Method for recovering and extracting precious metal from mill tailings

Abstract

The invention discloses a method for recovering and extracting precious metals from mill tailings, and belongs to the technical field of resource recovery. The method for recovering and extracting the precious metal from the mill tailings comprises the following steps that (1) the collected tailings are subjected to classification, crushing and ore grinding treatment and then placed in a filter press, moisture is removed, drying is conducted, and pretreated tailings are obtained; (2) the pretreated tailings are added into a flotation reagent, precious metal mineral particles are attached to bubbles and float to the water surface under the action of stirring and air inflation, and a foam layer is formed; (3) collecting the foam layer to obtain concentrate; and (4) the concentrate is concentrated, shrunk, dried and smelted, and the precious metal is obtained. The method can effectively improve the recovery rate of the precious metal.

Description

Technical Field

[0001] The invention belongs to the technical field of resource recovery, and in particular relates to a method for recovering and extracting precious metals from ore dressing tailings. Background Art

[0002] With the continuous growth of global demand for precious metals and the increasing depletion of mineral resources, how to efficiently recover and extract precious metals from a large amount of tailings has become an important issue in the mining industry. Precious metals such as gold and silver have a wide range of application values ​​in electronics, aerospace, jewelry and other fields due to their unique physical and chemical properties. In recent years, with the advancement of science and technology and the development of emerging industries, the demand for precious metals has shown an increasing trend year by year. However, traditional mineral mining and mineral processing methods can often only extract part of the precious metals in the ore, and a large amount of precious metals still remain in the tailings. These tailings not only occupy a large amount of land resources, but also may cause potential harm to the environment and ecosystem. Therefore, recovering and extracting precious metals from tailings can not only improve the utilization rate of resources and reduce resource waste, but also reduce damage to the environment, which has important economic and environmental significance.

[0003] Patent CN 104846195 B discloses a method for recovering low-grade precious metals from beneficiation tailings. It includes the steps of tailings raw material flotation, Nelson beneficiator re-selection, Nelson tailings oxidation roasting pretreatment, slag cyanidation leaching, etc., tailings flotation to enrich gold in flotation concentrate, the flotation concentrate is re-selected by the Nelson beneficiator re-selection method to recover the coarse gold therein, the Nelson tailings are pre-treated by oxidation roasting, and the treated slag is subjected to cyanidation leaching process to recover the fine gold lost in the Nelson tailings. The invention realizes gold recovery in stages, improves the gold recovery rate, solves the problem of low precious metal recovery rate of flotation tailings using traditional processes, and improves the recovery rate of precious metals; gold concentrate and iron concentrate are produced at the same time, and the comprehensive utilization rate of tailings is improved, but there is still room for improvement in the recovery rate of precious metals. Summary of the invention

[0004] The object of the present invention is to provide a method for recovering and extracting precious metals from ore dressing tailings, so as to solve the technical problem of low precious metal recovery rate in the prior art.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for recovering and extracting precious metals from ore dressing tailings, comprising the following steps:

[0007] Step (1): the collected tailings are classified, crushed, and ground, and then placed in a filter press to remove moisture and dry to obtain pretreated tailings;

[0008] Step (2): adding the pretreated tailings to the flotation reagent, and under the action of stirring and aeration, the precious metal mineral particles are attached to the bubbles and float to the water surface to form a foam layer;

[0009] Step (3): collecting the foam layer to obtain a concentrate;

[0010] Step (4): Concentrating, shrinking, drying and smelting the concentrate to obtain precious metals.

[0011] Preferably, in step (2), the flotation reagent comprises a modified collector and a composite frother.

[0012] Preferably, the preparation method of the modified collector comprises the following steps:

[0013] Q1: Magnesium chloride hexahydrate and benzonitrile are added to a container containing N,N-dimethylformamide, stirred at room temperature, and then sodium hydrosulfide hydrate is added and stirred continuously. After the reaction is completed, saturated sodium chloride and distilled water are added, extracted, dried, and concentrated by rotary evaporation to obtain intermediate 1;

[0014] Q2: Add ethyl bromopyruvate to ethanol, mix, and then add dropwise to intermediate 1, stir at room temperature, and then heat under reflux. After the reaction is completed, adjust the pH, stir, extract, dry, and purify to obtain intermediate 2;

[0015] Q3: Slowly add hydrazine hydrate to the methanol containing intermediate 2, heat under reflux and stir. After stirring, cool and solid precipitates. Filter and wash to obtain intermediate 3.

[0016] Q4: Dissolve the intermediate 3 and potassium hydroxide in methanol, then slowly add carbon disulfide, stir at room temperature, heat to reflux, cool after reflux, slowly add ice water to the reaction solution, adjust the pH, filter out solid precipitation, wash with water, recrystallize, and dry to obtain a modified collector.

[0017] In the above process, the synthetic reaction formula of the modified collector is as follows:

[0018]

[0019] The results of mass spectrometry analysis were: m / z: 261.00 (100.0%), 262.01 (12.0%), 263.00 (9.2%), 262.00 (2.7%), 264.00 (1.3%), 263.01 (1.1%).

[0020] Preferably, in Q1, the molar ratio of magnesium chloride hexahydrate, benzonitrile and sodium hydrosulfide hydrate is (5.33-5.86): (4.85-5.34): (10.67-11.74), the stirring time at room temperature is 10-20 min, the stirring time is continued for 12-16 h, the volume ratio of saturated sodium chloride and distilled water is 7:1, ethyl acetate and saturated sodium chloride are used for cross-extraction, and anhydrous sodium sulfate is used for drying; in Q2, the molar ratio of ethyl bromopyruvate and intermediate 1 is (5.33-5.86): (4.85-5.34), the stirring time at room temperature is 1-2 h, the reflux stirring time is 4-6 h, the pH is adjusted to 8-8.3, stirred for 30-45 min, cross-extracted with saturated sodium chloride and dichloromethane, dried with anhydrous sodium sulfate, and purified using a mixed solution of petroleum ether and ethyl acetate with a volume ratio of 5:1 as an eluent.

[0021] Preferably, in Q3, the molar ratio of hydrazine hydrate to intermediate 2 is (10.9-13.1):(3.63-4.36), and the reflux stirring time is 4-6h; in Q4, the molar ratio of intermediate 3, potassium hydroxide and carbon disulfide is (3.09-4.64):(9.27-13.91):(7.72-11.58), the stirring time at room temperature is 30-45min, the heating reflux time is 8-10h, the pH is adjusted to 5-6, and recrystallization is carried out with methanol.

[0022] Preferably, the method for preparing the composite foaming agent comprises the following steps:

[0023] S1: Add sodium hypochlorite aqueous solution to a container, then add 1-methylpyrazole-5-carboxylic acid, stir at room temperature, acidify after stirring, solid precipitates, filter to obtain compound A; add compound A to a container, add thionyl chloride dropwise, stir under reflux, concentrate under reduced pressure after stirring, and obtain compound B;

[0024] S2: adding methyl pyridine-3-acetate and tetrahydrofuran to a container, adding tetrahydrofuran containing lithium bis(trimethylsilyl)amide dropwise under nitrogen protection and low temperature, stirring, and then adding tetrahydrofuran containing compound B dropwise. After the addition is completed, stirring is continued. After the stirring is completed, distilled water is added to quench the reaction, the pH is adjusted, extraction is performed, washing is performed, drying is performed, vacuum filtration is performed, concentration is performed, and purification is performed to obtain compound C;

[0025] S3: Compound C is added to a container, sulfuric acid aqueous solution is added dropwise, heated under reflux and stirred, after stirring, distilled water is added to dilute, pH is adjusted, extraction is performed, washing is performed, drying is performed, vacuum filtration is performed and concentrated, and purification is performed to obtain compound D; Compound D is dissolved in methanol, sodium borohydride is added under ice bath conditions, stirred at room temperature, after stirring is completed, vacuum concentration is performed, pH is adjusted, extraction is performed, drying is performed, vacuum filtration is performed and concentrated, and purification is performed to obtain compound E;

[0026] S4: Add sodium hydride to the N,N-dimethylformamide solution containing compound E, stir at room temperature, then dropwise add the N,N-dimethylformamide solution containing iodomethane, continue stirring, and after the stirring is completed, quench the reaction with a saturated aqueous ammonium chloride solution, extract, wash, dry, concentrate by vacuum filtration, and purify to obtain a composite foaming agent.

[0027] In the above process, the synthetic reaction formula of the composite foaming agent is as follows:

[0028]

[0029] The results of mass spectrometry analysis were: m / z: 251.08 (100.0%), 253.08 (32.1%), 252.09 (13.2%), 254.08 (4.5%), 252.08 (1.1%), 253.09 (1.0%).

[0030] Preferably, in S1, the dosage ratio of the sodium hypochlorite aqueous solution and 1-methylpyrazole-5-carboxylic acid is (24-36) mL: (2-2.5) g, the volume fraction of the sodium hypochlorite aqueous solution is 10vt%, the stirring time at room temperature is 10-12h, and the solution is acidified with 2mol / L hydrochloric acid; the dosage ratio of compound A and thionyl chloride is (1-1.5) g: (5-7.5) mL, and the stirring time is 5-8h.

[0031] Preferably, in S2, the molar ratio of methyl pyridine-3-acetate, lithium bis(trimethylsilyl)amide and compound B is (13.08-18.31):(14.33-20.06):(6.2-8.68), the low temperature is -78 to -80°C, the stirring time is 1-2h, the continued stirring time is 1-1.5h, the pH is adjusted to 4-5 with 2mol / L hydrochloric acid, extracted with ethyl acetate, washed with saturated sodium chloride, dried with anhydrous sodium sulfate, and purified with a 100-200 mesh silica gel column during the purification process, using a mixed solution of petroleum ether and ethyl acetate in a volume ratio of 4:1 as an eluent.

[0032] Preferably, in S3, the dosage ratio of compound C and aqueous sulfuric acid solution is (1-1.5) g: (5-7.5) mL, the volume fraction of aqueous sulfuric acid solution is 50 vt%, the heating reflux stirring temperature is 90-110°C, the stirring time is 1-2 h, and the pH is adjusted to 7-7.2 with 4 mol / L sodium hydroxide solution; the dosage ratio of compound D and sodium borohydride is (0.5-1) g: (0.16-0.32) g, the stirring time at room temperature is 1-2 h, and the pH is adjusted to 5-6 with 2 mol / L hydrochloric acid.

[0033] Preferably, in S4, the molar ratio of sodium hydride to compound E is (0.84-1.01):(0.42-0.5), the stirring time at room temperature is 10-20 min, the stirring time is continued for 1-2 h, the mixture is extracted with ethyl acetate 3-5 times, washed with distilled water and saturated sodium chloride, and dried with anhydrous sodium sulfate.

[0034] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0035] 1. The present invention firstly uses benzonitrile, magnesium chloride hexahydrate, ethyl bromopyruvate, hydrazine hydrate and carbon disulfide as raw materials to prepare a modified collector, then uses 1-methylpyrazole-5-carboxylic acid, sodium hypochlorite, thionyl chloride, pyridine-3-acetic acid methyl ester and iodomethane as raw materials to prepare a composite foaming agent, and the modified collector and the composite foaming agent are simultaneously used as flotation agents in a mineral processing process, which can effectively improve the recovery efficiency of precious metals.

[0036] 2. The present invention uses benzonitrile, magnesium chloride hexahydrate, ethyl bromopyruvate, hydrazine hydrate and carbon disulfide as raw materials to prepare a modified collector. The use of the modified collector can effectively improve the recovery efficiency of precious metals. The sulfur and nitrogen coordination atoms in the modified collector have lone pairs of electrons and can form coordination bonds with the empty orbits of precious metals. The formation of this coordination bond forms a close chelate relationship between the modified collector and the precious metal. Since different metals have different binding abilities with these coordination atoms, the modified collector can show high selectivity for precious metals. This selectivity promotes that precious metals can be effectively separated from tailings during the extraction process, while reducing interference and extraction of other non-precious metal elements; a close coordination chelate relationship is formed between the modified collector and the precious metal, and precious metals can be effectively captured and extracted from tailings, which not only improves the extraction efficiency of precious metals, but also reduces the loss during the extraction process, thereby improving the recovery rate of precious metals.

[0037] 3. The present invention uses 1-methylpyrazole-5-carboxylic acid, sodium hypochlorite, thionyl chloride, pyridine-3-acetic acid methyl ester and iodomethane as raw materials to prepare a composite foaming agent. The nitrogen atom on the pyridine ring in the composite foaming agent has a lone pair of electrons, which can form a coordination bond with the noble metal ion to form a stable complex. The presence of the complex can change the existence state of the noble metal ion in the tailings, making it easier to release and extract from the tailings, thereby improving the purity of the noble metal; and the composite foaming agent can reduce the surface tension of the tailings suspension, increase the stability and number of bubbles, and then increase the contact area and contact time between the bubbles and the tailings particles, improve the adsorption and migration efficiency of the noble metal ions, and improve the extraction efficiency of the noble metal. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Example 1

[0040] This embodiment discloses a method for preparing a modified collector, comprising the following steps:

[0041] Q1: 11.36 g of magnesium chloride hexahydrate and 5.2 g of benzonitrile were added to a container containing 220 mL of N,N-dimethylformamide, and stirred at room temperature for 15 min. Then, 8.3 g of sodium hydrosulfide hydrate was added and stirring was continued for 16 h. After the reaction was completed, saturated sodium chloride and distilled water were added, and the volume ratio of saturated sodium chloride to distilled water was 7:1. Ethyl acetate and saturated sodium chloride were used for cross extraction, and the mixture was dried with anhydrous sodium sulfate and concentrated by rotary evaporation to obtain intermediate 1;

[0042] Q2: 10.91 g of ethyl bromopyruvate was added to 300 mL of ethanol, mixed, and then added dropwise to 7.29 g of intermediate 1, stirred at room temperature for 2 h, and then heated under reflux for 6 h. After the reaction was completed, the pH was adjusted to 8, stirred for 45 min, cross-extracted with saturated sodium chloride and dichloromethane, dried with anhydrous sodium sulfate, and purified with a mixed solution of petroleum ether and ethyl acetate in a volume ratio of 5:1 as an eluent to obtain intermediate 2;

[0043] Q3: 5.83 g of hydrazine hydrate was slowly added to 300 mL of methanol containing 9.31 g of intermediate 2, and the mixture was heated under reflux and stirred for 6 h. After the stirring was completed, the mixture was cooled, and solid was precipitated. The solid was filtered and washed to obtain intermediate 3.

[0044] Q4: 8.62 g of intermediate 3 and 6.49 g of potassium hydroxide were dissolved in 500 mL of methanol, and then 7.34 g of carbon disulfide was slowly added. After stirring at room temperature for 45 min, the mixture was heated to reflux for 10 h. After the reflux, the mixture was cooled and ice water was slowly added to the reaction solution. The pH was adjusted to 5. Solid precipitated, which was filtered, washed with water, recrystallized with methanol, and dried to obtain a modified collector.

[0045] This embodiment discloses a method for preparing a composite foaming agent, comprising the following steps:

[0046] S1: 30 mL of a 10 vt% sodium hypochlorite aqueous solution was added to a container, followed by adding 2.25 g of 1-methylpyrazole-5-carboxylic acid, and stirring at room temperature for 12 h. After stirring, acidification was performed with 2 mol / L hydrochloric acid, and solids were precipitated. Compound A was obtained by suction filtration. 1.25 g of compound A was added to a container, and 6.25 mL of thionyl chloride was added dropwise. The mixture was stirred at reflux for 8 h. After stirring, the mixture was concentrated under reduced pressure to obtain compound B.

[0047] S2: 2.38 g of methyl pyridine-3-acetate and 10 mL of tetrahydrofuran were added to a container, and under nitrogen protection, at -78°C, 10 mL of tetrahydrofuran containing 2.88 mL of lithium bis(trimethylsilyl)amide was added dropwise, and stirred for 2 h, and then 5 mL of tetrahydrofuran containing 1.33 g of compound B was added dropwise. After the addition was completed, stirring was continued for 1.5 h. After the stirring was completed, distilled water was added to quench the reaction, and the pH was adjusted to 4 with 2 mol / L hydrochloric acid. The mixture was extracted with ethyl acetate, washed with saturated sodium chloride, dried with anhydrous sodium sulfate, and concentrated by filtration under reduced pressure. During the purification process, a 100-200 mesh silica gel column was used for purification, and a mixed solution of petroleum ether and ethyl acetate with a volume ratio of 4:1 was used as an eluent for purification to obtain compound C;

[0048] S3: 1.25 g of compound C was added to a container, 6.25 mL of a 50 vt% aqueous sulfuric acid solution was added dropwise, and the mixture was heated to reflux at 110°C with stirring for 2 h. After the stirring was completed, distilled water was added to dilute the mixture, and the pH was adjusted to 7 with a 4 mol / L sodium hydroxide solution. The mixture was extracted, washed, dried, concentrated by filtration under reduced pressure, and purified to obtain compound D. 0.75 g of compound D was dissolved in 15 mL of methanol, 0.24 g of sodium borohydride was added under ice bath conditions, and the mixture was stirred at room temperature for 2 h. After the stirring was completed, the mixture was concentrated under reduced pressure, and the pH was adjusted to 5 with 2 mol / L hydrochloric acid. The mixture was extracted, dried, concentrated by filtration under reduced pressure, and purified to obtain compound E.

[0049] S4: Add 0.033 g of sodium hydride to 1 mL of N,N-dimethylformamide solution containing 0.11 g of compound E, stir at room temperature for 15 min, then dropwise add 0.2 mL of N,N-dimethylformamide solution containing 0.015 g of iodomethane, and continue stirring for 2 h. After stirring, quench the reaction with saturated aqueous ammonium chloride solution, extract with ethyl acetate 5 times, wash with distilled water and saturated sodium chloride, dry with anhydrous sodium sulfate, concentrate with vacuum filtration, and purify to obtain a composite foaming agent.

[0050] This embodiment discloses a method for recovering and extracting precious metals from ore dressing tailings, comprising the following steps:

[0051] Step (1): the collected tailings are classified, crushed, and ground, and then placed in a filter press to remove moisture and dry to obtain pretreated tailings;

[0052] Step (2): adding the pretreated tailings to a flotation reagent containing a modified collector and a composite frother, and under the action of stirring and aeration, the precious metal mineral particles are attached to the bubbles and float to the water surface to form a foam layer;

[0053] Step (3): collecting the foam layer to obtain a concentrate;

[0054] Step (4): Concentrating, shrinking, drying and smelting the concentrate to obtain precious metals.

[0055] Example 2

[0056] This embodiment discloses a method for preparing a modified collector, comprising the following steps:

[0057] Q1: 10.82 g of magnesium chloride hexahydrate and 4.95 g of benzonitrile were added to a container containing 220 mL of N,N-dimethylformamide, and stirred at room temperature for 15 min. Then, 7.9 g of sodium hydrosulfide hydrate was added and stirring was continued for 16 h. After the reaction was completed, saturated sodium chloride and distilled water were added, and the volume ratio of saturated sodium chloride to distilled water was 7:1. Ethyl acetate and saturated sodium chloride were used for cross extraction, and the mixture was dried with anhydrous sodium sulfate and concentrated by rotary evaporation to obtain intermediate 1;

[0058] Q2: 10.39 g of ethyl bromopyruvate was added to 300 mL of ethanol, mixed, and then added dropwise to 6.94 g of intermediate 1, stirred at room temperature for 2 h, and then heated under reflux for 6 h. After the reaction was completed, the pH was adjusted to 8, stirred for 45 min, cross-extracted with saturated sodium chloride and dichloromethane, dried with anhydrous sodium sulfate, and purified with a mixed solution of petroleum ether and ethyl acetate in a volume ratio of 5:1 as an eluent to obtain intermediate 2;

[0059] Q3: 5.29 g of hydrazine hydrate was slowly added to 300 mL of methanol containing 8.46 g of intermediate 2, heated under reflux and stirred for 6 h. After stirring, the mixture was cooled, solid precipitated, filtered and washed to obtain intermediate 3;

[0060] Q4: Dissolve 6.89g of intermediate 3 and 5.19g of potassium hydroxide in 500mL of methanol, then slowly add 5.87g of carbon disulfide, stir at room temperature for 45min, heat to reflux for 10h, cool after reflux, slowly add ice water to the reaction solution, adjust pH to 5, solid precipitates, filter, wash with water, recrystallize with methanol, and dry to obtain a modified collector.

[0061] This embodiment discloses a method for preparing a composite foaming agent, comprising the following steps:

[0062] S1: 24 mL of a 10 vt% sodium hypochlorite aqueous solution was added to a container, followed by 2.5 g of 1-methylpyrazole-5-carboxylic acid, and stirred at room temperature for 12 h. After stirring, the mixture was acidified with 2 mol / L hydrochloric acid, and solids were precipitated. The solids were filtered to obtain compound A. 1.5 g of compound A was added to a container, and 7.5 mL of thionyl chloride was added dropwise. The mixture was stirred at reflux for 8 h. After stirring, the mixture was concentrated under reduced pressure to obtain compound B.

[0063] S2: 1.98 g of methyl pyridine-3-acetate and 10 mL of tetrahydrofuran were added to a container, and under nitrogen protection, 10 mL of tetrahydrofuran containing 2.4 mL of lithium bis(trimethylsilyl)amide was added dropwise at -78°C, and stirred for 2 h, and then 5 mL of tetrahydrofuran containing 1.11 g of compound B was added dropwise. After the addition was completed, stirring was continued for 1.5 h. After the stirring was completed, distilled water was added to quench the reaction, and the pH was adjusted to 4 with 2 mol / L hydrochloric acid. The mixture was extracted with ethyl acetate, washed with saturated sodium chloride, dried with anhydrous sodium sulfate, and concentrated by filtration under reduced pressure. During the purification process, a 100-200 mesh silica gel column was used for purification, and a mixed solution of petroleum ether and ethyl acetate with a volume ratio of 4:1 was used as an eluent for purification to obtain compound C;

[0064] S3: 1.5 g of compound C was added to a container, 5 mL of a 50 vt% aqueous sulfuric acid solution was added dropwise, and the mixture was heated to reflux at 110°C and stirred for 2 h. After the stirring was completed, distilled water was added to dilute the mixture, and the pH was adjusted to 7 with a 4 mol / L sodium hydroxide solution. The mixture was extracted, washed, dried, concentrated by filtration under reduced pressure, and purified to obtain compound D. 0.5 g of compound D was dissolved in 15 mL of methanol, and 0.32 g of sodium borohydride was added under ice bath conditions. The mixture was stirred at room temperature for 2 h. After the stirring was completed, the mixture was concentrated under reduced pressure, and the pH was adjusted to 5 with 2 mol / L hydrochloric acid. The mixture was extracted, dried, concentrated by filtration under reduced pressure, and purified to obtain compound E.

[0065] S4: Add 0.03 g of sodium hydride to 1 mL of N,N-dimethylformamide solution containing 0.12 g of compound E, stir at room temperature for 15 min, then dropwise add 0.2 mL of N,N-dimethylformamide solution containing 0.015 g of iodomethane, and continue stirring for 2 h. After stirring, quench the reaction with saturated aqueous ammonium chloride solution, extract with ethyl acetate 5 times, wash with distilled water and saturated sodium chloride, dry with anhydrous sodium sulfate, concentrate with vacuum filtration, and purify to obtain a composite foaming agent.

[0066] This embodiment discloses a method for recovering and extracting precious metals from ore dressing tailings, comprising the following steps:

[0067] Step (1): the collected tailings are classified, crushed, and ground, and then placed in a filter press to remove moisture and dry to obtain pretreated tailings;

[0068] Step (2): adding the pretreated tailings to a flotation reagent containing a modified collector and a composite frother, and under the action of stirring and aeration, the precious metal mineral particles are attached to the bubbles and float to the water surface to form a foam layer;

[0069] Step (3): collecting the foam layer to obtain a concentrate;

[0070] Step (4): Concentrating, shrinking, drying and smelting the concentrate to obtain precious metals.

[0071] Example 3

[0072] This embodiment discloses a method for preparing a modified collector, comprising the following steps:

[0073] Q1: 11.9 g of magnesium chloride hexahydrate and 5.45 g of benzonitrile were added to a container containing 220 mL of N,N-dimethylformamide, and stirred at room temperature for 15 min. Then, 8.69 g of sodium hydrosulfide hydrate was added and stirring was continued for 16 h. After the reaction was completed, saturated sodium chloride and distilled water were added, and the volume ratio of saturated sodium chloride to distilled water was 7:1. Ethyl acetate and saturated sodium chloride were used for cross extraction, and the mixture was dried with anhydrous sodium sulfate and concentrated by rotary evaporation to obtain intermediate 1;

[0074] Q2: 11.43 g of ethyl bromopyruvate was added to 300 mL of ethanol, mixed, and then added dropwise to 7.64 g of intermediate 1, stirred at room temperature for 2 h, and then heated under reflux for 6 h. After the reaction was completed, the pH was adjusted to 8, stirred for 45 min, cross-extracted with saturated sodium chloride and dichloromethane, dried with anhydrous sodium sulfate, and purified with a mixed solution of petroleum ether and ethyl acetate in a volume ratio of 5:1 as an eluent to obtain intermediate 2;

[0075] Q3: 6.36 g of hydrazine hydrate was slowly added to 300 mL of methanol containing 10.16 g of intermediate 2, heated under reflux and stirred for 6 h. After the stirring was completed, the mixture was cooled, solid precipitated, filtered and washed to obtain intermediate 3;

[0076] Q4: Dissolve 10.35g of intermediate 3 and 7.79g of potassium hydroxide in 500mL of methanol, then slowly add 8.8g of carbon disulfide, stir at room temperature for 45min, heat to reflux for 10h, cool after reflux, slowly add ice water to the reaction solution, adjust pH to 5, solid precipitates, filter, wash with water, recrystallize with methanol, and dry to obtain a modified collector.

[0077] This embodiment discloses a method for preparing a composite foaming agent, comprising the following steps:

[0078] S1: 36 mL of a 10 vt% sodium hypochlorite aqueous solution was added to a container, followed by 2 g of 1-methylpyrazole-5-carboxylic acid, and the mixture was stirred at room temperature for 12 h. After the stirring was completed, the mixture was acidified with 2 mol / L hydrochloric acid, and a solid was precipitated. The solid was filtered to obtain compound A. 1 g of compound A was added to a container, and 5 mL of thionyl chloride was added dropwise. The mixture was stirred at reflux for 8 h. After the stirring was completed, the mixture was concentrated under reduced pressure to obtain compound B.

[0079] S2: 2.77 g of methyl pyridine-3-acetate and 10 mL of tetrahydrofuran were added to a container, and under nitrogen protection, 10 mL of tetrahydrofuran containing 3.36 mL of lithium bis(trimethylsilyl)amide was added dropwise at -78°C, and stirred for 2 h, and then 5 mL of tetrahydrofuran containing 1.55 g of compound B was added dropwise. After the addition was completed, stirring was continued for 1.5 h. After the stirring was completed, distilled water was added to quench the reaction, and the pH was adjusted to 4 with 2 mol / L hydrochloric acid. The mixture was extracted with ethyl acetate, washed with saturated sodium chloride, dried with anhydrous sodium sulfate, and concentrated by filtration under reduced pressure. During the purification process, a 100-200 mesh silica gel column was used for purification, and a mixed solution of petroleum ether and ethyl acetate with a volume ratio of 4:1 was used as an eluent for purification to obtain compound C;

[0080] S3: Add 1g of compound C to a container, add dropwise 7.5mL of 50vt% sulfuric acid aqueous solution, heat under reflux at 110°C and stir for 2h, add distilled water to dilute, adjust pH=7 with 4mol / L sodium hydroxide solution, extract, wash, dry, filter and concentrate under reduced pressure, purify to obtain compound D; dissolve 1g of compound D with 15mL of methanol, add 0.16g of sodium borohydride under ice bath condition, stir at room temperature for 2h, concentrate under reduced pressure after stirring, adjust pH=5 with 2mol / L hydrochloric acid, extract, dry, filter and concentrate under reduced pressure, purify to obtain compound E;

[0081] S4: Add 0.036 g of sodium hydride to 1 mL of N,N-dimethylformamide solution containing 0.1 g of compound E, stir at room temperature for 15 min, then dropwise add 0.2 mL of N,N-dimethylformamide solution containing 0.015 g of iodomethane, and continue stirring for 2 h. After stirring, quench the reaction with saturated aqueous ammonium chloride solution, extract with ethyl acetate 5 times, wash with distilled water and saturated sodium chloride, dry with anhydrous sodium sulfate, concentrate with vacuum filtration, and purify to obtain a composite foaming agent.

[0082] This embodiment discloses a method for recovering and extracting precious metals from ore dressing tailings, comprising the following steps:

[0083] Step (1): the collected tailings are classified, crushed, and ground, and then placed in a filter press to remove moisture and dry to obtain pretreated tailings;

[0084] Step (2): adding the pretreated tailings to a flotation reagent containing a modified collector and a composite frother, and under the action of stirring and aeration, the precious metal mineral particles are attached to the bubbles and float to the water surface to form a foam layer;

[0085] Step (3): collecting the foam layer to obtain a concentrate;

[0086] Step (4): Concentrating, shrinking, drying and smelting the concentrate to obtain precious metals.

[0087] Example 4

[0088] This embodiment discloses a method for preparing a modified collector, comprising the following steps:

[0089] Q1: 11.09 g of magnesium chloride hexahydrate and 5.08 g of benzonitrile were added to a container containing 220 mL of N,N-dimethylformamide, and stirred at room temperature for 15 min. Then, 8.1 g of sodium hydrosulfide hydrate was added and stirring was continued for 16 h. After the reaction was completed, saturated sodium chloride and distilled water were added, and the volume ratio of saturated sodium chloride to distilled water was 7:1. Ethyl acetate and saturated sodium chloride were used for cross extraction, and the mixture was dried with anhydrous sodium sulfate and concentrated by rotary evaporation to obtain intermediate 1;

[0090] Q2: 10.65 g of ethyl bromopyruvate was added to 300 mL of ethanol, mixed, and then added dropwise to 7.12 g of intermediate 1, stirred at room temperature for 2 h, and then heated under reflux for 6 h. After the reaction was completed, the pH was adjusted to 8, stirred for 45 min, cross-extracted with saturated sodium chloride and dichloromethane, dried with anhydrous sodium sulfate, and purified with a mixed solution of petroleum ether and ethyl acetate in a volume ratio of 5:1 as an eluent to obtain intermediate 2;

[0091] Q3: 5.56 g of hydrazine hydrate was slowly added to 300 mL of methanol containing 8.89 g of intermediate 2, heated under reflux and stirred for 6 h. After the stirring was completed, the mixture was cooled, solid precipitated, filtered and washed to obtain intermediate 3;

[0092] Q4: Dissolve 7.76g of intermediate 3 and 7.14g of potassium hydroxide in 500mL of methanol, then slowly add 8.07g of carbon disulfide, stir at room temperature for 45min, heat and reflux for 10h, cool after reflux, slowly add ice water to the reaction solution, adjust pH=5, solid precipitates, filter, wash with water, recrystallize with methanol, and dry to obtain a modified collector.

[0093] This embodiment discloses a method for preparing a composite foaming agent, comprising the following steps:

[0094] S1: 33 mL of a 10 vt% sodium hypochlorite aqueous solution was added to a container, followed by adding 2.1 g of 1-methylpyrazole-5-carboxylic acid, and stirring at room temperature for 12 h. After stirring, the mixture was acidified with 2 mol / L hydrochloric acid, and solids were precipitated. The solids were filtered to obtain compound A. 1.1 g of compound A was added to a container, and 5.5 mL of thionyl chloride was added dropwise. The mixture was stirred at reflux for 8 h. After stirring, the mixture was concentrated under reduced pressure to obtain compound B.

[0095] S2: 2.18 g of methyl pyridine-3-acetate and 10 mL of tetrahydrofuran were added to a container, and under nitrogen protection, 10 mL of tetrahydrofuran containing 2.64 mL of lithium bis(trimethylsilyl)amide was added dropwise at -78°C, and stirred for 2 h, and then 5 mL of tetrahydrofuran containing 1.22 g of compound B was added dropwise. After the addition was completed, stirring was continued for 1.5 h. After the stirring was completed, distilled water was added to quench the reaction, and the pH was adjusted to 4 with 2 mol / L hydrochloric acid. The mixture was extracted with ethyl acetate, washed with saturated sodium chloride, dried with anhydrous sodium sulfate, and concentrated by filtration under reduced pressure. During the purification process, a 100-200 mesh silica gel column was used for purification, and a mixed solution of petroleum ether and ethyl acetate with a volume ratio of 4:1 was used as an eluent for purification to obtain compound C;

[0096] S3: 1.1 g of compound C was added to a container, 5.5 mL of a 50 vt% aqueous sulfuric acid solution was added dropwise, and the mixture was heated to reflux at 110°C with stirring for 2 h. After the stirring was completed, distilled water was added to dilute the mixture, and the pH was adjusted to 7 with a 4 mol / L sodium hydroxide solution. The mixture was extracted, washed, dried, concentrated by filtration under reduced pressure, and purified to obtain compound D. 0.6 g of compound D was dissolved in 15 mL of methanol, 0.2 g of sodium borohydride was added under ice bath conditions, and the mixture was stirred at room temperature for 2 h. After the stirring was completed, the mixture was concentrated under reduced pressure, and the pH was adjusted to 5 with 2 mol / L hydrochloric acid. The mixture was extracted, dried, concentrated by filtration under reduced pressure, and purified to obtain compound E.

[0097] S4: Add 0.032 g of sodium hydride to 1 mL of N,N-dimethylformamide solution containing 0.12 g of compound E, stir at room temperature for 15 min, then dropwise add 0.2 mL of N,N-dimethylformamide solution containing 0.015 g of iodomethane, and continue stirring for 2 h. After stirring, quench the reaction with saturated aqueous ammonium chloride solution, extract with ethyl acetate 5 times, wash with distilled water and saturated sodium chloride, dry with anhydrous sodium sulfate, concentrate with vacuum filtration, and purify to obtain a composite foaming agent.

[0098] This embodiment discloses a method for recovering and extracting precious metals from ore dressing tailings, comprising the following steps:

[0099] Step (1): the collected tailings are classified, crushed, and ground, and then placed in a filter press to remove moisture and dry to obtain pretreated tailings;

[0100] Step (2): adding the pretreated tailings to a flotation reagent containing a modified collector and a composite frother, and under the action of stirring and aeration, the precious metal mineral particles are attached to the bubbles and float to the water surface to form a foam layer;

[0101] Step (3): collecting the foam layer to obtain a concentrate;

[0102] Step (4): Concentrating, shrinking, drying and smelting the concentrate to obtain precious metals.

[0103] Comparative Example 1: Compared with Example 1, in the preparation process of the modified collector in Comparative Example 1, ethyl bromopyruvate was not added, and other conditions remained unchanged.

[0104] Comparative Example 2: Compared with Example 1, in the preparation process of the composite foaming agent in Comparative Example 2, no pyridine-3-acetic acid methyl ester is added, and other conditions remain unchanged.

[0105] Comparative Example 3: Compared with Example 1, in Comparative Example 3, no modified collector is added during the recovery and extraction process, and other conditions remain unchanged.

[0106] Comparative Example 4: Compared with Example 1, in Comparative Example 4, no composite foaming agent is added during the recovery and extraction process, and other conditions remain unchanged.

[0107] According to the methods of Examples 1-4 and Comparative Examples 1-4, precious metals in the beneficiation tailings were recovered and extracted, the content of heavy metals was tested according to GB / T 17418.7-2010, and the recovery rate of precious metals was calculated. The test results are shown in Table 1:

[0108] Table 1

[0109]

[0110] It can be seen from the test results in Table 1 that the present invention can make the precious metals have an excellent recovery rate through the methods of Examples 1-4. By comparing Comparative Example 1 with Examples 1-4, it can be seen that the addition of ethyl bromopyruvate can make the precious metals in the tailings have an excellent recovery rate; by comparing Comparative Example 2 with Examples 1-4, it can be seen that the addition of methyl pyridine-3-acetate can make the precious metals in the tailings have an excellent recovery rate; by comparing Comparative Example 3 with Examples 1-4, it can be seen that the addition of a modified collector can make the precious metals in the tailings have an excellent recovery rate; by comparing Comparative Example 4 with Examples 1-4, it can be seen that the addition of a composite foaming agent can make the precious metals in the tailings have an excellent recovery rate.

[0111] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0112] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for recovering and extracting precious metals from ore dressing tailings, characterized in that: The following steps are involved: Step (1): the collected tailings are classified, crushed, and ground, and then placed in a filter press to remove moisture and dry to obtain pretreated tailings; Step (2): adding the pretreated tailings to the flotation reagent, and under the action of stirring and aeration, the precious metal mineral particles are attached to the bubbles and float to the water surface to form a foam layer; Step (3): collecting the foam layer to obtain a concentrate; Step (4): concentrating, shrinking, drying and smelting the concentrate to obtain precious metals; In the step (2), the flotation reagent includes a modified collector and a composite frother; The structural formula of the modified collector is as follows: The structural formula of the composite foaming agent is as follows:

2. The method for recovering and extracting precious metals from ore dressing tailings according to claim 1, characterized in that: The modified collector is prepared by using benzonitrile, magnesium chloride hexahydrate, ethyl bromopyruvate, hydrazine hydrate and carbon disulfide as raw materials; the composite foaming agent is prepared by using 1-methylpyrazole-5-carboxylic acid, sodium hypochlorite, thionyl chloride, pyridine-3-acetic acid methyl ester and iodomethane as raw materials.

3. The method for recovering and extracting heavy metals from ore dressing tailings according to claim 2, characterized in that: The preparation method of the modified collector, The following steps are involved: Q1: Magnesium chloride hexahydrate and benzonitrile are added to a container containing N,N-dimethylformamide, stirred at room temperature, and then sodium hydrosulfide hydrate is added and stirred continuously. After the reaction is completed, saturated sodium chloride and distilled water are added, extracted, dried, and concentrated by rotary evaporation to obtain intermediate 1; Q2: Add ethyl bromopyruvate to ethanol, mix, and then add dropwise to intermediate 1, stir at room temperature, and then heat under reflux. After the reaction is completed, adjust the pH, stir, extract, dry, and purify to obtain intermediate 2; Q3: Slowly add hydrazine hydrate to the methanol containing intermediate 2, heat under reflux and stir. After stirring, cool and solid precipitates. Filter and wash to obtain intermediate 3. Q4: Dissolve the intermediate 3 and potassium hydroxide in methanol, then slowly add carbon disulfide, stir at room temperature, heat to reflux, cool after reflux, slowly add ice water to the reaction solution, adjust the pH, filter out solid precipitation, wash with water, recrystallize, and dry to obtain a modified collector.

4. The method for recovering and extracting heavy metals from ore dressing tailings according to claim 3, characterized in that: In the Q1, the molar ratio of magnesium chloride hexahydrate, benzonitrile and sodium hydrosulfide hydrate is (5.33-5.86): (4.85-5.34): (10.67-11.74), the stirring time at room temperature is 10-20 minutes, the stirring time is continued for 12-16 hours, the volume ratio of saturated sodium chloride and distilled water is 7:1, ethyl acetate and saturated sodium chloride are used for cross-extraction, and anhydrous sodium sulfate is used for drying; in the Q2, the molar ratio of ethyl bromopyruvate and intermediate 1 is (5.33-5.86): (4.85-5.34), the stirring time at room temperature is 1-2 hours, the reflux stirring time is 4-6 hours, the pH is adjusted to 8-8.3, stirred for 30-45 minutes, cross-extracted with saturated sodium chloride and dichloromethane, dried with anhydrous sodium sulfate, and purified using a mixed solution of petroleum ether and ethyl acetate with a volume ratio of 5:1 as an eluent.

5. The method for recovering and extracting heavy metals from ore dressing tailings according to claim 3, characterized in that: In the Q3, the molar ratio of hydrazine hydrate and intermediate 2 is (10.9-13.1): (3.63-4.36), and the reflux stirring time is 4-6h; in the Q4, the molar ratio of intermediate 3, potassium hydroxide and carbon disulfide is (3.09-4.64): (9.27-13.91): (7.72-11.58), the stirring time at room temperature is 30-45min, the heating reflux time is 8-10h, the pH is adjusted to 5-6, and recrystallization is carried out with methanol.

6. The method for recovering and extracting heavy metals from ore dressing tailings according to claim 2, characterized in that: The preparation method of the composite foaming agent comprises the following steps: S1: Add sodium hypochlorite aqueous solution to a container, then add 1-methylpyrazole-5-carboxylic acid, stir at room temperature, acidify after stirring, solid precipitates, filter to obtain compound A; add compound A to a container, add thionyl chloride dropwise, stir under reflux, concentrate under reduced pressure after stirring, and obtain compound B; S2: adding methyl pyridine-3-acetate and tetrahydrofuran to a container, adding tetrahydrofuran containing lithium bis(trimethylsilyl)amide dropwise under nitrogen protection and low temperature, stirring, and then adding tetrahydrofuran containing compound B dropwise. After the addition is completed, stirring is continued. After the stirring is completed, distilled water is added to quench the reaction, the pH is adjusted, extraction is performed, washing is performed, drying is performed, vacuum filtration is performed, concentration is performed, and purification is performed to obtain compound C; S3: Compound C is added to a container, sulfuric acid aqueous solution is added dropwise, heated under reflux and stirred, after stirring, distilled water is added to dilute, pH is adjusted, extraction is performed, washing is performed, drying is performed, vacuum filtration is performed and concentrated, and purification is performed to obtain compound D; Compound D is dissolved in methanol, sodium borohydride is added under ice bath conditions, stirred at room temperature, after stirring is completed, vacuum concentration is performed, pH is adjusted, extraction is performed, drying is performed, vacuum filtration is performed and concentrated, and purification is performed to obtain compound E; S4: Add sodium hydride to the N,N-dimethylformamide solution containing compound E, stir at room temperature, then dropwise add the N,N-dimethylformamide solution containing iodomethane, continue stirring, and after the stirring is completed, quench the reaction with a saturated aqueous ammonium chloride solution, extract, wash, dry, concentrate by vacuum filtration, and purify to obtain a composite foaming agent.

7. The method for recovering and extracting heavy metals from ore dressing tailings according to claim 6, characterized in that: In S1, the dosage ratio of sodium hypochlorite aqueous solution and 1-methylpyrazole-5-carboxylic acid is (24-36) mL: (2-2.5) g, the volume fraction of sodium hypochlorite aqueous solution is 10 vt%, the stirring time at room temperature is 10-12 h, and 2 mol / L hydrochloric acid is used for acidification; the dosage ratio of compound A and thionyl chloride is (1-1.5) g: (5-7.5) mL, and the stirring time is 5-8 h.

8. The method for recovering and extracting heavy metals from ore dressing tailings according to claim 6, characterized in that: In the S2, the molar ratio of methyl pyridine-3-acetate, lithium bis(trimethylsilyl)amide and compound B is (13.08-18.31):(14.33-20.06):(6.2-8.68), the low temperature is -78 to -80°C, the stirring time is 1-2h, the stirring time is continued for 1-1.5h, the pH is adjusted to 4-5 with 2mol / L hydrochloric acid, extracted with ethyl acetate, washed with saturated sodium chloride, dried with anhydrous sodium sulfate, and purified with a 100-200 mesh silica gel column during the purification process, using a mixed solution of petroleum ether and ethyl acetate in a volume ratio of 4:1 as an eluent.

9. The method for recovering and extracting heavy metals from ore dressing tailings according to claim 6, characterized in that: In the S3, the dosage ratio of compound C and aqueous sulfuric acid solution is (1-1.5) g: (5-7.5) mL, the volume fraction of aqueous sulfuric acid solution is 50 vt%, the heating reflux stirring temperature is 90-110°C, the stirring time is 1-2 h, and the pH is adjusted to 7-7.2 with 4 mol / L sodium hydroxide solution; the dosage ratio of compound D and sodium borohydride is (0.5-1) g: (0.16-0.32) g, the stirring time at room temperature is 1-2 h, and the pH is adjusted to 5-6 with 2 mol / L hydrochloric acid.

10. The method for recovering and extracting heavy metals from ore dressing tailings according to claim 6, characterized in that: In the S4, the molar ratio of sodium hydride to compound E is (0.84-1.01): (0.42-0.5), the stirring time at room temperature is 10-20 min, the stirring time is continued for 1-2 h, and the mixture is extracted with ethyl acetate for 3-5 times, washed with distilled water and saturated sodium chloride, and dried with anhydrous sodium sulfate.

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