Adsorbent for precious metal gold in electroplating wastewater

Abstract

The invention discloses an adsorbent for precious metal gold in electroplating wastewater, and belongs to the technical field of precious metal gold adsorption. The invention provides an adsorbent for precious metal gold in electroplating wastewater. The adsorbent is an NH2-MIL-125 (at) TiO2 composite material. The invention also discloses application of the adsorbent in adsorption of Au (III) in electroplating wastewater. The invention discloses an adsorbent for precious metal gold in electroplating wastewater, the adsorbent has high adsorption capacity for Au (III), the adsorption capacity is far higher than that of a traditional adsorption material, and the recovery efficiency of Au (III) is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of noble metal gold adsorption, and particularly relates to an adsorbent for noble metal gold in electroplating wastewater. Background Art

[0002] In modern industrial production and the field of science and technology, noble metal gold (Au) is widely used due to its unique physical and chemical properties, especially the increasing demand in industries such as electronics and medicine. However, as a non-renewable resource, the scarcity of gold makes it particularly important to recover gold from secondary resources such as gold-containing waste liquids. Traditional gold recovery methods, such as metal displacement method, electrolytic separation method, ion exchange method, solvent extraction method, and membrane separation technology, although achieving gold recovery to a certain extent, often have problems such as high cost, complex operation, poor selectivity, high energy consumption, and difficult treatment of waste residues.

[0003] With the development of materials science, Metal-Organic Frameworks (MOFs) materials have become potential candidate materials for gold recovery due to their large specific surface area, high porosity, and good structural tunability. Abundant research results have been achieved in the adsorption and recovery of gold by MOFs, but problems such as limited adsorption sites and poor water stability have restricted their wide application in practical applications. To solve these problems, researchers have regulated the MOF structure through functional group modification and defect engineering to prepare modified MOF adsorbents with high adsorption capacity, high selectivity, and strong water stability.

[0004] Currently, researchers have particularly focused on the amino-functionalized MOF material NH 2 -MIL-125, which exhibits excellent adsorption performance for Au(III) due to the presence of amino functional groups. However, the water stability and service life of NH 2 -MIL-125 limit its potential in industrial applications. Summary of the Invention

[0005] The present invention aims to provide an adsorbent for noble metal gold in electroplating wastewater, which has a high adsorption capacity for Au(III), far higher than traditional adsorption materials, and effectively improves the recovery efficiency of Au(III).

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] An adsorbent for noble metal gold in electroplating wastewater, wherein the adsorbent is an NH 2 -MIL-125@TiO 2 composite material.

[0008] The present invention also provides the application of the adsorbent in adsorbing Au(III) in electroplating wastewater.

[0009] The present invention also provides a method for preparing an NH 2 -MIL-125@TiO 2 composite material for manufacturing the adsorbent, comprising the following steps:

[0010] S1. Prepare NH 2 -MIL-125: Completely dissolve 2-aminoterephthalic acid and tetrabutyl titanate in an N,N-dimethylformamide-methanol solution, stir evenly, transfer to a high-pressure reaction kettle lined with polytetrafluoroethylene for reaction, cool to room temperature, wash, and dry to obtain NH 2 -MIL-125 powder;

[0011] S2. Dissolve the NH 2 -MIL-125 obtained in step S1 and thioacetamide in absolute ethanol, stir evenly to obtain a reaction solution;

[0012] S3. Seal the reaction solution obtained in step S2 in a high-pressure reaction kettle lined with polytetrafluoroethylene, heat for reaction, cool to room temperature, wash, and dry to obtain NH 2 -MIL-125@TiO 2 composite material.

[0013] Preferably, in step S1, the reaction temperature in the high-pressure reaction kettle is 100-200 °C, and the reaction time is 10-48 h.

[0014] Preferably, in step S1, the drying temperature is 60-80 °C, and the drying time is 4-8 h.

[0015] Preferably, in step S3, the heating reaction temperature is 160-220 °C, and the heating reaction time is 1-4 h.

[0016] Preferably, in step S3, the drying temperature is 60-80 °C, and the drying time is 4-8 h.

[0017] Compared with the prior art, the present invention has the following advantages and technical effects:

[0018] (1) The present invention discloses an adsorbent for noble metal gold in electroplating wastewater, which shows significant advantages in the fields of electroplating wastewater treatment and Au(III) recovery. The adsorbent is an NH 2 -MIL-125@TiO 2 constructed with a core-shell structure, where NH 2 -MIL-125 serves as the core and TiO 2As the shell. This structure not only enhances the water stability of the material but also significantly improves the adsorption capacity for Au(III), with a maximum adsorption capacity of up to 2062.1 mg / g, far exceeding that of traditional adsorption materials.

[0019] (2) In the treatment of electroplating wastewater, this adsorbent exhibits efficient heavy metal removal ability. Especially when treating complex water bodies containing multiple heavy metals, the selective adsorption efficiency for Au(III) is as high as 100%. Even when the concentration of other metal cations is ten times higher than that of Au(III), the adsorption efficiency still remains above 95%. In addition, the adsorbent can still maintain an Au(III) adsorption efficiency of above 95% after five rounds of cyclic use, showing extremely high recyclability and water stability.

[0020] In summary, the present invention not only provides an efficient Au(III) adsorbent but also offers an environmentally friendly and economical solution for the purification of electroplating wastewater and the recovery of precious metals, having important industrial application value and environmental significance.

[0021] The technical solution of the present invention will be further described in detail below through the accompanying drawings and examples. Description of the Drawings

[0022] Figure 1 Characterization results of NH2-MIL-125, N / T-1, N / T-2, and N / T-4 provided for Examples 1-4 respectively, where Figure 1 (a) in is the PXRD pattern, Figure 1 (b) in is the Ti 2p spectrum of NH2-MIL-125 and N / T-1;

[0023] Figure 2 Electron microscopy results provided for Examples 1-4, where Figure 2 (a) in is the SEM image of NH 2 -MIL-125 with a scale bar of 500 nm, Figure 2 (b) in is the SEM image of N / T-1 with a scale bar of 500 nm, Figure 2 (c) in is the SEM image of N / T-2 with a scale bar of 500 nm, Figure 2 (d) in is the SEM image of N / T-4 with a scale bar of 500 nm, Figure 2 (e) in is the TEM image of NH 2 -MIL-125 with a scale bar of 500 nm, Figure 2 (f) in is the TEM image of N / T-1 with a scale bar of 500 nm, Figure 2 (g) in is the TEM image of N / T-2 with a scale bar of 500 nm, Figure 2In (h) is the N / T-4 TEM image, and the scale bar is 500 nm;

[0024] Figure 3 are the stability results of the materials provided in Example 1 and Example 2, where Figure 3 In (a) is NH 2 -MIL-125 XRD patterns in different pH solutions, Figure 3 In (b) is the XRD pattern of N / T-1 in different pH solutions, Figure 3 In (c) is NH 2 -MIL-125 and N / T-1 Ti dissolution diagrams;

[0025] Figure 4 are the statistical graphs of the adsorption capacities of NH 2 -MIL-125, N / T-1, N / T-2, and N / T-4 composite materials for Au(III) provided in Examples 1-4 respectively;

[0026] Figure 5 are the thermodynamic results of the adsorption of Au(III) by N / T-1 provided in Example 2;

[0027] Figure 6 are the results of the recovery of Au from the circuit board leaching solution by N / T-1 provided in Example 2, where Figure 6 In (a) is the selectivity of Au(III) adsorption in the simulated solution, Figure 6 In (b) is the initial ion concentration in the real circuit board leaching solution, Figure 6 In (c) are the selectivity results of Au(III) adsorption;

[0028] Figure 7 are the results of the cyclic experiment of N / T-1 for the recovery of Au(III) from the gold-containing waste liquid, where Figure 7 In (a) is the statistical graph of the cyclic stability experiment of N / T-1, Figure 7 In (b) are the PXRD patterns of N / T-1 after cycling and desorption;

[0029] Figure 8 are the results of the PXRD patterns and FTIR spectra of N / T-1 before and after adsorption, where Figure 8 In (a) are the PXRD patterns of N / T-1 before and after adsorption, Figure 8 In (b) are the results of the FTIR spectra of N / T-1 before and after adsorption. Detailed implementation manners

[0030] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and examples.

[0031] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings as understood by those of ordinary skill in the field to which the present invention pertains.

[0032] In the present invention, unless otherwise specified, other test materials and instrument devices are all conventional test materials in this field and can all be obtained through commercial channels.

[0033] Example 1 This example provides a preparation method of NH 2 -MIL-125, including the following steps:

[0034] A1. Completely dissolve 0.5 g of 2-aminoterephthalic acid and 0.5 mL of tetrabutyl titanate in a mixed solvent prepared from 9 mL of N,N-dimethylformamide and 1.0 mL of methanol, stir evenly to obtain a mixed solution;

[0035] A2. Transfer the mixed solution obtained in step A1 to a 25.0 mL high-pressure reaction kettle lined with polytetrafluoroethylene, react at 150 °C for 24 h, cool to room temperature, wash twice with dimethylformamide solution and methanol solution respectively, and dry at 60 °C for 8 h to obtain NH 2 -MIL-125 powder.

[0036] Example 2 This example provides a preparation method of NH 2 -MIL-125@TiO 2 composite material, including the following steps:

[0037] S1. Prepare NH 2 -MIL-125, and the preparation method is the same as that in Example 1;

[0038] S2. Dissolve 0.1 g of NH 2 -MIL-125 obtained in step S1 and 0.4 g of thioacetamide in 60 mL of absolute ethanol, stir evenly to obtain a reaction solution;

[0039] S3. Seal the reaction solution obtained in step S2 in a high-pressure reaction kettle lined with polytetrafluoroethylene, heat and react at 200 °C for 1 h, cool to room temperature, wash three times with absolute ethanol, and dry at 60 °C for 8 h to obtain NH 2 -MIL-125@TiO 2 composite material, that is, adsorbent N / T-1.

[0040] Example 3 This example provides an adsorbent N / T-2, and the preparation method is the same as that in Example 2, the difference is that in step S3, the heating reaction time is 2 h.

[0041] Example 4: This example provides an adsorbent N / T-4. The preparation method is the same as that of Example 2, except that in step S3, the heating reaction time is 4 h.

[0042] The effects of the composite materials provided in the above examples were verified through the following tests.

[0043] 1. Characterization of composite materials: (1) Powder X-ray diffractometer (PXRD): Appropriate amounts of the materials NH 2 -MIL-125, N / T-1, N / T-2, and N / T-4 provided in Examples 1-4 were placed in a sample cell, and a DX-2700B type powder X-ray diffractometer was used for testing. The scanning speed, scanning step size, and scanning range were set to 10° / min, 0.02°, and 5-50°, respectively.

[0044] (2) X-ray photoelectron spectrometer (XPS): Appropriate amounts of the materials NH 2 -MIL-125, N / T-1, N / T-2, and N / T-4 provided in Examples 1-4 were pressed into tablets for sample preparation, and an ESCALAB 250XI type X-ray photoelectron spectrometer was used to test the samples.

[0045] (3) Scanning electron microscope (SEM): Appropriate amounts of NH 2 -MIL-125, N / T-1, N / T-2, and N / T-4 provided in Examples 1-4 were adhered to conductive tape. After gold spraying, a JSM-6700F type scanning electron microscope was used to observe the morphology of the samples.

[0046] (4) Inductively coupled plasma optical emission spectrometer (ICP-OES): The concentrations of Au(III) and other metal cations in the solution were detected using an ICP-5000 type inductively coupled plasma optical emission spectrometer. Among them, standard solutions of Au(III) and other metal cations with different concentration gradients need to be configured, and the calibration curve R 2 value is required to be above 0.999 to ensure the accuracy of concentration measurement.

[0047] (5) Fourier transform infrared spectrometer (FTIR): Appropriate amounts of the materials NH 2 -MIL-125, N / T-1, N / T-2, and N / T-4 provided in Examples 1-4 were prepared into samples by the potassium bromide tablet pressing method, and a Nicolet 700 type infrared spectrometer was used for scanning. The wavelength range was set to 4000-400 cm -1 . The results are as Figures 1 - 3 .

[0048] From Figure 1As can be seen from (a) in [reference], the characteristic peaks of NH 2 -MIL-125 can be clearly identified in the PXRD patterns of N / T-1 in Example 2 and N / T-2 in Example 3. With the extension of the sulfidation treatment time, the framework structure of NH 2 -MIL-125 is gradually destroyed. Among them, the characteristic peaks of NH 2 -MIL-125 in Example 4 completely disappear, and the characteristic peaks of anatase TiO 2 appear at 25.7°, 48.7° and 62.9°, indicating that NH 2 -MIL-125 is gradually transformed into TiO 2 .

[0049] From Figure 1 (b) in [reference], it can be seen that compared with the relevant peak positions in the original NH 2 -MIL-125, the Ti2p spectrum of the N / T-1 composite material shows a shift. The peaks appearing at lower binding energies reveal the existence of Ti 3+ , which means that oxygen vacancies, open Ti metal sites and linker defects are formed in N / T-1.

[0050] From Figure 2 [reference], it can be seen that the sulfided NH 2 -MIL-125 basically maintains its original disk-like structure. With the extension of the treatment time, flower-like TiO 2 nanosheets are formed on the surface of NH 2 -MIL-125. After 1 hour of treatment, the material shows an obvious core-shell structure, and the thickness of its shell layer is about 5 nm. And with the extension of the treatment time, the thickness of the TiO 2 shell layer gradually increases, and N / T-4 has completely changed into a flower-like structure composed of flaky TiO 2 .

[0051] 2. Stability: To investigate the water stability of NH 2 -MIL-125 and N / T-1, appropriate amounts of NH 2 -MIL-125 and N / T-1 were soaked in solutions with different pH values for 7 days. Subsequently, filtration was carried out using a 0.22 μm filter membrane, and the titanium ion concentration in the filtrate was measured by ICP-OES (ICP-500, Focused Photonics Inc). The filtered materials were collected and dried, and their PXRD was measured. The results are as shown in Figure 3 .

[0052] From Figure 3 (a) and (b) in [reference], it can be seen that NH 2After being immersed in the pH range of 2 - 7 for 7 days, the XRD patterns of -MIL-125 and N / T-1 showed no obvious changes. As can be seen from (c) in Figure 3 , and the metal dissolution concentration was significantly lower than that of NH 2 -MIL-125, indicating that the water stability of N / T-1 after sulfidation treatment was significantly improved compared to the original NH 2 -MIL-125, which was due to the protective effect of the shell TiO 2 .

[0053] 3. Batch adsorption experiments and recycling experiments: HAuCl 4 ·4H 2 O was used as the Au(III) compound to investigate the adsorption performance of the adsorbent. The pH of the solution was adjusted to 4 using 0.1 M HNO 3 or NaOH. 20 mg of N / T-1 provided in Example 2 was added to 50 mL of the Au(III) solution, and its initial concentration was set to 10 to 100 mg·L -1 . The solution was shaken at 298 K for 2.0 h to reach the adsorption equilibrium, and the residual concentration of Au(III) was measured using ICP-OES (ICP-500, Focused Photonics Inc). The adsorption isotherms of the adsorbent at 288 K, 298 K, and 308 K could be obtained using a similar method. The specific experimental parameter settings were as follows: the volume, pH, and initial concentration of the Au(III) solution were 50 mL, 4, and 200 - 400 mg·L -1 , respectively, the dosage of the adsorbent was 5 mg, and the adsorption time was 48 h.

[0054] Recycling experiments: Recycling experiments were tested using the same experimental procedure as the batch adsorption experiments. After the previous round of experiments ended, the adsorbent was recovered, and 20.0 mg of the recovered adsorbent was desorbed with 50.0 mL of the eluent (1% HNO 3 + 1% thiourea) for 1 h. After the desorption process was completed, the adsorbent was recovered through suction filtration, washing, and drying steps. The recovered adsorbent was used for the next round of adsorption experiments.

[0055] Calculation of the adsorption capacity of the adsorbent: During the adsorption experiment, a certain volume of liquid was periodically taken from the solution as the test solution, and the residual concentration of Au(III) in the filtrate was measured after filtering with a 0.22 μm filter membrane. The equilibrium adsorption capacity (q e ) of the adsorbent was calculated using the following formula:

[0056]

[0057] where C 0 , C e, V, and m are the concentration of Au(III) under the initial conditions (mg·L -1 ), the concentration of Au(III) at equilibrium (mg·L -1 ), the volume of the Au(III) solution (L), and the mass of the adsorbent (g), respectively. The results are as shown in Figures 4 - 5 .

[0058] As can be seen from Figure 4 , the adsorption capacity of the original NH 2 -MIL-125 is 798.12 mg·L -1 . With the extension of the sulfidation treatment time, its adsorption capacity gradually increases, and the adsorption capacity of N / T-1 is the best, which is 1221.97 mg·L -1 . This is because with the extension of the etching time, ligand deficiencies gradually occur inside NH 2 -MIL-125, the number of defect structures increases, the pore structure becomes larger, and the exposed active sites gradually increase, resulting in a gradual increase in the adsorption capacity. However, when the time is extended to 4 hours, the material completely transforms from NH 2 -MIL-125 to TiO 2 , and its adsorption sites significantly decrease, and the adsorption performance significantly deteriorates.

[0059] As can be seen from Figure 5 , the adsorption process of N / T-1 for Au(III) better conforms to the Langmuir model, which is monolayer adsorption. With the increase in temperature, the adsorption amount of N / T-1 for Au(III) increases, indicating that this adsorption process is endothermic. At 308 K, the adsorption amount of N / T-1 for Au(III) is as high as 2226.75 mg·L -1 .

[0060] 4. Selectivity and Recovery of Au(III) in Real Waste Printed Circuit Boards

[0061] Selectivity: Simulated gold-containing wastewater was prepared with pure water, and the concentrations of various interfering metal cations (Cu 2+ , Zn 2+ , Co 2+ , Cd 2 + , Mn 2+ and Ni 2+ ) were approximately ten times the concentration of Au(III). The results are as shown in Figure 6 (a). The adsorption efficiency of N / T-1 for Au(III) can still reach more than 95%, and the above six interfering ions have little effect on the adsorption performance of N / T-1.

[0062] Recovery of Au(Ⅲ) from real waste printed circuit boards: One printed circuit board was immersed in aqua regia solution. After digestion for 8 h, the leaching solution was obtained. The leaching solution was diluted 10 times and the solution was adjusted to pH = 4. An appropriate amount of N / T-1 was added, and the concentrations of various metal cations in the filtrate were measured.

[0063] As can be seen from Figure 6 (b) therein, the concentrations of Cu, Fe, Ni, Cd, and Au in the leaching solution were 18397.3, 1016.9, 675.7, 90.2, and 4.5 mg / L respectively, and it also contained a small amount of Pb, Zn, Co, Sn, and Mn. As can be seen from Figure 6 (c) therein, N / T-1 still had good adsorption performance for Au(Ⅲ) in the leaching solution of real waste printed circuit boards, and its adsorption efficiency for Au(Ⅲ) could still reach 100%, and N / T-1 had less adsorption for other metal ions.

[0064] As can be seen from Figure 7 (a) therein, the cyclic performance of N / T-1 for an Au(Ⅲ) solution with an initial concentration of 50.0 mg / L was tested, and it was found that the removal efficiency of N / T-1 for Au(Ⅲ) was still as high as 96% after 5 cycles. An eluent (1% HNO 3 + 1% thiourea) could elute 70% of the gold adsorbed on N / T-1. As can be seen from Figure 7 (b) therein, the PXRD pattern of N / T-1 did not change significantly after the cyclic experiment, indicating that it had good cyclic stability.

[0065] Adsorption mechanism: As can be seen from Figure 8 (a) therein, the characteristic peaks of the PXRD of N / T-1 after the adsorption experiment did not change significantly, and new characteristic peaks of Au 0 appeared at 38.2°, 44.4°, and 64.6°, indicating that Au(Ⅲ) was adsorbed by N / T-1 and reduced to elemental gold. As shown in Figure 8 (b) therein, the C-NH stretching vibration peak shifted from the original 1259 cm -1 to 1255 cm -1 after the adsorption experiment. The amino group in N / T-1 was the main adsorption site for Au(Ⅲ). In addition, the intensity of the C-NH stretching vibration peak decreased significantly, indicating that the amino group might be consumed during the reduction of Au(Ⅲ). The peak of the -OH stretching vibration shifted from the original 3366 cm -1 to 3354 cm -1 after gold adsorption, which might be related to the complexation between Au(Ⅲ) and the unsaturated coordinated Ti atoms.

[0066] In summary, the rich pore structure in N / T-1 significantly increases the exposed adsorption sites, facilitating the mass transfer of Au(III) and its binding to the amino groups and coordinatively unsaturated titanium sites inside the pores, thereby greatly enhancing its adsorption performance. In addition, the protonated -NH 2 groups and the positive charges provided by the open coordinatively unsaturated titanium metal sites in N / T-1 can adsorb Au(III) through electrostatic interaction, i.e., AuCl - ions. Most importantly, the adsorbed Au(III) can be reduced to elemental gold by the -NH 2 groups and attached to the adsorbent. In addition, due to the protective effect of the TiO 2 shell on the core NH 2 -MIL-125 after sulfuration treatment, the stability of N / T-1 is greatly improved.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements do not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An adsorbent for precious metal gold in electroplating wastewater, characterized in that: The adsorbent is a NH2-MIL-125@TiO2 composite material.

2. Use of the adsorbent as claimed in claim 1 in the adsorption of Au(III) in electroplating wastewater.

3. A method for preparing an NH2-MIL-125@TiO2 composite material, used for preparing the adsorbent according to claim 1, characterized in that: The steps include: S1. Preparation of NH2-MIL-125: 2-aminoterephthalic acid and tetrabutyl titanate are completely dissolved in N,N-dimethylformamide-methanol solution, stirred evenly, transferred to a polytetrafluoroethylene-lined autoclave for reaction, cooled to room temperature, washed, and dried to obtain NH2-MIL-125 powder; S2, dissolving the NH2-MIL-125 and thioacetamide obtained in step S1 in anhydrous ethanol, stirring evenly to obtain a reaction solution; S3. The reaction solution obtained in step S2 is sealed in a polytetrafluoroethylene-lined high-pressure reactor, heated for reaction, cooled to room temperature, washed, and dried to obtain the NH2-MIL-125@TiO2 composite material.

4. The preparation method according to claim 3, characterized in that: In step S1, the reaction temperature in the high-pressure reactor is 100-200° C., and the reaction time is 10-48 hours.

5. The preparation method according to claim 3, characterized in that: In step S1, the drying temperature is 60-80°C and the drying time is 4-8h.

6. The preparation method according to claim 3, characterized in that: In step S3, the heating reaction temperature is 160-220° C., and the heating reaction time is 1-4 h.

7. The preparation method according to claim 3, characterized in that: In step S3, the drying temperature is 60-80°C and the drying time is 4-8h.

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