Hydrogel composite material capable of synchronously removing cadmium and arsenic as well as preparation method and application of hydrogel composite material

Abstract

The invention discloses a hydrogel composite material capable of synchronously removing cadmium and arsenic as well as a preparation method and application of the hydrogel composite material. According to the method, k-carrageenan hydrogel is used as a carrier material to load an nZVI-silicate mineral material, gel is formed through interaction of hydrogen bonds in the nZVI-silicate mineral material, and when the gel is soaked in a potassium ion solution or a solution of other metal cations, the network structure of the gel is enhanced through the cationic cross-linking effect, so that the hydrogel composite material for synchronously removing cadmium and arsenic is obtained. In the cooling and solidification process of the nZVI-silicate mineral and k-carrageenan mixed solution, the outer surface of the nZVI-silicate mineral and k-carrageenan mixed solution firstly makes contact with cold air to form a preliminary solidification layer, the oxidation speed of internal nZVI is slowed down, the oxidation problem of the internal nZVI is avoided, meanwhile, internal gel solidification is slow, a relatively loose structure is formed, subsequent permeation and crosslinking of metal cations are facilitated, and the corrosion resistance of the nZVI-silicate mineral and k-carrageenan mixed solution is improved. The finally obtained hydrogel composite material can realize synchronous removal of cadmium and arsenic.

Description

Technical Field

[0001] The invention belongs to the field of soil heavy metal pollution control, and specifically relates to a cadmium and arsenic simultaneous removal hydrogel composite material and a preparation method and application thereof. Background Art

[0002] Heavy metal pollution in soil, especially cadmium (Cd) and arsenic (As) pollution, has become a major challenge facing the global environment. These heavy metal elements have become an important topic in soil pollution research due to their persistence, difficulty in degradation, and harm to the ecological environment and human health. The long-term presence of cadmium and arsenic in the soil will not only destroy the soil microbial community and affect the growth of crops, but also enter the human body through the food chain, causing chronic poisoning, kidney damage, cancer and other health problems. Therefore, the development of efficient soil cadmium and arsenic remediation technology is crucial for environmental protection and social welfare.

[0003] Currently, passivation remediation technology has become one of the main strategies for controlling soil heavy metal pollution because of its simple operation, high cost-effectiveness and significant remediation effect. This method reduces the bioavailability of heavy metals by adjusting the chemical form of heavy metals in the soil or enhancing their binding strength with the solid phase components of the soil. Nano-zero-valent iron-loaded silicate mineral materials (nZVI-silicate minerals) combine the efficient solidification ability of iron-based materials for arsenic and the effective passivation properties of silicate minerals for cadmium, and can simultaneously reduce the bioavailability of cadmium and arsenic in the soil. However, the main limitation of passivation materials is that they cannot reduce the total amount of cadmium and arsenic in the soil, and some passivators may lose their effectiveness under changing environmental conditions, leading to secondary pollution.

[0004] Loading the passivation material into the hydrogel can achieve the effective recovery of the repair material and achieve the goal of heavy metal removal. However, when nZVI-silicate minerals are loaded into the hydrogel, due to the high activity of nZVI, it is easy to cause the monomer inactivation during the hydrogel synthesis process, thus hindering the successful preparation of the hydrogel. In addition, how to minimize the oxidation of nZVI during the loading process is also a key issue. In view of this, it is particularly important to choose a suitable hydrogel carrier for nZVI-silicate minerals. Summary of the invention

[0005] In order to solve the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a method for preparing a cadmium and arsenic simultaneous removal hydrogel composite material.

[0006] The preparation method of the present invention uses k-carrageenan hydrogel as a carrier material to load nZVI-silicate mineral material. K-carrageenan is a polysaccharide molecule containing a sulfate group, has good gel-forming ability, and can form a gel through hydrogen bond interaction when the temperature of the dissolving solution drops below 40°C. In addition, when the gel is further immersed in a potassium ion or other metal cation solution, its network structure can be enhanced by cationic cross-linking. In the preparation process, the nZVI-silicate mineral material is added to the k-carrageenan solution and fully mixed and cooled to obtain a gel solid. Subsequently, the gel is immersed in a metal cation solution, which not only strengthens the network structure of the hydrogel, but also the iron oxide layer formed by oxidation on the surface of nZVI may interact with sulfate or other negative ions in k-carrageenan to promote the occurrence of cross-linking reactions. Therefore, k-carrageenan hydrogel is a suitable carrier for loading nZVI-silicate minerals. Regarding the oxidation problem of nZVI in the hydrogel composite material, during the cooling and solidification process of the mixed solution of nZVI-silicate mineral and k-carrageenan, its outer surface first contacts cold air to form a preliminary solidification layer. This layer has a dense structure and low permeability to oxygen and water, which helps slow down the oxidation rate of the internal nZVI. As the cooling process progresses, the internal gel solidifies slowly, forming a relatively loose structure. This structural characteristic is not only conducive to the subsequent penetration and cross-linking of metal cations, but also isolates nZVI from the external environment to the greatest extent, thereby avoiding its rapid oxidation.

[0007] Another object of the present invention is to provide a cadmium and arsenic simultaneous removal hydrogel composite material prepared by the above method.

[0008] Another object of the present invention is to provide the application of the above-mentioned cadmium and arsenic synchronous removal hydrogel composite material for removing cadmium and arsenic in water or soil. During the application process, the nZVI-silicate mineral@hydrogel composite material can simultaneously adsorb cadmium and arsenic in water and soil environments. At the same time, due to its large volume, it can be recovered through a filter screen after adsorption in the water body. When used in the soil, it can be put into a mesh bag, and the composite material can be recovered together with the mesh bag after application, so as to achieve the simultaneous removal of cadmium and arsenic to the greatest extent.

[0009] To achieve the above object, the present invention provides the following solutions:

[0010] A method for preparing a cadmium and arsenic simultaneous removal hydrogel composite material comprises the following steps:

[0011] (1) mixing a silicate mineral with an alkali or alkaline salt, calcining, washing, and drying to obtain a modified silicate mineral;

[0012] (2) grinding and sieving the silicate mineral and / or the modified silicate mineral of step (1), adding the silicate mineral to the metal ion solution, mixing, then dropping a reducing agent to generate nano zero-valent metal on the surface of the silicate mineral and / or the modified silicate mineral in situ, continuing the reaction for a period of time after the dropwise addition is completed to ensure the generation of a uniform and stable composite material, washing, and drying to obtain a nZVI-silicate mineral;

[0013] (3) The nZVI-silicate mineral and k-carrageenan solution are uniformly mixed to obtain a mixed solution, which is then molded and allowed to stand to form a hydrogen-bonded cross-linked hydrogel composite material; the hydrogen-bonded cross-linked hydrogel composite material is immersed in a metal cation solution to strengthen the network structure by chemical cross-linking. After the cross-linking is completed, the hydrogel is taken out, and after washing and drying, the nZVI-silicate mineral@hydrogel composite material is obtained.

[0014] Preferably, the silicate minerals in steps (1) and (2) are at least one of molybdenum tailings, zeolite, fly ash, sepiolite and kaolin.

[0015] Preferably, the silicate mineral in step (1) needs to be sieved through a 50-200 mesh sieve.

[0016] Preferably, the alkali or alkaline salt in step (1) is at least one of NaOH, Na2CO3, KOH, K2CO3, Ca(OH)2 and CaCO3.

[0017] Preferably, the mass ratio of the alkali or alkaline salt to the silicate mineral in step (1) is (1-5):(0.5-2); more preferably 2:1.

[0018] Preferably, the calcination temperature in step (1) is 300-1000°C; more preferably 600°C.

[0019] Preferably, the calcination time in step (1) is 2 to 8 hours; more preferably 4 hours.

[0020] Preferably, the calcined product in step (1) is washed by alternating washing with 0.01-0.1 mol / L hydrochloric acid solution and deionized water until the pH value of the solution after washing is neutral; more preferably, the concentration of the hydrochloric acid solution is 0.05 mol / L.

[0021] Preferably, the drying method in step (1) is to place the mixture in an oven for drying at a temperature of 40 to 120° C. for a drying time of 6 to 24 hours.

[0022] Preferably, the silicate mineral in step (2) and / or the modified silicate mineral in step (1) needs to pass through a sieve of 50 to 150 meshes.

[0023] Preferably, the metal ion in the metal ion solution in step (2) is Fe 2+ , Fe 3+ and Mn 2+ At least one of Fe 2+ ; The metal ion solution is at least one of FeSO4 solution, Fe2(SO4)3 solution, FeCl2 solution, FeCl3 solution, MnSO4 solution and MnCl2 solution, more preferably FeSO4 solution; the mass ratio of metal salt to water in the metal ion solution is (1-10): (100-500), more preferably (1-2):100.

[0024] Preferably, the mass ratio of the silicate mineral in step (2) and / or the modified silicate mineral in step (1) to the metal salt in the metal ion solution is (1-100):(1-10); more preferably 1:(2-3); most preferably 1:2.5.

[0025] Preferably, the silicate mineral in step (2) and / or the modified silicate mineral in step (1) is mixed with the metal ion solution by ultrasound and stirring, and the ultrasound time is 20 to 60 minutes; the stirring time is 1 to 8 hours, and the stirring rate is 100 to 500 r / min.

[0026] Preferably, the reducing agent in step (2) is sodium borohydride (NaBH4); the reducing agent is added dropwise in the form of a reducing agent solution, wherein the mass ratio of the reducing agent to water is (1-5):(1-500); more preferably (1-3):100; and most preferably 1.9:100.

[0027] Preferably, the molar ratio of the reducing agent to the metal ion in step (2) is 200:(5-100); more preferably 200:(20-80).

[0028] Preferably, the reducing agent droplet acceleration rate in step (2) is 50 to 150 drops / min; more preferably 60 drops / min.

[0029] Preferably, after the reducing agent is added dropwise in step (2), the stirring reaction is continued for 0.5 to 5 hours; more preferably for 2 hours.

[0030] Preferably, the washing in step (2) is washing with water, and the drying is conventional freeze-drying in the art.

[0031] Preferably, in the k-carrageenan solution of step (3), the mass ratio of k-carrageenan to water is (0.5-3):(50-500); more preferably (2.0-3.5):100; and the dissolution temperature of the k-carrageenan is 45-85°C.

[0032] Preferably, the nZVI-silicate mineral in step (3) needs to pass through a sieve of 50 to 200 meshes.

[0033] Preferably, the mass ratio of the nZVI-silicate mineral to k-carrageenan in step (3) is (0.5-3):(0.5-10); more preferably (0.5-2.0):(2.0-3.5).

[0034] Preferably, the uniform mixing method in step (3) is ultrasonic dispersion and mechanical stirring, the ultrasonic dispersion time is 5 to 60 minutes; the mechanical stirring speed is 150 to 300 rpm, the stirring time is 5 to 120 minutes, and the stirring temperature is 45 to 85°C.

[0035] Preferably, the mold for the casting in step (3) is a cubic silicone mold with a length, width and height of 0.5 to 2 cm.

[0036] Preferably, the metal cation in the metal cation solution in step (3) is K + , Ca 2+ and Fe 3+ At least one of, more preferably K + ; The metal cation solution is at least one of KCl, CaCl2 and FeCl3; the mass ratio of metal salt to water in the metal cation solution is (1-10): (50-200); more preferably (5-7): 100.

[0037] Preferably, the static molding time in step (3) is 30 to 240 minutes.

[0038] Preferably, the soaking time in step (3) is 12 to 48 hours; more preferably 24 to 40 hours.

[0039] Preferably, the washing in step (3) is washing with water, and the drying is conventional freeze-drying in the art.

[0040] The above preparation method produces a cadmium and arsenic simultaneous removal hydrogel composite material.

[0041] The above-mentioned cadmium and arsenic simultaneous adsorption-removal composite material is used to remove cadmium and arsenic from water or soil.

[0042] The soil is paddy field soil, and the hydrogel composite material is applied according to 0.1-1% of the mass of the water body or 1-5% of the mass of the soil.

[0043] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0044] (1) The development of the hydrogel composite material of the present invention realizes the effective recovery of nZVI-silicate mineral passivation materials, is beneficial to the simultaneous adsorption and removal of cadmium and arsenic, and provides a more efficient and sustainable solution for the remediation of cadmium and arsenic contaminated soil.

[0045] (2) The composite material of the present invention has a simple preparation process and low cost, and the material has good biosafety, meets the requirements of environmental friendliness and sustainable development, and has great potential for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a physical picture of the nZVI-AMT@KL hydrogel composite material in Example 2.

[0047] Figure 2 The removal rates of cadmium and arsenic in a mono-system and the removal rates of cadmium and arsenic in a binary system by the material described in Example 2 are shown.

[0048] Figure 3 is the removal rate of cadmium and arsenic in soil by the material described in Example 2. DETAILED DESCRIPTION

[0049] The present invention is further described in detail below in conjunction with examples and drawings, but the embodiments of the present invention are not limited thereto.

[0050] If no specific conditions are specified in the examples of the present invention, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. All raw materials, reagents, etc., whose manufacturers are not specified, are conventional products that can be purchased commercially.

[0051] Example 1

[0052] (1) At room temperature, 3.00 g of ferrous sulfate powder was added to a beaker containing 300 mL of deionized water. After stirring until completely dissolved, 1.2 g of molybdenum tailings (taken from the tailings pond of Baishizhang molybdenum and tungsten mine in Wuhua County, Meizhou City, Guangdong Province: SiO278.35%, Al2O3 10.95%, CaO 0.64%, MgO 0.42%, Fe2O3 1.54%, and the remainder was impurities) was added. After ultrasonication for 30 minutes, the mixture was transferred to a 1000 mL three-necked flask. The suspension in the three-necked flask was mechanically stirred at 200 r / min for 2 h. 1.90 g of NaBH4 was dissolved in 100 mL of water to prepare a NaBH4 solution, and the NaBH4 solution was added to the flask at a drop rate of 60 drops / min. After the addition was completed, the reaction was continued for 2 hours to ensure the formation of a uniform and stable composite material. After the reaction, the mixture was poured into a beaker, the composite material was recovered from the solution by an external magnetic field, and washed three times with deionized water. Finally, the composite material was placed in a vacuum dryer at -50°C to obtain a molybdenum tailings material loaded with nano-zero-valent iron (nZVI-MT).

[0053] (2) Add 3g k-carrageenan to a beaker containing 100mL deionized water, stir at 60°C until completely dissolved, add 1.5g nZVI-MT, ultrasonically disperse for 10min, mechanically stir at 200r / min for 20min to obtain a mixed solution, pour into a mold, and stand for 60min to form a hydrogen bond cross-linked hydrogel. It is further immersed in a 6% (w / v) potassium chloride solution for 30h to strengthen the network structure by chemical cross-linking. After cross-linking is completed, take out the hydrogel and wash it with deionized water several times. Then place the composite hydrogel material at -50°C and vacuum dry to obtain nZVI-molybdenum tailings@hydrogel composite material (nZVI-MT@KL).

[0054] Example 2

[0055] (1) Molybdenum tailings (SiO278.35%, Al2O3 10.95%, CaO 0.64%, MgO 0.42%, Fe2O3 1.54%, the remainder is impurities) taken from the tailings pond of Baishizhang molybdenum and tungsten mine in Wuhua County, Meizhou City, Guangdong Province were mixed with NaOH particles in a mass ratio of 1:2 and calcined in a muffle furnace at 600℃ for 4 hours. The calcined product was taken out and washed alternately with 0.05mol / L hydrochloric acid solution and deionized water until the material was neutral. After drying at 80℃, it was ground and passed through a 60-mesh sieve to obtain modified molybdenum tailings.

[0056] (2) At room temperature, 3.00 g of ferrous sulfate powder was added to a beaker containing 300 mL of deionized water, and stirred until completely dissolved. Then, 1.2 g of modified molybdenum tailings was added, and after ultrasonication for 30 minutes, the mixture was transferred to a 1000 mL three-necked flask. The suspension in the three-necked flask was mechanically stirred at a speed of 200 r / min for 2 h. 1.90 g of NaBH4 was dissolved in 100 mL of water to prepare a NaBH4 solution, and the NaBH4 solution was added to the flask at a drop rate of 60 drops / min. After the addition was completed, the reaction was continued for 2 hours to ensure the formation of a uniform and stable composite material. After the reaction was completed, the mixture was poured into a beaker, and the composite material was recovered from the solution by an external magnetic field and washed three times with deionized water. Finally, the composite material was placed in a vacuum dryer at -50 ° C to obtain a modified molybdenum tailing material (nZVI-AMT) loaded with nano zero-valent iron.

[0057] (3) 3 g k-carrageenan was added to a beaker containing 100 mL of deionized water, stirred at 60 °C until completely dissolved, and then 1.5 g nZVI-AMT was added. Ultrasonic dispersion was performed for 10 min, and mechanical stirring was performed at 200 r / min for 20 min to obtain a mixed solution. The solution was molded and allowed to stand for 60 min to obtain a hydrogen bond cross-linked hydrogel. The hydrogel was further immersed in a 6% (w / v) potassium chloride solution for 30 h to strengthen the network structure by chemical cross-linking. After cross-linking was completed, the hydrogel was taken out and washed with deionized water several times. The composite hydrogel material was then placed in a vacuum dryer at -50 °C to obtain an nZVI-modified molybdenum tailings@hydrogel composite material (nZVI-AMT@KL).

[0058] Comparative Example 1

[0059] The difference from Example 2 is that the hydrogel composite material that was allowed to solidify was not further immersed in a 6% (w / v) potassium chloride solution for 30 hours to chemically cross-link and strengthen the network structure. The remaining steps remained the same. After freeze-drying the hydrogel composite material, it was immersed in an aqueous solution, and it was found that the gel structure completely collapsed and dissolved.

[0060] Comparative Example 2

[0061] (1) Molybdenum tailings (SiO278.35%, Al2O3 10.95%, CaO 0.64%, MgO 0.42%, Fe2O3 1.54%, the remainder is impurities) taken from the tailings pond of Baishizhang molybdenum and tungsten mine in Wuhua County, Meizhou City, Guangdong Province were mixed with NaOH particles in a mass ratio of 1:2 and calcined in a muffle furnace at 600℃ for 4 hours. The calcined product was taken out and washed alternately with 0.05mol / L hydrochloric acid solution and deionized water until the material was neutral. After drying at 80℃, it was ground and passed through a 60-mesh sieve to obtain modified molybdenum tailings.

[0062] (2) At room temperature, 3.00 g of ferrous sulfate powder was added to a beaker containing 300 mL of deionized water, and stirred until completely dissolved. Then, 1.2 g of modified molybdenum tailings was added, and after ultrasonication for 30 minutes, the mixture was transferred to a 1000 mL three-necked flask. The suspension in the three-necked flask was mechanically stirred at a speed of 200 r / min for 2 h. 1.90 g of NaBH4 was dissolved in 100 mL of water to prepare a NaBH4 solution, and the NaBH4 solution was added to the flask at a drop rate of 60 drops / min. After the addition was completed, the reaction was continued for 2 hours to ensure the formation of a uniform and stable composite material. After the reaction was completed, the mixture was poured into a beaker, and the composite material was recovered from the solution by an external magnetic field and washed three times with deionized water. Finally, the composite material was placed in a vacuum dryer at -50 ° C to obtain a modified molybdenum tailing material (nZVI-AMT) loaded with nano zero-valent iron.

[0063] (2) 3 g of polyvinyl alcohol powder was added to a beaker containing 100 mL of deionized water and stirred at 90 °C until completely dissolved. Then, 1.5 g of nZVI-AMT was added. During the ultrasonic dispersion process, it was found that a violent local polymerization reaction occurred between the polyvinyl alcohol solution and nZVI-AMT, resulting in the inability of the latter to achieve uniform dispersion and stable loading in the polyvinyl alcohol matrix.

[0064] Figure 1 This is a physical picture of the nZVI-AMT@KL composite hydrogel in Example 2. It can be seen that the hydrogel loaded with nZVI-AMT was successfully prepared. It can be seen from the right figure that the hydrogel is yellowish brown on the outside and black on the inside. This is related to the nZVI component in the composite hydrogel. The nZVI on the surface of the hydrogel is gradually oxidized into iron oxide or hydroxide in an aerobic environment, so the surface appears yellowish brown. The interior of the hydrogel is relatively closed, and oxygen and water permeate slowly, so the nZVI inside the hydrogel can maintain its original form for a certain period of time, presenting an unoxidized black state.

[0065] Example 3

[0066] Weigh 50 mg of the nZVI-AMT@KL material prepared in Example 2 into a 50 ml centrifuge tube, and add 30 mL of a 100 ppm Cd(II) solution (prepared from 0.274 g Cd(NO3)2·4H2O crystals and 1000 mL 0.01 mol / L NaNO3) into the centrifuge tube. Oscillate at 180 r / min at 25°C, take out after 24 hours of adsorption, take 5 ml of the solution and filter it through a 0.45 μm acetate fiber filter, and determine the cadmium content in the filtrate by atomic absorption spectrophotometry. The removal rate of cadmium ions in the adsorption solution is as follows: Figure 2 shown.

[0067] Example 4

[0068] Weigh 50 mg of the nZVI-AMT@KL material prepared in Example 2 into a 50 ml centrifuge tube, and add 30 mL of a 100 ppm As(III) solution (prepared from 0.173 g NaAsO2 crystals and 1000 ml 0.01 mol / L NaNO3) into the centrifuge tube. Oscillate at 180 r / min at 25°C, take out after 24 hours of adsorption, take 5 ml of the solution and filter it through a 0.45 μm acetate fiber filter, and determine the arsenic content in the filtrate by atomic fluorescence spectrometry. The removal rate of arsenic ions in the adsorption solution is as follows: Figure 2 shown.

[0069] Example 5

[0070] Weigh 50 mg of the nZVI-AMT@KL material prepared in Example 2 into a 50 ml centrifuge tube, and add 30 ml of an As-Cd composite solution (prepared by 0.173 g of NaAsO2 crystals, 0.274 g of Cd(NO3)2·4H2O crystals and 1000 ml of 0.01 mol / L NaNO3) with As(III) and Cd(II) concentrations of 100 ppm to the centrifuge tube. Oscillate at a constant speed of 180 r / min at 25°C, take out after adsorption for 24 hours, take 5 ml of the solution and filter it through a 0.45 μm acetate fiber filter head, and determine the arsenic and cadmium contents in the filtrate by atomic fluorescence spectroscopy and atomic absorption spectrophotometry. The removal rate of cadmium and arsenic ions in the adsorption solution is as follows: Figure 2 shown.

[0071] Example 6

[0072] Weigh 100g of soil contaminated with cadmium and arsenic, with soil cadmium and arsenic concentrations of 3.08 and 45.15mg / kg respectively. Add 200% of the maximum field water holding capacity of the soil to simulate the flooded state of the rice field. Add 2% of the soil mass to the hydrogel material prepared in the above Example 2, and incubate at a constant temperature of 25±2°C for 14 days. Then, air-dry the soil sample, grind it, pass it through a 100-mesh sieve, and boil it with nitric acid-hydrochloric acid-hydrofluoric acid-perchloric acid. The contents of arsenic and cadmium in the boiled solution were determined by atomic fluorescence spectroscopy and atomic absorption spectrophotometry, respectively. The results of the total cadmium and arsenic removal rate in the soil are shown in the figure. Figure 3 shown.

[0073] Example 7

[0074] (1) Molybdenum tailings (SiO278.35%, Al2O3 10.95%, CaO 0.64%, MgO 0.42%, Fe2O3 1.54%, the remainder is impurities) taken from the tailings pond of Baishizhang molybdenum and tungsten mine in Wuhua County, Meizhou City, Guangdong Province were mixed with NaOH particles in a mass ratio of 1:2 and calcined in a muffle furnace at 600℃ for 4 hours. The calcined product was taken out and washed alternately with 0.05mol / L hydrochloric acid solution and deionized water until the material was neutral. After drying at 80℃, it was ground and passed through a 60-mesh sieve to obtain modified molybdenum tailings.

[0075] (2) At room temperature, 3.00 g of ferrous sulfate powder was added to a beaker containing 300 mL of deionized water, and stirred until completely dissolved. Then, 1.2 g of modified molybdenum tailings was added, and after ultrasonication for 30 minutes, the mixture was transferred to a 1000 mL three-necked flask. The suspension in the three-necked flask was mechanically stirred at a speed of 200 r / min for 2 h. 1.90 g of NaBH4 was dissolved in 100 mL of water to prepare a NaBH4 solution, and the NaBH4 solution was added to the flask at a drop rate of 60 drops / min. After the addition was completed, the reaction was continued for 2 hours to ensure the formation of a uniform and stable composite material. After the reaction was completed, the mixture was poured into a beaker, and the composite material was recovered from the solution by an external magnetic field and washed three times with deionized water. Finally, the composite material was placed in a vacuum dryer at -50 ° C to obtain a modified molybdenum tailing material (nZVI-AMT) loaded with nano zero-valent iron.

[0076] (3) Add 2.5g k-carrageenan to a beaker containing 100mL deionized water, stir at 60°C until completely dissolved, add 0.5g nZVI-AMT, ultrasonically disperse for 10min, mechanically stir at 200r / min for 20min to obtain a mixed solution, pour into a mold, and stand for 60min to form a hydrogen bond cross-linked hydrogel. It is further immersed in a 5% (w / v) potassium chloride solution for 40h to strengthen the network structure by chemical cross-linking. After cross-linking is completed, take out the hydrogel and wash it with deionized water several times. Then place the composite hydrogel material at -50°C and vacuum dry to obtain nZVI-modified molybdenum tailings@hydrogel composite material (nZVI-AMT@KL-1).

[0077] Example 8

[0078] (1) Molybdenum tailings (SiO278.35%, Al2O3 10.95%, CaO 0.64%, MgO 0.42%, Fe2O3 1.54%, the remainder is impurities) taken from the tailings pond of Baishizhang molybdenum and tungsten mine in Wuhua County, Meizhou City, Guangdong Province were mixed with NaOH particles in a mass ratio of 1:2 and calcined in a muffle furnace at 600℃ for 4 hours. The calcined product was taken out and washed alternately with 0.05mol / L hydrochloric acid solution and deionized water until the material was neutral. After drying at 80℃, it was ground and passed through a 60-mesh sieve to obtain modified molybdenum tailings.

[0079] (2) At room temperature, 3.00 g of ferrous sulfate powder was added to a beaker containing 300 mL of deionized water, and stirred until completely dissolved. Then, 1.2 g of modified molybdenum tailings was added, and after ultrasonication for 30 minutes, the mixture was transferred to a 1000 mL three-necked flask. The suspension in the three-necked flask was mechanically stirred at a speed of 200 r / min for 2 h. 1.90 g of NaBH4 was dissolved in 100 mL of water to prepare a NaBH4 solution, and the NaBH4 solution was added to the flask at a drop rate of 60 drops / min. After the addition was completed, the reaction was continued for 2 hours to ensure the formation of a uniform and stable composite material. After the reaction was completed, the mixture was poured into a beaker, and the composite material was recovered from the solution by an external magnetic field and washed three times with deionized water. Finally, the composite material was placed in a vacuum dryer at -50 ° C to obtain a modified molybdenum tailing material (nZVI-AMT) loaded with nano zero-valent iron.

[0080] (3) 3.5 g k-carrageenan was added to a beaker containing 100 mL of deionized water, stirred at 60 ° C until completely dissolved, and then 2.0 g nZVI-AMT was added. Ultrasonic dispersion was performed for 10 min, and mechanical stirring was performed at 200 r / min for 20 min to obtain a mixed solution. The mixture was molded and allowed to stand for 60 min to form a hydrogen bond cross-linked hydrogel. It was further immersed in a 7% (w / v) potassium chloride solution for 24 h to strengthen the network structure by chemical cross-linking. After the cross-linking was completed, the hydrogel was taken out and washed with deionized water several times. The composite hydrogel material was then placed in a vacuum dryer at -50 ° C to obtain the nZVI-modified molybdenum tailings@hydrogel composite material (nZVI-AMT@KL-2).

[0081] Example 9

[0082] (1) Molybdenum tailings (SiO278.35%, Al2O3 10.95%, CaO 0.64%, MgO 0.42%, Fe2O3 1.54%, the remainder is impurities) taken from the tailings pond of Baishizhang molybdenum and tungsten mine in Wuhua County, Meizhou City, Guangdong Province were mixed with NaOH particles in a mass ratio of 1:2 and calcined in a muffle furnace at 600℃ for 4 hours. The calcined product was taken out and washed alternately with 0.05mol / L hydrochloric acid solution and deionized water until the material was neutral. After drying at 80℃, it was ground and passed through a 60-mesh sieve to obtain modified molybdenum tailings.

[0083] (2) At room temperature, 3.00 g of ferrous sulfate powder was added to a beaker containing 300 mL of deionized water, and stirred until completely dissolved. Then, 1.2 g of modified molybdenum tailings was added, and after ultrasonication for 30 minutes, the mixture was transferred to a 1000 mL three-necked flask. The suspension in the three-necked flask was mechanically stirred at a speed of 200 r / min for 2 h. 1.90 g of NaBH4 was dissolved in 100 mL of water to prepare a NaBH4 solution, and the NaBH4 solution was added to the flask at a drop rate of 60 drops / min. After the addition was completed, the reaction was continued for 2 hours to ensure the formation of a uniform and stable composite material. After the reaction was completed, the mixture was poured into a beaker, and the composite material was recovered from the solution by an external magnetic field and washed three times with deionized water. Finally, the composite material was placed in a vacuum dryer at -50 ° C to obtain a modified molybdenum tailing material (nZVI-AMT) loaded with nano zero-valent iron.

[0084] (3) Add 2.0g k-carrageenan to a beaker containing 100mL deionized water, stir at 60°C until completely dissolved, add 1.2g nZVI-AMT, ultrasonically disperse for 10min, mechanically stir at 200r / min for 20min to obtain a mixed solution, pour into a mold, and stand for 60min to form a hydrogen bond cross-linked hydrogel. It is further immersed in a 5.5% (w / v) potassium chloride solution for 36h to strengthen the network structure by chemical cross-linking. After cross-linking is completed, take out the hydrogel and wash it with deionized water several times. Then place the composite hydrogel material at -50°C and vacuum dry to obtain nZVI-modified molybdenum tailings@hydrogel composite material (nZVI-AMT@KL-3).

[0085] Table 1 The test of the maximum adsorption amount of cadmium and arsenic in water is based on Example 5, where the constant temperature incubation time at 25°C is 24h. The test of the total amount of cadmium and arsenic in soil is based on Example 6, where the constant temperature incubation time at 25±2°C is 14d.

[0086] Table 1 The remediation effect of each embodiment on cadmium and arsenic in the composite pollution system

[0087]

[0088] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a cadmium and arsenic simultaneous removal hydrogel composite material, characterized in that: The following steps are involved: (1) mixing a silicate mineral with an alkali or alkaline salt, calcining, washing, and drying to obtain a modified silicate mineral; (2) grinding and sieving the silicate mineral and / or the modified silicate mineral of step (1), adding the mixture to the metal ion solution, mixing, then dropping a reducing agent and continuing the reaction for a period of time, washing, and drying to obtain nZVI-silicate mineral; (3) The nZVI-silicate mineral and k-carrageenan solution are mixed evenly and then molded, allowed to stand to form, and then immersed in a metal cation solution. After cross-linking is completed, the hydrogel is taken out, washed, and dried to obtain a nZVI-silicate mineral@hydrogel composite material.

2. The method for preparing a cadmium and arsenic simultaneous removal hydrogel composite material according to claim 1, characterized in that: The metal ion in the metal ion solution of step (2) is Fe 2+ , Fe 3+ and Mn 2+ At least one of; The mass ratio of the silicate mineral in step (2) and / or the modified silicate mineral in step (1) to the metal salt in the metal ion solution is (1-100): (1-10); The mass ratio of the nZVI-silicate mineral to k-carrageenan in step (3) is (0.5-3): (0.5-10); The silicate minerals in steps (1) and (2) are at least one of molybdenum tailings, zeolite, fly ash, sepiolite and kaolin.

3. The method for preparing a cadmium and arsenic simultaneous removal hydrogel composite material according to claim 1 or 2, characterized in that: In the k-carrageenan solution of step (3), the mass ratio of k-carrageenan to water is (0.5-3):(50-500); the dissolution temperature of the k-carrageenan is 45-85°C; The metal cation in the metal cation solution of step (3) is K + , Ca 2+ and Fe 3+ At least one of; The mass ratio of metal cation to water in the metal cation solution of step (3) is (1-10):(50-200).

4. The method for preparing a cadmium and arsenic simultaneous removal hydrogel composite material according to claim 1 or 2, characterized in that: The alkali or alkaline salt in step (1) is at least one of NaOH, Na2CO3, KOH, K2CO3, Ca(OH)2 and CaCO3; The mass ratio of the alkali or alkaline salt to the silicate mineral in step (1) is (1-5): (0.5-2); The calcination temperature in step (1) is 300-1000° C. and the calcination time is 2-8 hours.

5. The method for preparing a cadmium and arsenic simultaneous removal hydrogel composite material according to claim 1 or 2, characterized in that: The static molding time in step (3) is 30 to 240 minutes; The soaking time in step (3) is 12 to 48 hours.

6. The method for preparing a cadmium and arsenic simultaneous removal hydrogel composite material according to claim 1 or 2, characterized in that: The reducing agent in step (2) is sodium borohydride; the reducing agent is added dropwise in the form of a reducing agent solution, wherein the mass ratio of the reducing agent to water is (1-5): (1-500); The molar ratio of the reducing agent to the metal ion in step (2) is 200:(5-100); The reducing agent drop acceleration rate in step (2) is 50 to 150 drops / min; After the reducing agent in step (2) is added dropwise, the reaction is continued with stirring for 0.5 to 5 hours.

7. The method for preparing a cadmium and arsenic simultaneous removal hydrogel composite material according to claim 1 or 2, characterized in that: The metal ion solution in step (2) is at least one of FeSO4 solution, Fe2(SO4)3 solution, FeCl2 solution, FeCl3 solution, MnSO4 solution and MnCl2 solution; The mass ratio of the metal salt to water in the metal ion solution of step (2) is (1-10): (100-500); The metal cation solution in step (3) is at least one of KCl, CaCl2 and FeCl3.

8. A cadmium and arsenic simultaneous removal hydrogel composite material prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the cadmium and arsenic simultaneous removal hydrogel composite material as described in claim 8 in removing cadmium and arsenic from water or soil.

10. The use according to claim 9, characterized in that: The hydrogel composite material is applied at 0.1-1% of the mass of water or 1-5% of the mass of soil.

Images