CN116536522A - Triazine leaching agent, preparation method and application thereof, and method for extracting noble metal from ore - Google Patents

Abstract

The invention relates to the technical fields of hydrometallurgy and mineral processing, and provides a triazine leaching agent, a preparation method and application thereof, and a method for extracting precious metals in ores. The present invention adopts carbon disulfide or carboxylic acid organic matter and the H atom on the N atom in the triazine ring of the reaction reagent, Cl atom or the H atom on the atom such as N, O, S on the branch chain to generate substitution reaction, and then will have coordination The active groups are assembled on the triazine ring structure to form a triazine organic compound with multi-dentate coordination function, that is, the triazine leaching agent of the present invention. The triazine leaching agent prepared by the invention is low-toxic or non-toxic, green and environmentally friendly, has a fast leaching rate and a high gold leaching rate, can leach gold and silver under alkaline conditions, has no corrosion to equipment, and can realize gold and silver in the normal environment. The high-efficiency leaching under pressure has broad application prospects.

Description

A triazine leaching agent, its preparation method and application, and a method for extracting ore precious metal method

technical field

The invention relates to the technical fields of hydrometallurgy and mineral processing, in particular to a triazine leaching agent, a preparation method and application thereof, and a method for extracting precious metals in ores.

Background technique

Gold is a golden-yellow metal with soft quality, strong ductility and strong metallic luster. At present, the main minerals of gold include natural gold, gold sulfide, gold selenide, silver-gold ore, etc. Gold often coexists with silver, and with yellow Iron ore, galena, sphalerite and other minerals are closely related and often grow together.

At present, the most commonly used method for extracting gold from ores is the cyanidation method, which uses cyanide as a leaching agent to extract gold. It is the main method for extracting gold from ores in modern times and has long dominated gold production. However, cyanide is highly toxic and seriously threatens the ecological environment, so the research and development of non-cyanide gold leaching agents is imminent.

In the Chinese invention patent with the application number CN201810173568.1, a method for leaching arsenic carbonaceous gold ore containing pyrolusite under high pressure-non-cyanidation is disclosed, in which cyanuric acid is used as the gold leaching agent, but it needs to be extracted in an acidic system. The effective extraction of gold can only be realized under the condition of pressurization. The acidic condition is easy to cause corrosion to the equipment, and the pressurized condition requires the use of high-pressure equipment, resulting in high leaching costs.

Contents of the invention

In view of this, the present invention provides a triazine leaching agent, its preparation method and application, and a method for extracting precious metals in ores. The triazine leaching agent provided by the invention is non-toxic and environment-friendly, can efficiently leaching gold and silver under alkaline and normal pressure conditions, has no corrosion to equipment, and has low requirements on leaching equipment.

In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

A preparation method of triazine leaching agent, comprising the following steps:

Mix a reagent containing a triazine ring, an alkali metal hydroxide, a reagent containing a coordinating group, and water to perform a substitution reaction to obtain a triazine leaching agent; the reagent containing a coordinating group is carbon disulfide or a carboxylic acid organic matter.

Preferably, the reagent containing triazine ring is one or more of cyanuric acid, trisodium cyanurate, melamine, thiocyanic acid, trisodium thiocyanate and cyanuric chloride kind;

The alkali metal hydroxide is sodium hydroxide or potassium hydroxide;

The carboxylic acid organic matter is one or more of sodium chloroacetate, sodium acetate, sodium formate, sodium glycinate and sodium humate.

Preferably, the molar ratio of the reagent containing a triazine ring to the alkali metal hydroxide is (0.01-0.5):(0.1-2);

The molar ratio of the compound containing a triazine ring to the reagent containing a coordination group is (0.01-0.5):(0.03-2).

Preferably, the temperature of the substitution reaction is 30-90° C., and the time is 1-6 hours.

The present invention also provides the triazine leaching agent prepared by the preparation method described in the scheme above.

The present invention also provides the application of the triazine leaching agent described in the above scheme to extract precious metals in ores, and the precious metals are gold and/or silver.

The present invention also provides a method for extracting precious metals in ores, comprising the following steps:

Mixing ore powder containing precious metals with water to obtain slurry; the precious metals are gold and/or silver;

The ore pulp, the triazine leaching agent described in the above scheme and iron salt are mixed, and leaching is carried out under alkaline conditions to obtain a leach solution containing precious metals; the iron salt is ferricyanide and/or ferrocyanide.

Preferably, the mass ratio of the water to the ore powder containing precious metal is (1-10):1; the mass fraction of the powder with a particle size of -74 μm in the ore powder containing precious metal is greater than 80%.

Preferably, the amount of the triazine leaching agent is 0.01-5% of the water quality in the pulp;

The ferricyanide is potassium ferricyanide and/or sodium ferricyanide; the ferrocyanide is potassium ferrocyanide and/or sodium ferrocyanide; the iron salt and the water in the pulp The dosage ratio is (0.001～0.1)mol:1L.

Preferably, the pH value of the alkaline condition is 9-13; the temperature of the leaching is 25-50° C., the time is 6-48 hours, and the pressure of the leaching is normal pressure.

The invention provides a preparation method of a triazine leaching agent, which comprises the following steps: mixing a reagent containing a triazine ring, an alkali metal hydroxide, a reagent containing a coordination group, and water for a substitution reaction to obtain a triazine class leaching agent; the reagent containing coordination groups is carbon disulfide or carboxylic acid organic matter. The triazine ring has three modifiable sites, and other groups or functional groups can be introduced into the triazine ring through reactions to form a series of triazine compounds with different properties; the present invention utilizes the structural characteristics of the triazine ring and adopts carbon disulfide Or the H on the N atom in the triazine ring in the carboxylic acid organic matter and the reaction reagent, the Cl atom (such as -NH-, -NCl-) or the H atom on the N, O, S atom on its branch chain (such as -NH ₂ , -OH, -SH) undergo substitution reactions, and then assemble groups with coordination (such as amine groups, carboxyl groups, etc.) onto the triazine ring structure to form triazines with multi-dentate coordination functions Organic matter, that is, the triazine leaching agent of the present invention. The triazine leaching agent prepared by the present invention has low toxicity or even non-toxicity, and is a green and environmentally friendly leaching agent; the triazine leaching agent of the present invention can exist stably under alkaline conditions, and realizes the leaching of gold under alkaline conditions. , silver, compared with the acidic system, it has no corrosion to the equipment and has low requirements on the leaching equipment; moreover, the triazine leaching agent prepared by the present invention contains multiple coordination atoms (such as N, O, S), and belongs to the poly Dental ligands, which can form stable metal coordination ions with gold and silver ions under normal pressure, so as to achieve efficient leaching under normal pressure and reduce leaching costs. In addition, the preparation method of the triazine leaching agent provided by the invention is simple and easy to operate.

The present invention also provides a method for extracting precious metals in ores, comprising the following steps: mixing precious metal-containing ore powder with water to obtain ore pulp; the precious metals are gold and/or silver; Mix the above-mentioned triazine leaching agent and iron salt, and perform leaching under alkaline conditions to obtain a leaching solution containing precious metals. The present invention uses the triazine leaching agent described in the above scheme to extract precious metals such as gold and silver, the operation method is simple, the gold and silver leaching rate is high, and it is environmentally friendly; the present invention also adds ferricyanide or ferrocyanide to the leaching system , ferricyanide or ferrocyanide can exist stably in the alkaline leaching solution, and can act as an oxidant, making the solution potential higher (>200mV vs. SHE), which can catalyze the oxidative leaching of gold and silver, shorten the leaching time, and then Realize the efficient leaching of gold and silver.

Description of drawings

Fig. 1 is the flow chart of preparing triazine leaching agent and extracting gold and silver in ore according to the present invention.

Detailed ways

The invention provides a kind of preparation method of triazine leaching agent, comprises the following steps:

Mix a reagent containing a triazine ring, an alkali metal hydroxide, a reagent containing a coordinating group, and water to perform a substitution reaction to obtain a triazine leaching agent; the reagent containing a coordinating group is carbon disulfide or a carboxylic acid organic matter.

In the present invention, the reagent containing triazine ring is preferably one of cyanuric acid, trisodium cyanurate, melamine, cyanuric acid, trisodium cyanurate and cyanuric chloride one or more, more preferably melamine; the alkali metal hydroxide is preferably sodium hydroxide or potassium hydroxide, the present invention by adding alkali metal hydroxide, the insoluble triazine ring organic matter or reaction product in the reaction process Transform into water-soluble organic sodium/potassium salts; the carboxylic acid organic matter is preferably one or more of sodium chloroacetate, sodium acetate, sodium formate, sodium glycinate and sodium humate.

In the present invention, the molar ratio of the reagent containing a triazine ring to the alkali metal hydroxide is preferably (0.01-0.5):(0.1-2), more preferably 0.1:0.2; The molar ratio of the ring compound to the reagent containing the coordinating group is (0.01～0.5):(0.03～2), more preferably 0.1:0.3; the ratio of the reagent containing the triazine ring to water is preferably It is 0.01～0.05mol:1L.

In a specific embodiment of the present invention, in the mixture obtained by mixing the reagent containing a triazine ring, the alkali metal hydroxide, the reagent containing a coordinating group, and water, the concentration of the reagent containing a triazine ring is preferably 0.01 ~0.5mol/L, the concentration of the alkali metal hydroxide is preferably 0.1~2mol/L, and the concentration of the reagent containing a coordination group is preferably 0.03~2mol/L.

In the present invention, the temperature of the substitution reaction is preferably 30°C to 90°C, more preferably 30°C, 40°C, 50°C, 70°C or 90°C, more preferably 50°C, and the time of the substitution reaction is preferably 1 to 6 hours, more preferably 2 to 5 hours; in specific embodiments of the present invention, it is preferred to first dissolve the reagent containing the triazine ring in water at 30 to 90° C. Next, add a reagent containing a coordination group to the solution, and carry out a substitution reaction at 30-90°C after the addition is complete.

In the present invention, taking the melamine and carbon disulfide as an example, the reaction formula of the substitution reaction is as follows:

C ₃ N ₆ H ₆ +6CS ₂ +6NaOH＝C ₉ N ₆ S ₁₂ Na ₆ +6H ₂ O

In the present invention, taking the melamine and sodium chloroacetate as an example, the reaction formula of the substitution reaction is as follows:

C ₃ N ₆ H ₆ +6ClCH ₂ COONa+6NaOH=C ₃ N ₆ (CH ₂ COONa) ₆ +6NaCl+6H ₂ O

In the present invention, taking described cyanuric acid and carbon disulfide as example, the reaction formula of described substitution reaction is as follows:

C ₃ N ₃ H ₃ O ₃ +3CS ₂ +3NaOH＝C ₆ N ₃ O ₃ S ₆ Na ₃ +3H ₂ O

In the present invention, taking the thiocyanate and carbon disulfide as an example, the reaction formula of the substitution reaction is as follows:

C ₃ N ₃ H ₃ S ₃ +3CS ₂ +3NaOH＝C ₆ N ₃ S ₉ Na ₃ +3H ₂ O

After the substitution reaction is completed, the present invention preferably cools the resulting product feed liquid to room temperature and then filters it, and washes the resulting solid product to obtain the triazine leaching agent. The triazine leaching agent prepared by the present invention can be stable under alkaline conditions. exist.

The present invention also provides the triazine leaching agent prepared by the preparation method described in the scheme above.

The present invention also provides the application of the triazine leaching agent described in the above scheme to extract precious metals in ores, and the precious metals are gold and/or silver.

The present invention also provides a method for extracting precious metals in ores, comprising the following steps:

Mixing ore powder containing precious metals with water to obtain slurry; the precious metals are gold and/or silver;

The ore pulp, the triazine leaching agent described in the above scheme and iron salt are mixed, and leaching is carried out under alkaline conditions to obtain a leach solution containing precious metals; the iron salt is ferricyanide and/or ferrocyanide.

The invention mixes precious metal-containing ore powder and water to obtain ore slurry; the precious metal is gold and/or silver. In a specific embodiment of the present invention, the precious metal-containing ore is preferably a sulfide-type gold concentrate; the mass fraction of the powder with a particle size of -74 μm in the precious metal-containing ore powder is preferably greater than 80%, more preferably 85% to 95%; the precious metal-containing ore powder is preferably obtained by crushing precious metal-containing ore; the mass ratio of the water to the precious metal-containing ore powder is preferably (1-10):1, more preferably It is 2.5:1.

After the ore pulp is obtained, the present invention mixes the ore pulp, the triazine leaching agent described in the above scheme and iron salt, and performs leaching under alkaline conditions to obtain a leach solution containing precious metals. In the present invention, the amount of the triazine leaching agent is preferably 0.01 to 5% of the water quality in the pulp, more preferably 0.1 to 2%, and even more preferably 0.5%; the iron salt is ferricyanide And/or ferrocyanide, described ferricyanide is preferably potassium ferricyanide and/or sodium ferricyanide; Described ferrocyanide is preferably potassium ferrocyanide and/or sodium ferrocyanide; The The amount ratio of the iron salt to the water in the pulp is preferably (0.001-0.1) mol:1L (that is, the concentration of the iron salt is 0.001-0.2mol/L based on the volume of water in the pulp), more preferably 0.001mol:1L, 0.005mol:1L, 0.01mol:1L, 0.05mol:1L or 0.1mol:1L, more preferably 0.01mol:1L.

In the present invention, the initial pH value of the alkaline condition is preferably 9-13, more preferably 10-11; in a specific embodiment of the present invention, it is preferable to use a pH regulator to adjust the pH value of the mixture, The pH adjusting agent is preferably a sodium hydroxide solution or a sulfuric acid solution; the present invention has no special requirements on the concentration of the sodium hydroxide solution and the sulfuric acid solution, and the pH value of the mixture can be adjusted to the above-mentioned range; The leaching temperature is preferably 25-50°C, more preferably 25°C. In a specific embodiment of the present invention, the leaching can be carried out at room temperature without additional heating or cooling; the leaching time is preferably 6-48h, more preferably 24h; the pressure of the leaching is preferably normal pressure; the leaching is preferably carried out in an air atmosphere; the leaching is preferably carried out under stirring conditions, and the stirring speed is preferably 200-500r/ min, more preferably 350r/min.

The technical solutions in the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The raw materials used in the following examples and comparative examples are all sulfide-type gold concentrates, and the sulfide-type gold concentrates are finely ground to -74 μm, accounting for 85%, and their chemical composition (wt.%) is shown in Table 1.

The chemical composition (wt.%) of table 1 gold concentrate

*The unit is g/t.

Example 1

Prepare the triazine leaching agent according to the flow process in Fig. 1, and extract the gold and silver in the ore, the steps are as follows:

Dissolve the reagent containing triazine ring (cyanuric acid, melamine, melamine or cyanuric chloride) in water at 50°C, then add sodium hydroxide, and then add carbon disulfide under the stirring condition of 200r/min , the concentration of the reagent containing the triazine ring in the resulting mixed solution is 0.1mol/L, the concentration of sodium hydroxide is 0.2mol/L, and the concentration of carbon disulfide is 0.3mol/L; react at 50°C for 3h, and after the reaction is completed, the The solution is cooled to room temperature, filtered and washed to obtain a triazine extractant that can exist stably under alkaline conditions.

Mix the ground sulfide-type gold concentrate with water to make slurry (the mass ratio of water and finely ground sulfide-type gold concentrate is 2.5:1), and then add triazine leaching agent and ferricyanide Potassium chloride, wherein the addition of triazine leaching agent is 0.5wt.% of the water quality in the pulp, based on the volume of water in the pulp, the concentration of potassium ferricyanide in the mixture obtained after mixing is 0.01mol/L, using pH The regulator adjusted the initial pH value to 11, and then leached for 24 hours under the conditions of an air atmosphere, a temperature of 25° C. and a stirring speed of 350 r/min. After the leaching is over, take the leaching solution to detect the concentration of gold and silver, and calculate the leaching rate. Table 2 shows the effect of reagent types containing triazine rings on the leaching rates of gold and silver.

The impact of the kind of reagent containing triazine ring on the gold and silver leaching rate in table 2

Types of reagents containing triazine rings Gold leaching rate/% Silver leaching rate/% Cyanuric acid 85.7 89.0 Melamine 95.1 97.8 Thiocyanuric acid 91.4 94.8 Cyanuric chloride 72.0 78.1

According to the data in Table 2, it can be seen that when melamine is used to synthesize triazine leaching agents, the leaching rates of gold and silver are the best, which are 95.1% and 97.8% respectively.

Example 2

The preparation of the triazine leaching agent and the process of extracting gold and silver using the triazine leaching agent are the same as in Example 1, and the reagent containing a coordination group is carbon disulfide or a carboxylic acid organic compound.

The preparation conditions of the leaching agent are: the concentration of melamine is 0.1mol/L, the temperature of the aqueous solution is 50°C, the stirring speed is 200r/min, the amount of sodium hydroxide is 0.2mol/L, the concentration of carbon disulfide or carboxylic acid organic matter is 0.3mol/L, and the reaction time is 3h .

Leaching conditions: gold concentrate is mixed with water to form a slurry (the mass ratio of water and finely ground gold concentrate is 2.5:1), the amount of triazine leaching agent is 0.5wt.% of the water quality in the slurry, and the amount of water in the slurry is 0.5wt.%. In terms of water volume, the concentration of potassium ferricyanide in the mixture obtained after mixing is 0.01mol/L, the initial pH value is 11, and it is leached for 24 hours under the conditions of air atmosphere, temperature 25°C and stirring speed 350r/min.

After the leaching is over, take the leaching solution to detect the concentration of gold and silver. The effects of carbon disulfide or carboxylic acid organic species on the leaching rate of gold and silver are shown in Table 3.

Table 3 Effect of carbon disulfide or carboxylic acid organic species on the leaching rate of gold and silver

Carbon disulfide or carboxylic acid organic species Gold leaching rate/% Silver leaching rate/% carbon disulfide 95.1 97.8 Sodium Chloroacetate 90.9 92.4 sodium glycinate 93.5 82.6 sodium humate 72.9 80.8

According to the results in Table 3, it can be seen that when the leaching agent is prepared by substitution reaction of carbon disulfide and melamine, the leaching rates of gold and silver are the best, which are 95.1% and 97.8%, respectively.

Example 3

The preparation of triazine leaching agents and the process of extracting gold and silver using triazine leaching agents are the same as in Example 1, and the temperatures for preparing leaching agents are 30°C, 40°C, 50°C, 70°C or 90°C, respectively.

Preparation conditions of leaching agent: melamine concentration 0.1mol/L, stirring speed 200r/min, sodium hydroxide addition 0.2mol/L, carbon disulfide concentration 0.3mol/L, reaction time 3h.

Leaching conditions: gold concentrate is mixed with water to form a slurry (the mass ratio of water and finely ground gold concentrate is 2.5:1), and the amount of triazine leaching agent is 0.5wt.% of the water quality in the slurry. In terms of the volume of reclaimed water, the concentration of potassium ferricyanide in the mixture obtained after mixing is 0.01mol/L, the initial pH value is 11, and it is leached for 24 hours under the conditions of air atmosphere, temperature 25°C and stirring speed 350r/min.

After the leaching is over, take the leaching solution to detect the concentration of gold and silver. The influence of the temperature of the prepared leaching agent solution on the leaching rate of gold and silver is shown in Table 4.

Table 4 prepares the influence of leaching agent solution temperature on gold, silver leaching rate

Preparation of leaching agent solution temperature/°C Gold leaching rate/% Silver leaching rate/% 30 50.3 68.2 40 73.0 85.7 50 95.1 97.8 70 96.1 97.4 90 95.3 97.6

According to the data in Table 4, it can be seen that the higher the temperature of the prepared leaching agent solution, the faster the reaction rate, and the better the effect of the prepared leaching agent on leaching gold and silver. The leaching rate of gold and silver did not increase significantly.

Example 4

The preparation of the triazine leaching agent and the process of extracting gold and silver using the triazine leaching agent are the same as in Example 1, only the concentration of potassium ferricyanide during leaching is changed.

Preparation conditions of leaching agent: melamine concentration 0.1mol/L, solution temperature 50°C, stirring speed 200r/min, sodium hydroxide addition 0.2mol/L, carbon disulfide concentration 0.3mol/L, reaction time 3h.

Leaching conditions: gold concentrate is mixed with water to form a slurry (the mass ratio of water and finely ground gold concentrate is 2.5:1), the amount of triazine leaching agent is 0.5wt.%, the initial pH value is 11, ferricyanide The concentration of potassium chloride is shown in Table 5; it was leached for 24 hours under the conditions of air atmosphere, temperature 25°C and stirring speed 350r/min.

After the leaching is over, take the leaching solution to detect the concentration of gold and silver. The influence of potassium ferricyanide concentration on gold and silver leaching rate is shown in Table 5.

The impact of table 5 potassium ferricyanide concentration on gold, silver leaching rate

Potassium ferricyanide concentration/(mol/L) Gold leaching rate/% Silver leaching rate/% 0.001 62.6 73.9 0.005 85.9 89.1 0.01 95.1 97.8 0.05 95.6 97.5 0.1 95.9 98.1

According to the results in Table 5, it can be seen that when the concentration of potassium ferricyanide is 0.01mol/L, the leaching rate of gold and silver is higher, and when the concentration of potassium ferricyanide continues to increase, the leaching rate of gold and silver does not increase significantly .

Comparative example 1

Other leaching conditions were the same as in Example 1, except that the leaching agent was changed to trisodium cyanurate. After leaching for 24 hours at a pH value of 11, the gold leaching rate was 14.1%, and the silver leaching rate was 20.7%.

Comparative example 2

Other leaching conditions were the same as in Example 1, except that the leaching agent was changed to trisodium thiocyanate, and the leaching was performed for 24 hours at a pH value of 11. The gold leaching rate was 5.8%, and the silver leaching rate was 8.3%.

The results of the above examples show that the preparation method of the triazine leaching agent provided by the present invention is simple, non-toxic and environmentally friendly, and can realize efficient leaching of gold and silver in ores under normal pressure and alkaline conditions.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. The preparation method of the triazine leaching agent is characterized by comprising the following steps of:

mixing a reagent containing a triazine ring, alkali metal hydroxide, a reagent containing a coordination group and water for substitution reaction to obtain a triazine leaching agent; the reagent containing the coordination group is carbon disulfide or carboxylic acid organic matters.

2. The method according to claim 1, wherein the triazine ring-containing reagent is one or more of cyanuric acid, trisodium cyanuric acid, melamine, cyanuric acid, trisodium cyanuric acid and cyanuric chloride;

the alkali metal hydroxide is sodium hydroxide or potassium hydroxide;

the carboxylic acid organic matter is one or more of sodium chloroacetate, sodium acetate, sodium formate, sodium glycinate and sodium humate.

3. The process according to claim 1, wherein the molar ratio of the triazine ring-containing reagent to the alkali metal hydroxide is (0.01 to 0.5): 0.1 to 2;

the molar ratio of the triazine ring-containing compound to the reagent containing a coordinating group is (0.01-0.5): 0.03-2.

4. The method according to claim 1, wherein the temperature of the substitution reaction is 30 to 90 ℃ for 1 to 6 hours.

5. The triazine leaching agent prepared by the preparation method of any one of claims 1 to 4.

6. Use of a triazine leachable agent as claimed in claim 5 for extracting precious metals from ores, the precious metals being gold and/or silver.

7. A method for extracting precious metals from ores, comprising the steps of:

mixing ore powder containing noble metal with water to obtain ore pulp; the noble metal is gold and/or silver;

mixing the ore pulp, the triazine leaching agent and the ferric salt, and leaching under alkaline conditions to obtain leaching solution containing noble metals; the iron salt is ferricyanide and/or ferrocyanide.

8. The method according to claim 7, wherein the mass ratio of the water to the noble metal-containing ore powder is (1-10): 1; the mass fraction of the powder with the granularity of-74 mu m in the ore powder containing noble metal is more than 80 percent.

9. The method according to claim 7, wherein the amount of triazine leaches is 0.01-5% of the water mass in the pulp;

the ferricyanide is potassium ferricyanide and/or sodium ferricyanide; the ferrocyanide is potassium ferrocyanide and/or sodium ferrocyanide; the dosage ratio of the ferric salt to the water in the ore pulp is (0.001-0.1) mol to 1L.

10. The method according to claim 7, wherein the alkaline condition has a pH of 9 to 13; the leaching temperature is 25-50 ℃, the time is 6-48 h, and the leaching pressure is normal pressure.