Layered rare earth chlorinated carbonate as well as preparation method and application thereof

Abstract

The invention provides layered rare earth chlorinated carbonate as well as a preparation method and application thereof. When the rare earth chlorinated carbonate or the rare earth chlorinated carbonate-based composite material is used as a phosphorus removal agent, compared with a rare earth carbonate / supported rare earth carbonate adsorbent, the adsorption rate is remarkably improved under the condition of the same phosphorus adsorption amount. Or under the same adsorption time, the phosphorus adsorption capacity is obviously improved. In addition, the rare earth chlorinated carbonate has good adsorption selectivity (competitive ion interference resistance) and has practical application value.

Description

Technical Field

[0001] The invention belongs to the technical field of adsorption materials, and particularly relates to a layered rare earth chlorinated carbonate, a preparation method and an application thereof. Background Art

[0002] Phosphorus pollution refers to the excessive accumulation of phosphorus in the environment, which is one of the main culprits that have negative impacts on ecosystems and human health. The main sources of phosphorus pollution include agricultural activities, domestic sewage and industrial emissions. Severe phosphorus pollution leads to eutrophication of water bodies, deterioration of water quality, reduction of biodiversity, and causes problems with drinking water safety. Among them, eutrophication of water bodies refers to a water pollution phenomenon caused by excessive phosphorus content in water bodies, which is characterized by the accumulation of excessive nutrients (such as phosphorus, nitrogen, etc.) in water bodies. High phosphorus content in water bodies triggers the excessive growth of aquatic organisms such as algae, leading to an imbalance in the aquatic ecosystem. Therefore, all countries have started to control water quality and discharge standards based on phosphorus concentration. However, there are differences in standards between different countries and regions: in the United States, for lakes and rivers in some states, the total phosphorus (TP) concentration limit is usually between 0.01 and 0.1 mg / L, while the phosphorus discharge limit for urban sewage treatment plants requires a total phosphorus concentration of less than 1 mg / L (less than 0.5 mg / L for Class 1A); according to the EU Water Framework Directive, the total phosphorus concentration limit for lakes and rivers in the EU is usually between 0.02 and 0.1 mg / L, and the total phosphorus discharge limit for urban sewage treatment plants is usually 2 mg / L; the total phosphorus concentration limit set by Ontario, Canada for some lakes and rivers is usually between 0.03 and 0.1 mg / L, while the total phosphorus discharge limit for urban sewage treatment plants is required to be below 1 to 2 mg / L; in China, for different water types, the total phosphorus concentration limit for specific lakes is usually between 0.03 and 0.1 mg / L, while the total phosphorus discharge limit for urban sewage treatment plants is usually below 1 to 2 mg / L. These limits are designed to protect water quality and aquatic ecosystems, and their specific values may vary depending on factors such as region, water type, and industry.

[0003] Rare earth elements have excellent phosphorus adsorption and precipitation capabilities, effectively binding phosphate ions in water, thereby reducing phosphorus levels. Rare earth carbonates (RE2(CO3)3·8H2O), a common rare earth compound, exhibit excellent phosphorus removal properties. Although rarely soluble, the carbonate ions in these carbonates can exchange with phosphate ions in solution to form even more insoluble rare earth phosphates. Removing the resulting phosphate precipitate from water through precipitation, filtration, or sedimentation can effectively reduce phosphorus concentrations in water.

[0004] In general, rare earth carbonate adsorbents for phosphorus removal can be used in various water bodies, including natural waters, sewage, and industrial wastewater. The advantages of using rare earth carbonates as phosphorus removal adsorbents include high phosphorus removal efficiency, good precipitation properties, and fewer byproducts compared to other phosphorus removal methods. However, the phosphorus adsorption rate and adsorption capacity of rare earth carbonate adsorbents based on the RE2(CO3)3·8H2O active material still need to be further improved. Summary of the Invention

[0005] The present invention provides a layered rare earth carbonate chloride-based adsorbent comprising a layered rare earth carbonate chloride, wherein some of the interlayer carbonate ions of the layered rare earth carbonate chloride are replaced with chloride ions. The chemical formula of the layered rare earth carbonate chloride can be RECO3Cl·xH2O. By replacing some of the interlayer carbonate ions of the rare earth carbonate (RE2(CO3)3·8H2O) with chloride ions, the adsorbent modifies its activity, increases its reaction rate, and enhances its adsorption capacity. The present invention also provides a method for preparing the layered rare earth carbonate chloride-based adsorbent, namely, preparing the layered rare earth carbonate chloride-based adsorbent via a coprecipitation method.

[0006] Another object of the present invention is to provide a composite material comprising the aforementioned layered rare earth chlorinated carbonate-based adsorbent and a carrier. The addition of the carrier aids in dispersing the active substance, provides more active adsorption sites, and reduces the impact of the nanomaterial on water during use.

[0007] Another object of the present invention is to provide a use of the above-mentioned layered rare earth chlorinated carbonate-based adsorbent or composite modified material adsorbent for phosphorus adsorption.

[0008] Specifically, the purpose of the present invention is achieved through the following solutions:

[0009] A rare earth chlorocarbonate having the chemical formula RECO3Cl·xH2O, wherein RE represents one or more of the rare earth metal elements La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), Lu (lutetium), Sc (scandium) or Y (yttrium).

[0010] x is the number of crystal waters, which can be 0, 1, 2, 3, 4 or 5.

[0011] According to an embodiment of the present invention, the chemical formula of the rare earth chlorocarbonate may be LaCO3Cl·3H2O or CeCO3Cl·3H2O.

[0012] According to an embodiment of the present invention, the rare earth chlorinated carbonate has a layered structure and a flake-like particle morphology, for example, Figure 5 The morphology shown in (a) or (b).

[0013] The present invention also provides a method for preparing the rare earth chlorocarbonate as described above, which is a coprecipitation method and comprises the following steps:

[0014] Separately preparing a rare earth chloride solution and an alkali metal carbonate and / or bicarbonate solution; after the two solutions are dissolved, adding the carbonate and / or bicarbonate solution to the rare earth chloride solution to form a precipitate, and stirring and allowing to stand after the addition of the two solutions is complete;

[0015] wherein the rare earth chloride in the rare earth chloride solution is controlled to be in large excess, so that after the rare earth chloride and the alkali metal carbonate and / or bicarbonate are completely reacted according to the theoretical molar ratio, the concentration of the excess rare earth chloride in the mixture solution after the reaction is above 1.5 mol / L (in terms of rare earth ion concentration);

[0016] The standing is carried out in the solution wherein the concentration of rare earth chloride in the reaction mixture solution is 1.5 mol / L or higher based on the rare earth ion concentration.

[0017] According to an embodiment of the present invention, when carbonate is used, the theoretical molar ratio of rare earth ions and carbonate required in the precipitation is 1:1; when bicarbonate is used, carbon dioxide is produced, so the theoretical molar ratio of rare earth ions and bicarbonate required in the precipitation is 1:1.3.

[0018] According to an embodiment of the present invention, the reaction further comprises filtering and drying steps after standing.

[0019] According to an embodiment of the present invention, the rare earth elements of the rare earth chloride salt solution used include La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), Lu (lutetium), Sc (scandium) or Y (yttrium) rare earth chloride salt or a solution of a hydrated rare earth chloride salt.

[0020] According to an embodiment of the present invention, the rare earth chloride salt solution used may also be a mixed solution of two or more rare earth chloride salts.

[0021] According to an embodiment of the present invention, in the carbonate and / or bicarbonate solution used, the carbonate includes sodium carbonate, potassium carbonate, ammonium carbonate, lithium carbonate, cesium carbonate, rubidium carbonate, etc., and the bicarbonate includes sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, lithium bicarbonate, cesium bicarbonate or rubidium bicarbonate, etc.

[0022] According to an embodiment of the present invention, the carbonate or bicarbonate used may be a mixed solution of one or both of the above carbonates and bicarbonates.

[0023] According to an embodiment of the present invention, the rare earth ion concentration of the rare earth chloride salt solution used is 0.5 to 5 mol / L, for example, 1 to 3 mol / L.

[0024] According to an embodiment of the present invention, the carbonate and / or bicarbonate solution used has a carbonate ion and / or bicarbonate ion concentration of 0.05 to 3 mol / L, such as 1 to 2 mol / L.

[0025] According to an embodiment of the present invention, the stirring time is 1 to 48 hours.

[0026] According to an embodiment of the present invention, the standing time is 1 to 48 hours.

[0027] According to an embodiment of the present invention, the stirring and the standing are performed at room temperature.

[0028] The present invention also provides a rare earth chlorinated carbonate-based composite material, which is composed of the rare earth chlorinated carbonate and a carrier.

[0029] In the present invention, the rare earth carbonate chloride is compounded with a carrier, thereby reducing the adverse effects of the nano effect of the active ingredient rare earth carbonate chloride on the water body.

[0030] According to an embodiment of the present invention, in the rare earth chlorocarbonate-based composite material, the mass percentage of rare earth chlorocarbonate is 10-60%, such as 20-50%.

[0031] According to an embodiment of the present invention, the carrier is zeolite, diatomaceous earth, bentonite, clay, hydrotalcite, polyacrylamide, carbon nanotube, molecular sieve, etc.; preferably, the carrier is zeolite.

[0032] Among relevant carriers, zeolite is a widely occurring natural mineral, a type of silicate mineral. Its main components are layered silicates and aluminates, with a porous crystal structure. The pores and voids within the zeolite crystal structure give it strong adsorption and ion exchange capabilities. Zeolite's crystal structure is composed of a series of SiO4 and AlO4 tetrahedral units, connected by shared oxygen atoms to form a layered structure. The voids and pores between these layers can accommodate water molecules, ions, and other molecules and substances, giving zeolite properties such as adsorption, dehydration, ion exchange, and molecular sieving. Zeolite's porous crystal structure and large specific surface area provide more adsorption sites and reaction surfaces, increasing access to active catalyst components or adsorbents, thereby enhancing catalytic activity and adsorption capacity. Zeolite has high thermal and chemical stability, exhibiting good stability under harsh conditions such as high temperatures and acid and alkaline conditions, making it suitable for high-temperature catalysis and adsorption applications. The inventors have discovered that by combining zeolite as a carrier with the aforementioned rare earth chlorinated carbonate-based adsorbent to prepare a composite material, the zeolite can be effectively utilized to immobilize and protect the active components. Using this composite material as an adsorbent can effectively reduce the loss of rare earth-based active ingredients and ensure the stability of the adsorbent during use. In addition, by utilizing the high specific surface area and large particle size of zeolite, the nano-effect of rare earth chlorocarbonate particles is suppressed, reducing the adverse effects of the adsorbent on water bodies.

[0033] Based on this, another object of the present invention is to provide a composite material, which is a composite modified material of the above-mentioned rare earth chlorinated carbonate-based adsorbent and a zeolite carrier, utilizing the properties of the zeolite carrier to provide more active sites and reduce the impact of nanomaterials on water bodies when used.

[0034] The present invention also provides a method for preparing the above-mentioned rare earth chlorinated carbonate-based composite material, comprising the following steps:

[0035] A rare earth chloride solution and an alkali metal carbonate and / or bicarbonate solution are separately prepared. After the two solutions are dissolved, a carrier is added to either or both of the two solutions. One of the two solutions is then added to the other to form a precipitate. The amount of rare earth chloride in the rare earth chloride solution must be controlled to be excessive until the concentration of the excess rare earth chloride in the mixture solution is above 1.5 mol / L after the rare earth chloride and the alkali metal carbonate and / or bicarbonate have completely reacted according to the theoretical molar ratio. After the two solutions are added, the mixture is stirred and allowed to stand.

[0036] According to an embodiment of the present invention, when carbonate is used, the theoretical molar ratio of rare earth ions and carbonate required in the precipitation is 1:1; when bicarbonate is used, carbon dioxide is produced, so the theoretical molar ratio of rare earth ions and bicarbonate required in the precipitation is 1:1.3.

[0037] According to an embodiment of the present invention, the reaction further comprises filtering and drying steps after standing.

[0038] According to an embodiment of the present invention, the preparation method of the rare earth chlorinated carbonate-based composite material is the same as the preparation method of the above-mentioned rare earth chlorinated carbonate, except that before the rare earth chloride solution and the alkali metal carbonate and / or bicarbonate solution are mixed, the carrier is added to either one of the above-mentioned two solutions or to both solutions at the same time, and then a coprecipitation reaction is carried out.

[0039] The present invention also provides an adsorbent, specifically an adsorbent for adsorbing phosphorus in water. The adsorbent includes the above-mentioned rare earth chlorinated carbonate or rare earth chlorinated carbonate-based composite material.

[0040] The present invention also provides application of the adsorbent as a water dephosphorization agent.

[0041] According to an embodiment of the present invention, in the adsorption system, the pH of the solution is 4 to 10, such as 6 to 8, such as 7.

[0042] The present invention achieves the following beneficial effects:

[0043] When used as a phosphorus removal agent, the rare earth carbonate chloride or rare earth carbonate chloride-based composite material provided by the present invention significantly improves the adsorption rate compared to rare earth carbonate / supported rare earth carbonate adsorbents under conditions of identical phosphorus adsorption. Alternatively, the phosphorus adsorption capacity is significantly improved under the same adsorption time. Furthermore, the rare earth carbonate chloride has good adsorption selectivity (resistance to competing ion interference) and has practical application value.

[0044] The synthesis process of the rare earth chlorinated carbonate-based composite material provided by the present invention can adjust the proportion of the active ingredient rare earth chlorinated carbonate in the composite material according to the phosphorus concentration level of the treated water body, thereby achieving phosphorus removal at different concentrations. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is the adsorption kinetics test result diagram of comparative example and example samples.

[0046] Figure 2 Graph showing the phosphorus adsorption data for the samples of Comparative Example 1 and Example 1 under different pH environments (the left side of each of the three groups of data is the test result for the sample of Comparative Example 1, and the right side is the test result for the sample of Example 1).

[0047] Figure 3 The X-ray diffraction patterns of the comparative example and the example samples are shown in FIG.

[0048] Figure 4 The infrared spectra of the sample in Example 1 before and after adsorption are shown.

[0049] Figure 5 These are SEM images of the sample of Example 1 before and after adsorption [(a) and (b) are the test results of the sample of Example 1 before adsorption; (c) and (d) are the test results of the sample of Example 1 after adsorption].

[0050] Figure 6 The following are the X-ray diffraction test results of the sample in Example 1 and the standard diffraction pattern of LaCO3Cl·3H2O. DETAILED DESCRIPTION

[0051] In order to further understand the present invention, the scheme of the present invention is described in detail below in combination with comparative examples and embodiments, but the present invention is not limited to these embodiments. Any other changes, replacements or combined simplifications made under the core guiding idea of the patent of the present invention are included in the scope of protection of the patent of the present invention.

[0052] Comparative Example 1

[0053] Prepare 100 ml of 1 mol / L LaCl3 solution and 100 ml of 1 mol / L NaHCO3 solution. After both are completely dissolved, add the NaHCO3 solution to the LaCl3 solution at a rate of 4 ml / min, stir for 24 hours, let stand for 24 hours, filter and dry to obtain the sample of Comparative Example 1.

[0054] Comparative Example 2

[0055] Prepare 90 ml of 0.667 mol / L LaCl3 solution and 10 ml of 1 mol / L Na2CO3 solution. After complete dissolution, add Na2CO3 solution to the LaCl3 solution at a rate of 0.1 ml / min, stir for 24 h, let stand for 24 h, filter, wash three times with water, and dry at room temperature to obtain the sample of Comparative Example 2.

[0056] Comparative Example 3

[0057] Prepare 90 ml of 1.22 mol / L LaCl3 solution and 10 ml of 1 mol / L Na2CO3 solution. After complete dissolution, add Na2CO3 solution to the LaCl3 solution at a rate of 0.1 ml / min, stir for 24 h, let stand for 24 h, filter, wash three times with water, and dry at room temperature to obtain the comparative example 3 sample.

[0058] Comparative Example 4

[0059] Untreated zeolite powder (the zeolite powder used in Example 8 is the same type)

[0060] Comparative Example 5

[0061] Prepare 50 ml of 1 mol / L LaCl3 solution, add 5 g of zeolite powder after complete dissolution, stir for 24 hours, let stand for 24 hours, filter and dry to obtain sample 5 of Comparative Example 5.

[0062] Comparative Example 6

[0063] Prepare 50 ml of 1 mol / L LaCl3 solution, add 5 g of zeolite powder after complete dissolution, stir for 3 h, add 50 ml of 0.5 mol / L Na2CO3 solution, stir for 24 h, let stand for 24 h, filter and dry to obtain sample 6 of comparative example.

[0064] Example 1

[0065] Prepare 90 ml of 1.78 mol / L LaCl3 solution and 10 ml of 1 mol / L Na2CO3 solution. After complete dissolution, add Na2CO3 solution to the LaCl3 solution at a rate of 0.1 ml / min, stir for 24 h, let stand for 24 h, filter, wash three times with water, and dry at room temperature to obtain the sample of Example 1.

[0066] The X-ray diffraction test results of the obtained samples are as follows Figure 6 As shown. Figure 6 It can be seen that the sample in Example 1 is LaCO3Cl·3H2O.

[0067] Example 2

[0068] Prepare 90 ml of 2.33 mol / L LaCl3 solution and 10 ml of 1 mol / L Na2CO3 solution. After complete dissolution, add Na2CO3 solution to the LaCl3 solution at a rate of 0.1 ml / min, stir for 24 h, let stand for 24 h, filter, wash three times with water, and dry at room temperature to obtain the sample of Example 2.

[0069] Example 3

[0070] Prepare 90 ml of 3.44 mol / L LaCl3 solution and 10 ml of 1 mol / L Na2CO3 solution. After complete dissolution, add Na2CO3 solution to the LaCl3 solution at a rate of 0.1 ml / min, stir for 24 h, let stand for 24 h, filter, wash three times with water, and dry at room temperature to obtain the sample of Example 3.

[0071] Example 4

[0072] Prepare 90 ml of 3.44 mol / L LaCl3 solution and 10 ml of 1 mol / L Na2CO3 solution. After complete dissolution, add Na2CO3 solution to the LaCl3 solution at a rate of 0.1 ml / min, stir for 3 h, let stand for 1 h, filter, wash three times with water, and dry at room temperature to obtain the sample of Example 4.

[0073] Example 5

[0074] Prepare 90 ml of 3.44 mol / L LaCl3 solution and 10 ml of 1 mol / L K2CO3 solution. After complete dissolution, add K2CO3 solution to the LaCl3 solution at a rate of 0.1 ml / min, stir for 3 h, let stand for 1 h, filter, wash three times with water, and dry at room temperature to obtain the sample of Example 5.

[0075] Example 6

[0076] Prepare 90 ml of 3.44 mol / L LaCl3 solution and 20 ml of 1 mol / L NaHCO3 solution. After complete dissolution, add NaHCO3 solution to the LaCl3 solution at a rate of 0.2 ml / min, stir for 12 h, let stand for 12 h, filter, wash three times with water, and dry at room temperature to obtain the sample of Example 6.

[0077] Example 7

[0078] Prepare 90 ml of 3.44 mol / L CeCl3 solution and 10 ml of 1 mol / L Na2CO3 solution. After complete dissolution, add Na2CO3 solution to the CeCl3 solution at a rate of 0.1 ml / min, stir for 24 h, let stand for 24 h, filter, wash three times with water, and dry at room temperature to obtain the sample of Example 7.

[0079] Example 8

[0080] Prepare 90 ml of a 3.44 mol / L LaCl₃ solution and 10 ml of a 1 mol / L Na₂CO₃ solution. After the LaCl₃ is completely dissolved, add 5 g of zeolite powder and stir for 3 h. Then, add the Na₂CO₃ solution to the LaCl₃ solution at a rate of 0.1 ml / min, stir for 24 h, let it stand for 24 h, filter, wash three times with water, and dry at room temperature to obtain the sample of Example 8.

[0081] The X-ray diffraction test results of the samples obtained in Comparative Examples 1-3, 6 and Examples 2-8 are as follows: Figure 3 As shown. Figure 3 It can be seen that the samples prepared in Comparative Examples 1-3 and 6 are lanthanum carbonate octahydrate (La2(CO3)3·8H2O). The samples obtained in Examples 2-6 and 8 are all lanthanum carbonate chloride trihydrate (LaCO3Cl·3H2O), and the sample obtained in Example 7 is cerium carbonate chloride trihydrate (CeCO3Cl·3H2O).

[0082] Test Example 1

[0083] 1.1 Phosphorus adsorption performance test method:

[0084] A certain amount of the samples obtained in the comparative example and the example were respectively placed in a certain amount of conical flasks, a phosphorus-containing solution of a certain volume concentration was added, the pH of the solution was adjusted with HCl and NaOH, and the solution was placed in a constant temperature shaker at a temperature of 25°C and a speed of 180 rpm for adsorption. After a period of adsorption, the supernatant was filtered through a 0.045 μm filter membrane, and the phosphorus concentration in the solution was determined according to the national standard GB11893-89, thereby calculating the phosphorus adsorption capacity of the adsorbent.

[0085] Comparative Examples and Adsorption Kinetics Test Results (See Figure 1 )

[0086] The specific test conditions are as follows: 0.25 g of adsorbent (0.25 g is the amount of supported adsorbent used in the case of a supported adsorbent) is added to 500 ml of phosphorus solution, the solution is adjusted to pH 7, and adsorption is performed on a constant temperature shaker at 25°C and 180 rpm. A small amount of the supernatant is collected at adsorption times of 1, 2, 4, 6, 8, 12, 24, 36, 48, and 60 hours. After filtering through a 0.045 μm filter, the phosphorus concentration in the solution is measured to calculate the phosphorus adsorption capacity of the adsorbent.

[0087] Adsorption kinetics results show that the layered rare earth salt-based adsorbents prepared in Examples 1-8 of the present invention, when compared to the comparative example, adsorb the same amount of phosphorus in a nearly 25% shorter adsorption time. Alternatively, under the same adsorption time or pH conditions, the adsorbents of the present invention significantly increase the amount of phosphorus adsorbed. Figure 1 The corresponding adsorption data are listed in Table 1.

[0088] Table 1

[0089]

[0090] 1.2 Phosphate adsorption capacity of Comparative Example 1 and Example 1 under different pH environments

[0091] 0.05 g of the samples obtained in Comparative Example 1 and Example 1 were respectively placed in a 150 ml conical flask, 100 ml of a phosphorus-containing solution with a concentration of 60 mg P / L was added, and the pH of the solution was adjusted to 4, 7, and 10 with HCl and NaOH. The solution was placed in a constant temperature shaker at a temperature of 25 ° C and a speed of 180 rpm for adsorption. After 48 hours of adsorption, the supernatant was filtered through a 0.045 μm filter membrane, and the phosphorus content in the solution was determined according to the national standard GB11893-89, thereby calculating the phosphorus adsorption capacity of the adsorbent. The test results are as follows: Figure 2 shown.

[0092] 1.3 X-ray diffraction patterns of the sample in Example 1 before and after adsorption

[0093] The X-ray diffraction test was performed on the sample of Example 1 in Section 1.1 before and after adsorption. The results are as follows: Figure 3 As shown. Figure 3 It can be seen that the main phase of the sample in Example 1 changes before and after adsorption. The main component of the sample in Example 1 after adsorption is lanthanum phosphate hydrate, which proves that it has adsorbed a large amount of phosphate.

[0094] 1.4 Infrared spectra of the sample in Example 1 before and after adsorption

[0095] The infrared characterization of the sample of Example 1 in Section 1.1 before and after adsorption was carried out, and the results were as follows Figure 4 As shown. Figure 4 It can be seen that the functional groups contained in the sample of Example 1 changed significantly before and after adsorption. The characteristic vibration signal of phosphate appeared after adsorption, indicating that the adsorbent adsorbed and bound the phosphate.

[0096] 1.5 SEM images of Example 1 before and after adsorption

[0097] The SEM test of the sample of Example 1 in Section 1.1 before and after adsorption was carried out, and the results are as follows Figure 5 As shown. Figure 5 It can be seen that the adsorbent of Example 1 is mainly lamellar before adsorption, and the appearance of the adsorbent changes significantly after adsorption, which corresponds to the phenomenon of phase transformation before and after adsorption in Section 1.3.

[0098] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A rare earth chlorinated carbonate having the chemical formula RECO3Cl·xH2O, wherein: RE represents one or more of the rare earth metal elements La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), Lu (lutetium), Sc (scandium) or Y (yttrium); x is the number of crystal waters, which can be 0, 1, 2, 3, 4 or 5.

2. The rare earth chlorinated carbonate according to claim 1, characterized in that The chemical formula of the rare earth chlorocarbonate is LaCO3Cl·3H2O or CeCO3Cl·3H2O.

3. The rare earth chlorinated carbonate according to claim 1 or 2, characterized in that The rare earth chlorinated carbonate has a layered structure and a flaky particle shape.

4. The method for preparing the rare earth chlorocarbonate according to any one of claims 1 to 3, characterized in that: It is a coprecipitation method, comprising the following steps: Separately preparing a rare earth chloride solution and an alkali metal carbonate and / or bicarbonate solution; after the two solutions are dissolved, adding the carbonate and / or bicarbonate solution to the rare earth chloride solution to form a precipitate, and stirring and allowing to stand after the addition of the two solutions is complete; The rare earth chloride in the rare earth chloride solution is controlled to be in large excess until the rare earth chloride and the alkali metal carbonate and / or bicarbonate are completely reacted according to the theoretical molar ratio, and the concentration of the excess rare earth chloride in the mixture solution after the reaction, calculated as the rare earth ion concentration, is above 1.5 mol / L. The standing is carried out in a solution where the concentration of the rare earth chloride in the reaction mixture solution is above 1.5 mol / L based on the rare earth ion concentration.

5. The preparation method according to claim 4, characterized in that When carbonate is used, the theoretical molar ratio of rare earth ions and carbonate required in the precipitation is 1:1; when bicarbonate is used, carbon dioxide is produced, so the theoretical molar ratio of rare earth ions and bicarbonate required in the precipitation is 1:1.

3.

6. The preparation method according to claim 4 or 5, characterized in that The rare earth elements in the rare earth chloride salt solution used include La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), Lu (lutetium), Sc (scandium) or Y (yttrium) rare earth chloride salt or hydrated rare earth chloride salt solution; Preferably, in the carbonate and / or bicarbonate solution used, the carbonate includes sodium carbonate, potassium carbonate, ammonium carbonate, lithium carbonate, cesium carbonate, and rubidium carbonate, and the bicarbonate includes sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, lithium bicarbonate, cesium bicarbonate, or rubidium bicarbonate; Preferably, the rare earth ion concentration of the rare earth chloride salt solution used is 0.5 to 5 mol / L; Preferably, the carbonate and / or bicarbonate solution used has a carbonate ion and / or bicarbonate ion concentration of 0.05 to 3 mol / L.

7. A rare earth chlorinated carbonate-based composite material, characterized in that: The composite material is composed of the rare earth chlorinated carbonate according to any one of claims 1 to 3 and a carrier; The carrier is zeolite, diatomaceous earth, bentonite, clay, hydrotalcite, polyacrylamide, carbon nanotube or molecular sieve.

8. The method for preparing the rare earth chlorinated carbonate-based composite material according to claim 7, characterized in that: The steps include: A rare earth chloride solution and an alkali metal carbonate and / or bicarbonate solution are separately prepared. After the two solutions are dissolved, a carrier is added to either or both of the two solutions. One of the two solutions is then added to the other to form a precipitate. The amount of rare earth chloride in the rare earth chloride solution must be controlled to be excessive until the concentration of the excess rare earth chloride in the mixture solution is above 1.5 mol / L after the rare earth chloride and the alkali metal carbonate and / or bicarbonate have completely reacted according to the theoretical molar ratio. After the two solutions are added, the mixture is stirred and allowed to stand.

9. An adsorbent for phosphorus adsorption in water, characterized in that: The adsorbent comprises the rare earth chlorocarbonate according to any one of claims 1 to 3 or the rare earth chlorocarbonate-based composite material according to claim 7.

10. Use of the adsorbent according to claim 9 as a water phosphorus removal agent.

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