CN108862369B

CN108862369B - Method for producing nano zinc oxide by using leached residues of electrolytic zinc acid method

Info

Publication number: CN108862369B
Application number: CN201810817117.7A
Authority: CN
Inventors: 孙晓明; 孙际童; 钟琳灏
Original assignee: Individual
Current assignee: Chongqing Dongqun Technology Co ltd
Priority date: 2018-07-24
Filing date: 2018-07-24
Publication date: 2020-02-21
Anticipated expiration: 2038-07-24
Also published as: CN108862369A

Abstract

The present disclosure relates to a method for producing nanometer zinc oxide by using leaching residue of an electrolytic zincate method, which comprises a primary leaching step, an optional purification step, a desulfurization step, a calcium zincate synthesis step, a primary calcination step, a secondary leaching step, a pressurization crystallization step, a decompression decomposition step, an optional rinsing step and a secondary calcination step. The method disclosed by the invention realizes secondary utilization of leaching slag while solving the environmental protection problem, realizes resource utilization while solving various heavy metal pollution, changes the sulfate ions as pollution sources into valuables by calcium sulfate conversion, realizes calcium zincate synthesis under the zinc ammonia environment for the first time, obtains nano zinc oxide by calcium zincate, does not need ammonia distillation, is simple and easy to implement, greatly reduces the energy consumption of the process, also avoids the problems of high-temperature and high-pressure potential safety hazards and equipment corrosion caused by ammonia distillation, creatively utilizes the decomposition condition of ammonium carbonate in the process, and realizes the recycling of carbon dioxide by pressure difference.

Description

Method for producing nano zinc oxide by using leached residues of electrolytic zinc acid method

Technical Field

The invention belongs to the technical field of comprehensive utilization of resources and comprehensive application of new materials, relates to environment-friendly treatment and resource utilization of leaching residues of an electrolytic zincic acid method, and particularly relates to a method for producing nano zinc oxide by using the leaching residues of the electrolytic zincic acid method.

Background

The leaching slag of the electrolytic zincate method is the most main pollutant in the electrolytic zinc industry, and belongs to the leaching slag generated by the conventional leaching method in the lead-zinc smelting process and the sulfur slag (leaching slag) generated by the normal pressure oxygen leaching and the pressure oxygen leaching in the national hazardous waste catalogue. The treatment and resource utilization of the leaching residue by the electrolytic zincate method are problems which need to be solved urgently. Meanwhile, the production and consumption of zinc in China are at the top of the world, domestic zinc resources cannot meet the production, and a large amount of zinc raw materials need to be imported every year. The method is developed to realize the high-efficiency resource utilization of the zinc in the leaching residue of the electrolytic zincic acid method, and has important significance for solving the environmental protection pressure and relieving the domestic zinc raw material supply problem.

Calcium zincate has a wide range of uses. The application of calcium zincate to the negative electrode material of the alkaline secondary zinc electrode is a new direction developed in recent years and is continuously mature and industrialized; compared with the traditional zinc oxide desulfurizer, the calcium zincate is a normal-temperature desulfurizer with desulfurization active components, and the sulfur capacity is greatly increased; the calcium zincate as the feed additive is not only beneficial to the absorption of animals but also beneficial to reducing the environmental pollution. The calcium zincate can also be widely used for glaze, paint, coating additives and the like. Calcium zincate can also be used as raw material for electrolytic zinc and zinc oxide.

The preparation method of calcium zincate in the prior art is limited to experimental exploration and is not mature. For example, Chinese patents CN1397498A and CN1595688A both disclose the synthesis of calcium zincate by ball milling, among which, Chinese patent CN1397498A discloses that Ca (OH)₂And ZnO are put into a ball milling tank according to the proportion in the chemical formula of calcium zincate, a proper amount of water is added, ball milling is carried out for 8 to 18 hours under the protection of argon atmosphere, and then the ball milling is carried out for 30 to 80 hoursBaking at the temperature of 10-15 hours to obtain a product; U.S. Pat. No. 5,460,899 discloses a method of using ZnO and Ca (OH)₂A method for generating calcium zincate by reaction in alkali liquor; chinese patent CN2012100305744 discloses a soluble zinc salt and Ca (OH) in a stoichiometric ratio₂Preparing into emulsion to generate calcium zincate. In the method, finished high-purity zinc oxide or finished zinc salt is used as a starting raw material, the raw material is expensive, the reaction condition is harsh, the energy consumption is high, the reaction is incomplete, the yield is low, the reaction specificity is poor, the interference of impurities is easy, the total preparation process cost is high, and the method is not suitable for industrial application.

Zinc oxide is an oxide of zinc, is poorly soluble in water, and is soluble in acids and strong bases. Zinc oxide is a commonly used chemical additive, and is widely applied to the manufacture of products such as plastics, silicate products, synthetic rubber, lubricating oil, paint, coating, ointment, adhesive, food, batteries, flame retardant and the like. The zinc oxide has large energy band gap and exciton constraint energy, high transparency and excellent normal temperature luminous performance, and is applied to products such as liquid crystal displays, thin film transistors, light emitting diodes and the like in the semiconductor field.

Chinese patent CN102863007 discloses a method for producing zinc oxide from leaching residue of electrolytic zincate method, which comprises leaching, purifying, ammonia evaporation crystallization, rinsing, drying and calcining the leaching residue of electrolytic zinc by ammonia-ammonium carbonate to produce zinc oxide, wherein zinc content in the leaching residue of electrolytic zinc is low, zinc concentration in complexing liquid is difficult to exceed 3% in practical application, so that ammonia evaporation energy consumption is too high, and environmental protection treatment pressure of the process is increased due to the existence of a large amount of sulfate radicals.

Disclosure of Invention

Problems to be solved by the invention

The technical scheme provided by the disclosure solves the problems that the existing zinc raw material is in shortage, the method for preparing zinc oxide by calcium zincate is good, and the existing method for preparing zinc oxide by leaching residues by an electrolytic zincate method is high in energy consumption, large in environment-friendly treatment pressure and the like.

Means for solving the problems

In order to solve the problems in the prior art, the present disclosure provides a method for producing nano zinc oxide by leaching residue by an electrolytic zincate method, comprising the following steps:

primary leaching step: mixing and stirring the leaching residue of the electrolytic zincate method and a first leaching agent, and then filtering to obtain a first leaching solution, wherein the first leaching agent is a mixed aqueous solution of ammonia and ammonium bicarbonate, or a mixed aqueous solution of ammonia and ammonium carbonate, or a mixed aqueous solution of ammonia, ammonium bicarbonate and ammonium carbonate;

optionally, purifying the first leach liquor obtained in the primary leach step;

and (3) desulfurization: adding calcium oxide and/or calcium hydroxide into the first leaching solution, stirring, and then filtering to obtain a first solid and a first filtrate;

calcium zincate synthesis step: adding calcium hydroxide and/or calcium oxide into the first filtrate, stirring, and then filtering to obtain a second solid and a second filtrate;

a primary calcination step: calcining the second solid at the temperature of 150-1050 ℃, preferably 150-350 ℃;

a secondary leaching step: adding a second leaching agent into the calcined product obtained in the primary calcination step, stirring, and then filtering to obtain a second leaching solution, wherein the second leaching agent is a mixed aqueous solution of ammonia and ammonium bicarbonate, or a mixed aqueous solution of ammonia and ammonium carbonate, or a mixed aqueous solution of ammonia, ammonium bicarbonate and ammonium carbonate;

a step of pressure crystallization: adding an active agent into the second leaching solution, and introducing pressurized carbon dioxide to obtain slurry containing crystals;

and (3) a decompression decomposition step: filtering the slurry obtained in the pressure crystallization step in a sealed environment to obtain a third solid and a third filtrate, and reducing the pressure of the third filtrate to normal pressure to decompose part of ammonium carbonate in the third filtrate into ammonia and carbon dioxide;

optionally, rinsing the third solid with water;

and (3) secondary calcination: and drying the third solid, and calcining at the temperature of 450-900 ℃ to obtain a nano zinc oxide product with the average particle size of 10-100 nm.

In the method for producing nano zinc oxide by using the leached residues of the electrolytic zinc acid method, the mass concentration of total ammonia in the first leaching agent is 5-15%, and the amount of effective carbonate in the first leaching agent is 100-200% of the amount of sulfate in the leached residues of the electrolytic zinc acid method; the mass concentration of total ammonia in the second leaching agent is 6-12%, and the mass concentration of effective carbonate in the second leaching agent is 8-15%.

In the method for producing nano zinc oxide by using the leached residues of the electrolytic zincate method, the concentration of zinc ammino ions (calculated by the mass of zinc element) in the first leached solution is 10-25 g/L.

In the method for producing nano zinc oxide by using the leached residues of the electrolytic zincate method provided by the further embodiments of the present disclosure, the amount of the substance of calcium oxide and/or calcium hydroxide added in the desulfurization step is 100% to 130%, preferably 100% to 110% of the amount of the substance of sulfate radical in the first leached solution.

In the method for producing nano zinc oxide by using the leached residue of the electrolytic zincate method, in the calcium zincate synthesis step, the ratio of the amount of substances of calcium hydroxide and/or calcium oxide to the amount of substances of zinc ammino ions in the first filtrate is 1-1.2: 2, preferably 1-1.1: 2.

In the method for producing nano zinc oxide by using the leaching residue of the electrolytic zincate method, provided by the further embodiment of the disclosure, in the pressure crystallization step, the crystallization pressure is 0.3-0.6 MPa.

In the method for producing nano zinc oxide by using the leached residues of the electrolytic zincate method, the reaction for decomposing part of ammonium carbonate in the third filtrate into ammonia and carbon dioxide is carried out at the temperature of 70-90 ℃ in the decompression decomposition step.

In the method for producing nano zinc oxide by using the leaching residue of the electrolytic zincate method, provided by the further embodiment of the disclosure, the active agent is one or more of sodium hexametaphosphate and sodium dodecyl benzene sulfonate.

In the method for producing nano zinc oxide by using the leaching residue of the electrolytic zincate method provided by the further embodiment of the disclosure, carbon dioxide is introduced into the second filtrate obtained in the calcium zincate synthesis step, and the second filtrate introduced with the carbon dioxide is used as a first leaching agent and is recycled for primary leaching of the leaching residue of the electrolytic zincate method.

In the method for producing nano zinc oxide by using the leaching residue of the electrolytic zincate method, in the step of decompressing and decomposing, after the third filtrate is decompressed to normal pressure:

collecting carbon dioxide released by decomposing ammonium carbonate, and recycling the carbon dioxide for pressure crystallization;

and collecting the third filtrate after being decompressed to normal pressure, and recycling the third filtrate for secondary leaching.

ADVANTAGEOUS EFFECTS OF INVENTION

The present disclosure achieves the following advantageous technical effects in one or more aspects:

1) the sulfate in the leaching slag of the electrolytic zincate method is converted into carbonate, so that the metal salt in the slag is more difficult to dissolve in water, the environmental protection problem is solved, and the secondary utilization of the leaching slag (which can be used as a raw material of cement and fired bricks) is realized.

2) The ammonia such as zinc, copper, cadmium and the like in the leaching residue of the electrolytic zincic acid method can enter the complexing solution by complexing ions, thereby solving the pollution of various heavy metals and realizing the resource utilization of the heavy metals.

3) Sulfate ions as a pollution source are converted into valuables by calcium sulfate.

4) The synthesis of calcium zincate is realized for the first time in the zinc ammonia environment, and the nano zinc oxide is obtained through the calcium zincate; (ii) a The reaction selectivity of synthesizing calcium zincate from the zinc ammine complex ions is high, simple and rapid.

5) The process disclosed by the invention realizes leaching and separation of zinc through circulation of carbonate, and solves the environmental protection problem in the existing ammonia circulation process because the surplus water brought by steam influences the process water balance.

6) The method breaks the inherent method that the traditional ammonia-ammonium bicarbonate method zinc complex leaching process destroys the complex environment by heating and evaporating ammonia to realize zinc ion crystallization separation, creatively adds calcium oxide or calcium hydroxide into an ammonium sulfate-zinc ammonia complex system to shift the balance of zinc ammine complex ion-zinc hydroxide/calcium zincate, realizes the selective crystallization separation of zinc element by the balance shift principle on the premise of not destroying the dissolved ammonia environment, breaks the inherent method that the traditional ammonia-ammonium bicarbonate method zinc complex leaching process destroys the complex environment by heating and evaporating ammonia to realize the zinc ion crystallization separation, and avoids the phenomenon that the traditional heating and ammonia evaporation method destroys the ammonia environment to cause the massive coprecipitation of impurities. The process disclosed by the invention is simple and easy to implement without ammonia distillation, greatly reduces the energy consumption of the process, and also avoids the problems of high-temperature and high-pressure potential safety hazards caused by ammonia distillation, equipment corrosion and extra environmental protection treatment burden caused by evaporation and volatilization of a large amount of ammonia.

7) The decomposition condition of ammonium carbonate is creatively utilized in the process, and the recycling of carbon dioxide is realized through pressure difference.

Detailed Description

Various exemplary embodiments, features and aspects of the disclosure are described in detail below. The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

Furthermore, in the following detailed description, numerous specific details are set forth in order to provide a better understanding of the present disclosure. In some instances, methods, means, reagents and devices well known to those skilled in the art are not described in detail, but those skilled in the art can implement the technical solutions of the present disclosure based on the general knowledge in the art.

Noun interpretation

As used herein, unless otherwise indicated, "zinc ammonium sulfate" is a generic term for compounds formed from zinc ammine complex ions and sulfate radicals, and includes [ Zn (NH)₃)₄]SO₄Zinc tetra-ammino sulfate and Zn (NH)₃)₃]SO₄(triamino zinc sulfate), [ Zn (NH)₃)₂]SO₄Zinc diammine sulfate and Zn (NH)₃)]SO₄(zinc ammonium sulfate), and the like.

In this context, unless otherwise stated, "zinc ammine complex ion" is a generic term for each level of ammine zinc complex ion, and includes [ Zn (NH)₃)₄]²⁺(Zinc tetraammine ion), [ Zn (NH)₃)₃]²⁺(Triammine Zinc ion), [ Zn (NH)₃)₂]²⁺(Diaminato zinc ion), [ Zn (NH)₃)]²⁺(zinc ion ammine), and the like.

As used herein, unless otherwise indicated, "available carbonate" in a solution (including, but not limited to, various liquors of a first leaching agent, a first leach solution, a second leaching agent, and the like) refers to the sum of carbonate and bicarbonate in the solution.

"optional" or "optionally" means that the subsequently described step may or may not be performed, and that the expression includes instances where the subsequently described step is performed and instances where the subsequently described step is not performed.

Chemical reaction formula

1. One-time leaching

a. Replacement of sulfate with carbonate/bicarbonate

CaSO₄+(NH₄)₂CO₃＝CaCO₃+(NH₄)₂SO₄

MgSO₄+(NH₄)₂CO₃＝MgCO₃+(NH₄)₂SO₄

PbSO₄+(NH₄)₂CO₃＝PbCO₃+(NH₄)₂SO₄

Or

CaSO₄+NH₄HCO₃＝CaCO₃+(NH₄)₂SO₄+H₂O+CO₂

MgSO₄+NH₄HCO₃＝MgCO₃+(NH₄)₂SO₄+H₂O+CO₂

PbSO₄+NH₄HCO₃＝PbCO₃+(NH₄)₂SO₄+H₂O+CO₂

b. Zinc oxide leaching

ZnO+(i-2)NH₃+(NH₄)₂SO₄＝[Zn(NH₃)_i]SO₄+H₂O (i is an integer of 2 to 4)

2. Desulfurization of

CaO+H₂O＝Ca(OH)₂

Ca(OH)₂₊+(NH₄)₂SO₄＝CaSO₄↓+NH₃·H₂O

[Zn(NH₃)_i]SO₄+Ca(OH)₂＝[Zn(NH₃)_i](OH)₂+CaSO₄↓

3. Calcium zincate synthesis

2[Zn(NH₃)_i](OH)₂+Ca(OH)₂+2H₂O＝Ca(OH)₂·2Zn(OH)₂·2H₂O+2iNH₃

(i is an integer of 1 to 4)

4. Primary calcination

Ca(OH)₂·2Zn(OH)₂·2H₂O＝Ca(OH)₂+2ZnO+4H₂O

Or

Ca(OH)₂·2Zn(OH)₂·2H₂O＝CaO+2ZnO+5H₂O

5. Secondary leaching

ZnO+(i-2)NH₃+(NH₄)₂CO₃＝[Zn(NH₃)_i]CO₃+H₂O (i is an integer of 2 to 4)

6. Pressure crystallization

2NH₃·H₂O+CO₂＝(NH₄)₂CO₃+H₂O

3[Zn(NH₃)_i]CO₃+3H₂O＝ZnCO₃·2Zn(OH)₂·H₂O+2(NH₄)₂CO₃+(3i-4)NH₃(i is an integer of 2 to 4)

7. Decomposition under reduced pressure

(NH₄)₂CO₃+H₂O＝2NH₃·H₂O+CO₂

8. Second calcination

ZnCO₃·2Zn(OH)₂·H₂O＝3ZnO+CO₂+3H₂O

The concrete process steps

Step 1 one leaching

Mixing the leaching residue of the electrolytic zincate method with a prepared first leaching agent according to a certain proportion, and stirring and leaching, wherein the first leaching agent can be selected from: a mixed aqueous solution of ammonia and ammonium bicarbonate; a mixed aqueous solution of ammonia and ammonium carbonate; a mixed aqueous solution of ammonia, ammonium bicarbonate and ammonium carbonate. And filtering after leaching to obtain a first leaching solution.

The total ammonia concentration and the available carbonate concentration in the first leaching agent are not particularly limited, and can be selected by a person skilled in the art according to factors such as sulfate and zinc content in each batch of electrolytic zinc acid method leaching residues and the like according to actual needs.

In the preferred scheme, the mass concentration of the total ammonia in the first leaching agent is 5-15%, more preferably 6-8%, and the preferred concentration range can achieve sufficient leaching effect and avoid waste and environmental protection problems caused by excessive ammonia.

In a preferable scheme, the amount of available carbonate in the first leaching agent is approximately matched with the amount of sulfate in the leaching residue of the electrolytic zincate method, and a certain excess is allowed so as to achieve the purposes of fully converting the sulfate in the leaching residue into carbonate and not excessively increasing the treatment pressure of a subsequent process. For example, the amount of the substance of the available carbonate in the first leaching agent is 100% to 200% of the amount of the substance of sulfate in the leaching residue of the electrolytic zincate process.

The weight ratio of the first leaching agent to the electrolytic zincate process leaching residue is not particularly limited as long as the zinc component can be leached. Preferably, the weight ratio of the leaching agent to the leaching residue of the electrolytic zincate method is 3:1 to 5:1, so that not only can a satisfactory leaching effect be obtained, but also the waste of the leaching agent is avoided.

The leaching temperature is not particularly limited as long as the zinc component in the leaching residue of the electrolytic zincate process is leached. Preferably, the leaching is carried out at ambient temperature, for example at 15 to 30 ℃. The leaching residue of the electrolytic zincate method and the leaching agent are mixed and stirred, the stirring time is not particularly limited, and the stirring time is preferably 1 to 4 hours, more preferably 1 to 2 hours. After stirring, filtration was carried out.

In the leaching process, a plurality of metal sulfates in the leaching residue of the electrolytic zincate method are converted into more insoluble carbonates to be filtered and removed, and zinc elements are converted into zinc ammine complex ions (mainly zinc ammine complex ions at each stage) to enter the first leaching solution. The first leach solution is sent to a subsequent desulfurization process. The concentration of the zinc ammine complex ions in the first leaching solution is not particularly limited, but the concentration (by mass of zinc element) of the zinc ammine complex ions in the first leaching solution is preferably 10-25 g/L, so that the treatment efficiency of the process is optimal, good yield and purity are obtained in the subsequent calcium zincate synthesis step, and the comprehensive economic benefit is optimal. If the concentration of the zinc ammine complex ions in the original leached liquid is not in the preferred range, optionally concentrating or diluting the leached liquid, and adjusting the concentration of the zinc ammine complex ions in the leachate to be in the preferred range of 10-25 g/L.

Step 2 purification

Step 2 is an optional step, and step 2 is optionally performed, if necessary. Purifying the first leaching solution by a known method to remove impurity elements such as iron, manganese, lead, copper and the like. An exemplary purification method is to add zinc powder for displacement and then filtering to remove heavy metal contaminants, but various other known purification methods may be used. The purification step helps to increase the purity of the final product.

Step 3 desulfurization

In the desulfurization step, calcium hydroxide and/or calcium oxide is added into the first leaching solution containing zinc ammine complex ions to convert sulfate radicals in the leaching solution into insoluble calcium sulfate. If the concentration of zinc ammine ions in the first leach solution is too high, there may be simultaneous shift in the balance of zinc ammine ions-zinc hydroxide in the leach solution, and a very small proportion of the zinc component may co-precipitate with the calcium sulphate in the form of zinc hydroxide.

In the desulfurization step, calcium hydroxide and/or calcium oxide is added in an amount approximately matching the sulfate radical content in the first leachate, for example, the amount of the substance of calcium hydroxide and/or calcium oxide added in the desulfurization step is 100% to 130%, more preferably 100% to 110%, of the amount of the substance of sulfate radical in the first leachate. Proper addition of calcium hydroxide and/or calcium oxide is helpful for controlling the process cost and improving the purity and quality of the finished zinc product.

In the desulfurization step, calcium hydroxide and/or calcium oxide is added into the first leaching solution, and the mixture is stirred to react to generate solid precipitate. The reaction temperature is not particularly limited, but since the reaction can be smoothly carried out without heating, it is particularly preferable to carry out the reaction at room temperature (for example, 15 to 25 ℃), which not only saves energy but also reduces environmental pollution caused by ammonia volatilization. The stirring time is not particularly limited as long as a precipitate is obtained, and stirring is preferably performed for 1 to 2 hours.

And filtering after stirring to obtain a first solid and a first filtrate. The primary component of the first solid is calcium sulphate, and if the concentration of zinc ammine ions in the leach solution is high, some zinc hydroxide co-precipitated with the calcium sulphate may also be present in the first solid. The first filtrate continues to be used for the subsequent calcium zincate synthesis.

Step 4 calcium zincate Synthesis

The ratio of the amount of the calcium hydroxide and/or calcium oxide to the amount of the zinc ammine complex ion in the first filtrate is preferably 1 to 1.2:2, more preferably 1 to 1.1: 2. The reaction temperature is not particularly limited, and may be, for example, 15 to 90 ℃, preferably 20 to 90 ℃, and more preferably 30 to 60 ℃; or the reaction temperature of 15-25 ℃ is also preferably selected, and the temperature range has the advantages of no need of heating, energy conservation and reduction of ammonia volatilization. Filtering can be carried out after the reaction is carried out for 0.5-2 hours (preferably 0.5-1 hour), and long-time reaction and ageing processes are not needed. Filtering to obtain a second solid and a second filtrate. The main component of the second solid is calcium zincate. In addition, carbon dioxide can be introduced into the second filtrate and then recycled as the first leaching agent for leaching the leaching residue of the electrolytic zincate method.

Step 5 primary calcination

In this step, the second solid obtained in step 4 is calcined to decompose calcium zincate. The calcination temperature is 150-1050 ℃, preferably 150-350 ℃. The product obtained by calcining is a mixture, and if the calcining temperature is 150-350 ℃, the main components of the calcined product are zinc oxide and calcium hydroxide; if higher calcination temperatures are used, the calcined product may contain zinc oxide, calcium hydroxide and/or calcium oxide.

Step 6 Secondary leaching

And adding a prepared second leaching agent into the mixture containing the zinc oxide and the calcium hydroxide (or the calcium oxide) obtained in the primary calcination step, and performing stirring leaching, preferably stirring for 1-4 hours. The second leaching agent can be a mixed aqueous solution of ammonia and ammonium bicarbonate, or a mixed aqueous solution of ammonia and ammonium carbonate, or a mixed aqueous solution of ammonia, ammonium bicarbonate and ammonium carbonate, preferably an ammonia-ammonium carbonate aqueous solution, wherein the total ammonia mass concentration is 6-12%, and the effective carbonate mass concentration is 8-15%.

In this step, calcium hydroxide (or calcium oxide) in the mixture obtained by the primary calcination reacts with carbonate/bicarbonate in the second leaching agent to form calcium carbonate precipitate, and zinc oxide in the mixture is converted into zinc ammonium carbonate ([ Zn (NH)₃)_i]CO₃And i is an integer of 1 to 4). And after the reaction is finished, filtering to remove calcium carbonate precipitate, wherein the filtrate obtained by filtering is a second leaching solution containing zinc ammine complex ions and is used for the subsequent step of pressure crystallization.

Step 7 pressure crystallization

And adding an active agent into the second leaching solution, wherein the active agent is preferably sodium hexametaphosphate or sodium dodecyl benzene sulfonate, and the dosage of the active agent is preferably 0.01-0.05% of the estimated quality of the final product. The second leach solution is then pressurized with carbon dioxide gas to convert the free ammonia in the second leach solution to ammonium carbonate and the zinc component is freed of complexing conditions and precipitated as basic zinc carbonate. The crystallization pressure is controlled to be 0.3-0.6 MPa, and the reaction temperature in the process is lower than that in the process. As the ammonium carbonate in the aqueous solution can be automatically decomposed when reaching 70 ℃ under normal pressure, the pressure difference can be effectively utilized industrially to realize the recycling of the carbon dioxide, and the consumption of the carbon dioxide in the process is reduced, therefore, the optimal reaction temperature in the step is controlled to be 70-90 ℃. The slurry containing basic zinc carbonate crystals is obtained in the step and sent to the next step.

Step 8 decomposition under reduced pressure

The slurry after completion of crystallization was filtered in a sealed environment (an environment in which a pressurized state was maintained) to obtain a third solid and a third filtrate. The main component of the third solid is basic zinc carbonate, and ammonium carbonate is dissolved in the third filtrate. And decompressing the third filtrate to normal pressure, so that part of ammonium carbonate in the third filtrate is decomposed into ammonia and carbon dioxide. The released carbon dioxide gas can be used for cyclic pressure crystallization, and the ammonia is mainly present in the solution in the form of free ammonia. The preferable decomposition reaction temperature is 70-90 ℃, the reaction is carried out for 1-2 hours in the normal pressure environment at the temperature, and the ammonium carbonate in the water solution can be decomposed by about 60-70%. The liquid after the decomposition reaction has complexing conditions again and can be circularly used for secondary leaching.

Step 9 rinsing

Step 9 is an optional step, and step 9 is optionally performed, if necessary. And (3) adding water into the third solid with the basic zinc carbonate as the main component obtained in the step (8) for rinsing, wherein the liquid-solid ratio is 5-10: 1, and the rinsing times are 1-2.

Step 10 Secondary calcination

And drying a third solid with the main component of basic zinc carbonate, and then calcining at the temperature of 450-900 ℃. And decomposing the basic zinc carbonate to obtain nano zinc oxide solid with the average particle size of 10-100 nm.

Embodiments of the present disclosure will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present disclosure and should not be construed as limiting the scope of the present disclosure. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

Example 1

The zinc content of the leaching residue of the electrolytic zinc acid method of Sichuan company is 8.46 percent, and the sulfur content is 14.09 percent.

2000 g of electrolytic zinc acid leaching residue is put into 10000 ml of ammonia-ammonium carbonate mixed solution (the total ammonia mass concentration is 10%, and the carbonate mass concentration is 5.5%) to be stirred and leached, the leaching temperature is normal temperature, the stirring time is 2 hours, then the filtering is carried out, the zinc content (calculated by zinc oxide equivalent) in the filtered liquid is 1.47%, and the sulfate radical mass concentration in the liquid is 8.8%. According to the inspection data, the zinc recovery rate is 86.9%.

And purifying the filtered zinc-ammonia complex solution.

256.7 g of calcium oxide is added into the purified zinc ammine complex solution for precipitating sulfate radicals, and the solution is filtered after reacting for 1 hour.

18 g of calcium hydroxide were added for the synthesis of calcium zincate, and filtered after stirring for 1 hour. The solid obtained by filtering is dried for 2 hours at 105 ℃, and then calcined for 2 hours at 300 ℃, and the calcium zincate is decomposed into zinc oxide and calcium hydroxide.

50 g of calcined solid is taken, 500 ml of ammonia-ammonium carbonate mixed solution (the mass concentration of ammonia is 10 percent, and the mass concentration of carbonate is 12 percent) is added for stirring and leaching, the stirring time is 2 hours, and then the filtration is carried out.

Adding 3 mg of sodium dodecyl benzene sulfonate into the filtered filtrate, heating to 70 ℃, putting into a reaction kettle, introducing compressed carbon dioxide gas into the reaction kettle for reaction, controlling the pressure to be 0.3MPa, sampling and checking, stopping adding the carbon dioxide when the concentration of zinc in the liquid is lower than 0.5%, pumping into a positive pressure filter for filtering.

And adding water into the filtered basic zinc carbonate according to the liquid-solid ratio of 10:1 for rinsing twice, drying the rinsed basic zinc carbonate at 105 ℃ for 2 hours, calcining at 800 ℃ for 2 hours, and inspecting and analyzing the obtained zinc oxide product, wherein the content of zinc oxide is 99.76%, and the average particle size is 47.1 nm.

Example 2

The zinc content of the leaching residue obtained by the electrolytic zinc acid method of a company in Yunnan is 7.98 percent, and the sulfur content is 16.01 percent.

2000 g of electrolytic zinc acid leaching residue is put into 10000 ml of ammonia-ammonium carbonate mixed solution (the total ammonia mass concentration is 10 percent, and the carbonate mass concentration is 6 percent) for stirring and leaching, the leaching temperature is normal temperature, the stirring time is 2 hours, then the filtering is carried out, the zinc content (calculated by zinc oxide equivalent) in the filtered liquid is 1.367 percent, and the sulfate radical mass concentration in the liquid is 9.61 percent. According to the inspection data, the zinc recovery rate is 86.63%.

And purifying the filtered zinc-ammonia complex solution.

280 g of calcium oxide is added into the purified zinc ammine complex solution for precipitating sulfate radicals, and the solution is filtered after reacting for 1 hour.

16 g of calcium hydroxide was added for the synthesis of calcium zincate, and filtered after stirring for 1 hour. The solid obtained by filtering is dried for 2 hours at 105 ℃, and then calcined for 2 hours at 300 ℃, and the calcium zincate is decomposed into zinc oxide and calcium hydroxide.

50 g of the calcined solid is taken and put into 500 ml of ammonia-ammonium carbonate mixed solution (the mass concentration of ammonia is 10 percent, and the mass concentration of carbonate is 12 percent) for stirring and leaching for 2 hours, and then the solid is filtered.

And adding water into the filtered basic zinc carbonate according to the liquid-solid ratio of 10:1 for rinsing twice, drying the rinsed basic zinc carbonate at 105 ℃ for 2 hours, calcining at 800 ℃ for 2 hours, and inspecting and analyzing the obtained zinc oxide product, wherein the zinc oxide content is 99.80%, and the average particle size is 42.3 nm.

Having described embodiments of the present disclosure, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. The method for producing the nano zinc oxide by using the leaching residues of the electrolytic zincic acid method is characterized by comprising the following steps of:

a primary calcination step: calcining the second solid at the temperature of 150-1050 ℃;

optionally, rinsing the third solid with water;

2. The method for producing nano zinc oxide by using the leaching residue of the electrolytic zinc acid method according to claim 1, wherein in the primary calcination step, the calcination temperature is 150-350 ℃.

3. The method for producing nano zinc oxide by using the electrolytic zinc acid method leaching residue according to claim 1, wherein the mass concentration of total ammonia in the first leaching agent is 5-15%, and the amount of available carbonate in the first leaching agent is 100-200% of the amount of sulfate in the electrolytic zinc acid method leaching residue;

the mass concentration of total ammonia in the second leaching agent is 6-12%, and the mass concentration of effective carbonate in the second leaching agent is 8-15%.

4. The method for producing nano zinc oxide by using the leached residues of the electrolytic zincate method according to any one of claims 1 to 3, wherein the concentration of zinc ammine complex ions in the first leached solution is 10 to 25g/L based on the mass of zinc element.

5. The method for producing nano zinc oxide by using the leached residues of the electrolytic zincate process according to any one of claims 1 to 3, characterized in that the amount of the substance of calcium oxide and/or calcium hydroxide added in the desulfurization step is 100 to 130% of the amount of the substance of sulfate radical in the first leached solution.

6. The method for producing nano zinc oxide by using the leached residues of the electrolytic zincate process according to claim 5, characterized in that the amount of the substance of calcium oxide and/or calcium hydroxide added in the desulfurization step is 100 to 110% of the amount of the substance of sulfate radical in the first leached solution.

7. The method for producing nano zinc oxide by using the leached residues of the electrolytic zincate method according to any one of claims 1 to 3, wherein in the calcium zincate synthesis step, the ratio of the amount of the substance of calcium hydroxide and/or calcium oxide to the amount of the substance of zinc ammine complex ion in the first filtrate is 1-1.2: 2.

8. The method for producing nano zinc oxide by using the leached residues of the electrolytic zincate method according to claim 7, wherein in the calcium zincate synthesis step, the ratio of the amount of the substance of calcium hydroxide and/or calcium oxide added to the first filtrate to the amount of the substance of zinc ammine complex ion in the first filtrate is 1-1.1: 2.

9. The method for producing nano zinc oxide by using the leached residues of the electrolytic zincate method according to any one of claims 1 to 3, wherein in the step of pressure crystallization, the crystallization pressure is 0.3 to 0.6 MPa.

10. The method for producing nano zinc oxide by using the leached residues of the electrolytic zincate method according to any one of claims 1 to 3, wherein the reaction of decomposing part of ammonium carbonate in the third filtrate into ammonia and carbon dioxide in the decompression decomposition step is carried out at a temperature of 70-90 ℃.

11. The method for producing nano zinc oxide by using the leaching residue of the electrolytic zincate method according to any one of claims 1 to 3, wherein the active agent is one or more of sodium hexametaphosphate and sodium dodecyl benzene sulfonate.

12. The method for producing nano zinc oxide by using the leaching residue of the electrolytic zincate process according to any one of claims 1 to 3, wherein carbon dioxide is introduced into the second filtrate obtained in the calcium zincate synthesizing step, and the second filtrate introduced with carbon dioxide is used as a first leaching agent and is recycled for primary leaching of the leaching residue of the electrolytic zincate process.

13. The method for producing nano zinc oxide by using the leached residues of the electrolytic zincate method according to any one of claims 1 to 3, characterized in that in the step of reduced pressure decomposition, after the third filtrate is reduced to normal pressure: