Method for recovering lead, zinc and cadmium from ammonia-process zinc smelting purification slag

Abstract

The invention relates to a method for recovering lead, zinc and cadmium from ammonia-process zinc smelting purification slag, which comprises the following steps: carrying out first ball milling on the ammonia-process zinc smelting purification slag, returning the obtained refined purification slag to carry out purification treatment on ammonia-process zinc smelting leachate, and separating to obtain secondary purification slag; and the secondary purification residues are sequentially subjected to second ball milling and leaching treatment, obtained leaching liquid is subjected to cadmium replacement treatment and separation to obtain replaced liquid, the replaced liquid is returned to the leaching treatment until the zinc content is larger than 100 g / L, then evaporation concentration and cooling crystallization are sequentially conducted, and separation is conducted to obtain a crystal product containing zinc sulfate heptahydrate. According to the method provided by the invention, the purification slag containing lead, cadmium and zinc can be comprehensively recycled, metal zinc in the purification slag is returned to an ammonia-process zinc smelting system for secondary purification, the use amount of an auxiliary material zinc powder can be reduced, part of zinc in the obtained purification liquid is recycled to a zinc main system for producing zinc ingots, and the production cost is reduced. And meanwhile, sponge lead, sponge cadmium, zinc sulfate heptahydrate and other products are obtained, and remarkable economic benefits are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of hydrometallurgical zinc smelting, and in particular to a method for recovering lead, zinc and cadmium from purified slag produced during zinc smelting by ammonia process. Background Art

[0002] Ammonia zinc smelting is an important zinc smelting method with the advantages of wide raw material adaptability, short process flow, simple purification process, low energy consumption and high zinc recovery rate. It plays an important role in promoting the development of hydrometallurgical zinc smelting.

[0003] In the ammonia zinc smelting process, it is usually necessary to use zinc slag to put it into a spiral purifier for preliminary purification of the leachate. The zinc slag replaces impurities such as lead and cadmium in the leachate into the slag. During the purification process, as the replacement reaction proceeds, impurities such as lead and cadmium will wrap around the zinc slag, so that the wrapped zinc cannot play a purification role, resulting in purified slag with high content of lead, zinc and cadmium. At this time, the purified slag generally contains 10-20% zinc and 5-10% cadmium. In the existing production process, the purified slag is mainly processed by direct sale, without separating and recovering zinc and cadmium. Even if it is recovered, the problem of low zinc recovery rate will occur, and the zinc and cadmium in the purified slag are not included in the pricing when it is sold, which will not only lead to economic losses, but also lead to waste of zinc and cadmium resources.

[0004] CN114540639A discloses a method for removing impurities from ammonia zinc smelting leachate, comprising the following steps: heating the leachate, adding activated carbon, stirring and filtering to obtain a filtrate; adding a mixture of zinc powder, graphite powder and activated carbon to the filtrate, stirring until the reaction is completed, separating the solid and the liquid, and collecting the filtrate and the filtrate, respectively, wherein the mass ratio of zinc powder, graphite powder and activated carbon is (4.5-5.5):(3.5-4.2):1. Although this method can reduce the amount of zinc powder used by adding graphite powder and activated carbon, it cannot fundamentally solve the problem of recycling the purified slag, and the cost of the additional reagent is high.

[0005] Therefore, how to realize the resource recovery and utilization of lead, cadmium and zinc-containing purification slag is a technical problem that needs to be solved in this field. Summary of the invention

[0006] In view of the above problems, the purpose of the present invention is to provide a method for recovering lead, zinc and cadmium from purified slag of ammonia zinc smelting. Compared with the prior art, the method provided by the present invention can comprehensively recycle the purified slag containing lead, cadmium and zinc, and the metallic zinc in the purified slag is returned to the ammonia zinc smelting system for secondary purification, which can reduce the amount of auxiliary material zinc powder, and the obtained purified liquid recovers part of the zinc to the zinc main system to produce zinc ingots. At the same time, products such as sponge lead, sponge cadmium and zinc sulfate heptahydrate are obtained, which has significant economic benefits.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for recovering lead, zinc and cadmium from ammonia zinc smelting purification slag, the method comprising the following steps:

[0009] (1) subjecting the purified slag from zinc smelting by ammonia process to a first ball milling to obtain refined purified slag; returning the refined purified slag to the purification treatment of the leaching solution from zinc smelting by ammonia process to separate and obtain secondary purified slag;

[0010] (2) subjecting the secondary purification slag obtained in step (1) to a second ball milling and a leaching treatment in sequence to separate the sponge lead and the leachate;

[0011] (3) subjecting the leaching solution obtained in step (2) to cadmium replacement treatment to separate the sponge cadmium and the replacement solution, and returning the replacement solution to the leaching treatment in step (2) until the zinc content of the replacement solution is greater than 100 g / L;

[0012] (4) The replaced liquid obtained in step (3) is sequentially subjected to evaporation concentration and cooling crystallization to separate and obtain a crystalline product containing zinc sulfate heptahydrate.

[0013] The present invention is directed to treating the purified slag of zinc smelting by ammonia process containing lead, zinc and cadmium. First, the purified slag of zinc smelting by ammonia process is ground by a first ball mill to reuse the metal zinc contained therein, and the refined purified slag is returned to the purification process of zinc smelting by ammonia process for purification of the leaching solution of zinc smelting by ammonia process, which not only improves the utilization rate of the purified slag, but also reduces the cost of the purification process of zinc smelting by ammonia process, and the obtained purified solution is sent to the subsequent purification process; then, the secondary purified slag is subjected to a second ball mill, and after ball milling, leaching treatment is performed to leach the zinc and cadmium contained therein into the leaching solution, and the lead therein is separated to obtain sponge lead; then, the leaching solution is subjected to cadmium replacement treatment to separate the sponge cadmium and the replaced liquid; finally, the replaced liquid with a zinc content reaching a certain concentration is evaporated, concentrated and cooled for crystallization to obtain a feed-grade zinc sulfate heptahydrate product. The present invention proposes a method for recycling and utilizing purified slag of zinc smelting by ammonia process, successfully overcomes the defect that the purified slag is difficult to utilize in the existing process, improves the utilization rate of the purified slag and the recovery rate of zinc, and has significant economic benefits.

[0014] In the present invention, the separation may be any method suitable for separating solid residue and solution in the art, such as filtration.

[0015] In the present invention, the zinc content of the replaced liquid is greater than 100 g / L, for example, it may be 110 g / L, 120 g / L or 130 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0016] Preferably, the purified slag from zinc smelting by ammonia process in step (1) contains, by mass percentage, 65-75% of lead, for example, 65%, 68%, 70%, 72%, 74% or 75%, but not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable; 10-20% of zinc, for example, 10%, 12%, 14%, 16%, 18% or 20%, but not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable; 5-10% of cadmium, for example, 5%, 6%, 7%, 8%, 9% or 10%, but not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable.

[0017] Preferably, the particle size of the refined and purified slag after the first ball milling in step (1) is ≤0.85 mm, for example, it can be 0.85 mm, 0.84 mm, 0.83 mm, 0.82 mm, 0.81 mm or 0.80 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0018] Preferably, the first ball milling time is 10-15 min, for example, 10 min, 11 min, 12 min, 13 min, 14 min or 15 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] Preferably, in the purification treatment of step (1), the refined purified slag is added at 1.5-2.5 times the theoretical amount, for example, it can be 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, 2 times, 2.1 times, 2.2 times, 2.3 times, 2.4 times or 2.5 times, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] In the present invention, the theoretical amount of the refined purified slag refers to the amount of refined purified slag required to completely replace the lead and cadmium in the ammonia zinc smelting leaching solution with zinc in the refined purified slag.

[0021] Preferably, the temperature of the purification treatment is 55-65°C, for example, it can be 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C or 65°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] Preferably, the purification treatment time is 10-15 minutes, for example, it can be 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes or 15 minutes, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] Preferably, in step (2), the particle size after the second ball milling is ≤0.85 mm, for example, it can be 0.85 mm, 0.80 mm or 0.75 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0024] Preferably, the leaching agent used in the leaching treatment in step (2) includes acid solution.

[0025] Preferably, the acid solution comprises sulfuric acid.

[0026] In the present invention, the leaching treatment is generally performed by first mixing the ball-milled secondary purification slag and water at a liquid-solid ratio of (3-4):1, and then adding sulfuric acid (generally concentrated sulfuric acid with a concentration of ≥98% (analytical grade)) to adjust to the target pH value for leaching.

[0027] Preferably, the liquid-to-solid ratio of the secondary purified slag and water after ball milling is (3-4):1, for example, it can be 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1 or 4:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] Preferably, the pH value of the leaching treatment is 1-2, for example, 1, 1.2, 1.4, 1.6, 1.8 or 2, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] Preferably, the temperature of the leaching treatment is 75-85°C, for example, it can be 75°C, 76°C, 78°C, 80°C, 82°C, 84°C or 85°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] Preferably, the leaching treatment time is 60-90 min, for example, it can be 60 min, 65 min, 70 min, 75 min, 80 min, 85 min or 90 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Preferably, the replacement agent used in the cadmium replacement treatment in step (3) includes zinc powder.

[0032] Preferably, in the cadmium replacement treatment, zinc powder is added at 1-1.2 times of the theoretical amount, for example, 1 times, 1.1 times or 1.2 times, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] In the present invention, the theoretical amount of zinc powder refers to the amount of zinc powder required to completely replace the cadmium in the leaching solution with zinc in the zinc powder.

[0034] Preferably, the temperature of the cadmium replacement treatment is 60-65°C, for example, 60°C, 61°C, 62°C, 63°C, 64°C or 65°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] Preferably, the cadmium replacement treatment time is 15-20 min, for example, 15 min, 16 min, 17 min, 18 min, 19 min or 20 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] Preferably, the temperature of the evaporation concentration in step (4) is 85-95°C, for example, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C or 95°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, after the separation in step (4), a crystallization mother liquor is also obtained.

[0038] Preferably, the crystallization mother liquor is returned to the evaporation concentration in step (4).

[0039] Preferably, the method comprises the following steps:

[0040] (1) subjecting the purified slag from zinc smelting by ammonia process to a first ball milling to a particle size of ≤0.85 mm to obtain refined purified slag, and returning the refined purified slag to the purification treatment of the leaching solution from zinc smelting by ammonia process, wherein the refined purified slag is added at 1.5-2.5 times of the theoretical amount, the purification treatment temperature is 55-65° C., the purification treatment time is 10-15 min, and then the secondary purified slag is separated;

[0041] (2) subjecting the secondary purification slag obtained in step (1) to a second ball milling to a diameter of ≤0.85 mm, and then subjecting the slag to a leaching treatment for 60-90 min at a pH of 1-2 and a temperature of 75-85° C. using sulfuric acid as a leaching agent, to separation to obtain sponge lead and a leachate;

[0042] (3) using zinc powder to perform cadmium replacement treatment on the leaching solution obtained in step (2) at a temperature of 60-65° C. for 15-20 min, wherein the zinc powder is added at 1-1.2 times the theoretical amount, and sponge cadmium and replacement liquid are separated, and the replacement liquid is returned to the leaching treatment in step (2) until the zinc content of the replacement liquid is greater than 100 g / L;

[0043] (4) The replaced liquid obtained in step (3) is evaporated and concentrated at a temperature of 85-95° C., and then cooled and crystallized to obtain a crystalline product containing zinc sulfate heptahydrate and a crystallization mother liquor, and the crystallization mother liquor is returned to the evaporation and concentration.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) The method provided by the present invention aims at solving the problem that the purified slag from ammonia zinc smelting cannot be fully recycled. The method can separate zinc, lead and cadmium from the purified slag and produce sponge lead, sponge cadmium and zinc sulfate heptahydrate products with added value, thereby improving the utilization rate of the purified slag and the recovery rate of zinc.

[0046] (2) The method provided by the present invention can effectively separate valuable metals such as lead, zinc, and cadmium from the purified slag, so that the valuable metals have an open circuit. Compared with the purified slag that cannot be recycled, the recovery rate of cadmium can be increased from 0% to more than 80.70%, the recovery rate of zinc can be increased from 0% to more than 87.15%, and the lead grade in the purified slag can be increased from 65-75% to more than 90.57%.

[0047] (3) In the method provided by the present invention, the refined purified slag is returned to the purification treatment of the ammonia zinc smelting leaching solution, thereby reducing the purification cost of the ammonia zinc smelting leaching solution and reducing the zinc powder consumption per ton of zinc ingot from 35-40 kg / ton to 30-35 kg / ton. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a schematic diagram of the process of the method described in Example 1 of the present invention. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0050] Example 1

[0051] This embodiment provides a method for recovering lead, zinc and cadmium from ammonia zinc smelting purification slag, such as Figure 1 As shown, the method comprises the following steps:

[0052] (1) Ammonia zinc smelting purified slag containing 72.66% lead, 12.55% zinc and 6.4% cadmium by mass percentage was subjected to a first ball milling for 15 minutes until the passing rate of a 20-mesh test sieve was 100%, thereby obtaining refined purified slag, and the refined purified slag was returned to the purification treatment of ammonia zinc smelting leaching solution. The purification treatment conditions and the composition of the ammonia zinc smelting leaching solution are shown in Table 1. Numbers 1, 2 and 3 in Table 1 respectively represent samples of ammonia zinc smelting leaching solution with different volumes;

[0053] Then, secondary purification slag and purified liquid are obtained by separation, and the purified liquid is sent to the next purification process; the parameters of the obtained purified liquid and secondary purification slag, as well as the purification rate of lead and the purification rate of cadmium in the ammonia zinc smelting leaching solution are shown in Table 2, purification rate = [1-(mass of target element in the purified liquid / mass of target element in the ammonia zinc smelting leaching solution)] × 100%.

[0054] Table 1

[0055]

[0056] Table 2

[0057]

[0058] It can be seen from the data in Tables 1 and 2 that the purification rate of lead in the ammonia zinc smelting leaching solution by the refined purification slag in the present invention can still reach more than 69.05%, and the purification rate of cadmium can reach more than 72.58%, and the enrichment rate of lead in the obtained secondary purification slag can reach more than 77.92%.

[0059] (2) Taking the method numbered 2 in step (1) as an example, multiple operations are performed to make the output of the secondary purification slag reach the dosage requirement for leaching treatment, wherein the secondary purification slag contains 81.25% lead, 5.91% zinc, and 7.00% cadmium, and then a second ball milling is performed to ≤0.85 mm, and then water is added at a liquid-to-solid ratio of 3:1, and then concentrated sulfuric acid is added to control the pH value for leaching treatment. The conditions of the leaching treatment are shown in Table 3, and numbers 1, 2, and 3 in Table 3 respectively represent samples of secondary purification slag of different masses;

[0060] Then, sponge lead and leachate are separated and the sponge lead is sold. The parameters of the obtained leachate and sponge lead, as well as the leaching rate of zinc, the leaching rate of cadmium and the recovery rate of lead are shown in Table 4, where "%" represents the mass percentage. Leaching rate = (mass of target element in secondary purification slag - mass of target element in sponge lead) / mass of target element in secondary purification slag × 100%, and lead recovery rate = mass of lead in sponge lead / mass of lead in ammonia zinc smelting purification slag × 100%.

[0061] Table 3

[0062]

[0063] Table 4

[0064]

[0065] It can be seen from the data in Tables 3 and 4 that the leaching treatment step in the present invention can make the zinc leaching rate reach more than 83.56%, the cadmium leaching rate reach more than 80.67%, and lead is almost not leached. The lead content of the sponge lead is greater than 90.57%, the zinc content is less than 1.32%, and the cadmium content is less than 1.45%. The sponge lead can recover more than 99.89% of the lead in the ammonia zinc smelting purification slag.

[0066] (3) Taking the method No. 2 in step (2) as an example, the obtained leaching solution containing 0.01 g / L lead, 21.67 g / L zinc, and 18.24 g / L cadmium is subjected to cadmium replacement treatment using zinc powder. The treatment conditions are shown in Table 5. Numbers 1, 2, and 3 in Table 5 represent leaching solution samples of different volumes, respectively;

[0067] Then, the sponge cadmium and the replaced liquid are separated, and the sponge cadmium is used for external sale. The parameters of the replaced liquid (without cyclic leaching) and the sponge cadmium, as well as the cadmium replacement rate, cadmium recovery rate and zinc recovery rate are shown in Table 6, where "%" represents the mass percentage content. The cadmium replacement rate = (the mass of cadmium in the leaching solution - the mass of cadmium in the replaced liquid) / the mass of cadmium in the leaching solution × 100%, the cadmium recovery rate = the mass of cadmium in the sponge cadmium / the mass of cadmium in the ammonia zinc smelting purification slag × 100%, and the zinc recovery rate = (the mass of zinc in the ammonia zinc smelting purification slag - the mass of zinc in the sponge lead - the mass of zinc in the sponge cadmium) / the mass of zinc in the ammonia zinc smelting purification slag × 100%.

[0068] Table 5

[0069]

[0070] Table 6

[0071]

[0072] It can be seen from the data in Tables 5 and 6 that the cadmium replacement treatment step in the present invention can make the cadmium replacement rate in the leaching solution reach more than 87.17%, the cadmium content of the sponge cadmium reach more than 82.03%, the zinc content reach less than 6.34%, and the lead content reach less than 0.13%. The present invention can recover more than 80.70% of the cadmium in the ammonia zinc smelting purification slag and more than 87.15% of the zinc in the ammonia zinc smelting purification slag.

[0073] Taking the replaced liquid obtained by number 2 in step (3) as an example, it is returned to the leaching treatment method represented by number 2 in step (2), and the leaching treatment and cadmium replacement treatment are repeated until the replaced liquid contains 0.014 g / L lead, 104.61 g / L zinc, and 2.98 g / L cadmium.

[0074] (4) The replaced liquid containing 0.014 g / L lead, 104.61 g / L zinc, and 2.98 g / L cadmium was evaporated and concentrated under the conditions shown in Table 7. Numbers 1 and 2 in Table 7 represent samples of replaced liquid with different volumes, respectively;

[0075] Then, cooling and crystallization are performed to separate and obtain a crystalline product containing zinc sulfate heptahydrate and a crystalline mother liquor. The crystalline mother liquor is returned to the evaporation and concentration. The parameters of the obtained crystalline product and the crystalline mother liquor are shown in Table 8.

[0076] Table 7

[0077]

[0078] Table 8

[0079]

[0080] It can be seen from the data in Tables 7-8 that the content of zinc sulfate heptahydrate in the crystalline product obtained in the present invention reaches more than 98.1%, the zinc content reaches more than 22.31%, the arsenic content reaches less than 0.0013%, the lead content reaches less than 0.0035%, the cadmium content reaches less than 0.65%, and the pass rate of 800 μm test sieve reaches more than 97.36%, which meets the standard of feed-grade additive zinc sulfate heptahydrate (GB / T 25865-2010).

[0081] Based on the data in Tables 1-8, the present invention can fully separate and recover the lead in the ammonia zinc smelting purification slag with a lead content of 72.66%, purify it into sponge lead with a lead content of more than 90.57%, the cadmium grade of sponge cadmium reaches more than 82.03%, and the grade of zinc sulfate heptahydrate crystalline product reaches more than 98.1%, which meets the standard of feed-grade additive zinc sulfate heptahydrate (GB / T 25865-2010), the lead recovery rate reaches more than 99.89%, the cadmium recovery rate reaches more than 80.70%, and the zinc recovery rate reaches more than 87.15%.

[0082] Example 2

[0083] This embodiment provides a method for recovering lead, zinc and cadmium from ammonia zinc smelting purification slag, which is different from the method used in sample No. 2 in Table 1 of Example 1 only in that the purification treatment temperature is 50°C.

[0084] Example 3

[0085] This embodiment provides a method for recovering lead, zinc and cadmium from ammonia zinc smelting purification slag, which is different from the method used in sample No. 2 in Table 1 of Example 1 only in that the purification treatment temperature is 80°C.

[0086] For the same sample, the only difference between Example 2-3 and Example 1 is that the temperature of the purification treatment is not within the preferred range of the present invention. In Example 1, the purification rate of lead can reach 69.90%, and the purification rate of cadmium can reach 79.17%, while in Example 2, the purification rate of lead can only reach 62.14%, and the purification rate of cadmium can only reach 64.07%. In Example 3, the purification rate of lead can only reach 64.58%, and the purification rate of cadmium can only reach 66.71%. It can be seen that the present invention can further improve the purification effect of the ammonia zinc smelting leachate by preferably setting the temperature of the purification treatment.

[0087] Example 4

[0088] This embodiment provides a method for recovering lead, zinc and cadmium from ammonia zinc smelting purification slag, which is different from the method used in sample No. 2 in Table 3 of Example 1 only in that the pH value of the leaching treatment is 3.

[0089] For the same sample, the only difference between Example 4 and Example 1 is that the pH value of the leaching treatment is not within the preferred range of the present invention. In Example 1, the leaching rate of zinc can reach 86.43%, and the leaching rate of cadmium can reach 81.53%, while in Example 4, the leaching rate of zinc can only reach 83.33%, and the leaching rate of cadmium can only reach 78.59%. It can be seen that the present invention can further improve the leaching effect of the secondary purification slag by preferably setting the pH value of the leaching treatment.

[0090] Example 5

[0091] This embodiment provides a method for recovering lead, zinc and cadmium from ammonia zinc smelting purification slag, which is different from the method used in sample No. 2 in Table 5 of Example 1 only in that the temperature of the cadmium replacement treatment is 50°C.

[0092] Example 6

[0093] This embodiment provides a method for recovering lead, zinc and cadmium from ammonia zinc smelting purification slag, which is different from the method used in sample No. 2 in Table 5 of Example 1 only in that the temperature of the cadmium replacement treatment is 75°C.

[0094] For the same sample, the only difference between Examples 5-6 and Example 1 is that the temperature of the cadmium replacement treatment is not within the preferred range of the present invention. The cadmium replacement rate in Example 1 can reach 87.35%, while the cadmium replacement rate in Example 5 can only reach 84.78%, and the cadmium replacement rate in Example 6 can only reach 85.44%. It can be seen that the present invention can further improve the replacement effect of cadmium in the leachate by preferably setting the temperature of the cadmium replacement treatment.

[0095] In summary, the method provided by the present invention can comprehensively recycle the purification slag containing lead, cadmium and zinc to obtain products such as sponge lead, sponge cadmium and zinc sulfate heptahydrate, and has significant economic benefits.

[0096] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for recovering lead, zinc and cadmium from purified slag from ammonia zinc smelting, characterized in that: The method comprises the following steps: (1) subjecting the purified slag from zinc smelting by ammonia process to a first ball milling to obtain refined purified slag; returning the refined purified slag to the purification treatment of the leaching solution from zinc smelting by ammonia process to separate and obtain secondary purified slag; (2) subjecting the secondary purification slag obtained in step (1) to a second ball milling and a leaching treatment in sequence to separate the sponge lead and the leachate; (3) subjecting the leaching solution obtained in step (2) to cadmium replacement treatment to separate the sponge cadmium and the replacement solution, and returning the replacement solution to the leaching treatment in step (2) until the zinc content of the replacement solution is greater than 100 g / L; (4) The replaced liquid obtained in step (3) is sequentially subjected to evaporation concentration and cooling crystallization to separate and obtain a crystalline product containing zinc sulfate heptahydrate.

2. The method according to claim 1, characterized in that The purified slag from zinc smelting by ammonia process in step (1) contains 65-75% lead, 10-20% zinc and 5-10% cadmium by mass percentage.

3. The method according to claim 1 or 2, characterized in that: Step (1) the particle size of the refined and purified slag after the first ball milling is ≤0.85 mm; Preferably, the first ball milling time is 10-15 min.

4. The method according to any one of claims 1 to 3, characterized in that: In the purification treatment of step (1), the refined purified slag is added at 1.5-2.5 times the theoretical amount; Preferably, the temperature of the purification treatment is 55-65°C; Preferably, the purification treatment takes 10-15 minutes.

5. The method according to any one of claims 1 to 4, characterized in that: Step (2) The particle size after the second ball milling is ≤0.85 mm.

6. The method according to any one of claims 1 to 5, characterized in that: The leaching agent used in the leaching treatment in step (2) includes acid solution; Preferably, the acid solution comprises sulfuric acid; Preferably, the pH value of the leaching treatment is 1-2; Preferably, the temperature of the leaching treatment is 75-85°C; Preferably, the leaching treatment time is 60-90 minutes.

7. The method according to any one of claims 1 to 6, characterized in that: The replacement agent used in the cadmium replacement treatment in step (3) includes zinc powder; Preferably, in the cadmium replacement treatment, zinc powder is added at 1-1.2 times the theoretical amount; Preferably, the temperature of the cadmium replacement treatment is 60-65°C; Preferably, the cadmium replacement treatment lasts for 15-20 minutes.

8. The method according to any one of claims 1 to 7, characterized in that: The temperature of the evaporation concentration in step (4) is 85-95°C.

9. The method according to any one of claims 1 to 8, characterized in that: After the separation in step (4), a crystallization mother liquor is obtained; Preferably, the crystallization mother liquor is returned to the evaporation concentration in step (4).

10. The method according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: (1) subjecting the purified slag from zinc smelting by ammonia process to a first ball milling to a particle size of ≤0.85 mm to obtain refined purified slag, and returning the refined purified slag to the purification treatment of the leaching solution from zinc smelting by ammonia process, wherein the refined purified slag is added at 1.5-2.5 times of the theoretical amount, the purification treatment temperature is 55-65° C., the purification treatment time is 10-15 min, and then the secondary purified slag is separated; (2) subjecting the secondary purification slag obtained in step (1) to a second ball milling to a diameter of ≤0.85 mm, and then subjecting the slag to a leaching treatment for 60-90 min at a pH of 1-2 and a temperature of 75-85° C. using sulfuric acid as a leaching agent, to separation to obtain sponge lead and a leachate; (3) using zinc powder to perform cadmium replacement treatment on the leaching solution obtained in step (2) at a temperature of 60-65° C. for 15-20 min, wherein the zinc powder is added at 1-1.2 times the theoretical amount, and sponge cadmium and replacement liquid are separated, and the replacement liquid is returned to the leaching treatment in step (2) until the zinc content of the replacement liquid is greater than 100 g / L; (4) The replaced liquid obtained in step (3) is evaporated and concentrated at a temperature of 85-95° C., and then cooled and crystallized to obtain a crystalline product containing zinc sulfate heptahydrate and a crystallization mother liquor, and the crystallization mother liquor is returned to the evaporation and concentration.

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