A method for efficiently removing Microcystis aeruginosa from water

Abstract

The present invention provides a method for efficiently removing Microcystis aeruginosa from water. Electrolytic manganese slag and NaHSO3 are added to an algae-containing environment, and algae reduction is carried out under visible light. The algae-containing environment includes Microcystis aeruginosa. NaHSO3 promotes the aggregation of electrolytic manganese slag with algae cells mainly through adsorption, thereby allowing the algae cells to settle. The precipitated aggregates cause the cells to lose activity. In addition, NaHSO3 activates oxides such as iron and manganese in the electrolytic manganese slag, accelerating the reaction rate and damaging some algae cell membranes. In summary, this study provides a new method for rapid algae removal using electrolytic manganese slag.

Description

Technical Field

[0001] The invention relates to a method for removing algae from electrolytic manganese slag using NaHSO3, and belongs to the technical field of environmental treatment. Background Art

[0002] Cyanobacteria, as major photosynthetic microorganisms, are widely present in nature. However, their proliferation in eutrophic water bodies leads to algal blooms, posing a significant threat to drinking water treatment. They can also clog filters, consume oxygen in the water, and produce secondary metabolites, which can damage taste and smell. Microcystis aeruginosa (M. aeruginosa) is a common bloom-forming cyanobacteria in freshwater ecosystems. Due to its buoyancy-controlled properties, annual growth cycle with a unique storage strategy, efficient nitrogen absorption, and resistance to zooplankton, it is prone to causing algal blooms, which can cause serious environmental problems. Therefore, there is an urgent need to find a reliable method for removing harmful cyanobacterial cells.

[0003] Traditional cyanobacteria removal methods, such as physical filtration and the use of algaecides, have the disadvantages of low efficiency, high cost, or high toxicity, and harmful substances released by cell rupture, such as algal toxins, can cause secondary pollution to the water environment. Chemical coagulation methods, such as those based on iron or aluminum salts, have been widely studied for the removal of cyanobacteria. Although they have the advantage of high efficiency, the residual Fe / Al is high and harmful to human health. Tannins, laterite / clay, and chitosan have been used as cyanobacteria flocculants instead of metal coagulants. Although they reduce the residual metal content, it usually takes a long time for the algae removal effect to appear, and the sustained inhibition of algae growth remains an unresolved problem. Biological methods (microbial bioflocculant-related bioflocculant, microbial-related bioflocculant, and self-flocculation) perform well in terms of environmental impact, but they usually require strain specificity, have long treatment operation cycles, and are difficult to manage. Therefore, the development of efficient and environmentally friendly algae removal methods remains a difficult problem that needs to be solved.

[0004] Electrolytic manganese slag is a hazardous solid waste generated during the production of metallic manganese. During the production process, manganese ore (generally manganese carbonate) is leached in sulfuric acid, and the resulting solution is electrolyzed to produce manganese powder. For every ton of manganese metal produced, approximately 10-12 tons of electrolytic manganese slag are generated. It is estimated that China produces 10 million tons of electrolytic manganese slag annually, with cumulative production exceeding 150 million tons. China has become the world's largest producer of electrolytic manganese slag, accounting for approximately 98.5% of the global total. Currently, most electrolytic manganese slag is directly dumped into landfills without any effective treatment and is rarely reused. The electromagnetic radiation emitted not only occupies large tracts of arable land but also poses significant environmental risks due to its hazardous nature. Harmful elements in electrolytic manganese slag, especially manganese, continuously leach into nearby soil and water, posing a significant threat to human health. This pollution is exacerbated during the rainy season through erosion and leaching from rainwater. These environmental issues caused by electrolytic manganese slag have attracted significant public attention. Therefore, the effective utilization of electrolytic manganese slag is one of the problems that need to be solved urgently.

[0005] According to current literature, the resource utilization of electrolytic manganese slag primarily focuses on valuable element recovery, stabilization and solidification, electroremediation, building materials, sewage treatment materials, soil conditioners, and other functional materials. Rapid industrialization, rapid population expansion, and unplanned urbanization have not only caused severe water pollution but also generated large amounts of industrial and urban waste, damaging soil and air. The unmanaged discharge of urban excreta and industrial hazardous waste has contaminated life-sustaining water systems, impacting sustainable human development. Therefore, wastewater recycling and treatment has long been a primary means of alleviating water shortages. The use of adsorbents to treat wastewater is increasingly favored as a simple, efficient, long-term, and renewable treatment method. Using electrolytic manganese slag as an adsorbent to remove pollutants (particularly algae) would not only reduce the manufacturing cost of wastewater treatment materials but also enable the utilization of these wastes, further minimizing environmental damage.

[0006] Minerals have the ability to adsorb pollutants, and numerous studies have applied them to pollutant removal. For example, bentonite is often used to adsorb and immobilize radioactive uranium. Muir and Bajda studied the adsorption of gasoline, diesel, engine oil, and used engine oil by zeolites and organic zeolites (in powder form). Electrolytic manganese slag, a metallurgical solid waste, is primarily composed of aluminosilicates. Based on its physicochemical properties, electrolytic manganese slag has been found to share similar adsorption properties with bentonite, geopolymers, waste concrete, silica gel, and activated alumina. Therefore, electrolytic manganese slag is also a viable adsorbent for wastewater treatment. For example, Lan et al. prepared a novel material by grinding electrolytic manganese slag with NaOH. They achieved the immobilization of Hg(II), Zn(II), and Cu(II) through ion exchange, electrostatic adsorption, and certain forms of hydroxyl complexation, achieving leaching toxicity that met national standards. Some researchers have found that natural minerals can effectively remove algae from water. Due to differences in their surface structure and physical and chemical properties, different types of minerals have different effects and rates on algae removal. In addition, some natural minerals have positive charges on their surfaces, which have unique advantages in adsorbing and removing algae cells with negative charges on their surfaces. For example, WANG et al. investigated the removal of harmful algae, marine calcite, by natural sphalerite under different physical and chemical conditions. SUKENIK et al. used bentonite modified with cationic surfactants to remove cyanobacteria and cyanobacterial toxins from lake water. Electrolytic manganese slag contains a large amount of active substances such as SiO2, Fe2O3, Al2O3 and MnO. The variable valence metal ions it contains can provide catalytic sites for various pollutants in water bodies and have the effect of adsorbing and removing algae cells in the water environment. Therefore, research on algae removal by electrolytic manganese slag is of great practical significance.

[0007] Although natural organic adsorbents are considered to be effective, cheap, easily available and environmentally friendly, the silicon-oxygen structure of natural minerals such as bentonite has a strong hydrophilicity, resulting in poor adsorption of pollutants. The ability of minerals to remove pollutants alone is limited. Therefore, researchers usually further modify natural minerals to improve their adsorption parameters for pollutants. Many scholars have also studied the modification of electrolytic manganese slag to improve the adsorption of organic pollutants. For example, Shu et al. modified electrolytic manganese slag to use it as an efficient adsorbent to remove methylene blue. By studying the kinetics, isotherms and related thermodynamic parameters, the results showed that electrolytic manganese slag can be used as a low-cost, environmentally friendly potential adsorbent to remove methylene blue from wastewater. Ma Mengyu modified electrolytic manganese slag to achieve a higher specific surface area and pore volume, and the adsorption removal rate of cadmium in water reached 99.2%. Li et al. used Na2CO3 and HNO3 to modify electrolytic manganese slag to prepare a catalyst, activating the abundant Fe and Mn in the electrolytic manganese slag to produce a large amount of hydroxyl radicals (·OH) and sulfate radicals (SO4· - ) and superoxide radicals (O2· -) for oxidative degradation of organic pollutants. Li et al. discovered that electrolytic manganese slag, using a two-step NaOH and NaAlO2 method, synthesized an economical and practical zeolite material for adsorbing metal ions in wastewater. The results showed that modified electrolytic manganese slag is a promising adsorbent and a highly effective adsorbent for wastewater treatment. Recently, a new method using bisulfite for modification has gained increasing application, significantly improving the adsorption capacity of the modified material. For example, Sun Bo et al. reported a new method for rapidly degrading organic pollutants by activating manganese oxides with bisulfite. Zhou et al. reported that electrolytic manganese slag is rich in active components (α-MnO2) that can be activated to produce a large number of free radicals, effectively degrading tetrachlorophenol. Zhu et al. found that adding KMnO4 to the algae solution treated with NaHSO3 in an Al2(SO4)3 coagulation process could avoid color issues, neutralize the zeta potential of algal cells, and form more compact flocs without damaging the integrity of the algal cells, accelerating their removal. It can be seen that the use of bisulfite to achieve modification can not only improve the degradation rate of pollutants, but also reduce the risk of aggravating water pollution due to the release of algal toxins due to algal cell rupture. It is an effective modification method.

[0008] Electrolytic manganese slag, as an industrial waste, is produced in large quantities and poses significant environmental risks. However, it possesses the important characteristic of being an adsorbent and is inexpensive, meaning that if utilized, it can be transformed into valuable resources. From the perspectives of economic efficiency, effectiveness, and resource utilization, electrolytic manganese slag possesses the potential for high adsorption and can be applied to pollutant removal, particularly algae. However, research on the flocculation and algae removal of electrolytic manganese slag is limited, and the adsorption, removal, and degradation mechanisms of electrolytic manganese slag on algae in water bodies are unclear. Previous studies on algal cell removal have reported even fewer reports on the use of electrolytic manganese slag for the removal of Microcystis aeruginosa. Therefore, the use of electrolytic manganese slag to remove cyanobacterial cells has certain scientific significance and innovation. Therefore, in order to utilize waste and accelerate the removal of algae pollutants in water environments, based on the properties of electrolytic manganese slag itself, the present invention uses electrolytic manganese slag as an algaecide, targets Microcystis aeruginosa, a dominant algae species in Xiangxi River blooms, and selects NaHSO3, which has a strong reducing property, to assist the electrolytic manganese slag in achieving rapid removal of M. aeruginosa. Summary of the Invention

[0009] In response to the above technical problems, the present invention provides a method for removing algae by electrolytic manganese slag under the action of NaHSO3, preferably for removing M. aeruginosa, by adjusting the concentration of electrolytic manganese slag, NaHSO3 concentration, pH and other factors on the removal rate of chlorophyll a.

[0010] The method of using NaHSO3 to promote the removal of algae from electrolytic manganese slag is to add electrolytic manganese slag and NaHSO3 into an algae-containing environment and perform algae reduction under visible light.

[0011] The algae-containing environment includes Microcystis aeruginosa.

[0012] The concentration of algae is 1.00×10 6 cells / mL-1.00×10 7 cells / mL.

[0013] The concentration of electrolytic manganese slag is 1.0-2.0g / L.

[0014] The concentration of NaHSO3 is 0.50mmol / L-1.50mmol / L.

[0015] The pH in the algae-reducing environment is 7.0-9.5.

[0016] By monitoring changes in organic matter, cell apoptosis, and TOC content during the reaction, as well as observing the surface structure of M. aeruginosa after the reaction, we found that NaHSO3 promotes electrolytic manganese slag aggregation primarily through adsorption with algal cells, leading to cell sedimentation and the resulting aggregates, which inactivate the cells. Furthermore, NaHSO3 activates oxides such as iron and manganese in the electrolytic manganese slag, accelerating the reaction and damaging some algal cell membranes. In summary, this study provides a new method for rapid algae removal from electrolytic manganese slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the effect of electrolytic manganese slag concentration on the removal of chlorophyll a by Microcystis aeruginosa.

[0018] Figure 2 The effect of NaHSO3 concentration on the removal of chlorophyll a by electrolytic manganese slag.

[0019] Figure 3 The effect of pH on the removal of chlorophyll a by electrolytic manganese slag promoted by NaHSO3.

[0020] Figure 4 SEM images of algae cells ab before treatment with electrolytic manganese slag promoted by NaHSO3; cd after treatment with electrolytic manganese slag promoted by NaHSO3.

[0021] Figure 5 EOM diagram; a Before NaHSO3 promoted electrolytic manganese slag treatment; bc NaHSO3 promoted electrolytic manganese slag treatment. Figure 6 Figure 2 is a flow cytometer measurement diagram of Microcystis aeruginosa, where a is before treatment with electrolytic manganese slag promoted by NaHSO3; b is after treatment with electrolytic manganese slag promoted by NaHSO3.

[0022] Figure 7 This is a graph showing the changes in TOC in BG-11 culture medium before and after NaHSO3 promoted algae removal by electrolytic manganese slag.

[0023] Figure 8 Mn under different reaction conditions 2+ Release amount.

[0024] Figure 9 This is the XRD pattern of electrolytic manganese slag. DETAILED DESCRIPTION

[0025] Algae culture: M. aeruginosa (FACHB-905) was purchased from the Wuhan Institute of Hydrobiology, Chinese Academy of Sciences, and cultured in a light incubator using BG-11 medium. During the culture period, the algae were shaken 4-5 times a day and the position of the incubator was changed to reduce the effect of uneven lighting. The culture temperature was 25±1°C, the light intensity was 2000 Lx, and the light-dark ratio was 12h:12h. Sterile operation was maintained throughout the experimental operation. When the algae grew to the logarithmic phase (2.00×10 6 cells / mL) were taken out and centrifuged at 3000 r / min for 10 min. To ensure the activity of the algal cells, the collected algal cells were resuspended in BG-11 culture medium for experiments.

[0026] Electrolytic manganese slag (from an electrolytic manganese slag plant in Yichang City, passed through a 100-mesh sieve)

[0027] Characterization of electrolytic manganese slag

[0028] The surface morphology of electrolytic manganese slag was determined using a scanning electron microscope (SEM, JSM-7500F, JEOL, Japan). The crystal structure was determined using an X-ray diffractometer (XRD, D / max2500, Rigaku, Japan). The mineral surface area, pore size, and pore volume were determined using a surface area analyzer (JW-BK112, Beijing Jingwei Gaobo). The characteristic infrared spectral peaks of the samples were determined using an ATR-FTIR spectrometer (Nicolet, Is50, Thermo Fisher Scientific, USA).

[0029] Characterization of electrolytic manganese slag

[0030] The crystal structure of the sample was characterized and analyzed by X-ray powder diffractometer (XRD). The XRD pattern of electrolytic manganese slag is shown in Figure 9 .from Figure 9It can be seen that the electrolytic manganese slag contains characteristic peaks of SiO2 and CaSO4·2H2O with good crystal form, among which CaSO4·2H2O comes from the reaction of CaMn(CO3)2 and CaCO3 in manganese carbonate ore with sulfuric acid during the manganese ore leaching process. The electrolytic manganese slag also contains a small amount of muscovite (KAl2Si3AlO 10 (OH)2), albite (Na,Ca)Al(Si,Al)3O8 and kaolinite (KAl2Si3AlO 10 (OH)2).

[0031] XRF analysis of the various elements in electrolytic manganese slag was performed. Table 1 shows that the contents of SiO₂, SO₃, Al₂O₃, MnO, MgO, CaO, and Fe₂O₃ in the slag totaled 96.71%, primarily composed of clay minerals. The slag also contained a high SO₃ content, primarily in the form of CaSO₄·2H₂O. The SiO₂ content was 31.49%, indicating that the slag is an industrial waste high in SiO₂ and CaSO₄·2H₂O. Its pH was 6.3, indicating a weak acidity.

[0032] Table 1 Chemical composition of electrolytic manganese slag

[0033]

[0034] Methods for measuring indicators

[0035] Chlorophyll a determination: 10.00 mL of each of the blank and reacted algae solutions were centrifuged at 5000 rpm for 5 minutes. The supernatant was removed and 10.00 mL of 95% ethanol was added to the precipitate. The mixture was refrigerated at 4°C overnight. The supernatant, obtained after centrifugation at 5000 rpm for 5 minutes, was measured using a UV spectrophotometer at 665, 649, and 470 nm. Chlorophyll a content was calculated using the following formula:

[0036] Chla (mg / L) = 13.7 × A 665 -5.76×A 649 (3-1)

[0037] Determination of dissolved oxygen: Add electrolytic manganese slag to 200.00 mL of 2.00 × 10 6 cells / mL algae solution, and insert the dissolved oxygen meter probe into the algae solution of the control group and the treatment group to measure the dissolved oxygen content every 4 hours. The measurement was repeated 3 times and the average value was taken.

[0038] Determination of total organic carbon (TOC) in algal liquid: 2.00 mL of algal liquid before and after reaction was filtered through a 0.22 mm filter membrane, and the supernatant was tested for total organic carbon content using a total organic carbon analyzer (TOC, Multi N / C 2000, Germany).

[0039] Observation of algal cell surface structure: 100.00 mL of untreated blank algal solution and algal solution treated with electrolytic manganese slag were centrifuged at 4000 rpm for 10 min. The supernatant was discarded, and the collected algal cells were fixed with 1 mL of 2% glutaraldehyde for 2 h. The cells were then washed three times with 1.00 mL of 0.1 mol / L phosphate buffer (pH 6.80), each for 10 min. The samples were then dehydrated with 1.00 mL of 50%, 70%, and 90% ethanol in a gradient of 15 min, and then dehydrated twice with 100% ethanol, each for 30 min, before drying. For measurement, the samples were attached to the sample stage with double-sided tape. After being gold-coated using an ion sputtering instrument, the samples were observed and photographed under a Hitachi scanning electron microscope.

[0040] Algal cell membrane integrity test: 1.00 mL of M. aeruginosa culture medium (treated with electrolytic manganese slag) and 1.00 mL of M. aeruginosa culture medium (normally grown) were centrifuged at 4000 rpm for 5 minutes. The supernatant was discarded and the cells were rinsed twice with ultrapure water. The cells were centrifuged again, the supernatant discarded, and 1.00 mL of ultrapure water was added to mix thoroughly. 61.00 μL of PI solution (1.00 mg / mL) was then added to give a final concentration of 65.20 mg / L. The cells were stained in the dark for 15 minutes. The cells were analyzed by flow cytometry using an FL2 detector, and the data were analyzed using BD FACSuite Software.

[0041] Extraction and Determination of Extracellular Organic Matter (EOM): The EOM extraction method was based on the method of Chu et al. Specifically, 5 ml of the sample to be tested was placed in a centrifuge tube and centrifuged at 9000 rpm for 10 minutes at 4°C. The supernatant was then filtered through a 0.45 μm cellulose acetate membrane. Three-dimensional fluorescence spectra were measured using an F4600 fluorescence spectrophotometer. Measurement conditions were: excitation wavelength (Ex) scanning range: 220-400 nm, step size: 10 nm; emission wavelength (Em) scanning range: 240-450 nm, step size: 2 nm; excitation and emission slits: 5 nm; scanning speed: 12000 nm / min. Instrument stability was verified using Raman scattering intensities at 350 nm excitation and 397 nm emission wavelengths using ultrapure water. The three-dimensional fluorescence spectra were set to zero to eliminate the influence of Rayleigh scattering, and the ultrapure water spectral data were blank-subtracted to eliminate the influence of Raman scattering.

[0042] Extraction and analysis of microcystin: ① Extraction and purification of microcystin: Take 40 mL of algae solution before and after the reaction, centrifuge at 6000 r / min for 15 minutes, mix thoroughly with 20.00 mL of extract W (methanol) = 75%: 1.00 g of algae pulp, freeze and thaw repeatedly in liquid nitrogen 3 times, then ultrasonically crush for 1 hour, centrifuge at 6000 r / min for 15 minutes, and take the supernatant; repeat the above operation 3 times, and collect the supernatant. The supernatant is diluted with pure water, and the extracted sample is filtered through a mixed cellulose ester microporous filter membrane and passed through C 18 Solid phase extraction column was used for enrichment and purification. Solid phase extraction conditions: 10.00 mL 100% methanol and 10-15 mL pure water to activate C 18 During the activation of the cartridge, C 18 The column dried up. The extracted sample was passed through the column at a flow rate of 20 mL / min, and the solid-phase extraction column was then eluted with pure water. After enrichment, the sample was sequentially eluted with elution solution (20 mL of elution solution consisted of: 10 mL of pure water, 10 mL of 20% methanol). The microcystins were then eluted with elution solution (0.10 mL of trifluoroacetic acid diluted to 100 mL with 100% methanol), and the eluate was collected. The collected eluate was concentrated to dryness using a rotary evaporator at 40°C, diluted to 2 mL with 75% methanol, and filtered through a 0.45 μm nylon cellulose membrane before high-performance liquid chromatography analysis. The microcystin content was calculated using a prepared standard curve. ② Determination of microcystins: Analysis was performed using high-performance liquid chromatography with ultraviolet detection (HPLC-UV), and the microcystin content was calculated using the external standard method. The chromatographic column was a Kromasil C18 column (4.6 mm × 250 mm, 5 μm), and the column temperature was 40°C. The mobile phase is V 甲醇 :V 水 =70:30, flow rate is 0.60mL / min, UV detection wavelength is 238nm, and injection volume is 20.00uL.

[0043] Example 1

[0044] Take 200.00 mL of sterilized culture medium and add algal cells in the logarithmic growth phase to the culture medium so that the initial algal density is 2.00×10 6 cells / mL, an initial pH of 7.50, a temperature of 25°C, a certain amount of natural minerals, and a light incubator for a certain reaction time. Chlorophyll a removal rate was used as the evaluation standard, with two replicates for each experimental group.

[0045] Take 200.00 mL of sterilized culture medium and add the initial algae density of 2.00×10 6cells / mL, algae cells in the logarithmic growth phase, with an initial pH of 7.50, a temperature of 25°C, and a constant amount of electrolytic manganese slag. The amount of electrolytic manganese slag was varied using the control variable method. The specific parameters and setting conditions were as follows: the mineral concentration gradient of electrolytic manganese slag was 1.00 g / L, 1.50 g / L, and 2.00 g / L; the NaHSO3 concentration was 1.00 mmol / L, the pH was 7.5, and the algae density was 2.00×10 6 cell / mL. All experiments were conducted in a light incubator. Chlorophyll a removal rate was used as the evaluation criterion, and changes in chlorophyll a in algal cells were measured to reflect the effect of electrolytic manganese slag on algal cell biomass. The mechanism of algal cell removal by electrolytic manganese slag was revealed by monitoring changes in dissolved oxygen and nutrients in the culture medium during algae removal, as well as changes in algal cell morphology, algal toxin release, and cell membrane integrity after algae removal. Two replicates were set up for each experimental group.

[0046] The removal rate of chlorophyll a by M. aeruginosa at different electrolytic manganese slag concentrations is shown in Figure 2. Figure 1 When the concentration of NaHSO3 is 1.00mmol / L, pH is 7.5, and the algae density is 2.00×10 6 Under the condition of 1.50 g / L electrolytic manganese slag, the chlorophyll a removal rate first increased with the amount of electrolytic manganese slag and then gradually reached equilibrium. At an electrolytic manganese slag concentration of 1.50 g / L, the chlorophyll a removal rate reached 96.44%. As the electrolytic manganese slag concentration continued to increase, the chlorophyll a removal rate no longer increased and tended to stabilize. The adsorption between electrolytic manganese slag and algal cells depends on contact and adhesion. When the algal density is constant, increasing the amount of electrolytic manganese slag can enhance the interaction between electrolytic manganese slag particles and algal cells, thereby increasing the adsorption effect. As the electrolytic manganese slag dosage continues to increase, the interaction between algal cells and electrolytic manganese slag particles tends to saturate, and the removal effect tends to stabilize.

[0047] Example 2

[0048] The method and steps were the same as those in Example 1, except that the concentrations of NaHSO3 were 0.50 mmol / L, 1.00 mmol / L, and 1.50 mmol / L, respectively; the concentration of electrolytic manganese slag was 1.00 g / L, the pH was 7.5, and the algae density was 2.00 × 10 6 All experiments were carried out in a light incubator. - The effect of the concentration on the removal rate of chlorophyll a is shown in the following table. Figure 2 As shown. When HSO3 - When the concentration of HSO3 increased from 0.50mmol / L to 1.00mmol / L, the removal rate of chlorophyll a increased from 76.10% to 96.90%.- When the dosage is 20%, the removal rate of chlorophyll a decreases. This is because the main components of electrolytic manganese slag contain Fe2O3, MnO, etc., and Mn, Fe, etc. have rich redox chemical properties and inherent catalytic activity, while Fe 3+ Fe 2+ The conversion rate and total conversion amount are also related to the concentration range of NaHSO3 dosage. Different conversion amounts can also improve the activation effect of electrolytic manganese slag. However, when the NaHSO3 dosage is excessive, HSO3 - As a reducing agent, it will affect the activity of the entire system. Therefore, in the removal of Microcystis aeruginosa, an appropriate NaHSO3 concentration should be selected to avoid affecting the chlorophyll a removal rate due to excessive NaHSO3 addition.

[0049] Example 3

[0050] The method and steps are the same as those in Example 1, except that the concentration of electrolytic manganese slag is 1.00 g / L, the concentration of NaHSO3 is 1.00 mmol / L, the pH is 7.5, and the algae density is 2.00×10 6 cell / mL, the pH was adjusted to 7.5, 8.5 and 9.5 respectively, and placed in a light incubator for reaction. Studies have shown that the pH value of algal bloom water will change regularly with the stage of bloom, algal cell density and even temperature and light changes. Therefore, it is necessary to determine the effect of pH on degradation efficiency. This experiment studied the effect of NaHSO3 on the removal of M. aeruginosa by promoting electrolytic manganese slag at an initial pH of 6.5-9.5 (reference surface water environmental quality standards). Figure 3 As shown in the figure, when the dosage of electrolytic manganese slag is 1.00 g / L, the concentration of NaHSO3 is 1.00 mmol / L, and the algae density is 2.00×10 6 cell / mL, the removal rate of chlorophyll a gradually decreased with the increase of pH value. This may be due to the - It is related to the morphology at different pH values. When the pH value is weakly acidic, it is favorable for Fe, Mn ions and HSO3 - When the pH is greater than 9, Fe 3+ Precipitation is likely to occur, reducing removal efficiency. On the other hand, M. aeruginosa does not thrive in acidic conditions, so algae removal rates are higher when the water pH is slightly acidic. During M. aeruginosa blooms, the water pH typically tends to be alkaline, as the density of the algae increases. Therefore, when using this system for bloom control, pH control is crucial for optimal algae removal.

[0051] Changes in algal cell morphology

[0052] The morphological changes of M. aeruginosa were studied in depth by scanning electron microscopy to further understand the mechanism. Figure 4 A and Figure 4 As can be seen in middle b, the initial algal cell shape is close to spherical, with complete structure and good morphology, and there are filaments outside the cell, which may be due to its naturally released metabolites. Figure 4 Middle C and Figure 4 Figures d and middle show the microstructure of M. aeruginosa cells after treatment with electrolytic manganese slag promoted by NaHSO3. The electrolytic manganese slag acts directly on the cell surface, and some of it directly penetrates the cell membrane. The cell surface shows obvious and severe depressions, and even lysis occurs, causing damage to the algae cells and leading to a large amount of release of intracellular substances. This shows that the cells rupture during the reaction, affecting the metabolism of the algae cells.

[0053] Changes in extracellular organic matter in algae

[0054] The effect of NaHSO3 on the three-dimensional fluorescence characteristics of organic pollutants released from algal cells by electrolytic manganese slag Figure 5 As shown in Table 3-2, it can be seen that without adding NaHSO3, the fluorophores of electrolytic manganese slag algae liquid are Figure 5 The a in the middle is concentrated in the T zone of Ex / Em: (270-280 / 320-350); the A zone of Ex / Em: (250-260 / 380-460); and the C zone of Ex / Em: (320-360 / 420-460), representing high excitation wavelength tryptophan-like, ultraviolet humic acid-like and visible humic acid-like, respectively. Figure 5 Zhongb and Figure 5 Middle c is the three-dimensional fluorescence image after adding NaHSO3 to promote electrolytic manganese slag treatment for 30min and 60min. Figure 5 As can be seen in Figure b, after 30 minutes of reaction, the contour lines in regions T, A, and C became somewhat sparse, indicating that during the first 30 minutes of reaction, NaHSO3-assisted electrolytic manganese slag had a certain effect on removing organic matter from the cells. After 60 minutes of the experiment, the contour lines in these three regions became significantly tighter, indicating that the cell membrane was damaged, and organic matter within the cells leaked out, resulting in an increase in organic matter content. This corresponds to the cell surface damage observed previously by SEM electron microscopy, indicating that the NaHSO3-assisted electrolytic manganese slag algae removal process is somewhat destructive to algae cells.

[0055] Apoptosis of algal cells

[0056] In recent years, flow cytometry has been widely used to evaluate the viability and membrane integrity of algal cells during the inactivation of algal cells. With the help of nucleic acid stains, flow cytometry can quickly and sensitively measure the activity of each cyanobacterial cell. Figure 6 A and Figure 6 As shown in b. Figure 6 The a in the middle is M.aeruginosa that grows and reproduces normally. Figure 6 Figure b in the middle shows M. aeruginosa cells after treatment with electrolytic manganese slag promoted by NaHSO3. Normal algae cells have no damaged cell membranes, so PI molecules cannot enter the cells, so they appear negative, meaning that 97.59% of the algae cells are living cells. Figure 6 In middle b, the algae cells in the red area are in a positive state of PI, indicating that the algae cells are damaged, and 16.80% are in a negative state of PI, indicating that 16.80% of the algae cell membranes are damaged.

[0057] TOC changes

[0058] When the cell wall and cell membrane of algae cells are damaged, the organic matter in the algae cells will be released into the external BG-11 culture medium. Therefore, in order to further study the damage of the cell wall and cell membrane of algae cells, the changes in TOC content in BG-11 were measured. Figure 7 As shown in the figure, the algae cells not treated with NaHSO3-promoted electrolytic manganese slag showed normal growth and reproduction, with little change in TOC values ​​over time. However, the TOC values ​​in the algae solution treated with NaHSO3-promoted electrolytic manganese slag increased with reaction time, thereby inhibiting the growth and survival of M. aeruginosa. This is because the free radicals produced during the NaHSO3-promoted electrolytic manganese slag reaction damaged the cell walls and membranes of the algae cells, leading to cytoplasm leakage and increased TOC values ​​in the BG-11 culture medium, thus inhibiting the growth and survival of M. aeruginosa.

[0059] Process Mn 2+ Release

[0060] NaHSO3 promotes the treatment of Mn in electrolytic manganese slag for M. aeruginosa 2+ The release of Figure 4-9 As shown in Figure 2, as the reaction time progresses, the Mn 2+ In the GB-11 culture medium, Mn 2+ There is a downward trend. First, the alkaline environment where M. aeruginosa survives inhibits the production of Mn 2+ The release of Mn is followed by the release of humic acid in the organic matter leaked from damaged algal cells. 2+It has a fixing effect, and different humic acids have different solidification effects. Zou et al. found that the curing efficiency of chitosan-insoluble humic acid composite material for Mn in electrolytic manganese slag reached 55.7%. The reason is that chitosan molecules contain a large number of hydroxyl and amino groups, and after high temperature treatment, it becomes a better adhesive and has a good adsorption effect on heavy metal ions. Therefore, NaSHO3 can not only promote the rapid removal of M. aeruginosa by electrolytic manganese slag, but also achieve the removal of Mn to a certain extent. 2+ The fixing effect.

Claims

1. A method for efficiently removing Microcystis aeruginosa from water, characterized in that: Electrolytic manganese slag and NaHSO3 are added to an algae-containing environment, and algae reduction is carried out under visible light. The concentration of the electrolytic manganese slag is 1.0-2.0 g / L, and the concentration of NaHSO3 is 0.50mmol / L-1.50 mmol / L. The algae-containing environment includes Microcystis aeruginosa.

2. The method for efficiently removing Microcystis aeruginosa in water according to claim 1, wherein: The concentration of algae is 1.00×10 6 cells / mL-1.00×10 7 cells / mL.

3. The method for efficiently removing Microcystis aeruginosa in water according to claim 1, wherein: The pH in the algae-reducing environment is 7.0-9.5.

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