A method for preparing copper-containing nanomaterials by using circuit board etching waste liquid and landfill leachate

Abstract

The application discloses a method for preparing copper-containing nanometer material by using circuit board etching waste liquid and landfill leachate. The circuit board etching waste liquid and the landfill leachate are mixed and stirred uniformly to obtain a mixed mother liquor; the mixed mother liquor is preheated to obtain a preheated mother liquor; the preheated mother liquor is pumped into a supercritical water generator to obtain a supercritical mother slurry; the supercritical mother slurry is released to normal pressure and cooled to room temperature, centrifuged and solid-liquid separated, and the obtained solid part is metal nanometer mud; the metal nanometer mud is dried to obtain dried metal nanometer mud; and the dried metal nanometer mud is calcined and ground to obtain the copper-containing nanometer material. The application initiatively and cooperatively utilizes the circuit board etching waste liquid and the landfill leachate to prepare nanometer metal material, and the preparation process does not need to add other chemical reagents, the preparation process is simple, the flow is short, and the benefit is remarkable; the average particle diameter of the prepared copper-containing nanometer material is less than 79 nm, and the copper content of the copper-containing nanometer material can be up to 99%.

Description

Technical Field

[0001] This invention belongs to the field of hazardous waste resource utilization, specifically relating to a method for preparing copper-containing nanomaterials using circuit board etching waste liquid and landfill leachate. Background Technology

[0002] Copper etching is one of the most critical processes in printed circuit board (PCB) manufacturing. It involves applying an etching solution to a copper foil substrate to remove unwanted copper. When the etching capacity of the solution decreases to a certain level, it is defined as etching wastewater. PCB etching wastewater contains high concentrations of copper and other harmful chemicals, which are detrimental to the environment and human health, potentially leading to water pollution, soil contamination, and ecosystem damage. Furthermore, the pH value of etching wastewater is often unstable, which may affect the acidity or alkalinity of the environment in which it is discharged.

[0003] In the current global industrial landscape, my country has risen to become a world-leading producer of printed circuit boards (PCBs). With the booming development of the electronics manufacturing industry, my country's annual PCB production has continued to climb, and correspondingly, the etching waste generated during PCB production has also increased, especially acidic copper chloride etching waste, which now exceeds 2.8 million tons annually and continues to grow. The copper content in the etching waste is approximately 120 to 180 grams per liter (g / L), meaning that effective recycling and utilization of etching waste resources can not only save resources but also bring potential economic benefits.

[0004] Recycling circuit board etching wastewater is no easy task. Besides high concentrations of copper and hydrochloric acid, it also contains a certain amount of other inorganic and organic substances. The presence of these impurities increases the difficulty of wastewater treatment and resource recovery. Overcoming these technical challenges to achieve efficient and environmentally friendly recycling, especially in the application of etching wastewater to prepare nanoscale metal materials, remains a pressing issue for the industry.

[0005] Landfill leachate is a high-concentration organic wastewater generated during the landfill process. Its properties change depending on the operating time of the landfill, and if not properly disposed of, it can be harmful to the environment.

[0006] Therefore, if copper-containing nanomaterials can be prepared by synergistically utilizing circuit board etching waste liquid and landfill leachate, it will not only broaden the resource utilization path of circuit board etching waste liquid, but also open up a new direction for the treatment of landfill leachate. Summary of the Invention

[0007] Objective of this invention: The objective of this invention is to provide a method for preparing copper-containing nanomaterials using circuit board etching waste liquid and landfill leachate. This invention features a simple preparation process, a short procedure time, and significant benefits.

[0008] Technical solution: The objective of this invention is achieved through the following technical solution:

[0009] This invention provides a method for preparing copper-containing nanomaterials using circuit board etching waste liquid and landfill leachate, comprising the following steps:

[0010] (1) Mix the circuit board etching waste liquid and landfill leachate, stir evenly to obtain a mixed mother liquor;

[0011] (2) Preheat the mother liquor obtained in step (1) to obtain preheated mother liquor;

[0012] (3) Pump the preheated mother liquor obtained in step (2) into a supercritical water generator to obtain supercritical mother slurry;

[0013] (4) Release the supercritical mother slurry obtained in step (3) to atmospheric pressure and cool it to room temperature, centrifuge it, and separate the solid and liquid components. The solid part obtained is metal nano mud.

[0014] (5) Dry the metal nano mud obtained in step (4) to obtain dried metal nano mud;

[0015] (6) The dried metal nano mud obtained in step (5) is calcined and ground to obtain copper-containing nanomaterials.

[0016] The reaction mechanism of the preparation method of the present invention is as follows:

[0017] After mixing circuit board etching waste liquid and landfill leachate, during the stirring process, organic pollutants, ammonia nitrogen, and phosphorus pollutants in the landfill leachate coordinate with copper ions and a small amount of iron ions in the circuit board etching waste liquid to form complexes. These complexes diffuse uniformly within the long-chain organic pollutants. Under supercritical water conditions, the metal complexes undergo dehydration, forming nanoscale metal oxides that precipitate from the liquid phase. Simultaneously, due to changes in the oxidation and solubility characteristics of supercritical water, water-soluble organic pollutants decompose and mineralize, forming short-chain organic matter or carbon dioxide. Some incompletely decomposed organic pollutants separate from the supercritical water. The carbon-chain organic matter adsorbs onto the surface of the metal oxides, while the precipitated organic pollutants fill the spaces between the metal oxide particles, effectively preventing the aggregation of metal nano-oxides. Under supercritical conditions, ammonia nitrogen pollutants ionize and dissociate, forming nitrogen gas and hydrogen free radicals. These hydrogen free radicals promote the reduction and precipitation of some metal ions. During calcination, the organic pollutants are completely mineralized and decomposed, forming carbon dioxide which is then discharged, thus achieving removal.

[0018] Preferably, in step (1), the volume ratio of the circuit board etching waste liquid to the landfill leachate is 5 to 45:100.

[0019] Preferably, in step (2), the preheating temperature is 150 to 350°C.

[0020] Preferably, in step (3), the pressure in the supercritical water generator is 20-40 MPa and the operating temperature is 375-625°C.

[0021] Preferably, in step (3), the preheated mother liquor is kept in a supercritical water generator for 5 to 45 minutes.

[0022] Preferably, in step (4), the centrifugation speed is 2000-12000 rpm and the centrifugation time is 5-15 minutes.

[0023] Preferably, in step (5), the drying temperature is 60-180°C and the drying time is 2-4 hours.

[0024] Preferably, in step (6), the calcination temperature is 240-480°C and the calcination time is 0.5-2.5 hours.

[0025] Preferably, in step (6), the grinding time is 0.5 to 4.5 hours.

[0026] Beneficial effects:

[0027] This invention features a simple preparation process, a short procedure, and significant benefits. It innovatively utilizes circuit board etching wastewater and landfill leachate to prepare nanoscale metallic materials without adding any other chemical reagents. The prepared copper-containing nanomaterials have an average particle size of less than 79 nm, and the copper oxide content can reach up to 99%. Attached Figure Description

[0028] Figure 1 This is a flowchart of the preparation method of the present invention. Detailed Implementation

[0029] The technical solution of the present invention will be described in detail below through specific embodiments, but the scope of protection of the present invention is not limited to the embodiments described.

[0030] Unless otherwise specified, specific techniques or conditions in the embodiments shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods. Unless otherwise specified, the experimental materials used in the following embodiments are all commercially available products.

[0031] The flowchart of the preparation method of this invention is shown below. Figure 1 .

[0032] Sampling and basic properties description of circuit board etching waste liquid and landfill leachate in the examples:

[0033] The circuit board etching waste liquid used in the experiment was taken from Jiangmen Chongda Circuit Technology Co., Ltd. It was an acidic copper chloride etching waste liquid with a copper content of 146 g / L and an iron content of 3.58 g / L.

[0034] The landfill leachate used in the experiment was taken from Zhuji Sanfeng Environmental Energy Co., Ltd. The concentrated landfill leachate of this batch had a COD concentration of 3639 mg / L, a total phosphorus concentration of 294 mg / L, and an ammonia nitrogen concentration of 1062 mg / L.

[0035] Example 1: Effect of the volume ratio of circuit board etching waste liquid and landfill leachate on the average particle size and copper oxide content of the prepared copper-containing nanomaterials

[0036] Preparation of copper-containing nanomaterials:

[0037] Circuit board etching waste liquid and landfill leachate were mixed in volume ratios of 2.5:100, 3:100, 4:100, 5:100, 25:100, 45:100, 47.5:100, 50:100, and 52.5:100, and stirred evenly to obtain a mixed mother liquor. The mother liquor was preheated to 150°C to obtain a preheated mother liquor. The preheated mother liquor was pumped into a supercritical water generator and held for 5 minutes to obtain a supercritical mother slurry, wherein the supercritical pressure was 20 MPa and the supercritical generator operating temperature was 375°C. The supercritical mother slurry was released to atmospheric pressure and cooled to room temperature, and centrifuged at 2000 rpm for 15 minutes to separate the solid and liquid components. The obtained solid fraction was a metallic nano-sludge. The metal nano-sludge was dried for 2 hours, then calcined for 0.5 hours, and then ground for 0.5 hours to obtain copper-containing nanomaterials. The drying temperature was 60℃ and the calcination temperature was 240℃.

[0038] Particle size analysis: The average particle size of the prepared copper-containing nanomaterial samples was analyzed using a nanoparticle size analyzer (NanotracFlex).

[0039] Detection of copper oxide content in copper-containing nanomaterials: The copper oxide content in copper-containing nanomaterials was detected in accordance with the standard "Chemical Reagent Copper Oxide (Powder)" (GB674-1978).

[0040] The test results of this embodiment are shown in Table 1.

[0041] Table 1. Effect of the volume ratio of circuit board etching waste liquid and landfill leachate on the average particle size and copper oxide content of the prepared copper-containing nanomaterials.

[0042]

[0043] As shown in Table 1, when the volume ratio of circuit board etching waste liquid to landfill leachate is less than 5:100 (as shown in Table 1, when the volume ratio of circuit board etching waste liquid to landfill leachate is 4:100, 3:100, 2.5:100, and even lower ratios not listed in Table 1), less circuit board etching waste liquid is added and more landfill leachate is added. Under supercritical water conditions, the dehydration reaction efficiency of metal complexes decreases, and the decomposition and mineralization effect of water-soluble organic pollutants deteriorates, resulting in poor precipitation and diffusion of metal nano-oxides and agglomeration. Consequently, the average particle size of the prepared copper-containing nanomaterials increases significantly as the volume ratio of circuit board etching waste liquid to landfill leachate decreases, while the copper oxide content of the prepared copper-containing nanomaterials decreases significantly as the volume ratio of circuit board etching waste liquid to landfill leachate decreases. When the volume ratio of circuit board etching waste liquid to landfill leachate is 5–45:100 (as shown in Table 1, with volume ratios of 5:100, 25:100, and 45:100), after mixing the circuit board etching waste liquid and landfill leachate, during the stirring process, organic pollutants, ammonia nitrogen, and phosphorus pollutants in the landfill leachate coordinate with copper ions and a small amount of iron ions in the circuit board etching waste liquid to form complexes. The formed complexes diffuse uniformly in the long-chain organic pollutants. Under supercritical water conditions, the metal complexes undergo a dehydration reaction to form nanoscale metal oxides, which precipitate from the liquid phase. Simultaneously, due to changes in the oxidation and dissolution characteristics of supercritical water, water-soluble organic pollutants decompose and mineralize to form short-chain organic matter or carbon dioxide. Some incompletely decomposed organic pollutants separate from the supercritical water. The carbon-chain organic matter adsorbs onto the surface of the metal oxide, while the precipitated organic pollutants fill the spaces between the metal oxide particles, thus effectively preventing the aggregation of metal nano-oxides. Under supercritical conditions, ammonia nitrogen pollutants undergo ionization and dissociation, forming nitrogen gas and hydrogen free radicals. These hydrogen free radicals can promote the reduction and precipitation of some metal ions. Ultimately, the prepared copper-containing nanomaterials all have an average particle size of less than 79 nm and a copper oxide content exceeding 92%. When the volume ratio of circuit board etching waste liquid to landfill leachate is greater than 45:100 (as shown in Table 1, the volume ratios of circuit board etching waste liquid to landfill leachate are 47.5:100, 50:100, 52.5:100, and higher ratios not listed in Table 1), the circuit board etching waste liquid is added in excess, while the amount of landfill leachate is insufficient. After mixing the circuit board etching waste liquid and landfill leachate, the coordination effect between organic pollutants, ammonia nitrogen, and phosphorus pollutants in the landfill leachate and copper and iron ions in the circuit board etching waste liquid deteriorates during the stirring process, resulting in a reduction in the formation of complexes. Consequently, the average particle size of the prepared copper-containing nanomaterials increases significantly with further increases in the volume ratio of circuit board etching waste liquid to landfill leachate, while the copper oxide content of the prepared copper-containing nanomaterials decreases significantly with further increases in the volume ratio of circuit board etching waste liquid to landfill leachate.

[0044] Therefore, considering both benefits and costs, a volume ratio of PCB etching waste liquid to landfill leachate of 5–45:100 is most advantageous for reducing the average particle size of the prepared copper-containing nanomaterials and for increasing the copper oxide content of the prepared copper-containing nanomaterials.

[0045] Example 2: Effect of residence time in a supercritical water generator on the average particle size and copper oxide content of the prepared copper-containing nanomaterials

[0046] Circuit board etching waste liquid and landfill leachate were mixed at a volume ratio of 45:100 and stirred evenly to obtain a mixed mother liquor. The mother liquor was preheated to 250℃ to obtain a preheated mother liquor. The preheated mother liquor was pumped into a supercritical water generator and held for 2.5 minutes, 3 minutes, 4 minutes, 5 minutes, 25 minutes, 45 minutes, 50 minutes, 55 minutes, and 60 minutes to obtain a supercritical slurry, wherein the supercritical pressure was 30 MPa and the supercritical generator operating temperature was 500℃. The supercritical slurry was released to atmospheric pressure and cooled to room temperature, and centrifuged at 7000 rpm for 10 minutes to separate the solid and liquid components. The obtained solid component was a metal nano-sludge. The metal nano-sludge was dried for 3 hours, then calcined for 1.5 hours, and then ground for 2.5 hours to obtain copper-containing nanomaterials, wherein the drying temperature was 120℃ and the calcination temperature was 360℃.

[0047] The particle size detection and copper oxide content detection in copper-containing nanomaterials are the same as in Example 1. The test results of this example are shown in Example 2.

[0048] Table 2. Effect of residence time in the supercritical water generator on the average particle size and copper oxide content of the prepared copper-containing nanomaterials.

[0049] Residence time in supercritical water generator Average particle size (nanometers) Copper oxide content 2.5 minutes 105.62 87.39％ 3 minutes 95.37 89.66％ 4 minutes 86.95 92.54％ 5 minutes 71.32 95.83％ 25 minutes 67.69 96.42％ 45 minutes 65.73 98.04％ 50 minutes 89.16 95.16％ 55 minutes 99.38 93.29％ 60 minutes 102.75 92.57％

[0050] As shown in Table 2, when the residence time in the supercritical water generator is less than 5 minutes (as shown in Table 2, residence times of 4 minutes, 3 minutes, 2.5 minutes, and even lower values ​​not listed in Table 2), the short residence time of the mixture in the supercritical water generator reduces the efficiency of the dehydration reaction of the metal complex, worsens the precipitation effect of nanoscale metal oxides, and reduces the metal ion reduction effect. Consequently, the average particle size of the prepared copper-containing nanomaterials increases significantly with decreasing residence time in the supercritical water generator, and decreases significantly with decreasing residence time in the supercritical water generator. When the residence time in the supercritical water generator is 5–45 minutes (as shown in Table 2, residence times of 5 minutes, 25 minutes, and 45 minutes), under supercritical water conditions, the metal complex undergoes a dehydration reaction to form nanoscale metal oxides, which precipitate from the liquid phase. Simultaneously, due to changes in the oxidation and solubility characteristics of supercritical fluids, water-soluble organic pollutants decompose and mineralize, forming short-chain organic matter or carbon dioxide. Some incompletely decomposed organic pollutants separate from the supercritical water. The carbon-chain organic matter adsorbs onto the surface of the metal oxide, while the precipitated organic pollutants fill the spaces between the metal oxide particles, effectively preventing the aggregation of metal nano-oxides. Under supercritical conditions, ammonia nitrogen pollutants ionize and dissociate, forming nitrogen gas and hydrogen free radicals. These hydrogen free radicals can promote the reduction and precipitation of some metal ions. Ultimately, the prepared copper-containing nanomaterials have an average particle size of less than 72 nm and a copper oxide content exceeding 95%. When the residence time in the supercritical water generator is greater than 45 minutes (as shown in Table 2, residence times of 50 minutes, 55 minutes, 60 minutes, and higher values ​​not listed in Table 2), the mixture has an excessively long residence time in the supercritical water generator. This leads to excessive dehydration of the metal complex and precipitation of nanoscale metal oxides. Consequently, the average particle size of the prepared copper-containing nanomaterials increases significantly with further increases in residence time in the supercritical water generator, while the copper oxide content of the prepared copper-containing nanomaterials decreases significantly with further increases in residence time in the supercritical water generator.

[0051] Therefore, considering both benefits and costs, a residence time of 5–45 minutes in the supercritical water generator is most conducive to reducing the average particle size of the prepared copper-containing nanomaterials and most conducive to increasing the copper oxide content of the prepared copper-containing nanomaterials.

[0052] Example 3: Effect of calcination time on the average particle size and copper oxide content of the prepared copper-containing nanomaterials

[0053] Circuit board etching waste liquid and landfill leachate were mixed at a volume ratio of 45:100 and stirred evenly to obtain a mixed mother liquor. The mother liquor was preheated to 350℃ to obtain a preheated mother liquor. The preheated mother liquor was pumped into a supercritical water generator and held for 45 minutes to obtain a supercritical slurry, wherein the supercritical pressure was 40 MPa and the supercritical generator operating temperature was 625℃. The supercritical mother liquor was released to atmospheric pressure and cooled to room temperature, and centrifuged at 12000 rpm for 5 minutes to separate the solid and liquid components, and the obtained solid part was metal nano-sludge. The metal nano-sludge was dried for 4 hours, and then calcined for 0.25 hours, 0.3 hours, 0.4 hours, 0.5 hours, 1.5 hours, 2.5 hours, 2.75 hours, 3 hours, and 3.25 hours. The calcined metal nano-sludge was then ground for 4.5 hours to obtain copper-containing nanomaterials, wherein the drying temperature was 180℃ and the calcination temperature was 480℃.

[0054] The particle size detection and copper oxide content detection in copper-containing nanomaterials are the same as in Example 1. The test results of this example are shown in 3.

[0055] Table 3. Effects of calcination time on the average particle size and copper oxide content of the prepared copper-containing nanomaterials.

[0056] Calcination time Average particle size (nanometers) Copper oxide content 0.25 hours 83.91 86.29％ 0.3 hours 78.43 89.32％ 0.4 hours 71.82 94.47％ 0.5 hours 66.54 98.13％ 1.5 hours 64.21 98.75％ 2.5 hours 63.89 99.24％ 2.75 hours 69.04 97.53％ 3 hours 75.47 95.31％ 3.25 hours 80.29 95.02％

[0057] As shown in Table 3, when the calcination time is less than 0.5 hours (e.g., 0.4 hours, 0.3 hours, 0.25 hours, and lower values ​​not listed in Table 3), the calcination time is short, the material is not fully calcined, and the organic pollutants are not completely mineralized and decomposed. This results in a significant increase in the average particle size of the prepared copper-containing nanomaterials as the calcination time decreases, and a significant decrease in the copper oxide content of the prepared copper-containing nanomaterials as the calcination time decreases. When the calcination time is 0.5–2.5 hours (e.g., 0.5 hours, 1.5 hours, and 2.5 hours in Table 3), the organic pollutants are completely mineralized and decomposed during the calcination process, forming carbon dioxide which is then released and removed. Ultimately, the average particle size of the prepared copper-containing nanomaterials is less than 67 nanometers, and the copper oxide content is higher than 98%. When the calcination time is greater than 2.5 hours (as shown in Table 3, calcination times of 2.75 hours, 3 hours, 3.25 hours and higher values ​​not listed in Table 3), the calcination time is too long, and the phosphate adsorbed in the material is prone to sintering together. As a result, the average particle size of the prepared copper-containing nanomaterials increases significantly with further increase in calcination time, and the copper oxide content of the prepared copper-containing nanomaterials decreases with further increase in calcination time.

[0058] Therefore, considering both benefits and costs, a calcination time of 0.5 to 2.5 hours is most conducive to reducing the average particle size of the prepared copper-containing nanomaterials and most conducive to increasing the copper oxide content of the prepared copper-containing nanomaterials.

[0059] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A method for preparing copper-containing nanomaterials using circuit board etching waste liquid and landfill leachate, characterized in that, Includes the following steps: (1) Mix the circuit board etching waste liquid and landfill leachate, stir evenly, and obtain a mixed mother liquor; (2) Preheat the mixed mother liquor obtained in step (1) to obtain a preheated mother liquor; (3) Pump the preheated mother liquor obtained in step (2) into a supercritical water generator to obtain supercritical mother slurry; (4) Release the supercritical mother slurry obtained in step (3) to normal pressure and cool it to room temperature, centrifuge it, and separate the solid and liquid components. The solid part obtained is metal nano mud. (5) Dry the metal nano mud obtained in step (4) to obtain dried metal nano mud; (6) The dried metal nano mud obtained in step (5) is calcined and ground to obtain copper-containing nanomaterials; In step (1), the volume ratio of the circuit board etching waste liquid to the landfill leachate is 5~45:100; In step (3), the pressure in the supercritical water generator is 20~40MPa and the operating temperature is 375~625℃; In step (3), the preheated mother liquor is kept in a supercritical water generator for 5 to 45 minutes; In step (6), the calcination temperature is 240~480℃ and the calcination time is 0.5~2.5 hours.

2. The method according to claim 1, characterized in that, In step (2), the preheating temperature is 150~350℃.

3. The method according to claim 1, characterized in that, In step (4), the centrifugation speed is 2000~12000 rpm and the centrifugation time is 5~15 minutes.

4. The method according to claim 1, characterized in that, In step (5), the drying temperature is 60~180℃ and the drying time is 2~4 hours.

5. The method according to claim 1, characterized in that, In step (6), the grinding time is 0.5 to 4.5 hours.

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