Advanced arsenic removal method for arsenic-containing gypsum and arsenic liquid treatment method

Abstract

The invention provides an arsenic-containing gypsum deep arsenic removal method and an arsenic liquid treatment method, and the method specifically comprises the following steps: carrying out first-step arsenic removal on gypsum by using HCl-H3PO4 mixed acid, then carrying out second-step arsenic removal by using HNO3-H3PO4 mixed acid, and finally carrying out third-step arsenic removal by using H2SO4-HNO3 mixed acid. MgO2 (having the effects of oxidizing trivalent arsenic and precipitating pentavalent arsenic) and NH3.H2O (having the effects of adjusting pH and precipitating pentavalent arsenic) are added into the arsenic-removed liquid to completely remove arsenic in the arsenic-removed liquid. The method is suitable for deep arsenic removal treatment of the arsenic-containing gypsum, after three-step arsenic removal, the arsenic leaching toxicity of the gypsum is lower than 5 mg / L, and the arsenic content is lower than 0.1%. The method is also suitable for arsenic treatment of the liquid after arsenic removal, and the arsenic concentration is reduced to 0.5 mg / L or below after precipitation of MgO2 and NH3.H2O.

Description

Technical Field

[0001] The invention relates to the technical field of chemical environmental protection, and in particular to a method for deep arsenic removal from arsenic-containing gypsum and a method for treating arsenic liquid. Background Art

[0002] During the smelting process, the neutralization of polluted acid will produce a large amount of arsenic-containing gypsum. According to my country's "Hazardous Waste Identification Standard Toxic Substance Content Identification" (GB5085.6-2007), the content of arsenic and arsenic compounds in solids is less than 0.1wt%, which is regarded as general solid waste. At the same time, the national standard stipulates that the arsenic leaching toxicity of arsenic-containing solid waste stored in the environment shall not exceed 5mg / L. Often, these gypsums in smelting exceed national standards and are classified as hazardous solid wastes. The storage and accumulation in the environment will cause serious environmental pollution problems.

[0003] At present, there are chemical methods for arsenic removal technology: chemical reactions are carried out using chemical reagents such as alkali solution and acid solution to dissolve and separate arsenic from gypsum. Biological method: arsenic is dissolved and removed from gypsum using microbial metabolic activities. Physical method: arsenic is removed by physical separation processes such as heat treatment, electrochemistry, and membrane separation. There are also some costly bipolar membrane electrodialysis, redox coupling methods, etc. Among the currently disclosed technologies, chemical arsenic removal is the most widely used. Guan Qingjun disclosed a method for deep arsenic removal from arsenic gypsum in CN 116812960A, which mainly uses a single acid wash + phase reconstruction to treat arsenic-containing gypsum. This method is complicated to operate, requires a high temperature of 95°C, has high energy consumption, and does not dispose of the removed arsenic, which has the risk of polluting the environment. Jia Yongfeng disclosed a method for resource treatment of arsenic-containing gypsum and the application of the low-arsenic gypsum obtained by treatment in CN110395919A, which mainly involves mixing arsenic-containing gypsum with an acidic solution and then recrystallizing it. The disadvantage of this method is that recrystallization requires a high temperature and high pressure device and is inefficient. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention discloses a method for deep arsenic removal from arsenic-containing gypsum and disposal of arsenic liquid. The method treats the arsenic-containing gypsum in two steps of mixing strong acid and one step of mixing weak acid, which can effectively reduce the arsenic content and arsenic leaching toxicity in the arsenic-containing gypsum at room temperature. In addition, the arsenic removal liquid is synergistically treated with oxidizing MgO2 and alkaline NH3·H2O, which effectively reduces the arsenic concentration in the arsenic liquid and further enhances the arsenic disposal capacity.

[0005] The technical solution of the present invention is as follows: a method for deep arsenic removal from arsenic-containing gypsum, the method specifically comprising the following steps:

[0006] S1) First step arsenic removal with strong acid: Grind some arsenic drying gypsum residue, then pour into the prepared HCl-H3PO4 mixed acid, stir at a certain rate for a period of time, separate the solid and liquid after stirring, and dry the solid to obtain the first step arsenic removal gypsum and the first step arsenic removal liquid;

[0007] S2) Strong acid second step arsenic removal: The first step arsenic removal gypsum obtained in S1) is ground, and then poured into the prepared HNO3-H3PO4 mixed acid, stirred at a certain rate for a period of time, and after the stirring is completed, the solid-liquid separation and the solid drying are performed to obtain the second step arsenic removal gypsum and the second step arsenic removal liquid;

[0008] S3) Weak acid third step arsenic removal: The second step arsenic removal gypsum obtained in S2) is ground, and then the prepared H2SO4-HNO3 mixed acid is poured into it, and stirred at a certain rate for a period of time. After the stirring is completed, the solid and liquid are separated and the solid is dried to obtain the gypsum with deep arsenic removal and the third step arsenic removal liquid.

[0009] Furthermore, the specific process parameters in S1) are: the arsenic content of the dried gypsum slag is 0.3% to 4%, the grinding particle size is 50 to 100 mesh, the solid-liquid ratio of the mixed acid and gypsum slag is 4:1 to 6:1, the stirring rate is 400 to 600 rpm, and the stirring time is 0.5 to 1 h.

[0010] Furthermore, the specific process parameters in S2) are as follows: the grinding particle size of the arsenic-removing gypsum in the second step is 50-100 mesh, the mixed acid is a mixture of HNO3 and H3PO4, wherein the concentration of HNO3 is 0.4M-0.8M, the concentration of H3PO4 is 0.05M-0.15M, the solid-liquid ratio of the mixed acid and gypsum slag is 4:1-6:1, the stirring rate is 400-600rpm, and the stirring time is 0.5-1h.

[0011] Furthermore, in the second step of S3), the arsenic-removing gypsum grinding particle size is 50-100 mesh, the mixed acid is H2SO4 and HNO3, the pH value of the mixed acid is 2.5-3.5, the solid-liquid ratio of the mixed acid to the gypsum slag is 4:1-6:1, the stirring rate is 400-600rpm, and the stirring time is 0.5-1h.

[0012] Furthermore, after the deep arsenic removal in S3), the arsenic leaching toxicity of the gypsum is lower than 5 mg / L and the arsenic content is lower than 0.1%.

[0013] Further, the amount of MgO2 added in S4) is Mg 2+ The molar ratio of As is 2-3:1, the amount of NH3·H2O added is such that the pH reaches 9-12, the stirring rate is 300-500 rpm, and the stirring time is 1-2 h.

[0014] Another object of the present invention is to provide a method for solidifying and disposing the arsenic solution obtained by the above method, which specifically comprises the following steps: combining the first step dearsenic solution, the second step dearsenic solution and the third step dearsenic solution to obtain a mixed dearsenic solution, adding MgO2 (which has the function of oxidizing trivalent arsenic and precipitating pentavalent arsenic) to the mixed dearsenic solution, wherein Mg 2+ The molar ratio of As is 2-3:1, and then NH3·H2O (which has the function of adjusting pH and precipitating pentavalent arsenic) is added to adjust the pH to 9-12. The stirring rate is 300-500 rpm, and the stirring time is 1-2 hours. After the reaction is completed, the solid arsenic liquid and the ammonium magnesium arsenate precipitated solid arsenic slag are obtained by filtration.

[0015] Furthermore, the arsenic concentration of the arsenic solid solution is lower than 0.5 mg / L.

[0016] A kind of gypsum is prepared by adopting the above method.

[0017] The beneficial effects of the present invention are as follows: due to the adoption of the above technical solution, the HCl-H3PO4 mixed strong acid and the HNO3-H3PO4 mixed strong acid in the present invention can remove the arsenic in the specifically adsorbed state in the gypsum;

[0018] A mixture of H2SO4-HNO3 weak acid can remove the nonspecifically adsorbed arsenic in gypsum;

[0019] The entire process is carried out at room temperature and pressure, which is convenient and low-cost;

[0020] Moreover, MgO2 in the arsenic liquid solidification treatment has the functions of oxidizing trivalent arsenic and precipitating pentavalent arsenic, and NH3·H2O has the functions of adjusting pH and precipitating pentavalent arsenic. The reagents and methods are efficient and convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope of protection of the present invention. In each of the drawings, similar components are numbered similarly.

[0022] Figure 1 The SEM spectrum of gypsum after deep arsenic removal in the embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0024] The present invention discloses a method for deep arsenic removal from arsenic-containing gypsum and disposal of arsenic liquid, which comprises the following steps:

[0025] 1) First step of strong acid arsenic removal: Take some dried gypsum slag with arsenic content of 0.3% to 4%, grind it to 50 to 100 mesh, then pour in the prepared HCl-H3PO4 mixed acid (HCl concentration is 0.4M to 0.8M, H3PO4 concentration is 0.05M to 0.15M), the mixed acid and gypsum slag are in a solid-liquid ratio of 4:1 to 6:1. The stirring rate is 400 to 600 rpm, the stirring time is 0.5 to 1h, and after the stirring is completed, the solid and liquid are separated and the solid is dried to obtain the first step of arsenic removal gypsum and the first step of arsenic removal liquid.

[0026] 2) Strong acid second step arsenic removal: Grind the first step arsenic removal gypsum in step 1) to 50-100 mesh, then pour in the prepared HNO3-H3PO4 mixed acid (HNO3 concentration is 0.4M-0.8M, H3PO4 concentration is 0.05M-0.15M), the mixed acid and gypsum slag are in a solid-liquid ratio of 4:1-6:1. The stirring rate is 400-600rpm, the stirring time is 0.5-1h, and after the stirring is completed, the solid-liquid separation and the solid drying are performed to obtain the second step arsenic removal gypsum and the second step arsenic removal liquid.

[0027] 3) Weak acid third step arsenic removal: Grind some of the second step arsenic removal gypsum in step 2) to 50-100 mesh, then pour in H2SO4-HNO3 mixed acid with a pH of 2.5-3.5, and the mixed acid and gypsum slag are in a solid-liquid ratio of 4:1-6:1. The stirring rate is 400-600rpm, and the stirring time is 0.5-1h. After the stirring is completed, the solid-liquid separation and the solid drying are performed to obtain the gypsum with deep arsenic removal (the gypsum leaching toxicity is less than 5mg / L and the arsenic content is less than 0.1%) and the third step arsenic removal liquid.

[0028] 4) Arsenic solution solidification treatment: The first step dearsenic solution, the second step dearsenic solution and the third step dearsenic solution are combined to obtain a mixed dearsenic solution, and MgO2 (which has the function of oxidizing trivalent arsenic and precipitating pentavalent arsenic) is added to the mixed dearsenic solution. 2+ The molar ratio of As is 2-3:1, and then NH3·H2O (which has the function of adjusting pH and precipitating pentavalent arsenic) is added to adjust the pH to 9-12. The stirring rate is 300-500 rpm, and the stirring time is 1-2 hours. After the reaction is completed, the solid arsenic liquid and the solid arsenic slag ammonium magnesium arsenate precipitate are obtained by filtration.

[0029] Preferably, step 1) strong acid first step arsenic removal: take some dried gypsum slag with 1% arsenic content and grind it to 75 mesh, then pour in the prepared HCl-H3PO4 mixed acid (HCl concentration is 0.6M, H3PO4 concentration is 0.1M), the mixed acid and gypsum slag are in a solid-liquid ratio of 5:1. The stirring rate is 500rpm, the stirring time is 0.8h, after the stirring is completed, the solid and liquid are separated and the solid is dried to obtain the first step arsenic removal gypsum and the first step arsenic removal liquid;

[0030] Preferably, step 2) strong acid second step arsenic removal: take some first step arsenic removal gypsum in step 1) and grind it to 75 mesh, then pour in the prepared HNO3-H3PO4 mixed acid (HNO3 concentration is 0.6M, H3PO4 concentration is 0.1M), the mixed acid and gypsum slag are in a solid-liquid ratio of 5:1. The stirring rate is 500rpm, the stirring time is 0.5h, after the stirring is completed, the solid-liquid separation and the solid drying are carried out to obtain the second step arsenic removal gypsum and the second step arsenic removal liquid;

[0031] Preferably, step 3) weak acid third step arsenic removal: take some of the second step arsenic removal gypsum in step 2) and grind it to 75 mesh, then pour in H2SO4-HNO3 mixed acid with a pH of 3.2, and the mixed acid and gypsum slag are in a solid-liquid ratio of 5:1. The stirring rate is 450rpm, and the stirring time is 1h. After the stirring is completed, the solid-liquid separation and the solid drying are performed to obtain the gypsum with deep arsenic removal (the gypsum leaching toxicity is less than 5mg / L and the arsenic content is less than 0.1%) and the third step arsenic removal liquid;

[0032] Preferably, step 4) solidification treatment of the arsenic solution: the first step arsenic removal solution, the second step arsenic removal solution and the third step arsenic removal solution are combined to obtain a mixed arsenic removal solution, and MgO2 (which has the function of oxidizing trivalent arsenic and precipitating pentavalent arsenic) is added to the mixed arsenic removal solution, wherein Mg 2+ The molar ratio of As to water was 3:1, and then NH3·H2O (which has the function of adjusting pH and precipitating pentavalent arsenic) was added to adjust the pH to 12. The stirring rate was 400 rpm, and the stirring time was 1.5 h. After the reaction was completed, solid arsenic slag magnesium ammonium arsenate precipitate was obtained by filtration.

[0033] Embodiment 1:

[0034] A method for deep arsenic removal from arsenic-containing gypsum and disposal of arsenic liquid comprises the following steps:

[0035] 1) First-step arsenic removal with strong acid: Grind some dried gypsum slag with arsenic content of 1.5% to 80 mesh, then pour in the prepared HCl-H3PO4 mixed acid (HCl concentration is 0.5, H3PO4 concentration is 0.08M), the mixed acid and gypsum slag are in a solid-liquid ratio of 4:1. The stirring rate is 400rpm, the stirring time is 0.5h, and after the stirring is completed, the solid-liquid separation and the solid drying are performed to obtain the first-step arsenic removal gypsum and the first-step arsenic removal liquid.

[0036] 2) Strong acid second step arsenic removal: Grind the first step arsenic removal gypsum in step 1) to 50 mesh, then pour in the prepared HNO3-H3PO4 mixed acid (HNO3 concentration is 0.4M, H3PO4 concentration is 0.05M), the mixed acid and gypsum slag are in a solid-liquid ratio of 4:1. The stirring rate is 500rpm, the stirring time is 0.7h, and after the stirring is completed, the solid-liquid separation and the solid drying are performed to obtain the second step arsenic removal gypsum and the second step arsenic removal liquid.

[0037] 3) Weak acid third step arsenic removal: Grind some of the second step arsenic removal gypsum in step 2) to 75 mesh, then pour in H2SO4-HNO3 mixed acid with a pH of 3.5, and the mixed acid and gypsum slag are in a solid-liquid ratio of 4:1. The stirring rate is 450rpm, and the stirring time is 0.5h. After the stirring is completed, the solid-liquid separation and the solid drying are performed to obtain the gypsum with deep arsenic removal (the gypsum leaching toxicity is 0.85mg / L and the arsenic content is 0.042%) and the third step arsenic removal liquid.

[0038] 4) Arsenic solution solidification treatment: The first step dearsenic solution, the second step dearsenic solution and the third step dearsenic solution are combined to obtain a mixed dearsenic solution, and MgO2 (which has the function of oxidizing trivalent arsenic and precipitating pentavalent arsenic) is added to the mixed dearsenic solution. 2+ The molar ratio of As was 2.5:1, and then NH3·H2O (which has the function of adjusting pH and precipitating pentavalent arsenic) was added to adjust the pH to 12. The stirring rate was 350 rpm, and the stirring time was 1 h. After the reaction was completed, solid arsenic liquid (arsenic concentration was 0.28 mg / L) and solid arsenic slag ammonium magnesium arsenate precipitate were obtained by filtration.

[0039] Embodiment 2:

[0040] A method for deep arsenic removal from arsenic-containing gypsum and disposal of arsenic liquid comprises the following steps:

[0041] 1) First-step arsenic removal with strong acid: Grind some dried gypsum slag with arsenic content of 2.3% to 100 mesh, then pour in the prepared HCl-H3PO4 mixed acid (HCl concentration is 0.7M, H3PO4 concentration is 0.12M), and the mixed acid and gypsum slag are in a solid-liquid ratio of 5:1. The stirring rate is 470rpm, and the stirring time is 0.6h. After the stirring is completed, the solid and liquid are separated and the solid is dried to obtain the first-step arsenic removal gypsum and the first-step arsenic removal liquid.

[0042] 2) Strong acid second step arsenic removal: Grind the first step arsenic removal gypsum in step 1) to 60 mesh, then pour in the prepared HNO3-H3PO4 mixed acid (HNO3 concentration is 0.7M, H3PO4 concentration is 0.09M), the mixed acid and gypsum slag are in a solid-liquid ratio of 5:1. The stirring rate is 520rpm, the stirring time is 0.8h, and after the stirring is completed, the solid-liquid separation and the solid drying are performed to obtain the second step arsenic removal gypsum and the second step arsenic removal liquid.

[0043] 3) Weak acid third step arsenic removal: Grind some of the second step arsenic removal gypsum in step 2) to 70 mesh, then pour in H2SO4-HNO3 mixed acid with a pH of 3.1, and the mixed acid and gypsum slag are in a solid-liquid ratio of 5:1. The stirring rate is 490rpm, and the stirring time is 0.7h. After the stirring is completed, the solid-liquid separation and the solid drying are performed to obtain the gypsum with deep arsenic removal (the gypsum leaching toxicity is 0.72mg / L and the arsenic content is 0.034%) and the third step arsenic removal liquid.

[0044] 4) Arsenic solution solidification treatment: The first step dearsenic solution, the second step dearsenic solution and the third step dearsenic solution are combined to obtain a mixed dearsenic solution, and MgO2 (which has the function of oxidizing trivalent arsenic and precipitating pentavalent arsenic) is added to the mixed dearsenic solution. 2+ The molar ratio of As to As was 2.2:1, and then NH3·H2O (which has the function of adjusting pH and precipitating pentavalent arsenic) was added to adjust the pH to 11. The stirring rate was 400 rpm, and the stirring time was 1.3 h. After the reaction was completed, solid arsenic liquid (arsenic concentration was 0.31 mg / L) and solid arsenic slag ammonium magnesium arsenate precipitate were obtained by filtration.

[0045] Embodiment 3:

[0046] A method for deep arsenic removal from arsenic-containing gypsum and disposal of arsenic liquid comprises the following steps:

[0047] 1) First-step arsenic removal with strong acid: Grind some dried gypsum slag with arsenic content of 0.7% to 75 mesh, then pour in the prepared HCl-H3PO4 mixed acid (HCl concentration is 0.6M, H3PO4 concentration is 0.1M), and the mixed acid and gypsum slag are in a solid-liquid ratio of 5:1. The stirring rate is 500rpm, and the stirring time is 0.6h. After the stirring is completed, the solid and liquid are separated and the solid is dried to obtain the first-step arsenic removal gypsum and the first-step arsenic removal liquid.

[0048] 2) Strong acid second step arsenic removal: Grind the first step arsenic removal gypsum in step 1) to 75 mesh, then pour in the prepared HNO3-H3PO4 mixed acid (HNO3 concentration is 0.6M, H3PO4 concentration is 0.1M), the mixed acid and gypsum slag are in a solid-liquid ratio of 5:1. The stirring rate is 500rpm, the stirring time is 0.7h, and after the stirring is completed, the solid-liquid separation and the solid drying are performed to obtain the second step arsenic removal gypsum and the second step arsenic removal liquid.

[0049] 3) Weak acid third step arsenic removal: Grind some of the second step arsenic removal gypsum in step 2) to 75 mesh, then pour in H2SO4-HNO3 mixed acid with a pH of 3.5, and the mixed acid and gypsum slag are in a solid-liquid ratio of 5:1. The stirring rate is 500rpm, and the stirring time is 1h. After the stirring is completed, the solid-liquid separation and the solid drying are performed to obtain the gypsum with deep arsenic removal (the gypsum leaching toxicity is 0.66mg / L and the arsenic content is 0.031%) and the third step arsenic removal liquid.

[0050] 4) Arsenic solution solidification treatment: The first step dearsenic solution, the second step dearsenic solution and the third step dearsenic solution are combined to obtain a mixed dearsenic solution, and MgO2 (which has the function of oxidizing trivalent arsenic and precipitating pentavalent arsenic) is added to the mixed dearsenic solution. 2+ The molar ratio of arsenic to As was 3:1, and then NH3·H2O (which has the function of adjusting pH and precipitating pentavalent arsenic) was added to adjust the pH to 12. The stirring rate was 3400 rpm, and the stirring time was 1 h. After the reaction was completed, solid arsenic liquid (arsenic concentration was 0.26 mg / L) and solid arsenic slag ammonium magnesium arsenate precipitate were obtained by filtration.

[0051] Embodiment 4:

[0052] A method for deep arsenic removal from arsenic-containing gypsum and disposal of arsenic liquid comprises the following steps:

[0053] 1) First-step arsenic removal with strong acid: Grind some dried gypsum slag with arsenic content of 3.6% to 50 mesh, then pour in the prepared HCl-H3PO4 mixed acid (HCl concentration is 0.8M, H3PO4 concentration is 0.15M), the mixed acid and gypsum slag are in a solid-liquid ratio of 6:1. The stirring rate is 600rpm, the stirring time is 0.5-1h, and after the stirring is completed, the solid-liquid separation and the solid drying are performed to obtain the first-step arsenic removal gypsum and the first-step arsenic removal liquid.

[0054] 2) Strong acid second step arsenic removal: Grind the first step arsenic removal gypsum in step 1) to 50 mesh, then pour in the prepared HNO3-H3PO4 mixed acid (HNO3 concentration is 0.8M, H3PO4 concentration is 0.15M), the mixed acid and gypsum slag are in a solid-liquid ratio of 6:1. The stirring rate is 600rpm, the stirring time is 1h, and after the stirring is completed, the solid-liquid separation and the solid drying are performed to obtain the second step arsenic removal gypsum and the second step arsenic removal liquid.

[0055] 3) Weak acid third step arsenic removal: Grind some of the second step arsenic removal gypsum in step 2) to 50 mesh, then pour in H2SO4-HNO3 mixed acid with a pH of 2.5, and the mixed acid and gypsum slag are in a solid-liquid ratio of 6:1. The stirring rate is 600rpm, and the stirring time is 1h. After the stirring is completed, the solid-liquid separation and the solid drying are performed to obtain the gypsum with deep arsenic removal (the gypsum leaching toxicity is 0.49mg / L and the arsenic content is 0.025%) and the third step arsenic removal liquid.

[0056] 4) Arsenic solution solidification treatment: The first step dearsenic solution, the second step dearsenic solution and the third step dearsenic solution are combined to obtain a mixed dearsenic solution, and MgO2 (which has the function of oxidizing trivalent arsenic and precipitating pentavalent arsenic) is added to the mixed dearsenic solution. 2+The molar ratio of As is 3:1, and then NH3·H2O (which has the function of adjusting pH and precipitating pentavalent arsenic) is added to adjust the pH to 12. The stirring rate is 500 rpm, the stirring time is 2 h, and after the reaction is completed, solid arsenic slag ammonium magnesium arsenate precipitate is obtained by filtration.

[0057] The arsenic leaching toxicity and arsenic content of gypsum in Examples 1-4 were measured respectively, and the measurement results are shown in Table 1.

[0058] The test method of As leaching toxicity is as follows: take an appropriate amount of dry sample in a polytetrafluoroethylene bottle, add a leaching agent (a mixed acid solution of sulfuric acid and nitric acid with a pH of 3.20±0.05) with a liquid-solid ratio of 10:1L / kg to the bottle, and leaching for (18±2)h in a flip-type oscillating device with a rotation speed of (30±2)r / min. After the leaching process is completed, filter the suspension and determine the As concentration in the filtrate.

[0059] As element content test: weigh 2g of dry solid sample and place it in a 1L polytetrafluoroethylene beaker, then add 250mL of 6mol / LHCl solution for digestion, then make the volume to 500mL, determine the As element concentration in the digestion solution, and calculate the mass fraction.

[0060] Table 1 Arsenic leaching toxicity and arsenic content in gypsum

[0061] Example 1 Example 2 Example 3 Example 4 Arsenic leaching toxicity 0.85mg / L 0.72mg / L 0.66mg / L 0.49mg / L Arsenic content 0.042％ 0.034％ 0.031％ 0.025％ .

[0062] The embodiments of the present application provide a method for deep arsenic removal from arsenic-containing gypsum and a method for treating arsenic liquid, which are described in detail. The description of the above embodiments is only used to help understand the method and its core idea of ​​the present application; at the same time, for those skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

[0063] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. As mentioned throughout the specification and claims, "including" and "comprising" are open-ended terms, so they should be interpreted as "including / including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problems within a preset error range and basically achieve the technical effects. The subsequent description of the specification is a preferred embodiment of the present application, but the description is for the purpose of illustrating the general principles of the present application, and is not used to limit the scope of the present application. The scope of protection of the present application shall be subject to that defined in the attached claims.

[0064] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such a product or system. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the product or system including the elements.

[0065] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0066] The above description shows and describes several preferred embodiments of the present application, but as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the present application, and should be within the scope of protection of the claims attached to the present application.

Claims

1. A method for deep arsenic removal from arsenic-containing gypsum, characterized in that: The method specifically comprises the following steps: S1) First step arsenic removal with strong acid: Grind some arsenic drying gypsum residue, then pour into the prepared HCl-H3PO4 mixed acid, stir at a certain rate for a period of time, separate the solid and liquid after stirring, and dry the solid to obtain the first step arsenic removal gypsum and the first step arsenic removal liquid; S2) Strong acid second step arsenic removal: The first step arsenic removal gypsum obtained in S1) is ground, and then poured into the prepared HNO3-H3PO4 mixed acid, stirred at a certain rate for a period of time, and after the stirring is completed, the solid-liquid separation and the solid drying are performed to obtain the second step arsenic removal gypsum and the second step arsenic removal liquid; S3) Weak acid third step arsenic removal: The second step arsenic removal gypsum obtained in S2) is ground, and then the prepared H2SO4-HNO3 mixed acid is poured into it, and stirred at a certain rate for a period of time. After the stirring is completed, the solid and liquid are separated and the solid is dried to obtain the gypsum with deep arsenic removal and the third step arsenic removal liquid.

2. The method according to claim 1, characterized in that The specific process parameters in S1) are: the arsenic content of the dried gypsum slag is 0.3% to 4%, the grinding particle size is 50 to 100 meshes, the solid-liquid ratio of the mixed acid and gypsum slag is 4:1 to 6:1, the stirring rate is 400 to 600 rpm, and the stirring time is 0.5 to 1 h.

3. The method according to claim 1, characterized in that The specific process parameters in S2) are as follows: the grinding particle size of the arsenic-free gypsum in the second step is 50-100 mesh, the mixed acid is a mixture of HNO3 and H3PO4, wherein the concentration of HNO3 is 0.4M-0.8M, the concentration of H3PO4 is 0.05M-0.15M, the solid-liquid ratio of the mixed acid to the gypsum slag is 4:1-6:1, the stirring rate is 400-600rpm, and the stirring time is 0.5-1h.

4. The method according to claim 1, characterized in that In the first step of S3), the arsenic removal gypsum grinding particle size is 50-100 mesh, the mixed acid is H2SO4 and HNO3, the pH value of the mixed acid is 2.5-3.5, the solid-liquid ratio of the mixed acid and gypsum slag is 4:1-6:1, the stirring rate is 400-600rpm, and the stirring time is 0.5-1h.

5. The method according to claim 1, characterized in that After the deep arsenic removal in S3), the arsenic leaching toxicity of the gypsum is lower than 5 mg / L and the arsenic content is lower than 0.1%.

6. The method according to claim 1, characterized in that The method further comprises S4) solidification treatment of the arsenic liquid: combining the first step dearsenicating liquid, the second step dearsenicating liquid and the third step dearsenicating liquid to obtain a mixed dearsenicating liquid, adding MgO2 to the mixed dearsenicating liquid for reaction, and filtering after the reaction to obtain a solid arsenic liquid and a magnesium ammonium arsenate precipitated solid arsenic slag.

7. The method according to claim 6, characterized in that The amount of MgO2 added in S4) is Mg 2+ The molar ratio of As is 2-3:1, the amount of NH3·H2O added is such that the pH reaches 9-12, the stirring rate is 300-500 rpm, and the stirring time is 1-2 h.

8. The method according to claim 7, characterized in that The arsenic concentration of the arsenic solid solution in S4) is lower than 0.5 mg / L.

9. A gypsum, characterized in that: The gypsum is prepared by the method according to any one of claims 1 to 5.

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