Method for separating arsenic and antimony from high-arsenic soot

Abstract

The invention discloses a method for separating arsenic and antimony from high-arsenic soot, and belongs to the technical field of non-ferrous metal metallurgy. Adding water into the high-arsenic soot for leaching, and cooling and filtering after leaching to obtain leaching residues and leaching liquid; an oxidizing agent is added into the obtained leachate for oxidizing leaching, cooling and filtering are conducted after leaching, and oxidizing slag and oxidizing liquid are obtained; a reducing agent SO2 is added into the obtained oxidation liquid for a reduction leaching reaction, and white arsenic is obtained; or, sulfide is added into the obtained oxidation liquid for vulcanization leaching, cooling and filtering are conducted after leaching, and arsenic sulfide slag and arsenic precipitation liquid are obtained; and sulfide is added into the obtained arsenic precipitation liquid for a neutralization reaction, filtering is conducted after the reaction, arsenic sulfide residues are obtained, and tail liquid enters a water treatment procedure. According to the method, the leaching rate of arsenic is increased through wet oxidation leaching, different reducing agents are adopted for arsenic reduction precipitation according to market requirements, different arsenic-containing products are produced, and efficient separation of arsenic and antimony in the high-arsenic soot is achieved.

Description

1. Technical Field:

[0001] The invention belongs to the technical field of nonferrous metal smelting, and in particular relates to a method for separating arsenic and antimony from high-arsenic fly ash. 2. Background technology:

[0002] The melting and boiling points of antimony, arsenic, and their oxides in high-arsenic antimony fly ash are similar. During the anode mud pyrometallurgical process, arsenic and antimony typically enter the smoke simultaneously. The smoke typically contains 28-50% antimony, 15-45% arsenic, and 1-5% lead. The remaining elements (silver, copper, bismuth, iron, etc.) are all less than 1%. There are three types of methods for separating arsenic and antimony from fly ash: pyrometallurgical, hydrometallurgical, and combined hydrometallurgical-hydrometallurgical separation. Pyrometallurgical methods primarily utilize the differences in boiling points of antimony and arsenic trioxides for step-by-step separation. These include roasting in a roaster to produce white arsenic, distillation in an electric rotary kiln, and the Furukawa process. For example, CN 102233229A discloses a method for directly separating antimony and arsenic from antimony arsenic smoke. This method utilizes the difference in volatilization temperatures between arsenic trioxide and antimony trioxide to achieve step-by-step volatilization. However, the pyrometallurgical process suffers from high energy consumption, incomplete separation of antimony and arsenic, and arsenic-containing dust pollution. Wet processes mainly include boiling water leaching of arsenic dust, oxidation leaching, the long well process, and the light and heat process. These can be summarized into two approaches. The first involves using a strong base to co-leach arsenic and antimony, followed by oxidation and precipitation of the antimony to achieve separation. For example, CN1312392A discloses a method for treating arsenic dust. This method uses a mixed alkali of Na2S and NaOH to leach antimony and arsenic, followed by oxidation of the alkali leaching solution with H2O2 to produce a crude sodium antimonate precipitate and a sodium arsenate solution. The second method involves oxidative leaching of arsenic with a dilute alkali, while the antimony remains in the slag for arsenic separation. For example, CN105648226A discloses a method for separating antimony and arsenic from antimony-arsenic dust by oxidation and alkaline leaching. This method mixes the antimony-arsenic dust with an alkaline solution and then introduces a gaseous oxidant to produce an arsenic-rich leachate and antimonate slag. The antimony slag is used as an antimony concentrate for the preparation of antimony oxide powder. The arsenic-rich solution is then evaporated and crystallized to produce the arsenate product. Disadvantages of wet processes include high reagent consumption and significant equipment corrosion. The combined pyrometallurgical-wet metallurgical method mainly involves first modifying the arsenic and antimony by pyrometallurgical method to improve the solubility of arsenic and antimony, and then separating the arsenic and antimony by wet metallurgical method. For example, CN201410065908.0 discloses a comprehensive recovery method for high-arsenic, antimony and oxygen smoke dust, which first mixes the antimony and arsenic smoke dust with sodium nitrate and alkali, calcines them at 400-680°C, and then leaches and filters them in water after calcination to obtain a sodium antimonate filter cake and a sodium arsenate solution. This method has a simple process flow and is easy to separate antimony and arsenic. However, due to the relatively high temperature during the calcination process, antimony and arsenic will inevitably volatilize, causing secondary pollution. In addition, the concentrated crystallization of the sodium arsenate solution consumes a lot of energy. 3. Summary of the invention:

[0003] The technical problem to be solved by the present invention is to address the problems of high energy consumption, incomplete arsenic and antimony separation, high reagent consumption, severe equipment corrosion, and susceptibility to secondary pollution in existing pyrometallurgical, hydrometallurgical, and combined pyrometallurgical and hydrometallurgical processes for treating high-arsenic fly ash. The present invention provides a novel method for separating arsenic and antimony from high-arsenic fly ash. The method utilizes wet oxidative leaching to improve the arsenic leaching rate. Based on market needs, different reducing agents are used for arsenic reduction and precipitation to produce different arsenic-containing products, achieving efficient separation of arsenic and antimony from high-arsenic fly ash.

[0004] In order to solve the above problems, the technical solution adopted by the present invention is:

[0005] The present invention provides a method for separating arsenic and antimony from high-arsenic fly ash, the method comprising the following steps:

[0006] a. Water leaching: Water is added to the high-arsenic fly ash for leaching. After leaching, the leaching residue is cooled and filtered to obtain the leaching residue and the leaching liquid. The leaching residue is returned to the antimony system to recover antimony, and the leaching liquid is further de-arsenicized.

[0007] b. Oxidative leaching: adding an oxidant to the leachate obtained in step a for oxidative leaching, cooling and filtering after leaching to obtain oxidation slag and oxidation liquid; the obtained oxidation slag is returned to the antimony system to recover antimony, and the oxidation liquid is further de-arsenicized;

[0008] c. Reduction leaching: adding a reducing agent SO2 to the obtained oxidizing solution to carry out a reduction leaching reaction to obtain white arsenic;

[0009] Alternatively, sulfide is added to the obtained oxidation solution for sulfide leaching, and after leaching, the temperature is lowered and filtered to obtain arsenic sulfide slag and arsenic precipitate; the obtained arsenic sulfide slag is sold, and the arsenic precipitate is further de-arsenified;

[0010] d. Precipitation and neutralization: Add sulfide to the obtained arsenic precipitate to carry out neutralization reaction. After the reaction, filter to obtain arsenic sulfide slag, and the tail liquid enters the water treatment process.

[0011] According to the above method for separating arsenic and antimony from high-arsenic fly ash, during the leaching in step a, the high-arsenic fly ash and water are mixed at a solid-to-liquid ratio of 1:4 to 20.

[0012] According to the above method for separating arsenic and antimony from high-arsenic fly ash, during the leaching in step a, the leaching temperature is controlled to be 55-100°C and the stirring time is 1-4 hours; and the temperature is lowered to 45-75°C.

[0013] According to the above method for separating arsenic and antimony from high-arsenic fly ash, the oxidant in step b is at least one of hydrogen peroxide, concentrated sulfuric acid, ozone and sodium hydroxide.

[0014] According to the above-mentioned method for separating arsenic and antimony from high-arsenic fly ash, during the oxidative leaching in step b, the volume mass ratio of the leachate to the oxidant added is 1L:10-35g; during the oxidative leaching, the leaching temperature is controlled to be 75-100°C and the continuous stirring time is 2-4h; and the temperature is lowered to 40-70°C during the cooling.

[0015] According to the above method for separating arsenic and antimony from high-arsenic fly ash, when the oxidant is added in step b, it is added slowly and the addition temperature is controlled to be 30-55°C.

[0016] According to the above-mentioned method for separating arsenic and antimony from high-arsenic fly ash, when the reducing agent SO2 is added to the oxidizing solution in step c for reduction leaching reaction, the amount of reducing agent SO2 introduced is 1 mg under the condition of introducing 0.1 to 0.8 L of oxidizing solution per second; during the reduction leaching reaction, the temperature is controlled at 65°C ± 5°C and the reaction time is 1.5h to 2h.

[0017] According to the above-mentioned method for separating arsenic and antimony from high-arsenic fly ash, the sulfide in step c is sodium sulfide or sodium sulfite; when sulfide is added to the oxidizing solution for leaching, the volume mass ratio of the oxidizing solution to the sulfide is 1L:15~55g, the leaching temperature is 35~70℃, and the leaching time is 1.5~3h.

[0018] According to the above-mentioned method for separating arsenic and antimony from high-arsenic fly ash, the sulfide in step d is at least one of sodium sulfide, hydrogen sulfide and polysulfide; when the sulfide is added to the arsenic precipitate for neutralization reaction, the volume mass ratio of the arsenic precipitate and the sulfide is 1L:3~50g; the temperature during the neutralization reaction is controlled at 48°C±8°C, and the stirring reaction time is 2~3h.

[0019] The positive beneficial effects of the present invention are:

[0020] 1. The present invention is the first to use redox leaching method on high-arsenic fly ash, integrating open-circuit arsenic and antimony to improve the arsenic leaching rate, and the arsenic leaching rate is as high as over 70%.

[0021] 2. The present invention is the first to add alkali sulfide to alkaline liquid to precipitate arsenic slag, breaking the traditional method of adding alkali sulfide to precipitate arsenic slag under acidic conditions, thereby effectively inhibiting the release of hydrogen sulfide gas, reducing occupational injuries, protecting the environment, and being beneficial to environmental protection.

[0022] 3. Compared with traditional wet treatment, the process of the present invention is short, the reaction speed is fast and the effect is good.

[0023] In summary, the present invention has significant economic and social benefits. 4. Specific implementation methods:

[0024] The present invention is further described below with reference to the following examples, but the scope of protection of the technical solution of the present invention is not limited thereto.

[0025] The following examples use high-arsenic fly ash from a domestic nonferrous metal smelter. The main components and their contents in the high-arsenic fly ash are: Sb 27.35%, As 51.71%, Bi 7.05%, Cu 2.38%, Pb 8.89%, and other impurities 2.62%.

[0026] Example 1:

[0027] The method for separating arsenic and antimony from high-arsenic fly ash of the present invention comprises the following detailed steps:

[0028] a. Water leaching: Prepare 250g of high-arsenic fly ash and 2.5L of clean water at a liquid-to-solid ratio of 10:1. Add the high-arsenic fly ash to water and stir evenly for leaching. Control the leaching temperature to 90°C and the stirring time to 2 hours. After leaching, cool to 50°C and filter to obtain leaching residue and leachate. The obtained leaching residue is returned to the antimony system to recover antimony, and the leachate is further de-arsenicized.

[0029] b. Oxidative leaching: adding hydrogen peroxide to the leachate obtained in step a at a ratio of 20 g of oxidant per liter of leachate for oxidative leaching (slowly adding the oxidant at a temperature of 40° C.), controlling the leaching temperature to 90° C. and continuously stirring for 2 hours; cooling to 45° C. after leaching and filtering to obtain oxidation slag and oxidation liquid; the obtained oxidation slag is returned to the antimony system for antimony recovery, and the oxidation liquid is further de-arsenicized;

[0030] c. Reduction leaching: 1.8 L of the obtained arsenic precipitate was subjected to a reduction leaching reaction by introducing 1 mg of pure SO2 gas at a rate of 0.2 L of arsenic precipitate per second. The temperature was controlled at 60°C and the reaction time was 1.5 h. 1.3 L of reduced solution was obtained, which was dried to yield 43.5 g of arsenic trioxide.

[0031] d. Precipitation and neutralization: Add 6.5 g of industrial sodium sulfate to 1.3 L of the reduced solution at a solid-liquid mass ratio of 0.5:1 for neutralization reaction. The temperature was controlled at 45°C and the stirring reaction time was 2 h. After the reaction, filtration was performed to obtain 12.5 g of As2S3. 0.9 L of the neutralized solution was returned to water for treatment.

[0032] After the leaching in this embodiment is completed, the arsenic leaching rate reaches 70%, and the antimony recovery rate is 99.95%.

[0033] Example 2:

[0034] The method for separating arsenic and antimony from high-arsenic fly ash of the present invention comprises the following detailed steps:

[0035] a. Water leaching: Prepare 200g of high-arsenic fly ash and 1.6L of clean water at a liquid-to-solid ratio of 8:1. Add the high-arsenic fly ash to the water and stir evenly for leaching. Control the leaching temperature to 90°C and the stirring time to 2 hours. After leaching, cool to 50°C and filter to obtain leaching residue and leachate. The obtained leaching residue is returned to the antimony system to recover antimony, and the leachate is further de-arsenicized.

[0036] b. Oxidative leaching: The leachate obtained in step a was added with hydrogen peroxide at a ratio of 20 g of oxidant per liter of leachate for oxidative leaching (the oxidant was added slowly at a temperature of 40° C.), the leaching temperature was controlled at 90° C., and the stirring time was continuous for 2 hours; after leaching, the temperature was lowered to 45° C. and filtered to obtain an oxidation slag with a wet weight of 275 g and an oxidation liquid of 2.2 L; the obtained oxidation slag was returned to the antimony system for antimony recovery, and the oxidation liquid was further de-arsenicized;

[0037] c. Sulfidation leaching: Sodium sulfide was added to 2.2 L of the obtained oxidation solution at a ratio of 22 g of sulfide per L of oxidation solution for sulfidation leaching. The leaching temperature was 50°C and the leaching time was 2 h. After leaching, the filtrate was filtered to obtain 1.8 L of filtrate, 116 g of filter residue wet weight, 94.3 g of which was fried to dryness, to obtain As2S3 with a grade of 79%;

[0038] d. Precipitation and neutralization: Add 10 g of industrial sodium sulfate to 1.8 L of the obtained filtrate for neutralization reaction. The temperature is controlled at 45°C and the stirring reaction time is 2 h. After the reaction, filter to obtain 15.5 g of As2S3. Return 0.3 L of the neutralized solution to water for treatment.

[0039] After the leaching in this embodiment is completed, the arsenic leaching rate reaches 75.5%, and the antimony recovery rate is 99.97%.

Claims

1. A method for separating arsenic and antimony from high-arsenic fly ash, characterized in that: The method comprises the following steps: a. Water leaching: Water is added to the high-arsenic fly ash for leaching. After leaching, the leaching residue is cooled and filtered to obtain the leaching residue and the leaching liquid. The leaching residue is returned to the antimony system to recover antimony, and the leaching liquid is further de-arsenicized. b. Oxidative leaching: adding an oxidant to the leachate obtained in step a for oxidative leaching, cooling and filtering after leaching to obtain oxidation slag and oxidation liquid; the obtained oxidation slag is returned to the antimony system to recover antimony, and the oxidation liquid is further de-arsenicized; c. Reduction leaching: adding a reducing agent SO2 to the obtained oxidizing solution to carry out a reduction leaching reaction to obtain white arsenic; Alternatively, sulfide is added to the obtained oxidation solution for sulfide leaching, and after leaching, the temperature is lowered and filtered to obtain arsenic sulfide slag and arsenic precipitate; the obtained arsenic sulfide slag is sold, and the arsenic precipitate is further de-arsenified; d. Precipitation and neutralization: Add sulfide to the obtained arsenic precipitate to carry out neutralization reaction. After the reaction, filter to obtain arsenic sulfide slag, and the tail liquid enters the water treatment process.

2. The method for separating arsenic and antimony from high-arsenic fly ash according to claim 1, characterized in that: During the leaching in step a, the high-arsenic fly ash and water are mixed at a solid-to-liquid ratio of 1:4 to 20.

3. The method for separating arsenic and antimony from high-arsenic fly ash according to claim 1, characterized in that: During the leaching in step a, the leaching temperature is controlled to be 55-100° C. and the stirring time is 1-4 hours; and the temperature is lowered to 45-75° C. during the cooling.

4. The method for separating arsenic and antimony from high-arsenic fly ash according to claim 1, characterized in that: The oxidant in step b is at least one of hydrogen peroxide, concentrated sulfuric acid, ozone and sodium hydroxide.

5. The method for separating arsenic and antimony from high-arsenic fly ash according to claim 1, characterized in that: During the oxidative leaching in step b, the volume mass ratio of the added leachate to the oxidant is 1L:10-35g; during the oxidative leaching, the leaching temperature is controlled to be 75-100°C and the continuous stirring time is 2-4h; and the temperature is lowered to 40-70°C during the cooling.

6. The method for separating arsenic and antimony from high-arsenic fly ash according to claim 1, characterized in that: When adding the oxidant in step b, add it slowly and control the addition temperature to be 30-55°C.

7. The method for separating arsenic and antimony from high-arsenic fly ash according to claim 1, characterized in that: When the reducing agent SO2 is added to the oxidizing solution in step c for the reduction leaching reaction, the amount of the reducing agent SO2 introduced is 1 mg under the condition of introducing 0.1 to 0.8 L of oxidizing solution per second; during the reduction leaching reaction, the temperature is controlled at 65°C ± 5°C and the reaction time is 1.5h to 2h.

8. The method for separating arsenic and antimony from high-arsenic fly ash according to claim 1, characterized in that: The sulfide in step c is sodium sulfide or sodium sulfite; when the sulfide is added to the oxidizing solution for leaching, the volume mass ratio of the oxidizing solution to the sulfide is 1L:15-55g, the leaching temperature is 35-70°C, and the leaching time is 1.5-3h.

9. The method for separating arsenic and antimony from high-arsenic fly ash according to claim 1, characterized in that: The sulfide in step d is at least one of sodium sulfide, hydrogen sulfide and polysulfide; when the sulfide is added to the arsenic precipitate for neutralization reaction, the volume mass ratio of the arsenic precipitate to the sulfide is 1L:3-50g; the temperature during the neutralization reaction is controlled at 48°C±8°C, and the stirring reaction time is 2-3h.