Method for recycling arsenic in red mud

Abstract

The invention provides a method for recycling arsenic in red mud, the red mud contains arsenic, and the method comprises the following steps: carrying out arsenic removal treatment on the red mud in a liquid environment by using strong base, and then carrying out first solid-liquid separation on a first mixed solution subjected to arsenic removal treatment to obtain arsenic-removed red mud and an arsenic-containing solution; the arsenic-containing liquid is oxidized, so that trivalent arsenic in the arsenic-containing liquid is converted into pentavalent arsenic, and second mixed liquid is obtained; and crystallizing the second mixed solution, and then carrying out second solid-liquid separation on the crystallized second mixed solution to obtain an arsenate product and crystallization mother liquor. According to the method, a new treatment mode is developed for arsenic in the red mud, arsenic can be recycled, and environmental arsenic pollution caused by red mud stockpiling can be avoided.

Description

Technical Field

[0001] The present application relates to the technical field of solid waste heavy metal pollution control, and in particular to a method for recovering arsenic from red mud. Background Art

[0002] Arsenic is a toxic element, known to the public for its high toxicity. However, in nature, it mostly exists in the form of low-toxic, insoluble arsenates, realgar, arsenopyrite and other sulfides. However, with the continuous development of mineral resources by humans, low-toxic, stable arsenides are destroyed and converted into highly toxic water-soluble arsenic such as sulfides, oxides, and arsenates, which are released.

[0003] Red mud is the residue produced when bauxite is leached with strong alkali in the alumina industry. Red mud contains a large amount of valuable elements such as TiO2, Al2O3, Na2O, Fe2O3, trace rare elements and heavy metals. At present, red mud is mainly used in the fields of building materials, metal smelting, agriculture, environmental protection, chemical industry, etc. The long-term natural accumulation of red mud occupies a large amount of land. At the same time, long-term accumulation is also very likely to cause leakage of the waterproof layer of the yard and serious alkalization of the surrounding soil. The arsenic in it directly pollutes the surface and groundwater resources. As a companion element of ore, arsenic can seriously harm the human cardiovascular system, nervous system, respiratory system, and reproductive system. The arsenic in the red mud wash can enter the yard with the red mud, and then enter the groundwater system through rainwater erosion, leakage of the yard anti-leakage layer, etc., polluting the drinking water resources in the surrounding areas and causing arsenic pollution. Summary of the invention

[0004] The present application provides a method for recovering arsenic from red mud to solve the following technical problem: providing a new method for recovering arsenic from red mud.

[0005] In a first aspect, the present application provides a method for recovering arsenic from red mud, wherein the red mud contains arsenic, and the method comprises:

[0006] Using a strong base to perform arsenic removal treatment on the red mud in a liquid environment, and then performing a first solid-liquid separation on the first mixed liquid after the arsenic removal treatment to obtain arsenic-removed red mud and arsenic-containing liquid;

[0007] oxidizing the arsenic-containing liquid to convert trivalent arsenic in the arsenic-containing liquid into pentavalent arsenic to obtain a second mixed liquid;

[0008] The second mixed solution is crystallized, and then the crystallized second mixed solution is subjected to a second solid-liquid separation to obtain an arsenate product and a crystallization mother solution.

[0009] Optionally, the strong base comprises sodium hydroxide.

[0010] Optionally, the weight ratio of the strong alkali to the red mud is 0.1 to 0.6.

[0011] Optionally, the leaching process parameters include: leaching temperature of 70°C to 100°C, and leaching time of 30min to 300min.

[0012] Optionally, the leaching process parameters include: leaching temperature of 90°C to 100°C, and leaching time of 90min to 150min.

[0013] Optionally, the oxidant used in the oxidation includes hydrogen peroxide.

[0014] Optionally, the oxidation time is 20 min to 120 min.

[0015] Optionally, the weight ratio of the arsenic-containing liquid to the oxidant is (25-100):1.

[0016] Optionally, the method further includes:

[0017] The dearsenicated red mud is washed, and then solid-liquid separation is performed to obtain target dearsenicated red mud and washing liquid; wherein the alkali content of the dearsenicated red mud is less than 3g / L.

[0018] Optionally, the method further includes:

[0019] The concentration of the crystallization mother liquor is adjusted to return the red mud for arsenic removal for recycling.

[0020] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0021] The method for recovering arsenic from red mud provided in an embodiment of the present application, wherein the red mud contains arsenic, and the method comprises: using a strong alkali to perform arsenic removal treatment on the red mud in a liquid environment, and then performing a first solid-liquid separation on the first mixed liquid after the arsenic removal treatment to obtain arsenic-removed red mud and an arsenic-containing liquid; oxidizing the arsenic-containing liquid to convert trivalent arsenic in the arsenic-containing liquid into pentavalent arsenic to obtain a second mixed liquid; crystallizing the second mixed liquid, and then performing a second solid-liquid separation on the crystallized second mixed liquid to obtain an arsenate product and a crystallization mother liquor. Using a strong alkali to leach the red mud slurry can remove the arsenic that is long-term entrained or adsorbed in structures such as goethite in the red mud, that is, most of the pentavalent arsenic in the red mud is leached, thereby achieving complete removal of harmful arsenic in the red mud; oxidizing the arsenic-containing liquid to fully convert the trivalent arsenic in the arsenic-containing liquid into pentavalent arsenic, thereby achieving the existence of the arsenic in the arsenic-containing liquid in the form of pentavalent arsenic, thereby obtaining a high-purity arsenate product in the subsequent crystallization. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0024] Figure 1 A schematic flow chart of a method for recovering arsenic from red mud provided in an embodiment of the present application;

[0025] Figure 2 A schematic diagram of an actual process of a method for recovering arsenic from red mud provided in an embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0027] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0028] In addition, in the description of the present application, the terms "include", "comprise", etc. mean "including but not limited to". In this document, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0029] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0030] In a first aspect, the present application provides a method for recovering arsenic from red mud, wherein the red mud contains arsenic. Figure 1 A schematic diagram of a method for recovering arsenic from red mud provided in an embodiment of the present application; see Figure 1 , the method comprising:

[0031] S1, using a strong base to perform arsenic removal treatment on the red mud in a liquid environment, and then performing a first solid-liquid separation on the first mixed liquid after the arsenic removal treatment to obtain arsenic-removed red mud and arsenic-containing liquid;

[0032] In the embodiment of the present application, the red mud slurry is leached with a strong alkali, which can deeply remove the arsenic that has been entrained or adsorbed in structures such as goethite in the red mud for a long time, that is, most of the pentavalent arsenic in the red mud is leached, thereby achieving the complete removal of harmful arsenic in the red mud. The above-mentioned use of a strong alkali to remove arsenic from the red mud in a liquid environment may include: first mixing the solid red mud with the solid strong alkali, and then removing arsenic from the red mud under the action of solvent water (liquid environment). Alternatively, the above-mentioned strong alkali can also be in liquid form to remove arsenic from the solid red mud. In addition, the liquid-to-solid ratio of the above-mentioned solution for arsenic removal is 3 to 8.

[0033] In some embodiments, the strong base comprises sodium hydroxide.

[0034] In the embodiment of the present application, the strong alkali can be sodium hydroxide, which can remove the arsenic that has been entrained in the red mud for a long time or adsorbed in the structure such as goethite, that is, most of the pentavalent arsenic in the red mud can be leached, thereby achieving the complete removal of harmful arsenic in the red mud. In addition, the leaching of the red mud slurry by sodium hydroxide can avoid the introduction of impurity ions, and the sodium ions introduced by sodium hydroxide can also be used for the subsequent stabilization of sodium arsenate.

[0035] In some embodiments, the weight ratio of the strong alkali to the red mud is 0.1 to 0.6.

[0036] In the embodiment of the present application, the weight ratio of the strong alkali to the red mud can be 0.1 to 0.6, which can fully remove the arsenic that has been entrained or adsorbed in the structure of goethite and the like in the red mud for a long time. The strong alkali will react completely with the trivalent arsenic in the arsenic-containing red mud in a short time, thereby entering the leachate and being separated from the red mud. For example, the weight ratio of the strong alkali to the red mud can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, etc.

[0037] In some embodiments, the leaching process parameters include: leaching temperature of 70°C to 100°C, and leaching time of 30 min to 300 min.

[0038] In some embodiments, the leaching process parameters include: leaching temperature of 90°C to 100°C, and leaching time of 90 min to 150 min.

[0039] In the embodiment of the present application, the leaching temperature can be 70°C to 100°C, and the leaching time can be 30min to 300min, which can ensure that most of the pentavalent arsenic in the red mud can be completely dissolved in the solution, thereby achieving complete removal of harmful arsenic in the red mud, so that the red mud after subsequent washing can be better directly returned to the yard for storage. Exemplarily, the above-mentioned leaching temperature can be 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, etc., and the leaching time can be 30min, 40min, 50min, 70min, 90min, 100min, 150min, 200min, 250min, 300min, etc. Further, the above-mentioned leaching temperature can be 90°C, 92°C, 94°C, 96°C, 100°C, etc., and the leaching time can be 90min, 100min, 110min, 120min, 130min, 140min, 150min, etc.

[0040] S2, oxidizing the arsenic-containing liquid to convert trivalent arsenic in the arsenic-containing liquid into pentavalent arsenic to obtain a second mixed liquid;

[0041] In some embodiments, the oxidizing agent used in the oxidation comprises hydrogen peroxide.

[0042] In some embodiments, the oxidation time is 20 min to 120 min.

[0043] In the embodiment of the present application, the oxidant used for oxidation can be hydrogen peroxide, which not only ensures that hydrogen peroxide converts all trivalent arsenic in the arsenic-containing liquid into pentavalent arsenic, but also avoids the introduction of impurity ions into the arsenic-containing liquid. The oxidation time can be 20min to 120min, which can ensure that all low-valent ions in the arsenic-containing liquid can be converted into high-valent ions, and the reaction can be complete within 20min to 120min. Exemplarily, the above oxidation time can be 20min, 30min, 40min, 50min, 70min, 100min, 110min, 120min, etc. The above oxidation can be carried out at room temperature (20°C to 30°C) to further reduce the solubility of sodium arsenate in the solution and facilitate subsequent crystallization.

[0044] In some embodiments, the weight ratio of the arsenic-containing liquid to the oxidant is (25-100):1.

[0045] In the embodiment of the present application, a considerable amount of trivalent arsenic ions exist in the arsenic-containing liquid, and adding a certain amount of hydrogen peroxide can effectively convert trivalent arsenic into pentavalent arsenic. Exemplarily, the weight ratio of the arsenic-containing liquid to the oxidant is 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 55:1, 60:1, 65:1, 70:1, 75:1, 80:1, 85:1, 90:1, 95:1, 100:1, etc.

[0046] S3, crystallizing the second mixed solution, and then performing a second solid-liquid separation on the crystallized second mixed solution to obtain an arsenate product and a crystallization mother liquor.

[0047] In the embodiments of the present application, the mixed slurry is crystallized at room temperature (15°C to 40°C), pentavalent arsenic therein is precipitated in the form of sodium arsenate decahydrate, and dried to be sold as a product or used as a raw material for preparing elemental arsenic.

[0048] In some embodiments, the method further comprises:

[0049] S4. Washing the dearsenicated red mud, and then performing solid-liquid separation to obtain target dearsenicated red mud and washing liquid; wherein the alkali content of the target dearsenicated red mud is less than 3 g / L.

[0050] In the embodiment of the present application, the dearsenicized red mud is washed with water, and then solid-liquid separation is performed to obtain the target dearsenicized red mud and washing liquid. The alkali content of the target dearsenicized red mud is less than 3g / L, so that the target dearsenicized red mud can be directly stored to reduce pollution to the environment. The target dearsenicized red mud can also be returned to the dilution slurry to further absorb the arsenic accumulated in the circulating mother liquor in the alumina production process, and finally converted into arsenic-containing red mud again. The washing liquid is returned to the evaporation workshop of alumina production for recycling.

[0051] In some embodiments, the method further comprises:

[0052] S5. Adjust the concentration of the crystallization mother liquor to return the red mud for arsenic removal for recycling.

[0053] In the embodiment of the present application, the concentration of the above-mentioned crystallization mother liquor is adjusted to return to leaching the red mud for recycling and utilization to achieve resource utilization.

[0054] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0055] Raw material red mud used in the embodiment: 5 kg of red mud produced by an aluminum oxide production enterprise was used as an experimental sample. The arsenic in the red mud exists in the form of long-term entrainment or adsorption in structures such as goethite. The red mud includes red mud accompanying washing liquid and red mud matrix, that is, the arsenic in the red mud is mainly composed of arsenic in the accompanying washing liquid and a small amount of adsorbed arsenic. Please refer to the components of the red mud accompanying washing liquid shown in Table 1 and the main components of the red mud matrix shown in Table 2.

[0056] Table 1 Red mud accompanying washing liquid composition

[0057] Red mud comes with lotion ingredients As Al Ca Fe Si Concentration mg / L 6.1 <![CDATA[1.5×10 3 ]]> 1.4 ＜0.1 0.8

[0058] Table 2 Main chemical components of red mud matrix

[0059]

[0060]

[0061] Example 1

[0062] A method for recovering arsenic from red mud comprises: S11, using a strong alkali to perform arsenic removal treatment on the red mud in a liquid environment, and then performing a first solid-liquid separation on the first mixed liquid after the arsenic removal treatment to obtain arsenic-removed red mud and arsenic-containing liquid; wherein the strong alkali is sodium hydroxide, the liquid-to-solid ratio of the solution formed by the strong alkali, red mud and water is 8, the weight ratio of sodium hydroxide to red mud is 0.1, the leaching temperature is 70° C., and the leaching time is 30 min;

[0063] The specific steps are as follows: in a primary reaction tank of an aluminum plant, sodium hydroxide and red mud are added at a ratio of 0.1 between alkali and material, and 70°C hot water is added at a ratio of 8 between liquid and solid for leaching, and the leaching reaction is stirred for 30 minutes to obtain arsenic-containing slurry. After the reaction is completed, the slurry is sent to a primary sedimentation tank for static sedimentation, and the supernatant in the sedimentation tank is filtered by a filter press to obtain arsenic-free red mud and arsenic-containing liquid;

[0064] S21, oxidizing the arsenic-containing liquid to convert trivalent arsenic in the arsenic-containing liquid into pentavalent arsenic, to obtain a second mixed liquid; wherein the oxidizing agent is hydrogen peroxide, the weight ratio of hydrogen peroxide to the arsenic-containing liquid is 1:100, and the oxidation time is 120 min;

[0065] The specific steps are as follows: the arsenic-containing liquid enters the secondary reaction tank, is mixed with hydrogen peroxide and the arsenic-containing liquid at a weight ratio of 1:100, and is subjected to stirring oxidation reaction at room temperature for 120 minutes.

[0066] S31, crystallizing the second mixed solution, and then performing a second solid-liquid separation on the crystallized second mixed solution to obtain an arsenate product and a crystallization mother liquor;

[0067] The specific steps are as follows: the mixed slurry is sent to a secondary sedimentation tank for standing crystallization for 2 hours, and after the crystallization is completed, it is filtered to obtain white sodium arsenate crystals and crystallization mother liquor; the white sodium arsenate crystals of the oxidized crystals are dried at 40°C to obtain the sodium arsenate product

[0068] S41, washing the dearsenicated red mud, and then performing solid-liquid separation to obtain target dearsenicated red mud and washing liquid; wherein the alkali content of the target dearsenicated red mud is less than 3g / L; the dearsenicated red mud is directly pumped to the red mud yard for storage, and the washing liquid is returned to the evaporation workshop for recycling.

[0069] S51, adjusting the concentration of the crystallization mother liquor to return to the red mud for arsenic removal treatment for recycling, that is, adding an appropriate amount of sodium hydroxide to the crystallization mother liquor and returning to the leaching step S11.

[0070] Example 2

[0071] A method for recovering arsenic from red mud, comprising: S12, using a strong alkali to perform arsenic removal treatment on the red mud in a liquid environment, and then performing a first solid-liquid separation on the first mixed liquid after the arsenic removal treatment to obtain arsenic-removed red mud and arsenic-containing liquid; wherein the strong alkali is sodium hydroxide, the liquid-to-solid ratio of the solution formed by the strong alkali, red mud and water is 8, the weight ratio of sodium hydroxide to red mud is 0.5, the leaching temperature is 90° C., and the leaching time is 120 min;

[0072] The specific steps are as follows: in a primary reaction tank of an aluminum plant, sodium hydroxide and red mud are added at a ratio of 0.5 between alkali and material, and 90°C hot water is added at a ratio of 8 between liquid and solid for leaching, and the leaching reaction is stirred for 120 minutes to obtain arsenic-containing slurry. After the reaction is completed, the slurry is sent to a primary sedimentation tank for static sedimentation, and the supernatant in the sedimentation tank is filtered by a filter press to obtain arsenic-free red mud and arsenic-containing liquid;

[0073] S22, oxidizing the arsenic-containing liquid to convert trivalent arsenic in the arsenic-containing liquid into pentavalent arsenic, to obtain a second mixed liquid; wherein the oxidizing agent is hydrogen peroxide, the weight ratio of hydrogen peroxide to the arsenic-containing liquid is 1:50, and the oxidation time is 60 minutes;

[0074] The specific steps are as follows: the arsenic-containing liquid enters the secondary reaction tank, is mixed with hydrogen peroxide and the arsenic-containing liquid at a weight ratio of 1:50, and is stirred and oxidized for 60 minutes at room temperature;

[0075] S32, crystallizing the second mixed solution, and then performing a second solid-liquid separation on the crystallized second mixed solution to obtain an arsenate product and a crystallization mother liquor;

[0076] The specific steps are as follows: the mixed slurry is sent to a secondary sedimentation tank for standing crystallization for 2 hours, and after the crystallization is completed, it is filtered to obtain white sodium arsenate crystals and crystallization mother liquor; the white sodium arsenate crystals of the oxidized crystallization product are dried at 40°C to obtain the sodium arsenate product;

[0077] S42, washing the dearsenicated red mud, and then performing solid-liquid separation to obtain target dearsenicated red mud and washing liquid; wherein the alkali content of the target dearsenicated red mud is less than 3g / L; the dearsenicated red mud is directly pumped to the red mud yard for storage, and the washing liquid is returned to the evaporation workshop for recycling;

[0078] S52, adjusting the concentration of the crystallization mother liquor to return to the red mud for arsenic removal treatment for recycling. That is, adding an appropriate amount of sodium hydroxide to the crystallization mother liquor and returning to the leaching step S12.

[0079] Example 3

[0080] A method for recovering arsenic from red mud, comprising: S13, using a strong alkali to perform arsenic removal treatment on the red mud in a liquid environment, and then performing a first solid-liquid separation on the first mixed liquid after the arsenic removal treatment to obtain arsenic-removed red mud and arsenic-containing liquid; wherein the strong alkali is sodium hydroxide, the liquid-solid ratio of the solution formed by the strong alkali, red mud and water is 3, the weight ratio of sodium hydroxide to red mud is 0.6, the leaching temperature is 100° C., and the leaching time is 300 min;

[0081] The specific steps are as follows: in a primary reaction tank of an aluminum plant, sodium hydroxide and red mud are added at a ratio of 0.6 between alkali and material, and 100°C hot water is added at a ratio of 3 between liquid and solid for leaching, and the leaching reaction is stirred for 300 minutes to obtain arsenic-containing slurry. After the reaction is completed, the slurry is sent to a primary sedimentation tank for static sedimentation, and the supernatant in the sedimentation tank is filtered by a filter press to obtain arsenic-free red mud and arsenic-containing liquid;

[0082] S23, oxidizing the arsenic-containing liquid to convert trivalent arsenic in the arsenic-containing liquid into pentavalent arsenic, to obtain a second mixed liquid; wherein the oxidizing agent is hydrogen peroxide, the weight ratio of hydrogen peroxide to the arsenic-containing liquid is 1:25, and the oxidation time is 20 minutes;

[0083] The specific steps are as follows: the arsenic-containing liquid enters the secondary reaction tank, is mixed with hydrogen peroxide and the arsenic-containing liquid in a weight ratio of 1:25, and is stirred and oxidized for 20 minutes at room temperature.

[0084] S33, crystallizing the second mixed solution, and then performing a second solid-liquid separation on the crystallized second mixed solution to obtain an arsenate product and a crystallization mother liquor;

[0085] The specific steps are as follows: the mixed slurry is sent to a secondary sedimentation tank for standing crystallization for 2 hours, and after the crystallization is completed, it is filtered to obtain white sodium arsenate crystals and crystallization mother liquor; the white sodium arsenate crystals of the oxidized crystallization product are dried at 40°C to obtain the sodium arsenate product;

[0086] S43, washing the dearsenicated red mud, and then performing solid-liquid separation to obtain target dearsenicated red mud and washing liquid; wherein the alkali content of the target dearsenicated red mud is less than 3g / L; the dearsenicated red mud is directly pumped to the red mud yard for storage, and the washing liquid is returned to the evaporation workshop for recycling;

[0087] S53, adjusting the concentration of the crystallization mother liquor to return the red mud for arsenic removal treatment for recycling, that is, adding an appropriate amount of sodium hydroxide to the crystallization mother liquor and returning it to the S13 leaching step.

[0088] Example 4

[0089] A method for recovering arsenic from red mud comprises: S14, using a strong alkali to perform arsenic removal treatment on the red mud in a liquid environment, and then performing a first solid-liquid separation on the first mixed liquid after the arsenic removal treatment to obtain arsenic-removed red mud and arsenic-containing liquid; wherein the strong alkali is sodium hydroxide, the liquid-to-solid ratio of the solution formed by the strong alkali, red mud and water is 5, the weight ratio of sodium hydroxide to red mud is 0.3, the leaching temperature is 90° C., and the leaching time is 90 min;

[0090] The specific steps are as follows: in a primary reaction tank of an aluminum plant, sodium hydroxide and red mud are added at a ratio of 0.3 between alkali and material, and 90°C hot water is added at a ratio of 5 between liquid and solid for leaching, and the leaching reaction is stirred for 90 minutes to obtain arsenic-containing slurry. After the reaction is completed, the slurry is sent to a primary sedimentation tank for static sedimentation, and the supernatant in the sedimentation tank is filtered by a filter press to obtain arsenic-free red mud and arsenic-containing liquid;

[0091] S24, oxidizing the arsenic-containing liquid to convert trivalent arsenic in the arsenic-containing liquid into pentavalent arsenic, to obtain a second mixed liquid; wherein the oxidizing agent is hydrogen peroxide, the weight ratio of hydrogen peroxide to the arsenic-containing liquid is 1:30, and the oxidation time is 30 minutes;

[0092] The specific steps are as follows: the arsenic-containing liquid enters the secondary reaction tank, is mixed with hydrogen peroxide and the arsenic-containing liquid at a weight ratio of 1:30, and is stirred and oxidized for 30 minutes at room temperature;

[0093] S34, crystallizing the second mixed solution, and then performing a second solid-liquid separation on the crystallized second mixed solution to obtain an arsenate product and a crystallization mother liquor;

[0094] The specific steps are as follows: the mixed slurry is sent to a secondary sedimentation tank for standing crystallization for 2 hours, and after the crystallization is completed, it is filtered to obtain white sodium arsenate crystals and crystallization mother liquor; the white sodium arsenate crystals of the oxidized crystallization product are dried at 40°C to obtain the sodium arsenate product;

[0095] S44, washing the dearsenicated red mud, and then performing solid-liquid separation to obtain target dearsenicated red mud and washing liquid; wherein the alkali content of the target dearsenicated red mud is less than 3g / L; the dearsenicated red mud is directly pumped to the red mud yard for storage, and the washing liquid is returned to the evaporation workshop for recycling;

[0096] S54, adjusting the concentration of the crystallization mother liquor to return the red mud for arsenic removal treatment for recycling, that is, adding an appropriate amount of sodium hydroxide to the crystallization mother liquor and returning it to the S14 leaching step.

[0097] Example 5

[0098] A method for recovering arsenic from red mud comprises: S15, using a strong alkali to perform arsenic removal treatment on the red mud in a liquid environment, and then performing a first solid-liquid separation on the first mixed liquid after the arsenic removal treatment to obtain arsenic-removed red mud and arsenic-containing liquid; wherein the strong alkali is sodium hydroxide, the liquid-to-solid ratio of the solution formed by the strong alkali, red mud and water is 4, the weight ratio of sodium hydroxide to red mud is 0.4, the leaching temperature is 80° C., and the leaching time is 240 min;

[0099] The specific steps are as follows: in a primary reaction tank of an aluminum plant, sodium hydroxide and red mud are added at a ratio of 0.4 between alkali and material, and 80°C hot water is added at a ratio of 4 between liquid and solid for leaching, and the leaching reaction is stirred for 240 minutes to obtain arsenic-containing slurry. After the reaction is completed, the slurry is sent to a primary sedimentation tank for static sedimentation, and the supernatant of the sedimentation tank is filtered by a filter press to obtain arsenic-free red mud and arsenic-containing liquid;

[0100] S25, oxidizing the arsenic-containing liquid to convert trivalent arsenic in the arsenic-containing liquid into pentavalent arsenic, to obtain a second mixed liquid; wherein the oxidizing agent is hydrogen peroxide, the weight ratio of hydrogen peroxide to the arsenic-containing liquid is 1:50, and the oxidation time is 60 minutes;

[0101] The specific steps are as follows: the arsenic-containing liquid enters the secondary reaction tank, is mixed with hydrogen peroxide and the arsenic-containing liquid at a weight ratio of 1:50, and is stirred and oxidized for 60 minutes at room temperature;

[0102] S35, crystallizing the second mixed solution, and then performing a second solid-liquid separation on the crystallized second mixed solution to obtain an arsenate product and a crystallization mother liquor;

[0103] The specific steps are as follows: the mixed slurry is sent to a secondary sedimentation tank for standing crystallization for 2 hours, and after the crystallization is completed, it is filtered to obtain white sodium arsenate crystals and crystallization mother liquor; the white sodium arsenate crystals of the oxidized crystallization product are dried at 40°C to obtain the sodium arsenate product;

[0104] S45, washing the dearsenicized red mud, and then performing solid-liquid separation to obtain target dearsenicized red mud and washing liquid; wherein the alkali content of the target dearsenicized red mud is less than 3 g / L; the dearsenicized red mud is directly pumped to the red mud yard for storage, and the washing liquid is returned to the evaporation workshop for recycling;

[0105] S55, adjusting the concentration of the crystallization mother liquor to return to the red mud for arsenic removal treatment for recycling. That is, adding an appropriate amount of sodium hydroxide to the crystallization mother liquor and returning to the leaching step S15.

[0106] Example 6

[0107] A method for recovering arsenic from red mud, comprising: S16, using a strong alkali to perform arsenic removal treatment on the red mud in a liquid environment, and then performing a first solid-liquid separation on the first mixed liquid after the arsenic removal treatment to obtain arsenic-removed red mud and arsenic-containing liquid; wherein the strong alkali is sodium hydroxide, the liquid-to-solid ratio of the solution formed by the strong alkali, red mud and water is 6, the weight ratio of sodium hydroxide to red mud is 0.2, the leaching temperature is 90° C., and the leaching time is 150 min;

[0108] The specific steps are as follows: in a primary reaction tank of an aluminum plant, sodium hydroxide and red mud are added at a ratio of 0.2 between alkali and material, and 90°C hot water is added at a ratio of 6 between liquid and solid for leaching, and the leaching reaction is stirred for 150 minutes to obtain arsenic-containing slurry. After the reaction is completed, the slurry is sent to a primary sedimentation tank for static sedimentation, and the supernatant in the sedimentation tank is filtered by a filter press to obtain arsenic-free red mud and arsenic-containing liquid;

[0109] S26, oxidizing the arsenic-containing liquid to convert trivalent arsenic in the arsenic-containing liquid into pentavalent arsenic, to obtain a second mixed liquid; wherein the oxidizing agent is hydrogen peroxide, the weight ratio of hydrogen peroxide to the arsenic-containing liquid is 1:25, and the oxidation time is 100 min;

[0110] The specific steps are as follows: the arsenic-containing liquid enters the secondary reaction tank, is mixed with hydrogen peroxide and the arsenic-containing liquid in a weight ratio of 1:25, and is stirred and oxidized for 100 minutes at room temperature;

[0111] S36, crystallizing the second mixed solution, and then performing a second solid-liquid separation on the crystallized second mixed solution to obtain an arsenate product and a crystallization mother liquor;

[0112] The specific steps are as follows: the mixed slurry is sent to a secondary sedimentation tank for standing crystallization for 2 hours, and after the crystallization is completed, it is filtered to obtain white sodium arsenate crystals and crystallization mother liquor; the white sodium arsenate crystals of the oxidized crystallization product are dried at 40°C to obtain the sodium arsenate product;

[0113] S46, washing the dearsenicated red mud, and then performing solid-liquid separation to obtain target dearsenicated red mud and washing liquid; wherein the alkali content of the target dearsenicated red mud is less than 3 g / L; the dearsenicated red mud is directly pumped to the red mud yard for storage, and the washing liquid is returned to the evaporation workshop for recycling;

[0114] S56, adjusting the concentration of the crystallization mother liquor to return to the red mud for arsenic removal treatment for recycling. That is, adding an appropriate amount of sodium hydroxide to the crystallization mother liquor and returning to the S16 leaching step.

[0115] The components of the washing liquid of the dearsenicized red mud in Examples 1-6 were analyzed, and the analysis results are shown in Table 3; the components of the sodium arsenate in Examples 1-6 were analyzed, and the analysis results are shown in Table 4.

[0116] Table 3 Dearsenicated red mud washing liquid composition (mg / L)

[0117]

[0118]

[0119] Table 4 Composition of sodium arsenate (wt%)

[0120] Serial number As Al Ca Fe Si Example 1 19.28 0.022 0.0065 ＜0.005 ＜0.005 Example 2 19.25 0.051 0.0073 ＜0.005 ＜0.005 Example 3 19.30 0.01 ＜0.005 ＜0.005 ＜0.005 Example 4 19.24 0.037 ＜0.005 ＜0.005 ＜0.005 Example 5 19.19 0.019 0.0051 ＜0.005 ＜0.005 Example 6 19.30 0.021 0.0069 ＜0.005 ＜0.005

[0121] As can be seen from Table 3, after further alkaline washing treatment, the arsenic content in the arsenic-free slag obtained from the arsenic-free red mud is extremely low, and the residual arsenic in the arsenic-free red mud after washing is also reduced to less than 0.05 mg / L, solving the problem of arsenic pollution in the red mud dump. As can be seen from Table 4, the arsenic-containing compound precipitated by oxidation-crystallization is Na3AsO4·10H2O, and the arsenic content of the crystal is close to the theoretical arsenic content, which can be further used in the production of other arsenic-containing products.

[0122] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0123] (1) In the embodiment of the present application, red mud is used to treat red mud. First, arsenic in the red mud is removed with a strong alkali, and then the red mud is sent to a red mud dump for storage, making the storage safer, and the water generated in the process can also be recycled;

[0124] (2) Separate the arsenic pollution in red mud storage from the arsenic accumulated during the transportation of red mud, thereby reducing the pollution to the environment caused by the transportation and storage processes;

[0125] (3) On the basis of harmless treatment of red mud, the arsenic resources in it are utilized to increase the output of alumina production.

[0126] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for recovering arsenic from red mud, characterized in that: The red mud contains arsenic, and the method comprises: Using a strong base to perform arsenic removal treatment on the red mud in a liquid environment, and then performing a first solid-liquid separation on the first mixed liquid after the arsenic removal treatment to obtain arsenic-removed red mud and arsenic-containing liquid; oxidizing the arsenic-containing liquid to convert trivalent arsenic in the arsenic-containing liquid into pentavalent arsenic to obtain a second mixed liquid; The second mixed solution is crystallized, and then the crystallized second mixed solution is subjected to a second solid-liquid separation to obtain an arsenate product and a crystallization mother solution.

2. The method according to claim 1, characterized in that The strong base includes sodium hydroxide.

3. The method according to claim 1 or 2, characterized in that: The weight ratio of the strong alkali to the red mud is 0.1 to 0.

6.

4. The method according to claim 1, characterized in that: The leaching process parameters include: leaching temperature of 70°C to 100°C, and leaching time of 30min to 300min.

5. The method according to claim 4, characterized in that The leaching process parameters include: leaching temperature of 90° C. to 100° C., and leaching time of 90 min to 150 min.

6. The method according to claim 1, characterized in that The oxidant used in the oxidation includes hydrogen peroxide.

7. The method according to claim 1 or 6, characterized in that: The oxidation time is 20 min to 120 min.

8. The method according to claim 1, characterized in that: The weight ratio of the arsenic-containing liquid to the oxidant is (25-100):

1.

9. The method according to claim 1, characterized in that: The method further comprises: The dearsenicated red mud is washed, and then solid-liquid separation is performed to obtain target dearsenicated red mud and washing liquid; wherein the alkali content of the target dearsenicated red mud is less than 3g / L.

10. The method according to claim 1, characterized in that The method further comprises: The concentration of the crystallization mother liquor is adjusted to return the red mud for arsenic removal for recycling.

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