Beneficiation method for comprehensively recovering valuable metal from high-iron copper oxide gold ore

Abstract

The invention discloses a beneficiation method for comprehensively recovering valuable metal from high-iron copper oxide gold ore, and belongs to the field of mineral processing engineering. The method comprises the technological processes of ore grinding, iron magnetic separation, Nelson gold separation, classified ore grinding of tailings II, copper sulfide gold flotation and copper oxide gold ore flotation. According to the method, iron separation is conducted firstly, then gold reselection is conducted, and then the copper sulfide gold ore and the copper oxide gold ore are treated respectively, so that the recovery rate of each metal mineral is guaranteed, and the overall resource utilization rate is greatly increased; according to the method, efficient separation of iron, gold, copper sulfide and copper oxide is achieved through a staged treatment method, and resource waste caused by mineral co-smelting in a traditional method is avoided; the recovery rate of copper and gold can be increased, the metal loss is reduced, and the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of mineral processing engineering, and in particular is a ore dressing method for recovering copper, gold and iron from high-silicon, high-mud oxide copper-gold ore. Background Art

[0002] The formation process of copper oxide is the process of copper ore being converted from copper sulfide ore to oxide mineral in the natural environment, especially under weathering. The formation of copper oxide is mainly completed through oxidation, weathering and dissolution. Specifically, the formation of copper oxide (CuO) goes through the following steps: The formation of copper oxide usually begins with the weathering of copper ore, especially the weathering of copper sulfide minerals (such as chalcopyrite, chalcocite, etc.) in the surface or shallow oxidation zone. The original copper sulfide ore is exposed to oxygen and moisture in the air, and will gradually oxidize and convert into minerals such as copper oxide (CuO). During the weathering process, copper ions (Cu2+) are dissolved by water and oxygen. Over time, these copper ions react with other chemicals in the environment to form different copper oxide minerals, the most common of which is copper oxide.

[0003] The formation process of iron oxide refers to the process in which iron ore (such as iron sulfide ore, iron ore) is gradually transformed into different types of oxide minerals (such as hematite, magnetite, limonite, etc.) in the natural environment, especially under the action of oxygen and water. This process is the result of weathering, oxidation and hydrolysis of iron ore, involving chemical reactions and geological evolution. The formation of iron oxide is the result of iron reacting with oxygen, water and other substances in the natural environment. Iron minerals are gradually transformed into different types of iron oxide minerals through processes such as weathering, oxidation and hydrolysis. This process is affected by factors such as oxidation conditions, environmental humidity, and temperature, forming common iron oxide minerals such as hematite, magnetite, and limonite. Iron oxide minerals are not only important minerals in geological processes, but also have important value in human industrial applications, especially in steel production and other metal refining.

[0004] Iron sulfide is gradually oxidized into hematite, limonite and magnetite when it comes into contact with water and oxygen. Therefore, it is inevitable that copper oxide ores contain iron oxide. High-iron copper-gold ore is a type of ore resource containing gold, copper and other valuable metals, which is widely distributed all over the world. The ore mainly contains metal elements such as gold, copper and iron. Due to its complex composition, the ore dressing process faces great challenges. Traditional beneficiation methods usually use flotation, gravity separation, cyanide leaching and other processes, but these methods often have the following problems: (1) Low metal recovery rate: When traditional methods are used to treat high-iron copper-gold ore, the recovery rate of copper and gold is low. The presence of iron minerals often has an adverse effect on the recovery of copper and gold. (2) Waste of resources: Due to the high content of copper, iron and other metals in gold ore, traditional processes may have a negative impact on the recovery of gold during copper recovery, resulting in waste of gold resources. (3) Environmental pollution problems: Although the cyanide leaching process can effectively extract gold, it will produce toxic cyanide waste liquid, causing environmental pollution and ecological damage. (4) Complex process and high cost: Some common treatment methods require multiple complex process steps, including dosing, sorting, washing, etc., which results in a long overall beneficiation process and high energy consumption, increasing production costs. Therefore, how to effectively recover metals, especially gold and copper, from high-iron oxide copper-gold ores and improve their comprehensive recovery rate has become a technical challenge faced by the mining industry. Summary of the invention

[0005] The purpose of the present invention is to provide a beneficiation method for comprehensively recovering valuable metals from high-iron copper-gold ore. In view of the shortcomings of the current process technology for processing high-iron copper-gold ore, combined with the characteristics of the ore, the present invention aims to overcome the shortcomings of the prior art through innovative beneficiation technology and provide an efficient beneficiation method that can comprehensively recover valuable metals such as gold, copper, and iron from high-iron copper-gold ore. This method can improve the recovery rate of copper and gold, reduce metal loss, reduce production costs, and ultimately obtain gold concentrate, copper sulfide concentrate, copper oxide concentrate, and iron concentrate.

[0006] The specific steps of the present invention are as follows:

[0007] (1) Grinding: The grinding concentration of the raw ore is 55-65%, the grinding fineness is less than 0.074 mm, and the content is 50-60%, and the mass percentage concentration of the ore pulp is 30-36%;

[0008] (2) Magnetic separation of iron: The ore pulp obtained in step (1) is fed into a magnetic separator, and after a roughing separation and a concentrating separation, an iron concentrate and tailings I are obtained. The magnetic field strength of the roughing separation is 0.4-0.6T, and the magnetic field strength of the concentrating separation is 0.3-0.5T. The iron grade of the obtained iron concentrate is 58-62%, and the recovery rate is 68-74%;

[0009] (3) Nelson gold selection: feed tailings I into Nelson, the centrifugal field strength is 60-90G, and the gold concentrate discharge time is 30min-50min; obtain gold concentrate and tailings II; the gold grade of the obtained gold concentrate is 2000-2600g / t, and the gold recovery rate is 15-20%;

[0010] (4) Tailings II Classification Grinding: Tailings II are first fed into the hydrocyclone, the overflow fineness of the hydrocyclone is 75-85%, the hydrocyclone overflow enters the thickener for sedimentation and thickening, the concentration is 28-32%, the hydrocyclone underflow is fed into the ball mill, and 500-1000g / t of Na 2 CO 3 and 500-1500g / t of ammonium sulfate of the raw ore to obtain the ore pulp after grinding;

[0011] (5) Copper sulfide gold flotation: add a regulator and a collecting frother to the overflow obtained in step (4), the dosage of which is 1000-2000 g / t and 150-250 g / t respectively, and obtain copper sulfide concentrate and tailings III after 1-2 roughing, 1-3 concentrating and 1-2 scavenging, and the dosage of each reagent is 1000-2000 g / t and 150-250 g / t respectively. After 1-2 roughing, 1-3 concentrating and 1-2 scavenging, copper sulfide concentrate and tailings III are obtained, and the copper sulfide concentrate has a copper grade of 18-22%, a copper recovery rate of 58-65%, a gold grade of 35-50 g / t, and a gold recovery rate of 60-65%;

[0012] (6) Flotation of oxidized copper and gold ores: adding a sulfiding agent, ammonium sulfate and a collector to the tailings III obtained in step (5) in order, with the amounts of 1000-3000 g / t, 1-3 kg / t and 300-500 g / t respectively, and obtaining oxidized copper concentrate and tailings IV after 1-2 roughing, 1-3 cleaning and 1-2 scavenging. The obtained copper concentrate has a copper grade of 14-16%, a copper recovery rate of 25-35%, a gold content of 30-45 g / t and a gold recovery rate of 8-12%;

[0013] The copper grade of the oxidized copper-gold ore is 0.8-1.2%, the gold grade is 2.0-3.0 g / t, the iron grade is 40-50%, the copper oxidation rate is 50-70%, and the gangue minerals are chlorite, talc, tremolite, mica, etc.

[0014] The adjusting agent composition and ratio in step (5) are water glass: ammonium sulfate in a ratio of 1:2, and the collecting agent composition and ratio are isobutyl xanthate propylene ester: butyl ammonium black medicine: O-isobutyl-N-isopropylthiocarbamate in a ratio of 1:2:1.

[0015] The sulfiding agent in step (6) is sodium sulfide: sodium hydrosulfide: (NH 4 ) 2 S 3The ratio of the collector is octyl hydroxamic acid: butyl xanthate and isopentyl xanthate in a ratio of 1:1:1.

[0016] Compared with the existing recovery method of copper-gold oxide ore, the present invention has the following advantages:

[0017] 1. The setting of the magnetic separation process position of the present invention is a very important innovation. At present, magnetic separation is generally set at the crushing stage (after coarse crushing, medium crushing, fine crushing, etc.) or after the flotation of copper and gold oxide, but the present invention is set after the first grinding to separate iron minerals from non-iron minerals (such as gold minerals and copper minerals). The main reasons are as follows: (1) A part of copper and gold minerals are closely interwoven with iron minerals. If iron is pre-selected in the crushing stage, it will cause the loss of copper and gold minerals; (2) Due to the high iron content, the iron minerals are selected before flotation, ① reducing the processing capacity of the second stage grinding, reducing the power consumption, steel ball consumption, equipment wear, etc. of the second stage grinding; ② after this part of the iron minerals are selected, the grade of copper and gold in the remaining tailings is improved, which is beneficial to improve the grade and recovery rate of copper concentrate and gold concentrate.

[0018] 2. The setting of the Nelson equipment of the present invention, the gravity separation equipment mainly relies on the difference in specific gravity of minerals to separate gold minerals from waste rock or other low-specific gravity minerals. After the iron minerals are selected in advance, the minerals with similar specific gravity to the gold minerals are reduced, the mismatch rate of gravity selection is reduced, and the grade and recovery rate of the gold concentrate selected by Nelson are improved. Compared with other configuration processes, the gold grade of the gold concentrate in this process is increased by 500g / t, and the recovery rate is increased by 5-10%.

[0019] 3. Efficient separation: The present invention achieves efficient separation of iron, gold, copper sulfide and copper oxide through a staged treatment method, avoiding the waste of resources in the traditional method of mineral co-smelting.

[0020] 4. High resource utilization rate: The present invention selects iron first, then reselects gold, and then processes the sulfide copper-gold ore and the oxidized copper-gold ore separately, which not only ensures the recovery rate of each metal mineral, but also greatly improves the overall resource utilization rate.

[0021] 5. The advantages of the combined collector (components are propylene isobutyl xanthate: ammonium butylate: O-isobutyl-N-isopropylthiocarbamate in a ratio of 1:2:1) are as follows: (1) propylene isobutyl xanthate is a highly hydrophobic collector with good selectivity for sulfide ores; ammonium butylate has a strong collecting ability and can be efficiently adsorbed on the surface of sulfide ores to enhance the recovery rate; O-isobutyl-N-isopropylthiocarbamate has a good reaction with copper sulfide minerals, enhancing selectivity and reducing interference from gangue minerals. ; (2) The ratio of the three collectors is 1:2:1. Through reasonable matching, the collection efficiency of copper minerals in the ore can be improved. This synergistic effect helps to balance the recovery rate and the quality of the concentrate product; (3) There are many types of copper sulfide minerals, such as chalcopyrite, bornite, covellite and chalcocite. Combined dosing can be suitable for the properties of different copper sulfide minerals; (4) Through the complementarity between collectors, it helps to reduce the kinetic barriers of the flotation process, making the flotation process more efficient, shortening the flotation time and reducing the amount of drugs used.

[0022] 6. The advantages of the combined collector (components are octyl hydroxamic acid: butyl xanthate, isopentyl xanthate in a ratio of 1:1:1) are as follows: (1) Octyl hydroxamic acid has a strong collector effect on copper oxide ores and can form a stable chelate with the surface of copper oxide, significantly improving the flotation recovery rate of copper oxide; Butyl xanthate and isopentyl xanthate can help copper minerals that are not completely oxidized or partially sulfided during the flotation process and increase the flotation selectivity of the minerals; (2) The three work synergistically to accelerate the flotation kinetics, making copper oxide particles easier to float and improving the flotation efficiency; (3) It has a significant effect on fine-grained copper oxide and has excellent selective collector ability for fine-grained and difficult-to-float copper oxide (such as malachite, azurite, and chernozemite); (4) Octyl hydroxamic acid is highly targeted and has a low affinity for silicon-containing and iron-containing gangue; when used in combination, xanthates can focus on the active sites of copper minerals, reducing the amount of reagents used and tailings pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a process flow chart of Example 1 of the present invention. DETAILED DESCRIPTION

[0024] The following is a further description of a ore dressing method for recovering valuable metals from high-iron oxide copper-gold ore according to the present invention in conjunction with specific embodiments.

[0025] Embodiment 1:

[0026] Ore: A high-iron oxidized copper-gold mine in Xinjiang, the copper grade of the oxidized copper-gold mine is 0.8%, the gold grade is 2.0g / t, the iron grade is 41.5%, the copper oxidation rate is 50%, and the gangue minerals are chlorite, talc, etc. Figure 1 The process flow diagram of this embodiment is as follows:

[0027] (1) Grinding: The grinding concentration of the raw ore is 55%, the grinding fineness is less than 0.074 mm, and the content is 50%, and the ore pulp with a mass percentage concentration of 30% is obtained;

[0028] (2) Magnetic separation of iron: The slurry obtained in step (1) is fed into a magnetic separator, and after a roughing separation and a concentrating separation, an iron concentrate and tailings I are obtained. The magnetic field strength of the roughing separation is 0.4T, and the magnetic field strength of the concentrating separation is 0.3T. The iron grade of the obtained iron concentrate is 58%, and the recovery rate is 68.20%;

[0029] (3) Nelson gold selection: feed tailings I into Nelson, the centrifugal field strength is 60G, and the gold concentrate discharge time is 30min; obtain gold concentrate and tailings II, the gold grade of the obtained gold concentrate is 2120g / t, and the gold recovery rate is 15.5%;

[0030] (4) Tailings II Classification Grinding: Tailings II is first fed into the hydrocyclone, the overflow fineness of the hydrocyclone is 75%, the overflow of the hydrocyclone enters the thickener for sedimentation and thickening, the concentration is 28%, the underflow of the hydrocyclone is fed into the ball mill, and 500g / t of Na 2 CO 3 and 500g / t of ammonium sulfate of the raw ore to obtain the ore pulp after grinding;

[0031] (5) Copper sulfide gold flotation: add a regulator and a collector frother to the ore pulp after grinding in step (5), with the dosage of 1000 g / t and 150 g / t respectively. After 1 roughing, 2 cleaning and 2 scavenging, a copper sulfide concentrate and tailings III are obtained. The copper grade in the copper sulfide concentrate is 18.60%, the copper recovery rate is 64.5%, the gold grade is 36.40 g / t, and the gold recovery rate is 64.6%. The regulator component is water glass: ammonium sulfate in a ratio of 1:2; the collector component is isobutyl xanthate propylene ester: butyl ammonium black medicine: O-isobutyl-N-isopropylthiocarbamate in a ratio of 1:2:1.

[0032] (6) Flotation of oxidized copper and gold ore: a sulfiding agent, ammonium sulfate and a collector are sequentially added to the tailings III obtained in step (5), and the amounts thereof are 1000 g / t, 1 kg / t and 300 g / t, respectively. After one roughing, three cleaning and two scavenging, oxidized copper concentrate and tailings IV are obtained. The obtained copper concentrate has a copper grade of 14%, a copper recovery rate of 25.80%, contains 30 g / t of gold and a gold recovery rate of 8.2%, wherein the sulfiding agent comprises sodium sulfide: sodium hydrosulfide: (NH 4 ) 2 S 3 The ratio is 1:1:1; the collector is octyl hydroxamic acid: butyl xanthate, isopentyl xanthate in a ratio of 1:1:1;

[0033] The final total copper recovery rate was 90.3%, the total gold recovery rate was 88.3%, and the iron recovery rate was 68.20%.

[0034] Example 2

[0035] Ore: A foreign copper-gold oxidized mine with a copper grade of 1.0%, a gold grade of 2.5g / t, an iron grade of 45%, a copper oxidation rate of 60%, and gangue minerals such as tremolite and mica;

[0036] (1) Grinding: The grinding concentration of the raw ore is 58.5%, the grinding fineness is less than 0.074 mm, and the content is 55%, and the ore pulp with a mass percentage concentration of 33.5% is obtained;

[0037] (2) feeding the slurry obtained in step (1) into a magnetic separator, and obtaining iron concentrate and tailings I after a roughing and a concentrating process, wherein the magnetic field strength of the roughing process is 0.5 T, and obtaining iron concentrate and tailings I after a concentrating process, wherein the magnetic field strength of the concentrating process is 0.4 T, and the obtained iron concentrate has an iron grade of 60.6% and a recovery rate of 72.4%;

[0038] (3) Nelson gold selection: feed tailings I into Nelson, the centrifugal field strength is 75G, and the gold concentrate discharge time is 40min; obtain gold concentrate and tailings II. The gold grade of the obtained gold concentrate is 2435g / t, and the gold recovery rate is 18.4%;

[0039] (4) Tailings II Classification Grinding: Tailings II is first fed into the hydrocyclone, the overflow fineness of the hydrocyclone is 80%, the overflow of the hydrocyclone enters the thickener for sedimentation and thickening, the concentration is 30%, the underflow of the hydrocyclone is fed into the ball mill, and 750g / t of Na 2 CO 3 and 750g / t of ammonium sulfate of the raw ore to obtain the ore pulp after grinding;

[0040] (5) Copper sulfide gold flotation: add a regulator and a collector frother to the ore pulp after grinding obtained in step (4), with the dosage of 1500 g / t and 200 g / t respectively, and obtain copper sulfide concentrate and tailings III after 2 roughing, 3 cleaning and 1 scavenging. The copper sulfide concentrate has a copper grade of 20.56%, a copper recovery rate of 61.3%, a gold grade of 41.5 g / t and a gold recovery rate of 62.2%. The regulator component is water glass: ammonium sulfate in a ratio of 1:2; the collector component is isobutyl xanthate propylene ester: butyl ammonium black medicine: O-isobutyl-N-isopropylthiocarbamate in a ratio of 1:2:1.

[0041] (6) Flotation of oxidized copper and gold ore: a sulfiding agent, ammonium sulfate and a collector are sequentially added to the tailings III obtained in step (5), and the amounts thereof are 2000 g / t, 2 kg / t and 400 g / t, respectively. After one roughing, two cleaning and two scavenging, oxidized copper concentrate and tailings IV are obtained. The obtained copper concentrate has a copper grade of 15.2%, a copper recovery rate of 30.4%, a gold content of 41.5 g / t and a gold recovery rate of 9.1%. The sulfiding agent is composed of sodium sulfide: sodium hydrosulfide: (NH 4 ) 2 S 3 The ratio of the collector is octyl hydroxamic acid: butyl xanthate and isopentyl xanthate in a ratio of 1:1:1.

[0042] The final total copper recovery rate was 91.7%, the total gold recovery rate was 89.7%, and the iron recovery rate was 72.4%.

[0043] Example 3

[0044] Ore: A foreign copper-gold oxidized mine with a copper grade of 1.2%, a gold grade of 3.0 g / t, an iron grade of 50%, a copper oxidation rate of 70%, and gangue minerals such as talc and tremolite;

[0045] (1) Grinding: The grinding concentration of the raw ore is 65%, the grinding fineness is less than 0.074 mm, and the content is 60%, and the mass percentage concentration of the ore pulp is 36%;

[0046] (2) feeding the slurry obtained in step (1) into a magnetic separator, and obtaining iron concentrate and tailings I after a roughing and a concentrating. The magnetic field intensity of the roughing is 0.6 T, and the magnetic field intensity of the concentrating is 0.5 T. The iron grade of the obtained iron concentrate is 61.5%, and the recovery rate is 73.8%;

[0047] (3) Nelson gold selection: feed tailings I into Nelson, the centrifugal field strength is 90G, and the gold concentrate discharge time is 50min; obtain gold concentrate and tailings II; the gold grade of the obtained gold concentrate is 2580g / t, and the gold recovery rate is 19.6%;

[0048] (4) Tailings II Classification Grinding: Tailings II is first fed into the hydrocyclone, the overflow fineness of the hydrocyclone is 85%, the overflow of the hydrocyclone enters the thickener for sedimentation and thickening, the concentration is 32%, the underflow of the hydrocyclone is fed into the ball mill, and 1000g / t of Na 2 CO 3 and 1500g / t of ammonium sulfate of the raw ore to obtain the ore pulp after grinding;

[0049] (5) Copper sulfide gold flotation: add a regulator and a collector frother to the ore pulp after grinding obtained in step (4), with the dosage of 2000 g / t and 250 g / t respectively, and obtain copper sulfide concentrate and tailings III after 2 roughing, 3 cleaning and 1 scavenging. The copper sulfide concentrate has a copper grade of 21.8%, a copper recovery rate of 58.5%, a gold grade of 50 g / t and a gold recovery rate of 60.4%. The regulator component is water glass: ammonium sulfate in a ratio of 1:2; the collector component is isobutyl xanthate propylene ester: butyl ammonium black medicine: O-isobutyl-N-isopropylthiocarbamate in a ratio of 1:2:1;

[0050] (6) Flotation of oxidized copper and gold ore: a sulfiding agent, ammonium sulfate and a collector are sequentially added to the tailings slurry III obtained in step (5), and the dosages thereof are 3000 g / t, 3 kg / t and 500 g / t, respectively. After 2 roughing selections, 3 cleaning selections and 2 scavenging selections, oxidized copper concentrate and tailings IV are obtained. The obtained copper concentrate has a copper grade of 15.7%, a copper recovery rate of 34.1%, a gold content of 44.6 g / t and a gold recovery rate of 11.5%. The sulfiding agent is composed of sodium sulfide: sodium hydrosulfide: (NH 4 ) 2 S 3 The ratio of the collector is octyl hydroxamic acid: butyl xanthate and isopentyl xanthate in a ratio of 1:1:1.

[0051] The final total copper recovery rate was 92.6%, the total gold recovery rate was 91.5%, and the iron recovery rate was 73.8%.

Claims

1. A method for comprehensive recovery of valuable metals from high-iron copper-gold ore, characterized in that: The specific steps are as follows: (1) Grinding: The grinding concentration of the raw ore is 55-65%, the grinding fineness is less than 0.074 mm, and the content is 50-60%, and the mass percentage concentration of the ore pulp is 30-36%; (2) Magnetic separation of iron: The slurry obtained in step (1) is fed into a magnetic separator, and after a roughing separation and a concentrating separation, iron concentrate and tailings I are obtained; (3) Nelson gold selection: feed tailings I into Nelson, the centrifugal field strength is 60-90G, the gold concentrate discharge time is 30min-50min, and gold concentrate and tailings II are obtained; (4) Tailings II classification grinding: Tailings II are first fed into a hydrocyclone, and the hydrocyclone overflow fineness is 75-85%. The hydrocyclone overflow enters a thickener for precipitation and thickening, and the concentration is 28-32%. The hydrocyclone underflow is fed into a ball mill, and 500-1000g / t of Na2CO3 and 500-1500g / t of ammonium sulfate are added to obtain a ground slurry; (5) Flotation of copper sulfide and gold: add a conditioning agent and a collecting frother to the pulp after grinding in step (4), with the dosage of 1000-2000 g / t and 150-250 g / t respectively, and obtain copper sulfide concentrate and tailings III after 1-2 roughing, 1-3 cleaning and 1-2 scavenging; (6) Flotation of oxidized copper and gold ore: Sulphiding agent, ammonium sulfate and collector are sequentially added to the tailings III obtained in step (5), with the dosages of 1000-3000 g / t, 1-3 kg / t and 300-500 g / t respectively. After 1-2 roughing, 1-3 cleaning and 1-2 scavenging, oxidized copper concentrate and tailings IV are obtained.

2. The ore dressing method for recovering valuable metals from high-iron oxide copper-gold ore according to claim 1, characterized in that: The copper grade of the original ore is 0.8-1.2%, the gold grade is 2.0-3.0g / t, the iron grade is 40-50%, the copper oxidation rate is 50-70%, and the gangue minerals are chlorite, talc, tremolite, mica, etc.

3. The ore dressing method for recovering valuable metals from high-iron oxide copper-gold ore according to claim 1, characterized in that: In step (2), the primary roughing magnetic field strength is 0.4-0.6T, and the primary fine selection magnetic field strength is 0.3-0.5T.

4. The ore dressing method for recovering valuable metals from high-iron oxide copper-gold ore according to claim 1, characterized in that: The adjusting agent composition and ratio in step (5) are water glass: ammonium sulfate in a ratio of 1:2, and the collecting agent composition and ratio are isobutyl xanthate propylene ester: butyl ammonium black medicine: O-isobutyl-N-isopropylthiocarbamate in a ratio of 1:2:

1.

5. The ore dressing method for recovering valuable metals from high-iron oxide copper-gold ore according to claim 1, characterized in that: The sulfiding agent component in step (6) is sodium sulfide: sodium hydrosulfide: (NH4)2S3 in a ratio of 1:1:1; the collecting agent is octyl hydroxamic acid: butyl xanthate, isopentyl xanthate in a ratio of 1:1:1.

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