Mercury and selenium separation method

Abstract

The invention belongs to the technical field of hydrometallurgy, and discloses a mercury-selenium separation method. The method comprises the following steps: adding sodium sulfite and sodium sulfide into mercury-selenium-containing acid mud for leaching reaction, and filtering and washing to obtain mercury slag and a selenium-containing solution; washing the mercury slag with water, separating mercury through vacuum distillation, and condensing mercury steam to obtain fine mercury; sulfuric acid and hydrochloric acid are added into the selenium-containing solution to adjust the pH value to 1.5-1.8, acidification selenium precipitation is carried out, filtering and washing are carried out, and crude selenium and selenium-precipitated liquid are obtained; and adding ferrous sulfate, sodium sulfide, lime and hydrogen peroxide into the selenium-deposited liquid to react, and filtering to obtain wastewater residues and treated liquid. According to the invention, waste water, waste gas and surrounding soil environment pollution cannot be caused; mercury and selenium are well separated and enriched, and the recovery rate reaches 99% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgy, and in particular relates to a mercury-selenium separation method. Background Art

[0002] Valuable elements such as selenium and mercury contained in copper, lead and zinc concentrates enter the acid-making process with flue gas during the smelting process and are eventually enriched in the acid-making sludge. Therefore, the acid sludge contains heavy metal elements such as mercury, selenium, arsenic and lead. However, due to the complex composition of acid sludge and the difficulty in handling it, it is often stored in a long-term pile. However, the pile will pollute the environment, and the non-ferrous metals in the acid sludge cannot be recycled, resulting in a waste of resources.

[0003] At present, CN112458318A discloses a method for recovering selenium-mercury acid mud, which is used to recover selenium and mercury in the acid mud. The method uses a pyrometallurgical method to evaporate mercury first, which results in selenium loss and low recovery rate. Summary of the invention

[0004] The purpose of the invention is to develop a mercury-selenium separation method with high recovery rate.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] A method for separating mercury and selenium comprises the following steps:

[0007] (1) adding sodium sulfite and sodium sulfide to the acid mud containing mercury and selenium to carry out leaching reaction, filtering and washing to obtain mercury slag and selenium-containing solution;

[0008] (2) washing the mercury slag with water and separating the mercury by vacuum distillation, and condensing the mercury vapor to obtain refined mercury;

[0009] (3) adding sulfuric acid and hydrochloric acid to the selenium-containing solution to adjust the pH to 1.5-1.8 for acidification and selenium precipitation, filtering and washing to obtain crude selenium and selenium precipitation liquid, preferably, the pH is adjusted to 1.5;

[0010] (4) Add ferrous sulfate, sodium sulfide, lime and hydrogen peroxide to the selenium precipitation liquid for reaction, and then filter to obtain wastewater residue and treated liquid.

[0011] Preferably, in step (1), the concentration of sodium sulfite is 220-300 g / l, the concentration of sodium sulfide is 1.5-3%, the reaction temperature is 75-80°C, the reaction time is 3-5 hours, and the liquid-solid ratio is (3-5): 1. Furthermore, the concentration of sodium sulfite is 240 g / l, the concentration of sodium sulfide is 2%, and the liquid-solid ratio is 3:1.

[0012] Preferably, the washing water in step (2) is returned to be used for the leaching solution in step (1).

[0013] Preferably, the sulfur dioxide generated during the acidification and selenium precipitation process in step (3) is introduced into an absorption tower for neutralization with alkaline solution and sprayed, and the generated sodium sulfite is used for the leaching solution in step (1).

[0014] Preferably, the crude selenium in step (3) is dried and then melted to obtain selenium blocks.

[0015] Preferably, the selenium block is oxidized to obtain selenium dioxide, and / or the selenium block is distilled to obtain refined selenium.

[0016] Preferably, the wastewater slag in step (4) is smelted in a closed manner, and the slag is used to produce ecological building materials; the treated liquid is used for the leaching solution in step (1).

[0017] The technical principles of the present invention are as follows:

[0018] Sodium selenosulfate is generated by the reaction of selenium and sodium sulfite, while other metals and impurities are almost insoluble. At the same time, a small amount of sodium sulfide is added during the reaction to convert the dissolved heavy metals into sulfides and precipitate in the slag. This characteristic is used to achieve the purpose of separating selenium. After selenium is leached, mercury is enriched in the form of sulfides. Mercury sulfides are very stable and insoluble in water and alkaline solutions. Because the alkaline treatment process is adopted and the production equipment is a closed system, it will not cause the dispersion and volatilization of mercury. The mercury-enriched slag is transferred to a qualified unit for disposal.

[0019] The mercury slag after water washing is subjected to mercury distillation through a special vacuum distillation device, and the mercury vapor after distillation enters a condensation device, and 99.99% of refined mercury can be recovered after condensation.

[0020] After purification and impurity removal, the leaching liquid is added with sulfuric acid and hydrochloric acid for acidification and selenium precipitation, and filtered and washed to obtain crude selenium powder. A small amount of sulfur dioxide is generated during the acidification and selenium precipitation process. The gas containing sulfur dioxide is introduced into the absorption tower through the collecting air pipe through the induced draft fan for alkaline solution neutralization and spraying. After ball ring adsorption, it can meet the emission standards. The generated sodium sulfite is reused in the leaching solution to save costs.

[0021] The liquid after selenium precipitation is treated by adding auxiliary materials such as ferrous sulfate, sodium sulfide, lime, and hydrogen peroxide, and all harmful components in the liquid after selenium precipitation are precipitated and reused. The wastewater slag produced is disposed of in a closed smelting furnace and turned into slag for the production of ecological building materials.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) Wastewater: It can be seen from the process flow that the selenium precipitation liquid produced is reused in the production process after treatment, and no wastewater is discharged. Waste gas: Although SO2 gas is produced during the production process of this process, the gas can be absorbed by concentrated NaOH solution to produce Na2SO3 for reuse. The chemical reaction process of SO2 reducing H2SeO3 can be carried out in the gas collecting hood, and the NaOH solution is discharged after absorption, which has no impact on the environment. Solid waste: The leaching slag (mercury slag) produced by the process is vacuum distilled to produce refined mercury, and the waste slag is handed over to a qualified disposal unit for recycling and disposal. The wastewater slag can be smelted at high temperature into slag and then used in the production of ecological building materials. It can be seen that according to the disposal and utilization process and the actual disposal and utilization situation, the production process of material disposal and utilization will not cause wastewater, waste gas, and surrounding soil environmental pollution;

[0024] (2) Mercury and selenium are well separated and enriched, with a recovery rate of over 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0026] In order to further illustrate the present invention, the mercury-selenium separation method provided by the present invention is described in detail below in conjunction with examples, but they should not be construed as limiting the scope of protection of the present invention.

[0027] A method for separating mercury and selenium comprises the following steps:

[0028] (1) adding sodium sulfite and sodium sulfide to the acid mud containing mercury and selenium to carry out leaching reaction, filtering and washing to obtain mercury slag and selenium-containing solution;

[0029] (2) washing the mercury slag with water and separating the mercury by vacuum distillation, and condensing the mercury vapor to obtain refined mercury, wherein the washing water is returned to the leaching solution of step (1);

[0030] (3) adding sulfuric acid and hydrochloric acid to the selenium-containing solution to adjust the pH to 1.5 for acidification and selenium precipitation, filtering and washing to obtain crude selenium and selenium precipitation liquid, wherein the sulfur dioxide generated during the acidification and selenium precipitation process is introduced into an absorption tower for neutralization and spraying with alkaline solution, and the generated sodium sulfite is used for the leaching solution of step (1);

[0031] (4) adding ferrous sulfate, sodium sulfide, lime and hydrogen peroxide to the selenium precipitation liquid for reaction, filtering to obtain wastewater slag and treated liquid, wherein the wastewater slag is smelted in a closed manner to become slag and then used to produce ecological building materials; the treated liquid is used for the leaching solution of step (1).

[0032] Taking the actual production of 98.39t of this material as an example, the separation effect of this material according to the above process flow is ideal, and the material and metal balance are shown in Table 1. The mercury in the material mainly exists in the form of basic salts and sulfates. The basic salts are insoluble in water and alkaline solutions. Selenium mainly exists in the form of metal elements and selenious acid. Other heavy metals are trace harmful elements entrained in the raw materials.

[0033] Table 1 Material and metal balance

[0034]

[0035]

[0036] As can be seen from Table 1, selenium and mercury were well separated and enriched, with a recovery rate of more than 99%, and only a small part was mechanically lost during the production process or entrained in the raw material packaging bags.

[0037] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for separating mercury and selenium, characterized in that: The following steps are involved: (1) adding sodium sulfite and sodium sulfide to the acid mud containing mercury and selenium to carry out leaching reaction, and then filtering and washing to obtain mercury slag and selenium-containing solution; (2) washing the mercury slag with water and separating the mercury by vacuum distillation, and condensing the mercury vapor to obtain refined mercury; (3) adding sulfuric acid and hydrochloric acid to the selenium-containing solution to adjust the pH to 1.5-1.8 for acidification and selenium precipitation, filtering and washing to obtain crude selenium and selenium precipitation liquid; (4) Add ferrous sulfate, sodium sulfide, lime and hydrogen peroxide to the selenium precipitation liquid for reaction, and then filter to obtain wastewater residue and treated liquid.

2. The method according to claim 1, characterized in that In the step (1), the concentration of sodium sulfite is 220-300 g / l, the concentration of sodium sulfide is 1.5-3%, the reaction temperature is 75-80° C., the reaction time is 3-5 hours, and the liquid-to-solid ratio is (3-5):

1.

3. The method according to claim 1, characterized in that The washing water in step (2) is returned to be used for the leaching solution in step (1).

4. The method according to claim 1, characterized in that: The sulfur dioxide generated during the acidification and selenium precipitation process in step (3) is introduced into an absorption tower for neutralization and spraying with alkaline solution, and the generated sodium sulfite is used for the leaching solution in step (1).

5. The method according to claim 1, characterized in that The crude selenium in step (3) is dried and then melted to obtain selenium blocks.

6. The method according to claim 5, characterized in that The selenium block is oxidized to obtain selenium dioxide, and / or the selenium block is distilled to obtain refined selenium.

7. The method according to claim 1, characterized in that The wastewater slag in step (4) is smelted in a closed manner to become slag, which is then used to produce ecological building materials; the treated liquid is used for the leaching solution preparation in step (1).

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