CN115532235A - Lanthanum-based adsorbent and preparation method and application thereof - Google Patents

Abstract

The invention discloses a lanthanum-based adsorbent and its preparation method and application. The lanthanum-based adsorbent is a complex formed by a benzimidazole carboxylic acid derivative and a lanthanum salt. The lanthanum salt includes lanthanum chloride heptahydrate , Lanthanum nitrate hexahydrate and lanthanum hydroxide. The lanthanum-based adsorbent prepared by the present invention is effective against antimonate (Sb(V)), phosphate (P(V)), arsenite (As(III)), arsenate (As(V)) and antimonite The maximum adsorption capacity of (Sb(III)) was 896.5mg/g, 426.9mg/g, 271.7mg/g, 154.6mg/g and 91.5mg/g; The removal rates of P(V), As(III), As(V) and Sb(III) were 97.8%, 97.0%, 87.3%, 79.3% and 80.4%, respectively; the position of Sb(V) on the adsorbent surface The point utilization rate reaches 50.1%, which has a relatively high point utilization rate. In addition, in the mixed solution, La‑MGs has a good selectivity for Sb(V).

Description

A kind of lanthanum-based adsorbent and its preparation method and application

technical field

The invention relates to the field of heavy metal adsorbents, in particular to a lanthanum-based adsorbent and its preparation method and application.

Background technique

Oxygenate contamination in aqueous solutions, especially arsenite (As(III)) and antimony (Sb(III)) contamination, poses a great threat to human health even at low concentrations due to their high toxicity and carcinogenicity , which has attracted worldwide attention. Drinking water is considered to be a major route of contamination with oxo-acid radicals such as arsenic(III) and antimony(III), which can cause serious health problems such as skin lesions, neurological symptoms and even cancer, a feature that calls for effective removal methods . Adsorption technology is considered to be an efficient and simple technology, and its efficiency is higher compared to other technologies. However, targeted removal of specific pollutants in solution is difficult due to the varying degrees of matching between adsorbents and different pollutants.

In recent years, efforts have been made to design and construct rational adsorption structures to improve the adsorption performance for target pollutants. Advanced functional materials, such as metal oxides, metal-organic frameworks, biomass-based materials, and covalent organic frameworks, have been used to explore the relationship between adsorption configuration and pollutant removal performance. The study found that UiO-66-SH-A with higher lattice defects has a larger adsorption capacity and faster rate for As(III)/As(V) due to the formation of a stable adsorption configuration. In addition, MOFUiO-66-3C4N exhibited strong uranyl adsorption capacity in both simulated seawater and natural seawater, mainly due to the increased coordination between the adsorbent and uranium due to the smaller nanopockets. So far, exploring the effect of matching degree on the adsorption performance of pollutants on adsorbents is still a great challenge and few studies have been carried out.

The Chinese patent with publication number CN113019305B discloses the preparation and application of porous basic lanthanum carbonate phosphate adsorbent. The preparation includes: subjecting a mixed solution of lanthanum chloride, urea and sodium citrate to a hydrothermal reaction at 120-180° C. to obtain the adsorbent. The adsorbent of the invention has faster adsorption rate, higher adsorption capacity and selectivity for phosphate, and has good regeneration and recycling properties.

The Chinese patent with the publication number CN103240060A designed and synthesized a new type of organometallic gel, which is a gel formed by forming complexes between benzimidazole carboxylic acid derivatives and metal lead ions to bind small solvent molecules. The results of SEM showed that the metal-organic gel presents an interwoven three-dimensional network structure. The adsorption experiments on methyl orange dye molecules show that the metal organic gel can efficiently and selectively adsorb methyl orange molecules in the water phase, so it is a new material for treating water polluted by methyl orange dye molecules.

The Chinese patent whose publication number is CN113019305B utilizes lanthanum chloride to make an adsorbent, which has a faster adsorption rate for phosphate. Disposal of methyl orange dye molecule polluting water. At present, there is no technology to apply lanthanum chloride and benzimidazole carboxylic acid derivatives to remove oxoacid ion pollution in water.

Contents of the invention

The technical problem to be solved by the present invention is to provide a lanthanum-based adsorbent and a preparation method thereof, which can efficiently and quickly capture antimonate in sewage, and at the same time, the phosphate in sewage has an influence on the removal of antimonate smaller.

The invention also provides the application of a lanthanum-based adsorbent for targeted removal of antimonate radicals from oxoacid radicals.

In order to solve the above-mentioned technical problems, the technical solution adopted in the present invention is: a lanthanum-based adsorbent, which is a complex formed by a benzimidazole carboxylic acid derivative and a lanthanum salt, and the lanthanum salt includes heptahydrate lanthanum chloride, hexahydrate Hydrated lanthanum nitrate and lanthanum hydroxide.

Due to the different matching degrees between the synthesized lanthanum-based adsorbent of the present invention and different pollutants, the coordination force between the adsorbent and the pollutants is different, thereby affecting the adsorption performance of the material. Compared with the prior art, the lanthanum-based adsorbent synthesized by the present invention can efficiently and rapidly capture oxoacids, especially antimonate, and it is found that the phosphate in the mixed solution has little effect on the removal of antimonate. Therefore, lanthanum-based adsorbent is a new type of material for treating water polluted by oxoacid radicals.

In a preferred embodiment of the present invention, the benzimidazole carboxylic acid derivative is 1,3-dicarboxymethyl-2-methylbenzimidazole (MG), and the lanthanum salt is heptahydrate chloride lanthanum.

In the experiment, it was found that the lanthanum-based adsorbent La-MGs formed by 1,3-dicarboxymethyl-2-methylbenzimidazole (MG) and lanthanum salt had better adsorption performance on Sb(V) than 2-methylbenzo Lanthanum-based adsorbent La-MCs formed by imidazole (MC) and lanthanum salt. The lanthanum-based adsorbent synthesized with 1,3-dicarboxymethyl-2-methylbenzimidazole (MG) as an organic ligand has a porous structure that can efficiently, rapidly and selectively capture the Antimonate, so as to realize the selective removal of oxo-acid in wastewater. In the formed lanthanum-based adsorbent La-MGs, when the anion is lanthanum chloride, the adsorption performance for Sb(V) is better than that of lanthanum-based adsorbents whose anions are lanthanum nitrate hexahydrate and lanthanum hydroxide.

In a preferred embodiment of the present invention, the molar ratio of the benzimidazole carboxylic acid derivative to the lanthanum chloride is 1.25-5 mmol: 2.5-10 mmol. Further preferably, the molar ratio of the benzimidazole carboxylic acid derivative to the lanthanum chloride is 1.25-5 mmol: 2.5-5 mmol.

The invention also discloses a preparation method of a lanthanum-based adsorbent, comprising the following steps:

S1, dissolving the lanthanum salt in a solvent to form a lanthanum salt solution;

S2. Add benzimidazole carboxylic acid derivatives to the lanthanum salt solution of S1, mix evenly, heat and dry, and obtain a lanthanum-based adsorbent after the reaction is completed.

In a preferred embodiment of the present invention, the temperature of heating and drying in S2 is 120° C. to 180° C., and the time is 8 to 24 hours. Different time and temperature will have different adsorption properties of the material. The currently selected temperature and time are to make the material obtain the maximum adsorption capacity. The formed morphology structure is a porous structure with nanosheets stacked, and the morphology changes significantly after adsorbing different pollutants.

In a preferred embodiment of the present invention, the benzimidazole carboxylic acid derivative is 1,3-dicarboxymethyl-2-methylbenzimidazole (MG), and the lanthanum salt is heptahydrate chloride lanthanum.

In a preferred embodiment of the present invention, the molar ratio of the benzimidazole carboxylic acid derivative to the lanthanum salt is 1.25-5 mmol: 2.5-10 mmol.

In a preferred embodiment of the present invention, the solvent in S1 is water, methanol and absolute ethanol; preferably, the solvent in S1 is absolute ethanol.

The molar volume ratio of the benzimidazole carboxylic acid derivative, the lanthanum salt, and absolute ethanol is 1.25˜5 mmol: 2.5˜10 mmol: 30-60 mL.

The mixing method in S2 is ultrasonic mixing for 30-60 minutes.

The invention also discloses an application of using the lanthanum-based adsorbent for targeted removal of oxygen-containing acid radicals in sewage.

In a preferred embodiment of the present invention, the sewage includes oxoacids and other heavy metal ions, and the oxoacids include antimonate (Sb(V)), phosphate (P(V)), arsenous acid radical (As(III)), arsenate radical (As(V)) and antimonite radical (Sb(III)), and in the process of targeted removal of said oxoacid radicals, phosphate radicals and nitrate radicals in sewage are not affected , the impact of sulfate; preferably, the oxoacid for targeted removal is antimonate (Sb(V)).

Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention regulates the coordination force between the pollutant and the adsorption site by changing the matching degree of the pollutant and the adsorbent, thereby affecting the adsorption of the pollutant on the surface of the adsorption material. removal performance. The lanthanum-based adsorbent prepared by the present invention is effective against antimonate (Sb(V)), phosphate (P(V)), arsenite (As(III)), arsenate (As(V)) and antimonite The maximum adsorption capacity of (Sb(III)) was 896.5mg/g, 426.9mg/g, 271.7mg/g, 154.6mg/g and 91.5mg/g respectively; The removal rates of P(V), As(III), As(V) and Sb(III) were 97.8%, 97.0%, 87.3%, 79.3% and 80.4%, respectively; the position of Sb(V) on the adsorbent surface The point utilization rate reaches 50.1%, which has a relatively high point utilization rate. In addition, La-MGs have good selectivity for Sb(V) in the mixed solution. This work explores the influence of the local coordination environment of the adsorption site on the adsorption performance from the perspective of removal objects, and provides a new idea for the selective and efficient adsorption of pollutants.

Description of drawings

The lanthanum-based adsorbent of two kinds of ligands is to the adsorption performance of Sb(V) of Fig. 1;

Figure 2 The adsorption properties of three different anion-based lanthanum-based adsorbents for Sb(V);

The adsorption properties of lanthanum-based adsorbents obtained in three different solvents to Sb(V) in Fig. 3;

The adsorption performance of the lanthanum-based adsorbent obtained by the ratio of metal ions and organic ligands to Sb(V) in Fig. 4;

Figure 5. Morphological changes before and after capturing different pollutants by lanthanum-based adsorbents;

Figure 6Sb(V) adsorption performance on lanthanum-based adsorbent;

Figure 7P (V) adsorption performance on lanthanum-based adsorbent;

The adsorption performance of Fig. 8As(III) on lanthanum-based adsorbent;

Figure 9As (V) in the adsorption performance of lanthanum-based adsorbent;

Figure 10Sb(III) adsorption performance on lanthanum-based adsorbent;

Figure 11 Selectivity experiment of La-MGs at low concentration. C _Sb(V) = 2 mM, V = 50 mL, adsorbent dose = 1.0 g/L, pH = 3, t = 24 h, T = 25 °C.

detailed description

Example 1

The lanthanum-based adsorbent in this example uses 1,3-dicarboxymethyl-2-methylbenzimidazole as the organic ligand, lanthanum chloride heptahydrate as the metal center, and water, methanol and anhydrous Ethanol is used as solvent and prepared by solvothermal method.

(1) Mix the metal salt heptahydrate lanthanum chloride, 1,3-dicarboxymethyl-2-methylbenzimidazole and absolute ethanol, and obtain a mixed solution after ultrasonic mixing for 30 minutes; the metal salt heptahydrate chlorination The molar volume ratio of lanthanum, 1,3-dicarboxymethyl-2-methylbenzimidazole and absolute ethanol is 8mmol:4mmol:40mL.

(2) Put the mixed solution obtained in the step (1) into an oven for reaction at a temperature of 120° C. for 12 hours to obtain the lanthanum-based adsorbent La-MGs.

Example 2

(1) Mix the metal salt lanthanum chloride heptahydrate, 2-methylbenzimidazole (MC) and absolute ethanol, and obtain a mixed solution after ultrasonic mixing for 30 minutes; wherein the metal salt lanthanum chloride heptahydrate, 2-methyl The molar volume ratio of benzimidazole (MC) to absolute ethanol is 8mmol:4mmol:40mL.

(2) Put the mixed solution obtained in the step (1) into an oven for reaction at a temperature of 120° C. for 12 hours to obtain the lanthanum-based adsorbent La-MCs.

Lanthanum-based adsorbents were prepared from organic ligands 2-methylbenzimidazole (MC) and 1,3-dicarboxymethyl-2-methylbenzimidazole (MG) and metal salt lanthanum chloride heptahydrate, respectively. As shown in Figure 1, it was found in the experiment that the lanthanum-based adsorbent La-MGs formed by 1,3-dicarboxymethyl-2-methylbenzimidazole (MG) and lanthanum salt has better adsorption performance on Sb(V) than Lanthanum-based adsorbent La-MCs formed by 2-methylbenzimidazole (MC) and lanthanum salt. The lanthanum-based adsorbent synthesized with 1,3-dicarboxymethyl-2-methylbenzimidazole (MG) as an organic ligand has a porous structure that can efficiently, quickly and selectively capture antimonate in mixed solutions, In this way, the selective removal of oxygen-containing acid radicals in wastewater can be realized.

Example 3

(1) Mix lanthanum salt, 1,3-dicarboxymethyl-2-methylbenzimidazole and absolute ethanol, and obtain a mixed solution after ultrasonic mixing for 45 minutes; among them, lanthanum salt, 1,3-dicarboxymethyl -The molar volume ratio of 2-methylbenzimidazole to absolute ethanol is 8mmol:4mmol:40mL. Wherein the lanthanum salts are lanthanum chloride heptahydrate, lanthanum nitrate hexahydrate and lanthanum hydroxide respectively.

(2) The mixed solution obtained in the step (1) is placed in an oven to react, the temperature of the reaction is 120° C., and the time is 12 hours, and the anions are respectively lanthanum chloride, lanthanum nitrate hexahydrate, and lanthanum hydroxide. Powder solid LaCl ₃ -MGs, light yellow powder solid La(NO ₃ ) ₃ -MGs and white block estimated La(OH) ₃ -MGs.

In the lanthanum-based adsorbent La-MGs formed as shown in Figure 2, the adsorption performance of Sb(V) with lanthanum chloride as an anion is sequentially better than that of lanthanum nitrate hexahydrate and lanthanum hydroxide.

Example 4

(1) Mix the metal salt lanthanum chloride heptahydrate, 1,3-dicarboxymethyl-2-methylbenzimidazole with the solvent, and ultrasonically mix for 30 minutes to obtain a mixed solution; wherein the metal salt lanthanum chloride heptahydrate, The molar volume ratio of 1,3-dicarboxymethyl-2-methylbenzimidazole to solvent is 8mmol:4mmol:40ml. Wherein the solvent is selected as water, methanol and absolute ethanol respectively.

(2) Put the mixed solution obtained in the step (1) into an oven for reaction at a temperature of 120° C. for 12 hours to obtain the lanthanum-based adsorbent La-MGs.

As shown in Figure 3, the adsorption performance of lanthanum-based adsorbents obtained in three different solvents on Sb(V) was the best among the lanthanum-based adsorbents prepared from absolute ethanol, La-MGs, for Sb(V).

Example 5

(1) Mix metal salt lanthanum chloride heptahydrate, 1,3-dicarboxymethyl-2-methylbenzimidazole and absolute ethanol, and ultrasonically mix for 30 minutes to obtain a mixed solution; the volume of absolute ethanol is 40mL , the ratios of metal salt lanthanum chloride heptahydrate and 1,3-dicarboxymethyl-2-methylbenzimidazole are 0.5:1, 1:1, and 2:1, respectively.

(2) Put the mixed solution obtained in the step (1) into an oven for reaction at a temperature of 120° C. for 12 hours to obtain the lanthanum-based adsorbent La-MGs.

Figure 4 shows the adsorption properties of lanthanum-based adsorbents obtained by the ratio of metal ions to organic ligands to Sb(V). When the ratio of 2:1, the obtained lanthanum-based adsorbent has the best adsorption performance for Sb(V). Therefore, the optimal ratio range of metal salt lanthanum chloride heptahydrate and 1,3-dicarboxymethyl-2-methylbenzimidazole is 1:1-2:1.

Example 6

(1) Mix the metal salt heptahydrate lanthanum chloride, 1,3-dicarboxymethyl-2-methylbenzimidazole and absolute ethanol, and obtain a mixed solution after ultrasonic mixing for 30 minutes; the metal salt heptahydrate chlorination The molar volume ratio of lanthanum, 1,3-dicarboxymethyl-2-methylbenzimidazole and absolute ethanol is 8mmol:4mmol:40mL.

(2) Put the mixed solution obtained in the step (1) into an oven for reaction at a temperature of 120° C. for 8 hours to obtain the lanthanum-based adsorbent La-MGs.

Example 7

(1) Mix the metal salt heptahydrate lanthanum chloride, 1,3-dicarboxymethyl-2-methylbenzimidazole and absolute ethanol, and obtain a mixed solution after ultrasonic mixing for 30 minutes; the metal salt heptahydrate chlorination The molar volume ratio of lanthanum, 1,3-dicarboxymethyl-2-methylbenzimidazole and absolute ethanol is 8mmol:4mmol:40mL.

(2) Put the mixed solution obtained in the step (1) into an oven for reaction at a temperature of 180° C. for 24 hours to obtain the lanthanum-based adsorbent La-MGs.

Adding the lanthanum-based adsorbent obtained in Example 1 to an initial concentration of 1g/L (initial concentrations of five pollutions) five kinds of pollutant solutions reacted for 24h, then tested the residual concentration of species pollutants in the solution to obtain lanthanum-based adsorption The adsorption amounts of the five pollutants (Sb(V), P(V), As(III), As(V) and Sb(III)) were 896.5mg/g, 426.9mg/g, 271.7mg/g g, 154.6mg/g and 91.5mg/g, as shown in Figure 6-10. Figure 5 shows the morphology changes of the lanthanum-based adsorbent before and after capturing different pollutants. The formed morphology structure is a porous structure with nanosheets stacked, and the morphology changes significantly after adsorbing different pollutants.

Application example 1

Prepare an initial concentration of 2mM Sb(V) solution by adding a predetermined amount of F ^- , NO ₃ ^- , H ₂ PO ₄ ^- , AsO ₂ ^- , SbO ₂ ^- , SO ₄ ^2- and AsO ₄ ^2- To detect the influence of interfering ions on the adsorption performance of Sb (V), get 50mL in the Erlenmeyer flask, add 50mg of the lanthanum-based adsorbent prepared in Example 1 respectively in the Erlenmeyer flask, at 25 ° C, 180r/min conditions , put it into a constant temperature shaking box, react for 24 hours, take out the Erlenmeyer flask, and filter through a 0.45um filter membrane for later use. The concentration of residual As in the solution was detected by ICP, the concentration of residual Sb was detected by atomic absorption spectrometer, and the concentration of residual P(V), F ^- , NO ₃ ^- , Cl ^- and SO ₄ ^2- was detected by ion chromatography.

The calculation of the adsorption capacity (Q _e ) of Sb(V), P(V), As(III), As(V), Sb(III), F ^- , NO ₃ ^- , Cl ^- and SO ₄ ^2- follows the following formula:

In the formula: C ₀ is the concentration of different pollutants in the initial solution (mg/L); C _e is the concentration of different pollutants in the solution after adsorption (mg/L); Q _e is the concentration of different pollutants in the lanthanum-based adsorbent The adsorption capacity of the concentration (mg/g); V is the volume of the solution to be adsorbed in the Erlenmeyer flask (mL); m is the mass of the lanthanum-based adsorbent added (mg).

According to the above formula, the adsorption performance of the lanthanum-based adsorbent pair for different pollutants can be calculated when the solution concentration is 2 mM, and the specific results are shown in Figure 11. During the targeted removal of antimonate (Sb(V)), it is not affected by phosphate, nitrate, and sulfate in sewage. Selection experiments show that the lanthanum-based adsorbent has good selectivity to Sb(V), and can selectively capture Sb(V) from eight pollutants. The site utilization ratios of different pollutants adsorbed on La-MGs are shown in Table 1, among which the utilization ratio of Sb(V) adsorption sites was 50.1%.

Table 1. Site utilization of different pollutants adsorbed on La-MGs

a: The total amount of adsorption sites in La-MGs adsorbent is 8 mM.

Claims (10)

1. A lanthanum-based adsorbent characterized by being a complex of a benzimidazole carboxylic acid derivative and a lanthanum salt, the lanthanum salt comprising lanthanum chloride heptahydrate, lanthanum nitrate hexahydrate, and lanthanum hydroxide.

2. The lanthanum-based sorbent of claim 1, wherein the benzimidazole carboxylic acid derivative is 1,3-dicarboxymethyl-2-Methylbenzimidazole (MG) and the lanthanum salt is lanthanum chloride heptahydrate.

3. The lanthanum-based sorbent according to claim 1, wherein the molar ratio of the benzimidazole carboxylic acid derivative to the lanthanum chloride is 1.25 to 5mmol: 2.5-10 mmol.

4. A preparation method of a lanthanum-based adsorbent is characterized by comprising the following steps:

s1, dissolving lanthanum salt in a solvent to form a lanthanum salt solution;

and S2, adding benzimidazole carboxylic acid derivatives into the lanthanum salt solution of the S1, uniformly mixing, heating and drying, and obtaining the lanthanum-based adsorbent after the reaction is finished.

5. The method for preparing a lanthanum-based adsorbent according to claim 4, wherein the temperature for heating and drying in S2 is 120 ℃ to 180 ℃ for 8 to 24 hours.

6. The method of claim 4, wherein the benzimidazole carboxylic acid derivative is 1,3-dicarboxymethyl-2-Methylbenzimidazole (MG), and the lanthanum salt is lanthanum chloride heptahydrate.

7. The method of preparing a lanthanum-based sorbent according to claim 4, wherein the molar ratio of the benzimidazole carboxylic acid derivative to the lanthanum salt is 1.25 to 5mmol: 2.5-10 mmol.

8. The method for producing a lanthanum-based adsorbent according to claim 4, wherein the solvent in S1 is water, methanol, and absolute ethanol; preferably, the solvent in S1 is absolute ethanol.

9. Use of a lanthanum-based sorbent according to any of claims 1 to 3 for the targeted removal of oxygenates from wastewater.

10. The use of the lanthanum-based sorbent for the targeted removal of oxygenates in wastewater according to claim 9, characterized in that oxygenates and other heavy metal ions are included in the wastewater, the oxygenates include antimonates (Sb (V)), phosphates (P (V)), arsenites (As (III)), arsenates (As (V)) and antimonites (Sb (III)), and the targeted removal of the oxygenates is not affected by phosphates, nitrates, sulfates in the wastewater; preferably, the targeted removal of the oxo acid is antimonate (Sb (V)).

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