CN113058571B

CN113058571B - Preparation method of bifunctional polymer adsorbent and application of bifunctional polymer adsorbent in gold recovery

Info

Publication number: CN113058571B
Application number: CN202110307562.0A
Authority: CN
Inventors: 邱建丁; 李学晶; 梁汝萍
Original assignee: Nanchang University
Current assignee: Nanchang University
Priority date: 2021-03-23
Filing date: 2021-03-23
Publication date: 2022-05-20
Anticipated expiration: 2041-03-23
Also published as: CN113058571A

Abstract

The invention discloses a preparation method of a bifunctional polymer adsorbent and application of the bifunctional polymer adsorbent in gold recovery, and belongs to the technical field of adsorption materials. Dopamine (DA) and Tetrafluoroterephthalonitrile (TFN) are subjected to aromatic nucleophilic reaction to form polymer PDA-TFN, and then cyano is converted into amide under alkaline conditions to prepare bifunctional polymer adsorbent PDA-TFN-A. PDA-TFN-A contains A large number of indole structures and amide functional groups, and can be specifically combined with Au (III) to improve the adsorption quantity. PDA-TFN-A can reduce Au (III) into Au (0), and has good recovery performance on gold. The method for synthesizing the bifunctional polymer is simple, low in cost, environment-friendly, economical and efficient, and is expected to be used for recovering gold in electronic waste liquid through the synergistic effect of adsorption and reduction.

Description

Preparation method of bifunctional polymer adsorbent and application of bifunctional polymer adsorbent in gold recovery

Technical Field

The invention belongs to the technical field of adsorption materials, and particularly relates to a preparation method of a bifunctional polymer adsorbent and application of the bifunctional polymer adsorbent in gold recovery.

Background

With the advent of economic integration, the electronic industry has become the major strategic development industry of countries around the world with its characteristics of low consumption, no pollution, high added value, etc. It is known that the development of the electronic industry generates a great deal of electronic garbage and electronic equipment waste, wherein the contained precious metals may cause waste (Mon, M.; Ferrando-Soria, J.; Grancha, T.; Fortea-P rez, F.R.; Gascon, J.; Leyva-P rez, A.; Armentano, D.; Pardo, E.Select gold recovery and catalysis in a high grade flexible metal-degraded metal-synthesized metal-7867, J.Am.chem.Soc.2016,138, 7864-7867). Gold is widely used as a popular noble metal in the fields of chemical engineering and the like. Although the gold content in the electronic garbage is far higher than that of natural ore, serious resource waste is caused due to the lack of a high-selectivity, high-yield and environment-friendly extraction technology. Therefore, new technical materials for recovering gold from such electronic wastes are important for the sustainable development of the future (Cao, W.; Dai, F.; Hu, R.; Tang, B.Z. ecological sulfur conversion to functional polyurethanes catalysts of sulfur, acids, and amines.J.Am.chem.Soc.2020,142, 978-986). Methods for recovering gold reported so far include chemical precipitation, redox, solvent extraction, ion exchange, adsorption, and the like. Among them, the chemical precipitation method often causes secondary pollution after treatment, such as generation of a large amount of waste residues, and has negative effects in practical application and ecological environment development (Yue, C.; Sun, H.; Liu, W. -J.; Guan, B.; Deng, X.; Zhang, X.; Yang, P.environmental benign, rapid, and selective extraction of gold from organisms and water electronic materials, Angew.Chem.2017,56, 9331-. Gold is extracted by using the redox principle in industry, and the problems of harsh reaction conditions, serious environmental pollution and high energy consumption exist all the time due to the use of toxic oxidizing reagents. Solvent extraction and ion exchange methods have difficulties with cumbersome operations and low yields (Raiguel, S.; Gijsemanns, L.; Van den Bossche, A.; Onghena, B.; Binnemans, K.solvent extraction of gold (iii) with ethylene carbonate ACS Sustain. chem. Eng.2020,8, 13713. quadrature, M.I.; Hewitt, D.M.; Dai, X.; Brunt, S.D.ion extraction and passage for recovering gold free solutions. hydrometallurgy 2010,100, 136. 143). Adsorption methods that are simple to operate, economical and efficient are of wide interest to researchers (Gurung, m.; Adhikari, b.b.; morsiada, s.; Kawakita, h.; Ohto, k.; Inoue, k.; Alam, S.N-amino modified proton tannin: a new stable material for selective adsorption, preconcentration and recovery of precursors metals from ionic chlorine chloride solution, bioreesor. technol.2013,129, 108-117). Adsorbing materials such as resins, carbon materials, ion imprinting, and activated carbon are widely used for gold recovery, but have the disadvantages of long treatment time, complicated operation, and inability to recycle. Therefore, designing and using an economical, efficient and degradable polymer is of great importance for recovering gold from secondary resources such as waste electrical appliances, electronic equipment and the like.

Dopamine (DA) is a cheap, readily available, biodegradable, environmentally friendly natural biomolecule, Polydopamine (PDA) rich in amino and hydroxyl functional groups, which can form indole units by autopolymerization, with excellent complexing power for metal ions (Sun, D.T.; Pen, L.; Reeder, W.S.; Moosavi, S.M.; Tiana, D.; Britt, D.K.; Oveisi, E.; Queen, W.L.Rapid, selective, heavy metal, reactive, free from water by a metal/polymeric, composite, CeACS. Sci.2018,4, 349-). In order to prevent the dopamine from dissolving in practical application and improve the adsorption performance of the dopamine on Au (III), the dopamine is modified through crosslinking. So far, no report is found for preparing bifunctional polymer adsorbent based on dopamine functionalized derivative for recovering noble metal.

Disclosure of Invention

The invention aims to provide a preparation method of a bifunctional polymer adsorbent and gold recovery application thereof, the method for preparing the bifunctional polymer adsorbent has the characteristics of simple operation, environmental friendliness, economy and high efficiency, has the advantages of high adsorption capacity, rapid adsorption kinetics and high selectivity on gold, and can be used for recovering gold from electronic waste liquid.

The invention provides a preparation method of a bifunctional polymer adsorbent, which comprises the following steps:

1) dopamine and tetrafluoroterephthalonitrile are used as reaction raw materials, anhydrous potassium carbonate is used as a catalyst, anhydrous tetrahydrofuran/N, N-dimethylformamide is added into the reaction raw materials, and a reaction mixed solution is obtained after the anhydrous tetrahydrofuran/N, N-dimethylformamide is uniformly mixed;

2) sealing the reaction mixture liquid, vacuumizing, introducing nitrogen, stirring at 80-90 ℃ for 2-4 days, taking out, cooling to room temperature, and stirring for 20-28h to obtain a reaction mixture;

3) and filtering the reaction mixture, collecting the precipitate, removing impurities from the precipitate, drying in vacuum to obtain a brownish black polymer, and carrying out post-treatment on the polymer under an alkaline condition to obtain the bifunctional polymer adsorbent.

Further, the mass ratio of the dopamine, the tetrafluoroterephthalonitrile and the anhydrous potassium carbonate in the step 1) is (1.8-2.0): 1: (2.6-2.8).

Further, the volume ratio of the tetrahydrofuran to the N, N-dimethylformamide in the anhydrous tetrahydrofuran/N, N-dimethylformamide in the step 1) is (8.5-9.5): 1.

further, step 3) ofThe precipitation and impurity removal is to drop HCl solution until no CO exists₂Discharging to remove unreacted potassium carbonate, washing precipitate with water, tetrahydrofuran, N-dimethylformamide and acetone respectively, and performing Soxhlet extraction in tetrahydrofuran and acetone for 22-26 h.

Further, the concentration of the HCl solution is 0.5 mol/L.

Further, the alkaline condition in the step 3) is an aqueous solution of NaOH; the post-treatment is to mix the polymer and NaOH aqueous solution, stir for 2-4 days at 60-80 ℃, filter, separate and wash the product with deionized water, then transfer to a Soxhlet extractor to wash with tetrahydrofuran and acetone for 22-26h, and perform vacuum drying.

Further, the concentration of the NaOH solution is 6 mol/L.

The invention also provides an application of the bifunctional polymer adsorbent in gold adsorption:

and adding the bifunctional polymer adsorbent prepared by the method into a solution to be treated containing gold (III), keeping the temperature constant, oscillating to obtain a suspension, adsorbing by using the bifunctional polymer adsorbent, and reducing the gold (III) in the suspension into gold (0).

Further, the content of gold (III) in the solution to be treated containing gold (III) is 50-2500 ppm; and/or the solution to be treated containing gold (III) is subjected to pH adjustment to 1-9 by adopting a pH adjusting agent before being mixed with the bifunctional polymer adsorbent; preferably, the pH is 2.

Further, the constant temperature is 20-30 ℃; the oscillation time of the adsorption isotherm experiment is 22-26 h; the oscillation time of the kinetic experiment is 2-180 min.

Further, the method also comprises the step of filtering the suspension after adsorption and reduction by using a 0.22 mu m microporous filter membrane.

Compared with the prior art, the invention has the beneficial effects that:

the invention takes dopamine and tetrafluoroterephthalonitrile as raw materials, prepares polymer PDA-TFN through aromatic nucleophilic reaction, and amidates PDA-TFN under alkaline condition to prepare bifunctional polymer adsorbent PDA-TFN-A, PDA-TFN-A contains A large amount of functional groups such as amino, imino and amide, etc., and can be specifically combined with Au (III), thereby improving the adsorption capacity to Au (III); in addition, PDA-TFN-A can also reduce adsorbed Au (III) into Au (0), and has excellent recovery performance on gold. The bifunctional polymer adsorbent designed by the invention has the advantages of simple preparation method, low cost, environmental friendliness, economy and high efficiency, and can be used for recovering gold from electronic waste liquid through the synergistic effect of the efficient adsorption and reduction of the adsorbent on gold.

Drawings

FIG. 1 is A schematic diagram of the preparation of PDA-TFN-A.

FIG. 2 is an SEM image of PDA-TFN-A.

FIG. 3 is an infrared spectrum of DA, TFN, PDA-TFN and PDA-TFN-A.

FIG. 4 is A diagram of the adsorption isotherm of PDA-TFN-A on Au (III).

FIG. 5 is A graph showing the adsorption kinetics of PDA-TFN-A to Au (III).

FIG. 6 is an XRD pattern before and after adsorption of Au (III) by PDA-TFN-A.

FIG. 7 is A graph showing the adsorption selectivity of PDA-TFN-A to Au (III).

Detailed Description

The technical solution of the present invention will be described more clearly and completely with reference to the following examples, which are only a part of the examples of the present invention, but not all of them, which are conventional processes unless otherwise specified, and raw materials which are commercially available from the public unless otherwise specified. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making creative efforts, fall within the protection scope of the present invention.

Example 1: preparation method and characterization of bifunctional polymer adsorbent

Placing 1.8964g dopamine, 1.0005g Tetrafluoroterephthalonitrile (TFN) and 2.764g anhydrous potassium carbonate in a three-neck round-bottom flask, adding 80mL anhydrous tetrahydrofuran/N, N-dimethylformamide (9:1v/v), mixing well, sealing, vacuumizing for 20min with a vacuum pump, introducing nitrogen and stirring at 85 ℃ for 3 days under nitrogen atmosphere, taking out and cooling to room temperatureThe nitrogen source was removed, stirring was continued at room temperature for 24h, the mixture was taken out and the precipitate collected by filtration and 0.5mol/L HCl solution was added dropwise until free of CO₂Is discharged to remove unreacted K₂CO₃Washing the precipitate with water, tetrahydrofuran, N-dimethylformamide and acetone respectively, performing Soxhlet extraction in tetrahydrofuran and acetone for 24h, and vacuum drying at 60 ℃ for 12h to obtain a brownish black polymer PDA-TFN; a single neck round bottom flask was charged with 2g of prepared PDA-TFN and 100mL of 6mol/L NaOH solution, the mixture was stirred at 70 ℃ for 3 days, after filtration, separation and washing of the product with deionized water, transferred to A Soxhlet extractor and washed with tetrahydrofuran and acetone, respectively, for 24h, and vacuum dried at 60 ℃ for 8h to produce bifunctional polymer adsorbent PDA-TFN-A. FIG. 1 is A schematic diagram of the preparation process of PDA-TFN-A.

The morphology of PDA-TFN-A is observed by A Scanning Electron Microscope (SEM) (figure 2), and the result of the SEM shows that the bifunctional polymer adsorbent PDA-TFN-A presents A random rough surface. FIG. 3 is an infrared spectrum of DA, TFN, PDA-TFN and PDA-TFN-A, and it was found by comparing the infrared spectrA of DA and TFN that the infrared spectrum of PDA-TFN formed after chemical crosslinking of DA and TFN was 1112cm in the infrared spectrum^-1A new stretching vibration peak appears, which is attributed to newly generated aromatic ether bonds, and TFN 1319cm is observed^-1The C-F bond at (C-F) disappeared while the cyano group of TFN (2222 cm) was retained^-1) Thus, the synthesis of PDA-TFN was successful. After amidation of PDA-TFN under alkaline condition, cyano group (2217 cm) in infrared spectrum of PDA-TFN-A is generated^-1) Disappeared at 1667cm^-1And A new carbonyl (C ═ O) stretching vibration peak appears, and the results show that the bifunctional polymer adsorbent PDA-TFN-A is successfully prepared by the method.

Example 2: application of bifunctional polymer adsorbent in gold adsorption

The pH of the au (iii) solution was optimized. The result shows that the adsorption efficiency of the bifunctional polymer adsorbent PDA-TFN-A to Au (III) is the maximum when the pH value of the Au (III) solution is 2.0. When the pH of the solution is higher than 5.0, the efficiency of adsorption of Au (III) by PDA-TFN-A is low due to OH in the chloride aqueous solution^-With Cl^-Compete for the formation of hydroxyl-containing gold complexes. Therefore, the optimum reaction pH for the aqueous Au (III) solution was chosen to be 2.0.

The adsorption capacity and adsorption kinetic behavior of the bifunctional polymer adsorbent PDA-TFN-A on Au (III) were studied. Dissolving potassium chloroaurate in ultrapure water to prepare Au (III) solutions with different concentrations, adjusting the pH value of the solution to 2.0 by using HCl or NaOH, adding 5mg of PDA-TFN-A into 20mL of the Au (III) aqueous solution after the pH value is adjusted, oscillating the solution in A thermostatic water bath for 24 hours, separating precipitates by using A0.22 mu m membrane filter, measuring the concentration of the residual Au (III) in the filtrate by using an inductively coupled plasmA mass spectrometry (ICP-MS), and calculating the adsorption amount of the PDA-TFN-A to the Au (III). Due to the larger driving force of the solid-liquid interface concentration gradient, the adsorption capacity of the PDA-TFN-A to the Au (III) is increased along with the increase of the Au (III) concentration until the adsorption equilibrium is reached, and the maximum adsorption capacity of the PDA-TFN-A to the Au (III) is 2771.8mg/g (figure 4). The adsorption capacity of the PDA-TFN-A to Au (III) is increased along with the prolonging of the adsorption time, when the adsorption time is within 10min, the adsorption capacity is increased sharply along with the prolonging of the adsorption time, then the adsorption capacity is increased slowly, and when the adsorption time is 15min, the adsorption capacity of the Au (III) is saturated (figure 5).

The PDA-TFN-A before and after adsorbing Au (III) is characterized by X-ray diffraction spectrum (XRD). From the XRD results, the adsorbents adsorbing Au (iii) showed characteristic diffraction peaks of Au (0) at (111), (200), (220) and (311), respectively, indicating good reduction behavior of PDA-TFN-A to Au (iii) (fig. 6).

The selective adsorption of Au (III) by PDA-TFN-A was investigated. By adding other metal ions (Cd) commonly found in electronic waste liquid²⁺、Cr²⁺、Pb²⁺、Cu²⁺、Ni²⁺、Co²⁺、Na⁺、K⁺、Mg²⁺、Al³⁺、Zn²⁺、Hg²⁺、Ca²⁺) The results of examining the selectivity of PDA-TFN-A on the adsorption of Au (III) show that the adsorption of PDA-TFN-A on other metal ions is very small, and the adsorption selectivity of PDA-TFN-A on Au (III) is very high (FIG. 7).

Therefore, the bifunctional polymer adsorbent PDA-TFN-A prepared by the method has A synergistic effect of efficient adsorption and reduction on Au (III), and has the advantages of high adsorption capacity, high adsorption speed and good selectivity. The PDA-TFN-A has the best adsorption performance under the acidic condition of pH 2.0, and shows that the PDA-TFN-A has good application potential for recovering gold from the acidic electronic waste liquid.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, many modifications and variations can be made without departing from the principle of the present invention, and these modifications and variations should also be considered as included in the protection scope of the present invention.

Claims

1. A method for preparing a bifunctional polymeric adsorbent, comprising:

1) dopamine and tetrafluoroterephthalonitrile are used as reaction raw materials, anhydrous potassium carbonate is used as a catalyst, anhydrous tetrahydrofuran and N, N-dimethylformamide are added into the reaction raw materials, and a reaction mixed solution is obtained after the anhydrous tetrahydrofuran and the N, N-dimethylformamide are uniformly mixed; the volume ratio of the anhydrous tetrahydrofuran to the N, N-dimethylformamide is (8.5-9.5): 1;

3) filtering the reaction mixture, collecting the precipitate, removing impurities from the precipitate, drying in vacuum to obtain a brownish black polymer, and carrying out post-treatment on the polymer under an alkaline condition to obtain the bifunctional polymer adsorbent; the alkaline condition is NaOH aqueous solution; the post-treatment is to mix the polymer and NaOH aqueous solution, stir for 2-4 days at 60-80 ℃, filter, separate and wash the product with deionized water, then transfer to a Soxhlet extractor to wash with tetrahydrofuran and acetone for 22-26h, and perform vacuum drying.

2. The method for preparing the bifunctional polymer adsorbent according to claim 1, wherein the mass ratio of the dopamine, the tetrafluoroterephthalonitrile and the anhydrous potassium carbonate in the step 1) is (1.8-2.0): 1: (2.6-2.8).

3. The method for preparing the bifunctional polymer adsorbent according to claim 1, wherein the step 3) of removing impurities is dropwise adding HCl solution until no CO is generated₂Discharging, washing the precipitate with water, tetrahydrofuran, N-dimethylformamide and acetone respectively, and performing Soxhlet extraction in tetrahydrofuran and acetone for 22-26 h.

4. Use of the bifunctional polymeric adsorbent obtained by the preparation method of any one of claims 1-3 for adsorbing gold.

5. The application of the bifunctional polymer adsorbent in gold adsorption according to claim 4, wherein the application method comprises the steps of adding the bifunctional polymer adsorbent into a solution to be treated containing trivalent gold, oscillating at constant temperature to obtain a suspension, adsorbing by the bifunctional polymer adsorbent, and reducing trivalent gold in the suspension to zero valent gold.

6. The use of the bifunctional polymeric adsorbent according to claim 5 for adsorbing gold, wherein the trivalent gold content of the solution to be treated containing trivalent gold is 50-2500 ppm; and/or the solution to be treated containing the trivalent gold needs to be adjusted to the pH value of 1-9 by adopting a pH regulator before being mixed with the bifunctional polymer adsorbent.

7. The use of the bifunctional polymeric adsorbent of claim 6 for adsorbing gold, wherein the pH is 2.

8. The use of the bifunctional polymeric adsorbent according to claim 5 for adsorbing gold, wherein the constant temperature is 20-30 ℃; the oscillation time of the adsorption isotherm experiment is 22-26h, and the oscillation time of the kinetic experiment is 2-180 min.

9. The use of the bifunctional polymeric adsorbent of claim 5 for adsorbing gold, further comprising filtering the suspension after adsorption and reduction with a 0.22 μm microporous membrane.