A method for treating copper foil wastewater by using multi-source alkali instead of liquid alkali

Abstract

This invention relates to a method for treating copper foil wastewater using multi-source alkali instead of liquid alkali, comprising the following steps: (1) preparation of multi-source alkali slurry; (2) primary neutralization and precipitation; (3) secondary deep precipitation and copper recovery; and (4) tertiary fine-tuning and pretreatment before reuse. This invention achieves "waste treatment with waste" by using multi-source alkali derived from industrial waste to replace liquid alkali, thereby reducing treatment costs while improving the purity and efficiency of copper resource recovery.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment technology, and specifically relates to a method for treating copper foil wastewater using multi-source alkali instead of liquid alkali. Background Technology

[0002] Electrolytic copper foil is a fundamental material for industries such as printed circuit boards (PCBs) and lithium batteries. During copper foil production, the processes of raw foil manufacturing, surface treatment, and cleaning generate a large amount of rinsing wastewater. This type of wastewater typically exhibits four high characteristics: high copper ion concentration (usually 0.2-0.8 g / L), high acidity (pH value between 2.0 and 4.5), high salinity (containing a large amount of sulfate ions), and trace amounts of associated heavy metals (such as Zn). 2+ Cr 3+ Ni 2+ wait).

[0003] Currently, copper foil wastewater treatment technologies are mainly divided into three categories: Chemical precipitation: This is currently the most widely used method. By adding an alkaline agent (mainly liquid alkali NaOH or lime milk Ca(OH)2) to the wastewater to adjust the pH, copper ions are precipitated as copper hydroxide or basic copper carbonate, thereby achieving removal and recovery.

[0004] Membrane separation and ion exchange methods: such as using reverse osmosis (RO) or chelating resins (e.g., CH-90Na) to concentrate wastewater, recover copper, and reuse the water. However, this method can lead to a shortened membrane lifespan (usually requiring replacement every 3 months to 1 year) when operating under low pH conditions, and the investment cost is high.

[0005] Electrochemical method: High-purity copper can be directly recovered through electrolysis with a recovery rate of up to 99.9%, but the equipment investment is large and it is sensitive to impurity ions in the wastewater.

[0006] Current processing technologies have the following problems: Liquid alkali (NaOH) is costly to use: current mainstream processes rely on liquid alkali to adjust pH. With fluctuating alkali prices, reagent costs account for 40%-60% of wastewater treatment operating costs. For large copper foil plants with a daily processing capacity of thousands of tons, this is a heavy economic burden.

[0007] The sludge production is large and difficult to treat: the copper hydroxide sludge produced by simply using liquid alkali precipitation has a high water content, large volume, and easily adsorbs a large amount of organic matter, making the sludge hazardous waste with extremely high disposal costs. According to statistics, traditional processes generate tens of kilograms of hazardous waste sludge for every 1 kg of copper removed.

[0008] High effluent hardness affects reuse: While using lime as an alternative alkali source is low-cost, it introduces a large amount of calcium ions. During subsequent wastewater reuse (such as in an RO system), calcium sulfate scale easily forms, causing membrane system blockage and severely impacting system stability.

[0009] Low resource utilization: Many patents and processes focus only on "meeting emission standards" and neglect "resource recycling". Even if recycling is carried out, the purity of the recycled copper products is low and cannot be directly returned to the foil production process. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a method for treating copper foil wastewater by using multi-source alkali instead of liquid alkali. This method achieves "waste treatment with waste" by using multi-source alkali made from industrial waste to replace liquid alkali, thereby reducing treatment costs and improving the purity and efficiency of copper resource recovery.

[0011] This invention provides a method for treating copper foil wastewater using multi-source alkali instead of liquid alkali, comprising the following steps: (1) Collect industrial waste alkali residue and prepare a multi-source alkali suspension with a mass fraction of 10%-20%. Filter and homogenize the suspension to obtain multi-source alkali slurry. (2) Introduce the copper foil production wastewater into the primary reaction tank, add the above-mentioned multi-source alkaline slurry under stirring, and control the reaction pH value to 5.5-6.5; (3) The effluent from the primary reaction tank is allowed to flow by gravity to the secondary reaction tank. The above-mentioned multi-source alkali slurry is added under stirring, and the pH value is controlled to 7.5-8.5. (4) The effluent from the secondary reaction tank is introduced into the tertiary reaction tank, acid is added to adjust the pH to 7.0-8.5, and scale inhibitors and flocculants are added; the effluent after adjustment enters the ultrafiltration system containing a multi-media filter to remove residual suspended solids, and finally enters the reverse osmosis system for desalination treatment; finally, the effluent obtained is reused in the copper foil production cleaning process.

[0012] Preferably, the industrial waste alkali residue in step (1) includes one or more of the following: carbide slag, steel plant waste alkali solution, and papermaking sludge. The main components of the multi-source alkali are Ca(OH)2, NaOH, and a small amount of silicates and calcium carbonate, which are characterized by strong alkalinity and low cost. The effective alkali content (calculated as CaO+NaOH) in the multi-source alkali is not less than 40%.

[0013] Preferably, the pH value of the copper foil production wastewater in step (2) is 2.0-3.5.

[0014] Preferably, the reaction time in step (2) is controlled within 15-30 minutes.

[0015] The main purpose of step (2) is to quickly neutralize the large amount of free acid in the wastewater, while simultaneously reducing the free acid content of Fe. 3+ Al 3+ Plasma forms hydroxide precipitates.

[0016] Preferably, the reaction time in step (3) is controlled to be 15-30 minutes.

[0017] Within the pH range of step (3), copper ions (Cu) 2+ A stable copper hydroxide precipitate is formed. Simultaneously, calcium ions introduced from the multi-source alkali react with some sulfate ions to form calcium sulfate precipitate, acting as a co-precipitate to adsorb trace organic matter in the wastewater. The precipitate enters an inclined tube sedimentation tank for sludge-water separation. The bottom copper-containing sludge is dewatered by a filter press to obtain a copper concentrate with a high copper content (copper grade up to 15%-25%), which can be recovered as a raw material for copper smelting. The copper-containing sludge can also be further purified using a low-cost ammonia leaching-extraction process to produce electrowinning copper.

[0018] In steps (2) and (3), the amount of alkali added is controlled by linking ORP (oxidation-reduction potential) and pH meter to avoid drastic pH fluctuations caused by excessive addition of multiple alkali sources.

[0019] Preferably, the pH value of the effluent from the secondary reaction tank in step (4) is 10-11.

[0020] The key to this invention lies in utilizing the "synergistic effect" of multiple base sources: Buffering effect: OH- removal from multi-source bases - In addition, it contains weak base ions such as carbonate and silicate, which have a buffering effect on pH. Compared with the "abrupt" phenomenon of liquid alkali, multi-source alkali can make the pH of the reaction tank more stable, which is conducive to the growth of copper hydroxide crystals and improves sedimentation performance.

[0021] Adsorption and flocculation: The fine calcium carbonate particles and silicates in the multi-source alkali have adsorption activity, which can adsorb organic matter and colloids in wastewater, reduce the COD of the effluent, and reduce the pollution load of subsequent membrane treatment.

[0022] Economic efficiency: Multi-source alkali is derived from industrial waste residue, and its price is much lower than that of commercial liquid alkali, which can reduce treatment costs by 30%-50%.

[0023] Beneficial effects Compared with the prior art, the present invention has the following advantages: (1) Significantly reduce reagent costs: By using multi-source alkali from industrial waste to replace liquid alkali, the waste is utilized as a resource, and the reagent procurement cost is significantly reduced.

[0024] (2) Improve sludge properties and resource utilization: Due to the calcium and magnesium ions introduced by the multi-source alkali participating in the reaction, the sludge formed has a compact structure and low water content (the water content after pressure filtration can be less than 60%), and high copper grade, which is convenient for subsequent pyrometallurgical or hydrometallurgical recycling, and truly realizes resource utilization.

[0025] (3) Improve the quality of effluent and system stability: The adsorption effect of multi-source alkali reduces the organic matter and hardness in the effluent, effectively alleviating the risk of scaling and fouling in the subsequent RO membrane system and extending the membrane life.

[0026] (4) Significant environmental benefits: It has achieved “waste treatment”, not only treating copper foil wastewater, but also disposing of industrial solid waste such as carbide slag, reducing the impact of solid waste stockpiling on the environment. Detailed Implementation

[0027] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0028] Example 1 Taking the wastewater from a lithium battery copper foil factory as an example, the wastewater volume is 100m³. 3 / h, Water quality: Cu 2+ Concentration 500 mg / L, pH=3.0, SO4 2- Concentration 1500 mg / L.

[0029] Preparation of multi-source alkali slurry: Take carbide slag (Ca(OH)2 content 65%) from a nearby chemical plant and waste alkali liquid from a steel plant (containing NaOH 5%) and mix them at a mass ratio of 3:1. Add water to prepare a multi-source alkali suspension with a mass fraction of 15%. Filter and homogenize the suspension to obtain multi-source alkali slurry.

[0030] Primary neutralization and precipitation treatment: Wastewater is continuously introduced into the primary reaction tank, mechanical stirring is started, and the prepared multi-source alkaline slurry is continuously added. The reaction pH is precisely controlled to stabilize at 6.0, and the reaction is carried out for 20 minutes.

[0031] Secondary deep sedimentation and copper recovery: The effluent from the primary reaction tank flows by gravity into the secondary reaction tank, where uniform stirring is maintained. Multi-source alkaline slurry is continuously added to stabilize the pH of the water at 8.0, and the reaction continues for 30 minutes. After the reaction is complete, the wastewater enters an inclined tube sedimentation tank with a surface loading rate of 1.0 m³. 3 / m 2 •h, static sedimentation separation.

[0032] Sludge treatment: Copper-containing sludge is enriched at the bottom of the sedimentation tank and is transported to a plate and frame filter press for dewatering via a screw pump. The filter press pressure is 0.6 MPa and the filter press time is 40 minutes. The final product is high-purity copper sludge with a water content of 55%. The copper content is tested to be 18% and the impurity content is extremely low. It can be directly sold to copper smelters as smelting raw materials, realizing the resource utilization of solid waste.

[0033] Three-stage fine-tuning and pretreatment before reuse: The supernatant from the inclined tube sedimentation tank is introduced into the three-stage reaction tank, where dilute sulfuric acid is used to adjust the pH of the water to 7.5. Then, 2 mg / L of scale inhibitor and 3 mg / L of flocculant are added sequentially, and the mixture is stirred for 10 minutes to capture fine suspended particles and colloidal impurities in the water. The treated wastewater first enters a multi-media filter to remove residual suspended solids, then flows through an ultrafiltration (UF) system for deep purification, and finally enters a reverse osmosis (RO) desalination system.

[0034] Treatment effect: The entire system operates continuously and stably, with the final product water conductivity <100μS / cm and the effluent Cu 2+ <0.3 mg / L, Zn 2+ Cr 3+ The trace heavy metal ions are completely within the standard, and the water quality fully meets the "Emission Standard of Pollutants for Copper, Nickel and Cobalt Industry" (GB 25467-2010), and all of it is recycled for the rinsing process of the copper foil production line.

[0035] Example 2 Taking the wastewater treatment project of a high-end electronic copper foil manufacturing enterprise as an example, the wastewater volume is 80m³. 3 / h, raw water quality parameters: Cu 2+ Concentration 220 mg / L, pH=2.5, SO4 2- With a concentration of 950 mg / L and low organic matter content in the water, the requirements for the purity of the reclaimed water and the stability of the membrane system are extremely high.

[0036] Preparation of multi-source alkali slurry: Carbide slag and papermaking white mud are mixed at a mass ratio of 2:1, and water is added to prepare a multi-source alkali suspension with a mass fraction of 10%. After being filtered through a 100-mesh fine filter and homogenized and stirred for 25 minutes, multi-source alkali slurry is obtained.

[0037] Primary neutralization and precipitation: Wastewater enters the primary reaction tank, with a stirring rate of 100 r / min. Multi-source alkali slurry is added to adjust the pH to 5.5, and the reaction is carried out for 15 minutes.

[0038] Secondary deep sedimentation: The effluent flows by gravity to the secondary reaction tank, and slurry is continuously added to adjust the pH to 7.5. The reaction is carried out for 20 minutes, and the surface loading of the inclined tube sedimentation tank is set at 0.8 m. 3 / m 2 ·h.

[0039] Three-stage fine-tuning and reuse: The pH of the secondary effluent is stabilized at 10.2 and introduced into the tertiary reaction tank. Dilute sulfuric acid is used to adjust the pH to 7.0, and 1.5 mg / L scale inhibitor and 2.5 mg / L flocculant are added. After sufficient reaction, the water undergoes deep treatment through a combination of multi-media filtration, ultrafiltration and reverse osmosis.

[0040] Treatment effect: Final effluent Cu² + <0.15mg / L, and the conductivity of the produced water is ≤80μS / cm, fully meeting the standards for ultrapure water cleaning and reuse of high-end electronic copper foil.

[0041] Example 3 The complex wastewater from the integrated copper foil processing plant is a mixture of raw foil wastewater, surface treatment wastewater, and equipment rinsing wastewater. The wastewater is of complex quality, high in impurities, and has a volume of 120 m³. 3 / h, Raw water quality: Cu 2+ Concentration 750 mg / L, pH=3.5, SO4 2- The concentration is 2200 mg / L, and it also contains high concentrations of organic matter, colloidal impurities, and Ni. 2+ Zn 2+ The effluent often contains multiple heavy metals, and traditional liquid alkali treatment processes can easily lead to excessive levels of these metals in the treated water, as well as severe scaling and fouling of the membrane system.

[0042] Preparation of multi-source alkali slurry: Carbide slag, steel plant waste alkali liquid and papermaking white mud are mixed in a mass ratio of 4:2:1 to prepare a multi-source alkali suspension with a mass fraction of 20%. After filtration and homogenization, multi-source alkali slurry is obtained.

[0043] Primary neutralization and sedimentation: Wastewater enters the primary reaction tank, slurry is added under stirring at 130 r / min, pH is adjusted to 6.5, and reaction is carried out for 30 minutes.

[0044] Secondary deep sedimentation: Slurry is added to the secondary reaction tank to adjust the pH to 8.5, and the reaction is carried out for 30 minutes to fully precipitate heavy metals such as copper, nickel, and zinc ions. The surface loading of the sedimentation tank is 1.2 m³. 3 / m 2 •h, excellent mud-water separation effect.

[0045] Three-stage fine-tuning and reuse: The pH of the secondary effluent is 10.8, and the pH in the tertiary reaction tank is adjusted to 8.0. 2.5 mg / L scale inhibitor and 3.5 mg / L flocculant are added to thoroughly remove fine impurities. After further treatment by the complete membrane system, it is reused in production.

[0046] Treatment effect: Effluent Cu 2+ <0.25mg / L, all heavy metal and COD indicators meet the standards, and the produced water can be stably reused in production.

Claims

1. A method for treating copper foil wastewater using multi-source alkali instead of liquid alkali, characterized in that, Includes the following steps: (1) Collect industrial waste alkali residue and prepare a multi-source alkali suspension with a mass fraction of 10%-20%. Filter and homogenize the suspension to obtain multi-source alkali slurry. (2) Introduce the copper foil production wastewater into the primary reaction tank, add the above-mentioned multi-source alkaline slurry under stirring, and control the reaction pH value to 5.5-6.5; (3) The effluent from the primary reaction tank is allowed to flow by gravity to the secondary reaction tank. The above-mentioned multi-source alkali slurry is added under stirring, and the pH value is controlled to 7.5-8.

5. (4) The effluent from the secondary reaction tank is introduced into the tertiary reaction tank, acid is added to adjust the pH to 7.0-8.5, and scale inhibitors and flocculants are added; the effluent after adjustment enters the ultrafiltration system containing a multi-media filter to remove residual suspended solids, and finally enters the reverse osmosis system for desalination treatment; finally, the effluent obtained is reused in the copper foil production cleaning process.

2. The method according to claim 1, characterized in that, The industrial waste alkali residue in step (1) includes one or more of the following: carbide slag, steel plant waste alkali liquid, and papermaking white mud.

3. The method according to claim 1, characterized in that, The pH value of the copper foil production wastewater in step (2) is 2.0-3.

5.

4. The method according to claim 1, characterized in that, The reaction time in step (2) is controlled to be 15-30 minutes.

5. The method according to claim 1, characterized in that, The reaction time in step (3) is controlled to be 15-30 minutes.

6. The method according to claim 1, characterized in that, The pH value of the effluent from the secondary reaction tank in step (4) is 10-11.