A hydrothermal carbon composite material, a preparation method and application thereof

Abstract

The application belongs to the technical field of adsorbents, and particularly relates to a hydrothermal carbon composite material, a preparation method thereof and application thereof. The application provides a hydrothermal carbon composite material, which comprises a biomass hydrothermal carbon matrix and polyaluminum hydrochloride crystals loaded on the biomass hydrothermal carbon matrix. In the process of adsorbing phosphate, the biomass hydrothermal carbon matrix and the polyaluminum hydrochloride crystals play a synergistic role, and the adsorption effect on phosphate can be further improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of adsorbents, and particularly relates to a hydrothermal carbon composite material and a preparation method and application thereof. BACKGROUND

[0002] As a current scarce resource, phosphorus is an important element of biological cytoplasm and is also an essential element for plant growth. At present, the phosphorus ore resources in the world are extremely unevenly distributed in various countries. The wide use of phosphorus ore, the relatively low yield, the lack of corresponding substitutes and other phenomena mean that the phosphorus ore resources will be rapidly exhausted in the future. At present, with the rapid development of agriculture, the overuse of chemical fertilizers and the random discharge of breeding manure, not only a large amount of phosphorus resources is wasted, but also water body eutrophication and other phenomena are caused. Therefore, it is imminent to develop simple and feasible low-cost phosphorus recovery technology to reduce the increasing consumption of phosphorus and curb its harm to water bodies. Such research has significant environmental and social benefits.

[0003] At present, the main ways for recovering phosphorus from wastewater include biological method, chemical precipitation method, ion exchange method and adsorption method. The most widely used biological method for removing phosphorus at home and abroad is the activated sludge method, but the reaction conditions are relatively harsh, and the operation and maintenance costs are too high. The chemical precipitation method is limited due to the large amount of reagents used, the need to add flocculants to improve the coagulation effect, the high cost of conventional flocculants and the toxicity of the flocculants. The ion exchange method uses strong alkaline anion exchange resins to exchange with phosphate anions in wastewater, but the price of ion exchange resins is relatively high. The adsorption method is particularly suitable for the treatment of low-concentration wastewater due to its small occupied area, simple process and convenient operation.

[0004] At present, porous substances have been used as adsorbents and ion exchangers in water purification and pollution control. In the study of adsorption method, finding new adsorbents is the key to developing new phosphorus removal processes. Compared with expensive activated carbon and graphene, low-cost and environmentally friendly biochar materials are more concerned. The biochar reported in the literature for adsorbing phosphate is mostly pyrolytic carbon, and the preparation process is too complex, and the adsorption effect on phosphate is not good. SUMMARY

[0005] The purpose of the present application is to provide a hydrothermal carbon composite material and a preparation method and application thereof. The hydrothermal carbon composite material provided by the present application has excellent adsorption effect on phosphate.

[0006] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] The present application provides a hydrothermal carbon composite material, which comprises a biomass hydrothermal carbon matrix and polyaluminum hydrochloride crystals loaded on the biomass hydrothermal carbon matrix.

[0008] Preferably, the chemical composition of the polyaluminum hydrochloride crystal is Al 24 O 11 (OH) 44 Cl6.

[0009] Preferably, the loading percentage of the polyaluminum hydrochloride crystal in the hydrothermal carbon composite material is 1.5% to 70%.

[0010] The present application also provides a preparation method of the hydrothermal carbon composite material as described in the technical solution, comprising the following steps:

[0011] Mixing the biomass raw material and the aluminum chloride solution, and obtaining the hydrothermal carbon composite material through hydrothermal reaction.

[0012] Preferably, the biomass raw material comprises one or more of corn straw, rice straw and sorghum straw.

[0013] Preferably, the molar concentration of the aluminum chloride solution is 0.5 to 3 mol / L.

[0014] Preferably, the usage ratio of the biomass raw material and the aluminum chloride solution is 5g: 50 to 100 mL.

[0015] Preferably, the temperature of the hydrothermal reaction is 220 to 280℃, and the holding time is 3 to 7h.

[0016] Preferably, the hydrothermal reaction is carried out under stirring; and the stirring speed is 100 to 300 rpm.

[0017] The present application also provides an application of the hydrothermal carbon composite material as described in the technical solution or the hydrothermal carbon composite material prepared by the preparation method as described in the technical solution in adsorbing phosphate.

[0018] The present application provides a hydrothermal carbon composite material, comprising a biomass hydrothermal carbon matrix and polyaluminum hydrochloride crystals loaded on the biomass hydrothermal carbon matrix. In the adsorption process of phosphate, the biomass hydrothermal carbon matrix and the polyaluminum hydrochloride crystals play a synergistic role. The biomass hydrothermal carbon matrix can adsorb phosphate on the surface of the biomass hydrothermal carbon matrix through electrostatic adsorption and functional group adsorption, and then the polyaluminum hydrochloride crystals as active sites react with phosphate to generate aluminum phosphate precipitate, further improving the adsorption effect of phosphate. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 SEM images of the hydrothermal carbon composite materials obtained in Examples 2 to 4 and Comparative Example 5;

[0020] Figure 2XRD patterns of the hydrothermal carbon composite materials obtained in Examples 2-3 and Comparative Example 5, and the material obtained by adsorbing phosphate onto the hydrothermal carbon composite material of Example 3;

[0021] Figure 3 Adsorption effect of the hydrothermal carbon composite materials obtained in Example 1, Comparative Examples 1-2 on phosphate;

[0022] Figure 4 Adsorption effect of the hydrothermal carbon composite materials obtained in Example 1, Comparative Examples 3-4, Comparative Example 6, and pretreated corn stalks on phosphate;

[0023] Figure 5 Adsorption effect of the hydrothermal carbon composite materials obtained in Example 2, Comparative Example 6, and aluminum chloride on phosphate;

[0024] Figure 6 Adsorption effect of the hydrothermal carbon composite materials obtained in Examples 2-4, Comparative Example 5 on phosphate;

[0025] Figure 7 Adsorption effect of the hydrothermal carbon composite material obtained in Example 3 on phosphate at different addition amounts;

[0026] Figure 8 Adsorption effect of the hydrothermal carbon composite material obtained in Example 3 on phosphate at different pH values. DETAILED DESCRIPTION

[0027] The present application provides a hydrothermal carbon composite material, comprising a biomass hydrothermal carbon substrate and polyaluminum hydrochloride crystals loaded on the biomass hydrothermal carbon substrate.

[0028] In the present application, the chemical composition of the polyaluminum hydrochloride crystals is preferably Al 24 O 11 (OH) 44 Cl6.

[0029] In the present application, the loading percentage of the polyaluminum hydrochloride crystals in the hydrothermal carbon composite material is preferably 1.5%-70%, and further preferably 1.79%, 36.45%, 59.71% or 64.52%.

[0030] The present application also provides a preparation method of the hydrothermal carbon composite material described in the above technical solution, comprising the following steps:

[0031] The biomass raw material and the aluminum chloride solution are mixed and subjected to a hydrothermal reaction to obtain the hydrothermal carbon composite material.

[0032] In the present application, all the preparation raw materials are commercially available products well known to those skilled in the art, unless otherwise specified.

[0033] In the present application, the biomass raw material preferably comprises one or more of corn stalks, rice stalks and sorghum stalks.

[0034] In the present application, the biomass raw material is preferably subjected to pretreatment before mixing; the pretreatment preferably comprises sequentially performing ash removal, air drying, crushing and sieving treatment. In the present application, the mesh size of the sieve used in the sieving treatment is preferably 40 mesh.

[0035] In the present application, the concentration of the aluminum chloride solution is preferably 0.5-3 mol / L. In the present application, the ratio of the amount of the biomass raw material to the amount of the aluminum chloride solution is preferably 5 g: 50-100 mL.

[0036] The present application does not have special limitations on the mixing process, and any process known to those skilled in the art can be used.

[0037] In the present application, the temperature of the hydrothermal reaction is preferably 220-280℃, further preferably 230-270℃, and more preferably 240-260℃; the holding time is preferably 3-7 h, and further preferably 4-5 h. In the present application, the hydrothermal reaction is preferably performed under stirring; the stirring speed is preferably 100-300 rpm. In the present application, the hydrothermal reaction is preferably performed in a high-temperature and high-pressure reaction kettle.

[0038] In the present application, during the hydrothermal process, the biomass raw material is carbonized by hydrothermal carbonization to form hydrothermal carbon, and amorphous aluminum is converted into polyaluminum hydroxide crystals and loaded on the hydrothermal carbon. In the process of adsorbing phosphates, the hydrothermal carbon matrix and the polyaluminum hydroxide crystal structure play a synergistic role, further improving the adsorption effect of phosphates; and the composite material with adsorbed phosphates is easy to recycle.

[0039] After the hydrothermal reaction, the present application further preferably comprises sequentially performing cooling, primary filtration, water washing, secondary filtration and drying on the obtained reaction liquid.

[0040] In the present application, the cooling method is preferably natural cooling to room temperature. The present application does not have special limitations on the water washing process, and any process known to those skilled in the art can be used. In the present application, the primary filtration and secondary filtration methods are both preferably vacuum filtration. In the present application, the drying method is preferably drying in an oven at 105℃ for more than 6 h.

[0041] In the present application, the liquid obtained after filtration can be recycled as a raw material for hydrothermal reaction, which not only reduces the cost but also reduces the environmental pressure, providing a new idea for green and sustainable production of hydrothermal carbon-based phosphate adsorption materials loaded with polyaluminum hydroxide crystals.

[0042] The application takes abundant and low-cost agricultural waste as raw material, and successfully prepares functional biomass-based hydrothermal carbon through a simple one-step method, has low cost and simple process, and has remarkable environmental and social benefits.

[0043] The application also provides application of the hydrothermal carbon composite material in adsorbing phosphate.

[0044] The application is not limited to the type of the phosphate, and has high adsorption effect on any type of phosphate.

[0045] In the application, the process of the application preferably comprises:

[0046] The hydrothermal carbon composite material and the phosphate solution are mixed, the container containing the mixed solution is placed in a shaking table for shaking, and the ion chromatograph is used to determine the content of the phosphate in the liquid.

[0047] In the application, the concentration of the phosphate solution is preferably 300-1000 mg / L, and the pH value of the phosphate solution is preferably 3-11.

[0048] In the application, the ratio of the amount of the hydrothermal carbon composite material to the amount of the phosphate solution is preferably 1g: 150-3000 mL.

[0049] In the application, the temperature of the shaking is preferably 30 DEG C, the rotation speed is preferably 150 rpm, and the time is preferably 60-1440 min, and further preferably 180-360 min.

[0050] In the application, the process of the detection preferably comprises:

[0051] The liquid obtained after the shaking is extracted by using a disposable needle, filtered by a 0.22 mu m needle filter, collected in a centrifuge tube, and the phosphate in the liquid is quantitatively determined by the ion chromatograph.

[0052] In order to further illustrate the application, the hydrothermal carbon composite material, the preparation method and the application thereof provided by the application are described in detail below in combination with the drawings and examples, but they should not be understood as limiting the protection scope of the application.

[0053] Example 1

[0054] The corn straw is dedusted, dried and broken, and sieved by using a 40-mesh sieve, and the pretreated corn straw is obtained.

[0055] 5g of the pretreated corn stalks and 50 mL of an AlCl3 solution with a concentration of 0.5 mol / L were placed in a high-temperature and high-pressure reaction kettle, and a hydrothermal reaction was performed under the conditions of a stirring rate of 200 rpm and a temperature of 220°C, and the reaction was kept for 4 h. After the reaction was completed, the obtained reaction liquid was naturally cooled to room temperature, and the obtained reaction liquid was washed with water and vacuum filtered, and then placed in an oven at 105°C for drying for more than 6 h to obtain the hydrothermal carbon composite material (denoted as (CS+Al 0.5 )-220); wherein the loading percentage of the polyaluminum hydrochloride crystal on the hydrothermal carbon composite material was 1.79%.

[0056] Example 2

[0057] The corn stalks were dusted, air-dried and broken, and sieved using a sieve with a mesh size of 40 to obtain pretreated corn stalks.

[0058] 5g of the pretreated corn stalks and 50 mL of an AlCl3 solution with a concentration of 2 mol / L were placed in a high-temperature and high-pressure reaction kettle, and a hydrothermal reaction was performed under the conditions of a stirring rate of 200 rpm and a temperature of 220°C, and the reaction was kept for 4 h. After the reaction was completed, the obtained reaction liquid was naturally cooled to room temperature, and the obtained reaction liquid was washed with water and vacuum filtered, and then placed in an oven at 105°C for drying for more than 6 h to obtain the hydrothermal carbon composite material (denoted as (CS+Al2)-220); wherein the loading percentage of the polyaluminum hydrochloride crystal on the hydrothermal carbon composite material was 36.45%.

[0059] Example 3

[0060] The corn stalks were dusted, air-dried and broken, and sieved using a sieve with a mesh size of 40 to obtain pretreated corn stalks.

[0061] 5g of the pretreated corn stalks and 50 mL of an AlCl3 solution with a concentration of 2 mol / L were placed in a high-temperature and high-pressure reaction kettle, and a hydrothermal reaction was performed under the conditions of a stirring rate of 200 rpm and a temperature of 260°C, and the reaction was kept for 4 h. After the reaction was completed, the obtained reaction liquid was naturally cooled to room temperature, and the obtained reaction liquid was washed with water and vacuum filtered, and then placed in an oven at 105°C for drying for more than 6 h to obtain the hydrothermal carbon composite material ((CS+Al2)-260); wherein the loading percentage of the polyaluminum hydrochloride crystal on the hydrothermal carbon composite material was 59.71%.

[0062] Example 4

[0063] The corn stalks were dusted, air-dried and broken, and sieved using a sieve with a mesh size of 40 to obtain pretreated corn stalks.

[0064] Put 5 g of pretreated corn stalks and 50 mL of AlCl3 solution with a concentration of 2 mol / L into a high-temperature and high-pressure reaction kettle, and perform a hydrothermal reaction under the condition that the stirring rate is 200 rpm and the temperature is 280℃, and keep the temperature for 4 h. After the reaction is completed, the obtained reaction liquid is naturally cooled to room temperature, and the obtained reaction liquid is washed with water and vacuum filtered, and then placed in an oven at 105℃ for drying for more than 6 h to obtain the hydrothermal carbon composite material (denoted as (CS+Al2)-280); wherein the loading percentage of polyaluminum hydrochloride crystals on the hydrothermal carbon composite material is 64.52%.

[0065] Comparative Example 1

[0066] The hydrothermal carbon composite material (denoted as (CS+Fe 0.5 )-220) is prepared in the manner of Example 1, except that the AlCl3 solution is replaced by FeCl3 solution.

[0067] Comparative Example 2

[0068] The hydrothermal carbon composite material (denoted as (CS+Mg 0.5 )-220) is prepared in the manner of Example 1, except that the AlCl3 solution is replaced by MgCl2 solution.

[0069] Comparative Example 3

[0070] The hydrothermal carbon composite material obtained in Example 1 is calcined under the condition that the calcination is performed in a nitrogen atmosphere at 650℃ for 1 h to obtain a composite material (denoted as (CS+Al 0.5 )-220-650).

[0071] Comparative Example 4

[0072] The hydrothermal carbon composite material obtained in Example 1 is calcined under the condition that the calcination is performed in a small amount of air atmosphere at 400℃ for 1 h to obtain a composite material (denoted as (CS+Al 0.5 )-220-400).

[0073] Comparative Example 5

[0074] The hydrothermal carbon composite material (denoted as (CS+Al2)-180) is prepared in the manner of Example 2, except that the hydrothermal temperature is replaced by 180℃.

[0075] Comparative Example 6

[0076] The hydrothermal carbon composite material (denoted as CS-220) is prepared in the manner of Example 1, except that no AlCl3 solution is added.

[0077] Performance Test

[0078] Test Example 1

[0079] The hydrothermal carbon composite materials obtained in Examples 2-4 and Comparative Example 5 were subjected to scanning electron microscope detection, and the obtained SEM images are shown in Figure 1 From Figure 1 it can be seen that obvious crystal cluster structures can be found on the hydrothermal carbon composite materials obtained in the present application, indicating that in the hydrothermal process, the aluminum form migrates and transforms, and the aluminum aggregates to form a cluster crystal structure from an unstable amorphous state, and is relatively stably loaded on the carbon carrier.

[0080] Test Example 2

[0081] The hydrothermal carbon composite materials obtained in Examples 2-3 and Comparative Example 5 and the material obtained after the (CS+Al2)-260 obtained in Example 3 in the test example adsorbed phosphate were subjected to X-ray diffraction detection, and the obtained XRD images are shown in Figure 2 From Figure 2 it can be seen that in the hydrothermal process, the aluminum form migrates and transforms, and the amorphous aluminum gradually aggregates and transforms to generate Al 24 O 11 (OH) 44 Cl6crystal structure, and when the temperature is increased to 260℃, the crystallization peak is more obvious; and after the phosphate adsorption process, the Al 24 O 11 (OH) 44 Cl6crystal structure is sharply reduced, and in this process, the aluminum and the phosphate generate a precipitate reaction to form an AlPO4structure.

[0082] Test Example 3

[0083] The hydrothermal carbon composite materials obtained in Example 1 and Comparative Examples 1-2 were used as adsorption materials to verify the adsorption effect on phosphate;

[0084] 0.1g of the adsorption material and 30mL of a potassium dihydrogen phosphate solution with a concentration of 500mg / L (pH value is 5.28) were weighed into a conical flask, the conical flask was placed in a shaker at 30℃, and the rotation number was 150rpm, and the shaking time was 180min. After the shaking was completed, the reacted liquid was extracted through a disposable needle, filtered through a 0.22μm needle filter, and collected in a centrifuge tube, and the phosphate components in the liquid were quantitatively determined by an ion chromatograph;

[0085] The obtained test result graph is shown in Figure 3 From Figure 3 it can be seen that under the same conditions, the aluminum shows more excellent phosphate adsorption effect, and the adsorption amount of the hydrothermal carbon composite material prepared from the aluminum is 2 times higher than that of the hydrothermal carbon composite material prepared from magnesium and 5 times higher than that of the composite material prepared from iron.

[0086] Test Example 4

[0087] The hydrothermal carbon composite materials obtained in Example 1, Comparative Examples 3-4 and Comparative Example 6 and pretreated corn stalks (denoted as CS) were used as adsorbent materials to verify the adsorption effect on phosphates;

[0088] 0.1 g of the adsorbent material and 30 mL of a potassium dihydrogen phosphate solution with a concentration of 500 mg / L were weighed into a conical flask, and the conical flask was placed in a shaker at 30°C, with a rotation speed of 150 rpm, and shaken for 180 min. After shaking, the reacted liquid was extracted by a disposable needle, filtered through a 0.22 μm needle filter, and collected in a centrifuge tube. The phosphate content in the liquid was quantitatively determined by an ion chromatograph.

[0089] The obtained test result graph is shown in Figure 4 From Figure 4 it can be seen that the corn stalks treated by hydrothermal treatment can improve the adsorption capacity for phosphates, and the addition of metals can further improve the removal effect of the hydrothermal carbon material on phosphates. If modified by anaerobic calcination, the adsorption capacity for phosphates is reduced. Although a small amount of oxygen is introduced during calcination, the adsorption performance of the hydrothermal carbon is slightly improved.

[0090] Test Example 5

[0091] The hydrothermal carbon composite materials obtained in Example 2 and Comparative Example 6 and aluminum chloride were used as adsorbent materials to verify the adsorption effect on phosphates.

[0092] 0.1 g of the hydrothermal carbon adsorbent material or 0.1182456 g of aluminum chloride hexahydrate (at this time, the aluminum content is equal to the aluminum content loaded on the (CS+Al2)-220 material) and 30 mL of a potassium dihydrogen phosphate solution with a concentration of 500 mg / L were weighed into a conical flask, and the conical flask was placed in a shaker at 30°C, with a rotation speed of 150 rpm, and shaken for 180 min. After shaking, the reacted liquid was extracted by a disposable needle, filtered through a 0.22 μm needle filter, and collected in a centrifuge tube. The phosphate content in the liquid was quantitatively determined by an ion chromatograph.

[0093] The obtained test result graph is shown in Figure 5 From Figure 5 it can be seen that by comparing (CS+Al2)-220 with CS-220 without adding metals under the same reaction conditions, the phosphate adsorption results prove that the addition of polyaluminum chloride crystals can greatly improve the adsorption performance of the hydrothermal carbon on phosphates. When the aluminum content is the same, it can be found by comparing the use of aluminum loaded on the hydrothermal carbon and the direct use that the loading of aluminum on the hydrothermal carbon can significantly improve the adsorption performance on phosphates, which is related to the form of aluminum.

[0094] Test Example 6

[0095] The hydrothermal carbon composite material obtained in Examples 2-4 and Comparative Example 5 was used as the adsorbent material to verify the adsorption effect on phosphate;

[0096] 0.1 g of the adsorbent material and 30 mL of a potassium dihydrogen phosphate solution with a concentration of 500 mg / L were weighed into a conical flask, and the conical flask was placed in a shaker at 30°C, with a rotation speed of 150 rpm, and shaken for 180 min. After shaking, the reacted liquid was extracted through a disposable needle, filtered through a 0.22 μm needle filter, and collected in a centrifuge tube. The phosphate content in the liquid was quantitatively determined by ion chromatography;

[0097] The test results are shown in the graph of Figure 6 It can be seen from Figure 6 that as the hydrothermal temperature increases, the adsorption performance of the hydrothermal carbon on phosphate also improves significantly. When the hydrothermal temperature is 260°C, the adsorption performance on phosphate is best, and when the hydrothermal temperature is further increased, the adsorption performance decreases. This may be because the polyaluminum hydrochloride clusters in (CS+Al2)-280 overlap, and the active sites cannot fully play their role.

[0098] Test Example 7

[0099] The hydrothermal carbon composite material obtained in Example 3 was used as the adsorbent material to verify the adsorption effect of different amounts of adsorbent material on phosphate:

[0100] 0.01 g, 0.05 g, 0.1 g, 0.15 g, and 0.2 g of the adsorbent material and 30 mL of a potassium dihydrogen phosphate solution with a concentration of 500 mg / L were weighed into a conical flask, and the conical flask was placed in a shaker at 30°C, with a rotation speed of 150 rpm, and shaken for 180 min. After shaking, the reacted liquid was extracted through a disposable needle, filtered through a 0.22 μm needle filter, and collected in a centrifuge tube. The phosphate content in the liquid was quantitatively determined by ion chromatography;

[0101] The test results are shown in the graph of Figure 7 It can be seen from Figure 7It can be seen that with the increase of hydrothermal carbon addition amount from 0.01 g to 0.2 g, the adsorption amount of phosphate first increases and then decreases, and the removal rate increases from 4.32% to 96.42%. The increase of the removal rate is because increasing the hydrothermal carbon addition amount can increase more adsorption sites for phosphate adsorption. When the hydrothermal carbon addition amount is 0.05 g, the adsorption amount of phosphate reaches the highest value of 117.37 mg / g. With the further increase of the hydrothermal carbon addition amount, the adsorption amount decreases instead. This is because the active sites overlap, reducing the effective contact area between phosphate and active sites and increasing the diffusion path length between them. Therefore, more hydrothermal carbon may reduce its adsorption efficiency.

[0102] Test Example 8

[0103] The hydrothermal carbon composite material obtained in Example 3 was used as the adsorption material to verify the adsorption effect on phosphate with different pH values.

[0104] 0.1 g of the adsorption material and 30 mL of potassium dihydrogen phosphate solution with a concentration of 500 mg / L (pH values were 3, 5, 7, 9 and 11, respectively) were placed in a conical flask. The conical flask was placed in a shaking bed at 30°C, and the shaking speed was 150 rpm. After shaking for 180 min, the reacted liquid was extracted through a disposable needle, filtered through a 0.22 μm needle filter, and collected in a centrifuge tube. The phosphate content in the liquid was quantitatively determined by an ion chromatograph.

[0105] The test result graph is shown in Figure 8 From Figure 8 It can be seen that with the increase of the initial pH from 3 to 11, the adsorption capacity of phosphate first increases and then decreases. When the initial pH of the solution is 7, the adsorption amount is the highest, which is 124.86 mg / g. When the pH of the solution is less than 7, the hydrothermal carbon is protonated, and the surface is positively charged, which can adsorb anions. When the pH is greater than 7, the hydrothermal carbon is deprotonated, and H + is released into the solution. At this time, the surface charge of the hydrothermal carbon is negative, and there is an electrostatic repulsion between the hydrothermal carbon and phosphate. The electrostatic repulsion increases with the increase of pH. At the same time, the presence of OH - will compete with phosphate for the active sites of metal aluminum, so when the pH is greater than 7, the adsorption amount of phosphate begins to decrease. When the pH is less than 7, the adsorption amount of phosphate remains at a high level.

[0106] Although the above examples have made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained according to the present embodiments without creativity, which belong to the protection scope of the present application.

Claims

1. A hydrothermal carbon composite, characterized in that, The biomass hydrothermal carbon composite material comprises a biomass hydrothermal carbon matrix and polyaluminum hydrochloride crystals loaded on the biomass hydrothermal carbon matrix. The polyaluminum hydroxide chloride salt crystals have a chemical composition of Al 24 O 11 (OH) 44 Cl6.

2. The hydrothermal carbon composite according to claim 1, characterized in that The loading percentage of the polyaluminum hydrochloride crystals in the biomass hydrothermal carbon composite material is 1.5% to 70%.

3. The method for preparing the hydrothermal carbon composite according to claim 1 or 2, characterized in that, The method comprises the following steps: The biomass raw material and the aluminum chloride solution are mixed, and a hydrothermal reaction is performed to obtain the biomass hydrothermal carbon composite material.

4. The production method according to claim 3, characterized by, The biomass raw material comprises one or more of corn stalks, rice stalks and sorghum stalks.

5. The preparation method according to claim 3, characterized in that, The molar concentration of the aluminum chloride solution is 0.5 to 3 mol / L.

6. The production method according to claim 5, wherein The usage ratio of the biomass raw material to the aluminum chloride solution is 5 g: 50 to 100 mL.

7. The method of any one of claims 3 to 6, wherein the method further comprises the step of: The temperature of the hydrothermal reaction is 220 to 280 ℃, and the holding time is 3 to 7 h.

8. The preparation method according to claim 7, characterized in that, The hydrothermal reaction is performed under stirring, and the stirring speed is 100 to 300 rpm.

9. Application of the biomass hydrothermal carbon composite material of claim 1 or 2 or the biomass hydrothermal carbon composite material prepared by the preparation method of any one of claims 3 to 8 in adsorbing phosphate.

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