阅读说明：本技术 一种把六价硒还原为四价硒的方法 (Method for reducing hexavalent selenium into tetravalent selenium ) 是由 梁鉴华 王波 陈应红 刘威 陈秋旭 梅占强 叶道明 于 2021-09-08 设计创作，主要内容包括：本发明提供了一种把六价硒还原为四价硒的方法,涉及化学品回收技术领域。本发明提供的把六价硒还原为四价硒的方法,包括以下步骤：将六价硒化合物溶于水中形成六价硒溶液,将六价硒溶液加热至70-90℃；往六价硒溶液中加入盐酸,搅拌,反应至溶液电位值为900-960mv时,停止反应。本发明通过利用盐酸的还原性使溶液体系达到硒的还原电位,使难以被常规还原剂(如亚硫酸钠)还原为单质的六价硒还原为易于被还原为单质的四价硒,从而使硒能有效回收为单质。(The invention provides a method for reducing hexavalent selenium into tetravalent selenium, and relates to the technical field of chemical recovery. The method for reducing hexavalent selenium into tetravalent selenium provided by the invention comprises the following steps: dissolving a hexavalent selenium compound in water to form a hexavalent selenium solution, and heating the hexavalent selenium solution to 70-90 ℃; adding hydrochloric acid into the hexavalent selenium solution, stirring, and stopping the reaction until the potential value of the solution is 900-960 mv. The invention utilizes the reducibility of the hydrochloric acid to ensure that the solution system reaches the reduction potential of the selenium, so that the hexavalent selenium which is difficult to be reduced into simple substance by the conventional reducing agent (such as sodium sulfite) is reduced into the tetravalent selenium which is easy to be reduced into the simple substance, thereby effectively recycling the selenium into the simple substance.)

1. A method of reducing hexavalent selenium to tetravalent selenium, comprising the steps of:

(1) dissolving a hexavalent selenium compound in water to form a hexavalent selenium solution, and heating the hexavalent selenium solution to 70-90 ℃;

(2) adding hydrochloric acid into the hexavalent selenium solution, stirring, and stopping the reaction until the potential value of the solution is 900-960 mv.

2. The method of reducing hexavalent selenium to tetravalent selenium according to claim 1, wherein said step (2) of adding hydrochloric acid to the hexavalent selenium solution is performed by stopping the addition of hydrochloric acid immediately when the solution potential is 970-1100 mv.

3. The method of reducing hexavalent selenium to tetravalent selenium according to claim 2, wherein said step (2) of adding hydrochloric acid to the hexavalent selenium solution stops the addition of hydrochloric acid immediately when the solution potential is 1100mv, stirring, and stopping the reaction until the solution potential is 960 mv.

4. The method of reducing hexavalent selenium to tetravalent selenium according to claim 2, wherein said step (2) of adding hydrochloric acid to the hexavalent selenium solution stops the addition of hydrochloric acid immediately when the solution potential is 970mv, stirring, and stopping the reaction until the solution potential reaches 900 mv.

5. The method of reducing hexavalent selenium to tetravalent selenium according to claim 2, wherein said step (2) of adding hydrochloric acid to the hexavalent selenium solution stops the addition of hydrochloric acid immediately when the solution potential is 1000mv, stirring, and stopping the reaction until the solution potential reaches 930 mv.

6. The process for reducing hexavalent selenium to tetravalent selenium of claim 1, wherein said hexavalent selenium compound of step (1) is a selenate compound.

7. The method of reducing hexavalent selenium to tetravalent selenium of claim 6, wherein said selenate compound includes at least one of sodium selenate, potassium selenate, barium selenate.

8. The method of reducing hexavalent selenium to tetravalent selenium of claim 7, wherein said selenate compound is sodium selenate.

Technical Field

The invention relates to the technical field of chemical recovery, in particular to a method for reducing hexavalent selenium into tetravalent selenium.

Background

Selenium is a rare metal and is a raw material for producing selenium compounds, and the selenium compounds are widely used as glass decolorants, colorants, feed additives and the like. In addition, selenium also has important application in the fields of electronics, solar energy and the like, and has high value. In the production and recovery treatment processes of selenium, an oxidant is often required to be added, and after selenium in a solution is oxidized into hexavalent selenium, the solution is difficult to be reduced and precipitated in the subsequent reduction process, so that the hexavalent selenium is reduced into tetravalent selenium which is easy to be reduced by a conventional reducing agent, and the method has important significance for selenium recovery and resource utilization.

Chinese patent CN108558086A discloses a combined process for removing hexavalent selenium in water, which specifically comprises the following steps: (1) adding sodium sulfite; (2) adjusting the pH value; (3) ultraviolet irradiation; (4) adding trivalent ferric salt and alkali solution, stirring and then carrying out solid-liquid separation; (5) blowing air or oxygen into the liquid, or adding hydrogen peroxide solution and stirring; (6) adding alkali to adjust the pH value. Although the reduction of hexavalent selenium can be realized, the method has a long process and is not suitable for large-scale industrial application.

Disclosure of Invention

The invention mainly aims to provide a method for reducing hexavalent selenium into tetravalent selenium, aiming at reducing hexavalent selenium which is difficult to be reduced into simple substance by a conventional reducing agent (such as sodium sulfite) into simple substance into tetravalent selenium which is easy to be reduced into the simple substance by utilizing the reducibility of hydrochloric acid to enable a solution system to reach the reduction potential of selenium.

In order to achieve the above object, the present invention provides a method for reducing hexavalent selenium to tetravalent selenium, comprising the steps of:

(1) dissolving a hexavalent selenium compound in water to form a hexavalent selenium solution, and heating the hexavalent selenium solution to 70-90 ℃;

(2) adding hydrochloric acid into the hexavalent selenium solution, stirring, and stopping the reaction until the potential value of the solution is 900-960 mv.

In the technical scheme of the invention, the solution is reduced by utilizing the reducibility of hydrochloric acidThe system reaches the reduction potential of selenium, so that hexavalent selenium which is difficult to be reduced into simple substance by conventional reducing agent (such as sodium sulfite) is reduced into tetravalent selenium which is easy to be reduced into simple substance, thereby selenium can be effectively recovered into simple substance. The reaction equation involved in the reaction process is: SeO₄ ^2-+2H⁺+2Cl^-→SeO₃ ^2-+Cl₂↑+H₂O。

It should be noted that, in the process of reducing hexavalent selenium to tetravalent selenium, the temperature of the solution system has a very important influence on the potential value of the solution, and through a large number of experiments, the inventor finds that the potential value of the solution after the hydrochloric acid heating reaction can reach 900-960mv only when the temperature of the solution is in the range of 70-90 ℃, and beyond the temperature range, the potential value of the solution cannot be maintained between 900-960 mv.

As a preferred embodiment of the method for reducing hexavalent selenium to tetravalent selenium according to the present invention, in the step (2) of adding hydrochloric acid to the hexavalent selenium solution, the addition of hydrochloric acid is immediately stopped when the solution potential is 970-1100 mv.

In the technical scheme of the invention, the process of adding hydrochloric acid into the hexavalent selenium solution to carry out reduction reaction in the step (2) can be divided into two steps, wherein in the first step, the addition of the hydrochloric acid is stopped after the solution potential is controlled to be in the range of 970-1100mv when the hydrochloric acid is added; in the second step, the stirring is continued until the solution is completely reacted, and the potential value of the solution is changed along with the continuous reaction until the final potential value reaches 900-. In the first step, the hydrochloric acid is stopped immediately after the solution potential enters 970-1100mv, on one hand, the addition of the hydrochloric acid is ensured to reach the required amount for reducing the hexavalent selenium, so as to ensure the complete reaction of the hexavalent selenium; on the other hand, after the reaction is finished, the final potential value of the solution is not influenced by excessive hydrochloric acid, so that the addition amount of the hydrochloric acid is not excessive, and the waste of the hydrochloric acid can be avoided.

As a preferred embodiment of the method for reducing hexavalent selenium to tetravalent selenium according to the present invention, in the step (2) of adding hydrochloric acid to the hexavalent selenium solution, the hydrochloric acid is immediately stopped when the solution potential is 1100mv, stirring is performed, and the reaction is stopped when the solution potential reaches 960 mv.

As a preferred embodiment of the method for reducing hexavalent selenium to tetravalent selenium according to the present invention, in the step (2) of adding hydrochloric acid to the hexavalent selenium solution, the hydrochloric acid is immediately stopped when the solution potential is 970mv, stirring is performed, and the reaction is stopped when the solution potential reaches 900 mv.

As a preferred embodiment of the method for reducing hexavalent selenium to tetravalent selenium according to the present invention, in the step (2) of adding hydrochloric acid to the hexavalent selenium solution, the hydrochloric acid is immediately stopped when the solution potential is 1000mv, the stirring is performed, and the reaction is stopped when the solution potential reaches 930 mv.

As a preferred embodiment of the method for reducing hexavalent selenium to tetravalent selenium according to the present invention, the hexavalent selenium compound in the step (1) is a selenate compound.

As a preferred embodiment of the method for reducing hexavalent selenium to tetravalent selenium according to the present invention, the selenate compound includes at least one of sodium selenate, potassium selenate, and barium selenate.

As a preferred embodiment of the method for reducing hexavalent selenium to tetravalent selenium according to the present invention, the selenate compound is sodium selenate.

Compared with the prior art, the invention has the beneficial effects that:

(1) the technical scheme of the invention makes the solution system reach the reduction potential of selenium by utilizing the reducibility of hydrochloric acid, so that hexavalent selenium which is difficult to be reduced into simple substance by conventional reducing agent (such as sodium sulfite) is reduced into tetravalent selenium which is easy to be reduced into simple substance, thereby effectively recovering selenium into simple substance;

(2) the hexavalent selenium reduction method is simple, short in flow, low in cost and safe, only needs to add hydrochloric acid except the reduction reaction initial in the treatment process, does not generate compounds difficult to treat additionally after reduction, is environment-friendly, and is suitable for industrial large-scale application.

Detailed Description

To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to the following specific examples.

Example 1

The process of this example for reducing hexavalent selenium to tetravalent selenium comprises the following steps:

(1) 400mL of sodium selenate solution with the concentration of 290g/L is added into the reactor, and the temperature is raised to 70-90 ℃;

(2) slowly adding 400mL of hydrochloric acid until the potential of the solution system is 1100mv, stopping adding the hydrochloric acid, continuously stirring to react until the potential is 960mv, stopping the reaction, and detecting the content of the tetravalent selenium.

Example 2

The process of this example for reducing hexavalent selenium to tetravalent selenium comprises the following steps:

(1) 400mL of sodium selenate solution with the concentration of 290g/L is added into the reactor, and the temperature is raised to 70-90 ℃;

(2) slowly adding 400mL of hydrochloric acid, continuously stirring in the adding process until the reaction potential is 960mv, stopping the reaction, and detecting the content of the tetravalent selenium.

Example 3

The process of this example for reducing hexavalent selenium to tetravalent selenium comprises the following steps:

(1) 400mL of sodium selenate solution with the concentration of 290g/L is added into the reactor, and the temperature is raised to 70-90 ℃;

(2) slowly adding 430mL of hydrochloric acid until the potential of the solution system is 970mv, stopping adding the hydrochloric acid, continuously stirring to react until the potential is 900mv, stopping the reaction, and detecting the content of the tetravalent selenium.

Example 4

The process of this example for reducing hexavalent selenium to tetravalent selenium comprises the following steps:

(1) 400mL of sodium selenate solution with the concentration of 290g/L is added into the reactor, and the temperature is raised to 70-90 ℃;

(2) slowly adding 410mL of hydrochloric acid until the potential of the solution system is 1000mv, stopping adding the hydrochloric acid, continuously stirring to react until the potential is 930mv, stopping the reaction, and detecting the content of the tetravalent selenium.

Comparative example 1

The method for reducing hexavalent selenium to tetravalent selenium in the comparative example comprises the following steps:

(1) 400mL of sodium selenate solution with the concentration of 290g/L is added into the reactor, and the temperature is raised to 70-90 ℃;

(2) slowly adding 350mL of hydrochloric acid until the potential of the solution system is 1120mv, stopping adding the hydrochloric acid, continuously stirring to react until the potential is 980mv, stopping the reaction, and detecting the content of the tetravalent selenium.

Comparative example 2

The method for reducing hexavalent selenium to tetravalent selenium in the comparative example comprises the following steps:

(1) 400mL of sodium selenate solution with the concentration of 290g/L is added into the reactor, and the temperature is raised to 60-65 ℃;

(2) slowly adding 400mL of hydrochloric acid until the potential of the solution system is 1050mv, stopping adding the hydrochloric acid, continuously stirring to react until the potential is 980mv, stopping the reaction, and detecting the content of the tetravalent selenium.

Comparative example 3

The method for reducing hexavalent selenium to tetravalent selenium in the comparative example comprises the following steps:

(1) 400mL of sodium selenate solution with the concentration of 290g/L is added into the reactor, and the temperature is raised to 91-100 ℃;

(2) slowly adding 350mL of hydrochloric acid until the potential of the solution system is 1120mv, stopping adding the hydrochloric acid, continuously stirring to react until the potential is 975mv, stopping the reaction, and detecting the content of the tetravalent selenium.

The volumes and concentrations of the sodium selenate solutions in the examples 1 to 4 and the comparative examples 1 to 3 are the same, and the content information of the related substances is shown in the following table 1.

TABLE 1 Mass analysis of materials of examples 1 to 4 and comparative examples 1 to 3

The test results after completion of the reduction reactions of examples 1 to 4 and comparative examples 1 to 3 are shown in Table 2 below, Na₂SeO₃The concentration detection method is sodium thiosulfate redox titration method and an iodometry method is used as an auxiliary method.

Wherein the reduction rate is (Na)₂SeO₃Actual mass divided by Na₂SeO₃Theoretical mass) 100%.

TABLE 2 test results of examples 1 to 4 and comparative examples 1 to 3

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.