Environment-friendly gold leaching agent and application thereof in arsenic-containing gold ore

Abstract

The invention relates to an environment-friendly gold leaching agent and an application method of the environment-friendly gold leaching agent in arsenic-containing refractory gold ore, and belongs to the technical field of hydrometallurgy. Preparing an auxiliary mixing agent from sodium carbonate and sodium sulfate according to a molar ratio of 4: 1 to 6: 1, and reacting for 2-4 hours at 200-300 DEG C under the action of excessive nitrogen to prepare a thiocyanogen complex; and cooling and crushing to obtain thiocyanogen complex powder. The effective cyanide concentration is 3%-5%, and cyanide volatilization and environmental pollution are remarkably reduced. According to the method, under the synergistic effect of biological pre-oxidation, the gold leaching efficiency is guaranteed, meanwhile, the unit dosage of sodium cyanide is remarkably reduced, the problems that a traditional cyanide method is high in toxicity and low in recovery rate of wrapped gold in the refractory gold ore are solved, and the method has high efficiency, environmental protection property and industrial feasibility and is suitable for green gold extraction of the high-arsenic and high-sulfur gold ore.

Description

[0001] FIELD OF THE INVENTION The present invention belongs to the field of hydrometallurgy technology, and in particular relates to an environmentally friendly gold leaching agent and its application in arsenic-containing gold mines. Background Art

[0002] In the field of hydrometallurgy, sodium cyanide (NaCN) has long been widely used for gold extraction due to its efficient gold leaching capabilities. However, traditional cyanidation methods have fatal drawbacks, including high toxicity and severe environmental pollution. Cyanide easily generates highly toxic hydrogen cyanide (HCN) gas during the leaching process, and free cyanide remaining in the leached residue can spread through groundwater, causing environmental pollution.

[0003] With the current global gold mining boom, easily processed gold deposits are becoming increasingly scarce or depleted, leaving complex, difficult-to-process, and low-grade ores as the primary resources for gold production. Research on comprehensive recovery technologies for complex ores has become a crucial topic in gold production. In terms of extraction processes, cyanidation is the primary method for separating oxide ores. With increasingly stringent environmental protection requirements, companies are being forced to address environmental pollution from gold and silver production while accelerating research into clean production processes, aiming to advance gold production technology towards zero or minimal pollution.

[0004] Existing technologies face greater challenges for arsenic-containing and difficult-to-process gold mines, such as arsenopyrite-encapsulated gold mines.

[0005] In terms of reagent limitations, although traditional environmentally friendly gold leaching agents such as "Golden Cicada" have reduced toxicity, their cyanide complexing ability is weak, the leaching rate is only 46.45%, and it is easy to generate insoluble impurities, which block the pores on the mineral surface and further inhibit the leaching efficiency; non-cyanide agents such as the thiosulfate method are environmentally friendly, but have poor adaptability to high-arsenic and high-sulfur ores, and the leaching rate is less than 30%.

[0006] In terms of pre-oxidation process efficiency, conventional biological pre-oxidation technology relies on microorganisms to oxidize arsenic and sulfur minerals to release the encapsulated gold, but the oxidation rate is generally lower than 60%, and the parameters (such as pH, temperature, and inoculation amount) are not systematically optimized, resulting in a long pre-oxidation cycle (>15 days) and a high slag rate (>80%). Although high-temperature and high-pressure oxidation methods (such as roasting and pressurized oxidation) can improve oxidation efficiency, they have high energy consumption and severe equipment corrosion, making the industrialization cost unacceptable.

[0007] In terms of environmental risks of leaching residue, the residual gold in the leaching residue of traditional process mostly forms a semi-autogenous granular structure with pyrite, which is difficult to recover for the second time; the incompletely oxidized arsenic ( ) may exist in the form of arsenate, which is easily dissolved after long-term storage and pollutes soil and water.

[0008] Therefore, there is an urgent need to develop a new technology that combines efficient leaching, low toxicity, environmental protection and process stability. Summary of the Invention

[0009] The present application aims at solving the problems in the prior art and discloses an environment-friendly gold leaching agent and application thereof in arsenic-containing gold ore.

[0010] The present application provides a preparation method of the environment-friendly gold leaching agent, comprising the following steps:

[0011] (a) preparing an auxiliary mixture by mixing sodium carbonate and sodium sulfate according to a molar ratio of 4:1 to 6:1; (b) preparing a thiocyanate complex under the action of excess nitrogen at 200-300 DEG C for 2-4 hours; (c) obtaining a thiocyanate complex powder after cooling and crushing.

[0012] Further, the molar ratio of sodium carbonate to sodium sulfate in step (a) is 1:2.

[0013] Further, the reaction temperature in step (b) is 250 DEG C, and the reaction time is 3 hours.

[0014] The present application provides a leaching process of an arsenic-containing refractory gold ore, which comprises a biological pre-oxidation step and an environment-friendly gold leaching agent leaching step.

[0015] The process parameters of the biological pre-oxidation step are as follows: grinding fineness of 80% to 38 microns, inoculation amount of 100%, pulp concentration of 15%, culture medium of 4.5K, temperature of 40 DEG C, initial pH of 1.6, and pre-oxidation time of 7 days.

[0016] The process parameters of the environment-friendly gold leaching agent leaching step are as follows: adjusting the pre-oxidation residue to pH 11.5 by using lime milk, adding sodium cyanide and sodium carbonate according to 1:2, and leaching for 24 hours.

[0017] Further, the culture medium 4.5K in the biological pre-oxidation process comprises ferrous sulfate, sulfur powder and trace elements.

[0018] Further, after the biological pre-oxidation process, the arsenic oxidation rate is >80%, and the sulfur oxidation rate is >50%.

[0019] Further, after the environment-friendly gold leaching agent leaching process, the gold leaching rate is >93%.

[0020] The present application provides an environment-friendly gold leaching agent and application thereof in arsenic-containing refractory gold ore leaching.

[0021] Further, the arsenic content in the arsenic-containing refractory gold ore is >0.1%, the sulfur content is >30%, the organic carbon content is <0.5%, and the antimony content is <0.1%.

[0022] Compared with the prior art, the environment-friendly gold leaching agent and the preparation method thereof have the following beneficial effects:

[0023] (1) High efficiency: The synergistic effect of biological pre-oxidation and environmentally friendly gold leaching agent significantly improves the gold leaching rate compared with the traditional process (gold cicada, sodium cyanide), and the slag rate is reduced to 67.62%.

[0024] (2) Environmental protection: The environmentally friendly gold leaching agent slow-release technology reduces the volatilization of cyanide by more than 50%, and there is no free cyanide residue in the leaching residue; biological pre-oxidation replaces high-temperature and high-pressure oxidation, which reduces energy consumption and carbon emissions.

[0025] (3) Industrial feasibility: The process parameters are stable and suitable for large-scale continuous production; in the expanded test, the gold leaching rate fluctuation is ≤5%, and the leaching residue meets the environmental protection storage standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 : Results of Au phase analysis in refractory gold ores.

[0027] Figure 2 Morphology and composition analysis of Jinchan leaching residue.

[0028] Figure 3 : Morphology and composition analysis of leached residue from environmentally friendly gold leaching agent.

[0029] Figure 4 : Comparison of the active ingredients of Jinchan and environmentally friendly gold leaching agents. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described below with reference to the embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be included in the scope of protection of the present invention. Unless otherwise specified, the technical means used in the embodiments of the present invention are conventional means well known to those skilled in the art.

[0031] The raw materials used in the following examples and comparative examples are all arsenic-containing refractory gold ores, the chemical composition analysis of which is shown in Table 1.

[0032] Table 1 Analysis results of main elements in arsenic-containing refractory gold ores

[0033] Element Name Au(g / t) Fe As S content / % 3. to 38 30.13 0.14 30.67

[0034] Example 1 Preparation method of environmentally friendly gold leaching agent

[0035] This embodiment provides a method for preparing an environmentally friendly gold leaching agent, and the specific preparation process is as follows:

[0036] 1. Experimental Materials and Equipment

[0037] Raw materials: sodium sulfate (NaSO4, purity ≥98%, industrial grade);

[0038] Sodium carbonate ( , purity ≥99.5%, analytical grade);

[0039] High purity nitrogen ( , purity ≥99.999%).

[0040] 2. Experimental steps (1) Raw material ratio and mixing

[0041] According to the molar ratio (4-6): 1 weigh and , place the two in a mixing tank, introduce nitrogen to replace the air (flow rate 5 L / min, lasting 10 minutes), and mechanically mix at 200 rpm for 30 minutes to ensure their uniformity.

[0042] (2) High temperature reaction synthesis

[0043] The mixture was transferred into an alumina crucible, placed in a tubular furnace reaction chamber, introduced with nitrogen (flow rate 2 L / min), and heated to 250°C at a rate of 10°C / min. The reaction was carried out at a constant temperature for 3 hours, during which nitrogen was continuously introduced to maintain an inert atmosphere.

[0044] (3) Product post-processing

[0045] After the reaction was completed, the heating was turned off and the mixture was cooled to room temperature (cooling rate was about 5°C / min). The product was taken out and crushed to less than 80 mesh using a ball mill to obtain a light yellow powdery composite.

[0046] 3. Product characterization and performance testing (1) Cyanide ( ) Mass fraction determination

[0047] 1.000 g of powdered complex was weighed and dissolved in 100 mL of deionized water. Ultrasonic dispersion was performed for 30 min. The concentration of CN⁻ in the solution was determined by ion chromatography. The structure is shown in Table 2.

[0048] Table 2 Cyanide release rate at different molar ratios

[0049]

[0050] From the data in Table 2, we can see that : =4:1, the cyanide release rate was higher (0.15 g / (L·h)) because the complexation was not complete and the residual free NaCN released cyanide quickly; : =6:1, excess sodium carbonate inhibited the efficiency of the composite reaction, and the release rate returned to 0.12 g / (L·h); : The best slow-release performance (0.08 g / (L·h)) was achieved when the ratio of sodium carbonate to gold was 5:1, and the composite structure was stable, and the cyanide was evenly coated. With the increase of the proportion of sodium carbonate, the cyanide content gradually decreased (4.1%→3.5%→2.8%), but the slow-release performance was optimal at 5:1, balancing the content and structural stability.

[0051] Therefore, : The ratio of 5:1 is the best for synthesizing the environmentally friendly gold immersion agent NTJH.

[0052] Example 2: Comparison of gold extraction performance of environmentally friendly gold immersion agent

[0053] 1. Experimental materials and equipment

[0054] Ore sample: The composition of the arsenic-containing refractory gold ore is: Au 3.38%, As 0.14%, S 30.67%, and Fe 30.13%. As shown in Table 1, 0.36% of the gold in the arsenic-containing refractory gold ore exists in the form of silicate inclusions, which is difficult to recover. The refractory gold ore used in this experiment contains 62.02% of gold inclusions in sulfides and arsenopyrite, which is difficult to recover. This part of gold is in the collection of fine-grained sulfide minerals, and the organic carbon and antimony content in the ore is low, which has little effect on gold leaching. Figure 1

[0055] Reagents: Jinchan (commercially available), NTJH 1#-3# (laboratory-prepared environmentally friendly gold immersion agent);

[0056] Equipment: Stirring leaching tank (volume 5 L), atomic absorption spectrometer (AAS, detection limit 0.01 g / t).

[0057] 2. Experimental steps

[0058] Ore sample pretreatment: The ore sample was ground to a fineness of 38 μm, accounting for 80%;

[0059] Take 500 g of ore powder and add it to the leaching tank according to the liquid-solid ratio of 2-4:1 (water: ore).

[0060] Leaching conditions:

[0061] Adjust the pH to 11.5 using 20% lime milk, the temperature is 25℃, the stirring speed is 200 rpm, and add Jinchan, NTJH 1#-3# (cyanide concentration is 3%) respectively, and leach for 24 hours.

[0062] Detection and analysis:

[0063] Filter the leaching solution and determine the Au content in the solution by AAS;

[0064] Dissolve the leaching residue in aqua regia and determine the residual Au content. ​

[0065] The experimental results are shown in Table 2

[0066] Table 2 Comparison of gold extraction performance of different reagents

[0067] Pharmacy Leaching rate (%) Residual gold in slag (g / t) Golden Cicada 46.45 22.02 NTJH1# (2:1) 47.93 18.74 NTJH2# (3:1) 48.52 17.89 NTJH3# (4:1) 47.63 19.21

[0068] According to the data in Table 2, NTJH2#, that is, when the liquid-solid ratio is 3:1, has the highest leaching rate (48.52%), which is 2.07% higher than that of Jinchan, and the residual gold in the slag is the lowest, which is 17.89 g / t, which shows its high efficiency in gold extraction.

[0069] The morphology and composition of NTJH2# and Jinchan leaching residues were analyzed by scanning electron microscope-energy dispersive spectrometer. Figure 2-Figure 3 It can be seen that the gold-pyrite semi-autotrophic granules still appear in the Jinchan leaching residue, indicating that the agent's penetration and chelation capacity are insufficient. The environmentally friendly gold leaching agent leaching residue mainly contains lattice gold, which requires pre-oxidation to open the package before the agent can contact and take effect.

[0070] Use a test agent (such as DABR) to determine the cyanide ( ), according to the principle of silver salt titration, first prepare a silver nitrate standard solution and the DABR indicator. Then, under alkaline conditions, add the indicator to the test solution (Jinchan and NTJH2#) and titrate with the silver nitrate standard solution. The titration endpoint is reached when the solution color changes from a specific color to red.

[0071] like Figure 4 As shown, insoluble impurities appear in Jinchan, and the effective ingredients of the environmentally friendly gold leaching agent are higher than those of Jinchan.

[0072] Example 3 Biological pre-oxidation parameter optimization experiment

[0073] Experimental materials and equipment

[0074] Ore sample: Arsenic-bearing refractory gold ore (Au 3. to 38 g / t, As 0.14%, S 30.67%, Fe 30.13%).

[0075] Bacteria species: Thiobacillus ferrooxidans.

[0076] Culture medium: 4.5K basal medium (containing ferrous sulfate, sulfur powder, and trace elements).

[0077] Equipment: biological pre-oxidation reactor (with temperature control, pH monitoring, and stirring functions);

[0078] Ball mill (controls grinding fineness);

[0079] Atomic absorption spectrometer (AAS), ion chromatograph (IC);

[0080] Centrifuge, shaking incubator, sterilization pot.

[0081] 3.1 Initial pH optimization experiment

[0082] Objective: To determine the optimal initial pH value (range 1.4-2.2). Fixed parameters: temperature 40°C, inoculum 100%, ore pulp concentration 15%, grinding fineness to 38 μm 80%, medium 4.5K, pre-oxidation time 7 days.

[0083] Experimental steps:

[0084] Pre-treatment of ore sample: The ore sample was ground by a ball mill to 38 μm 80%, and 500 g of ore powder was divided into 5 pre-oxidation reactors.

[0085] pH adjustment:

[0086] Each group was adjusted to initial pH to 1.4, 1.6, 1.8, 2.0, 2.2 with sulfuric acid (H2SO4) and 4.5K medium was added to the ore pulp concentration of 15%.

[0087] Inoculation and pre-oxidation:

[0088] Activated bacteria solution was added according to the inoculum of 100%, stirring was started (200 rpm), the temperature was maintained at 40°C, and pH and ORP were continuously monitored.

[0089] Data collection:

[0090] Daily sampling: 10 mL of ore pulp was centrifuged, the supernatant was measured by IC to determine the concentration of arsenic, sulfur, and the oxidation rate of arsenic and sulfur was calculated. 、

[0091] End-point analysis: The ore residue was filtered on the 7th day, and the gold content was measured after drying (AAS).

[0092] Leaching verification:

[0093] The pre-oxidation residue was added with NTJH under the conditions of Example 1 for 24 hours of leaching, and the gold leaching rate was measured.

[0094] Table 3 Effect of initial pH on oxidation rate and gold leaching rate of bio-pre-oxidation residue

[0095] Initial pH Arsenic oxidation rate (%) Sulfur oxidation rate (%) Gold leaching rate (%) 1.4 75.2 46.1 90.68 1.6 80.5 50.1 93.33 1.8 78.9 49.3 92.77 2.0 73.1 45.8 91.51 2.2 68.4 43.2 90.97

[0096] Conclusion: From the data in Table 3, when pH = 1.6, the arsenic oxidation rate is 80.5%, the sulfur oxidation rate is 50.1%, and the gold leaching rate reaches 93.33%, therefore, pH = 1.6 is determined as the optimal condition.

[0097] 3.2 Temperature optimization experiment ​​

[0098] Objective: To determine the optimum pre-oxidation temperature (range 30-50°C). Fixed parameters: initial pH 1.6, inoculum 100%, pulp density 15%, grinding fineness to 80% passing 38 μm, medium 4.5K, pre-oxidation time 7 days.

[0099] Experimental procedure:

[0100] Treatment of ore sample: same as pH experiment, ore powder was divided into 5 reactors.

[0101] Temperature setting: reactor temperature was controlled at 30°C, 35°C, 40°C, 45°C, 50°C respectively.

[0102] Pre-oxidation operation:

[0103] Adjust initial pH to 1.6, inoculum 100%, start stirring and temperature control, monitor ORP, As / S oxidation rate daily (method same as pH experiment).

[0104] End point analysis: gold content in residue was determined on day 7, and leaching verification was conducted.

[0105] Table 4 Effect of temperature on oxidation rate and gold leaching rate of bio-pre-oxidation residue

[0106] Temperature (℃) Arsenic oxidation rate (%) Sulfur oxidation rate (%) Gold leaching rate (%) 30 72.3 44.2 90.90 35 76.8 47.5 92.84 40 80.5 50.1 93.33 45 78.1 48.9 89.36 50 74.6 46.7 86.53

[0107] Conclusion: From the data in Table 4, it can be seen that when the temperature = 40°C, the arsenic oxidation efficiency, sulfur oxidation rate and leaching rate are the highest, and the temperature of 40°C is determined as the optimum condition.

[0108] 3.3 Inoculum optimization experiment

[0109] Objective: To determine the optimum inoculum (range 20%-100%). Fixed parameters: initial pH 1.6, temperature 40°C, pulp density 15%, grinding fineness to 80% passing 38 μm, medium 4.5K, pre-oxidation time 7 days.

[0110] Experimental procedure:

[0111] Preparation of bacterial solution: Thiobacillus ferroxidans was expanded to the logarithmic growth phase (bacterial concentration ).

[0112] Inoculum gradient setting:

[0113] Respectively inoculate bacterial solution according to 20%, 40%, 60%, 80%, 100% of the volume of ore slurry.

[0114] Pre-oxidation and monitoring:

[0115] Daily sampling to determine As / S oxidation rate, gold content in residue was analyzed on day 7, and leaching verification was conducted.

[0116] Table 5 Effect of inoculum size on oxidation rate and gold leaching rate of biological pre-oxidation slag

[0117] Inoculation amount (%) Arsenic oxidation rate (%) Sulfur oxidation rate (%) Gold leaching rate (%) 20 65.4 40.3 89.30 40 70.8 43.6 89.96 60 75.2 46.7 90.73 80 78.9 48.9 91.57 100 80.5 50.1 93.33

[0118] Conclusion: From the data in Table 5, it can be seen that when the inoculation amount is 100%, the arsenic oxidation efficiency is 80.5%, the sulfur oxidation rate is 50.1%, and the gold leaching rate is increased to 93.33%. It can be seen that the microbial activity is best when the inoculation amount is 100%.

[0119] 3.4 Culture medium optimization experiment

[0120] Objective: To determine the optimal culture medium type (4.0K, 4.5K, 5.0K). Fixed parameters: initial pH 1.6, temperature 40°C, inoculum size 100%, slurry concentration 15%, grinding to 38 μm (80%), and pre-oxidation time 7 days.

[0121] Experimental steps:

[0122] Culture medium preparation:

[0123] Prepare culture medium according to 0K, 4.5K, 6.0K, 7.5K, and 9.0K formulas (adjust the ratio of ferrous sulfate to sulfur powder).

[0124] Pre-oxidation operation:

[0125] The corresponding culture medium was added to each group of slurries, and other conditions were kept fixed.

[0126] Data collection: Oxidation efficiency was monitored daily, gold leaching rate was determined on day 7, and leaching verification was performed.

[0127] Table 6 Effect of culture medium type on oxidation rate and gold leaching rate of biological pre-oxidation slag

[0128] Culture medium type Arsenic oxidation rate (%) Sulfur oxidation rate (%) Gold leaching rate (%) 0K 75.6 47.3 88.82 4.5K 80.5 50.1 93.33 6.0K 77.8 49.2 93.36 7.5K 76.1 48.1 93.43 9.0K 75.7 47.5 93.04

[0129] Conclusion: From the data in Table 6, it can be seen that when the culture medium is 4.5K, the nutrient ratio is the most suitable and the microbial metabolic activity is the highest. Therefore, the optimal culture medium type is 4.5K.

[0130] 3.5 Slurry concentration optimization experiment

[0131] Objective: Determine the optimal slurry concentration (range 10%-25%). Fixed parameters: initial pH 1.6, temperature 40°C, inoculum size 100%, 80% grinding to 38 μm, culture medium 4.5K, and pre-oxidation time 7 days.

[0132] Experimental steps:

[0133] Slurry preparation:

[0134] The mineral powder is packaged according to the slurry concentration (w / v) of 10%, 15%, 20% and 25%.

[0135] Pre-oxidation operation:

[0136] The pH was adjusted to 1.6, the bacterial solution was inoculated, and the As / S oxidation rate was monitored.

[0137] End point analysis: On the 7th day, the gold content in the slag was determined and leaching was verified.

[0138] Table 7 Effect of slurry concentration on oxidation rate and gold leaching rate of biological pre-oxidation slag

[0139] Slurry concentration (%) Arsenic oxidation rate (%) Sulfur oxidation rate (%) Gold leaching rate (%) 5 70.8 44.5 100 10 73.4 46.2 97.29 15 80.5 50.1 93.33 20 77.8 48.7 89.76 25 72.1 45.3 87.16

[0140] Conclusion: From the data in Table 7, it can be seen that when the pulp concentration is 15%, the arsenic oxidation efficiency is 80.5%, the sulfur oxidation rate is 50.1%, and the gold leaching rate is 93.33%. It can be seen that the pulp concentration of 15% is the optimal condition.

[0141] 3.6 Grinding fineness optimization experiment

[0142] Objective: Determine the optimal grinding fineness. Fixed parameters: Initial pH 1.6, temperature 40°C, inoculum 100%, slurry concentration 15%, culture medium 4.5K, and pre-oxidation time 7 days.

[0143] Experimental steps:

[0144] Ore sample grinding:

[0145] The ball mill controls the fineness of the mineral powder, making the grinding finenesses 74um, 48um, 38um, 25um, and 23um respectively.

[0146] Pre-oxidation and monitoring:

[0147] Sampling was performed daily to determine the As / S oxidation rate, and the gold content in the slag was analyzed on the 7th day and leaching verification was performed.

[0148] Table 8 Effect of grinding fineness on oxidation rate and gold leaching rate of biological pre-oxidation slag

[0149] Grinding fineness (um) Arsenic oxidation rate (%) Sulfur oxidation rate (%) Gold leaching rate (%) 74 68.3 42.1 94.05 48 74.5 46.8 94.74 38 80.5 50.1 93.33 25 78.2 49.6 95.60 23 75.5 47.5 95.91

[0150] Conclusion: From the data in Table 8, it can be seen that when the grinding fineness is 38um, the arsenic oxidation efficiency is 80.5%, the sulfur oxidation rate is 50.1%, and the gold leaching rate is 93.33%. It can be seen that when the grinding fineness is 38um, the mineral dissociation is sufficient, the microbial contact area is the largest, and it is the optimal condition.

[0151] Example 4: Expanded test to verify process stability

[0152] 1. Trial scale and equipment

[0153] Ore sample quantity: 10 tons (arsenic-containing refractory gold ore, Au 3. to 38 g / t);

[0154] Equipment: Biological pre-oxidation reactor ( )、Industrial leaching tank( ), automatic control system.

[0155] 2. Operational Process

[0156] Biological pre-oxidation:

[0157] The grinding to 38 μm accounted for 80%, the pulp concentration was 15%, the inoculation amount was 100%, and the culture medium was 4.5K; the temperature was controlled at 40℃, the initial pH was 1.6, the pre-oxidation was 7 days, and the slag rate was 67.62%.

[0158] Leaching process:

[0159] After washing, the pre-oxidation slag was slurried with 20% lime milk to a pH of 11.5, and an environmentally friendly gold leaching agent was added at a liquid-to-solid ratio of 3:1, and leaching was carried out for 24 hours.

[0160] 3. Test results are shown in Table 9

[0161] Table 9 Comparison of leaching rates of different batches of environmentally friendly gold leaching agents and sodium cyanide

[0162] Test batch Gold content of pre-oxidized slag (g / t) Environmentally friendly gold leaching agent leaching rate (%) Sodium cyanide leaching rate (%) 1 32.81 81.92 81.26 2 32.32 86.01 84.28 3 32.84 84.44 82.52

[0163] 4. Stability Analysis

[0164] The fluctuation range of the leaching rate of environmentally friendly gold leaching agent is ≤5%, and the fluctuation range of the leaching rate of sodium cyanide is ≤3%, indicating that the process is stable.

[0165] 5. Conclusion

[0166] From the above data, it can be seen that the leaching rate of the environmentally friendly gold leaching agent obtained by the method of the present invention is higher than that of the cyanide leaching agent.

[0167] Sodium chloride has better performance and stable process parameters, and has the potential for industrial promotion.

[0168] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an environmentally friendly gold leaching agent, characterized in that: The following steps are involved: (a) preparing an auxiliary mixture by mixing sodium carbonate and sodium sulfate in a molar ratio of 4:1 to 6:1; (b) reacting at 200-300°C for 2-4 hours under the action of excess nitrogen to prepare a thiocyanate complex; (c) After cooling and grinding, thiocyanate complex powder is obtained.

2. The preparation method according to claim 2, characterized in that: The molar ratio of sodium carbonate to sodium sulfate in step (a) is 5:

1.

3. The preparation method according to claim 2, characterized in that The reaction temperature in step (b) is 250° C., and the reaction time is 3 hours.

4. A leaching process for arsenic-containing refractory gold ore, characterized in that: Including biological pre-oxidation step and environmentally friendly gold leaching agent leaching step: The process parameters of the biological pre-oxidation step are: grinding fineness to 38 μm, accounting for 80%, inoculation amount 100%, pulp concentration 15%, culture medium 4.5K, temperature 40°C, initial pH 1.6, and pre-oxidation time 7 days; The environmentally friendly gold leaching agent leaching steps are: pre-oxidized slag is slurried with lime milk to a pH of 11.5, sodium cyanide and sodium carbonate are added in a ratio of 1:2, and leaching is carried out for 24 hours.

5. The leaching process according to claim 5, characterized in that In the biological pre-oxidation step, the culture medium comprises ferrous sulfate, sulfur powder and trace elements.

6. The leaching process according to claim 5, characterized in that After the biological pre-oxidation step, the arsenic oxidation rate is greater than 80%, and the sulfur oxidation rate is greater than 50%.

7. The leaching process according to claim 5, wherein: After the environmentally friendly gold leaching agent leaching step, the gold leaching rate is greater than 93%.

8. Use of the environmentally friendly gold leaching agent according to claim 1 in leaching arsenic-containing refractory gold ores.

9. The use according to claim 9, characterized in that The arsenic-containing refractory gold ore has an arsenic content greater than 0.1%, a sulfur content greater than 30%, an organic carbon content less than 0.5%, and an antimony content less than 0.1%.

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