Method for efficiently removing algae based on activation of calcium peroxide by trace copper ions

Abstract

The application discloses a method for efficiently removing algae based on activation of calcium peroxide by trace copper ions, and under the conditions that the Cu(II) dosage is only 15 micromoles, the Cu(II) / CaO2 molar ratio is 1:7, and the pH is neutral, the removal rate of algae cells is higher than 97% for the algae with a concentration of 1.0-2.5*10 6 cells per milliliter. ‑1 The removal rate of algae cells is higher than 97%. The system utilizes the alkalinity of CaO2 to promote the cycle of Cu(II) / Cu(I), generates more Cu(III) and active free radicals such as ∙OH, ∙O2 ‑ 、 1 O2, significantly improves the oxidation and algae removal ability of the system; the mild oxidizing property of CaO2 can inhibit the direct attack of copper ions on algae cells, and reduces the release risk of dissolved algae organic matter and microcystin; after the reaction, Ca(OH)2 generated by the hydrolysis of CaO2 can simultaneously precipitate the algae cells and copper ions in the water body, so that the residual copper concentration is reduced to 30.1 micromoles per liter. ‑1 The following effectively avoids the risk of secondary pollution of heavy metals. That is, the coupling system successfully overcomes the defects of traditional H2O2, such as fast decomposition, narrow pH application range, inconvenient transportation and the like, and has the characteristics of high algae removal efficiency, strong adaptability, environmental friendliness and the like, and has good popularization and application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment and environmental governance, and particularly relates to a method for efficiently removing algae based on micro-copper ion (Cu(II)) activated calcium peroxide (CaO2), which is suitable for efficient governance of algae pollution in eutrophic water bodies. BACKGROUND

[0002] With the rapid development of industry and agriculture, a large amount of nitrogen and phosphorus pollutants are discharged into water bodies, leading to the problem of water eutrophication worldwide. Algal pollution can pose a serious threat to aquatic environments and human health. Algal outbreaks not only reduce water transparency and consume dissolved oxygen, but also release microcystin-LR (MC-LR) which has hepatotoxicity and can accumulate in the food chain to harm human health.

[0003] Current algal pollution control technologies mainly include physical methods, biological methods and chemical methods. Physical methods mainly include direct fishing, shading, dissolved air flotation, membrane separation, ultraviolet method, ultrasonic method, etc., which are fast but high in cost and cannot inhibit the reproduction of algae; biological methods such as microbial algicidal method, aquatic plant algicidal method and aquatic animal predation, etc. are eco-friendly but are easily affected by environmental factors and have a long treatment cycle; chemical methods can be applied to in-situ algal bloom emergency control and are the main method for algal treatment in water. In-situ chemical governance method applies a certain amount of algicidal agent to the water body where algal blooms occur to quickly inhibit the growth of algal cells and cause massive lysis and death of algal cells, thereby achieving the purpose of controlling the development of algal blooms. In order to achieve the ideal removal effect, the selection of algicidal agent is particularly important, which usually needs to have strong cytotoxicity or strong oxidizing property. The main active substances in commonly used algicidal agents include copper-containing products, photocatalysts, strong oxidizing agents, etc. (CN118833897A). Among them, the oxidizing agent algicidal technology has been widely studied due to its high efficiency. However, most of the current chemical oxidizing agents have invasive destruction to algal cells, leading to cell lysis and the release of algal metabolic products (CN109354143A), for example, traditional oxidizing agents such as Cl2 and ClO2 can easily cause cell rupture and release MC-LR, and generate toxic by-products; KMnO4 and O3 can strengthen the coagulation effect, but at high doses, they can cause cell lysis and exacerbate the release of AOM. In comparison, hydrogen peroxide (H2O2) has selective algistatic properties and is environmentally friendly, but its rapid decomposition characteristics result in low utilization rate of oxidizing agents, and the acidic reaction conditions (pH = 2~4) limit its application range.

[0004] In recent years, CaO2 has emerged as a solid source of H2O2. CaO2 is a thermally stable inorganic peroxide solid, and calcium is one of the essential elements for living organisms, so it is very safe to use CaO2 in water treatment. Compared with liquid H2O2, CaO2 is a mild oxidizing agent that can release H2O2 and Ca2+ Self-coagulation is achieved, and both oxidation and coagulation functions are combined (CN112062236A). However, the single CaO2 system has weak oxidation ability, slow degradation rate and high effluent pH, and needs to be combined with other combined processes to improve efficiency.

[0005] To improve the oxidation efficiency, a new catalytic combined process is developed. Studies have shown that Fe(II) can catalyze CaO2 to promote the aggregation of algal pollutants, and the cell viability and integrity are well preserved, and fluorescent organic matter is effectively removed. However, Fe-based homogeneous Fenton method usually has a narrow pH range (pH=2~4), and the reaction process is easy to cause iron sludge accumulation and secondary pollution.

[0006] Copper-based algicides have become one of the hotspots in the field due to their inherent bactericidal and algal control properties and broad-spectrum catalytic performance. The principle of copper-based algicides is that copper ions (Cu(II)) interfere with the normal metabolism and biochemical reactions of algal cell wall surface sulfur groups through strong affinity, thereby inhibiting algal growth (CN118833897A), and can also catalyze H2O2 to generate high-valence copper (Cu(III)) and a large amount of reactive oxygen species (ROS), which further attack the surface morphology and internal tissue structure of algal cells, leading to the destruction of cell integrity and a significant decrease in cell activity, resulting in a significantly higher algal removal effect than iron-based catalysts (CN118975553A). However, current research on Cu(II) ion alone for algal removal is still limited to the application of copper sulfate (CuSO4), which has the obvious defects of CuSO4 overdosing, easy to cause algal cell rupture leading to AOM release, and unable to effectively degrade the released AOM. Therefore, under the premise of maintaining high-efficiency algal removal, it is urgent to develop precise control technology for Cu(II) to reduce the risk of secondary pollution by coupling with oxidation systems. The current surface water environmental quality standard III water standard limit value in China is that the Cu content shall not exceed 15 μM (1 mg∙L -1 )(CN119385149A), and at the usually used dosage (0.39 μM~15 μM), copper-based algicides are considered to have no significant impact on human health. Recently, CN116477746A discloses a technology for removing acid orange with a removal efficiency of more than 95% by using trace Cu(II) (initial concentration of 15 μM~120 μM) to activate percarbonate, but the application of copper-based catalytic CaO2 in the field of algal removal has not been reported.

[0007] Therefore, the present application innovatively proposes a trace Cu(II) / CaO2 system oxidation and coagulation synergistic algal removal process, which continuously generates Cu(III) and ∙OH, ∙O2 - 、 1O2, etc. to strengthen the inactivation of algal cells and the degradation of AOM; meanwhile, the Ca(OH)2 after the reaction can promote the formation of algal flocs through electro-neutralization and net capture, and is conducive to the precipitation of copper ions, so as to ensure that the residual copper concentration is far lower than the standard limit value of the surface water environmental quality standard III water standard. The technology has the advantages of efficient algae removal, effective control of AOM release and low ecological risk, and breaks through the dual bottleneck of low utilization rate of oxidants and secondary pollution in the traditional chemical method. SUMMARY

[0008] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a method for efficiently removing algae based on micro Cu(II) (15 μM) activated CaO2, which utilizes the alkaline environment of CaO2 to promote the recycling of copper ions (Cu(II) / Cu(I)) and the continuous generation of active free radicals (∙OH, ∙O2 - 、 1 ) by constructing a Cu(II) / CaO2 coupled system, and realizes the efficient removal of algae in the pH=5.0~9.0 range, that is, the system has the characteristics of high algae removal efficiency, strong adaptability and simple operation.

[0009] In order to achieve the above purpose, the present application provides a method for efficiently removing algae based on micro Cu(II) activated CaO2, comprising the following steps:

[0010] S1: Preparation of oxidant quencher: prepare 0.1 mol∙L -1 of Na2S2O3 solution as an oxidant quencher for standby;

[0011] S2: Preparation of Cu(II) solution: prepare 15.0 mmol∙L -1 of high-concentration Cu(II) solution 100 mL for standby;

[0012] S3: Preparation of algal cell-containing water sample to be treated, and adjustment of pH to be close to the pH of natural water body, then taking 500 mL of the water sample to be treated, adding a certain amount of Cu(II) and oxidant to form an oxidation-coagulation system, controlling the Cu(II) concentration in the solution to be lower than 15 μM (1 mg∙L -1 ), and adjusting the reaction kinetics of the oxidation-coagulation system through a staged stirring procedure;

[0013] S4: Sampling detection: after standing and precipitation, filtering the supernatant, adding Na2S2O3 solution to terminate the reaction, measuring the absorbance value of the algal solution using a ultraviolet spectrophotometer, and calculating the removal rate of algal cells, and analyzing the detection results.

[0014] The method for efficiently removing algae based on trace Cu(II) activated CaO2, 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, copper chloride.

[0015] The method for efficiently removing algae based on trace Cu(II) activated CaO2, further improved, 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 algae-containing cells is 1.0~5×10 6 cells·mL⁻¹.

[0016] The method for efficiently removing algae based on trace Cu(II) activated CaO2, further improved, in step 3, the Cu(II) is added to the algae-containing water body in the form of a solution, and the dosage concentration is trace level; the oxidizing agent is at least one of CaSO3, H2O2, CaO2.

[0017] The method for efficiently removing algae based on trace Cu(II) activated CaO2, further improved, the molar concentration of Cu(II) and CaO2 dosage ratio includes 0:7 (pure CaO2), 1:0 (pure Cu(II)), 1:3~20, and the Cu(II) concentration in the solution is fixed at 15 μM. When the Cu(II) concentration in the target water body to be treated is ≥15 μM, the method of the present application can achieve effective removal of algae in the water body by directly adding sufficient CaO2 without the need for additional catalysts, which is conducive to further reducing costs.

[0018] The method for efficiently removing algae based on trace Cu(II) activated CaO2, further improved, in step 3, the initial pH value of the oxidation-coagulation system is 5.0~9.0.

[0019] The method for efficiently removing algae based on trace Cu(II) activated CaO2, further improved, in step 3, the system generates substances with strong oxidizing properties through trace Cu(II) catalysis of CaO2 slow-release H2O2, which include but are not limited to Cu(III) and ∙OH, ∙O2 - 、 1 O2 and other active free radicals, and the system can also promote the regeneration of copper ions.

[0020] The method for efficiently removing algae based on trace Cu(II) activated CaO2, further improved, in step 3, the Ca(OH)2 generated after the reaction of the system can promote the formation of algae flocs through electro-neutralization and net capture, and is conducive to the precipitation of copper ions, realizing the synergistic effect of oxidation and coagulation.

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

[0022] Compared with the prior art, the present application has the following advantages:

[0023] (1) Compared with the traditional Fe / Fenton system, the trace Cu(II) / CaO2 system can achieve more than 95% of the removal rate of algae cells in the range of pH=5.0~9.0, and does not need to frequently adjust the pH of the water; (2) CaO2 as a solid H2O2 source successfully overcomes the defect of rapid decomposition of traditional H2O2, and improves the utilization rate of oxidants; (3) Ca(OH)2 generated by hydrolysis of CaO2 after reaction can promote the precipitation of Cu(II) at the same time, so that the residual Cu concentration in the effluent is as low as 30.1 μg·L -1 (lower than the limit value (Cu≤1 mg / L) of the "Surface Water Environmental Quality Standard"), effectively avoiding the residual 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 algae cells and reduce the release risk of dissolved AOM and MC-LR. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

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

[0026] Figure 2 Figure 2 is a chart showing the change of solution pH and residual Cu content after trace Cu(II) activated different oxidants in Example 1;

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

[0028] Figure 4 Figure 4 is a chart showing the change of solution pH and residual Cu content after different Cu(II) / CaO2 dosing ratios in Example 1;

[0029] Figure 5Figure for comparison of removal effects of different initial pH on M. aeruginosa in Example 1;

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

[0031] Figure 7 Figure for effects of different initial concentrations of algal cells on removal of M. aeruginosa by trace Cu(II) / CaO2 system in Example 1;

[0032] Figure 8 Figure for changes of Zeta potential and Chl-a removal rate in Example 2;

[0033] Figure 9 Figure for morphological structures of M. aeruginosa cells observed by SEM in different reaction systems in Example 2, wherein a and b are controls, c and d are Cu(II) system alone, e and f are CaO2 system alone, and g and h are trace Cu(II) / CaO2 system;

[0034] Figure 10 Figure for changes of extracellular MC-LR content during treatment of M. aeruginosa by different systems in Example 2. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer and easier to understand, the present application will be described in detail below in combination with the drawings and specific preferred embodiments in the specification. If specific conditions are not indicated in the embodiments, the conventional conditions or the conditions suggested by the manufacturers are adopted. The reagents and apparatus required for the experiments are all conventional commercially available products meeting the industry standards, if the manufacturers are not indicated.

[0036] A method for efficiently removing algae based on trace Cu(II)-activated CaO2 provided by the present application will be described in detail below.

[0037] Example 1

[0038] In this embodiment, the removal efficiency of trace Cu(II) / CaO2 oxidation system on algae in water is explored, and the specific process is as follows:

[0039] (1) Source of algae: the algae selected in this experiment is M. aeruginosa, which is the dominant algae species of cyanobacterial bloom outbreak in China, and its number is FACHB-905, which is purchased from Freshwater Algae Culture Collection of Institute of Hydrobiology, Chinese Academy of Sciences (Wuhan).

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

[0041] (3) Preparation of experimental algal water: After Microcystis aeruginosa grew to the logarithmic phase, the algal suspension was centrifuged at 4000 r·min -1 for 5-10 min to collect the logarithmic phase Microcystis aeruginosa. The algal cells were then 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 the pH was adjusted to 7.0 with 0.1 mmol·L -1 HCl and 0.1 mmol·L -1 NaOH to approach the pH of natural water bodies. The experimental algal water was obtained and ready for use.

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

[0043] (4) Experimental method: First, 500 mL of pre-prepared algal water was transferred to several groups of 1 L beakers, and the pH was adjusted to 7.0. Each group had three parallel samples. Then, a certain amount of high-concentration copper sulfate solution was added to each group of algal water solution, followed by a certain amount of oxidizing agent. The oxidation-coagulation experiment was carried out on a coagulation stirrer. The coagulation conditions were: stirring, standing and settling, and the removal of Microcystis aeruginosa in the water body was completed. After standing was completed, 2 mL of supernatant was taken 2 cm below the liquid surface using a pipette, and 0.1 mol·L -1 sodium thiosulfate solution was added to terminate the reaction. Finally, the absorbance value of the Microcystis aeruginosa solution was measured at an absorption wavelength of 680 nm using a UV spectrophotometer. The removal rate of Microcystis aeruginosa cells was calculated by measuring the OD 680 before and after the reaction. The calculation formula is shown in equation (1):

[0044]

[0045] where OD 680i is the absorbance value of the initial Microcystis aeruginosa solution before the reaction; OD680t t represents the absorbance value of the Microcystis aeruginosa solution at time t.

[0046] Except for parameter design, all the following parameter optimization batch experiments were conducted using the basic experimental methods described above.

[0047] ① Comparison of different oxidants

[0048] The effects of trace Cu(II) activation of different oxidants (CaSO3, CaO2, H2O2) on the removal rate of Microcystis aeruginosa were compared. Experimental design: 0.5 mL of 15.0 mmol∙L⁻¹ Cu(II) was added to each group of algal aqueous solutions. -1 A high-concentration copper sulfate solution resulted in a Cu(II) concentration of 15 μM (1 mg∙L⁻¹). -1 Then, CaSO3, CaO2, and H2O2 are added as oxidants to make their concentrations in the solution 100 μM.

[0049] Depend on Figure 1 It can be seen that there are significant differences in the removal efficiency of different oxidants combined with trace amounts of Cu(II) for Microcystis aeruginosa. The Cu(II) / CaO2 system has an algae removal rate 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 differences in mechanism are mainly reflected in three aspects: (1) The hydroxyl radicals (E0=2.7 V) generated by the Cu(II) / CaO2 system are greater than the SO4 generated by the Cu(II) / CaSO3 system. 2- Free radicals (E0=2.6 V) have stronger oxidizing power; (2) CaSO4 and Ca(OH)2 will be formed in the Cu(II) / CaSO3 system and the Cu(II) / CaO2 system, respectively. Ca(OH)2 (Ksp=5.5×10 -6 M 2 Compared to CaSO4 (Ksp=9.1×10⁻⁶), -6 M 2 (3) The characteristic of CaO2 slowly releasing H2O2 overcomes the rapid decomposition defect of directly adding H2O2, while Ca 2+ By inducing algal cells to release extracellular polymeric substances (EPS), colony aggregation and sedimentation are promoted. Figure 2 It can be seen that the Cu(II) / CaO2 system maintains a neutral environment (pH=7.8) while the residual Cu concentration is only 30.1 μg∙L. -1 It is significantly lower than Cu(II) / CaSO3 (761.9 μg∙L⁻¹). -1 ) and Cu(II) / H2O2 system (734.3 μg∙L) -1The pH change mechanism can be attributed to the following: in the Cu(II) / H₂O₂ system, Cu²⁺ hydrolyzes to generate Cu(II)-OH and H⁺, while some Cu(II) reacts with H₂O₂ to further release protons, causing the pH to drop to 5.5. In the CaO₂ system, although the generated Ca(OH)₂ is alkaline, it can react with the H⁺ generated from the hydrolysis of Cu²⁺ to achieve dynamic pH equilibrium. The difference in residual copper stems from the strong adsorption of heavy metals by Ca(OH)₂ generated from the hydrolysis of CaO₂, while the Cu(II) / CaSO₃ and Cu(II) / H₂O₂ systems lack effective solid-phase precipitation carriers. These results indicate that the trace Cu(II) / CaO₂ system possesses advantages such as high algae removal efficiency, stable pH, and high efficiency in heavy metal removal.

[0050] Therefore, the present invention selects trace Cu(II) / CaO2 as the optimal system.

[0051] ② Comparison of different Cu(II) / CaO2 addition ratios

[0052] The effect of different Cu(II) / CaO2 dosage ratios on the removal efficiency of Microcystis aeruginosa was investigated. Experimental design: Cu(II) / CaO2 dosage 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, with a fixed Cu(II) concentration of 15 μM (1 mg∙L⁻¹) in the solution. -1 ).

[0053] Depend on Figure 3 It can be seen that when using trace amounts of Cu(II) (1:0) alone, the removal rate of algal cells by Cu(II) is only 3.6%, indicating limited removal efficiency. When using CaO2 alone (0:7), it is also unable to effectively remove algal cells in a short time. However, the trace Cu(II) / CaO2 composite system significantly improves the algae removal efficiency. When the molar ratio is 1:3, the algae removal rate reaches 71.2%; as the CaO2 dosage increases to 1:7, the algae removal rate further increases to 97.6%. The mechanism lies in the fact 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 stabilize, indicating that there is an optimal dosage ratio. Figure 4It was found that when CaO2 was added alone, the pH of the algal solution increased from 7.0 to 8.8 (CaO2→Ca(OH)2), while the addition of Cu(II) alone caused the pH to drop to 5.9. In the composite system, when the Cu(II) / CaO2 molar ratio was 1:3 and 1:7, the pH of the algal solution after the reaction decreased from 8.8 to 7.5 and 7.9, respectively, compared to the CaO2 treatment alone, which is attributed to the release of H⁺ from the reaction of Cu(II) with H₂O₂. However, the higher the amount of CaO2 added, the higher the pH of the algal solution after the reaction. When a trace amount of Cu(II) was added alone, the residual Cu content in the solution was 595.4 μg∙L⁻¹. -1 With the addition of CaO2, the residual Cu content in the algal solution decreased significantly. When the molar ratio of trace Cu(II) / CaO2 was 1:7, the residual Cu content reached its lowest value of 30.1 μg∙L. -1 (Cu(OH)2 precipitate is formed), and the addition of excessive CaO2 did not further reduce its residual concentration.

[0054] Therefore, the optimal Cu(II) / CaO2 addition ratio is selected as 1:7 in this invention.

[0055] ③ Effects of different pH values

[0056] The effects of different pH values ​​on the removal of Microcystis aeruginosa using a 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 algae-containing aqueous solutions were adjusted with NaOH to 5.0, 6.0, 7.0, 8.0, and 9.0, respectively.

[0057] Depend on Figure 5 It can be seen that the trace Cu(II) / CaO2 system maintains high algae removal efficiency within a pH range of 5.0–9.0, with a removal rate exceeding 95%. Its broad pH adaptability stems from the dynamic transformation of active species: under acidic conditions, H2O2 generated from CaO2 hydrolysis promotes the reduction of Cu(II) to Cu(I), as shown in reaction (2), which in turn catalyzes the generation of highly oxidizing hydroxyl radicals (∙OH) from H2O2, as shown in reaction (3); in neutral to alkaline environments, as shown in reaction (3), Cu(I) / H2O2 reacts to generate high-valence copper species (Cu(III)), whose oxidation potential remains stable within a pH range of 3.0–9.0 and exhibits selective oxidation capability. Studies have confirmed that this system achieves continuous and efficient oxidation across a wide pH range through a pH-dependent reactive oxygen species 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 Cu(II) is converted to Cu(I) and H⁺ is generated, and the dual effects make the pH fluctuation after reaction not significant. The residual Cu content remains stable in the range of pH 5.0-9.0, that is, the system has broad-spectrum pH adaptability.

[0058]

[0059] ④Influence of different initial concentrations of algal cells

[0060] Under the conditions of fixed Cu(II) / CaO2 molar ratio (1:7) and neutral pH (pH=7.0), the influence of different initial concentrations of algal cells on the algal removal efficiency of the micro Cu(II) / CaO2 coupling system was investigated. The experimental design: the algal cell density was diluted to 1.0×10 6 cells·mL -1 , 2.5×10 6 cells·mL -1 , 5.0×10 6 cells·mL -1 respectively by ultrapure water, and the pH was adjusted to 7.0 by 0.1 mmol·L -1 HCl and 0.1 mmol·L -1 NaOH, that is, the experimental algae-containing water with different initial concentrations of algal cells was obtained.

[0061] It can be seen from Figure 7 that the removal efficiency presents a downward trend with the increase of the initial concentration of algal cells. When the initial concentration of algal cells is 1.0×10 6 cells·mL -1 and 2.5×10 6 cells·mL -1 , the removal rates of algal cells are 100% and 99.1% respectively. When the initial concentration of algal cells rises to a high concentration of 5.0×10 6 cells·mL -1 , the removal rate of algal cells by the micro Cu(II) / CaO2 oxidation and coagulation system is slightly reduced to 92.5%, because under the same experimental conditions, the higher the algal cell concentration in water, the smaller the attack of ROS on the algal cells. According to the long-term monitoring data of Taihu Lake in China, the density of cyanobacteria in this region usually fluctuates in the interval of 5×10 4 ~2.5×10 6 cells·mL -1 . Therefore, the micro Cu(II) / CaO2 oxidation and coagulation system can realize efficient removal of algal cells in a wide range of algal cell concentrations with a lower dosage.

[0062] Therefore, the initial concentration of algal cells is selected as 2.5×10 6cells∙mL -1 Conduct follow-up experiments.

[0063] Example 2

[0064] This embodiment explores the removal mechanism of algae in water by a trace Cu(II) / CaO2 oxidation system. The specific process is as follows:

[0065] ①Characteristic analysis of cellular Zeta potential and chlorophyll a (Chl-a)

[0066] Analysis results of cellular Zeta potential and Chl-a ( Figure 8 The results showed that in the trace Cu(II) / CaO2 oxidation system, the Zeta potential increased from an initial -26.43 mV to -8.46 mV (an absolute decrease of 68%), simultaneously achieving a 94.03% removal of Chl-a. In contrast, the Zeta potential and Chl-a removal rate did not change significantly in the systems with separate Cu(II) and CaO2 additions. This indicates that the synergistic relationship between the absolute decrease in Zeta potential and algae removal efficiency is only evident in the Cu(II) / CaO2 system. Unlike the potential decrease caused by ozone and potassium permanganate pre-oxidation, which is attributed to the release of intracellular organic matter (IOM) induced by oxidative stress, the positive potential migration characteristic of this system indicates that it achieves algal inactivation through a non-destructive pathway, effectively avoiding the risk of secondary pollution caused by damage to cell integrity.

[0067] ② Scanning electron microscopy characterization analysis (SEM)

[0068] SEM analysis results ( Figure 9 The results showed that the algal cells in the control group (a, b) maintained a regular spherical shape, with smooth surfaces and intact cell membranes. However, treatment with Cu(II) alone (c, d) resulted in rough and deformed cell surfaces, cell membrane damage, and promoted metabolite secretion in some cells. This may be due to the reduction of intracellular Cu(II) to the more toxic Cu(I), which then disrupts cell structure. Treatment with CaO2 alone (e, f) caused algal cells to coagulate but largely maintained structural integrity, with only a few cells showing slight shrinkage. In the trace Cu(II) / CaO2 composite system (g, h), a large amount of oxidant adhered to the algal cell surface, but its morphology and surface characteristics showed no significant change compared to the control group. This indicates that the system only induced a small number of algal cells to rupture and release IOM, suggesting that the generated ROS did not cause large-scale algal cell lysis; only a small portion of algal cells ruptured.

[0069] ③ Determination of microcystin (MC-LR) content

[0070] Figure 10The variation of extracellular MC-LR content during the treatment of Microcystis aeruginosa by different systems is shown in the chart. The results show that the addition of Cu(II) alone can cause a slight increase in the concentration of extracellular MC-LR, which confirms that Cu(II) can destroy the structure of algal cells, leading to the release of intracellular MC-LR. Since Cu(II) itself does not have oxidation properties, it cannot effectively degrade the released MC-LR. The experiment also found that when CaO2 is used alone, the concentration of extracellular MC-LR does not decrease significantly, which indicates that CaO2 has little effect on the integrity of the algal cell membrane, and the amount of ROS it produces is limited, resulting in no significant effect on the oxidative degradation of MC-LR. It is worth noting that in the trace Cu(II) / CaO2 composite oxidation system, the concentration of extracellular MC-LR changes with time and shows a dynamic characteristic of first increasing and then decreasing. This rule shows that at the initial stage of the reaction, the ROS produced by the system will partially destroy the algal cells, promoting the release of intracellular MC-LR; as the reaction continues, the released MC-LR is gradually oxidized and degraded by the ROS produced by the system. Finally, the concentration of MC-LR can be reduced to below the safety limit (1.0 μg∙L -1 ) of drinking water specified by the World Health Organization (WHO). The results show that the trace Cu(II) / CaO2 oxidation system not only effectively removes Microcystis aeruginosa, but also significantly controls the residual concentration of MC-LR, thereby effectively avoiding the risk of secondary pollution.

[0071] In summary, the present application creatively develops a method for efficient algae removal based on trace Cu(II) activated CaO2, and through batch experiments, the effects of oxidant selection, Cu(II) / CaO2 dosage ratio, initial pH, and initial concentration of algal cells on the removal of algae in water are investigated. The results show that the algae removal efficiency of the trace Cu(II) / CaO2 oxidation system is better than that of Cu(II) / CaSO3 and Cu(II) / H2O2; when the Cu(II) dosage is only 15 μM (1 mg∙L -1 ), the molar ratio of Cu(II) / CaO2 is 1:7, and the initial concentration of algal cells is 1.0~2.5×10 6 cells∙mL -1 , the removal rate of algal cells is as high as 97%; the system has a neutral pH after reaction, and the residual Cu concentration is as low as 30.1 μg∙L -1The following, and the advantages of the initial pH does not affect the efficiency of algae. Mechanism studies found that trace Cu(II) / H2O2 system can significantly improve the algae cell Zeta potential (-26.43→-8.46 mV), increase the removal rate of chlorophyll a (94.03%), conducive to the removal of algae; At the same time, trace Cu(II) / H2O2 system does not lead to a large number of algae cell rupture, the release of organic matter can be effectively degraded, can reduce the risk of secondary pollution. Compared with a single component, the coupling system has the characteristics of high efficiency of algae removal, strong adaptability, environmental friendly, etc., has broad application prospect.

[0072] It should be noted that the above examples are only preferred embodiments of the present application, not the limitation of the scope of protection of the present application. The technical solutions disclosed by the present application allow various forms of adjustment and improvement within the scope of the core idea of the present application. Any reasonable changes made by those skilled in the art based on the technical principles of the present application, including but not limited to process parameter adjustment, implementation modification or equivalent technology replacement, etc., as long as it does not deviate from the basic principles and technical concept of the present application, should be included in the legal protection scope defined by the claims of the present patent application.

Claims

1. A method for efficient algae removal based on activation of calcium peroxide by trace copper ions, characterized in that, The method comprises the following steps: S1: Preparation of oxidant quencher: A 0.1 mol L -1 solution of Na2S2O3 was prepared as an oxidant quencher for later use. S2: Preparation of Cu(II) solution: 15.0 mmol L -1 High concentration Cu(II) solution 100 mL standby; S3: preparing the algal cell-containing water sample to be treated, adjusting the pH to be close to the pH of the natural water body, then taking 500 mL of the water sample to be treated, adding a certain amount of Cu(II) and oxidant CaO2 to form an oxidation-coagulation system, controlling the Cu(II) concentration in the system to be lower than 15 μM, and the molar ratio of Cu(II) to CaO2 to be 1:3-20, and regulating the reaction kinetics of the oxidation-coagulation system through a staged stirring procedure; S4: sampling detection: after standing and precipitation, the supernatant was filtered, Na2S2O3 solution was added to terminate the reaction, the absorbance value of the algae solution was measured by using ultraviolet spectrophotometer, and the removal rate of algae cells was calculated, and the detection results were analyzed; in the reaction process, Cu(II) catalyzes CaO2 to release H2O2 to generate substances with strong oxidizing properties, including but not limited to Cu(III) and ∙OH, ∙O2 - , 1 O2 active free radicals, and the system can promote the regeneration of copper ions; at the same time, Ca(OH)2 generated after the reaction of the system promotes the formation of algae flocs through electro-neutralization and net capture, and is beneficial to the precipitation of copper ions, realizing the synergistic effect of oxidation-coagulation-precipitation.

2. The method for efficient algae removal based on micro-copper ion activated calcium peroxide according to claim 1, characterized in that, In the step S2, the Cu(II) solution is configured by selecting one or more of copper sulfate pentahydrate, anhydrous copper sulfate and copper chloride.

3. The method for high-efficiency algae removal based on micro-copper ion activated calcium peroxide according to claim 1, characterized in that, The algal cells in the step S3 include but are not limited to one or more of cyanobacteria, green algae or diatoms; the initial concentration of the algal cells is 1.0-5×10 6 cells·mL⁻¹.

4. The method for high-efficiency algae removal based on micro-copper ion activated calcium peroxide according to claim 1, characterized in that, In the step S3, the initial pH value in the oxidation-coagulation system is 5.0-9.

0.

5. The method for high-efficiency algae removal based on micro-copper ion activated calcium peroxide according to claim 1, characterized in that, The concentration of residual copper after the reaction in step S4 is less than 30.1 μg·L -1 The removal rate of algal cells is higher than 97%.

6. The method for high-efficiency algae removal based on micro-copper ion-activated calcium peroxide according to any one of claims 2-5, characterized in that, The oxidation-coagulation system is applied to the treatment of algal pollution in eutrophic water bodies.

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