Method for realizing cyclic degradation of HEDP by activating PMS with cobaltosic oxide by using stepped reaction device

Abstract

The invention relates to a method for realizing cyclic degradation of HEDP by activating PMS with cobaltosic oxide by using a stepped reaction device, the stepped reaction device comprises a plurality of stepped structures which are connected in sequence and are provided with gradually reduced top openings, and cobaltosic oxide is wrapped with filter paper and then is fixed in each stepped structure; wastewater containing hydroxyethylidene-1, 1-diphosphonic acid is pumped into the first stepped structure at the highest point, PMS is pumped at the same time, a first-stage reaction is carried out, along with the proceeding of the reaction, a reaction solution is gradually increased, when the first stepped structure is filled with the reaction solution, the reaction solution fully reacts under the action of gravity and seepage, and then the reaction solution flows into the second stepped structure; and continuously carrying out the reaction of the second stage, and entering the next stepped structure of the stepped reaction device according to the same method to carry out the reaction of the next stage until the reaction is completed.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental engineering and relates to a method for realizing the cyclic degradation of HEDP by activating PMS with cobalt tetroxide by using a step reaction device. Background Art

[0002] HEDP (hydroxyethylidene diphosphonic acid) is a commonly used organic phosphoric acid scale and corrosion inhibitor, widely used in industrial circulating cooling water systems in power, chemical, metallurgical, and fertilizer industries. However, due to its high stability and resistance to degradation, high levels of HEDP in industrial wastewater can cause excessive total phosphorus concentrations and pollute the environment. Therefore, effective measures are needed to remove HEDP from wastewater.

[0003] At present, there are many difficulties in the degradation of HEDP. Although physical and chemical methods can effectively remove organic phosphorus, the steps are cumbersome and the cost is high. For example, oxidation degradation is required in the early stage, followed by chemical precipitation, which is not conducive to operation. The biodegradation method cannot meet the requirements of wastewater treatment, reuse and discharge because the conventional biodegradation rate of HEDP is less than 5%. In addition, although some advanced oxidation processes have good treatment effects, they often have problems such as harsh reaction conditions, high energy consumption, and secondary pollution to the environment. For example, some methods require the use of large amounts of chemical reagents, or need to be carried out under extreme temperature and pressure conditions, and toxic and harmful by-products may be produced during the degradation process.

[0004] The existing HEDP degradation method specifically has the following deficiencies:

[0005] 1. Traditional chemical methods: Such as chemical precipitation, which requires the addition of large amounts of chemical reagents, is prone to secondary pollution and has unsatisfactory treatment results. Methods such as flocculation and precipitation have low HEDP removal rates and are difficult to meet the requirements of advanced treatment.

[0006] 2. Biodegradation method: Conventional biodegradation rate is low and easily affected by environmental factors, making it difficult to stably remove HEDP.

[0007] 3. Advanced Oxidation Processes (AOPs): While traditional AOPs (such as the Fenton process and ozone catalytic oxidation) can effectively degrade organic matter, they suffer from high operating costs, demanding equipment requirements, and the generation of large amounts of solid waste, such as iron sludge. Furthermore, when treating high-concentration organophosphorus wastewater, they often require large amounts of oxidants and catalysts, resulting in poor economic efficiency.

[0008] 4. Other methods: such as electrochemical advanced oxidation method, although it has a good degradation effect on HEDP, it requires specific electrode materials and electrolyte conditions, large equipment investment, high energy consumption, and is difficult to apply on a large scale.

[0009] 5. The easy leaching of cobalt ions is the biggest difficulty in using cobalt tetroxide as a catalyst.

[0010] In summary, the existing HEDP degradation technology has many problems, which limit its application scope and treatment effect. Therefore, there is an urgent need to develop an efficient, mild, environmentally friendly and low-cost degradation method to overcome the shortcomings of existing technology and meet the increasingly stringent wastewater treatment and environmental protection requirements. Summary of the Invention

[0011] In view of this, the object of the present invention is to provide a method for cyclically degrading HEDP by activating PMS with cobalt tetroxide using a step reaction device.

[0012] In order to achieve the above object, the present invention provides the following technical solutions:

[0013] A method for cyclically degrading HEDP (hydroxyethylidene diphosphonic acid) by activating PMS (peroxymonosulfate) with cobalt tetraoxide using a step reaction device. The step reaction device comprises a plurality of step structures connected in sequence and with gradually lowering top openings. Cobalt tetraoxide is wrapped with filter paper and fixed in each step structure. Wastewater containing hydroxyethylidene diphosphonic acid is pumped into the first step structure at the highest point, and PMS is pumped into the step structure at the same time to carry out a first-stage reaction. As the reaction proceeds, the amount of reaction solution gradually increases. When the reaction solution fills the first step structure and fully reacts under the action of gravity and seepage, it flows into the second step structure to continue the second-stage reaction. In the same manner, the reaction solution enters the next step structure of the step reaction device to carry out the next-stage reaction until the reaction is completed.

[0014] Preferably, two layers of porous baffles, one above the other, are provided in each stepped structure, and a material stacking area is formed between the two layers of porous baffles for fixing cobalt trioxide.

[0015] Preferably, multiple layers of filter paper are provided in the last stepped structure to intercept the leaching of cobalt trioxide.

[0016] Preferably, the step reaction device includes a first side plate assembly and an internal baffle assembly, the first side plate assembly includes front and rear side plates and a right side plate, the front and rear side plates are arranged on one side of the internal baffle assembly, the right side plate is arranged on the lowest point side of the device and is provided with a water outlet;

[0017] The internal baffle assembly includes a left baffle, a lower baffle, a right baffle and a baffle with holes, the plurality of left baffles are arranged in a stepped manner, the plurality of lower baffles are arranged on the bottom side of the left baffle, the plurality of right baffles are respectively connected to the plurality of baffles with holes and the left baffle, and the baffle with holes is arranged between the left baffle and the right baffle and located above the lower baffle;

[0018] The left baffle, the lower baffle, the right baffle and the baffle with holes cooperate to form a plurality of step structures.

[0019] Further preferably, the left baffle, the lower baffle, the right baffle and the baffle with holes are fixed by gluing.

[0020] Further preferably, a space is reserved between the left baffle and the right baffle.

[0021] Further preferably, a connecting pipe is provided on the outside of the water outlet hole opened on the right side panel.

[0022] Further preferably, the stepped structure can be increased or decreased according to actual needs.

[0023] Preferably, the ratio of PMS, cobalt trioxide, and HEDP is 10 mg:20 mg:8 μmol, and cobalt trioxide is evenly distributed and fixed in each ladder structure.

[0024] Preferably, the reaction conditions are: stirring rate 400-600 r / min, temperature 25-35° C., pH=3.6-10.

[0025] More preferably, the reaction conditions are: stirring rate 500 r / min, temperature 30° C., pH=7-8.5.

[0026] Preferably, when the wastewater contains a small amount of bicarbonate, sodium bicarbonate is added to the wastewater so that the total mass of bicarbonate is equal to that of PMS.

[0027] More preferably, the concentration of bicarbonate in the wastewater is 0 to 5 mmol / L, more preferably 0.5 to 2 mmol / L, and even more preferably 1 mmol / L.

[0028] The working principle of the present invention is as follows:

[0029] 1. Reaction system composition

[0030] Synergistic Effect of Basic Components: PMS and cobalt oxide catalyst are simultaneously added to HEDP-containing wastewater to create a ternary reaction system. HEDP serves as the target degradation product, PMS acts as an oxidant, and cobalt oxide acts as a catalyst. The three work together to trigger a complex redox reaction chain, promoting the breakdown of HEDP's molecular structure and the degradation of its performance.

[0031] Precise dosage of key substances: The dosage of each substance is flexibly adjusted based on water quality characteristics and treatment objectives. In standard mode, 40mL (200 μmol / L) of HEDP solution is used as the base, along with 10mg of PMS and 20mg of cobalt tetroxide. This ratio has been experimentally verified to achieve an optimal balance between efficiency and cost. In actual applications, for high-concentration wastewater, the dosage of PMS and catalyst can be appropriately increased. For larger water volumes, the components are proportionally expanded to ensure reaction efficiency.

[0032] 2. Reaction condition control

[0033] Precise temperature control strategy: The optimal reaction temperature range is 25-35°C, with 30°C being the optimal practical value. In this temperature range, catalyst activity is fully stimulated, achieving both high free radical generation rate and stability. A water bath heating device is equipped to monitor and control the bath temperature in real time, maintaining a reaction temperature fluctuation within ±1°C. In low-temperature environments, a moderate reaction delay or a slight temperature increase is used to accelerate the reaction. In high-temperature environments, enhanced heat dissipation is used to prevent catalyst deactivation and the occurrence of side reactions.

[0034] Efficient stirring: A magnetic stirrer maintains homogeneous stirring of the solution at a stirring rate of 400-600 rpm, with 500 rpm being the standard. This speed eliminates mass transfer resistance and ensures sufficient collision between the PMS, catalyst, and HEDP. For high-viscosity wastewater, the speed is increased appropriately; for low-viscosity water, the speed is slightly reduced, balancing mixing efficiency with energy consumption control to maintain uniform mass transfer in the liquid phase.

[0035] 3. Activation of catalyst

[0036] Electronic Structure Catalytic Mechanism: Cobalt tetroxide's unique electron configuration and surface lattice properties disrupt the PMS electron cloud density upon contact with PMS molecules, weakening the O-O double bonds within them. This not only reduces the activation energy for PMS decomposition but also accelerates the generation of sulfate and hydroxyl radicals. These radicals, leveraging their high reactivity, attack HEDP molecules, dismantling their stable PC and PO backbones, leading to their gradual mineralization into inorganic phosphate, CO2, and H2O.

[0037] In-depth analysis of active sites: oxygen vacancies enriched on the surface of cobalt tetroxide and Co 3+ The active center is the key site for activating PMS. Oxygen vacancies adsorb PMS and distort its geometric configuration; Co 3+ This provides an electron transfer channel, catalyzing the cleavage of the O-O bond. Recycling studies have shown that the active sites of cobalt tetroxide can be restored after a simple regeneration process, ensuring multiple rounds of catalytic efficiency.

[0038] 4. Optimization of influencing factors

[0039] pH-sensitive control response: System pH is a key influencing factor. Within the pH range of 4 to 10, HEDP degradation initially increases and then stabilizes as the pH rises. Above pH 10, excessive hydroxide ions occupy the catalyst's active sites, inhibiting free radical production and causing the degradation rate to decline. Real-time monitoring with an online pH meter and fine-tuning of the acid and base levels using an automated titration system stabilizes the reaction solution's pH within the optimal range of 7 to 8.5.

[0040] Careful matching of catalyst dosage: Cobalt tetroxide dosage is positively correlated with HEDP degradation, but excess can cause free radical dissipation and catalyst particle agglomeration. Orthogonal experiments have shown that 20-30 mg of catalyst combined with 40 mL (200 μmol / L) of HEDP solution achieves the best balance between degradation efficiency, cost-effectiveness, and stability.

[0041] Directed adaptation of the ion environment: the addition of anions has a significant effect on the reaction. - It can not only supplement carbon sources and adjust pH, but also moderately promote the generation of free radicals; SO4 2- 、NO3 - Because it competes with free radicals for active sites, it inhibits degradation at high concentrations. Based on the actual ion spectrum of the water, precise dosing or impurity removal is performed to optimize the reaction microenvironment.

[0042] Through the above comprehensive and detailed technical layout and optimization strategy, the present invention not only solves the HEDP degradation problem, but also opens up a new path for the treatment of phosphorus-containing wastewater, and has outstanding technological innovation value and practical guiding significance.

[0043] The beneficial effects of the present invention are:

[0044] The invention provides a method for realizing the degradation of HEDP by activating PMS with cobalt tetroxide using a step reaction device. The method comprises the following steps: pumping wastewater containing HEDP into the first step of the step reaction device, adding potassium persulfate (PMS) and cobalt tetroxide, and performing a first-stage reaction. As the reaction proceeds, the amount of the reaction solution gradually increases. When the first step is filled with the reaction solution, the reaction solution flows into the second step of the step reaction device under the action of gravity, and continues the second-stage reaction. The reaction solution then enters the next step of the step reaction device in the same manner, and performs the next-stage reaction until the reaction is completed.

[0045] The present invention utilizes a stepped reaction apparatus, enabling reactions to proceed sequentially under different conditions and stages, with each stage optimized for specific reaction requirements. This multi-stage reaction design not only enhances reaction flexibility but also significantly improves the utilization efficiency of the solid catalyst, ensuring efficient and thorough reactions, thereby enabling complex multi-step reaction processes.

[0046] The core innovation of this invention lies in the use of a step-by-step reaction apparatus to introduce a cobalt trioxide (Co3O4) catalyst into a potassium persulfate (PMS) activation system. This provides a novel solution to the HEDP (hydroxyethylidene diphosphonic acid) degradation challenge, achieving faster, more thorough, and environmentally friendly HEDP degradation while reducing reaction costs and environmental impact. The invention utilizes a recycling process, significantly reducing cobalt ion leaching. Specific advantages are as follows:

[0047] 1. The present invention introduces a stepped reaction device to solve the problem of insufficient mixing between stages in existing reactors, which leads to uneven contact between reactants and reactants, and between reactants and catalysts, and reduces mass transfer efficiency. During the reaction process, the solution is first pumped into the first highest point of the stepped structure formed by the left baffle, the lower baffle, the right baffle, and the perforated baffle. As the reaction proceeds, the solution gradually increases. When the liquid level reaches a certain height, it automatically flows into the buffer chamber of the next step under the action of gravity to continue the next stage of the reaction. In this way, the internal liquid gravity can be used as the flow power, replacing the conventional pump power, avoiding the accumulation of fluid resistance. The liquid contacts the solid reactants or catalysts at each level from bottom to top, so that the reactants are fully mixed with the reactants and the reactants and the catalyst are fully mixed, thereby increasing the reaction efficiency. This step-by-step design enables the reaction to be carried out in sequence under different conditions and stages, and each stage can be optimized according to specific reaction requirements. The multi-stage reaction design of the present application not only improves the flexibility of the reaction, but also significantly improves the utilization efficiency of the solid catalyst, ensures the high efficiency and thoroughness of the reaction, thereby realizing a complex multi-step reaction process, and thus can solve the problem of insufficient mixing between stages of the existing reactor, resulting in uneven contact between reactants and reactants, and reactants and catalysts, which reduces the mass transfer efficiency.

[0048] 2. From the perspective of improving degradation efficiency, the cobalt tetroxide catalyst can effectively activate PMS and promote its decomposition to produce active free radicals. These active free radicals have extremely strong oxidizing ability and can undergo rapid redox reactions with HEDP molecules, thereby achieving a high degree of HEDP degradation in a relatively short period of time. Compared with traditional methods, the reaction time is greatly shortened, effectively solving the problem of low degradation efficiency in existing technologies.

[0049] Deep oxidation: Cobalt trioxide catalyst has a highly effective activation effect on PMS, which can promote its decomposition to produce a variety of strong oxidizing active substances, such as sulfate radicals (SO4 - ), hydroxyl radicals (·HO), etc. These free radicals have extremely high redox potentials and can undergo rapid redox reactions with HEDP molecules, effectively breaking chemical bonds such as PC and PO in HEDP molecules, thereby achieving deep oxidative degradation of HEDP.

[0050] Fast Response: Compared to traditional degradation methods, the present invention achieves significant degradation results in a shorter time. For example, under experimental conditions, the present invention's method can achieve a HEDP degradation rate of over 70% within 60 minutes, while traditional methods such as biodegradation may take hours or even days to achieve a similar degree of degradation. This effectively solves the problem of low degradation efficiency in existing technologies, significantly shortens wastewater treatment time, and improves treatment efficiency.

[0051] 3. In terms of mild reaction conditions, the degradation process of the present invention can be carried out under mild conditions such as room temperature and normal pressure, without the need for extreme conditions such as high temperature and high pressure, which reduces the requirements for equipment and energy consumption, makes the operation simpler and safer, and is conducive to practical application and promotion, avoiding the safety hazards and high cost problems caused by harsh reaction conditions in traditional methods.

[0052] Feasible at room temperature and pressure: The degradation process can proceed smoothly under normal conditions such as relatively mild temperatures (e.g., around 30 degrees Celsius) and normal pressure. It eliminates the need for extreme conditions such as high temperature and pressure, reducing the requirements for reaction equipment and energy consumption, and avoiding the safety hazards and equipment corrosion problems associated with high temperature and pressure. This makes the operation simpler and safer, facilitating practical application and promotion, and is particularly suitable for large-scale wastewater treatment systems.

[0053] Wide pH adaptability: Experimental studies have shown that the present invention can maintain a good degradation effect in a wide pH range of 4 to 10, which enables it to adapt to the wastewater treatment needs under different water quality conditions. There is no need for strict acid-base adjustment of the wastewater, which further simplifies the treatment process and reduces treatment costs.

[0054] 4. From the perspective of environmental friendliness, the PMS and cobalt tetroxide catalysts used will not introduce substances harmful to the human body and the environment during the reaction process, and the degradation products are harmless to the environment and will not cause secondary pollution. They meet current environmental protection requirements and have significant environmental advantages compared to some methods in the existing technology that produce toxic and harmful by-products.

[0055] Green and harmless: The PMS and cobalt tetroxide catalysts used are environmentally friendly materials. The reaction process does not introduce toxic and hazardous substances such as heavy metal ions and organic solvents that are harmful to humans and the environment. The degradation products, primarily inorganic phosphates, carbon dioxide, and water, are harmless to the environment and do not cause secondary pollution. This meets increasingly stringent environmental protection requirements and is beneficial to protecting the ecological environment and human health.

[0056] Sustainable development: This invention provides a clean and efficient solution for the treatment of HEDP wastewater, which helps to reduce the total phosphorus content in industrial wastewater and reduce the risk of eutrophication of water bodies. It is of great significance to promote the sustainable development of the chemical and environmental fields.

[0057] 5. In terms of cost control, the cobalt tetroxide catalyst has good stability and recyclability, allowing for multiple recycling, reducing the cost of the catalyst. Furthermore, PMS is a relatively inexpensive and readily available oxidant, further reducing the cost of the entire degradation process, making it more economically competitive and meeting the cost control needs of large-scale wastewater treatment.

[0058] Low Oxidant Cost: PMS, a common peroxide oxidant, is relatively inexpensive and widely available. Compared to expensive imported oxidants or specialized chemical reagents, using PMS significantly reduces raw material costs. Furthermore, due to the efficient degradation performance of the present invention, the required amount of PMS is relatively small, further reducing treatment costs.

[0059] Significant overall economic benefits: From a process cost perspective, this invention eliminates the need for complex equipment and demanding reaction conditions, reducing equipment investment and operating energy consumption. Combined with the cost advantages of both the catalyst and the oxidant, the overall degradation process is effectively cost-effective. Compared to traditional advanced oxidation processes (such as the Fenton process and ozone catalytic oxidation), this method offers greater economic competitiveness and meets the cost control requirements of large-scale wastewater treatment, providing strong support for industrial enterprises in reducing wastewater treatment costs and improving economic efficiency.

[0060] 6. Solve the problems of the existing technology. The existing technology has many problems such as low degradation efficiency, harsh conditions, high cost and easy secondary pollution. The present invention effectively overcomes these problems by activating PMS to degrade HEDP through cobalt tetroxide catalyst, providing a new and effective solution for the degradation of HEDP. It is expected to be widely used in the chemical and environmental fields and promote the sustainable development of related industries.

[0061] In summary, the present invention exhibits significant advantages in terms of efficient HEDP degradation, adaptability to mild reaction conditions, environmental friendliness, and cost control, providing an ideal solution to the technical difficulties of existing HEDP degradation, and has broad application prospects and important practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to make the purpose, technical solutions and beneficial effects of the present invention more clear, the present invention provides the following drawings for illustration:

[0063] Figure 1 Schematic diagram of the structure of the step reaction device; among them, 1, 5, 9, 13, 17-left baffle; 2, 6, 10, 14, 18-lower baffle; 3, 7, 11, 15, 19-right baffle; 4, 8, 12, 16, 20-perforated baffle; 21-water outlet; 22-front and rear side panels; 23-right side panel; A-first step.

[0064] Figure 2 It is a structural schematic diagram of the ladder structure of the present invention.

[0065] Figure 3 It is a structural schematic diagram of the upper and lower arrangements of the perforated baffles of the present invention.

[0066] Figure 4 This is the effect of PMS dosage on the degradation effect.

[0067] Figure 5 The effect of different reaction temperatures on the degradation effect.

[0068] Figure 6 This is the effect of pH on the degradation of HEDP.

[0069] Figure 7 is the effect of anions on the degradation of HEDP, where A is bicarbonate, B is sulfate, and C is nitrate.

[0070] Figure 8 This is the effect of the amount of cobalt trioxide catalyst on the degradation effect.

[0071] Figure 9 The present invention uses a step reaction device to realize the method of activating PMS with cobalt tetroxide to degrade HEDP, wherein A is the HEDP degradation effect and B is cobalt leaching.

[0072] In the figure: 1, 5, 9, 13, 17 - left baffle; 2, 6, 10, 14, 18 - lower baffle; 3, 7, 11, 15, 19 - right baffle; 4, 8, 12, 16, 20 - baffles with holes; 21 - water outlet; 22 - front and rear side panels; 23 - right side panel; A - stepped structure. DETAILED DESCRIPTION

[0073] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0074] Referring to Examples 1 to 5, intermittent beaker experiments were used to screen the reaction conditions.

[0075] Reference Example 1: HEDP degradation under basic conditions

[0076] Preparation of reaction materials: Prepare 40 mL of HEDP solution (concentration of 200 μmol / L) using ultrapure water.

[0077] Reaction procedure: 10 mg of PMS and 20 mg of cobalt tetroxide were added to the HEDP solution. The reaction system was placed in a 30°C water bath and magnetically stirred at 500 rpm to start the reaction.

[0078] Reaction process monitoring: within 60 minutes of reaction, samples were taken at 3, 6, 10, 25, 45, and 60 minutes to analyze the degradation of HEDP and the dissolution of cobalt ions.

[0079] Results: The experimental results showed that under the reaction conditions, the HEDP degradation rate gradually increased over time, reaching over 85% at 60 minutes. Furthermore, the amount of cobalt ion dissolution remained stable and within an acceptable range during the reaction. This demonstrates that the cobalt tetroxide catalyst exhibits good catalytic activity and stability in this system, effectively degrading HEDP without excessive catalyst dissolution, which could lead to a decrease in catalytic performance or introduce additional environmental concerns.

[0080] Reference Example 2: Effect of PMS dosage on degradation effect ( Figure 4 )

[0081] Preparation of reaction materials: same as in Example 1.

[0082] Reaction operation: In the reaction system, the amount of PMS was adjusted to 5 mg, and other conditions were the same as in Example 1.

[0083] Results: Compared with Example 1, the HEDP degradation rate decreased somewhat, reaching only approximately 60% after 60 minutes. This indicates that the PMS dosage significantly affects the degradation efficiency. Increasing the PMS dosage appropriately can increase the generation of active free radicals in the system, thereby accelerating the HEDP degradation rate. However, increasing the PMS dosage also leads to increased costs. Therefore, in practical applications, it is necessary to comprehensively consider factors such as degradation efficiency and cost to determine the optimal PMS dosage.

[0084] Reference Example 3: Effect of different reaction temperatures on degradation effect ( Figure 5 )

[0085] Preparation of reaction materials: same as in Example 1.

[0086] Reaction operation: The reaction temperature was adjusted to 20°C and 40°C respectively, and other conditions were the same as in Example 1, and experiments were carried out respectively.

[0087] Analysis of the results showed that at 20°C, the HEDP degradation rate was approximately 55%, indicating a slow degradation rate. At 40°C, the degradation rate reached approximately 75%, indicating an accelerated degradation rate. However, compared to 30°C, the degradation rate at 40°C was not significantly improved, and this may lead to increased energy consumption. Considering both degradation efficiency and energy consumption, the optimal reaction temperature was determined to be approximately 30°C. At this temperature, the catalyst activity and free radical generation reached an optimal balance, enabling efficient and economical HEDP degradation.

[0088] Figure 6The effect of pH on HEDP degradation shows that within the range of pH = 3.6 to 10, pH changes will not affect HEDP degradation.

[0089] Reference Example 4: Effect of anions on HEDP degradation and cobalt ion dissolution ( Figure 7 )

[0090] Preparation of reaction materials: same as in Example 1.

[0091] Reaction procedure: Different amounts of sodium bicarbonate (NaHCO3), sodium sulfite (NaSO3) and sodium nitrate (NaNO3) were added to the reaction system, with other conditions being the same as in Example 1, to study the effects of anions on HEDP degradation and cobalt ion dissolution.

[0092] Results: The experiment showed that as the amount of sodium bicarbonate added increased, the degradation of HEDP first increased and then decreased, showing an effect of first promoting and then inhibiting. When the amount added was 10 mg, the degradation rate reached over 90%; when the amount added was further increased to 20 mg, the degradation rate dropped to about 70%. At the same time, the dissolution of cobalt ions also changed with the increase in the amount of sodium bicarbonate added, first increasing moderately and then stabilizing. 2- and NO3 - It has little effect on HEDP degradation and cobalt ion dissolution. When the addition amount is within the range of 10-20 mg, the degradation rate fluctuates by no more than 5%, and the change in the amount of cobalt ion dissolution is also relatively stable. This provides an important reference for adjusting the reaction conditions according to the water quality in practical applications. For example, when treating wastewater containing a certain amount of bicarbonate, the degradation effect of HEDP can be enhanced by adding an appropriate amount of sodium bicarbonate, while when treating wastewater containing SO3 2- or NO3 - When treating wastewater, there is no need to specially adjust the concentration of these ions.

[0093] from Figure 7 As can be seen in A, under the conditions of PMS / Co3O4, HCO 3- The concentration gradually increases from 0mM, 0-5mM has a better auxiliary effect, 0.5-2mM has a better auxiliary effect, and at 1mM HCO 3- The degradation rate is the best, HCO 3- When it exceeds 1mM, the auxiliary effect gradually decreases, and when it reaches 40mM, it has a very obvious counter-effect and inhibitory effect.

[0094] Reference Example 5: Effect of Cobalt Tetroxide Catalyst Amount on Degradation Effect ( Figure 8 )

[0095] Preparation of reaction materials: same as in Example 1.

[0096] Reaction operation: the amount of cobalt trioxide catalyst was adjusted to 5 mg, 15 mg, 25 mg, and 30 mg respectively. Other conditions were the same as those in Example 1.

[0097] Analysis of the results showed that when the cobalt oxide dosage was 5 mg, the HEDP degradation rate was only about 60%. When the dosage was increased to 15 mg, the degradation rate increased to about 78%. At 25 mg, the degradation rate reached about 90%. When further increased to 30 mg, the degradation rate only rose slightly to about 92%, but the amount of cobalt ion dissolution increased slightly. This indicates that increasing the catalyst dosage in moderation is beneficial to improving the degradation effect, but excessive use can lead to catalyst particle agglomeration, reduce active sites, increase costs and dissolution risks. About 25 mg can basically meet the requirements of efficient and stable degradation.

[0098] Example 1

[0099] A method for cyclically degrading HEDP (hydroxyethylidene diphosphonic acid) by activating PMS (peroxymonosulfate) with cobalt tetraoxide using a step reaction apparatus. The step reaction apparatus comprises a plurality of sequentially connected step structures with gradually decreasing top openings. Cobalt tetraoxide is wrapped with filter paper and fixed within each step structure. Wastewater containing hydroxyethylidene diphosphonic acid is pumped into the first step structure at the highest point, and PMS is simultaneously pumped into the first stage of the reaction. As the reaction proceeds, the reaction solution gradually increases. When the reaction solution fills the first step structure and fully reacts under the effects of gravity and seepage, it flows into the second step structure to continue the second stage of the reaction. Following the same method, the reaction solution enters the next step structure of the step reaction apparatus and proceeds to the next stage of the reaction until the reaction is complete. The step reaction apparatus of this embodiment comprises five steps, and accordingly, five stages of reaction are carried out.

[0100] like Figures 1 to 3 As shown, Figure 1 This is a schematic diagram of the overall structure of a multi-stage stepped solid-liquid two-phase batch reaction device. Figure 2 yes Figure 1 Structural diagram of the middle ladder structure A, Figure 3It is a structural schematic diagram of the upper and lower arrangements of baffles with holes. The present invention provides a multi-stage stepped solid-liquid two-phase intermittent reaction device: it includes a first side plate assembly and an internal baffle assembly, the first side plate assembly includes front and rear side plates 22 and a right side plate 23, the internal baffle assembly includes a left baffle (the corresponding installation position of the left baffle is indicated by numbers 1, 5, 9, 13, and 17 in the accompanying drawings to facilitate understanding of the technical solution), a lower baffle (the corresponding installation position of the lower baffle is indicated by numbers 2, 6, 10, 14, and 18 in the accompanying drawings to facilitate understanding of the technical solution), a right baffle (the corresponding installation position of the right baffle is indicated by numbers 3, 7, 11, 15, and 19 in the accompanying drawings to facilitate understanding of the technical solution) and a baffle with holes (the corresponding installation position of the baffle with holes is indicated by numbers 4, 8, 12, 16, and 20 in the accompanying drawings to facilitate understanding of the technical solution). The above-mentioned solution can solve the problem that insufficient mixing between stages of existing reactors leads to uneven contact between reactants and reactants, and reactants and catalysts, thereby reducing mass transfer efficiency. It can be understood that the above-mentioned solution can enable reactants and reactants, and reactants and catalysts to be fully mixed, thereby increasing reaction efficiency.

[0101] In this embodiment, the first side plate assembly and the inner baffle assembly are used to cooperate to form a multi-step stepped structure A of the device.

[0102] The first side panel assembly includes front and rear side panels 22 and a right side panel 23 . The front and rear side panels 22 are arranged on one side of the internal baffle assembly. The right side panel 23 is arranged on the lowest point of the device and is provided with a water outlet 21 .

[0103] When in use, the device is assembled first, and the assembly process is: glue and install the left baffle 1 and the right baffle 3 from top to bottom between the front and rear side panels 22, reserve space between the left baffle 1 and the right baffle 3, and then install the lower baffle 2 and the perforated baffle 4. The left baffle 1 is glued to the lower baffle 2, and the right baffle 3 is glued to the perforated baffle 4, so as to form a through "L"-shaped path, completing the step structure A at the highest point, which is the first step; then, according to the reaction needs, select an appropriate position, glue the left baffle 5 to the perforated baffle 4 and the lower baffle 2, and then install Install the right baffle 7, reserve space between the left baffle 5 and the right baffle 7, then install the lower baffle 6 and the perforated baffle 8, the left baffle 5 is glued to the lower baffle 6, and the right baffle 7 is connected to the perforated baffle 8 to form a through "L"-shaped path, completing the second step structure setting; further according to the reaction needs, select an appropriate position, glue the left baffle 9 to the perforated baffle 8 and the lower baffle 6, and then install the right baffle 11, reserve space between the left baffle 9 and the right baffle 11, and then install the lower baffle 10 and the perforated baffle 12, the left baffle 9 and the The lower baffle 10 is connected, and the right baffle 11 is connected to the baffle with holes 12 to form a through "L"-shaped path, completing the third step structure setting; in the next step, according to the reaction needs, select an appropriate position, glue the left baffle 13 to the baffle with holes 12 and the lower baffle 10, and then install the right baffle 15, leaving space between the left baffle 13 and the right baffle 15, and then install the lower baffle 14 and the baffle with holes 16, the left baffle 13 is connected to the lower baffle 14, and the right baffle 15 is connected to the baffle with holes 16 to form a through "L"-shaped path, completing the fourth step structure setting; Then, according to the reaction needs, select an appropriate position, glue the left side plate 17 to the perforated baffle 16 and the lower baffle 14, and then install the right baffle 19, leaving space between the left baffle 17 and the right baffle 19, and then install the lower baffle 18 and the perforated baffle 20. The left baffle 17 is connected to the lower baffle 18, and the right baffle 19 is connected to the perforated baffle 20 to form a continuous "L"-shaped path, completing the fifth step structure. After the installation is completed, glue the left baffle 17 to the perforated baffle 20 and the lower baffle 18, and set the water outlet 21 at the appropriate position of the right side plate 23. The perforated baffle 20 can be installed up and down. During installation, step slots are set on the corresponding baffles on both sides to facilitate the positioning of the uppermost perforated baffle 20. This structure further adds a baffle structure on the basis of the single perforated baffle 20, so that the two baffles at the corresponding positions form a stacking area, which is convenient for placing the catalyst.

[0104] The left baffle (1, 5, 9, 13, 17), the lower baffle (2, 6, 10, 14, 18), the right baffle (3, 7, 11, 15, 19) and the perforated baffle (4, 8, 12, 16, 20) cooperate to form a plurality of step structures A.

[0105] Secondly, the left baffles (1, 5, 9, 13, 17), the lower baffles (2, 6, 10, 14, 18), the right baffles (3, 7, 11, 15, 19) and the perforated baffles (4, 8, 12, 16, 20) are fixed together by gluing. By using gluing and a stepped gradient design instead of pipe connections, interstage blockage and leakage problems can be avoided.

[0106] Then, a space is reserved between the left baffle (1, 5, 9, 13, 17) and the right baffle (3, 7, 11, 15, 19).

[0107] Furthermore, a connecting pipe is provided outside the water outlet 21 provided on the right side plate 23. The connecting pipe facilitates connection with an external pipeline.

[0108] Preparation of reaction materials: Prepare 40 mL of HEDP solution (concentration of 200 μmol / L) using ultrapure water.

[0109] Reaction procedure: Add 10 mg of PMS and 20 mg of cobalt tetroxide (cobalt tetroxide is evenly divided and fixed in each step structure) to the above HEDP solution. Place the reaction system in a 30°C water bath and start the reaction with magnetic stirring at 500 rpm.

[0110] Reaction process monitoring: within 60 minutes of reaction, samples were taken at 3, 6, 10, 25, 45, and 60 minutes to analyze the degradation of HEDP and the dissolution of cobalt ions.

[0111] Results: The experimental results showed that under the reaction conditions, the HEDP degradation rate gradually increased over time, reaching over 85% at 60 minutes. Furthermore, the amount of cobalt ion dissolution remained stable and within an acceptable range during the reaction. This demonstrates that the cobalt tetroxide catalyst exhibits good catalytic activity and stability in this system, effectively degrading HEDP without excessive catalyst dissolution, which could lead to a decrease in catalytic performance or introduce additional environmental concerns.

[0112] from Figure 9 As can be seen from Figure A, the effect of running during the day and stopping at night decreased at 6400 minutes. Compared with the intermittent beaker experiment, the reaction effect of the step reaction device is significantly better. The reason may be that the form of the circulating cobalt tetroxide is not affected. Figure 9As can be seen in Figure B, the dissolution of Co ions gradually decreases and stabilizes.

[0113] The reaction consumed a total of 87.5L of wastewater, and the reactor used 7.5g of cobalt tetroxide. The original plan was to use 20mg of cobalt tetroxide per 40ml of HEDP in the beaker experiment, meaning 7.5g of cobalt tetroxide per 15L of HEDP. This far exceeded the original plan. This situation is precisely the advantage of the continuous reactor of the present invention, which can greatly reduce costs and improve efficiency. In addition, during the experiment, it was found that alternating day and night, starting the reactor during the day and stopping it at night, actually prolonged the reaction duration and improved the degradation effect. (Note: At 4000 minutes, the cobalt tetroxide was removed and dried and used the next day.)

[0114] Example 2

[0115] Effect of different reaction temperatures on degradation effects

[0116] Preparation of reaction materials: same as in Example 1.

[0117] Reaction operation: The reaction temperature was adjusted to 10°C, 20°C, 30°C, 40°C, and 50°C, respectively. Other conditions were the same as in Example 1, and experiments were carried out respectively.

[0118] Analysis of the results showed that at 0°C, HEDP degradation was approximately 5%, indicating almost no degradation. At 10°C, HEDP degradation was slow, reaching approximately 25%. At 20°C, HEDP degradation was relatively slow, reaching approximately 55%. At 30°C, the degradation rate reached approximately 70%, accelerating the rate. At 40°C and 50°C, the degradation rate remained approximately 70%, showing no improvement. Considering both degradation efficiency and energy consumption, the optimal reaction temperature was determined to be approximately 30°C. At this temperature, the catalyst activity and free radical generation reached an optimal balance, enabling efficient and economical HEDP degradation.

[0119] Example 3

[0120] Effect of different pH on degradation effect

[0121] Preparation of reaction materials: same as in Example 1.

[0122] Reaction operation: The pH was adjusted to 3.6, 7, 10, and 12, respectively. Other conditions were the same as in Example 1, and experiments were carried out respectively.

[0123] Analysis of the results: At pH 3.6, the HEDP degradation rate was approximately 70%. At pH 7 and 10, the HEDP degradation rate was approximately 70%, comparable to that at pH 3.6, with an improved rate. At pH 12, the HEDP degradation rate was approximately 40%, indicating a decrease in degradation rate. Strong alkaline environments inhibit the reaction. Therefore, the present invention does not change the pH; the original pH of 3.6 is sufficient. Alternatively, to maintain a neutral environment, the pH can be maintained at 7.

[0124] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for cyclically degrading HEDP by activating PMS with cobalt tetroxide using a step reaction device, characterized in that: The step reaction device includes a plurality of step structures connected in sequence with gradually lowered top openings. Cobaltous oxide is wrapped with filter paper and fixed in each step structure. Wastewater containing hydroxyethylidene diphosphonic acid is pumped into the first step structure at the highest point, and PMS is pumped into the first stage reaction at the same time. As the reaction proceeds, the reaction solution gradually increases. When the reaction solution fills the first step structure and fully reacts under the action of gravity and seepage, it flows into the second step structure to continue the second stage reaction. According to the same method, it enters the next step structure of the step reaction device to carry out the next stage reaction until the reaction is completed.

2. The method according to claim 1, characterized in that The step reaction device: The step reaction device includes a first side plate assembly and an internal baffle assembly, the first side plate assembly includes front and rear side plates and a right side plate, the front and rear side plates are arranged on one side of the internal baffle assembly, the right side plate is arranged on the lowest point side of the device and is provided with a water outlet; The internal baffle assembly includes a left baffle, a lower baffle, a right baffle and a baffle with holes, the plurality of left baffles are arranged in a stepped manner, the plurality of lower baffles are arranged on the bottom side of the left baffle, the plurality of right baffles are respectively connected to the plurality of baffles with holes and the left baffle, and the baffle with holes is arranged between the left baffle and the right baffle and located above the lower baffle; The left baffle, the lower baffle, the right baffle and the baffle with holes cooperate to form a plurality of step structures.

3. The method according to claim 1, characterized in that The ratio of PMS, cobalt tetroxide, and HEDP is 10 mg:20 mg:8 μmol, and cobalt tetroxide is evenly divided and fixed in each ladder structure.

4. The method according to claim 1, wherein The reaction conditions are: stirring rate 400-600 r / min, temperature 25-35° C., pH=3.6-10.

5. The method according to claim 4, characterized in that The reaction conditions are: stirring rate 500 r / min, temperature 30° C., pH=7-8.

5.

6. The method according to claim 1, characterized in that When the wastewater contains a small amount of bicarbonate, sodium bicarbonate is added to the wastewater to make the total mass of bicarbonate equal to that of PMS.

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