How to recover silver

Abstract

To provide a method for efficiently recovering silver contained in slag resulting from calcined slimes in noble metal refining.SOLUTION: A method for recovering silver includes coarsely crushing slag formed in a noble metal refining process, making the coarsely crushed slag into slurry and grinding it (preferably, the grinding is performed until the cumulative undersize 80% particle size (D80) becomes 80 μm or less), floating the ground slurry in the presence of a collector and a foamer to recover the float (preferably, the recovered float is repeatedly subjected to a calcining process for noble metal refining or a calcining sliming process to obtain unrefined silver).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for recovering silver from slag generated in the smelting process of precious metals. Specifically, for example, roasted sediment separated in a roasting furnace in a precious metal smelting process and chloride leaching sediment of copper electrolytic slime contain precious metals such as gold, silver, and platinum. The present invention relates to a method for efficiently separating and recovering silver from slag generated from these sediments. [Background technology]

[0002] Conventionally, methods for recovering silver are known, such as the method described in JP-A-4-236731 (Patent Document 1) and the method described in JP-A-2001-316736 (Patent Document 2). The method of Patent Document 1 involves roasting copper electrolytic slime to recover roasted sediment containing precious metals, bismuth, lead, antimony, etc. (roasting process), adding iron to the roasted sediment and melting it to obtain precious lead containing reduced precious metals and slag containing lead, antimony, etc. (melting process), and then slagizing the impurities contained in the precious lead to obtain crude silver (silver separation process).

[0003] The method of Patent Document 2 involves repulping the chloride leaching precipitate of copper electrolytic slime, adding iron powder, simultaneously reducing silver and lead to remove chlorine, thereby precipitating metallic silver and lead, melting this mixture in an oxidation furnace, oxidizing the lead to form slag, while separating and recovering crude metallic silver. Note that Patent Document 1 distinguishes between the roasting process and the precipitation process, but there are also cases where silver is recovered from the precious lead and slag generated from a roasting and precipitation furnace that performs the roasting and precipitation process, which combines the roasting and precipitation processes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 4-236731 [Patent Document 2] JP 2001-316736 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the conventional precious metal refining process using copper electrolytic slime as a starting material described in Patent Document 1, crude silver is recovered through a roasting process, a slag process, and a silver separation process, and then silver is recovered by electrolytic refining. In addition, a sulfuric acid conversion product of the chloride leaching precipitate of copper electrolytic slime may be applied to the above-mentioned precious metal refining process. In this method, since the refractory used in the roasting furnace, slag furnace, and silver separation furnace is infiltrated with precious metals, the refractory is treated in a slag process to recover the precious metals. At this time, there is a problem that the total amount of impurities such as aluminum oxide and magnesium oxide that constitute the refractory is transferred to the slag, which promotes the suspension of precious lead, thereby hindering the recovery of silver. In addition, the separation method described in Patent Document 2 has a problem that raw materials containing a large amount of lead cannot be treated because there is no process for removing lead (for example, roasting and slag).

[0006] The present invention provides a method for efficiently recovering silver contained in slag generated from roasted sediment in precious metal refining, etc. The silver recovery method of the present invention can increase the silver yield in precious metal refining. [Means for solving the problem]

[0007] The present invention is a method for recovering silver having the following configuration. [1] A method for recovering silver, comprising roughly crushing precious metal-containing slag, forming the roughly crushed slag into a slurry and grinding the slurry, and flotation-separating the ground slurry in the presence of a collector and a foaming agent to recover a float, the method being characterized in that a mercaptobenzothiazole-based compound is used as a collector at a pH of 4 to 8 to recover a float containing concentrated silver. [2] A method for recovering float ore by roughly crushing precious metal-containing slag, forming the roughly crushed slag into a slurry and grinding the slurry in the presence of a collector and a foaming agent, comprising the steps of: 80 ) is ground to 80 μm or less, the slurry concentration during grinding is set to 50 to 80 mass%, and the slurry concentration during flotation is set to 30 to 40 mass%, When using 2-mercaptobenzothiazole sodium salt (MCB4) as a collector, add it before the start of grinding. When using potassium amylxanthate (PAX) as a collector, adjust the pH to 11 or less and add it before the start of flotation after grinding. Carry out flotation within one hour after grinding.A method for recovering silver, comprising recovering float in which silver is concentrated.

[0008] [Specific explanation] The first method of the present invention is a method for recovering silver, which comprises roughly crushing precious metal-containing slag, forming the roughly crushed slag into a slurry and grinding it, and floting the ground slurry in the presence of a collector and a foaming agent to recover float, wherein a mercaptobenzothiazole-based compound is used as a collector, and float recovery of silver-enriched float is performed at a pH of 4 to 8. In a second method of the present invention, precious metal-containing slag is roughly crushed, the roughly crushed slag is turned into a slurry and ground, and the ground slurry is subjected to flotation in the presence of a collector and a foaming agent to recover float, wherein the cumulative 80% particle diameter (D 80 ) is ground to 80 μm or less, the slurry concentration during grinding is set to 50 to 80 mass%, and the slurry concentration during flotation is set to 30 to 40 mass%, When using 2-mercaptobenzothiazole sodium salt (MCB4) as a collector, add it before the start of grinding. When using potassium amylxanthate (PAX) as a collector, adjust the pH to 11 or less and add it before the start of flotation after grinding. Carry out flotation within one hour after grinding. This is a method for recovering silver, characterized by recovering float in which silver is concentrated.

[0009] The silver recovery method of the present invention is a method for recovering silver generated during the smelting process of precious metals. Precious metal-containing slag This method recovers silver from copper electrolytic slime and the roasted sediment of the sulfuric acid conversion product of the chloride leaching sediment of copper electrolytic slime. For example, precious metals such as gold, silver, and platinum are contained in the roasted sediment of the sulfuric acid conversion product of the chloride leaching sediment of copper electrolytic slime. The silver recovery method of the present invention recovers silver from these sediments. Precious metal-containing slag Silver was concentrated from floating ore In addition, the waste generated from the roasting and sintering furnace, which performs the roasting and sintering process, is collected. Contains precious metals The method of the present invention can also be applied to recovering silver from slag.

[0010] The above roasted sediment and chloride leaching sediment were generated Contains precious metals The slag is roughly crushed. The roughly crushing may be carried out by crushing the slag into a size suitable for the subsequent grinding.

[0011] The roughly crushed slag is placed in a ball mill or the like, and water is added to make a slurry. The slurry is then preferably sieved to a size of 80% under sieve (D 80 ) is ground to 80μm or less. D 80 If the diameter is larger than 80 μm, the silver recovery rate decreases. 80 Although there is no lower limit, for example, 30 μm or more is preferable. Even if the ore is ground to less than 30 μm, the efficiency of flotation remains the same, and there is an energy loss in grinding.

[0012] The slurry concentration during grinding is preferably 50-80% by mass (1-4 kg / L), more preferably about 65% by mass (2 kg / L). If the slurry concentration is less than 50% by mass, it will lead to a decrease in efficiency and an increase in cost, and if the slurry concentration exceeds 80% by mass, it will be undesirable because the fluidity will deteriorate and the efficiency will decrease.

[0013] If the time between grinding and flotation is long, the condition of the particle surface (e.g., oxidation state, etc.) may change, which may affect the subsequent flotation step and reduce the silver yield, so it is preferable to carry out flotation promptly after grinding, for example within one hour.

[0014] The ground slurry is floated in the presence of a collector and a frother. Xanthate salts and mercaptobenzothiazole compounds can be used as collectors. Xanthate salts such as PAX (potassium amyl xanthate) can be used as xanthate salts, and mercaptobenzothiazole compounds such as MCB4 (2-mercaptobenzothiazole sodium salt) can be used as frothers. Methyl isobutyl carbinol (MIBC) can be used as frothers.

[0015] Since PAX is less dependent on the pH of the slurry in silver recovery, there is no particular restriction on the pH range, but it is recommended to adjust the pH to 11 or less, for example. MCB4 has high selectivity for silver selenide. When using MCB4, it is recommended to adjust the pH to 4 to 8 for flotation. If the pH is less than 4, the silver recovery rate decreases, and even if the pH exceeds 8, the silver recovery rate also decreases, so this is not recommended. In addition, PAX is recommended to be added before the start of flotation after grinding, and MCB4 is recommended to be added before the start of grinding.

[0016] The slurry concentration during flotation is preferably 30 to 40 mass % (425 to 667 g / L), more preferably around 35 mass % (500 g / L). If it exceeds 40 mass %, the efficiency of flotation decreases.

[0017] This flotation separates the silver into float ore, which is concentrated in silver, and tailings, which contains a lot of lead, and the float ore is then recovered. The recovered float ore is dewatered to produce silver concentrate, which can be repeatedly fed into the roasting furnace or roasting furnace of a precious metal smelter to recover the silver.

[0018] Without flotation, all of the silver contained in the slag would be lost, but by returning the float to the precious metal refining process, the silver contained in the float is recovered, and only the small amount of silver contained in the tailings is lost, which can dramatically improve the overall silver yield of the precious metal refining process. Effect of the Invention

[0019] The method of the present invention can recover high-grade silver by roughly crushing the slag, grinding it, and flotation it to recover the float, thereby increasing the silver yield. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] [Example] Examples of the present invention are shown together with comparative examples. Metal concentrations in the liquid and slag were measured by ICP-OES and XRF. The composition of the slag used is shown in Table 1.

[0021] [Table 1]

[0022] The raw slag was roughly crushed and then ground. 2 kg of raw material and 1 kg of water were placed in an 8 L ball mill, and the balls with a diameter of 35 mm were loaded at a loading rate of approximately 30% and a critical rotation speed of 70%, and the milling was performed at the D shown in Tables 2 and 3. 80 The ore was ground to a concentration of 100%. The slurry concentration during grinding is shown in Table 2. The ground slurry was removed and fed to a flotation machine, where a collector and a foaming agent (MIBC, added at 50g / t) were added and the pH was adjusted to perform flotation. The amount of collector added, the pH during flotation, and the slurry concentration during flotation are shown in Tables 2 and 3. The float produced by flotation and the remaining tailings were collected, dewatered, dried and weighed, and the metal components were measured. The results are shown in Tables 2 and 3.

[0023] As shown in Tables 2 and 3, the floats of Tests No. 1 to 11, which were subjected to grinding and flotation, had a higher silver content than Slag 1. Similarly, the floats of Tests No. 12 and 13 had a higher silver content than Slag 2. The floats obtained here can be returned to the roasting process or the roasting and sintering process to recover silver. In contrast to Slag 1 and Slag 2, which are not subjected to flotation, all of the silver contained therein is lost, whereas in Samples No. 1 to 13, the floats can be returned to the precious metal smelting process, and only the trace amounts of silver contained in the tailings are lost. This makes it possible to dramatically improve the overall silver yield of precious metal smelting.

[0024] In addition, slag 1 is used as the raw material, 80 Regarding the tests (Nos. 1 to 3 and 5 to 10) in which the particle size was 80 μm or less, in tests Nos. 1 to 3 using PAX, the silver migration rate in the float ore was 75% or more and the silver concentration in the tailings was 0.9% by mass or less, while in tests Nos. 5 to 10 using MCB4, the silver migration rate in the float ore was 56% or more and the silver concentration in the tailings was 1.8% by mass or less, indicating a high silver recovery rate. In addition, slag 1 is used as the raw material, MCB 4 is used, and D 80In Tests No. 5 to 10, in which the particle size was 80 μm or less, the silver migration rate of the float in Tests No. 8 and No. 9, which have a pH outside the range of 4 to 8, is lower than the lowest value of 66% among Tests No. 5 to 7 and No. 10, which are in the pH range of 4 to 8, and the silver concentration in the tailings is also higher than the highest value of 1.4% among Tests No. 5 to 7 and No. 10. Therefore, when using MCB4, it is preferable to adjust the pH to 4 to 8.

[0025] [Table 2]

[0026] [Table 3]

Claims

1. A method for recovering silver, comprising roughly crushing precious metal-containing slag, forming the roughly crushed slag into a slurry and grinding the slurry, and flotation-separating the ground slurry in the presence of a collector and a foaming agent to recover float, the method being characterized in that a mercaptobenzothiazole-based compound is used as a collector, and floatation is performed at pH 4 to 8 to recover float in which silver is concentrated.

2. In a method for recovering float ore, the method comprises the steps of roughly crushing precious metal-containing slag, forming the roughly crushed slag into a slurry, grinding the slurry, and flotation-separating the ground slurry in the presence of a collector and a foaming agent, and recovering float ore by collecting a float ore having a cumulative 80% particle diameter (D ８０ a slurry concentration during grinding of the ore is set to 50-80% by mass, a slurry concentration during flotation of the ore is set to 30-40% by mass, when 2-mercaptobenzothiazole sodium salt (MCB4) is used as a collector, it is added before the start of grinding, when potassium amyl xanthogenate (PAX) is used as a collector, it is adjusted to a pH of 11 or less and added before the start of flotation after grinding, and flotation is carried out within one hour after grinding to recover a float in which silver is concentrated.

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