Method for recovering copper element in electroplating wastewater for preparing catalyst

Abstract

The invention discloses a method for recovering a copper element in electroplating wastewater for preparing a catalyst, and belongs to the technical field of wastewater treatment and catalyst preparation.The method comprises the steps that copper-containing electroplating wastewater and a recovery agent containing Si-H bonds are mixed and subjected to ultrasonic treatment, and drying is conducted after supernate is removed through centrifugation; and roasting the dried powder in an air atmosphere and a reducing atmosphere in sequence, and cooling to obtain the reverse water gas shift reaction catalyst. In the copper-containing electroplating wastewater, the copper element concentration is greater than or equal to 100 mg L <-1 >, and the NH4 < + > concentration is greater than or equal to 1 mg L <-1 >; the recycling agent containing the Si-H bond comprises silicon hydrogen end capped siloxy alkene or photovoltaic waste silicon powder. The method disclosed by the invention has the characteristics of simple process, easiness in batch treatment and high economical efficiency, and copper in the wastewater can be selectively recovered and directly converted into the 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 invention relates to the technical field of wastewater treatment and catalyst preparation, and in particular to a method for recovering copper elements in electroplating wastewater for preparing catalysts. Background Art

[0002] Electroplating copper is one of the most widely used processes in the electroplating industry. Electroplating copper 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, and aerospace. However, the production of plated parts will lead to the generation of copper-containing wastewater. The copper ion concentration in copper-containing wastewater is usually 50~500 mg L -1 In the range of 2000 to 4000 ppm, the copper ion concentration in some high-concentration copper-containing wastewater (such as waste plating solution) can even reach 1000 to 5000 mg L -1 If copper-containing wastewater is not properly disposed of, it will cause environmental pollution problems, affect human health, and cause 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 takes a complicated process to realize the recovery and reuse of copper resources in the wastewater, which has low economic value. In the prior art, most electroplating wastewater treatment methods are to first precipitate and separate copper ions through simple precipitation, adsorption and other methods to form solid waste residues to reduce the harm of wastewater. However, if these waste residues are not properly treated, it will not be possible to effectively reuse copper resources and will cause secondary pollution.

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

[0005] The Chinese patent document with the publication number CN108529789A discloses a method for treating copper-containing electroplating wastewater by 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, then a sulfide solution is added and stirred for reaction. After the reaction is completed, solid-liquid separation is carried out to obtain pretreated wastewater and copper sulfide precipitate; partial 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 and stirred for 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 meeting the discharge standard 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: A method for recovering copper elements in electroplating wastewater for preparing a catalyst, comprising the following steps: Mix the copper-containing electroplating wastewater with a recovery agent containing Si-H bonds and ultrasonicate, centrifuge to remove the supernatant and then dry it. Place the dried powder in an air atmosphere and a reducing atmosphere for roasting successively, and cool to obtain a reverse water-gas shift reaction catalyst; In the copper-containing electroplating wastewater, the concentration of copper element ≥ 100 mg / L -1 , NH 4+ concentration ≥ 1 mg / L -1 ; The recovery agent containing Si-H bonds includes siloxene capped with silicon hydride or photovoltaic waste silicon powder; The conditions for roasting in an air atmosphere are 400 - 850 °C, 1 - 8 h; The conditions for roasting in a reducing atmosphere are 300 - 600 °C, 1 - 8 h.

[0009] 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 be associated into a Cu-O-Si catalytic active intermediate with high activity and high stability, and then the reverse water-gas shift reaction catalyst loaded with zero-valent copper is obtained by reduction. The silicon hydride reduction method of the present invention can selectively recover the copper element 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 effect. 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.

[0010] 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.

[0011] Preferably, the mass ratio of the dosage of the recovery agent containing Si-H bond to the mass of copper element in copper-containing electroplating wastewater is 0.5 - 20:1.

[0012] More preferably, the recovery agent containing Si-H bond is a silicon hydride-terminated siloxene, and the silicon hydride-terminated siloxene is synthesized by the following method: 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-terminated siloxene.

[0013] When the recovery agent containing Si-H bond 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.

[0014] Preferably, in the copper-containing electroplating wastewater, the concentration of copper element ≥ 100 mg L -1 , NH 4+ concentration ≥ 5 mg L -1 .

[0015] Preferably, the conditions for mixed ultrasonic treatment 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.

[0016] Preferably, the reducing atmosphere is a hydrogen atmosphere or a hydrogen-argon mixed atmosphere (5% H 2 / Ar).

[0017] More preferably, the conditions for calcination in air atmosphere are 850 °C for 2 h, and the conditions for calcination in 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.

[0018] The present invention also provides an application of an inverse water-gas shift reaction catalyst in the synthesis of CO from a CO 2 source and an H 2 source. The inverse water-gas shift reaction catalyst is prepared by the method of recovering copper elements from electroplating wastewater for preparing the catalyst.

[0019] Specifically, in a reactor, reaction gases hydrogen and carbon dioxide are introduced, and at the same time N 2 is used as an internal standard and a balance gas, and the inverse water-gas shift reaction catalyst is used to catalyze the reaction to generate CO, and the reaction temperature is 300 - 600 °C.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:[[]] (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 inverse water-gas shift reaction catalyst, without the need for subsequent steps such as copper desorption and purification like traditional recovery technologies, and has the characteristics of simple process, easy batch processing, and high economy.

[0021] (2) The silicon hydride-terminated siloxene recovery agent used in the present invention has the strongest effect on copper element 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.

[0022] (3) Through experimental exploration, it is found that only by using the silicon hydride reduction method can the copper element in copper-containing ammonia electroplating wastewater be recovered and reused as a highly active inverse 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.

[0023] (4) The present invention utilizes the natural advantages of copper-containing electroplating wastewater. The inverse 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, approximately 16 times that of the copper salt catalyst (2.2 mmol g -1 h -1 ). The CO selectivity can reach 100%, and the stability is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is an FTIR spectrum, where A is a siloxene capped with silicon hydride, and B is photovoltaic waste silicon powder before and after hydrofluoric acid etching (before etching: waste silicon powder, after etching: waste silicon powder HF).

[0025] 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.

[0026] Figure 3 is a schematic diagram for comparing the catalytic performances of waste copper n-siloxene (n = 1, 2, 3) and copper n-siloxene (n = 1, 2, 3) (reaction temperature is 500 °C).

[0027] Figure 4 is a schematic diagram for comparing the catalytic activities and stabilities of waste copper 1-siloxene and copper 1-siloxene at a reaction temperature of 400 °C.

[0028] Figure 5 is a schematic diagram for 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.

[0029] 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 for comparing catalytic activities.

[0030] Figure 7 is a schematic diagram for 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 EMBODIMENTS

[0031] The present invention will be further illustrated below in conjunction with 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 operating 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.

[0032] 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 , NH 4 + : 170 mg L -1 ), copper wastewater 2 (Cu: 2408 mg L -1 , NH 4 + : 22.4 mg L -1 ), copper wastewater 3 (Cu: 317 mg L -1 , NH 4 + : 8.95 mg L -1 ). Taking copper wastewater 1 as an example, the composition of copper wastewater 1 is specifically shown in Table 1; Table 1 Main components in copper wastewater 1

[0033] 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 CaSi 2 -NaOH). Mix 4 g of CaSi 2 -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.

[0034] The photovoltaic waste silicon powder comes from the waste of the photovoltaic industry, specifically the photovoltaic waste silicon powder containing Si-H bonds. The photovoltaic waste silicon powder is the waste generated by the diamond wire saw cutting of silicon wafers during the preparation of solar cells, mainly composed of micron-sized and sub-micron-sized silicon particles, and there is a dense oxide layer (SiO 2layers), metal impurities (such as Al, Fe, Mg, Ni, etc.) and organic impurities. The particle size of this part of photovoltaic waste silicon powder is about a few micrometers and cannot be directly recycled. In existing purification technologies, the recovery rate of the above photovoltaic waste silicon powder is 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.

[0035] Example 1 (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, and then centrifuge (11000 r min -1 , 6 min), filter off the supernatant, and dry the precipitate in a vacuum drying oven for 12 h. The dried powder is successively calcined in air (850 °C, 2 h) and a 5% H 2 / Ar (500 °C, 2 h) mixed gas. The corresponding samples corresponding to copper wastewater 1, 2, and 3 are respectively recorded as waste copper 1-siloxene, waste copper 2-siloxene, and waste copper 3-siloxene. 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 electroplating wastewater are 43 mg g -1 , 146 mg g -1 and 23 mg g -1 .

[0036] (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 tube furnace, and plug quartz wool at both ends. Pass in CO 2 and H 2 as reaction gases, N 2 as an internal standard and balance gas, and the reaction gas ratio is CO 2 : H 2 : N 2 = 1:4:1 (molar ratio), the total flow rate is 15 mL min -1 , and the reaction temperature is set at 300 - 500 °C, and the products are monitored online by gas chromatography.

[0037] 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 with it, taking 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 has a nanosheet structure, in which copper, oxygen, and silicon are evenly distributed on the sheet contour. The catalytic performance of 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. Taking waste copper 1-siloxene as an example, the catalytic stability of this series of samples is shown 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.

[0038] Example 2 (1) Take 40 mL of copper-containing electroplating wastewater (copper wastewater 1) and place it into 2 different centrifuge tubes respectively. Add 90 mg of photovoltaic waste silicon powder (the original and HF-etched ones, denoted as waste silicon powder and waste silicon powder HF respectively) and mix and ultrasonicate (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 air (850 °C, 2 h) and a 5% H 2 / Ar (500 °C, 2 h) mixed gas. 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, magnetically stir 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.

[0039] (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. Pass in CO 2 and H 2 as reaction gases, N 2 as an internal standard and balance gas, and the reaction gas ratio is CO 2 : H 2 : N 2= 1:4:1 (molar ratio), total flow rate is 15 mL min -1 The reaction temperature was set at 600 °C, and the products were monitored online by gas chromatography.

[0040] 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 treatment with HF, more surface silicon hydride can be exposed (as shown in B in 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 waste copper 1-waste silicon powder and waste copper 1-waste silicon powder HF after experiencing the initial activation period were approximately 13 and 22 mmol g -1 h -1 respectively. The CO selectivity was nearly 100%, and the reaction could continue for at least 44 h without deactivation.

[0041] Comparative Example 1 (1) 40 mL of copper-containing electroplating wastewater (copper wastewater 1) was taken and placed in three different beakers. After adding 90 mg of the carrier material (the silicon hydride-capped siloxene, photovoltaic waste silicon powder, and silica carrier synthesized in the above steps), the mixture was impregnated and evaporated to dryness under magnetic stirring at 80 °C and 400 r min -1 . The evaporated powder was placed in a vacuum drying oven and dried for 12 h. The dried powder was successively calcined in air (850 °C, 2 h) and a 5% H 2 / Ar (500 °C, 2 h) mixed gas. The corresponding samples were denoted as waste copper 1 im / siloxene, waste copper 1 im / waste silicon powder, and waste copper 1 im / silica.

[0042] (2) The reverse water-gas shift reaction was carried out on a mobile-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. CO 2 and H 2 were introduced as reaction gases, and N 2 was used as an internal standard and balance gas. The reaction gas ratio was CO 2 : H 2 : N 2 = 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.

[0043] The waste copper 1 im / siloxene, waste copper 1 im / waste silicon powder, and waste copper 1im None of the SiO2 samples had any catalytic activity ( Figure 6 ). This indicates that the conventional preparation method of the catalyst (impregnation method) cannot recycle copper wastewater to obtain a catalyst with good performance. This indirectly verifies the superiority of the silicon hydride reduction method in the above examples, which can selectively recover copper elements in wastewater and reuse them as highly active reverse water gas shift reaction catalysts.

[0044] Comparative Example 2 1) Take 40 mL of CuCl solutions with the same copper element concentration as the copper electroplating wastewater (copper wastewater 1, copper wastewater 2, and copper wastewater 3 are denoted as solution 1, solution 2, and solution 3 respectively) and place them in 3 different centrifuge tubes. Add 90 mg of the silicon hydride-terminated siloxene synthesized in the above steps to each tube, mix and ultrasonicate (100 W) at room temperature for 5 min, then centrifuge (11000 r min 2 -1, 6 min), filter off the supernatant, and dry the precipitate in a vacuum drying oven for 12 h. The dried powder is first calcined in air (850 °C, 2 h) and then in a 5% H -1 2 / Ar (500 °C, 2 h) mixed gas. The corresponding samples for solutions 1, 2, and 3 are denoted as copper 1-siloxene, copper 2-siloxene, and copper 3-siloxene respectively. 2 2 / Ar (500 °C, 2 h) mixed gas. The corresponding samples for solutions 1, 2, and 3 are denoted as copper 1-siloxene, copper 2-siloxene, and copper 3-siloxene respectively.

[0045] 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, plug both ends with quartz wool. Pass CO 2 and H 2 as reaction gases, and N 2 as an internal standard and balance gas. The ratio of the reaction gases is CO 2 : H 2 : N 2 = 1: 4: 1 (molar ratio), and the total flow rate is 15 mL min -1 -1. The reaction temperature is set at 300 °C to 500 °C, and the products are monitored online by gas chromatography.

[0046] The catalytic performance of the copper n-siloxene (n = 1, 2, 3) samples prepared from CuCl 2 reagents 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 are 19.0, 31.2, and 23.0 mmol g -1 -1 h -1 -1 respectively. These are much lower than the corresponding waste copper n-siloxene samples (97.1, 58.7, and 104.5 mmol g -1 -1 h-1 ). 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 approximately 16 times that of the latter (2.2 mmol g -1 h -1 ). This is because the CuCl Figure 4 solution lacks components beneficial to enhancing catalytic activity. After a series of troubleshooting experiments (mixing each known component in the wastewater with copper to form a mixed solution as a precursor for preparing the catalyst, 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. 2

[0047] Comparative Example 3 (1) Take 40 mL of CuCl 2 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 and ultrasonicate (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 air (850 °C, 2 h) and a 5% H 2 / Ar (500 °C, 2 h) mixed gas. The calcined sample is denoted as copper 1 - waste silicon powder.

[0048] (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 tubular reaction furnace, and plug both ends with quartz wool. Introduce CO 2 and H 2 as reaction gases, and N 2 as an internal standard and balance gas. The ratio of the reaction gases is CO 2 : H 2 : N 2 = 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.

[0049] 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 CuCl 2The solution lacks components that are beneficial for enhancing the catalytic activity, which is consistent with the results in Comparative Example 2.

[0050] Comparative Example 4 (1) Respectively take 40 mL of copper-containing electroplating wastewater (copper wastewater 2, copper wastewater 3) and place them into two different centrifuge tubes. Add 90 mg of silica carrier and 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 successively placed in air (850 °C, 2 h) and 5% H 2 / Ar (500 °C, 2 h) mixed gas for calcination. The samples after calcination corresponding to copper wastewater 2 and 3 are respectively denoted as waste copper 2-silica and waste copper 3-silica.

[0051] (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 the quartz tube of a tubular reaction furnace, and plug quartz wool at both ends. Introduce CO 2 and H 2 as reaction gases, N 2 as an internal standard and balance gas. The ratio of the reaction gases is CO 2 : H 2 : N 2 = 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.

[0052] The catalytic activities of the waste copper 2-silica and waste copper 3-silica samples obtained in this comparative example are extremely low, far inferior to 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 the complex wastewater and converted into copper catalytic components, so the effect is not good.

[0053] The above-described embodiments have elaborated on 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 do not limit the present invention. Any modifications, supplements, or substitutions in a similar manner within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recovering copper from electroplating wastewater for preparing a catalyst, characterized in that: The following steps are involved: The copper-containing electroplating wastewater is mixed with a recovery agent containing Si-H bonds and subjected to ultrasonic treatment. The supernatant is removed by centrifugation and then dried. The dried powder is placed in an air atmosphere and then in a reducing atmosphere for roasting. After cooling, a reverse water-gas shift reaction catalyst is obtained. In copper-containing electroplating wastewater, the copper concentration is ≥100 mg L -1 , NH 4+ Concentration ≥1 mg L -1 ; Recycling agents containing Si-H bonds include siloxane terminated with silicon hydrogen or photovoltaic waste silicon powder; The calcination conditions in air atmosphere are 400-850 °C, 1-8 h; The calcination conditions under reducing atmosphere are 300-600 ℃, 1-8 h.

2. The method for recovering copper from 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 recovering copper from electroplating wastewater for preparing a catalyst according to claim 1, characterized in that: The recovery agent containing Si-H bonds is siloxane terminated with silicon hydrogen.

4. The method for recovering copper from electroplating wastewater for preparing a catalyst according to claim 1, characterized in that: The copper concentration in the copper-containing electroplating wastewater is ≥100 mg L -1 , NH 4+ Concentration ≥5 mg L -1 .

5. The method for recovering copper from electroplating wastewater for preparing a catalyst according to claim 1, characterized in that: The conditions for mixed ultrasound were 100-200 W, 0-50 °C, 5-10 min, and the conditions for centrifugation to remove the supernatant were 10000-12000 r min -1 , 5-10 min.

6. The method for recovering copper from electroplating wastewater for preparing catalyst according to claim 1, characterized in that: The reducing atmosphere is a hydrogen atmosphere or a hydrogen-argon mixed atmosphere.

7. The method for recovering copper from electroplating wastewater for preparing catalyst according to claim 1, characterized in that: The copper loading in the reverse water gas shift reaction catalyst is ≥ 1wt%.

8. Use 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, characterized in that: The reverse water-gas shift reaction catalyst is prepared by the method for recovering copper from electroplating wastewater for preparing catalyst as described in any one of claims 1-7.

9. The use of the reverse water gas shift reaction catalyst according to claim 8 in a process of catalyzing CO synthesis from a CO2 source and a H2 source, characterized in that: In the reactor, hydrogen and carbon dioxide are introduced as reaction gases, and N2 is used as an internal standard and balance gas. CO is generated by catalytic reaction using the reverse water-gas shift reaction catalyst, and the reaction temperature is 300-600°C.

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