015] Beneficial effects of the present invention: In view of the problems that the synthetic raw materials of the existing low-toxic gold leaching agent are complex, the cost is high, the synthetic process is not easy to control and is easy to produce toxic gases, the synthetic gold leaching agent is highly toxic, the dosage is large, and the leaching effect is not ideal, the inventor of the present application has found through multiple experimental studies that a new type of polycyanamide low-toxic gold leaching agent can be synthesized by only using two raw materials, sodium cyanate and manganese dioxide, through a stage of low-temperature roasting, and then mixed with citric acid as an additive to obtain a new type of low-toxic gold leaching agent that can be comparable to the gold leaching effect of sodium cyanide. The present invention has the advantages of non-toxic and cheap synthetic raw materials, simple types, simple synthetic process, easy control of the process, no harmful gas generation, and the synthetic product has the advantages of low toxicity and environmental protection, fast leaching speed, high gold leaching rate, small dosage, etc., and has good potential to replace sodium cyanide for gold extraction. DETAILED DESCRIPTION

[0016] The present invention is further described below in conjunction with examples and experimental data.

[0017] The chemical composition (wt.%) of a gold-containing oxide ore is shown in Table 1. The following gold leaching experiments were all conducted using this gold ore.

[0018] Table 1 Chemical element analysis of gold-containing oxide ore / %

[0019] Note: *Unit: g / t.

[0020] Example 1

[0021] (1) Select sodium cyanate and manganese dioxide as raw materials, weigh a certain amount of sodium cyanate and manganese dioxide, 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.

[0022] (2) The mixed material was transferred to a porcelain boat, and then placed in a muffle furnace and heated up with the furnace at a heating rate of 10 °C / min. When the temperature rose to 500 °C, it was kept at this temperature for 30 min. The atmosphere during the heating and holding process was N2: O2 in a volume ratio of 6:1.

[0023] (3) After the roasting is completed, the product is placed in the air to cool naturally to room temperature. After being taken out, it is mixed with sodium citrate in a mass ratio of 95:5 to obtain a low-toxic gold leaching agent.

[0024] (3) The synthetic gold leaching agent was used to leach the gold ores in Table 1. The leaching test conditions were: liquid-to-solid ratio 2:1, low-toxic gold leaching agent dosage 0.05 wt.%, pH 11, and leaching time 24 h.

[0025] The influence of raw material ratio on the gold leaching effect of the synthetic low-toxic agent is shown in Table 2.

[0026] Table 2 Effect of raw material ratio on gold leaching effect of synthetic low-toxic reagent

[0027] It can be seen from Table 2 that the raw material ratio has a great influence on the gold leaching rate. When the mass ratio of sodium cyanate to manganese dioxide is 4:1, the gold leaching rate reaches a maximum value of 96.5%. Under this condition, the free cyanide concentration in the leachate is 32.3 mg / L.

[0028] Example 2 (1) Select sodium cyanate and manganese dioxide as raw materials, weigh a certain amount of sodium cyanate and manganese dioxide in a mass ratio of 4:1, put them in a sealed bag and shake them well to ensure that the raw materials are fully mixed.

[0029] (2) The mixed material was transferred to a porcelain boat, and then placed in a muffle furnace and heated up with the furnace at a heating rate of 10 °C / min. When the temperature reached the temperature set in Table 3, it was kept at this temperature for 30 min. The atmosphere during the heating and holding process was N2: O2 in a volume ratio of 6:1.

[0030] (3) After the roasting is completed, the product is placed in the air to cool naturally to room temperature. After being taken out, it is mixed with sodium citrate in a mass ratio of 95:5 to obtain a low-toxic gold leaching agent.

[0031] (4) The synthetic gold leaching agent was used to leach the gold ores in Table 1. The leaching test conditions were: liquid-to-solid ratio 2:1, low-toxic gold leaching agent dosage 0.05 wt.%, pH 11, and leaching time 24 h.

[0032] The effect of holding temperature on the gold leaching effect of the synthetic low-toxic agent is shown in Table 3.

[0033] Table 3 Effect of holding temperature on the gold leaching effect of synthetic low-toxic reagent

[0034] It can be seen from Table 3 that the holding temperature has a great influence on the gold leaching rate. When the holding temperature is 500 °C, the gold leaching rate reaches a maximum value of 96.5%. Under this condition, the free cyanide concentration in the leaching solution is 32.3 mg / L.

[0035] Example 3

[0036] (1) Select sodium cyanate and manganese dioxide as raw materials, weigh a certain amount of sodium cyanate and manganese dioxide in a mass ratio of 4:1, put them in a sealed bag and shake them well to ensure that the raw materials are fully mixed.

[0037] (2) The mixed material was transferred to a porcelain boat, and then placed in a muffle furnace and heated up with the furnace at a heating rate of 10 °C / min. When the temperature rose to 500 °C, the holding time was adjusted at this temperature (see Table 4). The atmosphere during the heating and holding process was N2: O2 in a volume ratio of 6:1.

[0038] (3) After the roasting is completed, the product is placed in the air to cool naturally to room temperature. After being taken out, it is mixed with sodium citrate in a mass ratio of 95:5 to obtain a low-toxic gold leaching agent.

[0039] (4) The synthetic gold leaching agent was used to leach the gold ores in Table 1. The leaching test conditions were: liquid-to-solid ratio 2:1, low-toxic gold leaching agent dosage 0.05 wt.%, pH 11, and leaching time 24 h.

[0040] The effect of holding time on the gold leaching effect of the synthetic low-toxic agent is shown in Table 4.

[0041] Table 4 Effect of holding time on gold leaching effect of synthetic low-toxic reagent

[0042] It can be seen from Table 4 that the holding time has a relatively small effect on the gold leaching rate. When the holding time is 30 min, the gold leaching rate reaches a maximum value of 96.5%. Therefore, the synthesis reaction rate is very fast. Under this condition, the free cyanide concentration in the leaching solution is 32.3 mg / L.

[0043] Example 4

[0044] (1) Select sodium cyanate and manganese dioxide as raw materials, weigh a certain amount of sodium cyanate and manganese dioxide in a mass ratio of 4:1, put them in a sealed bag and shake them well to ensure that the raw materials are fully mixed.

[0045] (2) Transfer the mixed material to a porcelain boat, and then adjust the calcination atmosphere as shown in Table 5. Place the porcelain boat containing the mixed material in a muffle furnace and heat it up with the furnace at a heating rate of 10 °C / min. When the temperature rises to 500 °C, keep it at this temperature for 30 min.

[0046] (3) After the roasting is completed, the product is placed in the air to cool naturally to room temperature. After being taken out, it is mixed with sodium citrate in a mass ratio of 95:5 to obtain a low-toxic gold leaching agent.

[0047] (4) The synthetic gold leaching agent was used to leach the gold ores in Table 1. The leaching test conditions were: liquid-to-solid ratio 2:1, low-toxic gold leaching agent dosage 0.05 wt.%, pH 11, and leaching time 24 h.

[0048] The effect of roasting atmosphere on the gold leaching effect of the synthesized low-toxic agent is shown in Table 5.

[0049] Table 5 Effect of roasting atmosphere on the gold leaching effect of synthetic low-toxic reagent

[0050] It can be seen from Table 5 that the roasting atmosphere has a great influence on the gold leaching rate. When the oxygen content is high, the gold leaching rate and the free cyanide concentration in the leachate are both low. When the volume ratio of N2: O2 is 6:1, the gold leaching rate reaches a maximum value of 96.5%, and the free cyanide concentration in the leachate under this condition is 32.3 mg / L.

[0051] Example 5

[0052] (1) Select sodium cyanate and manganese dioxide as raw materials, weigh a certain amount of sodium cyanate and manganese dioxide in a mass ratio of 4:1, put them in a sealed bag and shake them well to ensure that the raw materials are fully mixed.

[0053] (2) The mixed material was transferred to a porcelain boat, and then placed in a muffle furnace and heated up with the furnace at a heating rate of 10 °C / min. When the temperature rose to 500 °C, it was kept at this temperature for 30 min. The atmosphere during the heating and holding process was N2: O2 in a volume ratio of 6:1.

[0054] (3) After roasting, the product is placed in the air to cool naturally to room temperature. After being taken out, it is mixed with sodium citrate in the mass ratio shown in Table 6 to obtain a low-toxic gold leaching agent.

[0055] (4) The synthetic gold leaching agent was used to leach the gold ores in Table 1. The leaching test conditions were: liquid-to-solid ratio 2:1, low-toxic gold leaching agent dosage 0.05 wt.%, pH 11, and leaching time 24 h.

[0056] The effect of sodium citrate addition on the gold leaching effect of the synthetic low-toxic agent is shown in Table 6.

[0057] Table 6 Effect of sodium citrate addition on gold leaching effect of synthetic low-toxic reagent

[0058] As shown in Table 6, the amount of sodium citrate added has a great influence on the gold leaching rate. When no sodium citrate is added, the gold leaching rate is 85.6%. With the increase of the amount of sodium citrate added, the gold leaching rate gradually increases. When the mass ratio of roasted product: sodium citrate is 95:5, the gold leaching rate reaches a maximum of 96.5%. Continuing to increase the amount of sodium citrate, the gold leaching rate does not increase significantly.

[0059] Example 6

[0060] (1) Select sodium cyanate and manganese dioxide as raw materials, weigh a certain amount of sodium cyanate and manganese dioxide in a mass ratio of 4:1, put them in a sealed bag and shake them well to ensure that the raw materials are fully mixed.

[0061] (2) The mixed material was transferred to a porcelain boat, and then placed in a muffle furnace and heated up with the furnace at a heating rate of 10 °C / min. When the temperature rose to 500 °C, it was kept at this temperature for 30 min. The atmosphere during the heating and holding process was N2: O2 in a volume ratio of 6:1.

[0062] (3) After roasting, the product is placed in the air to cool naturally to room temperature. After being taken out, it is mixed with sodium citrate in a mass ratio of 95:5 to obtain a low-toxic gold leaching agent.

[0063] (4) The gold ore in Table 1 was leached using the synthetic gold leaching agent and sodium cyanide. The amounts of the synthetic gold leaching agent and sodium cyanide were adjusted as shown in Table 7. The other leaching test conditions were: liquid-solid ratio 2:1, pH 11.

[0064] The gold leaching rate and free cyanide concentration under different low-toxic gold leaching agents and sodium cyanide dosages and time conditions are shown in Table 7.

[0065] Table 7 Comparison of gold leaching effects of synthetic low-toxic reagents and sodium cyanide

[0066] It can be seen from Table 7 that when the amount of the leaching agent is 0.01%, the leaching rate of the low-toxic leaching agent reaches 86.5% after leaching for 6 hours, which is significantly higher than the leaching rate of sodium cyanide, which is 72.9%. With the increase of leaching time, the leaching rates of both leaching agents increase. After leaching for 24 hours, the leaching rate of the low-toxic leaching agent reaches 92.2%, and the leaching rate of sodium cyanide reaches 87.6%, which is basically equivalent to the leaching rate of 88.3% of the low-toxic leaching agent for 12 hours. In addition, under the same leaching agent dosage and leaching time conditions, the free cyanide concentration in the leaching solution of the low-toxic leaching agent is significantly lower. The leaching rate and free cyanide concentration under other leaching agent dosages and leaching time conditions also basically follow the above rules. Therefore, compared with sodium cyanide, the low-toxic leaching agent synthesized by the present invention has lower toxicity and better leaching effect.

Claims

1. A method for preparing a low-toxic and high-efficiency gold leaching agent, characterized in that Prepare according to the following steps: (1) Raw material mixing: Mix the raw materials sodium cyanate and manganese dioxide evenly under sealed conditions; (2) Calcination: The mixed material is placed in a high-temperature heating container and calcined under a controlled atmosphere to obtain a calcined product; (3) Preparation of gold leaching agent: Mix the roasted product with sodium citrate to obtain a low-toxic and high-efficiency gold leaching agent.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of the raw materials sodium cyanate and manganese dioxide is 4: (0.5-1.5).

3. The preparation method according to claim 2, characterized in that: The mass ratio of the raw materials sodium cyanate and manganese dioxide is 4:

1.

4. The preparation method according to claim 1, characterized in that: In step (2), the calcination process conditions are as follows: the mixed raw material is heated with the furnace, the heating rate is 5-20°C / min, the insulation temperature is 450-550°C, the calcination atmosphere has a N2:O2 volume ratio of 4:1-8:1, and the insulation time is greater than 20 min.

5. The preparation method according to claim 4, characterized in that: The heating rate is 10 °C / min; the holding temperature is 500 °C; the calcination atmosphere is N2:O2 volume ratio of 6:1 to 8:1; and the holding time is 20 to 60 min.

6. The preparation method according to claim 1, characterized in that: In step (3), the mass ratio of the roasted product to sodium citrate is 100:(1-10).

7. The preparation method according to claim 5, characterized in that: In step (3), the mass ratio of the calcined product to sodium citrate is 100:(3-10).

8. The low-toxic and high-efficiency gold leaching agent prepared by the preparation method according to any one of claims 1 to 7 is used to leach gold from gold-containing raw materials including gold ore, anode mud and electronic waste.

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