CN114014443A

CN114014443A - Preparation method and application of constructed wetland dephosphorization matrix

Info

Publication number: CN114014443A
Application number: CN202111300694.7A
Authority: CN
Inventors: 尹洪斌
Original assignee: Nanjing Institute of Geography and Limnology of CAS
Current assignee: Nanjing Institute of Geography and Limnology of CAS
Priority date: 2021-11-04
Filing date: 2021-11-04
Publication date: 2022-02-08

Abstract

The invention discloses a preparation method and application of a constructed wetland dephosphorization matrix, and provides a constructed wetland matrix with low cost and high phosphorus fixation capacity, which is prepared by taking clay minerals and biochar as raw materials, synchronously loading lanthanum-aluminum or only loading lanthanum as a phosphorus fixation material, and performing extrusion molding, high-temperature calcination and other methods aiming at the problems that the conventional constructed wetland matrix has low phosphorus fixation capacity, alkaline effluent pH value, difficult overcoming of high organic matter interference in the effluent, poor mechanical strength and the like. According to the scheme, the clay mineral powder and the biochar are physically mixed and stirred, a mixed solution (or a single lanthanum chloride solution) of lanthanum chloride and polyaluminium chloride in a certain mass ratio is placed in the mixed material, and the mixture is burned at high temperature for 1-2 hours to obtain the composite material; the method is simple and low in cost, and the prepared phosphorus removal matrix material has the characteristics of large phosphorus fixation capacity, strong water permeability, strong mechanical hardness and the like, and has the characteristics of no secondary pollution and no generation of residual waste liquid.

Description

Preparation method and application of constructed wetland dephosphorization matrix

Technical Field

The invention relates to the technical field of water pollution treatment, in particular to a preparation method and application of a phosphorus removal substrate for an artificial wetland.

Background

A large number of researches show that phosphorus is a limiting factor for lake eutrophication, and the increase of the phosphorus concentration in the lake water body can cause algal bloom. Therefore, controlling the concentration and level of phosphorus in lakes is considered to be a key to the eutrophication management of lakes. The sources of the lake phosphorus are mainly divided into endogenous sources and exogenous sources. Exogenous mainly refers to the input from rivers, and enhancing the input of exogenous phosphorus is an effective means for managing and treating the eutrophication of lakes. The artificial wetland is a water treatment ecological system which is developed on the basis of a natural or semi-natural purification system, is formed by artificially mixing mediums such as stones, sand, soil, coal slag and the like according to a certain proportion, is closed at the bottom and is selectively implanted with aquatic vegetation, and the main purposes of water resource protection and continuous utilization are achieved. Because the artificial wetland is an ecological water treatment mode, has the characteristics of small investment, low cost, low energy consumption, low management requirement and the like, and is widely applied to the aspects of treating domestic sewage, industrial wastewater, storm runoff, eutrophic water and the like to obtain better effect. Generally, the constructed wetland comprises basic elements such as substrates, plants, microorganisms and the like, and the purpose of removing water pollutants in a synergistic manner is achieved. The wetland substrate is a core component in the wetland, and the processes of physical adsorption, chemical precipitation, microbial conversion, decomposition and the like of pollutants such as nitrogen, phosphorus and the like on the wetland substrate are all carried out at the position, so that the wetland substrate plays a significant role in removing the pollutants entering the lake. Research shows that the removal of the total phosphorus in the inlet water by the substrate accounts for 50% or more, and the removal of the total phosphorus in the inlet water by the wetland plants only accounts for about 10-15%. Therefore, the research and development or the selection of the proper wetland substrate play a decisive role in the aspects of the overall pollutant removal efficiency, the operation effect and the like of the wetland.

In view of the important function of the selection and use of the substrate on the operation and construction of the artificial wetland, the source of the substrate raw materials, the characteristics of easy availability, economy, pollutant removal efficiency, safety (no secondary pollution), blockage (or permeability) prevention and control, adaptability to the growth of plants and microorganisms and the like are comprehensively considered when the substrate of the artificial wetland is selected. Therefore, the selection of the substrate needs to consider a plurality of factors and is the difficulty and core of the construction of the artificial wetland. At present, the selection of artificial wetland substrates is mainly focused on the following types of materials internationally: the natural material. Such materials are selected primarily from natural gravel, sand, shale, and clean soil or sediment. The materials have the characteristics of wide material sources, low price, easy obtainment and the like. But because the adsorption capacity of the adsorbent to pollutants such as nitrogen, phosphorus and the like is small, the adsorbent is very easy to saturate. ② the industrial and agricultural wastes mainly comprise sawdust, iron-aluminum mud of water purification plants, steel slag, crop shells (coconut shells, fruit shells and the like), and animal shells (oyster shells, lobster shells and the like). A plurality of researches report that the materials are widely applied to artificial wetland substrates, wherein steel slag and iron-aluminum mud of water treatment plants are particularly widely used. The natural minerals mainly use natural mineral materials as the substrate of the artificial wetland, and the materials mainly comprise: mineral materials such as zeolite, limestone, dolomite, calcite, pyrite, vermiculite and the like. The material has the characteristics of wide material source, low price and easy obtainment. However, in general, these materials have limited ability to remove phosphorus from water bodies and are prone to saturation over time. Fourthly, artificial synthesis. The artificial synthetic varieties are many, and mainly comprise novel ceramsite, modified clay, activated carbon, biochar, synthetic fiber and the like. The artificially synthesized material has the characteristics of environmental friendliness and high pollutant adsorption capacity. However, the artificial wetland is expensive, which results in high construction and operation costs of the artificial wetland.

In recent years, along with the stricter water outlet threshold of water body pollutant concentration in many countries in the world, the requirement of people on the pollutant removal performance of the constructed wetland substrate is increased. In view of the wide application of the current artificial wetland substrate, important industrial and agricultural wastes such as steel slag, iron and aluminum sludge of water treatment plants, modified clay in artificial synthetic materials and novel artificial synthetic materials are widely applied to the construction of the artificial wetland. These materials are widely used mainly because they contain high levels of active ingredients such as iron, aluminum or calcium. In recent years, lanthanum and lanthanum-containing load materials are widely applied to control of phosphorus release in water bodies and bottom sludge. Compared with the traditional constructed wetland substrate material based on calcium, aluminum, iron and the like, the lanthanum-loaded material has the characteristics of stable dephosphorization effect, difficult resolution and the like. Active ingredients (calcium, aluminum, iron, lanthanum and the like) in the matrix material can form metal precipitates with dissolved phosphate radicals in the sewage, so that the concentration of phosphorus in most of water bodies is reduced. In addition, because the wetland has the function of intercepting exogenous granular phosphorus, most suspended particles can be intercepted by the wetland, and the total phosphorus concentration in the effluent is reduced. The organic phosphorus retained in the wetland substrate and plants is decomposed again into inorganic phosphorus under the long-term action of microorganisms, and the inorganic phosphorus is continuously captured by the substrate in the wetland. However, although a large number of studies on substrates of artificial wetlands have been made internationally, the following problems still remain:

(1) the industrial and agricultural wastes are still widely applied as main artificial wetland substrates, but the risk of secondary release of pollutants exists. From the international publication of relevant documents, various steelmaking/iron slag is still the core of the constructed wetland substrate. The steel slag contains high calcium, iron and other components, has large particle size and good water permeability, and is widely used in artificial wetlands in Europe, America and other countries. Although these by-products have a higher phosphorus removal efficiency, they still have a higher risk of secondary pollutant release.

The waste steel/iron slag contains high heavy metals (lead, cadmium and the like), and after the dephosphorization performance reaches saturation, the heavy metals in the steel slag can be released to the surrounding environment to cause secondary pollution. In addition, the steel slag has high calcium content and high alkalinity, so that the pH value of the water outlet concentration of the water body is strong alkalinity (more than or equal to 10). Therefore, although high phosphorus removal benefits are obtained, the effluent with too high a pH value can generate toxicity to surrounding organisms, and the growth of surrounding plants is difficult to meet under high alkaline conditions. Moreover, because many of the waste residues from the steel/iron works have certain economic value and can be refined again, the availability of the waste residues in developing countries is also difficult to achieve compared with countries such as Europe and America.

The iron-aluminum mud of the water treatment plant also has higher phosphorus removal efficiency because the iron-aluminum mud of the water treatment plant contains higher active iron and aluminum content, and the main reason is that the tap water plant adds a certain concentration of polyaluminium or polyferric to meet the purification requirement of the water body. However, the water treatment plant sludge is generally in the form of powder or irregular particles, has low strength, and gradually disintegrates under long-term water immersion, thereby causing clogging of the wetland. In order to improve the hydraulic conductivity, the iron-aluminum mud is generally selected to be granulated and subjected to other heat treatment molding modes to form large-particle concretions, which may further increase the use cost of the iron-aluminum mud. In addition, the iron and aluminum in the purification plant contain higher nitrogen content (generally exchangeable ammonia nitrogen), so that the iron and aluminum can release higher-concentration ammonia nitrogen in the use process to cause secondary nitrogen pollution.

(2) The existing artificial synthetic wetland substrate has the problems of high cost, unsatisfactory solid phosphorus capacity and treatment efficiency and the like. Compared with industrial and agricultural wastes, the artificially synthesized substances have the characteristics of relatively small ecological risk, safe use and the like. However, the substrate cost is too high, so that the construction cost of the artificial wetland is obviously increased, and the like. At present, only a few commercial artificial wetland synthetic matrixes or compound products with high phosphorus fixation efficiency exist internationally. For example, a commercial Filtralite was reported abroad

The main components of the modified clay are calcium and magnesium, and the modified clay has high alkalinity (pH is more than or equal to 10) and the class diameter of 0.5-4 mm. Indoor simulation experiment research shows that the removal rate of the phosphorus in the inlet water reaches more than 90 percent, but the phosphorus removal rate has the defect of overlarge outlet water alkalinity (pH value)>10) And thus may limit its practical use. In addition, highly alkaline substrate materials may also be unsatisfactory for plant growth. In addition, some emerging artificial synthetic materials such as synthetic fibers and recyclable cement have good phosphorus removal effect. However, synthetic fibers are still expensive and cannot be widely popularized and used. The recyclable cement has the problems of overhigh pH value of the effluent and the like, and the large-scale use of the cement is also limited.

In summary, from the current artificial wetland substrates developed internationally or used in large scale, no commercial product with the artificial wetland substrate satisfying the requirements of large phosphorus fixation capacity, strong water seepage type, environmental friendliness and easy availability exists. In addition, the localization of the substrate materials of the artificial wetland is also a factor which needs to be considered in substrate research and development, which reduces the cost and price of the researched artificial wetland. In a word, the research and development of the artificial wetland substrate with high phosphorus fixation capacity, environmental friendliness and moderate price is very urgent, and is also the development direction of the artificial wetland substrate in the future.

Disclosure of Invention

The invention aims to provide a preparation method and application of an artificial wetland dephosphorization matrix, and provides an artificial wetland matrix with low cost and high phosphorus fixation capacity, which is prepared by taking clay minerals and biochar as raw materials, synchronously loading lanthanum and aluminum or only loading lanthanum as phosphorus fixation materials, and performing extrusion molding, high-temperature calcination and the like, aiming at the problems that the international industrialized and mature artificial wetland dephosphorization matrix is unavailable at present, and the conventional artificial wetland matrix has low phosphorus fixation capacity and alkaline effluent pH value and is difficult to overcome the interference of high organic matters in incoming water.

The constructed wetland substrate prepared by the method can effectively remove substances such as phosphorus and the like in living pollution and river incoming water, effectively reduce the flux of phosphorus entering the lake, and can make a contribution to the control of the phosphorus entering the lake.

In order to solve the technical problems, the invention provides the following technical scheme:

a preparation method of a phosphorus removal substrate for an artificial wetland comprises the following steps:

(1) taking attapulgite raw ore, physically screening, removing impurities, drying at low temperature or airing, mechanically crushing, and screening to prepare attapulgite clay powder for later use; using some biological carbon which is sold in the market or prepared artificially, mechanically crushing,

sieving to obtain charcoal powder;

(2) taking attapulgite clay powder and charcoal powder, mixing uniformly, mixing the mixed material with a loading solution, fully infiltrating for more than or equal to 24 hours to obtain a mixed material, and extruding to obtain a columnar carrier with the diameter of 4-6 mm and the length of 3-8 mm; the water content of the columnar carrier is not more than 10%.

(3) And (3) taking the columnar carrier, and sintering at the high temperature of 300-600 ℃ for 1-2 h to obtain the dephosphorization matrix.

In an optimized scheme, the negative carrier liquid is one or a mixture of a lanthanum chloride solution and a polyaluminium chloride solution. When the negative carrier liquid is lanthanum chloride, the mass fraction of lanthanum in the mixed material is 2-5%. When the negative carrier liquid is polyaluminium chloride, the mass fraction of aluminium in the mixed material is 1-4%. When the negative carrier liquid is a lanthanum chloride solution and a polyaluminium chloride solution, the mass fraction of lanthanum in the mixed material is 2-5%, and the mass fraction of aluminium is 1-4%.

In the optimized scheme, in the step (3), the high-temperature calcination temperature is 500 ℃, and the calcination time is 1 h.

According to an optimized scheme, the mass ratio of the attapulgite clay powder to the charcoal powder is (1-2): 1; preferably, the mass ratio of the attapulgite clay powder to the charcoal powder is 1: 1.

according to an optimized scheme, the water content of the mixed material is 10-20%, and is generally 10-15%.

According to an optimized scheme, the attapulgite crude ore is medium-grade or high-grade attapulgite crude ore; the content of calcium oxide in the attapulgite raw ore is less than or equal to 10 percent; the powder sieve mesh number of the attapulgite clay powder and the charcoal powder is more than or equal to 100 meshes.

In the scheme, the biochar can be prepared from straw biochar and low-cost materials; in the embodiment, the biochar is prepared by mainly adopting corn straws and corncobs as raw materials.

According to the optimized scheme, when the negative carrier liquid is a lanthanum chloride solution and a polyaluminium chloride solution, the lanthanum chloride solution and the polyaluminium chloride solution can be mixed and then infiltrated into a mixed material to load lanthanum and aluminum at one time, and finally the requirement that the load capacity of lanthanum is 5% and the load capacity of aluminum (polyaluminium chloride) is 2% is met, and the phosphorus removal substrate prepared under the condition has the most excellent performance.

According to the optimized scheme, the phosphorus removal matrix prepared by the preparation method is used for deeply purifying wetland pollution and effectively removing indexes such as phosphorus, organic matters, chromaticity and the like in a water body, the artificial wetland phosphorus removal matrix prepared by the invention has the characteristics of high solid phosphorus content, low cost, no alkalinity of effluent, high material mechanical strength, strong water permeability and the like, is very suitable for being used as an artificial wetland matrix, can be used as an important component of the artificial wetland, is used for removing phosphorus-containing water bodies such as domestic sewage, river incoming water and the like, and has wide application prospect.

Compared with the prior art, the invention has the following beneficial effects: the invention adopts the attapulgite clay as the raw material, the content of calcium (namely the content of dolomite calcium oxide is less than 10 percent) of the selected attapulgite clay is strictly controlled, and the attapulgite clay is preferably medium-grade or above. The preparation method comprises mixing attapulgite clay powder and charcoal powder at a certain mass ratio, adding negative carrier liquid, mixing, standing for a certain time, and infiltrating. And (3) placing the mixed material in an extruder, carrying out physical molding to obtain a columnar carrier (with the diameter of 6mm and the length of 5-8 mm), calcining the columnar carrier at high temperature, and drying to obtain the industrial wetland dephosphorization matrix.

The scheme of the application mainly comprises the following creation points:

(1) mixing attapulgite and charcoal, and adjusting the optimal proportion to be 1: 1: because the artificial wetland matrix is soaked in the water body for a long time or is in a flooded state, pollutants in the incoming water need to be removed efficiently. The characteristics require that the artificial wetland matrix has stronger mechanical strength, does not disintegrate or dissolve in water, and has larger water seepage characteristic so as to prevent the wetland from being blocked. Namely, the developed artificial wetland substrate can not exist in a powder state, and needs large particle shape, column shape or other physical properties; the traditional easily-disintegrated material can only maintain the operation period of 1-2 months, thereby leading to the loss of the wetland function.

Therefore, in order to improve the mechanical properties of the matrix, the composition of the materials and the mechanical composition must be optimally adjusted. In general, a matrix material such as an attapulgite material in a powder state is not suitable for use as an artificial wetland matrix because it is very likely to cause clogging of a wetland system. The applicant tries to prepare the substrate of the artificial wetland by taking the attapulgite as the raw material, but the material after high-temperature calcination is easy to disintegrate. This is mainly due to the fact that clay materials do not have compressive resistance after sintering and the clay particles have poor cohesion. Therefore, the applicant has searched for an auxiliary material for enhancing the mechanical strength of the substrate of the artificial wetland. Through a large amount of selection, the applicant finds that the biochar material and the attapulgite powder are physically mixed, the strength of the loaded material is obviously increased after high-temperature calcination, and only part of the material is lost in high-strength simulation oscillation. The strength of the attapulgite powder and the biochar mixed material after high-temperature burning is related to the adding proportion of the biochar, and the mechanical strength of the prepared material is increased along with the increase of the biochar. Considering the economic cost of the prepared material and the strength of the prepared material, the strength of the material can meet the requirement of the artificial wetland substrate when the proportion of the biochar is 50 percent of the whole material.

(2) The high-temperature calcination parameters of the mixed material are 300-600 ℃ and high-temperature sintering is carried out for 1-2 h, wherein the most preferable calcination parameters are as follows: the high-temperature calcination temperature is 500 ℃, and the calcination time is 1 h; in terms of the optimum heat treatment time of the substrate and the calcination temperature, it is necessary to find the optimum balance point in terms of fixed capacity, mechanical properties, and economy. Generally, as the temperature increases, the mechanical properties of the matrix material are greatly enhanced. However, the temperature is too high, which leads to gasification loss of the loaded lanthanum-aluminum metal, and further influences the later phosphorus removal performance. The too high heat treatment temperature increases the manufacturing cost of the material, so the calcination temperature of the material is not easy to be too high. And when the calcination temperature reaches a certain degree, the mechanical property of the material meets the requirement of the wetland substrate, and the heating temperature is not required to be further increased. A large number of studies show that the heat treatment temperature of the attapulgite is influenced by the grade of the attapulgite. The low-grade attapulgite clay generally refers to the content of dolomite, calcite and other impurities, and the calcium oxide component of the attapulgite clay generally exceeds 10 percent and can reach 30 percent or more. After high-temperature treatment, particularly at a temperature of more than 600 ℃, dolomite and calcite in the components of the attapulgite material can be decomposed into substances such as calcium oxide and the like, but the pH value of a water body can be sharply increased to 11 or above when meeting water. Therefore, the phosphorus fixing performance and the capacity of the material can be greatly improved. Such as Gan et al (Water Research,2009,43(11): 2907-. However, after the medium and high grade attapulgite is subjected to heat treatment, the phosphorus removal performance of the material is not greatly improved, and the high temperature (more than 500 ℃) can cause the mineral structure of the material to be greatly changed, so that the adsorption and treatment of water body pollutants such as phosphorus and the like are not facilitated. In addition, the medium-high grade attapulgite does not contain the calcium component of carbonate, the pH value of the attapulgite is basically unchanged when meeting water after heat treatment, and the pH value of the attapulgite does not change when meeting water after being combined with charcoal and calcined at high temperature.

For the mixed materials, the heating temperature of the attapulgite and the biochar also generates difference due to the components of the materials. Compared with the pure attapulgite clay, the attapulgite clay has the advantages of higher temperature for consolidation, lower physical and mechanical strength and water disintegration. After the biochar is added, the calcining temperature of the material is obviously reduced. The physical and mechanical strength of the mixed material (the biochar and the attapulgite) with the calcining temperature of about 500 ℃ can meet the requirement of the artificial wetland substrate. As the proportion of biochar increases, its mechanical strength also increases significantly at relatively low temperatures and short calcination times. In addition, the high temperature calcination temperature of the mixed material is also closely related to the final holding amount of the supported metal. After the temperature is too high, the metal loaded by the material is lost, the specific surface area and the adsorption point position of the material are greatly reduced, and the phosphorus fixation capacity and the effect of the material are further reduced. If the temperature exceeds 500 ℃, a large amount of lanthanum and aluminum in the material can be lost, and the phosphorus removal effect of the material is obviously reduced. Comprehensively considering the aspects of the mechanical strength of the material, the holding amount of the loaded metal, the economical efficiency of the material preparation and the like, the temperature of 500 ℃ is selected and the mixture is calcined for 1 hour and used as the heating temperature of the mixed material.

(3) The load components are mixed by polyaluminium chloride and lanthanum chloride, the load capacity of the lanthanum chloride is 5%, and the load capacity of the polyaluminium chloride is 2%; in the aspect of increasing the phosphorus-fixing capacity, in view of the problems of high organic matter content, high water pH value and the like commonly existing in the current eutrophic water body, a phosphorus-locking material with high phosphorus-fixing capacity needs to be developed urgently. The lanthanum-supported material has excellent performance in terms of phosphorus-locking stability, improvement of phosphorus-fixing capacity of the material, and the like, because of being widely adopted as a supported metal of the material in recent years. However, the simple lanthanum-loaded material has the problems of low organic matter resistance efficiency and the like, that is, when the organic matter content in the water body is high (generally expressed by DOC concentration, which exceeds 20mg/L), the phosphorus removal performance of the lanthanum-loaded material is greatly reduced. In order to overcome the problem, aluminum with a certain proportion is introduced into the load material, so that the problem of interference of high organic matter content of the water body is solved. Considering that the loading of lanthanum is considered to be within 5% internationally at present, the lanthanum does not generate toxicity to surrounding aquatic organisms. Therefore, the supported amount of lanthanum is preferably 5%. The load of the aluminum is helpful for improving the phosphorus fixation capacity of the load material, and on the one hand, the aluminum increases the phosphorus fixation adsorption sites of the material, so that the phosphorus fixation capacity of the material is improved. The material is acidic due to too large loading amount of aluminum, so the loading amount of aluminum is preferably 1-4%, and the optimal ratio is 2%.

(4) In order to meet the requirement of mass production, a large-scale drum type calcining furnace which is generally adopted in the market and the attapulgite clay enterprises at present is selected as calcining equipment in the selection of the calcining process. The length of the calcining furnace body is 15-18 meters, the diameter is 3-5 meters, and the rotating speed is 1-3 meters per hour. The mixed material of the attapulgite and the biochar is extruded into a semi-finished product by an automatic conveyer belt and is transported to a furnace end. The temperature of the furnace end is gradually transmitted to the whole furnace body, the temperature is about 400 ℃ and 700 ℃, and the temperature is about 500 ℃. Heating the materials at the furnace end for 10-30 minutes, then rotating the furnace body, and gradually conveying the materials to the bottom of the furnace body along with the rotation of the furnace body. The transmission speed of the whole material in the furnace body is controlled to reach the bottom of the furnace body within about 30 minutes, and the whole heating time is controlled to be preferably 1 hour.

The method has simple process and low cost, and the prepared phosphorus removal matrix material has the characteristics of large phosphorus fixation capacity, strong water permeability, large machinery (strong hardness) and the like, and has the characteristics of no secondary pollution and no generation of residual waste liquid. The prepared product can be applied to a substrate material of the artificial wetland or the application of strengthening the substrate of the artificial wetland, and the prepared substrate can synchronously remove phosphorus, organic matters, chromaticity and the like in sewage, thereby effectively strengthening the purification strength of the wetland on pollutants.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a graph of material loss rates for phosphorus removal substrates prepared according to the protocol A1-A5 of the present invention;

FIG. 2 is a graph of material loss rates for phosphorus removal substrates prepared according to the protocol of the present invention B1-B5;

FIG. 3 is a graph of material loss rates for phosphorus removal substrates prepared according to the C1-C5 embodiment of the present invention;

FIG. 4 shows the phosphorus removal efficiency of the phosphorus removal substrate prepared by the scheme of the invention B1-B5;

FIG. 5 shows the phosphorus removal efficiency of the phosphorus removal substrate prepared by the scheme of the invention C1-C5;

FIG. 6 shows the phosphorus removal efficiency of phosphorus removal substrates prepared by the schemes of H1 and H3 of the present invention at different pH values;

FIG. 7 shows the phosphorus removal efficiency of phosphorus removal substrates prepared by the schemes of H1 and H3 according to the invention under different organic matter conditions;

FIG. 8 shows the phosphorus removal matrix material loss rate produced by the embodiment of example 3, C4;

FIG. 9 is a schematic diagram of the phosphorus fixation capacity of the phosphorus removal substrate prepared by the solution C4 of the present invention and other artificial wetland substrates;

FIG. 10 is a schematic diagram of the effect of the phosphorus removal substrate prepared by the embodiment of C4;

FIG. 11 is a graph of phosphorus content distribution after application of phosphorus removal matrix prepared according to the protocol C4 of the present invention;

FIG. 12 is a graph showing the phosphorus removal efficiency of phosphorus removal substrates prepared by the protocol D1-F5 of the present invention;

FIG. 13 is a graph showing the phosphorus removal efficiency of phosphorus removal substrates prepared by the protocol G1-H5 of the present invention;

FIG. 14 shows the phosphorus removal efficiency of phosphorus removal substrates prepared according to the H1 protocol under different pH and organic matter conditions;

FIG. 15 shows the phosphorus removal efficiency of phosphorus removal substrates prepared according to the H3 protocol under different pH and organic matter conditions.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1: comparative example of selection of parameters for sintering temperature and load type

(1) taking attapulgite raw ore (medium-grade or high-grade attapulgite raw ore, wherein the content of calcium oxide in the attapulgite raw ore is less than or equal to 10%), physically screening, removing impurities, drying, mechanically crushing, and screening (the mesh number is more than 100 meshes) to obtain attapulgite clay powder for later use; mechanically pulverizing biochar, and sieving (mesh number is more than 100) to obtain charcoal powder;

(2) taking the mass ratio of 1: 1, mixing the attapulgite clay powder and the charcoal powder uniformly, mixing the mixed material with a loading solution, fully infiltrating for 30h to obtain a mixed material, wherein the water content of the mixed material is 15%, and extruding to obtain a columnar carrier with the diameter of 6mm and the length of 8 mm;

According to the scheme disclosed by the embodiment 1, a parameter change embodiment is carried out, wherein the method is divided into (i) polyaluminium chloride load according to the type of the load liquid, the negative carrier liquid is polyaluminium chloride, and the mass fraction of aluminum in the mixed material is 2%; loading lanthanum chloride, wherein the negative carrier liquid is lanthanum chloride, and the mass fraction of lanthanum in the mixed material is 5%; loading polyaluminium chloride and lanthanum chloride, wherein the negative carrier liquid is the mixture of lanthanum chloride and polyaluminium chloride, the mass fraction of aluminum in the mixed material is 2%, and the mass fraction of lanthanum is 5%;

specific example parameters are given in table one below:

watch 1

Detection experiment:

according to the protocol disclosed in example 1 (A1-A5, B1-B5, C1-C5), the corresponding phosphorus removal substrates were prepared and tested according to the following methods, respectively:

1. loss rate of material: and (3) taking 1-2g of the dephosphorization matrix, placing the dephosphorization matrix in 100ml of deionized water, oscillating for 24 hours at constant temperature, and calculating the loss rate of the material. Loss ratio (%) of material, loss dry weight of material/weight of material.

The specific detection results are shown in fig. 1, 2 and 3: wherein FIG. 1 is the material loss rate of the phosphorus removal substrate prepared by the protocol A1-A5; FIG. 2 is a graph of material loss rates for phosphorus removal substrates prepared by the protocol of B1-B5; FIG. 3 is a graph of material loss rates for phosphorus removal substrates prepared by the C1-C5 protocol.

As can be seen from fig. 1-3, when the negative carrier fluid is any one of or a mixture of a lanthanum chloride solution and a polyaluminum chloride solution, the material loss rate of the prepared phosphorus removal substrate gradually decreases with the increase of the sintering temperature regardless of the loading amount of the negative carrier fluid and the selection of the type of the loading fluid; when the sintering temperature reaches 600 ℃, the material loss rate is higher than that of the phosphorus removal substrate with the sintering temperature of 500 ℃, so the most excellent sintering temperature in the scheme is 500 ℃, and the sintering time is 2 hours.

2. And (3) phosphorus removal efficiency: 1.0g of phosphorus-removing substrate was taken and placed in 40ml of phosphorus solutions of 50mg/L and 200mg/L, respectively, and shaken at a constant temperature for 24 hours (25 ℃, 160 rpm). After centrifugal filtration, the concentration of the phosphorus solution is measured, and the phosphorus removal efficiency of the material is calculated.

The specific detection results are shown in fig. 4 and 5: wherein FIG. 4 shows the phosphorus removal efficiency of the phosphorus removal substrate prepared by the scheme B1-B5, and FIG. 5 shows the phosphorus removal efficiency of the phosphorus removal substrate prepared by the scheme C1-C5.

As can be seen from fig. 4-5, when the negative carrier liquid is a mixture of a lanthanum chloride solution and a polyaluminum chloride solution, the loading efficiency is excellent, and the phosphorus removal efficiency of the C1-C5 embodiments is sequentially reduced.

And (4) conclusion: from the above, based on the material loss rate and the phosphorus removal efficiency, the sintering parameters in the comprehensive limiting scheme are as follows: the temperature is 500 ℃, the time is 1h, and under the parameter, the material loss rate and the phosphorus removal efficiency of the product are the most excellent.

Example 2: parameter control test of loading mass fraction of loading liquid

(3) and (3) taking the columnar carrier, and sintering at the high temperature of 500 ℃ for 1h to obtain the dephosphorization matrix.

According to the scheme disclosed in example 3, the load component was changed as shown in table two:

watch two

Detection experiment:

according to the protocol disclosed in example 2 (D1-D4, E1-E5, F1-F5, G1-G5, H1-H5), the corresponding phosphorus removal substrates were prepared, and tested according to the following methods, respectively:

1. and (3) phosphorus removal efficiency: 1.0g of phosphorus-removing substrate was taken and placed in 40ml of phosphorus solutions of 50mg/L and 200mg/L, respectively, and shaken at a constant temperature for 24 hours (25 ℃, 160 rpm). After centrifugal filtration, the concentration of the phosphorus solution is measured, and the phosphorus removal efficiency of the material is calculated.

And (4) conclusion: as can be seen from the attached drawings 12 and 13, when the negative carrier liquid is a mixture of lanthanum chloride and polyaluminium chloride, the mass fraction of aluminum in the mixed material is 2%, and the mass fraction of lanthanum is 5%, the phosphorus removal rate of the phosphorus removal substrate (H3) prepared under the parameter condition is high, and compared with the schemes of H4 and H5, the phosphorus removal substrate has lower cost and is more economical and practical.

2. pH interference detection assay: 0.5g of the phosphorus removal substrate prepared by the H1 and H3 schemes is taken and placed in 25ml of phosphorus solution with the concentration of 50 mg/L. Adjusting the initial pH value to 4-10. The pH value of the solution is adjusted by dilute hydrochloric acid or dilute alkali. And (3) placing the mixed solution in a constant-temperature shaking table for reacting for 24 hours, carrying out centrifugal filtration, measuring the concentration of the adsorbed phosphorus, and calculating the phosphorus removal efficiency of the material.

The specific detection is shown in fig. 6: as can be seen from the figure, the phosphorus removal efficiency of the phosphorus removal substrate is influenced by the change interference of the environmental pH, while the lanthanum-aluminum load material prepared by H3 is less influenced by the pH, the overall phosphorus removal rate is relatively stable, while the pure lanthanum load material prepared by H1 is greatly influenced by the pH, and when the pH is more than 8, the phosphorus removal rate is greatly reduced.

3. The organic matter interference test comprises the following detection methods:

taking 0.5g of the phosphorus removal substrate prepared by the H1 and H3 schemes, placing the substrate in 25ml of phosphorus solution with the concentration of 50mg/L, simultaneously adding humic acid with different concentrations, and measuring the total carbon (TOC) concentration to be 20mg/L, 50mg/L and 100mg/L respectively. The initial pH of the reaction solution was adjusted to 7.0. The pH value of the solution is adjusted by dilute hydrochloric acid or dilute alkali. And (3) placing the mixed solution in a constant-temperature shaking table for reacting for 24 hours, carrying out centrifugal filtration, measuring the concentration of the adsorbed phosphorus, and calculating the phosphorus removal efficiency of the material.

The specific detection results are shown in fig. 7: as can be seen from the figure, in an environment with a pH of 7, as the total carbon (TOC) concentration increases, the phosphorus removal rate of the phosphorus removal substrate gradually decreases, i.e., organic matter in the environment interferes with the phosphorus removal rate of the phosphorus removal substrate.

4. The detection method of the interference system with coexisting pH and organic matters comprises the following steps:

according to the material preparation method in the embodiment 2, 1.0g of the phosphorus removal substrate prepared by the schemes H1 and H3 is respectively placed in 40ml of phosphorus solution with the concentration of 50mg/L, the pH value and the TOC concentration in the dissolution are adjusted, the specific parameters are shown in the following table, and the substrate is shaken at constant temperature for 24 hours (25 ℃, 160 rpm). After centrifugal filtration, the concentration of the phosphorus solution is measured, and the phosphorus removal efficiency of the material is calculated

And (4) conclusion: the specific detection results are shown in the attached figures 14 and 15: the eutrophic water body has a high pH value and is rich in organic matters. These working conditions inevitably have a great influence on the phosphorus fixation (phosphorus removal) effect of the material. In order to overcome the problems, the method selects to load the bimetallic material, thereby overcoming the problem that a single aluminum or single lanthanum load material is sensitive to the pH value of the water body and the reaction of the water body with high organic matter content respectively, and ensuring the dephosphorization effect of the dephosphorization matrix; as can be seen from the above table, the parameters disclosed by H3 are adopted to carry out bimetallic loading, the sintering parameters are 'temperature 500 ℃ and time 1H', the phosphorus removal rate of the phosphorus removal matrix prepared under the conditions is stable, the external interference is small, and the application effect in eutrophic water is excellent.

Example 3: example of modification of the Attapulgite/charcoal ratio by Mass

(2) taking the mass ratio of 2: 1, mixing the attapulgite clay powder and the charcoal powder uniformly, mixing the mixed material with a loading solution, fully infiltrating for 30h to obtain a mixed material, wherein the water content of the mixed material is 15%, and extruding to obtain a columnar carrier with the diameter of 6mm and the length of 8 mm; the negative carrier liquid is loaded by polyaluminium chloride and lanthanum chloride, the negative carrier liquid is formed by mixing the lanthanum chloride and the polyaluminium chloride, the mass fraction of aluminum in the mixed material is 2%, and the mass fraction of lanthanum is 5%;

Detection experiment:

1-2g of the phosphorus removal substrate prepared in example 3 and C4 was placed in 100ml of deionized water, and the loss rate of the material was calculated by shaking the substrate at a constant temperature for 24 hours. Loss ratio (%) of material, loss dry weight of material/weight of material.

The specific detection results are shown in fig. 8: as can be seen from the figure, when the attapulgite clay powder and the charcoal powder are mixed by mass ratio of 2: 1, after being uniformly mixed, the loss rate of the prepared material is far greater than that of a phosphorus removal substrate prepared by a C4 scheme; the application therefore defines the mass ratio of the attapulgite clay powder to the charcoal powder as 1: 1, the loss rate of the material is lower under the condition of the parameter.

Example 4: high solid phosphorus capacity

0.5g of the phosphorus removal substrate prepared in C4 in example 1 was placed in 25ml of a phosphorus solution with a concentration of 10mg/L to 1000mg/L, and the pH of the initial reaction solution was 7.0. And (3) placing the mixed solution in a constant-temperature shaking table for reacting for 24 hours, carrying out centrifugal filtration, measuring the concentration of the phosphorus after adsorption, and calculating the phosphorus removal efficiency and the adsorption quantity of the material. And (3) utilizing the equilibrium concentration and the adsorption capacity of the solution to make a graph, utilizing a nonlinear fitting method to calculate the maximum solid phosphorus capacity of the material, and comparing the maximum solid phosphorus capacity with the solid phosphorus capacity of the constructed wetland substrate of the current commercial or common material.

The specific detection results are shown in fig. 9: in the embodiment, the phosphorus-fixing capacity of the phosphorus-removing substrate prepared by C4 and the phosphorus-fixing capacity of the commercial artificial wetland substrate are compared by taking the phosphorus-removing substrate prepared by C4 as a control, and the phosphorus-fixing capacity of the phosphorus-removing substrate prepared by C4 is far higher than that of other common materials.

Example 5: effect of practical application

Several phosphorus removal substrates were obtained from C4 in example 1. The substrate is placed in an organic glass tube with the length of 50cm and the inner diameter of 10ml, the filling height of the material is 40cm, and the upper part and the lower part of the material are respectively filled with 5cm of quartz sand. And ensure the whole packed column to be sealed and water-tight. The peristaltic pump is adopted to feed water from the lower part of the column body and slowly pass through the whole column body. The concentration of the phosphorus solution is 10mg/L, and the water conservancy residence time is 8 hours. And taking out the aqueous solution at intervals to test the concentration of phosphorus in the solution, calculating the phosphorus removal efficiency of the column, and carrying out the whole experiment for 120 days.

The specific application effect graphs are shown in fig. 10 and fig. 11: as can be seen from the figure, the phosphorus removal matrix material prepared by the method has the characteristics of large phosphorus fixation capacity, strong water permeability, strong mechanical hardness and the like, and has the characteristics of no secondary pollution and no generation of residual waste liquid. The prepared product can be applied to a substrate material of the artificial wetland or the application of strengthening the substrate of the artificial wetland, and the prepared substrate can synchronously remove phosphorus, organic matters, chromaticity and the like in sewage, thereby effectively strengthening the purification strength of the wetland on pollutants.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of a phosphorus removal substrate for an artificial wetland is characterized by comprising the following steps: the method comprises the following steps:

(1) taking attapulgite raw ore, physically screening, removing impurities, drying, mechanically crushing, and screening to obtain attapulgite clay powder for later use; mechanically pulverizing biochar, and sieving to obtain charcoal powder;

(2) uniformly mixing attapulgite clay powder and charcoal powder, mixing the mixed material with a loading solution, fully infiltrating for 24-30 h to obtain a mixed material, and extruding to obtain a columnar carrier;

2. The preparation method of the artificial wetland dephosphorization matrix according to claim 1, which is characterized by comprising the following steps: the negative carrier liquid is one or a mixture of lanthanum chloride solution and polyaluminium chloride solution.

3. The preparation method of the artificial wetland dephosphorization matrix according to claim 2, which is characterized by comprising the following steps: when the negative carrier liquid is lanthanum chloride, the mass fraction of lanthanum in the mixed material is 2-5%.

4. The preparation method of the artificial wetland dephosphorization matrix according to claim 2, which is characterized by comprising the following steps: when the negative carrier liquid is polyaluminium chloride, the mass fraction of aluminium in the mixed material is 1-4%.

5. The preparation method of the artificial wetland dephosphorization matrix according to claim 2, which is characterized by comprising the following steps: when the negative carrier liquid is a lanthanum chloride solution and a polyaluminium chloride solution, the mass fraction of lanthanum in the mixed material is 2-5%, and the mass fraction of aluminium is 1-4%.

6. The preparation method of the artificial wetland dephosphorization matrix according to claim 1, which is characterized by comprising the following steps: in the step (3), the high-temperature calcination temperature is 500 ℃, and the calcination time is 1 h.

7. The preparation method of the artificial wetland dephosphorization matrix according to claim 1, which is characterized by comprising the following steps: the mass ratio of the attapulgite clay powder to the charcoal powder is (1-2): 1.

8. the preparation method of the artificial wetland dephosphorization matrix according to claim 1, which is characterized by comprising the following steps: the water content of the mixed material is 10-20%.

9. The preparation method of the artificial wetland dephosphorization matrix according to claim 1, which is characterized by comprising the following steps: the attapulgite crude ore is medium-grade or high-grade attapulgite crude ore; the content of calcium oxide in the attapulgite raw ore is less than or equal to 10 percent; the powder sieve mesh number of the attapulgite clay powder and the charcoal powder is more than or equal to 100 meshes.

10. The application of the phosphorus removal substrate prepared by the preparation method according to any one of claims 1 to 9 is characterized in that: the dephosphorization matrix is used for deep purification of wetland pollution, and effectively removes phosphorus, organic matters and chromaticity in a water body.