Method for producing food-grade zinc sulfate by using zinc hypoxide
Through the full wet process of zinc suboxide and classic chemical purification process, the problem of high production cost of food-grade zinc sulfate is solved, efficient recycling and resource application of zinc is achieved, production costs are reduced and environmental benefits are improved.
Patent Information
- Application Number
- CN202411211180.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2024-12-13
AI Technical Summary
The existing food-grade zinc sulfate production process is costly and lacks low-cost and highly operable process methods.
Using zinc oxide as raw material, deep separation of zinc and zinc sulfate production through leaching, silver salt dechlorination and silver sulfate regeneration, co-precipitation to remove heavy metal impurities, replacement removal of copper and cadmium, concentration and crystallization, etc., can achieve deep separation of zinc and zinc sulfate production, and use full humidity process and classic chemical purification process.
It realizes efficient recycling and resource application of zinc, reduces production costs, improves economic and environmental benefits, and has feasible processes and strong operability.
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Figure CN119118189A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of safe disposal of solid waste and resource recycling in the nonferrous metal smelting industry, and in particular to a method for producing food-grade zinc sulfate by using zinc suboxide. Background Art
[0002] The production of food-grade zinc sulfate generally uses roasted zinc oxide as raw material, and produces qualified products through a series of processes including sulfuric acid leaching, leaching solution purification, purification solution concentration, and crystallization. However, the production cost of this process is relatively high. Summary of the invention
[0003] The technical problem to be solved by the present invention is to provide a method for producing food-grade zinc sulfate by using zinc suboxide, which has feasible process, strong operability and low cost.
[0004] In order to solve the above problems, the present invention discloses a method for producing food-grade zinc sulfate using zinc suboxide, comprising the following steps: ⑴ Leaching: In a leaching tank filled with pure water, zinc hypochlorite and sulfuric acid with a volume concentration of 93% are added in sequence for leaching. After the leaching is completed, vacuum filtration is performed using a short-fiber polyester filter cloth with a filtration accuracy of <5 μm to obtain a clear and transparent crude zinc sulfate solution and leaching residue, respectively; the volume mass ratio of the pure water to the zinc hypochlorite is L / S=2.5-3:1; the amount of sulfuric acid added is 350-450 mL / kg zinc hypochlorite; the leaching residue is sold to a lead smelting enterprise as a raw material for pyrometallurgical lead smelting; ⑵Silver salt dechlorination and silver sulfate regeneration: The crude zinc sulfate solution is added to the dechlorination reaction tank, stirring is started, reagent-grade silver sulfate is added at once according to 1.0-1.05 times of the theoretical silver consumption of the total amount of chloride ions in the solution, the stirring reaction time is 30 minutes, the reaction temperature is 15-25° C., and the mixture is filtered and washed with pure water until neutral, to obtain a silver chloride precipitate and a dechlorinated liquid respectively; the silver chloride precipitate is first reacted with zinc powder in the presence of sulfuric acid to obtain sponge silver; the sponge silver is dissolved with nitric acid, and the sulfuric acid is converted to obtain regenerated silver sulfate, and the regenerated silver sulfate enters the dechlorination reaction tank to carry out a silver salt dechlorination cycle reaction; ⑶Co-precipitation to remove heavy metal impurities: Start stirring at 180 r / min, heat the dechlorinated liquid of the filtrate to 80±5°C, add 25 mL of a 30% H2O2 solution per liter of the dechlorinated liquid, and then add 14 g of a reagent-grade neutralizing agent, basic zinc carbonate, per liter of the dechlorinated liquid, and react for 4 hours. The reaction end point pH is 5.4-5.6. After liquid-solid separation, the insoluble hydroxide precipitate and the precipitated liquid are obtained respectively; ⑷Replacement and removal of copper, cadmium and lead: The precipitated liquid is added into a zinc powder displacement stirring tank, and then 0.5 mol / L dilute sulfuric acid is added to adjust the pH to 5, and then 30-35 g of zinc powder with 80% effective zinc is slowly added per 10 L of the precipitated liquid to carry out a displacement reaction, and a high-purity zinc sulfate solution with a pH of ≈ 6 and a byproduct copper-cadmium slag are obtained through liquid-solid separation; the copper-cadmium slag is sold to a copper smelting enterprise for recycling; ⑸ Concentrated crystallization to produce food grade zinc sulfate: The high-purity zinc sulfate solution is adjusted to pH=5.5 by sulfuric acid, and then concentrated by vacuum evaporation to obtain a concentrated solution and a condensate; the concentrated solution is cooled, crystallized, liquid-solid separated, and dried to obtain the terminal product food-grade zinc sulfate; the condensate is returned to step (1); and the filtrate is returned to step (3).
[0005] The resistivity of pure water at 25° C. in step (1) is 18 MΩ·cm.
[0006] The leaching conditions in step (1) are that the heating temperature is 80-90° C., the stirring speed is 180 r / min, and the leaching time is 2 h.
[0007] The regenerated silver sulfate in step (2) is prepared as follows: ① The silver chloride precipitate was uniformly mixed with 100-mesh pure zinc powder of 1.1 times the theoretical consumption, and then a 10 g / L dilute sulfuric acid solution was added at a liquid-solid volume mass ratio of L / S=20:1, and the reaction time was stirred at 10-15°C for 40 min, and the sponge silver was obtained by filtration; ② For every 100g of sponge silver, add 125mL of analytical pure nitric acid, control the liquid-to-solid ratio L / S=3, temperature 20℃±5℃, time 30min process conditions to dissolve the sponge silver; after the dissolution is completed, add 28~30mL of analytical pure sulfuric acid, the silver sulfate precipitation time is 10min, filter to obtain regenerated silver sulfate, and the obtained conversion liquid is used for the next dissolution of sponge silver.
[0008] The conditions for the replacement reaction in step (4) are a reaction temperature of 60-70° C. and a reaction time of 60 min.
[0009] The multiple of evaporation concentration in step (5) is 2.5 to 3 times, and the cooling crystallization conditions refer to a temperature of 15 to 20° C. and a time of 1 to 2 hours.
[0010] Compared with the prior art, the present invention has the following advantages: 1. The present invention directly utilizes the solid hazardous waste zinc oxide produced by non-ferrous enterprises as raw material, adopts a full wet process, and leaches zinc and other elements therein into a solution at one time. Through a classical chemical purification process, the harmful elements and zinc are deeply separated, and a food-grade zinc sulfate product that meets the quality requirements is prepared, thereby achieving the reduction and resource application of solid waste, which not only saves production costs, but also has high economic benefits and obvious environmental benefits.
[0011] 2. The process of the present invention is feasible, operable and has a high metal recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.
[0013] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION
[0014] like Figure 1 As shown, a method for producing food-grade zinc sulfate using zinc oxide comprises the following steps: ⑴ Leaching: In the leaching tank filled with pure water, zinc hypochlorite and sulfuric acid with a volume concentration of 93% are added in sequence for leaching, the heating temperature is 80~90℃, the stirring speed is 180r / min, and the leaching time is 2h. After the leaching is completed, vacuum filtration is performed with a short-fiber polyester filter cloth with a filtration accuracy of <5μm to obtain a clear and transparent crude zinc sulfate solution and leached residue, respectively.
[0015] The resistivity of pure water at 25°C is 18 MΩ·cm, and the volume mass ratio of pure water to zinc chloride (L / kg) L / S = 2.5~3:1; the amount of sulfuric acid added is 350~450mL / kg zinc chloride; the leached slag is sold to lead smelting enterprises as a raw material for pyrometallurgical lead smelting.
[0016] ⑵Silver salt dechlorination and silver sulfate regeneration: Add the crude zinc sulfate solution into the dechlorination reaction tank, start stirring, add reagent grade silver sulfate at 1.0-1.05 times the theoretical silver consumption of the total amount of chloride ions in the solution, stir for 30 minutes, and the reaction temperature is 15-25°C. Filter and wash with pure water until neutral to obtain silver chloride precipitate and dechlorinated liquid respectively.
[0017] The silver chloride precipitate first reacts with zinc powder in the presence of sulfuric acid to produce sponge silver; the sponge silver is dissolved in nitric acid and converted into sulfuric acid to obtain regenerated silver sulfate, which enters the dechlorination reaction tank for a silver salt dechlorination cycle reaction. The specific process is as follows: ① The silver chloride precipitate was uniformly mixed with 100-mesh pure zinc powder of 1.1 times the theoretical consumption, and then a 10 g / L dilute sulfuric acid solution was added at a liquid-solid volume mass ratio of L / S=20:1, and the reaction time was stirred at 10-15°C for 40 min, and the sponge silver was obtained by filtration; ② For every 100g of sponge silver, add 125mL of analytical pure nitric acid (65%~68%), control the liquid-to-solid ratio L / S=3, temperature 20℃±5℃, and time 30min to dissolve the sponge silver; after the dissolution, add 28~30mL of analytical pure sulfuric acid (95%~98%), the silver sulfate precipitation time is 10min, and the regenerated silver sulfate is obtained by filtration. The obtained conversion liquid is used for the next dissolution of sponge silver to realize closed-loop production.
[0018] ⑶Co-precipitation to remove heavy metal impurities: Start stirring at 180r / min, heat the dechlorinated liquid of the filtrate to 80±5℃, add 25mL of 30% H2O2 solution (about 10 times the theoretical consumption of divalent impurity ions iron, manganese and cobalt in the solution) per liter of dechlorinated liquid, and then add 14g of reagent-grade neutralizing agent basic zinc carbonate per liter of dechlorinated liquid. React for 4h, and the reaction end point pH is 5.4~5.6, so that the heavy metal impurities such as iron, aluminum, copper, manganese, lead, arsenic, antimony, cobalt, nickel, chromium, indium, tin, etc. in the solution are purified in the form of insoluble hydroxide precipitates, and the insoluble hydroxide precipitates and precipitated liquid are obtained after liquid-solid separation.
[0019] ⑷Replacement and removal of copper, cadmium and lead: The precipitated liquid is added to the zinc powder replacement stirring tank, and then 0.5mol / L dilute sulfuric acid is added to adjust the pH to 5, and then 30-35g of zinc powder with 80% effective zinc is slowly added for each 10L of the precipitated liquid for replacement reaction. The reaction temperature is 60-70℃ and the reaction time is 60min, so as to replace the copper, cadmium and lead ions in the solution. After liquid-solid separation, a high-purity zinc sulfate solution with a pH of ≈ 6 and a by-product copper-cadmium slag are obtained respectively; the copper-cadmium slag is sold to copper smelting enterprises for recycling.
[0020] ⑸ Concentrated crystallization to produce food grade zinc sulfate: The high-purity zinc sulfate solution is adjusted to pH=5.5 with sulfuric acid, and then concentrated by vacuum evaporation, with the evaporation concentration multiple being 2.5-3 times, to obtain a concentrated solution and a condensate; the concentrated solution is cooled and crystallized at 15-20° C. for 1-2 hours, and then liquid-solid separation and drying are performed to obtain the terminal product, food-grade zinc sulfate; the condensate is returned to step (1); and the filtrate is returned to step (3).
[0021] The main reaction equation of the present invention is as follows: MeO+H2SO4=MeSO4+H2O Me—Zn, Cu, Cd, Co, Ni, Sn, Mn, Pb, Fe, Cr In2O+H2SO4=In2SO4+H2O Cr2O3+3H2SO4=Cr2(SO4)3+3H2O Al2O3+3H2SO4=Al2(SO4)3+3H2O As2O3+3H2O=2H3AsO3 Sb2O3+3H2O=2H3SbO3 MeCl2+Ag2SO4=2AgCl↓+3MeSO4 2AgCl+Zn=2Ag+ZnCl2 H2SO4+Zn=H2↑+ZnSO4 3Ag+4HNO3=3AgNO3+NO↑+2H2O 2AgNO3+H2SO4=Ag2SO4↓+2HNO3 2FeSO4+H2O2+2H2O+2ZnCO3·3Zn(OH)2=2ZnSO4+3Zn(OH)2↓+2Fe(OH)3↓+2CO2↑ 2H3AsO3+3H2O2+2FeSO4+2ZnCO3·3Zn(OH)2=2FeAsO4↓+3Zn(OH)2↓+2ZnSO4+2CO2↑+6H2O H3SbO3+H3AsO3+H2O2=AsSbO4↓+4H2O Al2(SO4)3+6H2O= 2Al(OH)3↓+3H2SO4 2H3AsO3+2H2O2+Bi2(SO4)3=2BiAsO4↓+3H2SO4+2H2O MeSO4+Zn=ZnSO4+Me Me—Cu, Cd, Co, Ni, Sn, Pb, Fe Example 1 The chemical composition of zinc oxide is shown in Table 1.
[0022] Table 1 Chemical composition of zinc oxide Unit: % ⑴ Low-acid leaching of zinc oxide Pre-fill 25L pure water into a 50L leaching tank, start stirring at 180r / min, slowly add 10kg of accurately weighed zinc oxide, then add 4000mL of 93% sulfuric acid, leaching at 80℃ for 2h, filtering and washing.
[0023] The leaching results are shown in Table 1-1.
[0024] ⑵Silver salt dechlorination Add 30L of leachate into the dechlorination reaction tank, add 255g of reagent-grade silver sulfate, stir the reaction time for 30min, react at 20°C for 40min, filter and wash the silver chloride precipitate.
[0025] The dechlorination test results are shown in Table 1-2.
[0026] ⑶ Co-precipitation to remove heavy metal impurities Heat 25L of dechlorinated liquid to 80±5℃, add 25mL of 30% H2O2 solution (about 10 times the theoretical consumption of impurity ions such as iron, manganese, cobalt, arsenic and antimony in the solution) and 350g of basic zinc carbonate as a neutralizer per liter of dechlorinated liquid, control the temperature at 85℃ to react for 4h, and filter.
[0027] The co-precipitation test results are shown in Tables 1-3.
[0028] ⑷Replacement and removal of copper, cadmium and lead Add 20 L of the precipitated liquid from step (3) into the displacement tank, adjust the pH value to 5 with 0.5 mol / L dilute sulfuric acid, add 65 g of zinc powder with 80% effective zinc, raise the temperature to 70°C and displace for 60 min, and separate the liquid and solid at the displacement endpoint.
[0029] The replacement results are shown in Tables 1-4.
[0030] ⑸Concentrated crystallization to produce food grade zinc sulfate Take 15L of high-purity zinc sulfate solution obtained in step (4) and place it in a 20L 316L stainless steel barrel for evaporation and concentration. Stop concentrating when the slurry volume reaches about 5L; pass cooling water to crystallize for 2h, filter, and dry.
[0031] The results of the concentration crystallization test are shown in Tables 1-5.
[0032] The total recovery rate of metallic zinc in the whole process is 89.13%, the silver recovery rate is 99.9%, and the quality of the final product zinc sulfate meets the food grade standard (GB25579-2010).
Claims
1. A method for producing food-grade zinc sulfate using zinc oxide, comprising the following steps: ⑴ Leaching: In a leaching tank filled with pure water, zinc hypochlorite and sulfuric acid with a volume concentration of 93% are added in sequence for leaching. After the leaching is completed, vacuum filtration is performed using a short-fiber polyester filter cloth with a filtration accuracy of <5 μm to obtain a clear and transparent crude zinc sulfate solution and leaching residue, respectively; the volume mass ratio of the pure water to the zinc hypochlorite is L / S=2.5-3:1; the amount of sulfuric acid added is 350-450 mL / kg zinc hypochlorite; the leaching residue is sold to a lead smelting enterprise as a raw material for pyrometallurgical lead smelting; ⑵Silver salt dechlorination and silver sulfate regeneration: The crude zinc sulfate solution is added to the dechlorination reaction tank, stirring is started, reagent-grade silver sulfate is added at once according to 1.0-1.05 times of the theoretical silver consumption of the total amount of chloride ions in the solution, the stirring reaction time is 30 minutes, the reaction temperature is 15-25° C., and the mixture is filtered and washed with pure water until neutral, to obtain a silver chloride precipitate and a dechlorinated liquid respectively; the silver chloride precipitate is first reacted with zinc powder in the presence of sulfuric acid to obtain sponge silver; the sponge silver is dissolved with nitric acid, and the sulfuric acid is converted to obtain regenerated silver sulfate, and the regenerated silver sulfate enters the dechlorination reaction tank to carry out a silver salt dechlorination cycle reaction; ⑶Co-precipitation to remove heavy metal impurities: Start stirring at 180 r / min, heat the dechlorinated liquid of the filtrate to 80±5°C, add 25 mL of a 30% H2O2 solution per liter of the dechlorinated liquid, and then add 14 g of a reagent-grade neutralizing agent, basic zinc carbonate, per liter of the dechlorinated liquid, and react for 4 hours. The reaction end point pH is 5.4-5.
6. After liquid-solid separation, the insoluble hydroxide precipitate and the precipitated liquid are obtained respectively; ⑷Replacement and removal of copper, cadmium and lead: The precipitated liquid is added into a zinc powder displacement stirring tank, and then 0.5 mol / L dilute sulfuric acid is added to adjust the pH to 5, and then 30-35 g of zinc powder with 80% effective zinc is slowly added per 10 L of the precipitated liquid to carry out a displacement reaction, and a high-purity zinc sulfate solution with a pH of ≈ 6 and a byproduct copper-cadmium slag are obtained through liquid-solid separation; the copper-cadmium slag is sold to a copper smelting enterprise for recycling; ⑸ Concentrated crystallization to produce food grade zinc sulfate: The high-purity zinc sulfate solution is adjusted to pH=5.5 by sulfuric acid, and then concentrated by vacuum evaporation to obtain a concentrated solution and a condensate; the concentrated solution is cooled, crystallized, liquid-solid separated, and dried to obtain the terminal product food-grade zinc sulfate; the condensate is returned to step (1); and the filtrate is returned to step (3).
2. A method for producing food-grade zinc sulfate using zinc suboxide as claimed in claim 1, characterized in that: The resistivity of pure water at 25° C. in step (1) is 18 MΩ·cm.
3. A method for producing food-grade zinc sulfate using zinc suboxide as claimed in claim 1, characterized in that: The leaching conditions in step (1) are that the heating temperature is 80-90° C., the stirring speed is 180 r / min, and the leaching time is 2 h.
4. A method for producing food-grade zinc sulfate using zinc suboxide as claimed in claim 1, characterized in that: The regenerated silver sulfate in step (2) is prepared as follows: ① The silver chloride precipitate was uniformly mixed with 100-mesh pure zinc powder of 1.1 times the theoretical consumption, and then a 10 g / L dilute sulfuric acid solution was added at a liquid-solid volume mass ratio of L / S=20:1, and the reaction time was stirred at 10-15°C for 40 min, and the sponge silver was obtained by filtration; ② For every 100g of sponge silver, add 125mL of analytical pure nitric acid, control the liquid-to-solid ratio L / S=3, temperature 20℃±5℃, time 30min process conditions to dissolve the sponge silver; after the dissolution is completed, add 28~30mL of analytical pure sulfuric acid, the silver sulfate precipitation time is 10min, filter to obtain regenerated silver sulfate, and the obtained conversion liquid is used for the next dissolution of sponge silver.
5. A method for producing food-grade zinc sulfate using zinc suboxide as claimed in claim 1, characterized in that: The conditions for the replacement reaction in step (4) are a reaction temperature of 60-70° C. and a reaction time of 60 min.
6. A method for producing food-grade zinc sulfate using zinc suboxide as claimed in claim 1, characterized in that: The multiple of evaporation concentration in step (5) is 2.5 to 3 times, and the cooling crystallization conditions refer to a temperature of 15 to 20° C. and a time of 1 to 2 hours.