Iron-modified silicon-calcium-based mineral material and application of iron-modified silicon-calcium-based mineral material in passivating and repairing cadmium-arsenic pollution

Abstract

The invention provides an iron-modified silicon-calcium-based mineral material and application of the iron-modified silicon-calcium-based mineral material in passivating and repairing cadmium and arsenic pollution. According to the technical scheme disclosed by the invention, high-temperature slag of a yellow phosphorus production process is selected as a silicon-calcium-based mineral raw material, and the silicon-calcium-based mineral material loaded with spherical nanoscale iron minerals is prepared through the steps of ferric salt dipping, alkali liquor dropwise adding, natural settling, thermal reaction and cleaning. According to the mineral loading modification scheme, the adsorption capacity of the material to cadmium ions, arsenate ions and arsenite ions is remarkably improved at the same time, and the disclosed iron-modified silicon-calcium-based mineral material can adsorb cadmium and arsenic pollutants at the same time and can be used for removing the cadmium ions, the arsenate ions or (and) the arsenite ions in a water body; and the silicon-calcium-based waste can also be used as a passivation repair material for treating cadmium and arsenic pollution of a soil environment, and the application way of the silicon-calcium-based waste is expanded.

Description

Technical Field

[0001] The present invention relates to the field of heavy metal pollution remediation materials, and particularly to an iron-modified calcium silicate-based mineral material and its application in passivating and remediating cadmium and arsenic pollution. Background Art

[0002] With the continuous attention of the country to environmental protection, the phosphorus chemical industry has actively promoted the green upgrading of production processes. However, the phosphorus chemical production brings various phosphorus-based and calcium silicate-based solid wastes, which are difficult to dispose of and have few resource utilization methods, restricting the transformation and upgrading of the phosphorus chemical industry. Among them, the phosphorus content in phosphorus-based waste is still not low, and its resource utilization has received extensive attention. While the phosphorus content in mining wastes such as calcium silicate-based solid wastes (such as high-temperature slag produced by the yellow phosphorus production process) is low and has received less attention. They are mainly used in cement, concrete production, etc., with defects in low-value utilization and low resource recovery efficiency.

[0003] Previous research results showed that the high-temperature slag from the yellow phosphorus production process is rich in silicon and calcium elements, contains a small amount of phosphorus elements, and has strong alkalinity, and may be used as a soil acidity regulating material or a heavy metal passivating material (Ouyang Tingting et al., 2021). If the high-temperature slag from the yellow phosphorus production process can be made into an efficient soil remediation material, under the background of the strong demand for the research and development of low-cost environmental remediation materials, it not only solves the problem of solid waste disposal in the yellow phosphorus production industry but also provides a new way for resource utilization and improves the utilization efficiency of high-temperature slag. However, due to the low phosphate content, there are few adsorption groups for heavy metal pollutants such as cadmium ions on the surface of the original high-temperature slag, and it mainly relies on alkaline precipitation of heavy metals, resulting in low solid retention performance for heavy metals. It is necessary to increase its surface action sites and improve the adsorption capacity through modification methods. At the same time, the high-temperature slag from the yellow phosphorus production process lacks functional groups that can react with anionic metalloid pollutants such as arsenate ions and arsenite ions, and cannot be used for the treatment and remediation of arsenic pollution or arsenic-containing composite pollution. Therefore, the modification method suitable for the high-temperature slag from the yellow phosphorus production process and its application in the field of soil environmental remediation still need to be deeply explored.

[0004] Mineral loading methods are commonly used for modifying remediation materials. Different modification methods can improve the remediation effect of materials on cadmium, arsenic pollution, or cadmium-arsenic combined pollution. For example, Patent 202010386679.8 developed a composite adsorbent loaded with nano-zinc sulfide sepiolite, enhancing the adsorption capacity of sepiolite for cadmium ions in water. Patent 201811464074.5 proposed a technical solution for loading an iron-manganese binary complex on sepiolite, simultaneously improving the adsorption efficiency of the material for divalent cadmium ions and trivalent arsenic. However, the modification effect of the mineral loading method is affected by factors such as the type of mineral loading. For example, the sulfide / phosphate mineral loading method is mainly used to improve the performance of materials in fixing cationic pollutants, and the iron mineral loading method is mainly used to enhance the interaction mechanism between materials and arsenate. Moreover, there are significant differences in the application effects of the same loading method on different raw materials. So far, there has been no report on the modification research of calcium-silicate-based materials using the mineral loading method, and there is a lack of understanding of the influence of the iron mineral loading process on the efficiency of calcium-silicate-based materials in adsorbing pollutants such as cadmium and arsenic. The preparation and application technical solutions of high-efficiency arsenic-cadmium combined pollution remediation materials based on iron-modified calcium-silicate-based materials need to be developed. Summary of the Invention

[0005] In view of the above deficiencies, the present invention provides an iron-modified calcium-silicate-based mineral material. This material uses the high-temperature slag from the yellow phosphorus production process as the calcium-silicate-based raw material. By loading iron minerals, the adsorption capacity of the material for cadmium ions and inorganic arsenic pollutants is simultaneously improved, and it can be used to treat cadmium-arsenic pollution in water or fix cadmium and arsenic pollutants in soil. The specific technical solution is as follows:

[0006] An iron-modified calcium-silicate-based mineral material, and its preparation method is as follows:

[0007] (1) Collect the calcium-silicate-based raw material and disperse it in an iron salt solution.

[0008] (2) Place it on a magnetic stirrer and, under the condition of magnetic stirring at 700 rpm, gradually add an alkali solution until the pH reaches 11.5 - 12.5.

[0009] (3) Naturally settle for 30 h - 60 h, and then place it in a reactor for thermal reaction under aerobic conditions.

[0010] (4) Take out the above product, wash off the free iron ions with deionized water until the pH difference between the two elution solutions is less than 0.2 units, and end the elution operation; freeze-dry the solid to obtain the iron-modified calcium-silicate-based mineral material.

[0011] The calcium-silicon-based raw material is the high-temperature slag in the yellow phosphorus production process, preferably the water-quenched product of molten slag, mainly composed of calcium silicate, silicon dioxide and calcium carbonate minerals, with a pH of 9-12, the total content of silicon and calcium elements not less than 45%, the phosphorus element content less than 1%, but the effective phosphorus content not less than 3% of the total phosphorus, and the iron element content less than 1%.

[0012] The iron salt is ferric nitrate or ferric chloride, with a concentration of 0.4 mol / L.

[0013] The alkali solution is potassium hydroxide solution, with a concentration of 1-5 mol / L.

[0014] The mixing ratio of the calcium-silicon-based raw material and the iron salt solution is 1 g of calcium-silicon-based raw material: 5 mmol of iron element - 1 g of calcium-silicon-based raw material: 20 mmol of iron element, preferably 1 g of calcium-silicon-based raw material: 10 mmol of iron element.

[0015] The natural sedimentation time is preferably 60 h.

[0016] The thermal reaction temperature is 70-120 °C, preferably 90 °C; the thermal reaction time is 12-48 h, preferably 16 h.

[0017] The iron-modified calcium-silicon-based mineral material is any material obtained according to the above preparation method.

[0018] The iron minerals loaded on the iron-modified calcium-silicon-based mineral material include iron oxide and iron phosphate, which are spherical nano-scale iron minerals.

[0019] The present invention claims to protect the application of the iron-modified calcium-silicon-based mineral material in removing cadmium ions, arsenate ions or (and) arsenite ions from water.

[0020] The present invention claims to protect the application of the iron-modified calcium-silicon-based mineral material in treating cadmium and arsenic pollution in the soil environment.

[0021] The present invention claims to protect the application of the iron-modified calcium-silicon-based mineral material in treating cadmium and arsenic composite-polluted water bodies or soil environments.

[0022] The technical solution proposed by the present invention has the following advantages:

[0023] (1) Taking the silicon-calcium-based high-temperature slag from the yellow phosphorus production process as the object, the strong alkalinity and elemental composition characteristics of the silicon-calcium-based material are fully explored, and an iron modification method is designed. Through the reaction of iron salts with the surface groups of the silicon-calcium-based high-temperature slag in a suitable atmosphere, the synthesis of nano-scale trivalent iron minerals mainly composed of iron oxide and iron phosphate and their loading on the material are realized. The synthesized iron minerals are small in size and highly active, which increases the specific surface area and micropore content of the material, not only enhancing the adsorption capacity of the material for arsenate ions and arsenite ions, but also significantly improving the adsorption capacity of the material for cadmium ions. If the preparation method is used for the pure solution system iron mineral synthesis process without the presence of high-temperature slag, only goethite (α-FeOOH) can be synthesized, and its morphology and adsorption capacity are significantly different from those of iron oxide / iron phosphate minerals, and the synthesized goethite is mainly suitable for the adsorption and removal of arsenic pollutants in existing reports, and the adsorption effect on cadmium ions is relatively weak. Therefore, the present invention proposes a technical solution that can effectively convert the silicon-calcium-based high-temperature slag of the yellow phosphorus production process into an efficient environmental functional material.

[0024] (2) The material can react with cadmium and arsenic pollutants through multiple mechanisms. The main mechanisms include: the material has a certain alkalinity, which can promote the adsorption and precipitation of cadmium ions in a high pH environment; the calcium ions inherent in the surface of the material can adsorb cadmium ions through ion exchange, and fix arsenate ions and arsenite ions through precipitation or co-precipitation mechanisms; the material can react with cadmium ions through surface adsorption, complexation, precipitation and co-precipitation through the silicon hydroxyl, iron hydroxyl, phosphate, silicate and other groups on the mineral components; the iron minerals contained on the surface of the material can adsorb arsenate ions and arsenite ions through surface adsorption, monodentate complexation, bidentate complexation and other mechanisms.

[0025] (3) The iron-modified silicon-calcium-based mineral material proposed in this technical solution can be used to remove cadmium and (and) arsenic pollutants in wastewater, and can also be used to treat cadmium, arsenic or cadmium-arsenic combined pollution in the soil environment. It has a wide range of applications and provides a new type of environmental functional material for environmental pollution control, expanding the recycling path of low-phosphorus and high-calcium industrial waste resources.

[0026] (4) Traditional calcium-silicon-based high-temperature slag materials have strong alkalinity and may have potential adverse effects on soil physical and chemical properties and physiological activities of plants, animals and microorganisms after being introduced into the soil environment as a conditioner or repair material. The pH of the modified calcium-silicon-based mineral material is appropriately reduced after modification, which reduces the potential environmental risks of the applied material and is more green and friendly to the soil environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 These are the scanning electron microscope and transmission electron microscope test results of the iron-modified silicon-calcium based mineral material in Example 1.

[0028] Figure 2It is the adsorption isotherm of the iron-modified calcium silicate-based mineral material on cadmium ions, arsenate ions, and arsenite ions in Example 2.

[0029] Figure 3 It is the adsorption result of the iron-modified calcium silicate-based mineral material on the composite pollutant of cadmium ions and arsenite ions in Example 3.

[0030] Figure 4 It is the adsorption result of the iron-modified calcium silicate-based mineral material on the composite pollutant of cadmium ions and arsenate ions in Example 4.

[0031] Figure 5 It is the influence result of adding the iron-modified calcium silicate-based mineral material on soil pH, Eh, available cadmium, and available arsenic concentrations in Example 5.

[0032] Figure 6 It is the influence result of adding the iron-modified calcium silicate-based mineral material on soil pH, Eh, available cadmium, and available arsenic concentrations in Example 6. Specific implementation manners

[0033] The technical solutions of the present invention will be further described below in conjunction with specific implementation methods.

[0034] The following examples are only used to illustrate the present invention, but are not used to limit the protection scope of the present invention. Unless otherwise specified, the reagents and technical means used in the examples are all conventional means well known to those skilled in the art.

[0035] Example 1

[0036] Collect the molten water-quenched product (H) of the yellow phosphorus production process, grind it through 100 meshes, and use it as the precursor of the calcium silicate-based material. The characterization results show that the main components of the H material are calcium silicate, silicon dioxide, and calcium carbonate minerals. The silicon and calcium element contents are 16.3% and 33.8% respectively, the pH is 11.34, the total phosphorus content is 6.53 g / kg, the available phosphorus content is 0.28 g / kg, and the iron content is 0.26%.

[0037] Weigh 6 g of material H into a 250 mL beaker, add 150 mL of 0.4 mol / L ferric nitrate solution, and stir it at 700 rpm on a magnetic stirrer. Slowly drip 5 mol / L potassium hydroxide solution until the pH of the suspension is 11.8. Let it settle naturally for 60 h, put it into a reactor, and conduct a thermal reaction at 90 °C for 16 h under aerobic conditions to achieve the mineral phase transformation of iron. Take out the above product, wash off the free iron ions with deionized water until the pH change of the two eluates is less than 0.1; freeze-dry the solid to obtain the iron-modified calcium silicate-based mineral material (Fe@H). At the same time, conduct alkali titration-thermal reaction-elution-drying of the iron salt solution without H material to prepare the control iron material (FeOOH).

[0038] The characterization results show that there are significant differences in the colors of the three materials. The iron-modified calcium silicate-based mineral material changes from the grayish-white color of the raw material to dark brown, while the control iron material is yellow. The results of electron microscopy analysis indicate that the iron-modified calcium silicate-based mineral material is loaded and wrapped with a large number of spherical particles of nanometer size on the surface of the original material. The EDX results show that a relatively high content of iron element appears on the material. The results of mineral composition analysis show that the iron-modified calcium silicate-based mineral material mainly loads iron oxide and iron phosphate minerals, while the XRD pattern of the control iron material is that of pure goethite.

[0039] The characterization results of the physicochemical properties of Fe@H show that the pH of Fe@H is 10.25, lower than that of material H (11.34). The decrease in pH improves the environmental friendliness of the material. The pH of Fe@H zpc is 3.59, higher than that of material H (2.57). The specific surface area of Fe@H is 245 cm 2 / g, significantly higher than 5.59 cm 2 / g of material H. The iron content of Fe@H is 29.1%. The strong alkalinity, high pH zpc and high surface area of the loaded material are beneficial for the material to adsorb and fix heavy metal pollutants such as cadmium in the environment. At the same time, the loaded iron minerals help to fix arsenic pollutants.

[0040] Example 2

[0041] Using 0.01 mol / L sodium nitrate solution as the substrate, prepare cadmium nitrate, disodium hydrogen arsenate or sodium arsenite pollution solutions, and adjust the pH of the solutions to 5.0 ± 0.2. Weigh H and Fe@H prepared in Example 1, and mix them with the pollution solutions at a solid-liquid ratio of 1 g:500 mL. Oscillate at 150 rpm for 72 h at room temperature. Filter, dilute, and determine the cadmium or arsenic concentration by ICP-OES, calculate the adsorption amount of the material to the pollutants, and draw the adsorption isotherms of the material to cadmium ions, arsenate ions or arsenite ions. In the experiment, the adsorption amounts of arsenate ions and arsenite ions are both converted to the adsorption amount of arsenic element per unit material.

[0042] As Figure 2 shown, the adsorption amounts of Fe@H to cadmium ions, arsenate ions and arsenite ions are significantly higher than those of material H. The fitting results of the Langmuir adsorption isotherm model show that the saturated adsorption amounts of Fe@H to cadmium ions, arsenite ions and arsenate ions are 154 mg / g, 85.2 mg / g and 63.4 mg / g respectively, while the adsorption amounts of material H are only 44.7 mg / g, 27.2 mg / g and 16.1 mg / g.

[0043] Example 3

[0044] Using 0.01 mol / L sodium nitrate solution as the base, prepare a cadmium nitrate and sodium arsenite composite pollution solution, and adjust the pH of the solution to 4.0 ± 0.2. Weigh the Fe@H prepared in Example 1, mix it with the pollution solution at a solid-liquid ratio of 1 g:500 mL, and oscillate at 150 rpm for 72 h at room temperature. Filter, dilute, and measure the cadmium or arsenic concentration by ICP-OES to calculate the adsorption amount of the material for the composite pollutant. The pollution solutions include: (1) Cd pollution solution with a Cd concentration of 112 mg / L; (2) As(III) pollution solution with an As(III) concentration of 75 mg / L; (3) Cd&As(III) pollution solution with a Cd concentration of 112 mg / L and an As(III) concentration of 75 mg / L; (4) H-Cd&As(III) pollution solution with a Cd concentration of 224 mg / L and an As(III) concentration of 75 mg / L; (5) Cd&H-As(III) pollution solution with a Cd concentration of 112 mg / L and an As(III) concentration of 150 mg / L. In the experiment, the adsorption amounts of arsenate ions and arsenite ions are both converted to the adsorption amount of arsenic element per unit material.

[0045] As Figure 3 shown, in the cadmium-arsenic composite pollution solution system, Fe@H can simultaneously adsorb cadmium ions and arsenic pollutants. When arsenite ions are present in the solution, the adsorption amount of Fe@H for cadmium ions does not change significantly, and the adsorption amount increases with the increase of the initial cadmium concentration. When cadmium ions are present in the solution, the adsorption amount of Fe@H for arsenite ions increases significantly; the increase of the initial concentration of arsenic pollutants or cadmium ions will both increase the adsorption amount of the material for arsenic, indicating the existence of synergistic adsorption.

[0046] Example 4

[0047] Using a 0.01 mol / L sodium nitrate solution as the base, a composite pollution solution of cadmium nitrate and disodium hydrogen arsenate was prepared, and the pH of the solution was adjusted to 4.0 ± 0.2. Weigh the Fe@H prepared in Example 1 and mix it with the pollution solution at a solid-liquid ratio of 1 g:500 mL. Shake it at 150 rpm for 72 h at room temperature. Filter, dilute, and determine the cadmium or arsenic concentration by ICP-OES, and calculate the adsorption capacity of the material for the composite pollutants. The pollution solutions include: (1) Cd pollution solution with a Cd concentration of 112 mg / L; (2) As(V) pollution solution with an As(III) concentration of 75 mg / L; (3) Cd&As(V) pollution solution with a Cd concentration of 112 mg / L and an As(V) concentration of 75 mg / L; (4) H-Cd&As(III) pollution solution with a Cd concentration of 224 mg / L and an As(V) concentration of 75 mg / L; (5) Cd&H-As(V) pollution solution with a Cd concentration of 112 mg / L and an As(V) concentration of 150 mg / L. In the experiment, the adsorption capacities of arsenate ions and arsenite ions were both converted to the adsorption capacity of arsenic element per unit material.

[0048] As Figure 3 shown, in the cadmium-arsenic composite pollution solution system, Fe@H can adsorb cadmium ions and arsenic pollutants simultaneously. When arsenate ions are present in the solution, the adsorption capacity of Fe@H for cadmium ions does not change significantly, and the adsorption capacity increases with the increase of the initial cadmium concentration. When cadmium ions are present in the solution, the adsorption capacity of Fe@H for arsenate ions increases significantly; the increase of the initial concentration of arsenic pollutants or cadmium ions will both increase the adsorption capacity of the material for arsenic, indicating the existence of co-adsorption.

[0049] Example 5

[0050] Weigh the two materials H and Fe@H prepared in Example 1 and mix them with the polluted soil respectively; the dosage of the materials is 2% or 5% (mass fraction). Add deionized water to adjust the soil moisture content to 70% of the saturated water holding capacity to simulate the dryland soil reaction system. Place the samples in a constant temperature incubator and cultivate them at 25 °C for 30 days. Take them out, freeze-dry, and analyze the soil physical and chemical properties and the availability of cadmium, arsenic, etc.

[0051] The results show that:

[0052] After adding H, the soil pH increased from 4.79 in the control group to 9.13 - 9.77, and the soil Eh decreased from 256 mV to 111 mV - 132 mV; the soil pH value increased with the increase of the material dosage. In the Fe@H treatment group, the soil pH increased to 6.78 - 8.27, lower than that of the H treatment group; the soil Eh decreased to 185 mV - 237 mV, higher than that of the H treatment group; with the increase of the material dosage, the soil pH value increased while the Eh value decreased.

[0053] After adding H, the concentration of available cadmium extracted by calcium chloride in the soil decreased from 0.127 mg / kg to 0.001 mg / kg - 0.003 mg / kg, a decrease of 97.7% - 98.9%. The concentration of arsenic extracted in the solution decreased from 0.698 mg / kg in the control group to 0.366 mg / kg - 0.541 mg / kg, a decrease of 22.6% - 47.6%. The cobalt concentration decreased by 83.34% - 87.87%, the nickel concentration decreased by 48.21% - 55.45%, the copper concentration decreased by -8.40% - 48.38%, the zinc concentration decreased by 97.90% - 97.98%, and the lead concentration decreased by 97.54% - 97.87%. At the same time, the concentration of available arsenic extracted by sodium dihydrogen phosphate in the soil decreased from 7.36 mg / kg to 5.66 - 6.17 mg / kg, a decrease of 16.1% - 23.1%.

[0054] After adding Fe@H, the concentration of available cadmium extracted by calcium chloride in the soil decreased to 0.004 mg / kg - 0.006 mg / kg, a decrease of 95.3% - 97.0%. The concentration of arsenic extracted in the solution decreased by 83.9% - 90.4%, the cobalt concentration decreased by 91.59% - 91.91%, the nickel concentration decreased by 61.57% - 68.63%, the copper concentration decreased by 74.85% - 83.34%, the zinc concentration decreased by 96.99% - 97.59%, and the lead concentration decreased by 98.82% - 98.84%. At the same time, the concentration of available arsenic extracted by sodium dihydrogen phosphate in the soil decreased to 4.00 - 4.98 mg / kg, a decrease of 32.3% - 45.6%. While maintaining the passivation effect on cadmium in the soil, the modified material significantly reduced the bioavailability of arsenic in the soil and exerted a fixation effect on pollutants such as lead.

[0055] Further analyzing the changes in the occurrence forms of cadmium and arsenic in the soil, it was found that: the proportions of acid-soluble, reducible, oxidizable, and residual cadmium in the control group soil were 38.42%, 41.76%, 11.43%, and 8.39%, respectively. After adding 5% of Fe@H, the proportions of acid-soluble, reducible, oxidizable, and residual cadmium were 45.87%, 36.68%, 7.96%, and 9.48%, respectively. The material promoted the transformation of reducible and oxidizable cadmium in the soil into acid-soluble and residual cadmium. The proportions of non-specifically adsorbed, specifically adsorbed, weakly crystalline iron and manganese oxide-bound, crystalline iron and manganese oxide-bound, and residual arsenic in the control group soil were 0.88%, 8.89%, 26.46%, 31.87%, and 31.90%, respectively. After adding 5% of Fe@H, the proportions of non-specifically adsorbed, specifically adsorbed, weakly crystalline iron and manganese oxide-bound, crystalline iron and manganese oxide-bound, and residual arsenic were 0.17%, 6.76%, 40.27%, 31.01%, and 21.79%, respectively. The material promoted the transformation of adsorbed arsenic in the soil into weakly crystalline iron and manganese oxide-bound arsenic.

[0056] Example 6

[0057] Weigh the two materials, H and Fe@H, prepared in Example 1, and mix them with the contaminated soil respectively; the dosage of the materials is 2% or 5% (mass fraction). Add deionized water to adjust the soil moisture content to 100% of the saturated water holding capacity, and make a 1 cm water layer appear on the upper layer of the soil to simulate the flooded soil environment conditions of paddy fields. Place the samples in a constant temperature incubator and culture them at 25°C for 30 days. Take them out, freeze-dry, and analyze the physical and chemical properties of the soil and the availability of cadmium, arsenic, etc.

[0058] The results showed that:

[0059] After adding H, the soil pH increased from 5.33 in the control group to 8.71 - 9.80, and the soil Eh decreased from 256 mV to 121 mV - 129 mV; both the pH and Eh values of the soil increased with the increase in the dosage of the material. In the Fe@H treatment group, the soil pH increased to 7.03 - 8.35, lower than that in the H treatment group; the soil Eh was 160 mV - 207 mV, higher than that in the H treatment group; with the increase in the dosage of the material, the pH value of the soil increased while the Eh value decreased.

[0060] After adding H, the concentration of available cadmium extracted by calcium chloride in the soil decreased from 0.140 mg / kg to 0.003 mg / kg, and at the same time, the concentration of arsenic extracted in the solution decreased from 0.881 mg / kg in the control group to 0.359 mg / kg - 0.617 mg / kg, a decrease of 30.0% - 59.3%; the concentration of available arsenic extracted by sodium dihydrogen phosphate in the soil decreased from 8.31 mg / kg to 6.05 mg / kg - 6.17 mg / kg.

[0061] After adding Fe@H, the concentration of available cadmium extracted by calcium chloride in the soil decreased to 0.003 mg / kg - 0.007 mg / kg, and at the same time, the concentration of arsenic extracted in the solution decreased to 0.094 mg / kg - 0.133 mg / kg, with a decrease of 95.3% - 97.7% and 84.9% - 89.3% respectively. The concentration of available arsenic extracted by sodium dihydrogen phosphate decreased to 4.50 mg / kg - 5.58 mg / kg, with a decrease of 32.9% - 45.9%. While maintaining the passivation effect on cadmium in the soil, the modified material significantly reduces the bioavailability of arsenic in the soil.

Claims

1. A preparation method of an iron-modified calcium silicate-based mineral material, characterized in that, the steps are as follows: Collect calcium silicate-based raw materials, disperse them in an iron salt solution; place them on a magnetic stirrer and stir magnetically at 700 rpm, and gradually add an alkali solution dropwise until the pH reaches 11.5 - 12.5; let it settle naturally for 30 h - 60 h, and then put it into a reactor to carry out a thermal reaction under aerobic conditions; take out the above product, wash and elute the free iron ions, and freeze-dry the solid.

2. The preparation method of the iron-modified calcium silicate-based mineral material according to claim 1, characterized in that: The calcium silicate-based raw material is the high-temperature slag of the yellow phosphorus production process, preferably the water-quenched product of molten slag, with a pH of 9 - 12, the total content of silicon and calcium elements not less than 45%, the phosphorus element content less than 1%, and the effective phosphorus content not less than 3% of the total phosphorus.

3. The preparation method of the iron-modified calcium silicate-based mineral material according to claim 1, characterized in that: The iron salt is ferric nitrate or ferric chloride, with a concentration of 0.4 mol / L; the alkali solution is a potassium hydroxide solution, with a concentration of 1 - 5 mol / L.

4. The preparation method of the iron-modified calcium silicate-based mineral material according to claim 1, characterized in that: The mixing ratio of the calcium silicate-based raw material and the iron salt solution is 1 g of calcium silicate-based raw material : 5 mmol of iron element - 1 g of calcium silicate-based raw material : 20 mmol of iron element; the thermal reaction temperature is 70 - 120 °C, and the thermal reaction time is 12 - 48 h.

5. The preparation method of the iron-modified calcium silicate-based mineral material according to claim 1, characterized in that: The preferred mixing ratio of the calcium silicate-based raw material and the iron salt solution in the preparation method is 1 g of calcium silicate-based raw material : 10 mmol of iron element; the preferred thermal reaction temperature is 90 °C; the preferred thermal reaction time is 16 h.

6. An iron-modified calcium silicate-based mineral material prepared by the preparation method according to claim 1.

7. Use of the iron-modified calcium silicate-based mineral material according to claim 6 for removing cadmium ions, arsenate ions, and arsenite ions singly or in combination present in water.

8. Application of the iron-modified calcium silicate-based mineral material according to claim 6 in the treatment of cadmium and arsenic pollution singly or in combination present in the soil environment.

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