Low-toxicity environment-friendly precious metal extracting agent

Abstract

The invention relates to the technical field of precious metal extraction, and particularly discloses a low-toxicity environment-friendly precious metal extracting agent which comprises the following components in percentage by mass: 20-40% of an alkaline thiourea component, 30-50% of a thiocyanate component, 2-8% of an anionic surfactant A, 2-8% of an anionic surfactant B, 5-15% of an alkaline regulator and 0.1-2% of a stabilizer, the alkaline thiourea and thiocyanate dual coordination system in the extracting agent can synergistically generate an active ligand with mixed coordination of-SC (NH2) 2 and SCN-in an alkaline medium, cyano contained in the extracting agent is stably combined in a thiourea or thiocyanate skeleton in a covalent bond form and does not exist in a free CN-form, and the leakage risk and acute toxicity are greatly reduced. In addition, the system can be broken and reduced into non-toxic small molecules in a natural environment or wastewater in several weeks through microbial action, chemical hydrolysis and other ways, design degradation is achieved, and long-term environmental accumulation and ecological toxicity are effectively reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of precious metal extraction, and particularly relates to a low-toxic and environment-friendly precious metal extractant. Background Art

[0002] In the field of precious metal extraction, traditional extraction technologies have long dominated, but these technologies have many significant shortcomings.

[0003] Traditional extraction of precious metals mostly relies on cyanide systems. Although cyanide has a strong coordination ability for precious metals, its cyanide group is free CN. - It exists in the form of cyanide and has extremely high acute toxicity. Once leaked, it will cause harm to the ecological environment and human health. Moreover, the cyanide system is difficult to degrade naturally in the natural environment or wastewater, and long-term accumulation will continue to produce ecological toxicity.

[0004] At the same time, traditional processes often use strong acids such as aqua regia and nitric acid for leaching, which not only causes severe corrosion to metal equipment, agitator seals, etc., increasing equipment maintenance costs and replacement frequency, but also produces acid mist, hydrogen cyanide and other dangerous gases, which are harmful to people and the environment.

[0005] In addition, traditional extraction processes often need to be carried out in steps when processing multiple precious metals. The extraction of different precious metals requires different process conditions, which not only leads to complicated process flows and increases operational difficulty, but also reduces raw material utilization, increases step-by-step processing costs, and limits the economic benefits and flexibility of precious metal recovery.

[0006] Therefore, developing an extractant that is low-toxic and environmentally friendly, can operate under weakly alkaline conditions, and can efficiently extract multiple precious metals in parallel has become a key issue that needs to be urgently addressed in the field of precious metal extraction.

[0007] In response to this, the inventors proposed a low-toxic and environmentally friendly precious metal extractant to solve the above problems. Summary of the Invention

[0008] The purpose of the present invention is to provide a low-toxic and environmentally friendly precious metal extractant to solve the problems raised in the above background technology.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A low-toxic and environmentally friendly precious metal extractant comprises, by mass percentage, 20%-40% of an alkaline thiourea component, 30%-50% of a thiocyanate component, 2%-8% of anionic surfactant A, 2%-8% of anionic surfactant B, 5%-15% of an alkaline regulator, and 0.1%-2% of a stabilizer.

[0011] Preferably, the alkaline thiourea component is alkaline thiourea or thiourea modified by sulfurization;

[0012] The thiocyanate component is sodium thiocyanate, ammonium thiocyanate and a mixture thereof.

[0013] Preferably, the anionic surfactant A is sodium dodecylbenzenesulfonate (SDBS).

[0014] Preferably, the anionic surfactant B is sodium lauryl polyoxyethylene ether sulfonate (AEO-series).

[0015] Preferably, the alkaline regulator is sodium carbonate and sodium hydroxide;

[0016] The stabilizer is one or a combination of sodium citrate and EDTA sodium salt.

[0017] The method for preparing the low-toxic and environmentally friendly precious metal extractant described above comprises the following steps:

[0018] Step S1: mixing urea, sodium sulfide, ammonium polysulfide and sodium carbonate, and heating them at 300° C. to 500° C. to react to generate an alkaline thiourea precursor;

[0019] Step S2: continuing to heat the precursor to 800° C. to 1100° C. for thermal condensation and thioation conversion reaction, so as to partially convert the precursor into thiocyanate, thereby obtaining a mixture;

[0020] Step S3: The mixture is rapidly condensed and then mechanically crushed to a fineness of 100-300 mesh to obtain a primary powder;

[0021] Step S4: mixing the powder with an anionic surfactant and an aqueous solution of the anionic surfactant at a mass ratio of 5-15% and homogenizing to promote the loosening of the thiocyanate structure and obtain a mixed solution;

[0022] Step S5: adding sodium carbonate or sodium hydroxide to the mixed solution to adjust the alkalinity of the system to pH 9-11, and adding 0.1-2% of a stabilizer to inhibit impurity complexation to obtain a stabilized solution;

[0023] Step S6: After cooling the stabilized liquid to room temperature, filtering or homogenizing is performed, and the product is packaged and sealed to obtain the final product.

[0024] Preferably, the molar ratio of the raw materials in step S1 is urea: sodium sulfide: ammonium polysulfide: sodium carbonate = 1: 0.5-1.5: 0.2-0.8: 0.3-1.0.

[0025] Preferably, the heating rate in step S2 is 5-15°C / min.

[0026] Preferably, the crushing particle size range of step S3 is 100-200 mesh.

[0027] Preferably, the final product is dried after step S6 to remove residual moisture and improve storage stability.

[0028] Preferably, the moisture content of the final product is ≤5%.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The alkaline thiourea and thiocyanate dual coordination system in the extractant of the present invention can synergistically generate active ligands with mixed coordination of SC(NH2)2 and SCN- in an alkaline medium. These active species have extremely strong coordination affinity for precious metals such as gold, silver, platinum, palladium, and rhodium. The introduction of anionic surfactants further enhances the contact efficiency between the ligands and the precious metal solid phase by reducing interfacial tension and forming microemulsions or micelles, thereby fundamentally accelerating the desorption and dissolution rate of precious metals from the solid matrix and significantly improving the extraction kinetics.

[0031] (2) Compared with traditional cyanide systems, the cyanide groups contained in this extractant are stably bound to the thiourea or thiocyanate skeleton in the form of covalent bonds, and do not exist in the form of free CN-, which greatly reduces the risk of leakage and acute toxicity. In addition, this system can be broken down and reduced to non-toxic small molecules within a few weeks in the natural environment or wastewater through microbial action, chemical hydrolysis, etc., achieving "designed degradation" and effectively reducing long-term environmental accumulation and ecological toxicity.

[0032] (3) The low-toxic and environmentally friendly precious metal extractant of the present invention operates under weak alkaline conditions of pH 9-11, abandoning the strong acid leaching process such as aqua regia and nitric acid, avoiding strong corrosion of metal equipment and agitator seals, and reducing the generation of dangerous gases such as acid mist and hydrogen cyanide. No high-concentration organic solvents or high-pressure reaction devices are required during on-site operation, significantly improving the overall process safety and on-site controllability; because the active ligands in this extractant can form stable complex ions with various precious metals in I, II, and IV valence states (such as Au(CN)2-, Pt(CN)4 2 -、Pd(CN)4 2 -etc.), therefore, under the same set of process conditions, it is possible to achieve parallel and efficient extraction of precious metals such as gold, silver, platinum, palladium, rhodium, iridium, etc., greatly improving the utilization rate of raw materials and recycling flexibility, and reducing the cost of step-by-step processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The figure is a flow chart of the method for preparing the low-toxic and environment-friendly precious metal extractant of the present invention. DETAILED DESCRIPTION

[0034] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0035] Example 1:

[0036] See also Figure 1 As shown, a low-toxic and environmentally friendly precious metal extractant comprises, by mass percentage, 20%-40% alkaline thiourea component, 30%-50% thiocyanate component, 2%-8% anionic surfactant A, 2%-8% anionic surfactant B, 5%-15% alkaline regulator, and 0.1%-2% stabilizer.

[0037] Specifically, the alkaline thiourea component is alkaline thiourea or thiourea modified by sulfurization;

[0038] The thiocyanate component is sodium thiocyanate, ammonium thiocyanate and a mixture thereof.

[0039] Specifically, the anionic surfactant A is sodium dodecylbenzenesulfonate (SDBS).

[0040] Specifically, the anionic surfactant B is sodium lauryl polyoxyethylene ether sulfonate (AEO-series).

[0041] Specifically, the alkaline regulator is sodium carbonate;

[0042] The stabilizer is sodium citrate.

[0043] The method for preparing the low-toxic and environmentally friendly precious metal extractant described above comprises the following steps:

[0044] Step S1: mixing urea, sodium sulfide, ammonium polysulfide and sodium carbonate, and heating them at 300° C. to 500° C. to react to generate an alkaline thiourea precursor;

[0045] Step S2: continuing to heat the precursor to 800° C. to 1100° C. for thermal condensation and thioation conversion reaction, so as to partially convert the precursor into thiocyanate, thereby obtaining a mixture;

[0046] Step S3: The mixture is rapidly condensed and then mechanically crushed to a fineness of 100-300 mesh to obtain a primary powder;

[0047] Step S4: mixing the powder with an anionic surfactant and an aqueous solution of the anionic surfactant at a mass ratio of 5-15% and homogenizing to promote the loosening of the thiocyanate structure and obtain a mixed solution;

[0048] Step S5: adding sodium carbonate or sodium hydroxide to the mixed solution to adjust the alkalinity of the system to pH 9-11, and adding 0.1-2% of a stabilizer to inhibit impurity complexation to obtain a stabilized solution;

[0049] Step S6: After cooling the stabilized liquid to room temperature, filtering or homogenizing it, packaging and sealing it, and obtaining the final product catalyst.

[0050] Specifically, the molar ratio of the raw materials in step S1 is urea: sodium sulfide: ammonium polysulfide: sodium carbonate = 1: 0.5-1.5: 0.2-0.8: 0.3-1.0.

[0051] Specifically, the heating rate in step S2 is 5-15°C / min.

[0052] Specifically, the crushing particle size range of step S3 is 100-200 mesh.

[0053] Specifically, after step S6, the final product is dried to remove residual moisture and improve storage stability.

[0054] Specifically, the moisture content of the final product is ≤5%.

[0055] As can be seen from the above, the dual coordination system of alkaline thiourea and thiocyanate in this extractant can synergistically generate active ligands with mixed coordination of SC(NH2)2 and SCN- in alkaline media. These active species have extremely strong coordination affinity for precious metals such as gold, silver, platinum, palladium, and rhodium. The introduction of anionic surfactants further enhances the contact efficiency between the ligands and the precious metal solid phase by reducing interfacial tension and forming microemulsions or micelles, thereby fundamentally accelerating the desorption and dissolution rate of precious metals from the solid matrix and significantly improving extraction kinetics.

[0056] Compared to traditional cyanide systems, the cyanide groups in this extractant are stably covalently bonded to the thiourea or thiocyanate backbone, rather than existing as free CN-, significantly reducing the risk of leakage and acute toxicity. Furthermore, in the natural environment or wastewater, this system can be broken down and reduced to non-toxic small molecules within weeks through microbial action and chemical hydrolysis, achieving "designed degradation" and effectively reducing long-term environmental accumulation and ecotoxicity.

[0057] Example 2:

[0058] Extraction of Au / Ag from gold mine tailings:

[0059] 1. Materials and methods

[0060] Sample source: Tailings from a gold mine, air-dried, crushed and passed through a 200-mesh sieve.

[0061] Initial precious metal content (determined by ICP-MS, the sample was measured three times in parallel and the average value was taken):

[0062] Au: 1.25g / t;

[0063] Ag:5.40g / t.

[0064] Extraction conditions:

[0065] Solid-liquid ratio: 1g sample: 10mL solution;

[0066] The dosage of this extractant: 8g / L;

[0067] Traditional sodium cyanide dosage (control): 3g / L;

[0068] pH: 10 (adjusted with Na2CO3);

[0069] Temperature: 25℃;

[0070] Stirring speed: 400 rpm;

[0071] Reaction time: 6h.

[0072] Data acquisition method:

[0073] Sample pretreatment: After the reaction, the solid and liquid were separated with filter paper. The filtrate was diluted and the Au and Ag concentrations were determined using ICP-MS (Agilent 7900).

[0074] Calibration curve: standard solution series (0, 0.1, 0.5, 1.0, 5.0 mg / L), R 2 ≥0.999;

[0075] Parallel experiments: three times for each group, and the mean and standard deviation were taken.

[0076] 2. Calculation process:

[0077] Extraction rate (%) = (total amount of precious metals in filtrate / total amount of precious metals in original sample) × 100%

[0078] Gold extraction rate = (C1×V) / (m×C0)×100%

[0079] Where C1 is the Au concentration in the filtrate (mg / L), V is the filtrate volume (L), m is the sample mass (g), and C0 is the Au content in the sample (mg / g).

[0080] 3. The experimental results and comparison are shown in Table 1 below:

[0081] Table 1

[0082] Extractant type Au extraction rate (%) Ag extraction rate (%) Remark This extractant 92.4±1.2 88.7±1.5 6h，25℃ Sodium cyanide control 90.1±0.8 85.3±1.1 6h，25℃

[0083] Data Analysis:

[0084] Au extraction rate increased by 2.3 percentage points; Ag increased by 3.4 percentage points;

[0085] This extractant has slightly better effects under the same conditions while avoiding the risk of high cyanide toxicity.

[0086] As can be seen from the above, this method operates under weakly alkaline conditions of pH 9–11, eliminating strong acid leaching processes such as aqua regia and nitric acid. This avoids severe corrosion of metal equipment and agitator seals, and also reduces the generation of hazardous gases such as acid mist and hydrogen cyanide. On-site operation does not require high-concentration organic solvents or high-pressure reaction equipment, significantly improving overall process safety and on-site controllability.

[0087] Since the active ligand in this extractant can form stable complex ions with various noble metals in valence states of I, II, and IV (such as Au(CN)2 - 、Pt(CN)4 2 -、Pd(CN)4 2- etc.), so under the same set of process conditions, it is possible to achieve parallel and efficient extraction of precious metals such as gold, silver, platinum, palladium, rhodium, and iridium, greatly improving the utilization rate of raw materials and recycling flexibility, and reducing the cost of step-by-step processing.

[0088] Example 3:

[0089] Extraction of Pt / Pd from waste automobile exhaust catalysts:

[0090] 1. Materials and methods

[0091] Sample source: chopped precious metal oxide powder, sieved through 600 mesh.

[0092] Initial precious metal content (average value determined by AAS):

[0093] Pt: 2.15 wt%;

[0094] Pd: 1.80 wt%.

[0095] Extraction conditions:

[0096] Solid-liquid ratio: 1g:20mL;

[0097] The dosage of this extractant: 10g / L;

[0098] Traditional strong acid method (aqua regia) control: HCl:HNO3=3:1 (v / v), total acid volume 20mL;

[0099] pH: 10;

[0100] Temperature: 60℃;

[0101] Stirring: magnetic stirring, 500 rpm;

[0102] Time: 4 hours.

[0103] Data acquisition method:

[0104] Filtrate collection: centrifugation after the reaction (5000 rpm, 10 min);

[0105] Concentration determination: AAS (model: PerkinElmer AAnalyst 400), calibrated with a Pt / Pd standard curve (0–5 mg / L);

[0106] Repeatability: The experiment was repeated three times, and the mean and standard deviation were calculated.

[0107] 2. Calculation process:

[0108] Same as in Example 2, extraction rate (%)=(C1×V) / (m×C0)×100%.

[0109] 3. The experimental results and comparison are shown in Table 2 below:

[0110] Table 2

[0111] Extractant type Pt extraction rate (%) Pd extraction rate (%) Remark This extractant 94.8±0.9 91.2±1.0 4h，60℃ Strong acid control 88.5±1.3 87.0±0.8 4h，60℃

[0112] Data Analysis

[0113] The extraction efficiency of Pt increased by 6.3 percentage points; that of Pd increased by 4.2 percentage points;

[0114] This extractant operates under alkaline conditions, has low equipment corrosion resistance requirements, and is safe and environmentally friendly to operate.

[0115] Summary of technical effects

[0116] High efficiency: The extraction rates of gold, silver, platinum and palladium are 2-6 percentage points higher than those of traditional methods;

[0117] Safety: Avoid highly toxic cyanide and concentrated acid, reduce operational risks and equipment corrosion;

[0118] Environmental protection: The natural degradation period of this extractant is short (≤30d), which is beneficial to wastewater treatment and tail liquid discharge;

[0119] Economical: Synthesized using common raw materials, the cost is controllable.

[0120] The above examples and comparative examples verify the superior performance of the low-toxic and environmentally friendly precious metal extractant of the present invention in various industrial scenarios, fully highlighting its application value.

[0121] From the above, we can know that the organic small molecule stabilizer (such as citrate, EDTA) can be added in appropriate amounts to the extractant formula to preferentially complex common interfering ions (Fe 3+ 、Cu 2+ etc.), inhibiting the coordination of these impurities with thiourea / thiocyanate, thereby further ensuring the extraction selectivity of the target precious metals and reducing the difficulty of subsequent separation and purification.

[0122] The synthetic raw materials (urea, sodium sulfide, ammonium polysulfide, sodium carbonate, surfactants, etc.) are low-cost and widely available. The mild process conditions eliminate the need for high-energy, high-pressure equipment, resulting in significantly lower energy consumption per unit product than traditional strong acid or cyanide systems. Combined with high extraction rates and readily biodegradable properties, this significantly reduces wastewater treatment costs and environmental protection expenditures, thereby enhancing the economic sustainability of the entire extraction process.

[0123] Example 4:

[0124] Purpose of the experiment

[0125] Verify that under the synergistic effect of weak alkaline and anionic surfactant (SDBS), thiocyanate (SCN - ) to the covalently bound “cyano” (–CN) and sulfide ion (S 2 -) conversion efficiency and evaluate its 3+ / Ag + Synergistic improvement effect of complexation extraction performance.

[0126] 2. Materials and Reagents

[0127] Synthetic "ore" sample: Au 3+ and Ag + The standard mixed salt solution is impregnated with a quartz sand carrier, dried, and sintered to prepare a "gold and silver-rich tailings" solid powder (particle size <200 mesh);

[0128] Low-toxic and environmentally friendly extraction agent formula:

[0129] Sodium thiocyanate (NaSCN) 0.20 mol / L;

[0130] Anionic surfactant A (sodium dodecylbenzenesulfonate, SDBS) 0.01 mol / L;

[0131] Sodium carbonate 0.10 mol / L (adjust pH ≈ 10);

[0132] Reaction conditions: 25°C, 400 rpm, reaction time 4 h;

[0133] Analytical instruments:

[0134] Ion chromatography (IC) was used to determine the concentrations of SCN- and CN-;

[0135] ICP-MS (Agilent 7900) was used to determine the concentrations of gold and silver ions;

[0136] pH meter, magnetic stirrer, constant temperature water bath.

[0137] 3. Experimental Procedure

[0138] SCN-transformation experiments

[0139] 0.20 M NaSCN solution (100 mL) was mixed with 0.01 M SDBS and 0.10 M Na2CO3 to obtain a reaction solution;

[0140] The mixture was stirred at 25°C and 400 rpm for 4 h, and the SCN- and CN- concentrations at the initial and final times were measured by ion chromatography to obtain reagent conversion data.

[0141] Precious metal extraction experiment

[0142] Add 5.00g of "gold and silver-rich tailings" powder (equivalent to Au 3+ About 6.25 mg, Ag + The reaction was continued under the same conditions for 4 h;

[0143] After the reaction, the solid and liquid were separated using a 0.45 μm filter membrane, the filtrate was taken and the volume was fixed to 100 mL, and the Au and Ag concentrations C1 were determined by ICP-MS.

[0144] 4. Data Acquisition and Calculation

[0145] SCN-→CN- conversion rate

[0146]

[0147] C SCN,0 =0.20mol / L, V=0.100L

[0148] IC measures the final moment C SCN =0.050mol / L, C CN =0.140mol / L.

[0149] Precious metal extraction rate

[0150]

[0151] The initial Au content in the sample C0,Au=6.25mg / 5.00g=1.25mg / g, and Ag is similar;

[0152] ICP-MS measured Au Cl,Au=5.94 mg / L,Ag Cl,Ag=24.3 mg / L in the filtrate.

[0153] 5. The results are shown in Table 3 below:

[0154] Table 3

[0155]

[0156] 6. Highlighted technical effects

[0157] High conversion efficiency: 70% SCN - Under weak alkaline + SDBS conditions, it was converted into a covalently bound cyanide group (–CN), verifying the mechanism of “cyanide replacing free cyanide” in the formulation system;

[0158] Excellent extraction: In the same system, the extraction rates of Au and Ag reached 95.1% and 90.0%, respectively, fully demonstrating the synergistic effect of –CN complexing activity and anionic surfactants;

[0159] Green and safe: a large number of SCN - Is "cured" in the thiourea / thiocyanate skeleton, not in the form of free CN - The form exists, reducing the potential risk of acute toxicity;

[0160] The process is simple: the whole process is carried out at room temperature, with weak alkali, without strong acid or free cyanide, which greatly improves the safety of equipment and operation.

[0161] This example intuitively demonstrates the dual technical advantages of the present invention in terms of thiocyanate conversion mechanism and efficient recovery of precious metals through quantitative chemical analysis, rigorous calculations and comparative tables.

[0162] The preparation method of the extractant is step-by-step and modular, and is fully applicable to conventional chemical reactors at normal pressure, normal temperature or medium temperature. The finished product can be obtained by simple crushing, mixing and pH adjustment. It is easy to quickly promote in industrial sites such as mining, electronic waste recycling, and tailings treatment, without the need for complicated equipment modification or special reagent matching.

[0163] In the description of this specification, the reference terms "one embodiment", "some embodiments", "examples", "specific examples" or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0164] In the drawings of the embodiments disclosed in the present invention, only the structures related to the embodiments disclosed in the present invention are involved. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of the present invention can be combined with each other.

[0165] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. Low-toxic and environmentally friendly precious metal extractant, characterized in that: The extractant comprises, by mass percentage, 20%-40% of an alkaline thiourea component, 30%-50% of a thiocyanate component, 2%-8% of anionic surfactant A, 2%-8% of anionic surfactant B, 5%-15% of an alkaline regulator, and 0.1%-2% of a stabilizer.

2. The low-toxic and environmentally friendly precious metal extractant according to claim 1, characterized in that: The alkaline thiourea component is alkaline thiourea or thiourea modified by sulfurization; The thiocyanate component is sodium thiocyanate, ammonium thiocyanate and a mixture thereof.

3. The low-toxic and environmentally friendly precious metal extractant according to claim 1, characterized in that: The anionic surfactant A is sodium dodecylbenzenesulfonate; According to the low-toxic and environmentally friendly precious metal extractant of claim 1, the anionic surfactant B is sodium lauryl polyoxyethylene ether sulfonate.

4. The low-toxic and environmentally friendly precious metal extractant according to claim 1, characterized in that: The alkaline regulator is sodium carbonate and sodium hydroxide; The stabilizer is one or a combination of sodium citrate and EDTA sodium salt.

5. The method for preparing a low-toxic and environmentally friendly precious metal extractant according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step S1: mixing urea, sodium sulfide, ammonium polysulfide and sodium carbonate, and heating them at 300° C. to 500° C. to react to generate an alkaline thiourea precursor; Step S2: continuing to heat the precursor to 800° C. to 1100° C. for thermal condensation and thioation conversion reaction, so as to partially convert the precursor into thiocyanate, thereby obtaining a mixture; Step S3: The mixture is rapidly condensed and then mechanically crushed to a fineness of 100-300 mesh to obtain a primary powder; Step S4: mixing the primary powder with an aqueous solution of anionic surfactant A and anionic surfactant B at a mass ratio of 5-15% and homogenizing to promote the loosening of the thiocyanate structure and obtain a mixed solution; Step S5: adding sodium carbonate or sodium hydroxide to the mixed solution to adjust the alkalinity of the system to pH 9-11, and adding 0.1-2% of a stabilizer to inhibit impurity complexation to obtain a stabilized solution; Step S6: After cooling the stabilized liquid to room temperature, filtering or homogenizing is performed, and the product is packaged and sealed to obtain the final product.

6. The low-toxic and environmentally friendly precious metal extractant according to claim 5, characterized in that: The molar ratio of the raw materials in step S1 is urea: sodium sulfide: ammonium polysulfide: sodium carbonate = 1: 0.5-1.5: 0.2-0.8: 0.3-1.

0.

7. The low-toxic and environmentally friendly precious metal extractant according to claim 5, characterized in that: The heating rate in step S2 is 5–15°C / min.

8. The low-toxic and environmentally friendly precious metal extractant according to claim 5, characterized in that: The pulverization particle size range of step S3 is 100-200 mesh.

9. The low-toxic and environmentally friendly precious metal extractant according to claim 5, characterized in that: After step S6, the final product is dried to remove residual moisture and improve storage stability.

10. The low-toxic and environmentally friendly precious metal extractant according to claim 5, characterized in that: The moisture content of the final product is ≤5%.

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