CN106276819A - A kind of method being catalyzed reduction selenium - Google Patents

Abstract

The invention discloses a method for catalytically reducing selenium. Ferric ions are used as a catalyst, and a reducing agent is added to a solution containing hexavalent selenium to react to reduce selenium into simple selenium. The invention realizes the goal of short process and direct reduction to simple selenium, and solves the technical problem in the prior art that it is difficult to reduce hexavalent selenium to simple selenium in one step by using a reducing agent. The present invention also realizes rapid and efficient reduction, and only needs 1-2 hours of reaction time to achieve a selenium reduction rate of not less than 98%, which obviously shortens the time for selenium reduction and improves the reduction rate. The reduction process of the present invention requires mild conditions, short reaction process and good effect, and the required reagents and equipment are all common hydrometallurgical industrial equipment and reagents, which is very easy to realize industrial production and application as a whole.

Description

A method for catalytic reduction of selenium

technical field

The invention relates to a method for catalytically reducing selenium, in particular to a method for catalytically reducing hexavalent selenium into elemental selenium.

Background technique

According to incomplete statistics, China's selenium consumption in 2013 was about 1,800 tons, more than 50% of global consumption, of which more than 1,500 tons were imported, and more than 300 tons were produced by domestic copper smelting enterprises. At present, 90% of selenium in China is produced from copper and lead anode slime. The main processes for producing selenium are: sulfated roasting and soda roasting. It is separated in the form of elemental or oxide, and then is collected and reduced to produce elemental selenium. However, during the oxidation separation process, selenium is easily peroxidized into hexavalent selenium compounds, and such high-valent selenium compounds seriously reduce the recovery rate of selenium.

Moreover, the problem of selenium resource recovery in selenium-containing urban minerals represented by toner cartridges is becoming increasingly serious. For such complex resources, smelting enterprises often use strong oxidation methods to separate selenium from raw materials, and the separated selenium mostly exists in the form of hexavalent selenium. The recovery of hexavalent selenium hinders the comprehensive utilization of selenium-containing complex urban mineral resources . At present, the recovery technologies of high-priced selenium mainly include electrowinning, ion exchange, reverse osmosis, photocatalytic reduction, concentrated hydrochloric acid cooking reduction, metal (such as aluminum, zinc, copper) replacement, etc. However, after ion exchange, reverse osmosis, etc. are used to separate and purify hexavalent selenium ions from other impurities, a further reduction process is still required. This type of reduction process mainly uses concentrated hydrochloric acid reduction, evaporation carbon reduction and other processes. Overall The selenium recovery process is long, complicated steps, high energy consumption, low production capacity and difficult for large-scale industrial application.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the problem of recovering high-priced selenium in the prior art and provide a simple, fast and efficient method for directly reducing hexavalent selenium to simple selenium, thereby reducing the waste of selenium resources and improving the recovery rate of selenium , to solve the problem of lack of selenium resources in my country.

In order to solve the problems of the technologies described above, the technical solution proposed by the present invention is:

The invention relates to a method for catalytically reducing selenium. Ferric ions are used as catalysts, and a reducing agent is added to a solution containing hexavalent selenium for reaction to reduce selenium into simple selenium. The specific operation method is to add ferric ions and reducing agent to the solution containing hexavalent selenium to react, and obtain selenium simple substance after solid-liquid separation.

The method for the above-mentioned catalytic reduction of selenium, preferably, the ferric ion is added in the form of soluble iron salt, and the soluble iron salt includes but not limited to ferric sulfate, ferric chloride; The added amount is more than 10% of the selenium ion concentration in the solution.

In the above method for catalytic reduction of selenium, preferably, the standard oxidation-reduction potential of the reducing agent is lower than the standard oxidation-reduction potential of hexavalent selenium converted into simple selenium. The addition amount of the reducing agent is more than 1.2 times of the theoretical amount for reducing all the selenium ions in the hexavalent selenium-containing solution to simple selenium.

In the above method for catalytic reduction of selenium, preferably, the reducing agent is selected from one or more of hydrazine hydrate, sulfur dioxide, sulfite and sodium borohydride.

The above method for catalytic reduction of selenium preferably further includes the step of adjusting the pH value of the hexavalent selenium-containing solution: adjusting the pH value of the hexavalent selenium-containing solution to be less than 1 by adding sulfuric acid or hydrochloric acid.

In the above method for catalytic reduction of selenium, preferably, the hexavalent selenium-containing solution is a selenic acid or selenate solution containing hexavalent selenium, including selenium containing hexavalent selenium produced in chemical or metallurgical scientific research or industrial production. solution.

In the above method for catalytic reduction of selenium, preferably, the reaction temperature is generally not higher than 100°C.

After a large amount of literature research and exploratory experimental research, the inventor found that ferric ions can be used as a catalyst for the reduction of hexavalent selenium ions, so that a series of reducing agents including sulfur dioxide can effectively reduce hexavalent selenium ions into simple selenium , overcoming the technical problem that reducing agents such as sulfur dioxide cannot reduce hexavalent selenium ions to simple selenium.

The present invention utilizes the catalytic effect of ferric ions to reduce the reaction activation energy of hexavalent selenium reduction. In the reduction process, the reducing agent first reacts with ferric ions to generate active ferrous ions, which are then converted into active ferrous ions. Hexavalent selenium ions are reduced to tetravalent selenite ions while being oxidized to ferric ions for restoration, and then the selenite ions are directly reduced to selenium by the reducing agent, thereby realizing the whole process of catalytic reduction.

Compared with the prior art, the present invention has the advantages of:

(1) The present invention realizes the goal of short process and direct reduction to simple selenium, and solves the technical problem that it is difficult to reduce hexavalent selenium to simple selenium in one step by using a reducing agent in the prior art.

(2) The present invention realizes fast and efficient reduction, only needs 1-2 hours of reaction time, can realize selenium reduction rate not lower than 98%, obviously shortens the time of selenium reduction, improves reduction rate.

(3) The reduction process of the present invention requires mild conditions, short reaction process and good effect, and the required reagents and equipment are all common hydrometallurgical industrial equipment and reagents, which is very easy to realize industrial production and application as a whole.

Description of drawings

Figure 1 is an X-ray diffraction detection diagram of the reduction product of Example 1 of the present invention.

Fig. 2 is a scanning electron microscope detection diagram of the reduction product of Example 1 of the present invention.

Fig. 3 is an X-ray diffraction detection diagram of the reduction product of Example 3 of the present invention.

detailed description

In order to facilitate the understanding of the present invention, the invention will be described more comprehensively and in detail below in conjunction with the accompanying drawings and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

Unless otherwise defined, all technical terms used hereinafter have the same meanings as commonly understood by those skilled in the art. The terminology used herein is only for the purpose of describing specific embodiments, and is not intended to limit the protection scope of the present invention.

Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

Example 1:

A kind of method of catalytic reduction selenium of the present invention, concrete steps are as follows:

(1) Sodium selenate (Na ₂ SeO ₄ ) was dissolved in ultrapure water to prepare a sodium selenate solution, so that the selenium content in the solution was 10 g/L, and then sulfuric acid was added to adjust the solution until the hydrogen ion concentration was 1 mol/L;

(2) Get the acidic sodium selenate solution prepared by 100mL step (1), add ferric sulfate solid and fully stir until ferric sulfate solid dissolves completely (the addition of ferric sulfate makes the iron ion concentration in the solution be 0.5g/L);

(3) Pass into the solution subsequently industrial-grade sulfur dioxide gas (gas flow rate is 1L/min), while using a water bath to control the temperature of the reaction system to be 60°C, react for 2 hours, and the solid product obtained after filtration is elemental selenium.

The remaining selenium content in the solution obtained after the detection step (3) is filtered, and the final selenium reduction rate is 99.95%.

Carry out X-ray diffraction detection (as shown in Figure 1) and scanning electron microscope detection (as shown in Figure 2) to the solid product that step (3) obtains; As can be seen from Figure 1, solid product is the black selenium simple substance of trigonal crystal form; By It can be seen from Figure 2 that the selenium element is an irregular particle with agglomeration phenomenon, and the particle size is different. The solid product obtained in step (3) is dissolved after being boiled with concentrated nitric acid, and the solution is detected by an inductively coupled plasma atomic emission spectrometer. After the solid product is dissolved, the inductively coupled plasma atomic emission spectrometer detection result shows that the purity of the selenium element is 99.75%.

Example 2:

A kind of method of catalytic reduction selenium of the present invention, concrete steps are as follows:

(1) Sodium selenate (Na ₂ SeO ₄ ) was dissolved in ultrapure water to prepare a sodium selenate solution, so that the selenium content in the solution was 10 g/L, and then hydrochloric acid was added to adjust the solution until the hydrogen ion concentration was 1 mol/L;

(2) Get the acidic sodium selenate solution prepared by 100mL step (1), add ferric sulfate solid and fully stir until ferric sulfate solid dissolves completely (the addition of ferric sulfate makes the iron ion concentration in the solution be 0.5g/L);

(3) Add 8 g of sodium borohydride to the solution, and simultaneously use a water bath to control the temperature of the reaction system to 50° C., react for 2 hours, and the solid product obtained after filtration is elemental selenium.

The residual selenium content in the solution obtained after the detection step (3) is filtered, and the final selenium reduction rate is 99.98%. The X-ray diffraction detection and scanning electron microscope detection of the reduction product are similar to Example 1, which is trigonal black selenium simple substance. The solid product is boiled with concentrated nitric acid and then dissolved, and the solution is detected by an inductively coupled plasma atomic emission spectrometer, and the result shows that the purity of the selenium element is 98.92%.

Example 3:

A kind of method of catalytic reduction selenium of the present invention, concrete steps are as follows:

(1) Sodium selenate (Na ₂ SeO ₄ ) was dissolved in ultrapure water to prepare a sodium selenate solution, so that the selenium content in the solution was 10 g/L, and then hydrochloric acid was added to adjust the solution until the hydrogen ion concentration was 1 mol/L;

(2) Get the acidic sodium selenate solution prepared by 100mL step (1), add ferric sulfate solid and fully stir until ferric sulfate solid dissolves completely (the addition of ferric sulfate makes the iron ion concentration in the solution be 0.5g/L);

(3) Add 8 g of sodium borohydride to the solution, and simultaneously use a water bath to control the temperature of the reaction system to 0° C., react for 2 hours, and the solid product obtained after filtration is elemental selenium.

The residual selenium content in the solution obtained after the detection step (3) is filtered, and the final selenium reduction rate is 99.96%. The X-ray diffraction pattern of the reduction product is shown in Figure 3, which shows that the reduction product is an amorphous red selenium simple substance, and the scanning electron microscope detection is similar to that of Example 1. The solid product is boiled with concentrated nitric acid and then dissolved, and the solution is detected by an inductively coupled plasma atomic emission spectrometer, and the result shows that the purity of selenium is 99.01%.

Example 4:

A kind of method of catalytic reduction selenium of the present invention, concrete steps are as follows:

(1) Choose 200mL pressurized oxidative acid leaching to process selenium tellurium waste material solution (contain 2.1g/L hexavalent selenate ion, the selenite ion of 5g/L through ion chromatography detection wherein), add sulfuric acid to adjust to the solution The hydrogen ion concentration is 2mol/L;

(2) fully stir after adding ferric sulfate solid in the solution after step (1) until ferric chloride solid dissolves completely (the add-on of ferric sulfate makes iron ion concentration in the solution be 1g/L);

(3) Add 20 g of solid sodium sulfite to the solution, and simultaneously use a water bath to control the temperature of the reaction system to 80° C., react for 2 hours, and the solid product obtained after filtration is elemental selenium.

The remaining selenium content in the solution obtained after the detection step (3) is filtered, and the final selenium reduction rate is 99.24%. The X-ray diffraction detection and scanning electron microscope detection of the reduction product are similar to Example 1, which is trigonal black selenium simple substance. The solid product was boiled with concentrated nitric acid and dissolved, and the solution was detected by an inductively coupled plasma atomic emission spectrometer, and the result showed that the purity of selenium was 91.23%.

Example 5:

A kind of method of catalytic reduction selenium of the present invention, concrete steps are as follows:

(1) Select 200mL of selenium-tellurium mixture acidic oxidation leaching solution (contains 5.2g/L hexavalent selenium ions and 18.9g/L tetravalent selenium ions through ion chromatography), add sodium hydroxide to adjust the concentration of hydrogen ions in the solution 3mol/L;

(2) fully stir after adding ferric sulfate solid in the solution after step (1) until ferric sulfate solid dissolves completely (the add-on of ferric sulfate makes iron ion concentration in the solution be 2g/L);

(3) Then pass into the solution industrial-grade sulfur dioxide (gas flow rate is 0.7L/min), while using a water bath to control the temperature of the reaction system to be 25 ° C, react for 2 hours, and the solid product obtained after filtration is elemental selenium.

The remaining selenium content in the solution obtained after the detection step (3) is filtered, and the final selenium reduction rate is 99.53%. The X-ray diffraction detection and scanning electron microscope detection of the reduction product are similar to Example 1, which is trigonal black selenium simple substance. The solid product was boiled with concentrated nitric acid and then dissolved. The solution was detected by an inductively coupled plasma atomic emission spectrometer, and the result showed that the purity of the selenium element was 96.26%.

Comparative example:

The difference between this comparative example and Example 5 is only that it does not contain the process of adding iron sulfate in step (2), and other process parameters are the same as in Example 5. In the final solution, the hexavalent selenium ion concentration is 5.1g/L, and the hexavalent selenium ion The reduction rate is only 2%.

From the comparison of the above examples and comparative examples, it can be seen that the method for catalytic reduction of selenium in the present invention realizes the efficient reduction of selenium, and the reduction rate of hexavalent selenium is not less than 98%, which is much higher than that of conventional methods.

Claims (7)

1. A method for catalytic reduction of selenium, characterized in that, using ferric ions as a catalyst, adding a reducing agent in a solution containing hexavalent selenium and reacting makes selenium reduction into selenium simple substance. 2. the method for catalytic reduction selenium as claimed in claim 1, is characterized in that, described ferric ion is added with the form of soluble iron salt, and described soluble iron salt is iron sulfate or ferric chloride, and described The added amount of ferric ions is more than 10% of the concentration of selenium ions in the solution. 3. The method for catalytic reduction of selenium according to claim 1, characterized in that, the standard redox potential of the reducing agent is lower than the standard redox potential of hexavalent selenium converted into simple selenium. 4. The method for catalytic reduction of selenium as claimed in claim 3, wherein the reducing agent is selected from one or more of hydrazine hydrate, sulfur dioxide, sulfite and sodium borohydride. 5. The method for catalytic reduction of selenium according to any one of claims 1 to 4, further comprising the step of adjusting the pH value of the solution containing hexavalent selenium: adjusting the solution containing hexavalent selenium by adding sulfuric acid or hydrochloric acid pH is less than 1. 6. The method for catalytic reduction of selenium according to any one of claims 1 to 4, characterized in that, the hexavalent selenium-containing solution is selenic acid or selenate solution containing hexavalent selenium, including chemical or metallurgical Solutions containing hexavalent selenium produced in scientific research or industrial production. 7. The method for catalytic reduction of selenium according to any one of claims 1 to 4, characterized in that the solution containing hexavalent selenium also contains tetravalent selenous acid or selenite compound.