Preparation method and application of recyclable Schwertmannite-based pellets capable of synchronously removing cadmium and arsenic

Abstract

The invention provides a preparation method of recyclable Schwertmannite-based pellets capable of synchronously removing cadmium and arsenic, and belongs to the field of pollution control and remediation, and the preparation method comprises the following steps: adding sodium alginate into water to obtain a sodium alginate aqueous solution, and then adding corn starch to obtain sol; uniformly mixing polyethylene nanoparticles with deionized water to obtain a medium; adding Schwertmannite into the medium to obtain a mixed solution, and centrifuging to obtain a precipitate; putting the precipitate into the sol, and uniformly mixing until mixed sol is formed; dropwise adding the mixed sol into a FeCl2 solution, crosslinking at room temperature to obtain microspheres, and drying to obtain the Schwertmannite-based microspheres. The small ball can be used for repairing cadmium and arsenic polluted soil. The preparation method is simple, mild in condition and easy to operate, materials only need to be scattered into soil, resource utilization of waste is achieved, and large-scale preparation and popularization can be achieved.

Description

Technical Field

[0001] The invention belongs to the field of pollution control and remediation, and specifically relates to a preparation method and application of a recyclable cadmium and arsenic simultaneous removal Schottky mineral-based small ball. Background Art

[0002] Soil quality is crucial to food safety and even national security. Cadmium and arsenic are widely present in the soil of China's rice-growing areas. Sewage irrigation, organic fertilizers and fertilization, and the use of pesticides are the main causes of cadmium and arsenic contamination in rice fields. Cadmium is a highly toxic heavy metal of global concern. Compared with other heavy metals, cadmium and arsenic have relatively strong migration capabilities in soil, are easily enriched in organisms, and enter the human body through the food chain, posing serious health risks to humans. Therefore, it is crucial to find scientific and effective methods to repair cadmium and arsenic contaminated paddy soil.

[0003] Up to now, the ecological and health risks of heavy metals in soil are still mainly stabilization, and the total amount of heavy metals in the soil has not decreased. If the soil environment changes after stabilization, the fixed heavy metals may be released again to cause pollution risks. The existing "Agricultural Land Soil Environmental Management Measures (Trial)" and "Agricultural Land Soil Environmental Quality Standards" are based on the total amount of pollutants in the soil. Reducing the total amount of heavy metals in polluted soil, improving soil quality, and ensuring the safety of agricultural products are effective strategies for reduction and remediation (pollution reduction and purification). Therefore, research and development to remove the total amount of heavy metals in the soil is one of the important research directions for soil heavy metal pollution reduction and remediation.

[0004] Chinese patent 202311531957.4 discloses a preparation of a floatable hollow microsphere material and its application in soil cadmium reduction. The patent uses modified rectorite mixed with polyvinyl alcohol, sodium alginate, sodium ethylenediaminetetraacetic acid, and saponin, and then cross-linked to obtain a floatable 3D-hollow microsphere material. When the soil is moist, it is applied to the soil for heavy metal adsorption. After water is poured into the field to make the material float, a filter is used to directly recover the floating microsphere material or a filter is set at the drain outlet to collect and remove the soil. Although this patent truly achieves the reduction of heavy metals in the soil for a single polluting heavy metal, the density of the floatable 3D-hollow microsphere material is relatively low. After being applied to the rice field, it will float directly on the water surface. On the one hand, the sphere is not in full contact with the solution, and the adsorption efficiency is limited. On the other hand, the sphere cannot be in close contact with the soil to more efficiently remove cadmium from the soil. Chinese patent 202011509168.7 discloses a magnetic composite material for removing heavy metals from soil, its preparation and application. The material makes full use of the superparamagnetism of Fe3O4, which is convenient for separation by magnetic separation and can truly reduce the content of heavy metals. The above patent can effectively remove heavy metals through simple external magnetic field enrichment and separation, but the electric field effect between magnetic particles and soil and the redox effect between magnetic particles and pollutants in the soil will affect the physical and chemical properties, enzyme activity and greenhouse gas emissions of the soil, and will also affect the structure, function and metabolism of soil microbial communities, thereby affecting the entire soil ecosystem.

[0005] Cadmium and arsenic usually coexist in contaminated soil and have different chemical behaviors, making simultaneous remediation difficult. Methods such as adsorption, chemical precipitation, electrochemical method, ion exchange, membrane separation technology, and plant remediation technology have been established and developed and used to remove cadmium-arsenic complex pollution, among which adsorption can achieve the total amount of cadmium and arsenic in the soil. Schmidt mineral has shown good potential in pollutant remediation due to its unique mineral structure. Existing studies have shown that Schmidt mineral has good adsorption performance for anionic arsenic, but limited adsorption performance for cationic cadmium, so it is necessary to further modify Schmidt mineral to achieve cadmium-arsenic synergistic remediation. Past experience has shown that it is convenient to realize the recycling of remediation materials in the form of a microsphere, so the present invention uses Schmidt mineral to develop a recyclable, efficient, and environmentally friendly rice field cadmium-arsenic combined removal microsphere. Summary of the invention

[0006] In order to solve the problems of insufficient material functional effects and limited application in the above-mentioned prior art, and to form a simple and environmentally friendly cadmium pollution repair functional material, the present invention discloses a recyclable cadmium and arsenic simultaneous removal schreberite-based small ball preparation method and application. The repair material of the present invention has a wide range of applications and can be used in water environments and flooded soils; the raw materials of this material are easy to obtain, environmentally friendly, the preparation process is simple, the conditions are mild, and it can be widely promoted for preparation and use; this material is easy to use, and it only needs to be sprinkled into the environment to work, and it is easy to recycle and can be recycled for multiple times.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] The present invention provides a method for preparing a recyclable cadmium and arsenic simultaneous removal schreberite-based small ball, comprising the following steps:

[0009] (1) adding sodium alginate into water, and stirring while heating in a water bath to completely dissolve the sodium alginate to obtain a sodium alginate aqueous solution;

[0010] (2) adding corn starch to the solution of step (1), heating in a water bath, stirring until the solution becomes clear, cooling to room temperature and setting aside for use to obtain a sol;

[0011] (3) mixing polyethylene nanoparticles and deionized water at room temperature to obtain a medium;

[0012] (4) adding Schroeder mineral to the medium described in step (3) at room temperature to cause the polyethylene nanoparticles and the Schroeder mineral to aggregate by oscillation to obtain a mixed solution;

[0013] (5) After centrifuging the mixed solution in step (4), discarding the supernatant, taking out the precipitate and drying it;

[0014] (6) placing the precipitate obtained in step (5) into the sol in step (2) and mixing them evenly until a mixed sol is formed;

[0015] (7) The mixed sol described in step (6) was dripped dropwise into the FeCl2 solution, and the microspheres were prepared after cross-linking at room temperature. The microspheres were washed several times with deionized water to remove the excess Fe 2+ ;

[0016] (8) Drying the microspheres described in step (7) to obtain Schmidtite-based microspheres.

[0017] Furthermore, in step (1), the water bath heating temperature is 60-90°C, the stirring time is 30-60min; and the mass concentration of sodium alginate in the sodium alginate aqueous solution is 5-30 g / L.

[0018] Furthermore, in step (2), the water bath heating temperature is 60-90° C., the stirring time is 60-90 min; and the mass concentration of corn starch in the sol is 35-140 g / L.

[0019] Furthermore, in step (3), the polyethylene nanoparticles are selected from low-density polyethylene nanoparticles (LDPEs), and the concentration of the polyethylene in the medium is 20 mg / L.

[0020] Furthermore, in step (4), schreiberite is a naturally occurring iron-containing mineral that is commonly found in acid mine drainage and contains a large amount of -OH and SO4 2- The research found that schreberite has a highly efficient passivation ability for arsenic and can be used for the efficient passivation of arsenic in polluted water and soil. However, schreberite cannot be used for the passivation of heavy metal cadmium, and its use in soil remediation may even increase the biological activity of cadmium. Therefore, the present invention combines schreberite with polyethylene nanoparticles to achieve the simultaneous removal of cadmium and arsenic.

[0021] In one embodiment of the present invention, the Schmidt mineral is prepared by hydrogen peroxide oxidation. The specific steps are as follows: ① 1 L of an acidic aqueous solution with a pH of 3.0 is prepared with 98% concentrated sulfuric acid and placed in a beaker, and 16.45 g of FeSO4•7H2O is added to 1 L of the above solution with a pH of 3.0 and stirred to dissolve; ② 5.3 mL of 30% H2O2 solution is added at a rate of 1 mL / 120min under stirring with a mechanical stirrer (speed 140 rpm). During the synthesis process, NaOH needs to be added to maintain the pH in the system at 2.4-2.5 for 24 h to generate Schmidt mineral (Sch). ③ After washing the generated Sch with a mixed solution of deionized water and ethanol (1:1) for 3-5 times, centrifuge at 4500 rpm, collect the solid, and then freeze-dry (-80°C). After the dried Sch is ground into powder with a mortar, it is placed in a ziplock bag for standby use.

[0022] Furthermore, in step (4), the concentration of the Schreiber mineral in the mixed solution is 10-100 mg / L, the pH of the water environment in which the polyethylene nanoparticles and the Schreiber mineral are oscillated and aggregated is 6-8, hydrochloric acid or sodium hydroxide is used to adjust the pH of the initial solution, the oscillation rate is 180-300 rpm, and the oscillation time is 60-300 min.

[0023] Furthermore, in step (5), the centrifugation temperature is 20-30°C, the centrifugation speed is 5000-8000 r / min, the centrifugation time is 3-5 min, and the drying temperature is 20-30°C.

[0024] Furthermore, in step (6), the amount of the precipitate added to the sol in step (5) is 0.04-1.6 g / L; the mixing is carried out by stirring, the stirring time is 90-300 min, and the stirring temperature is 60-90°C.

[0025] Furthermore, in step (7), the mass concentration of the FeCl2 solution is 20-30 g / L, and the cross-linking time is 24-48 h. Ferric chloride is used as a cross-linking agent to increase the content of the oxidant in the product.

[0026] Furthermore, in step (8), the drying temperature is 20-35°C, and the drying time is 18-24 hours.

[0027] The invention also provides a Schottky mineral-based ball prepared by the method.

[0028] The present invention also provides an application of the small ball, including adding the Schmidt mineral-based small ball into polluted water or polluted soil according to the pollution conditions, and stirring the small ball to make it evenly distributed in the polluted medium, so as to achieve a degradation effect.

[0029] Furthermore, the amount of the balls added depends on the cadmium and arsenic pollution conditions in the environment. When the cadmium concentration in the environment is ≤1ppb and / or the arsenic concentration is ≤1ppb, the amount applied (mass ratio) per kilogram of polluted water or soil is 15%~20%; when the cadmium concentration in the environment is >1ppb and / or the arsenic concentration is >1ppb, the amount applied per kilogram of polluted water or soil is 25%~30%.

[0030] In one embodiment of the present invention, when the cadmium concentration in the environment is ≤1ppb and the arsenic concentration is ≤1ppb, 0.15-0.20 kg of the small ball is added to each kilogram of polluted water / soil. When the cadmium concentration in the environment is greater than 1ppb and the arsenic concentration is greater than 1ppb, 0.25-0.30 kg of the small ball is added to each kilogram of polluted water / soil.

[0031] Furthermore, the pellets can be used to repair cadmium and arsenic pollution in paddy fields. After the pellets are evenly spread into flooded paddy fields, the pellets can achieve the effect of reducing cadmium and arsenic in the soil.

[0032] Furthermore, the small ball can be used to repair cadmium-arsenic contaminated aqueous solutions. After the small ball is added into the cadmium-arsenic contaminated water body, the small ball can achieve the effect of removing the total amount of cadmium and arsenic in the solution.

[0033] Furthermore, the small balls can be used for the remediation of cadmium and arsenic contaminated soil. After the small balls are evenly spread into the cadmium and arsenic contaminated soil to loosen the soil, when the soil moisture content reaches more than 60% through artificial regulation or precipitation, the small balls can achieve the effect of removing the total amount of cadmium and arsenic pollution in the soil.

[0034] It can be seen from the above technical solutions that the present invention has the following beneficial effects:

[0035] 1. The starch and sodium alginate in the raw materials of the present invention have good biocompatibility, are easy to obtain, low in cost, non-toxic and harmless, and biodegradable. The synthesis method of Schmidt's mineral is mature, simple to operate, has a short synthesis time period and low cost, especially the chemical oxidation method;

[0036] 2. The present invention is simple to operate by using modified Schmidt mineral recycling pellets to repair cadmium-arsenic contaminated soil. The pellets only need to be directly sprinkled on flooded rice fields for in-situ repair of cadmium-arsenic contaminated rice fields. After the repair cycle is over, the pellets will float on the surface of the flooded rice fields due to water absorption, so the pellets can be recycled and reused. In addition, the pellets can be applied throughout the year, so during the non-rice growing period (such as winter or early spring in the south), the pellets can improve soil quality, increase soil fertility, and promote the activity of microorganisms in the soil, thereby promoting soil ecological balance, and can achieve rapid reduction of cadmium and arsenic in plant tissues and permanent removal of the total amount of cadmium in the soil. The pellets can be used not only in contaminated rice fields, but also in ordinary soil environments and water environments, and have a wide range of applications.

[0037] 3. In the present invention, the Schreiberite, polyethylene and starch all have an adsorption effect on cadmium and arsenic in the soil. The Schreiberite and polyethylene aggregate to form heterogeneous aggregates through ligand exchange and electrostatic action. The surface of the Schreiberite contains abundant hydroxyl groups, sulfate groups and other groups, which have a strong fixation ability for cadmium and arsenic in the soil; polyethylene has a high specific surface area and abundant pores. After the two are aggregated, they can not only solve the problem of easy agglomeration of the Schreiberite, but also remove cadmium and arsenic in the soil at the same time, and effectively reduce the total amount of cadmium and arsenic in the soil; the addition of starch enhances the flexibility of the ball, and the addition of polyethylene enhances the mechanical strength of the ball. At the same time, the gel formed by starch and polyethylene creates a stable reaction environment for the Schreiberite, which improves the ability of the Schreiberite to fix cadmium in the soil; arsenic is electrostatically adsorbed on the Schreiberite to form a surface complex, which is conducive to the adsorption of cadmium;

[0038] 4. During the application process, after the small balls enter the flooded rice fields, they sink into the soil because their density is greater than that of water. The cadmium and arsenic ions in the soil will be fixed on the small balls. While fixing the cadmium and arsenic in the soil, they will absorb water and swell. After completing the repair cycle, they will float on the water surface for easy recycling and reuse. The small balls have a compact structure and the materials are not easy to disperse, so they will not cause secondary pollution to the soil. The preparation method of the present invention is simple, the conditions are mild, and the operation is simple. It is only necessary to sprinkle the materials into the soil, thereby realizing the resource utilization of waste and can be prepared and promoted in large quantities. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 This is a photo of the recyclable cadmium and arsenic simultaneous removal schreberite-based beads prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0041] In order to make the invention purpose, technical scheme and beneficial technical effect of the present invention clearer, the present invention is described in detail below in conjunction with specific embodiments. It should be understood that the embodiments described in this specification are only for explaining the present invention, not for limiting the present invention.

[0042] Example 1

[0043] A recyclable cadmium and arsenic simultaneous removal schreberite-based small ball, the preparation method is as follows:

[0044] (1) Prepare 30 g / L sodium alginate aqueous solution, heat in a 90 °C water bath, and stir for 30 min to completely dissolve it;

[0045] (2) Add 90 g / L corn starch to the solution described in (1), heat in a water bath at 90°C, stir for 60 min until the solution becomes clear, cool to room temperature and set aside to obtain a sol;

[0046] (3) mixing low-density polyethylene and deionized water at room temperature, wherein the concentration of low-density polyethylene is 20 mg / L, to obtain a medium;

[0047] (4) adding 60 mg / L of Schreiber mineral to the medium described in (3) at room temperature, wherein the Schreiber mineral is prepared by the method described in the invention, oscillating and aggregating the low-density polyethylene and the Schreiber mineral, adjusting the pH of the initial solution with hydrochloric acid or sodium hydroxide, so that the pH of the water environment for the oscillation aggregation of the low-density polyethylene and the Schreiber mineral is 6, the oscillation rate is 200 rpm, and the oscillation time is 180 min, to obtain a mixed solution;

[0048] (5) Centrifuge the mixed solution in (4) at 5000 r / min for 5 min at 25°C, discard the supernatant, take out the precipitate, and dry it at 25°C;

[0049] (6) Add the material described in (5) at a concentration of 1.0 g / L into the sol of (2) and mix them evenly, stirring at 60°C for 120 min until a mixed sol is formed;

[0050] (7) The sol described in (6) was dripped dropwise into a 20 g / L FeCl2 solution. After cross-linking at room temperature for 24 h, small spheres were obtained. The small spheres were washed several times with deionized water to remove excess Fe. 2+ ;

[0051] (8) Drying the microspheres described in (7) at 25°C for 18 h to obtain Schroeder mineral-based microspheres; Figure 1 This is a photo of the recyclable cadmium and arsenic simultaneous removal Schottky mineral-based beads prepared in Example 1. It can be seen that the diameter is about 2-3 mm.

[0052] Test Example 1

[0053] The effect of using recyclable cadmium and arsenic simultaneous removal schmidt mineral-based beads to remove cadmium and arsenic (Cd=10 mg / L, As=2 mg / L) in aqueous solution:

[0054] 50 ml of the cadmium and arsenic contaminated solution was placed in a 250 ml conical flask, and 0.5 g of the Schmidt mineral-based beads prepared in Example 1 were added, mixed thoroughly, and cultured at room temperature for 3 days. After the residual cadmium and arsenic in the solution were extracted, quantitative detection and analysis were performed using inductively coupled plasma mass spectrometry.

[0055] At the same time, a blank control experiment was established, and 50 ml of cadmium-arsenic contaminated solution was placed in a 250 ml conical flask, mixed thoroughly, and incubated at room temperature for 3 days. After the residual arsenic in the solution was extracted, it was quantitatively detected and analyzed using inductively coupled plasma mass spectrometry.

[0056] Comparative Example 1-1

[0057] Remediation of cadmium contaminated solution (Cd=10 mg / L) using polyethylene nanoparticles

[0058] 50 ml of cadmium-contaminated solution was placed in a 250 ml conical flask, and 0.07 g of polyethylene nanoparticles was added. The mixture was mixed thoroughly and incubated at room temperature for 3 days. After the residual cadmium in the solution was extracted, it was quantitatively detected and analyzed using inductively coupled plasma mass spectrometry.

[0059] Comparative Example 1-1'

[0060] Remediation of cadmium-contaminated solution (Cd=10 mg / L) using Schroeder mineral

[0061] Take 50 ml of cadmium-contaminated solution and put it into a 250 ml conical flask, add 0.21 g of Schroeder mineral, mix thoroughly and incubate at room temperature for 3 days. After extracting the residual cadmium in the solution, inductively coupled plasma mass spectrometry was used for quantitative detection and analysis.

[0062] Comparative Example 1-2

[0063] Remediation of arsenic-contaminated solution (As=2 mg / L) using polyethylene nanoparticles

[0064] 50 ml of arsenic-contaminated solution was placed in a 250 ml conical flask, and 0.07 g of polyethylene nanoparticles was added. The mixture was mixed thoroughly and incubated at room temperature for 3 days. After the residual arsenic in the solution was extracted, it was quantitatively detected and analyzed using inductively coupled plasma mass spectrometry.

[0065] Comparative Example 1-2'

[0066] Remediation of arsenic contaminated solution (As=2 mg / L) using Schroeder mineral

[0067] Take 50 ml of arsenic-contaminated solution and put it into a 250 ml conical flask, add 0.21 g of Schroeder mineral, mix thoroughly and incubate at room temperature for 3 days. After extracting the residual arsenic in the solution, inductively coupled plasma mass spectrometry was used for quantitative detection and analysis.

[0068] Comparative Examples 1-3

[0069] The cadmium-contaminated solution (Cd=10 mg / L) was repaired using the Schroeder mineral-based beads prepared in Example 1 of the present invention

[0070] 50 ml of the cadmium-contaminated solution was placed in a 250 ml conical flask, and 0.5 g of the Schott mineral-based beads prepared in Example 1 were added, mixed thoroughly, and cultured at room temperature for 3 days. After the residual cadmium in the solution was extracted, quantitative detection and analysis was performed using inductively coupled plasma mass spectrometry.

[0071] Comparative Examples 1-4

[0072] The arsenic contaminated solution (As=2 mg / L) was repaired using the Schmidtite-based beads prepared in Example 1 of the present invention.

[0073] 50 ml of the arsenic-contaminated solution was placed in a 250 ml conical flask, and 0.5 g of the Schott mineral-based beads prepared in Example 1 were added, mixed thoroughly, and cultured at room temperature for 3 days. After the residual arsenic in the solution was extracted, it was quantitatively detected and analyzed by inductively coupled plasma mass spectrometry.

[0074] The removal performance of the pellets of the present invention in Example 1 and the comparative example on cadmium and arsenic in the cadmium and arsenic composite pollution / cadmium pollution / arsenic pollution solution was compared and analyzed, and the specific results are shown in Table 1:

[0075] Table 1

[0076]

[0077] As shown in Table 1, after 3 days of culture without adding any repair material (blank), the total cadmium and total arsenic removal rates in the solution were 0. Adding the pellets of the present invention (Test Example 1) can simultaneously and efficiently remove the total cadmium (85.30%) and total arsenic (60.50%) in the solution, which is better than the single cadmium-contaminated and arsenic-contaminated solutions. The removal capacity of arsenic and cadmium using single polyethylene nanoparticles or Schmidt minerals (Comparative Examples 1-1, 1-1', 1-2, 1-2') is lower than that using the pellets of the present invention (Comparative Examples 1-3, 1-4).

[0078] Test Example 2

[0079] The effect of recyclable cadmium and arsenic simultaneous removal by Schmidt mineral-based pellets on the removal of cadmium and arsenic (Cd=1.217mg / kg, As=73.43mg / kg) from rice fields:

[0080] The cadmium and arsenic in the paddy field were removed by using the Schmidt mineral-based pellets prepared in Example 1 of the present invention:

[0081] 10 g of cadmium-arsenic compound-contaminated paddy field soil was placed in a 250 ml conical flask, 2 g of the Schmidt mineral-based pellets prepared in Example 1 were added, and deionized water was added. The water management was in accordance with the conventional farmland water management for rice growth. A 2 cm water layer was maintained during the culture period, and the mixture was fully mixed and cultured at room temperature for 7 days. After the residual cadmium and arsenic in the soil were extracted, quantitative detection and analysis were performed using inductively coupled plasma mass spectrometry.

[0082] At the same time, a blank control experiment was established. 10 g of cadmium-arsenic compound-contaminated paddy field soil was placed in a 250 ml conical flask, and deionized water was added. The water management was in accordance with the conventional farmland water management for rice growth. A 2 cm water layer was maintained during the incubation period, and the mixture was fully mixed and incubated at room temperature for 7 days. After the residual cadmium and arsenic in the soil were extracted, inductively coupled plasma mass spectrometry was used for quantitative detection and analysis.

[0083] Comparative Example 2-1

[0084] Repair of cadmium-contaminated rice fields using the Schmidt mineral-based pellets prepared in Example 1 of the present invention

[0085] 10 g of cadmium-contaminated paddy field soil was placed in a 250 ml conical flask, 2 g of the Schmidt mineral-based pellets prepared in Example 1 were added, and deionized water was added. The water management was in accordance with the conventional farmland water management for rice growth. A 2 cm water layer was maintained during the culture period, and the soil was fully mixed and cultured at room temperature for 7 days. After the residual cadmium and arsenic in the soil were extracted, quantitative detection and analysis were performed using inductively coupled plasma mass spectrometry.

[0086] Comparative Example 2-2

[0087] Using the Schmidt mineral-based pellets prepared in Example 1 of the present invention to repair arsenic-contaminated rice fields

[0088] 10 g of arsenic-contaminated paddy field soil was placed in a 250 ml conical flask, 2 g of the Schmidt mineral-based pellets prepared in Example 1 were added, and deionized water was added. The water management was in accordance with the conventional farmland water management for rice growth. A 2 cm water layer was maintained during the culture period, and the mixture was fully mixed and cultured at room temperature for 7 days. After the residual cadmium and arsenic in the soil were extracted, quantitative detection and analysis were performed using inductively coupled plasma mass spectrometry.

[0089] The removal performance of the pellets of the present invention in Example 1 on cadmium and arsenic in soils with cadmium and arsenic combined pollution / cadmium pollution / arsenic pollution was compared and analyzed, and the specific results are shown in Table 2:

[0090] Table 2

[0091]

[0092] It can be seen from Table 2 that the removal rate of the cadmium and arsenic composite contaminated soil by adding the small balls of the present invention (total cadmium removal rate 69.73%, total arsenic removal rate 57.26%) is better than that of the cadmium / arsenic single contaminated soil (total cadmium removal rate 65.49%, total arsenic removal rate 51.24%).

[0093] Test Example 3

[0094] Recyclable cadmium and arsenic simultaneous removal The recycling effect of Schottky mineral-based beads in removing cadmium and arsenic in aqueous solution:

[0095] The Schmidt mineral-based beads prepared in Example 1 were selected to explore the removal rate of cadmium and arsenic in the solution after multiple applications. After each treatment, 0.43 mol / L HNO3 was used to desorb the circulating beads, and the beads were re-placed into the untreated original cadmium and arsenic contaminated solution to test the degree of retention of the material's own removal ability after 3 repeated uses of the Schmidt mineral-based beads. Other application methods are the same as in Test Example 1. The specific results are shown in Table 3.

[0096] Table 3

[0097]

[0098] It can be seen from Table 3 that the three-cycle effect of adding the small balls of the present invention on the cadmium-arsenic composite contaminated solution is better than that on the cadmium / arsenic single contaminated solution.

[0099] Test Example 4

[0100] Recyclable cadmium and arsenic simultaneous removal Schmidt mineral-based pellets Recycling effect of cadmium and arsenic removal in rice fields:

[0101] The Schmidt mineral-based beads prepared in Example 1 were selected to explore the removal rate of cadmium and arsenic in soil after multiple applications. After each treatment, 0.43 mol / L HNO3 was used to desorb the circulating beads, and the beads were re-placed into the untreated original cadmium and arsenic composite contaminated soil to test the degree of retention of the material's own removal ability after 3 repeated uses of the Schmidt mineral-based beads. Other application methods are the same as those in Test Example 2. The specific results are shown in Table 4.

[0102] Table 4

[0103]

[0104] It can be seen from Table 4 that the three-cycle effect of adding the small balls of the present invention on the cadmium-arsenic composite contaminated soil is better than that on the cadmium / arsenic single contaminated soil.

[0105] According to the above test examples 1-4, the small balls of the present invention are used to repair cadmium and arsenic single / compound contaminated soil: after the small ball head is added into the contaminated solution / contaminated soil, the small ball can realize its function of removing cadmium / arsenic pollutants.

[0106] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a recyclable cadmium and arsenic simultaneous removal schreberite-based ball, characterized in that: The following steps are involved: (1) adding sodium alginate into water, and stirring while heating in a water bath to completely dissolve the sodium alginate to obtain a sodium alginate aqueous solution; (2) adding corn starch to the solution of step (1), heating in a water bath, stirring until the solution becomes clear, cooling to room temperature and setting aside for use to obtain a sol; (3) mixing polyethylene nanoparticles and deionized water at room temperature to obtain a medium; (4) adding Schroeder mineral to the medium described in step (3) at room temperature to cause the polyethylene nanoparticles and the Schroeder mineral to aggregate by oscillation to obtain a mixed solution; (5) After centrifuging the mixed solution in step (4), discarding the supernatant, taking out the precipitate and drying it; (6) placing the precipitate obtained in step (5) into the sol in step (2) and mixing them evenly until a mixed sol is formed; (7) The mixed sol described in step (6) was dripped dropwise into the FeCl2 solution, and the microspheres were prepared after cross-linking at room temperature. The microspheres were washed several times with deionized water to remove the excess Fe 2+ ; (8) Drying the microspheres described in step (7) to obtain Schmidtite-based microspheres.

2. The method for preparing a recyclable cadmium and arsenic simultaneous removal schreberite-based small ball according to claim 1, characterized in that: In step (1), the water bath heating temperature is 60-90°C, the stirring time is 30-60 min; and the mass concentration of sodium alginate in the sodium alginate aqueous solution is 5-30 g / L.

3. The method for preparing a recyclable cadmium and arsenic simultaneous removal schreberite-based small ball according to claim 1, characterized in that: In step (2), the water bath heating temperature is 60-90° C., and the stirring time is 60-90 min. In the sol, the mass concentration of corn starch is 35-140 g / L.

4. The method for preparing a recyclable cadmium and arsenic simultaneous removal schreberite-based small ball according to claim 1, characterized in that: In step (3), the polyethylene nanoparticles are selected from low-density polyethylene nanoparticles (LDPEs), and the concentration of the polyethylene in the medium is 20 mg / L.

5. The method for preparing recyclable cadmium and arsenic simultaneous removal schreberite-based beads according to claim 1, characterized in that: In step (4), the concentration of the Schreiber mineral in the mixed solution is 10-100 mg / L, the pH of the water environment in which the polyethylene nanoparticles and the Schreiber mineral are oscillated and aggregated is 6-8, hydrochloric acid or sodium hydroxide is used to adjust the pH of the initial solution, the oscillation rate is 180-300 rpm, and the oscillation time is 60-300 min.

6. The method for preparing recyclable cadmium and arsenic simultaneous removal schreberite-based beads according to claim 1, characterized in that: In step (5), the centrifugation temperature is 20-30°C, the centrifugation speed is 5000-8000 r / min, the centrifugation time is 3-5 min, and the drying temperature is 20-30°C.

7. The method for preparing recyclable cadmium and arsenic simultaneous removal schreberite-based beads according to claim 1, characterized in that: In step (6), the amount of the precipitate added to the sol in step (5) is 0.04-1.6 g / L; the mixing is carried out by stirring, the stirring time is 90-300 min, and the stirring temperature is 60-90°C.

8. The method for preparing recyclable cadmium and arsenic simultaneous removal schreberite-based beads according to claim 1, characterized in that: In step (7), the mass concentration of the FeCl2 solution is 20-30 g / L, and the cross-linking time is 24-48 h.

9. Schmidtite-based beads prepared by the method according to any one of claims 1 to 8.

10. The use of the Schmidtite-based beads according to claim 9, characterized in that: The method comprises adding the Schmidt mineral-based small balls into polluted water or polluted soil according to the pollution conditions, and uniformly distributing the small balls in the polluted medium through stirring to achieve degradation.

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