CN106517294B - Process for producing metal oxide - Google Patents

Process for producing metal oxide Download PDF

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CN106517294B
CN106517294B CN201510572391.9A CN201510572391A CN106517294B CN 106517294 B CN106517294 B CN 106517294B CN 201510572391 A CN201510572391 A CN 201510572391A CN 106517294 B CN106517294 B CN 106517294B
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salt solution
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carbon dioxide
ammonia gas
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CN106517294A (en
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冯宗玉
黄小卫
岳梅
王猛
崔大立
王良士
王春梅
魏煜青
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Grirem Advanced Materials Co Ltd
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Abstract

The invention discloses a preparation method of metal oxide. The preparation method comprises the following steps: carrying out precipitation reaction on the metal salt solution by using ammonia gas and carbon dioxide gas, and controlling the mass ratio of the ammonia gas to the carbon dioxide gas to ensure that the pH value of a mixed system is 2.0-10.0 to obtain slurry; carrying out solid-liquid separation on the slurry to obtain waste liquid containing ammonium ions and metal carbonate and/or metal basic carbonate; roasting the metal carbonate and/or the metal basic carbonate to obtain metal oxide and waste gas containing carbon dioxide gas; the ammonia gas is obtained by adjusting the pH value of the wastewater containing ammonium ions through alkaline substances and carrying out steam stripping enrichment. Controlling to obtain metal oxide products with different crystal forms, particle sizes and appearances by gas-liquid reaction and adjusting the mass ratio of the three raw materials; and the ammonia gas is recycled by waste water, CO2The gas can also be recycled by waste gas, so the method has the advantages of short flow, low raw material cost, closed circulation of ammonium, low carbon, environmental protection and controllable product performance.

Description

Process for producing metal oxide
Technical Field
The invention relates to the field of hydrometallurgy, in particular to a preparation method of a metal oxide.
Background
At present, the conventional method for preparing metal oxide in industrial production is chemical liquid phase precipitation, i.e. using metal compound solution as raw material, mixing it with precipitant solution to form insoluble metal hydroxide, carbonate or oxalate, etc., and obtaining corresponding metal oxide through pyrolysis or dehydration. Common precipitating agents for chemical liquid precipitation include: ammonium precipitants (mainly including ammonium carbonate, ammonium bicarbonate and ammonia water); alkali metal hydroxide, carbonate and bicarbonate precipitants (mainly sodium hydroxide, sodium carbonate and sodium bicarbonate, etc.); oxalic acid precipitant, etc. all belong to liquid-liquid reaction in the process of liquid-phase reaction, the product performance is greatly influenced by the supersaturation degree of the system in the reaction process, the uneven powder granularity caused by overhigh local supersaturation degree is easy to occur, and the product performance can hardly meet the application requirement. Meanwhile, the three precipitants also have the problems of ammonia nitrogen, high sodium salt and oxalic acid waste water, and the alkali metal hydroxide, carbonate and bicarbonate precipitants easily cause the problem of low product purity. In addition, the precipitated metal carbonates and metal oxalates need to be roasted to obtain rare earth oxides, and a large amount of by-product carbon dioxide greenhouse gas is generated, and at present, CO is treated in the industry2The emission of greenhouse gases has not yet presented an effective solution.
There is a chinese patent application which discloses the preparation of nano metal oxides by using inorganic metal salts as raw materials, reacting metal components with organic amines through aqueous solutions of metal inorganic salts to produce precipitates, and adding one or more organic compounds as stabilizers during the precipitation. The method takes organic amine as a precipitator and adds an organic compound as a stabilizer, so that a large amount of wastewater containing ammonia and COD can be generated, and meanwhile, heterogeneous precipitation in the liquid phase reaction process is difficult to avoid.
In addition, Chinese patent documents report that the method takes nitric acid or hydrochloric acid aqueous solution of rare earth as a raw material, and carbonate is directly added or carbon dioxide is introduced for precipitation; or dissolving the rare earth oxide by nitric acid or hydrochloric acid, controlling the concentration of rare earth ions to be 0.1-0.4 mol/L, and adding carbonate or carbon dioxide for precipitation. Both patent applications use carbon dioxide as a precipitant to prepare rare earth oxides. However, since the reaction raw material used in the preparation method is rare earth nitrate or chloride salt prepared by dissolving nitric acid or hydrochloric acid, the acidity of the solution system is very high, and in the actual reaction process, carbon dioxide gas is directly introduced for reaction, so that metal carbonate cannot be obtained at all.
In view of the above problems, it is desirable to provide a green method for preparing high-quality metal oxide, which can simultaneously solve the problems of ammonia-containing wastewater and CO widely existed in the industry at present2The problem of large emission of greenhouse gases.
Disclosure of Invention
The invention mainly aims to provide a preparation method of a metal oxide, which aims to solve the problem of environmental pollution caused by ammonia nitrogen wastewater, greenhouse gas emission and the like in the preparation process of the metal oxide in the prior art, thereby realizing green, low-carbon and cyclic development of the non-ferrous metal hydrometallurgy industry.
In order to achieve the above object, according to one aspect of the present invention, there is provided a method for preparing a metal oxide, the method comprising: step S1, carrying out precipitation reaction on the metal salt solution by using ammonia gas and carbon dioxide gas, and controlling the mass ratio of the ammonia gas and the carbon dioxide gas to ensure that the pH value of the mixed system is within the range of 2.0-10.0 to obtain slurry; step S2, carrying out solid-liquid separation on the slurry to obtain waste liquid containing ammonium ions and metal carbonate and/or metal basic carbonate; and step S3, roasting the metal carbonate and/or the metal basic carbonate to obtain metal oxide and waste gas containing carbon dioxide gas; wherein, the ammonia gas is obtained by steam stripping and enrichment after the pH of the wastewater containing ammonium ions is adjusted by alkaline substances.
Further, the metal salt solution is a single metal salt solution or a mixed solution of a plurality of metal salt solutions.
Further, in step S1, the mass ratio of the ammonia gas to the carbon dioxide gas is 1.2:1 to 1: 4.
Further, ammonia gas is obtained by the following steps: adding an alkaline substance into the wastewater containing ammonium ions to adjust the pH value to 3.0-6.0 to obtain a solid-liquid mixture; carrying out solid-liquid separation on the solid-liquid mixture to obtain a filtrate; continuously adding alkaline substances into the filtrate to obtain ammonia water; and carrying out stripping enrichment on ammonia water to obtain ammonia gas.
Further, in step S1, the pressure of the mixed system is controlled to be 0.1-0.95 MPa, and the temperature is controlled to be 10-95 ℃ for 0.5-4 hours.
Further, in step S1, the metal salt solution includes any one of an alkali metal salt solution, an alkaline earth metal salt solution, a transition metal salt solution, a gallium salt solution, a germanium salt solution, a tin salt solution, and an antimony salt solution.
Further, the alkali metal salt solution includes a sodium salt solution; the alkaline earth metal solution comprises calcium salt solution or magnesium salt solution; the transition metal salt solution includes any one of a rare earth salt solution, a zirconium salt solution, a hafnium salt solution, a cobalt salt solution, a nickel salt solution, a copper salt solution, and a zinc salt solution.
Further, the metal salt solution is one or more of chloride solution, nitrate solution, sulfate solution, acetate solution and perchlorate solution.
Further, the carbon dioxide gas is industrial grade carbon dioxide gas or is recovered from waste gas containing carbon dioxide gas, and the waste gas containing carbon dioxide gas is one or more of carbon dioxide gas and/or metal carbonate precipitation gas, metal carbonate roasting kiln gas, oxalate roasting kiln gas and boiler flue gas obtained in step S3.
Further, the wastewater containing ammonium ions is wastewater generated in an industrial production process, and the wastewater generated in the industrial production process comprises wastewater generated in a metal extraction separation process and/or wastewater generated in a metal precipitation process; wherein the wastewater generated in the metal precipitation process comprises the waste liquid containing ammonium ions obtained in step S2.
Further, the alkaline substance is one or more of calcium hydroxide, calcium oxide, magnesium hydroxide, light burned dolomite, sodium hydroxide and potassium hydroxide, and preferably the alkaline substance is calcium oxide or sodium hydroxide.
Further, step S3 includes: and roasting the metal carbonate and/or the metal basic carbonate at the high temperature of 400-1100 ℃ for 0.5-12 hours to obtain metal oxide and waste gas containing carbon dioxide gas.
By applying the technical scheme of the invention, the metal salt solution, ammonia gas and CO are mixed2Mixing the gas, preparing metal oxide by gas-liquid reaction, and regulating the solution of metal salt, ammonia gas and CO2The gas mass ratio enables the pH of the reaction system to be controllable, so that metal carbonate or basic carbonate with different compositions, structures and appearances can be obtained, and metal oxide products with different crystal forms, particle sizes and appearances can be obtained by roasting. In the preparation method of the invention, ammonia gas is obtained by wastewater recovery treatment, carbon dioxide gas is also obtained by waste gas recovery or is industrial-grade carbon dioxide, and the wastewater and the waste gas can be generated by the preparation steps or other process steps in industrial production. Therefore, the preparation method has the advantages of short flow of the whole preparation process, closed circulation of ammonium, low cost of raw materials, low carbon, environmental protection and controllable product performance.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic flow diagram of a process for preparing metal oxides in accordance with a preferred embodiment of the present invention;
FIG. 2 is a schematic flow chart showing a method for preparing a metal oxide according to another preferred embodiment of the present invention;
fig. 3 shows SEM images of cerium oxide powder in example 3;
FIG. 4 shows an SEM photograph of cerium carbonate powder in example 4;
fig. 5 shows SEM images of cerium oxide powder in example 4; and
FIG. 6 shows an SEM image of the zirconia powder in example 7.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
In order to solve the problem of environmental pollution caused by ammonia nitrogen wastewater, greenhouse gas emission and the like existing in the preparation process of metal oxides in the prior art, in a typical embodiment of the present invention, a preparation method of metal oxides is provided, as shown in fig. 1, the preparation method comprises: step S1, carrying out precipitation reaction on the metal salt solution by using ammonia gas and carbon dioxide gas, and controlling the mass ratio of the ammonia gas and the carbon dioxide gas to ensure that the pH value of the mixed system is within the range of 2.0-10.0 to obtain slurry; step S2, carrying out solid-liquid separation on the slurry to obtain waste liquid containing ammonium ions and metal carbonate and/or metal basic carbonate; and step S3, roasting the metal carbonate and/or the metal basic carbonate to obtain metal oxide and waste gas containing carbon dioxide gas; wherein, the ammonia gas is obtained by steam stripping and enrichment after the pH of the wastewater containing ammonium ions is adjusted by alkaline substances.
The preparation method of the metal oxide of the invention comprises the steps of mixing the metal salt solution with ammonia gas and CO2Mixing gas, preparing metal oxide by gas-liquid reaction, and regulating metal salt solution, ammonia gas and CO2The gas mass ratio enables the pH of the reaction system to be controllable, so that metal carbonates or basic carbonates with different physical properties can be obtained, and metal oxide products with different crystal forms, particle sizes and appearances can be obtained by roasting. In the preparation method, ammonia gas is obtained by wastewater recovery treatment, carbon dioxide gas can be obtained by waste gas recovery or industrial-grade carbon dioxide, and the wastewater and the waste gas can be generated by the preparation steps and other process steps in industrial production. Therefore, the preparation method has the advantages of short flow of the whole preparation process, closed circulation of ammonium, low cost of raw materials, low carbon, environmental protection and controllable product performance.
In the above step S1 of the present invention, the effects of ammonia and carbon dioxide are as follows: firstly, adjusting the pH value of a carbonization system; ② the raw material for synthesizing metal carbonate and/or metal basic carbonate; and thirdly, the crystal form, the appearance, the granularity and the pore structure of the prepared metal oxide can be adjusted by adjusting the relative dosage of ammonia gas and carbon dioxide gas and the introduction mode. In the actual preparation process, a crystal form regulator can be added to control the growth rate of each crystal face so as to control the crystal form of the formed metal oxide, and the specific crystal form regulator includes but is not limited to one or more of crystal form metal carbonate, polyacrylic acid, sodium pyrophosphate, EDTA, alkali metal salts of EDTA, triethanolamine and inorganic acid, and the adding amount is controlled, and is usually not more than 5% of the weight of the obtained metal oxide. In addition, after the carbonization reaction is finished, a dispersing agent can be added to adjust the surface charge of the particles so as to obtain metal carbonate and/or metal basic carbonate with good dispersibility, thereby being further beneficial to obtaining metal oxides with different physical properties. The commonly used dispersant types comprise one or a mixture of sodium polycarboxylate, sodium polyacrylate, polyethylene glycol with the molecular weight of 600-10000 and sodium dodecyl sulfate; the addition mode of the dispersing agent can be directly added into the whole reaction system after the carbonization reaction, and added into the metal carbonate and/or metal basic carbonate wet cake after the filtration; the amount of dispersant added is generally not more than 5% by weight of the resulting metal oxide.
The two gases can be added into the metal salt solution or the base solution according to different types or structures of products to be prepared, or other raw materials can be added into the metal salt solution or the base solution simultaneously in a concurrent manner.
The chemical reaction formula of step S1 is as follows:
Mz++zNH3+z/2CO2+z/2H2O→M(CO3)z/2+zNH4 +(ii) a Or is that
2Mz++2zNH3+z/2CO2+3z/2H2O→M2(OH)z(CO3)z/2+2zNH4 +
Wherein M isz+Is a metal cation.
The chemical reaction formula of step S3 is as follows:
Figure BDA0000799189330000041
or is that
Figure BDA0000799189330000042
In the step of recovering and treating the wastewater containing ammonium ions in the preparation method, the pH is adjusted by adding an alkaline substance, and ammonia gas can be recovered by stripping and enriching through reaction heat or external heat. The specific reaction equation is as follows:
xNH4 ++A(OH)x→xNH4OH+Ax+(ii) a Or, 2xNH4 ++A2Ox+x H2O→2xNH4OH+2Ax+
Wherein, A (OH) x/A2O x is alkaline substance, and ammonia gas is released from the ammonium hydroxide solution by using reaction heat and/or heating mode;
NH4OH→NH3↑+H2O。
the steps can generate salt-containing slurry while recovering ammonia gas, and the slurry can be respectively recycled for filtrate and solid slag after solid-liquid separation.
When the wastewater containing ammonium ions with different concentrations is treated, the concentration of the recovered ammonia gas is different, and the ammonia gas can be used for carbonization reaction when the concentration of the ammonia gas is more than or equal to 50%; similarly, the concentration of the recovered carbon dioxide gas from different sources is different, and the carbon dioxide gas can be used for the carbonization reaction when the concentration of the carbon dioxide gas is more than or equal to 50 percent. In addition, as shown in fig. 2, the carbon dioxide gas may use one or more of other metal carbonate precipitation gas, metal carbonate roasting kiln gas, oxalate roasting kiln gas and boiler flue gas, in addition to the carbon dioxide-containing waste gas generated in step S3; it may also be a commercial grade carbon dioxide gas. The industrial grade carbon dioxide gas is commercial carbon dioxide gas with purity of more than 99.8%, and can be prepared by heating limestone at high temperature to decompose to obtain carbon dioxide gas according to the equation
Figure BDA0000799189330000051
The step of recovering ammonia from the wastewater containing ammonium ions comprises the following steps: adding an alkaline substance into the wastewater containing ammonium ions to adjust the pH value to 3.0-6.0 to obtain an ammonium hydroxide solution; and (3) carrying out stripping enrichment on the ammonium hydroxide solution by using reaction heat and/or external heating to obtain ammonia gas. In order to prevent the wastewater containing ammonium ions from also containing heavy metal ions such as Fe, Al, Zn, Cu and the like, the pH value is controlled within the range of 3.0-6.0, and the ions can be precipitated and removed; then adding alkaline substance to convert the ammonium ion in the relatively pure waste water into ammonium hydroxide solution, and obtaining ammonia gas under the action of stripping enrichment of reaction heat and/or external heating generated by adding alkaline substance into the waste water.
In the above preparation method of the present invention, the metal salt solution may be applied to a single metal salt solution or a mixed solution of a plurality of metal salt solutions.
In the step S1, the metal salt solution, the ammonia gas, and the carbon dioxide gas may be mixed in the following manner: introducing ammonia gas and carbon dioxide gas into a metal salt solution; adding the three into the base solution in a three-strand parallel flow mode; thirdly, a tower type reaction kettle is adopted, the metal salt solution, ammonia gas and carbon dioxide gas are fed from different positions, and the gas phase and the liquid phase are mixed in a countercurrent mode. In either mixing mode, the gas flow rate and the flow rate of the metal salt solution are adjustable. If the second mode is adopted, ammonia gas and carbon dioxide gas can be firstly controlled to be introduced into the base solution to synthesize the composite precipitator, different flow rates of the ammonia gas and the carbon dioxide are controlled, the proportions of the synthesized composite precipitator are different, and the prepared precipitate particles have different compositions and structures.
The mixing process of step S1 can be selected according to the type and structure of the product to be prepared, and in a preferred embodiment of the present invention, the mass ratio of ammonia gas to carbon dioxide gas is preferably controlled to be 1.2:1 to 1: 4.
When ammonia gas and carbon dioxide gas are mixed, a mass flow meter can be adopted to regulate and control the prepared product by controlling the mass ratio of the ammonia gas and the carbon dioxide gasThe morphological structure of (1). The relative quality of the ammonia gas and the carbon dioxide gas is adjusted, so that the pH value in the reaction process is favorably regulated and controlled, and the composition, the granularity and the surface charge state of precipitated particles are influenced; on the other hand, carbonate or basic carbonate with different structures and compositions can be generated, so that the crystal form and the appearance of the oxide are regulated and controlled; on the other hand, a precursor composed of a core-shell structure or a multilayer structure can be generated, and the oxide powder material with a special pore channel structure can be prepared through pyrolysis. The metal carbonate and/or metal hydroxycarbonate products to be produced differ in the ammonia and carbon dioxide gas mass ratios. Moreover, for some metal ions, especially transition metal ions, there are more types of metal hydroxycarbonates, e.g. zirconium hydroxycarbonate, which can exist in several forms: zr2(OH)2CO2·nH2O、ZrO2CO2·nH2O、Zr(OH)2CO2·nH2O and ZrOCO3·nH2And O. In the continuous mixing process, the mass ratio of the ammonia gas to the carbon dioxide gas is controlled to be 1.2: 1-1: 4, so that a plurality of metal carbonates and/or metal alkali carbonates corresponding to most metal salt solutions can be prepared. Before the ammonia gas and the carbon dioxide gas are mixed, one of the gases can be introduced, and the pH of the system can be adjusted to the pH required by the precipitation of the metal carbonate and/or the metal basic carbonate.
The mixing process of the metal salt solution, the ammonia gas and the carbon dioxide gas can be continuous mixing or intermittent mixing. And intermittently mixing the metal salt solution, the ammonia gas and the carbon dioxide gas, wherein the ammonia gas and the carbon dioxide gas are intermittently introduced into the mixed system to be mixed at the same time, or the ammonia gas and the carbon dioxide gas are alternately introduced into the mixed system to be mixed.
When ammonia gas and carbon dioxide gas are intermittently introduced into the mixing system at the same time for mixing; because the preparation method of the metal oxide belongs to gas-liquid two-phase reaction, the precipitated ions generated in the reaction process exist in a gas phase, and the diffusion of the precipitated ions takes time; meanwhile, the intermittent introduction can also ensure that the precipitated particles generated firstly have enough time to nucleate and grow to a certain degree, so that the crystal seed effect is achieved, the crystallization is induced, the nucleation energy required by the subsequent precipitation is reduced, and when the gas is continuously introduced, the precipitation can be generated on the surface of the crystal particles generated firstly, thereby improving the crystallinity of the precipitated particles.
In the practical application process, particularly in the field of catalytic application, special requirements are often placed on the pore structure and the multilayer structure of the metal oxide, but at present, the preparation of the metal oxide with the two structures mostly adopts a template method, so that the production cost is high, the requirements on equipment are high, and a large amount of high-COD wastewater can be generated. And by alternately introducing ammonia gas and carbon dioxide gas into the mixed system, a metal oxide having a porous structure or a multilayer structure can be prepared. The ammonia gas and the carbon dioxide gas are alternately introduced, and the interval time is controlled, so that the precipitated particles have a multilayer structure of metal hydroxide, metal carbonate and/or metal basic carbonate. Further, during the roasting process, according to the difference of the decomposition temperature of the metal hydroxide, the metal carbonate and/or the metal basic carbonate and the CO released by the decomposition of the metal carbonate and/or the metal basic carbonate2The gas plays a pore-forming role, so that the metal oxide has a porous structure and/or a multilayer structure. For the mixed metal salt solution system, ammonia gas and carbon dioxide gas are alternately introduced according to the difference of pH values required by different metal ion precipitation, and the composite metal oxide with a porous structure and/or a multilayer structure can also be prepared.
In the above production method of the present invention, the pressure in the reaction system in step S1 is not particularly limited as long as the metal salt solution can be carbonized to form the metal carbonate and/or the metal hydroxycarbonate. The pressure intensity of the reaction system is increased, so that the carbonization reaction time is favorably shortened. Meanwhile, for ammonia gas or carbon dioxide gas with lower concentration, the pressure of the reaction system can be increased to promote the reaction to be rapidly carried out. Therefore, in order to further increase the reaction speed or shorten the carbonization time, in another preferred embodiment of the present invention, in the step S1, the mixed system is controlled to last for 0.5 to 4 hours under the conditions of the pressure of 0.1 to 0.95MPa and the temperature of 10 to 95 ℃. The reaction temperature has an influence on the size and surface charge state of the prepared precipitated particles, and the carbonization reaction temperature can be determined according to the properties of the metal oxide to be prepared. The low temperature is favorable for generating small-granularity precipitate particles, the high temperature promotes ion diffusion, and the generated precipitate particles have large granularity, uniform granularity distribution and good solid-liquid separation effect. Within the temperature range, the diversified requirements of forming various different particle sizes by various metal carbonates can be met. The reaction time is greatly influenced by the factors such as the reaction scale, the flow rate of ammonia gas and carbon dioxide gas, the pressure intensity and the like. The reaction scale is large, the gas flow is small, the pressure intensity is small, and the reaction time is long; the reaction time is short due to small scale, large gas flow and large pressure intensity; the gas flow and the pressure can be determined according to the reaction scale, so that the reaction time is controlled to be 0.5-4 hours, the full carbonization reaction is ensured, and meanwhile, the waste of gas raw materials and energy caused by too long reaction time is avoided.
The metal salt solution to which the above preparation method of the present invention is applicable includes, but is not limited to, any one of an alkali metal salt solution, an alkaline earth metal salt solution, a transition metal salt solution, a gallium salt solution, a germanium salt solution, a tin salt solution, and an antimony salt solution. More preferably, the alkali metal salt solution comprises a sodium salt solution; the alkaline earth metal solution comprises calcium salt solution or magnesium salt solution; the transition metal salt solution includes any one of a rare earth salt solution, a zirconium salt solution, a hafnium salt solution, a cobalt salt solution, a nickel salt solution, a copper salt solution, and a zinc salt solution. The salt solutions of different metals have wide industrial application range and high application value, the metal oxide with high purity, controllable granularity and morphology, good dispersibility and excellent physical properties can be prepared at low cost by using the preparation method, the preparation process flow is short, the ammonium is in closed circulation, the raw material cost is low, and the preparation method is low-carbon and environment-friendly.
In the salt solution of the metal species, the specific species of the salt solution is any one or more of a chloride solution, a nitrate solution, a sulfate solution, an acetate solution, and a perchlorate solution.
In the preparation method of the present invention, the carbon dioxide gas in step S1 is industrial-grade carbon dioxide gas or is recovered from waste gas containing carbon dioxide gas, and the waste gas containing carbon dioxide gas is one or more of carbon dioxide gas and/or metal carbonate precipitation gas, metal carbonate roasting kiln gas, oxalate roasting kiln gas and boiler flue gas obtained in step S3.
The carbon dioxide gas used in the invention can be gas generated in the processes as a raw material, and the carbon dioxide gas is obtained through compression, purification or other treatment steps, so that the process gas is reasonably utilized, low carbon and emission reduction are realized, and the environmental protection requirement is met; but also realizes the effective application of the carbon dioxide gas. From the perspective of effective recycling of raw material cost and energy consumption, the process provided by the invention becomes a high-efficiency and low-energy-consumption metal oxide preparation process really suitable for enterprises.
Similarly, the ammonia gas required in the preparation method is obtained by recycling the waste water containing the ammonium ions through the alkaline substance, the source of the waste water containing the ammonium ions can be various, the waste water containing the ammonium ions generated in the step S1 can be the waste water containing the ammonium ions generated in other industrial processes (including a metal extraction separation process and/or a carbonate precipitation process), the types and the contents of the impurity ions in the waste water are not limited, and the ammonia gas can be recycled by treating and recycling the ammonia gas through the recycling treatment step. Meanwhile, alkaline substances are used for adjusting the pH value, ammonia gas is extracted through reaction heat and/or external heating, the ammonia gas with heat is used for carbonization reaction, energy supply in the carbonization reaction process can be reduced, effective utilization of energy in the whole circulation step is achieved, and the preparation method is a low-energy-consumption and efficient metal oxide preparation process and is suitable for large-scale application of enterprises.
In the step of recycling and treating the wastewater containing the ammonium ions, the alkaline substance for adjusting the pH value of the wastewater mainly has the function of adjusting the pH value of a wastewater system containing the ammonium ions to generate ammonium hydroxide, and ammonia gas escapes from an ammonium hydroxide solution through reaction heat and/or external heating. Any basic substance capable of achieving the above object is suitable for use in the present invention. From the viewpoint of reasonable utilization of energy and cost, the alkaline substance may be one or more of calcium hydroxide, calcium oxide, magnesium hydroxide, light burned dolomite, sodium hydroxide and potassium hydroxide. Preferably, the alkaline substance is any one of calcium oxide and sodium hydroxide.
The alkaline substance is added into the wastewater containing ammonium ions, and the method has the following advantages: first, reaction heat is released, which facilitates the escape of ammonia gas and reduces energy consumption. In consideration of the production cost, the alkaline substance is preferably calcium oxide or sodium hydroxide, which are low in cost and emit a large amount of reaction heat. Secondly, the wastewater containing ammonium ions may contain impurity metal ions such as heavy metal impurity ions of Fe, Al, Zn, Cu and the like, and the impurity ions can be converted into precipitates by adding alkaline substances to adjust the pH value of the system and removed by solid-liquid separation; thirdly, the ammonia gas prepared by the method has higher purity than commercial ammonia water, ammonium bicarbonate and other precipitants, and can be directly used for carbonization reaction to obtain a high-purity metal oxide product; fourthly, the ammonia gas escapes through the reaction heat and/or external heating mode, and the ammonia gas has a certain temperature, so that the energy consumption in the carbonization reaction process can be reduced.
In the above step S3 of the present invention, the temperature at which the metal carbonate and/or the metal hydroxycarbonate is decomposed to oxide by calcination differs for different metal carbonates and/or metal hydroxycarbonates; meanwhile, according to different property requirements of the metal oxide to be prepared, under the condition of ensuring full decomposition into the oxide, the method can be realized by adjusting the roasting temperature, atmosphere (air atmosphere, oxygen atmosphere, reducing atmosphere, inert atmosphere and the like) and roasting time (0.5-12 hours). If the roasting gradual reduction rate of the metal oxide is required, the metal oxide can be fully decomposed into the metal oxide by increasing the roasting temperature and prolonging the roasting time, but the energy consumption is increased by too high roasting temperature and too long roasting time, so that the production cost is increased. For the variable-valence metal element, the firing atmosphere thereof may be adjusted, such as air atmosphere, oxygen atmosphere, reducing atmosphere. In the air atmosphere, the presence of oxygen oxidizes the metal to form a high-valence metal oxide.
In another preferred embodiment of the present invention, the step S3 includes: and roasting the metal carbonate and/or the metal basic carbonate at the high temperature of 450-1100 ℃ for 0.5-12 hours to obtain metal oxide and carbon dioxide gas. Controlling the temperature and time of calcination within the above ranges can achieve complete decomposition of almost all of the metal carbonate and/or metal hydroxycarbonate to metal oxide. In addition, carbon dioxide gas generated in the roasting process can be recycled and purified to be returned for carbonization reaction, so that the emission of greenhouse gas is reduced, and the environmental protection requirement is met; but also realizes the effective application of the carbon dioxide gas. The method has obvious advantages in terms of raw material cost, energy consumption and chemical raw material recycling, so that the method becomes a high-efficiency and low-energy-consumption metal oxide preparation method really applicable to enterprises.
The advantageous effects of the present invention will be further described with reference to specific examples.
The detection methods used in the following examples are as follows:
measuring the constant and trace elements of the product by using an inductively coupled plasma mass spectrometer, an inductively coupled plasma emission spectrometer and an F-type atomic absorption spectrophotometer of Beijing general analytical instruments, Inc.;
the granularity of the product is detected by a TopSizer Euromax laser granularity analyzer of Zhuhai Euromax Instrument Limited;
the surface morphology of the product is measured by a scanning electron microscope TM3000 from Hitachi, Japan.
The specific surface, the pore diameter and the pore volume data of the product are measured by adopting a Quadrasorb SI-KR/4MP automatic specific surface and pore diameter distribution tester of the Congta company of America.
Example 1
Preparing a cerium chloride solution with the concentration of 1.2mol/L (the absolute purity is 99.5 percent), adding the cerium chloride solution into a precipitation reactor, introducing ammonia gas into the precipitation reactor until the pH value of the system reaches 6-7, and then introducing ammonia gas and industrial-grade carbon dioxide gas (the concentration is 99.8 percent) into the precipitation reactor at the mass ratio of 1:1.3 of ammonia gas to carbon dioxide gas to perform carbonization reaction; in the carbonization reaction process, a reaction system is open and normal pressure, external heating is not needed, but ammonia gas participating in the reaction has certain heat, so that the temperature of the reaction system is about 45 ℃, the carbonization reaction lasts for 2.5 hours to obtain cerium carbonate slurry, cerium carbonate is obtained by filtering, washing and spin-drying, and filtered waste liquid is recovered after filtering, namely ammonium chloride wastewater; and (3) roasting the dried cerium carbonate at 700 ℃ for 2 hours to obtain cerium oxide powder, and recovering carbon dioxide gas generated by roasting in the roasting process. The cerium oxide powder was tested to have a purity of 99.8%.
Adding a proper amount of calcium oxide into the recovered ammonium chloride wastewater. And (3) controlling the reaction temperature to be 88-94 ℃ in the reaction process, continuously escaping and collecting ammonia gas, wherein the concentration of the ammonia gas is 98%, and circularly returning the ammonia gas for precipitating the cerium chloride solution.
Example 2
Preparing a cerium chloride solution with the concentration of 0.5mol/L, adding the cerium chloride solution into a precipitation reactor, introducing ammonia gas into the precipitation reactor until the pH value of the system reaches 6-7, and then introducing ammonia gas and industrial carbon dioxide gas (the concentration of the carbon dioxide is 99.8%) into the precipitation reactor at the mass ratio of the ammonia gas to the carbon dioxide gas of 1.2:1 to perform a carbonization reaction; in the carbonization reaction process, a reaction system is open and normal pressure, external heating is not needed, but the temperature of the reaction system is about 65 ℃ because ammonia gas participating in the reaction has certain heat, basic cerium carbonate slurry is obtained after the carbonization reaction lasts for 3 hours, basic cerium carbonate slurry is obtained by filtering, washing and spin-drying, and meanwhile, filtered waste liquid is recovered after filtering, namely ammonium chloride wastewater; and (3) roasting the dried cerium carbonate at 700 ℃ for 2 hours to obtain cerium oxide powder, and recovering carbon dioxide gas generated by roasting in the roasting process. The cerium oxide powder was found to have a particle size of 3.365 μm and a particle size distribution (D)90-D10)/(2D50) Is 0.98.
Adding a proper amount of calcium oxide into the waste water containing ammonium chloride. And (3) controlling the reaction temperature to be 68-72 ℃ in the reaction process, continuously escaping and collecting ammonia gas, wherein the concentration of the ammonia gas is 90%, and circularly returning the ammonia gas for precipitating the cerium chloride solution.
Example 3
Preparing a cerium chloride solution with the concentration of 0.5mol/L (the absolute purity is 99.5 percent), adding the cerium chloride solution into a precipitation reactor, introducing ammonia gas into the precipitation reactor until the pH value of the system reaches 4.5-5.5, and then introducing ammonia gas and industrial-grade carbon dioxide gas (the concentration of the carbon dioxide is 99.8 percent) into the precipitation reactor at the mass ratio of the ammonia gas to the carbon dioxide gas of 1:2.5 to perform carbonization reaction; in the carbonization reaction process, the reaction system is open and normal pressure, the temperature of the reaction system is maintained at about 95 ℃ by heating, cerium carbonate slurry is obtained after the carbonization reaction lasts for 2 hours, cerium carbonate is obtained by filtering, washing and spin-drying, and meanwhile, the filtered waste liquid is recovered after filtering, namely the ammonium chloride wastewater; and (3) roasting the dried cerium carbonate at 700 ℃ for 2 hours to obtain cerium oxide powder, and recovering carbon dioxide gas generated by roasting in the roasting process. Through SEM observation, as shown in FIG. 3, the cerium oxide powder has a primary particle size of 100-120nm, and a large number of pore channel structures exist between primary particles and between secondary particles formed by agglomeration of the primary particles, and the pore volume can reach 0.38cc/g, the average pore diameter is 17.89nm, and the absolute purity is 99.9%.
And adding a proper amount of calcium oxide into the waste water containing ammonium chloride, controlling the reaction temperature to be 65-75 ℃ in the reaction process, continuously escaping and collecting ammonia gas, and circularly returning the ammonia gas for precipitating the cerium chloride solution.
Example 4
Adding a proper amount of deionized water into a precipitation reactor, introducing ammonia gas into the precipitation reactor until the pH value of the system reaches 6-7, and then respectively adding a cerium chloride solution (with the concentration of 1mol/L), ammonia gas and carbon dioxide gas into the precipitation system, wherein the mass ratio of the ammonia gas to the carbon dioxide gas is 1.1: 1. In the carbonization reaction process, a reaction system is open and normal pressure, external heating is not needed, but the temperature of the reaction system is about 45 ℃ because ammonia gas participating in the reaction has certain heat, cerium carbonate slurry is obtained after the carbonization reaction lasts for 4 hours, cerium carbonate is obtained by filtering, washing and spin-drying, and meanwhile, the filtered waste liquid is recovered, namely ammonium chloride waste water; the cerium carbonate was calcined at 700 ℃ for 2 hours to obtain cerium oxide powder. By observing the morphology of the synthesized cerium carbonate powder, as shown in fig. 4, the cerium carbonate powder is in a clustered short rod shape, the length of the cerium carbonate powder is 600-800 nm, and the diameter of the cerium carbonate powder is about 300 nm. As shown in fig. 5, the calcined cerium oxide powder had relatively dispersed short rods.
And adding a proper amount of calcium oxide into the wastewater containing ammonium chloride, controlling the reaction temperature to be 88-94 ℃ in the reaction process, continuously escaping and collecting ammonia gas, and circularly returning the ammonia gas for precipitating the cerium chloride solution.
Example 5
Preparing a copper chloride solution with the concentration of 1.5mol/L, adding the copper chloride solution into a precipitation reaction kettle, introducing ammonia gas into the precipitation reaction kettle until the pH value of the system reaches 9-10, and then introducing ammonia gas and carbon dioxide gas into the precipitation reactor at the speed of 1.2:1 by mass of the ammonia gas and the carbon dioxide gas for carbonization reaction; in the carbonization reaction process, the reaction system is at normal pressure, the temperature of the reaction system is about 25 ℃, the carbonization reaction lasts for 3 hours to obtain basic copper carbonate slurry, the basic copper carbonate slurry is filtered, washed and dried to obtain basic copper carbonate, and meanwhile, the filtered waste liquid is recovered after the filtration, namely the ammonium chloride wastewater; and (3) roasting the dried basic copper carbonate at 400 ℃ for 5 hours to obtain copper oxide powder, and recovering carbon dioxide gas generated by roasting in the roasting process to be reused for copper chloride solution precipitation.
The copper oxide powder has a particle size of 1.782 μm and a particle size distribution (D)90-D10)/(2D50) 0.73, uniform particles and narrow particle size distribution. The SEM micro-morphology is spheroidal. The copper oxide powder can be used as a colorant for glass and porcelain, and as an organic synthesis catalyst.
And adding a proper amount of sodium hydroxide into the wastewater containing the ammonium chloride obtained in the process, controlling the reaction temperature to be 68-72 ℃ in the reaction process, continuously escaping and collecting ammonia gas, and circularly returning the ammonia gas for the precipitation of the copper chloride solution.
Example 6
Adding zinc nitrate with the concentration of 2.0mol/L into a precipitation reaction kettle, introducing ammonia gas into the precipitation reaction kettle until the pH value of the system reaches 6.0-6.5, and then introducing ammonia gas and carbon dioxide gas into the precipitation reactor at the mass ratio of 1:1 to perform carbonization reaction; in the carbonization reaction process, the reaction system is open and normal pressure, the temperature of the reaction system is about 10 ℃, after the carbonization reaction lasts for 2.5 hours, basic zinc carbonate slurry is obtained, basic zinc carbonate is obtained by filtering, washing and spin-drying, and meanwhile, filtered waste liquid is recovered after filtering, namely ammonium nitrate waste water; and (3) roasting the dried basic zinc carbonate at 400 ℃ for 5 hours to obtain zinc oxide powder, and recovering carbon dioxide gas generated by roasting in the roasting process to be reused for the precipitation of a zinc nitrate solution.
The zinc oxide powder has a particle size of 0.982 μm and a particle size distribution (D)90-D10)/(2D50) 0.57, useful as vulcanization activators and reinforcing agents for natural rubber, synthetic rubber and latex, and colorants.
The pH value of the waste water containing ammonium nitrate is adjusted by calcium oxide, solid-liquid separation is carried out when the pH value is 6.0, elements such as Fe, Al and heavy metal ions in the waste liquid are removed, and the removal rate of impurity ions is about 99.9%. And (2) continuously adding a proper amount of calcium oxide into the waste water containing ammonium nitrate, controlling the reaction temperature to be 65-75 ℃ in the reaction process, continuously escaping and collecting ammonia gas, wherein the concentration of the ammonia gas is 99%, and circularly returning the ammonia gas for the precipitation of the zinc nitrate solution.
Example 7
Preparing a zirconium oxychloride solution with the concentration of 1.5mol/L, adding the zirconium oxychloride solution into a precipitation reaction kettle, adjusting the pH value of a system in the precipitation reaction kettle to 2.0-3.0, and then introducing ammonia gas and carbon dioxide gas into the precipitation reactor at the mass ratio of 1:4 to perform a carbonization reaction; in the carbonization reaction process, the reaction system is open and normal pressure, the temperature of the reaction system is about 65 ℃, the carbonization reaction lasts for 4 hours to obtain basic zirconium carbonate slurry, the basic zirconium carbonate slurry is filtered, washed and dried to obtain basic zirconium carbonate, and meanwhile, the filtered waste liquid is recovered after the filtration, namely the ammonium chloride wastewater; and (3) roasting the dried basic zirconium carbonate at 1000 ℃ for 4 hours to obtain zirconium oxide powder, and recovering carbon dioxide gas generated by roasting in the roasting process to be reused for the precipitation of zirconium oxychloride solution.
The carbonization reaction yield is 99.85% through tests, the prepared zirconium oxide powder is in a cubic phase, the primary particle size is 100-150 nm, the particle dispersibility is good, as shown in figure 6, the SEM microscopic morphology is spherical, and the powder can be used as a raw material of zirconium ceramic.
And (2) adding a proper amount of sodium hydroxide into the wastewater containing the ammonium chloride generated in the process, controlling the reaction temperature to be between 90 and 95 ℃ in the reaction process, continuously escaping and collecting ammonia gas, wherein the concentration of the ammonia gas is 95 percent, and circularly returning the ammonia gas for the precipitation of the zirconium oxychloride solution.
Example 8
Preparing a cerium acetate solution with the concentration of 0.1mol/L, adding the cerium acetate solution into a precipitation reactor, adjusting the pH value of a system in the precipitation reactor to 5.5-6, and then introducing ammonia gas and industrial-grade carbon dioxide gas (the concentration is 99.8%) into the precipitation reactor at the mass ratio of the ammonia gas to the carbon dioxide gas of 1:2 to perform a carbonization reaction; controlling the pressure of a reaction system to be 0.5MPa in the carbonization reaction process, enabling the temperature of the reaction system to be about 70 ℃ through external heating, obtaining cerium carbonate slurry after the carbonization reaction lasts for 1h, filtering, washing and spin-drying to obtain cerium carbonate, recovering filtered waste liquid after filtering, namely waste water containing ammonium ions, and continuously recovering ammonia gas by adopting the steps; and (3) roasting the dried cerium carbonate at 1000 ℃ for 3 hours to obtain cerium oxide powder, and recovering carbon dioxide gas generated by roasting in the roasting process.
The cerium oxide powder was found to have a particle size of 3.721 μm and a particle size distribution (D)90-D10)/(2D50) 0.83, and the morphology was petaloid as observed by SEM (not shown).
And (3) adjusting the pH value of the wastewater containing ammonium ions generated in the precipitation process by using calcium oxide, and performing solid-liquid separation when the pH value is 4.0 to remove elements such as Fe, Al and heavy metal ions in the wastewater, wherein the removal rate of impurity ions is about 98.5%. And (2) continuously adding a proper amount of calcium oxide into the wastewater containing ammonium ions, introducing the calcium oxide into an ammonia evaporation concentration tower, ensuring the temperature at the top of the tower to be 86-93 ℃, continuously escaping ammonia, and circularly returning the ammonia for the precipitation of the cerium acetate solution.
Example 9
Preparing a cerium-zirconium mixed chloride solution with the concentration of 1.5mol/L, adding the solution into a precipitation reaction kettle, introducing ammonia gas into the precipitation reaction kettle until the pH value of the system reaches 7-8, and then introducing ammonia gas and carbon dioxide gas into the precipitation reactor at the speed of 1.1:1 of the mass ratio of the ammonia gas to the carbon dioxide gas to carry out carbonization reaction; controlling the pressure of a reaction system to be 0.95MPa in the carbonization reaction process, enabling the temperature of the reaction system to be about 50 ℃ through external heating, obtaining cerium carbonate slurry after the carbonization reaction lasts for 0.5h, filtering, washing and spin-drying to obtain a cerium-zirconium composite oxide precursor, recovering filtered waste liquid after filtering, namely ammonium chloride waste water, and continuously recovering ammonia gas by adopting the steps; and (3) roasting the dried cerium-zirconium composite oxide precursor at 700 ℃ for 3 hours to obtain cerium-zirconium composite oxide powder, and recovering carbon dioxide gas generated by roasting in the roasting process to be reused for precipitation of a cerium-zirconium mixed chloride solution.
The test shows that the yield of the carbonization reaction is 99.91 percent, and the specific surface of the prepared cerium-zirconium composite oxide powder reaches 137m2A particle size of 2.659 μm in a particle size distribution (D)90-D10)/(2D50) Is 0.76, and the SEM micro-morphology is similar to a sphere (not shown), thereby meeting the application requirements of the automobile exhaust catalytic promoter.
And adding a proper amount of calcium oxide into the wastewater containing ammonium chloride, introducing the calcium oxide into an ammonia evaporation concentration tower, ensuring the temperature of the tower top to be 86-93 ℃, continuously escaping ammonia, and circularly returning the ammonia for the precipitation of the cerium-zirconium mixed chloride solution.
Example 10
Preparing a cerium chloride solution with the concentration of 1.2mol/L (the absolute purity is 99 percent), starting feeding from an upper inlet of the tower type reaction kettle, and simultaneously introducing ammonia gas and carbon dioxide gas from a lower inlet of the tower type reaction kettle to carry out carbonization reaction in a countercurrent mode. Wherein the mass ratio of the ammonia gas to the carbon dioxide gas is 1: 1.3. In the carbonization reaction process, the pressure of a reaction system is 0.3MPa, the temperature of the reaction system is 18 ℃, the carbonization reaction lasts for 4 hours to obtain cerium carbonate slurry, the cerium carbonate slurry is filtered, washed and dried to obtain cerium carbonate, and meanwhile, the filtered waste liquid is recovered after the filtration, namely the ammonium chloride wastewater; and (3) roasting the dried cerium carbonate in a tunnel kiln at 1100 ℃ for 12 hours to obtain cerium oxide powder, and recovering carbon dioxide gas generated by roasting in the roasting process to be reused for the precipitation of a cerium chloride solution. The cerium oxide powder has a purity of 99.2% and a carbonization yield of 99.8%.
And adding calcium oxide into the wastewater containing ammonium chloride, adding a proper amount of calcium oxide, controlling the reaction temperature to be 88-94 ℃ in the reaction process, continuously escaping and collecting ammonia gas, wherein the concentration of the ammonia gas is 90%, and recycling the ammonia gas for precipitation of a cerium chloride solution.
Comparative example 1
Preparing a cerium chloride solution with the concentration of 1.2mol/L (the absolute purity is 99.5 percent), adding the cerium chloride solution into a precipitation reactor, adjusting the pH value of a system in the precipitation reactor to 6-7, and then adding ammonium bicarbonate into the cerium chloride solution for precipitation reaction; in the precipitation reaction process, the reaction system is open and normal pressure, the temperature of the reaction system is about 45 ℃, the cerium carbonate slurry is obtained after the precipitation reaction lasts for 2.5 hours, the cerium carbonate slurry is obtained by filtering, washing and drying, the dried cerium carbonate is roasted for 2 hours at 700 ℃, and cerium oxide powder is obtained. The test shows that the purity of the cerium oxide powder is 99.1%, the impurity Fe content in the powder is increased, and compared with the Fe content in the raw material, the impurity Fe content is increased by 237 ppm.
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:
(1) the metal oxide prepared by the method has high purity, controllable granularity and morphology, good dispersibility and excellent physical properties, and can meet the increasingly improved special physical property requirements of high-grade and new materials on the metal oxide. For example, the zirconium-based ceramic material has the requirements of large primary particle size for zirconia powder, high specific surface area and multiple pore channels for cerium-zirconium composite oxide by the cerium-zirconium co-catalyst material.
(2) The carbon dioxide gas in the preparation process of the metal oxide can be recycled, so that the recycling of greenhouse gas is realized, and the effects of low carbon and emission reduction are achieved.
(3) The ammonia-containing wastewater commonly existing in the industry is circularly applied to the carbonization and precipitation process, so that the ammonia nitrogen discharge is effectively reduced, and a thought is provided for the green circular development of the industry.
(4) The invention has the characteristics of simple process, closed cyclic utilization of chemical raw materials, low production cost and the like, and is suitable for industrial mass production.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (11)

1. A method for producing a metal oxide, comprising:
step S1, carrying out precipitation reaction on the metal salt solution in a precipitation reactor by using ammonia gas and carbon dioxide gas, wherein the reaction system is open at normal pressure in the carbonization reaction process, and the mass ratio of the ammonia gas and the carbon dioxide gas is controlled to ensure that the pH value of the mixed system is within the range of 2.0-10.0 to obtain slurry; the mixing process of the metal salt solution, the ammonia gas and the carbon dioxide gas is intermittent mixing, and specifically, the ammonia gas and the carbon dioxide gas are alternately introduced into a mixing system to be mixed;
step S2, performing solid-liquid separation on the slurry to obtain waste liquid containing ammonium ions and metal carbonate and/or metal basic carbonate; and
step S3, roasting the metal carbonate and/or the metal basic carbonate to obtain the metal oxide and waste gas containing carbon dioxide gas;
wherein the ammonia gas is obtained by adjusting the pH of the wastewater containing ammonium ions by alkaline substances and then carrying out steam stripping enrichment;
the carbon dioxide gas in the step S1 is recovered from a carbon dioxide-containing waste gas or is an industrial-grade carbon dioxide gas, and the carbon dioxide-containing waste gas is the carbon dioxide gas obtained in the step S3;
the wastewater containing ammonium ions is wastewater generated in an industrial production process, and the wastewater generated in the industrial production process comprises wastewater generated in a metal precipitation process or wastewater generated in a metal extraction separation process; wherein the wastewater generated in the metal precipitation process comprises the waste liquid containing ammonium ions obtained in step S2;
in the step S1, a crystal form regulator is added to control the growth rate of each crystal face so as to control the crystal form of the formed metal oxide, and the adding amount is not more than 5% of the weight of the obtained metal oxide.
2. The method of claim 1, wherein the metal salt solution is a single metal salt solution or a mixed solution of a plurality of metal salt solutions.
3. The method according to claim 1, wherein in the step S1, the mass ratio of the ammonia gas to the carbon dioxide gas is 1.2:1 to 1: 4.
4. The preparation method according to claim 1, wherein the ammonia gas is obtained by stripping and enriching the wastewater containing ammonium ions after the pH of the wastewater is adjusted by alkaline substances, and the method comprises the following steps:
adding the alkaline substance into the wastewater containing ammonium ions to adjust the pH value to 3.0-6.0 to obtain a solid-liquid mixture;
carrying out solid-liquid separation on the solid-liquid mixture to obtain a filtrate;
continuously adding the alkaline substance into the filtrate to obtain ammonia water; and carrying out stripping enrichment on the ammonia water to obtain the ammonia gas.
5. The preparation method according to any one of claims 1 to 3, wherein in the step S1, the pressure of the mixed system is controlled to be 0.1 to 0.95MPa, and the temperature is controlled to be 10 to 95 ℃ for 0.5 to 4 hours.
6. The production method according to any one of claims 1 to 3, wherein in the step S1, the metal salt solution includes any one of an alkali metal salt solution, an alkaline earth metal salt solution, a transition metal salt solution, a gallium salt solution, a germanium salt solution, a tin salt solution, and an antimony salt solution.
7. The method according to claim 6, wherein the alkali metal salt solution comprises a sodium salt solution; the alkaline earth metal salt solution comprises a calcium salt solution or a magnesium salt solution; the transition metal salt solution includes any one of a rare earth salt solution, a zirconium salt solution, a hafnium salt solution, a cobalt salt solution, a nickel salt solution, a copper salt solution, and a zinc salt solution.
8. The method according to claim 7, wherein the metal salt solution is any one or more of a chloride solution, a nitrate solution, a sulfate solution, an acetate solution, and a perchlorate solution.
9. The method according to any one of claims 1 to 3, wherein the alkaline substance is one or more of calcium hydroxide, calcium oxide, magnesium hydroxide, light burned dolomite, sodium hydroxide, and potassium hydroxide.
10. The method according to claim 9, wherein the alkaline substance is calcium oxide or sodium hydroxide.
11. The production method according to any one of claims 1 to 3, wherein the step S3 includes:
and roasting the metal carbonate and/or the metal basic carbonate at the high temperature of 400-1100 ℃ for 0.5-12 hours to obtain the metal oxide and the waste gas containing the carbon dioxide gas.
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