Method and device for pre-treating recycled acid liquor to remove oxalate

Abstract

The invention discloses a method and a device for pre-treating recycled acid liquor to remove oxalate, and the method comprises the following steps: adding oxalic acid and / or soluble oxalate into acid waste liquor to enable reaction liquor to generate new oxalate precipitate, and then carrying out solid-liquid separation to obtain new oxalate filter residue and acid filtrate; the method is characterized by further comprising the following steps: (1) directly carrying out oxidation reaction on the acidic filtrate or carrying out oxidation reaction after blending for at least 2 hours, so that oxalate C2O4 < 2-> or other organic impurities in the acidic filtrate are partially or completely removed through chemical reaction to obtain oxidized acidic filtrate; and (2) directly feeding the oxidized acidic filtrate or feeding the oxidized acidic filtrate into a corresponding circuit board acidic corrosion production line as a regenerated metal corrosion liquid for recycling. According to the method, the oxalate impurity content index or the oxalate impurity and organic matter impurity index in the acidic filtrate obtained through oxalic acid treatment is reduced after oxidation treatment.

Description

A method and device for pre-treating recycled acid solution to remove oxalate radicals Technical Field

[0001] The invention belongs to the technical field of removing impurities from recycled acidic etching waste liquid during circuit board manufacturing, and particularly relates to a method and device for removing oxalate radicals from recycled acid liquid through pretreatment. Background Art

[0002] The existing printed circuit board (PCB) etching process often produces a large amount of waste liquid containing copper or copper-tin. The following introduces three commonly used acidic metal etching liquids in the PCB industry and the waste liquids produced during the etching process.

[0003] The first type of acidic metal etching solution is nitric acid-based tin stripping solution. Its primary components are nitric acid or nitric acid and ferric nitrate, and it may contain additives. It is used to remove the tin metal resist layer on copper circuit boards. Nitric acid-based tin stripping solution corrodes tin metal, producing nitric acid-based tin stripping waste liquid containing tin and copper. This waste liquid primarily contains Sn(NO3)2 and a small amount of Cu(NO3)2. The main chemical reactions during use of nitric acid-based tin stripping solution are as follows: Sn + 4HNO3 → Sn(NO3)2 + 2NO2↑ + 2H2O, Cu + 4HNO3 → Cu(NO3)2 + 2NO2↑ + 2H2O.

[0004] The second type of acidic metal etching solution is a sulfuric acid-based microetching solution, used to reduce the thickness of the copper layer on copper circuit boards or to microetch the copper surface before coating with ink or film. The main components of these sulfuric acid-based microetching solutions are sulfuric acid + an oxidant, or sulfuric acid + ferric sulfate + an oxidant, and they may also contain microetching solution additives. Microetching with this sulfuric acid-based microetching solution produces sulfuric acid-based microetching waste liquid containing copper sulfate. The specific chemical reactions of microetching (using hydrogen peroxide or sodium persulfate as the oxidant) are as follows: Copper corrosion reaction: Cu + H2SO4 + H2O2 → CuSO4 + 2H2O, or Cu + Fe2(SO4)3 → CuSO4 + 2FeSO4, or Cu + Na2S2O8 → NaSO4 + CuSO4; Ferric sulfate regeneration reaction: 2FeSO4 + Na2S2O8 → NaSO4 + Fe2(SO4)3.

[0005] The third type of acidic metal etching solution is an acidic copper chloride etching solution, which is used to etch copper circuit patterns on copper circuit boards. The acidic copper chloride etching solution consists mainly of hydrochloric acid and copper chloride, which are further subdivided into iron-containing and iron-free copper chloride etching solutions, and may also contain etching additives. In existing circuit board acidic copper chloride etching processes, a solution containing hydrochloric acid and an oxidizing agent are added during the etching process to immediately oxidize and regenerate the CuCl or CuCl and FeCl2 in the etching solution into copper etching agents CuCl2 and FeCl3. The oxidizing agent is preferably sodium chlorate or hydrogen peroxide. These two oxidizing agents are inexpensive and can regenerate the copper chloride or ferric chloride copper etching agent while maintaining the etching solution composition and etching performance, allowing the etching process to continue while meeting process requirements. The etching and regeneration reactions of the acidic copper chloride etching solution are shown in the following chemical formula. Therefore, after etching the circuit board, the acidic copper chloride etching solution produces acidic copper chloride etching waste liquid containing newly generated copper chloride during the etching process.

[0006] Etching reaction: Cu+CuCl2→2CuCl, Cu+FeCl3→CuCl+FeCl2 (this reaction also occurs in iron-containing etching solution).

[0007] Copper etching agent regeneration reaction: 2CuCl+[O]+2HCl→2CuCl2+2H2O, CuCl+FeCl3→CuCl2+FeCl2, 2FeCl2+[O]+2HCl→2FeCl3+H2O (this reaction also occurs in iron-containing etching solution).

[0008] From the above reaction formula, we know that the solution containing hydrochloric acid added to the etching machine during etching is called etching liquid in the industry, and the solution overflowing from the etching machine when the etching working liquid is full is etching waste liquid.

[0009] There are three existing methods for treating the acidic copper and / or tin-containing waste liquids produced by the above three acidic metal corrosive liquids: electrolysis, oxalic acid treatment, and chemical treatment using copper hydroxide or copper carbonate.

[0010] ⑴Electrolysis

[0011] Electrolysis is currently the most commonly used method for recycling and reusing acidic copper chloride etching wastewater. It uses the acidic copper chloride etching wastewater as an electrolyte for electrolysis, depositing metallic copper on the cathode. In some electrolysis processes, the acidic solution after copper extraction can also be used as a regenerated etching solution for recycling in the etching process. This method has the advantages of both copper recovery and recycling the wastewater into an etching solution, without any residual chemical components that could adversely affect the etching process. However, it also requires high electricity consumption and equipment investment.

[0012] ⑵Oxalic acid method

[0013] The oxalic acid method uses oxalic acid to react with wastewater to form oxalate precipitates. After solid-liquid separation, the copper and / or tin in the wastewater are removed and an acidic filtrate is obtained, thereby recovering the metals in the wastewater and recycling the acidic filtrate. The chemical reaction of the oxalic acid method for treating acidic copper- and / or tin-containing wastewater is as follows:

[0014] (1) Reaction of nitric acid-type tin stripping wastewater with oxalic acid: Sn(NO3)2+Cu(NO3)2+2H2C2O4→4HNO3+CuC2O4↓+SnC2O4↓

[0015] (2) Reaction of sulfuric acid type micro-etching waste liquid with oxalic acid: Iron-free: CuSO4+H2C2O4→H2SO4+CuC2O4↓ Iron-containing: CuSO4+Fe2(SO4)3+H2C2O4→H2SO4+Fe2(SO4)3+CuC2O4↓

[0016] (3) Reaction of acidic copper chloride etching waste liquid with oxalic acid: Iron-free: CuCl2+H2C2O4→2HCl+CuC2O4↓ Iron-containing: CuCl2+FeCl3+H2C2O4→2HCl+FeCl3+CuC2O4↓

[0017] Among them, for acidic wastewater containing iron and copper, the reaction between trivalent iron ions and oxalic acid will not produce a large amount of FeC2O4; this is because the trivalent iron ions in the wastewater must be reduced to divalent iron before reacting with oxalic acid to form FeC2O4 precipitate. The solubility product of FeC2O4 is 3.2×10 -7 , the solubility product of CuC2O4 is 4.4×10 -10 When the reaction equivalent number of copper ions in the acidic waste liquid containing iron and copper is greater than the reaction equivalent number of oxalic acid, it is difficult for the acidic waste liquid containing iron and copper to react with oxalic acid to generate ferrous oxalate precipitate.

[0018] The advantages of the oxalic acid method are its simplicity, low investment in recovery equipment, and high economic benefits. However, its disadvantages are that when the acidic filtrate after solid-liquid separation is directly recycled back into the production line, insoluble oxalates can clog the etching solution nozzles, impacting production. Insoluble oxalates can also adhere to circuit boards, reducing product quality. Prolonged recycling of the acidic filtrate treated with the oxalic acid method can also corrode titanium components in the production line. This impact on circuit etching quality is particularly pronounced in acid copper chloride etching, making the oxalic acid method difficult to promote for the treatment of acid copper chloride etching wastewater.

[0019] Currently, the existing methods for treating acidic copper chloride etching waste liquid mainly adopt electrolysis and chemical treatment methods of copper hydroxide or copper carbonate.

[0020] The inventors have found that the reason for the above-mentioned defects of the oxalic acid method is that the acidic filtrate after solid-liquid separation still contains a small amount of oxalic acid, and may also contain soluble sodium oxalate and / or ammonium oxalate, and insoluble copper oxalate and / or stannous oxalate. In addition, based on the inventors' research and development practices and production experience, it was found that in the oxalic acid method for copper extraction, where the amount of copper ions in the waste liquid that can react is greater than the amount of oxalic acid that can react, the acidic filtrate obtained after solid-liquid separation generally contains 30 to 50 g / L of oxalate C2O4. 2- Since the acidic metal corrosion liquid on the production line contains a large amount of copper ions and / or tin ions, when the acidic filtrate is returned to the production line for use, the oxalate impurities therein will react with these copper ions and / or tin ions to newly generate insoluble oxalates, rather than the current industry belief that insoluble oxalates remain simply due to incomplete filtration during solid-liquid separation in the oxalic acid method.

[0021] Although all three metal-corroding acid solutions use oxidants or oxidizing acids during the process, the applicant discovered through repeated experiments that when the acidic filtrate is directly returned to the production line for use, the oxalic acid remaining therein cannot be promptly removed using the oxidant or oxidizing acid used in the process. This is because the acidic metal-corroding solution on the production line comes into contact with the metal and may contain low-valent metal ions. The oxidant or oxidizing acid used in the process will preferentially react with the metal it comes into contact with and / or the low-valent metal ions in the solution, making it difficult to oxidize and remove the remaining oxalate. Therefore, to address the above-mentioned shortcomings of the oxalic acid method, it is necessary to eliminate the oxalate in the acidic filtrate after solid-liquid separation before reuse, so that it can be recycled back into the production line as a regenerated metal-corroding solution, thereby avoiding the problems caused by the above-mentioned oxalic acid method.

[0022] Furthermore, when organic matter adheres to the object being etched (e.g., the polymer resist coating on a circuit board during etching), the three metal-etching acids mentioned above will dissolve these organic matter during use, resulting in the production of wastewater containing organic impurities. To prevent the accumulation of organic impurities in the acidic filtrate during reuse, which could affect production quality and efficiency, the organic impurities in the acidic filtrate must be oxidized and degraded before reuse as a regenerated metal-etching solution.

[0023] ⑶ Chemical treatment using copper hydroxide or copper carbonate

[0024] The chemical treatment using copper hydroxide or copper carbonate is to mix the acidic copper chloride etching waste liquid with copper hydroxide or copper carbonate to react to generate copper hydroxide precipitate or basic copper carbonate precipitate. The solution obtained after solid-liquid separation is a chloride salt solution, so it cannot be reused in the etching production line and can only be discharged after industrial wastewater treatment.

[0025] Summary of the Invention

[0026] The first object of the present invention is to provide a method for removing oxalate by pre-treating recycled acid solution, so that the oxalate impurity content index or the oxalate impurity index and the organic impurity index in the acidic filtrate obtained by oxalic acid treatment are reduced after oxidation treatment.

[0027] The second object of the present invention is to provide a device for removing oxalate from recycled acid solution by pre-treatment. The above method can be implemented using this device to achieve the purpose of removing oxalate and / or other organic impurities in the pre-treatment.

[0028] The first object of the present invention is achieved through the following technical solutions.

[0029] A method for removing oxalate radicals by pre-treating recycled acidic liquid, comprising adding oxalic acid and / or soluble oxalate to the acidic waste liquid to cause a new oxalate precipitate to form in the reaction liquid, and then performing solid-liquid separation to obtain a new oxalate residue and an acidic filtrate; the method further comprising the following steps:

[0030] (1) The acidic filtrate is directly or after being prepared and subjected to oxidation reaction, and the oxidation reaction time is at least 2 hours, so that the oxalate C2O4 in the acidic filtrate is converted to 2- Or other organic impurities are partially or completely removed through chemical reactions to obtain an oxidized acidic filtrate;

[0031] (2) The oxidized acidic filtrate is directly or after being prepared as a regenerated metal corrosion liquid and then fed back to the corresponding circuit board acid corrosion production line for recycling.

[0032] The acidic waste liquid described in the present invention is an acidic waste liquid containing copper and / or tin, specifically the waste liquid produced after the acidic metal corrosion liquid is processed, more specifically at least one of nitric acid-type tin stripping waste liquid, sulfuric acid-type micro-etching waste liquid, and acidic copper chloride etching waste liquid; the soluble oxalate is one or a combination of more than one of potassium oxalate, sodium oxalate, and ammonium oxalate; therefore, the new oxalate precipitate that appears after adding oxalic acid and / or soluble oxalate to the acidic waste liquid is mainly stannous oxalate and / or copper oxalate.

[0033] The present invention performs oxidation reaction on the acidic filtrate by specifically adopting at least one of the following two methods, so that the content of oxalate in the acidic filtrate after oxidation treatment reaches the use requirement below the process set value:

[0034] ① Using an electrolytic cell to perform electrochemical oxidation reaction on the acidic filtrate to obtain oxidized acidic filtrate;

[0035] ② Using an oxidant to carry out an oxidation reaction with the acidic filtrate to obtain an oxidized acidic filtrate.

[0036] The process setting value of the oxalate content described in the present invention is set according to actual production requirements and the degree of negative impact caused by residual oxalate that can be accepted by the process.

[0037] The oxidant is specifically at least one of ozone, oxygen, chlorine, hydrogen peroxide, sodium percarbonate, potassium percarbonate, ammonium percarbonate, ammonium persulfate, sodium persulfate, potassium persulfate, sodium chlorate, potassium chlorate, sodium perchlorate, potassium perchlorate, chlorine dioxide, and nitric acid.

[0038] Preferably, at least one of hydrogen peroxide, percarbonate, ozone, oxygen, and persulfate is selected for the acidic filtrate obtained by treating sulfuric acid-type micro-etching waste liquid; at least one of hydrogen peroxide, chlorate, chlorine, ozone, oxygen, percarbonate, perchlorate, and chlorine dioxide is selected for the acidic filtrate obtained by treating acidic copper chloride etching waste liquid; and nitric acid is used for the acidic filtrate obtained by treating nitric acid-type tin stripping waste liquid.

[0039] More preferably, hydrogen peroxide and / or persulfate are selected for the acidic filtrate obtained by treating sulfuric acid-type micro-etching waste liquid; hydrogen peroxide and / or chlorate are selected for the acidic filtrate obtained by treating acidic copper chloride etching waste liquid.

[0040] When the present invention uses an electrolytic cell to perform an electrochemical oxidation reaction on the acidic filtrate, the electrolytic cell is divided into an anode cell area and a cathode cell area by an electrolytic cell separator, and the acidic filtrate is put into the anode cell area. In the cathode cell area, an aqueous solution of an electrolyte is used as a cathode electrolyte, and then the electrode power supply is turned on to oxidize the acidic filtrate in the anode cell area.

[0041] The electrolytic cell separator of the present invention is at least one of a cation exchange membrane, an anion exchange membrane, a reverse osmosis membrane, a bipolar membrane, a proton membrane, a non-ion selective membrane, and a filter cloth. The non-ion selective membrane is a material having through-pores that allow at least some ions or molecules to pass through but is non-selective for cations and anions.

[0042] Preferably, the electrolytic cell separator is a cation exchange membrane and / or filter cloth. The electrolytic cell separator effectively confines oxalate ions in the anolyte to the anode tank and reduces the presence of other reducing substances in the catholyte near the electrolytic anode, thereby effectively removing oxalate and other organic impurities from the acidic filtrate. The acidic filtrate has a low metal ion concentration, with oxalate ions being the primary reducing substance. Therefore, electrochemical oxidation can effectively eliminate the oxalate ions in the anolyte.

[0043] An electrochemical reaction occurs at the electrolytic anode in which oxalate ions are oxidized, and oxygen and / or chlorine are generated depending on the composition of the acidic filtrate.

[0044] Electrolysis anode: C2O42- -2e→2CO2

[0045] 4[OH]-4e→2H2O+O2 (electrolyte without chloride ions)

[0046] 2Cl - -2e→Cl2 (electrolyte containing chloride ions)

[0047] Electrolysis cathode: 2H + +2e → H2 and / or Cu 2+ +2e→Cu

[0048] The oxygen and / or chlorine generated by electrolysis at the electrolytic anode will also undergo the following chemical reaction with oxalic acid and / or oxalate in the acidic filtrate: H2C2O4+Cl2→2HCl+2CO2↑ CuC2O4+Cl2→CuCl2+2CO2↑

[0049] From the above chemical reaction formula, electrochemical oxidation reaction is carried out to acidic filtrate using electrolyzer, and oxalate and / or insoluble oxalate impurities in acidic filtrate can be effectively eliminated.At the same time, the applicant has also found through a large number of experiments that, because the electrochemical oxidation scheme is mainly used for direct electrochemical oxidation of oxalic acid and / or oxalate by electrolytic anode, when acidic filtrate only has trace oxalic acid and / or oxalate, the chance of needing to remove the object contacting electrolytic anode is smaller, and the efficiency of electrochemical oxidation is lower.Therefore, when taking electrochemical oxidation scheme, it is preferred to use a combination of electrochemical oxidation and oxidant oxidation to oxidize acidic filtrate.In addition, the electrolyte containing nitric acid easily damages electrolytic anode, and divalent tin is easily oxidized to insoluble tin dioxide after contacting electrolytic anode, so the acidic filtrate obtained by nitric acid type tin stripping waste liquid preferably adopts the above-mentioned scheme of using oxidant and acidic filtrate to carry out oxidation reaction.

[0050] When the present invention uses an oxidant to carry out an oxidation reaction with the acidic filtrate, the chemical reactions of the oxalic acid impurities in the acidic filtrate with various oxidants are as follows: H2C2O4+O3→2CO2↑+O2↑+H2O 2H2C2O4+O2→4CO2↑+2H2O H2C2O4+Cl2→2CO2↑+2HCl H2C2O4+H2O2→2CO2↑+2H2O 6H2C2O4+2Na2CO3·3H2O2→2Na2CO3+12CO2↑+12H2O H2C2O4+2NaClO3+2H + →2Na + +2CO2↑+2ClO2+2H2O H2C2O4+2NaClO4+H + →2Na ++2CO2↑+2ClO2+O2↑+2H2O H2C2O4+Na2S2O8 2- →H2SO4+Na2SO4+2CO2↑ H2C2O4+(NH4)2S2O8→H2SO4+(NH4)2SO4+2CO2↑ 5H2C2O4+2ClO2→2HCl+4H2O+10CO2↑

[0051] Similarly, the insoluble copper oxalate or stannous oxalate in the acidic filtrate undergoes an oxidation reaction with the oxidant, for example: 3CuC2O4+NaClO3+6HCl→3CuCl2+NaCl+3H2O+6CO2↑ SnO+2HNO3→Sn(NO3)2+H2O

[0052] The acidic filtrate contains a low concentration of metal ions, with oxalate ions being the primary reducing agent. This effectively prevents the oxidant from being consumed by other reducing agents, such as low-valent metal ions, and allows the oxidant to primarily oxidize and eliminate the oxalate ions in the reaction solution. During the chemical reaction, the oxidant also simultaneously oxidizes organic impurities in the acidic filtrate, degrading them and preventing the accumulation of organic impurities in the recycled acid solution and the formation of colloids. During the reaction, the oxidant partially generates chlorine dioxide, which decomposes into chloric acid and hypochlorous acid upon contact with water. Upon contact with hot water, it decomposes into hypochlorous acid, chlorine, and oxygen, all of which can participate in the oxidation reaction.

[0053] The present invention can be improved as follows: When an oxidant is used to oxidize the acidic filtrate, the reaction can be carried out at room temperature, under heating, or under cooling conditions, depending on the oxidizing ability of the oxidant in the reaction solution. Preferably, when it is found that the oxidation reaction rate of the oxidant is lower than the process design requirements, the reaction temperature of the reaction solution is adjusted to meet the process requirements. Preferably, when the oxidant is hydrogen peroxide, the operating temperature of the reaction solution is controlled at 50°C to 95°C, preferably 65°C to 90°C. When ozone is used for the oxidation reaction, the operating temperature of the reaction solution is controlled at 3°C ​​to 25°C to allow more ozone to dissolve in the reaction solution for the oxidation reaction.

[0054] The applicant also found that although the sulfuric acid type micro-etching solution itself contains hydrogen peroxide or sodium persulfate oxidant, and the nitric acid type tin stripping solution itself contains oxidizing nitric acid, it is difficult for these oxidants to react and eliminate oxalate radicals at their own concentrations. Therefore, if the solution of oxidizing the acidic filtrate with an oxidant alone is used in step (1), when the oxidant used to oxidize the acidic filtrate obtained by treating the sulfuric acid type micro-etching waste liquid with the oxalic acid method is only hydrogen peroxide or persulfate and its concentration is less than or equal to the corresponding oxidant concentration in the sulfuric acid type micro-etching solution used in the work, or when the oxidant used to oxidize the acidic filtrate obtained by treating the nitric acid type tin stripping waste liquid with the oxalic acid method is only nitric acid and its concentration is less than or equal to the nitric acid concentration in the nitric acid type tin stripping solution used in the work, the oxidation reaction in step (1) needs to be supplemented with heating to remove the oxalate radical impurities, preferably heated to ≥55°C.

[0055] The concentration of each compound component or one of the ions contained in the regenerated metal etching solution obtained in step (2) meets the process requirements for the production and use of the metal etching solution. When the regenerated metal etching solution is reused for acid etching, it is the regenerated etching sub-liquid.

[0056] The present invention prepares the acidic filtrate or the oxidized acidic filtrate to accelerate the oxidation reaction in step (1) and / or to ensure that the concentration of the compound component or one of the ions contained in the compound component that changes in concentration during the preparation process or the reaction process after preparation meets the process requirements in the regenerated metal etching solution. When preparing the acidic filtrate, at least one of an inorganic acid, an inorganic salt, other components of the acidic metal etching solution, and an oxidation catalyst is added to the acidic filtrate. The oxidation catalyst is any oxidation catalyst in the prior art. When preparing the oxidized acidic filtrate, the preparation is carried out according to the components of the acidic metal etching solution used in production; specifically, at least one of an inorganic acid, an organic acid, an inorganic salt, an organic acid salt, and other additives required in production is added, and the concentration of the compound component or one of the ions contained in the compound component that changes in concentration during the preparation process meets the concentration requirements of the acidic metal etching solution used in production. Among them, when the acidic filtrate or the oxidized acidic filtrate contains a certain inorganic salt, organic salt, or organic impurity that exceeds the upper limit set by the process, the solubility of these substances in the solution can be reduced by adding inorganic acid, so that they are saturated and precipitated and filtered out to prepare a regenerated metal corrosion solution that meets the use requirements.

[0057] The present invention can be improved as follows: during the oxidation reaction in step (1), the redox potential of the reaction solution is monitored, and when the oxidation reaction rate is lower than the requirements of the process design, the electrolysis current and / or the amount of oxidant added are adjusted.

[0058] The present invention can be improved as follows: when the acidic filtrate is oxidized by using an oxidant, the reaction mixture is stirred to make the reactants uniform and improve the reaction efficiency.

[0059] The present invention can be improved as follows: when the acidic filtrate is subjected to an oxidation reaction in an electrolytic cell, a redox potentiometer is used to monitor the anolyte. When the acidic filtrate is subjected to an oxidation reaction in an oxidant, a thermometer is used for control, and / or the oxidant feed is controlled by using a redox potentiometer, an oxidant automatic titrator, a potentiometer, or a metering feed pump, so that the oxidation reaction proceeds safely.

[0060] The present invention can also be improved as follows: when an oxidant is used to carry out an oxidation reaction under heating conditions, the acidic water vapor released during the heating reaction is cooled and refluxed into the oxidation reaction tank using a condenser reflux pipe to reduce environmental pollution caused by overflow of acid gas.

[0061] The present invention can also be improved as follows: the oxidizing gas released during the oxidation reaction is introduced back into the reaction liquid through a gas-liquid mixer to participate in the oxidation reaction again.

[0062] The present invention can also be improved as follows: the oxidation reaction adopts a front- and back-stage progressive oxidation treatment process, that is, the oxidizing gas escaped from the front-stage oxidation reaction is used as the oxidant of the back-stage oxidation reaction and is introduced into the reaction liquid of the back-stage oxidation reaction, which reduces the processing cost and reduces environmental pollution.

[0063] The present invention can also be improved as follows: the new oxalate filter residue is subjected to a primary water washing or a primary dilute acid washing, and the primary washing waste liquid obtained contains a certain amount of acid liquid and copper and tin salts. The primary washing waste liquid can be mixed with the acidic filtrate to carry out an oxidation reaction together. After the acidic filtrate is oxidized, it can be directly or adjusted and fed back to the corresponding production line for recycling.

[0064] The process setpoint for the oxalate in the acidic filtrate after oxidation treatment is determined based on actual production requirements and the degree of negative impact of residual oxalate that is acceptable to the process. After extensive testing, the inventors determined that the qualified quality control requirement for the regenerated metal etching solution recycled into the circuit board acid etching production line is an oxalate impurity content of less than 6 g / L, preferably less than 2 g / L, and more preferably a non-detected (ND) result, i.e., an oxalate impurity content of less than 2 mg / L.

[0065] The second object of the present invention is achieved through the following technical solutions.

[0066] A device for pre-treating recycled acid solution to remove oxalate radicals comprises a precipitation reaction tank and a solid-liquid separator, and is characterized in that it also comprises an electrolytic tank and / or an oxidation reaction tank; wherein the precipitation reaction tank is connected to the solid-liquid separator via a pump and a pipeline, and the solid-liquid separator is connected to the electrolytic tank and / or the oxidation reaction tank via a pump and a pipeline.

[0067] The precipitation reaction tank is used for reacting the acidic waste liquid containing copper and / or tin with oxalic acid and / or soluble oxalate to generate new oxalate precipitate.

[0068] The solid-liquid separator is used to separate the solid-liquid mixture from the precipitation reaction tank. The solid-liquid separator is a filter press, a filter, or a centrifuge.

[0069] The electrolytic cell is used to remove oxalate and / or insoluble oxalate impurities and organic impurities in the acidic filtrate through electrochemical reaction. The electrolytic cell is provided with an electrolytic cell divider, which is divided into an anode cell region and a cathode cell region. The electrolytic cell divider is at least one of a cation exchange membrane, an anion exchange membrane, a proton membrane, a bipolar membrane, a reverse osmosis membrane, a non-ion selective membrane, and a filter cloth. Preferably, a cation exchange membrane and / or a filter cloth is used.

[0070] The anode material of the electrolytic cell is at least one of an electrode with a surface of gold and / or platinum, a titanium-based coating electrode, and conductive graphite, and the cathode material is at least one of an electrode with a surface of titanium and / or copper, stainless steel, and conductive graphite.

[0071] The oxidation reaction tank is used to oxidize the acidic filtrate to remove oxalate and organic impurities. A thermometer and a hot / cold temperature exchanger are preferably installed within the tank, allowing the acidic filtrate to undergo oxidation with the oxidant under heating or cooling conditions. The thermometer is used to monitor the reaction temperature of the reaction solution. The hot / cold temperature exchanger is used to exchange heat with the reaction solution during the oxidation reaction to control the temperature, ensuring a safe and efficient oxidation reaction.

[0072] The present invention can be improved as follows: a temporary storage tank is added for temporarily storing materials or serving as a chemical reaction tank under normal pressure. The temporary storage tank is connected between the solid-liquid separator and the electrolytic cell and / or oxidation reaction tank, and feeds the acidic filtrate directly or after mixing into the electrolytic cell and / or oxidation reaction tank; and / or is connected to the electrolytic cell and / or oxidation reaction tank to temporarily store or mix the oxidized acidic filtrate.

[0073] The present invention can be improved as follows: in addition to installing a thermometer and a hot and cold temperature exchanger in the oxidation reaction tank, an oxidation-reduction potentiometer (ORP meter), an oxidant automatic titrator, and a potentiometer are also installed to control the feeding of the oxidant during the oxidation reaction, or to use a metering feeding pump to control the feeding of the oxidant according to the process requirements. The oxidant automatic titrator is an instrument that uses a program to simulate the chemical titration detection process of a laboratory technician to intermittently measure the concentration of the oxidant in the acidic solution, and is preferably dedicated to the detection of the oxidant concentration in the sulfuric acid solution. The potentiometer is a potentiometer structure composed of a copper rod and a graphite conductive rod, which uses the principle of galvanic corrosion to detect the concentration of the oxidant in the acidic solution; it uses a copper rod as an anode and a graphite conductive rod as a cathode, and the two electrodes are connected by a conductive wire. A voltmeter is connected in series in the connection line for display control. The greater the potential difference, the higher the oxidant concentration.

[0074] The present invention can also be improved as follows: to save production materials and reduce the storage of chemicals, at least one of the electrolytic cell, the oxidation reaction cell, and the temporary storage cell connected to the electrolytic cell and / or the oxidation cell is connected to the circuit board acid etching production line through a pump and a pipeline, and the regenerated metal etching liquid is transported to the tin stripping production line, the etching machine, and the micro-etching machine for on-site production reuse. The circuit board acid etching production line can be a tin stripping production line, an etching machine, and a micro-etching machine, all of which are market products of the prior art, and serve as production equipment for processing circuit boards using recycled acid liquid.

[0075] The present invention can also be improved as follows: at least one of an ORP meter, a hydrometer, a liquid level meter, and a thermometer is installed in the electrolytic cell to ensure that the electrochemical reaction process is safe and controllable.

[0076] The present invention can also be improved as follows: a condensation reflux pipe is added to the oxidation reaction tank so that the acid gas escaping from the reaction liquid is cooled and refluxed into the oxidation reaction tank to reduce environmental pollution.

[0077] The present invention can also be improved as follows: a gas-liquid mixer is added to the electrolytic cell and / or oxidation reaction cell to redirect the oxidizing gas escaping from the cell back into the oxidation reaction liquid for utilization or waste gas treatment. The gas-liquid mixer can be a vacuum ejector or a spray tower.

[0078] The present invention can also be improved as follows: a combination of an electrolytic cell and an oxidation reaction cell or a combination of two or more oxidation reaction cells is provided to constitute a front- and rear-stage progressive oxidation reaction treatment device, wherein the front-stage electrolytic cell / oxidation reaction cell is connected to the rear-stage oxidation reaction cell through a gas pipeline, so that the rear-stage oxidation reaction liquid absorbs the oxidizing gas escaped from the front-stage oxidation reaction liquid and is used as the rear-stage oxidant, thereby achieving the purpose of fully utilizing the oxidant and reducing the treatment cost.

[0079] The present invention can also be improved as follows: a refrigerator or a heater is added to provide cooling or heating for the cold and hot temperature exchanger.

[0080] The present invention can also be improved as follows: each tank can be provided with an agitator for uniformly stirring the solution, which can be an impeller agitator or a liquid flow agitator.

[0081] The present invention can also be improved as follows: an automatic logic program controller is added and connected to the sensor and / or metering feeding pump provided in the device to form a combination; the sensor is selected from at least one of a thermometer, a liquid level meter, a redox potentiometer, a acidity meter, a pH meter, a photoelectric colorimeter, a hydrometer, an oxidant automatic titrator, and a potentiometer; the sensor signal output end of the sensor is connected to the sensor signal input end of the automatic logic program controller, and the control signal output end of the automatic logic program controller is connected to at least one control signal output end of the valve, pump, feeding equipment, electrolysis power supply, etc. of the device of the present invention, so that the device can operate safely and automatically according to the pre-programmed program.

[0082] The present invention can also be improved as follows: an overflow buffer tank is added to solve the problem of liquid flow between tanks.

[0083] The present invention can also be improved as follows: a new oxalate filter residue washing tank is added for washing with water to produce a pure insoluble new oxalate product.

[0084] Compared with the prior art, the present invention has the following beneficial effects:

[0085] 1) The present invention pre-treats oxalate and / or other organic impurities in the acidic filtrate obtained by treating acidic waste liquids of three acidic metal etching solutions commonly used in the printed circuit board industry with an oxalic acid method, so that the oxalate content index and COD index of the recycled acidic filtrate meet production and use requirements. This effectively solves the defects of the acidic filtrate obtained by treating the acidic waste liquid with the existing oxalic acid method, such as insoluble oxalate clogging the etching solution nozzle, affecting production, adhering to the circuit board and reducing the product quality of the circuit board, and corroding titanium parts in the production line. The acidic filtrate obtained by treating the acidic waste liquid with the oxalic acid method can be recycled without affecting etching production or reducing the etching quality of the circuit board. This not only better achieves the goals of environmentally friendly recycling, energy conservation and emission reduction, but also reuses production raw materials to reduce production material costs. Moreover, it enables the oxalic acid method to be better promoted and applied in the treatment of acidic waste liquid.

[0086] 2) The present invention performs pre-treatment on the acidic filtrate to remove oxalate and / or other organic impurities, thereby achieving the effect of turning waste into treasure and realizing the production goals of material recycling, energy saving and emission reduction.

[0087] 3) The present invention performs pre-treatment on the acidic filtrate to remove oxalate and / or other organic impurities, and no new pollution source is added during the process.

[0088] 4) The present invention pre-treats the acidic filtrate to remove oxalate and / or other organic impurities, thereby overcoming the drawbacks of existing oxalic acid methods for treating acidic wastewater and effectively meeting the technical requirements for recycling wastewater from circuit board production. Compared with chemical treatment methods using copper hydroxide or copper carbonate, the present oxalic acid method can achieve acid recycling. Compared with electrolysis, the oxalic acid method has lower equipment investment costs and produces higher economic benefits.

[0089] 5) The process of the present invention is simple, safe and reliable to operate, and is a low-energy consumption, environmentally friendly treatment and recycling process. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] FIG1 is a flow chart of an apparatus and process for pre-treating recycled acid solution to remove oxalate according to Example 1 of the present invention.

[0091] FIG2 is a flow chart of an apparatus and process for pre-treating recycled acid solution to remove oxalate according to Example 2 of the present invention.

[0092] FIG3 is a flow chart of an apparatus and process for pre-treating recycled acid solution to remove oxalate according to Example 3 of the present invention.

[0093] FIG4 is a flow chart of an apparatus and process for pre-treating recycled acid solution to remove oxalate according to Example 4 of the present invention.

[0094] FIG5 is a schematic diagram of an apparatus and process for pre-treating the recycled acid solution to remove oxalate according to Example 5 of the present invention.

[0095] FIG6 is a flow chart of an apparatus and process for pre-treating recycled acid solution to remove oxalate according to Example 6 of the present invention.

[0096] FIG7 is a flow chart of an apparatus and process for pre-treating recycled acid solution to remove oxalate according to Example 7 of the present invention.

[0097] Reference numerals:

[0098] 1-precipitation reaction tank, 2-solid-liquid separator, 3-oxidation reaction tank, 4-hot and cold temperature exchanger, 5-tin stripping production line, 6-etching machine, 7-vacuum ejector, 8-spray tower, 9-temporary storage tank, 10-impeller agitator, 11-liquid flow agitator, 12-sensor, 13-automatic program logic controller, 14-overflow buffer tank, 15-valve, 16-pump, 17-acidic waste liquid, 18-acidic filtrate, 19-oxidant, 20-oxalic acid, 21-soluble oxalate, 22-new oxalate filter residue, 23-oxidized acidic filtrate, 24-tin stripping or etching processed circuit board, 25 -nitric acid, 26-sulphuric acid, 27-hydrochloric acid, 28-additives, 29-electrolytic cell, 30-metal copper, 31-sodium hydroxide solution, 32-electrolysis power supply, 33-condensation reflux pipe, 34-clean water, 35-oxidizing gas, 36-regenerated metal corrosion solution, 37-barium chloride, 38-catholyte, 39-metering feed pump, 40-oxidation reaction solution, 41-electrolytic cell separator, 42-electrolysis anode, 43-electrolysis cathode, 44-new oxalate filter residue cleaning tank, 45-acidic ferric chloride solution, 46-refrigeration machine, 47-heater, 48-ferric sulfate, 49-exhaust gas treatment tank. DETAILED DESCRIPTION

[0099] The present invention will be further described below through specific embodiments.

[0100] The precipitation reaction tank 1M used in the embodiment of the present invention 3 , Oxidation reaction tank 1M 3 、The electrolytic cell volume is 2M 3 (The anode tank area and cathode tank area are 1M each 3 ), vacuum ejectors, spray towers, condenser reflux pipes, temporary storage tanks, overflow buffer tanks, and agitators are all products manufactured by Yegao Environmental Protection Equipment Manufacturing Co., Ltd. in Foshan, Guangdong, China. Sensors, PLCs, microetchers, etchers, tin stripping lines, solid-liquid separators, refrigerators, heaters, valves, pumps, and chemical raw materials are all commercially available products. In addition to the above, those skilled in the art may also select other products with similar performance to those listed above according to conventional selection, and all of these products can achieve the objectives of the present invention.

[0101] Example 1

[0102] As shown in FIG1 , the apparatus and process flow for pre-treating recycled acid solution to remove oxalate according to Example 1 of the present invention are shown. The apparatus includes a precipitation reaction tank 1, a solid-liquid separator 2, an oxidation reaction tank 3, a hot and cold temperature exchanger 4, an impeller stirrer 10, a sensor 12, three temporary storage tanks, a heater 47, a valve, and a pump.

[0103] The precipitation reaction tank 1 is connected to the solid-liquid separator 2 through a pump 16-1 and a pipeline. The solid-liquid separator 2 is connected to the oxidation reaction tank 3 through a pump 16-2 and a pipeline. The oxidation reaction tank 3 is connected to the temporary storage tank 9-3 through a pump 16-3 and a pipeline.

[0104] The solid-liquid separator 2 is a filter press.

[0105] The oxidation reaction tank 3 is equipped with a sensor 12 and a hot-cold temperature exchanger 4 ; the sensor 12 is a thermometer, and the hot-cold temperature exchanger 4 is provided with a heater 47 .

[0106] The acidic waste liquid 17 is a nitric acid type tin stripping waste liquid, the main components of which are nitric acid, tin nitrate and a small amount of copper nitrate. It is temporarily stored in the temporary storage tank 9-1 and sent to the precipitation reaction tank 1 through a pump and a pipeline.

[0107] The acidic filtrate 18 is mainly composed of nitric acid, which contains a small amount of oxalic acid and trace amounts of insoluble tin oxalate and copper oxalate; the new oxalate filter residue 22 obtained by the oxidation reaction is stannous oxalate and a small amount of copper oxalate.

[0108] The additive 28 is a tin stripping solution additive.

[0109] In this example, the following steps are used to eliminate the oxalate impurities in the acidic filtrate before recycling.

[0110] 1. Start pump 16-1 to quantitatively add acidic waste liquid 17 to precipitation reaction tank 1. Start impeller agitator 10 within the tank and add oxalic acid to precipitation reaction tank 1. The amount of oxalic acid added should be 1:1 times the sum of the reactive equivalents of stannous ions and copper ions in acidic waste liquid 17. This will cause the reaction liquid to produce stannous oxalate and copper oxalate precipitation. Sn(NO3)2+H2C2O4→2HNO3+SnC2O4↓ Cu(NO3)2+H2C2O4→2HNO3+CuC2O4↓

[0111] 2. Start pump 16-2 to send the solid-liquid mixture in precipitation reaction tank 1 to solid-liquid separator 2 for pressure filtration. The resulting filter residue is temporarily stored in temporary storage tank 9-2, while the acidic filtrate 18 is drained into oxidation reaction tank 3;

[0112] Concentrated nitric acid 25 is added to the oxidation reaction tank 3. The hot and cold temperature exchanger 4 and heater 47 are turned on to heat the oxidation reaction liquid from room temperature to 90°C. Since the oxidation reaction liquid is mainly composed of nitric acid, its oxidizing properties are enhanced at high temperatures, oxidizing and removing oxalate impurities. The reaction process lasts for 2 hours, and an oxidized acidic filtrate 23 is obtained. H2C2O4 + 2HNO3 → 2H2O + 2NO2↑ + 2CO2↑

[0113] 3. The oxidized acidic filtrate in the oxidation reaction tank 3 is tested for oxalic acid impurities. After obtaining a qualified result, it is pumped to the temporary storage tank 9-3 for temporary storage.

[0114] 4. Add concentrated nitric acid 25 and additive 28 to the temporary storage tank 9-3 to prepare the regenerated metal etching solution 36, which is reused as a production raw material in the tin stripping production line.

[0115] The process parameters of this embodiment are listed in Table 1. The oxalate concentration of the regenerated metal etching solution 36 was detected to be ND, and the regenerated metal etching solution 36 can be used as a production raw material.

[0116] Example 2

[0117] As shown in FIG2 , the apparatus and process flow for pre-treating recycled acid solution to remove oxalate radicals according to Example 2 of the present invention are shown. The apparatus includes a precipitation reaction tank 1, two solid-liquid separators 2, an oxidation reaction tank 3, a hot and cold temperature exchanger 4, a micro-etching machine 6, two liquid flow agitators, sensors 12 - 1 and 12 - 2, three temporary storage tanks, a condensation reflux pipe 33, a heater 47, valves, and a pump.

[0118] The precipitation reaction tank 1 is connected to the solid-liquid separator 2-1 through a pump 16-2 and a pipeline. The solid-liquid separator 2-1 is then connected to the oxidation reaction tank 3 through a pump 16-3 and a pipeline. The oxidation reaction tank 3 is connected to the temporary storage tank 9-3 through a pump 16-4 and the solid-liquid separator 2-2. The temporary storage tank 9-3 leads to the etching machine 6 through a pump 16-5 and a pipeline.

[0119] The etching machine 6 is a micro-etching machine. The micro-etching process of the circuit board copper surface carried out in the etching machine 6 is to put the micro-etched circuit board 24 into the etching machine 6 for micro-etching, and the output acidic waste liquid 17 is pumped to the temporary storage tank 9-1 through a pipeline for temporary storage.

[0120] The solid-liquid separator 2-1 is a filter press and 2-2 is a filter.

[0121] A condensation reflux pipe 33 is installed at the gas outlet of the oxidation reaction tank 3 , and the condensation reflux pipe 33 is used to cool and reflux the overflowed acid steam from the oxidation reaction tank 3 .

[0122] The precipitation reaction tank 1 and the oxidation reaction tank 3 are provided with liquid flow agitators 11 - 1 and 11 - 2 , respectively.

[0123] The oxidation reaction tank 3 is provided with sensors 12-1 and 12-2, and a hot and cold temperature exchanger 4; the hot and cold temperature exchanger 4 is provided with a heater 47; the sensor 12-1 is a thermometer, and the sensor 12-2 is a meter for detecting hydrogen peroxide concentration by sulfuric acid solution titration method.

[0124] The acidic waste liquid 17 is the copper-containing waste liquid after the micro-etching of sulfuric acid and hydrogen peroxide.

[0125] The acidic filtrate 18 mainly comprises sulfuric acid, hydrogen peroxide and additive 28, and a small amount of oxalic acid and copper oxalate.

[0126] The new oxalate filter residue 22 is copper oxalate.

[0127] The oxidant 19 is 50% hydrogen peroxide, a small amount of ammonium percarbonate and ammonium persulfate.

[0128] The additive 28 is cyclohexylamine.

[0129] In this embodiment, the following steps are used to eliminate oxalate impurities and organic impurities in the acidic filtrate before recycling.

[0130] 1. Start pump 16-2 to quantitatively add acidic waste liquid 17 to precipitation reaction tank 1. After starting liquid flow agitator 11-1, add oxalic acid 20 to initiate copper oxalate precipitation reaction. The amount of oxalic acid added is 0.9 times the weight of the reactive copper ion in the reaction solution.

[0131] 2. After the precipitation reaction is completed, pump 16-3 is started to transfer the solid-liquid mixture in precipitation reaction tank 1 to solid-liquid separator 2-1 for filter press. The resulting acidic filtrate 18 is then drained into oxidation reaction tank 3. The hot and cold temperature exchanger 4, heater 47, and liquid flow agitator 11-2 are started to heat the oxidation reaction liquid from room temperature to 70°C. The acidic vapor is then cooled and refluxed into oxidation reaction tank 3 via condenser reflux line 33. Since the oxidation reaction liquid originally contains hydrogen peroxide, its own oxidizing properties are enhanced at high temperatures, oxidizing and removing the oxalate impurities. The reaction process lasts for 8 hours.

[0132] 3. The oxidized acidic filtrate in the oxidation reaction tank 3 was tested for oxalate impurities, and the result was 6.2 g / L.

[0133] In order to ensure that the acidic filtrate meets the quality requirements for production material recycling after oxidation treatment, the following improvement methods are further adopted: lengthening the reaction time, increasing the oxidant concentration or raising the temperature of the reaction liquid; after the oxalate content of the acidic filtrate is treated by the improved method to meet the process requirements, that is, after the oxalate impurities are less than 6 grams / liter, it is sent to the temporary storage tank 9-3 for temporary storage, and then sulfuric acid 26, oxidant 19 hydrogen peroxide and additives 28 are added to prepare a regenerated metal etching solution 36, which is then returned to the micro-etching machine for use.

[0134] The process parameters of this embodiment are listed in Table 1.

[0135] Example 3

[0136] As shown in FIG3 , the device and process flow for pre-treating the recycled acid solution to remove oxalate according to Example 3 of the present invention are shown. The device includes a precipitation reaction tank 1, two solid-liquid separators 2, an oxidation reaction tank 3, a hot and cold temperature exchanger 4, an etching machine 6, two liquid flow agitators, sensors 12 - 1 and 12 - 2, three temporary storage tanks, a processing circuit board 24, a condensation reflux pipe 33, a heater 47, a valve and a pump.

[0137] In this embodiment, the connection method of the precipitation reaction tank 1, the solid-liquid separators 2-1 and 2-2, the oxidation reaction tank 3, the temporary storage tank, and the etching machine 6 is the same as that of Example 2.

[0138] The precipitation reaction tank 1 and the oxidation reaction tank 3 are respectively provided with liquid flow agitators 11-1 and 11-2.

[0139] The etching machine 6 is a micro-etching machine. The micro-etching process of the circuit board copper surface carried out in the etching machine 6 is to put the micro-etched circuit board 24 into the etching machine 6 for micro-etching, and the output acidic waste liquid 17 is pumped to the temporary storage tank 9-1 through a pipeline for temporary storage.

[0140] The solid-liquid separator 2-1 is a filter press and 2-2 is a filter.

[0141] A condensation reflux pipe 33 is installed at the gas outlet of the oxidation reaction tank 3 , and the condensation reflux pipe 33 is used to cool and reflux the overflowed acid steam from the oxidation reaction tank 3 .

[0142] The oxidation reaction tank 3 is provided with sensors 12-1 and 12-2, and a hot and cold temperature exchanger 4; the hot and cold temperature exchanger 4 is provided with a heater 47; the sensor 12-1 is a thermometer, and the sensor 12-2 is a potentiometer composed of a copper rod and a graphite conductive rod to detect the persulfate concentration.

[0143] The acidic waste liquid 17 is a micro-etching liquid of sulfuric acid, ferric sulfate and persulfate, which contains copper and iron after use.

[0144] The acidic filtrate 18 mainly contains sulfuric acid, ferric sulfate, a small amount of copper sulfate, persulfate and a trace amount of oxalic acid and copper oxalate.

[0145] The new oxalate filter residue 22 is copper oxalate.

[0146] The oxidant 19 is a mixture of sodium persulfate, potassium persulfate and ammonium persulfate.

[0147] In this embodiment, the following steps are used to eliminate the oxalate impurities in the acidic filtrate by oxidation reaction before reuse.

[0148] 1. Start pump 16-2 to quantitatively add acidic waste liquid 17 to precipitation reaction tank 1. Start liquid flow agitator 11-1 and add oxalic acid 20 to initiate copper oxalate precipitation reaction. The amount of oxalic acid added is 0.5 times the weight of the reactive copper ion in the reaction solution.

[0149] 2. After the precipitation reaction is completed, pump 16-3 is started to transfer the solid-liquid mixture in precipitation reaction tank 1 to solid-liquid separator 2-1 for filter pressing. The resulting acidic filtrate 18 is then drained into oxidation reaction tank 3. Heater 47, hot and cold temperature exchanger 4, and liquid agitator 11-2 are then turned on to heat the oxidation reaction liquid from room temperature to 60°C. Sodium persulfate, an oxidizing agent 19, is then added to the oxidation reaction liquid and the reaction is continued for 36 hours. During the reaction, the vapor of the acidic filtrate is cooled by condensation reflux pipe 33 and refluxed into oxidation reaction tank 3.

[0150] 3. The oxidized acidic filtrate in the oxidation reaction tank 3 was sampled and tested. The result of the oxalate impurity content was 3.2 g / L, which was barely considered to meet the process requirements. Therefore, the pump 16-4 was turned on to pump the solution in the oxidation reaction tank 3 to the temporary storage tank 9-3.

[0151] 4. Supplement the solution in the temporary storage tank 9-3 with sulfuric acid 26, oxidant 19 and ferric sulfate 48 to prepare a regenerated metal corrosion solution 36.

[0152] 5. According to the micro-etching process requirements, start the pump 16-5 to add the regenerated metal etching liquid 36 into the etching machine 6 for recycling.

[0153] The process parameters of this embodiment are listed in Table 1.

[0154] Example 4

[0155] As shown in FIG4 , the device and process flow for pre-treating the recycled acid solution to remove oxalate according to Example 4 of the present invention are shown. The device mainly includes a precipitation reaction tank 1, two solid-liquid separators 2, an etching machine 6, four temporary storage tanks 9, four sensors, an overflow buffer tank 14, an electrolytic cell 29, an exhaust gas treatment tank 49, valves and a pump.

[0156] The electrolytic cell 29 has an electrolytic cell separator 41 that separates it into an anode cell area and a cathode cell area. The electrolytic cell separator 41 is a bipolar membrane. The electrolytic anode 42 is a multi-stacked titanium-based coated electrode, and the electrolytic cathode 43 is a titanium plate, which are respectively connected to the positive and negative poles of the electrolytic power supply 32.

[0157] The precipitation reaction tank 1 is connected to the temporary storage tank 9-3 through the solid-liquid separators 2-1 and 2-2; the temporary storage tank 9-3 is connected to the anode tank area of ​​the electrolytic cell 29 to transport the acidic filtrate thereto; the anode tank area of ​​the electrolytic cell 29 is connected to the etching machine 6 through the temporary storage tank 9-4.

[0158] The solid-liquid separators 2-1 and 2-2 are a filter press and a filter respectively.

[0159] In this embodiment, the acidic filtrate is subjected to electrochemical oxidation treatment in the anode region of the electrolytic cell 29. The treated oxidized acidic filtrate 23 is pumped to the temporary storage tank 9-4 for temporary storage. The catholyte 38 in the cathode region of the electrolytic cell 29 is the etching waste liquid 17.

[0160] The etching machine 6 is provided with sensors 12-1, 12-2, and 12-3, and the anode tank area of ​​the electrolytic cell 29 is provided with a sensor 12-4; the sensor 12-1 is a pH meter, 12-2 is a hydrometer, 12-3 is an ORP meter, and 12-4 is an ORP meter.

[0161] The etching process in the etcher 6 is as follows: A circuit board 24 is placed into the etcher for etching. The etcher controls the addition of a mixture of hydrochloric acid and ferric chloride using a pH meter 12-1, the addition of solution 23 using a hydrometer 12-2, and the addition of the oxidizing agent sodium chlorate using an ORP meter 12-3. The acidic waste liquid 17 produced during the etching process is piped to a temporary storage tank 9-1 for temporary storage, and then from there to the precipitation reaction tank 1.

[0162] The acidic waste liquid 17 is an acidic copper chloride iron-containing etching waste liquid, the main components of which are hydrochloric acid, copper chloride and ferric chloride, wherein the copper ion concentration is 130 g / L.

[0163] The acidic filtrate 18 mainly contains hydrochloric acid, ferric chloride, a small amount of cupric chloride, oxalic acid, copper oxalate and organic impurities in the ink resist layer.

[0164] The main component of the new oxalate filter residue 22 is copper oxalate.

[0165] The oxidant 19 is sodium chlorate, which is used to regenerate the etching agents CuCl2 and FeCl3 in the etching machine.

[0166] In this embodiment, the following steps are used to eliminate oxalate and organic impurities in the acidic filtrate by oxidation reaction before reuse.

[0167] 1. Start pump 16-2 to quantitatively add acidic waste liquid 17 to precipitation reaction tank 1. After turning on impeller agitator 10 in the tank, add oxalic acid 20 to initiate copper oxalate precipitation reaction. The amount of oxalic acid added is 0.6 times the weight of the reactive copper ion in the reaction solution.

[0168] 2. Start pump 16-3 to send the solid-liquid mixture in the precipitation reaction tank 1 to solid-liquid separators 2-1 and 2-2 for pressure filtration and fine filtration, and drain the obtained acidic filtrate 18 to temporary storage in temporary storage tank 9-3.

[0169] 3. According to the process requirements, the acidic filtrate 18 in the temporary storage tank 9-3 is added to the anode tank area of ​​the electrolytic tank 29. The electrolytic power supply 32 is turned on to allow the oxalate in the electrolyte to be adsorbed around the anode and collide with the anode to cause an electrochemical oxidation reaction. During the reaction, the working current of the electrolytic power supply is controlled by the ORP meter. The ORP value of the anode electrolyte is controlled to 680mV and the electrochemical oxidation reaction lasts for 36 hours. The electrochemical reaction is as follows: Anode: C2O4 2- -2e→2CO2 2Cl - -2e→Cl2 cathode: Cu 2+ +2e→Cu Fe 3+ +1e→Fe 2+

[0170] Chemical reactions in the anolyte: H2C2O4+Cl2→2HCl+2CO2↑ 2FeCl2+Cl2→2FeCl3 2FeCl3+H2C2O4→2FeCl2+2HCl+2CO2↑

[0171] 4. The oxidized acidic filtrate 23 in the electrolytic cell 29 is pumped to the temporary storage tank 9-4 for temporary storage. The oxalate concentration is detected to be 0.63 g / L. The impurity detection result is considered to be barely acceptable and is processed in a qualified manner. That is, it is directly returned to the etching machine 6 for recycling according to the process requirements.

[0172] 5. During the entire operation, the acidic waste gas emitted from each tank is drained into the tail gas treatment tank 41 for environmental protection treatment.

[0173] The process parameters of this embodiment are listed in Table 1.

[0174] Example 5

[0175] As shown in FIG5 , the apparatus and process flow for pre-treating the recycled acid solution to remove oxalate according to Example 5 of the present invention are shown. The apparatus includes a precipitation reaction tank 1, multiple solid-liquid separators, an oxidation reaction tank 3, an etching machine 6, a vacuum ejector 7, multiple temporary storage tanks, an agitator 10, two overflow buffer tanks, seven sensors 12, a programmable logic controller 13, an electrolytic cell 29, an exhaust gas treatment tank 49, valves, and a pump.

[0176] The electrolytic cell 29 is provided with an electrolytic cell separator 41, which separates it into an anode cell area and a cathode cell area. The electrolytic cell separator 41 is a cation exchange membrane. The electrolytic anode 42 is a platinum-plated electrode, and the electrolytic cathode 43 is copper, which are respectively connected to the positive and negative poles of the electrolytic power supply 32.

[0177] Precipitation reaction tank 1 is connected to temporary storage tank 9-3 via solid-liquid separator 2-1, overflow buffer tank 14-2, and solid-liquid separator 2-2. Temporary storage tank 9-3 is connected to the anode tank area of ​​electrolytic cell 29, supplying acidic filtrate thereto; the anode tank area is then connected to oxidation reaction tank 3 via temporary storage tank 9-4. Oxidation reaction tank 3 is connected to temporary storage tank 9-5 via solid-liquid separator 2-3, and then to etching machine 6.

[0178] The solid-liquid separator 2-1 is a filter press, and the solid-liquid separators 2-2 and 2-3 are filters.

[0179] The oxidation reaction tank 3 is provided with a vacuum ejector 7 as an oxidizing gas collection and reflux device; the vacuum ejector 7 receives the chlorine gas escaping from the anode tank area of ​​the electrolytic cell 29 through a gas pipeline and drains it into the subsequent oxidation reaction tank 3 to participate in the chemical reaction.

[0180] The etching process in the etching machine 6 is as follows: the etched circuit board 24 is put into the etching machine for etching, and the produced acidic waste liquid 17 is pumped to the temporary storage tank 9-1 through a pipeline for temporary storage, and then sent to the precipitation reaction tank 1 from the temporary storage tank 9-1.

[0181] The acidic waste liquid 17 is acidic copper chloride etching waste liquid, wherein the main components are hydrochloric acid, copper chloride, and a trace amount of sodium chloride.

[0182] The acidic filtrate 18 is mainly composed of hydrochloric acid and contains a small amount of copper chloride, a trace amount of oxalic acid and organic impurities in the resist layer.

[0183] The soluble oxalate 21 is sodium oxalate.

[0184] The oxidant 19-1 is sodium chlorate, 19-2 is chlorine gas, and 19-3 is a mixed solution of sodium perchlorate and chlorine dioxide.

[0185] Sensors 12-1, 12-2, and 12-3 are provided in the etching machine 6, a sensor 12-4 is provided in the anode tank area of ​​the electrolytic cell 29, a sensor 12-5 is provided in the cathode tank area, and sensors 12-6 and 12-7 are provided in the oxidation reaction tank 3; the sensor 12-1 is an ORP meter, 12-2 is a hydrometer, 12-3 is a acidity meter, 12-4 is an ORP meter, 12-5 is a hydrometer, 12-6 is an ORP meter, and 12-7 is a liquid level meter.

[0186] The automatic logic program controller 13 is used for automatic operation control of the entire device, receives sensing signals from various sensors, and outputs control signals to the electrolysis power supply and pump.

[0187] In this embodiment, the following steps are used to eliminate the oxalate impurities in the acidic filtrate by oxidation reaction before recycling.

[0188] 1. Connect the entire device to the power supply. The automatic program logic controller collects data from each sensor and transmits it to the controller for processing, and performs industrial control according to the pre-programmed process.

[0189] 2. Pump 16-2 is turned on to quantitatively add acidic waste liquid 17 to the precipitation reaction tank 1. After the impeller agitator 10 in the tank is turned on, a mixture of oxalic acid 20 and soluble oxalate 21 is added to cause a copper oxalate precipitation reaction, wherein the weight of the oxalate added to the mixture is 0.8 times the reactive equivalent number of copper ions in the reaction solution.

[0190] 3. Start pump 16-3 to send the solid-liquid mixture in the precipitation reaction tank 1 to solid-liquid separators 2-1 and 2-2 for pressure filtration and fine filtration, and drain the obtained acidic filtrate 18 to temporary storage in temporary storage tank 9-3.

[0191] 4. Acidic filtrate 18 is added to the anode and cathode regions of the electrolytic cell 29 performing the oxidation reaction in the front stage, and the electrolytic power supply is turned on to operate. Sensor 12-4 controls the working state of the electrolytic power supply and monitors the oxidation reaction process; sensor 12-5 monitors the copper ion concentration at the cathode to prevent hydrogen evolution;

[0192] During the reaction, the anolyte undergoes an oxidation reaction on the oxalate impurities and electrolytically deposits chlorine, while the cathode electrolytically deposits copper. When the sensor 12-4 rises to the set value of 1000mV, the electrolytic power supply 32 operates intermittently to maintain the reaction for 15 hours. After the electrolytic reaction is completed, the pump 16-6 is started to pump the anolyte into the temporary storage tank 9-4 for temporary storage. After the pump 16-6 is shut down, the pump 16-5 is turned on to re-add the acidic filtrate 18 to the anode tank area of ​​the electrolytic tank and the electrolytic power supply is automatically closed to continue the operation.

[0193] 5. The oxidized acidic filtrate 23-1 in the temporary storage tank 9-4 is pumped into the oxidation reaction tank 3. The pump 16-8 is turned on to allow the vacuum ejector 7 to suck the chlorine Cl2 escaping from the previous oxidation reaction liquid 40-1 and part of the tail gas escaping from the oxidation reaction tank 3 itself, and mix them into the oxidation reaction liquid 40-2 in the oxidation reaction tank 3 for oxidation reaction. During the process, the oxidant 19-3 is additionally added to accelerate the elimination of oxalate impurities. The reaction process lasts for 15 hours.

[0194] 6. The sensor 12-6 in the oxidation reaction tank 3 is used to monitor the reaction process. After the reaction is completed according to the time, the pump 16-8 is shut down and the pump 16-9 is started. The solution in the pumping tank is filtered and drained to the temporary storage tank 9-5 for temporary storage. The oxidized acidic filtrate 23-2 that has been oxidized for a total of 30 hours is sampled and tested for the content of oxalate impurities and organic impurities, and the result is qualified.

[0195] 7. According to the process requirements, the oxidized acidic filtrate 23-2 in the temporary storage tank 9-5 is mixed with hydrochloric acid to become a regenerated metal corrosion liquid (i.e., regenerated etching liquid), which can be pumped back to the etching machine 6 for recycling.

[0196] 8. During the operation of the device, the tail gas from each tank is led to the tail gas treatment tank 49 for environmental protection treatment.

[0197] 9. During the operation of the device, the automatic logic program controller 13 controls the addition of the oxidant 19-1 through the sensor 12-1, the sensor 12-3 controls the addition of the regeneration etching sub-liquid, and the sensor 12-2 detects the copper ion concentration.

[0198] The process parameters of this embodiment are listed in Table 1.

[0199] Example 6

[0200] As shown in FIG6 , the device and process flow for pre-treating the recycled acid solution to remove oxalate ions according to Example 6 of the present invention are shown. The device includes a precipitation reaction tank 1, five solid-liquid separators 2, an oxidation reaction tank 3, a hot and cold temperature exchanger 4, an impeller stirrer 10, an oxidation reaction tank sensor 12, a condensation reflux pipe 33, five temporary storage tanks, a new oxalate residue cleaning tank 44, a heater 47, valves, and a pump.

[0201] Temporary storage tank 9-1 temporarily stores acidic wastewater 17 and is connected to precipitation reaction tank 1. Precipitation reaction tank 1 is connected to temporary storage tank 9-2 via solid-liquid separator 2-1, solid-liquid separator 2-2, and overflow buffer tank 14. New oxalate residue cleaning tank 44 is also connected to temporary storage tank 9-2 via solid-liquid separator 2-3 and solid-liquid separator 2-4. Temporary storage tank 9-2 is connected to oxidation reaction tank 3 via a pipeline.

[0202] The oxidation reaction tank 3 is equipped with sensors 12-1, 12-2 and 12-3, as well as a hot and cold temperature exchanger 4 and a condensation reflux pipe 33; the hot and cold temperature exchanger 4 is provided with a heater 47; the sensor 12-1 is a thermometer, the sensor 12-2 is an ORP meter, and the sensor 12-3 is a liquid level gauge.

[0203] The solid-liquid separator 2-1 is a centrifuge, the solid-liquid separators 2-2 and 2-3 are filter presses, and the solid-liquid separators 2-4 and 2-5 are filters.

[0204] The acidic waste liquid 17 is acidic copper chloride etching waste liquid, the main components of which are hydrochloric acid, copper chloride, sodium chloride and ammonium chloride. The acidic waste liquid 17 comes from an acidic copper chloride etching machine.

[0205] The acidic filtrate 18 mainly contains hydrochloric acid, a small amount of copper chloride, sodium chloride, ammonium chloride, a trace amount of oxalic acid, copper oxalate, ammonium oxalate and organic impurities.

[0206] The new oxalate filter residue 22 is copper oxalate.

[0207] The temporary storage tank 9 - 4 is loaded with an oxidant 19 , specifically a sodium chlorate solution, which is added to the oxidation reaction tank 3 using a metering pump 39 under the control of the sensor 12 - 2 .

[0208] In this embodiment, the following steps are used to eliminate oxalate impurities and organic impurities in the acidic filtrate by oxidation reaction before reuse.

[0209] 1. The acidic waste liquid 17 in the temporary storage tank 9-1 is quantitatively added to the precipitation reaction tank 1, the impeller stirrer 10-1 is started, and oxalic acid 20 is metered into the precipitation reaction tank 1 to cause a copper oxalate precipitation reaction. The amount of oxalic acid added is 0.4 times the weight of the reactive equivalent number of copper ions in the reaction solution.

[0210] 2. Start the pump 16-3 and the solid-liquid separator 2-1 to separate the solid-liquid mixture in the precipitation reaction tank 1 to obtain copper oxalate of the new oxalate filter residue 22, and the acidic filtrate 18 is pumped to the temporary storage tank 9-2 for temporary storage after fine filtration.

[0211] 3. The new oxalate filter residue 22 is washed with water, and the waste water is pumped back to the temporary storage tank 9-2 for temporary storage.

[0212] 4. Under the control of sensor 12-3, the acidic filtrate 18 in the temporary storage tank 9-2 is added to the oxidation reaction tank 3 for heating reaction. During this process, the metering pump 39 is controlled by sensor 12-2 to add the sodium chlorate solution in the temporary storage tank 9-4 to the oxidation reaction tank 3 for oxidation reaction. At the same time, the acidic water vapor escaping from the oxidation reaction tank 3 is collected and refluxed using a condenser. The oxidation reaction process lasts 36 hours.

[0213] 5. According to the process, the acidic filtrate that has been oxidized in the oxidation reaction tank 3 is sampled and tested for oxalate impurity content, and the result is ND, thereby obtaining the oxidized acidic filtrate 23, which is then pumped into the tank 9-5 for temporary storage.

[0214] 6. According to the process design, the solution in the temporary storage tank 9-5 is finely filtered by the filter 2-5 to become the regenerated metal corrosion liquid (i.e., regenerated etching liquid) and is directly recycled.

[0215] The process parameters of this embodiment are listed in Table 1.

[0216] Example 7

[0217] As shown in FIG7 , the apparatus and process flow for pre-treating the recycled acid solution to remove oxalate according to Example 7 of the present invention are shown. The apparatus includes a precipitation reaction tank 1, two solid-liquid separators 2, two oxidation reaction tanks 3, two hot and cold temperature exchangers 4, two vacuum ejectors 7, four temporary storage tanks 9, an impeller agitator 10, two refrigerators 46, and multiple valves and pumps.

[0218] Temporary storage tank 9-1 temporarily stores acidic wastewater 17 and is connected to precipitation reaction tank 1. Precipitation reaction tank 1 is connected to temporary storage tank 9-3 via solid-liquid separator 2-1, overflow buffer tank 14, and solid-liquid separator 2-2. Temporary storage tank 9-3 is connected to oxidation reaction tanks 3-1 and 3-2 via pipelines. Oxidation reaction tanks 3-1 and 3-2 are each connected to temporary storage tank 9-4.

[0219] The oxidation reaction tanks 3-1 and 3-2 are respectively equipped with vacuum ejectors 7-1 and 7-2. The vacuum ejector 7-1 is used to introduce oxidizing gas into the oxidation reaction tank 3-1 to fully mix it with the oxidation reaction liquid. The vacuum ejector 7-2 serves as an oxidizing gas collection and reflux device, receiving the oxidizing gas escaping from the oxidation reaction tank 3-1 through a gas pipeline and directing it to the subsequent oxidation reaction tank 3-2 to participate in the chemical reaction.

[0220] The oxidation reaction tanks 3-1 and 3-2 are both equipped with thermometers and ORP meters. Specifically, sensors 12-1 and 12-3 are thermometers, and sensors 12-2 and 12-4 are ORP meters.

[0221] Oxidation reaction tanks 3-1 and 3-2 are equipped with hot and cold temperature exchangers 4-1 and 4-2, respectively, and are equipped with refrigerants 46-1 and 46-2, respectively. Chillers 46-1 and 46-2 are used to regulate the temperature of the reaction liquids in oxidation reaction tanks 3-1 and 3-2, respectively, to facilitate the dissolution of ozone. Sensor 12-2 controls the amount of ozone added, and sensor 12-4 monitors the oxidation reaction in oxidation reaction tank 3-2.

[0222] The acidic waste liquid 17 is acidic copper chloride etching waste liquid, and its main components are hydrochloric acid and copper chloride.

[0223] The acidic filtrate 18 mainly contains hydrochloric acid, a small amount of copper chloride and a trace amount of oxalic acid.

[0224] The new oxalate filter residue 22 is copper oxalate.

[0225] The oxidant 19 is ozone.

[0226] In this embodiment, the following steps are used to eliminate oxalate impurities and organic impurities in the acidic filtrate by oxidation reaction before reuse.

[0227] 1. Start pump 16-1 to feed acidic waste liquid 17 into precipitation reaction tank 1. Start impeller agitator 10 and add oxalic acid 20 to initiate copper oxalate precipitation reaction. The amount of oxalic acid added is equal to the weight of the reactive copper ion equivalents in the reaction solution.

[0228] 2. After the precipitation reaction is completed, pumps 16-2 and 16-3 are turned on to send the solid-liquid mixture in the precipitation reaction tank 1 to the solid-liquid separators 2-1 and 2-2 for separation. The resulting filter residue is temporarily stored in the tank 9-2, and the acidic filtrate 18 is pumped to the tank 9-3.

[0229] 3. The solution in the temporary storage tank 9-3 is pumped to the oxidation reaction tank 3-1 and tank 3-2 respectively, and the refrigerators 46-1 and 46-2 and the pumps 16-6 and 16-7 are started to cool the oxidation reaction liquid 40-1 to 5°C and the oxidation reaction liquid 40-2 to 8°C; and ozone 19 is added to the oxidation reaction tank 3-1 to carry out an oxidation reaction for 15 hours. During the process, the oxidizing gas 35 escaping from the oxidation reaction tank 3-1, specifically chlorine, ozone, and oxygen, is drained into the subsequent oxidation reaction tank 3-2 and simultaneously participates in the oxidation reaction for 24 hours.

[0230] 4. The solutions in the oxidation reaction tanks 3-1 and 3-2 are sampled and tested respectively. After the oxalate impurity results of the solutions in the two tanks are both ND, the oxidized acidic filtrate 23 in the oxidation reaction tanks 3-1 and 3-2 is pumped into the temporary storage tank 9-4 as the regenerated metal corrosion solution (i.e., regenerated etching sub-liquid) for temporary storage.

[0231] The process parameters of this embodiment are listed in Table 1.

[0232] Table 1 Note: 1. Because the performance of common commercially available ORP meters in sulfuric acid solution systems is difficult to meet the process requirements, an automatic oxidant titrator for sulfuric acid solution or a potentiometer composed of a copper rod and a graphite conductive rod is used to control the addition of the oxidant in the sulfuric acid oxidation reaction.

[0233] 2. ND, which stands for Not Detected, means that the content of the substance being measured is extremely low and exceeds the detection range of the instrument.

[0234] 3. The qualified reuse process standard for the oxalate impurity concentration in the regenerated metal etching solution 36, specifically the qualified reuse process standard for the oxalate impurity concentration in the oxidized acidic filtrate 23, is based on the process parameter values ​​that can meet production conditions summarized by the applicant after long-term experiments and is tentatively determined as the execution standard of the process of the present invention.

Claims

1. A method for removing oxalate by pre-treatment of recycled acid solution, wherein oxalic acid and / or soluble oxalate is added to acidic waste liquid containing copper and / or tin, so that new oxalate precipitate appears in the reaction solution, and then solid-liquid separation is performed to obtain new oxalate filter residue and acidic filtrate; characterized in that: The following steps are also included: (1) subjecting the acidic filtrate to oxidation reaction directly or after preparation, wherein the oxidation reaction time is at least 2 hours, so that the oxalate C2O4 in the acidic filtrate is reduced to 2- Or other organic impurities are partially or completely removed through chemical reactions to obtain an oxidized acidic filtrate; (2) The oxidized acidic filtrate is directly or after being prepared as a regenerated metal corrosion liquid and then fed back to the corresponding circuit board acid corrosion production line for recycling.

2. The method for removing oxalate by pre-treating the recycled acid solution according to claim 1, characterized in that: The acidic filtrate is subjected to oxidation reaction by adopting at least one of the following two methods, so that the content of oxalate in the acidic filtrate after oxidation treatment reaches the use requirement below the process set value: ① Using an electrolytic cell to perform an electrochemical oxidation reaction on the acidic filtrate to obtain an oxidized acidic filtrate; ② Use an oxidant to carry out an oxidation reaction with the acidic filtrate to obtain an oxidized acidic filtrate.

3. The method for removing oxalate by pre-treating the recycled acid solution according to claim 2, characterized in that: The oxidant is specifically at least one of ozone, oxygen, chlorine, hydrogen peroxide, sodium percarbonate, potassium percarbonate, ammonium percarbonate, ammonium persulfate, sodium persulfate, potassium persulfate, sodium chlorate, potassium chlorate, sodium perchlorate, potassium perchlorate, chlorine dioxide, and nitric acid.

4. The method for removing oxalate by pre-treating the recycled acid solution according to claim 3, characterized in that: For the acidic filtrate obtained from the treatment of sulfuric acid type micro-etching waste liquid, at least one of hydrogen peroxide, percarbonate, ozone, oxygen, and persulfate is selected; for the acidic filtrate obtained from the treatment of acidic cupric chloride etching waste liquid, at least one of hydrogen peroxide, chlorate, chlorine, ozone, oxygen, percarbonate, perchlorate, and chlorine dioxide is selected; for the acidic filtrate obtained from the treatment of nitric acid type tin stripping waste liquid, nitric acid is used.

5. The method for removing oxalate by pre-treating the recycled acid solution according to claim 4, characterized in that: When an electrolytic cell is used to carry out an electrochemical oxidation reaction on an acidic filtrate, an electrolytic cell is used which is divided into an anode cell area and a cathode cell area by an electrolytic cell separator, and the acidic filtrate is put into the anode cell area, an aqueous electrolyte solution is used as a cathode electrolyte in the cathode cell area, and then an electrode power supply is turned on to oxidize the acidic filtrate in the anode cell area; the electrolytic cell separator is at least one of a cation exchange membrane, an anion exchange membrane, a reverse osmosis membrane, a bipolar membrane, a proton membrane, a non-ion selective diaphragm and a filter cloth.

6. The method for removing oxalate by pre-treating the recycled acid solution according to claim 5, characterized in that: When electrochemical oxidation is employed, it is combined with an oxidizing agent to oxidize the acidic filtrate.

7. The method for removing oxalate by pre-treating the recycled acid solution according to claim 3 or 6, characterized in that: When it is found that the oxidation reaction rate of the oxidant is lower than the requirements of the process design, the reaction temperature of the reaction liquid is adjusted to meet the process requirements.

8. The method for removing oxalate by pre-treating the recycled acid solution according to claim 7, characterized in that: When preparing the acidic filtrate, at least one of an inorganic acid, an inorganic salt, other components in the acidic metal corrosive liquid and an oxidation catalyst is added to the acidic filtrate; When the oxidized acidic filtrate is prepared, the concentration of the compound component or one of the ions contained in the compound component that changes in concentration during the preparation process reaches the concentration requirement in the production and use of the acidic metal corrosive liquid.

9. The method for removing oxalate by pre-treating the recycled acid solution according to claim 8, characterized in that: When the acidic filtrate is subjected to oxidation reaction in an electrolytic cell, a redox potentiometer is used to monitor the anolyte; When the acidic filtrate is subjected to oxidation reaction by using an oxidant, a thermometer is used for control, and / or a redox potentiometer, an oxidant automatic titrator, a potentiometer, or a metering feed pump is used to control the feeding of the oxidant.

10. The method for removing oxalate by pre-treating the recycled acid solution according to claim 9, characterized in that: When an oxidation reaction is carried out using an oxidant under heating conditions, the acidic water vapor emitted during the heating reaction is cooled by a condensation reflux pipe and led back to the oxidation reaction tank.

11. The method for removing oxalate by pre-treating the recycled acid solution according to claim 10, characterized in that: The oxidation reaction adopts a front-end and back-end progressive oxidation treatment process, that is, the oxidizing gas escaped from the front-end oxidation reaction is used as the oxidant of the back-end oxidation reaction and is introduced into the reaction liquid of the back-end oxidation reaction.

12. The method for removing oxalate by pre-treating the recycled acid solution according to claim 11, characterized in that: The oxalate impurity content of the regenerated metal etching liquid that is fed back into the circuit board acid etching production line for recycling is controlled to be below 6 grams per liter.

13. A device for pre-treating recycled acid solution to remove oxalate using the method of claim 1, comprising a precipitation reaction tank and a solid-liquid separator, characterized in that: It also includes an electrolytic tank and / or an oxidation reaction tank; wherein the precipitation reaction tank is connected to the solid-liquid separator through a pump and a pipeline, and the solid-liquid separator is connected to the electrolytic tank and / or the oxidation reaction tank through a pump and a pipeline.

14. The device for removing oxalate radicals by pre-treatment of recycled acid solution according to claim 13, characterized in that: The electrolytic cell is provided with an electrolytic cell separator, which is divided into an anode cell area and a cathode cell area. The electrolytic cell separator is at least one of a cation exchange membrane, an anion exchange membrane, a proton membrane, a bipolar membrane, a reverse osmosis membrane, a non-ion selective diaphragm and a filter cloth; the anode material of the electrolytic cell is selected from at least one of an electrode with a surface of gold and / or platinum, a titanium-based coating electrode, and conductive graphite, and the cathode material is at least one of an electrode with a surface of titanium and / or copper, stainless steel, and conductive graphite.

15. The device for removing oxalate radicals by pre-treatment of recycled acid solution according to claim 14, characterized in that: A thermometer and a hot and cold temperature exchanger are installed in the oxidation reaction tank.

16. The device for removing oxalate radicals by pre-treatment of recycled acid solution according to claim 15, characterized in that: A temporary storage tank is added to temporarily store materials or used as a chemical reaction tank under normal pressure; the temporary storage tank is connected between the solid-liquid separator and the electrolytic tank and / or the oxidation reaction tank, and / or is connected to the electrolytic tank and / or the oxidation reaction tank.

17. The device for removing oxalate radicals by pre-treatment of recycled acid solution according to claim 16, characterized in that: A redox potentiometer, an oxidant automatic titrator, or a potentiometer is installed in the oxidation reaction tank to control the feeding of the oxidant during the oxidation reaction, or a metering feeding pump is used to control the feeding of the oxidant according to the process requirements.

18. The device for removing oxalate radicals by pre-treatment of recycled acid solution according to claim 17, characterized in that: The electrolytic cell, the oxidation reaction cell, and at least one of the temporary storage cells connected to the electrolytic cell and / or the oxidation cell are connected to the circuit board acid corrosion production line through pumps and pipelines, and the regenerated metal corrosion liquid is transported to the tin stripping production line, etching machine, and micro-etching machine for on-site production reuse.

19. The device for removing oxalate radicals by pre-treatment of recycled acid solution according to claim 18, characterized in that: At least one of a redox potentiometer, a hydrometer, a liquid level meter and a thermometer is installed in the electrolytic cell.

20. The device for removing oxalate radicals by pre-treatment of recycled acid solution according to claim 19, characterized in that: A condensation reflux pipe is added to the oxidation reaction tank so that the acid gas escaping from the reaction liquid can be cooled and refluxed into the oxidation reaction tank.

21. The device for removing oxalate radicals by pre-treatment of recycled acid solution according to claim 20, characterized in that: A gas-liquid mixer is added to the electrolytic cell and / or the oxidation reaction cell, and the gas-liquid mixer is a vacuum ejector or a spray tower.

22. The device for removing oxalate radicals by pre-treatment of recycled acid solution according to claim 21, characterized in that: A combination of an electrolytic cell and an oxidation reaction cell or a combination of two or more oxidation reaction cells is arranged to form a front-end and rear-end progressive oxidation reaction treatment device, wherein the front-end electrolytic cell / oxidation reaction cell is connected to the rear-end oxidation reaction cell through a gas pipeline, so that the rear-end oxidation reaction liquid absorbs the oxidizing gas escaped from the front-end oxidation reaction liquid and is used as the rear-end oxidant.

23. The device for removing oxalate radicals by pre-treatment of recycled acid solution according to claim 22, characterized in that: A refrigerator or a heater is added to provide cooling or heating for the cold and hot temperature exchanger; and a stirrer is added to each tank to stir the solution evenly.

24. The device for removing oxalate radicals by pre-treatment of recycled acid solution according to claim 23, characterized in that: An automatic logic program controller is added and connected to the sensor and / or metering feeding pump provided in the device to form a combination; the sensor is selected from at least one of a thermometer, a liquid level meter, a redox potentiometer, an acidity meter, a pH meter, a photoelectric colorimeter, a hydrometer, an oxidant automatic titrator, and a potentiometer; the sensor signal output end of the sensor is connected to the sensor signal input end of the automatic logic program controller, and the control signal output end of the automatic logic program controller is connected to at least one control signal output end of the valve, pump, feeding equipment, electrolysis power supply, etc. of the device of the present invention, so that the device can operate safely and automatically according to the pre-programmed program.

25. The device for removing oxalate radicals by pre-treatment of recycled acid solution according to claim 24, characterized in that: An overflow buffer tank is added to solve the liquid flow problem between tanks; and a new oxalate residue washing tank is added for water washing to produce pure insoluble new oxalate products.

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