Iron-rich biochar for water pollution control and ecological restoration, and preparation method and application thereof

Abstract

The application discloses a kind of iron-rich biochar for water pollution control and ecological restoration and its preparation method and application, belong to water ecological management technical field, its preparation method includes the following steps: S1. iron-rich plant is crushed, and then soaked with lye, to obtain pretreated powder material;S2. the pretreated powder material is subjected to microcarbonization treatment, then soaked in activation liquid, to obtain activated biomass;S3. the activated biomass is subjected to secondary pyrolysis carbonization treatment, to obtain iron-rich biochar for water pollution control and ecological restoration.The application is through the synergistic process of "microcarbonization-activation liquid filling-secondary carbonization", and adopts sulfonated modified polyvinyl alcohol as pore framework material, effectively solves the problem that traditional biochar pore is easy to collapse, and adsorption site is not sufficient exposure, the prepared iron-rich biochar has high specific surface area and abundant adsorption site, and shows excellent adsorption removal capacity for cadmium ion in water.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water body ecological management. Specifically, it is a kind of iron-rich biochar for water pollution control and ecological restoration and its preparation method and application. BACKGROUND

[0002] The cadmium-containing waste gas, waste water and waste residue generated in the industrial production process of non-ferrous metal smelting, electroplating, battery manufacturing, etc. will directly pollute rivers and lakes and farmland irrigated with them. As a highly toxic heavy metal element, cadmium has high mobility and is difficult to degrade, and is easily enriched in organisms through the food chain, posing a serious threat to the stability of aquatic ecosystems and human health.

[0003] At present, the ecological restoration technology for cadmium-containing polluted water bodies mainly includes biochar adsorption method, chemical precipitation method, membrane separation method and biological remediation method, etc. Among them, the chemical precipitation method is easy to produce a large amount of sludge, causing secondary pollution, the membrane separation method has high cost and poor adaptability to complex water body environment, the biological remediation method is environmentally friendly but has a long remediation period, which is difficult to meet the emergency management demand. The biochar adsorption method has the characteristics of wide raw material sources, simple operation, economic benefits and flexibility, etc. However, the traditional biochar has insufficient adsorption sites and adsorption capacity for cadmium ions. Iron-based modification as an effective modification means, by introducing iron oxides and other active components, the redox characteristics of iron are used to promote the morphological transformation and fixation of cadmium, which to some extent improves the number of adsorption sites and the binding strength of biochar to heavy metals. However, due to the introduction of iron components in the modification process, the pore channels are easily blocked, and the conventional pore expanding methods (such as using pore expanding agents) are easy to cause pore collapse or shrinkage due to insufficient skeleton support in the high-temperature carbonization process, so that the specific surface area and porosity of biochar are limitedly improved, and the adsorption sites and target pollutants are difficult to effectively contact, which ultimately affects the adsorption purification effect.

[0004] Therefore, how to develop a biochar material with high adsorption porosity and multiple adsorption sites, and controllable cost and easy to scale production, for improving the purification effect of heavy metal polluted water body, has become one of the key problems to be solved in the current water body ecological management technology field. SUMMARY

[0005] Therefore, the technical problem to be solved by the present application is to provide an iron-rich biochar for water pollution control and ecological restoration, to solve the problems of low porosity, few adsorption sites and poor exposure of active adsorption sites of existing biochar, which makes it difficult to efficiently adsorb cadmium ions in water.

[0006] To solve the above technical problems, the present application provides the following technical scheme: a preparation method of an iron-rich biochar for water pollution control and ecological restoration, comprising the following steps:

[0007] S1. crushing and treating the plant rich in iron element (iron-rich plant), soaking in alkali solution, filtering, drying, and obtaining pretreated powder;

[0008] S2. heating the pretreated powder under a protective atmosphere, performing micro-carbonization treatment to form a preliminary pore structure, and after cooling, soaking in an activation solution, the activation solution being a mixed solution of sulfonated modified polyvinyl alcohol and pore-expanding agent, filtering, drying, and obtaining activated biomass;

[0009] S3. performing secondary pyrolysis carbonization treatment on the activated biomass under a protective atmosphere, cooling, and obtaining iron-rich biochar for water pollution control and ecological restoration.

[0010] Further, the preparation of sulfonated modified polyvinyl alcohol includes the following contents:

[0011] A1. adding 3-trihydroxysilyl-1-propanesulfonic acid dropwise into a polyvinyl alcohol aqueous solution to obtain a mixed solution;

[0012] A2. adjusting the pH of the mixed solution, heating, and performing sulfonation reaction to obtain a modified polyvinyl alcohol solution;

[0013] A3. removing the solvent in the modified polyvinyl alcohol solution, drying, and obtaining sulfonated modified polyvinyl alcohol.

[0014] Further, in the mixed solution of step A1, the mass fraction of polyvinyl alcohol is 5-10%, and the mass ratio of polyvinyl alcohol to 3-trihydroxysilyl-1-propanesulfonic acid is 1:0.4-0.6.

[0015] Further, in the mixed solution of step A2, the pH is 1-2, the heating temperature is 60-80 ℃, and the reaction time is 20-30 h.

[0016] Further, in the activation solution, the mass fraction of sulfonated modified polyvinyl alcohol is 4-6%, the pore-expanding agent is one or a mixture of NaHCO3 and KHCO3, and the mass ratio of sulfonated modified polyvinyl alcohol to pore-expanding agent is 1:0.4-0.6.

[0017] Further, in step S2, the heating temperature is 300-350 ℃.

[0018] Further, the alkali solution is one or a mixture of NaOH solution and KOH solution, and the concentration is 0.5-2 mol / L.

[0019] Further, the secondary pyrolysis carbonization is carried out in a staged heating mode, and the staged heating includes two stages of pre-sintering and final sintering: the pre-sintering temperature is 280-320 DEG C, the heating rate is 5-10 DEG C / min, and the holding time is 15-25 min; the final sintering temperature is 600-700 DEG C, the heating rate is 3-8 DEG C / min, and the holding time is 30-60 min; the iron-rich biomass is subjected to the staged heating carbonization in an inert gas atmosphere, so that the obtained biochar material has sufficient pore expansion time, the formation and stability of the pore expansion structure are ensured, and higher porosity and specific surface area are obtained.

[0020] Further, the iron-rich plant is Siberian Iris planted in an acidic iron-rich environment, and the Siberian Iris is not only a landscape plant, but also a main force for removing heavy metals (such as cadmium) in the substrate (such as soil, gravel, etc.), which helps to establish a substrate-plant-biochar ecological system.

[0021] The application further provides an iron-rich biochar for water pollution control and ecological restoration, which is prepared by the preparation method.

[0022] The application further provides an application of the iron-rich biochar for water pollution control and ecological restoration, which is applied to water treatment to remove heavy metal ions in water.

[0023] The technical scheme of the application achieves the following beneficial technical effects:

[0024] 1. The iron-rich plant absorbs iron elements during growth, so that the iron elements are enriched in the plant, and a high iron load is obtained, and the problem of uneven distribution of iron elements in the biochar caused by modification of exogenous substances is fundamentally avoided. The iron-rich biochar obtained by the iron-rich plant combined with the secondary carbonization process and the enhanced modification of the activation liquid has a large specific surface area, rich pore structure, and more adsorption sites and active functional groups, can effectively adsorb cadmium ions in water, and greatly improves the water purification effect.

[0025] 2. By micro-carbonization treatment, the biomass is preliminarily carbonized to form initial pores with certain structural strength, which is helpful for the activated liquid to fill the micro-carbonized biomass material, and the pore-expanding agent in the activated liquid mainly plays a role in gas production and pore expansion in the carbonization process, so that the biochar can obtain larger pore diameter and higher porosity, but as the carbonization proceeds, the structure after pore expansion is prone to collapse or pore shrinkage due to poor strength and support, which affects the pore expansion effect, and the polyvinyl alcohol is used to dope and coat the pore-expanding agent, which can form a strong carbonization skeleton at high temperature, combine with the biochar to form a three-dimensional porous structure, effectively support the pore structure after pore expansion, avoid the occurrence of pore collapse or pore shrinkage in the pore expansion process, and ensure the stability of the pore structure, thereby greatly improving the specific surface area of the biochar.

[0026] 3. By sulfonating modification of polyvinyl alcohol, the compatibility and infiltration performance of polyvinyl alcohol with biomass can be improved, so that the activated liquid can uniformly penetrate and effectively fill the biomass, and meanwhile, the 3-trihydroxysilyl-1-propanesulfonic acid introduced in the application has silicon hydroxyl and sulfonic acid groups, which have double reactivity, the sulfonic acid group can enhance the hydrophilicity and improve the infiltration effect, and the silicon hydroxyl can condense with each other to obtain dynamic reversible Si-O-Si crosslinking points, form a three-dimensional network elastomer, and make the PVA have certain flexibility and elasticity, improve the deformation ability of the material after pore expansion, and realize effective pore expansion of the pore-expanding agent. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The scanning electron microscope image of the iron-rich biochar prepared in Example 1. DETAILED DESCRIPTION

[0028] Example 1

[0029] An iron-rich biochar for water pollution control and ecological restoration is prepared by the following steps:

[0030] S1. Siberian Iris of Beijing nursery is used as plant raw material, washed with water, dried and ground, soaked in 1 mol / L NaOH solution for 4 h, filtered, dried, and pretreated powder is obtained;

[0031] S2. The pretreated powder is heated under nitrogen protection atmosphere, the heating temperature is 320 DEG C, and the heat preservation time is 30 min, the micro-carbonization treatment is carried out, the initial pore structure is formed, after cooling to room temperature, it is put into 40 DEG C activated liquid for 1 h, filtered, dried, and activated biomass is obtained; wherein the activated liquid is a mixed solution with a mass ratio of sulfonated modified polyvinyl alcohol and NaHCO3 of 2:1, and the mass fraction of sulfonated modified polyvinyl alcohol in the activated liquid is 5%;

[0032] S3. The activated biomass is subjected to secondary pyrolysis carbonization under a nitrogen protective atmosphere in a staged heating manner, including a pre-sintering stage and a final sintering stage: the pre-sintering temperature is 300 DEG C, the heating rate is 7.5 DEG C / min, and the holding time is 20 min; the final sintering temperature is 650 DEG C, the heating rate is 5 DEG C / min, and the holding time is 45 min; after the secondary pyrolysis carbonization is completed, cooling, sieving, and loading into a sample bag are performed to obtain the iron-rich biochar for water pollution control and ecological restoration;

[0033] The preparation of the sulfonated modified polyvinyl alcohol includes the following contents:

[0034] A1. 3-trihydroxysilyl-1-propanesulfonic acid is added dropwise into a polyvinyl alcohol aqueous solution to obtain a mixed solution, the mass fraction of the polyvinyl alcohol in the mixed solution is 8%, and the mass ratio of the polyvinyl alcohol to the 3-trihydroxysilyl-1-propanesulfonic acid is 2:1;

[0035] A2. The pH of the mixed solution is adjusted to 1-2 with hydrochloric acid, and heating is performed to 70 DEG C to perform a sulfonation reaction, the reaction time is 24 h, and a modified polyvinyl alcohol solution is obtained;

[0036] A3. The solvent in the modified polyvinyl alcohol solution is removed, and drying is performed to obtain the sulfonated modified polyvinyl alcohol.

[0037] Example 2

[0038] A method for preparing an iron-rich biochar for water pollution control and ecological restoration includes the following steps:

[0039] S1. Siberian Iris of Beijing nursery is used as a plant raw material, washed with water, dried and ground, soaked in a 0.5 mol / L KOH solution for 4 h, filtered, and dried to obtain pretreated powder;

[0040] S2. The pretreated powder is heated under a nitrogen protective atmosphere at a heating temperature of 300 DEG C for 30 min to perform microcarbonization treatment, and then soaked in an activation liquid at 40 DEG C for 1 h, filtered, and dried to obtain activated biomass; wherein the activation liquid is a mixed solution with a mass ratio of sulfonated modified polyvinyl alcohol to KHCO3 of 1:0.4, and the mass fraction of the sulfonated modified polyvinyl alcohol in the activation liquid is 4%;

[0041] S3. The activated biomass is subjected to secondary pyrolysis carbonization under a nitrogen protective atmosphere in a staged heating manner, including a pre-sintering stage and a final sintering stage: the pre-sintering temperature is 280 ℃, the heating rate is 5 ℃ / min, and the holding time is 25 min; the final sintering temperature is 600 ℃, the heating rate is 3 ℃ / min, and the holding time is 60 min; after the secondary pyrolysis carbonization is completed, cooling, sieving, and loading into a sample bag are performed to obtain the iron-rich biochar for water pollution control and ecological restoration;

[0042] The preparation of the sulfonated modified polyvinyl alcohol includes the following contents:

[0043] A1. 3-trihydroxysilyl-1-propanesulfonic acid is added dropwise into a polyvinyl alcohol aqueous solution to obtain a mixed solution, the mass fraction of polyvinyl alcohol in the mixed solution is 5%, and the mass ratio of polyvinyl alcohol to 3-trihydroxysilyl-1-propanesulfonic acid is 1:0.4;

[0044] A2. The pH of the mixed solution is adjusted to 1-2 with hydrochloric acid, and heating is performed to 60 ℃ to perform a sulfonation reaction, the reaction time is 30 h, and a modified polyvinyl alcohol solution is obtained;

[0045] A3. The solvent in the modified polyvinyl alcohol solution is removed, and drying is performed to obtain sulfonated modified polyvinyl alcohol.

[0046] Example 3

[0047] A method for preparing an iron-rich biochar for water pollution control and ecological restoration includes the following steps:

[0048] S1. Siberian Iris of Beijing nursery is used as a plant raw material, washed with water, dried and ground, soaked in a 2 mol / L NaOH solution for 4 h, filtered, and dried to obtain pretreated powder;

[0049] S2. The pretreated powder is heated under a nitrogen protective atmosphere at a heating temperature of 350 ℃ for 30 min to perform microcarbonization treatment, and then soaked in an activation liquid at 40 ℃ for 1 h, filtered, and dried to obtain activated biomass; wherein the activation liquid is a mixed solution with a mass ratio of sulfonated modified polyvinyl alcohol to NaHCO3 of 1:0.6, and the mass fraction of sulfonated modified polyvinyl alcohol in the activation liquid is 6%;

[0050] S3. The activated biomass is subjected to secondary pyrolysis carbonization under a nitrogen protective atmosphere in a staged heating manner, including a pre-sintering stage and a final sintering stage: the pre-sintering temperature is 320 DEG C, the heating rate is 10 DEG C / min, and the holding time is 15 min; the final sintering temperature is 700 DEG C, the heating rate is 8 DEG C / min, and the holding time is 30 min; after the secondary pyrolysis carbonization is completed, cooling, sieving, and loading into a sample bag are performed to obtain the iron-rich biochar for water pollution control and ecological restoration;

[0051] The preparation of the sulfonated modified polyvinyl alcohol includes the following contents:

[0052] A1. 3-trihydroxysilyl-1-propanesulfonic acid is added dropwise into the polyvinyl alcohol aqueous solution to obtain a mixed solution, the mass fraction of polyvinyl alcohol in the mixed solution is 10%, and the mass ratio of polyvinyl alcohol to 3-trihydroxysilyl-1-propanesulfonic acid is 1:0.6;

[0053] A2. The pH of the mixed solution is adjusted to 1-2 with hydrochloric acid, and heating is performed to 80 DEG C to perform a sulfonation reaction, the reaction time is 20 h, and a modified polyvinyl alcohol solution is obtained;

[0054] A3. The solvent in the modified polyvinyl alcohol solution is removed, and drying is performed to obtain sulfonated modified polyvinyl alcohol.

[0055] Comparative Example 1

[0056] The difference between the present comparative example and Example 1 is only that no microcarbonization treatment is performed, and the specific process is as follows:

[0057] An iron-rich biochar for water pollution control and ecological restoration is prepared from the following steps:

[0058] S1. Siberian Iris from a Beijing nursery is used as a plant raw material, washed with water, dried and ground, soaked in a 1 mol / L NaOH solution for 4 h, filtered, and dried to obtain pretreated powder;

[0059] S2. The pretreated powder is soaked in an activation liquid at 40 DEG C for 1 h, filtered, and dried to obtain activated biomass; the activation liquid is a mixed solution of sulfonated modified polyvinyl alcohol and NaHCO3 in a mass ratio of 2:1, and the mass fraction of sulfonated modified polyvinyl alcohol in the activation liquid is 5%;

[0060] S3. The activated biomass is pyrolyzed and carbonized under a nitrogen protective atmosphere by means of staged temperature rising, which includes two stages of pre-sintering and final sintering: the pre-sintering temperature is 300 DEG C, the temperature rising rate is 7.5 DEG C / min, the holding time is 20 min, the final sintering temperature is 650 DEG C, the temperature rising rate is 5 DEG C / min, the holding time is 45 min, after the pyrolysis and carbonization is completed, cooling, sieving, loading into a sample bag, and an iron-rich biochar for water pollution control and ecological restoration is obtained;

[0061] The preparation of the sulfonated modified polyvinyl alcohol includes the following contents:

[0062] A1. 3-trihydroxysilyl-1-propanesulfonic acid is added dropwise into the polyvinyl alcohol aqueous solution to obtain a mixed solution, the mass fraction of polyvinyl alcohol in the mixed solution is 8%, and the mass ratio of polyvinyl alcohol to 3-trihydroxysilyl-1-propanesulfonic acid is 2:1;

[0063] A2. The pH of the mixed solution is adjusted to 1-2 with hydrochloric acid, and heated to 70 DEG C for sulfonation reaction, the reaction time is 24 h, and a modified polyvinyl alcohol solution is obtained;

[0064] A3. The solvent in the modified polyvinyl alcohol solution is removed, and dried to obtain sulfonated modified polyvinyl alcohol.

[0065] Comparative Example 2

[0066] The difference between this comparative example and Example 1 is only that no modified polyvinyl alcohol is added, and the specific process is as follows:

[0067] An iron-rich biochar for water pollution control and ecological restoration is prepared by the following steps:

[0068] S1. Siberian Iris of Beijing nursery is used as plant raw material, washed with water, dried and ground, soaked in 1 mol / L NaOH solution for 4 h, filtered and dried to obtain pretreated powder;

[0069] S2. The pretreated powder is heated under a nitrogen protective atmosphere, the heating temperature is 320 DEG C, and the holding time is 30 min, to perform microcarbonization treatment to form a preliminary pore structure, and after cooling to room temperature, it is soaked in a 40 DEG C NaHCO3 solution with a mass fraction of 2.5% for 1 h, filtered and dried to obtain activated biomass;

[0070] S3. The activated biomass is subjected to secondary pyrolysis carbonization under a nitrogen protective atmosphere by means of staged heating, which includes two stages of pre-sintering and final sintering: the pre-sintering temperature is 300 ℃, the heating rate is 7.5 ℃ / min, and the holding time is 20 min; the final sintering temperature is 650 ℃, the heating rate is 5 ℃ / min, and the holding time is 45 min; after the secondary pyrolysis carbonization is completed, cooling, sieving, and loading into a sample bag are performed to obtain the iron-rich biochar for water pollution control and ecological restoration.

[0071] Comparative Example 3

[0072] The difference between this comparative example and Example 1 is only that the polyvinyl alcohol is not modified, and the specific process is as follows:

[0073] An iron-rich biochar for water pollution control and ecological restoration is prepared by the following steps:

[0074] S1. Siberian Iris from a Beijing nursery is used as a plant raw material, washed with water, dried and ground, soaked in a 1 mol / L NaOH solution for 4 h, filtered, and dried to obtain pretreated powder;

[0075] S2. The pretreated powder is heated under a nitrogen protective atmosphere at a heating temperature of 320 ℃ for 30 min to perform microcarbonization treatment to form a preliminary pore structure; after cooling to room temperature, the activated biomass is obtained by soaking in an activation liquid at 40 ℃ for 1 h, filtering, and drying; the activation liquid is a mixed solution of polyvinyl alcohol and NaHCO3 with a mass ratio of 2:1, and the mass fraction of polyvinyl alcohol in the activation liquid is 5%;

[0076] S3. The activated biomass is subjected to secondary pyrolysis carbonization under a nitrogen protective atmosphere by means of staged heating, which includes two stages of pre-sintering and final sintering: the pre-sintering temperature is 300 ℃, the heating rate is 7.5 ℃ / min, and the holding time is 20 min; the final sintering temperature is 650 ℃, the heating rate is 5 ℃ / min, and the holding time is 45 min; after the secondary pyrolysis carbonization is completed, cooling, sieving, and loading into a sample bag are performed to obtain the iron-rich biochar for water pollution control and ecological restoration.

[0077] Comparative Example 4

[0078] The difference between this comparative example and Example 1 is only that the microcarbonization treatment is not performed, and the polyvinyl alcohol is not modified, and the specific process is as follows:

[0079] An iron-rich biochar for water pollution control and ecological restoration is prepared by the following steps:

[0080] S1. Using Siberian iris from Beijing Nursery as plant material, after rinsing with water, it was dried and ground, soaked in a 1 mol / L NaOH solution for 4 h, filtered, and dried to obtain pretreated powder.

[0081] S2. The pretreated powder is soaked in an activation solution at 40℃ for 1 hour, filtered, and dried to obtain activated biomass; wherein the activation solution is a mixed solution of polyvinyl alcohol and NaHCO3 in a mass ratio of 2:1, and the mass fraction of polyvinyl alcohol in the activation solution is 5%;

[0082] S3. The activated biomass was subjected to secondary pyrolysis carbonization under a nitrogen protective atmosphere using a staged heating method. The staged heating included two stages: pre-sintering and final sintering. The pre-sintering temperature was 300 ℃, the heating rate was 7.5 ℃ / min, and the holding time was 20 min. The final sintering temperature was 650 ℃, the heating rate was 5 ℃ / min, and the holding time was 45 min. After the secondary pyrolysis carbonization was completed, the biomass was cooled, sieved, and placed into a sample bag to obtain iron-rich biochar for water pollution control and ecological restoration.

[0083] Proof of effectiveness

[0084] The iron-rich biochar prepared in Examples 1-3 and Comparative Examples 1-4 were used to prepare samples, and their specific surface area and Cd were measured. 2+ The removal rate was measured, and the specific test results are shown in Table 1:

[0085] Cd(NO3)2·4H2O was used to prepare Cd 2+ A 20 mg / L solution was prepared using NaNO3 as the supporting electrolyte, and the pH of the solution was adjusted to 5.5 with dilute HNO3 and NaOH. 0.02 g of the iron-rich biochar prepared in Examples 1-3 and Comparative Examples 1-4 was weighed into a centrifuge tube, and 20 ml of prepared Cd2O3 solution was added. 2+ The solution was shaken at 20°C for 8 h in a constant temperature shaking incubator, centrifuged at 4000 r / min for 5 min, and the supernatant was collected. Cd was determined by inductively coupled plasma mass spectrometry (ICP-MS). 2+ The mass concentration Ce is calculated using the following formula: Removal rate RE = (C0 - Ce) / C0 × 100%, where C0 and Ce are Cd and Ce, respectively. 2+ Initial and adsorption equilibrium concentrations (mg / L).

[0086] Table 1

[0087]

[0088] As can be seen from Examples 1-3 and Comparative Examples 1-4, and in conjunction with the data in Table 1, the iron-rich biochar prepared by this invention (Examples 1-3) has a specific surface area of ​​367 m². 2 / g or more, Cd 2+ The removal rate reached 98.9% or more, with a high specific surface area and excellent Cd 2+ Adsorption capacity.

[0089] Obviously, the above examples are only examples for clearly illustrating, but not limitation to the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments are not required to be exhausted, and the obvious changes or variations derived therefrom are still within the protection scope of the patent application claims.

Claims

1. A method for preparing iron-rich biochar for water pollution control and ecological restoration, characterized in that, The method comprises the following steps: S1. crushing and treating the plant rich in iron elements, soaking in alkaline solution, filtering, and drying to obtain pretreated powder; S2. heating the pretreated powder in a protective atmosphere, performing micro-carbonization treatment to form a preliminary pore structure, and then soaking in an activation solution after cooling, filtering, and drying to obtain activated biomass; in the activation solution, the mass fraction of sulfonated modified polyvinyl alcohol is 4-6%, the pore expanding agent is one or a mixture of both of NaHCO3 and KHCO3, and the mass ratio of sulfonated modified polyvinyl alcohol to pore expanding agent is 1:(0.4-0.6); the heating temperature is 300-350 ℃; S3. performing secondary pyrolysis carbonization treatment on the activated biomass in a protective atmosphere, and cooling to obtain iron-rich biochar for water pollution control and ecological restoration; the secondary pyrolysis carbonization is performed in a staged heating manner, which comprises pre-sintering and final sintering: the pre-sintering temperature is 280-320 ℃, the heating rate is 5-10 ℃ / min, and the holding time is 15-25 min; the final sintering temperature is 600-700 ℃, the heating rate is 3-8 ℃ / min, and the holding time is 30-60 min; The preparation of sulfonated modified polyvinyl alcohol comprises the following steps: A1. adding 3-trihydroxysilyl-1-propanesulfonic acid dropwise into a polyvinyl alcohol aqueous solution to obtain a mixed solution; A2. adjusting the pH of the mixed solution, heating, and performing sulfonation reaction to obtain a modified polyvinyl alcohol solution; A3. removing the solvent in the modified polyvinyl alcohol solution and drying to obtain sulfonated modified polyvinyl alcohol.

2. The method according to claim 1, wherein the method comprises the following steps: 1) mixing iron-containing material with biomass to form a mixture; 2) drying the mixture; 3) heating the mixture to form a mixture of iron-containing material and biomass; 4) carbonizing the mixture of iron-containing material and biomass to form the iron-enriched biochar. In the mixed solution of step A1, the mass fraction of polyvinyl alcohol is 5-10%, and the mass ratio of polyvinyl alcohol to 3-trihydroxysilyl-1-propanesulfonic acid is 1:(0.4-0.6).

3. The method according to claim 1, wherein the method is characterized in that, In step A2, the pH of the mixed solution is adjusted to 1-2, the heating temperature is 60-80 ℃, and the reaction time is 20-30 h.

4. The method according to claim 1, wherein the method is characterized in that, The plant rich in iron elements is Siberian Iris planted in an acidic iron-rich environment.

5. An iron-rich biochar for water pollution control and ecological restoration, characterized in that, The iron-rich biochar is prepared by the preparation method of any one of claims 1-4.

6. The use of iron-rich biochar for water pollution control and ecological restoration, characterized in that, The iron-rich biochar of claim 5 is used for removing heavy metal ions in water in water pollution control and ecological restoration.

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