Goethite-humic acid-silica composite material, method for preparing the same, and use thereof

Abstract

The application discloses a ferrihydrite-humic acid-silicon dioxide composite material and a preparation method and application thereof, and belongs to the technical field of heavy metal pollution remediation materials. The composite material is prepared by compounding ferrihydrite, humic acid and silicon dioxide in a mass ratio of 8:1:(0.25-1) through a coprecipitation method. The core of the application is that the silicon dioxide is introduced as a skeleton, which effectively prevents the agglomeration of ferrihydrite particles, optimizes the distribution of humic acid, solves the problem of adsorption site competition in a binary composite material, and realizes the synergistic effect of the three. The composite material has the characteristics of large specific surface area, rich functional groups and good stability, exhibits high efficient synchronous adsorption capacity for anionic arsenic and cationic cadmium in water, has large adsorption capacity and fast rate, and is particularly suitable for efficient remediation of arsenic and cadmium composite pollution environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heavy metal pollution remediation materials, in particular to a ferrihydrite-humic acid-silicon dioxide composite material and a preparation method and application thereof. BACKGROUND

[0002] Due to conventional mining activities, heavy metal pollution problems are increasingly serious, among which arsenic (As) and cadmium (Cd) are two typical sulfur affinity elements, which often coexist in sulfide minerals, especially in industrial and mining intensive areas, and the enrichment concentration of As and Cd in water sediments can reach several tens of times of the background value, resulting in pollution problems in the water and soil environment. As and Cd can form ionic state complex pollution in the environment, enter the human body through water organisms (such as algae-fish food chain), and induce cancer and liver and kidney damage. Moreover, As mainly exists in the form of oxygen-containing arsenic ions in the environment, and Cd mainly exists in the form of metal cations, and the behaviors and transformation mechanisms of As and Cd in the environment are different, so the research on the remediation of As and Cd complex pollution has always been a hot spot and difficulty.

[0003] At present, common heavy metal remediation technologies mainly include chemical precipitation, adsorption, ecological remediation, and electrochemistry, etc. Among them, the adsorption method mainly uses modified materials or natural minerals to specifically capture heavy metal ions, and through surface complexation, ion exchange and other mechanisms, it can realize the simultaneous adsorption of arsenic and cadmium, has low cost, and produces small amount of sludge, thereby significantly reducing the risk of secondary pollution. Common adsorption materials mainly include metal oxides, biochar or natural minerals (zeolite, montmorillonite), etc., among which metal oxides have a large specific surface area and good treatment effect on As, Cd and other heavy metals in the environment. Iron oxides widely exist in the environment and have various forms, among which ferrihydrite (Fh) is a popular material for heavy metal treatment due to its high reactivity, large specific surface area, and rich pore structure. Ferrihydrite can control the migration and transformation of As, Cd and other heavy metal ions, and adsorb heavy metals through ligand exchange reaction or complexation reaction. However, as a single composite agent, ferrihydrite is unstable and is easily transformed into hematite or goethite which has weaker adsorption capacity, and is prone to aggregation, thereby reducing the adsorption area. Therefore, there are many researches on the synthesis of composite materials using ferrihydrite as a base material. At present, the common method is to combine ferrihydrite and humic acid (HA), and the combination of ferrihydrite and humic acid can significantly inhibit the transformation of ferrihydrite, making the structure of ferrihydrite more stable. The combination of the two provides a rougher surface of the composite and more functional groups, thereby improving the adsorption capacity and stability of the composite material. However, the problem of ferrihydrite aggregation has not been solved, and humic acid occupies part of the binding sites of ferrihydrite, which has a certain competitive effect with heavy metals. SUMMARY

[0004] The application aims to provide a ferrihydrite-humic acid-silicon dioxide composite material and a preparation method and application thereof.

[0005] To achieve the above-mentioned purpose, the application provides a preparation method of a ferrihydrite-humic acid-silicon dioxide composite material, comprising the following steps:

[0006] (1) preparing ferrihydrite:

[0007] FeCl3·6H2O is dissolved in deionized water, and the pH is adjusted to 7.0±0.2 by using a NaOH solution; after stirring and reaction, the red-brown ferrihydrite powder is obtained through centrifugation, washing and freeze-drying;

[0008] (2) preparing a humic acid solution:

[0009] The humic acid is dissolved in a NaOH solution to prepare the humic acid solution;

[0010] (3) preparing a ferrihydrite-humic acid-silicon dioxide composite material:

[0011] The ferrihydrite obtained in step (1), the humic acid solution obtained in step (2) and silicon dioxide are mixed, and the pH is adjusted to 7.0±0.2; after stirring and reaction, the black-brown ferrihydrite-humic acid-silicon dioxide composite material is obtained through centrifugation, washing and freeze-drying.

[0012] Preferably, the solid mass ratio of the ferrihydrite, the humic acid and the silicon dioxide is 8:1:0.25-1.

[0013] Preferably, the solid mass ratio of the ferrihydrite, the humic acid and the silicon dioxide is 8:1:0.25.

[0014] Preferably, in steps (1) and (2), the molar concentration of the NaOH solution is 1 moL / L.

[0015] Preferably, in step (2), the mass concentration of the humic acid solution is 1 g / L.

[0016] The application further provides a ferrihydrite-humic acid-silicon dioxide composite material prepared by the above-mentioned preparation method.

[0017] The application further provides application of the ferrihydrite-humic acid-silicon dioxide composite material in remediation of As and Cd combined pollution in the environment.

[0018] The core improvement of the application is that silicon dioxide (SiO2) is introduced on the basis of ferrihydrite (Fh)-humic acid (HA), and the SiO2 itself has a high specific surface area and a porous structure, and when it is added in the co-precipitation process, an inert and rigid three-dimensional network skeleton is formed. Physically, the space steric hindrance is formed to block the ferrihydrite nanoparticles, preventing them from directly contacting and agglomerating. Meanwhile, the huge surface energy provides more attachment sites for the humic acid, so that the humic acid is uniformly distributed on the surface of the ferrihydrite, reduces the occupation of the humic acid to the adsorption sites of the ferrihydrite, and solves the problem of adsorption site competition. Therefore, the effective specific surface area and porosity of the composite material are greatly increased, so that more active sites can be exposed and contacted with the pollutants.

[0019] Therefore, the ferrihydrite-humic acid-silicon dioxide composite material, the preparation method and the application thereof have the following beneficial effects:

[0020] (1) synergistic effect and structure optimization: the application creatively introduces silicon dioxide on the basis of the ferrihydrite-humic acid binary system, the silicon dioxide acts as an inert skeleton, effectively prevents the agglomeration of the ferrihydrite nanoparticles, increases the specific surface area and porosity of the composite material, and exposes more active sites. Meanwhile, it optimizes the distribution of the humic acid in the composite material, reduces the shielding of the humic acid to the iron hydroxyl sites on the surface of the ferrihydrite, and realizes the functional complementation and synergistic effect of the ferrihydrite, the humic acid and the silicon dioxide.

[0021] (2) excellent simultaneous adsorption performance: the composite material prepared by the application has high adsorption capacity and fast adsorption rate for arsenic in anion form and cadmium in cation form. Under the optimal ratio, the theoretical maximum adsorption capacity of the composite material for arsenic is 83.33 mg / g, and the theoretical maximum adsorption capacity of the composite material for cadmium is 10.00 mg / g, which is significantly better than single ferrihydrite and binary composite material.

[0022] (3) stable and efficient adsorption: the adsorption of the composite material for arsenic mainly relies on the ligand exchange of the surface of the ferrihydrite, and the adsorption of the composite material for cadmium mainly relies on the complexation and chelation of the functional groups of the humic acid. The addition of silicon dioxide enables the two adsorption mechanisms to fully play on a more optimal structure platform, and the adsorption process is more in line with the Freundlich model, which is a multilayer chemical adsorption on a non-uniform surface, has strong binding capacity, and is stable, thereby effectively solving the problem of unstable adsorption of pure ferrihydrite for cadmium.

[0023] (4) Environment-friendly and economically feasible: the raw materials used in the application are environment-friendly materials, widely available, low in cost, simple in preparation process, mild in conditions, easy to scale up production, and have good industrial application potential and market prospect.

[0024] The technical solutions of the application are described in further detail below with reference to the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Figure is a comparison chart of the removal rates of As and Cd by the FAS composite materials with different proportions in the application examples 1-4;

[0026] Figure 2 Figure is a pseudo-first-order and pseudo-second-order kinetics fitting curve diagram of the adsorption of As by the Fh material in the application comparative example 2;

[0027] Figure 3 Figure is a pseudo-first-order and pseudo-second-order kinetics fitting curve diagram of the adsorption of Cd by the Fh material in the application comparative example 2;

[0028] Figure 4 Figure is a pseudo-first-order and pseudo-second-order kinetics fitting curve diagram of the adsorption of As by the FA material in the application comparative example 1;

[0029] Figure 5 Figure is a pseudo-first-order and pseudo-second-order kinetics fitting curve diagram of the adsorption of Cd by the FA material in the application comparative example 1;

[0030] Figure 6 Figure is a pseudo-first-order and pseudo-second-order kinetics fitting curve diagram of the adsorption of As by the FAS-1 material in the application example 1;

[0031] Figure 7 Figure is a pseudo-first-order and pseudo-second-order kinetics fitting curve diagram of the adsorption of Cd by the FAS-1 material in the application example 1;

[0032] Figure 8 Figure is an adsorption kinetics curve diagram of As by the Fh material in the application comparative example 2, the FA material in the application comparative example 1 and the FAS-1 material in the application example 1;

[0033] Figure 9 Figure is an adsorption kinetics curve of Cd by the Fh material in the application comparative example 2, the FA material in the application comparative example 1 and the FAS-1 material in the application example 1. DETAILED DESCRIPTION

[0034] The technical solutions of the present application are further described below by means of the drawings and examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application shall be equivalent replacements and shall be included in the protection scope of the present application. In addition, it should be understood that after reading the content of the present application, those skilled in the art can make various modifications or modifications to the present application, and these equivalent forms also fall within the scope defined by the claims attached to the present application and are within the protection scope of the present application.

[0035] Reference to "embodiment" in this text means that the specific features, structures or properties described in connection with the embodiment can be included in at least one embodiment of the present application. The word "embodiment" appearing at various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit the independence or association between other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the technical features mentioned in each embodiment can be combined in any way to form a corresponding implementable technical solution.

[0036] Unless otherwise defined, the meanings of the technical terms used herein are the same as those commonly understood by those skilled in the art to which the present application belongs; the use of related terms herein is only for the purpose of describing specific embodiments and is not intended to limit the present application.

[0037] Unless otherwise specified, the reagents, instruments, equipment, etc. used in the present application are the reagents, instruments and equipment commonly used by those skilled in the art; the test standards use the national standards or international standards commonly used in the art, and no redundant description is made here.

[0038] The raw materials and equipment used in the following examples are as follows:

[0039] Raw materials: ferric chloride hexahydrate (FeCl3·6H2O, analytical pure), sodium hydroxide (NaOH, analytical pure), humic acid (HA, analytical pure), silicon dioxide (SiO2, gas phase 20 nm, analytical pure), deionized water.

[0040] Equipment: constant temperature magnetic stirrer, centrifuge (speed 0~10000r / min), freeze dryer, pH meter, electronic balance, inductively coupled plasma mass spectrometer (ICP-MS, used for determination of As, Cd concentration).

[0041] Example 1

[0042] The present embodiment provides a preparation method of a ferrihydrite-humic acid-silicon dioxide composite material, which specifically comprises the following steps:

[0043] (1) Preparation of ferrihydrite by coprecipitation

[0044] Dissolve 40 g of FeCl3·6H2O in 500 ml of deionized water, and adjust the pH of the FeCl3·6H2O solution to 7.0±0.2 with a 1 mol / L NaOH solution. Stir the solution on a constant-temperature magnetic stirrer for 2 h, centrifuge at 4000 r for 5 min, remove the supernatant, and repeat the centrifugation three times to wash the precipitate. Then, freeze-dry the precipitate in a freeze dryer for 24 h to obtain a reddish-brown powder of ferrihydrite, which is ground and stored in a sealed container at 4℃.

[0045] (2) Preparation of a humic acid solution

[0046] Dissolve HA with 100 ml of a 1 mol / L NaOH solution to prepare a 1 g / L HA solution for use.

[0047] (3) Preparation of a ferrihydrite-humic acid-silicon dioxide composite material

[0048] Add Fh, the HA solution, and silicon dioxide in a solid mass ratio of 8:1:0.25, and adjust the pH of the solution to 7.0±0.2. Stir the solution on a constant-temperature magnetic stirrer for 2 h, centrifuge at 4000 r for 10 min, remove the supernatant, repeat the centrifugation three times to wash the precipitate, and freeze-dry the precipitate in a freeze dryer for 24 h to obtain a blackish-brown ferrihydrite-humic acid-silicon dioxide composite powder material FAS-1, which is ground and stored in a sealed container at 4℃.

[0049] Example 2

[0050] The present example provides a method for preparing a ferrihydrite-humic acid-silicon dioxide composite material, which differs from Example 1 only in that in step (3), Fh, the HA solution, and silicon dioxide are added in a solid mass ratio of 8:1:0.5, and finally a blackish-brown ferrihydrite-humic acid-silicon dioxide composite powder material FAS-2 is obtained.

[0051] Example 3

[0052] The present example provides a method for preparing a ferrihydrite-humic acid-silicon dioxide composite material, which differs from Example 1 only in that in step (3), Fh, the HA solution, and silicon dioxide are added in a solid mass ratio of 8:1:0.75, and finally a blackish-brown ferrihydrite-humic acid-silicon dioxide composite powder material FAS-3 is obtained.

[0053] Example 4

[0054] The embodiment provides a preparation method of a ferrihydrite-humic acid-silicon dioxide composite material, and the difference from the embodiment 1 is that in step (3), the Fh, the HA solution and the silicon dioxide are mixed according to a solid mass ratio of 8:1:1, and finally a black-brown ferrihydrite-humic acid-silicon dioxide composite powder material FAS-4 is prepared.

[0055] Comparative example 1

[0056] The difference between the comparative example and the embodiment 1 is that no silicon dioxide is added, the mass ratio of the fixed ferrihydrite to the humic acid is 8:1, and a ferrihydrite-humic acid binary composite material is prepared and marked as FA.

[0057] Comparative example 2

[0058] The difference between the comparative example and the embodiment 1 is that the pure ferrihydrite prepared in step (1) of the embodiment 1 is directly used and marked as Fh.

[0059] The composite materials prepared in the embodiment 1-4 are added into a composite pollution solution with an initial concentration of 50 mg / L As and 15 mg / L Cd at a dosage of 1 g / L, and oscillation is carried out at 25 DEG C, pH=7 and 150 r / min for 48 h. The supernatant is taken by centrifugation to measure the residual concentrations of As and Cd, the removal rate is calculated, and the results are shown in Table 2. Figure 1 As can be seen from Table 2, Figure 1 When the SiO2 addition ratio is 0.25 (namely FAS-1, the ratio is 8:1:0.25), the synchronous removal effect on As and Cd is best, and the comprehensive performance is better than that of other ratios.

[0060] In order to further explore the adsorption behavior and mechanism of the FAS-1 composite material prepared in the embodiment 1 in the arsenic-cadmium composite pollution system, isothermal adsorption experiments are carried out, and the materials of the comparative example 1 and the comparative example 2 are compared. The As and Cd composite pollution solutions with five concentration gradients shown in Table 1 are set.

[0061] Table 1: Concentration of composite pollution liquid

[0062]

[0063] Under constant temperature conditions, the experimental data are fitted by using a Langmuir isothermal adsorption model and a Freundlich isothermal adsorption model respectively, so as to reveal the adsorption mechanism. Among them,

[0064] The formula of the Langmuir isothermal adsorption model is as follows:

[0065] ;

[0066] In the formula, Q eQe is the adsorption capacity of the adsorbent for the adsorbate at the adsorption equilibrium, with the unit of mg / g; Qm m Qm is the maximum adsorption capacity of the adsorbent (the maximum adsorption capacity when a monolayer is formed on the surface of the adsorbent), with the unit of mg / g; K L K is the Langmuir adsorption constant, with the unit of L / mg, which is related to the binding energy between the adsorbent and the adsorbate and the adsorption heat; C e Ce is the equilibrium concentration of the adsorbate in the solution at the adsorption equilibrium, with the unit of mg / L.

[0067] The formula of the Freundlich isothermal adsorption model is as follows:

[0068] ;

[0069] In the formula, K F is the Freundlich adsorption constant, which represents the adsorption capacity; n is the adsorption strength parameter, which reflects the difficulty of the adsorption process. Q e Qe is the adsorption capacity of the adsorbent for the adsorbate at the adsorption equilibrium, with the unit of mg / g; C e Ce is the equilibrium concentration of the adsorbate in the solution at the adsorption equilibrium, with the unit of mg / L.

[0070] The isothermal adsorption model fitting parameters of each material for As and Cd are shown in Tables 2 and 3, respectively.

[0071] Table 2: As isothermal adsorption model fitting parameters

[0072]

[0073] Table 3: Cd isothermal adsorption model fitting parameters

[0074]

[0075] According to the Langmuir model fitting results, the theoretical maximum adsorption capacity (Q m ) of the FAS-1 material of Example 1 of the present application for As is 83.33 mg / g, which is higher than that of the pure ferrihydrite Fh (79.37 mg / g) and the binary composite material FA (74.63 mg / g). This indicates that, after introducing SiO2 by coprecipitation, the structure of the material is optimized, and the adsorption capacity for As in the composite system is effectively improved. For the FAS-1 and FA materials, the fitting correlation coefficient R 2 of the Freundlich model (both 0.99) is better than that of the Langmuir model (0.95 and 0.96), indicating that the adsorption process is more consistent with the multilayer chemical adsorption on a non-uniform surface, which is consistent with the rich functional groups and complex microstructure on the surface of the composite material.

[0076] The maximum theoretical adsorption capacity (Q m ) of FAS-1 material for Cd reached 10.00 mg / g, which was much higher than that of FA (7.73 mg / g) and nearly 4 times of that of Fh (2.64 mg / g). This result clearly proved that the introduction of humic acid (HA) greatly enhanced the capture of Cd through its strong complexation, and the addition of SiO2 further optimized the structure, making the adsorption performance optimal. The adsorption of the material for Cd could be well described by the Freundlich model (R 2 ≥ 0.97), which strongly proved that its adsorption behavior was a typical multilayer adsorption. In addition, the Langmuir affinity constant K L (0.70) of FAS-1 was also much higher than that of Fh (0.17) and FA (0.42), indicating that FAS-1 material had the strongest binding capacity with Cd ions.

[0077] Among them, the isothermal adsorption of Fh material for As and Cd is more in line with the Langmuir type model, indicating that the surface of Fh is relatively uniform, mainly single-layer chemical adsorption. The surface of Fh is mainly iron hydroxyl functional groups, and the adsorption sites for As and Cd are relatively simple and have similar energy, which meets the ideal assumption of the Langmuir model, which is a typical adsorption behavior of inorganic oxides.

[0078] FA and FAS-1 material are more in line with the Freundlich model adsorption, and the surface becomes highly non-uniform, and the adsorption mechanism becomes complex. Because after the introduction of humic acid (HA), the surface of the material is no longer single iron hydroxyl, but is covered with various functional groups (such as carboxyl, phenolic hydroxyl, etc.) on the HA macromolecule, so the adsorption behavior changes from the ideal L type to the F type which is more in line with the actual complex situation, that is, multi-point and multi-molecular layer adsorption on the non-uniform surface. The addition of SiO2 further separates Fh and HA as a skeleton, increasing the complexity of the material surface and the accessibility of active sites. This makes the non-uniform characteristics of the material play to the extreme. Especially for the adsorption of Cd, the R 2 of the Freundlich model reaches a perfect 1.00, which strongly proves that the adsorption of FAS-1 material is a typical multilayer adsorption process on a highly complex non-uniform surface.

[0079] To verify the effectiveness of the embodiments of the present application, we carried out adsorption kinetics experiments on three materials Fh, FA and FAS-1. The common adsorption kinetics model, pseudo-first-order (PFO) kinetics model and pseudo-second-order (PSO) kinetics model, were used to fit the kinetics process of As and Cd adsorption by Fh, FA and FAS, and the adsorption rate and mechanism of As and Cd by the three materials were analyzed and summarized. The pseudo-first-order kinetics model (PFO) is usually related to physical adsorption or diffusion steps, while the pseudo-second-order kinetics model (PSO) represents that chemical adsorption is the dominant process. The above three materials were respectively added to the composite pollution solution containing As and Cd (initial concentration As = 50 mg / L, Cd = 15 mg / L), continuously oscillated at constant temperature (25℃), sampled at preset time points, and the residual concentration of As and Cd in the solution was measured, and the adsorption capacity and removal rate were calculated.

[0080] The fitting results are shown in Figures 2-7 and Table 4, from which Figures 2-7 and Table 4, the fitting degree of PSO equation is higher than that of PFO for As and Cd adsorption by Fh, FA and FAS-1, which indicates that the rate controlling step of As and Cd by the three materials is chemical adsorption, i.e. chemical bonding (such as complexation, ion exchange, etc.) between adsorbate and material surface functional groups. Among them, Fh adsorption is mainly through ligand exchange to form stable inner circle complex on the surface of Fh, which is a high affinity chemical bond, which is the fundamental reason why Fh can efficiently remove arsenic. However, pure Fh cannot stably adsorb Cd and cause competitive desorption, while FA and FAS-1 with HA can achieve efficient and stable adsorption of Cd, which conforms to the pseudo-second-order kinetics model. Mainly because Cd 2+ exists in the form of Cd 2+ HA is a natural macromolecular polymer, and these functional groups are excellent metal ion chelating sites. Cd 2+ is firmly captured mainly through ion exchange and complexation / chelation with these functional groups. Finally, SiO2 is introduced as the skeleton, which not only disperses Fh, but also provides more attachment surface for HA molecules, so as to maximize the exposure of internal chelating sites such as carboxyl and phenolic hydroxyl groups, greatly improving the capture efficiency and capacity of As and Cd, which is the fundamental reason why FAS-1 performs much better than FA.

[0081] Table 4: Adsorption kinetics fitting degree R 2

[0082]

[0083] As Figure 8As shown, the three materials have similar adsorption trends for As, which are fast at first and then slow. Among them, the FAS-1 material is always at the top in the whole adsorption process, has the fastest adsorption rate and the highest final removal rate (96.76% at 2880 min), and the performance of Fh is close to that of FA, but the adsorption performance of the FA material is slightly lower than that of Fh, which is consistent with the isothermal adsorption experiment results, indicating that the introduction of Fh into the HA material may tightly wrap or cover the surface of the Fh nanoparticles through electrostatic attraction, hydrogen bonding or complexation, etc. Although this introduces new functional groups, it also partially occupies some of the iron hydroxyl sites on the surface of Fh, resulting in a decrease in the adsorption capacity of As, while the introduction of SiO2 skeleton into the FAS-1 material optimizes the material structure, effectively prevents material aggregation, greatly increases the contact area of the composite material, and thus increases the adsorption capacity of As.

[0084] As shown in Figure 9 The adsorption of Cd on the Fh material shows a significant desorption phenomenon, and the adsorption rate decreases from 30.83% to 11.34% finally, while the FA and FAS-1 materials do not show desorption phenomenon, and their adsorption rates monotonically increase with time and tend to be stable. This proves that the introduction of HA successfully solves the fundamental defect that Fh cannot stably adsorb Cd in the composite system. The carboxyl, phenolic hydroxyl and other functional groups on HA provide stable and high-affinity adsorption sites for Cd through strong chelation, so that it is no longer displaced by As.

[0085] Among them, the performance of the FAS-1 material again surpasses that of the FA material, and is more stable and efficient than the FA material. The FAS not only has the fastest initial adsorption rate (the removal rate reaches 44.94% in 5 minutes), but also has the highest equilibrium adsorption rate (74.86% finally), which is much higher than that of FA (56.96%). This shows that the introduction of SiO2, by constructing a more excellent dispersion and porous structure, makes the HA functional groups more uniformly dispersed and has less steric hindrance, thereby maximizing the adsorption capacity for Cd.

[0086] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit them. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can still be modified or equivalently replaced, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for preparing a hydroferroic acid-humic acid-silica composite material for the remediation of As and Cd combined pollution in the environment, characterized in that, Includes the following steps: (1) Preparation of ferrohydrate: FeCl3·6H2O was dissolved in deionized water, and the pH was adjusted to 7.0±0.2 with NaOH solution. After stirring and reacting, the mixture was centrifuged, washed, and freeze-dried to obtain reddish-brown ferrohydrate powder. (2) Preparation of humic acid solution: Humic acid solution is prepared by dissolving humic acid in NaOH solution; (3) Preparation of ferrous ore-humic acid-silica composite material: The ferrohydrate obtained in step (1), the humic acid solution obtained in step (2) and silica were mixed, the pH was adjusted to 7.0±0.2, and after stirring and reaction, the mixture was centrifuged, washed and freeze-dried to obtain a dark brown ferrohydrate-humic acid-silica composite material. The solid mass ratio of ferrohydrate, humic acid and silica is 8:1:0.25~1.

2. The preparation method of the ferroalloy-humic acid-silica composite material for remediation of As and Cd combined pollution in the environment according to claim 1, characterized in that: The solid mass ratio of ferrohydrate, humic acid and silica is 8:1:0.

25.

3. The method for preparing a hydroferroic acid-humic acid-silica composite material for remediation of As and Cd combined pollution in the environment according to claim 1, characterized in that: In both steps (1) and (2), the molar concentration of the NaOH solution is 1 mol / L.

4. The method for preparing a ferrous ore-humic acid-silica composite material for remediation of As and Cd combined pollution in the environment according to claim 1, characterized in that: In step (2), the mass concentration of the humic acid solution is 1 g / L.

5. A hydrofer emery-humic acid-silica composite material for the remediation of As and Cd combined pollution in the environment, characterized in that: The composite material is prepared by the preparation method according to any one of claims 1-4.

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