A polyaniline nanomaterial, a composite film and a preparation method and application thereof

Abstract

The application belongs to the technical field of precious metal recovery, and specifically discloses a polyaniline nanomaterial, a composite film and a preparation method and application thereof. The polyaniline nanomaterial is prepared through oxidative self-polymerization of m-phenylenediamine under the induction of copper ions, and includes the following steps: m-phenylenediamine solution, an inducer solution containing copper ions and an oxidant solution are sequentially added into a reactor for reaction; and then the reaction product is subjected to suction filtration and ultrasonic treatment to obtain the polyaniline nanomaterial. The preparation method of the polyaniline composite film includes the following steps: the polyaniline nanomaterial is mixed with a crosslinking agent, and subjected to ultrasonic oscillation and drying; and the obtained polyaniline mixed solution is loaded on the surface of a nylon film to form a film under nitrogen blowing. The polyaniline composite film is used to realize high-efficiency selective recovery of precious metals in wastewater by combining the characteristics of adsorption and membrane separation.

Description

Technical Field

[0001] This invention belongs to the field of precious metal recycling technology, specifically relating to a polyaniline nanomaterial, a composite membrane, its preparation method, and its application. Background Technology

[0002] Gold, as a representative of precious metals, is a scarce metal and plays an irreplaceable role as a financial reserve in industrial production, electronic communications, medical devices, and aerospace. In recent years, with the rapid development of electronic devices and the accelerated pace of product updates, the amount of electronic waste generated has also increased significantly. Simultaneously, with the rapid development of human society and science and technology, the demand for gold is growing, but as a precious and scarce resource in nature, its supply is limited. Therefore, recycling and reusing gold from secondary resources such as electronic waste not only reduces the environmental damage caused by electronic waste but also avoids resource waste.

[0003] Currently, improving the utilization rate of gold resources and achieving efficient and selective gold recovery is of paramount importance. In the context of economic globalization, gold, as a scarce precious metal, plays a crucial role in various industries. With the continuous mining of gold resources, rational gold leaching technologies have attracted increasing attention. Currently, gold leaching technologies mainly include cyanidation and non-cyanidation methods. Cyanidation leaching is currently the most common method for processing gold ore worldwide; however, cyanide itself is highly toxic and harmful to the environment. Many scholars have begun to focus on research into non-cyanidation gold leaching, with common methods including halogenation, thiosulfate, and thiourea methods. Currently, methods for recovering gold from gold-bearing wastewater mainly include chemical precipitation, ion exchange, electrochemical methods, composite methods, and membrane separation. Although these technologies are relatively mature, they still suffer from high costs, complex processes, poor selectivity, and low gold recovery efficiency. How to efficiently and selectively recover gold from different leaching solutions is one of the urgent problems that the gold industry needs to solve.

[0004] Currently, the main methods for removing precious metal ions from electronic wastewater include chemical precipitation, ion exchange, electrochemical methods, and membrane separation. Among these, chemical precipitation requires the addition of large amounts of flocculants, increasing operating costs and resulting in low removal efficiency; the product is typically sludge containing precious metal ions, requiring secondary treatment and recycling. Ion exchange requires pretreatment of the ion exchange material, leading to high operating costs and limiting its application to low-concentration wastewater. Electrochemical methods are limited by diffusion current density, resulting in high costs for treating low-concentration heavy metal wastewater. Summary of the Invention

[0005] This invention aims to solve at least one of the technical problems existing in the prior art, and proposes a polyaniline nanomaterial, a composite membrane, its preparation method, and its application. This invention combines the characteristics of adsorption and membrane separation methods, and achieves efficient and selective recovery of precious metals from wastewater by preparing polyaniline nanomaterials with a large number of composite noble metal sites and fabricating them into a polyaniline composite membrane.

[0006] To address the aforementioned technical problems, a first aspect of the present invention provides a method for preparing polyaniline nanomaterials, comprising the following steps:

[0007] A solution of m-phenylenediamine, a solution of an inducing agent containing copper ions, and a solution of an oxidizing agent were sequentially added to a reactor to carry out the reaction; then the reaction product was filtered and ultrasonically treated to obtain the polyaniline nanomaterial.

[0008] Specifically, the polyaniline nanomaterials of this invention are prepared by the oxidative self-polymerization reaction of m-phenylenediamine under the induction of copper ions. The resulting polyaniline nanomaterials have abundant amino functional groups, which can effectively capture noble metals in electronic wastewater and exhibit excellent selectivity. Furthermore, compared to the formation of other polyaniline powders, it also features high yield and is environmentally friendly.

[0009] Preferably, the copper ion-containing inducing agent solution includes a CuCl2·2H2O solution with a concentration of 15750-31500 mg / L.

[0010] Preferably, the oxidant solution includes a NaIO4 solution with a concentration of 100,000-200,000 mg / L.

[0011] Preferably, the concentration of the m-phenylenediamine solution is 25,000-50,000 mg / L.

[0012] Preferably, the volume ratio of the m-phenylenediamine solution, the copper ion-containing inducing agent solution, and the oxidizing agent solution is (1-3):(1-3):1.

[0013] Preferably, the m-phenylenediamine solution, the copper-containing inducing agent solution, and the oxidizing agent solution are added to the reactor sequentially at intervals of 2-4 minutes, and the reactor is placed on a shaker for reaction.

[0014] Preferably, the reaction time is 1-5 hours, and the entire reaction process is carried out at room temperature and pressure.

[0015] Preferably, the filtration and ultrasonication are performed 3-5 times to wash away unreacted m-phenylenediamine solution and excessive copper-containing inducing agent and oxidizing agent solutions.

[0016] A second aspect of the present invention provides a polyaniline nanomaterial prepared by the above preparation method, wherein the polyaniline nanomaterial has a particle size of 10-40 nm, and the nanoscale polyaniline particles can provide more composite sites for noble metals.

[0017] A third aspect of the present invention provides a method for preparing a polyaniline composite film, comprising the following steps:

[0018] (1) The above polyaniline nanomaterials are mixed with a crosslinking agent, and then subjected to ultrasonic oscillation and drying to obtain a polyaniline mixture;

[0019] (2) The polyaniline mixture is loaded onto the surface of a nylon membrane under nitrogen purging and normal temperature and pressure to form the polyaniline composite membrane.

[0020] Preferably, the crosslinking agent comprises a glutaraldehyde solution.

[0021] Preferably, in the polyaniline mixture, the mass concentration ratio of polyaniline nanomaterials to glutaraldehyde solution is (12-15):1.

[0022] Preferably, in step (1), the ultrasonic oscillation and the drying time are both 0.5-1 hours.

[0023] Preferably, in step (2), the pressure of the nitrogen purging is 0.2-0.4 bar.

[0024] Specifically, the polyaniline composite membrane prepared by this invention is formed by simple crosslinking of polyaniline nanomaterials with a crosslinking agent (such as glutaraldehyde solution). It can be formed by measuring different volumes of a polyaniline mixture and loading it onto a nylon membrane under nitrogen gas, thus achieving a simple and low-cost process. Furthermore, compared to existing methods (such as mixing polyaniline powder, heptamethylimine, and N-methylpyrrolidone to form a film-forming solution, and then using a film scraper to form the polyaniline membrane), the preparation method of this invention requires less material and has lower sensitivity to reaction conditions (such as reaction temperature).

[0025] A fourth aspect of the present invention provides a polyaniline composite film prepared by the above-described preparation method.

[0026] The fifth aspect of the present invention provides the application of the above-described polyaniline in the selective recovery of precious metals.

[0027] Preferably, the precious metal includes gold, palladium, or platinum.

[0028] Compared with the prior art, the above-described technical solution of the present invention has at least the following technical effects or advantages:

[0029] (1) This invention prepares polyaniline nanomaterials by undergoing an oxidative self-polymerization reaction of m-phenylenediamine under the induction of copper ions. The prepared polyaniline nanoparticles are then crosslinked with a crosslinking agent to form a polyaniline solution, which is then loaded onto a nylon membrane under nitrogen to form a polyaniline composite membrane. This preparation method is low-cost and environmentally friendly. Simultaneously, this invention utilizes the abundant amino functional groups on the polyaniline membrane to capture noble metal ions in electronic wastewater. Compared with conventional membrane separation methods, the composite membrane method exhibits excellent selectivity for noble metals during the noble metal recovery process and can omit the step of noble metal ion enrichment, achieving the effect of directly reducing noble metal ions to their elemental state, thus reducing the installation and operating costs of the device.

[0030] (2) The polyaniline composite membrane prepared by the present invention has excellent acid resistance and mechanical stability, which can effectively prevent the composite membrane from swelling in the solution and maintain the integrity of the membrane.

[0031] (3) When the polyaniline composite membrane prepared by the present invention is used to recycle precious metals, it can be repeatedly used in acidic solution to reduce precious metals. The composite sites on the material will spontaneously regenerate, so it can be recycled. After recycling precious metals, high-purity precious metals can be obtained by washing with thiourea and then heat treatment in air. The purification process is simple and convenient.

[0032] (5) The precious metal recovery device used in this invention is simple and does not require the consumption of large amounts of chemical reagents. The polyaniline composite membrane prepared by the oxidative self-polymerization reaction of m-phenylenediamine can avoid secondary pollution, and the prepared composite membrane has high stability in acidic environments, so it can be directly applied to acidic precious metal wastewater. At the same time, the amino groups on the composite membrane have redox potentials and high selectivity for precious metals, which can facilitate the rapid recovery of precious metals from wastewater. In addition, the polyaniline composite membrane can maintain good selective recombination for precious metal ions, and exhibits excellent recovery performance in practical electronic wastewater applications. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the preparation process of the polyaniline nanomaterials in Example 1;

[0034] Figure 2 SEM image of the polyaniline nanomaterials prepared in Example 1;

[0035] Figure 3 This is a photograph of the polyaniline composite film prepared in Example 2;

[0036] Figure 4 A schematic diagram of a device for recovering gold using a polyaniline composite membrane;

[0037] Figure 5Transmission curves for gold recovery from polyaniline composite membranes with different polyaniline loadings;

[0038] Figure 6 Transmission curves of gold recovery from polyaniline composite membranes at different flow rates in different devices;

[0039] Figure 7 The graph shows the cycle performance of the polyaniline composite membrane.

[0040] Figure 8 The graph shows the performance of polyaniline composite membrane in the recovery of gold from electronic wastewater.

[0041] Figure 9 This is a graph showing the adsorption data of palladium on the polyaniline composite membrane.

[0042] Figure 10 This is a graph showing the adsorption data of platinum on a polyaniline composite membrane. Detailed Implementation

[0043] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art.

[0044] Example 1: Preparation of polyaniline nanomaterials

[0045] A method for preparing polyaniline nanomaterials, Figure 1 This is a schematic diagram of the preparation process of polyaniline nanomaterials, which specifically includes the following steps:

[0046] (1) Weigh 2g of m-phenylenediamine (MPD) and add it to 80mL of water to prepare an MPD solution with a concentration of 20000mg / L;

[0047] (2) Weigh 1.26g CuCl2·2H2O and add it to 80mL of water to prepare a CuCl2 solution with a concentration of 15750mg / L;

[0048] (3) Weigh 4g of NaIO4 and add it to 40mL of water to prepare a NaIO4 solution with a concentration of 100000mg / L;

[0049] (4) The three solutions prepared in steps (1), (2) and (3) are poured into the reactor at two-minute intervals. The reactor is placed on a shaker and reacted for 2 hours. The whole process is carried out at room temperature and pressure. Then, the collected nanoparticles are filtered and sonicated three times to wash away the unreacted MPD ligand, excessive NaIO4 oxidant and inducible copper ions to obtain the polyaniline sodium (PmPD) nanomaterial of this embodiment.

[0050] Figure 2 The images shown are scanning electron microscope (SEM) images of the PmPD nanomaterials prepared in Example 1. Figure 2 As can be seen, PmPD nanoparticles exhibit a morphology of stacked spheres with a particle size of approximately 10-40 nm, providing a large number of composite sites for composite noble metals.

[0051] Example 2: Preparation of polyaniline composite film

[0052] A method for preparing a polyaniline composite film includes the following steps:

[0053] (1) The PmPD nanomaterials prepared in Example 1 were crosslinked with glutaraldehyde solution at a mass concentration ratio of 12.5:1 in the mixed solution system. After 0.5 hours of ultrasonic oscillation and 0.5 hours of oven drying, a PmPD mixture was obtained.

[0054] (2) Under nitrogen purging at 0.2 bar, at room temperature and pressure, the PmPD mixture obtained in step (1) is loaded onto the surface of a nylon membrane using a Millipore device to form a PmPD composite membrane.

[0055] Figure 3 This is a photograph of the PmPD composite film prepared in Example 2. Figure 3 It can be seen that the PmPD composite membrane has a good, uniform and stable morphology.

[0056] Example 3: Application Experiment of Polyaniline Composite Membrane for Recovering Precious Metals

[0057] Figure 4 The diagram shows a device for recovering precious metals using a polyaniline composite membrane. The specific recovery process is as follows: under a nitrogen pressure of 0.2 bar, a solution containing precious metals is passed through a Millipore device loaded with the PmPD composite membrane of this invention, thereby achieving the purpose of recovering precious metals. The following application experiments were conducted using this recovery device.

[0058] Experiment 1: Gold Recovery Experiment Using Polyaniline Composite Membranes with Different Loadings

[0059] Following the preparation method of the polyaniline composite film in Example 2, PmPD nanomaterials loaded with 3.93 mg / cm³ were prepared. 2 7.85 mg / cm 2 11.73 mg / cm 2 and 15.70 mg / cm 2 A series of polyaniline composite membranes were prepared, and these membranes were then placed in Millipore devices. 300 mL of a HAuCl4 solution with a gold ion concentration of 40 mg / L was measured. At a fixed flow rate of 2.5 mL / min, the gold ion solution was passed through the PmPD composite membrane using nitrogen gas. One sample was collected every 10 mL. The gold ion concentration in the samples was detected using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the transmittance curves of the PmPD composite membranes were plotted. The results are shown below. Figure 5 As shown.

[0060] Depend on Figure 5 It can be seen that when the loading of the PmPD composite membrane is 3.93 mg / cm³, 2 At that time, the penetration volume of gold through the PmPD composite membrane was 30 mL; when the loading was 7.85 mg / cm³, the penetration volume was 30 mL. 2 At that time, the penetration volume of gold through the PmPD composite membrane was 60 mL; when the loading was 11.73 mg / cm³, the penetration volume was 60 mL. 2 At that time, the penetration volume of gold through the PmPD composite membrane was 150 mL; when the loading was 15.70 mg / cm³, the penetration volume was 150 mL. 2 At that time, the penetration volume of gold through the PmPD composite membrane was 300 mL. The experimental results show that the higher the loading of the PmPD composite membrane, the better its gold recovery effect, that is, the amount of gold composited by the PmPD composite membrane is positively correlated with the loading of the film-forming material.

[0061] Experiment 2: Gold Recovery Experiment Using Polyaniline Composite Membranes at Different Flow Rates

[0062] The loaded PmPD nanomaterials prepared in Experiment 1 had a concentration of 11.73 mg / cm³. 2 A polyaniline composite membrane was packed into a Millipore apparatus. 300 mL of a HAuCl4 solution with a gold ion concentration of 40 mg / L was measured. At flow rates of 1 mL / min, 2.5 mL / min, 5 mL / min, and 10 mL / min, the gold ion solution was passed through the PmPD composite membrane under nitrogen gas. One sample was collected every 10 mL. The gold ion concentration in the samples was detected using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the transmittance curves of the PmPD composite membrane were plotted. The results are shown below. Figure 6 As shown.

[0063] Depend on Figure 6The results show that at a flow rate of 1 mL / min, the penetration volume of gold through the PmPD composite membrane is 400 mL; at a flow rate of 2.5 mL / min, it is 150 mL; at a flow rate of 5 mL / min, it is 170 mL; and at a flow rate of 10 mL / min, it is 90 mL. The experimental results indicate that the slower the flow rate of the PmPD composite membrane device, the better its gold recovery effect; that is, the amount of gold composited by the PmPD composite membrane is inversely correlated with the device flow rate.

[0064] Experiment 3: Cyclicity Experiment of Gold Recovery from PmPD Composite Membrane

[0065] The loaded PmPD nanomaterials prepared in Experiment 1 had a concentration of 3.93 mg / cm³. 2 A polyaniline composite membrane was placed in a Millipore device. 750 mL of a HAuCl4 solution with a gold ion concentration of 40 mg / L was measured for a cyclic regeneration experiment. The 40 mg / L HAuCl4 solution was injected into a storage tank, and the device flow rate was set to 2.5 mL / min. Under nitrogen atmosphere, the HAuCl4 solution passed through the PmPD composite membrane, and one sample was collected every 10 mL. The gold ion concentration in the samples was detected using inductively coupled plasma optical emission spectrometry (ICP-OES). When the gold coagulation of the PmPD composite membrane reached a breakthrough point of 2 mg / L, the PmPD composite membrane was backwashed with a mixed solution of 1 M thiourea and hydrochloric acid. The concentration of gold enriched during backwashing was recorded to obtain the cyclic performance of the PmPD composite membrane for gold. The results are as follows: Figure 7 As shown in the figure, the horizontal axis Effluent Vloume represents the effluent volume, and the vertical axis Effluent Au(Ⅲ) concentration represents the gold effluent concentration.

[0066] Depend on Figure 7It can be seen that the PmPD composite membrane treated 170 mL of gold-containing solution in the first filtration before the breakthrough point; then, it was filtered and rinsed with 50 mL of thiourea / HCl solution (Thiourea & HCl cleaning) to achieve gold elution and membrane regeneration. Notably, the concentration of gold enriched in the first 10 mL of thiourea eluent reached 460 mg / L, more than 11 times the concentration in the initial solution. Experimental results show that the gold enriched on the PmPD composite membrane can be extracted, demonstrating good practical application value. The regenerated PmPD composite membrane could treat almost the same volume of Au(III) solution (approximately 170 mL) in the second filtration cycle, indicating that the PmPD membrane can be fully recovered, achieving the same composite performance as the previous cycle, demonstrating good cycling performance. Simultaneously, the PmPD composite membrane recovers the precious metals from the membrane via thiourea. Compared to immersion recovery, this invention can recover a large amount of precious metals in a short time, is faster, and directly regenerates the material for future experiments.

[0067] Experiment 4: Gold Recovery Efficiency of PmPD Composite Membrane in Actual Electronic Wastewater

[0068] The loaded PmPD nanomaterials prepared in Experiment 1 had a concentration of 11.73 mg / cm³. 2 A polyaniline-poly(mPD) composite membrane was installed in a Millipore apparatus. Circuit boards were digested with aqua regia to obtain actual gold-containing electronic wastewater. Under a fixed flow rate of 2.5 mL / min, the actual electronic wastewater was passed through the PmPD composite membrane. The filtrate sample was collected, and the concentration of metal ions in the sample was detected using inductively coupled plasma atomic emission spectrometry (ICP-AES). The gold recovery efficiency of the PmPD composite membrane in the actual electronic wastewater was obtained, and the results are as follows: Figure 8 As shown.

[0069] Depend on Figure 8 It can be seen that the PmPD composite membrane has a gold recovery efficiency of 100%, which is far higher than the recovery rate of other metal ions. The experimental results show that the PmPD composite membrane has excellent selectivity for gold and has broad application prospects in the field of gold recovery from electronic waste liquid.

[0070] Experiment 5: Recovery of Platinum and Palladium Noble Metals Using PmPD Nanomaterials

[0071] The PmPD-loaded nanomaterials prepared in Example 1 were used to adsorb and recover platinum and palladium metal ions. 15 mg of PmPD nanomaterials were placed in platinum and palladium solutions with concentrations of 10-2000 mg / L. The adsorption isotherms of the PmPD nanomaterials for platinum and palladium metal ions were studied under ambient temperature and pressure conditions. The results are as follows: Figure 9-10 As shown,

[0072] Depend on Figure 9-10 It can be seen that PmPD nanomaterials not only have selective recycling properties for gold, but also have strong adsorption and recycling properties for precious metal ions such as platinum and palladium, indicating that the material also has good universality for other precious metals.

[0073] For those skilled in the art, several simple deductions or substitutions can be made without departing from the inventive concept, without requiring creative effort. Therefore, any simple improvements made to this invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention. The above embodiments are preferred embodiments of this invention, and all processes similar to this invention and equivalent changes should fall within the scope of protection of this invention.

Claims

1. The application of a polyaniline composite membrane in the selective recovery of precious metals, characterized in that, The polyaniline composite film is prepared by a method comprising the following steps: (1) The polyaniline nanomaterials were mixed with a crosslinking agent, and then subjected to ultrasonic vibration and drying to obtain a polyaniline mixture; The crosslinking agent includes a glutaraldehyde solution; in the polyaniline mixture, the mass concentration ratio of polyaniline nanomaterials to glutaraldehyde solution is (12-15):1; (2) The polyaniline mixture is loaded onto the surface of a nylon membrane under nitrogen purging and normal temperature and pressure to form a film, thereby obtaining the polyaniline composite membrane. The polyaniline nanomaterial is prepared by the following steps: A solution of m-phenylenediamine, a solution of an inducing agent containing copper ions, and a solution of an oxidizing agent were sequentially added to a reactor to carry out the reaction; then the reaction product was filtered and ultrasonically treated to obtain the polyaniline nanomaterial. The copper ion-containing inducing agent solution includes a CuCl2·2H2O solution with a concentration of 15750-31500 mg / L; the oxidizing agent solution includes a NaIO4 solution with a concentration of 100000-200000 mg / L; the m-phenylenediamine solution has a concentration of 25000-50000 mg / L; and the volume ratio of the m-phenylenediamine solution, the copper ion-containing inducing agent solution, and the oxidizing agent solution is (1-3):(1-3):

1.

2. The application according to claim 1, characterized in that, The reaction time is 1-5 hours.

3. The application according to claim 1, characterized in that, The particle size of the polyaniline nanomaterial is 10-40 nm.

4. The application according to claim 1, characterized in that, In step (1), the ultrasonic oscillation and the drying time are both 0.5-1 hour; in step (2), the nitrogen purging pressure is 0.2-0.4 bar.

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