Irreversible Covalent Organic Framework for Efficient and Selective Gold Recovery and Preparation Method thereof

Abstract

The disclosure discloses an irreversible covalent organic framework for efficient and selective gold recovery and a preparation method thereof, and belongs to the technical field of precious metal recovery from an aqueous solution. In the disclosure, metal trifluoromethanesulfonate is used as a catalyst, and a solvothermal method is used to prepare a mother covalent organic framework, and then the corresponding structural unit is used to perform an exchange reaction to prepare an irreversible amide-linked covalent organic framework material. The disclosure solves the problem of preparation of high-stability irreversible covalent organic framework, the introduced amide bond gives the covalent organic framework the ability to quickly and selectively recover precious metal gold from an aqueous solution, and the covalent organic framework can be used repeatedly. The application of the covalent organic framework as an efficient adsorbent in the field of adsorption and separation is expanded, and a new material is provided for efficient recovery or removal of metal salts.

Claims

1. A method for preparing an irreversible covalent organic framework material, comprising the following steps: (1) under action of a catalyst, first performing a condensation reaction on a triamino compound represented by formula I-1 and a p-dicarboxaldehyde compound represented by formula II-1; and (2) then adding and mixing a p-diformyl chloride compound represented by formula III-1 for performing an exchange reaction; or, (1) under action of the catalyst, first performing a condensation reaction on a p-diamino compound represented by formula I-2 and a tricarboxaldehyde compound represented by formula II-2; and (2) then adding and mixing a triformyl chloride compound represented by formula III-2 for performing an exchange reaction; ##STR00005## wherein A is selected from nitrogen, benzene ring and s-triazine ring; and B is selected from phenyl, biphenyl and triphenyl.

2. The method of claim 1, wherein the catalyst in step (1) is a metal trifluoromethanesulfonate.

3. The method of claim 1, wherein the condensation reaction in step (1) is carried out in an organic solvent, and the organic solvent comprises one or a mixture of more of dioxane, mesitylene, tetrahydrofuran and N,N-dimethylacetamide.

4. The method of claim 1, wherein an amount of the catalyst used is 5-10% of a total mass of two reactants as structural units.

5. The method of claim 1, wherein the p-diformyl chloride compound 1-1.5 times equivalent of the p-dicarboxaldehyde compound, or the triformyl chloride compound 1-1.5 times equivalent of the tricarboxaldehyde compound is added for the exchange reaction.

6. The method of claim 1, wherein a temperature of the exchange reaction is 4-25 C.

7. An irreversible covalent organic framework material prepared by the method of claim 1.

8. A method of use of the irreversible covalent organic framework material of claim 7, comprising: using the irreversible covalent organic framework material to perform gas storage, catalysis, sensing or separation.

9. The method of claim 8, wherein the irreversible covalent organic framework material is applied as an adsorbent in selective adsorption of gold ions.

10. The method of claim 9, wherein the using the irreversible covalent organic framework material comprises: placing the irreversible covalent organic framework material in an aqueous solution containing gold ions, adding acid, uniformly mixing and centrifuging the mixed solution, and recovering and eluting solid powder to obtain the gold adsorbed on the covalent organic framework.

Description

BRIEF DESCRIPTION OF FIGURES

[0035] FIG. 1 is a schematic diagram of the structure of an amide-linked covalent organic framework prepared in Example 1.

[0036] FIG. 2A is an experimental and simulated X-ray powder diffraction pattern of the mother covalent organic framework TzBA prepared in Example 1, and FIG. 2B is an infrared spectrum of the monomers Tz and BA and the prepared TzBA.

[0037] FIG. 3A is an experimental and simulated X-ray powder diffraction pattern of the covalent organic framework JNU-1 prepared in Example 1, and FIG. 3B is an infrared spectrum of the monomers Tz and TaCl and the prepared JNU-1.

[0038] FIG. 4A is a powder X-ray diffraction pattern of the amide-linked covalent organic framework JNU-1 prepared after the exchange of the mother covalent organic framework TzBA prepared in Example 1 with a monomer, and FIG. 4B is an infrared spectrum of the amide-linked covalent organic framework JNU-1 prepared after the exchange of the mother covalent organic framework TzBA prepared in Example 1 with the monomer.

[0039] FIG. 5 is a scanning electron micrograph of JNU-1 prepared in Example 1.

[0040] FIG. 6A shows the adsorption kinetic curve of JNU-1 against gold; FIG. 6B shows the effect of hydrochloric acid concentration on gold recovery; FIG. 6C shows the adsorption isotherm of JNU-1 against gold at 25 C.-55 C.; and FIG. 6D shows the effect of the concentration of interfering ions on the selective gold recovery rate of JNU-1.

[0041] FIG. 7 shows repetitive gold recovery of JNU-1 prepared in Example 1.

DETAILED DESCRIPTION

Example 1

[0042] Preparation of an amide-linked covalent organic framework for efficient and selective gold recovery: the amide-linked covalent organic framework with high stability and crystallinity is prepared by a monomer exchange method to realize efficient and selective recovery of gold from an aqueous solution, including the following steps:

[0043] 1) 36.4 mg (0.10 mmol) of 4,4,4-(1,3,5-triazine-2,4,6-triyl)trianiline (Tz), 34.5 mg (0.164 mmol) of 4,4-biphenyldicarboxaldehyde (BA), and 3.5 mg of scandium trifluoromethanesulfonate are dissolved in a mixed solvent of dioxane and mesitylene (2:1, 3 mL) respectively, ultrasonic treatment is performed to obtain a uniformly mixed solution, and the reaction solution is reacted at 60 C. for 1 day;

[0044] 2) after a reaction tube cools to room temperature, 30.5 mg (0.15 mmol) of terephthaloyl chloride is added, ultrasonic treatment is performed for 10 minutes and then reaction is performed at 4 C. for 2 days to obtain red solid; and the obtained red solid is centrifuged and cleaned with 10 mL of tetrahydrofuran thrice, subjected to Soxhlet extraction and cleaning with acetone, and finally vacuum dried to obtain the amide-linked covalent organic framework JNU-1 with a yield of 82.6%.

[0045] FIG. 1 is a schematic diagram of an amide-linked covalent organic framework for efficient and selective gold recovery prepared in the present example.

[0046] FIG. 2A is an experimental and simulated X-ray powder diffraction pattern of the mother covalent organic framework TzBA prepared in the present example, and FIG. 2B is an infrared spectrum of the monomers Tz and BA used in the experiment and the prepared TzBA. It can be seen from FIG. 2A that the diffraction peaks of the prepared TzBA are similar to the simulated diffraction peaks of an AA stacking layer structure, indicating that the prepared TzBA is of an AA stacking layer structure. The appearance of the imine bond vibration peak at 1621 cm.sup.1 in FIG. 2B proves that the prepared covalent organic framework is of imine linkage.

[0047] FIG. 3A is an experimental and simulated X-ray powder diffraction pattern of the covalent organic framework JNU-1 prepared in the present example, and FIG. 3B is an infrared spectrum of the monomers Tz and TaCl used in the experiment and the prepared JNU-1. It can be seen from FIG. 3A that the diffraction peaks of the prepared JNU-1 are similar to the simulated diffraction peaks of an AA stacking layer structure, indicating that the prepared JNU-1 is of an AA stacking layer structure. The appearance of the amide bond vibration peak at 1656 cm.sup.1 in FIG. 3B proves that the prepared covalent organic framework is of amide linkage.

[0048] FIG. 4A is a powder X-ray diffraction pattern of the amide-linked covalent organic framework JNU-1 prepared after the exchange of the mother covalent organic framework TzBA prepared in the present example with a monomer, and FIG. 4B is an infrared spectrum of the amide-linked covalent organic framework JNU-1 prepared after the exchange of the mother covalent organic framework TzBA prepared in the present example with the monomer. It can be seen from FIG. 4A that a new diffraction peak appears at 4.69 degrees, indicating the success of the exchange process. The main diffraction peak intensity of the JNU-1 after exchange is much higher than that of the TzBA, indicating that the crystallinity of the material is greatly improved after exchange. Disappearance of the peak of the imine bond and appearance of the peak of the amide bond after the exchange in FIG. 4B indicate the success of the exchange process.

[0049] FIG. 5 is a scanning electron micrograph of JNU-1 prepared in the present example.

Example 2

[0050] Preparation of an amide-linked covalent organic framework for efficient and selective gold recovery: the steps and methods are basically the same as that in Example 1, and the difference is that the 4,4,4-(1,3,5-triazine-2,4,6-triyl)trianiline and 4,4-biphenyldicarboxaldehyde in step 1) are replaced with 1,3,5-tris(4-formyl-phenyl)triazine and p-phenylenediamine, and in step 2), the terephthaloyl chloride is replaced with 1,3,5-trimesoyl chloride, and the other conditions remain unchanged:

[0051] The characterization results of the prepared covalent organic framework are similar to those of Example 1, and the yield of the obtained amide-linked covalent organic framework is 87.2%.

Example 3: Application in Adsorption and Recovery of Gold Ions

[0052] The amide-linked covalent organic framework prepared in Example 1 is used as an adsorption material. 1 mg of JNU-1 is taken and placed in 1 mL of a series of aqueous solutions with known gold ion concentrations (43-1181 mg L.sup.1) and containing 2 mol L.sup.1 hydrochloric acid and ultrasonic treatment is performed for 1 minute. Solid powder is recovered by centrifugation, and the covalent organic framework is eluted with 2 mL of a 1 mol L.sup.1 acidic thiourea hydrochloride solution.

[0053] FIG. 6A is an adsorption kinetic curve of JNU-1 against gold ions. It can be seen from the curve that the prepared amide-linked covalent organic framework can achieve adsorption equilibrium within 10 seconds for the adsorption of gold ions, indicating that the material has an ultra-high adsorption rate.

[0054] FIG. 6B shows the effect of acid concentration in an aqueous solution on the adsorption of gold ions: gold in the aqueous solution is adsorbed under different acidity conditions, and the results show that when the acid concentration is 2 mol L.sup.1, the material has the largest adsorption capacity for gold ions.

[0055] FIG. 6C shows the adsorption isotherms of JNU-1 for gold after solutions with different gold ion concentrations are adsorbed for 10 min at different temperatures ranging from 25 C. to 55 C. It can be seen from the adsorption isotherms at different temperatures that the increase in temperature is not conducive to the adsorption of gold. The adsorption curve of the prepared JNU-1 for gold satisfies the Langmuir adsorption model, and the maximum adsorption capacity of the JNU-1 for gold calculated by the model is 1124 mg g.sup.1.

[0056] FIG. 6D shows the effect of the concentration of interfering ions on the selective gold recovery rate of JNU-1: ions of different concentrations are adsorbed simultaneously with gold ions, and the results show that when the concentration of interfering ions is the same as that of gold ions, JNU-1 can still maintain an adsorption efficiency of 80% or above. When the concentration of interfering ions is 10 times that of gold ions, JNU-1 can still maintain an adsorption efficiency of 70% or above, indicating that JNU-1 has high selectivity.

Example 4: Repeatability Test

[0057] After vacuum drying the eluted JNU-1 in Example 3, the JNU-1 is continuously used for the next step of gold adsorption. The results show that the prepared JNU-1 can still maintain an adsorption efficiency of 85% or above after four repetitions, indicating that the prepared material has a high reusable effect (as shown in FIG. 7).

Comparative Example 1

[0058] Referring to Example 3, the adsorption material is replaced with a mother imine-linked covalent organic framework TzBA, and other conditions are unchanged to perform adsorption.

[0059] 1 mg of TzBA is taken and placed in 1 mL of aqueous solution, and the solution is stirred and ultrasonic treated for 1 min; then solid powder is recovered by centrifugation, and the covalent organic framework is eluted with 2 mL of a 1 mol L.sup.1 acidic thiourea solution. The maximum adsorption capacity calculated by the Langmuir model is 415 mg g.sup.1. It can be seen that the adsorption of gold ions by the exchanged amide-linked covalent organic framework is significantly improved.