Pan fiber-based gold-adsorbing material, manufacturing method therefor, and gold recovery method using same

Abstract

The present invention relates to a polyacrylonitrile (PAN) fiber-based gold-adsorbing material, a manufacturing method therefor, and a gold recovery method using same, wherein the gold-adsorbing material is capable of achieving excellent gold adsorption characteristics, durability, ease of manufacturing, and usability through a structure in which an alkylamine compound is fixed to a PAN fiber. The PAN fiber gold-adsorbing material according to the present invention is used to adsorb gold ions in water and is characterized in that the alkylamine compound is fixed onto the PAN fiber surface.

Description

PAN fiber-based gold adsorption material, its manufacturing method, and gold recovery method using the same

[0001] [Cross-reference to related applications] This application claims priority to Korean Patent Application No. 10-2024-0021089, filed February 14, 2024, which is incorporated herein by reference.

[0002] The present invention was made with the support of the Ministry of Science and ICT of the Republic of Korea under the project identification number 1711191619 and project number 2020M3H4A3106366, and the management expert organization of the project is the National Research Foundation of Korea. The research project name is “Nanomaterial Technology Development”, the research project title is “Development of Customized Module Technology to Ensure Efficient Field Applicability of Extreme Environment Responsive Filters”, and the research period is from January 1, 2023 to December 31, 2023.

[0003] The present invention relates to a PAN fiber-based gold adsorption material, a method for manufacturing the same, and a method for recovering gold using the same, and more particularly, to a PAN fiber-based gold adsorption material capable of implementing excellent gold adsorption properties, excellent durability, excellent ease of manufacturing, and excellent usability through a structure in which an alkylamine compound is fixed to a polyacrylonitrile (PAN) fiber, a method for manufacturing the same, and a method for recovering gold using the same.

[0004] Adsorbent materials are used to recover gold from industrial waste, such as electrical and electronic waste. To maximize surface area and improve recovery efficiency, their diameters are decreasing, from hundreds of micrometers to several nanometers. While this decrease in diameter improves gold recovery efficiency, its small size makes it difficult to recover the adsorbent after use, and the high pressure drop it causes during the gold recovery process reduces economic feasibility.

[0005] On the other hand, if the diameter of the gold adsorption material is mm, no pressure drop occurs during the gold recovery process, but there is a problem that the pores of the adsorption material are blocked by suspended solids, reducing the adsorption efficiency of the adsorption material.

[0006] In addition, the adsorption selectivity for gold ions (Au ions) must be considered during the gold recovery process using an adsorbent material. In addition to gold ions, various metallic ions exist during the gold recovery process. It is known that up to 14 types of metallic ions, including copper (Cu), nickel (Ni), cobalt (Co), and zinc (Zn), can coexist with gold ions. These metallic ions block the pores of the gold adsorbent material, reducing its adsorption efficiency. Therefore, the gold adsorbent material is required to selectively adsorb only gold ions in an environment where these metallic ions exist.

[0007] Korean Patent Publication No. 2284087 discloses a porous adsorbent material for gold ion adsorption, comprising porous polymer particles coated with a polyphenol compound, with a diameter of 1 to 100 μm. However, due to its small size, recovery of the adsorbent material is expected to be difficult, and irradiation with a light source of a specific wavelength is essential for gold ion adsorption. Furthermore, there is a risk that the pores of the adsorbent material may be clogged by various suspended solids during the gold recovery process.

[0008] U.S. Patent Publication No. US 10301180 discloses a method for regenerating activated carbon used in a gold recovery process. However, it does not disclose a configuration for recovering activated carbon used in a gold recovery process, so it is expected that there will be difficulties in recovering the gold adsorption material as described above.

[0009] Mesoporous Silica Derived from Municipal Solid Waste Incinerator (MSWI) Ash Slag: Synthesis, Characterization, and Use as Supports for Au(III) Recovery , Yosep Hand, etc., 2021, Materials, 14, 6894, presents a technology to manufacture silica particles with a porous structure and adsorb gold ions. However, the recovery of silica particles is not easy, and the problem of the pores of the silica particles being blocked by metallic ions that can coexist during the gold recovery process is not considered.

[0010] In addition, International Patent Publication No. WO2019-131946 discloses a technology for recovering gold from a solution containing a gold cyano complex using a crosslinking resin containing a vinyl amine unit, and U.S. Patent Publication No. US 4,723,998 presents a technology for recovering gold from carbonate minerals using an ion exchange resin.

[0011] Meanwhile, various alkylamines have been proposed as gold adsorption materials based on their excellent adsorption and reduction capabilities (see Non-patent Document 2). However, alkylamines are highly hydrophilic and readily dissolve in aqueous solutions, making their application as gold adsorption materials challenging.

[0012] To address the high water solubility problem of alkylamines, the present applicant and inventors have proposed a "core-shell gold adsorption material having a three-dimensional radial pore structure" as disclosed in Korean Patent Publication No. 2023-0148067 (Patent Document 5). The gold adsorption material disclosed in Patent Document 5 forms a three-dimensional radial pore structure inside a gold adsorption material made of polyacrylonitrile (PAN) and immobilizes amine functional groups within the pores, thereby suppressing the amine functional groups from dissolving in an aqueous solution.

[0013] [Prior Art Literature]

[0014] [Patent Document]

[0015] (Patent Document 1) Korean Patent Publication No. 2284087 (Published on August 2, 2021)

[0016] (Patent Document 2) U.S. Patent Publication No. US 10301180 (Published on May 28, 2019)

[0017] (Patent Document 3) International Patent Publication No. WO2019-131946 (Published on July 4, 2019)

[0018] (Patent Document 4) U.S. Patent Publication No. US 4723998 (Published on February 9, 1988)

[0019] (Patent Document 5) Korean Patent Publication No. 2023-0148067 (published on October 24, 2023)

[0020] (Patent Document 6) International Patent Publication No. WO2023-001810 (Published on January 26, 2023)

[0021] [Non-patent literature]

[0022] (Non-patent Document 1) Mesoporous Silica Derived from Municipal Solid Waste Incinerator (MSWI) Ash Slag: Synthesis, Characterization and Use as Supports for Au(III) Recovery , Yosep Hand, etc., 2021, Materials, 14, 6894

[0023] (Non-patent Document 2) Gold(III) recovery using synthetic chelating resins with amine, thio and amine / mercaptan functionalities, AM Donia, AA Atia, KZ Elwakeel, Separation and Purification Technology, Volume 42, Issue 2, 15 March 2005, Pages 111-116

[0024] The present invention has been devised to solve the above problems, and its purpose is to provide a PAN fiber-based gold adsorption material capable of improving the durability of the gold adsorption material through a structure in which an alkylamine compound is fixed to a polyacrylonitrile (PAN) fiber.

[0025] In addition, another purpose of the present invention is to provide a technology that can improve the ease of recovery of a gold adsorption material by implementing a gold adsorption material based on PAN fiber having a diameter of ㎛ size and suppress the pressure drop phenomenon caused by the gold adsorption material during the gold recovery process.

[0026] In addition, another purpose of the present invention is to provide a PAN fiber-based gold adsorption material that exhibits the highest level of gold adsorption characteristics compared to known gold adsorption materials including nanometer (nm) sized gold adsorption materials.

[0027] In addition, another purpose of the present invention is to provide a PAN fiber-based gold adsorption material that exhibits high gold recovery efficiency even in an environment where various metallic ions coexist.

[0028] In order to achieve the above purpose, a PAN fiber-based gold adsorption material according to the present invention is for adsorbing gold ions in water, and is characterized by forming a structure in which an alkylamine compound is fixed on the surface of the PAN fiber.

[0029] The maximum gold adsorption capacity of the PAN fiber-based gold adsorption material is 600 mg / g or more.

[0030] The molecular weight of the alkylamine compound is 25,000 g / mol or more.

[0031] The alkylamine compound is fixed by an amination reaction between the alkylamine compound and the PAN fiber, and the number of grafted molecules of the alkylamine compound at the time of completion of the amination reaction is less than 1 mmol / g.

[0032] Alkylamine compounds are branched alkylamine compounds.

[0033] The branched alkylamine compound is one or a combination of bPEI (branched poly(ethyleneimine)), iso-buthylamine, sec-butylamine, iso-amylamine, PEA (phosphoethanolamine), trimethylamine, and iso-propylamine.

[0034] The method for manufacturing a PAN fiber-based gold adsorption material according to the present invention comprises: introducing PAN fiber into an aqueous solution of an alkylamine compound, fixing the alkylamine compound to the surface of the PAN fiber through an amination reaction, thereby manufacturing a PAN fiber-based gold adsorption material; and is characterized in that the number of grafted molecules of the alkylamine compound at the time of completion of the amination reaction is less than 1 mmol / g.

[0035] The maximum gold adsorption capacity of the manufactured PAN fiber-based gold adsorption material is 600 mg / g or more.

[0036] The gold recovery method using a PAN fiber-based gold adsorption material according to the present invention comprises the steps of acidifying a treatment solution containing gold ions; and introducing a PAN fiber-based gold adsorption material into the treatment solution under acidic conditions. When the gold adsorption material is introduced into the treatment solution under acidic conditions, the amine functional group provided in the alkylamine compound is hydrogen ion (H). +) to form an electrically positive (+) polar state, gold ions combine with anions to form a negative (-) polar state, other metallic ions present in the solution to be treated maintain a positive ion state, and the gold ions in the negative (-) polar state are adsorbed to the amine functional group in the positive (+) polar state, while other metallic ions maintaining a positive ion state are not adsorbed to the amine functional group in the positive (+) polar state.

[0037] The PAN fiber-based gold adsorption material and its manufacturing method according to the present invention and the gold recovery method using the same have the following effects.

[0038] The maximum gold ion adsorption capacity is 1463 mg / g, which is significantly superior to that of micrometer-sized and millimeter-sized gold adsorption materials. Furthermore, it exhibits the highest level of gold adsorption characteristics compared to nanometer-sized gold adsorption materials.

[0039] Furthermore, as high-molecular-weight alkylamine compounds are fixed to the PAN surface at a low introduction density, the crystallinity and strength of the PAN fibers are suppressed, while gold adsorption characteristics are improved. Furthermore, the target solution is acidified to selectively adsorb only anionic gold ions, resulting in excellent adsorption selectivity for gold ions.

[0040] Figure 1 is a schematic diagram of a PAN fiber-based gold adsorption material according to one embodiment of the present invention.

[0041] Figures 2a to 2d are schematic diagrams showing that alkylamine compounds of various molecular weights are fixed on the surface of PAN fiber.

[0042] Figure 3 is a schematic diagram showing the introduction of bPEI to the surface of PAN fiber by an amination reaction.

[0043] Figure 4a shows the FT-IR analysis results of gold adsorption materials each immobilized with DETA, TETA, TEPA, and bPEI manufactured according to Experimental Example 1.

[0044] Figure 4b shows the number of moles of grafted molecules of DETA, TETA, TEPA, and bPEI, respectively, in the gold adsorption material manufactured according to Experimental Example 1.

[0045] Figure 4c shows the weight of gold adsorption materials each immobilized with DETA, TETA, TEPA, and bPEI manufactured according to Experimental Example 1.

[0046] Figure 4d shows the XRD analysis results of gold adsorption materials each immobilized with DETA, TETA, TEPA, and bPEI manufactured according to Experimental Example 1.

[0047] Figure 4e shows the tensile strength characteristics of gold adsorption materials each immobilized with DETA, TETA, TEPA, and bPEI manufactured according to Experimental Example 1.

[0048] Figure 4f shows the results of measuring the maximum adsorption capacity of gold adsorption materials each immobilized with DETA, TETA, TEPA, and bPEI manufactured according to Experimental Example 1.

[0049] Figures 5a to 5d are experimental results showing changes in the characteristics of a gold adsorption material according to the amination reaction time.

[0050] Figures 6a to 6f are experimental results showing the gold recovery rate according to the pH of a solution in which gold ions are present.

[0051] Figures 7a to 7l are experimental results showing the gold recovery rate according to the gold ion concentration.

[0052] Figure 7m shows the results of an isothermal adsorption experiment of a gold adsorption material according to Ci.

[0053] Figure 7n is a schematic diagram summarizing the maximum adsorption capacity results of a gold adsorption material according to the present invention and a known gold adsorption material.

[0054] Figure 8 shows the experimental results showing the gold recovery characteristics in an environment where gold ions and 14 types of metallic ions coexist.

[0055] Figure 9 is an experimental result showing the regeneration characteristics of a gold adsorption material according to the present invention.

[0056] Figure 10a is an experimental result showing the pressure drop characteristics of a gold adsorption material according to the present invention.

[0057] Figure 10b is a photograph showing a gold adsorption material according to the present invention woven into an arbitrary shape.

[0058] Figure 11 is a microscope image of a gold adsorption material on which bPEI having molecular weights of 10,000, 25,000, and 70,000 g / mol is fixed, respectively.

[0059] Hereinafter, with reference to the drawings, a PAN fiber-based gold adsorption material, a method for manufacturing the same, and a method for recovering gold using the same according to one embodiment of the present invention will be described in detail.

[0060] PAN fiber-based gold adsorption material

[0061] The present invention not only realizes excellent gold recovery characteristics by utilizing the gold adsorption characteristics of alkylamine, but also presents a technology that can improve the durability of a gold adsorption material by suppressing the high water solubility of alkylamine.

[0062] As previously described in the "Background Art," the excellent gold adsorption properties of alkylamines are well known (see Non-Patent Document 2). Limiting the high water solubility of alkylamines is crucial for their use as gold adsorption materials. As one method for limiting the high water solubility of alkylamines, the present inventors have proposed the technology disclosed in Patent Document 5.

[0063] The present inventors, in line with the research of the technology disclosed in Patent Document 5, developed a gold adsorption material having an easier manufacturing method, better gold adsorption characteristics, better durability, and better usability.

[0064] While the maximum adsorption capacity of the gold adsorption material disclosed in Patent Document 5 (see FIGS. 9a and 9b of Patent Document 5) is less than 600 mg / g, the maximum adsorption capacity of the gold adsorption material according to the present invention is 1463 mg / g, which is more than twice as excellent (see Experimental Example 4 described below). This maximum adsorption capacity of the gold adsorption material according to the present invention is the highest level of gold adsorption properties not only compared to fibrous gold adsorption materials but also compared to nanometer (nm)-sized gold adsorption materials that exhibit relatively excellent gold adsorption properties based on their high specific surface area (see Experimental Example 4 and Table 2 described below). In addition, while the gold adsorption material of Patent Document 5 is a millimeter (mm)-sized granular material, the gold adsorption material according to the present invention is a fibrous material with a diameter of ㎛, and thus can be woven into various shapes such as pellets, thereby expanding its usability. Above all, in the case of Patent Document 5, a structure is proposed in which radial pores are formed inside a gold adsorption material and amine functional groups are fixed to the pores in order to suppress the water solubility of amine functional groups, but the present invention can be said to be an advanced technology in that it can manufacture a gold adsorption material in a very simple way and effectively suppress the water solubility of alkylamines.

[0065] The gold adsorption material according to the present invention has a structure in which an alkylamine compound is fixed to the surface of a polyacrylonitrile fiber (hereinafter referred to as "PAN fiber") having a diameter of the order of μm (see Fig. 1). The alkylamine compound fixed to the surface of the PAN fiber contains an abundance of various amine functional groups such as primary amine, secondary amine, and tertiary amine, thereby exhibiting excellent gold adsorption characteristics. In addition, since the alkylamine compound is fixed to the PAN fiber without damaging the crystallinity of the PAN fiber, the water solubility of the alkylamine compound is suppressed.

[0066] The technology for immobilizing amine functional groups on the surface of PAN is a well-known technology, and PAN with immobilized amine functional groups is used as an adsorbent material for various purposes. For example, as disclosed in Patent Document 6, PAN with immobilized amine functional groups is being utilized for carbon dioxide capture purposes.

[0067] The technical reason why the gold adsorption material according to the present invention has an advancement over the known technology, even though it has a structure in which an alkylamine compound is fixed to a PAN fiber similar to the known technology, is that it has a structure in which the water solubility of the alkylamine is suppressed and it has high gold adsorption characteristics.

[0068] In the case of the PAN technology with a known amine functional group fixed therein, as in Patent Document 6, the adsorbent material is exposed to an atmospheric environment, and therefore the high water solubility of alkylamine is not a characteristic that should be considered when manufacturing the adsorbent material. In other words, since the adsorbent material is exposed to an atmospheric environment and carbon dioxide is captured by alkylamine, the high water solubility of alkylamine does not affect its characteristics as a carbon dioxide adsorbent material.

[0069] On the other hand, when utilizing PAN with an immobilized alkylamine compound as a gold adsorption material for adsorbing gold ions in water, the high water solubility of the alkylamine has a critical impact on its usability as a gold adsorption material. To suppress the high water solubility of the alkylamine, the alkylamine must be stably immobilized on the support. For example, the PAN and the alkylamine must form a stable chemical bond.

[0070] In this way, it is possible to suppress the high water solubility of alkylamines through a stable chemical bond between PAN and alkylamines, and the high water solubility of alkylamines is closely related to the crystallinity of PAN. In other words, even if PAN and alkylamines form a stable chemical bond, if the crystallinity of PAN is damaged due to the bond between PAN and alkylamines, the mechanical strength such as tensile strength will decrease, and the gold adsorption material will inevitably dissolve in a strongly acidic environment.

[0071] Therefore, the chemical bond between PAN and alkylamine must be induced within a range where the crystallinity of PAN is minimized, so that the high water solubility of alkylamine can be suppressed and the dissolution of the gold adsorption material can be prevented.

[0072] The surface of the PAN fiber has nitrile groups (-C≡N) distributed at a uniform density. The alkylamine compound is fixed (grafted) to the PAN fiber in a form in which the amine functional group of the alkylamine compound substitutes the nitrile group (-C≡N). The crystallinity of the PAN fiber is determined by the degree of substitution of the nitrile group (-C≡N) with the alkylamine compound. That is, the higher the ratio of the nitrile groups (-C≡N) on the surface of the PAN fiber to the substitution of the alkylamine compound, the lower the crystallinity of the PAN. In other words, the higher the introduction density of the alkylamine compound, the lower the crystallinity of the PAN. Therefore, it is necessary to lower the introduction density of the alkylamine compound to suppress the water solubility of the alkylamine compound.

[0073] Meanwhile, by lowering the introduction density of the alkylamine compound, the decrease in crystallinity of PAN can be alleviated and the high water solubility of the alkylamine compound can be suppressed. However, if the introduction density of the alkylamine compound is lowered, the number of amine functional groups capable of adsorbing gold ions in water is reduced, so the gold adsorption characteristics are bound to deteriorate.

[0074] The present invention provides a solution to this problem by introducing a high molecular weight alkylamine compound having a molecular weight of 25,000 g / mol or more, which can cause steric hindrance, thereby lowering the introduction density of the alkylamine compound and simultaneously enabling the expression of excellent gold adsorption characteristics. Referring to Table 1 of Experimental Example 3 described below, when an alkylamine compound having a molecular weight of less than 25,000 g / mol is applied, the strength characteristics are poor, and excellent gold adsorption characteristics cannot be expected.

[0075] When introducing a high molecular weight alkylamine compound, since the molecular size of the alkylamine compound is large, a repulsive force, i.e., steric hindrance, occurs between the nitrile groups (-C≡N) on the PAN surface and the alkylamine compound in close proximity during the reaction, and ultimately, the alkylamine compounds fixed on the PAN surface form a form spaced apart from each other by a certain distance. In other words, nitrile groups (-C≡N) that are not bonded to alkylamine compounds exist between the alkylamine compounds fixed on the PAN surface, which means that the introduction density of the alkylamine compound is low. Referring to the schematic diagrams of FIGS. 2a to 2d, when introducing DETA, a low molecular weight alkylamine compound (see (a)), DETA is fixed to the PAN surface with a high introduction density in the form of 1:1 matching with the nitrile group (-C≡N) on the PAN surface, whereas as shown in (b) to (d) of FIG. 2, as the molecular weight of the alkylamine compound increases (TETA <TEPA<bPEI) 알킬아민 분자간 입체장애로 인해 알킬아민 화합물의 도입밀도가 낮아지게 된다.

[0076] Meanwhile, high-molecular-weight alkylamine compounds have significantly more amine functional groups than low-molecular-weight alkylamine compounds. Therefore, introducing high-molecular-weight alkylamine compounds allows for lowering the alkylamine compound introduction density while simultaneously improving gold adsorption properties.

[0077] As the alkylamine compound having a molecular weight of 25,000 g / mol or more, a branched alkylamine compound may be used. In addition, the branched alkylamine compound may be any one of bPEI (branched poly(ethyleneimine)), iso-buthylamine, sec-butylamine, iso-amylamine, PEA (phosphoethanolamine), trimethylamine, and iso-propylamine, or a combination thereof.

[0078] PAN fibers on which alkylamine compounds are fixed are obtained by polymerizing acrylonitrile and spinning the polyacrylonitrile obtained by the polymerization, and all PAN fibers manufactured through this process are applicable to the present invention. In addition, the diameter of the PAN fibers applicable to the present invention is not limited to a numerical value, but in one embodiment, it can have a diameter of 1 to 500 μm. For reference, PAN fibers having a diameter of 50 μm were used in Experimental Examples 1 to 5 described below.

[0079] Manufacturing method of PAN fiber-based gold adsorption material

[0080] An alkylamine aqueous solution containing an alkylamine compound is prepared, and PAN fibers are mixed with the alkylamine aqueous solution to induce an amination reaction. Through the amination reaction, the nitrile groups (-C≡N) on the surface of the PAN fibers are replaced with the amine functional groups of the alkylamine compound, thereby fixing the alkylamine compound to the surface of the PAN fibers. In other words, a layer of an alkylamine compound of a certain thickness is formed on the surface of the PAN fibers through the amination reaction.

[0081] The amine functional group of an alkylamine compound encompasses various functional groups including an amine group (-NH2), and may mean, for example, one of primary amine, secondary amine, tertiary amine, and quaternary amine, or a combination thereof.

[0082] To promote the amination reaction, a non-metallic Lewis acid catalyst or a metal Lewis acid catalyst may be added to the alkylamine aqueous solution. As the non-metallic Lewis acid catalyst, any one of BF3·2H2O, acetic acid, and hydrochloric acid may be used, and as the metal Lewis acid catalyst, AlCl3·6H2O may be used.

[0083] The amination reaction can be achieved by mixing PAN fibers in an alkylamine aqueous solution, and the mixture can be heated to a certain temperature to induce hydrothermal synthesis to promote the amination reaction. In one example, the amination reaction can be induced through hydrothermal synthesis by charging an autoclave with a mixed solution of an alkylamine aqueous solution and PAN fibers.

[0084] When the alkylamine compound is fixed on the surface of the PAN fiber by an amination reaction and the unreacted alkylamine compound on the surface of the PAN fiber is removed using ultrapure water and a chemical, the method for manufacturing a PAN fiber-based gold adsorption material according to one embodiment of the present invention is completed. Fig. 3 is a schematic diagram showing that bPEI is introduced to the surface of the PAN fiber by an amination reaction.

[0085] Gold recovery method using PAN fiber-based gold adsorption material

[0086] First, the solution to be treated containing gold ions is acidified.

[0087] Referring to Experimental Example 4 described below, the higher the acidity of the solution to be treated, the higher the gold recovery efficiency, and preferably, the pH of the solution to be treated should be maintained at a condition of 4 or lower. The acidification of the solution to be treated can be controlled by adding a weak or strong acid to the solution to be treated. In addition to gold ions, up to 14 types of metallic ions, including copper (Cu), nickel (Ni), cobalt (Co), and zinc (Zn), can coexist with gold ions in the solution to be treated.

[0088] Next, the PAN fiber-based gold adsorption material according to the present invention is added to the treatment solution under acidic conditions, and gold ions present in the treatment solution are adsorbed to the gold adsorption material.

[0089] When the gold adsorption material of the present invention is added to a treatment solution under acidic conditions, the amine functional group present in the alkylamine compound is hydrogen ion (H + ) and forms an electrically positive (+) polar state, and gold ions are anions, for example, chloride ions (Cl - ) and forms a (-) polar state. Meanwhile, other metallic ions present in the solution to be treated, such as copper (Cu), nickel (Ni), cobalt (Co), and zinc (Zn), maintain a cationic state even under acidic conditions.

[0090] Accordingly, gold ions in the (-) polar state are adsorbed to the amine functional group in the (+) polar state, and other metallic ions that maintain a cationic state are not adsorbed to the amine functional group in the (+) polar state. In addition, gold ions in the (-) polar state adsorbed to the amine functional group in the (+) polar state are converted to a metallic form (Au) through a reduction reaction. 0 ) is crystallized and grown. Referring to Experimental Example 4 described below, in the form of a metal (Au 0 ) is crystallized in a brick-by-brick form on the surface of the PAN fiber.

[0091] Referring to Experimental Example 4 described below, even when 0.5 g / L of the PAN fiber-based gold adsorption material according to the present invention is injected into an environment containing 0.1 ppm of gold ions, a gold recovery efficiency close to 100% is exhibited. This result is a result of significantly improved gold recovery characteristics compared to the gold adsorption material of Patent Document 5, which exhibited a gold recovery efficiency of approximately 80% when 1 g / L of the gold adsorption material was injected into an environment containing 0.1 ppm of gold ions.

[0092] In addition, the maximum adsorption amount of the gold adsorption material according to the present invention was 1463 mg / g, which is more than twice as good as the maximum adsorption amount (less than 600 mg / g) of the gold adsorption material of Patent Document 5, which shows the best gold adsorption characteristics among millimeter (mm)-sized gold adsorption materials, and is the highest level of gold adsorption characteristics even compared to nanometer-sized gold adsorption materials. In addition, in an environment where gold ions and 14 kinds of metallic ions coexist, even when the concentration of the 14 kinds of metallic ions is 100 times that of the gold ions, the gold adsorption material of the present invention shows a gold recovery efficiency of 99.4% or more.

[0093] Meanwhile, the PAN fiber-based gold adsorption material of the present invention, which has completed the adsorption of gold ions, can be regenerated by placing it in an aqueous solution containing a mixture of thiourea and HCl. When the gold adsorption material, to which gold ions have been adsorbed, is placed in an aqueous solution containing a mixture of thiourea and HCl, the gold is eluted, and when the gold adsorption material is subsequently washed with NaOH or the like, the regeneration of the gold adsorption material is completed.

[0094] The PAN fiber-based gold adsorption material according to the present invention exhibits a gold recovery efficiency of over 90% even after repeated gold ion adsorption and regeneration. Referring to Experimental Example 4 described below, when gold ion adsorption and regeneration were repeated five times, a gold recovery efficiency close to 100% was maintained, and even after 10 repetitions, a gold recovery efficiency of over 90% was exhibited.

[0095] Above, a PAN fiber-based gold adsorption material, a manufacturing method thereof, and a gold recovery method using the same according to one embodiment of the present invention have been described. Below, the present invention will be described in more detail through experimental examples.

[0096] Experimental Example 1: Preparation of PAN fiber-based gold adsorption material

[0097] Alkylamine aqueous solutions were prepared in which each of various alkylamine compounds, namely DETA (99%, Sigma Aldrich), TETA (97%, Sigma Aldrich), TEPA (technical grade, Sigma Aldrich), and bPEI (molecular weight 70,000 g / mol, 30% aqueous solution, Alfa Aesar) was dissolved at a concentration of 10 wt%. Then, 5 g of PAN fiber was added to 70 mL of each alkylamine aqueous solution and swelled for 1 hour. Then, the fiber was transferred to a 100 mL high-pressure autoclave, and BF3·2H2O, an amination reaction catalyst, was additionally added, and then left at 160°C for 6 hours. The PAN fibers after the reaction were sequentially washed with ultrapure water, 1 M HCl solution, NaOH solution, and ultrapure water to remove unreacted alkylamine molecules, and then dried at 80°C for 24 hours.

[0098] Experimental Example 2: Analysis of Crystallinity and Strength Characteristics of PAN Fiber-Based Gold Adsorption Materials

[0099] The effects of the molecular weight of alkylamine compounds and the introduction density of alkylamine compounds on the crystallinity and strength characteristics of PAN fiber-based gold adsorption materials were analyzed.

[0100] Figure 4a shows the FT-IR analysis results of the gold adsorption material on which DETA, TETA, TEPA, and bPEI were each fixed, manufactured according to Experimental Example 1, Figure 4b shows the number of moles of grafted molecules of DETA, TETA, TEPA, and bPEI, manufactured according to Experimental Example 1, and Figure 4c shows the weight of the gold adsorption material on which DETA, TETA, TEPA, and bPEI were each fixed, manufactured according to Experimental Example 1. In addition, Fig. 4d is an XRD analysis result of a gold adsorption material having DETA, TETA, TEPA, and bPEI fixed thereon, manufactured according to Experimental Example 1, Fig. 4e shows the tensile strength characteristics of a gold adsorption material having DETA, TETA, TEPA, and bPEI fixed thereon, manufactured according to Experimental Example 1, and Fig. 4f is a result of measuring the maximum adsorption capacity of a gold adsorption material having DETA, TETA, TEPA, and bPEI fixed thereon, manufactured according to Experimental Example 1.

[0101] Referring to Fig. 4a, in the case of the gold adsorption material (DETA@PANF) on which DETA is fixed, 1590 cm corresponding to the primary amine (-NH2) -1 It can be seen that a peak is observed. This is the result of the easy fixation of the primary amine (-NH2), which is relatively short and linear, on the surface of the PAN fiber. On the other hand, in the case of the gold adsorption materials (TETA@PANF, TEPA@PANF, bPEI@PANF) on which TETA, TEPA, and bPEI, which have a molecular weight greater than DETA, are fixed, the peak corresponding to the secondary amine (-NH-) is 1650 cm -1 Peak and 1570 cm -1 Peaks were observed. The predominant observation of secondary amines (-NH-) indicates that high molecular weight alkylamines and branched alkylamines were fixed on the PAN fibers, which means that the introduction densities of TETA, TEPA, and bPEI were lower than those of DETA.

[0102] This tendency of introduction density is more clearly confirmed through the results of the measurement of the number of grafted molecules (mmol / g) in Fig. 4b. Referring to Fig. 4b, as the molecular weight of the alkylamine compound fixed to the gold adsorption material increases (DETA <TETA<TEPA<bPEI) PAN 섬유 표면에 도입된 알킬아민 화합물의 도입분자 몰수의 감소됨을 확인할 수 있다. 특히, bPEI가 도입된 금 흡착소재의 경우, 도입분자 몰수의 0에 수렴되는 결과를 나타내었는데 이는 bPEI의 분자량(70,000 g / mol)이 DETA, TETA 그리고 TEPA 보다 월등히 크기 때문이다. 이러한 결과를 도 4c의 금 흡착소재의 무게측정결과와 함께 보면, 도 4c에 알킬아민 화합물의 증가할수록 금 흡착소재의 무게가 증가하는 경향을 나타내고 있는데, 이는 bPEI의 도입밀도가 낮음에도 불구하고 즉, bPEI의 도입분자 몰수가 작음에도 불구하고 bPEI의 분자량이 커 bPEI가 도입된 금 흡착소재의 무게가 가장 큼을 의미한다.

[0103] The molecular weight and introduction density results of the alkylamine compound as described above directly affect the crystallinity and strength characteristics of the gold adsorption material.

[0104] Looking at the XRD analysis results in Fig. 4d, in the case of the gold adsorption materials (DETA@PANF, TETA@PANF, TEPA@PANF) to which DETA, TETA, and TEPA are introduced, the 16.8 and 29.2 peaks, which are the unique peaks of the PAN fiber, disappear or are diluted by the introduction of the alkylamine compound. On the other hand, in the case of the gold adsorption material (bPEI@PANF) to which bPEI is introduced, the unique peak of the PAN fiber is maintained. These results indicate that as the introduction density of the alkylamine compound increases and the substitution rate of the nitrile group (-C≡N) on the surface of the PAN fiber increases, the crystallinity of the PAN fiber decreases. In addition, as the introduction density of the alkylamine compound decreases, the decrease in the crystallinity of the PAN fiber is suppressed.

[0105] The crystallinity of the PAN fiber is directly related to the strength characteristics of the gold adsorption material, which can be confirmed through the tensile strength characteristics of Fig. 4e. As shown in Fig. 4e, it can be confirmed that the tensile strength of the gold adsorption material increases as the molecular weight of the alkylamine compound increases, that is, as the introduction density of the alkylamine compound decreases. In particular, in the case of the gold adsorption material introduced with bPEI, it can be seen that it exhibits a tensile strength characteristic of 150 MPa at a strain of approximately 8%, which is significantly superior to that of other gold adsorption materials.

[0106] Through the above analysis results, it can be seen that the higher the molecular weight of the alkylamine compound and the lower the introduction density of the alkylamine compound, the better the crystallinity and strength characteristics of the gold adsorption material.

[0107] Furthermore, the crystallinity and strength characteristics of the gold adsorption material have the same tendency as the gold adsorption characteristics of the gold adsorption material. Referring to Fig. 4f, it can be seen that, similar to the crystallinity and strength characteristics of the gold adsorption material, the maximum adsorption capacity of the gold adsorption material increases as the introduction density of the alkyl amanne compound decreases. In particular, the gold adsorption material introduced with bPEI exhibits a maximum adsorption capacity of 1463 mg / g.

[0108] Experimental Example 3: Gold adsorption characteristics of gold adsorption materials according to the amount of bPEI introduced.

[0109] Through Experimental Example 2, it was confirmed that as the molecular weight of the alkylamine compound increases, the introduction density of the alkylamine compound decreases, and as the introduction density of the alkylamine compound decreases, the decrease in crystallinity of the PAN fiber is suppressed, thereby securing excellent strength characteristics of the gold adsorption material, and through this, the gold adsorption characteristic of the gold adsorption material introduced with bPEI was shown to be the best result.

[0110] In Experimental Example 3, an experiment was conducted to determine the optimal conditions for bPEI introduction. While the amination reaction in Experimental Example 1 was performed at 160°C for 6 hours, the results were examined by applying amination reaction times of 0 to 8 hours under the same temperature conditions. All other experimental conditions were identical to those in Experimental Example 1.

[0111] Figure 5a shows the change in weight of a gold adsorption material according to the amination reaction time, Figure 5b shows the change in density of a gold adsorption material according to the amination reaction time, Figure 5c shows the change in strength of a gold adsorption material according to the amination reaction time, and Figure 5d shows the change in maximum adsorption capacity of a gold adsorption material according to the amination reaction time.

[0112] Referring to Figures 5a and 5b, it can be seen that as the amination reaction time increases, the weight and density of the gold adsorption material increase. In addition, as shown in Figure 5c, as the amination reaction time increases, the strength of the gold adsorption material also tends to increase, but there was no change in the strength after 6 hours of amination reaction. In the case of the gold adsorption characteristics, as shown in Figure 5d, as the amination reaction time increases, the maximum adsorption capacity of the gold adsorption material tends to increase, and equilibrium was reached after 7 hours of amination reaction. This means that the amination reaction between the PAN fibers of bPEI was completed after 7 hours.

[0113] When the results of FIGS. 5c and 5d are related to the results of the grafted molecule molecule measurement of FIG. 4b, it can be seen that the gold adsorption material on which DETA, TETA, and TEPA are each fixed at the point where the amination reaction is completed shows a result in which the grafted molecule molecule exceeds 1.75 mmol / g, whereas the gold adsorption material on which bPEI is fixed shows a result in which the grafted molecule molecule is less than 1 mmol / g, or more precisely, a result in which the grafted molecule molecule molecule converges to 0.

[0114] Through the above experimental results, it can be seen that as the molecular weight of the alkylamine compound fixed to the surface of the PAN fiber increases, the number of moles of the introduced alkylamine compound decreases, and excellent crystallinity and strength characteristics are exhibited, thereby improving the gold adsorption characteristics. It was confirmed that the gold adsorption material fixed to the PAN fiber with bPEI having a molecular weight of 70,000 g / mol is an experimental example that matches this.

[0115] Meanwhile, in order to confirm the effect of the molecular weight of the alkylamine compound on the gold adsorption material, the strength characteristics of the gold adsorption material according to the molecular weight of bPEI were analyzed. As described above, the strength characteristics of the gold adsorption material are directly related to the number of moles of the introduced alkylamine compound, the crystallinity of the gold adsorption material, and the gold adsorption characteristics. Therefore, by analyzing the strength characteristics of the gold adsorption material according to the molecular weight of bPEI, the overall characteristic changes of the gold adsorption material according to the molecular weight of bPEI can be inferred.

[0116] Table 1 below shows the density, breaking strength (Force at Break), and elongation at Break of gold adsorbents immobilized on PAN fibers using bPEI with different molecular weights. The gold adsorbents were prepared according to the method described in Experimental Example 1, and the amination reaction conditions were 160°C for 6 hours.

[0117] Referring to Table 1, the gold adsorption material fixed with bPEI having a molecular weight of 700 to 10,000 exhibits a breaking strength of 17.5 cN or less and a breaking elongation of 3.26% or less, whereas the gold adsorption material applied with bPEI having a molecular weight of 25,000 exhibits a breaking strength of 89.79 cN and a breaking elongation of 12.96%, indicating that the strength characteristics are significantly improved. In addition, it can be confirmed that the gold adsorption material applied with bPEI having a molecular weight of 75,000 also exhibits excellent breaking strength (90.61 cN) and breaking elongation (13.39%). These results show that the strength characteristics of the gold adsorption material can be improved by applying an alkylamine compound having a molecular weight of 25,000 g / mol or more, and furthermore, it can be inferred that the overall characteristics of the gold adsorption material, i.e., the number of moles of introduced molecules, the crystallinity of the gold adsorption material, and the gold adsorption characteristics, can be improved by applying an alkylamine compound having a molecular weight of 25,000 g / mol or more.

[0118] In addition, Fig. 11 is a microscope image of a gold adsorption material on which bPEI having molecular weights of 10,000 (top), 25,000 (middle), and 70,000 (bottom) g / mol is fixed, respectively. It was confirmed that the gold adsorption material on which bPEI having molecular weight of 10,000 is fixed has low breaking strength and breaking elongation, and thus exhibits a brittle characteristic.

[0119] <Strength characteristics of gold adsorption materials immobilized with bPEI having different molecular weights> bPEI molecular weight (g / mol) Fiber Density (g cm-3) Force at break (cN) Elongation at break (%) 700 1.28 12.10.5 71300 1.27 12.3 1.44 5000 1.28 12.8 1.01 10000 1.27 17.5 3.26 25000 1.27 89.79 12.96 70000 1.28 90.6 113.39

[0120] Experimental Example 4: Gold recovery characteristics of gold adsorption material with bPEI

[0121] Through Experimental Example 3, it was confirmed that the gold adsorption characteristics of the gold adsorption material subjected to 7 hours of amination reaction were excellent, and various gold recovery experiments were conducted using the gold adsorption material manufactured under these conditions.

[0122] First, we examined the gold recovery rate according to the pH of the solution containing gold ions. Specifically, the gold recovery rate was measured by adjusting the pH of a solution containing 100 ppm of gold ions between 1 and 12 in increments of 1. The gold adsorption material was added at a concentration of 0.5 g / L, and the gold adsorption reaction time was 24 hours at room temperature.

[0123] As a result of the experiment, as shown in Fig. 6a, a gold recovery rate of 100% was observed under pH conditions of 4 or lower. In addition, under conditions exceeding pH 4, the gold recovery rate significantly decreased as the pH increased. SEM analysis (see Figs. 6b to 6e) and XRD analysis (see Fig. 6f) were performed on the gold adsorption material in which gold was adsorbed under pH conditions of 1, 4, 8, and 12, and the results confirmed that the adsorbed substance was gold (Au).

[0124] The gold recovery rate was investigated by varying the gold ion concentration. Specifically, the gold ion concentration in the solution was set to 0.1, 0.2, 0.5, 1, 2, 5, 10, 100, 500, and 1000 ppm, and the gold recovery rate was measured, along with FESEM and EDS analyses.

[0125] Referring to Fig. 7a, it can be confirmed that the gold recovery rate reaches 100% even under conditions of low gold ion concentrations of 10 ppm or less. Figs. 7b to 7g are FESEM images of gold adsorption materials adsorbed at gold ion concentrations of 0.1, 1, 10, 100, 500, and 1000 ppm, and Figs. 7h to 7l are FESEM-EDS analysis results for gold adsorption materials adsorbed at a gold ion concentration of 1000 ppm, which show that the substance adsorbed to the gold adsorption material is gold crystals.

[0126] In addition, an isothermal adsorption experiment was conducted to measure the maximum adsorption capacity of the gold adsorption material.

[0127] Figure 7m shows the results of the isotherm adsorption experiment of the gold adsorption material according to Ci, which shows that the adsorption capacity (qe, mg / g) of the gold adsorption material for gold ions increases at the equilibrium concentration (Ce, mg / L) as Ci increases. The isotherm data for gold recovery were fitted using three representative isotherm models: Langmuir, Freundlich, and Sips. The Sips equation showed good agreement with the isotherm data compared to the Langmuir and Freundlich models, and the coefficient of determination (R 2 ) showed a value close to 1 (0.99). As a result of calculating the maximum adsorption capacity of the gold adsorption material according to the Sips model, the maximum adsorption capacity was 1463 mg / g (see Table 2 below).

[0128] <Isothermal adsorption test results of the gold adsorption material according to the present invention>LangmuirFreundlichSipsq m K L R 2 nK F R 2 q m k s NR 2 1068.630.00860.943.21113.680.971462.960.0361.730.99

[0129] The maximum adsorption capacity of 1463 mg / g of the gold adsorption material according to the present invention is a characteristic that is far superior to not only the known ㎛-sized and millimeter-sized gold adsorption materials but also the fibrous gold adsorption materials, despite having a relatively low specific surface area compared to nano-sized gold adsorption materials (see Fig. 7n and Table 3), and this can be attributed to the structural stability of the gold adsorption material, such as crystallinity and strength characteristics, being secured as described above. In addition, an adsorption selectivity test of the gold adsorption material according to the present invention was conducted.

[0130] Considering that other metallic ions coexist with gold ions during the recovery of gold ions, 14 kinds of metallic ions that can coexist with gold ions were allowed to exist together with gold ions, and gold recovery experiments were conducted using them. The initial concentration of gold ions was 10 mg / L, and the concentrations of coexisting metallic ions were set to 1 (10 mg / L), 10 (100 mg / L), and 100 (1000 mg / L) times the concentration of gold ions, respectively. The adsorption time was carried out for 24 hours at room temperature with stirring at 200 rpm. In addition, the pH of the solution was set to 1. The 14 metallic ions are copper (Cu(II)), chromium (Cr(III)), iron (Fe(III)), aluminum (Al(III)), nickel (Ni(II)), zinc (Zn(II)), cobalt (Co(II)), cadmium (Cd(II)), lead (Pb(II)), manganese (Mn(II)), sodium (Na(I)), potassium (K(I)), magnesium (Mg(II)), and calcium (Ca(II)) ions in the form of nitrates (ACS reagent, Sigma Adrich).

[0131] As a result of conducting a gold recovery experiment in an environment where 14 types of metallic ions coexisted with gold ions, as shown in Fig. 8, when the concentration of gold ions and the concentration of 14 types of metallic ions were the same, the gold recovery rate was over 99.9%, and when the concentration of 14 types of metallic ions was 10 times that of gold ions, a gold recovery rate of approximately 99.5% was shown. In addition, when the concentration of 14 types of metallic ions was 100 times that of gold ions, a gold recovery rate of approximately 99.4% was shown.

[0132] Experimental Example 5: Regeneration characteristics of gold adsorption material with bPEI introduced

[0133] An experiment was conducted to determine whether there was a change in the gold adsorption performance when the gold adsorption material used in the gold recovery process was regenerated and then applied to the gold recovery process again. Specifically, the gold adsorption material manufactured according to Experimental Example 3 was added at a concentration of 0.5 g / L to a 10 ppm gold ion solution to perform gold ion adsorption, and then the gold adsorption material was regenerated by leaving it in an aqueous solution containing 0.5 mol / L thiourea and 0.1 M HCl simultaneously for 24 hours. This adsorption and regeneration process was repeated 10 times.

[0134] As a result of the experiment, as shown in Fig. 9, even after adsorption and regeneration were repeated 10 times, the gold recovery rate was over 99%, and the gold adsorption rate was 100% until the 5th repetition and then gradually decreased, showing a gold adsorption rate of approximately 91% after 10 repetitions.

[0135] Experimental Example 6: Pressure drop characteristics of gold adsorption material with bPEI introduced

[0136] The gold adsorption material manufactured according to Experimental Example 3 was prepared in powder form (ALPP) and pellet form (ALPFt), and then packed into a column, and the pressure drop was measured. The powder form (ALPP) was prepared by pulverizing the gold adsorption material manufactured according to Experimental Example 3 using a ball mill, and the pellet form (ALPFt) was prepared by needle-punching the gold adsorption material manufactured according to Experimental Example 3 into pellet form. 5 g each of the powder form (ALPP) and pellet form (ALPFt) were packed into a column with an inner diameter of 1.5 cm and a height of 15 cm, and the pressure drop was measured while passing ultrapure water upward at a rate of 1 to 8 L / min.

[0137] As a result of the experiment, as shown in Fig. 10a, when the powder type (ALPP) was filled, ΔP increased exponentially, whereas when the pellet type (ALPFt) was filled, ΔP was relatively very low. Through these results, it can be seen that the gold recovery process can be efficiently performed by weaving the gold adsorption material according to the present invention into a pellet type (ALPFt). For reference, Fig. 10b is a photograph showing that the gold adsorption material according to the present invention can be woven into various shapes, in which the gold adsorption material is woven into the shape of the letters 'KIST'.

[0138]

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Claims

1. For adsorbing gold ions in water, A PAN fiber-based gold adsorption material characterized by forming a structure in which an alkylamine compound is fixed on the surface of the PAN fiber.

2. In paragraph 1, A PAN fiber-based gold adsorption material characterized by a maximum gold adsorption capacity of 600 mg / g or more.

3. In paragraph 1, A PAN fiber-based gold adsorption material, characterized in that the molecular weight of the above alkylamine compound is 25,000 g / mol or more.

4. In paragraph 1, A PAN fiber-based gold adsorption material characterized in that the above alkylamine compound is fixed by an amination reaction between the alkylamine compound and the PAN fiber, and the number of grafted molecules of the alkylamine compound at the time of completion of the amination reaction is less than 1 mmol / g.

5. In paragraph 1, A PAN fiber-based gold adsorption material characterized in that the above alkylamine compound is a branched alkylamine compound.

6. In paragraph 5, A PAN fiber-based gold adsorption material characterized in that the branched alkylamine compound is one or a combination of bPEI (branched poly(ethyleneimine)), iso-buthylamine, sec-butylamine, iso-amylamine, PEA (phosphoethanolamine), trimethylamine, and iso-propylamine.

7. A PAN fiber-based gold adsorption material is manufactured by placing PAN fiber in an aqueous solution of an alkylamine compound and fixing the alkylamine compound to the surface of the PAN fiber through an amination reaction. A method for manufacturing a PAN fiber-based gold adsorption material, characterized in that the number of grafted molecules of an alkylamine compound at the time of completion of the amination reaction is less than 1 mmol / g.

8. In paragraph 7, A method for producing a PAN fiber-based gold adsorption material, characterized in that the molecular weight of the above alkylamine compound is 25,000 g / mol or more.

9. In paragraph 7, A method for manufacturing a PAN fiber-based gold adsorption material, characterized in that the maximum gold adsorption capacity of the manufactured PAN fiber-based gold adsorption material is 600 mg / g or more.

10. In paragraph 7, A method for manufacturing a PAN fiber-based gold adsorption material, characterized in that the alkylamine compound is one or a combination of bPEI (branched poly(ethyleneimine)), iso-buthylamine, sec-butylamine, iso-amylamine, PEA (phosphoethanolamine), trimethylamine, and iso-propylamine.

11. In a gold recovery method using a PAN fiber-based gold adsorption material described in any one of clauses 1 to 6, A step of acidifying a treatment solution containing gold ions; and It comprises a step of introducing a PAN fiber-based gold adsorption material into a treatment solution under acidic conditions; When a gold adsorption material is added to a treatment solution under acidic conditions, the amine functional group in the alkylamine compound produces hydrogen ions (H + ) and forms an electrically (+) polar state, gold ions form a (-) polar state by combining with anions, and other metallic ions present in the solution to be treated maintain a cationic state. A gold recovery method using a PAN fiber-based gold adsorption material, characterized in that gold ions in a (-) polar state are adsorbed to amine functional groups in a (+) polar state, and other metallic ions that maintain a cationic state are not adsorbed to amine functional groups in a (+) polar state.

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