Gold leaching process using high-safety bromine-containing substance

Abstract

The invention discloses a gold leaching process using a high-safety bromine-containing substance, and belongs to the technical field of gold extraction. According to the method, the dibromo dimethyl hydantoin and the calcium bromide are prepared into the leaching solution according to a certain proportion, efficient gold leaching is achieved by adjusting parameters such as the pH value and the leaching time under the condition of the metal ion catalyst, and the gold can be effectively adsorbed, analyzed and recycled through the leached pregnant solution. Meanwhile, bromine in the leachate is recycled through an electrochemical method, bromine is prevented from permeating into the environment, the dosage of chemicals is reduced, a complete gold leaching and chemical circulating system is constructed, the gold leaching efficiency is improved, the environmental risk is reduced, the technical applicability is expanded, and the defects that traditional liquid bromine gold leaching is large in toxicity, low in leaching rate and leaching efficiency and the like are overcome.

Description

Technical Field

[0001] The invention belongs to the technical field of gold extraction and relates to a process for leaching gold using bromine-containing substances and recovering bromine. Background Art

[0002] In the field of gold extraction technology, cyanide leaching has long occupied a dominant position. With its relatively mature process technology and high gold extraction efficiency, it is widely used in gold production companies around the world. However, the inherent characteristics of cyanide have brought many serious problems. Its high toxicity makes it easy to cause serious safety accidents if it is not careful in the use, storage and transportation links, posing a direct threat to the life safety of operators. More importantly, a large amount of cyanide-containing wastewater and waste residue are produced during the cyanide leaching process. If not properly handled, it will cause irreversible deep pollution to the soil, water and atmospheric environment. Cyanide-containing wastewater discharged into natural water bodies will poison aquatic organisms, destroy the water ecological balance, and cause a sharp decline in water biodiversity; it will remain in the soil for a long time, change the physical and chemical properties of the soil, make it difficult for vegetation to grow, and cause the risk of land desertification; the volatiles during the storage of waste residues also pollute the surrounding air, endanger the health of residents and the stability of the ecological environment, and cause a series of environmental and social problems. Therefore, the exploration of cyanide-free or low-cyanide gold leaching technology is becoming more and more urgent.

[0003] Bromine gold leaching technology came into being under this background and has attracted widespread attention from researchers. Compared with traditional cyanide and thiosulfate leaching processes, bromine gold leaching technology shows unique advantages. Its gold dissolution rate is significantly accelerated, which greatly shortens the gold leaching cycle and improves production efficiency, which meets the needs of modern industrialized rapid production. At the same time, the gold leaching rate is higher, which can more fully extract the gold resources in the ore, reduce resource waste, and improve the economic benefits and resource utilization of the mine. However, the defects of traditional liquid bromine gold leaching technology seriously restrict its large-scale industrial promotion. Liquid bromine itself is highly toxic, and its volatile characteristics cause the bromine concentration in the workplace air to exceed the standard, irritating the human respiratory tract, eyes and skin mucosa, causing health problems such as coughing, dyspnea, and burns, and increasing the risk of occupational diseases; once leaked to the environment, it will cause local ecological disasters and seriously damage the ecological chain. Furthermore, the high corrosiveness of liquid bromine has strict requirements on the material of gold leaching equipment, greatly increasing equipment investment and maintenance costs, shortening the service life of equipment, and frequent equipment replacement affects production continuity and stability, reducing the economic benefits and market competitiveness of enterprises, which has become a key problem that needs to be overcome in the development of the industry.

[0004] The US patent number US11214848B2 discloses a "method for purifying precious metals" involving the use of bromine compounds to extract gold. Its technical measures include adding hydrogen peroxide to increase the oxidation capacity of the leaching solution, thereby improving the leaching effect. However, hydrogen peroxide consumes hydrogen ions in the system and converts into water, resulting in excessive consumption of hydrogen peroxide, which greatly increases the leaching cost.

[0005] The master's thesis of Shandong University of Technology, "Study on the Pretreatment of Refractory Gold Concentrate at Normal Temperature and Pressure with Strong Alkali and Experimental Study on Bromination Leaching (Author: Li Zongzhan)," also involves the use of bromine compounds to extract gold. The bromine-containing substances used are mainly sodium bromide and dibromohydantoin, but no catalyst is used. The leaching efficiency and leaching effect are poor. Figures 3-31 of the thesis show that the leaching time is as long as 7 hours, and the Au leaching rate is only 90%. Summary of the invention

[0006] In view of the problems existing in the prior art, the technical problem to be solved by the present invention is to provide a gold leaching process using a highly safe bromine-containing substance, firstly, to overcome the shortcomings of the strong toxicity of cyanide and liquid bromine by adopting a new gold leaching material; secondly, to further improve the gold leaching rate and leaching efficiency of gold-containing ores; and thirdly, to realize the electrochemical regeneration of the bromination agent.

[0007] The technical solution of the present invention is as follows: A gold leaching process using a highly safe bromine-containing substance comprises the following steps: 1) Preparation of leaching solution: at normal temperature and pressure, dibromodimethylhydantoin, calcium bromide and metal ion catalyst are prepared into leaching solution, and the pH value of the leaching solution is adjusted to 2-5; 2) Add the prepared leaching solution to the slurry containing gold ore and stir to leach.

[0008] Preferably, the metal ion catalyst is Cu 2+ or Fe 3+ or Co 3+ Or Ni 3+ ; The slurry concentration is 30%~48%, and the dosage is 0.05~0.5kg per ton of slurry.

[0009] Further preferably, for ores with a Cu content exceeding 1%, Cu 2+ As a catalyst, its dosage is in the range of 0.1-0.3 kg per ton of slurry; for ores with an iron content of more than 20%, Fe 3+ As a catalyst, the dosage is 0.2-0.4 kg per ton of ore pulp.

[0010] Preferably, the slurry concentration is 30% to 48%, the amount of dibromodimethylhydantoin used is 60 to 140 kg per ton of slurry, and the amount of calcium bromide used is 40 to 120 kg per ton of slurry.

[0011] Preferably, the leaching time in step 2) is 2 to 5 hours.

[0012] Preferably, the method further comprises the following steps: 3) Use a double-chamber electrolytic cell to electrochemically recover bromine: the anode electrolytic cell uses graphite as the anode material, the auxiliary electrolyte in the cathode electrolytic cell is a 1-3 mol / L sodium hydroxide solution, the electrolysis voltage is controlled at 3-5 V, and the current density is 100-300 A / m².

[0013] Further preferably, a semi-permeable membrane is arranged between the cathode electrolyzer and the anode electrolyzer; the cathode electrolyzer is used to store auxiliary electrolyte and produce hydrogen byproduct; and the anode electrolyzer is used to convert bromide ions into bromine.

[0014] The present invention has the following beneficial effects: First, the present invention uses dibromodimethylhydantoin, calcium bromide and metal ion catalyst as the main components of gold leaching. Dibromodimethylhydantoin has no obvious irritating odor, is not volatile, has high stability and is less corrosive to metals, is non-toxic and non-irritating to humans, and does not pollute the environment. Calcium bromide is a crystalline solid that is almost non-volatile at normal temperature and pressure. Therefore, compared with the liquid bromine gold leaching process, the gold leaching material of the present invention has better safety performance.

[0015] Second, the present invention uses dibromodimethylhydantoin, calcium bromide and metal ion catalyst for leaching. The active bromine atoms contained in dibromodimethylhydantoin and calcium bromide can combine with Au ions and undergo redox reactions. The metal ion catalyst promotes the dissolution of gold in the leaching solution, thereby promoting the efficient leaching of gold. Experiments show that the method of the present invention is significantly superior to the prior art in terms of Au leaching rate, Au adsorption rate, Au resolution rate and bromine recovery rate. In terms of leaching efficiency, a high Au leaching rate can be obtained with a leaching time of only 4 hours, and the leaching efficiency is significantly improved.

[0016] Third, the present invention realizes the electrochemical regeneration of the bromination agent, forms a closed loop to prevent bromine from penetrating into the environment, and ensures the safe collection and utilization of hydrogen byproducts, thereby improving the resource utilization and environmental friendliness of the entire gold leaching process.

[0017] Fourth, the present invention can more accurately improve the gold leaching efficiency and reduce the cost by selecting the catalyst in a targeted manner. Experiments have shown that for ores with a high Cu content, the use of Cu 2+ As a catalyst, for ores with high iron content, Fe 3+ As a catalyst, indicators such as Au leaching rate are significantly better than those of other metal ion catalysts. DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with embodiments, comparative examples and experimental data.

[0019] Comparative Example 1 Take the raw ore with Au grade of 2.91g / t and copper content of 6.74%, prepare the leaching solution of liquid bromine + sodium bromide system (liquid bromine 0.1mol / L, sodium bromide 2mol / L), control the pH range to 1.3~2.0, temperature to 70℃, liquid-solid ratio to 4:1, and leaching time to 4h. After testing, the Au leaching rate is 70.41%.

[0020] The activated carbon with a particle size of 2 mm was used for adsorption treatment, and the adsorption time was 3 hours. After testing, the Au adsorption rate was 83.38%.

[0021] The activated carbon after adsorption was decomposed with a mixture of caustic soda and sodium cyanide in a mass ratio of 4:1 at 130°C for 1.5 hours. The decomposition rate was 89%.

[0022] Example 1

[0023] Preparation of leaching solution: Add appropriate amount of water to dibromodimethylhydantoin and calcium bromide at normal temperature and pressure, and add metal ion catalyst to prepare leaching solution. Adjust the pH value of the leaching solution to 3.

[0024] The prepared leaching solution was added to the slurry containing gold ore (the original ore was the same as that in comparative example 1, and the slurry concentration was 35%), and the leaching time was 4 hours. After testing, the Au leaching rate was 92.36%.

[0025] In this embodiment, the amount of dibromodimethylhydantoin used is 80 kg per ton of ore pulp, the amount of calcium bromide used is 60 kg per ton of ore pulp, and the Cu content in the ore pulp is regulated by adding copper sulfate. 2+ The catalyst concentration is 0.2 kg / t.

[0026] After leaching, activated carbon with a particle size of 2 mm was used for adsorption treatment for 3 hours. After testing, the Au adsorption rate was 90.15%.

[0027] The activated carbon after adsorption was decomposed with a mixture of caustic soda and sodium cyanide in a mass ratio of 4:1 at 130°C for 1.5 hours. The decomposition rate was 92%.

[0028] The double-chamber electrolytic cell is used to electrochemically recover bromine: the anode electrolytic cell uses graphite as the anode material, the auxiliary electrolyte in the cathode electrolytic cell is a 2mol / L sodium hydroxide solution, the electrolysis voltage is controlled at 4V, and the current density is 200A / m². The bromide is converted into bromine at the anode and reused. After testing, the bromine recovery rate is 66%.

[0029] A semi-permeable membrane is arranged between the cathode electrolyzer and the anode electrolyzer; the cathode electrolyzer is used to store auxiliary electrolyte and produce hydrogen byproduct; the anode electrolyzer is used to convert bromide ions into bromine, realize electrochemical regeneration of bromination reagent, and form a closed loop to prevent bromine from penetrating into the environment.

[0030] Example 2

[0031] Under the same conditions as in Example 1, the Fe content in the slurry was regulated by adding ferric sulfate. 3+ The catalyst concentration is 0.3kg / t, replacing Cu 2+ Catalyst. Adjust pH to 4.

[0032] After testing, the Au leaching rate was 85.48%; the Au adsorption rate was 88.36%; the Au resolution rate was 91%; and the bromine recovery rate was 63%.

[0033] Example 3

[0034] Under the same conditions as in Example 2, the original ore was replaced with an ore with an Au grade of 3.01 g / t, a copper content of 0.15%, and an Fe content of 24.62%. The Fe content in the slurry was regulated by adding ferric sulfate. 3+ The catalyst concentration is 0.3kg / t, replacing Cu 2+ Catalyst. Adjust pH to 4.

[0035] After testing, the Au leaching rate was 90.48%; the Au adsorption rate was 91.36%; the Au resolution rate was 90.5%; and the bromine recovery rate was 67%.

[0036] Example 4

[0037] Under the same conditions as in Example 3, copper sulfate was added to control the Cu content in the slurry. 2+ The catalyst concentration is 0.3kg / t, replacing Fe 3+ Catalyst. Adjust pH to 4.

[0038] After testing, the Au leaching rate was 81.97%; the Au adsorption rate was 86.16%; the Au resolution rate was 88.5%; and the bromine recovery rate was 64%.

[0039] Example 5

[0040] Under the same conditions as in Example 1, the amount of dibromodimethylhydantoin was changed to 60 kg per ton of pulp, and the amount of calcium bromide was changed to 100 kg per ton of pulp. 3+ The catalyst concentration is 0.05kg / t, replacing Cu 2+ Catalyst. Adjust pH to 2.

[0041] After testing, the Au leaching rate was 90.56%, the Au adsorption rate was 91.33%, the Au resolution rate was 93%, and the bromine recovery rate was 66%.

[0042] Example 6

[0043] Under the same conditions as in Example 1, the amount of dibromodimethylhydantoin was changed to 140 kg per ton of pulp, and the amount of calcium bromide was changed to 40 kg / t per ton of pulp. 3+ The catalyst concentration is 0.5kg / t, replacing Cu 2+ Catalyst. Adjust pH to 5.

[0044] After testing, the Au leaching rate was 78.16%, the Au adsorption rate was 93.21%, the Au resolution rate was 91.4%, and the bromine recovery rate was 65%.

[0045] Example 7

[0046] Under the same conditions as in Example 1, the anode of the double-chamber electrolyzer was graphite, the cathode sodium hydroxide was adjusted to 2.5 mol / L, the electrolysis voltage was adjusted to 4.5 V, and the current density was adjusted to 250 A / m². After testing, the bromine recovery rate was 71%.

[0047] It should be noted that the range of catalyst dosage for different metal ions is somewhat different. For ores with higher Cu content (higher sulfur content generally refers to the Cu content in the ore being higher than 1%), Cu 2+ As a catalyst, its dosage can be within the range of 0.1-0.3 kg per ton of slurry; for ores with high iron content (ores with high iron content generally refer to ores with iron content higher than 20%), Fe 3+ As a catalyst, the dosage is about 0.2 to 0.4 kg per ton of ore pulp.

Claims

1. A gold leaching process using a highly safe bromine-containing substance, characterized in that The following steps are involved: 1) Preparation of leaching solution: at normal temperature and pressure, dibromodimethylhydantoin, calcium bromide and metal ion catalyst are prepared into leaching solution, and the pH value of the leaching solution is adjusted to 2-5; 2) Add the prepared leaching solution to the slurry containing gold ore and stir to leach.

2. The gold leaching process using a high-safety bromine-containing substance as claimed in claim 1, characterized in that: The metal ion catalyst is Cu 2+ or Fe 3+ or Co 3+ Or Ni 3+ ; The slurry concentration is 30%~48%, and the dosage is 0.05~0.5kg per ton of slurry.

3. The gold leaching process using a high-safety bromine-containing substance as claimed in claim 2, characterized in that: For ores with a Cu content exceeding 1%, use Cu 2+ As a catalyst, its dosage is in the range of 0.1-0.3 kg per ton of slurry; for ores with an iron content of more than 20%, Fe 3+ As a catalyst, the dosage is 0.2-0.4 kg per ton of ore pulp.

4. The gold leaching process using a high-safety bromine-containing substance as claimed in claim 1, characterized in that: The slurry concentration is 30%~48%, the dosage of dibromodimethylhydantoin is 60~140kg per ton of slurry; the dosage of calcium bromide is 40~120kg per ton of slurry.

5. The gold leaching process using a high-safety bromine-containing substance as claimed in claim 1, characterized in that: Step 2) The leaching time is 2 to 5 hours.

6. The gold leaching process using a high-safety bromine-containing substance as claimed in claim 1, 2, 3, 4 or 5, characterized in that The following steps are also included: 3) Use a double-chamber electrolytic cell to electrochemically recover bromine: the anode electrolytic cell uses graphite as the anode material, the auxiliary electrolyte in the cathode electrolytic cell is a 1-3 mol / L sodium hydroxide solution, the electrolysis voltage is controlled at 3-5 V, and the current density is 100-300 A / m².

7. The gold leaching process using a high-safety bromine-containing substance as claimed in claim 6, characterized in that: A semi-permeable membrane is arranged between the cathode electrolytic cell and the anode electrolytic cell; The cathode electrolyzer is used to store auxiliary electrolyte and produce hydrogen byproduct; the anode electrolyzer is used to convert bromide ions into bromine.