Application of multifunctional slow-release microspheres cooperatively constructed based on double peroxides in water treatment

Abstract

The invention relates to a preparation method of a sustained-release microsphere, which is constructed based on the synergistic combination of calcium peroxide (CaO2) and magnesium peroxide (MgO2), is used for consolidating the river regulation effect, and belongs to the technical field of environmental functional materials. Core components of the microspheres comprise CaO2 powder and MgO2 powder which are mixed according to the mass ratio of (4: 1)-(1: 1). The preparation method comprises the following steps: adding CaO2 and MgO2 composite powder into a disc granulator in batches by adopting a low-temperature dry-method rotary granulation process, regulating the rotating speed (20-40 rpm) and the temperature (25-50 DEG C) in stages, synchronously spraying a small amount of deionized water or other solutions as an adhesive, and controlling the humidity to be less than or equal to 5% to prepare spherical particles with the particle size of 1.5-5 mm. According to the invention, the performance of a common CaO2 repairing agent is further optimized on the basis of the common CaO2 repairing agent. The method has the advantages of easily available raw materials, simple process, convenience in operation and low energy consumption, is suitable for the fields of water body remediation and bottom mud passivation, and has industrial popularization value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental remediation materials, in particular to application of multifunctional slow-release microspheres based on double peroxide synergistic construction in water treatment. Specifically, it relates to a synergistic material applied to river and lake water body and sediment endogenous pollution control, which inhibits sediment pollution release through synergistic effect of adsorption and chemical passivation, is suitable for river and lake water body with low transparency, still having risk of river and lake blackening and malodorous after engineering treatment, and secondary eutrophication, and helps to realize stable and long-term maintenance of treatment effect. BACKGROUND

[0002] Release of endogenous pollutants in sediment is widely considered as one of the important driving factors for long-term recurrence of water body eutrophication and black-odor phenomenon. Although exogenous pollution input has been controlled to some extent in most water bodies, long-term accumulated pollutants (such as sulfides, organic matter, nitrogen and phosphorus) in sediment may still be released into overlying water through desorption, reduction and dissolution or biological mineralization when the environmental conditions of water body change (such as pH fluctuation, dissolved oxygen concentration decrease, and microbial activity enhancement), inducing phenomena such as secondary eutrophication, blackening and malodorous. Relevant investigation and environmental assessment results show that most urban river channels in China currently have different degrees of sediment endogenous pollution problems. The main performances include: ① Sulfides accumulate under anaerobic conditions, and when the dissolved oxygen in water body increases, FeS, MnS and other sulfides in sediment are easily oxidized, causing water body blackening; ② The deposited organic matter is decomposed under anaerobic conditions, releasing hydrogen sulfide, methyl mercaptan and other gases, causing significant malodorous; ③ Nutrients such as nitrogen and phosphorus have high concentration in interstitial water, which are easily released into water body under disturbance or reducing environment, becoming a potential risk source for water bloom recurrence. In recent years, practices in many places show that even if the black-odor water body is treated, if the endogenous sediment is not effectively controlled, the water body may appear blackening and malodorous in a short period of time, seriously affecting the sustainability of treatment effect. Therefore, it is of great significance to develop sustainable and efficient endogenous pollution control materials for improving the systematization and long-term nature of water environment treatment.

[0003] Traditional water body treatment technologies such as sediment dredging, aeration, chemical agent addition and covering isolation have certain limitations. For example, dredging can directly remove contaminated sediment, but the construction cost is high, the period is long, and the structure and function of the benthic ecosystem may be damaged. Chemical passivation agents (such as aluminum salts, iron salts, and lanthanum modified clay) can achieve suspended particle settling and short-term phosphorus fixation, but the residual metal ions may cause ecological toxicity risks, cause sediment hardening, and microbial activity decreases, etc. At the same time, organic pollutants (such as COD) often migrate from water to sediment, and the overall load does not decrease. Strong oxidizing agents such as hydrogen peroxide can quickly oxidize and decompose organic pollutants, but their strong oxidizing nature can also destroy the indigenous microbial community structure, and have no obvious removal effect on nitrogen and phosphorus pollutants. In addition, the addition or planting of microbial agents and aquatic plants has certain ecological restoration function, but it is easily limited by water temperature, dissolved oxygen, nutrient salt and other environmental factors, and has high maintenance cost and poor stability.

[0004] In summary, the existing treatment technologies generally have the problems of single function, difficulty in synergistically controlling black and odorous combined pollution, and high ecological risk. Therefore, developing an environmental functional material with multiple functions such as long-term phosphorus passivation, organic pollution degradation and black and odorous relief, and ecological safety has become a key direction that needs to be broken through in the field of water sediment remediation. In recent years, the oxygen release-passivation combined remediation strategy based on peroxide has attracted widespread attention. CaO2 can slowly release reactive oxygen species (ROS) and hydroxyl radicals (·OH) in the water environment, achieving multiple effects such as water aeration, organic pollutant oxidation and degradation, and phosphorus passivation. However, calcium hydroxide is generated during the hydrolysis process, which can easily cause the rapid increase of local pH in water and sediment, disturb the microbial community structure, and affect the stability of the sediment micro-ecosystem. At the same time, the release rate of active oxygen of CaO2 is fast, which rapidly decays in 1-7 days, making it difficult to meet the sustainability needs of long-term treatment. Compared with CaO2, MgO2, as a homologous compound, has similar oxidation remediation performance, but its oxygen release process is more moderate and persistent, the pH fluctuation is less, and it has better performance in organic phosphorus fixation and ecological adaptability. SUMMARY

[0005] To solve the technical problems of single function, short action time, and great ecological disturbance in the process of treating endogenous pollution in sediment in the prior art, the application provides application of multifunctional slow-release microspheres based on double peroxide collaborative construction in water treatment. The method uses CaO2 and MgO2 as main functional components, and uses a low-temperature dry method rotary granulation process to prepare composite microspheres. The microspheres have the functions of slow-release oxygen and collaborative phosphorus removal, can effectively prolong the action period of peroxide in water, and overcome the defects of the traditional CaO2 powder treatment, such as too fast reaction rate, severe pH fluctuation, and obvious ecological disturbance. The technical core of the application includes two aspects: one is the collaborative combination of CaO2 and MgO2, and the other is the molding and slow-release structure construction of the microspheres, so as to ensure the sustainable release of active oxygen substances and improve the treatment persistence. The prepared functional microspheres can realize the stable control of phosphorus in sediment and the effective degradation of organic matter (COD) in water through the triple action mechanism of "multi-stage oxygen release-collaborative passivation-ecological adaptation", and can significantly relieve the blackening and odor.

[0006] The application aims to provide application of multifunctional slow-release microspheres based on double peroxide collaborative construction in water treatment, which includes long-acting phosphorus passivation, organic pollutant degradation, and black and odorous relief.

[0007] In some embodiments of the application, the multifunctional slow-release microspheres are prepared by the following method: CaO2 and MgO2 are uniformly mixed, added into a granulator in batches, and granulated by using a low-temperature dry method rotary granulation process, a binder is sprayed in the process of granulation, and the multifunctional slow-release microspheres are obtained by sieving.

[0008] In some embodiments of the application, the mass ratio of CaO2 to MgO2 is (4:1) to (1:1).

[0009] In some embodiments of the application, the purity of CaO2 is 75%, and the particle size is 50-100 μm; the purity of MgO2 is 25%, and the particle size is 30-80 μm.

[0010] In some embodiments of the application, the low-temperature dry method rotary granulation process is performed in stages: 20-25 rpm in the initial nucleation stage, and 30-40 rpm in the later round rolling stage; the temperature is controlled at 25-50℃, the granulation time is 25-45 min, and the humidity is ≤5%.

[0011] Further, the low-temperature dry method rotary granulation process uses a disc granulator with a polytetrafluoroethylene anti-sticking layer on the inner wall.

[0012] In some embodiments of the present application, the adhesive comprises one or more of water, ethanol, a starch solution, a hydroxypropyl methylcellulose solution, a polyvinylpyrrolidone solution, and a sodium alginate solution.

[0013] In some embodiments of the present application, the adhesive is used in an amount of 2-5% of the total material mass.

[0014] In some embodiments of the present application, the multifunctional slow-release microspheres have a particle size of 1.5-5 mm.

[0015] In some embodiments of the present application, the multifunctional slow-release microspheres are used in an amount of 0.1-0.3 kg / m 2 .

[0016] In the present application, CaO2 and MgO2 are synergistically combined to achieve the following technical advantages: ① in terms of chemical behavior, a pH buffer system is formed to improve the multi-mechanism phosphorus fixation efficiency; ② in terms of release kinetics, the combination of rapid release and sustained release mechanisms enhances the material repair durability; and ③ in terms of ecological compatibility, the ecological disturbance caused by pH mutation is reduced, and the system stability is improved. This strategy can effectively compensate for the short-term effectiveness, environmental sensitivity, and ecological risk problems of single CaO2, and provides technical support for long-term, safe, and stable control of endogenous pollutants in black and odorous water body sediments.

[0017] The above technical solution of the present application has the following advantages compared with the prior art: Synergistic effect and slow-release control: the composite microspheres are prepared by compounding CaO2 and MgO2 and using a low-temperature dry method rotary granulation process. The defects of CaO2 powder, such as fast action and significant pH impact, are solved. The microspheres can realize multiple effects such as sediment endogenous phosphorus treatment and COD removal, and alleviate black and odorous by using a three-level mechanism of multi-stage oxygen release-synergistic passivation-ecological adaptation, providing an innovative scheme with engineering feasibility and environmental friendliness for the treatment of eutrophic black and odorous water bodies. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to specific embodiments of the present application and in conjunction with the accompanying drawings, in which, Figure 1 is the morphology of the microspheres obtained by synergistically compounding CaO2 and MgO2 in a mass ratio of 2.33:1 in the present application.

[0019] Figure 2 is the concentration change of overlying water DO (a), SO4 2- (b), COD (c), and NTU (d) in the 30d passivation experiment of the present application.

[0020] Figure 3are the changes of total phosphorus (a) and soluble active phosphorus (b) levels in overlying water in the 30d passivation experiment of the application. DETAILED DESCRIPTION

[0021] The application will be further described below in conjunction with the drawings and specific examples, so that those skilled in the art can better understand the application and implement it, but the examples are not limiting to the application.

[0022] Example 1: Preparation of CaO2 and MgO2 compounded microspheres: Take 50g of commercially available CaO2 (purity ~75%) and MgO2 (purity ~25%) and mix them evenly in a mass ratio of 2.33:1, then pour them into a disc granulator in batches, control the speed of the granulator at 20-40 rpm throughout the process, and control the temperature at 30-50℃. Spray 5-20 mL of deionized water during the granulation process, and granulate for 20-40 min to obtain CaO2 and MgO2 compounded microspheres with a particle size of 1.5-5 mm. Figure 1 ).

[0023] Example 2: Performance of CaO2 and MgO2 compounded microspheres: A laboratory simulation device was built, and different proportions of microspheres were put into the reactor for a 30d passivation experiment. The experiment was carried out in a cylindrical reactor with a diameter of 8 cm, a height of 30 cm, and an effective volume of 1.5 L. First, pretreated fresh sediment was added to each reactor to the 10 cm mark, and then 750 mL of on-site collected overlying water was added to each reactor to the 25 cm mark using the siphon method. The reactor without adding peroxide was considered as the control group, and the experimental groups were the addition of CaO2 and MgO2 powders alone, and the compounded microspheres of CaO2 and MgO2 with a mass ratio of 2.33:1. (The uniform addition amount of peroxide was 0.18 kg / m 2 ).

[0024] Figure 2 (a) is the diachronic change of DO concentration in overlying water within 30d of each experimental group, as shown in the figure, the DO concentration of overlying water in the control group remains at a low level throughout the experimental period, indicating that the water-sediment ecosystem in the experimental device of the control group is in an anoxic state. The experimental groups significantly improved the anoxic phenomenon of the overlying water, and the DO concentration of the overlying water was significantly improved compared with the control group. The SO4 2- level in the overlying water was measured synchronously, and the change trend of SO4 2- was basically consistent with that of DO. It is confirmed that the addition of peroxide improves the oxidation degree of the overlying water, and S 2- is oxidized to form SO4 2-The COD and NTU of the overlying water in each experimental group were significantly lower than those in the control group. The changes of the NTU and COD concentrations of the overlying water in each experimental group were as follows Figure 2 (c-d). It can be seen from the figure that compared with the long-term higher NTU level of the control group, the test groups all showed good NTU reduction effect. The average removal rates of CaO2, MgO2 and CaO2:MgO2=2.33:1 groups on NTU were 44.43%, 51.64% and 56.11% respectively. The average removal rates on COD were 39.11%, 36.80% and 43.86% respectively.

[0025] Figure 3 (a) and 3(b) are the changes of the TP and SRP concentrations of the overlying water in each group within 30 days. It can be seen that compared with the control group, the addition of peroxide in the test group significantly reduced the TP and SRP levels in the overlying water, and the effect of CaO2:MgO2=2.33:1 microspheres was better than that of the MgO2 single addition test group, and was equivalent to that of the CaO2 single addition group.

[0026] Obviously, the above examples are only examples for clarity, and are not limited to the embodiments. Based on the above description, other different forms of changes or variations can also be made by those skilled in the art. Here, it is not necessary and impossible to enumerate all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. Application of multifunctional sustained-release microspheres based on double peroxide synergistic construction in water body treatment, characterized in that, The water body treatment includes long-acting phosphorus passivation, organic pollutant degradation and black and odorous relief.

2. Use according to claim 1, characterized in that, The multifunctional slow-release microspheres are prepared by the following method: CaO2 and MgO2 are uniformly mixed, added into a granulator in batches, and granulated by using a low-temperature dry method rotary granulation process; a binder is sprayed during the granulation process; and the multifunctional slow-release microspheres are obtained by sieving.

3. Use according to claim 2, characterized in that, The mass ratio of CaO2 to MgO2 is (4:1) to (1:1).

4. Use according to claim 2, characterized in that, The low-temperature dry method rotary granulation process is performed in stages: 20-25 rpm in the initial nucleation stage and 30-40 rpm in the later rolling stage; the temperature is controlled at 25-50 DEG C; the granulation time is 25-45 min; and the humidity is less than or equal to 5%.

5. Use according to claim 2, characterized in that, The binder includes one or more of water, ethanol, a starch solution, a hydroxypropyl methylcellulose solution, a polyvinylpyrrolidone solution and a sodium alginate solution.

6. Use according to claim 2, characterized in that, The amount of the binder is 2-5% of the total material mass.

7. Use according to claim 2, characterized in that, The particle size of the multifunctional slow-release microspheres is 1.5-5 mm.

8. The use according to claim 1, characterized in that, The amount of multifunctional sustained-release microspheres is 0.1-0.3 kg / m 2 .

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