Treatment method and treatment system for cadmium-containing wastewater

Abstract

The invention discloses a cadmium-containing wastewater treatment method and system, and the treatment method comprises the following steps: S1, culturing selenastrum capricornutum and microcystis aeruginosa, carrying out cell digestion, centrifuging, and dispersing to obtain mixed algae cells; s2, co-incubating the mixed algae cells and a sodium selenite solution to obtain incubated mixed algae cells; and S3, adding the incubated mixed algae cells into the cadmium-containing wastewater for treatment. Through the combined action of the selenastrum capricornutum and the microcystis aeruginosa, a large amount of cadmium ions in the cadmium-containing wastewater can be absorbed, the purpose of wastewater purification is achieved, and the method has the advantages of being low in energy consumption, high in efficiency, free of secondary pollution, low in treatment cost, green, clean, sustainable in development and the like.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a treatment method and a treatment system for cadmium-containing wastewater. Background Art

[0002] Cadmium telluride thin-film solar cells have the advantages of low cost, high efficiency, strong weak light performance and good temperature stability. They are groundbreaking achievements in the global photovoltaic field. Cadmium-containing wastewater is generated in the production process of thin-film solar cells. Cadmium-containing wastewater mainly consists of activation layer removal wastewater and chemical etching cleaning wastewater. Activation layer removal wastewater comes from the wastewater generated by washing the substrate glass after activation annealing with pure water. The main pollutants are SS, Cd 2+ , Cl - Chemical etching cleaning wastewater comes from the wastewater generated by cleaning the substrate glass with a mixture of phosphoric acid and nitric acid. The main pollutants are total phosphorus, acid, COD, Cd 2+ 、Te 2- , sulfides, etc.

[0003] At present, the traditional treatment methods for cadmium-containing heavy metal wastewater mainly include physical, chemical and biological methods, including precipitation method, ferrite method, membrane separation method, ion exchange method, etc. However, there are shortcomings in the use of the above traditional methods to remove heavy metal ions in water bodies: the chemical precipitation method will produce a large amount of sediment during the treatment process, causing secondary pollution, and the consumption of chemical agents is large; the ferrite method requires a temperature of 70°C or even higher, and the reaction is slow, takes a long time, and consumes high energy; the membrane separation method has high equipment investment costs, complex membrane component design, and the membrane is easily contaminated; the resin in the ion exchange method is easily contaminated or oxidized, regenerated frequently, with high operating costs, and poor adsorption and exchange effects for complexed metal ions. In summary, there are still many problems in the prior art that have not been solved. Summary of the invention

[0004] In order to solve the defects in the prior art, the present invention provides a method and a system for treating cadmium-containing wastewater. Through the combined action of Lunar Algae and Microcystis aeruginosa, a large amount of cadmium ions in the cadmium-containing wastewater can be absorbed, so as to achieve the purpose of purifying the wastewater. The method has the advantages of low energy consumption, high efficiency, no secondary pollution, low treatment cost, green cleaning, sustainable development, etc.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for treating cadmium-containing wastewater, comprising the following steps:

[0007] S1, culturing Lunaea capricornis and Microcystis aeruginosa, digesting the cells, and then dispersing them after centrifugation to obtain mixed algae cells;

[0008] S2, incubating the mixed algae cells with a sodium selenite solution to obtain incubated mixed algae cells;

[0009] S3. adding the incubated mixed algae cells into cadmium-containing wastewater for treatment.

[0010] Preferably, the culturing in S1 is specifically: culturing both Lunaea capricornis and Microcystis aeruginosa in a sterile culture medium, and the culture conditions are: temperature: 25°C, light: 4000lx, light / dark time: 12 / 12h.

[0011] Preferably, the cell digestion in S1 is performed by using trypsin digestion.

[0012] Preferably, the concentration ratio of the algae cells of Lutruncatum capricorni and Microcystis aeruginosa in the mixed algae cells in S1 is 1:(3-7). More preferably, the concentration ratio of the algae cells of Lutruncatum capricorni and Microcystis aeruginosa in the mixed algae cells is 1:5.

[0013] Preferably, the ratio of the number of the mixed algae cells to the amount of the sodium selenite is (3-8)×10 7 : (0.2-0.4) cells / mmol. More preferably, the ratio of the number of the mixed algae cells to the amount of sodium selenite is 6×10 7 :0.3 pieces / mmol.

[0014] Preferably, the ratio of the number of the mixed algae cells to the amount of cadmium ions in the cadmium-containing wastewater is (3-8)×10 7 More preferably, the ratio of the number of the mixed algae cells to the amount of cadmium ions in the cadmium-containing wastewater is 6×10 7 :0.3 pieces / mmol.

[0015] Preferably, the co-incubation time in S2 is 6 hours.

[0016] Preferably, the treatment time described in S3 is 3 to 5 days.

[0017] Preferably, the condition for completing the processing in S3 is that the color of the mixed algae cells after incubation changes from green to white, and blue-green luminescence is observed under ultraviolet light.

[0018] Preferably, the cadmium-containing wastewater is cadmium-containing wastewater generated in the production process of thin-film solar cells.

[0019] In a second aspect, the present invention provides a treatment system for cadmium-containing wastewater, comprising a sedimentation tank, a reaction tank, a buffer tank and a pure water system connected in sequence;

[0020] The sedimentation tank is used to perform preliminary solid impurity removal on the cadmium-containing wastewater;

[0021] The reaction tank is used to react the cadmium-containing wastewater treated by the sedimentation tank with mixed algae cells of Lunaea capricornis and Microcystis aeruginosa and sodium selenite;

[0022] The buffer tank is used to temporarily store the cadmium-containing wastewater treated by the reaction tank;

[0023] The pure water system is used to treat the cadmium-containing wastewater temporarily stored in the buffer tank to meet the reuse requirements.

[0024] Preferably, in the reaction tank, the concentration ratio of the algae cells of Lutruncatum capricorni and Microcystis aeruginosa in the mixed algae cells is 1:(3-7).

[0025] Preferably, in the reaction tank, the ratio of the number of the mixed algae cells to the amount of the sodium selenite is: (3-8)×10 7 :(0.2~0.4)pcs / mmol.

[0026] Preferably, in the reaction tank, the ratio of the number of the mixed algae cells to the amount of cadmium ions in the cadmium-containing wastewater is: (3-8)×10 7 :0.3 pieces / mmol.

[0027] Preferably, in the reaction tank, the mixed algae cells of Lutruncatum capricornis and Microcystis aeruginosa are first incubated with sodium selenite for a period of time and then added into the reaction tank.

[0028] The mechanism of action of the present invention is:

[0029] After adding Na2SeO3 to the mixed algae cells formed by the algae cells of Lunaea fasciata and Microcystis aeruginosa, the body defense system of the mixed microalgae was activated, stimulating and accelerating the production of various reaction enzymes in the algae cells, such as GSH (glutathionease), NADPH (reduced coenzyme II), NADPH-dependent reductase, etc. As the co-incubation time increases, Na2SeO3 is internalized through the osmotic process and reacts with the reducing biomolecules GSH and NADPH to produce selenium precursors in the thylakoid membrane or cytoplasm. Selenium precursors are beneficial to the growth of algae cells. After adding the cadmium-containing wastewater source, the selenium precursor reacts with Cd under the catalysis of relative reductases including TR (thioredoxin reductase) and GSH. 2+ Combined with other proteins, cadmium selenide nanoparticles (CdSe NPs) with protective protein molecules are formed, and finally, CdSe NPs accumulate in the algae cytoplasm to achieve the purpose of cadmium removal.

[0030] The beneficial effects of the present invention are:

[0031] The method for treating cadmium-containing wastewater of the present invention uses mixed algae cells of Algae hornwort and Microcystis aeruginosa to incubate with sodium selenite solution, and then adds them to cadmium-containing wastewater to remove cadmium ions. Algae hornwort and Microcystis aeruginosa have the ability to grow well under extreme environmental conditions (such as heavy metal pollution), and the rich binding sites and large surface area on the surface of the algae cells make them have extremely high adsorption efficiency for cadmium ions. Through the interaction of these two microalgae cells, cadmium ions have excellent removal effects at high and low concentrations. The removal rate of cadmium-containing wastewater treated by the method of the present invention is above 98%, and can reach up to 99.93%, which can be fully reused for production; the treated cadmium-containing wastewater can be recycled, achieving zero discharge of cadmium-containing wastewater; Cd 2+ After treatment, CdSe is generated, which can be recycled and used in photosensitive elements after certain treatment.

[0032] The two microalgae of the present invention can obtain carbon source and energy by photosynthesis, and no additional carbon source or organic matter supply is needed to ensure the growth of the microalgae. The wastewater contains a large amount of N and P elements, which provide good inorganic nutrition for the reproduction of the microalgae, making the microalgae grow fast and have abundant sources. The present invention is clean and environmentally friendly, does not generate waste, and saves energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a diagram of the treatment system for cadmium-containing wastewater according to the present invention. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solution of the invention, the present invention is further described in detail below in conjunction with specific implementation methods.

[0035] Example 1

[0036] The treatment method of cadmium-containing wastewater in this embodiment comprises the following steps:

[0037] (1) The algae Lunar Algae and Microcystis aeruginosa were preserved in 500 mL conical flasks by conventional subculture techniques and cultured in sterile culture medium; culture conditions: temperature: 25°C; light: 4000 lx; ​​light / dark time: 12 / 12 h;

[0038] (2) using trypsin digestion to digest the cells, and then centrifuging to obtain algal cells of Lunaea capricorni and algal cells of Microcystis aeruginosa;

[0039] (3) Disperse the algae cells of the Capricornis hornula in 10 mL of sterile ultrapure water to obtain 1×10 7 The algae cells of Microcystis aeruginosa were dispersed in 10 mL of sterile ultrapure water to obtain 5×107 The concentration of cells / mL is 1:5 (i.e., the algae cell concentration ratio of Lunaea capricornis and Microcystis aeruginosa is 1:5), and then the two are mixed to obtain mixed algae cells;

[0040] (4) adding a sterile Na2SeO3 solution with a concentration of 0.3 mmol / L to the mixed algae cells and incubating them for 6 hours;

[0041] (5) adding the mixed algae cells incubated in (4) into cadmium telluride solar wastewater with a cadmium ion concentration of 3 mg / L, and treating for 3 to 5 days;

[0042] (6) When the color of the mixed algae cells changes from green to white and blue-green luminescence is observed under ultraviolet light, the incubation is stopped, the isolated algae cells are collected, and the Cd 2+ concentration.

[0043] Example 2

[0044] Same as Example 1, except that:

[0045] In step (3), the algae cells of the capricornus crescentus were dispersed in 10 mL of sterile ultrapure water to obtain 1×10 7 The algae cells of Microcystis aeruginosa were dispersed in 10 mL of sterile ultrapure water to obtain 3×10 7 The concentration of cells / mL was 1:3 (i.e., the algal cell concentration ratio of Lunar New World and Microcystis aeruginosa was 1:3).

[0046] Example 3

[0047] Same as Example 1, except that:

[0048] In step (3), the algae cells of the capricornus crescentus were dispersed in 10 mL of sterile ultrapure water to obtain 1×10 7 The algae cells of Microcystis aeruginosa were dispersed in 10 mL of sterile ultrapure water to obtain 7×10 7 The concentration of cells / mL was 1:7 (i.e., the algal cell concentration ratio of Lunar New World and Microcystis aeruginosa was 1:7).

[0049] Example 4

[0050] Same as Example 1, except that:

[0051] In step (4), the concentration of the sterile Na2SeO3 solution is 0.2 mmol / L.

[0052] Example 5

[0053] Same as Example 1, except that:

[0054] In step (4), the concentration of the sterile Na2SeO3 solution is 0.4 mmol / L.

[0055] Example 6

[0056] Same as Example 1, except that:

[0057] In step (3), the concentration of the mixed algae cells of Lunaea capricornis and Microcystis aeruginosa is 3×10 7 cells / mL.

[0058] Example 7

[0059] Same as Example 1, except that:

[0060] In step (3), the concentration of the mixed algae cells of Lunaea capricornis and Microcystis aeruginosa is 7×10 7 cells / mL.

[0061] Example 8

[0062] This embodiment is a treatment system for cadmium-containing wastewater, such as Figure 1 As shown:

[0063] It includes a sedimentation tank 1, a reaction tank 2, a buffer tank 3 and a pure water system 4 which are connected in sequence;

[0064] The sedimentation tank 1 is used to perform preliminary solid impurity removal on the cadmium-containing wastewater;

[0065] The reaction tank 2 is used to react the cadmium-containing wastewater treated by the sedimentation tank with mixed algae cells of Lunaea capricornis and Microcystis aeruginosa and sodium selenite;

[0066] The buffer tank 3 is used to temporarily store the cadmium-containing wastewater after being treated by the reaction tank;

[0067] The pure water system 4 is used to treat the cadmium-containing wastewater temporarily stored in the buffer tank to meet the reuse requirements.

[0068] The specific process is as follows: the cadmium-containing wastewater is collected in sedimentation tank 1 and precipitated for ≥30 minutes. After preliminary solid impurity removal, it is transported to reaction tank 2, and the product of algae cells of Capricornis and Microcystis aeruginosa and incubated with sodium selenite solution for 6 hours is added. When the cadmium ion concentration in reaction tank 2 drops to the target concentration, the treated wastewater is transported from reaction tank 2 to buffer tank 3. When the wastewater reaches the specified liquid level in buffer tank 3, it is transported to pure water system 4. After being treated by pure water system 4, it can be sent to the water supply end for recycling.

[0069] Comparative Example 1

[0070] The treatment method of the cadmium-containing wastewater in this comparative example comprises the following steps:

[0071] (1) The algae Lunar Algae and Microcystis aeruginosa were preserved in 500 mL conical flasks by conventional subculture techniques and cultured in sterile culture medium; culture conditions: temperature: 25°C; light: 4000 lx; ​​light / dark time: 12 / 12 h;

[0072] (2) using trypsin digestion to digest cells, and then centrifuging to obtain algal cells of Lunaea capricorni and algal cells of Microcystis aeruginosa;

[0073] (3) Disperse the algae cells of the Capricornis hornula in 10 mL of sterile ultrapure water to obtain 1×10 7 The algae cells of Microcystis aeruginosa were dispersed in 10 mL of sterile ultrapure water to obtain 5×10 7 The concentration of cells / mL is 1:5 (i.e., the algae cell concentration ratio of Lunaea capricornis and Microcystis aeruginosa is 1:5), and then the two are mixed to obtain mixed algae cells;

[0074] (4) The mixed algae cells were mixed with a sterile Na2SeO3 solution with a concentration of 0.3 mmol / L and then directly added into cadmium telluride solar wastewater with a cadmium ion concentration of 3 mg / L for 3 to 5 days; the algae cells were collected and separated, and the Cd 2+ concentration.

[0075] Comparative Example 2

[0076] The treatment method of the cadmium-containing wastewater in this comparative example comprises the following steps:

[0077] (1) Microcystis aeruginosa was preserved in a 500 mL conical flask by conventional subculturing techniques and cultured in a sterile culture medium; culture conditions: temperature: 25°C; light: 4000 lx; ​​light / dark time: 12 / 12 h;

[0078] (2) digesting the cells by pancreatic enzyme digestion, and then centrifuging to obtain algal cells of Microcystis aeruginosa;

[0079] (3) The algae cells of Microcystis aeruginosa were dispersed in 10 mL of sterile ultrapure water to obtain 6×10 7 The concentration of cells / mL;

[0080] (4) adding a sterile Na2SeO3 solution with a concentration of 0.3 mmol / L to the algae cells of Microcystis aeruginosa and incubating for 6 hours;

[0081] (5) Add the algae cells incubated in (4) to cadmium telluride solar wastewater with a cadmium ion concentration of 3 mg / L and treat for 3 to 5 days; collect and separate the algae cells, and measure the Cd 2+ concentration.

[0082] Effect Example 1

[0083] The cadmium ion concentrations after treatment in the embodiments and comparative examples were measured, and the results are shown in Table 1.

[0084] Determination method: Regularly sample the cadmium-containing wastewater in the sedimentation tank and pure water system, and use flame atomic absorption spectrophotometry to determine Cd 2+ concentration.

[0085] Table 1

[0086]

[0087] Conclusion: It can be seen from Table 1 that the cadmium-containing wastewater treated by the method of the present invention has an excellent cadmium removal rate, which is above 98% and can reach up to 99.93%.

[0088] Through the investigation of the algae cell concentration of Capricornus ceratoniae and Microcystis aeruginosa in the mixed algae cells in Examples 1 to 3, it can be seen that the different ratios of the two microalgae will have a certain impact on the removal of cadmium ions, indicating that only when the two have a suitable ratio, after adding Na2SeO3, can the production of various reaction enzymes be stimulated to the maximum extent, otherwise it will cause one of the microalgae cells to grow too fast, affecting the production of reaction enzymes, and then affecting the production of selenium precursors, causing obstacles to cadmium removal. It can be seen from the test results of Examples 1 to 3 that the algae cell concentration ratio of Capricornus ceratoniae and Microcystis aeruginosa is 1:5, which is the optimal ratio of the two algae, and the cadmium ion concentration after treatment is the lowest.

[0089] By comparing the test results of Example 1 with those of Examples 4-5, it can be seen that Na2SeO3, as an important substance for activating the reaction enzymes in the mixed algae cells, plays an important role in the production of selenium precursors. If too little Na2SeO3 is added, the production of selenium precursors will be reduced, and even directly lead to insufficient selenium precursors; in addition, it is not conducive to the production of various reaction enzymes such as GSH and NADPH in the algae cells, resulting in the generation of Cd 2+ The synthesis yield is low, which greatly reduces the cadmium removal effect. If too much Na2SeO3 is added, it may cause certain cytotoxicity, thereby reducing the intracellular enzyme activity and cell viability, affecting the reaction of the enzyme and Na2SeO3, and then affecting the production of selenium precursors, which will also lead to Cd 2+ The synthesis yield is low, which affects the cadmium removal effect. It can be seen from the test results of Example 1 and Examples 4-5 that the concentration of Na2SeO3 solution is most suitable at 0.3mmol / L.

[0090] By comparing the test results of Example 1 with those of Examples 6 to 7, it can be seen that when the ratio of the two algae cells is constant, the total amount of mixed microalgae added also has a certain influence on the cadmium removal effect, because too much microalgae is added, which is easy to cause the crazy growth of microalgae cells, which is not conducive to the production of its reaction enzyme and affects the combination with Na2SeO3. In addition, more microalgae require more Na2SeO3 raw materials, which is easy to cause waste of resources and increase the difficulty of separating and harvesting microalgae cells; but if too little microalgae is added, it is impossible to complete the removal of high concentration Cd. 2+ removal.

[0091] Comparative Example 1 is a technical solution in which the algae cells are mixed with a sterile Na2SeO3 solution and then directly added to the cadmium-containing wastewater, without the prior incubation process of the algae cells and Na2SeO3. By comparing Example 1 of the present invention with Comparative Example 1, it can be seen that the incubation process of the algae cells and Na2SeO3 is extremely important, because the algae cells need the stimulation of Na2SeO3 to produce a reaction enzyme. During the incubation process, Na2SeO3 is internalized through an osmotic process and reacts with the reaction enzyme to produce a selenium precursor. Under the catalysis of the reaction enzyme, the selenium precursor continues to react with Cd 2+ Combined with the protective protein molecules, cadmium selenide nanoparticles are formed; without this incubation process, the production of the reaction enzyme and the reaction process will be directly affected, and the desired cadmium removal effect will not be achieved.

[0092] Comparative Example 2 is a technology for removing cadmium ions using only Microcystis aeruginosa. Compared with Example 1, it can be seen that the present invention utilizes the synergistic effect of two microalgae cells, Microcystis aeruginosa and Lunar Algae, to achieve better technical effects. This is because, in the early stage of incubation, Microcystis aeruginosa plays a major role and can react with a higher concentration of Na2SeO3 to generate a selenium precursor, which can then react with a higher concentration of Cd 2+ The CdSe NPs were synthesized by the reaction. As the incubation process progressed, the Cd 2+ The concentration will decrease, the concentration of Na2SeO3 will also decrease, and the reaction of Microcystis aeruginosa will slow down. At this time, the main role of Algae Lunar Algae is to make up for the lack of reaction of Microcystis aeruginosa, which can be used for low concentrations of Cd 2+ and Na2SeO3 to synthesize CdSe NPs. Therefore, the two microalgae cells interact with each other and promote the 2+ removal.

[0093] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for treating cadmium-containing wastewater, characterized in that: The following steps are involved: S1, culturing Lunaea capricornis and Microcystis aeruginosa, digesting the cells, and then dispersing them after centrifugation to obtain mixed algae cells; S2, incubating the mixed algae cells with a sodium selenite solution to obtain incubated mixed algae cells; S3. adding the incubated mixed algae cells into cadmium-containing wastewater for treatment.

2. The processing method according to claim 1, characterized in that: The concentration ratio of the algae cells of Lutruncatum capricorni and Microcystis aeruginosa in the mixed algae cells described in S1 is 1:(3-7).

3. The processing method according to claim 2, characterized in that: The ratio of the number of the mixed algae cells to the amount of the sodium selenite is (3-8)×10 7 :(0.2~0.4)pcs / mmol.

4. The processing method according to claim 3, characterized in that: The ratio of the number of the mixed algae cells to the amount of cadmium ions in the cadmium-containing wastewater is (3-8)×10 7 :0.3 pieces / mmol.

5. The processing method according to claim 4, characterized in that: The co-incubation time described in S2 is 6 h.

6. The processing method according to claim 5, characterized in that: The treatment time described in S3 is 3 to 5 days.

7. The processing method according to claim 1, characterized in that: The condition for completing the processing in S3 is that the color of the mixed algae cells after incubation changes from green to white, and blue-green luminescence is observed under ultraviolet light.

8. The processing method according to claim 1, characterized in that: The cadmium-containing wastewater is cadmium-containing wastewater generated during the production process of thin-film solar cells.

9. A system for treating cadmium-containing wastewater, characterized in that: It includes a sedimentation tank, a reaction tank, a buffer tank and a pure water system connected in sequence; The sedimentation tank is used to perform preliminary solid impurity removal on the cadmium-containing wastewater; The reaction tank is used to react the cadmium-containing wastewater treated by the sedimentation tank with mixed algae cells of Lunaea capricornis and Microcystis aeruginosa and sodium selenite; The buffer tank is used to temporarily store the cadmium-containing wastewater treated by the reaction tank; The pure water system is used to treat the cadmium-containing wastewater temporarily stored in the buffer tank to meet the reuse requirements.

10. The processing system according to claim 9, characterized in that In the reaction tank, the mixed algae cells of Lunaea capricornis and Microcystis aeruginosa are first incubated with sodium selenite for a period of time and then added into the reaction tank.

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