A method for extracting indium from low-indium-containing zinc oxide powder

Abstract

The invention provides a method for extracting indium from low-indium-containing secondary zinc oxide powder, and relates to the technical field of extracting indium from secondary zinc oxide powder. The method comprises four steps: step 1, pretreatment of the secondary zinc oxide powder; step 2, one-stage low-acid leaching treatment; step 3, two-stage high-acid leaching treatment; and step 4, mixed extraction. The invention provides a method for pretreating the low-indium-containing secondary zinc oxide powder on the basis of traditional two-stage acid leaching, and uses alkali washing and acid washing to remove pollutants and most of fluorine and chlorine on the surface of the low-indium-containing secondary zinc oxide powder to improve the efficiency of the subsequent leaching process. The method further uses microwave roasting treatment to promote the release of indium in the secondary zinc oxide powder and improve the subsequent leaching rate of indium. Furthermore, in the process of one-stage low-acid leaching, ultrasonic technology is introduced, and the cavitation effect of ultrasonic wave is used to destroy the adsorption layer on the surface of particles, increase the collision chance between particles, and thus improve the leaching rate of indium.

Description

Technical Field

[0001] The invention relates to the technical field of extracting indium from secondary zinc oxide powder, and in particular to a method for extracting indium from secondary zinc oxide powder with low indium content. Background Art

[0002] Indium is a metal element with the symbol In and the atomic number 49. It is located in the fifth period IIIA group of the periodic table. Its single substance is a silvery white metal with a slightly light blue color. It is very soft and can be scratched with a fingernail. It has strong plasticity and ductility and can be pressed into sheets. Metal indium is mainly used as a raw material for making low-melting alloys, bearing alloys, semiconductors, electric light sources, etc.

[0003] Low indium secondary zinc oxide powder refers to the secondary zinc oxide powder with relatively low indium content in zinc smelting industrial waste slag. Secondary zinc oxide is one of the main indium-rich waste slags in zinc smelting industrial waste slag. Its main components include secondary zinc oxide (Zn2O) and zinc oxide (ZnO), and also contain metal elements such as zinc, indium, arsenic, antimony, tin, silver, lead, cadmium, and bismuth. Due to the toxicity of elements such as lead, arsenic, and cadmium, their presence not only poses a potential threat to the environment, but also requires special attention during the treatment process to prevent pollution.

[0004] The raw material secondary zinc oxide powder used in the existing zinc smelting process of enterprises contains valuable metals such as rare metal In, however, the indium content is relatively low. Accordingly, the valuable metal indium in the low-indium secondary zinc oxide powder has the problem of low recovery or difficulty in recovery, and the recovery rate of indium mainly depends on the leaching process. In order to improve the leaching rate of indium in zinc oxide dust, conventional acid leaching processes often use methods such as increasing temperature, increasing leaching agent concentration, reducing mineral particle size, strengthening stirring, and extending leaching time. Therefore, the present invention proposes a method for extracting indium from low-indium secondary zinc oxide powder to solve the problems existing in the prior art. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a method for extracting indium from low-indium zinc oxide powder, which has the advantages of reducing the indium extraction effect and can solve the problems existing in the prior art.

[0006] To achieve the purpose of the present invention, the present invention is implemented by the following technical scheme: a method for extracting indium from low-indium-containing secondary zinc oxide powder, comprising the following steps:

[0007] Step 1: Pretreatment of zinc oxide powder

[0008] The prepared secondary zinc oxide powder is pretreated in sequence by alkali washing and acid washing, and then dried. After drying, the powder is crushed by a crusher to obtain secondary zinc oxide powder with uniform particle size, and then subjected to microwave roasting treatment;

[0009] Step 2: One-stage low-acid leaching treatment

[0010] Preparing a leaching solution: placing the pretreated zinc oxide powder in step 1 and the leaching solution in a mixing container for mixing to obtain a first mixed solution, then heating the temperature to 90° C. and maintaining the temperature for 15 to 20 minutes, placing the first mixed solution in an ultrasonic reactor for ultrasonic reaction for 30 to 50 minutes, and performing solid-liquid separation by filtering after the reaction to obtain a first acid leaching solution and a first leaching residue;

[0011] Step 3: Second stage high acid leaching treatment

[0012] Preparing a second-stage leaching solution: putting the first-stage leaching residue obtained in step 2 and the second-stage leaching solution into a mixing container for mixing, then heating to 90° C., performing a second-stage leaching, the leaching time being 50 to 80 minutes, and obtaining a second-stage acid leaching solution and a second-stage leaching residue;

[0013] Step 4: Mixed extraction

[0014] The second-stage pickling solution in step three and the first-stage pickling solution in step one are mixed to obtain a mixed pickling solution, which is then placed in an extraction container, and a neutralizing agent is added to neutralize the solution to obtain a neutralized solution and indium precipitated slag, thereby completing indium extraction.

[0015] A further improvement is that in the step 1, the specific method of alkali washing is: prepare an alkali washing solvent, add the alkali washing solvent to a mixing container, then add the secondary zinc oxide powder to the mixing container, stir, and after alkali washing for 40 to 60 minutes, separate the solid and liquid by filtering to obtain the first unreacted secondary zinc oxide powder, which is then washed with water.

[0016] A further improvement is that in the step 1, the specific method of pickling is: prepare a pickling solvent, add the pickling solvent to a mixing container, then add the secondary zinc oxide powder that has been pretreated by alkali washing into the mixing container, stir, pickle for 40 to 60 minutes, separate the solid and liquid by filtering to obtain a second unreacted secondary zinc oxide powder, and then wash with water.

[0017] A further improvement is that in step one, the specific method of microwave roasting treatment is: setting the parameters of the microwave roasting equipment, then placing the secondary zinc oxide powder after alkali washing and acid washing into the microwave roasting equipment, starting the microwave roasting equipment for processing, the processing time is 20 to 40 minutes, and naturally cooling after processing.

[0018] A further improvement is that in the step 2, the leaching solution is low-acid sulfuric acid, the concentration of the low-acid sulfuric acid is 15-20wt%, and the ratio of the leaching solution to the secondary zinc oxide powder is 5-7:1.

[0019] A further improvement is that in step 2, the working parameters of the ultrasonic reactor are: the ultrasonic frequency is 20-40 khz, and the reaction temperature is room temperature.

[0020] A further improvement is that in step three, the second stage leaching solution is high-acid sulfuric acid, and the concentration of high-acid sulfuric acid is 30-45wt%.

[0021] A further improvement is that in step 4, the neutralizing agent is calcium carbonate, and during the neutralization process, the pH value of the mixed pickling solution is set to 4.0-5.5.

[0022] The beneficial effects of the present invention are as follows: a method for extracting indium from low-indium-containing secondary zinc oxide powder provided by the present invention is provided with a method for pretreating the low-indium-containing secondary zinc oxide powder on the basis of traditional two-stage acid leaching, and the pollutants and most of the fluorine and chlorine on the surface of the low-indium-containing secondary zinc oxide powder are removed by alkali washing and acid washing to improve the efficiency of the subsequent leaching process, and then the release of indium in the secondary zinc oxide powder is promoted by microwave roasting treatment, thereby improving the subsequent indium leaching rate, and further, in the process of one-stage low-acid leaching, ultrasonic technology is introduced, and the cavitation effect of ultrasonic wave is utilized, which can destroy the adsorption layer on the surface of the particles, increase the collision chance between particles, and thus improve the leaching rate of indium. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the steps of the present invention. DETAILED DESCRIPTION

[0024] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The examples are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0025] In the following examples, all materials are purchased from the market, wherein the alkaline washing solvent is a mixed solution of sodium hydroxide and water, wherein the concentration of sodium hydroxide in the alkaline washing solvent is 0.4wt%, the acid washing solvent is dilute sulfuric acid with a mass fraction of 20%, and the mixing container has stirring and heating functions.

[0026] Unless otherwise specified, room temperature refers to 25±2℃.

[0027] Embodiment 1

[0028] according to Figure 1 As shown, this embodiment proposes a method for extracting indium from low-indium-containing zinc oxide powder, comprising the following steps:

[0029] Step 1: Pretreatment of zinc oxide powder

[0030] For low indium-containing secondary zinc oxide powder, in order to improve the extraction rate of indium, a variety of pretreatment methods are used to pretreat the secondary zinc oxide powder to avoid the influence of unnecessary components, thereby providing a guarantee for the subsequent indium extraction rate. Specifically, the secondary zinc oxide powder is treated by alkali washing, which is: prepare an alkali washing solvent, and add the alkali washing solvent to a mixing container, and then add the secondary zinc oxide powder to the mixing container, wherein the ratio of the secondary zinc oxide powder to the alkali washing solvent is 1:8, and stir, and the temperature in the mixing container needs to be raised to 60°C, and the stirring speed is 80rpm / min. After 60 minutes of alkali washing, solid-liquid separation is performed by filtering to obtain the first unreacted secondary zinc oxide powder, which is then washed with water. After 30 minutes of water washing, it is dried. The purpose of alkali washing is to remove fluorine and chlorine contained in the secondary zinc oxide powder to improve the efficiency of the subsequent leaching process, and then acid washing is performed. The acid washing method is similar to the alkali washing method, which is: prepare an acid washing solvent, and add the acid washing solvent to the mixing container, and then add the secondary zinc oxide powder that has been pretreated with alkali washing. Add the secondary zinc oxide powder and the pickling solvent in a ratio of 1:10 (mL:g) into a mixing container, stir, and heat the mixing container to 60°C, with a stirring speed of 80 rpm / min. After pickling for 60 minutes, perform solid-liquid separation by filtering to obtain a second unreacted secondary zinc oxide powder, and then wash it with water. After washing with water for 30 minutes, dry it. The purpose of pickling is to remove the oxide layer and other impurities on the surface and improve the leaching rate of indium. After conventional pretreatment, introduce microwave roasting treatment, the purpose of which is to change the physical structure of the secondary zinc oxide powder and make it more loose and porous, thereby promoting the release of indium in the secondary zinc oxide powder and improving the leaching rate of indium. Specifically, set the parameters of the microwave roasting equipment, and the parameters are: set the temperature to 550°C, then put the secondary zinc oxide powder after alkali washing and pickling treatment into the microwave roasting equipment, start the microwave roasting equipment for processing, the processing time is 40 minutes, and naturally cool it after processing. After cooling, the incompletely reacted secondary zinc oxide powder is obtained;

[0031] Step 2: One-stage low-acid leaching treatment

[0032] Prepare a leaching solution, the leaching solution is low-acid sulfuric acid, the low-acid sulfuric acid concentration is 20wt%, the ratio of the leaching solution to the secondary zinc oxide powder is 7:1 (mL:g), put the secondary zinc oxide powder pretreated in step 1 and the leaching solution into a mixing container for mixing, ensure that the powder is completely wetted, and obtain a first mixed solution after mixing, the purpose of which is to use a lower concentration of acid solution for leaching to extract useful components in the metal mineral, and then put the first mixed solution into an ultrasonic reactor for ultrasonic reaction. The working parameters of the ultrasonic reactor are: ultrasonic frequency is 20khz, reaction temperature is room temperature, and reaction time is 50min. In the process of a leaching, ultrasonic waves are introduced, and the cavitation effect of ultrasonic waves is used to destroy the adsorption layer on the surface of the particles, increase the collision chance between particles, and thus improve the leaching rate of indium. After the end, solid-liquid separation is performed by filtering to obtain an indium-containing solution.

[0033] Step 3: Second stage high acid leaching treatment

[0034] Prepare a second-stage leaching solution, the second-stage leaching solution is high-acid sulfuric acid, the high-acid sulfuric acid concentration is 30wt%, put the first-stage leaching residue and the second-stage leaching solution obtained in step 2 into a mixing container for mixing, then heat the mixing container to 90° C., perform second-stage leaching, the leaching time is 80min, during the leaching process, start stirring in the mixing container, the stirring speed is 90rpm / min, and obtain a second-stage pickling solution and a second-stage leaching residue;

[0035] Step 4: Mixed extraction

[0036] The two-stage pickling solution in step three and the one-stage pickling solution in step one are mixed to obtain a mixed pickling solution, which is then placed in an extraction container, and a neutralizer is added for neutralization to obtain a neutralized solution and indium precipitate slag to complete indium extraction, wherein the neutralizer is calcium carbonate, and during the neutralization process, the pH value of the mixed pickling solution is set to 4.0.

[0037] Embodiment 2

[0038] according to Figure 1 As shown, this embodiment proposes a method for extracting indium from low-indium-containing zinc oxide powder, comprising the following steps:

[0039] Step 1: Pretreatment of zinc oxide powder

[0040] For low indium-containing secondary zinc oxide powder, in order to improve the extraction rate of indium, a variety of pretreatment methods are used to pretreat the secondary zinc oxide powder to avoid the influence of unnecessary components, thereby providing a guarantee for the subsequent indium extraction rate. Specifically, the secondary zinc oxide powder is treated by alkali washing, which is: preparing an alkali washing solvent, and adding the alkali washing solvent to a mixing container, and then adding the secondary zinc oxide powder to the mixing container, wherein the ratio of the secondary zinc oxide powder to the alkali washing solvent is 1:8 (mL:g), stirring, and the mixing container needs to be heated to 60°C, the stirring speed is 80rpm / min, after alkali washing for 50min, solid-liquid separation is performed by filtering to obtain the first unreacted secondary zinc oxide powder, which is then washed with water, and after washing with water for 30min, it is dried. The purpose of alkali washing is to remove fluorine and chlorine contained in the secondary zinc oxide powder to improve the efficiency of the subsequent leaching process, and then acid washing is performed. The acid washing method is similar to that of alkali washing, which is: preparing an acid washing solvent, and adding the acid washing solvent to a mixing container, and then adding the secondary zinc oxide powder pretreated with alkali washing to the mixing container. Add zinc oxide powder into a mixing container, the ratio of secondary zinc oxide powder to pickling solvent is 1:10 (mL:g), stir, and heat the mixing container to 60°C, the stirring speed is 80rpm / min, after pickling for 50min, separate the solid and liquid by filtering to obtain the second unreacted secondary zinc oxide powder, then wash with water, wash with water for 30min, and then dry. The purpose of pickling is to remove the oxide layer and other impurities on the surface and improve the leaching rate of indium. After conventional pretreatment, microwave roasting treatment is introduced to change the physical structure of the secondary zinc oxide powder to make it more loose and porous, thereby promoting the release of indium in the secondary zinc oxide powder and improving the leaching rate of indium. Specifically, the parameters of the microwave roasting equipment are set, and the parameters are: the setting temperature is: 450°C, and then the secondary zinc oxide powder after alkali washing and pickling treatment is placed in the microwave roasting equipment, and the microwave roasting equipment is started for processing. The processing time is 50min, and it is naturally cooled after processing. After cooling, the incompletely reacted secondary zinc oxide powder is obtained;

[0041] Step 2: One-stage low-acid leaching treatment

[0042] Prepare a leaching solution, the leaching solution is low-acid sulfuric acid, the low-acid sulfuric acid concentration is 15wt%, the ratio of the leaching solution to the secondary zinc oxide powder is 5:1 (mL:g), put the secondary zinc oxide powder pretreated in step 1 and the leaching solution into a mixing container for mixing, ensure that the powder is completely wetted, and obtain a first mixed solution after mixing, the purpose of which is to use a lower concentration of acid solution for leaching to extract useful components in the metal mineral, and then put the first mixed solution into an ultrasonic reactor for ultrasonic reaction. The working parameters of the ultrasonic reactor are: ultrasonic frequency of 40khz, reaction temperature under room temperature, reaction time of 30min, during a leaching process, introduce ultrasonic waves, and use the cavitation effect of ultrasonic waves to destroy the adsorption layer on the surface of the particles, increase the collision chance between particles, and thus improve the leaching rate of indium. After the end, solid-liquid separation is performed by filtering to obtain an indium-containing solution;

[0043] Step 3: Second stage high acid leaching treatment

[0044] Prepare a second-stage leaching solution, the second-stage leaching solution is high-acid sulfuric acid, the high-acid sulfuric acid concentration is 45wt%, put the first-stage leaching residue and the second-stage leaching solution obtained in step 2 into a mixing container for mixing, the ratio is 1:1, then the temperature in the mixing container is raised to 90° C., and the second-stage leaching is performed for 50 minutes. During the leaching process, stirring is started in the mixing container, and the stirring speed is 90rpm / min to obtain a second-stage pickling solution and a second-stage leaching residue;

[0045] Step 4: Mixed extraction

[0046] The two-stage pickling solution in step three and the one-stage pickling solution in step one are mixed to obtain a mixed pickling solution, which is then placed in an extraction container, and a neutralizer is added for neutralization to obtain a neutralized solution and indium precipitate slag to complete indium extraction, wherein the neutralizer is calcium carbonate, and during the neutralization process, the pH value of the mixed pickling solution is set to 5.5.

[0047] In combination with Example 1 and Example 2, a method for pretreating the low-indium-containing secondary zinc oxide powder is set on the basis of the traditional two-stage acid leaching, and the pollutants and most of the fluorine and chlorine on the surface of the low-indium-containing secondary zinc oxide powder are removed by alkali washing and acid washing to improve the efficiency of the subsequent leaching process. The release of indium in the secondary zinc oxide powder can be promoted by microwave roasting treatment, and the subsequent indium leaching rate can be improved. Furthermore, in the process of a low-acid leaching, ultrasonic technology is introduced, and the cavitation effect of ultrasonic waves is used to destroy the adsorption layer on the surface of the particles, increase the collision chance between particles, and thus improve the leaching rate (i.e., recovery rate) of indium. The calculation formula is:

[0048] Indium recovery rate = (actual amount of indium recovered / theoretical amount of indium recovered) × 100%.

[0049] Among them, the indium amount corresponds to the indium content. Before starting the indium extraction process, the indium content in the raw material (such as secondary zinc oxide powder) is determined by measuring the indium content in the raw material (such as secondary zinc oxide powder). After the indium extraction process is completed, the same chemical analysis is performed on the indium precipitation slag to determine the remaining indium content therein. Therefore, based on the indium content in the raw material and the total amount of raw materials processed, the total amount of indium that should be recovered theoretically is calculated, and based on the indium content in the indium precipitation slag and the total amount of indium precipitation slag, the amount of indium actually recovered is calculated.

[0050] Furthermore, a control group was set up, in which the indium was extracted by the traditional one-stage low-acid leaching and two-stage high-acid leaching method, that is, the low-indium zinc oxide powder was crushed and dried, and then subjected to one-stage low-acid leaching and two-stage high-acid leaching. The recovery rates are compared as shown in the following table:

[0051] Embodiment 1 Embodiment 2 Control group Recovery rate (%) 77.6 76.2 65.2

[0052] As shown in the above table, the present invention can improve the recovery rate of indium in low-indium-containing secondary zinc oxide powder.

[0053] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the framework and scope of application of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for extracting indium from low-indium zinc oxide powder, characterized in that: The following steps are involved: Step 1: Pretreatment of zinc oxide powder The prepared secondary zinc oxide powder is pretreated in sequence by alkali washing and acid washing, and then dried. After drying, the powder is crushed by a crusher to obtain secondary zinc oxide powder with uniform particle size, and then subjected to microwave roasting treatment; Step 2: One-stage low-acid leaching treatment Preparing a leaching solution: putting the pretreated zinc oxide powder and the leaching solution in step 1 into a mixing container for mixing to obtain a first mixed solution, then heating the temperature to 90° C. and maintaining the temperature for 15 to 20 minutes, putting the first mixed solution into an ultrasonic reactor for ultrasonic reaction for 30 to 50 minutes, and then filtering to separate the solid and liquid to obtain a first acid leaching solution and a first leaching residue; Step 3: Second stage high acid leaching treatment Preparing a second-stage leaching solution: putting the first-stage leaching residue obtained in step 2 and the second-stage leaching solution into a mixing container for mixing, then heating to 90° C., performing a second-stage leaching, the leaching time being 50 to 80 minutes, and obtaining a second-stage acid leaching solution and a second-stage leaching residue; Step 4: Mixed extraction The second-stage pickling solution in step three and the first-stage pickling solution in step one are mixed to obtain a mixed pickling solution, which is then placed in an extraction container, and a neutralizing agent is added to neutralize the solution to obtain a neutralized solution and indium precipitated slag, thereby completing indium extraction.

2. The method for extracting indium from low-indium zinc oxide powder according to claim 1, characterized in that: In the step 1, the specific method of alkali washing is: prepare an alkali washing solvent, add the alkali washing solvent into a mixing container, then add the secondary zinc oxide powder into the mixing container, stir, and after alkali washing for 40 to 60 minutes, separate the solid and liquid by filtering to obtain the first unreacted secondary zinc oxide powder, which is then washed with water.

3. The method for extracting indium from low-indium zinc oxide powder according to claim 1, characterized in that: In the step 1, the specific method of pickling is: prepare a pickling solvent, add the pickling solvent to a mixing container, then add the secondary zinc oxide powder that has been pretreated by alkali washing into the mixing container, stir, pickle for 40 to 60 minutes, separate the solid and liquid by filtering to obtain a second unreacted secondary zinc oxide powder, and then wash with water.

4. The method for extracting indium from low-indium secondary zinc oxide powder according to claim 1, characterized in that: In the step 1, the specific method of microwave roasting treatment is: setting the parameters of the microwave roasting equipment, then putting the secondary zinc oxide powder after alkali washing and acid washing into the microwave roasting equipment, starting the microwave roasting equipment for processing, the processing time is 20 to 40 minutes, and naturally cooling after processing.

5. The method for extracting indium from low-indium secondary zinc oxide powder according to claim 1, characterized in that: In the step 2, the leaching solution is low-acid sulfuric acid, the concentration of the low-acid sulfuric acid is 15-20wt%, and the ratio of the leaching solution to the secondary zinc oxide powder is 5-7mL:1g.

6. The method for extracting indium from low-indium secondary zinc oxide powder according to claim 1, characterized in that: In the step 2, the working parameters of the ultrasonic reactor are: the ultrasonic frequency is 20-40 khz, and the reaction temperature is at room temperature.

7. The method for extracting indium from low-indium secondary zinc oxide powder according to claim 1, characterized in that: In the step 3, the second stage leaching solution is high-acid sulfuric acid, and the concentration of high-acid sulfuric acid is 30-45wt%.

8. The method for extracting indium from low-indium secondary zinc oxide powder according to claim 1, characterized in that: In step 4, the neutralizing agent is calcium carbonate, and during the neutralization process, the pH value of the mixed pickling solution is set to 4.0-5.5.

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