Preparation method, material and application of multifunctional water ecological purification porous matrix material

Abstract

The invention discloses a preparation method, material and application of a multifunctional water ecological purification porous matrix material, engineering waste mud is used for preparing modified dewatered mud cakes, the modified dewatered mud cakes are mixed with a modified porous matrix material to prepare a framework material, then the framework material is mixed with a functional material and quick lime, and pore expansion and granulation are performed to obtain the multifunctional water ecological purification porous matrix material. The three effects of nitrogen and phosphorus pollutant adsorption, slow-release oxygenation and plant growth promotion are integrated into a whole, an aerobic microenvironment can be established through slow-release long-acting oxygenation under the conditions that the dissolved oxygen of a water containing body subjected to pollution impact load is smaller than or equal to 2 mg / L, the total phosphorus content is larger than 0.4 mg / L or the total nitrogen content is larger than 2.0 mg / L and the water depth is 0.5 m-1. 5 m, the denitrification effect of aerobic microorganisms on the water body is improved, and the nitrogen removal effect of the aerobic microorganisms on the water body is improved. Meanwhile, phosphorus pollutants in the water body are adsorbed and fixed, the adaptability and stress resistance of the submerged plants in the early growth stage after replanting are enhanced, and field planting of the submerged plants is promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of ecological matrix modification, and more specifically, to a preparation method, material and application of a multifunctional water ecological purification porous matrix material. Background Art

[0002] The collection of rainwater and sewage by pipe networks around urban water bodies during rainy weather will produce a relatively serious impact load on the water body. The polluted water bodies under the pollution impact load conditions are prone to eutrophication, which will make the local water body anaerobic and cause the disappearance of submerged vegetation in the area. In recent years, the comprehensive management of eutrophic water bodies is divided into water quality control, bottom quality improvement, and water ecological restoration. The main role of submerged vegetation restoration is to provide oxygen to the water body through photosynthesis, build an aerobic microenvironment for the bottom mud and overlying water through plants, accelerate the decomposition and removal of nitrogen pollutants in the water by aerobic microorganisms, and thus achieve the denitrification effect of the water body. However, the oxygenation effect is obviously limited if it is only dependent on submerged plants. The oxygenation efficiency of water bodies is poor when the light intensity is low at night. People gradually put oxygenation measures in the process of bottom improvement, and use chemical oxygenators to achieve oxygenation of bottom mud and overlying water. However, the conventional chemical oxygenators on the market (sodium percarbonate, potassium persulfate, calcium peroxide, magnesium peroxide, etc.) can only oxygenate water bodies for no more than 2 days. The oxygenation effect is good but the maintenance time is short. In the process of bottom improvement and water quality control, multiple additions are often required to ensure the effect. The traditional physical oxygenation method of aeration often has the disadvantages of difficult equipment maintenance and poor short-term oxygenation efficiency.

[0003] At present, in order to achieve the long-term slow-release oxygen-enhancing effect of materials in the process of improving the bottom and regulating water quality, two preparation processes, oxygen loading and embedding, are often used. The oxygen loading process is to load oxygen molecules into the porous matrix under high pressure conditions after cleaning and exhausting the pores of the porous matrix material, such as the slow-release material recorded in patent number CN 108483623 B. Putting it into the water body can achieve the effect of slowly releasing oxygen, but it often brings the disadvantage of high energy consumption cost under high pressure conditions. The encapsulation process is a widely used preparation process, which often uses clay minerals, industrial solid waste, organic materials and other materials for encapsulation and dispersion, and is prepared by high-temperature sintering and low-temperature curing of a curing agent. The prepared material also has a good slow-release oxygen effect. For example, after the application of the technical solutions recorded in patent numbers CN109626554B, CN110283600B, CN110627183A, and CN112674001A, the oxygen release onset time is still limited to within 2-3 days. At the same time, the improvement of the dissolved oxygen content in the water body is limited. The dissolved oxygen in the water body increases and stabilizes at about 5~6 mg / L, and the beneficial effect on the colonization of submerged plants in the water body is relatively short.

[0004] Nowadays, in the process of vigorously developing urban construction and transformation and upgrading, a large amount of engineering waste mud has been generated in the construction of houses, subway tunnels, bridge pile foundations and other projects. In 2022, the national engineering mud output will exceed 300 million cubic meters, and the demand for waste mud treatment continues to rise. In the actual production process, sedimentation tank sedimentation, mud dehydration, solidification treatment, backfill utilization, greening planting soil improvement and other methods are often used to utilize the waste mud as a resource. If the mud cake and mud residue after sedimentation, mud dehydration and solidification treatment are landfilled, a large amount of land resources will be consumed and there will be certain environmental risks. How to utilize it to purify and improve the water ecology and improve the comprehensive management effect and sustainability is still very difficult. Summary of the invention

[0005] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0006] Another object of the present invention is to provide a preparation method, material and application of a multifunctional water ecological purification porous matrix material to solve the technical problem of short duration of the slow-release oxygen effect in water bodies when improving polluted water bodies and restoring submerged vegetation in the prior art.

[0007] In order to achieve these purposes and other advantages according to the present invention, the present invention provides a method for preparing a multifunctional water ecological purification porous matrix material, comprising the following steps: S1. Dewatering the engineering waste mud to obtain a dehydrated cement cake, acid-activating the dehydrated cement cake and washing it to neutrality, then immersing it in a ferric chloride solution and stirring and mixing it evenly, then standing and aging it for 2 hours, and then drying, grinding and sieving it to obtain a powdery modified dehydrated cement cake; S2, selecting a porous matrix material for alkali washing modification, washing to neutrality, drying, grinding and sieving, and obtaining a powdery modified porous mineral matrix material; S3, uniformly mixing the powdery modified dehydrated water cake obtained in step S1 and the powdery modified porous mineral matrix material obtained in step S2 to obtain a skeleton material; S4, mixing powdered calcium peroxide, ordinary Portland cement and ammonium acetate uniformly to obtain a functional material; S5. Evenly mix the skeleton material of step S3, the functional material of step S4 and quicklime to obtain a mixed material, expand the pores of the mixed material and perform granulation, solidify after granulation, screen out impurity particles after solidification, and the remaining particles with a particle size of 5-10 mm are the multifunctional water ecological purification porous matrix material.

[0008] Preferably, in step S2, the porous matrix material comprises medical stone, sepiolite, or attapulgite.

[0009] Preferably, in step S5, during the pore expansion and granulation, a hydrogen peroxide solution with a mass fraction of 30% is used as a binder and is used for foaming and pore expansion.

[0010] Preferably, in step S1, the dehydrated cement cake is obtained by mechanically dehydrating waste mud generated by the bored pile construction process, and the clay content in the dehydrated cement cake is 35%-50%, and the particle size of particles accounting for more than 90% by mass in the dehydrated cement cake is between 1 and 100 μm.

[0011] Preferably, in step S3, the mass ratio of the powdery modified dehydrated cement cake to the powdery modified porous mineral matrix material is 1:0.75-1.

[0012] Preferably, in step S4, the mass ratio of powdered calcium peroxide, ordinary Portland cement and ammonium acetate is 5-8:1:1.

[0013] Preferably, in step S5, the mass ratio of the framework material to the functional material is 1-1.5:0.75-1.

[0014] Preferably, in step S5, the amount of quicklime added in the mixed material is 1-5% by mass.

[0015] The present invention also provides a multifunctional water ecological purification porous matrix material, which is obtained by the preparation method of the multifunctional water ecological purification porous matrix material, and the particles have a spherical structure in appearance, are porous inside, and have a pore size range of 50-200 μm and a porosity range of 50%-65%.

[0016] The present invention also provides an application of a multifunctional water ecological purification porous matrix material, which is applied to the ecological restoration of a polluted water body, wherein the water depth of the polluted water body ranges from 0.5m to 1.5m, the dissolved oxygen of the polluted water body is ≤2mg / L, and the total phosphorus content is greater than 0.4mg / L or the total nitrogen content is greater than 2.0mg / L, and the input amount of the multifunctional water ecological purification porous matrix material is ≥3kg / m 2 .

[0017] The present invention has at least the following beneficial effects: (1) The dehydrated cement cake produced by mechanical dehydration of waste mud generated during the construction process is modified and then used to make skeleton materials. This can effectively reduce the use of traditional clay mineral skeleton materials and achieve the reduction and resource utilization of engineering waste. The materials prepared using modified dehydrated cement cake have better adsorption and fixation of phosphorus than conventional porous matrix materials. After pore expansion and granulation, a room temperature consolidation process can be used, avoiding the high energy consumption and high cost problems brought about by the traditional sintering process. The raw materials are simple and easy to obtain, and the preparation process is simple and environmentally friendly.

[0018] (2) The multifunctional water ecological purification porous matrix material prepared by combining the modified dehydrated water cake and the modified mineral matrix material into a skeleton material and a functional material can effectively achieve the three effects of water body nitrogen and phosphorus adsorption and transformation, slow release oxygenation to improve water body, and plant growth promotion. It makes up for the shortcomings of existing water body improvement materials with single effect and short effective time. It improves the deterioration of water quality under pollution shock load from many aspects, improves the adaptability and stress resistance of submerged plants in the early growth stage after replanting, and promotes the growth of submerged plants in the early stage of establishment.

[0019] (3) The multifunctional water ecological purification porous matrix material prepared by the present invention can not only be used for the restoration of submerged plants in anaerobic water bodies, but also can be applied to aquaculture anaerobic wastewater treatment, floating island plant matrix, ecological buffer zone filler and other fields.

[0020] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart of the preparation method of the multifunctional water ecological purification porous matrix material of the present invention; Figure 2 A curve chart showing the change of dissolved oxygen content over time after the multifunctional water ecological purification porous matrix material of Example 1 of the present invention is added into a simulated anaerobic water body; Figure 3 A curve chart showing the change of nitrogen and phosphorus content in a water body over time after the multifunctional water ecological purification porous matrix material of Example 1 of the present invention is added into a simulated nitrogen and phosphorus polluted water body; Figure 4 It is a curve diagram showing the change of dissolved oxygen content over time when different dosages of the multifunctional water ecological purification porous matrix material of Example 1 of the present invention are put into use; Figure 5 It is a curve chart showing the change of a single leaf of the submerged plant Vallisneria over time when different dosages of the multifunctional water ecological purification porous matrix material of Example 1 of the present invention are used; Figure 6 A curve diagram showing the change of plant length over time in the growth of the submerged plant Vallisneria ovalis when different dosages of the multifunctional water ecological purification porous matrix material of Example 1 of the present invention are applied; Figure 7 A curve chart showing the change of dissolved oxygen content over time after the matrix materials obtained in Comparative Examples 1 to 6 of the present invention are added to a simulated anaerobic water body; Figure 8 A curve chart showing the change of total nitrogen content in water bodies over time after the matrix materials obtained in Comparative Examples 1 to 6 of the present invention are added to simulated nitrogen and phosphorus polluted water bodies; Fig. 9 This is a curve chart showing the change of total phosphorus content in water bodies over time after the matrix materials obtained in Comparative Examples 1 to 6 of the present invention are added into simulated nitrogen and phosphorus polluted water bodies. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0023] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified; in the description of the present invention, the terms "lateral", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0024] The present invention provides a method for preparing a multifunctional water ecological purification porous matrix material, comprising the following steps: S1. Dehydrated cement cake is obtained by dehydrating engineering waste mud. The dehydrated cement cake is acid activated and washed to neutrality. Then, it is immersed in ferric chloride solution and stirred to mix evenly. Then, it is allowed to stand for 2 hours, and then dried, ground and sieved to obtain powdered modified dehydrated cement cake.

[0025] Wall protection mud is generally composed of water and bentonite. The waste mud generated after a series of construction processes mainly contains clay minerals such as bentonite and silty clay, which have the potential to serve as the skeleton of porous matrix materials. Clay minerals such as bentonite and silty clay themselves contain a variety of trace elements such as Ca and Mg, which have a good adsorption and fixation effect on phosphorus in water bodies. At the same time, the released trace Mg elements can be used by the growth of aquatic plants. The utilization of engineering waste mud realizes the reduction and resource utilization of engineering waste. The effect of fixing phosphorus can be enhanced by acid activation + iron ion loading modification of the waste mud, thereby realizing the effective conversion of phosphorus from water bodies to plants.

[0026] S2, select porous matrix materials for alkali washing and modification, wash to neutrality, dry, grind and sieve to obtain powdered modified porous mineral matrix materials. Conventional porous matrix materials not only have good nitrogen and phosphorus adsorption effects, but also contain trace elements that have a certain promoting effect on submerged plants.

[0027] S3, uniformly mixing the powdery modified dehydrated water cake obtained in step S1 and the powdery modified porous mineral matrix material obtained in step S2 to obtain a skeleton material.

[0028] S4. Evenly mix powdered calcium peroxide, ordinary Portland cement and ammonium acetate to obtain a functional material.

[0029] S5. Evenly mix the skeleton material of step S3, the functional material of step S4 and quicklime to obtain a mixed material, expand the pores of the mixed material and perform granulation, solidify after granulation, screen out impurity particles after solidification, and the remaining particles with a particle size of 5-10 mm are the multifunctional water ecological purification porous matrix material.

[0030] Using the dewatered cement cake produced by mechanical dehydration of the waste mud generated during the construction process as raw material can effectively reduce the use of traditional clay mineral skeleton materials, and at the same time achieve the reduction and resource utilization of engineering waste. The dewatered cement cake and the porous matrix material are modified and treated separately and then mixed as the skeleton material and the functional material to prepare the material, which can effectively achieve the three-in-one effect of water body nitrogen and phosphorus adsorption and conversion, slow release oxygenation to improve water body, and plant growth promotion, making up for the shortcomings of the existing water body improvement materials with a single effect and a short effective time. It improves the deterioration of water quality under the impact load of pollution from many aspects, improves the adaptability and stress resistance of submerged plants in the early growth stage after replanting, and promotes the growth of submerged plants in the early stage of colonization. The materials prepared by the room temperature consolidation process avoid the high energy consumption and high cost problems brought by the traditional sintering process. The raw materials are simple and easy to obtain, the preparation process is simple and environmentally friendly, and the multifunctional water ecological purification porous matrix material is not only used for the restoration of submerged plants in anaerobic water bodies, but also can be used for aquaculture anaerobic wastewater treatment, floating island plant matrix, ecological buffer zone filler and other aspects.

[0031] Example 1: Multifunctional water ecological purification porous matrix material prepared from dewatered cement cake from engineering waste sludge The engineering waste mud was taken from a bored pile construction site of a bridge project in Wuhan, Hubei Province. It was dehydrated by a plate-and-frame filter press to obtain a dehydrated cement cake, with a clay content of about 40% and a particle size between 1 and 100 μm accounting for 92.3%. The specific implementation process of using the dehydrated cement cake to prepare a multifunctional water ecological purification porous matrix material includes the following steps: Step 1, prepare 1mol / L sulfuric acid solution and 1mol / L ferric chloride solution, immerse the dehydrated cement cake in the sulfuric acid solution, stir it at 300rpm for 30min using a stirrer blade made of acid and alkali corrosion resistant material, and then let it stand for 3h. After acid activation, filter out the waste liquid with a filter cloth and wash it with pure water until neutral. Immerse the acid-activated mud cake material in the ferric chloride solution, stir it at 300rpm for 30min using a stirrer to mix evenly, and then let it stand for aging for 2h. After aging, filter the waste liquid with a filter cloth and dry it at 80°C. Grind the dried block-shaped modified dehydrated cement cake with a ball mill and pass it through a 100-mesh sieve to obtain a powdered modified dehydrated cement cake; Step 2: After preparing 1 mol / L sodium hydroxide solution, immerse the medical stone in the sodium hydroxide solution for 3 hours, remove it after soaking, wash it with pure water until it is neutral, dry it at 80°C, and grind it with a ball mill through a 100-mesh sieve to obtain a powdered modified porous mineral matrix material; Step 3, mixing the powdery modified dehydrated cement cake and the powdery modified porous matrix material in a mass ratio of 1:0.75 to prepare a skeleton material; Step 4: Mix powdered calcium peroxide, ordinary Portland cement and ammonium acetate in a mass ratio of 6:1:1 to prepare a functional material; Step 5. Mix the skeleton material and the functional material in a mass ratio of 1:1, add quicklime to ensure that the added amount accounts for 5% of the total mass fraction of the mixed material, and place it in a disc granulator after mixing. Use 30% by mass fraction of hydrogen peroxide dissolved oxygen to bond and foam the mixture. After granulation, place it in an oven at 25°C to air dry, sieve out impurities from the dried particles, and the remaining particles with a particle size between 5 and 10 mm are the multifunctional water ecological purification porous matrix materials.

[0032] Comparative Example 1: The difference between this embodiment and embodiment 1 is that pure water is selected as a binder for granulation in step five, and finally a multifunctional water ecological purification porous matrix material with a particle size of 5 to 10 mm is obtained by screening.

[0033] Comparative Example 2: The only difference between this embodiment and embodiment 1 is that the clay content of the dehydrated water cake screened in step 1 is 5%, and the particle size of 90% of the volume is between 1 and 100 μm, and finally a multifunctional water ecological purification porous matrix material with a particle size between 5 and 10 mm is obtained by screening.

[0034] Comparative Example 3: The only difference between this embodiment and embodiment 1 is that the clay content of the dehydrated water cake screened in step 1 is 60%, and 90% of the particles by volume have a particle size between 1 and 100 μm. Finally, a multifunctional water ecological purification porous matrix material with a particle size between 5 and 10 mm is obtained by screening.

[0035] Comparative Example 4: The only difference between this embodiment and Embodiment 1 is that in step three, the mass ratio of the powdery modified dehydrated water cake to the powdery modified porous mineral matrix material is 2:1, and finally a multifunctional water ecological purification porous matrix material with a particle size between 5 and 10 mm is obtained by screening.

[0036] Comparative Example 5: The only difference between this embodiment and Embodiment 1 is that in step three, the mass ratio of the powdery modified dehydrated water cake to the powdery modified porous mineral matrix material is 1:2, and finally a multifunctional water ecological purification porous matrix material with a particle size between 5 and 10 mm is obtained by screening.

[0037] Comparative Example 6: The only difference between this embodiment and embodiment 1 is that in step 4, the components of the functional material include ordinary Portland cement and ammonium acetate, and finally a multifunctional water ecological purification porous matrix material with a particle size of 5 to 10 mm is obtained by screening.

[0038] Embodiment 2: Performance measurement: The multifunctional water ecological purification porous matrix material prepared in Example 1 was observed to be spherical in appearance and porous inside with a pore size of 50-200 μm and a porosity of 50%-65%.

[0039] The oxygen release performance of the multifunctional water ecological purification porous matrix material prepared in Example 1 was measured by the following method: (1) Boil pure water and take 1L of water, place it in a sealed container and cool it to room temperature. Control the dissolved oxygen content in the water to be stable below 2mg / L within half an hour to prepare simulated anaerobic water. (2) 5 g of the multifunctional water ecological purification porous matrix material was placed in a sealed container and then the container was quickly closed. The dissolved oxygen content in the simulated anaerobic water was measured using a dissolved oxygen probe placed in the sealed container at 0, 1 h, 6 h, 12 h, 1 d, 3 d, 7 d, 14 d, 21 d, and 28 d, and a curve was drawn to obtain the following results: Figure 2 The graph shown is a graph of the dissolved oxygen content changing over time after the multifunctional water ecological purification porous matrix material is added to the simulated anaerobic water body.

[0040] The nitrogen and phosphorus adsorption performance of the multifunctional water ecological purification porous matrix material was determined by the following method: (1) Use NH4NO3 and KH2PO4 to prepare a simulated nitrogen and phosphorus polluted water body with a total nitrogen concentration of 4 mg / L and a phosphate concentration of 0.3 mg / L; (2) Take 500 mL of simulated nitrogen and phosphorus polluted water in a conical flask, put 2.5 g of multifunctional water ecological purification porous matrix material into the conical flask, use a syringe to take samples at 0, 5, 10, 15, 30, 45, 60, 120, 240, and 360 minutes respectively to detect the residual nitrogen and phosphorus content in the simulated nitrogen and phosphorus polluted water, calculate the adsorption and removal rate of ceramsite on nitrogen and phosphorus, draw a curve graph, and obtain the following results: Figure 3 The graph shown is a graph of the change of nitrogen and phosphorus content in the water body over time after the multifunctional water ecological purification porous matrix material is added to the simulated nitrogen and phosphorus polluted water body.

[0041] Figure 2 The change in dissolved oxygen content shows the oxygen release effect of the new slow-release oxygen-enhancing porous expanded clay prepared by dewatering the waste mud cake in simulated anaerobic wastewater. It can increase the dissolved oxygen content in the anaerobic water body from less than 2 mg / L to about 8 mg / L within 7 days, and maintain the dissolved oxygen content in the anaerobic water body at about 9 mg / L within 1 month. Figure 3 The prepared multifunctional water ecological purification porous matrix material can realize the adsorption and removal of nitrogen and phosphorus in nitrogen and phosphorus polluted water bodies. Under the conditions of simulated nitrogen and phosphorus wastewater, it can achieve a total nitrogen removal rate of 88.6% and a total phosphorus adsorption removal rate of about 78.6% in 6 hours. It can realize the enrichment of nitrogen and phosphorus pollutants in polluted water bodies and promote the absorption and utilization of nitrogen and phosphorus in water bodies by aquatic plants.

[0042] Embodiment 3: Preparation scheme comparison, using the performance measurement method of Example 2, the oxygen release performance in simulated anaerobic water and the nitrogen and phosphorus adsorption performance in simulated nitrogen and phosphorus polluted water of Comparative Examples 2-7 were also measured, and the results were as follows: Figure 7 , Figure 8 A graph showing changes over time.

[0043] Combination Figure 7 , Figure 8 , Fig. 9The curve chart analysis shows that for Example 1 and Comparative Example 1, by adding hydrogen peroxide solution in step five to react quickly with the supplementary amount of quicklime to generate oxygen bubbles, pore expansion and granulation are performed. On the one hand, the size of the material pores is increased and the porosity of the material is improved. On the other hand, the pores are supplemented with loaded oxygen, which increases the oxygen content and oxygen retention capacity inside the material, which is beneficial to reduce the problem of clogging the internal pores of the material and affecting the oxygen release effect during the process of fixing nitrogen and phosphorus elements, thereby improving the oxygenation effect, oxygenation sustainability, and nitrogen and phosphorus adsorption effect in specific sewage bodies; for Example 1 and Comparative Example 2 and Comparative Example 3, the clay content in Comparative Example 2 is low, the particle size is large, and the material structure bonding is poor. The clay content in Comparative Example 3 is high, the particle size is small, and the material structure bonding is tight. By setting and Screening improves the stability of the skeleton material structure and the stability of the pore structure, which is beneficial to ensure the stability of the material oxygen release process and the effect of adsorbing nitrogen and phosphorus, and also has great improvements in cost saving and green energy saving; for Example 1 and Comparative Example 4, the mass proportion of the powdery modified dehydrated water cake is too large, resulting in a relatively long oxygenation cycle in Comparative Example 4 and a poor oxygenation effect; for Example 1 and Comparative Example 5, the mass proportion of the powdery modified dehydrated water cake is too small, resulting in a weakened fixation effect on nitrogen and phosphorus, and a weakened growth promotion effect on submerged plants; for Example 1 and Comparative Example 6, in step 4, Example 1 adds powdered calcium peroxide to achieve an effective combination of adsorption and slow-release oxygen, and achieve long-term improvement of the anaerobic environment in the early stage of submerged plant planting and growth, making up for the problems of short oxygenation cycle and poor oxygenation effect of existing slow-release oxygen materials.

[0044] Embodiment 4: The application effect is measured. The multifunctional water ecological purification porous matrix material of the present invention is applied to the water body with dissolved oxygen ≤ 2mg / L, total phosphorus content > 0.4mg / L or total nitrogen content > 2.0mg / L after the polluted water body is subjected to the pollution shock load. It can improve the anaerobic state of the water body by increasing the dissolved oxygen content of the water body, adsorbing and fixing the nitrogen and phosphorus in the water body, thereby improving the adaptability and stress resistance of submerged plant replanting and restoration, and promoting the growth of submerged plants. The application of the multifunctional water ecological purification porous matrix material prepared by dewatering the cement cake of engineering waste mud in the process of submerged plant restoration in shallow lakes, the specific application steps are: 1) The water area of ​​Jinyin Lake in Wuhan City, Hubei Province is about 500m 2 After sampling and testing of the water body in a certain enclosure, the water body was about 1m deep, the transparency was 65cm, the dissolved oxygen content was 1.879mg / L, the total nitrogen content was 3.684mg / L, and the total phosphorus content was 0.247mg / L, which were lower than the surface water Class V index specified in the "Surface Water Environmental Quality Standard GB3838-2002". The multifunctional water ecological purification porous matrix material prepared in Example 1 was applied in the restoration area to restore the water body and plants; 2) First, multiple partitions of the same area were set up inside the enclosure through small enclosures, and multifunctional water ecological purification porous matrix materials were sprinkled into the water body in the area. The dosage was set to 1, 2, 3, 4, and 5 kg / m 2 , and set a dosage of 5kg / m 2 A control test was conducted with a common ceramsite control group and a blank control group. On the third day after spreading, submerged plant Vallisneria was planted, and the planting density was controlled at 60 plants / m 2 The curve of the dissolved oxygen content changing with time when different dosages of the multifunctional water ecological purification porous matrix material are applied is as follows: Figure 4 As shown. According to the maintenance and monitoring of the test area, the rotten floating plants were salvaged and cleaned. The growth of the plants on site was observed and counted at the time of planting, the 7th day, the 14th day, the 21st day and the 28th day. The curve of the growth of the submerged plant Vallisneria sinensis with the time of the single leaf is shown in the figure below. Figure 5 As shown in the figure, the curve of plant length change over time in the growth of submerged plant Vallisneria is as follows Figure 6 shown.

[0045] 3) By Figure 4-6 It can be seen that compared with the blank control, the multifunctional water ecological purification porous matrix material can effectively increase the dissolved oxygen content of the water body in the early growth of the submerged plant Vallisneria, while the ordinary ceramsite can promote the leaf growth and new leaf development of the submerged plant Vallisneria by enriching pollutants in the water body, effectively improving the adaptability and stress resistance of submerged plants in eutrophic water bodies under anaerobic conditions. In the parallel control process of different dosages, the dosage of the new slow-release oxygen-enhancing porous ceramsite was greater than 3kg / m 2 The growth of submerged plant Vallisneria salsa is not much different. Considering the cost of practical application, 3kg / m 2 The dosage is more appropriate.

[0046] In summary, the present invention provides a preparation method, material and application of a multifunctional water ecological purification porous matrix material prepared by utilizing cement cake dewatered from engineering waste mud. The multifunctional water ecological purification porous matrix material absorbs nitrogen and phosphorus pollutants, slow-release oxygenation and plant growth promotion through the porous structure after pore expansion, integrating the three effects into one with remarkable results, having a stable structure and reduced preparation cost. It can establish an aerobic microenvironment through slow-release long-acting oxygenation under the conditions of dissolved oxygen ≤2mg / L, total phosphorus content >0.4mg / L or total nitrogen content >2.0mg / L and water depth of 0.5m~1.5m in the polluted water body subjected to pollution shock load, thereby improving the denitrification effect of aerobic microorganisms on the water body, and at the same time adsorbing and fixing phosphorus pollutants in the water body, enhancing the adaptability and stress resistance of submerged plants in the early growth stage after replanting, and promoting the colonization of submerged plants. It has the characteristics of wide application range and high economic value.

[0047] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for preparing a multifunctional water ecological purification porous matrix material, characterized in that: The steps include: S1. Dewatering the engineering waste mud to obtain a dehydrated cement cake, acid-activating the dehydrated cement cake and washing it to neutrality, then immersing it in a ferric chloride solution and stirring and mixing it evenly, then standing and aging it for 2 hours, and then drying, grinding and sieving it to obtain a powdery modified dehydrated cement cake; S2, selecting a porous matrix material for alkali washing modification, washing to neutrality, drying, grinding and sieving, and obtaining a powdery modified porous mineral matrix material; S3, uniformly mixing the powdery modified dehydrated water cake obtained in step S1 and the powdery modified porous mineral matrix material obtained in step S2 to obtain a skeleton material; S4, mixing powdered calcium peroxide, ordinary Portland cement and ammonium acetate uniformly to obtain a functional material; S5. Evenly mix the skeleton material of step S3, the functional material of step S4 and quicklime to obtain a mixed material, expand the pores of the mixed material and perform granulation, solidify after granulation, screen out impurity particles after solidification, and the remaining particles with a particle size of 5-10 mm are the multifunctional water ecological purification porous matrix material.

2. The method for preparing the multifunctional water ecological purification porous matrix material according to claim 1, characterized in that: In step S2, the porous matrix material includes medical stone, sepiolite, and attapulgite.

3. The method for preparing the multifunctional water ecological purification porous matrix material according to claim 1, characterized in that: In step S5, during the pore expansion and granulation, a hydrogen peroxide solution with a mass fraction of 30% is used as a binder and is used for foaming and pore expansion.

4. The method for preparing the multifunctional water ecological purification porous matrix material according to claim 1, characterized in that: In step S1, the dehydrated cement cake is obtained by mechanically dehydrating the waste mud generated by the bored pile construction process, and the clay content in the dehydrated cement cake is 35%-50%, and the particle size of particles accounting for more than 90% by mass in the dehydrated cement cake is between 1 and 100 μm.

5. The method for preparing the multifunctional water ecological purification porous matrix material according to claim 1, characterized in that: In step S3, the mass ratio of the powdery modified dehydrated cement cake to the powdery modified porous mineral matrix material is 1:0.75-1.

6. The method for preparing the multifunctional water ecological purification porous matrix material according to claim 1, characterized in that: In step S4, the mass ratio of powdered calcium peroxide, ordinary Portland cement, and ammonium acetate is 5-8:1:

1.

7. The method for preparing the multifunctional water ecological purification porous matrix material according to claim 1, characterized in that: In step S5, the mass ratio of the framework material to the functional material is 1~1.5:0.75~1.

8. The method for preparing the multifunctional water ecological purification porous matrix material according to claim 7, characterized in that: In step S5, the amount of quicklime added in the mixed material is 1-5% by mass.

9. The method for preparing the multifunctional water ecological purification porous matrix material according to any one of claims 1 to 8 is characterized in that: The particles are spherical in appearance and porous inside, with pore sizes ranging from 50 to 200 μm and porosity ranging from 50% to 65%.

10. The use of the multifunctional water ecological purification porous matrix material according to claim 9, characterized in that: Applied to the ecological restoration of polluted water bodies, where the water depth of the polluted water bodies ranges from 0.5m to 1.5m, the dissolved oxygen of the polluted water bodies is ≤2mg / L, and the total phosphorus content is greater than 0.4mg / L or the total nitrogen content is greater than 2.0mg / L, and the input amount of multifunctional water ecological purification porous matrix materials is ≥3kg / m 2 .

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