Normal-pressure alkaline leaching pretreatment method for micro-fine particle gold ore based on sodium percarbonate reinforcement

Abstract

The invention discloses a micro-fine particle gold ore normal-pressure alkaline leaching pretreatment method based on sodium percarbonate reinforcement, and belongs to the field of precious metal metallurgy. The method comprises the following steps: adding an oxidizing agent sodium percarbonate in batches under the condition that air is filled into ore pulp, starting to monitor the oxidation potential and the pH value of a reaction system after adding, judging that the reaction reaches the end point when the sudden drop amplitude of the oxidation potential of the ore pulp within one hour is greater than or equal to 30mV and the pH value is increased by 0.3-0.5 unit, and stopping aeration to finish pretreatment; in the segmented oxidation process, the oxidation potential is controlled within the range of + 520 mV to + 550 mV by dynamically adjusting the air charging rate. According to the basic technical scheme, the gold leaching rate reaches 86.01%, the gold leaching rate reaches up to 88.92% through the optimized technical scheme, and the utilization rate of gold ore resources is remarkably increased.

Description

Technical Field

[0001] This invention belongs to the field of precious metal metallurgy, specifically relating to a pretreatment method for fine-grained sulfide-encapsulated gold ore. Background Technology

[0002] Because the gold particles in fine-grained sulfide-encapsulated gold deposits are tightly encapsulated by sulfides, conventional leaching methods are difficult to extract them effectively. Therefore, pretreatment of the minerals is usually required before leaching.

[0003] Currently, the main pretreatment methods for fine-grained sulfide-encapsulated gold ores include conventional alkaline leaching and H2O2 oxidation. Conventional alkaline leaching often uses pure oxygen under pressure, which requires stringent operating conditions, including a pressure of 0.6 MPa and a temperature of 80°C. This results in high equipment investment, high energy consumption, and a relatively low gold leaching rate. While H2O2 oxidation can be carried out at atmospheric pressure, it typically requires a temperature of 40°C, and H2O2 is prone to violent decomposition during the reaction, leading to unstable oxidation efficiency and unsatisfactory gold leaching rates.

[0004] Chinese patent application CN105039737A discloses a "gold extraction process for low-grade, refractory gold ores," which involves alkaline leaching pretreatment of sulfide-encapsulated gold-type ores. The core technology involves adding finely ground raw ore or cyanide tailings to a stirred and aerated reactor, mixing it with water to form a slurry, and then stirring with air or oxygen at atmospheric pressure and 10°C–100°C for pre-oxidation. Calcium oxide is then added to the pre-oxidized slurry for thorough alkaline treatment. The main drawback is that sulfides (such as FeS2) in the ore produce sulfate ions after pre-oxidation, which combine with calcium ions to form calcium sulfate precipitate. Simultaneously, silicon and aluminum components in the slurry may react with calcium hydroxide to form calcium silicate and calcium aluminate precipitates. These precipitates adhere to the surface of the ore particles, hindering the contact between cyanide ions and gold during subsequent cyanide leaching; they also increase the slurry viscosity, reducing stirring efficiency and solid-liquid separation.

[0005] Therefore, finding a pretreatment method that can improve the gold leaching rate of fine-grained sulfide-encapsulated gold ore under normal temperature and pressure conditions, and that is simple to operate and low in cost, has become an urgent problem to be solved in this field. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a pretreatment method for fine-grained gold ore under normal pressure based on sodium percarbonate enhancement, which aims to solve the problems of harsh operating conditions, large equipment investment, high energy consumption, low gold leaching rate and poor stability of oxidant in the existing pretreatment methods for fine-grained sulfide-encapsulated gold ore.

[0007] The technical solution of the present invention is as follows: A pretreatment method for fine-grained gold ore under normal pressure based on sodium percarbonate-enhanced alkaline leaching, comprising the following steps: Step 1: Raw material pretreatment: Grind the fine-grained sulfide-encapsulated gold ore to obtain gold ore powder; and prepare a sodium hydroxide solution as the reaction alkaline medium. Step 2, Slurry preparation: Under conditions of 20~30℃ and 100~103kPa, gold ore powder is mixed with sodium hydroxide solution, and water is added to adjust the slurry concentration to 35±2wt%; a catalyst is added, and the pH value of the system is measured. Step 3, Segmented Oxidation: Under the condition of air filling the slurry, sodium percarbonate oxidant is added in stages. After the addition is completed, the oxidation potential and the pH value of the reaction system are monitored. When the oxidation potential of the slurry decreases by ≥30mV within one hour, and the pH value increases by 0.3~0.5 units compared with the pH value measured in Step 2, the reaction is determined to have reached the endpoint, aeration is stopped, and the pretreatment is completed. During the segmented oxidation process, the oxidation potential is controlled within the range of +520mV~+550mV by dynamically adjusting the air filling rate.

[0008] Preferably, in step two, the catalyst is copper sulfate pentahydrate with an initial concentration of 0.01~0.03 g / L.

[0009] Preferably, in step two, the catalyst is a composite catalyst composed of copper sulfate and nickel sulfate, wherein the initial concentration of copper sulfate pentahydrate is 0.02~0.03 g / L and the initial concentration of nickel sulfate is 0.001~0.003 g / L.

[0010] Preferably, the method for atmospheric pressure alkaline leaching pretreatment of fine-grained gold ore based on sodium percarbonate enhancement is characterized in that: in step three, the addition of sodium percarbonate as an oxidant in stages refers to: adding 60% of the total amount initially, and then adding 20% ​​of the total amount in two separate stages after reacting for 4-8 hours, with an interval of 1-1.5 hours between the two additions.

[0011] Preferably, the method for atmospheric pressure alkaline leaching pretreatment of fine-grained gold ore based on sodium percarbonate enhancement described above is characterized in that: the initial amount of sodium percarbonate added in step three is 0.05~0.15 g / L of slurry.

[0012] More preferably, the initial amount of sodium percarbonate added in step three is 0.10 g / L of slurry.

[0013] Preferably, the sodium hydroxide solution in step two has a mass concentration of 1.3~1.5wt%.

[0014] More preferably, the sodium hydroxide solution in step two has a mass concentration of 1.3~1.5wt%.

[0015] More preferably, the sodium hydroxide solution in step two has a mass concentration of 1.3~1.5wt%.

[0016] The main reaction mechanism formula of this invention is as follows:

[0017] 2Na2CO3·3H2O2→2Na2CO3+3H2O2; H₂O₂ + FeS₂ → Fe 2+ +SO4 2- +2H + ; Na2CO3+H + →NaHCO3 + Na + .

[0018] The present invention has the following beneficial effects: First, low equipment investment and energy consumption: This invention is carried out at normal temperature (20-30℃) and normal pressure (100-103kPa), with mild operating conditions and no need for expensive equipment such as high-pressure reactors, thus reducing equipment investment and energy consumption.

[0019] Secondly, the oxidant has good stability: Sodium percarbonate can slowly release H2O2 in an alkaline environment, avoiding the violent decomposition of H2O2, improving the utilization rate of the oxidant, and simultaneously reducing the CO3 produced by decomposition. 2- It can buffer pH fluctuations, ensuring the stability of the reaction.

[0020] Third, high gold leaching rate: Experiments have shown that the basic technical solution of this invention achieves a gold leaching rate of 86.01%, while the optimized technical solution achieves a gold leaching rate as high as 88.92%. This significantly improves the utilization rate of gold ore resources.

[0021] Fourth, experiments have shown that the optimized technical solution of this invention utilizes Cu. 2+ -Ni 2+ Composite catalytic system, Cu 2+ and Ni 2+ The synergistic effect of the two ions significantly improves the gold leaching rate and enhances the reaction efficiency.

[0022] Fifth, in the optimized technical solution of this invention, the sodium percarbonate is added in a delayed manner. Because it can precisely match the kinetics of sulfide decomposition, in the early stage of the reaction (4-8 hours after the reaction begins), it ensures that the reagent can fully penetrate into the sulfide core layer, avoiding localized excessive oxidation and reagent waste, thus making the later reaction more complete. This further improves the thoroughness and stability of the reaction, and further increases the gold leaching rate. Attached Figure Description

[0023] Figure 1 This is a line graph showing the change of oxidation potential over time obtained in Embodiment 1 of the present invention.

[0024] Figure 2This is a line graph showing the change of oxidation potential over time obtained in Embodiment 2 of the present invention.

[0025] Figure 3 This is a line graph showing the change of oxidation potential over time obtained in Example 3 of the present invention.

[0026] Figure 4 This is a line graph showing the change of oxidation potential over time, obtained as a comparative example of the present invention. Detailed Implementation

[0027] The present invention will be further illustrated below with reference to embodiments, comparative examples, and experimental data.

[0028] Example 1 (Single Cu) 2+ (catalytic system)

[0029] Step 1: Raw material pretreatment: Select a fine-grained sulfide-encapsulated copper-gold ore (Au 4.8 g / t, pyrite encapsulation rate 76%), grind it to D90=40μm to obtain gold ore powder; and prepare a 1.5wt% sodium hydroxide solution as the reaction alkaline medium.

[0030] Step 2, Slurry Preparation: Under conditions of 22~25℃ and 100~103kPa, gold ore powder is mixed with... Sodium hydroxide solution was mixed, and water was added to adjust the slurry concentration to 35 wt%. Copper sulfate pentahydrate was added as a catalyst, with an initial concentration of 0.02 g / L. The pH was measured to be 12.8.

[0031] Step 3, Staged Oxidation: Under aeration by introducing air into the slurry, sodium percarbonate oxidant is added in stages. The first addition is 60% of the total amount (initial sodium percarbonate concentration 0.06 g / L slurry). After 1 hour of reaction, 0.02 g / L sodium percarbonate slurry is added, and the reaction continues for another hour before adding another 0.02 g / L sodium percarbonate slurry. After the addition is complete, the oxidation potential and pH value of the reaction system are monitored, and the oxidation potential is controlled within the range of +520 mV to +550 mV by dynamically adjusting the air introduction rate (ORP monitoring).

[0032] like Figure 1 23 hours after the start of oxidation, the oxidation potential of the slurry began to drop sharply, decreasing by 35mV within one hour, and the pH value increased by 0.4 units compared with the pH value measured in step two. The reaction was then determined to have reached its endpoint, and aeration was stopped 24 hours after the start of oxidation to complete the pretreatment.

[0033] Step 4, leaching: The low-toxicity leaching agent of polycyanamide was prepared using Example 1 of the patent application "A method for preparing a low-toxicity leaching agent of polycyanamide" with publication number CN119931040A. The leaching conditions were: liquid-to-solid ratio 2:1, dosage 0.05 wt.%, pH 12, and leaching time 24 h.

[0034] Leaching test: Gold leaching rate 86.01%, sulfur oxidation rate 82.3%.

[0035] Example 2, (Cu) 2+ -Ni 2+ (composite catalytic system)

[0036] Step 1, Raw material pretreatment: Same as Step 1 in Example 1.

[0037] Step 2, Slurry Preparation: Under conditions of 22-25℃ and 100-103 kPa, gold ore powder is mixed with sodium hydroxide solution, and water is added to adjust the slurry concentration to 35 wt%. A composite catalyst is added, which consists of copper sulfate pentahydrate and nickel sulfate, wherein the initial concentration of copper sulfate pentahydrate is controlled at 0.02 g / L, and the initial concentration of nickel sulfate is controlled at 0.003 g / L. The pH is measured to be 12.7.

[0038] Step 3, Staged Oxidation: Under aeration by introducing air into the slurry, sodium percarbonate oxidant is added in stages. The first addition is 60% of the total amount (initial sodium percarbonate concentration 0.06 g / L slurry). After 1 hour of reaction, 0.02 g / L sodium percarbonate slurry is added, and the reaction continues for another hour before adding another 0.02 g / L sodium percarbonate slurry. After the addition is complete, the oxidation potential and pH value of the reaction system are monitored, and the oxidation potential is controlled within the range of +520 mV to +550 mV by dynamically adjusting the air introduction rate (ORP monitoring).

[0039] like Figure 2 Seventeen hours after the start of oxidation, the oxidation potential of the slurry began to drop sharply, decreasing by 35 mV within one hour, and the pH value increased by 0.5 units compared with the pH value measured in step two. The reaction was then determined to have reached its endpoint, and aeration was stopped eighteen hours after the start of oxidation to complete the pretreatment.

[0040] Step 4, Immersion in gold: Same as step 4 in Example 1.

[0041] Leaching test: Gold leaching rate 88.1%, sulfur oxidation rate 91.5%.

[0042] Example 3, (Cu) 2+ -Ni 2+ (Combined catalysis + delayed oxidant replenishment)

[0043] Step 1, Raw material pretreatment: Same as Step 1 in Example 1.

[0044] Step 2, Slurry Preparation: The procedure is the same as Step 2 in Example 2. Measure the pH to 12.7.

[0045] Step 3, Staged Oxidation: Under aeration by introducing air into the slurry, sodium percarbonate oxidant is added in stages. The first addition is 60% of the total amount (initial sodium percarbonate concentration 0.06 g / L slurry). After 6 hours of reaction, 0.02 g / L sodium percarbonate slurry is added, and the reaction continues for another hour before another 0.02 g / L sodium percarbonate slurry is added. After the addition is complete, the oxidation potential and pH value of the reaction system are monitored, and the oxidation potential is controlled within the range of +520 mV to +550 mV by dynamically adjusting the air introduction rate (ORP monitoring).

[0046] like Figure 3 At 16 hours after the start of oxidation, the oxidation potential of the slurry began to drop sharply, decreasing by 33 mV within one hour, and the pH value increased by 0.4 units compared with the pH value measured in step two. The reaction was then determined to have reached its endpoint, and aeration was stopped at 17 hours after the start of oxidation to complete the pretreatment.

[0047] Step 4, Immersion in gold: Same as step 4 in Example 1.

[0048] Leaching test: Gold leaching rate 88.92%, sulfur oxidation rate 93.8%.

[0049] Comparative example (reaction system without catalyst)

[0050] Step 1, Raw material pretreatment: Same as Step 1 in Example 1.

[0051] Step 2, Slurry Preparation: This step differs from Step 2 in Example 1 in that copper sulfate pentahydrate was not added. The pH was measured to be 12.9.

[0052] Step 3, Segmented Oxidation: The difference from Step 2 in Example 1 is that, under aeration with air introduced into the slurry, sodium percarbonate is added simultaneously in stages. The first addition is 60% of the total amount (initial sodium percarbonate concentration 0.06 g / L slurry). After 1 hour of reaction, 0.02 g / L sodium percarbonate is added, and the reaction continues for another hour before another 0.02 g / L sodium percarbonate is added. After the additions are complete, the oxidation potential and pH of the reaction system are monitored, and the oxidation potential is controlled within the range of +520 mV to +550 mV by dynamically adjusting the air introduction rate (ORP monitoring).

[0053] like Figure 4 On the 27th hour of the reaction, the oxidation potential of the slurry began to drop sharply, decreasing by 37mV within one hour, and the pH value increased by 0.4 units compared with the pH value measured in step two. The reaction was then determined to have reached its endpoint, and aeration was stopped 28 hours after the start of oxidation to complete the pretreatment.

[0054] Step 4, Immersion in gold: Same as step 4 in Example 1.

[0055] Leaching test: Gold leaching rate 65.8%, sulfur oxidation rate 68.4%.

Claims

1. A method for the pretreatment of fine-grained gold ores by pressureless alkaline leaching based on sodium percarbonate intensification, characterized in that The following steps are taken: Step 1, raw material pretreatment: grinding the fine particle sulfidation wrapped gold ore to obtain gold ore powder; and preparing a sodium hydroxide solution as a reaction alkali medium; Step 2, preparation of ore slurry: under the conditions of 20-30℃ and 100-103kPa, the gold ore powder is mixed with the sodium hydroxide solution, water is added to adjust the concentration of the ore slurry to 35±2wt%, a catalyst is added, and the pH value of the system is measured; Step 3, staged oxidation: under the condition of air filling into the ore slurry, sodium percarbonate is added in stages, after the addition is completed, the oxidation potential and the pH value of the reaction system are monitored, when the oxidation potential of the ore slurry decreases by ≥30mV within one hour, and the pH value increases by 0.3-0.5 units compared with the pH value measured in step 2, it is determined that the reaction reaches the end point, aeration is stopped, and the pretreatment is completed; during the staged oxidation process, the air filling rate is dynamically adjusted to control the oxidation potential in the range of +520mV to +550mV.

2. The sodium percarbonate-strengthened fine gold ore atmospheric alkaline leaching pretreatment method according to claim 1, characterized in that: In step 2, the catalyst is copper sulfate pentahydrate with an initial concentration of 0.01-0.03g / L.

3. The sodium percarbonate reinforced microfine gold ore atmospheric alkaline leaching pretreatment method according to claim 1, characterized in that: In step 2, the catalyst is a composite catalyst composed of copper sulfate and nickel sulfate, wherein the initial concentration of copper sulfate pentahydrate is 0.02-0.03g / L, and the initial concentration of nickel sulfate is 0.001-0.003g / L.

4. The sodium percarbonate reinforced microfine gold ore atmospheric alkaline leaching pretreatment method according to claim 1, characterized by: In step 3, the staged addition of sodium percarbonate means that 60% of the total amount is added first, and after 4-8h of reaction, 20% of the total amount is added in two times with an interval of 1-1.5h.

5. The sodium percarbonate-strengthened fine-grained gold ore atmospheric alkaline leaching pretreatment method according to any one of claims 1 to 4, characterized in that: In step 3, the initial addition amount of sodium percarbonate is 0.05-0.15g / L of ore slurry.

6. The sodium percarbonate-strengthened fine gold ore atmospheric alkaline leaching pretreatment method according to claim 5, characterized in that: In step 3, the initial addition amount of sodium percarbonate is 0.10g / L of ore slurry.

7. The sodium percarbonate-strengthened fine gold ore atmospheric alkaline leaching pretreatment method according to any one of claims 1 to 4, characterized by: In step 2, the mass concentration of the sodium hydroxide solution is 1.3-1.5wt%.

8. The sodium percarbonate reinforced microfine gold ore atmospheric alkaline leaching pretreatment method according to claim 5, characterized by: In step 2, the mass concentration of the sodium hydroxide solution is 1.3-1.5wt%.

9. The sodium percarbonate reinforced microfine gold ore atmospheric alkaline leaching pretreatment method according to claim 6, characterized by: In step 2, the mass concentration of the sodium hydroxide solution is 1.3-1.5wt%.

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