Preparation method and application of nano zero-valent iron loaded recycled aggregate composite material for artificial wetland substrate

Abstract

The invention discloses a preparation method and application of a nano zero-valent iron loaded recycled aggregate composite material for an artificial wetland substrate, and relates to the technical field of water pollution treatment. NZVI is loaded on recycled aggregate, so that agglomeration and oxidation of the nZVI can be effectively prevented by virtue of a porous structure of the recycled aggregate, and the dispersity and stability of the nZVI are improved; further, the denitrification capability of the constructed wetland is enhanced. The method is used for constructed wetland sewage treatment. By using the recycled aggregate, the constructed wetland using the nano zero-valent iron loaded recycled aggregate composite material as a matrix has better denitrification capacity. Resource utilization of the building waste can be effectively achieved, natural resources and energy are saved, and the method has high economic prospects and environmental benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of water pollution treatment, and in particular to a preparation method and application of a nanometer zero-valent iron loaded recycled aggregate composite material for an artificial wetland matrix. Background Art

[0002] Constructed wetlands are an ecological engineering technology that uses the synergistic effects of plants, substrates and microorganisms to remove pollutants from water bodies. Due to their low cost and easy operation, constructed wetlands are widely used to treat agricultural runoff, domestic sewage, etc. In the process of sewage treatment by constructed wetlands, the adsorption effect of substrate materials is indispensable. Traditional substrate materials such as gravel and sand can provide mechanical support and adsorption functions to a certain extent. Because traditional substrate materials have a small number of pores on the surface, a small specific surface area, a single adsorption mode, and limited microbial attachment sites, their adsorption capacity for pollutants in water has an upper limit.

[0003] Compared with traditional artificial wetland matrix materials, recycled aggregate is an environmentally friendly material produced from construction waste. As an artificial wetland matrix, recycled aggregate can not only effectively utilize construction waste and reduce environmental burden, but also save natural resources and realize resource recycling. Recycled aggregate has the characteristics of a large number of surface pores, a large specific surface area and diverse adsorption modes. On the one hand, it increases the contact area between the matrix surface and pollutants in the water and improves the adsorption efficiency; on the other hand, recycled aggregate can provide more attachment sites for matrix microorganisms, thereby improving the denitrification capacity of artificial wetlands. In addition, the pore distribution on the surface of recycled aggregate is complex, and it has good modified loading potential.

[0004] In the relevant research on enhancing the denitrification potential of constructed wetlands, the loading modification of matrix materials has always been a hot topic. Matrix material-loaded nanomaterial particles have gradually attracted widespread attention from technicians due to their advantages such as high surface area, strong controllability and versatility. Among them, nano zero-valent iron (nZVI) particles have shown great potential in the field of sewage treatment due to their small particle size, high reactivity and environmental friendliness. However, nZVI is not stable enough and can easily agglomerate rapidly in water to form micro, millimeter-sized or even larger aggregates. In addition, it is precisely because of the high activity of nZVI particles that it is very easy to oxidize and be difficult to recycle during preparation, storage and application. Therefore, the practical application of nZVI in the treatment of sewage in constructed wetlands is greatly limited. Summary of the invention

[0005] In order to solve these problems, the present invention proposes a preparation method and application of a nano zero-valent iron-loaded recycled aggregate composite material for artificial wetland matrix. Loading nZVI on recycled aggregate can effectively prevent the agglomeration and oxidation of nZVI by virtue of the porous structure of recycled aggregate, improve the dispersibility and stability of nZVI, and thus enhance the denitrification capacity of artificial wetlands.

[0006] The method for preparing a nanometer zero-valent iron-loaded recycled aggregate composite material for an artificial wetland matrix of the present invention is carried out according to the following contents:

[0007] (1) ultrasonically clean the recycled aggregate and then dry it;

[0008] (2) After mixing the recycled aggregate in step (1) with ethanol, add ferrous sulfate solution, pump in sodium borohydride solution under anaerobic environment, and stir evenly;

[0009] (3) In an anaerobic environment, the sodium borohydride solution is evacuated, and the surface of the recycled aggregate treated in step (2) is cleaned with deionized water exposed to nitrogen, and then purged with nitrogen until dry.

[0010] Furthermore, the mass volume ratio of the recycled aggregate to ethanol is 1g:0.05-0.1mL.

[0011] Furthermore, the volume concentration of the ethanol is 30%.

[0012] Furthermore, the mass volume ratio of the recycled aggregate to the ferrous sulfate solution is 1g:0.5-1mL.

[0013] Furthermore, the mass concentration of the ferrous sulfate solution is 60-80%.

[0014] Furthermore, the concentration of the sodium borohydride solution is 0.5-2 mol / L, and the sodium borohydride solution is added in excess.

[0015] Furthermore, the pumping speed of the sodium borohydride into the conical flask is 30 to 60 mL / min.

[0016] The invention discloses an application of a nanometer zero-valent iron loaded regenerated aggregate composite material for an artificial wetland matrix. The nanometer zero-valent iron loaded regenerated aggregate composite material is used in the process of treating sewage in an artificial wetland.

[0017] Furthermore, the artificial wetland is used in the process of treating sewage, specifically: nano zero-valent iron loaded recycled aggregate composite material is filled in the artificial wetland as a matrix, and aquatic plants are planted on the matrix.

[0018] Furthermore, the artificial wetland sewage treatment is artificial wetland denitrification treatment, and the denitrification is the removal of ammonia nitrogen and nitrate nitrogen.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The present invention uses recycled aggregate to prepare nZVI composite materials. Compared with existing nZVI composite materials, the present invention uses recycled aggregate as the main raw material to effectively realize the resource utilization of construction waste, save natural resources and energy, and has higher economic prospects and environmental benefits.

[0021] (2) The nano zero-valent iron loaded recycled aggregate composite material prepared by the present invention has rich functional groups, high pore volume, large pore size and complex surface morphology. This complex surface morphology not only increases the contact area between the matrix surface and nitrogen-containing pollutants and provides more adsorption sites, but also creates larger gaps between irregularly shaped particles during the filling process. These gaps can promote the retention of small oxygen bubbles in the water, thereby increasing the dissolved oxygen concentration in the artificial wetland. Compared with traditional artificial wetland matrix materials, this feature helps artificial wetlands using nano zero-valent iron loaded recycled aggregate composite materials as a matrix have better denitrification capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 XRD image of recycled aggregate loaded with nano-zero-valent iron;

[0023] Figure 2 Figure 2. Removal rate of total nitrogen from farmland runoff by constructed wetlands;

[0024] Figure 3 Removal rate of total nitrogen from domestic sewage by constructed wetlands. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention more clearly understood, the spirit of the contents disclosed by the present invention will be described in detail below. After understanding the embodiments of the contents of the present invention, any technician in the relevant technical field can change and modify them according to the techniques taught by the contents of the present invention without departing from the spirit and scope of the contents of the present invention.

[0026] The exemplary embodiments of the present invention and the description thereof are used to explain the present invention but are not intended to limit the present invention.

[0027] Example: Preparation of recycled concrete aggregate loaded with nano-zero-valent iron particles

[0028] (1) Wash the recycled aggregate with deionized water until there is no dust or residue on the surface. Wash the washed recycled aggregate in a normal temperature ultrasonic cleaner for three times, each time for 30 minutes, until the fine particles in the pores on the surface of the material are completely removed.

[0029] (2) Add 100 mL of 30% ethanol solution to a conical flask. The ethanol solution is prepared by anhydrous ethanol and deionized water. Take 30 g of pretreated recycled aggregate and soak it in 100 mL of 1 mol / L ferrous sulfate solution. Seal the conical flask containing recycled aggregate and ferrous sulfate solution with a double-hole rubber stopper, and expose nitrogen from bottom to top through a long tube for 30 minutes to remove dissolved oxygen and create an anaerobic environment.

[0030] (3) A 1 mol / L sodium borohydride solution was pumped into the conical flask at a flow rate of 30 mL / min and stirred at a constant speed of 60 rpm on a magnetic stirrer. The sodium borohydride was in excess to ensure a sufficient reaction.

[0031] (4) After the reaction, the remaining solution was drained under an anaerobic environment, and the surface of the material was slowly and thoroughly cleaned with deionized water exposed to nitrogen to ensure that the remaining solution was completely washed away. The material was purged with nitrogen until it was dry and placed in a constructed wetland model as a matrix.

[0032] The following examples are some specific implementation cases and application cases of the present invention in practical applications, but are not limited to these.

[0033] Application Example 1: Treatment of farmland drainage by constructed wetland with nano-zero-valent iron loaded recycled aggregate as matrix

[0034] S1: Artificial wetland model: This embodiment designs and builds an artificial wetland model. The reactor size of this model is 15 cm in radius and 40 cm in height. The bottom is provided with a communicating vessel water inlet at the same height as the liquid level, and the interior is filled with 30 cm thick matrix material. Aquatic plant Acorus calamus is selected for planting, with a planting density of 20 plants per square meter. A vertical continuous flow water inlet method is adopted, and the hydraulic retention time is set to 7 days. After the inlet and outlet water reach stability after 90 days of operation, water sampling begins.

[0035] S2: Influent water quality indicators: COD 150mg / L, ammonia nitrogen 10mg / L, nitrate nitrogen 10mg / L.

[0036] S3: The hydraulic retention time of artificial wetlands to treat farmland drainage is 7 days.

[0037] S4: Effluent water quality indicators: COD 60mg / L, ammonia nitrogen 0.4mg / L, nitrate nitrogen 3mg / L; removal efficiency: ammonia nitrogen removal rate 96%, nitrate nitrogen removal rate 70%.

[0038] Application Example 2: Treatment of domestic sewage by constructed wetland with nano-zero-valent iron loaded recycled aggregate as matrix

[0039] S1: Artificial wetland model: In this embodiment, an artificial wetland model was designed and built. The reactor size of the model is 15 cm in radius and 40 cm in height. The bottom is provided with a communicating vessel water inlet at the same height as the liquid level, and the interior is filled with 30 cm thick matrix material. Aquatic plant Acorus calamus was selected for planting, with a planting density of 20 plants per square meter. A vertical continuous flow water inlet method was adopted, and the hydraulic retention time was set to 7 days. After the inlet and outlet water reached stability after 90 days of operation, water sampling began.

[0040] S2: Influent water quality: COD 300mg / L, ammonia nitrogen 30mg / L, nitrate nitrogen 20mg / L.

[0041] S3: The hydraulic retention time of artificial wetlands for treating domestic sewage is 7 days.

[0042] S4: Removal efficiency: COD removal rate 73%, ammonia nitrogen removal rate 97%, nitrate nitrogen removal rate 72%.

Claims

1. A method for preparing a nano zero-valent iron-loaded recycled aggregate composite material for an artificial wetland matrix, characterized in that It is carried out as follows: (1) ultrasonically clean the recycled aggregate and then dry it; (2) After mixing the recycled aggregate in step (1) with ethanol, add ferrous sulfate solution, pump in sodium borohydride solution under anaerobic environment, and stir evenly; (3) evacuating the sodium borohydride solution under an anaerobic environment, washing the surface of the recycled aggregate treated in step (2) with deionized water exposed to nitrogen, and blowing with nitrogen until dry, thereby obtaining the product.

2. The method for preparing a nano zero-valent iron loaded recycled aggregate composite material for an artificial wetland matrix according to claim 1, characterized in that The mass volume ratio of the recycled aggregate to ethanol is 1g:0.05-0.1mL.

3. The method for preparing a nano zero-valent iron loaded recycled aggregate composite material for an artificial wetland matrix according to claim 1 or 2, characterized in that The volume concentration of the ethanol is 30%.

4. The method for preparing a nano zero-valent iron loaded recycled aggregate composite material for an artificial wetland matrix according to claim 1, characterized in that The mass volume ratio of the recycled aggregate to the ferrous sulfate solution is 1g:0.5-1mL.

5. The method for preparing a nano zero-valent iron loaded recycled aggregate composite material for an artificial wetland matrix according to claim 1 or 4, characterized in that The mass concentration of the ferrous sulfate solution is 60-80%.

6. The method for preparing a nano zero-valent iron loaded recycled aggregate composite material for an artificial wetland matrix according to claim 1, characterized in that The concentration of the sodium borohydride solution is 0.5-2 mol / L, and the sodium borohydride solution is added in excess.

7. The method for preparing a nano zero-valent iron loaded recycled aggregate composite material for an artificial wetland matrix according to claim 1 or 6, characterized in that The sodium borohydride is pumped into the conical flask at a speed of 30 to 60 mL / min.

8. The use of a nano zero-valent iron loaded recycled aggregate composite material for an artificial wetland matrix as prepared in claim 1, characterized in that The nanometer zero-valent iron loaded recycled aggregate composite material is used in the process of treating sewage in artificial wetlands.

9. The use according to claim 8, characterized in that The artificial wetland is used in the process of treating sewage, specifically: the nano zero-valent iron loaded recycled aggregate composite material is filled in the artificial wetland as a matrix, and aquatic plants are planted on the matrix.

10. The use according to claim 8 or 9, characterized in that The artificial wetland sewage treatment is artificial wetland denitrification treatment, and the denitrification is the removal of ammonia nitrogen and nitrate nitrogen.

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