KR20210072914A - semiconductor based gold ion adsorbent that selectively adsorbs gold ions by light irradiation, and method for recovering gold using the same - Google Patents

Abstract

The present invention relates to a gold ion adsorbent comprising: semiconductor particles; and a polyphenol-based compound coated on the surface of the semiconductor particles, wherein the gold ion adsorbent selectively adsorbs the gold ions, and to a manufacturing method thereof, and specifically, to a porous adsorption material capable of effectively recovering gold while adsorbing the gold ions with high selectivity, and a manufacturing method thereof.

Description

{semiconductor based gold ion adsorbent that selectively adsorbs gold ions by light irradiation, and method for recovering gold using the same}

The present invention relates to a gold ion adsorbent selectively adsorbing gold ions by irradiation with light, and a method for recovering gold using the same.

In general, gold (Au) having a high purity of 99.995% or more is widely used in precision fields such as gold plating, printing for manufacturing printed circuit boards, semiconductor manufacturing, or pharmaceutical manufacturing. The demand for gold (Au) is continuously increasing as the industry develops, but gold (Au) has a disadvantage in that it has a high price due to the concentration of reserves and deposit areas.

Accordingly, gold (Au) recovery methods such as a metal precipitation method, an electrolysis method, and an extraction method using a gold adsorption resin are being studied in order to recycle gold (Au). The metal precipitation method (Patent Document 0001) is widely used because of its simple device, but it requires a large site, and for the selective recovery of gold (Au), it must go through a complex series of processes such as conditionalization and chemical precipitation. There is a problem that a large amount of chemical sludge is generated, causing environmental problems. The electrolysis method (Patent Document 0002) is easy to selectively recover gold (Au), but there are problems in that the cost required for the process is high, and the gold (Au) recovery rate is lowered when used for a long time. The extraction method using a gold adsorption resin (Patent Document 0003) has the advantage that gold contained in wastewater can be easily recovered, but in the process of extracting gold by incinerating the ion resin after adsorbing gold to the ion resin, tar ( tar) and coke (cokes) are generated, there is a problem that causes environmental problems.

Therefore, there is a need for research on a gold recovery method having high selectivity and recovery rate for gold while supplementing these conventional problems.

Republic of Korea Patent 10-0956050 Republic of Korea Patent Registration 10-0733838 Republic of Korea Patent Registration 10-0395400

An object of the present invention is to provide an adsorbent having high selectivity for gold ions and a high gold recovery rate, and a method for recovering gold using the same.

The gold ion adsorbent according to the present invention includes semiconductor particles; and a polyphenol-based compound coated on the surface of the semiconductor particles, and selectively adsorbs gold ions by light irradiation.

In the gold ion adsorbent according to an embodiment of the present invention, the minimum energy level of the conduction band of the semiconductor particles is higher than the minimum highest occupied molecular orbital (HOMO) energy level of the polyphenol-based compound, but the semiconductor particles The minimum energy level of the valence band of may be lower than the minimum HOMO energy level of the polyphenol-based compound.

In the gold ion adsorbent according to an embodiment of the present invention, electrons may be excited from a highest occupied molecular orbital (HOMO) of a polyphenol-based compound to a conduction band of a semiconductor particle.

In the gold ion adsorbent according to an embodiment of the present invention, the polyphenol-based compound may include any one or two or more selected from the group consisting of a catechol group, a galloyl group, a catechol group-containing functional group, and a galloyl group-containing functional group. .

In the gold ion adsorbent according to an embodiment of the present invention, the polyphenol-based compound may be any one or two or more selected from the group consisting of a tannin-based compound and a polydopamine-based compound.

In the gold ion adsorbent according to an embodiment of the present invention, the above-described tannin-based compound may be any one or two or more selected from the group consisting of tannic acid, gallotannin, and ellagitannins. have.

In the gold ion adsorbent according to an embodiment of the present invention, the semiconductor of the semiconductor particles may be silicon germanium, metal oxide, or metal nitride.

In the gold ion adsorbent according to an embodiment of the present invention, the above-described metal oxide is TiO ₂ , ZnO ₂ , ZnO, CaTiO, WO ₃ , SnO ₂ , MoO ₃ , Fe ₂ O ₃ , InP, GaAs, BaTiO ₃ , KNbO _3, SrTiO _3, and may be at least any one or more selected from the group consisting of Ta ₂ O _5.

In the gold ion adsorbent according to an embodiment of the present invention, the above-described metal nitride is BN, AlN, GaN, InN, CrN, Cr ₂ N, WN, W ₂ N, Mn ₆ N ₄ , Mn ₄ N, Fe ₄ N, Co ₄ N, Ni ₄ N, V ₃ N, Fe ₃ N, Co ₃ N, Ni ₃ N, Cu ₃ N, Ti ₂ N, Cr ₂ N, Mn ₂ N, Fe ₂ N, Co ₂ N, ThN ₂ and WN ₂ may be any one or two or more selected from the group consisting of.

In the gold ion adsorbent according to an embodiment of the present invention, the average diameter of the semiconductor particles may be 10 nm to 10 ㎛ ㎛.

The present invention includes a method for recovering gold ions as metallic Au using the above-described gold ion adsorbent.

The method according to an embodiment of the present invention may include putting a gold ion adsorbent into a solution containing gold ions and irradiating light.

In the method according to an embodiment of the present invention, the above-described light may include ultraviolet rays having a wavelength region of 400 nm or less.

The method according to an embodiment of the present invention may include desorbing metallic gold from the gold ion adsorbent by adding a gold ion adsorbent having metallic Au formed thereon to a leaching solution.

Since the gold ion adsorbent according to the present invention includes a polyphenol-based compound formed on semiconductor particles, it has the advantage of having high selectivity and recovery rate for gold ions when irradiated with light.

In addition, the gold recovery method according to the present invention has an advantage that gold can be easily recovered from the adsorbent material (gold ion adsorbent) through simple acid treatment by using the above-described gold ion adsorbent.

1 is an energy band diagram of a gold ion adsorbent,
2 is an SEM analysis result before the test of Example and after the gold ion adsorption test under dark/light conditions;
3 is a result of examining the effect of the light wavelength on the adsorption of gold ions before the test and under dark/light conditions of Example,
4 is an X-ray photoelectron spectroscopy (XPS) analysis result for investigating whether gold ions are adsorbed and the oxidation state of adsorbed gold in Example (TA-TiO _{2 );}
5 is an XRD analysis result of an _{example (TA-TiO 2} ) before/after gold ion adsorption test under dark/light conditions;
6 is a result of investigating the change in adsorption properties of _{Examples (TA-TiO 2} ) and Comparative Example (TiO ₂ ) according to the concentration of gold ions in the test solution (a mixture of gold ion adsorbent and gold ions) during the gold ion adsorption test;
7 shows the example before the test (TA-TiO ₂ ), the example after the gold ion adsorption test under light conditions (Au-TA-TiO ₂ (1-sun)), and the example after the gold ion desorption test ((Au-TA) -TiO ₂ After desorption) is the result of XRD analysis,
8 is a fluorescence lifetime analysis result for tannin (TA), Comparative Example (TiO ₂ ), Example (TA-TiO _{2 ),}
9 is a result of analyzing the metal selectivity change according to the presence or absence of light irradiation in Comparative Examples (TiO ₂ ) and Examples (TA-TiO _{2 ).}

Hereinafter, a gold ion adsorbent for selectively adsorbing gold ions by light irradiation and a gold recovery method using the same according to the present invention will be described in detail with reference to the accompanying drawings. The drawings introduced below are provided as examples so that the spirit of the present invention can be sufficiently conveyed to those skilled in the art. Accordingly, the present invention is not limited to the drawings presented below and may be embodied in other forms, and the drawings presented below may be exaggerated to clarify the spirit of the present invention. At this time, if there is no other definition in the technical terms and scientific terms used, it has the meaning commonly understood by those of ordinary skill in the technical field to which this invention belongs, and the gist of the present invention in the following description and accompanying drawings Descriptions of known functions and configurations that may be unnecessarily obscure will be omitted. Also, the singular forms used in the specification and appended claims may also be intended to include the plural forms unless the context specifically dictates otherwise. In this specification and the appended claims, the units used without special mention are based on weight, and in one example, the unit of % or ratio means weight % or weight ratio.

The present invention is a semiconductor particle; and a polyphenol-based compound coated on the surface of the semiconductor particles, and relates to a gold ion adsorbent comprising, selectively adsorbing gold ions by light irradiation.

The gold ion adsorbent according to the present invention includes a polyphenol-based compound formed on semiconductor particles and, by irradiating light, selectively adsorbs gold ions and reduces them to metallic Au, while having a high adsorption rate for gold ions. Metallic gold can be easily recovered (desorbed) from the adsorption material (gold ion adsorbent) through simple acid treatment after gold ion adsorption and reduction, which has the advantage of high recovery rate.

In detail, the polyphenol-based compound may generate hot electrons through absorption of light, and the generated hot electrons may reduce gold ions and effectively induce nucleation of gold atoms. In addition, by coating the polyphenol-based compound on the semiconductor particles, a larger amount of hot electrons can be generated compared to when the polyphenol-based compound is used alone, and the excited state of the hot electrons, specifically, the reduction reaction of gold ions It is possible to maintain the state in which it can participate for a long time, so that the adsorption capacity of gold ions can be remarkably improved.

1 is an energy band diagram of a gold ion adsorbent according to the present invention. At this time, the energy band diagram of the gold ion adsorbent is the energy band diagram in the electrochemical equilibrium state. In this case, the electrochemical equilibrium Fermi energy level (E _F) of the Fermi energy level (E _F) and the polyphenol-based compound (polyphenolic compounds) of the semiconductor particles are aligned in the same line condition. As shown, the minimum energy level of the conduction band of the semiconductor particles included in the gold ion adsorbent of the present invention is higher than the minimum highest occupied molecular orbital (HOMO) energy level of the polyphenol-based compound, The minimum energy level of the valence band of the particle is characterized in that it is lower than the minimum HOMO energy level of the polyphenol-based compound.

In addition, in the gold ion adsorbent according to the present invention, the semiconductor particles and the polyphenol-based compound may have a metal-carbon bond.

In general, when a metal-carbon bond is present, metal to-ligand charge transfer (MLCT) or ligand-to-metal charge transfer (LMCT) may occur. As the gold ion adsorbent according to the present invention satisfies the above-described energy level characteristics, charge transfer to the ligand (MLCT) may occur.

Accordingly, the lifetime of the excited electrons formed in the band gap between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) of the polyphenol-based compound when irradiated with light may be longer due to the semiconductor particles. have. In detail, electrons excited to the conduction band of the semiconductor particle by the charge transfer to the ligand move from the conduction band of the semiconductor particle to the HOMO of the polyphenol-based compound and recombine with the holes in the HOMO, so that the polyphenol-based compound The excited state of the hot electrons formed in the LUMO of

Therefore, the gold ion adsorbent according to the present invention may have significantly improved gold ion adsorption capacity and reduction rate by including the polyphenol-based compound formed on the semiconductor particles and irradiating light.

In the gold ion adsorbent according to the present invention, as in an example shown in FIG. 1 , electrons and holes may be excited by light energy in both the polyphenol-based compound and the semiconductor particles, and due to the presence of the semiconductor particles, the polyphenol-based compound The lifetime of the electrons excited by the compound is prolonged, which is advantageous for gold ion adsorption and reduction reactions. In detail, the electrons excited by the polyphenol-based compound and the semiconductor particles are recombined with the holes over time. The gold ion adsorbent according to the present invention includes both the polyphenol-based compound and the semiconductor particles, so that two materials (poly Due to the bonding of the phenol-based compound and semiconductor particles), the lifespan of the electrons formed in the polyphenol-based compound can be increased as the holes generated from the polyphenol-based compound and the electrons generated from the semiconductor particles recombine upon irradiation with light, thereby increasing The reduction rate can be improved.

The semiconductor of the semiconductor particle may be used without limitation as long as it satisfies the above-described bandgap characteristics and can inject electrons into the polyphenol-based compound, but may be, for example, silicon germanium, metal oxide, or metal nitride. Here, the metal oxide is a group consisting of TiO ₂ , ZnO ₂ , ZnO, CaTiO, WO ₃ , SnO ₂ , MoO ₃ , Fe ₂ O ₃ , InP, GaAs, BaTiO ₃ , KNbO ₃ , _{SrTiO 3} and Ta ₂ O ₅ . may be any one or two or more selected from, and the metal nitride is BN, AlN, GaN, InN, CrN, Cr ₂ N, WN, W ₂ N, Mn ₆ N ₄ , Mn ₄ N, Fe ₄ N, Co ₄ N , Ni ₄ N, V ₃ N, Fe ₃ N, Co ₃ N, Ni ₃ N, Cu ₃ N, Ti ₂ N, Cr ₂ N, Mn ₂ N, Fe ₂ N, Co ₂ N, ThN ₂ and WN ₂ It may be any one or two or more selected from the group consisting of, but is not limited thereto.

The polyphenol-based compound may be used without particular limitation as long as it has two or more hydroxyl groups adjacent to each other in the benzene ring, and more specifically, any one selected from the group consisting of a catechol group, a galloyl group, a catechol group-containing functional group, and a galloyl group-containing functional group It may include one or two or more. In this case, the catechol group-containing functional group or the galloyl group-containing functional group may mean a polycyclic hydrocarbon group including a catechol group or a galloyl group, wherein the polycyclic group means a group in which a catechol group or a galloyl group is directly connected or condensed with another cyclic group and the other ring group may be cycloalkyl, heterocycloalkyl, aryl, heteroaryl, or a combination thereof. In this case, the number of carbon atoms of the catechol group-containing functional group or the galloyl group-containing functional group is not particularly limited, but may be, for example, 7 to 50.

In terms of further improving gold ion adsorption capacity and reduction rate, the polyphenol-based compound may be any one or two or more selected from the group consisting of a tannin-based compound and a polydopamine-based compound. The tannin-based compound may be any one or two or more selected from the group consisting of tannic acid, gallotannin, and ellagitannins, and the polydopamine-based compound is polydopamine or polydopamine. It may be a derivative.

In the gold ion adsorbent according to an embodiment of the present invention, the average diameter (particle diameter) of the semiconductor particles is 5 nm to 500 μm, specifically 10 nm to 10 μm, more specifically 50 nm to 5 μm, in one embodiment There may be 100 to 500 nm, but is not limited thereto. However, as the average diameter of the semiconductor particles is larger, the influence of the polyphenol-based compound may be relatively reduced and the gold ion adsorption rate may be lowered. Therefore, it is preferable that the semiconductor particles satisfy the above-described average diameter range.

In terms of effectively increasing the amount of gold ions adsorbed by the polyphenol-based compound, the thickness of the polyphenol-based compound coating layer may be 1 nm to 100 nm, preferably 1 nm to 50 nm, but limited thereto it is not However, as the thickness of the polyphenol-based compound increases, the amount of electrons that can move between the polyphenol-based compound and the semiconductor particles may decrease. Therefore, the thickness of the polyphenol-based compound coating layer is 100 nm or less, preferably 50 nm or less. may be nm.

The present invention includes a method for preparing the gold ion adsorbent described above.

In detail, the method for preparing a gold ion adsorbent according to the present invention may include preparing a dispersion of semiconductor particles and a polyphenol-based compound solution and coating the polyphenol-based compound on the semiconductor particles by stirring. Thereafter, steps such as centrifugation, washing, separation and drying may be further performed in order to obtain a porous adsorbent material for adsorbing gold ions with high purity.

Here, the semiconductor particles and the polyphenol-based compound included in the gold ion adsorbent may satisfy the above-described energy level characteristics. In detail, the minimum energy level of the conduction band of the semiconductor particles included in the gold ion adsorbent of the present invention is higher than the minimum HOMO (highest occupied molecular orbital) energy level of the polyphenol-based compound. The minimum energy level of the valence band is characterized by being lower than the minimum HOMO energy level of the polyphenol-based compound.

For example, the dispersion of semiconductor particles may be prepared by dispersing the semiconductor particles in a solvent. In this case, the semiconductor of the semiconductor particles can be used without limitation as long as it satisfies the above-described band gap characteristics and can inject electrons into the polyphenol-based compound, but may be, for example, silicon germanium, metal oxide, or metal nitride. Here, the metal oxide is a group consisting of TiO ₂ , ZnO ₂ , ZnO, CaTiO, WO ₃ , SnO ₂ , MoO ₃ , Fe ₂ O ₃ , InP, GaAs, BaTiO ₃ , KNbO ₃ , _{SrTiO 3} and Ta ₂ O ₅ . may be any one or two or more selected from, and the metal nitride is BN, AlN, GaN, InN, CrN, Cr ₂ N, WN, W ₂ N, Mn ₆ N ₄ , Mn ₄ N, Fe ₄ N, Co ₄ N , Ni ₄ N, V ₃ N, Fe ₃ N, Co ₃ N, Ni ₃ N, Cu ₃ N, Ti ₂ N, Cr ₂ N, Mn ₂ N, Fe ₂ N, Co ₂ N, ThN ₂ and WN ₂ It may be any one or two or more selected from the group consisting of, but is not limited thereto.

Meanwhile, the average diameter (particle diameter) of the semiconductor particles may be 5 nm to 500 μm, specifically 10 nm to 10 μm, more specifically 50 nm to 5 μm, and in one embodiment, 100 to 500 nm.

The polyphenol-based compound solution may be prepared by dissolving the polyphenol-based compound in a solvent. In this case, the polyphenol-based compound may be any one or two or more tannin-based compounds selected from the group consisting of tannic acid, gallotannin, and ellagitannins, but is not limited thereto.

In addition, in the above-described manufacturing method, the solvent is preferably selected to disperse the semiconductor particles well and to dissolve the polyphenol-based compound well. For example, the solvent may be selected from water (H ₂ O), an alcohol solvent having 1 to 3 carbon atoms, and combinations thereof, but the present invention is not limited thereto. In one embodiment, the solvent included in the dispersion of the semiconductor particles and the polyphenol-based compound solution may be the same solvent, but of course, each solution may use a different solvent.

In this case, the amount of the solvent is not limited, but may contain semiconductor particles or polyphenol-based compounds in an amount of 1 to 50 mg/ml, specifically 5 to 20 mg/ml, per unit solvent volume.

The weight ratio of semiconductor particles: polyphenol-based compound may be 1: 0.01 to 10, specifically 1: 0.5 to 5, and more specifically 1: 0.8 to 3, but the present invention is not limited thereto, and the above-described semiconductor particles: Of course, the weight ratio of the polyphenol-based compound may be adjusted according to the size of the surface area of the semiconductor particles. For example, when the size of the surface area of the semiconductor particles is large, the weight of the polyphenol-based compound relative to the weight of the semiconductor particles may be further increased. In this case, the gold ion adsorbent may have a more improved gold ion adsorption rate, but is not limited to this analysis.

In the method for preparing a gold ion adsorbent according to the present invention, a polyphenol-based compound can be coated on semiconductor particles by simply stirring a semiconductor particle dispersion liquid and a polyphenol-based compound solution, and thus the conventional preparation of a gold ion adsorbent The method has the advantage that the process is relatively simple.

In addition, the present invention includes a method for recovering gold ions as metallic Au using the above-described gold ion adsorbent.

As the gold recovery method according to the present invention uses a gold ion adsorbent containing a polyphenol-based compound coated on semiconductor particles, gold can be easily recovered from an adsorption material (gold ion adsorbent) through simple acid treatment. There is this.

Specifically, as described above, the polyphenol-based compound excites hot electrons through absorption of light, and the excited hot electrons reduce gold ions and effectively induce nucleation of gold atoms. can do. In addition, by coating the polyphenol-based compound on the semiconductor particles, it is possible to maintain the excited state of hot electrons, specifically, the state capable of participating in the reduction reaction of gold ions for a longer time than when the polyphenol-based compound is used alone. adsorption capacity can be significantly improved.

Accordingly, the method according to the present invention may include putting a gold ion adsorbent including a polyphenol-based compound formed on semiconductor particles in a solution containing gold ions and irradiating light.

In this case, the light may include ultraviolet rays having a wavelength region of 400 nm or less, specifically, a wavelength region of 10 to 400 nm, and the polyphenol-based compound absorbs ultraviolet rays and excites hot electrons on the surface of the gold ion adsorbent. May increase the number of nuclei of metallic gold produced. On the other hand, when irradiating light that does not contain ultraviolet light, that is, when irradiating visible light and infrared light, the polyphenol-based compound may not absorb light, so that the reduction efficiency of gold ions may not be improved.

For example, the irradiation time of the light is not particularly limited as long as it can sufficiently adsorb gold ions, but may be, for example, 5 minutes or more, more preferably 10 minutes or more, and even more preferably 30 minutes or more. In such a range, the polyphenol-based compound absorbs ultraviolet rays to excite hot electrons to more easily adsorb and reduce gold ions. The upper limit of the light irradiation time is not particularly limited as it may vary depending on the concentration of gold ions. Of course, when the concentration of gold ions is high, the light irradiation time may be lengthened. As a specific example, the upper limit of the irradiation time of the light is not particularly limited, and as a specific example, it may be 60 hours, more specifically 20 hours, more specifically 10 hours, even more specifically 2 hours, but limited thereto no.

Furthermore, the method for recovering gold according to the present invention may include the step of desorbing metallic gold from the gold ion adsorbent by putting a gold ion adsorbent having metallic Au formed thereon into a leaching solution.

In this case, the leaching solution may be used without particular limitation as long as it can leach gold particles. In one embodiment, the leaching solution may be hydrochloric acid, nitric acid, sulfuric acid, or a mixture thereof.

In terms of further improving the desorption efficiency of gold particles, the molar concentration of the leaching solution may be 0.1M to 2.0M, preferably 0.5M to 1.5M, more preferably 0.8M to 1.2M. When the concentration of the leaching solution satisfies the above-mentioned range, it is preferable that 95 wt% or more of metallic gold can be desorbed from the gold ion absorbing material on which metallic gold is formed.

In addition, when a leaching solution containing a low concentration of 0.8M to 1.2M acid is used, it is good to reduce the risk of safety accidents for acidic solutions (leaching solutions) that may occur in the gold ion desorption process.

(analysis method)

Absorbance of TA, TiO ₂ NPs and TA-TiO ₂ NPs was measured using UV-vis-NIR spectroscopy (Perkin Elmer Lambda 1050). SEM images of TA, TiO ₂ NPs and TA-TiO ₂ NPs were measured using a field emission scanning electron microscope (SEM, Hitachi S-4800) with an acceleration voltage of 5 kV. The oxidation state of gold in TA-TiO ₂ and Au-TA-TiO ₂ was measured at 4 kV using XPS (X-ray photoelectron spectroscopy, Thermo VG scientific Sigma Probe, Thermo Fisher Scientific, Inc., Waltham, MA, USA). and 5 μA. _{Metallic gold in Au-TA-TiO 2} was detected at 45 kV and 200 mA using θ/2θ scan using high-resolution powder X-ray diffraction (XRD). The fluorescence lifetimes of TA, TiO ₂ NPs and TA-TiO ₂ NPs were analyzed using a 375 nm laser pulse using a Fluorescence Lifetime Spectrometer (FL920, Edinburgh Instruments).

(Example) TA-TiO ₂ Nanostructure synthesis

First, _{100 mg of water-dispersed TiO 2} nanoparticles (average particle size 200 nm) are dispersed in 9 mL of deionized water _{to prepare a TiO 2} nanoparticle dispersion, and 100 mg of tannic acid (TA) is dissolved in 10 mL of deionized water to dissolve tannic acid aqueous solution was prepared.

Next, the mixture was stirred to prepare a TA-TiO ₂ nanostructure coating the TA to TiO ₂ nanoparticles while at room temperature then a solution of 9 mL of the TiO ₂ nanoparticle dispersion and tannic acid aqueous solution of 1 mL 30 minutes. Thereafter, the TA-TiO ₂ nanostructures were washed several times with a mixed solvent of deionized water:ethanol 2: 1 (v/v), and swing-type centrifugation was performed at 1000 g for 3 minutes to remove excess TA not bound _{to TiO 2 .} did.

Finally, the TA-TiO ₂ nanostructure was dried using a vacuum oven.

(Comparative example)

_{Water-dispersed TiO 2} nanoparticles (average particle diameter of 200 nm) without tannin (TA) coating were used as a comparative example.

(Experimental Example 1) Gold ion adsorption test

A 10 mg/ml TA-TiO ₂ NPs aqueous dispersion and _{an aqueous solution of 10 mM HAuCl 4} in which the TA-TiO ₂ NPs of Example 1 were dispersed in deionized water were prepared, respectively.

TA-TiO ₂ NPs aqueous dispersion and HAuCl ₄ aqueous solution were mixed to make a mixed solution with a total volume of 3 ml, and _{the concentrations of HAuCl 4} were adjusted to 0.25, 0.33, 0.5, 1, 1.5 and 2 mM, respectively, and TA-TiO ₂ nano The concentration of the construct was set to 1 mg/ml.

Each of the mixtures was stirred at 150 rpm at room temperature for 3 hours under dark or light conditions. At this time, in the case of light conditions, 1-sun (irradiation intensity = 100 mW/cm2, artificial sunlight with AM (Air Mass) 1.5) was configured, and a xenon lamp (Solar simulator HAL-320, Asahi spectra Co., Ltd. , Tokyo, Japan) was used to irradiate the mixture for 3 hours.

Then, the mixture was centrifuged at 10,000 g for 3 minutes, the supernatant was separated, and the concentration of residual gold ions was analyzed through ICP-OES (Agilent ICP-OES 5110).

(Experimental Example 2) Gold ion desorption test

_{A gold ion desorption experiment was performed using Au-TA-TiO 2} NPs (1-sun) among the specimens subjected to the gold ion adsorption test of Experimental Example 1. Using hydrochloric acid (35% HCl, Sigma-Aldrich, St. Louis, MO, USA) and nitric acid (70% HNO ₃ , Sigma-Aldrich, St. Louis, MO, USA) solution, a low-concentration hydrochloric acid-nitric acid mixed solution ( Volume ratio of hydrochloric acid and nitric acid = 7:3 (v/v), concentration: hydrochloric acid 0.7 M, nitric acid 0.3 M) was prepared, and Au-TA-TiO ₂ (1-sun) was added to this solution for 3 hours. react After the reaction, the precipitate and the supernatant were separated by centrifugation at 10,000 ´ g for 3 minutes, and X-ray diffraction analysis was performed on the precipitate.

In the drawings below, TA-TiO ₂ is an example before the test, Au-TA-TiO ₂ (1-sun) is an example performed under light conditions, and Au-TA-TiO ₂ (dark) is performed under dark conditions. and TiO ₂ (dark) is a comparative example performed under dark conditions.

(Experimental Example 3) Metal Selectivity Test

_{The metal of TA-TiO 2} using a metal chloride mixed solution in which 9 metal chloride ions (Au, Pt, Cu, Co, Ni, Zn, Pd, Fe, Al), which are components of electronic waste, are mixed at a concentration of 1 mM Selectivity was investigated. First, TA-TiO ₂ was added to a mixed solution of 3 ml at a concentration of 1 mg/ml, followed by stirring at 300 rpm for 3 hours at room temperature under dark or light conditions. In this case, the light condition was irradiated with sunlight of AM 1.5 to the mixed solution using a xenon lamp. After the reaction, TA-TiO ₂ was centrifuged at 10,000 g for 5 minutes, the supernatant was separated and diluted with 10 ml of non-ionized water, and the concentration of residual metal ions was measured using ICP-OES (Agilent ICP-OES 5110). analyzed.

2 is an SEM analysis result before the test of Example and after the gold ion adsorption test under dark/light conditions. In detail, (a) of FIG. 2 _{is an SEM image of the example before the test (TA-TiO 2} ), and the SEM image of the example (Au-TA-TiO ₂ (dark)) after the test under dark conditions of FIG. 2 (b) image, and (c) of FIG. 2 _{is an SEM image of the Example (Au-TA-TiO 2} (1-sun)) after the test under bright conditions. In the figure, white particles represent gold nanoparticles. As shown, it can be confirmed that the Examples synthesize the most gold nanoparticles under light conditions. This suggests that the Examples have high gold ion adsorption properties under light irradiated conditions (light conditions).

3 is a result of examining the effect of the light wavelength on the adsorption of gold ions before the test and under dark/light conditions of Example. _{As shown, the absorbance of the example (Au-TA-TiO 2} (1-sun)) was the highest in the 400 to 600 nm region, which is the absorption region of the gold nanoparticles, after the light condition test. Through this, the example (Au-TA-TiO ₂ (1-sun)) after the light condition test is the example before the test (TA-TiO ₂ ) and the example after the dark condition test (Au-TA-TiO ₂ (dark) ), it can be seen that more gold nanoparticles are included. This is consistent with the result of FIG. 2 , and _{it can be seen that the example (TA-TiO 2} ) has high gold ion adsorption in the presence of light.

4 is an X-ray photoelectron spectroscopy (XPS) analysis result for investigating whether TA-TiO _{2 adsorbs gold ions and the oxidation state of adsorbed gold.} At this time, the gold adsorption experiment was performed under dark/light conditions for 3 hours using _{2 mM HAuCl 4 .} As shown, in the example before the test (TA-TiO ₂ ), the presence of the peak of Au 4f was not observed, but the example Au-TA-TiO ₂ (dark) and Au-TA- TiO ₂ (1-sun) was observed to have a peak of all Au 4f. In particular, it can be seen that the Au 4f of Au-TA-TiO ₂ (1-sun), an example performed under light conditions, has a higher intensity than the Au 4f peak _{of Au-TA-TiO 2 (dark) performed under dark conditions.} have. Through this, it can be seen that the embodiment (TA-TiO ₂ ) can be reduced to metallic gold by adsorbing gold ions regardless of whether or not light is irradiated, but has the highest gold ion adsorption rate under dark conditions in which light is present.

5 is an XRD analysis result of an _{example (TA-TiO 2} ) before/after gold ion adsorption test under dark/light conditions. As shown, in the example before the test (TA-TiO ₂ ), _{only TiO 2} related peaks exist, but Au-TA-TiO ₂ (dark) and Au-TA-TiO ₂ ( 1-sun), gold (Au) peaks were observed at 2θ = 38.14, 44.33, 64.54, and 77.53° in all XRD patterns. _{In particular, similar to the result of FIG. 4, the intensity of the Au peak of Au-TA-TiO 2} (1-sun), which is an example performed under bright conditions, is the same as that of the Au peak of Au-TA-TiO ₂ (dark) performed under dark conditions. It can be seen that the strength is higher than In this case, 2θ = 38.14, 44.33, 64.54 and 77.53° respectively correspond to the (111), (200), (220) and (311) planes of the face-centered cubic lattice (fcc) of gold (Au), respectively. As can be seen from the results, in the embodiment (TA-TiO ₂ ), a redox reaction between gold (Au) ions can reduce gold ions to metallic gold regardless of the presence of light, but the reaction is in the presence of light. It can be seen that under the

In the gold ion adsorption test, the adsorption change of Examples and Comparative Examples according to the concentration of gold ions in the test solution (a mixture of gold ion adsorbent and gold ion) was investigated, and the results are shown in FIG. 6 .

6 (a) shows the number (M, mmol/g) of gold ions adsorbed to _{Comparative Examples (TiO 2} ) and Examples (TA-TiO ₂ ) according to the concentration (C, mM) of gold ions in the test solution. It is the result of analysis. As shown, in the case of the comparative example (TiO ₂ ), gold ions were not adsorbed regardless of the concentration of gold ions, and in the case of the _{example Au-TA-TiO 2 (dark) performed under dark conditions, the comparative example} (TiO ₂ ) Although more gold ions were adsorbed, as the amount of gold ions in the test solution increased, more than 2 mmol/g gold ions could not be adsorbed, and Au-TA-TiO ₂ (1- sun) shows that the number of adsorbed gold ions increases as the amount of gold ions in the test solution increases. This suggests that the surface modification using TA improved the gold ion adsorption capacity, and this means that the gold ion adsorption capacity by the surface modification of TA was remarkably improved in the presence of light.

6 (b) shows the theoretical maximum number of adsorbed gold ions per unit mass _{of Comparative Example (TiO 2} ) and Example (TA-TiO ₂ ) calculated through Lineweaver-Burk plot _{(q max} , mmol/g) is a diagram showing As shown, the q _{max of TiO 2} as a comparative example performed under dark conditions was 0.018 mmol/g, and q _{max of TA-TiO 2 as} an example performed under dark conditions was 0.196 mmol/g, which is higher than the q _{max of TiO 2 .} increased. From this, it was confirmed that the TA coating improves the adsorption capacity. In addition, the q _{max of TA-TiO 2} was increased by 22.2 times (4.335 mmol/g) in the 1-sun condition under the light condition compared to the dark condition.

7 shows the example before the test (TA-TiO ₂ ), the example after the gold ion adsorption test under light conditions (Au-TA-TiO ₂ (1-sun)), and the example after the gold ion desorption test ((Au-TA) -TiO ₂ After desorption) As shown, the example before the test (TA-TiO ₂ ), the example after the gold ion adsorption test under light conditions (Au-TA-TiO ₂ (1-sun)) ) and after the gold ion desorption test (Au-TA-TiO ₂ After desorption), _{it can be seen that the peak of TiO 2} exists in all XRD patterns. Through this, the example (TA-TiO ₂ ) is a simple It can be seen that gold can be easily recovered without loss of adsorbent through acid treatment.

8 is a fluorescence lifetime analysis results for tannins (TA), comparative examples (TiO ₂ ) and examples (TA-TiO _{2 ).} At this time, tannin (TA) is a further comparative example. As shown, it can be seen that the lifetime of the excited electrons in the sample (TA-TiO ₂ ) is longer than that of the additional comparative example (TA) and the comparative example (TiO _{2 ).} In the case of the additional comparative example (TA), the lifetime of the excited electrons was 0.896 ns, in the case of the comparative example (TiO ₂ ), 163.4 ns, and in the case of the embodiment (TA-TiO ₂ ) was 362.1 ns, through which the semiconductor particles were It can be seen that the lifetime of the excited electrons can be improved by coating the polyphenol-based compound.

9 is a result of analyzing the metal selectivity change according to the presence or absence of light irradiation in Comparative Examples (TiO ₂ ) and Examples (TA-TiO _{2 ).} In the case of the comparative example (TiO ₂ ), ions other than iron ions were not adsorbed at all under dark conditions, and the adsorption rate of iron ions was close to 40%. In the case of Example (TA-TiO ₂ ), it was confirmed that the gold ion adsorption rate was increased under dark conditions, and the gold ion adsorption rate was close to 100% under light conditions, and the iron ion adsorption rate decreased to 10%. did. Through this, it can be seen that in the case of Example (TA-TiO ₂ ), the adsorption power and selectivity for gold ions are high under light conditions.

As described above, the present invention has been described with specific matters and limited examples and drawings, but these are only provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments, and the present invention is not limited to the above embodiments. Various modifications and variations are possible from these descriptions by those of ordinary skill in the art.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and not only the claims to be described later, but also all those with equivalent or equivalent modifications to the claims will be said to belong to the scope of the spirit of the present invention. .

Claims (14)

semiconductor particles; and a polyphenol-based compound coated on the surface of the semiconductor particles, wherein the gold ion adsorbent is characterized in that it selectively adsorbs gold ions by irradiation with light. The method of claim 1,
A minimum energy level of a conduction band of the semiconductor particle is higher than a minimum highest occupied molecular orbital (HOMO) energy level of the polyphenol-based compound, and a minimum energy level of a valence band of the semiconductor particle. is lower than the minimum HOMO energy level of the polyphenolic compound. 3. The method of claim 2,
The gold ion adsorbent, characterized in that electrons are excited from a highest occupied molecular orbital (HOMO) of the polyphenol-based compound to a conduction band of the semiconductor particles. The method of claim 1,
The polyphenol-based compound will include any one or two or more selected from the group consisting of a catechol group, a galloyl group, a catechol group-containing functional group, and a galloyl group-containing functional group. The method of claim 1,
The polyphenol-based compound is any one or two or more gold ion adsorbents selected from the group consisting of tannin-based compounds and polydopamine-based compounds. 6. The method of claim 5,
The tannin-based compound is any one or two or more gold ion adsorbents selected from the group consisting of tannic acid, gallotannin, and ellagitannins. The method of claim 1,
A gold ion adsorbent wherein the semiconductor of the semiconductor particles is silicon germanium, metal oxide or metal nitride. 8. The method of claim 7,
The metal oxide is selected from the group consisting of TiO ₂ , ZnO ₂ , ZnO, CaTiO, WO ₃ , SnO ₂ , MoO ₃ , Fe ₂ O ₃ , InP, GaAs, BaTiO ₃ , KNbO ₃ , _{SrTiO 3} and Ta ₂ O ₅ . Any one or two or more gold ion adsorbents. 8. The method of claim 7,
The metal nitride is BN, AlN, GaN, InN, CrN, Cr ₂ N, WN, W ₂ N, Mn ₆ N ₄ , Mn ₄ N, Fe ₄ N, Co ₄ N, Ni ₄ N, V ₃ N, Fe Any one or two selected from the group consisting of ₃ N, Co ₃ N, Ni ₃ N, Cu ₃ N, Ti ₂ N, Cr ₂ N, Mn ₂ N, Fe ₂ N, Co ₂ N, ThN ₂ and WN ₂ Gold ion adsorbent above. The method of claim 1,
The average diameter of the semiconductor particles is 10 nm to 10 ㎛ gold ion adsorbent. A method for recovering gold ions as metallic Au by using the gold ion adsorbent of any one of claims 1 to 10. 12. The method of claim 11,
The method includes putting a gold ion adsorbent into a solution containing gold ions and irradiating light. 13. The method of claim 12,
wherein the light comprises ultraviolet light having a wavelength region of 400 nm or less. 12. The method of claim 11,
The method comprising the step of desorbing metallic gold from the gold ion adsorbent by placing a gold ion adsorbent having metallic Au formed thereon into a leaching solution.

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