A method for simultaneous stabilization of arsenic and cadmium and its application

Abstract

This invention provides a method and application for the simultaneous stabilization of arsenic and cadmium. The method includes the following steps: S1, providing arsenic-cadmium solid waste containing arsenic and cadmium; S2, mixing the arsenic-cadmium solid waste and a composite reagent in an acidic solution to obtain a reaction solution; the composite reagent includes ferrous sulfate and ferrous sulfide, with a mass ratio of ferrous sulfate to ferrous sulfide of 0.5–3:1; S3, performing solid-liquid separation on the reaction solution to obtain a stabilized arsenic-cadmium residue. This invention can achieve simultaneous stabilization of arsenic and cadmium in solid waste, and the leaching toxicity of the stabilized residue sample meets relevant leaching toxicity standards.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment in the metallurgical industry, and particularly relates to a method and application for simultaneous stabilization treatment of arsenic and cadmium. Background Technology

[0002] Sulfuric acid production from non-ferrous smelting flue gas is one of the most important methods of sulfuric acid production. High-concentration SO2 flue gas, after purification by waste heat boilers and dust collection facilities, enters the sulfuric acid production system. Flue gas scrubbing generates a large amount of waste acid. Using the sulfidation-lime-neutralization iron salt method, sulfide slag, gypsum slag, and neutralization slag containing heavy metals such as arsenic, cadmium, and lead are produced, with gypsum slag being the most abundant. Non-ferrous smelting gypsum slag has high arsenic and cadmium content and activity, is easily leached, and poses a significant environmental risk. The issue of arsenic and cadmium in gypsum slag urgently requires close attention.

[0003] The main methods for treating and disposing of gypsum slag from non-ferrous smelting are stockpiling and landfilling. However, stockpiling occupies a large amount of land, while landfilling requires qualified hazardous waste treatment units, which is expensive. Furthermore, neither of these methods addresses the potential environmental risks of arsenic and cadmium. Therefore, there is an urgent need for an efficient and economical method for stabilizing gypsum slag treated with waste acid to reduce its potential environmental risks.

[0004] Arsenic and cadmium have opposite chemical properties, making simultaneous stabilization difficult. Current research on arsenic and cadmium treatment mainly focuses on soils contaminated with both arsenic and cadmium. Most studies employ modified composite materials for remediation, but these materials, having adsorbed arsenic and cadmium, still require further treatment. Furthermore, while the arsenic and cadmium content is relatively low in contaminated soils, it is higher and exists in more complex forms in arsenic- and cadmium-containing gypsum slag, rendering adsorption materials insufficient for achieving adequate remediation.

[0005] Therefore, it is necessary to provide a method and application for simultaneous stabilization of arsenic and cadmium to solve or alleviate the technical defect that it is difficult to significantly reduce the leaching rate of arsenic and cadmium in solid waste at the same time. Summary of the Invention

[0006] The main objective of this invention is to provide a method and application for simultaneous stabilization of arsenic and cadmium, which aims to solve or alleviate the technical problem that it is difficult to significantly reduce the leaching rate of arsenic and cadmium in solid waste at the same time.

[0007] To achieve the above objectives, the present invention provides an application of a composite agent in the simultaneous stabilization treatment of arsenic and cadmium, wherein the composite agent comprises ferrous sulfate and ferrous sulfide, and the mass ratio of ferrous sulfate to ferrous sulfide is 0.5 to 3:1.

[0008] This invention also provides a method for simultaneous arsenic and cadmium stabilization treatment of arsenic and cadmium solid waste, comprising the following steps:

[0009] S1, providing arsenic-cadmium solid waste, wherein the arsenic-cadmium solid waste contains arsenic and cadmium elements;

[0010] S2, the arsenic-cadmium solid waste and the composite agent are mixed in an acidic solution to obtain a reaction solution;

[0011] The composite agent includes ferrous sulfate and ferrous sulfide, wherein the mass ratio of ferrous sulfate to ferrous sulfide is 0.5 to 3:1.

[0012] S3, the reaction solution is subjected to solid-liquid separation treatment to obtain arsenic-cadmium stabilized separation residue.

[0013] Furthermore, the arsenic content in the arsenic-cadmium solid waste is ≤45000mg / kg, and the cadmium content is ≤900mg / kg.

[0014] Furthermore, the arsenic content in the arsenic-cadmium solid waste is 35,000–45,000 mg / kg, and the cadmium content is 700–900 mg / kg.

[0015] Furthermore, the occurrence phases of arsenic and cadmium elements in the arsenic-cadmium solid waste both include Ca3AsF4O. x - Contains sulfur, zinc, sodium, arsenic, calcium aluminate, zinc, silicon, fluorine, iron, cadmium, aluminum, sulfur, and arsenic-containing gypsum.

[0016] Furthermore, the mass ratio of the arsenic-cadmium solid waste to the composite agent is 4-6:1.

[0017] Furthermore, the pH of the acidic solution is 2 to 4.

[0018] Furthermore, the acidic solution comprises 1-3 mL of the arsenic-cadmium solid waste and 1 g of the composite agent; the acidic solution includes one or more of sulfuric acid solution and hydrochloric acid solution.

[0019] Furthermore, the mixing time of the mixing process is 20 to 48 hours.

[0020] Furthermore, the arsenic-cadmium solid waste includes gypsum residue from non-ferrous metallurgical smelting.

[0021] Compared with the prior art, the present invention has at least the following advantages:

[0022] This invention reduces the activity of arsenic and cadmium in gypsum slag, which has high arsenic and cadmium content and high leaching toxicity. It can significantly reduce the leaching rate of arsenic and cadmium in solid waste, solving the problem of high potential environmental risks of arsenic and cadmium in solid waste such as gypsum slag from non-ferrous smelting, and avoiding long-term stockpiling of solid waste. After stabilization treatment, the TCLP leaching toxicity of arsenic and cadmium in this invention meets the standards (As < 5 mg / L, Cd < 1 mg / L), providing technical support for the treatment and disposal of solid waste such as gypsum slag from non-ferrous smelting.

[0023] Specifically, this invention employs a composite reagent containing ferrous sulfate and ferrous sulfide, which has a simple composition. This not only simplifies the simultaneous stabilization process of arsenic and cadmium but also converts high-content, highly leaching-toxic arsenic and cadmium in solid waste into a more stable form. Furthermore, compared to other iron sources and other composite reagents, this invention significantly stabilizes arsenic and cadmium in solid waste, achieving unexpected technical benefits. In addition, by introducing an acidic solution, this invention further promotes the dissolution of arsenic and cadmium in the slag, ensuring its full reaction with the reagent. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0025] Figure 1 The XRD pattern of the gypsum residue in Example 1 of this invention;

[0026] Figure 2 MLA diagram of gypsum residue in Example 1 of this invention;

[0027] Figure 3 This is a comparative chart of the arsenic-cadmium TCLP leaching concentrations of each composite agent in Example 2 of this invention.

[0028] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0031] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of this invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to those described, used, or made of materials in the embodiments of this invention.

[0032] It should be noted that although Chinese invention patent CN105148447B discloses a method for mechanically activating and detoxifying arsenic-cadmium-containing acid slag, which involves mixing and ball-milling lead-zinc smelting slag, a detoxifying agent, and crushed arsenic-cadmium-containing acid slag, followed by adding water, stirring, and pressing to obtain a solidified block of arsenic-cadmium-containing acid slag; the leaching toxicity of arsenic and cadmium in the arsenic-cadmium-containing acid slag is 32.25 mg / L and 1.18 mg / L, respectively, and the detoxifying agent is kaolin:sodium sulfide:iron-manganese = 5:2:3, wherein the iron-manganese mixed detoxifying agent is prepared by ball-milling a mixture of iron powder and MnO2 in a molar ratio of 5:5-7:3, the synthesis of the detoxifying agent in the above patent is complex and costly, and its detoxification effect on arsenic and cadmium in smelting solid waste with high arsenic and cadmium leaching concentrations is unknown.

[0033] This invention provides an application of a composite agent in the simultaneous stabilization treatment of arsenic and cadmium. The composite agent includes ferrous sulfate and ferrous sulfide, and the mass ratio of ferrous sulfate to ferrous sulfide is 0.5 to 3:1, preferably 1 to 2:1.

[0034] As one application of the above, the present invention also provides a method for simultaneous arsenic and cadmium stabilization treatment of arsenic and cadmium solid waste, comprising the following steps:

[0035] S1 provides arsenic-cadmium solid waste containing arsenic and cadmium.

[0036] The arsenic content in the arsenic-cadmium solid waste can be ≤45000mg / kg, and the cadmium content can be ≤900mg / kg; further, the arsenic content in the arsenic-cadmium solid waste can be 35000~45000mg / kg, and the cadmium content can be 700~900mg / kg.

[0037] It should be noted that when the arsenic and cadmium content in the arsenic and cadmium solid waste is high and the form is complex, it is not possible to refer to the composite modified materials used in the arsenic and cadmium composite soil remediation research to adsorb arsenic and cadmium. The preferred method is to directly treat the arsenic and cadmium solid waste with reagents. However, the arsenic and cadmium stabilization processes are antagonistic, making it difficult to achieve both.

[0038] It should also be noted that the arsenic and cadmium elements in the arsenic-cadmium solid waste both occur in calcium arsenic compounds and arsenic-containing gypsum. Specifically, the arsenic element in the arsenic-cadmium solid waste is mainly present in Ca3AsF4O. x -Sulfur-containing zinc sodium, arsenic-calcium stone -Zinc-containing silicon fluorine iron cadmium aluminum sulfur two calcium arsenic compounds and arsenic-containing gypsum; cadmium element is also mainly present in Ca3AsF4O x - Contains two calcium arsenic compounds: sodium zinc sulfate, calcium arsenate, zinc silicon fluoride iron cadmium aluminum sulfur, and arsenic-containing gypsum. Because calcium arsenic compounds are unstable, highly soluble, and easily affected by CO2 in the air, the arsenic and cadmium in them have high activity and are easily leached. Therefore, they need to be converted into more stable compound forms. Based on the differences in the properties of arsenic and cadmium, this invention specifically selects reagents for compounding, thereby stabilizing arsenic and cadmium.

[0039] For example, the arsenic-cadmium solid waste may include or be non-ferrous smelting gypsum slag; the source of the non-ferrous smelting gypsum slag may include: gypsum slag produced in the lime neutralization stage after the waste acid generated from flue gas in copper, lead and zinc smelting is treated by sulfidation-lime neutralization-lime iron salt method.

[0040] S2, the arsenic-cadmium solid waste and the composite agent are mixed in an acidic solution to obtain a reaction solution.

[0041] The composite agent comprises ferrous sulfate and ferrous sulfide, wherein the mass ratio of ferrous sulfate to ferrous sulfide is 0.5 to 3:1, preferably 1 to 2:1.

[0042] In this invention, by using ferrous sulfate and ferrous sulfide as the composite agent, it has significant advantages in the stability of arsenic and cadmium compared to other forms of iron sources and other composite agents.

[0043] To optimize the simultaneous stabilization effect on the cadmium and arsenic solid waste, the mass ratio (slag-to-material ratio) of the arsenic and cadmium solid waste to the composite agent can be 4-6:1; the pH of the acidic solution can be 2-4, which can promote the dissolution of arsenic and cadmium and facilitate the dissolution of ferrous sulfide.

[0044] As a specific description of the acidic solution, the acidic solution consists of the sum of the arsenic-cadmium solid waste and the composite agent at a ratio of 1-3 mL:1 g, preferably 1-2 mL:1 g; the acidic solution may include one or more of sulfuric acid solution and hydrochloric acid solution.

[0045] The mixing time for the mixing treatment can be 20–48 hours; the stirring speed for the mixing treatment can be 400–500 rpm. Through this mixing treatment, the arsenic-cadmium solid waste can fully react with the composite agent in the acidic solution, thereby stabilizing the arsenic-cadmium and reducing its leaching concentration.

[0046] S3, the reaction solution is subjected to solid-liquid separation treatment to obtain a separated liquid and a stabilized arsenic-cadmium separation residue, wherein the arsenic-cadmium leaching rate of the separation residue is significantly reduced. After the solid-liquid separation, the solid product obtained from the solid-liquid separation can usually be dried.

[0047] This invention involves mixing the arsenic and cadmium solid waste with the composite agent in a specific ratio, adding an acidic solution, and magnetically stirring the mixture for a period of time. After centrifugation and drying, the separated residue is then sampled using the TCLP leaching toxicity method. The concentrations of arsenic and cadmium in the leachate meet the TCLP standards (As < 5 mg / L, Cd < 1 mg / L). In other words, the composite agent provided by this invention can achieve simultaneous stabilization of arsenic and cadmium in gypsum slag, and the leaching toxicity of the stabilized slag sample meets the relevant leaching toxicity standards.

[0048] It should be noted that arsenic and cadmium have opposite properties. Arsenic and cadmium exist as anions and cations, respectively, and the migration ability of both arsenic and cadmium is affected by pH and redox potential. Cadmium's migration ability generally decreases gradually with increasing pH and decreasing redox potential. Arsenic's migration ability generally increases gradually with increasing pH and decreasing redox potential. This is because increasing pH favors the precipitation of cationic heavy metals, but it also strengthens the electrostatic repulsion between the slag and arsenic oxyacid anions, thus increasing its migration. Therefore, addressing the antagonistic effect during arsenic and cadmium stabilization is key to achieving simultaneous stabilization of arsenic and cadmium in solid waste. This invention uses ferrous sulfate and ferrous sulfide as stabilizing agents. Ferrous sulfate hydrolyzes to produce acidity, while ferrous sulfide increases the pH of the system. Experiments were conducted to determine the appropriate dosage of these agents for arsenic and cadmium stabilization to ensure simultaneous arsenic and cadmium stabilization.

[0049] It should also be noted that, through the analysis of the basic properties of solid waste such as gypsum slag, this invention has found that it has high arsenic and cadmium content and complex occurrence forms; furthermore, for the two heavy metal elements with opposite properties, a single iron salt cannot simultaneously stabilize arsenic and cadmium, and arsenic in gypsum slag usually exists in both trivalent and pentavalent valence states.

[0050] Preliminary mechanistic studies have shown that this invention uses FeSO4 and FeS to stabilize gypsum slag. The iron ions in the iron salts can transform unstable arsenic into more stable ferric arsenate, while FeS provides sulfur ions to convert cadmium into cadmium sulfide. Simultaneously, it can precipitate trivalent arsenic as arsenic trisulfide. In this way, arsenic and cadmium in the gypsum slag are simultaneously stabilized, resulting in a slag mass reduction of approximately 30%. Furthermore, the acidic solution promotes the dissolution of calcium and arsenic compounds in the slag, thereby promoting the release of arsenic and cadmium and allowing them to fully react with the reagents.

[0051] The following are specific examples of the present invention:

[0052] Analysis example 1

[0053] 1. Obtain gypsum residue with a moisture content of less than 3%, an arsenic content of 40065 mg / kg, and arsenic in trivalent and pentavalent states with a mass ratio of trivalent to pentavalent arsenic of 1:7.2; and a cadmium content of 888 mg / kg.

[0054] Reference Figure 1-2 As shown, arsenic and cadmium are mainly present in Ca3AsF4O x - Contains sulfur-zinc-sodium, arsenic-calcium-containing zinc, silicon, fluorine, iron, cadmium, aluminum, sulfur, two calcium-arsenic compounds, and arsenic-containing gypsum.

[0055] The leaching toxicity test of gypsum residue was carried out using the TCLP method (US EPA test method, liquid-to-solid ratio 20 mL / 1 g, leachate volume 30 mL). The leaching toxicities of arsenic and cadmium in the gypsum residue were 1720.66 mg / L and 22.52 mg / L, respectively.

[0056] The main mineral composition and elemental occurrence phase analysis results of gypsum residue in MLA are shown in the table below:

[0057]

[0058] 2. Arsenic and cadmium stabilization treatment was carried out on the gypsum residue using stabilizing agents, specifically as follows:

[0059] Weigh 10g of gypsum residue, add stabilizing agent at a residue-to-material ratio of 2:1, then add acidic solution at a liquid-to-solid ratio of 3:2 mL / g (solid in liquid-to-solid ratio refers to the sum of gypsum residue and agent), and magnetically stir for 1 day after adding acidic solution to obtain reaction solution; wherein, the acidic solution is deionized water adjusted to pH=2 by H2SO4; the magnetic stirring speed is 500 rpm.

[0060] The reaction solution was centrifuged and filtered to obtain a separation liquid and a separation residue. The separation residue was dried and then subjected to a TCLP leaching toxicity test (US EPA test method, liquid-to-solid ratio 20 mL / 1 g) to detect the leaching concentration of arsenic and cadmium in the leaching solution. The volume of the leaching solution was 30 mL.

[0061] In this embodiment, the stabilizing agents are: FeCl3, reduced iron powder, FeS, FeSO4, Fe2(SO4)3, CaS, and Na2S.

[0062] Arsenic-cadmium stabilization treatments were performed using the aforementioned composite agents, and the specific results are as follows:

[0063] FeCl3 was used as a stabilizing agent to stabilize arsenic and cadmium in gypsum residue. The arsenic leaching concentration in the separated residue was 0.42 mg / L, and the cadmium leaching concentration was 8.62 mg / L.

[0064] Reduced iron powder was used as a stabilizing agent to stabilize arsenic and cadmium in gypsum slag. The arsenic leaching concentration of the separated slag was 20.50 mg / L and the cadmium leaching concentration was 7.85 mg / L.

[0065] FeS was used as a stabilizing agent to stabilize arsenic and cadmium in gypsum residue. The arsenic leaching concentration of the separated residue was 107.13 mg / L and the cadmium leaching concentration was 5.76 mg / L.

[0066] FeSO4 was used as a stabilizing agent to stabilize arsenic and cadmium in gypsum residue. The arsenic leaching concentration in the separated residue was 1.89 mg / L and the cadmium leaching concentration was 3.35 mg / L.

[0067] Fe2(SO4)3 was used as a stabilizing agent to stabilize arsenic and cadmium in gypsum residue. The arsenic leaching concentration of the separated residue was 26.69 mg / L and the cadmium leaching concentration was 8.13 mg / L.

[0068] CaS was used as a stabilizing agent to stabilize arsenic and cadmium in gypsum residue. The arsenic leaching concentration of the separated residue was 99.23 mg / L, and the cadmium leaching concentration was 0 mg / L.

[0069] Na2S was used as a stabilizing agent to stabilize arsenic and cadmium in gypsum residue. The arsenic leaching concentration of the separated residue was 814.35 mg / L and the cadmium leaching concentration was 3.71 mg / L.

[0070] Analysis example 2

[0071] Arsenic and cadmium stabilization treatment was carried out on gypsum residue (same as in Analytical Example 1) using a composite agent, specifically as follows:

[0072] Weigh 10g of gypsum residue, add the compound agent at a residue-to-material ratio of 2:1, and then add an acidic solution at a liquid-to-solid ratio of 3:2 mL / g (the solid in the liquid-to-solid ratio refers to the sum of the gypsum residue and the agent). After adding the acidic solution, stir magnetically for 1 day to obtain the reaction solution. The acidic solution is deionized water adjusted to pH=2 by H2SO4. The magnetic stirring speed is 500 rpm.

[0073] The reaction solution was centrifuged and filtered to obtain a separation solution and a separation residue. The separation residue was dried and then subjected to a TCLP leaching toxicity test (same as in Analytical Example 1) to detect the leaching concentration of arsenic and cadmium in the leaching solution. The volume of the leaching solution was 30 mL.

[0074] In this embodiment, the compound agents are as follows:

[0075] The first composite agent is Na2S + FeSO4, with a mass ratio of 1:1.

[0076] The second compound agent is Na2S + FeCl3, with a mass ratio of 1:1.

[0077] The third compound agent: CaS + FeSO4, with a mass ratio of 1:1;

[0078] The fourth compound agent: CaS + FeCl3, with a mass ratio of 1:1;

[0079] The fifth compound agent: FeS + FeSO4, with a mass ratio of 1:1;

[0080] The sixth compound agent: FeS + FeCl3, with a mass ratio of 1:1.

[0081] Arsenic and cadmium stabilization treatments were performed using the aforementioned composite agents, see [link to documentation]. Figure 3 As shown, the specific results are as follows:

[0082] The gypsum residue was treated with a first composite agent (Na2S + FeSO4 compound) to stabilize arsenic and cadmium. The arsenic leaching concentration of the separated residue was 25.20 mg / L and the cadmium leaching concentration was 8.48 mg / L.

[0083] The gypsum residue was stabilized with arsenic and cadmium using a second composite agent (Na2S and FeCl3). The arsenic leaching concentration of the separated residue was 1.05 mg / L and the cadmium leaching concentration was 8.79 mg / L.

[0084] The arsenic and cadmium leaching of gypsum residue was stabilized using a third compound agent (CaS + FeSO4 compound). The arsenic leaching concentration of the separated residue was 11.89 mg / L and the cadmium leaching concentration was 7.07 mg / L.

[0085] The arsenic and cadmium leaching of gypsum residue was stabilized using a fourth compound agent (CaS + FeCl3 compound). The arsenic leaching concentration of the separated residue was 83.14 mg / L and the cadmium leaching concentration was 12.81 mg / L.

[0086] The fifth composite agent (FeS+FeSO4 compound) was used to stabilize arsenic and cadmium in gypsum residue. The arsenic leaching concentration of the separated residue was 0.4 mg / L and the cadmium leaching concentration was 3.9 mg / L.

[0087] The arsenic and cadmium leaching of gypsum residue was stabilized using a sixth compound agent (FeS + FeCl3 compound). The arsenic leaching concentration of the separated residue was 0.16 mg / L and the cadmium leaching concentration was 8.99 mg / L.

[0088] Example 1

[0089] Weigh 18g of gypsum slag (same as in Analytical Example 1), add the composite reagent (FeS and FeSO4 mixed at a mass ratio of 1:1) at a slag-to-material ratio of 6:1, then add an acidic solution at a liquid-to-solid ratio of 2:1 mL / g (the solid in the liquid-to-solid ratio refers to the sum of the gypsum slag and the reagent), and magnetically stir for 1 day after adding the acidic solution to obtain the reaction solution; wherein, the acidic solution is deionized water adjusted to pH=2 by H2SO4; the magnetic stirring speed is 500 rpm.

[0090] The reaction solution was centrifuged and filtered to obtain a separation solution and a separation residue. The concentrations of arsenic and cadmium in the separation solution were both low, at 0.14 mg / L and 0.38 mg / L, respectively.

[0091] After drying the separated residue, a TCLP leaching toxicity test was conducted (same as in Analytical Example 1) to detect the leaching concentration of arsenic and cadmium in the leachate. The volume of the leachate was 30 mL.

[0092] The TCLP leaching toxicity results of this embodiment show that the arsenic leaching concentration in the separated residue is 4.6 mg / L and the cadmium leaching concentration is 0.8 mg / L, which meets the TCLP arsenic and cadmium toxicity leaching standards.

[0093] Example 2

[0094] Weigh 18g of gypsum slag (same as in Analytical Example 1), add the composite reagent (FeS and FeSO4 mixed at a mass ratio of 1:1) at a slag-to-material ratio of 5:1, then add an acidic solution at a liquid-to-solid ratio of 3:2 mL / g (the solid in the liquid-to-solid ratio refers to the sum of the gypsum slag and the reagent), and stir magnetically for 1 day after adding the acidic solution to obtain the reaction solution; wherein, the acidic solution is deionized water adjusted to pH=3 by H2SO4; the magnetic stirring speed is 500 rpm.

[0095] The reaction solution was centrifuged and filtered to obtain a separation solution and a separation residue. The separation residue was dried and then subjected to a TCLP leaching toxicity test (same as in Analytical Example 1) to detect the leaching concentration of arsenic and cadmium in the leaching solution. The volume of the leaching solution was 30 mL.

[0096] The TCLP leaching toxicity results of this embodiment show that the arsenic leaching concentration in the separation residue is 3.9 mg / L and the cadmium leaching concentration is 0.8 mg / L, which meets the TCLP arsenic and cadmium toxicity leaching standards.

[0097] Example 3

[0098] Weigh 18g of gypsum slag (same as in Analytical Example 1), add the composite reagent (FeS and FeSO4 mixed at a mass ratio of 1:2) at a slag-to-material ratio of 6:1, then add an acidic solution at a liquid-to-solid ratio of 3:2 mL / g (the solid in the liquid-to-solid ratio refers to the sum of the gypsum slag and the reagent), and magnetically stir for 1 day after adding the acidic solution to obtain the reaction solution; wherein, the acidic solution is deionized water adjusted to pH=2 by H2SO4; the magnetic stirring speed is 500 rpm.

[0099] The reaction solution was centrifuged and filtered to obtain a separation solution and a separation residue. The separation residue was dried and then subjected to a TCLP leaching toxicity test (same as in Analytical Example 1) to detect the leaching concentration of arsenic and cadmium in the leaching solution. The volume of the leaching solution was 30 mL.

[0100] The TCLP leaching toxicity results of this embodiment show that the arsenic leaching concentration in the separation residue is 1.9 mg / L and the cadmium leaching concentration is 0.9 mg / L, which meets the TCLP arsenic and cadmium toxicity leaching standards.

[0101] Comparative Example 1

[0102] Compared to Example 2, this comparative example adjusted the pH of the acidic solution to 6, the slag-to-material ratio to 2:1 (10g of gypsum slag), and kept other conditions unchanged; wherein, the acidic solution was deionized water adjusted to pH=6 by H2SO4.

[0103] The TCLP leaching toxicity results of this embodiment show that the arsenic leaching concentration in the separation residue is 0.24 mg / L and the cadmium leaching concentration is 5.23 mg / L, which does not meet the TCLP arsenic and cadmium toxicity leaching standards.

[0104] Comparative Example 2

[0105] Compared to Example 2, this comparative example adjusts the pH of the acidic solution to 1, the slag-to-material ratio to 2:1 (10g of gypsum slag), and keeps other conditions unchanged; wherein, the acidic solution is deionized water adjusted to pH=1 by H2SO4.

[0106] The TCLP leaching toxicity results of this embodiment show that the arsenic leaching concentration in the separation residue is 43.6 mg / L and the cadmium leaching concentration is 3.35 mg / L, which does not meet the TCLP arsenic and cadmium toxicity leaching standards.

[0107] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for simultaneous arsenic and cadmium stabilization treatment of arsenic-cadmium solid waste, characterized in that, Including the following steps: S1, providing arsenic-cadmium solid waste, wherein the arsenic-cadmium solid waste contains arsenic and cadmium; wherein the arsenic content in the arsenic-cadmium solid waste is 35,000~45,000 mg / kg and the cadmium content is 700~900 mg / kg; S2, the arsenic-cadmium solid waste and the composite agent are mixed in an acidic solution to obtain a reaction solution; the pH of the acidic solution is 2-4; The composite agent comprises ferrous sulfate and ferrous sulfide, wherein the mass ratio of ferrous sulfate to ferrous sulfide is 0.5~3:1; the mass ratio of arsenic-cadmium solid waste to the composite agent is 4~6:1; and the acidic solution comprises 1~3 mL of arsenic-cadmium solid waste to 1 g of the composite agent. S3, the reaction solution is subjected to solid-liquid separation treatment to obtain arsenic-cadmium stabilized separation residue; in the separation residue, the TCLP leaching concentration of arsenic is less than 5 mg / L and the TCLP leaching concentration of cadmium is less than 1 mg / L.

2. The method for simultaneous stabilization of arsenic and cadmium according to claim 1, characterized in that, The arsenic and cadmium elements in the arsenic-cadmium solid waste both contain Ca3AsF4O in their respective phases. x - Contains sulfur, zinc, sodium, arsenic, calcium aluminate, zinc, silicon, fluorine, iron, cadmium, aluminum, sulfur, and arsenic-containing gypsum.

3. The method for simultaneous stabilization of arsenic and cadmium according to claim 1, characterized in that, The acidic solution includes one or more of sulfuric acid solution and hydrochloric acid solution.

4. The method for simultaneous stabilization of arsenic and cadmium according to claim 1, characterized in that, The mixing time for the mixing process is 20-48 hours.

5. The method for simultaneous stabilization of arsenic and cadmium according to any one of claims 1-4, characterized in that, The arsenic and cadmium solid waste includes gypsum residue from non-ferrous metallurgical smelting

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