A treatment method for arsenic-containing desulfurized gypsum

Abstract

The present invention relates to the technical field of desulfurized gypsum treatment, and discloses a method for treating arsenic-containing desulfurized gypsum. The method comprises the following steps: (1) successively ball-milling the arsenic-containing desulfurized gypsum and screening it through a 100-mesh sieve; (2) soaking the arsenic-containing desulfurized gypsum in a soaking solution, and then performing solid-liquid separation, wherein the soaking solution contains an acid and a water-soluble organic matter, and the acid is selected from one or more of citric acid, nitric acid, and oxalic acid; (3) reacting the first solid-phase product, an alkaline solution, and a first oxidant, wherein the base in the alkaline solution is ammonia water and / or sodium hydroxide, and the first oxidant is hydrogen peroxide; (4) reacting the second solid-phase product, an acidic solution, and a second oxidant; (5) reacting the third solid-phase product with an organic alcohol solution. This method can effectively remove arsenic in the desulfurized gypsum and simultaneously oxidize calcium sulfite in the desulfurized gypsum.

Description

Technical Field

[0001] The present invention relates to the technical field of desulfurized gypsum treatment, and particularly to a method for treating arsenic-containing desulfurized gypsum. Background Art

[0002] Sulfur dioxide is an important precursor causing air pollution control phenomena such as acid rain. Extreme weather such as acid rain causes great harm to the environment. Therefore, it is necessary to control sulfur dioxide in the air. The main sulfur dioxide in flue gas comes from coal-fired boilers, mainly in various fields such as coal-fired power plants and the metallurgical industry.

[0003] In the limestone desulfurization process, limestone is crushed and ground into powder, mixed with water and stirred into an absorption slurry. The absorption slurry reacts with sulfur dioxide to absorb it and produce calcium sulfate through reaction, and sulfur dioxide is finally removed. However, in the actual process, the desulfurized gypsum produced gradually increases, and these gypsums face disposal problems. Currently, a lot of these gypsums have accumulated.

[0004] The resource utilization of desulfurized gypsum is the current mainstream direction. Desulfurized gypsum has a high purity and has many application fields, such as the building materials industry. However, desulfurized gypsum contains a certain amount of heavy metals and a high water content. Heavy metals have an important impact on the resource utilization of desulfurized gypsum. Therefore, the pretreatment of desulfurized gypsum plays an important role in its subsequent high-end resource utilization.

[0005] In the existing technology, insufficient attention has been paid to the pretreatment measures for the resource utilization of desulfurized gypsum, and the subsequent resource utilization process is relatively complex. In particular, the application research on arsenic-containing desulfurized gypsum is insufficient. The existing desulfurized gypsum in the oxidation stage generally focuses on the single treatment of calcium sulfite, and arsenic is not removed synchronously. Therefore, the collaborative research on the oxidation of calcium sulfite and arsenic removal in desulfurized gypsum is insufficient. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problem of insufficient collaborative research on the oxidation of calcium sulfite and arsenic removal in desulfurized gypsum existing in the prior art, and provide a method for treating arsenic-containing desulfurized gypsum. This method can effectively remove arsenic in desulfurized gypsum and simultaneously oxidize calcium sulfite in desulfurized gypsum.

[0007] To achieve the above purpose, on the one hand, the present invention provides a method for treating arsenic-containing desulfurized gypsum, which includes the following steps:

[0008] (1) Ball-mill the arsenic-containing desulfurized gypsum, sieve it through a 100-mesh sieve, and dry it in sequence;

[0009] (2) Immerse the arsenic-containing desulfurized gypsum treated in step (1) in an immersion liquid for immersion, and then perform solid-liquid separation to obtain a first solid-phase product. Among them, the immersion liquid contains an acid and a water-soluble organic matter, and the acid is selected from one or more of citric acid, nitric acid, and oxalic acid;

[0010] (3) React the first solid-phase product, the alkaline solution, and the first oxidant, followed by solid-liquid separation to obtain the second solid-phase product, where the base in the alkaline solution is ammonia water and / or sodium hydroxide, and the first oxidant is hydrogen peroxide;

[0011] (4) React the second solid-phase product, the acidic solution, and the second oxidant, followed by solid-liquid separation to obtain the third solid-phase product;

[0012] (5) React the third solid-phase product with the organic alcohol solution, followed by solid-liquid separation.

[0013] And / or, in step (1), the arsenic content in the arsenic-containing desulfurized gypsum is ≥0.2% by weight, and the calcium sulfite content is ≥2% by weight.

[0014] And / or, in step (2), the acid in the soaking solution is used in the form of an acid solution, and the concentration of the acid solution is 0.1 - 3 mol / L.

[0015] And / or, the liquid-solid ratio of the acid solution to the arsenic-containing desulfurized gypsum is 20 - 5 mL:1 g.

[0016] And / or, in step (2), the water-soluble organic matter is selected from one or more of methanol, ethylene glycol, and propanol.

[0017] And / or, the liquid-solid ratio of the water-soluble organic matter to the arsenic-containing desulfurized gypsum is 10 - 30 mL:1 g.

[0018] And / or, in step (2), the soaking conditions include: temperature ≥60°C, time ≥30 min.

[0019] And / or, in step (3), the concentration of the alkaline solution is 1 - 5 mol / L.

[0020] And / or, the liquid-solid ratio of the alkaline solution to the first solid-phase product is 5 - 20 mL:1 g.

[0021] And / or, in step (3), the first oxidant is used in the form of a first oxidant solution, and the concentration of the first oxidant solution is 20 - 35% by weight.

[0022] And / or, the volume ratio of the first oxidant solution to the alkaline solution is 1:10 - 100.

[0023] And / or, in step (3), the reaction conditions include: temperature ≥50°C, time ≥40 min.

[0024] And / or, in step (4), the acid in the acidic solution is selected from one or more of sulfuric acid, nitric acid, and hydrochloric acid.

[0025] And / or, in step (4), the concentration of the acidic solution < 5 mol / L.

[0026] And / or, the liquid-solid ratio of the dilute sulfuric acid to the second solid-phase product ≥ 5 mL:1 g.

[0027] And / or, in step (4), the second oxidant is hydrogen peroxide.

[0028] And / or, in step (4), the second oxidant is used in the form of a second oxidant solution, and the concentration of the second oxidant solution is 20 - 35 wt%.

[0029] And / or, the volume ratio of the second oxidant solution to the acidic solution is 1:10 - 40.

[0030] And / or, in step (4), the reaction conditions include: temperature ≥ 60 °C, time ≥ 30 min.

[0031] And / or, in step (5), the number of carbon atoms of the organic alcohol in the organic alcohol solution < 9.

[0032] And / or, the volume ratio of the organic alcohol to water in the organic alcohol solution is 5 - 20:1.

[0033] And / or, the liquid-solid ratio of the organic alcohol solution to the third solid-phase product > 10 mL:1 g.

[0034] And / or, in step (5), the reaction conditions include: temperature ≥ 100 °C, time ≥ 2 h.

[0035] Compared with the prior art, the present invention has at least the following advantages:

[0036] The method described in the present invention treats arsenic-containing desulfurized gypsum with specific chemical reagents in a specific order, which can not only effectively remove arsenic in the desulfurized gypsum, but also oxidize calcium sulfite in the desulfurized gypsum to improve the purity of calcium sulfate. Detailed Description of the Invention

[0037] The following provides a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0038] The endpoints and any values in the ranges disclosed in this document are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this document.

[0039] The first aspect of the present invention provides a method for treating arsenic-containing desulfurized gypsum, and the method includes the following steps:

[0040] (1) Ball-mill the arsenic-containing desulfurized gypsum in sequence, sieve it through a 100-mesh sieve, and dry it;

[0041] (2) Immerse the arsenic-containing desulfurized gypsum treated in step (1) in an immersion liquid, then perform solid-liquid separation to obtain a first solid-phase product. Among them, the immersion liquid contains an acid and a water-soluble organic matter, and the acid is selected from one or more of citric acid, nitric acid, and oxalic acid;

[0042] (3) React the first solid-phase product, an alkaline solution, and a first oxidant, and perform solid-liquid separation to obtain a second solid-phase product. Among them, the base in the alkaline solution is ammonia water and / or sodium hydroxide, and the first oxidant is hydrogen peroxide;

[0043] (4) React the second solid-phase product, an acidic solution, and a second oxidant, and perform solid-liquid separation to obtain a third solid-phase product;

[0044] (5) React the third solid-phase product with an organic alcohol solution, and perform solid-liquid separation.

[0045] In the method of the present invention, first, the arsenic-containing desulfurized gypsum is ball-milled and sieved to make the composition of the gypsum more uniform, which is conducive to the reaction of the desulfurized gypsum with the subsequent solution; in step (2), by placing the arsenic-containing desulfurized gypsum treated in step (1) in a solution containing a specific acid and an aqueous solution organic substance, the acid and the aqueous solution can penetrate into the arsenic-containing desulfurized gypsum, and part of the arsenic is converted into an easily soluble ionic state, which is convenient for subsequent reactions and removal; in step (3), the solid-phase product treated in step (2) is reacted with a solution containing a specific base and an oxidant. The oxidant can oxidize the ionic arsenic to a high-valent arsenic, and the high-valent arsenic is more likely to react with the base to form an ionic state, so it is easier to remove. Moreover, the alkaline solution and the oxidant penetrate into the arsenic-containing desulfurized gypsum, and the base combines with the oxidant to promote the reaction of the residual acid in the arsenic-containing desulfurized gypsum with the base to remove the acid radical ions. At the same time, part of the internal water molecules are broken to convert them into free water, and the free water can carry out the ionic metal ions, so as to remove the arsenic in the arsenic-containing desulfurized gypsum. In addition, the oxidant can oxidize calcium sulfite to improve the purity of calcium sulfate; in step (4), the solid product treated in step (3) is reacted with an acidic solution and a second oxidant, which can not only further oxidize calcium sulfite, but also the acid can neutralize the residual base in the arsenic-containing desulfurized gypsum, and the acid can also react with part of the arsenic to make the arsenic into an easily soluble ionic state. The ionic arsenic further reacts with the oxidant to further remove the residual As; in step (5), the solid product treated in step (4) is reacted with an organic alcohol solution. The organic alcohol solution enters the arsenic-containing desulfurized gypsum. According to the principle of similar solubility, the organic alcohol solution can wash the residual water-soluble reagents and organic matter components in the arsenic-containing desulfurized gypsum in the previous steps, and at the same time remove the trace arsenic dissolved in the solution. The method provided by the present invention treats the arsenic-containing desulfurized gypsum in a specific order and adds specific chemical reagents, which can not only effectively remove the arsenic in the arsenic-containing desulfurized gypsum, but also oxidize calcium sulfite in the desulfurized gypsum to improve the purity of calcium sulfate.

[0046] In the present invention, the arsenic-containing desulfurized gypsum can be the desulfurized gypsum generated during the desulfurization process of coal-fired power plants or the metallurgical industry. The arsenic-containing desulfurized gypsum contains components such as heavy metal arsenic, calcium sulfite, and calcium sulfate. In the specific implementation manner, in step (1), the content of arsenic in the arsenic-containing desulfurized gypsum is ≥0.2% by weight, preferably 0.2-5% by weight; the content of calcium sulfite is ≥2% by weight, preferably 5-20% by weight.

[0047] In the method of the present invention, after the arsenic-containing desulfurized gypsum is ball-milled and sieved, it needs to be dried under specific conditions. In the specific implementation manner, the drying temperature can be 80-100 °C, and the drying time can be 1-3 h.

[0048] In the present invention, in order to prevent high-purity desulfurized gypsum from containing chloride ions, the soaking solution in step (2) is a solution without chloride ions, that is, neither the acid nor the water-soluble organic matter contains chloride ions.

[0049] In a specific embodiment, the acid in the soaking solution in step (2) is used in the form of an acid solution, and the concentration of the acid solution can be 0.1 - 3 mol / L.

[0050] In a more specific embodiment, the liquid-solid ratio of the acid solution to arsenic-containing desulfurized gypsum can be 20 - 5 mL:1 g.

[0051] In the present invention, there is no particular limitation on the water-soluble organic matter, as long as it can be miscible with water. In a preferred embodiment, the water-soluble organic matter can be selected from one or more of methanol, ethylene glycol, and propanol.

[0052] In a more specific embodiment, the liquid-solid ratio of the water-soluble organic matter to arsenic-containing desulfurized gypsum can be 10 - 30 mL:1 g.

[0053] In the present invention, in order to allow the arsenic-containing desulfurized gypsum to react fully with the soaking solution and improve the reaction effect, the soaking temperature should not be too low and the soaking time should not be too short. In a specific embodiment, the soaking conditions in step (2) include: temperature ≥ 60 °C, time ≥ 30 min. In a preferred embodiment, the soaking conditions in step (2) include: temperature of 90 - 100 °C, time of 50 - 70 min.

[0054] In the present invention, in order to prevent calcium hydroxide from remaining in the product, the alkaline solution in step (3) cannot be a CaOH solution or a heavy metal alkaline solution. In a specific embodiment, the concentration of the alkaline solution in step (3) can be 1 - 5 mol / L.

[0055] In a more specific embodiment, the liquid-solid ratio of the alkaline solution to the first solid-phase product can be 5 - 20 mL:1 g.

[0056] In the present invention, in order to prevent the residual of chloride ions and heavy metals in the desulfurized gypsum, which affects the purity of the product and further the subsequent high-end resource utilization, the oxidant used in step (3) cannot contain Cl elements and heavy metals. In a specific embodiment, in step (3), the first oxidant can be used in the form of a first oxidant solution, and the concentration of the first oxidant solution can be 20 - 35 wt%.

[0057] In a more specific embodiment, the volume ratio of the first oxidant solution to the alkaline solution can be 1:10 - 100.

[0058] In step (3), in order to ensure full reaction, the temperature of the reaction cannot be too low, and the time of the reaction cannot be too short. In a specific embodiment, the conditions of the reaction in step (3) include: temperature ≥ 50 °C, time ≥ 40 min. In a preferred embodiment, the conditions of the reaction in step (3) include: temperature is 80 - 100 °C, time is 80 - 130 min.

[0059] In step (4), the acid in the acidic solution can be a conventional choice in the art. In a specific embodiment, the acid in the acidic solution in step (4) is selected from one or more of sulfuric acid, nitric acid, and hydrochloric acid.

[0060] In the present invention, the concentration of the acidic solution in step (4) cannot be too low. In a specific embodiment, the concentration of the acidic solution in step (4) < 5 mol / L.

[0061] In a more specific embodiment, the liquid-solid ratio of the dilute sulfuric acid to the second solid-phase product ≥ 5 mL:1 g.

[0062] In the present invention, the second oxidant can be a conventional choice in the art. In step (4), the second oxidant is mainly hydrogen peroxide.

[0063] In a specific embodiment, the second oxidant can be used in the form of a second oxidant solution, and the concentration of the second oxidant solution can be 20 - 35 wt%.

[0064] In a more specific embodiment, the volume ratio of the second oxidant solution to the acidic solution can be 1:10 - 40.

[0065] In step (4), in order to ensure full reaction, the temperature of the reaction cannot be too low, and the time of the reaction cannot be too short. In a specific embodiment, the conditions of the reaction in step (4) include: temperature ≥ 60 °C, time ≥ 30 min. In a preferred embodiment, the conditions of the reaction in step (4) include: temperature is 80 - 100 °C, time is 50 - 80 min.

[0066] In step (5), the organic alcohol in the organic alcohol solution can be common alcohols in the art as long as they can be fully miscible with water. In a specific embodiment, the number of carbon atoms of the organic alcohol in the organic alcohol solution in step (5) < 9. In a preferred embodiment, the number of carbon atoms of the organic alcohol in the organic alcohol solution < 4, for example, it can be methanol, propanol, ethylene glycol, and glycerol.

[0067] In a specific embodiment, the preparation process of the organic alcohol solution includes: mixing the organic alcohol and water; wherein, the volume ratio of the organic alcohol to water in the organic alcohol solution can be 5 - 20:1.

[0068] In a more specific embodiment, the liquid-solid ratio of the organic alcohol solution to the third solid-phase product is > 10 mL: 1 g.

[0069] In the present invention, in order to improve the reaction effect, the reaction temperature in step (5) is relatively high and the reaction time is relatively long. In a specific embodiment, the conditions for the reaction in step (5) include: temperature ≥ 100 °C, time ≥ 2 h.

[0070] In the present invention, after solid-liquid separation in step (5), it further includes drying the obtained solid product. In a specific embodiment, the drying temperature can be 100 - 110 °C, and the drying time can be 2 - 12 h.

[0071] The present invention will be described in detail below through examples, but the protection scope of the present invention is not limited thereto.

[0072] In the following examples, the content of heavy metal arsenic in arsenic-containing desulfurized gypsum is determined by inductively coupled plasma (ICP) method; the content of calcium sulfite in arsenic-containing desulfurized gypsum is determined according to "Iodometric Method for the Determination of Sulfites".

[0073] Example 1

[0074] This example selects arsenic-containing desulfurized gypsum from a power plant in Guizhou, which contains 2.12 wt% of arsenic and 6.78 wt% of calcium sulfite.

[0075] The treatment method of arsenic-containing desulfurized gypsum includes the following steps:

[0076] (1) Ball-mill the arsenic-containing desulfurized gypsum, pass it through a 100-mesh sieve, and then dry it at 105 °C for 2 h;

[0077] (2) Put the arsenic-containing desulfurized gypsum treated in step (1) into a citric acid solution with a concentration of 2 mol / L. The liquid-solid ratio of the citric acid solution to the arsenic-containing desulfurized gypsum is 15 mL: 1 g. Then add methanol to the citric acid solution to soak the arsenic-containing desulfurized gypsum. The liquid-solid ratio of methanol to the arsenic-containing desulfurized gypsum is 20 mL: 1 g. The soaking temperature is 90 °C, and the soaking time is 60 min. After soaking, filter, and then dry the obtained solid part at 90 °C for 2 h to obtain the first solid-phase product;

[0078] (3) Add the first solid-phase product to a sodium hydroxide solution with a concentration of 4 mol / L. The liquid-solid ratio of the sodium hydroxide solution to the first solid-phase product is 20 mL:1 g. Then, add a hydrogen peroxide solution with a concentration of 30 wt% to carry out the reaction. The volume ratio of the hydrogen peroxide solution to the sodium hydroxide solution is 1:30. The reaction temperature is 90 °C, and the reaction time is 90 min. After the reaction, filter, and then dry the obtained solid part at 105 °C for 6 h to obtain the second solid-phase product;

[0079] (4) Add the second solid-phase product to a sulfuric acid solution with a concentration of 1.2 mol / L. The liquid-solid ratio of the sulfuric acid solution to the second solid-phase product is 15 mL:1 g. Then, add a hydrogen peroxide solution with a concentration of 30 wt% to carry out the reaction. The volume ratio of the hydrogen peroxide solution to the sulfuric acid solution is 1:20. The reaction temperature is 90 °C, and the reaction time is 60 min. After the reaction, filter, and then dry the obtained solid part at 105 °C for 6 h to obtain the third solid-phase product;

[0080] (5) Prepare an ethanol solution by mixing ethanol and water in a volume ratio of 10:1. Then, place the third solid-phase product in the ethanol solution for reaction. The liquid-solid ratio of the ethanol solution to the third solid-phase product is 15 mL:1 g. The reaction temperature is 120 °C, and the reaction time is 3 min. After the reaction, filter, and then dry the obtained solid part at 105 °C for 6 h to obtain the powder.

[0081] Example 2

[0082] This example selects arsenic-containing desulfurized gypsum from a power plant in Zhejiang, which contains 0.78 wt% arsenic and 11.45 wt% calcium sulfite.

[0083] The treatment method of arsenic-containing desulfurized gypsum includes the following steps:

[0084] (1) Grind the arsenic-containing desulfurized gypsum, pass it through a 100-mesh sieve, and then dry it at 105 °C for 2 h;

[0085] (2) Put the arsenic-containing desulfurized gypsum treated in step (1) into a nitric acid solution with a concentration of 0.5 mol / L. The liquid-solid ratio of the nitric acid solution to the arsenic-containing desulfurized gypsum is 15 mL:1 g. Then, add ethylene glycol to the nitric acid solution to soak the arsenic-containing desulfurized gypsum. The liquid-solid ratio of ethylene glycol to the arsenic-containing desulfurized gypsum is 20 mL:1 g. The soaking temperature is 90 °C, and the soaking time is 60 min. After soaking, filter, and then dry the obtained solid part at 90 °C for 2 h to obtain the first solid-phase product.

[0086] (3) Add the first solid-phase product to a potassium hydroxide solution with a concentration of 2.5 mol / L. The liquid-solid ratio of the sodium hydroxide solution to the first solid-phase product is 18 mL:1 g. Then, add a hydrogen peroxide solution with a concentration of 30% by weight to carry out the reaction. The volume ratio of the hydrogen peroxide solution to the potassium hydroxide solution is 1:15. The reaction temperature is 90 °C, and the reaction time is 90 min. After the reaction, filter, and then dry the obtained solid part at 105 °C for 6 h to obtain the second solid-phase product;

[0087] (4) Add the second solid-phase product to a sulfuric acid solution with a concentration of 1.2 mol / L. The liquid-solid ratio of the sulfuric acid solution to the second solid-phase product is 20 mL:1 g. Then, add a hydrogen peroxide solution with a concentration of 30% by weight to carry out the reaction. The volume ratio of the hydrogen peroxide solution to the sulfuric acid solution is 1:15. The reaction temperature is 90 °C, and the reaction time is 60 min. After the reaction, filter, and then dry the obtained solid part at 105 °C for 6 h to obtain the third solid-phase product;

[0088] (5) Prepare an ethanol solution by mixing ethanol and water at a volume ratio of 10:1. Then, place the third solid-phase product in the ethanol solution to carry out the reaction. The liquid-solid ratio of the ethanol solution to the third solid-phase product is 20 mL:1 g. The reaction temperature is 110 °C, and the reaction time is 4 min. After the reaction, filter, and then dry the obtained solid part at 105 °C for 6 h to obtain the powder.

[0089] Example 3

[0090] In this example, arsenic-containing desulfurized gypsum from a smelting industry in Yunnan is selected, which contains 4.39% by weight of arsenic and 16.21% by weight of calcium sulfite.

[0091] The treatment method of arsenic-containing desulfurized gypsum includes the following steps:

[0092] (1) Grind the arsenic-containing desulfurized gypsum, pass it through a 100-mesh sieve, and then dry it at 105 °C for 4 h;

[0093] (2) Put the arsenic-containing desulfurized gypsum treated in step (1) into an oxalic acid solution with a concentration of 2.2 mol / L. The liquid-solid ratio of the oxalic acid solution to the arsenic-containing desulfurized gypsum is 15 mL:1 g. Then, add propanol to the oxalic acid solution to soak the arsenic-containing desulfurized gypsum. The liquid-solid ratio of propanol to the arsenic-containing desulfurized gypsum is 20 mL:1 g. The soaking temperature is 100, and the soaking time is 60 min. After soaking, filter, and then dry the obtained solid part at 90 °C for 2 h to obtain the first solid-phase product;

[0094] (3) Add the first solid-phase product to an ammonia water solution with a concentration of 3 mol / L. The liquid-solid ratio of the ammonia water solution to the first solid-phase product is 15 mL:1 g. Then, add a hydrogen peroxide solution with a concentration of 30% by weight to carry out a reaction. The volume ratio of the hydrogen peroxide solution to the potassium hydroxide solution is 1:10. The reaction temperature is 90 °C, and the reaction time is 120 min. After the reaction, filter, and then dry the obtained solid part at 105 °C for 6 h to obtain the second solid-phase product;

[0095] (4) Add the second solid-phase product to a sulfuric acid solution with a concentration of 1.4 mol / L. The liquid-solid ratio of the sulfuric acid solution to the second solid-phase product is 22 mL:1 g. Then, add a hydrogen peroxide solution with a concentration of 30% by weight to carry out a reaction. The volume ratio of the hydrogen peroxide solution to the sulfuric acid solution is 1:20. The reaction temperature is 90 °C, and the reaction time is 60 min. After the reaction, filter, and then dry the obtained solid part at 105 °C for 6 h to obtain the third solid-phase product;

[0096] (5) Prepare an ethanol solution by mixing ethanol and water at a volume ratio of 10:1. Then, place the third solid-phase product in the ethanol solution for reaction. The liquid-solid ratio of the ethanol solution to the third solid-phase product is 25 mL:1 g. The reaction temperature is 105 °C, and the reaction time is 5 min. After the reaction, filter, and then dry the obtained solid part at 105 °C for 8 h to obtain the powder.

[0097] Comparative Example 1

[0098] Carry out the implementation according to the method of Example 1, except that steps (2) and (3) are not carried out.

[0099] Comparative Example 2

[0100] Carry out the implementation according to the method of Example 2, except that steps (4) and (5) are not carried out.

[0101] Comparative Example 3

[0102] Carry out the implementation according to the method of Example 3, except that in step (2), a hydrochloric acid solution is used to replace the citric acid solution, and in step (3), calcium hydroxide is used to replace the calcium hydroxide solution.

[0103] Comparative Example 4

[0104] Carry out the implementation according to the method of Example 1, except that step (3) is not carried out.

[0105] Comparative Example 5

[0106] Carry out the implementation according to the method of Example 1, except that step (4) is not carried out.

[0107] Test Example

[0108] The arsenic removal rate in the examples and comparative examples was measured and calculated, and at the same time, the content of calcium sulfite in the arsenic-containing desulfurized gypsum after treatment in the examples and comparative examples was measured. The results are shown in Table 1.

[0109] The arsenic removal rate was measured and calculated by inductively coupled plasma (ICP). Among them, the calculation method of the arsenic removal rate was: (the content of arsenic element in the arsenic-containing desulfurized gypsum - the content of arsenic element in the desulfurized gypsum after pretreatment) / the content of arsenic element in the desulfurized gypsum × 100%.

[0110] The content of calcium sulfite in the arsenic-containing desulfurized gypsum after treatment was measured according to "Iodometric Method for the Determination of Sulfite".

[0111] Table 1

[0112]

[0113]

[0114] As can be seen from Table 1, the method described in the present invention can effectively remove arsenic in the arsenic-containing desulfurized gypsum and can effectively oxidize calcium sulfite in the arsenic-containing desulfurized gypsum.

[0115] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for treating arsenic-containing desulfurized gypsum, characterized in that, The method comprises the following steps: (1) Ball-milling the arsenic-containing desulfurized gypsum, sieving it through a 100-mesh sieve, and drying it; (2) Immersing the arsenic-containing desulfurized gypsum treated in step (1) in an immersion liquid, followed by solid-liquid separation to obtain a first solid-phase product, wherein the immersion liquid contains an acid and a water-soluble organic substance, and the acid is selected from one or more of citric acid, nitric acid, and oxalic acid; (3) Reacting the first solid-phase product, an alkaline solution, and a first oxidant, followed by solid-liquid separation to obtain a second solid-phase product, wherein the base in the alkaline solution is ammonia water and / or sodium hydroxide, and the first oxidant is hydrogen peroxide; (4) Reacting the second solid-phase product, an acidic solution, and a second oxidant, followed by solid-liquid separation to obtain a third solid-phase product; (5) Reacting the third solid-phase product with an organic alcohol solution, followed by solid-liquid separation; In step (2), the conditions for immersion include: temperature ≥ 60 °C, time ≥ 30 min; In step (3), the conditions for the reaction include: temperature ≥ 50 °C, time ≥ 40 min; In step (4), the conditions for the reaction include: temperature ≥ 60 °C, time ≥ 30 min.

2. The method according to claim 1, wherein In step (1), the arsenic content in the arsenic-containing desulfurized gypsum is ≥ 0.2 wt%, and the calcium sulfite content is ≥ 2 wt%.

3. The method according to claim 1 or 2, characterized in that, In step (2), the acid in the immersion liquid is used in the form of an acid solution, and the concentration of the acid solution is 0.1 - 3 mol / L; and / or, the liquid-solid ratio of the acid solution to the arsenic-containing desulfurized gypsum is 20 - 5 mL:1 g.

4. The method according to claim 3, wherein In step (2), the water-soluble organic substance is selected from one or more of methanol, ethylene glycol, and propanol; and / or, the liquid-solid ratio of the water-soluble organic substance to the arsenic-containing desulfurized gypsum is 10 - 30 mL:1 g.

5. The method according to claim 1 or 2, characterized in that, In step (3), the concentration of the alkaline solution is 1 - 5 mol / L; and / or, the liquid-solid ratio of the alkaline solution to the first solid-phase product is 5 - 20 mL:1 g.

6. The method according to claim 1 or 2, characterized in that, In step (3), the first oxidant is used in the form of a first oxidant solution, and the concentration of the first oxidant solution is 20 - 35 wt%; and / or, the volume ratio of the first oxidant solution to the alkaline solution is 1:10 - 100.

7. The method according to claim 1 or 2, characterized in that, In step (4), the acid in the acidic solution is selected from one or more of sulfuric acid, nitric acid, and hydrochloric acid; and / or, in step (4), the concentration of the acidic solution is < 5 mol / L; and / or, the liquid-solid ratio of sulfuric acid to the second solid-phase product is ≥ 5 mL:1 g.

8. The method according to claim 1 or 2, characterized in that, In step (4), the second oxidant is hydrogen peroxide; and / or, in step (4), the second oxidant is used in the form of a second oxidant solution, and the concentration of the second oxidant solution is 20 - 35 wt%; and / or, the volume ratio of the second oxidant solution to the acidic solution is 1:10 - 40.

9. The method according to claim 1 or 2, characterized in that, In step (5), the number of carbon atoms of the organic alcohol in the organic alcohol solution is < 9; and / or, the volume ratio of the organic alcohol to water in the organic alcohol solution is 5 - 20:1; and / or, the liquid-solid ratio of the organic alcohol solution to the third solid-phase product is > 10 mL:1 g.

10. The method according to claim 1 or 2, characterized in that In step (5), the conditions for the reaction include: temperature ≥ 100 °C and time ≥ 2 h.

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