Method for deep arsenic removal of arsenic-containing gypsum and method for arsenic liquid disposal

Abstract

The application provides a method for deep dearsenication of arsenic-containing gypsum and a method for arsenic liquid treatment, which specifically comprises the following steps: first, using HCl-H3PO4 mixed acid to perform first-step dearsenication on the gypsum, then using HNO3-H3PO4 mixed acid to perform second-step dearsenication, and finally using H2SO4-HNO3 mixed acid to perform third-step dearsenication. After dearsenication, MgO2 (which has the effects of oxidizing trivalent arsenic and precipitating pentavalent arsenic) and NH3H2O (which has the effects of adjusting pH and precipitating pentavalent arsenic) are added to completely remove arsenic in the dearsenication liquid. The application is suitable for deep dearsenication treatment of arsenic-containing gypsum, and after three-step dearsenication, the arsenic leaching toxicity of the gypsum is lower than 5 mg / L and the arsenic content is lower than 0.1%. The application is also suitable for arsenic treatment of the dearsenication liquid, and after precipitation by MgO2 and NH3H2O, the arsenic concentration is reduced to below 0.5 mg / L.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical environmental protection technology, and in particular to a method for deep dearsenification of arsenic-containing gypsum and a method for arsenic liquid disposal. BACKGROUND

[0002] A large amount of arsenic-containing gypsum is produced in the process of neutralizing waste acid. According to the Hazardous Waste Identification Standard Toxic Substance Content Identification (GB5085.6-2007) of China, the arsenic and arsenic compound content in solid is less than 0.1wt%, which is regarded as general solid waste. At the same time, the arsenic leaching toxicity of arsenic-containing solid waste stored in the environment shall not be higher than 5mg / L. The arsenic content in the gypsum in the smelting process often exceeds the national standard, which belongs to hazardous solid waste, and the storage and accumulation in the environment will cause serious environmental pollution problems.

[0003] Currently, there are chemical methods, biological methods, and physical methods for dearsenification. The chemical method uses chemical reagents such as lye and acid to react with arsenic in gypsum to remove arsenic. The biological method uses microbial metabolic activity to remove arsenic from gypsum. The physical method uses heat treatment, electrochemistry, and membrane separation to remove arsenic. There are also some high-cost methods such as bipolar membrane electrodialysis and oxidation-reduction coupling. Among the currently disclosed technologies, the chemical method is the most widely used. Gu Qingjun discloses a method for deep dearsenification of arsenic gypsum in CN116812960A, which mainly uses single acid washing + phase reconstruction to treat arsenic-containing gypsum. This method is complex to operate, requires high temperature of 95℃, has high energy consumption, and does not dispose of the removed arsenic, which has the risk of polluting the environment. Jia Yongfeng discloses a method for resourceful treatment of arsenic-containing gypsum and application of low-arsenic gypsum obtained by the treatment in CN110395919A. The method mainly mixes arsenic-containing gypsum with an acidic solution and then recrystallizes. The disadvantage of this method is that recrystallization requires a high-temperature and high-pressure device, and the efficiency is low. SUMMARY

[0004] In view of the problems existing in the prior art, the present application discloses a method for deep dearsenification of arsenic-containing gypsum and disposal of arsenic liquid. The method can effectively reduce the arsenic content and arsenic leaching toxicity of arsenic-containing gypsum at room temperature through two-step mixed strong acid and one-step mixed weak acid step-by-step treatment. In addition, the dearsenification liquid is treated by oxidation MgO2 and alkaline NH3·H2O to effectively reduce the arsenic concentration in the arsenic liquid, and further enhance the disposal capacity of arsenic.

[0005] The technical scheme of the present application is as follows: a method for deep dearsenification of arsenic-containing gypsum, which specifically comprises the following steps:

[0006] S1) First step of arsenic removal by strong acid: A certain amount of arsenic-containing dried gypsum residue is ground, then poured into the prepared HCl-H3PO4 mixed acid, stirred at a certain rate for a period of time, and then solid-liquid separation is performed after stirring. The first step of arsenic removal gypsum and the first step of arsenic removal liquid are obtained after drying the solid.

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

[0008] S3) Third step of arsenic removal by weak acid: The second step of arsenic removal gypsum obtained in S2) is ground, then poured into the prepared H2SO4-HNO3 mixed acid, stirred at a certain rate for a period of time, and then solid-liquid separation is performed after stirring. The third step of arsenic removal gypsum and the third step of arsenic removal liquid are obtained after drying the solid.

[0009] Further, the specific process parameters in S1) are: the arsenic content of the dried gypsum residue is 0.3% to 4%, the grinding particle size is 50 to 100 mesh, the solid-liquid ratio of the mixed acid and the gypsum residue 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] Further, the specific process parameters in S2) are: the second step of arsenic removal gypsum grinding particle size is 50 to 100 mesh, the mixed acid is HNO3 and H3PO4, the HNO3 concentration is 0.4M to 0.8M, the H3PO4 concentration is 0.05M to 0.15M, the solid-liquid ratio of the mixed acid and the gypsum residue is 4:1 to 6:1, the stirring rate is 400 to 600 rpm, and the stirring time is 0.5 to 1 h.

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

[0012] Further, the arsenic leaching toxicity of the third step of arsenic removal gypsum in S3) is less than 5mg / L and the arsenic content is less than 0.1%.

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

[0014] Another object of the present application also provides an arsenic liquid solidification treatment method obtained by the above method, specifically comprising the following steps: combining the first step arsenic removal liquid, the second step arsenic removal liquid and the third step arsenic removal liquid to obtain a mixed arsenic removal liquid, adding MgO2 (with the functions of oxidizing trivalent arsenic and precipitating pentavalent arsenic) to the mixed arsenic removal liquid, wherein Mg 2+ :As molar ratio is 2-3:1, then adding NH3·H2O (with the functions of adjusting pH and precipitating pentavalent arsenic) to adjust the pH to 9-12. The stirring rate is 300-500 rpm, the stirring time is 1-2 h, and after the reaction is completed, the arsenic solidification post-liquid and the arsenic acid magnesium precipitate arsenic residue are obtained by filtration.

[0015] Further, the arsenic concentration of the arsenic solidification post-liquid is lower than 0.5 mg / L.

[0016] A gypsum prepared by the above method.

[0017] The beneficial effects of the present application are: due to the above technical solutions, the HCl-H3PO4 mixed strong acid and the HNO3-H3PO4 mixed strong acid in the present application can remove the specific adsorption state arsenic in the gypsum;

[0018] The H2SO4-HNO3 mixed weak acid can remove the non-specific adsorption state arsenic in the gypsum;

[0019] The whole process is carried out at room temperature and normal pressure, which is convenient and low in cost;

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

[0021] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings needed to be used in the embodiments, and it should be understood that the following drawings only show some embodiments of the present application, and should not be regarded as limiting the scope of protection of the present application. In each drawing, similar components are marked with similar reference numerals.

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

[0023] The technical solutions in the embodiments of the present application will be described clearly and completely below, and obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments.

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

[0025] 1) Strong acid first step arsenic removal: Take several arsenic content of 0.3% ~ 4% of the dried gypsum slag grinding to 50 ~ 100 mesh, then pour into the configuration of HCl-H3PO4 mixed acid (HCl concentration of 0.4M ~ 0.8M, H3PO4 concentration of 0.05M ~ 0.15M), mixed acid and gypsum slag according to the solid-liquid ratio of 4:1 ~ 6:1. The stirring rate is 400 ~ 600 rpm, the stirring time is 0.5 ~ 1 h, after stirring, solid-liquid separation and solid drying to get the first step arsenic removal gypsum and the first step arsenic removal liquid.

[0026] 2) Strong acid second step arsenic removal: Take several first step arsenic removal gypsum in step 1) grinding to 50 ~ 100 mesh, then pour into the configuration of HNO3-H3PO4 mixed acid (HNO3 concentration of 0.4M ~ 0.8M, H3PO4 concentration of 0.05M ~ 0.15M), mixed acid and gypsum slag according to the solid-liquid ratio of 4:1 ~ 6:1. The stirring rate is 400 ~ 600 rpm, the stirring time is 0.5 ~ 1 h, after stirring, solid-liquid separation and solid drying to get the second step arsenic removal gypsum and the second step arsenic removal liquid.

[0027] 3) Weak acid third step arsenic removal: Take several second step arsenic removal gypsum in step 2) grinding to 50 ~ 100 mesh, then pour into the H2SO4-HNO3 mixed acid with pH of 2.5 ~ 3.5, mixed acid and gypsum slag according to the solid-liquid ratio of 4:1 ~ 6:1. The stirring rate is 400 ~ 600 rpm, the stirring time is 0.5 ~ 1 h, after stirring, solid-liquid separation and solid drying to get the gypsum after deep removal of arsenic (the leaching toxicity of this gypsum is lower than 5 mg / L and the arsenic content is lower than 0.1%) and the third step arsenic removal liquid.

[0028] 4) Arsenic liquid solidification disposal: The first step arsenic removal liquid, the second step arsenic removal liquid and the third step arsenic removal liquid are combined to get the mixed arsenic removal liquid, MgO2 (with the functions of oxidizing trivalent arsenic and precipitating pentavalent arsenic) is added to the mixed arsenic removal liquid, wherein the molar ratio of MgO2:As is 2-3:1, then NH3·H2O (with the functions of adjusting pH and precipitating pentavalent arsenic) is added to adjust the pH to 9 ~ 12. The stirring rate is 300 ~ 500 rpm, the stirring time is 1 ~ 2 h, after the reaction, the solid arsenic is filtered to get the solid arsenic and the solid arsenic slag arsenate magnesium precipitate. 2+ :As molar ratio of 2-3:1, then NH3·H2O (with the functions of adjusting pH and precipitating pentavalent arsenic) is added to adjust the pH to 9 ~ 12. The stirring rate is 300 ~ 500 rpm, the stirring time is 1 ~ 2 h, after the reaction, the solid arsenic is filtered to get the solid arsenic and the solid arsenic slag arsenate magnesium precipitate.

[0029] Preferably, step 1) strong acid first step arsenic removal: Take several arsenic content of 1% of the dried gypsum slag grinding to 75 mesh, then pour into the configuration of HCl-H3PO4 mixed acid (HCl concentration of 0.6M, H3PO4 concentration of 0.1M), mixed acid and gypsum slag according to the solid-liquid ratio of 5:1. The stirring rate is 500 rpm, the stirring time is 0.8 h, after stirring, solid-liquid separation and solid drying to get the first step arsenic removal gypsum and the first step arsenic removal liquid;

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

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

[0032] Preferably, step 4) arsenic liquid solidification disposal: combine the first step of arsenic removal liquid, the second step of arsenic removal liquid and the third step of arsenic removal liquid to obtain a mixed arsenic removal liquid, add MgO2 (which has the effects of oxidizing trivalent arsenic and precipitating pentavalent arsenic) to the mixed arsenic removal liquid, wherein the molar ratio of MgO2 to As is 3:1, then add NH3·H2O (which has the effects of adjusting pH and precipitating pentavalent arsenic) to adjust the pH to 12. The stirring rate is 400 rpm, the stirring time is 1.5 h, and after the reaction is completed, the arsenic residue ammonium magnesium arsenate precipitate is obtained by filtration. 2+ :As molar ratio of 3:1, then add NH3·H2O (which has the effects of adjusting pH and precipitating pentavalent arsenic) to adjust the pH to 12. The stirring rate is 400 rpm, the stirring time is 1.5 h, and after the reaction is completed, the arsenic residue ammonium magnesium arsenate precipitate is obtained by filtration.

[0033] Example 1:

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

[0035] 1) first step of arsenic removal by strong acid: take several 80 mesh dried gypsum residues with arsenic content of 1.5%, then pour them into the prepared HCl-H3PO4 mixed acid (HCl concentration is 0.5, H3PO4 concentration is 0.08 M), the mixed acid and gypsum residue are in a solid-liquid ratio of 4:1. The stirring rate is 400 rpm, the stirring time is 0.5 h, after stirring, solid-liquid separation is carried out, and the solid is dried to obtain the first step of arsenic removal gypsum and the first step of arsenic removal liquid.

[0036] 2) second step of arsenic removal by strong acid: take the first step of arsenic removal gypsum in step 1) and grind it to 50 mesh, then pour it into the prepared HNO3-H3PO4 mixed acid (HNO3 concentration is 0.4 M, H3PO4 concentration is 0.05 M), the mixed acid and gypsum residue are in a solid-liquid ratio of 4:1. The stirring rate is 500 rpm, the stirring time is 0.7 h, after stirring, solid-liquid separation is carried out, and the solid is dried to obtain the second step of arsenic removal gypsum and the second step of arsenic removal liquid.

[0037] 3) Weak Acid Third-Step Arsenic Removal: Grind the arsenic-removed gypsum from the second step (2) to a 75-mesh size. Add a H2SO4-HNO3 mixed acid with a pH of 3.5, with a solid-to-liquid ratio of 4:1. Stir at 450 rpm for 0.5 h. After solid-liquid separation and drying, the arsenic-removed gypsum (with a leaching toxicity of 0.85 mg / L and an arsenic content of 0.042%) and the third-step arsenic-removed solution are obtained.

[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 reaction mixture was stirred at a rate of 350 rpm for 1 hour. Afterwards, the reaction mixture was filtered to obtain a solid arsenic solution (arsenic concentration 0.28 mg / L) and a solid arsenic residue (magnesium ammonium arsenate precipitate).

[0039] Example 2:

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

[0041] 1) Strong Acid First-Step Dearsenicification: Grind dried gypsum slag with a 2.3% arsenic content to 100 mesh. Add a prepared HCl-H₃PO₄ mixed acid (HCl concentration: 0.7M, H₃PO₄ concentration: 0.12M) at a solid-to-liquid ratio of 5:1. Stir at 470 rpm for 0.6 h. After stirring, solid-liquid separation and drying of the solids yield the first-step dearsenicized gypsum and the first-step dearsenicized solution.

[0042] 2) Strong Acid Secondary Dearsenicification: Grind the first-stage dearsenicized gypsum from step 1) to a 60-mesh size. Add the prepared HNO₃-H₃PO₄ mixed acid (0.7 M HNO₃, 0.09 M H₃PO₄) to the gypsum slag at a solid-to-liquid ratio of 5:1. Stir at 520 rpm for 0.8 h. After stirring, separate the solid and liquid, and dry the solid to obtain the second-stage dearsenicized gypsum and the second-stage dearsenicized solution.

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

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

[0045] Example 3:

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

[0047] 1) Strong acid first step arsenic removal: Take some 0.7% arsenic content dried gypsum residue and grind to 75 mesh, then pour into the prepared HCl-H3PO4 mixed acid (HCl concentration is 0.6 M, H3PO4 concentration is 0.1 M), the mixed acid and gypsum residue are in solid-liquid ratio of 5:1. The stirring rate is 500 rpm, the stirring time is 0.6 h, after the stirring is completed, solid-liquid separation is performed 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: Take some first step arsenic removal gypsum in step 1) and grind to 75 mesh, then pour into the prepared HNO3-H3PO4 mixed acid (HNO3 concentration is 0.6 M, H3PO4 concentration is 0.1 M), the mixed acid and gypsum residue are in solid-liquid ratio of 5:1. The stirring rate is 500 rpm, the stirring time is 0.7 h, after the stirring is completed, solid-liquid separation is performed and the solid is dried to obtain the second step arsenic removal gypsum and the second step arsenic removal liquid.

[0049] 3) Weak acid third step arsenic removal: Take some second step arsenic removal gypsum in step 2) and grind to 75 mesh, then pour into H2SO4-HNO3 mixed acid with pH of 3.5, the mixed acid and gypsum residue are in solid-liquid ratio of 5:1. The stirring rate is 500 rpm, the stirring time is 1 h, after the stirring is completed, solid-liquid separation is performed and the solid is dried to obtain the gypsum after deep removal of arsenic (the leaching toxicity of this gypsum is 0.66 mg / 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 reaction mixture was stirred at a molar ratio of 3:1 to As, followed by the addition of NH3·H2O (which serves both to adjust the pH and precipitate pentavalent arsenic) to adjust the pH to 12. The stirring rate was 3400 rpm for 1 hour. After the reaction was completed, the solid arsenic solution (arsenic concentration 0.26 mg / L) was filtered to obtain a solid arsenic slag and magnesium ammonium arsenate precipitate.

[0051] Example 4:

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

[0053] 1) Strong Acid First-Step Dearsenicification: Grind dried gypsum slag with a 3.6% arsenic content to 50 mesh. Add a prepared HCl-H₃PO₄ mixed acid (HCl concentration: 0.8M, H₃PO₄ concentration: 0.15M) at a solid-to-liquid ratio of 6:1. Stir at 600 rpm for 0.5-1 hour. After stirring, separate the solid and liquid, and dry the solid to obtain the first-step dearsenicized gypsum and the first-step dearsenicized solution.

[0054] 2) Strong Acid Secondary Dearsenicification: Grind the first-stage dearsenicized gypsum from step 1) to a 50-mesh size. Add the prepared HNO₃-H₃PO₄ mixed acid (0.8 M HNO₃, 0.15 M H₃PO₄) to the gypsum slag at a solid-to-liquid ratio of 6:1. Stir at 600 rpm for 1 hour. After stirring, separate the solid and liquid, and dry the solid to obtain the second-stage dearsenicized gypsum and second-stage dearsenicized liquid.

[0055] 3) Weak Acid Third-Step Arsenic Removal: Grind the arsenic-removed gypsum from step 2) to a 50-mesh size. Add a H2SO4-HNO3 mixed acid with a pH of 2.5, with a solid-to-liquid ratio of 6:1. Stir at 600 rpm for 1 hour. After solid-liquid separation and drying, the arsenic-removed gypsum (with a leaching toxicity of 0.49 mg / L and an arsenic content of 0.025%) and the third-step arsenic-removed solution are obtained.

[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+:As molar ratio of 3:1, then add NH3·H2O (both adjust pH and precipitate pentavalent arsenic) to adjust pH to 12. The stirring rate is 500 rpm, the stirring time is 2 h, and the solid arsenic residue ammonium magnesium arsenate precipitate is obtained after filtration.

[0057] The gypsum arsenic leaching toxicity and arsenic content in examples 1-4 were measured respectively, and the determination results are shown in table 1.

[0058] As leaching toxicity test method: take a proper amount of dry sample in a polytetrafluoroethylene bottle, then add leaching agent to the bottle, and the liquid-solid ratio of leaching agent (pH = 3.20±0.05 of mixed acid solution of sulfuric acid and nitric acid) and the sample to be tested is 10:1L / kg, and leaching (18±2) h under the rotation speed of (30±2) r / min of the rolling type oscillation device. After the leaching process is completed, the suspension is filtered, and the concentration of As in the filtrate is measured.

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

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

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

[0062] The method for deep dearsenication of arsenic-containing gypsum and the method for arsenic liquid disposal provided in the embodiments of the application are described in detail. The above description of the embodiments is only used to help understand the method of the application and its core idea; meanwhile, for those skilled in the art, according to the idea of the application, the specific implementation and application range will be changed, and the above description should not be understood as a limitation of the application.

[0063] As used in the specification and claims, certain terms have particular meanings. One skilled in the art will understand that different manufacturers can refer to a component by different names. The specification and claims should not be construed as limited to components by a particular name, but should be construed by the component's function. As used in the specification and claims, "comprising" and "including" are meant to be interpreted as specifying open-ended claims that are not limited to the listed elements. "Approximately" means within a range that is acceptable to one of skill in the art, and that the stated technical problem is solved substantially. The description that follows is intended to illustrate the best mode of practicing the application, but is not intended to limit the scope of the application. The scope of the application is defined by the claims.

[0064] It should also be noted that, as used in the specification and the claims, the article "a", "an" and "the" are intended to mean that there is one or more of the items. The terms "comprising," "including," and "having" are meant to be interpreted as specifying the presence of one or more stated elements or components. The use of "about" in relation to a given numerical value means that the exact value is not critical to the application.

[0065] It should be understood that the term "and / or" as used herein is merely an open-closed relationship between associated objects, which means that there can be three relationships, for example, A and / or B, which means that there can be three cases: A alone, A and B together, and B alone. In addition, the character " / " in this article generally represents an "or" relationship between the front and rear associated objects.

[0066] The above description illustrates and describes the only preferred embodiments of the application, but as previously discussed, it is understood that the application is not limited to the disclosed forms, and should not be considered as excluding other embodiments, but for various other combinations, modifications and environments, and can be modified within the scope of the application described herein, by the above teachings or related art or knowledge. Any modification and change made by those skilled in the art without departing from the spirit and scope of the application should be within the scope of protection of the claims of the 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-dried gypsum residue, then pour it into the prepared HCl-H3PO4 mixed acid, stir it at a certain rate for a period of time, and after the stirring is completed, separate the solid and liquid and dry the solid to obtain the first-step arsenic-removed gypsum and the first-step arsenic-removed 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. After the stirring is completed, the solid-liquid separation is carried out and the solid is dried 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-removed gypsum obtained in S2) is ground, and then poured into the prepared H2SO4-HNO3 mixed acid, stirred at a certain rate for a period of time. After the stirring is completed, the solid-liquid separation 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 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 hour.

3. The method according to claim 1, characterized in that The specific process parameters in S2) are as follows: the arsenic removal gypsum in the second step is ground to a particle size of 50 to 100 mesh, the mixed acid is a mixture of HNO3 and H3PO4, wherein the HNO3 concentration is 0.4M to 0.8M, the 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, and the stirring time is 0.5 to 1h.

4. The method according to claim 1, characterized in that In the first step of S3), the arsenic removal gypsum is ground into a particle size of 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 400-600 rpm, and the stirring time is 0.5-1h.

5. The method according to claim 1, wherein 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 includes S4) solidification treatment of the arsenic solution: combining the first step dearsenication solution, the second step dearsenication solution and the third step dearsenication solution to obtain a mixed dearsenication solution, adding MgO2 to the mixed dearsenication solution for reaction, and filtering after the reaction to obtain a solid arsenic solution and a solid arsenic residue precipitated by magnesium ammonium arsenate.

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