A method for applying hydrothermal carbon-supported ferrooxate ore to heavy metal adsorption

Abstract

This invention discloses a method for applying hydrothermally loaded carbon oxalate ore to heavy metal adsorption. This method is the first to discover the role of hydrothermally loaded carbon oxalate ore in the adsorption of arsenic and cadmium, and particularly reveals its synergistic adsorption effect on arsenic and cadmium. Specifically, the presence of arsenic promotes the adsorption of cadmium. This invention avoids competitive adsorption between cadmium and arsenic, exhibiting high adsorption capacity for both, providing a new approach for the rapid and efficient simultaneous treatment of arsenic and cadmium in water.

Description

Technical Field

[0001] This invention relates to heavy metal adsorbents, and particularly to the application of hydrothermally carbon-supported ferrooxate in heavy metal adsorption. Background Technology

[0002] Cadmium and arsenic are two of the most typical heavy metals in wastewater pollution. They are highly biotoxic, difficult to degrade, and have a bioaccumulation effect, allowing them to persist in the environment for a long time and posing a serious threat to ecosystems and human health. Currently, the main methods for removing cadmium and arsenic ions from the aquatic environment include chemical precipitation, ion exchange, electrochemical methods, membrane separation, and adsorption. Among these, adsorption is the most widely used treatment technology in production activities because it is simple to operate, economical, and has a good removal effect on low concentrations of metal ions.

[0003] Traditional adsorption materials often cannot simultaneously adsorb cadmium and arsenic in wastewater because positively charged cadmium and negatively charged arsenic in wastewater tend to adsorb on surfaces with different charges due to electrostatic interactions, and they also compete for adsorption sites through surface complexation.

[0004] Recent studies have found that iron-carbon composite materials, with their porous structure, high specific surface area, and negatively charged oxygen-containing functional groups, can achieve simultaneous removal of cadmium and arsenic to a certain extent. However, current iron-carbon composite materials inevitably exhibit competitive adsorption between cadmium and arsenic when adsorbing combined pollutants, and the maximum adsorption capacity for both cadmium and arsenic is not ideal. In view of these problems, there is an urgent need to develop a novel material that can avoid competitive adsorption between cadmium and arsenic and possess high adsorption capacity for both.

[0005] Hydrothermal carbon-supported ferric oxalate, synthesized via a one-step method (disclosed in invention patent CN202110958312.3), is a novel iron-carbon composite material. In this material, Fe(III) is reduced in situ to Fe(II), and the ferric oxalate is distributed in a relatively dispersed form on the hydrothermal carbon surface. This facilitates the synergistic effect of the two materials in heterogeneous (Fenton-like) catalytic processes, allowing it to function as a photocatalyst for the degradation of organic matter. However, its application to the adsorption and treatment of inorganic substances or heavy metals remains insufficiently investigated. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to propose a method for the application of hydrothermal carbon-supported ferric oxalate in heavy metal adsorption. This method is the first to discover that hydrothermal carbon-supported ferric oxalate synthesized in a one-step process can simultaneously adsorb cadmium and arsenic, and the presence of arsenic can enhance the adsorption of cadmium by the material.

[0007] The technical solution of the present invention is as follows:

[0008] A method for applying hydrothermal carbon-supported ferric oxalate in heavy metal adsorption, wherein the hydrothermal carbon-supported ferric oxalate is used to adsorb arsenic in water.

[0009] The inventors unexpectedly discovered that the hydrothermal carbon-supported oxalate ore they prepared, in addition to its original catalytic degradation of organic matter, had a particularly significant adsorption effect on arsenic, with a removal rate of over 90%, and was unaffected by the presence of other heavy metals, especially cadmium, in the water.

[0010] The preparation method of the hydrothermal carbon-supported oxalate iron ore is as follows:

[0011] A reaction solution containing an aqueous solution of ferric salt and hydrothermal carbon-supported ferric oxalate precursor is subjected to a hydrothermal reaction; the reaction product obtained after the hydrothermal reaction is freeze-dried; wherein, the hydrothermal carbon-supported ferric oxalate precursor is selected from at least one of glucose, fructose, sucrose, maltose, starch, cellulose and lignin; the ferric salt is selected from at least one of ferric nitrate and ferric chloride; the freeze-drying temperature is -30℃ to -50℃, and the time is 10-14h; the mass ratio of the ferric salt to the hydrothermal carbon-supported ferric oxalate precursor, i.e., the iron-carbon ratio, is (0.1-5):1; the hydrothermal reaction temperature is 170-350℃, and the reaction time is 2-8h.

[0012] According to some preferred embodiments of the present invention, the iron-carbon ratio in the hydrothermal carbon-loaded oxalate ore is 1:1 or 2:1.

[0013] The inventors unexpectedly discovered that, under this preferred embodiment, the hydrothermal carbon-supported ferrooxate exhibits the best arsenic adsorption effect.

[0014] The present invention also provides another application method of the hydrothermal carbon-supported ferric oxalate for heavy metal adsorption, which is to adsorb cadmium in water through the hydrothermal carbon-supported ferric oxalate.

[0015] The inventors unexpectedly discovered that this hydrothermal carbon-supported oxalate ore can also adsorb and fix cadmium.

[0016] The present invention also provides another application method of the hydrothermal carbon-supported ferric oxalate in heavy metal adsorption, which is to perform joint and synergistic adsorption of arsenic and cadmium in water by means of the hydrothermal carbon-supported ferric oxalate. The joint and synergistic adsorption includes: adsorbing arsenic and cadmium simultaneously, adsorbing arsenic first and then adsorbing cadmium, and adsorbing cadmium first and then adsorbing arsenic. During the adsorption process, the adsorption of arsenic by the hydrothermal carbon-supported ferric oxalate enhances the adsorption of cadmium by the hydrothermal carbon-supported ferric oxalate.

[0017] Preferably, the combined adsorption involves adsorbing arsenic and cadmium, or adsorbing arsenic first and then cadmium.

[0018] The inventors unexpectedly discovered that the hydrothermal carbon-supported ferric oxalate can simultaneously adsorb arsenic and cadmium, which are competing elements for adsorption. In particular, the presence of arsenic can promote the adsorption of cadmium by the hydrothermal carbon-supported ferric oxalate.

[0019] For example, in the absence of arsenic, hydrothermal carbon-supported ferrooxatite can adsorb up to 21.9 mg / g of cadmium, while in the presence of an initial concentration of 50 mg / L of arsenic in the water, the adsorption capacity of hydrothermal carbon-supported ferrooxatite for cadmium can increase to 28.5 mg / g.

[0020] According to some preferred embodiments of the present invention, the adsorption is carried out at room temperature.

[0021] According to some preferred embodiments of the present invention, the adsorption time is 12-24 hours.

[0022] According to some preferred embodiments of the present invention, the pH of the water body is adjusted to 5-6.

[0023] According to some preferred embodiments of the present invention, the amount of hydrothermal carbon-supported ferrooxate added to the water is 0.9-1.1 g / L.

[0024] According to some preferred embodiments of the present invention, the combined synergistic adsorption capacity for arsenic reaches 165-170 mg / g, and the adsorption capacity for cadmium reaches 28-30 mg / g.

[0025] According to some preferred embodiments of the present invention, the combined synergistic adsorption achieves an adsorption concentration of 82.5-85 mg / L for arsenic in water and an adsorption concentration of 28-30 mg / L for cadmium.

[0026] According to some preferred embodiments of the present invention, the iron-carbon ratio in the hydrothermal carbon-loaded oxalate ore is 1:5 or 5:1.

[0027] The inventors unexpectedly discovered that, at this iron-carbon ratio, hydrothermal carbon-loaded ferrooxate has similar adsorption and removal capabilities for arsenic and cadmium.

[0028] The present invention has the following beneficial effects:

[0029] This invention is the first to discover the application of hydrothermal carbon-supported ferric oxalate synthesized in one step in the adsorption of heavy metals cadmium and arsenic, and unexpectedly discovered that it has a synchronous fixation effect on these two elements that originally had competitive adsorption effects. It provides a new material application method that can avoid competitive adsorption between cadmium and arsenic and has a high adsorption capacity for both cadmium and arsenic.

[0030] The present invention unexpectedly discovered that in Cd-As composite adsorption, the presence of cadmium does not affect the adsorption and fixation efficiency of As(V) on hydrothermal carbon-supported ferric oxalate, while the presence of As(V) promotes the adsorption capacity of Cd on hydrothermal carbon-supported ferric oxalate.

[0031] This invention unexpectedly discovered that in hydrothermal carbon-supported ferric oxalate ore, Cd and As(V) occupy different main adsorption sites. Cd can be fixed on the surface through electrostatic interaction and functional group complexation coordination, while As can be fixed on the surface through ligand exchange to form ferric arsenate and coordinate with inner spheres. In addition, after adsorbing a large amount of As(V), it can also promote the fixation of Cd by reducing the surface charge, enhancing electrostatic interaction, and forming Fe-As-Cd ternary complexes with anionic As(V) as bridges, thus achieving simultaneous and enhanced removal of Cd and As. Attached Figure Description

[0032] Figure 1 This is a statistical chart showing the co-adsorption performance of Cd-As on hydrothermal carbon-loaded ferrooxam with different iron-carbon ratios obtained in Example 3.

[0033] Figure 2 The adsorption kinetic curves obtained in Example 4 are shown in (a) and (b) respectively. (a) shows the kinetic curves of arsenic adsorption by hydrothermal carbon-supported ferric oxalate under different concentrations of cadmium; (b) shows the kinetic curves of cadmium adsorption by hydrothermal carbon-supported ferric oxalate under different concentrations of arsenic.

[0034] Figure 3 The isothermal adsorption curves obtained in Example 4 are shown in (a) and (b) are the isothermal adsorption curves of the adsorption capacity of arsenic on hydrothermal carbon-supported ferric oxalate by different concentrations of cadmium.

[0035] Figure 4 The curves showing the effects of different Cd and As addition orders on the adsorption capacity of hydrothermal carbon-supported ferric oxalate obtained in Example 5 are shown, where (a) shows the effect on the adsorption capacity of hydrothermal carbon-supported ferric oxalate on As, and (b) shows the effect on the adsorption capacity of hydrothermal carbon-supported ferric oxalate on Cd.

[0036] Figure 5 XPS full spectra of hydrothermal carbon-supported ferrooxamite obtained in Example 6 before adsorption (a), after adsorption of Cd alone (b), after adsorption of As alone (c), and after co-adsorption of As-Cd (d).

[0037] Figure 6 XPS O 1s full spectrum of hydrothermal carbon-supported ferrooxam obtained in Example 6 before adsorption (a), after adsorption of Cd alone (b), after adsorption of As alone (c), and after co-adsorption of As-Cd (d).

[0038] Figure 7 TEM image (a) of the hydrothermal carbon-supported ferrooxate raw material obtained in Example 6 and EDS surface scan images (b) of Fe, O, and C elements therein;

[0039] Figure 8 The image shows a TEM image (a) of hydrothermal carbon-supported ferrooxam after adsorption of cadmium and arsenic, and an EDS surface scan image (b) of Fe, O, and C elements in the hydrothermal carbon-supported ferrooxam. Detailed Implementation

[0040] The technical solutions of the present invention will be further described below with reference to embodiments thereof. The embodiments described below are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0041] Example 1

[0042] Hydrothermal carbon-supported oxalate ore is obtained through the following process:

[0043] (1) Take 10g of anhydrous glucose reagent and 70mL of ultrapure water into five 200mL beakers respectively, sonicate and stir to mix them thoroughly;

[0044] (2) Add 1g, 2g, 10g, 20g and 50g Fe(NO3)3·9H2O to these 5 beakers, continue to sonicate and stir to completely dissolve them, and obtain a mixed reaction solution;

[0045] (3) The five mixed reaction solutions were transferred into five 100 mL reaction vessels and hydrothermally reacted at 180 °C for 8 h. The mixture was then filtered using a mixed cellulose microporous membrane with a pore size of 0.22 μm to obtain the hydrothermal product after the reaction.

[0046] (4) The obtained hydrothermal products were freeze-dried at -40℃ for 12h to obtain hydrothermal carbon-loaded iron oxalate with iron-carbon ratios (i.e., the mass ratio of Fe(NO3)3·9H2O to glucose) of 1:10, 1:5, 1:1, 2:1 and 5:1 respectively.

[0047] Example 2

[0048] Adsorption solutions of different concentrations of Cd and As were prepared using the following process:

[0049] (1) Weigh out cadmium chloride and / or sodium arsenate according to the concentration requirements, put them into a container, and make up to 1L with ultrapure water to prepare an adsorption solution; the concentration of As in the adsorption solution is 0, 10, 20, 30 and 50 mg / L, and the concentration of Cd is 0, 10, 20, 30 and 50 mg / L, with a total of 25 mixing methods to obtain 25 adsorption solutions;

[0050] (2) Use NaOH and / or HCl to adjust the pH of the adsorption solution to 5.

[0051] Example 3

[0052] The effect of raw material ratio on adsorption capacity was tested using the following process:

[0053] (1) 20 mg of hydrothermal carbon-loaded ferric oxalate with different iron-carbon ratios obtained in Example 1 and 20 mL of adsorption solution containing 50 mg / L Cd and 50 mg / L As obtained in Example 2 were added to a 50 mL centrifuge tube.

[0054] (2) Use a mixer to continuously stir the centrifuge tube at 80 rpm for 24 hours at room temperature to achieve adsorption equilibrium;

[0055] (3) Take 1 mL of the suspension obtained after adsorption equilibrium, filter it through a 0.22 μm filter membrane, and collect the filtrate;

[0056] (4) The As content in the filtrate was determined by an atomic fluorescence spectrometer equipped with a liquid chromatography unit, and the Cd content in the filtrate was determined by an inductively coupled plasma mass spectrometer.

[0057] The test results are attached. Figure 1 As shown, the hydrothermal carbon-supported ferrooxam of the present invention exhibits good removal effects on both As and Cd. The adsorption effect on both As and Cd is optimal at an iron-to-carbon ratio of 2:1. Furthermore, the removal effect on As is particularly significant at specific iron-to-carbon ratios (1:1 or 2:1), while similar removal rates are achieved for As and Cd at other specific iron-to-carbon ratios (1:5 or 5:1).

[0058] Example 4

[0059] As-Cd co-adsorption tests were performed using the following procedure:

[0060] (1) 20 mg of hydrothermal carbon-supported ferric oxalate with an iron-carbon ratio of 2:1 obtained in Example 1 and 20 mL of adsorption solution with an As concentration of 30 mg / L and Cd concentrations of 0, 10, 20 and 30 mg / L obtained in Example 2 were added to a 50 mL centrifuge tube to test the kinetics of As adsorption by hydrothermal carbon-supported ferric oxalate under different Cd concentrations.

[0061] (2) 20 mg of hydrothermal carbon-supported ferric oxalate with an iron-to-carbon ratio of 2:1 obtained in Example 1 and 20 mL of adsorption solution with a Cd concentration of 30 mg / L and As concentrations of 0, 10, 20 and 30 mg / L obtained in Example 2 were added to a 50 mL centrifuge tube to test the adsorption kinetics of Cd by hydrothermal carbon-supported ferric oxalate under different As concentrations.

[0062] (3) 20 mg of hydrothermal carbon-supported ferric oxalate with an iron-carbon ratio of 2:1 obtained in Example 1 and 20 mL of adsorption solutions with different As and different Cd concentrations obtained in Example 2 were added to a 50 mL centrifuge tube to obtain the effect of different Cd concentrations on the adsorption capacity of hydrothermal carbon-supported ferric oxalate on As and the effect of different As concentrations on the adsorption capacity of hydrothermal carbon-supported ferric oxalate on Cd.

[0063] (4) Use a mixer to continuously stir the centrifuge tube at 80 rpm at room temperature to achieve adsorption equilibrium;

[0064] (5) Samples were taken from the centrifuge tubes in steps (1) and (2) after stirring for 0, 0.3, 0.5, 1, 2, 3, 6, 12 and 24 hours respectively in step (4), and samples were taken from the centrifuge tubes in step (3) after stirring for 24 hours in step (4).

[0065] (6) When sampling, transfer 1 mL of the suspension obtained after adsorption equilibrium, filter it through a 0.22 μm filter membrane, and collect the filtrate;

[0066] (7) The As content in the filtrate was determined by an atomic fluorescence spectrometer equipped with a liquid chromatography unit, and the Cd content in the filtrate was determined by an inductively coupled plasma mass spectrometer.

[0067] Based on the measurement results, data analysis was performed using SPSS, and the results are shown in the attached figure. Figure 2 The dynamic curves and attached figures shown Figure 3 The isothermal adsorption curve is shown.

[0068] Through append Figure 2 (a) and appendix Figure 3 (a) It can be seen that all As can be removed in about 10 hours after adsorption in the adsorbent solution with different Cd concentrations. Furthermore, the increase of Cd concentration in the adsorbent solution does not affect the amount of As adsorbed by the hydrothermal carbon-supported iron oxalate, indicating that the presence of Cd does not inhibit the adsorption and fixation of As by the hydrothermal carbon-supported iron oxalate.

[0069] Through append Figure 2 (b) and appendix Figure 3(b) It can be seen that as the initial concentration of As in the adsorbent increases, the adsorption capacity of hydrothermal carbon-supported ferric oxalate for Cd also increases accordingly, which enhances the adsorption capacity of hydrothermal carbon-supported ferric oxalate for Cd, indicating that the presence of As promotes the fixation of Cd by hydrothermal carbon-supported ferric oxalate.

[0070] Example 5

[0071] The following tests were conducted to determine whether Cd adsorption occurred before As adsorption or vice versa:

[0072] (1) Add 20 mg of hydrothermal carbon-loaded ferric oxalate with an iron-to-carbon ratio of 2:1 obtained in Example 1 and 20 mL of adsorption solution containing 50 mg / L Cd obtained in Example 2 into a 50 mL centrifuge tube.

[0073] (2) Use a mixer to continuously stir the centrifuge tubes at 80 rpm for 24 h at room temperature;

[0074] (3) Add As to the centrifuge tube after Cd adsorption equilibrium is reached, so that the concentration of As in the solution is 50 mg / L;

[0075] (4) Stir the centrifuge tube continuously at 80 rpm for 24 hours at room temperature;

[0076] (5) Add 20 mg of hydrothermal carbon-loaded ferric oxalate with an iron-to-carbon ratio of 2:1 obtained in Example 1 and 20 mL of adsorption solution containing 50 mg / L As obtained in Example 2 into a 50 mL centrifuge tube.

[0077] (6) Use a mixer to continuously stir the centrifuge tubes at 80 rpm for 24 hours at room temperature;

[0078] (7) Add Cd to the centrifuge tube after As adsorption equilibrium is reached, so that the concentration of Cd in the solution is 50 mg / L;

[0079] (8) The centrifuge tube was continuously stirred at 80 rpm at room temperature for 24 hours.

[0080] (9) During the 24h adsorption process in steps (2) and (6), samples were taken at 0, 0.5, 1, 2, 6, 12 and 24h respectively. During the 24h adsorption process in steps (4) and (8), samples were taken at 0, 0.5, 1, 2, 6, 12 and 24h respectively. The samples were filtered through a 0.22μm filter membrane and the filtrate was collected.

[0081] (10) The As content in the filtrate was determined by an atomic fluorescence spectrometer equipped with a liquid chromatography unit, and the Cd content in the filtrate was determined by an inductively coupled plasma mass spectrometer.

[0082] Based on the measurement results, the data was processed using SPSS and obtained as shown in the attached figure. Figure 4 The curve shown. (Attached) Figure 4 a) shows the effect of different Cd and As addition orders on the adsorption capacity of As by hydrothermal carbon-supported ferric oxalate. It can be seen that the three adsorption scenarios have no significant effect on the kinetic process of As adsorption by hydrothermal carbon-supported ferric oxalate. All three scenarios achieved complete removal of As within 24 hours, indicating that the presence of Cd does not affect the adsorption of As by hydrothermal carbon-supported ferric oxalate.

[0083] Appendix Figure 4 b shows the effect of different Cd and As addition orders on the adsorption capacity of Cd by hydrothermal carbon-supported ferrooxam. It can be seen that in the experimental groups where Cd and As coexist, and in the group where As was added first followed by Cd, the adsorption capacity of Cd increased from 22.1 mg / g to 28.1 mg / g. However, in the experimental group where Cd was added first followed by As, the adsorption capacity of Cd first reached 22.1 mg / g after 24 hours, and then rapidly increased to 28.1 mg / g after the addition of As. This indicates that the presence of As significantly promotes the adsorption and removal of Cd.

[0084] Example 6

[0085] Furthermore, the hydrothermal carbon-supported ferric oxalate (hereinafter referred to as Hum / HTC) with an iron-to-carbon ratio of 2:1 from Example 1 was characterized by XPS after undergoing single Cd adsorption, single As adsorption, and Cd-As composite adsorption at equal concentrations (50 mg / L) (hereinafter referred to as Hum / HTC-Cd, Hum / HTC-As, and Hum / HTC-Cd / As, respectively). The results are shown in the attached figure. Figure 5 As shown, the fine spectrum of O1s in the XPS full spectrum was analyzed, and the results are attached. Figure 6 As shown.

[0086] Furthermore, the adsorbate was analyzed using transmission electron microscopy combined with energy dispersive spectroscopy (TEM mapping), yielding the following results: Figure 7 The original hydrothermal carbon-supported ferrooxate transmission electron microscope and elemental surface scan images are shown below. Figure 8 The transmission electron microscope and elemental surface scan images of hydrothermal carbon-supported ferrooxate after Cd-As composite adsorption are shown.

[0087] From the appendix Figure 5It can be seen that the original Hum / HTC has characteristic peaks for Fe 2p, O 1s, and C 1s, indicating that the material mainly contains C, Fe, and O elements. After single Cd adsorption treatment, a Cd 3d signal peak appeared in the full spectrum, confirming that hydrothermal carbon-supported ferric oxalate can effectively adsorb and fix Cd. After single As adsorption treatment, an As 3d signal peak appeared in the full spectrum, also confirming that hydrothermal carbon-supported ferric oxalate can effectively adsorb and fix As. After simultaneous Cd-As adsorption treatment, both Cd 3d and As 3d signal peaks appeared in the full spectrum, and the intensity of the Cd 3d signal peak was stronger than that of single Cd adsorption treatment. This indicates that the hydrothermal carbon-supported ferric oxalate can achieve simultaneous fixation of Cd and As, and the presence of As promotes the adsorption and fixation of Cd.

[0088] For the appendix Figure 6 Analysis of the detailed O1s spectrum in the full XPS spectrum revealed that the O1s spectrum mainly consists of four peaks, corresponding to the metal oxide (MO), the hydroxyl groups bonded to the metal (M-OH), the hydroxyl groups on the HTC surface (C-OH), and the water molecules (H2O) adsorbed in the material. (See attached...) Figure 6It can be seen that after Hum / HTC adsorbs Cd or As, the relative area of ​​C-OH decreases, while the relative areas of M-OH and MO increase. This indicates that -OH on the hydrothermal carbon surface may act as adsorption sites to promote the adsorption and fixation of Cd and As. The decrease in C-OH content after Cd treatment is greater than that after As treatment, meaning that Cd has a stronger ability to occupy hydroxyl sites on the hydrothermal carbon surface than As, which may lead to most of the Cd being fixed on the hydrothermal carbon surface. After Cd-As co-treatment, the C-OH content further decreases, indicating that more surface hydroxyl sites are occupied. This may be because the adsorption of a large amount of As on hydrothermal carbon-supported ferrooxatite increases the surface electronegativity, enhancing the electrostatic interaction between hydrothermal carbon-supported ferrooxatite and Cd, resulting in more hydroxyl sites being occupied by Cd. The increased Fe-OH strength may be due to internal spherical coordination complexation reactions (e.g., (FeOH)₂CdOH and Fe₂O₂AsOH) on the Hum / HTC surface, which may lead to a significant enhancement in the material's adsorption capacity for As(V). Simultaneously, the peak percentage in the Hum / HTC-Cd / As sample (56.2%) is significantly higher than that in Hum / HTC-Cd (49.0%) and Hum / HTC-As (54.3%), indicating that the presence of As greatly promotes Cd adsorption. The adsorption capacity of Hum / HTC for As is much greater than that for Cd, meaning that in the As-Cd co-adsorption system, it is easier to form Fe-As-Cd ternary complexes via anionic As bridges to promote Cd fixation. In summary, Cd is likely mostly fixed by occupying hydroxyl sites on the hydrothermal carbon surface, while As(V) is more easily adsorbed and fixed on the ferrooxate surface. Furthermore, after hydrothermal carbon-loaded ferric oxalate adsorbs a large amount of As(V), it will enhance electrostatic interaction by reducing surface charge and promote the fixation of Cd(II) by forming Fe-As-Cd ternary complexes with anionic As(V) as bridges.

[0089] From the appendix Figure 7 Furthermore, the uniformly loaded ferric oxalate nanoparticles on the surface of the hydrothermal carbon spheres can be clearly observed, and surface scanning results show that the main elemental distribution in this region is C, O, and Fe. (From the attached...) Figure 8 Furthermore, a significant difference in the distribution of Cd and As can be observed. Cd is mainly uniformly distributed on the surface of the hydrothermal carbon spheres and shows a strong correlation with the distribution of carbon. As, on the other hand, shows a stronger signal in the region where it is distributed in ferrooxate and shows a strong correlation with the distribution of iron. This suggests that Cd and As may occupy different adsorption sites. Cd is mainly fixed on the surface of hydrothermal carbon, while As is fixed on the surface of ferrooxate. Therefore, Hum / HTC mainly fixes Cd on the surface of hydrothermal carbon through electrostatic interactions and functional group complexation coordination, while As fixation is mainly achieved through ligand exchange to form ferric arsenate on the surface of ferrooxate.

[0090] It should be noted that the above descriptions are merely preferred embodiments of the present invention and should not limit the scope of protection of the technical solutions of the present invention. Any modifications made to the technical solutions described in the foregoing embodiments, or equivalent substitutions of technical features, by those skilled in the art within the spirit and principles of the present invention, should be included within the scope of protection of the present invention.

Claims

1. A method for applying hydrothermally loaded carbon oxalate ore to heavy metal adsorption, characterized in that, The hydrothermal carbon-supported ferric oxalate is used to synergistically adsorb arsenic and cadmium from water. This synergistic adsorption includes any of the following adsorption methods: simultaneous adsorption of arsenic and cadmium, adsorption of arsenic first followed by adsorption of cadmium, or adsorption of cadmium first followed by adsorption of arsenic. During the adsorption process, the adsorption of arsenic by the hydrothermal carbon-supported ferric oxalate enhances the adsorption of cadmium. The preparation method of the hydrothermal carbon-supported ferric oxalate includes: preparing an aqueous solution containing a ferric salt and a hydrothermal carbon-supported ferric oxalate precursor... The reaction solution undergoes a hydrothermal reaction; the reaction product obtained after the hydrothermal reaction is freeze-dried; wherein, the hydrothermal carbon-supported ferric oxalate precursor is selected from one or more of glucose, fructose, sucrose, maltose, starch, cellulose, and lignin; the ferric salt is selected from ferric nitrate and / or ferric chloride; the freeze-drying temperature is -30℃ to -50℃, and the time is 10-14h; the mass ratio of the ferric salt to the hydrothermal carbon-supported ferric oxalate precursor, i.e., the iron-carbon ratio, is (0.1-5):1; the hydrothermal reaction temperature is 170-350℃, and the reaction time is 2-8h.

2. The application method according to claim 1, characterized in that, The adsorption occurs at room temperature.

3. The application method according to claim 1, characterized in that, The adsorption time is 12-24 hours.

4. The application method according to claim 1, characterized in that, The pH of the water body is adjusted to 5-6.

5. The application method according to claim 1, characterized in that, The amount of hydrothermal carbon-supported oxalate added to the water body is 0.9-1.1 g / L.

6. The application method according to claim 1, characterized in that, The combined synergistic adsorption method achieves an adsorption capacity of 165-170 mg / g for arsenic and 28-30 mg / g for cadmium; and / or, the combined synergistic adsorption method achieves an adsorption concentration of 82.5-85 mg / L for arsenic and 28-30 mg / L for cadmium in water.

7. The application method according to claim 1, characterized in that, The iron-carbon ratio in the hydrothermal carbon-loaded oxalate ore is 1:5 or 5:1.

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