A method for alkaline pre-oxidation of tellurium-containing gold ore

Abstract

The present invention discloses an alkaline pre-oxidation treatment method for tellurium-gold ore, which belongs to the technical field of hydrometallurgy. The process comprises: firstly crushing and grinding the tellurium-gold ore to fully dissociate the tellurium-gold mineral; then adding water to adjust the slurry concentration, using NaOH to adjust the pH value of the slurry, and adding dithiooxamide and an oxidant to adjust the slurry potential for alkaline leaching pretreatment. After the pretreatment is completed, a reducing substance is used to remove the residual oxidant, and then sodium cyanide is added to carry out a conventional cyanide leaching process for gold extraction. Compared with the current commonly used tellurium-gold ore pretreatment process, the present invention reduces the leaching potential of the tellurium-containing mineral by adding dithiooxamide, thereby significantly reducing the consumption of NaOH and oxidant in the alkaline leaching process, reducing the tellurium-gold ore treatment cost, and improving the economic benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgy and relates to a cyanide gold extraction pretreatment method for tellurium-containing gold ore. Background Art

[0002] Tellurium-gold ore is an important type of gold-bearing ore. Some of its gold-bearing minerals exist as tellurides, such as gold telluride (AuTe2). During conventional cyanide leaching, gold tellurides are more difficult to dissolve than native gold or gold-silver ores, primarily resulting in lower gold cyanide leaching rates. Therefore, tellurium-gold ore is considered a difficult-to-treat gold ore.

[0003] Currently, the industry's pretreatment of tellurium-bearing gold ores primarily utilizes a "fine grinding followed by alkaline leaching and oxidation" process. This process involves the tellurium-bearing minerals generating tellurites that enter the solution under alkaline oxidation conditions, thereby dissociating and releasing the gold-bearing minerals, facilitating subsequent cyanide leaching of the gold. However, this pretreatment process generally suffers from issues such as excessive alkali and oxidant consumption.

[0004] For example, the paper "Study on the Effect of Alkali Leaching Pretreatment of Tellurium-Gold Ore Based on Process Mineralogical Analysis" (Comprehensive Utilization of Minerals, Issue 4, 2022) states that tellurium-gold ore is a difficult-to-dissolve gold-bearing mineral, which affects the gold leaching rate. After alkaline leaching pretreatment, the tellurium-gold ore is oxidized, releasing the gold minerals. The grinding fineness was -0.037 mm (80%), the liquid-to-solid ratio was 2:1, the ventilation rate was 0.025 m / h, the initial slurry NaOH content was 50 g / L, and the alkaline leaching time was 24 hours. Comparison revealed a significant increase in the gold content of the native gold after alkaline leaching, indicating that the NaOH dosage was as high as 50 kg / t.

[0005] For example, Chinese invention patent application publication number CN 108220616 A discloses a "Method for Improving the Leaching Rate of Gold and Silver from Refractory Telluride-Type Flotation Gold Concentrate." During the alkaline leaching and oxidation process, the addition rates of NaOH and oxidant are both 5-10 kg / t. Furthermore, during the grinding process of the telluride-type flotation gold concentrate, a sulfide (one or more of sodium sulfide, sodium thiosulfate, and ammonium thiosulfate) is added as a leaching and decontamination agent. However, the addition of sodium sulfide only removes impurities and decontamination, but does not complex tellurium. Therefore, it is difficult to achieve the goal of lowering the tellurium oxidation potential, thereby reducing the leaching pH and oxidant consumption.

[0006] The extensive use of alkali / oxidants increases production costs, particularly when processing low-grade tellurium-bearing gold ores, further increasing operating cost pressures. On the other hand, excessive alkali concentrations and residual oxidants can also reduce gold and silver cyanide leaching rates and increase cyanide leaching agent consumption. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide an alkaline pre-oxidation treatment method for tellurium-containing gold ore, which reduces the oxidation potential of tellurium by coordination and complexation, thereby reducing the tellurium leaching pH value and oxidant consumption, and realizing low-cost and high-efficiency pretreatment of tellurium-containing gold ore.

[0008] The technical solutions of the present invention are as follows:

[0009] A method for alkaline pre-oxidation treatment of tellurium-gold ore is carried out according to the following steps:

[0010] (1) Tellurium-containing gold ore is crushed and ground to -0.037 mm, accounting for 90±2%;

[0011] (2) Add water to the milled tellurium-containing gold ore to adjust the slurry to control the slurry concentration to 35%~40%;

[0012] (3) Using NaOH to adjust the pH value of the slurry to 10-10.5 during the pre-oxidation process, and adding dithiooxamide; using NaClO3 to adjust the slurry potential to 350-400 mV during the pre-oxidation process, and stirring the reaction for 3-8 hours;

[0013] (4) Add reducing substances to adjust the pulp potential to no more than 100mV.

[0014] Preferably, in step (3), the mass concentration of dithiooxamide is controlled to be 0.04% to 0.1%.

[0015] Preferably, in step (4), the reducing substance is Na2S2O5 or Na2S2O3 or Na2SO3.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] First, the present invention adds a certain concentration of dithiooxamide during the pre-oxidation process, and utilizes the lone pair electrons of the sulfur atom and nitrogen atom in the dithiooxamide molecule to react with Te 4+ The formation of a stable complex reduces the potential required for the oxidation of tellurium-containing minerals, significantly increases the reaction rate, and at the same time reduces the pH value required for the pre-oxidation process, saving reagent costs.

[0018] Second, after the pre-oxidation process is completed, the present invention utilizes the reducing property of the reducing substance (Na2S2O5 or Na2S2O3 or Na2SO3) to consume the excess NaClO3 oxidant in the system, thereby avoiding the impact on the gold and silver cyanide leaching rate during the subsequent cyanide leaching dosing process and the excessive consumption of cyanide leaching reagents.

[0019] Third, after cyanide leaching, it was found through testing that the leaching rate of gold and silver was significantly improved by using the pretreatment method of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described below with reference to the following embodiments, comparative examples and experimental data.

[0021] The present invention uses a tellurium-containing gold ore sample from a gold mine in Shandong, in which the gold grade is 4.17 g / t, the silver grade is 12.52 g / t, and the tellurium grade is 31.44 g / t.

[0022] Example 1

[0023] A 10 kg sample of tellurium-gold ore was crushed and ground to a particle size of -0.037 mm, accounting for 90.74% of the sample. Water was added to adjust the slurry concentration to 36%. NaOH was used to adjust the slurry pH to 10-10.5 during pre-oxidation. Dithiooxamide was added and its concentration was adjusted to 0.07%. The slurry potential was measured to be 39 mV. NaClO₃ was added to adjust the slurry potential to 370±5 mV during pre-oxidation. The reaction was stirred at room temperature for 5 hours.

[0024] After the pre-oxidation, Na2S2O5 was added as a reducing substance to adjust the pulp potential to 87 mV, and then sodium cyanide was added and the mass concentration was adjusted to 0.06%, and conventional cyanide leaching was carried out for 48 hours.

[0025] After cyanide leaching, the gold and silver leaching rates were 90.65% and 75.60% respectively.

[0026] The results of the calculation of the main reagent consumption during the pretreatment and leaching process of this embodiment are shown in Table 1.

[0027] Table 1: Calculation of main agent consumption in Example 1

[0028]

[0029] As shown in Table 1, the alkaline leaching pre-oxidation of tellurium-containing gold ore not only improves the leaching rate of gold and silver, but also keeps the consumption of NaOH and NaClO3 at a low level.

[0030] Example 2

[0031] A 50kg sample of tellurium-gold ore was crushed and ground to a particle size of -0.037mm, accounting for 89.58%. Water was added to adjust the slurry concentration to 37%. NaOH was used to adjust the slurry pH to 10-10.5 during pre-oxidation. Dithiooxamide was added and its concentration was adjusted to 0.08%. The slurry potential was measured to be 37 mV. NaClO₃ was added to adjust the slurry potential to 380±5 mV during pre-oxidation. The reaction was stirred at room temperature for 6 hours.

[0032] After pre-oxidation, Na2S2O3 was added as a reducing agent to adjust the pulp potential to 93 mV. Sodium cyanide was then added to adjust the concentration to 0.06%, and conventional cyanide leaching was carried out for 48 hours. After cyanide leaching, the gold and silver leaching rates were 91.23% and 75.08%, respectively.

[0033] The results of the calculation of the main reagent consumption during the pretreatment and leaching process of this embodiment are shown in Table 2.

[0034] Table 2: Calculation of main agent consumption in Example 2

[0035]

[0036] As shown in Table 2, the alkaline leaching pre-oxidation of tellurium-containing gold ore not only improves the leaching rate of gold and silver, but also keeps the consumption of NaOH and NaClO3 at a low level.

[0037] Comparative Example 1

[0038] To further illustrate the present invention, a comparison without adding dithiooxamide was performed.

[0039] A 10kg sample of tellurium-gold ore was crushed and ground to a particle size of -0.037mm, accounting for 90.53%. Water was added to adjust the slurry concentration to 35%, and NaOH was used to adjust the slurry pH to 10-10.5 during pre-oxidation. The slurry potential was measured to be 37 mV. NaClO₃ was used to adjust the slurry potential to 370±5 mV during pre-oxidation. The reaction was stirred at room temperature for 6 hours.

[0040] After pre-oxidation, Na₂S₂O₅ was added as a reducing agent to adjust the pulp potential to 91 mV. Sodium cyanide was then added to adjust the mass concentration to 0.06%, and conventional cyanide leaching was performed for 48 hours. After cyanide leaching, the gold and silver leaching rates were 71.70% and 61.42%, respectively. These rates were significantly lower than those in Examples 1 and 2.

[0041] The results of the calculation of the main reagent consumption during the pretreatment and leaching process of this embodiment are shown in Table 3.

[0042] Table 3: Calculation of main agent consumption in comparative example 1

[0043]

[0044] From the test results and Table 3, it can be seen that although the consumption of NaOH and NaClO3 in the alkaline leaching pre-oxidation of tellurium-containing gold ore is also at a low level, the gold and silver leaching rate is low.

[0045] Comparative Example 2

[0046] The tellurium-bearing gold ore sample was crushed and ground to a particle size of -0.037 mm, accounting for 91.06%. The ground tellurium-bearing gold ore was slurried with water to a controlled slurry concentration of 36%. Conventional cyanide leaching was performed for 48 hours at a sodium cyanide concentration of 0.06%, yielding gold and silver leaching rates of 72.42% and 62.70%, respectively. This indicates that conventional cyanide leaching methods for this type of difficult-to-treat gold ore yield relatively low gold and silver leaching rates.

Claims

1. A method for alkaline pre-oxidation of tellurium-containing gold ore, characterized in that Follow these steps: (1) Tellurium-containing gold ore is crushed and ground to -0.037 mm, accounting for 90±2%; (2) Add water to the milled tellurium-containing gold ore to adjust the slurry to control the slurry concentration to 35%~40%; (3) Using NaOH to adjust the pH value of the slurry to 10-10.5 during the pre-oxidation process, and adding dithiooxamide; using NaClO3 to adjust the slurry potential to 350-400 mV during the pre-oxidation process, and stirring the reaction for 3-8 hours; (4) Add reducing substances to adjust the pulp potential to no more than 100mV.

2. The alkaline pre-oxidation method for tellurium-gold ore according to claim 1, characterized in that: In step (3), the mass concentration of dithiooxamide is controlled to be 0.04%~0.1%.

3. The alkaline pre-oxidation method for tellurium-gold ore according to claim 1 or 2, characterized in that: In step (4), the reducing substance is Na2S2O5 or Na2S2O3 or Na2SO3.

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