A method for recycling copper elements in electroplating wastewater for the preparation of catalysts

Abstract

The present invention discloses a method for recycling copper elements in electroplating wastewater for the preparation of catalysts, belonging to the technical fields of wastewater treatment and catalyst preparation. The method includes: mixing copper-containing electroplating wastewater with a recovery agent containing Si-H bonds, ultrasonicating, centrifuging to remove the supernatant, drying, roasting the dried powder successively in an air atmosphere and a reducing atmosphere, and cooling to obtain a reverse water-gas shift reaction catalyst; in the copper-containing electroplating wastewater, the concentration of copper elements is ≥100 mg L-1, and the concentration of NH4+ is ≥1 mg L-1; the recovery agent containing Si-H bonds includes silicon hydride-terminated siloxene or photovoltaic waste silicon powder. The method of the present invention has the characteristics of simple process, easy batch treatment and high economy, and can selectively recover copper in wastewater and directly convert it into a copper-silicon composite-based reverse water-gas shift reaction catalyst with high catalyst activity, high carbon monoxide selectivity and good stability.

Description

Technical Field

[0001] The present invention relates to the technical fields of wastewater treatment and catalyst preparation, and particularly relates to a method for recovering copper elements in electroplating wastewater for preparing a catalyst. Background Art

[0002] Copper electroplating is one of the most widely used processes in the electroplating industry. Copper electroplating can significantly improve the electrical conductivity, thermal conductivity and corrosion resistance of materials, and plays an important role in many fields such as electronics, automobiles, energy, aerospace, etc. However, the production of plated parts will lead to the generation of copper-containing wastewater. In copper-containing wastewater, the concentration of copper ions is usually in the range of 50~500 mg / L, and in some high-concentration copper-containing wastewater (such as waste plating solution), the concentration of copper ions even reaches 1000~5000 mg / L. If the copper-containing wastewater is not properly disposed of, it will cause environmental pollution problems and affect human health, resulting in serious waste of copper resources. Therefore, it is of great significance to find an effective method to recover copper elements in electroplating wastewater. -1 The concentration of copper ions in some high-concentration copper-containing wastewater (such as waste plating solution) even reaches 1000~5000 mg / L. -1 If the copper-containing wastewater is not properly disposed of, it will cause environmental pollution problems and affect human health, resulting in serious waste of copper resources. Therefore, it is of great significance to find an effective method to recover copper elements in electroplating wastewater.

[0003] However, the composition of electroplating wastewater is very complex, and it needs to go through cumbersome processes to realize the recycling of copper resources in the wastewater, and the economic value is relatively low. In the prior art, most of the treatment methods for electroplating wastewater are to first precipitate and separate copper ions through simple precipitation, adsorption and other means to form solid waste residues to reduce the harm of the wastewater. However, if these waste residues are not properly treated, neither the effective recycling of copper resources can be achieved, nor will secondary pollution be caused.

[0004] Chinese patent document with publication number CN110422948A discloses a treatment process for recovering metallic copper from electroplating copper sulfate wastewater. The invention inputs the copper-containing electroplating wastewater into a primary NF system for filtration, separates fresh water and concentrated solution, further deeply treats the fresh water through an RO system, the RO system generates pure water and recycles it to the copper plating cleaning production line, the concentrated solution is filtered and concentrated through multiple cycles of a secondary NF system and a concentration barrel, the concentrated solution is input into an electrodialyzer to electrolyze fresh water and concentrated solution, the fresh water is circulated and input into the original water barrel for storage, and the concentrated solution is input into a centrifugal electrolyzer to precipitate electrolytic copper. The method of the invention has a complex process and high equipment requirements.

[0005] The Chinese patent document with the publication number CN108529789A discloses a method for treating copper-containing electroplating wastewater by the sulfide precipitation method and recovering copper. In this invention, the pH value of the copper-containing electroplating wastewater is first adjusted to 1.5 - 3.0, and then a sulfide solution is added, followed by stirring and reacting. After the reaction is completed, solid-liquid separation is carried out to obtain pretreated wastewater and copper sulfide precipitate; a part of solid sulfide is added to the pretreated wastewater for the first stirring reaction; then the remaining solid sulfide is added for the second stirring reaction; after the second stirring reaction is completed, a flocculant is added for stirring reaction; after the reaction is completed, the pH of the system is adjusted to 7.0 - 8.0, and solid-liquid separation is carried out to obtain the supernatant that meets the discharge standards and mixed heavy metal sulfides. However, in this invention, the purity of the separated and recovered copper sulfide needs to be further improved.

[0006] Therefore, it is necessary to develop new technologies that are simple, efficient, and low-cost to realize the recycling and reuse of copper resources in electroplating wastewater. Summary of the Invention

[0007] In order to solve the problems of cumbersome processes and high costs in the existing copper element recovery technologies for electroplating wastewater, the present invention provides a method for recovering copper elements in electroplating wastewater for preparing a catalyst. This method has the characteristics of simple process, easy batch processing, and high economy. It can selectively recover copper in the wastewater with complex components and directly convert it into a high-value copper-silicon composite-based reverse water-gas shift reaction catalyst. The prepared copper-silicon composite-based reverse water-gas shift reaction catalyst has high activity, high selectivity for producing carbon monoxide, and good stability.

[0008] The specific technical solutions adopted are as follows:

[0009] A method for recovering copper elements in electroplating wastewater for preparing a catalyst, comprising the following steps:

[0010] Mix the copper-containing electroplating wastewater with a recovery agent containing Si-H bonds and ultrasonicate, centrifuge to remove the supernatant and then dry, and then calcine the dried powder successively in an air atmosphere and a reducing atmosphere, and cool to obtain a reverse water-gas shift reaction catalyst;

[0011] In the copper-containing electroplating wastewater, the concentration of copper element ≥ 100 mg L -1 , NH 4+ concentration ≥ 1 mg L -1 ;

[0012] The recovery agent containing Si-H bonds includes silicon hydride-terminated siloxene or photovoltaic waste silicon powder;

[0013] The conditions for calcination in an air atmosphere are 400 - 850 °C, 1 - 8 h;

[0014] The conditions for calcination in a reducing atmosphere are 300 - 600 °C, 1 - 8 h.

[0015] The common components of copper-containing electroplating wastewater are copper and other metal ions (usually nickel, chromium, zinc, etc.), acids or alkalis, organic additives, etc. The Si-H bond with certain reducibility has the strongest interaction with the copper element in the above substances, and can selectively reduce copper to elemental copper particles and form an interface where elemental copper and elemental silicon are in close contact. After calcination, it can also form a Cu-O-Si catalytically active intermediate with high activity and high stability, and then be reduced to obtain a reverse water-gas shift reaction catalyst loaded with zero-valent copper. The silicon hydride reduction method of the present invention can selectively recover copper elements in electroplating wastewater and prepare a highly active copper-silicon composite-based reverse water-gas shift reaction catalyst. The silicon hydride reduction method is the key to the process of the present invention. Traditional methods for preparing catalysts (such as the impregnation method, etc.) cannot achieve the same technical effects. Moreover, in the silicon hydride reduction method of the present invention, the performance of the catalyst prepared from copper-containing electroplating wastewater as the raw material far exceeds that of the catalyst prepared from high-purity copper salt solution as the raw material.

[0016] Ammonia-containing additives are often used in copper electroplating, and many copper-containing wastewaters contain ammonia compounds. The presence of NH 4+ helps to coordinate with copper and subsequently helps to form highly active copper catalytic species.

[0017] Preferably, the mass ratio of the dosage of the recovery agent containing Si-H bonds to the mass of copper elements in the copper-containing electroplating wastewater is 0.5-20:1.

[0018] More preferably, the recovery agent containing Si-H bonds is a silicon hydride-capped siloxene, and the silicon hydride-capped siloxene is synthesized by the following method:

[0019] Mix calcium silicide powder with NaOH solution and stir to react, then centrifuge further. The obtained precipitate is washed and dried, and the dried powder and hydrochloric acid solution are mixed and stirred to react under an inert gas atmosphere, and then centrifuged and washed further to obtain the silicon hydride-capped siloxene.

[0020] When the recovery agent containing Si-H bonds is selected as photovoltaic waste silicon powder, the photovoltaic waste silicon powder is treated by HF etching to expose more Si-H bonds on its surface.

[0021] Preferably, in the copper-containing electroplating wastewater, the concentration of copper elements ≥ 100 mg L -1 , NH 4+ concentration ≥ 5 mg L -1 .

[0022] Preferably, the conditions for mixed ultrasound are 100-200 W, 0-50 °C, 5-10 min, and the conditions for centrifuging to remove the supernatant are 10000-12000 r min -1 , 5-10 min.

[0023] Preferably, the reducing atmosphere is a hydrogen atmosphere or a hydrogen-argon mixed atmosphere (5% H2 / Ar).

[0024] More preferably, the conditions for calcination in an air atmosphere are 850 °C for 2 h, and the conditions for calcination in a reducing atmosphere are 500 °C for 2 h. High-temperature calcination can remove organic impurities, form highly active Cu-O-Si intermediates, and build strong metal-support interactions. The reducing atmosphere can partially reduce the oxidized copper species in the previous step to zero-valent copper with strong hydrogen dissociation ability.

[0025] The present invention also provides an application of a reverse water-gas shift reaction catalyst in the process of catalyzing the synthesis of CO from a CO2 source and a H2 source. The reverse water-gas shift reaction catalyst is prepared by the method of recycling copper elements in electroplating wastewater for preparing the catalyst.

[0026] Specifically, in a reactor, reaction gases hydrogen and carbon dioxide are introduced, and at the same time, N2 is used as an internal standard and a balance gas. The reverse water-gas shift reaction catalyst is used to catalyze the reaction to generate CO, and the reaction temperature is 300 - 600 °C.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) The recovery technology provided by the present invention can selectively recover copper in copper-containing electroplating wastewater and directly convert it into a high-value copper-silicon composite-based reverse water-gas shift reaction catalyst, without the need to undergo subsequent steps such as copper desorption and purification like traditional recovery technologies. It has the characteristics of simple process, easy batch processing, and high economy.

[0029] (2) The silicon hydride-terminated siloxene recovery agent used in the present invention has the strongest effect on copper elements among the many components of copper-containing electroplating wastewater, and can selectively extract and recover copper in the wastewater. The recovery efficiency of the absorbent is 146 mg of copper per gram of recovery agent.

[0030] (3) Through experimental exploration, it is found that only by using the silicon hydride reduction method can the copper elements in copper-containing ammonia electroplating wastewater be recycled and reused as a highly active reverse water-gas shift reaction catalyst, while the samples obtained by directly impregnating the wastewater onto the silicon hydride-terminated siloxene recovery agent or other carriers using the traditional impregnation method have almost no catalytic performance.

[0031] (4) The present invention utilizes the natural advantages of copper-containing electroplating wastewater. The reverse water-gas shift reaction catalyst prepared from the corresponding copper-containing electroplating wastewater has catalytic performance far exceeding that of the catalyst prepared from high-purity copper salt reagents. Under the reaction conditions of 400 °C, the CO production rate of this catalyst can reach 36 mmol g -1 h -1 , about 2.2 mmol g of the copper salt catalyst-1 h -1 16 times that of (), the CO selectivity can reach 100%, and the stability is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is an FTIR spectrum, where A is a silicon hydride-terminated siloxene, and B is photovoltaic waste silicon powder before and after hydrofluoric acid etching (before etching: waste silicon powder, after etching: waste silicon powder HF).

[0033] Figure 2 is a characterization picture of waste copper 1-siloxene in Example 1. Among them, A is a TEM image, B is a STEM image, and C-E respectively correspond to the distribution maps of copper, oxygen, and silicon elements of the contour in B.

[0034] Figure 3 is a schematic diagram comparing the catalytic performances of waste copper n-siloxene (n = 1, 2, 3) and copper n-siloxene (n = 1, 2, 3) (the reaction temperature is 500 °C).

[0035] Figure 4 is a schematic diagram comparing the catalytic activities and stabilities of waste copper 1-siloxene and copper 1-siloxene at a reaction temperature of 400 °C.

[0036] Figure 5 is a schematic diagram comparing the catalytic activities and stabilities of waste copper 1-waste silicon powder, waste copper 1-waste silicon powder HF, and copper 1-waste silicon powder at a reaction temperature of 600 °C.

[0037] Figure 6 is for waste copper 1-siloxene and waste copper 1 im / siloxene, waste copper 1 im / waste silicon powder and waste copper 1 im / silicon oxide at a reaction temperature of 500 °C.

[0038] Figure 7 is a schematic diagram comparing the catalytic activities of waste copper 2-siloxene, waste copper 3-siloxene, waste copper 2-silicon oxide, and waste copper 3-silicon oxide at a reaction temperature of 500 °C. DETAILED DESCRIPTION OF THE INVENTION

[0039] The present invention will be further clarified below in conjunction with the embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. The operation methods without specific conditions noted in the following embodiments are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

[0040] In the examples and comparative examples, calcium silicide, silica carrier, anhydrous copper chloride, and hydrofluoric acid were all obtained by purchase. The copper-containing electroplating wastewater was taken from 3 different cooperative electroplating factories. The copper wastewater from the 3 different cooperative electroplating factories was respectively denoted as copper wastewater 1 (Cu: 262 mg L -1 , NH4 + : 170 mg L -1 ), copper wastewater 2 (Cu: 2408 mg L -1 , NH4 + : 22.4 mg L -1 ), copper wastewater 3 (Cu: 317 mg L -1 , NH4 + : 8.95 mg L -1 ). Taking copper wastewater 1 as an example, the composition of copper wastewater 1 is specifically shown in Table 1;

[0041] Table 1 Main components in copper wastewater 1

[0042]

[0043] Preparation of silicon hydride-terminated siloxene: Mix 6 g of calcium silicide powder with 600 mL of NaOH solution (5 M), and stir magnetically at room temperature (500 r min -1 ) for 14 h. Then centrifuge the mixture (10000 r min -1 , 8 min), remove the supernatant, and wash the precipitate by centrifugation with water and ethanol respectively (11000 r min -1 , 8 min) once, and then dry it in vacuum (denoted as CaSi2-NaOH). Mix 4 g of CaSi2-NaOH powder with 400 mL of 1 M HCl solution under a nitrogen atmosphere and stir (30 °C, 600 r min -1 ) for 4.5 d. Then centrifuge the mixture (11000 r min -1 , 8 min), remove the supernatant, and wash the precipitate by centrifugation with ethanol (11000 r min -1 , 8 min) twice, and then dry it in vacuum. The obtained product is silicon hydride-terminated siloxene.

[0044] Photovoltaic waste silicon powder comes from the waste materials of the photovoltaic industry, specifically photovoltaic waste silicon powder containing Si-H bonds. Photovoltaic waste silicon powder is the waste material generated during the process of cutting silicon wafers with diamond wire saws in the preparation of solar cells. It is mainly composed of micron-sized and sub-micron-sized silicon particles, and there are dense oxide layers (SiO2 layers), metal impurities (such as Al, Fe, Mg, Ni, etc.), and organic impurities on the surface of the silicon particles. The particle size of this part of the photovoltaic waste silicon powder is about a few microns and it cannot be directly recycled. In existing purification technologies, the recovery rate of the above-mentioned photovoltaic waste silicon powder is relatively low, and the purity of the silicon ingot after purification is far lower than the requirements of solar grade, resulting in serious waste of silicon resources and even environmental pollution.

[0045] Example 1

[0046] (1) Take 40 mL of copper-containing electroplating wastewater (copper wastewater 1, copper wastewater 2, or copper wastewater 3) and place it in 3 different centrifuge tubes. Add 90 mg of the silicon hydride-terminated siloxene synthesized in the above steps, mix and ultrasonicate (100 W) at room temperature for 5 min, then centrifuge (11000 r min -1 , 6 min), filter off the supernatant, and place the precipitate in a vacuum drying oven for drying for 12 h. The dried powder is first calcined in air (850 °C, 2 h) and then in a 5% H2 / Ar (500 °C, 2 h) mixed gas. The corresponding samples for copper wastewater 1, 2, and 3 are denoted as waste copper 1-siloxene, waste copper 2-siloxene, and waste copper 3-siloxene respectively. The copper loadings of the above three samples measured by ICP are 4.3 wt%, 14.6 wt%, and 2.3 wt% respectively, that is, the recovery efficiencies of copper in the electroplating wastewater are 43 mg g -1 , 146 mg g -1 and 23 mg g -1 .

[0047] (2) The reverse water-gas shift reaction is carried out on a flowing-phase reaction device (atmospheric pressure). Take 10 mg of the sample prepared in step (1) and place it in a quartz tube of a tube furnace, and plug quartz wool at both ends. Introduce CO2 and H2 as reaction gases, and N2 as an internal standard and balance gas. The ratio of the reaction gases is CO2:H2:N2 = 1:4:1 (molar ratio), and the total flow rate is 15 mL min -1 , and the reaction temperature is set at 300 - 500 °C. The products are monitored online by gas chromatography.

[0048] The silicon hydride-terminated siloxene recovery agent used in this example has abundant surface silicon hydrides (as shown in A in Figure 1 ). The characterization results of the reverse water-gas shift catalyst prepared by recycling copper-containing electroplating wastewater using waste copper 1-siloxene as an example are shown in Figure 2Among A-E, it can be seen that the waste copper 1-siloxene as a whole presents a nanosheet structure, in which copper, oxygen, and silicon are evenly distributed on the sheet contour. The catalytic performance of the waste copper n-siloxene (n = 1, 2, 3) samples based on different wastewaters is as Figure 3 shown. The results show that at 500 °C, the CO production rates of waste copper 1-siloxene, waste copper 2-siloxene, and waste copper 3-siloxene are 97.1, 58.7, and 104.5 mmol g -1 h -1 respectively. The CO selectivity is nearly 100% for all. The catalytic stability of this series of samples is shown taking waste copper 1-siloxene as an example in Figure 4 , indicating that the CO production rate of this catalyst at 400 °C is about 36 mmol g -1 h -1 , and it can continuously react for at least 44 h without deactivation.

[0049] Example 2

[0050] (1) Take 40 mL of copper-containing electroplating wastewater (copper wastewater 1) respectively and place them in 2 different centrifuge tubes. Add 90 mg of photovoltaic waste silicon powder (original and HF-etched, denoted as waste silicon powder and waste silicon powder HF respectively) and mix ultrasonically (100 W) at room temperature for 5 min. Then centrifuge (9000 r min -1 , 6 min), filter off the supernatant, and place the precipitate in a vacuum drying oven for 12 h. The dried powder is successively calcined in a mixed gas of air (850 °C, 2 h) and 5% H2 / Ar (500 °C, 2 h). The samples after calcination are denoted as waste copper 1-waste silicon powder and waste copper 1-waste silicon powder HF corresponding to waste silicon powder and waste silicon powder HF respectively. The copper loadings of the above two samples measured by ICP are 0.25 wt% and 8.7 wt% respectively, that is, the recovery efficiencies of copper in the electroplating wastewater are 2.5 mg g -1 , and 87 mg g -1 respectively. The preparation process of waste silicon powder HF is as follows: Take 4 g of waste silicon powder and mix it with 400 mL of 5% HF aqueous solution, stir magnetically at 400 r min -1 at room temperature for half an hour, then centrifuge and separate. The precipitate product is centrifugally washed with ethanol once and then vacuum dried.

[0051] (2) The reverse water-gas shift reaction is carried out on a mobile-phase reaction device (atmospheric pressure). Take 10 mg of the sample prepared in step (1) and place it in a quartz tube of a tubular reaction furnace, and plug quartz wool at both ends. Introduce CO2 and H2 as reaction gases, and N2 as an internal standard and balance gas. The reaction gas ratio is CO2:H2:N2 = 1:4:1 (molar ratio), and the total flow rate is 15 mL min -1 . The reaction temperature is set at 600 °C, and the products are monitored online by gas chromatography.

[0052] There is still a small amount of surface silicon hydride on the surface of the photovoltaic waste silicon powder recovery agent used in this example. After being treated with HF, more surface silicon hydrides can be exposed (as shown in B of Figure 1 ). The catalytic performance of the reverse water gas shift catalyst prepared from the recovered copper-containing electroplating wastewater is as shown in Figure 5 . At 600 °C, the CO product rates reached by the waste copper 1-waste silicon powder and the waste copper 1-waste silicon powder HF after experiencing the initial activation period are about 13 and 22 mmol g -1 h -1 , respectively. The CO selectivity is nearly 100%, and it can continuously react for at least 44 h without deactivation.

[0053] Comparative Example 1

[0054] (1) Take 40 mL of copper-containing electroplating wastewater (copper wastewater 1) and place it in three different beakers. Add 90 mg of carrier materials (the silicon hydride-capped siloxene, photovoltaic waste silicon powder, and silica carrier synthesized in the above steps) respectively, and then impregnate and evaporate to dryness under magnetic stirring conditions at 80 °C and 400 r min -1 . The evaporated powder is placed in a vacuum drying oven and dried for 12 h. The dried powder is successively calcined in air (850 °C, 2 h) and a 5% H2 / Ar (500 °C, 2 h) mixed gas. The corresponding samples are denoted as waste copper 1 im / siloxene, waste copper 1 im / waste silicon powder, and waste copper 1 im / silica, respectively.

[0055] (2) The reverse water gas shift reaction is carried out on a mobile phase reaction device (atmospheric pressure). Take 10 mg of the sample prepared in step (1) and place it in a quartz tube of a tubular reaction furnace, and plug quartz wool at both ends. CO2 and H2 are introduced as reaction gases, and N2 is used as an internal standard and balance gas. The reaction gas ratio is CO2:H2:N2 = 1:4:1 (molar ratio), and the total flow rate is 15 mL min -1 . The reaction temperature is set at 500 °C, and the products are monitored online by gas chromatography.

[0056] The waste copper 1 im / siloxene, waste copper 1 im / waste silicon powder, and waste copper 1 im / silica samples obtained in this comparative example almost have no catalytic activity ( Figure 6 ). This shows that the conventional preparation method (impregnation method) of the catalyst cannot recycle copper wastewater to obtain a catalyst with good performance. This indirectly proves the superiority of the silicon hydride reduction method in the above example, which can selectively recover copper elements in wastewater and reuse them as highly active reverse water gas shift reaction catalysts.

[0057] Comparative Example 2

[0058] (1)40 mL of CuCl2 solution with the same copper element concentration as the copper-containing electroplating wastewater (copper wastewater 1, copper wastewater 2, and copper wastewater 3 are denoted as solution 1, solution 2, and solution 3 respectively) were separately placed into 3 different centrifuge tubes. 90 mg of the silane-capped siloxene synthesized in the above steps was added to each tube, and the mixture was ultrasonically mixed (100 W) at room temperature for 5 min, followed by centrifugation (11,000 r min -1 , 6 min). Then, the supernatant was filtered off, and the precipitate was dried in a vacuum drying oven for 12 h. The dried powder was calcined successively in air (850 °C, 2 h) and a 5% H2 / Ar (500 °C, 2 h) mixed gas. The corresponding samples for solutions 1, 2, and 3 were denoted as copper 1-siloxene, copper 2-siloxene, and copper 3-siloxene respectively.

[0059] (2)The reverse water-gas shift reaction was carried out on a flow-phase reaction device (atmospheric pressure). 10 mg of the sample prepared in step (1) was placed into a quartz tube of a tube furnace, and quartz wool was blocked at both ends. CO2 and H2 were introduced as reaction gases, and N2 was used as an internal standard and balance gas. The ratio of the reaction gases was CO2:H2:N2 = 1:4:1 (molar ratio), and the total flow rate was 15 mL min -1 . The reaction temperature was set to 300 °C to 500 °C, and the products were monitored online by gas chromatography.

[0060] The catalytic performance of the copper n-siloxene (n = 1, 2, 3) samples prepared from CuCl2 reagent corresponding to different wastewaters is as Figure 3 shown. At 500 °C, the CO production rates of copper 1-siloxene, copper 2-siloxene, and copper 3-siloxene were 19.0, 31.2, and 23.0 mmol g -1 h -1 respectively. These values are much lower than those of the corresponding waste copper n-siloxene samples (97.1, 58.7, and 104.5 mmol g -1 h -1 respectively). At 400 °C, the activity gap between waste copper 1-siloxene and copper 1-siloxene is even larger. The former (36 mmol g -1 h -1 ) is about 16 times that of the latter (2.2 mmol g -1 h -1 ). This is because the CuCl2 solution lacks components that are beneficial to improving catalytic activity. After a series of screening experiments (mixing the known components in the wastewater with copper one by one to prepare catalysts as precursors, and judging whether a certain component is beneficial to improving catalytic performance through catalytic performance), it is speculated that this component is most likely ammonia in the electroplating wastewater. Figure 4 ​

[0061] Comparative Example 3

[0062] (1)Take 40 mL of a CuCl₂ solution with the same copper element concentration as the copper-containing electroplating wastewater (copper wastewater 1) and place it in a centrifuge tube. Add 90 mg of photovoltaic waste silicon powder and mix ultrasonically (100 W) at room temperature for 5 min. Then centrifuge (9000 r min -1 , 6 min), filter off the supernatant, and place the precipitate in a vacuum drying oven to dry for 12 h. The dried powder is first placed in air (850 °C, 2 h) and then calcined in a 5% H₂ / Ar (500 °C, 2 h) mixed gas. The calcined sample is denoted as copper 1-waste silicon powder.

[0063] (2)The reverse water-gas shift reaction is carried out on a flow-phase reaction device (atmospheric pressure). Take 10 mg of the sample prepared in step (1) and place it in the quartz tube of a tubular reaction furnace, and plug quartz wool at both ends. Introduce CO₂ and H₂ as reaction gases, and N₂ as an internal standard and balance gas. The ratio of reaction gases is CO₂:H₂:N₂ = 1:4:1 (molar ratio), and the total flow rate is 15 mL min -1 . The reaction temperature is set at 600 °C, and the products are monitored online by gas chromatography.

[0064] The catalytic performance of copper 1-waste silicon powder is as Figure 5 shown. At 600 °C, the CO production rate of copper 1-waste silicon powder is about 3.8 mmol g -1 h -1 . It is much lower than the corresponding waste copper 1-waste silicon powder sample (13 mmol g -1 h -1 ). This is because the CuCl₂ solution lacks components beneficial to improving catalytic activity, which is consistent with the results in Comparative Example 2.

[0065] Comparative Example 4

[0066] (1)Take 40 mL of copper-containing electroplating wastewater (copper wastewater 2, copper wastewater 3) respectively and place them in two different centrifuge tubes. Add 90 mg of silica support and mix ultrasonically (100 W) at room temperature for 5 min. Then centrifuge (11000 r min -1 , 6 min), filter off the supernatant, and place the precipitate in a vacuum drying oven to dry for 12 h. The dried powder is first placed in air (850 °C, 2 h) and then calcined in a 5% H₂ / Ar (500 °C, 2 h) mixed gas. The corresponding samples for copper wastewater 2 and 3 after calcination are denoted as waste copper 2-silica and waste copper 3-silica respectively.

[0067] (2) The reverse water-gas shift reaction was carried out in a flowing-phase reaction device (atmospheric pressure). 10 mg of the sample prepared in step (1) was placed in a quartz tube of a tubular reaction furnace, and quartz wool was plugged at both ends. CO2 and H2 were introduced as reaction gases, and N2 was used as an internal standard and a balance gas. The ratio of the reaction gases was CO2:H2:N2 = 1:4:1 (molar ratio), and the total flow rate was 15 mL min -1 . The reaction temperature was set at 500 °C, and the products were monitored online by gas chromatography.

[0068] The catalytic activities of the waste copper 2-silica and waste copper 3-silica samples obtained in this comparative example were extremely low, far lower than those of the corresponding samples with siloxene as the carrier ( Figure 7 ). There is no reducing silicon hydride on the surface of the conventional silica carrier, and copper cannot be effectively extracted from complex wastewater and converted into a copper catalytic component, so the effect is not good.

[0069] The above-described embodiments have described the technical solutions of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, supplements, or similar replacements made within the principle scope of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for recycling copper elements in electroplating wastewater for preparing a catalyst, characterized in that, It includes the following steps: Mix the copper-containing electroplating wastewater with a recovery agent containing Si-H bonds, ultrasonicate, centrifuge to remove the supernatant, dry, and then calcine the dried powder successively in an air atmosphere and a reducing atmosphere, and cool to obtain a reverse water-gas shift reaction catalyst; In the copper-containing electroplating wastewater, the concentration of copper element is ≥ 100 mg / L -1 , NH 4+ concentration is ≥ 1 mg / L -1 ; The recovery agent containing Si-H bonds includes siloxene capped with Si-H or photovoltaic waste silicon powder; The conditions for calcination in an air atmosphere are 400 - 850 °C, 1 - 8 h; The conditions for calcination in a reducing atmosphere are 300 - 600 °C, 1 - 8 h.

2. The method for recycling copper elements in electroplating wastewater for preparing a catalyst according to claim 1, characterized in that The mass ratio of the dosage of the recovery agent containing Si-H bonds to the copper element in the copper-containing electroplating wastewater is 0.5 - 20:

1.

3. The method for recycling copper elements in electroplating wastewater for preparing a catalyst according to claim 1, characterized in that, The recovery agent containing Si-H bonds is siloxene capped with Si-H.

4. The method for recycling copper elements in electroplating wastewater for preparing a catalyst according to claim 1, characterized in that, In the copper-containing electroplating wastewater described, the concentration of copper element is ≥ 100 mg / L -1 , NH 4+ concentration is ≥ 5 mg / L -1 .

5. The method for recycling copper elements in electroplating wastewater for preparing a catalyst according to claim 1, characterized in that, The conditions for hybrid ultrasound are 100 - 200 W, 0 - 50 °C, 5 - 10 min, and the conditions for centrifuging to remove the supernatant are 10000 - 12000 r min -1 , 5 - 10 min.

6. The method for recycling copper elements in electroplating wastewater for preparing a catalyst according to claim 1, wherein The reducing atmosphere is a hydrogen atmosphere or a hydrogen-argon mixed atmosphere.

7. The method for recycling copper elements in electroplating wastewater for preparing a catalyst according to claim 1, wherein The copper loading in the reverse water-gas shift reaction catalyst is ≥1 wt%.

8. Use of a reverse water-gas shift reaction catalyst in the process of catalyzing the synthesis of CO from a CO2 source and an H2 source, characterized in that, The reverse water-gas shift reaction catalyst is prepared by the method for recovering copper elements from electroplating wastewater described in any one of claims 1 - 7 for preparing a catalyst.

9. Use of the reverse water gas shift reaction catalyst according to claim 8 in the process of catalyzing the synthesis of CO from a CO2 source and an H2 source, characterized in that, In a reactor, introduce reaction gases hydrogen and carbon dioxide, and at the same time use N2 as an internal standard and a balance gas, and use the reverse water-gas shift reaction catalyst to catalyze the reaction to generate CO, and the reaction temperature is 300 - 600 °C.

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