Method for detoxifying arsenic in soil based on inorganic solid waste modified material

Abstract

The application provides a method for soil arsenic detoxification based on inorganic solid waste modified material, comprising the following steps: treating inorganic solid waste by alkali etching with inorganic alkali to obtain modified inorganic solid waste; mixing the modified inorganic solid waste with a by-product containing sulfite generated in a wet flue gas desulfurization process to obtain a soil remediation agent; applying the soil remediation agent to the surface layer of arsenic-contaminated soil, and forming mixed soil by plowing and stirring; under the action of water in the mixed soil, trivalent arsenic in the mixed soil solution is oxidized into pentavalent arsenic, which is adsorbed and fixed on the surface of the modified inorganic solid waste together with original pentavalent arsenic in the soil, so that the effective state concentration and toxicity of arsenic in the soil are reduced. The application can realize the resource utilization of two types of solid waste at the same time, and can repair arsenic-contaminated soil, so that waste is treated by waste, the method can also be synchronized with greening or cultivation, and is easy to implement, simple and efficient, and has a popularization and application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of soil heavy metal pollution treatment, and particularly relates to a method for soil arsenic detoxification based on inorganic solid waste modified material. BACKGROUND

[0002] Arsenic compounds are highly toxic and can cause lung cancer, bladder cancer, liver cancer, kidney cancer and skin cancer and other cancers, and are determined as the first carcinogen by the international cancer prevention research institutions. According to the 2014 National Soil Pollution Status Investigation Bulletin, the soil environment problem of industrial and mining wasteland is prominent in China, and the over-standard point of industrial wasteland accounts for 34.9% of all points, and 2.7% of soil samples are contaminated by arsenic. Arsenic in soil can be transferred and accumulated in organisms and human bodies through food chains from crops or soil leaching solution, which poses a serious threat to the ecological environment and human health. Adsorbing and fixing arsenic with metal oxide minerals to reduce the effective concentration of arsenic is a main method for repairing arsenic contaminated soil.

[0003] The main components of inorganic solid waste such as fly ash, coal gangue and red mud are SiO2, Al2O3, CaO, Fe2O3 and TiO2. Among them, the presence of metal oxides makes these solid wastes have a certain adsorption performance on arsenic. However, due to the low specific surface area of these inorganic solid wastes and the high content of SiO2, the metal oxides are embedded in the particle interior, and their adsorption performance is very limited, and the efficiency of adsorbing and fixing arsenic in soil is very low. Therefore, the modification treatment of these solid wastes can increase the specific surface area and expose more metal oxide sites, which can improve the passivation efficiency of arsenic. In addition, arsenic usually exists in the form of arsenite (trivalent) and arsenate (pentavalent) in soil. Compared with pentavalent arsenic, trivalent arsenic is not easy to be adsorbed or precipitated in soil, so it has stronger migration, and its toxicity is about 25-60 times that of pentavalent arsenic. Therefore, it is necessary to oxidize trivalent arsenic by using certain technology to reduce the toxicity of arsenic and promote its adsorption and fixation by oxides.

[0004] Therefore, an inorganic solid waste is provided as an adsorption raw material, and a suitable modification treatment method is used to expose more metal oxide sites, and the inorganic solid waste is combined with an oxidation process to treat soil arsenic detoxification. This has important significance for efficient repair of arsenic contaminated soil and resource utilization of inorganic solid waste, and is also a technical problem to be solved. SUMMARY

[0005] The purpose of the present application is to provide a method for soil arsenic detoxification based on inorganic solid waste modified material to overcome the shortcomings of the prior art.

[0006] To solve the above technical problems, the present application adopts the following technical solutions: a method for soil arsenic detoxification based on inorganic solid waste modified material is provided, comprising the following steps:

[0007] S1, using inorganic alkali to perform alkali etching treatment on inorganic solid waste containing metal oxides to obtain modified inorganic solid waste;

[0008] S2, mixing the modified inorganic solid waste with a by-product containing sulfite generated in a wet flue gas desulfurization process to obtain a soil remediation agent;

[0009] S3, applying the soil remediation agent to the surface layer of the arsenic-contaminated soil, and forming a mixed soil through plowing and stirring;

[0010] S4, under the action of water in the mixed soil, trivalent arsenic in the mixed soil solution is oxidized to pentavalent arsenic, which is adsorbed and fixed on the surface of the modified inorganic solid waste together with the original pentavalent arsenic in the soil, thereby reducing the effective concentration and toxicity of arsenic in the soil.

[0011] The overall idea and reaction principle of the method for soil arsenic detoxification provided by the present application are as follows:

[0012] Firstly, the inorganic solid waste containing metal oxides is modified by alkali etching, and the inert components SiO2 and Al2O3 in the modified inorganic solid waste are partially etched and dissolved out, thereby exposing the metal oxide (iron oxide, titanium dioxide, magnesium oxide, etc.) sites with arsenic adsorption activity, and due to the dissolution of part of the components on the solid, a pore structure is formed, more surface is exposed, and the specific surface area of the material is increased; secondly, after the modified inorganic solid waste is compounded with the by-product containing sulfite in the wet flue gas desulfurization process to form a soil remediation agent, the soil remediation agent is applied to the surface layer of the arsenic-contaminated soil, and a mixed soil is formed through plowing and stirring; finally, under the action of water in the mixed soil, the exposed metal oxides of the modified inorganic solid waste can activate the dissolved sulfite to generate strong oxidizing groups such as sulfate radicals and hydroxyl radicals on the surface, so that trivalent arsenic is oxidized to pentavalent arsenic, which is adsorbed and fixed on the surface of the modified inorganic solid waste together with the original pentavalent arsenic in the soil, thereby reducing the effective concentration and toxicity of arsenic in the soil, and realizing the detoxification treatment of the arsenic-contaminated soil.

[0013] Further, in step S1, the inorganic solid waste containing metal oxides includes one or more combinations of fly ash, coal gangue, and red mud; and the metal oxides include one or more combinations of iron oxide, titanium dioxide, and magnesium oxide.

[0014] Further, in step S1, the inorganic alkali is selected from sodium hydroxide or potassium hydroxide.

[0015] Further, in step S1, the alkali etching treatment is selected from one of the following methods: mixing the inorganic solid waste containing metal oxides with inorganic alkali solid, and performing calcination treatment; or mixing the inorganic solid waste containing metal oxides with inorganic alkali aqueous solution, and performing hydrothermal reaction.

[0016] Preferably, the temperature of the calcination treatment is 200-600℃, the time of the calcination treatment is 0.5-3h, and the mass ratio of the inorganic solid waste containing metal oxides to the inorganic alkali solid is 3-10:1. More preferably, the temperature of the calcination treatment is 400-600℃, the time of the calcination treatment is 0.5-2h, and the modified inorganic solid waste obtained under the above conditions has a higher specific surface area.

[0017] Preferably, the temperature of the hydrothermal reaction is 50-90℃, the time of the hydrothermal reaction is 1-6h, the concentration of the inorganic alkali aqueous solution is 0.5-10mol / L, and the mass-to-volume ratio of the inorganic solid waste containing metal oxides to the inorganic alkali aqueous solution is 1:(1-5)g / mL.

[0018] Further, in step S2, the by-product containing sulfite generated in the wet flue gas desulfurization process includes one or more of the following: desulfurization gypsum by-product containing calcium sulfite generated in the limestone / lime-gypsum desulfurization process, by-product containing magnesium sulfite generated in the magnesium-based flue gas desulfurization process, and by-product containing sodium sulfite generated in the sodium-based desulfurization process.

[0019] Further, in step S2, the mass ratio of the modified inorganic solid waste to the by-product containing sulfite generated in the wet flue gas desulfurization process in the soil remediation agent is 5-30:1.

[0020] Further, in step S3, the application amount of the soil remediation agent in the soil contaminated by arsenic is 300-2000kg / acre.

[0021] Further, in step S4, the source of water in the soil includes one or more of the following: direct watering of the soil, natural rainfall, and watering of crops or plants in the soil under planting conditions.

[0022] In some preferable embodiments, the method for detoxifying arsenic in soil provided by the present application can be performed simultaneously with planting. Specifically, the soil remediation agent is applied to the surface layer of the arsenic-contaminated soil at an application amount of 300-2000 kg / mu, and mixed soil is formed by stirring through ploughing; and then planting of crops or plants is performed in the mixed soil. Under the planting condition, the watering process for the crops or plants increases the water content in the soil, and in the soil solution, the exposed metal oxides of the modified inorganic solid waste can activate the dissolved sulfite to generate strong oxidizing groups such as sulfate radicals and hydroxyl radicals on the surface, so as to realize oxidation of trivalent arsenic into pentavalent arsenic, which is adsorbed and fixed on the surface of the modified inorganic solid waste together with the original pentavalent arsenic in the soil. The above method has the advantages of short treatment period and high economic efficiency, and can realize simultaneous green planting or cultivation and detoxification of arsenic in soil.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] (1) The method for detoxifying arsenic in soil based on modified inorganic solid waste provided by the present application exerts the synergistic effect between inorganic solid waste and flue gas wet desulfurization by-products, and realizes oxidation and adsorption of trivalent arsenic in arsenic-contaminated soil, thereby achieving the effect of detoxification and remediation. Both the inorganic solid waste and the flue gas wet desulfurization by-products are common industrial solid wastes, and the method provided by the present application realizes resource utilization of the two types of solid wastes, reduces the solid wastes, and realizes adsorption of arsenic-contaminated soil.

[0025] (2) The method for detoxifying arsenic in soil based on modified inorganic solid waste provided by the present application is simple and economical and green, and does not need to add other active components (such as transition metal salts and organic surfactants) during the preparation process. The modified inorganic solid waste has a high specific surface area and exposes more oxide adsorption sites and catalytic active sites, thereby exerting a better adsorption and fixation effect on arsenic in soil.

[0026] (3) The method for detoxifying arsenic in soil based on modified inorganic solid waste provided by the present application can be performed simultaneously with green planting, and the water content in the soil can be increased by watering the crops or plants, so that trivalent arsenic in the soil solution is oxidized into pentavalent arsenic, which is adsorbed and fixed on the surface of the modified inorganic solid waste together with the original pentavalent arsenic in the soil, thereby reducing the effective concentration and toxicity of arsenic in the soil. The method has the advantages of short treatment period and high economic efficiency, and can realize simultaneous green planting or cultivation and detoxification of arsenic in soil, thereby having a wide popularization and application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The scanning electron microscope image of the modified fly ash prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0028] The technical solutions of the present application will be described clearly and completely in combination with the embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.

[0029] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0030] The present application will be further described in combination with specific embodiments, but not as a limitation of the present application.

[0031] The fly ash used in the embodiments of the present application has the following main component contents in percentage by weight: 28.4wt.% of aluminum oxide, 45.6wt.% of silicon dioxide, 4.2% of calcium oxide, 4.8% of iron oxide, 2.6% of titanium dioxide, and 3.5% of magnesium oxide.

[0032] The coal gangue used in the embodiments of the present application has the following main component contents in percentage by weight: 20.7wt.% of aluminum oxide, 43.3wt.% of silicon dioxide, 8.1% of iron oxide, 4.0% of titanium dioxide, and 2.4% of magnesium oxide.

[0033] The red mud used in the embodiments of the present application has the following main component contents in percentage by weight: 10.3wt.% of aluminum oxide, 19.5wt.% of silicon dioxide, 37.3% of iron oxide, 9.4% of sodium oxide, 2.0% of titanium dioxide, and 1.9% of magnesium oxide.

[0034] Embodiment 1

[0035] 20 grams of fly ash was mixed with 6.7 grams of sodium hydroxide particles and ground thoroughly, and then calcined at 600℃ for 0.5 hour. After cooling, it was washed with water, filtered and dried to obtain modified fly ash. The specific surface areas of the original fly ash and the modified fly ash were 0.6 square meters per gram and 5.4 square meters per gram, respectively, indicating that more surface was exposed after the alkali etching of the surface of the fly ash. The scanning electron microscope photo of the modified fly ash prepared in this embodiment is shown in FIG. 1, showing a porous structure. Figure 1

[0036] The ability of the modified fly ash to remove arsenic in water was studied to evaluate its potential to remove arsenic in soil solution.

[0037] ​Experiment 1: The concentration of total arsenic in the simulated solution is 10 ppm, in which the concentration of arsenite is 5 ppm and the concentration of arsenate is 5 ppm. The modified fly ash is added to the solution, and the dosage of the modified fly ash is 2 grams per liter. After 1 hour of adsorption, the residual arsenite concentration is measured to be 3.5 ppm, and the residual arsenate concentration is measured to be 0.3 ppm, i.e. the removal rate of trivalent arsenic is 30%, and the removal rate of total arsenic is 62%.

[0038] Experiment 2: The concentration of arsenic in the simulated solution is the same as that in Experiment 1. The raw fly ash is added to the solution, and the dosage of the raw fly ash is 2 grams per liter. After 1 hour of adsorption, the residual arsenite concentration is measured to be 4.9 ppm, and the residual arsenate concentration is measured to be 4.5 ppm, i.e. the removal rate of trivalent arsenic is 2%, and the removal rate of total arsenic is 6%.

[0039] Experiment 3: The concentration of arsenic in the simulated solution is the same as that in Experiment 1, and sodium sulfite is added to the solution, and the concentration of sodium sulfite is 0.5 millimole per liter. The modified fly ash is added to the solution, and the dosage of the modified fly ash is 2 grams per liter. After 1 hour, the residual arsenite concentration is measured to be 0 ppm, and the residual arsenate concentration is measured to be 0.4 ppm, i.e. the removal rate of trivalent arsenic is 100%, and the removal rate of total arsenic is 96%.

[0040] Experiment 4: The concentration of arsenic in the simulated solution and the concentration of sodium sulfite are the same as those in Experiment 3. The raw fly ash is added to the solution, and the dosage of the raw fly ash is 2 grams per liter. After 1 hour, the residual arsenite concentration is measured to be 4.3 ppm, and the residual arsenate concentration is measured to be 4.8 ppm, i.e. the removal rate of trivalent arsenic is 14%, and the removal rate of total arsenic is 9%.

[0041] Experiment 1 shows that pentavalent arsenic (arsenate) is more easily adsorbed than trivalent arsenic (arsenite).

[0042] By comparing Experiment 1 and Experiment 2, it can be seen that the adsorption performance of fly ash for arsenic is greatly improved after alkali etching modification, which can be attributed to the exposure of more metal oxide surfaces.

[0043] By comparing Experiment 1 and Experiment 3, it can be seen that the trivalent arsenic in the system is significantly oxidized, and the total arsenic removal rate is also significantly improved, which also indicates that the oxidation of trivalent arsenic promotes the removal of total arsenic.

[0044] By comparing Experiment 3 and Experiment 4, it can be seen that the modified fly ash has a stronger ability to activate sodium sulfite to oxidize trivalent arsenic than the raw fly ash.

[0045] Example 2

[0046] 20 grams of dried red mud are mixed with 2 grams of sodium hydroxide particles and thoroughly ground, and then calcined at 200°C for 3 hours. After cooling, it is washed with water, filtered and dried to obtain modified red mud. The specific surface area of the original red mud and the modified red mud is 0.4 square meters per gram and 4.5 square meters per gram, respectively, indicating that more surfaces are exposed after the red mud is etched by alkali.

[0047] The ability of the modified red mud to remove arsenic from water was investigated to evaluate its potential to remove arsenic from soil solutions.

[0048] Experiment 1: The concentration of total arsenic in the simulated solution was 10 ppm, of which the concentration of arsenite was 5 ppm and the concentration of arsenate was 5 ppm. Modified red mud powder was added to the solution at a dose of 2 g / L. After 1 hour of adsorption, the residual arsenite concentration was measured to be 3.9 ppm and the residual arsenate concentration was 0.7 ppm, i.e. the removal rate of trivalent arsenic was 22% and the removal rate of total arsenic was 54%.

[0049] Experiment 2: The concentration of arsenic in the simulated solution was the same as in Experiment 1. Raw red mud was added to the solution at a dose of 2 g / L. After 1 hour of adsorption, the residual arsenite concentration was measured to be 4.9 ppm and the residual arsenate concentration was 4.7 ppm, i.e. the removal rate of trivalent arsenic was 2% and the removal rate of total arsenic was 4%.

[0050] Experiment 3: The concentration of arsenic in the simulated solution was the same as in Experiment 1, and sodium sulfite was added at a concentration of 0.5 mmol / L. Modified red mud powder was added to the solution at a dose of 2 g / L. After 1 hour, the residual arsenite concentration was measured to be 0.3 ppm and the residual arsenate concentration was 0.9 ppm, i.e. the removal rate of trivalent arsenic was 94% and the removal rate of total arsenic was 88%.

[0051] Comparing Experiments 1-3 above, it can be seen that the modified red mud has stronger adsorption performance for arsenic than the raw red mud, and can activate the oxidation of trivalent arsenic by sulfite to promote the adsorption of arsenic.

[0052] Example 3

[0053] 20 g of coal gangue powder was mixed with 4 g of potassium hydroxide particles and ground thoroughly, and then calcined at 400°C for 2 hours. After cooling, it was washed with water, filtered and dried to obtain modified coal gangue. The specific surface area of the raw coal gangue and the modified coal gangue was 0.3 m2 / g and 5.7 m2 / g, respectively, indicating that more surface was exposed after the coal gangue was etched by alkali.

[0054] The ability of the modified coal gangue to remove arsenic from water was investigated to evaluate its potential to remove arsenic from soil solutions.

[0055] Experiment 1: The concentration of total arsenic in the simulated solution was 10 ppm, of which the concentration of arsenite was 5 ppm and the concentration of arsenate was 5 ppm. Modified coal gangue powder was added to the solution at a dose of 2 g / L. After 1 hour of adsorption, the residual arsenite concentration was measured to be 4.2 ppm and the residual arsenate concentration was 0.9 ppm, i.e. the removal rate of trivalent arsenic was 16% and the removal rate of total arsenic was 49%.

[0056] Experiment 2: The concentration of arsenic in the simulated solution is the same as that in Experiment 1. Raw coal gangue powder is added to the solution, and the dosage of the raw coal gangue powder is 2 grams per liter. After 1 hour of adsorption, the residual arsenite concentration is measured to be 4.9 ppm, and the residual arsenate concentration is 4.8 ppm, i.e., the removal rate of trivalent arsenic is 2%, and the total arsenic removal rate is 3%.

[0057] Experiment 3: The concentration of arsenic in the simulated solution is the same as that in Experiment 1, and sodium sulfite is added at a concentration of 0.5 millimoles per liter. Modified coal gangue powder is added to the solution, and the dosage of the modified coal gangue powder is 2 grams per liter. After 1 hour, the residual arsenite concentration is measured to be 0.5 ppm, and the residual arsenate concentration is 1.6 ppm, i.e., the removal rate of trivalent arsenic is 90%, and the total arsenic removal rate is 79%.

[0058] Comparing Experiments 1-3 above, it can be seen that the modified coal gangue has stronger adsorption performance for arsenic than the raw coal gangue, and can activate sulfite to oxidize trivalent arsenic and promote the adsorption of arsenic.

[0059] Example 4

[0060] 20 grams of fly ash are added to 100 milliliters of 0.5 molar potassium hydroxide solution, and the temperature is raised to 90°C. After hydrothermal treatment for 6 hours, the solid product is separated by filtration, and then filtered and dried to obtain a modified fly ash material. The specific surface areas of the raw fly ash and the modified fly ash are 0.6 square meters per gram and 4.5 square meters per gram, respectively, indicating that the surface of the fly ash is etched by the alkali, exposing more surface.

[0061] The ability of the modified fly ash to remove arsenic from water is studied to evaluate its potential for removing arsenic from soil solution. The total arsenic concentration in the simulated solution is 10 ppm, of which the arsenite concentration is 5 ppm and the arsenate concentration is 5 ppm. Sodium sulfite is added at a concentration of 0.5 millimoles per liter. Modified fly ash is added to the solution, and the dosage of the modified fly ash is 2 grams per liter. After 1 hour, the residual arsenite concentration is measured to be 0.1 ppm, and the residual arsenate concentration is 0.7 ppm, i.e., the removal rate of trivalent arsenic is 98%, and the total arsenic removal rate is 92%. This indicates that the modified fly ash has strong oxidation and adsorption removal capacity for arsenic.

[0062] Example 5

[0063] 20 grams of fly ash are added to 20 milliliters of 10 molar sodium hydroxide solution, and the temperature is raised to 50°C. After hydrothermal treatment for 1 hour, the solid product is separated by filtration, and then filtered and dried to obtain a modified fly ash material. The specific surface areas of the raw fly ash and the modified fly ash are 0.6 square meters per gram and 4.7 square meters per gram, respectively, indicating that the surface of the fly ash is etched by the alkali, exposing more surface.

[0064] The modified coal gangue was used to remove arsenic from water to evaluate its potential to remove arsenic from soil solution. The total arsenic concentration in the simulated solution was 10 ppm, of which the concentration of arsenious acid was 5 ppm and the concentration of arsenic acid was 5 ppm. Sodium sulfite was added at a concentration of 0.5 millimole per liter. Modified fly ash was added to the solution at a dosage of 2 grams per liter. After 1 hour, the residual arsenious acid concentration was measured to be 0 ppm and the residual arsenic acid concentration was 0.5 ppm, i.e. the removal rate of trivalent arsenic was 100% and the total arsenic removal rate was 95%. This indicates that the modified fly ash has strong oxidation and adsorption removal capacity for arsenic.

[0065] Application Example 1

[0066] The modified fly ash prepared by the method of Example 1 was used for the remediation of arsenic-contaminated soil.

[0067] 5 kilograms of modified fly ash was mixed with 1 kilogram of desulfurization gypsum to obtain 6 kilograms of soil remediation agent.

[0068] A certain arsenic-contaminated farmland was selected for remediation, and the effective arsenic (including effective trivalent arsenic and effective pentavalent arsenic) concentration was measured to be 37 milligrams per kilogram, including trivalent arsenic and pentavalent arsenic. A 2m 2 For the experimental area, 6 kilograms of modified fly ash and desulfurization gypsum were uniformly mixed to form a soil remediation agent, which was uniformly spread into the experimental area, and the soil and the remediation agent were plowed evenly. Water was poured once a day, and after 30 days, the effective arsenic concentration was measured to be reduced to 16 milligrams per kilogram, i.e. the effective arsenic concentration was reduced by 57%.

[0069] A comparative experiment was conducted in an adjacent plot without adding desulfurization gypsum, only adding 5 kilograms of modified fly ash, and after 30 days, the effective arsenic concentration was measured to be reduced to 25 milligrams per kilogram, i.e. the effective arsenic concentration was reduced by 32%. The comparison shows that desulfurization gypsum promotes the adsorption of arsenic, which is attributed to the fact that trivalent arsenic is more easily adsorbed and passivated by modified fly ash after being oxidized.

[0070] Application Example 2

[0071] The modified red mud prepared by the method of Example 2 was used for the remediation of arsenic-contaminated soil.

[0072] 0.7 kilograms of modified red mud powder was mixed with 0.2 kilograms of magnesium-containing by-product generated in the magnesium-based flue gas desulfurization process to obtain 0.9 kilograms of soil remediation agent. A certain arsenic-contaminated farmland was selected for remediation, and the effective arsenic concentration was measured to be 18 milligrams per kilogram, including trivalent arsenic and pentavalent arsenic. A 2m 2 For the experimental area, 0.9 kilograms of modified red mud powder and magnesium-containing desulfurization by-product were uniformly mixed to form a soil remediation agent, which was uniformly spread into the experimental area, and the soil and the remediation agent were plowed evenly. Water was poured once a day, and after 30 days, the effective arsenic concentration was measured to be reduced to 10 milligrams per kilogram, i.e. the effective arsenic concentration was reduced by 44%.

[0073] A comparative experiment was carried out in the adjacent plot without adding the desulfurization by-product containing magnesium sulfite, only 0.7 kg of modified red mud was added, and the concentration of available arsenic was reduced to 13 mg / kg after 30 days, i.e. the concentration of available arsenic was reduced by 27%. The comparison shows that the desulfurization by-product containing magnesium sulfite promotes the adsorption of arsenic, which is attributed to the fact that the trivalent arsenic is more easily adsorbed and passivated by the modified red mud after being oxidized.

[0074] Application Example 3

[0075] The modified coal gangue prepared by the method of Example 3 was used for the remediation of arsenic-contaminated soil.

[0076] 3 kg of modified coal gangue powder was mixed with 0.1 kg of by-product containing sodium sulfite generated in the sodium desulfurization process to obtain 3.1 kg of soil remediation agent. A certain arsenic-contaminated farmland was selected for remediation, and the measured concentration of available arsenic was 34 mg / kg, including trivalent arsenic and pentavalent arsenic. A 2m 2 For the experimental area, 3.1 kg of modified coal gangue powder and desulfurization by-product containing sodium sulfite were uniformly mixed into the soil remediation agent, and the soil and the remediation agent were plowed evenly, and watered once a day. After 30 days, the concentration of available arsenic was reduced to 21 mg / kg, i.e. the concentration of available arsenic was reduced by 38%.

[0077] A comparative experiment was carried out in the adjacent plot without adding the desulfurization by-product containing sodium sulfite, only 3 kg of modified fly ash was added, and the concentration of available arsenic was reduced to 26 mg / kg after 30 days, i.e. the concentration of available arsenic was reduced by 23%. The comparison shows that the desulfurization by-product containing sodium sulfite promotes the adsorption of arsenic, which is attributed to the fact that the trivalent arsenic is more easily adsorbed and passivated by the modified fly ash after being oxidized.

[0078] Application Example 4

[0079] The modified fly ash prepared by the method of Example 4 was used for the remediation of arsenic-contaminated soil.

[0080] 5 kg of modified fly ash was mixed with 1 kg of desulfurization gypsum to obtain 6 kg of soil remediation agent. A certain arsenic-contaminated farmland was selected for remediation, and the measured concentration of available arsenic was 41 mg / kg, including trivalent arsenic and pentavalent arsenic. A 2m 2 For the experimental area, 6 kg of modified fly ash and desulfurization gypsum were uniformly mixed into the soil remediation agent, and the soil and the remediation agent were plowed evenly, and watered once a day. After 30 days, the concentration of available arsenic was reduced to 27 mg / kg, i.e. the concentration of available arsenic was reduced by 34%.

[0081] In the adjacent plot, the comparative experiment was carried out without adding desulfurization gypsum, only 5 kg of modified fly ash was added, and the concentration of available arsenic was reduced to 33 mg / kg after 30 days, that is, the concentration of available arsenic was reduced by 20%. The comparison shows that the desulfurization gypsum promotes the adsorption of arsenic, which is attributed to the fact that the trivalent arsenic is oxidized and is more easily adsorbed and passivated by the modified fly ash.

[0082] The above merely describes preferred embodiments of the present application, and is not intended to limit the embodiments and protection scope of the present application. It should be understood by those skilled in the art that any equivalent replacement and obvious change made according to the content of the present application should be included in the protection scope of the present application.

Claims

1. A method for detoxification of arsenic in soil based on inorganic solid waste modified material, characterized in that, The method comprises the following steps: S1, alkali etching treatment is performed on inorganic solid waste containing metal oxides by using inorganic alkali to obtain modified inorganic solid waste; the inorganic alkali is selected from sodium hydroxide or potassium hydroxide; the inorganic solid waste containing metal oxides comprises one or a combination of more than one of fly ash, coal gangue and red mud; the metal oxides comprise one or a combination of more than one of iron oxide, titanium dioxide and magnesium oxide; S2, the modified inorganic solid waste is mixed with a by-product containing sulfite generated in a wet flue gas desulfurization process to obtain a soil remediation agent; The by-product containing sulfite generated in the wet flue gas desulfurization process comprises one or a combination of more than one of a desulfurization gypsum by-product containing calcium sulfite generated in a limestone / lime-gypsum desulfurization process, a by-product containing magnesium sulfite generated in a magnesium flue gas desulfurization process, and a by-product containing sodium sulfite generated in a sodium desulfurization process; S3, the soil remediation agent is applied to the surface layer of the arsenic-contaminated soil, and a mixed soil is formed by plowing and stirring; S4, under the action of water in the mixed soil, trivalent arsenic in the mixed soil solution is oxidized into pentavalent arsenic, which is adsorbed and fixed on the surface of the modified inorganic solid waste together with the original pentavalent arsenic in the soil, so that the effective state concentration and toxicity of arsenic in the soil are reduced; the source of water in the mixed soil comprises one or more of direct watering of the soil, natural rainfall and watering of the soil for crops or plants under planting conditions.

2. The method of claim 1, wherein, In step S1, the alkali etching treatment is selected from one of the following methods: the inorganic solid waste containing metal oxides is mixed with inorganic alkali solids and subjected to calcination treatment; or the inorganic solid waste containing metal oxides is mixed with an inorganic alkali aqueous solution and subjected to hydrothermal reaction.

3. The method of claim 2, wherein, The calcination treatment is performed at a temperature of 200-600 DEG C for 0.5-3 h; the mass ratio of the inorganic solid waste containing metal oxides to the inorganic alkali solid is 3-10:

1.

4. The method of claim 2, wherein, The hydrothermal reaction is performed at a temperature of 50-90 DEG C for 1-6 h; the concentration of the inorganic alkali aqueous solution is 0.5-10 mol / L; the mass-to-volume ratio of the inorganic solid waste containing metal oxides to the inorganic alkali aqueous solution is 1:(1-5) g / mL.

5. The method of claim 1, wherein, In step S2, the mass ratio of the modified inorganic solid waste to the by-product containing sulfite generated in the wet flue gas desulfurization process in the soil remediation agent is 5-30:

1.

6. The method of claim 1, wherein, In step S3, the application amount of the soil remediation agent in the arsenic-contaminated soil is 300-2000 kg / mu.

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