Method for efficiently removing algae based on trace copper ion activated calcium peroxide

Abstract

The invention discloses a method for efficiently removing algae based on trace copper ion activated calcium peroxide, and under the conditions that the addition amount of Cu (II) is only 15 mu M (1 mgL <-1 >), the molar ratio of Cu (II) to CaO2 is 1: 7, and the pH is neutral, the removal rate of algae cells with the concentration of 1.0-2.5 * 10 < 6 > cell smmL <-1 > is higher than 97%. According to the system, the circulation of Cu (II) / Cu (I) is promoted by utilizing the alkalinity of CaO2, more active free radicals such as Cu (III), OH, O2 <-> and < 1 > O2 are generated, and the oxidation algae removal capacity of the system is remarkably improved; the direct attack of copper ions on algae cells can be inhibited by the mild oxidizing property of CaO2, and the release risk of soluble algae organic matters and microcystic toxins is reduced; ca (OH) 2 generated by hydrolysis of CaO2 after the reaction can synchronously precipitate algae cells and copper ions in the water body, so that the concentration of residual copper is reduced to 30.1 mu gL <-1 > or below, and the risk of secondary pollution of heavy metals is effectively avoided. The coupling system successfully overcomes the defects that traditional H2O2 is fast in decomposition, narrow in pH application range, inconvenient to transport and the like, has the advantages of being high in algae removal efficiency, high in adaptability, environmentally friendly and the like, and has good application and popularization value.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment and environmental governance, and in particular to a method for efficiently removing algae based on the activation of calcium peroxide (CaO2) by trace copper ions (Cu(II)), which is suitable for the efficient treatment of algae pollution in eutrophic water bodies. Background Art

[0002] With the rapid development of industry and agriculture, large amounts of nitrogen and phosphorus pollutants are discharged into water bodies, resulting in the continued serious problem of eutrophication worldwide. Algal pollution poses a serious threat to aquatic ecosystems and human health. Algal blooms not only reduce water clarity and deplete dissolved oxygen, but also release microcystins (MC-LR), which are hepatotoxic and can accumulate through the food chain, posing a threat to human health.

[0003] Currently, algae pollution control technologies primarily include physical, biological, and chemical methods. Physical methods, including direct capture, shading, dissolved air flotation, membrane separation, ultraviolet (UV) methods, and ultrasound, offer rapid removal but are costly and unable to inhibit algae regrowth. Biological methods, such as microbial algae lysis, aquatic plant inhibition, and aquatic animal predation, are eco-friendly but susceptible to environmental constraints and require a long treatment cycle. Chemical methods can be used for both in-situ emergency algal bloom control and are also the primary method for ex-situ algae treatment in aquatic waters. In-situ chemical treatment involves applying a specific amount of algaecide to the water body affected by an algal bloom, rapidly inhibiting algal cell growth and causing massive cell lysis and death, thereby controlling the bloom's development. To achieve optimal removal results, the choice of algaecide is crucial; it typically requires strong cytotoxicity or oxidizing properties. Commonly used active ingredients in algaecides include copper-containing products, photocatalysts, and strong oxidants (CN118833897A). Oxidant algaecide technology has been widely studied due to its high efficiency. However, most current chemical oxidants are aggressive towards algal cells, leading to cell lysis and the undesirable release of algal metabolites (CN109354143A). For example, traditional oxidants such as Cl2 and ClO2 can easily cause cell rupture, releasing MC-LR and generating toxic byproducts. While KMnO4 and O3 enhance coagulation, high doses can trigger cell lysis and exacerbate AOM release. In contrast, hydrogen peroxide (H2O2) exhibits selective algae inhibition and is environmentally friendly, but its rapid decomposition results in low oxidant utilization, and the acidic reaction conditions (pH = 2-4) limit its application.

[0004] In recent years, CaO2 has emerged as a source of solid H2O2. CaO2 is a heat-stable inorganic peroxide solid, and calcium is one of the essential elements of organisms. Therefore, it is very safe to use CaO2 in water treatment. Compared with liquid H2O2, CaO2 is a mild oxidant. When it comes into contact with water, it can release H2O2 and Ca2+ in a long-term and stable manner.2+ It achieves self-coagulation, combining both oxidation and coagulation functions (CN112062236A). However, a single CaO2 system has weak oxidation capacity, slow degradation rate, and high effluent pH, requiring integration with other combined processes to improve efficiency.

[0005] To improve oxidation efficiency, novel catalytic combination processes have been developed. Studies have shown that Fe(II) can catalyze CaO2 to promote the aggregation of algal pollutants, effectively preserving cell viability and integrity and effectively removing fluorescent organic matter. However, Fe-based homogeneous Fenton processes typically have drawbacks such as a narrow reaction pH range (pH = 2-4) and the tendency for iron sludge accumulation during the reaction process to cause secondary pollution.

[0006] Copper-based algaecides, due to their inherent bactericidal and algae-control properties and broad-spectrum catalytic performance, have become a hot topic in this field. The principle behind copper-based algaecides is that copper ions (Cu(II)) disrupt algal metabolism and biochemical reactions through their strong affinity for sulfur-containing groups on the surface of algal cell walls, thereby inhibiting algal growth (CN118833897A). Furthermore, copper-based algaecides catalyze H2O2 to generate high-valent copper (Cu(III)) and a large number of reactive oxygen species (ROS), which attack the surface morphology and internal structure of algal cells, disrupting cell integrity and significantly reducing cell activity. Their algae removal effectiveness is significantly superior to that of iron-based catalysts (CN118975553A). However, current research on algae removal using Cu(II) ions alone is limited to the use of copper sulfate (CuSO4). This method has significant drawbacks, including excessive CuSO4 dosage, the potential for cell rupture and the release of AOM, and an inability to effectively degrade the released AOM. Therefore, while maintaining efficient algae removal, there is an urgent need to develop precise Cu(II) control technologies to reduce the risk of secondary contamination through coupled oxidation systems. At present, the limit of Cu content in Class III water of my country's surface water environmental quality standard shall not exceed 15 μM (1 mg∙L -1 (CN119385149A) states that copper-based algaecides are considered to have no significant impact on human health at commonly used doses (0.39 μM to 15 μM). Recently, CN116477746A disclosed a technique for removing acid orange using a percarbonate activated with trace amounts of Cu(II) (initial concentrations of 15 μM to 120 μM), achieving an efficiency of over 95%. However, the application of copper-based catalytic CaO2 in algae removal has not been reported.

[0007] In view of this, the present invention innovatively proposes a trace Cu(II) / CaO2 system oxidative coagulation synergistic algae removal process, in which trace Cu(II) (fixed at 15 μM) catalyzes CaO2 to continuously generate Cu(III) and ∙OH, ∙O2 - 、 1Active free radicals such as O2 enhance algal cell inactivation and AOM degradation. The resulting Ca(OH)2 promotes algal floc formation through electrical neutralization and netting, and facilitates copper ion precipitation, ensuring residual copper concentrations remain well below the Class III limit for surface water environmental quality standards. This technology combines the advantages of highly efficient algae removal, effective control of AOM release, and low ecological risk, overcoming the dual bottlenecks of low oxidant utilization and secondary pollution associated with traditional chemical methods. Summary of the Invention

[0008] In order to overcome the shortcomings of the existing technology, the purpose of the present invention is to provide a method for efficient algae removal based on trace Cu(II) (15 μM) activated CaO2, by constructing a Cu(II) / CaO2 coupling system and utilizing the alkaline environment of CaO2 to promote the circulation of copper ions (Cu(II) / Cu(I)) and the generation of active free radicals (∙OH, ∙O2 - 、 1 O2) is continuously generated, and efficient removal of algae in the range of pH = 5.0 ~ 9.0 is achieved. That is, the system has the characteristics of high algae removal efficiency, strong adaptability and simple operation.

[0009] In order to achieve the above object, the present invention provides a method for efficient algae removal based on the activation of CaO2 by trace amounts of Cu(II), comprising the following steps:

[0010] S1: Preparation of oxidant quencher: Prepare 0.1 mol∙L -1 The Na2S2O3 solution is used as an oxidant quencher;

[0011] S2: Prepare Cu(II) solution: 15.0 mmol∙L -1 100 mL of high concentration Cu(II) solution is reserved;

[0012] S3: Prepare a water sample containing algal cells and adjust the pH to a pH close to that of natural water. Then, take 500 mL of the water sample and add a certain amount of Cu(II) and oxidant to it. The concentration of Cu(II) in the solution is controlled to be less than 15 μM (1 mg∙L). -1 ), forming an oxidation-coagulation system, and regulating the reaction kinetics of the oxidation-coagulation system through a staged stirring program;

[0013] S4: Sampling and testing: After standing and settling, take the supernatant and filter it. Add Na2S2O3 solution to terminate the reaction. Use a UV spectrophotometer to measure the absorbance of the algae solution, calculate the removal rate of algae cells, and analyze the test results.

[0014] The above-mentioned method for efficient algae removal based on trace Cu(II) activation of CaO2 is further improved. In step 2, the configuration of the Cu(II) solution can be selected from but not limited to one or more of copper sulfate pentahydrate, anhydrous copper sulfate, and copper chloride.

[0015] The above method for efficient algae removal based on trace Cu(II) activated CaO2 is further improved, wherein in step 3, the algae cells include but are not limited to one or more of cyanobacteria, green algae or diatoms; the initial concentration of the algae cells is 1.0-5×10 6 cells·mL⁻¹.

[0016] The above-mentioned method for efficient algae removal based on trace Cu(II) activation of CaO2 is further improved. In step 3, the Cu(II) is added to the algae-containing water body in the form of a solution, and the addition concentration is at a trace level; the oxidant is at least one of CaSO3, H2O2, and CaO2.

[0017] The above-mentioned method for efficient algae removal based on trace amounts of Cu(II) activated with CaO2 is further improved, wherein the molar ratio of Cu(II) to CaO2 is 0:7 (pure CaO2), 1:0 (pure Cu(II)), and 1:3-20, with the Cu(II) concentration in the fixed solution being 15 μM. When the Cu(II) concentration in the target water body is ≥15 μM, the method of the present invention can directly add a sufficient amount of CaO2 to effectively remove algae from the water body without the need for additional catalysts, thereby further reducing costs.

[0018] The above-mentioned method for efficient algae removal based on trace Cu(II) activation of CaO2 is further improved in that, in step 3, the initial pH value of the oxidation-coagulation system is 5.0-9.0.

[0019] The above method for efficient algae removal based on trace Cu(II) activated CaO2 is further improved. In step 3, the system catalyzes the slow release of H2O2 by CaO2 through trace Cu(II) to generate substances with strong oxidizing properties. These substances include but are not limited to Cu(III) and ∙OH, ∙O2 - 、 1 O2 and other active free radicals, and the system can promote the regeneration of copper ions.

[0020] The above-mentioned method for efficient algae removal based on trace Cu(II) activated CaO2 is further improved. In step 3, the Ca(OH)2 generated after the reaction of the system can promote the formation of algae flocs through electrical neutralization and net capture, and is beneficial to the precipitation of copper ions, thereby achieving a synergistic effect of oxidation and coagulation.

[0021] The above-mentioned method for efficient algae removal based on trace Cu(II) activated CaO2 is further improved, wherein in step 4, the residual copper concentration after the reaction is less than 30.1 μg∙L -1 , the algae cell removal rate is higher than 97%.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] (1) Compared with the traditional Fe / Fenton system, the trace Cu(II) / CaO2 system can achieve an algal cell removal rate of over 95% in the pH range of 5.0-9.0 without the need for frequent pH adjustment of the water body. (2) CaO2, as a solid H2O2 source, successfully overcomes the defect of rapid decomposition of traditional H2O2 and improves the utilization rate of the oxidant. (3) After the reaction, the Ca(OH)2 generated by the hydrolysis of CaO2 can simultaneously promote the precipitation of Cu(II), reducing the residual Cu concentration in the effluent to as low as 30.1 μg∙L -1 (Below the limit of the Surface Water Environmental Quality Standard (Cu≤1 mg / L)), effectively avoiding the residue of heavy metals in the treated water, thereby reducing the risk of secondary pollution; (4) The trace Cu(II) / CaO2 system can avoid large-scale rupture of algal cells and reduce the risk of release of soluble AOM and MC-LR. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is a comparison of the removal effects of different oxidants activated by trace amounts of Cu(II) on Microcystis aeruginosa in Example 1;

[0026] Figure 2 This is a graph showing changes in solution pH and residual Cu content after activation of trace amounts of Cu(II) with different oxidants in Example 1;

[0027] Figure 3 This is a comparison chart of the removal effects of different Cu(II) / CaO2 addition ratios on Microcystis aeruginosa in Example 1;

[0028] Figure 4 Graph showing changes in solution pH and residual Cu content after reaction at different Cu(II) / CaO2 addition ratios in Example 1;

[0029] Figure 5This is a comparison chart of the removal effects of different initial pH values on Microcystis aeruginosa in Example 1;

[0030] Figure 6 Graph showing changes in solution pH and residual Cu content after reaction at different initial pH values in Example 1;

[0031] Figure 7 This is a graph showing the effect of different initial algal cell concentrations on the removal of Microcystis aeruginosa by the trace Cu(II) / CaO2 system in Example 1;

[0032] Figure 8 This is a graph showing changes in Zeta potential and Chl-a removal rate in Example 2;

[0033] Figure 9 Figures 2 and 3 are the morphological structures of Microcystis aeruginosa cells observed by SEM in different reaction systems in Example 2, where a and b are controls, c and d are Cu(II)-only systems, e and f are CaO2-only systems, and g and h are trace Cu(II) / CaO2 systems;

[0034] Figure 10 This is a diagram showing the changes in extracellular MC-LR content during the treatment of Microcystis aeruginosa with different systems in Example 2. DETAILED DESCRIPTION

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clearly understood, the present invention is now systematically described below in conjunction with the accompanying drawings and specific preferred embodiments. Where specific conditions are not specified in the examples, the experiments were conducted under conventional conditions or those recommended by the manufacturer. All reagents and equipment required for the experiments, without manufacturer identification, are commercially available products that comply with industry standards.

[0036] The following is a detailed description of the method for efficient algae removal based on trace Cu(II) activated CaO2 provided in this application.

[0037] Example 1

[0038] This example investigates the removal efficiency of a trace Cu(II) / CaO2 oxidation system on algae in water. The specific process is as follows:

[0039] (1) Source of algae: The algae species selected for this experiment is the dominant algae species in cyanobacteria blooms in my country, Microcystis aeruginosa, numbered FACHB-905, which was purchased from the Freshwater Algae Species Bank of the Institute of Hydrobiology, Chinese Academy of Sciences (Wuhan).

[0040] (2) Algae culture: Microcystis aeruginosa was cultured in sterilized BG11 medium. The prepared culture medium solution was divided into 250 mL conical flasks, sealed with a breathable membrane, and placed in a high-pressure steam sterilizer for sterilization at 121°C for 30 min. After the culture medium was removed and cooled to room temperature, the algae seeds were transferred to fresh sterilized BG11 medium at a ratio of 1:3 on a clean bench. After inoculation, the algae were cultured in a light incubator. The light incubator parameters were set as follows: temperature of 25±1°C, light-dark ratio of 12h:12h, and light intensity of 2500 lux. During the culture of Microcystis aeruginosa, the culture medium was manually shaken 2 to 3 times a day to increase dissolved oxygen for good growth of Microcystis aeruginosa.

[0041] (3) Experimental algae-containing water preparation: After Microcystis aeruginosa grows to the logarithmic phase, the algae suspension is placed in a centrifuge and centrifuged at 4000 r∙min. -1 The logarithmic phase Microcystis aeruginosa was collected by centrifugation at 500 nm for 5–10 min and diluted with ultrapure water with a resistivity of 18.2 MΩ∙cm to a cell density of 2.5 (±0.5) × 10 6 cells∙mL -1 and 0.1 mmol∙L -1 HCl and 0.1mmol∙L -1 Adjust the pH to 7.0 with NaOH to be close to the pH of natural water, and obtain the experimental algae-containing water for use.

[0042] Unless otherwise specified, this initial algal cell concentration was used in the following experiments.

[0043] (4) Experimental method: First, take 500 mL of pre-prepared algae-containing water and transfer it to several groups of 1 L beakers. Adjust the pH to 7.0. Set up three replicates in each group. Then, add a certain amount of high-concentration copper sulfate solution and a certain amount of oxidant to each group of algae-containing water solution. Perform an oxidation-coagulation experiment on a coagulation experiment mixer. The coagulation conditions are: stirring, settling and settling to complete the removal of Microcystis aeruginosa in the water. After the settling is completed, use a pipette to draw 2 mL of supernatant 2 cm below the liquid surface and add 0.1 mol·L -1 The reaction was terminated by sodium thiosulfate solution. Finally, the absorbance of the Microcystis aeruginosa solution was measured at an absorption wavelength of 680 nm using an ultraviolet spectrophotometer. The OD values before and after the reaction were determined. 680 The calculation formula for the removal rate of Microcystis aeruginosa cells is shown in equation (1): Where, OD 680i is the absorbance value of the initial Microcystis aeruginosa solution before the reaction; OD 680t is the absorbance value of the Microcystis aeruginosa solution at time t.

[0044] Except for parameter design, the following parameter optimization batch experiments were all conducted using the above basic experimental methods.

[0045] ① Comparison of different oxidants

[0046] The effects of different oxidants (CaSO3, CaO2, H2O2) activated by trace Cu(II) on the removal efficiency of Microcystis aeruginosa were compared. Experimental design: 0.5 mL of 15.0 mmol / L Cu(II) was first added to each group of algae solution. -1 The high concentration of copper sulfate solution was used to make the Cu(II) concentration in the solution 15 μM (1 mg∙L -1 ), and then CaSO3, CaO2, and H2O2 were added as oxidants so that their concentrations in the solution were all 100 μM.

[0047] Depend on Figure 1 It can be seen that there are significant differences in the removal efficiency of different oxidants and trace Cu(II) for Microcystis aeruginosa. The algae removal rate of the Cu(II) / CaO2 system is as high as 98.2%, which is significantly better than the Cu(II) / CaSO3 system (7.1%) and the Cu(II) / H2O2 system (40.18%). The difference in its mechanism is mainly reflected in three aspects: (1) The hydroxyl radicals (E0=2.7 V) generated by the Cu(II) / CaO2 system are higher than the SO4 generated by the Cu(II) / CaSO3 system. 2- Free radicals (E0=2.6 V) have stronger oxidizing ability; (2) CaSO4 and Ca(OH)2 are formed in the Cu(II) / CaSO3 system and the Cu(II) / CaO2 system, respectively. Ca(OH)2 (Ksp=5.5×10 -6 M 2 ) is higher than CaSO4 (Ksp=9.1×10 -6 M 2 ) It is easier to form stable flocs with algae; (3) The slow release of H2O2 by CaO2 overcomes the rapid decomposition defect of direct addition of H2O2. 2+ By inducing algal cells to release extracellular polymers (EPS), the colony aggregation and sedimentation are promoted. Figure 2 It can be seen that the residual Cu concentration in the Cu(II) / CaO2 system is only 30.1 μg∙L while maintaining a neutral environment (pH = 7.8). -1 , which is significantly lower than Cu(II) / CaSO3 (761.9 μg∙L -1 ) and Cu(II) / H2O2 system (734.3 μg∙L -1The pH change mechanism can be attributed to the following: Cu²⁺ in the Cu(II) / H⁺2 system hydrolyzes to form Cu(II)-OH and H⁺, while some Cu(II) reacts with H⁺2 to further release protons, causing the pH to drop to 5.5. While the Ca(OH)2 generated in the CaO2 system is alkaline, it reacts with the H⁺ generated by the hydrolysis of Cu²⁺2 within the system to achieve dynamic pH equilibrium. The difference in residual copper stems from the strong adsorption of heavy metals by the Ca(OH)2 produced by the hydrolysis of the CaO2 system, while the Cu(II) / CaSO3 and Cu(II) / H⁺2 systems lack an effective solid-phase precipitation carrier. This result indicates that the trace Cu(II) / CaO2 system combines the advantages of high algae removal efficiency, stable pH, and efficient heavy metal removal.

[0048] Therefore, the present invention selects trace Cu(II) / CaO2 as the optimal system.

[0049] ②Comparison of different Cu(II) / CaO2 dosage ratios

[0050] The effects of different Cu(II) / CaO2 dosing ratios on the removal of Microcystis aeruginosa were investigated. Experimental design: The Cu(II) / CaO2 dosing ratios were set to 0:7 (pure CaO2), 1:0 (pure Cu(II)), 1:3, 1:7, 1:10, 1:13, 1:17, and 1:20, and the Cu(II) concentration in the fixed solution was 15 μM (1 mg∙L -1 ).

[0051] Depend on Figure 3 It can be seen that when trace Cu(II) (1:0) is used alone for treatment, the removal rate of Cu(II) for algae cells is only 3.6%, and the removal effect is limited. When CaO2 (0:7) is used alone for treatment, algae cells cannot be effectively removed in a short time. However, the trace Cu(II) / CaO2 composite system significantly improved the algae removal efficiency. When the molar ratio was 1:3, the algae removal rate reached 71.2%; as the CaO2 dosage increased to 1:7, the algae removal rate further increased to 97.6%. The mechanism is that Cu(II) activates the H2O2 released by CaO2, which can generate Cu(III) and ROS, synergistically enhancing the oxidation capacity. However, when the CaO2 ratio exceeds 1:7, the removal efficiency tends to be stable, indicating that there is an optimal dosage ratio. Figure 4It can be seen that when CaO2 is added alone, the pH of the algae solution increases from 7.0 to 8.8 (CaO2→Ca(OH)2), while the addition of Cu(II) alone reduces the pH to 5.9. In the composite system, when the Cu(II) / CaO2 molar ratio is 1:3 and 1:7, the pH of the algae solution after the reaction decreases from 8.8 to 7.5 and 7.9, respectively, compared to the CaO2 treatment alone. This is attributed to the release of H⁺ by the reaction of Cu(II) with H⁺. However, the higher the CaO2 dosage, the higher the pH of the algae solution after the reaction. When a trace amount of Cu(II) is added alone, the residual Cu content in the solution is 595.4 μg∙L -1 With the addition of CaO2, the residual Cu content in the algae solution decreased significantly. When the molar ratio of trace Cu(II) / CaO2 was 1:7, the residual Cu content reached the lowest value of 30.1 μg∙L -1 (Cu(OH)2 precipitation is formed), and the addition of excess CaO2 does not further reduce its residual concentration.

[0052] Therefore, the optimal addition ratio of Cu(II) / CaO2 selected in the present invention is 1:7.

[0053] ③The influence of different pH

[0054] The effects of different pH values on the removal of Microcystis aeruginosa by the trace Cu(II) / CaO2 system were investigated. Experimental design: 0.1 mmol∙L -1 HCl and 0.1 mmol∙L -1 The pH values of the five groups of algae-containing aqueous solutions were adjusted by NaOH to 5.0, 6.0, 7.0, 8.0 and 9.0 respectively.

[0055] Depend on Figure 5 It can be seen that the trace Cu(II) / CaO2 system maintains high algae removal performance in the pH range of 5.0~9.0, with a removal rate of more than 95%. Its broad pH adaptability is due to the dynamic transformation of active species: under acidic conditions, H2O2 produced by CaO2 hydrolysis promotes the reduction of Cu(II) to Cu(I), as shown in reaction formula (2), and then catalyzes H2O2 to generate strong oxidizing hydroxyl radicals (∙OH), as shown in reaction formula (3); in neutral to alkaline environments, as shown in reaction formula (3), Cu(I) / H2O2 reacts to generate high-valent copper species (Cu(III)), whose oxidation potential is stable in the pH range of 3.0~9.0 and has selective oxidation ability. Studies have confirmed that the system achieves continuous and efficient oxidation in a wide pH range through a pH-dependent active oxygen regulation mechanism. Figure 6 It can be seen that the Cu(II) / CaO2 system has pH self-buffering properties: under acidic conditions, CaO2 provides OH - , OH in alkaline environment -The dual effects of promoting Cu valence conversion and H⁺ generation minimize post-reaction pH fluctuations. The residual Cu content remains stable within the pH range of 5.0-9.0, indicating that the system has broad pH adaptability.

[0056] ④The effect of different initial algal cell concentrations

[0057] Under the conditions of a fixed Cu(II) / CaO2 molar ratio (1:7) and neutral pH (pH=7.0), the effects of different initial algae cell concentrations on the algae removal efficiency of the trace Cu(II) / CaO2 coupling system were systematically investigated. Experimental design: Ultrapure water was used to dilute the algae cell density to 1.0×10 6 cells∙mL -1 , 2.5×10 6 cells∙mL -1 , 5.0×10 6 cells∙mL -1 and 0.1mmol∙L -1 HCl and 0.1 mmol∙L -1 The pH value was adjusted to 7.0 by using NaOH to obtain experimental algae-containing water with different initial algae cell concentrations.

[0058] Depend on Figure 7 It can be seen that with the increase of the initial concentration of algae cells, the removal efficiency shows a downward trend. When the initial concentration of algae cells is 1.0×10 6 cells∙mL -1 and 2.5×10 6 cells∙mL -1 When the initial concentration of algae cells increased to a high concentration of 5.0×10 6 cells∙mL -1 When the Cu(II) / CaO2 oxidation coagulation system was used, the removal rate of algae cells was slightly reduced to 92.5%. This is because under the same experimental conditions, the higher the concentration of algae cells in the water, the less the algae cells are attacked by ROS. According to the long-term monitoring data of the Taihu Lake waters in my country, the density of cyanobacteria in this area is usually 5×10 4 ~2.5×10 6 cells∙mL -1 Therefore, the trace Cu(II) / CaO2 oxidative coagulation system can achieve efficient removal of algae cells in a wide range of algae cell concentrations at a lower dosage.

[0059] Therefore, the initial concentration of algae cells was selected as 2.5×10 6 cells∙mL -1 Conduct follow-up experiments.

[0060] Example 2

[0061] This example explores the removal mechanism of algae in water by a trace Cu(II) / CaO2 oxidation system. The specific process is as follows:

[0062] ① Characterization and analysis of cell Zeta potential and chlorophyll a (Chl-a)

[0063] Analysis results of cell Zeta potential and Chl-a ( Figure 8 ) showed that in the trace Cu(II) / CaO2 oxidation system, the Zeta potential increased from an initial -26.43 mV to -8.46 mV (a 68% decrease in absolute value), while simultaneously achieving 94.03% Chl-a removal. However, the Zeta potential and Chl-a removal rates of the systems with the addition of Cu(II) and CaO2 alone did not change significantly, indicating that the synergistic relationship between the attenuation of the absolute value of the Zeta potential and algae removal efficiency was only apparent in the Cu(II) / CaO2 system. This potential decrease, unlike that caused by ozone and potassium permanganate pre-oxidation, is attributed to the release of intracellular organic matter (IOM) triggered by oxidative stress. Therefore, the positive potential shift characteristic of this system indicates that it achieves algae inactivation through a non-destructive pathway, effectively avoiding the risk of secondary pollution caused by damage to cell integrity.

[0064] ② Scanning electron microscopy characterization analysis (SEM)

[0065] SEM analysis results ( Figure 9 ) show that in the control group (a, b), algal cells maintained a regular spherical shape, with a smooth surface and intact cell membrane. However, the addition of Cu(II) alone (c, d) caused some cell surfaces to become rough and deformed, cell membranes to rupture, and metabolite secretion to be promoted. This may be due to the reduction of intracellular Cu(II) to the more toxic Cu(I), which in turn destroys the cell structure. When treated with CaO2 alone (e, f), the algal cells condensed but remained largely structurally intact, with only a few cells showing slight shrinkage. In the trace Cu(II) / CaO2 composite system (g, h), a large amount of oxidants attached to the algal cell surface, but their morphology and surface characteristics did not change significantly compared to the control group. In other words, this system only induced a small number of algal cells to rupture and release IOM, indicating that the ROS generated did not cause large-scale cell lysis and only a small number of algal cells ruptured.

[0066] ③Determination of microcystin (MC-LR) content

[0067] Figure 10The changes in extracellular MC-LR content during treatment of Microcystis aeruginosa with different systems are shown. The results show that the addition of Cu(II) alone causes a slight increase in extracellular MC-LR concentration, confirming that Cu(II) can disrupt the algal cell structure, leading to the release of intracellular MC-LR. Since Cu(II) itself lacks oxidative properties, it is unable to effectively degrade the released MC-LR. The experiment also found that the use of CaO2 alone did not significantly decrease the extracellular MC-LR concentration. This phenomenon suggests that CaO2 has a minimal effect on the integrity of the algal cell membrane and that the amount of ROS it produces is limited, resulting in a minimal oxidative degradation effect on MC-LR. Notably, in the trace Cu(II) / CaO2 combined oxidation system, the extracellular MC-LR concentration exhibits a dynamic pattern of first increasing and then decreasing over time. This pattern suggests that in the initial reaction, ROS generated by the system partially damage the algal cells, promoting the release of intracellular MC-LR. As the reaction proceeds, the released MC-LR is gradually oxidized and degraded by the ROS generated by the system. Ultimately, the MC-LR concentration can be reduced to the drinking water safety limit specified by the World Health Organization (WHO) (1.0 μg∙L -1 The results showed that the trace Cu(II) / CaO2 oxidation system could not only effectively remove Microcystis aeruginosa, but also significantly control the residual concentration of MC-LR, thereby effectively avoiding the risk of secondary pollution.

[0068] In summary, this paper creatively developed a highly efficient algae removal method based on the activation of CaO2 with trace amounts of Cu(II). Batch experiments investigated the effects of oxidant selection, Cu(II) / CaO2 dosage ratio, initial pH, and initial algae cell concentration on algae removal in water. The results showed that the algae removal efficiency of the trace Cu(II) / CaO2 oxidation system was superior to that of Cu(II) / CaSO3 and Cu(II) / H2O2. The results also showed that the Cu(II) / CaO2 oxidation system exhibited superior algae removal efficiency when the Cu(II) dosage was only 15 μM (1 mg∙L). -1 ), the Cu(II) / CaO2 molar ratio was 1:7, and the initial concentration of algal cells was 1.0~2.5×10 6 cells∙mL -1 The algal cell removal rate was as high as 97% when the reaction was complete. The system had a neutral pH after the reaction and the residual Cu concentration was as low as 30.1 μg∙L -1The Cu(II) / H2O2 system exhibits advantages such as a low-pressure solution (-26.43 to -8.46 mV) and algae removal efficiency that is unaffected by the initial pH. Mechanistic studies have revealed that the trace Cu(II) / H2O2 system significantly increases the zeta potential of algal cells (-26.43 to -8.46 mV) and enhances chlorophyll a removal efficiency (94.03%), facilitating algae removal. Furthermore, the trace Cu(II) / H2O2 system prevents extensive algal cell rupture, effectively degrading released organic matter and reducing the risk of secondary pollution. Compared to single components, this coupled system combines high algae removal efficiency with strong adaptability and environmental friendliness, offering broad application prospects.

[0069] It should be noted that the above embodiments are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. The technical solution disclosed in the present invention allows for various forms of adjustment and improvement within the scope of the core idea of the present invention. Any reasonable changes made by those skilled in the art based on the technical principles of the present invention, including but not limited to process parameter adjustments, implementation method modifications or equivalent technology replacements, etc., as long as they do not deviate from the basic principles and technical concepts of the present invention, should be included in the scope of legal protection defined by the claims of this patent application.

Claims

1. A method for efficient algae removal based on trace copper ion activation of calcium peroxide, characterized in that: The following steps are involved: S1: Preparation of oxidant quencher: Prepare 0.1 mol∙L -1 The Na2S2O3 solution is used as an oxidant quencher; S2: Prepare Cu(II) solution: 15.0 mmol∙L -1 100 mL of high concentration Cu(II) solution is reserved; S3: Prepare a water sample containing algal cells and adjust the pH to a pH close to that of natural water. Then, take 500 mL of the water sample and add a certain amount of Cu(II) and oxidant to it. The concentration of Cu(II) in the solution is controlled to be less than 15 μM (1 mg∙L). -1 ), forming an oxidation-coagulation system, and regulating the reaction kinetics of the oxidation-coagulation system through a staged stirring program; S4: Sampling and testing: After standing and settling, take the supernatant and filter it. Add Na2S2O3 solution to terminate the reaction. Use a UV spectrophotometer to measure the absorbance of the algae solution, calculate the removal rate of algae cells, and analyze the test results.

2. The method for efficient algae removal based on trace copper ion activation of calcium peroxide according to claim 1, characterized in that: In step 2, the configuration of the Cu(II) solution can be selected from but not limited to one or more of copper sulfate pentahydrate, anhydrous copper sulfate, and copper chloride.

3. The method for efficient algae removal based on trace copper ion activation of calcium peroxide according to claim 1, characterized in that: In step 3, the algae cells include but are not limited to one or more of cyanobacteria, green algae or diatoms; the initial concentration of the algae cells is 1.0-5×10 6 cells·mL⁻¹.

4. The method for efficient algae removal based on trace copper ion activation of calcium peroxide according to claim 1, characterized in that: In step 3, the Cu(II) is added to the algae-containing water in the form of a solution at a trace concentration; the oxidant is at least one of CaSO3, H2O2, and CaO2.

5. The method for efficient algae removal based on trace copper ion activation of calcium peroxide according to claim 1, characterized in that: The molar ratio of Cu(II) to CaO2 includes 0:7 (pure CaO2), 1:0 (pure Cu(II)), and 1:3-20, with the Cu(II) concentration in the fixed solution being 15 μM. The method of the present invention, when the Cu(II) concentration in the target water body is ≥15 μM, directly adding a sufficient amount of CaO2 can effectively remove algae from the water body without the need for additional catalyst, thereby further reducing costs.

6. The method for efficient algae removal based on trace copper ion activation of calcium peroxide according to claim 1, characterized in that: In step 3, the initial pH value of the oxidation-coagulation system is 5.0-9.

0.

7. The method for efficient algae removal based on trace copper ion activation of calcium peroxide according to claim 1, characterized in that: In step 3, the system catalyzes the slow release of H2O2 by CaO2 through a trace amount of Cu(II) to generate substances with strong oxidizing properties, including but not limited to Cu(III) and ∙OH, ∙O2 - 、 1 O2 and other active free radicals, and the system can promote the regeneration of copper ions.

8. The method for efficient algae removal based on trace copper ion activation of calcium peroxide according to claim 1, characterized in that: In step 3, the Ca(OH)2 generated after the reaction of the system can promote the formation of algal flocs through electrical neutralization and netting, and is beneficial to the precipitation of copper ions, thereby achieving a synergistic effect of oxidation-coagulation-precipitation.

9. The method for efficient algae removal based on trace copper ion activation of calcium peroxide according to claim 1, characterized in that: In step 4, the residual copper concentration after the reaction is less than 30.1 μg∙L -1 , the algae cell removal rate is higher than 97%.

10. A method for efficiently removing algae based on the activation of calcium peroxide by trace copper ions according to any one of claims 2 to 9, characterized in that: The trace Cu(II) / CaO2 coupling system can be applied to the treatment of algae pollution in eutrophic water bodies.

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