Fenton alumina copper catalytic treatment method for citric acid wastewater of power plant boiler

Abstract

The invention belongs to the technical field of industrial wastewater treatment, and discloses a Fenton aluminum oxide copper catalytic 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; an oxidizing agent and a Fenton catalyst are added into the pretreated wastewater for a Fenton oxidation reaction, Fenton oxidation reaction wastewater is generated, and the Fenton catalyst comprises at least one of aluminum scraps, aluminum alloy plated copper or a copper-aluminum intermediate compound; hydrochloric acid is added into the Fenton oxidation reaction wastewater, the pH is adjusted to be neutral, and treated target wastewater is obtained. Based on the method, efficient and environment-friendly power plant boiler citric acid wastewater treatment is realized.

Description

Technical Field

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

[0002] With the rapid development of the power industry, the need for chemical cleaning of high-performance boilers is increasing. During this process, large quantities of citric acid wastewater are generated. This wastewater contains high concentrations of organic matter, with a chemical oxygen demand (CODCr) of tens of thousands of mg / L, as well as heavy metal ions and trace amounts of ammonia nitrogen, posing a serious threat to the environment.

[0003] Traditional wastewater treatment methods, such as incineration, complexation sedimentation, and biological treatment, suffer from high costs, complex processes, and long treatment cycles. For example, incineration consumes large amounts of energy and can generate secondary pollution; complexation sedimentation requires the use of large amounts of chemicals, and the efficiency of heavy metal removal is limited by the complexing agents; and biological treatment methods, due to the biotoxicity of high concentrations of organic matter, struggle to maintain stable operation, with treatment cycles often lasting dozens of days.

[0004] In recent years, advanced oxidation technologies, such as Fenton oxidation and ozone oxidation, have been able to degrade some organic matter. However, these technologies also face bottlenecks such as complex equipment, high processing costs, and the inability to simultaneously remove heavy metals. For power plant cleaning sites in particular, existing treatment methods, with their long processing times, high costs, and insufficient ability to synergistically remove pollutants, are insufficient to meet application requirements. Summary of the Invention

[0005] The embodiment of the present invention provides a Fenton alumina copper catalytic treatment method for citric acid wastewater from power plant boilers, which at least solves the problems of the treatment methods in the prior art such as long treatment time, high cost, insufficient synergistic removal capacity of pollutants and the like that cannot meet application requirements.

[0006] According to a first aspect of an embodiment of the present invention, a Fenton alumina copper catalytic treatment method for citric acid wastewater from a power plant boiler is provided, comprising:

[0007] 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;

[0008] adding an oxidant and a Fenton catalyst into the pretreated wastewater to perform a Fenton oxidation reaction to generate Fenton oxidation reaction wastewater, wherein the Fenton catalyst comprises at least one of aluminum chips, aluminum alloy copper plating, or a copper-aluminum intermediate compound;

[0009] Hydrochloric acid is added to the Fenton oxidation reaction wastewater to adjust the pH to neutral to obtain treated target wastewater.

[0010] According to an embodiment of the present invention, the reaction time of the Fenton oxidation reaction is 3 hours.

[0011] According to an embodiment of the present invention, the oxidant is hydrogen peroxide, and the added amount is 1 ml / L to 10 ml / L.

[0012] 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.

[0013] According to an embodiment of the present invention, before adding the oxidant and the Fenton catalyst into the pretreated wastewater to carry out the Fenton oxidation reaction to generate Fenton oxidation reaction wastewater, the method further includes copper plating the aluminum chips.

[0014] According to an embodiment of the present invention, the copper plating treatment on the aluminum scraps includes:

[0015] 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;

[0016] 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.

[0017] 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.

[0018] According to an embodiment of the present invention, the added amount of the copper-aluminum intermediate compound is 1 g / L to 2 g / L.

[0019] 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.

[0020] 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.

[0021] Beneficial effects of the embodiments of the present invention: The Fenton aluminum oxide copper catalytic treatment method for citric acid wastewater from power plant boilers provided by the embodiments of the present invention achieves efficient and environmentally friendly wastewater treatment through the synergistic effect of lime precipitation and Fenton oxidation. First, lime powder can effectively react with citric acid in the wastewater to generate calcium citrate precipitate with low solubility, thereby reducing the content of organic matter in the wastewater, and at the same time preliminarily fixes some heavy metal ions, creating favorable conditions for subsequent treatment steps. Then, in the Fenton oxidation reaction step, by adding hydrogen peroxide and Fenton catalyst, the replacement reaction between aluminum and heavy metal ions such as copper and chromium in the wastewater is utilized to generate elemental metal precipitates, thereby completely removing heavy metal pollution in the wastewater. At the same time, the active substances generated during the Fenton oxidation reaction, such as hydroxyl radicals, can further decompose residual citric acid and ammonia nitrogen organic matter. Finally, by adding hydrochloric acid to the Fenton oxidation reaction wastewater to adjust the pH to neutral, it is ensured that the treated wastewater can be directly and safely discharged. Based on the above method, the treatment time of citric acid wastewater is shortened, no complex equipment is required, and industrial waste aluminum chips and common lime materials are fully utilized. The treatment cost is low, and the solid precipitate finally generated is mainly non-toxic and harmless calcium citrate, which not only meets the emission standards but also realizes the needs of on-site rapid treatment, and has significant environmental friendliness and economic advantages.

[0022] 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

[0023] 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.

[0024] Figure 1 A flow chart of a Fenton alumina-copper catalytic treatment method for citric acid wastewater from a power plant boiler provided in an embodiment of the present invention.

[0025] 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.

[0026] 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

[0027] 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.

[0028] The development of the power industry has led to an increase in the frequency of chemical cleaning of high-performance boilers. The resulting citric acid wastewater, containing high concentrations of organic matter, heavy metal ions, and trace amounts of ammonia nitrogen, poses a significant environmental threat. Traditional treatment methods are subject to high costs, complex processes, and long lead times. While advanced oxidation technologies can degrade some organic matter, they are complex, expensive, and unable to simultaneously remove heavy metals. Existing technologies are limited in terms of treatment time, cost, and ability to synergistically remove pollutants, making them difficult to meet the needs of power plant cleaning sites.

[0029] In order to solve the above problems, an embodiment of the present invention provides a Fenton alumina copper catalytic treatment method for citric acid wastewater from power plant boilers. Figure 1 A flow chart of a Fenton alumina copper catalytic treatment method for citric acid wastewater from a power plant boiler provided in an embodiment of the present invention is shown in FIG. Figure 1 As shown, the method includes the following steps.

[0030] 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.

[0031] Step S102, adding an oxidant and a Fenton catalyst to the pretreated wastewater to perform a Fenton oxidation reaction to generate Fenton oxidation reaction wastewater, wherein the Fenton catalyst comprises at least one of aluminum chips, copper-plated aluminum alloy, or a copper-aluminum intermediate compound;

[0032] Step S103: adding hydrochloric acid to the Fenton oxidation reaction wastewater to adjust the pH to neutral to obtain treated target wastewater.

[0033] First, lime powder is added to citric acid cleaning wastewater collected on-site from power plant boilers. Specifically, during the stirring process, the lime powder reacts chemically with the citric acid in the wastewater to form calcium citrate solids with extremely low solubility. This chemical precipitation removes the vast majority of the citric acid in the wastewater as a precipitate, achieving initial degradation of organic pollutants and some metal-organic complexes, significantly reducing the CODCr level in the wastewater. After stirring, the mixture is allowed to stand to allow the formed precipitate to fully flocculate and settle. The precipitate can then be separated from the supernatant through solid-liquid separation, yielding clarified pretreated wastewater.

[0034] Next, an oxidant (such as hydrogen peroxide) and a Fenton catalyst are added to the pretreated wastewater. The catalyst can be selected from aluminum chips, copper-plated aluminum alloys, or copper-aluminum intermediate compounds. Under the action of the catalyst, the oxidant decomposes to produce highly active OH radicals, which deeply oxidize and degrade residual organic matter and ammonia nitrogen, further reducing CODCr to within national emission standards. Simultaneously, the aluminum on the catalyst surface undergoes a replacement or micro-electrolysis reaction with heavy metal ions such as copper and chromium in the wastewater, depositing elemental metal on the aluminum surface, effectively removing heavy metal ions. The resulting aluminum hydroxide colloid acts as a cohesive adsorbent for trace pollutants, achieving the synergistic removal of organic matter, ammonia nitrogen, and heavy metal ions.

[0035] Finally, after the Fenton oxidation reaction is complete, hydrochloric acid is slowly added to the clear liquid obtained through solid-liquid separation to adjust the pH to neutral. This process not only dissolves residual alkaline substances, ensuring the effluent pH is around 7, but also stabilizes the alumina colloid and metal precipitate generated during the reaction, thereby obtaining target treated water that meets emission requirements. This process effectively degrades organic matter and ammonia nitrogen in the wastewater, completely removing heavy metal ions. The overall treatment process is rapid and simple, making it suitable for on-site environmental protection treatment needs of power plants.

[0036] In an optional embodiment, when the oxidant and the Fenton catalyst are added to the pretreated wastewater to carry out the Fenton oxidation reaction, the reaction time of the Fenton oxidation reaction is 3 hours.

[0037] In this embodiment, after lime pretreatment is completed and clarified pretreated wastewater is obtained by solid-liquid separation, an appropriate amount of oxidant (preferably hydrogen peroxide) and the Fenton catalyst are slowly injected into the pretreated wastewater to start the Fenton oxidation reaction. The reaction system is continuously stirred to maintain sufficient contact between the catalyst surface and the residual organic matter in the wastewater, and to ensure that hydrogen peroxide can continuously generate OH radicals throughout the reaction process. The reaction temperature can be naturally set in the range of room temperature to 60°C without the need for additional heating equipment; the pH value can be monitored during the reaction. If it is slightly increased due to the formation of aluminum hydroxide colloid, hydrochloric acid can also be used in a trace amount at the end to adjust it, but it is advisable not to destroy the activity of the free radicals.

[0038] The entire Fenton oxidation step lasts three hours. After sufficient free radical attack, the residual citric acid, organic corrosion inhibitors, and ammonia nitrogen in the wastewater are completely degraded. Simultaneously, the catalytic micro-electrolysis synergistically removes heavy metal ions, significantly reducing the CODCr value from over 20,000 mg / L to approximately 400 mg / L. In this embodiment, the three-hour reaction time ensures a deep purification effect while meeting the efficiency requirements of industrial on-site treatment, forming a fast and efficient composite oxidation process model.

[0039] In an optional embodiment, an oxidant and a Fenton catalyst are added to the pretreated wastewater to perform a Fenton oxidation reaction. In the process of generating Fenton oxidation reaction wastewater, the oxidant is hydrogen peroxide, and the addition amount is 1 ml / L to 10 ml / L.

[0040] In this embodiment, after lime pretreatment and pretreated wastewater, hydrogen peroxide is slowly and continuously added to the clarified liquor as the sole oxidant. To ensure a smooth and controllable reaction, the hydrogen peroxide concentration can be calibrated to approximately 30% (w / w) before the addition of the Fenton catalyst. The hydrogen peroxide is then accurately added at a rate of 1 mL / L to 10 mL / L based on the total volume of the wastewater. The addition rate can be controlled within 0.5 L / h to prevent the generation of violent bubbles due to transient overdosage, which could affect the contact between the catalyst and the wastewater.

[0041] Hydrogen peroxide is catalytically decomposed on the surface of aluminum chips or copper-aluminum intermediate compounds, rapidly forming highly active hydroxyl radicals (·OH). These radicals can efficiently break the carbon-carbon bonds and functional groups in the residual citric acid molecular structure, achieving deep oxidation of organic matter, and further reducing the CODCr in the wastewater from approximately 400 mg / L before the case to below 100 mg / L. At the same time, because ·OH can also oxidize and decompose the amino groups contained in the corrosion inhibitor, it has a significant degradation effect on ammonia nitrogen pollutants, with a removal rate of more than 99%.

[0042] During the addition of hydrogen peroxide, the agitator maintains the mixed liquid's rotational speed at approximately 300 rpm, and the reaction system temperature is maintained between room temperature and 60°C. No additional heating or cooling equipment is required, thus simplifying on-site operating conditions. The reaction duration is generally controlled between 2 and 4 hours to ensure efficient free radical generation and sufficient contact with organic matter. After Fenton oxidation is complete, catalyst residues are removed through precipitation and filtration to obtain a deeply oxidized clear liquid, providing a stable and reliable water quality foundation for subsequent neutralization, adjustment, and compliance with discharge standards.

[0043] In an optional embodiment, the particle size of the aluminum chips or aluminum alloy copper plating in the Fenton catalyst 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.

[0044] In this specific embodiment, after the aforementioned lime pretreatment and solid-liquid separation, the morphology and particle size of the Fenton catalyst are first optimized. The aluminum chips or copper-plated aluminum alloy particles used in this embodiment have a particle size between 3 and 5 mm, ensuring a balanced surface area and mechanical stability. This size provides ample active surface area, promoting the decomposition of the oxidant on the catalyst surface to generate OH radicals. Furthermore, it effectively prevents particles from sticking to each other or clogging pipes during the reaction, ensuring good fluidity and uniform contact of the wastewater during circulation and agitation.

[0045] Subsequently, the screened aluminum chips or aluminum alloy copper-plated particles are added to the clarified pretreated wastewater at a ratio of 5g / L to 10g / L. Under slow stirring conditions, the catalyst is fully suspended in the aqueous phase and in full contact with the residual organic pollutants and metal complexes in the wastewater. At this time, the added hydrogen peroxide rapidly decomposes on the catalyst surface, producing a large number of OH free radicals, which efficiently oxidize organic molecules. At the same time, a micro-battery effect is formed inside the aluminum substrate and the copper layer, accelerating the reduction and precipitation of heavy metal ions through electron transfer. During the reaction, the shear force between the catalyst particles and the wastewater medium can continuously peel off the surface passivation layer, ensuring the continuous and stable release of catalytic activity, so that pollutants such as CODCr, ammonia nitrogen and heavy metals are synergistically removed within a relatively short reaction time.

[0046] After the reaction is completed, the catalyst particles can be separated from the treated water by conventional solid-liquid separation technology. Thanks to the larger particle size design, the catalyst shows good recyclability during the sedimentation or filtration process, and can be efficiently recycled and reused without complex centrifugation or high-pressure screening, thereby reducing operating costs. In addition, the alumina colloid formed on the surface of the catalyst can further adsorb trace residual pollutants in the subsequent neutralization adjustment or coagulation sedimentation stage, thereby improving the stability of the effluent. Through the above method, this embodiment not only ensures efficient deep oxidation and heavy metal removal, but also greatly optimizes the recycling performance of the catalyst, meeting the comprehensive requirements of the on-site treatment of citric acid cleaning wastewater from power plant boilers for reaction rate, treatment efficiency and equipment reliability.

[0047] In an optional embodiment, before adding the oxidant and the Fenton catalyst to the pretreated wastewater to carry out the Fenton oxidation reaction to generate Fenton oxidation reaction wastewater, the method further includes copper plating the aluminum chips.

[0048] Specifically, first, based on the test results of the copper ion content in the citric acid cleaning wastewater of the on-site power plant boiler, the amount of aluminum chips used for copper plating is determined. In the present embodiment, the amount of aluminum chips used for copper plating can be 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. The cleaned and dried aluminum chips are put into the wastewater to be treated. Under gentle stirring, the copper ions dissolved in the wastewater undergo a replacement reaction with the aluminum surface, so that metallic copper is deposited on the surface of the aluminum chips to form an aluminum-copper composite catalyst with a uniform copper layer. This copper layer not only significantly improves the catalytic activity of the aluminum chips in the subsequent Fenton oxidation reaction, but also further promotes the precipitation and removal of heavy metal ions by setting up a micro-galvanic couple between the aluminum matrix and the heavy metal ions in the wastewater. The surface of the aluminum chips after copper plating presents a micron-scale rough structure, which can significantly increase the effective catalytic area and provide more active sites for the generation of OH radicals, thereby showing a higher reaction rate and better treatment efficiency in the subsequent degradation of organic pollutants.

[0049] In another optional embodiment, the copper plating treatment of aluminum chips can be carried out by immersion metal conversion reaction using a concentrated copper salt solution. The pre-prepared copper salt solution is placed in a reaction tank, and the aluminum chips are directly immersed and kept immersed for a short time, so that the copper ions are quickly reduced and deposited on the aluminum surface to form a dense and well-adhesive copper film. In this embodiment, the aluminum chips can be immersed in a copper sulfate solution with a concentration of 3%-5%, and the copper plating is completed after 10 seconds to 1 minute of reaction. This method has the advantages of simple operation and uniform plating. At the same time, the thickness of the copper layer can be adapted to the requirements of different wastewater treatment intensities by controlling the immersion time. The obtained copper-plated aluminum chips can generate active free radicals more efficiently in the subsequent Fenton oxidation process, further improving the synergistic removal effect of residual organic matter and metal-organic complexes, while alleviating the passivation problem of the catalyst and ensuring the stability of continuous operation.

[0050] In an optional embodiment, the particle size of the copper-aluminum intermediate compound is 3 mm to 5 mm, and the addition amount is 1 g / L to 2 g / L.

[0051] In this embodiment, lime powder is first added to citric acid cleaning wastewater collected from power plant boilers on-site. It reacts with the citric acid in the wastewater under stirring conditions to produce a calcium citrate precipitate with extremely low solubility. This precipitate is then allowed to fully flocculate and settle before solid-liquid separation, significantly reducing the organic matter content in the wastewater and providing a clear pretreatment solution for subsequent deep processing. Subsequently, hydrogen peroxide and a copper-aluminum intermediate compound catalyst are slowly added to the pretreated wastewater. This catalyst, prepared by high-temperature diffusion and having a fixed atomic ratio, such as CuAl2 or Cu9Al4, exhibits a uniform atomic distribution of copper and aluminum atoms in the crystal lattice, exhibiting extremely high reactivity and achieving optimal catalytic effects at extremely low dosages. On the catalyst surface, hydrogen peroxide is catalytically decomposed to produce OH radicals, which rapidly oxidize and degrade residual citric acid organic matter and ammonia nitrogen. Simultaneously, the aluminum in the catalyst undergoes a replacement and micro-electrolysis reaction with heavy metal ions such as copper and chromium in the wastewater, depositing elemental metals on the catalyst surface and forming aluminum hydroxide colloids. The latter exhibits excellent cohesive adsorption properties, achieving synergistic removal of organic matter, ammonia nitrogen, and heavy metal ions. After the reaction reaches the desired level, the clear liquid is recovered through solid-liquid separation, and hydrochloric acid is slowly added to the clear liquid to adjust the pH to neutral, completely dissolving the residual alkaline components and stabilizing the aluminum oxide colloid and metal precipitate. Ultimately, treated water that meets national Class I emission standards is obtained. The entire process is simple to operate, time-efficient, and highly efficient, making it ideally suited for on-site environmental management needs in power plants.

[0052] In an alternative embodiment, the lime powder has a purity greater than 95% and a particle size greater than 200 mesh, and is added in an amount 1.5 to 2 times the citric acid content of the power plant boiler citric acid wastewater. After the lime powder is added to the power plant boiler citric acid wastewater, the mixture is stirred for 30 minutes and allowed to stand for 4 hours.

[0053] In this embodiment, the selected lime powder must possess extremely high chemical purity and a fine particle structure, capable of reacting rapidly and thoroughly with the citric acid in the wastewater after being added to the citric acid wash wastewater from power plant boilers. The high purity of the lime powder prevents impurities from interfering with the reaction activity. The resulting precipitate, formed by the lime powder and the citric acid, has a uniform crystal structure and fine particles. This allows it to quickly form dense flocs during the subsequent standing process, effectively intercepting and settling organic pollutants and metal-organic complexes in the wastewater, achieving ultra-efficient initial purification. After the reaction is complete, conventional solid-liquid separation processes can be used to obtain clarified pretreated wastewater with minimal suspended particles, significantly reducing the carbon emission load and catalyst depletion risk in the subsequent Fenton oxidation stage.

[0054] After the above-mentioned pretreatment steps are completed, the pretreated wastewater must be fully mechanically stirred before adding the oxidant and Fenton catalyst to ensure that the lime precipitate is in full contact with the water body and further promote the aggregation and separation of fine particles. During the stirring process, by selecting a reasonable impeller structure and rotation speed, the suspended particles can be kept in a stable dispersed state, enhancing the collision and coagulation efficiency of the precipitate. Subsequently, the mixed liquid is allowed to stand until the precipitate is completely settled and clearly stratified, ensuring that the supernatant contains almost no visible solid particles, achieving a stable and reliable solid-liquid separation effect, and providing a high-quality water quality foundation for the subsequent Fenton oxidation reaction. This method not only ensures the high efficiency of the pretreatment stage, but also lays a solid process foundation for the continuous and automated operation of the entire wastewater treatment process.

[0055] 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.

[0056] The following content is based on on-site sampling and testing of citric acid cleaning wastewater from a power plant boiler. The main characteristics of the wastewater are as follows: CODCr≈20000mg / L, pH≈3, Cu 2 +≈1.5g / L, total Cr≈0.05g / L, Ni 2 +≈0.002g / L, total amount is about 5 tons.

[0057] Example 1

[0058] 75kg of aluminum chips with a particle size of approximately 3-5mm (corresponding to 10 times the mass of the copper content in the wastewater) were added to the above wastewater. After reacting for 2 minutes, the aluminum chips were removed and set aside for use. Subsequently, 15kg of lime powder was added and allowed to fully contact the wastewater with slow stirring for about 30 minutes to form a calcium citrate precipitate and significantly reduce the CODCr level. After sufficient flocculation, the copper-plated aluminum chips previously removed were added, and 15L of hydrogen peroxide was slowly added dropwise along the same stirring direction to generate OH radicals on the aluminum / copper surface. A continuous Fenton oxidation reaction was carried out for 3 hours. After the reaction was completed, the clarified liquid was obtained through solid-liquid separation, and the pH was adjusted to about 7 with hydrochloric acid to obtain the final treated water.

[0059] Example 2

[0060] First, take 15kg of aluminum chips with a particle size of 3-5mm (corresponding to twice the mass of the copper content in the wastewater), react in the original wastewater for 2 minutes, and then recycle it for later use. Then add 15kg of lime powder to the wastewater and stir for 30 minutes to complete the preliminary pretreatment. After the precipitate is fully precipitated, add the recovered copper-plated aluminum chips and slowly add 5L of hydrogen peroxide. Under the same conditions, carry out Fenton oxidation reaction for 3 hours. After the reaction is completed, solid-liquid separation is carried out, and the pH of the supernatant is adjusted to neutral with hydrochloric acid to obtain qualified effluent.

[0061] Example 3

[0062] Take 375kg of aluminum chips with a particle size of 3-5mm (corresponding to 50 times the mass of the copper content in the wastewater), react in the wastewater for 2 minutes, and then remove it for use. Then add 30kg of lime powder and flocculate while stirring for 30 minutes. After the precipitate is formed, add the recovered copper-plated aluminum chips, and slowly add 50L of hydrogen peroxide in the same stirring direction and react for 3 hours. After completing Fenton oxidation, the solid-liquid separation is carried out and the pH is adjusted to about 7 with hydrochloric acid to obtain a purified water sample.

[0063] Example 4

[0064] 150 kg of aluminum chips with a particle size of 3-5 mm (corresponding to 20 times the mass of the copper content in the wastewater) were added to the wastewater and allowed to react for 2 minutes before being recycled for later use. Then, 25 kg of lime powder was added and stirred for 30 minutes. After primary precipitation and separation, the recovered copper-plated aluminum chips were added and 30 L of hydrogen peroxide was slowly added. The reaction was continued for 3 hours. After the reaction was completed, a clear solution was obtained by solid-liquid separation and the pH was adjusted to about 7 with hydrochloric acid to complete the treatment.

[0065] Example 5

[0066] First, 15 kg of lime powder was added to the wastewater and stirred for 30 minutes to remove most of the citric acid. Then 5 kg of the copper-aluminum intermediate compound prepared by high-temperature diffusion was added (XRD analysis showed that it was mainly CuAl2 phase, and its XRD pattern analysis was as follows Figure 2 After standing for 2 minutes, 15L of hydrogen peroxide was added and the Fenton reaction was carried out for 1 hour. After the reaction, the pH was directly adjusted to about 7 with hydrochloric acid to obtain a treated water sample.

[0067] Example 6

[0068] Similar to Example 5, 15 kg of lime powder was first added to the wastewater and stirred for 30 minutes; then 10 kg of the copper-aluminum intermediate compound obtained by high-temperature diffusion was added (XRD showed that the CuAl phase was mixed with the Cu9Al4 phase, and its XRD pattern analysis was as follows Figure 3 As shown), 30 L of hydrogen peroxide was slowly added and the reaction was continued for 1 hour. Finally, the pH of the effluent was adjusted to neutral with hydrochloric acid to complete the wastewater treatment.

[0069] The effects after the above embodiments are shown in the following table:

[0070] Example CODCr after treatment (mg / l) Cu removal rate % Total Cr removal rate% Ni% 1 39 99.5 98.6 99.9 2 67 99.0 99.0 99.9 3 92 99.1 98.9 99.9 4 59 99.3 98.8 99.9 5 55 99.6 99.1 99.9 6 25 99.2 99.2 99.9

[0071] The treatment effects of the above six examples all show that the method of the present invention has extremely high purification efficiency for citric acid cleaning wastewater from power plant boilers. Its main characteristics and rules can be summarized as follows:

[0072] Stable and excellent heavy metal removal effect:

[0073] Whether copper-plating aluminum chips before reacting (Examples 1-4) or using a copper-aluminum intermediate compound (Examples 5-6), the removal rates for Cu, Cr, and Ni all reached over 98.6%, with Ni removal remaining constant at 99.9%. This demonstrates that this method can achieve highly efficient, synergistic removal of multiple heavy metal ions under varying catalyst forms and dosages.

[0074] Strong CODCr degradation ability:

[0075] In the aluminum scrap copper plating system (Examples 1-4), as the copper content on the aluminum scrap increases, the CODCr value after treatment does not decrease linearly (ranging from 39 mg / L to 92 mg / L), indicating that the generation of OH radicals and the organic matter oxidation efficiency are also affected by the H2O2 dosage and flocculation conditions.

[0076] The copper-aluminum intermediate compounds prepared by high-temperature diffusion (Examples 5-6), especially the CuAl / Cu9Al4 mixed phase (Example 6), showed higher organic matter oxidation activity with CODCr reduced to 25 mg / L, indicating that the crystal structure of the intermediate compound has a positive effect on the OH generation activity and catalytic stability.

[0077] Balance between process parameters and effects:

[0078] The dosage of aluminum chips varied widely from 15 kg (Example 2) to 375 kg (Example 3), but CODCr was better when the dosage was moderate (75-150 kg, corresponding to Examples 1 and 4), suggesting that excessive catalyst may cause excessive precipitation or competitive consumption of ·OH.

[0079] The amount of H2O2 added is directly related to the generation of ·OH, but in the aluminum chip system, the change of 15-50L did not significantly improve the CODCr and removal rate, indicating that catalyst activity and mixing efficiency are more critical.

[0080] Although Examples 5 and 6 do not carry out the copper plating step, good results can be achieved with only 5-10 kg of the intermediate compound, and its ·OH catalytic efficiency and material recycling potential are better than the aluminum scrap copper plating system.

[0081] Process simplicity and on-site applicability:

[0082] The overall process is "lime pretreatment - catalyst reaction - H2O2 oxidation - solid-liquid separation - pH adjustment", and the operation steps are coherent and clear.

[0083] The reaction time is concentrated within 1-3 hours, and no precise temperature control or additional additives are required. It meets the rapid processing requirements of power plants and has good engineering promotion value.

[0084] The treatment method of the embodiment of the present invention can stably and efficiently remove CODCr and heavy metals from wastewater under various catalyst forms and dosage conditions, and performs best when a copper-aluminum intermediate compound is used as a catalyst. It not only reduces the amount of catalyst used, but also further reduces the CODCr after treatment, achieving dual optimization of process economy and environmental benefits.

[0085] 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.

[0086] 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.

[0087] 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 Fenton alumina copper catalytic treatment method for citric acid wastewater from power plant boilers, 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 an oxidant and a Fenton catalyst into the pretreated wastewater to perform a Fenton oxidation reaction to generate Fenton oxidation reaction wastewater, wherein the Fenton catalyst comprises at least one of aluminum chips, aluminum alloy copper plating, or a copper-aluminum intermediate compound; Hydrochloric acid is added to the Fenton oxidation reaction wastewater to adjust the pH to neutral to obtain treated target wastewater.

2. The method according to claim 1, characterized in that The reaction time of the Fenton oxidation reaction is 3 hours.

3. The method according to claim 1, characterized in that The oxidant is hydrogen peroxide, and the added amount is 1 ml / L to 10 ml / L.

4. 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.

5. The method according to claim 1, wherein Before adding the oxidant and the Fenton catalyst into the pretreated wastewater to carry out the Fenton oxidation reaction to generate Fenton oxidation reaction wastewater, the method further includes copper plating the aluminum chips.

6. The method according to claim 5, 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.

7. The method according to claim 5, 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.

8. 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.

9. 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.

10. 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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