Aluminum-copper micro-electrolysis treatment method for citric acid wastewater of power plant boiler

Abstract

The invention belongs to the technical field of industrial wastewater treatment, and discloses an aluminum-copper micro-electrolysis treatment method for citric acid wastewater of a power plant boiler. The method comprises the following steps: adding lime powder into the citric acid wastewater of the power plant boiler, stirring and standing to obtain pretreated wastewater subjected to solid-liquid separation; a micro-electrolysis material is added into the pretreated wastewater, a micro-electrolysis reaction is carried out under the preset temperature condition, micro-electrolysis reaction wastewater is generated, and the micro-electrolysis material comprises at least one of aluminum scraps, aluminum alloy plated copper or a copper-aluminum intermediate compound; hydrochloric acid is added into the micro-electrolysis reaction wastewater, the pH is adjusted to be neutral, and treated target wastewater is obtained. Based on the method, efficient and environment-friendly treatment of the citric acid cleaning wastewater of the power plant boiler is realized.

Description

Technical Field

[0001] The present application relates to the technical field of industrial wastewater treatment, and in particular to a method for treating citric acid wastewater from power plant boilers using aluminum and copper micro-electrolysis. Background Art

[0002] With the rapid development of the power industry, the demand for chemical cleaning of high-parameter boilers is becoming increasingly frequent. The citric acid wastewater generated during the cleaning process contains high concentrations of organic matter (such as CODCr up to tens of thousands of mg / L), heavy metal ions (copper, chromium, etc.) and trace amounts of ammonia nitrogen, becoming an environmental governance problem that needs to be solved urgently.

[0003] Among traditional treatment methods, incineration consumes a lot of energy and is prone to secondary pollution; complexation and sedimentation require a large amount of chemical reagents, and the efficiency of heavy metal removal is limited by the complexing agents; biological methods are difficult to operate stably due to the biological toxicity of high-concentration organic matter, and the treatment cycle can take up to dozens of days. In recent years, although advanced oxidation technologies represented by Fenton oxidation and ozone oxidation can degrade some organic matter, they have bottlenecks such as complex equipment, high treatment costs, and the inability to simultaneously remove heavy metals. In particular, they are difficult to adapt to the technical requirements of power plant cleaning sites for fast, low-cost, and integrated treatment. Therefore, existing technologies generally have problems such as lengthy treatment processes, insufficient ability to synergistically remove pollutants, and poor economic efficiency. Summary of the Invention

[0004] An aluminum-copper micro-electrolysis method for treating citric acid wastewater from power plant boilers provided in an embodiment of the present invention at least solves the problems commonly existing in the prior art, such as lengthy treatment processes, insufficient synergistic removal capabilities of pollutants, and poor economic efficiency.

[0005] According to a first aspect of an embodiment of the present invention, a method for treating citric acid wastewater from a power plant boiler by micro-electrolysis of aluminum and copper is provided, comprising:

[0006] Adding lime powder to citric acid wastewater from a power plant boiler, stirring and allowing to stand to obtain pretreated wastewater with solid-liquid separation;

[0007] adding a micro-electrolysis material to the pretreated wastewater, performing a micro-electrolysis reaction under a preset temperature condition to generate micro-electrolysis reaction wastewater, wherein the micro-electrolysis material comprises at least one of aluminum chips, aluminum alloy copper plating, or a copper-aluminum intermediate compound;

[0008] Hydrochloric acid is added to the micro-electrolysis reaction wastewater to adjust the pH to neutral to obtain treated target wastewater.

[0009] According to an embodiment of the present invention, the preset temperature is 20° C. to 60° C., and the reaction time of the micro-electrolysis reaction is 3 hours.

[0010] According to an embodiment of the present invention, the particle size of the aluminum chips or the aluminum alloy copper plating is 3 mm to 5 mm, the added amount of the aluminum chips is 5 g / L to 10 g / L, and the added amount of the aluminum alloy copper plating is 5 g / L to 10 g / L.

[0011] According to an embodiment of the present invention, before adding the electrolytic material to the pretreated wastewater and performing a micro-electrolysis reaction under preset temperature conditions to generate micro-electrolysis reaction wastewater, the method further includes copper plating the aluminum chips.

[0012] According to an embodiment of the present invention, the copper plating treatment on the aluminum chips includes:

[0013] The amount of aluminum chips used for copper plating is determined according to the copper ion content in the citric acid wastewater of the power plant boiler, and the amount of aluminum chips used is 2 to 50 times the copper ion content in the citric acid wastewater of the power plant boiler;

[0014] The aluminum chips in the used amount are placed in the citric acid wastewater of the power plant boiler and reacted for at least 2 minutes to complete the copper plating treatment of the aluminum chips.

[0015] According to an embodiment of the present invention, the copper plating treatment of the aluminum scraps includes: immersing the aluminum scraps in a copper sulfate solution with a concentration of 3%-5%, and completing the copper plating after a reaction time of 10 seconds to 1 minute.

[0016] According to an embodiment of the present invention, the addition amount of the copper-aluminum intermediate compound is 1 g / L to 2 g / L.

[0017] According to an embodiment of the present invention, the purity of the lime powder is greater than 95%, the particle size is greater than 200 mesh, and the dosage is 1.5 to 2 times the citric acid content in the citric acid wastewater of the power plant boiler.

[0018] According to an embodiment of the present invention, after the lime powder is added to the citric acid wastewater from the power plant boiler, the stirring time is 30 minutes and the standing time is 4 hours.

[0019] Beneficial effects of the embodiments of the present invention: The aluminum-copper micro-electrolysis treatment method for citric acid wastewater from power plant boilers provided by the embodiments of the present invention achieves efficient and environmentally friendly treatment of citric acid cleaning wastewater from power plant boilers through the synergistic effect of lime precipitation and aluminum-copper micro-electrolysis. Specifically, high-purity lime powder is first added to react with the citric acid in the wastewater to generate a low-solubility calcium citrate precipitate, which significantly reduces the organic matter content in the wastewater (such as the initial CODCr value from tens of thousands of mg / L to about 400 mg / L), while preliminarily fixing some heavy metal ions; subsequently, aluminum chips, copper-plated aluminum chips or copper-aluminum intermediate compounds are introduced for micro-electrolysis reaction, and aluminum undergoes a replacement reaction with heavy metal ions such as copper and chromium in the wastewater to generate a single metal precipitate, completely removing heavy metal pollution. At the same time, the active substances generated in the micro-electrolysis process further decompose the residual citric acid and ammonia nitrogen organic matter, further reducing the CODCr value to below 100 mg / L and the ammonia nitrogen decomposition rate to more than 99%; finally, hydrochloric acid is used to adjust the pH to neutral to ensure that the treated wastewater can be directly and safely discharged. The entire process can be completed within 8 hours without the need for complex equipment. It utilizes industrial waste aluminum chips and common lime materials, with low processing costs. The final calcium citrate precipitate is non-toxic and harmless, meeting both emission standards and on-site rapid processing requirements, and is highly efficient, economical, and environmentally friendly.

[0020] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below so that other features, objects, and advantages of the invention are more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be derived from these drawings without inventive effort.

[0022] Figure 1 A flow chart of a method for treating citric acid wastewater from a power plant boiler using aluminum and copper micro-electrolysis is provided in an embodiment of the present invention.

[0023] Figure 2 This is an XRD pattern analysis diagram of the copper-aluminum intermediate compound of Example 5 provided in an embodiment of the present invention.

[0024] Figure 3 This is an XRD pattern analysis diagram of the copper-aluminum intermediate compound of Example 6 provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following describes embodiments of the present invention in more detail with reference to the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0026] The rapid development of the power industry has increased the demand for chemical cleaning of high-parameter boilers. The citric acid wastewater generated by cleaning contains high concentrations of organic matter, heavy metal ions, and trace amounts of ammonia nitrogen, posing a challenge to environmental governance. Traditional treatment methods such as incineration, complex sedimentation, and biological methods suffer from high energy consumption, large amounts of reagents, and long treatment cycles. While advanced oxidation technologies such as Fenton oxidation and ozone oxidation can degrade some organic matter, they suffer from bottlenecks such as complex equipment, high costs, and the inability to simultaneously remove heavy metals. Existing technologies generally suffer from long treatment processes, insufficient capacity for synergistic pollutant removal, and poor economic efficiency.

[0027] In order to solve the above problems, an embodiment of the present invention provides an aluminum-copper micro-electrolysis treatment method for citric acid wastewater from power plant boilers. Figure 1 A flowchart of a method for treating citric acid wastewater from a power plant boiler using aluminum and copper micro-electrolysis is provided in accordance with an embodiment of the present invention. Figure 1 As shown, the method includes the following steps.

[0028] Step S101: adding lime powder to citric acid wastewater from a power plant boiler, stirring and allowing to stand to obtain pretreated wastewater with solid-liquid separation.

[0029] Step S102: adding micro-electrolysis materials to pretreated wastewater, performing micro-electrolysis reaction under preset temperature conditions, and generating micro-electrolysis reaction wastewater. The micro-electrolysis materials include at least one of aluminum chips, aluminum alloy copper plating, or copper-aluminum intermediate compounds.

[0030] Step S103: adding hydrochloric acid to the micro-electrolysis reaction wastewater to adjust the pH to neutral to obtain treated target wastewater.

[0031] First, lime powder is added to citric acid wastewater from a power plant boiler, and after stirring and standing, solid-liquid separation pretreated wastewater is obtained.

[0032] In this embodiment, high-purity lime powder is added to citric acid wastewater, and the lime reacts with the citric acid in the wastewater to generate an insoluble calcium citrate precipitate. Continuous stirring can be performed during the addition process to ensure sufficient reaction, and after stirring, the mixture is allowed to settle to separate the solid and liquid layers. In practical applications, the supernatant can also be separated by a solid-liquid separation device (such as a centrifuge or a sedimentation tank) to obtain pretreated wastewater. This step can significantly reduce the chemical oxygen demand (CODCr) in the wastewater and create suitable conditions for subsequent micro-electrolysis.

[0033] After obtaining the pretreated wastewater, micro-electrolysis materials can be added to the pretreated wastewater to perform a micro-electrolysis reaction under preset temperature conditions to generate micro-electrolysis reaction wastewater. In this embodiment, the micro-electrolysis material includes at least one of aluminum chips, aluminum alloy copper plating, or a copper-aluminum intermediate compound.

[0034] In this embodiment, micro-electrolysis materials are added to the pre-treated wastewater. The materials can be selected from one or more of aluminum chips, aluminum alloy copper plating, or copper-aluminum intermediate compounds. Aluminum-based materials can form a micro-battery system in wastewater. Aluminum acts as the anode to undergo oxidation reaction to release electrons, and copper or copper-aluminum compounds act as the cathode to promote reduction reaction. In this process, heavy metal ions (such as Cu 2+ Cr 6+ ) are reduced to elemental deposits, while organic matter (such as citric acid) is decomposed into small molecules through electrochemical oxidation, and ammonia nitrogen is adsorbed and co-precipitated by aluminum hydroxide colloid. The reaction can be carried out at a controllable temperature to ensure a balance between reaction rate and treatment efficiency.

[0035] After the micro-electrolysis reaction is completed, hydrochloric acid is added to the micro-electrolysis reaction wastewater to adjust the pH to neutral to obtain the treated target wastewater.

[0036] In this embodiment, hydrochloric acid is slowly added to the wastewater to neutralize the alkaline substances (such as aluminum hydroxide) produced during the reaction process, and the pH of the wastewater is adjusted to a neutral range (6.5 to 7.5). After the adjustment is completed, solid-liquid separation is performed again to obtain clear and transparent target wastewater. In this embodiment, the CODCr value of the treated wastewater is significantly reduced, and the heavy metal ion concentration reaches a level that meets the emission standards and can be directly discharged into the environment or reused.

[0037] According to an embodiment of the present invention, by generating calcium citrate precipitate, most organic matter is quickly removed, while providing a stable reaction environment for micro-electrolysis. The aluminum-based material undergoes multiple reactions with pollutants in the wastewater, including oxidation-reduction, adsorption, and coagulation, achieving simultaneous degradation of organic matter and removal of heavy metals. Finally, aluminum chips can be used as machining waste, and copper ions are derived from the wastewater itself, achieving "waste treatment with waste"; the atomic-level mixed structure of the copper-aluminum intermediate compound (such as the CuAl2 phase) can enhance reaction activity.

[0038] In an optional embodiment, lime powder is added to the citric acid wastewater of a power plant boiler, stirred and allowed to stand to obtain pretreated wastewater for solid-liquid separation, the preset temperature is 20°C to 60°C, and the reaction time of the micro-electrolysis reaction is 3 hours.

[0039] In this embodiment, the wastewater temperature during the micro-electrolysis reaction stage can be controlled within a range from room temperature to 60°C, preferably within a range from 40°C to 60°C. Furthermore, the preset temperature is preferably 50°C. In actual operation, temperature control can be achieved by:

[0040] Waste heat utilization: If the cleaning wastewater is already at a relatively high temperature, the reaction can be carried out directly at its initial temperature without the need for additional heating. For example, the temperature of the wastewater after boiler cleaning is approximately 40°C to 50°C, which can be directly used for the reaction.

[0041] External heating: When the initial temperature of the wastewater is low, a steam coil or electric heater can be used to heat the reaction vessel (such as an acid-resistant enamel reactor), and the temperature can be monitored in real time by a temperature sensor to ensure that the temperature is stable within the set range.

[0042] Insulation measures: The outer wall of the reaction vessel can be wrapped with insulation material (such as aluminum silicate fiber felt) to reduce heat loss and maintain the thermal stability of the reaction system.

[0043] After the temperature reaches the preset range, the stirring device can be started (the speed can be 100-200 rpm), the micro-electrolysis material (such as aluminum chips or copper-plated aluminum chips) can be evenly dispersed in the pretreated wastewater, and the timer can be started. The reaction lasts for 3 hours, during which time indicators such as temperature fluctuations, pH changes, and pollutant degradation dynamics need to be regularly monitored. Specifically:

[0044] For temperature fluctuations, the temperature difference can be controlled within ±2°C through the PID temperature control system to avoid the reaction efficiency being affected by sudden temperature changes; for pH changes, the initial pH is alkaline (about 8-9) due to lime precipitation. As the micro-electrolysis reaction proceeds, the pH may gradually decrease. In practical applications, a small amount of hydrochloric acid can be used to fine-tune the reaction environment to maintain a stable environment; for the degradation dynamics of pollutants, CODCr and Cu can be sampled every hour for detection. 2+ Cr 6+ The degradation curve was drawn to verify the reaction progress.

[0045] In this process, the synergistic effects of temperature and time are as follows:

[0046] 40℃~50℃ range: At this temperature, the oxidation reaction of aluminum and the reduction reaction of copper are moderate, and the corrosion micropore structure formed on the surface of aluminum chips is uniform, which is conducive to electron transfer and pollutant adsorption. Experiments show that after 3 hours of reaction, CODCr can be reduced from 400mg / L to below 100mg / L, and Cu 2+The removal rate is over 98%.

[0047] 50°C to 60°C: Increasing temperature accelerates reaction kinetics, increasing the dissolution rate of aluminum and increasing the number of active hydrogen radicals (·H) and hydroxyl radicals (·OH) generated by micro-electrolysis, further promoting the oxidative decomposition of organic matter. For example, at 55°C, the CODCr degradation rate increases by approximately 30% compared to 40°C.

[0048] After 3 hours of reaction, stop stirring and let it stand for 10 minutes to allow the suspended aluminum hydroxide colloid to flocculate and settle. Take the supernatant for testing. The typical treatment effect is:

[0049] CODCr: It dropped from the initial 20,000 mg / L to about 400 mg / L after lime precipitation, and further dropped to 80-120 mg / L through micro-electrolysis.

[0050] Heavy metal ions: Cu 2+ The concentration dropped from 1.5g / L to <1mg / L, Cr 6+ From 0.05g / L to <0.1mg / L.

[0051] Ammonia nitrogen: Corrosion inhibitor decomposition rate>99%, residual ammonia nitrogen concentration<5mg / L.

[0052] In an optional embodiment, the particle size of aluminum chips or aluminum alloy copper plating is 3 mm to 5 mm, the added amount of aluminum chips is 5 g / L to 10 g / L, and the added amount of aluminum alloy copper plating is 5 g / L to 10 g / L.

[0053] In this embodiment, the micro-electrolysis material is aluminum chips or aluminum alloy copper-plated with a particle size of 3 mm to 5 mm. This size range has been verified by experiments to be the optimal balance between reaction activity and mechanical strength.

[0054] Aluminum chips can be obtained by mechanical cutting of industrial waste aluminum. This particle size range ensures that the material has a large specific surface area (about 0.5 to 1.2 m 2 / g), while also avoiding the rapid consumption or agglomeration of fine particles due to excessive reaction. Specifically, 3-5mm aluminum chips can form a stable microbattery network in wastewater. Smaller particles (e.g., <3mm) are prone to rapid dissolution, leading to runaway reactions, while larger particles (>5mm) reduce efficiency due to insufficient surface area.

[0055] In actual application, the dosage of aluminum chips can be dynamically adjusted according to the initial pollution load of wastewater (such as CODCr, heavy metal concentration) to ensure that it is within the range of 5g / L to 10g / L.

[0056] Specifically, for low-load wastewater (CODCr < 10,000 mg / L), 5-7 g / L of aluminum chips can be added. For example, for 5 tons of wastewater (volume 5,000 L), 25-35 kg of aluminum chips can be added; for high-load wastewater (CODCr > 20,000 mg / L), 8-10 g / L of aluminum chips can be added. Depending on specific implementation needs, copper-aluminum intermediate compounds can be combined to improve reaction efficiency.

[0057] When adding aluminum chips, you can first add 70% of the total amount, and then add the remaining 30% after 1 hour of reaction to maintain continuous reaction activity.

[0058] If aluminum alloy copper plating material is used (such as Al 6061 surface plated with a 5-10μm copper layer), the coating is uniform and firmly bonded. After copper plating, the material can be pickled (such as soaking in 5% dilute hydrochloric acid for 10 seconds) to remove surface oxides and expose the active surface.

[0059] In this embodiment, the dosage of the aluminum alloy copper plating material is also controlled at 5g / L to 10g / L, but its reaction efficiency is improved by about 20-30% compared with pure aluminum chips. The specific operation includes:

[0060] Immerse the copper-plated aluminum alloy in a 1% dilute sulfuric acid solution for 30 seconds to remove the surface passivation film and enhance the micro-electrolysis activity; sample the aluminum ion concentration every hour during the reaction. If the concentration drops by more than 30% (indicating rapid material consumption), 1 to 2 g / L of material needs to be added to maintain the reaction rate.

[0061] In an optional embodiment, before adding the electrolytic material to the pretreated wastewater and performing a micro-electrolysis reaction under preset temperature conditions to generate micro-electrolysis reaction wastewater, the aluminum chips are also copper-plated to enhance their catalytic activity.

[0062] In this embodiment, the surface of aluminum scraps is copper-plated to form aluminum-copper micro-couples, thereby improving the electron transfer efficiency of the micro-electrolysis reaction. Copper acts as a cathode to promote the reduction of heavy metal ions (such as Cu 2+ →Cu 0 ), while aluminum as the anode accelerates its own corrosion and releases active hydrogen, which together drive the oxidation and decomposition of organic matter.

[0063] Copper plating methods include raw wastewater copper plating and copper sulfate solution copper plating. The specific selection needs to be flexibly adjusted according to the copper ion concentration of the wastewater and the on-site conditions: for high-copper citric acid wastewater (Cu 2+ ≥1g / L), the original wastewater can be used for copper plating, and the copper ions in the wastewater can be directly used to achieve "waste treatment with waste"; for low-copper citric acid wastewater (Cu 2+ <1g / L) or fast copper plating is required, copper sulfate solution can be used for copper plating, and the uniformity of the plating layer can be ensured by externally supplementing the copper source.

[0064] The copper plating treatment process based on the copper ion content in the wastewater includes: determining the amount of aluminum chips used for copper plating according to the copper ion content in the citric acid wastewater of the power plant boiler, and the amount of aluminum chips used is 2 to 50 times the copper ion content in the citric acid wastewater of the power plant boiler; placing the used amount of aluminum chips in the citric acid wastewater of the power plant boiler to react for at least 2 minutes to complete the copper plating treatment of the aluminum chips.

[0065] Specifically, a sample of citric acid wastewater from a power plant boiler can be taken and the copper ion concentration can be determined by atomic absorption spectrometry (AAS) or inductively coupled plasma optical emission spectrometry (ICP-OES). 2+ is 1.5g / L).

[0066] The amount of copper plating is 2 to 50 times the copper ion content (by mass ratio). 2+ In actual operation, it is preferred to add 10 to 20 times to balance the cost and effect (in this example, 15 kg of aluminum chips is added).

[0067] An acid-resistant stirring tank (made of PP or FRP) can be used as the reaction vessel, equipped with a mechanical stirrer (rotating at 50-100 rpm). Aluminum chips are added to the wastewater in the reaction vessel and stirred continuously for 2 minutes or longer to ensure that the copper ions are fully replaced by metallic copper and adhere to the surface of the aluminum chips.

[0068] In this process, the initial temperature of the wastewater (usually 40-50°C) can be used without additional heating. When the surface of the aluminum chips changes from silvery white to reddish brown, the copper plating is completed.

[0069] Finally, the copper-plated aluminum chips can be scooped out using a sieve, rinsed with clean water to remove loose particles on the surface, and then drained for later use. The thickness of the copper plating layer can be observed using a scanning electron microscope (SEM).

[0070] For low-copper wastewater or scenarios where rapid copper plating is required, copper sulfate solution is used for copper plating. The method is as follows:

[0071] Prepare a 3% to 5% copper sulfate solution (for example, a 5% solution contains 50g / L of CuSO4·5H2O). Dissolve the copper sulfate solution and filter to remove impurities. Immerse the aluminum chips in the copper sulfate solution, ensuring complete immersion. The reaction time should be controlled between 10 seconds and 1 minute. A short reaction time (e.g., 30 seconds) can form a dense coating and avoid excessive corrosion of the aluminum substrate. Dynamic stirring: Use air pump bubbling or mechanical stirring (speed 50rpm) to promote solution flow and coating uniformity. During this process, the solution temperature can be maintained at 20-30°C. After copper plating is completed, remove the aluminum chips and rinse them with deionized water to remove residual copper sulfate.

[0072] In an optional embodiment, the copper-aluminum intermediate compound is added in an amount of 1 g / L to 2 g / L.

[0073] In this embodiment, the copper-aluminum intermediate compound can be prepared by a high-temperature diffusion method, and the specific process is as follows:

[0074] Pure copper powder (purity ≥99.9%) and aluminum powder (purity ≥99.5%) are weighed according to the atomic ratio of Cu:Al = 1:2 (corresponding to CuAl2 phase) or 9:4 (corresponding to Cu9Al4 phase), uniformly mixed and then pressed into a block; the mixed block is placed in a vacuum tube furnace, heated to 800°C to 1000°C under argon protection, and kept warm for 4 to 6 hours to allow the copper and aluminum atoms to fully diffuse to form a homogeneous compound; the synthesized block is coarsely crushed by a jaw crusher, and then particles with a particle size of 3 mm to 5 mm are screened out using a vibrating screening machine.

[0075] The dosage of copper-aluminum intermediate compound can be determined according to the amount of wastewater. For example, when treating 5 tons of wastewater, 5kg to 10kg of copper-aluminum intermediate compound should be added according to the dosage range of 1g / L to 2g / L.

[0076] When adding, the material can be added into the pretreated wastewater at one time, and a mechanical stirrer (rotating speed 150-200 rpm) can be used to evenly disperse it to avoid particle deposition.

[0077] The reaction temperature is controlled at 50°C (using waste water waste heat or external heating), the pH is maintained at 8.0-9.0 (the initial alkaline environment after lime precipitation), and the reaction time is shortened to 1-2 hours.

[0078] In the copper-aluminum intermediate compound, copper and aluminum are evenly distributed at the atomic level, forming a high-density micro-battery. Aluminum acts as an anode to quickly release electrons, and copper acts as a cathode to promote Cu 2+ Cr 6+ The reduction and deposition of heavy metal ions such as chlorinated hydrocarbons and the active free radicals (·OH, ·H) produced at the same time can effectively decompose citric acid and ammonia nitrogen pollutants.

[0079] After micro-electrolysis, the incompletely reacted copper-aluminum intermediate compound particles can be recovered by magnetic separation or sieve separation, and can be reused after washing with dilute hydrochloric acid (to remove surface oxides) and water.

[0080] In an optional embodiment, the purity of the lime powder is greater than 95%, the particle size is greater than 200 mesh, and the dosage is 1.5 to 2 times the citric acid content in the citric acid wastewater of the power plant boiler.

[0081] In this embodiment, industrial-grade lime powder with a purity greater than 95% (CaO content ≥ 95%) is used to prevent impurities (such as MgO and SiO2) from interfering with the formation of calcium citrate. Furthermore, the lime powder is screened to ensure a particle size greater than 200 mesh (i.e., a particle diameter less than 75 μm) to increase the specific surface area and accelerate the contact reaction with citric acid. In practice, a vibrating screen or airflow separator can be used to grade the lime to remove coarse particles and lumps, ensuring powder uniformity.

[0082] Before addition, the citric acid concentration in the wastewater must be measured (e.g., by acid-base titration or HPLC). The theoretical lime dosage should be calculated based on the citric acid content at a molar ratio of 1.5 to 2 times. For example, if the citric acid (C6H8O7) concentration in the wastewater is 10 g / L, its molar concentration is 0.052 mol / L. The lime (CaO, molar mass 56 g / mol) dosage range is: 0.052 mol / L × 1.5 × 56 g / mol = 4.37 g / L to 0.052 mol / L × 2 × 56 g / mol = 5.83 g / L.

[0083] When adding the lime, the reaction efficiency and excess coefficient need to be considered. Usually, 1.8 times of the theoretical value is used to ensure complete precipitation. For high-concentration wastewater (such as citric acid > 20g / L), lime can be added in batches to avoid local high pH that leads to premature formation of aluminum hydroxide colloid.

[0084] Lime powder is evenly distributed into the wastewater tank using a screw conveyor or pneumatic conveying system. Simultaneously, a high-speed agitator (300-500 rpm) is activated to ensure thorough dispersion of the lime particles. Stirring is continued for 30 minutes to allow the citric acid and lime to react fully to form calcium citrate (Ca3(C6H5O7)2·4H2O) precipitate. The pH value can be used to determine the end point of the reaction: when the pH rises to 10-11, the free citric acid has been largely consumed. After standing for 4 hours, solid-liquid separation is performed using a plate and frame filter press or centrifuge. The supernatant is collected and fed into the micro-electrolysis process.

[0085] The aluminum-copper micro-electrolysis treatment method for citric acid wastewater from power plant boilers provided by the embodiment of the present invention is described in detail below in conjunction with specific implementation.

[0086] Example 1

[0087] The aluminum-copper micro-electrolysis treatment method for citric acid wastewater from power plant boilers provided in an embodiment of the present invention was used to treat citric acid pickling liquid from a power plant. The main components of the wastewater were: chemical oxygen demand (CODCr) of 20,000 mg / L, pH of 3, copper ion concentration of 1.5 g / L, total chromium ion concentration of 0.05 g / L, nickel ion concentration of 0.002 g / L, the total amount of wastewater was approximately 5 tons, and the initial temperature of the wastewater was 40 degrees Celsius. The specific method is as follows:

[0088] Aluminum chips with a particle size of about 3 to 5 mm are selected and added into the wastewater at a weight 10 times the copper ion content in the wastewater (i.e. 75 kg). After reacting for 2 minutes, the copper-plated aluminum chips are fished out.

[0089] 15 kg of lime powder with a purity greater than 95% and a particle size greater than 200 mesh is added to the waste liquid and stirred for 30 minutes. The aluminum chips previously removed are then added back into the waste liquid. The reaction temperature is controlled within the preset range (40-60°C) for micro-electrolysis reaction, and the reaction lasts for 3 hours.

[0090] After the reaction is completed, solid-liquid separation is performed, the supernatant is taken and the pH is adjusted to neutral with hydrochloric acid to finally complete the wastewater treatment.

[0091] Example 2

[0092] The treatment method of the present invention was used to treat citric acid pickling liquid from a power plant, and the wastewater composition was the same as that in Example 1. The specific method is as follows:

[0093] Aluminum chips with a particle size of about 3 to 5 mm are selected and added into the wastewater at a weight twice the copper ion content in the wastewater (i.e. 15 kg). After reacting for 2 minutes, the copper-plated aluminum chips are fished out.

[0094] 15 kg of lime powder with a purity greater than 95% and a particle size greater than 200 mesh was added to the waste liquid and stirred for 30 minutes. The copper-plated aluminum chips previously removed were then added back into the waste liquid. The reaction temperature was controlled within the preset range (40-60°C) for micro-electrolysis reaction, and the reaction lasted for 3 hours.

[0095] After the reaction is completed, solid-liquid separation is performed, the supernatant is taken and the pH is adjusted to neutral with hydrochloric acid to finally complete the wastewater treatment.

[0096] Example 3

[0097] The treatment method of the present invention was used to treat citric acid pickling liquid from a power plant, and the wastewater composition was the same as that in Example 1. The specific method is as follows:

[0098] Aluminum chips with a particle size of about 3 to 5 mm are selected and added into the wastewater at a weight 50 times the copper ion content in the wastewater (i.e. 375 kg). After reacting for 2 minutes, the copper-plated aluminum chips are fished out.

[0099] 30 kg of lime powder with a purity greater than 95% and a particle size greater than 200 mesh is added to the waste liquid and stirred for 30 minutes. The copper-plated aluminum chips previously removed are then added back into the waste liquid. The reaction temperature is controlled within the preset range (40-60°C) for micro-electrolysis reaction, and the reaction lasts for 3 hours.

[0100] After the reaction is completed, solid-liquid separation is performed, the supernatant is taken and the pH is adjusted to neutral with hydrochloric acid to finally complete the wastewater treatment.

[0101] Example 4

[0102] The treatment method of the present invention was used to treat citric acid pickling liquid from a power plant, and the wastewater composition was the same as that in Example 1. The specific method is as follows:

[0103] Aluminum chips with a particle size of about 3 to 5 mm are selected and added into the wastewater at a weight 20 times the copper ion content in the wastewater (i.e. 150 kg). After reacting for 2 minutes, the copper-plated aluminum chips are fished out.

[0104] 25 kg of lime powder with a purity greater than 95% and a particle size greater than 200 mesh is added to the waste liquid and stirred for 30 minutes. The copper-plated aluminum chips previously removed are then added back into the waste liquid. The reaction temperature is controlled within the preset range (40-60°C) for micro-electrolysis reaction, and the reaction lasts for 3 hours.

[0105] After the reaction is completed, solid-liquid separation is performed, the supernatant is taken and the pH is adjusted to neutral with hydrochloric acid to finally complete the wastewater treatment.

[0106] Example 5

[0107] The treatment method of the present invention was used to treat citric acid pickling liquid from a power plant, and the wastewater composition was the same as that in Example 1. The specific method is as follows:

[0108] 15 kg of lime powder with a purity greater than 95% and a particle size greater than 200 mesh is added to the waste liquid and stirred for 30 minutes.

[0109] 5 kg of copper-aluminum intermediate compound (mainly composed of CuAl2 phase, whose XRD pattern analysis is as follows) prepared by high temperature diffusion method was used. Figure 2 The microelectrolysis reaction was carried out by controlling the reaction temperature within a preset range (40-60° C.) for 1 hour.

[0110] After the reaction is completed, solid-liquid separation is performed, the supernatant is taken and the pH is adjusted to neutral with hydrochloric acid to finally complete the wastewater treatment.

[0111] Example 6

[0112] The treatment method of the present invention was used to treat citric acid pickling liquid from a power plant, and the wastewater composition was the same as that in Example 1. The specific method is as follows:

[0113] 15 kg of lime powder with a purity greater than 95% and a particle size greater than 200 mesh is added to the waste liquid and stirred for 30 minutes.

[0114] 10 kg of copper-aluminum intermediate compound (mainly composed of CuAl phase and Cu9Al4 phase) prepared by high temperature diffusion method was mixed, and its XRD pattern analysis was as follows: Figure 3The microelectrolysis reaction was carried out by controlling the reaction temperature within a preset range (40-60° C.) for 1 hour.

[0115] After the reaction is completed, solid-liquid separation is performed, the supernatant is taken and the pH is adjusted to neutral with hydrochloric acid to finally complete the wastewater treatment.

[0116] Example 7

[0117] The treatment method of the present invention was used to treat citric acid pickling liquid from a power plant, and the wastewater composition was the same as that in Example 1. The specific method is as follows:

[0118] Aluminum chips with a particle size of about 3 to 5 mm are selected and copper plated in a 3% copper sulfate solution for 15 seconds before being fished out.

[0119] 15 kg of lime powder with a purity greater than 95% and a particle size greater than 200 mesh is added to the waste liquid and stirred for 30 minutes. Then, 75 kg of copper-plated aluminum chips are added to the waste liquid. The reaction temperature is controlled within a preset range (40-60°C) for micro-electrolysis reaction, and the reaction lasts for 3 hours.

[0120] After the reaction is completed, solid-liquid separation is performed, the supernatant is taken and the pH is adjusted to neutral with hydrochloric acid to finally complete the wastewater treatment.

[0121] The effects after treatment of the above embodiments are shown in the following table.

[0122] Example CODCr after treatment (mg / l) Cu removal rate % Total Cr removal rate% Ni% 1 29 99.5 98.6 99.9 2 47 99.0 99.0 99.9 3 83 99.1 98.9 99.9 4 63 99.3 98.8 99.9 5 35 99.6 99.1 99.9 6 15 99.2 99.2 99.9 7 46 99.1 97.9 99.9

[0123] Based on the above examples 1 to 7, the effectiveness of the treatment method provided by the embodiments of the present invention was verified. In each embodiment, the initial CODCr was 20000 mg / L, pH was 3, and the concentration of heavy metals (Cu 2+ 1.5g / L, Cr 6+ 0.05g / L, Ni 2+ 0.002g / L) of 5 tons of wastewater was used as the object, and different micro-electrolysis material combinations and process parameters were compared:

[0124] Examples 1-4: By adjusting the aluminum shavings dosage (2 to 50 times the copper ion content) in combination with lime pretreatment, efficient heavy metal removal (Cu removal rate 99.0%-99.5%, Cr removal rate 98.6%-99.0%) was achieved. However, the CODCr treatment effect fluctuated with the aluminum shavings dosage (29-83 mg / L). In Example 3, excessive aluminum shavings (375 kg) resulted in a high CODCr residue, indicating that the aluminum shavings dosage needs to be optimized.

[0125] Examples 5-6: Using copper-aluminum intermediate compounds (CuAl2 phase and mixed phase) prepared by high-temperature diffusion to replace aluminum chips significantly improved organic matter degradation efficiency. The mixed-phase material (CuAl / Cu9Al4) in Example 6 reduced CODCr to 15 mg / L, surpassing the single-phase material (Example 5, CODCr 35 mg / L), demonstrating that atomic-level hybrid structures can enhance microbattery activity.

[0126] Example 7: Aluminum scraps were quickly copper plated (15 seconds) using a copper sulfate solution. While ensuring the heavy metal removal rate, CODCr was controlled at 46 mg / L, verifying the feasibility of a low-cost copper plating process.

[0127] Common characteristics:

[0128] The lime pretreatment stage (15-30kg / 5t wastewater) effectively reduces CODCr to approximately 400mg / L, creating conditions for subsequent micro-electrolysis; the micro-electrolysis reaction temperature is controlled at 40-60℃, and the reaction time is 1-3 hours, taking into account both energy consumption and efficiency; the nickel ion removal rate is uniformly 99.9%, reflecting the strong adsorption characteristics of aluminum-based materials for trace heavy metals; the final effluent pH is neutralized to ensure discharge safety.

[0129] The copper-aluminum intermediate compound (especially the mixed phase) combined with optimized process parameters can achieve excellent results of CODCr < 50 mg / L and heavy metal removal rate > 99%, and the material reuse rate is high.

[0130] The steps described in the provided method embodiments may be performed in a different order and / or in parallel. In addition, the method embodiments may include additional steps and / or omit the steps shown. The scope of the present invention is not limited in this respect.

[0131] The term "embodiment" in this specification refers to specific features, structures, or characteristics described in conjunction with the embodiment that can be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor does it mean that it is mutually exclusive with other embodiments and is independent or optional. The various embodiments in this specification are described in a related manner, and the same or similar parts between the various embodiments are referenced to each other. In particular, for the embodiments of the device, equipment, and system, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts are referred to the partial description of the method embodiment.

[0132] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of the present invention. Therefore, the scope of the present invention shall be determined by the appended claims.

Claims

1. A method for treating citric acid wastewater from power plant boilers with aluminum and copper micro-electrolysis, characterized in that: include: Adding lime powder to citric acid wastewater from a power plant boiler, stirring and allowing to stand to obtain pretreated wastewater with solid-liquid separation; adding a micro-electrolysis material to the pretreated wastewater, performing a micro-electrolysis reaction under a preset temperature condition to generate micro-electrolysis reaction wastewater, wherein the micro-electrolysis material comprises at least one of aluminum chips, aluminum alloy copper plating, or a copper-aluminum intermediate compound; Hydrochloric acid is added to the micro-electrolysis reaction wastewater to adjust the pH to neutral to obtain treated target wastewater.

2. The method according to claim 1, characterized in that The preset temperature is 20° C. to 60° C., and the reaction time of the micro-electrolysis reaction is 3 hours.

3. The method according to claim 1, wherein The particle size of the aluminum chips or the aluminum alloy copper plating is 3 mm to 5 mm, the addition amount of the aluminum chips is 5 g / L to 10 g / L, and the addition amount of the aluminum alloy copper plating is 5 g / L to 10 g / L.

4. The method according to claim 3, characterized in that Before adding the electrolytic material to the pretreated wastewater and performing a micro-electrolysis reaction under preset temperature conditions to generate micro-electrolysis reaction wastewater, the method further includes copper plating the aluminum chips.

5. The method according to claim 4, characterized in that The copper plating treatment of the aluminum chips comprises: Determine the amount of aluminum chips used for copper plating according to the copper ion content in the citric acid wastewater of the power plant boiler, and the amount of aluminum chips used is 2 to 50 times the copper ion content in the citric acid wastewater of the power plant boiler; The aluminum chips in the used amount are placed in the citric acid wastewater of the power plant boiler and reacted for at least 2 minutes to complete the copper plating treatment of the aluminum chips.

6. The method according to claim 4, characterized in that The copper plating treatment of the aluminum scraps includes: immersing the aluminum scraps in a copper sulfate solution with a concentration of 3%-5%, and completing the copper plating after a reaction of 10 seconds to 1 minute.

7. The method according to claim 1, characterized in that The addition amount of the copper-aluminum intermediate compound is 1 g / L to 2 g / L.

8. The method according to claim 1, characterized in that The purity of the lime powder is greater than 95%, the particle size is greater than 200 meshes, and the dosage is 1.5 to 2 times the citric acid content in the citric acid wastewater of the power plant boiler.

9. The method according to claim 1, characterized in that After the lime powder is added to the citric acid wastewater from the power plant boiler, the stirring time is 30 minutes and the standing time is 4 hours.

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