A modified palygorskite, a riparian ecological substrate and a method for preparing the same

Abstract

The application discloses a modified attapulgite, a riverbank ecological base material and a preparation method thereof. The preparation method of the modified attapulgite comprises the following steps: taking biochar and potassium hydroxide, stirring after adding water, and then performing suction filtration; the product is dried, ground and sieved to obtain a powder; the powder is mixed with attapulgite powder, pyrolysis reaction is carried out in a protective gas atmosphere, the product is washed until the pH is 6.5-7.0 after the reaction is completed, and attapulgite-based biochar is obtained; iron chloride solution and thiourea solution are added into the attapulgite-based biochar, then stirring, drying and calcining are carried out in a protective gas atmosphere, then the product is mixed with water, the pH of the system is adjusted to 6.5-7.5 and is left to stand, and finally washing and drying are carried out. The modified attapulgite prepared in the application has a unique layer chain structure and rod-shaped crystal, can adsorb, complex and ion exchange pollutants in the environment, and has strong adsorption and soil nitrogen and phosphorus holding capacity.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of slope erosion control and ecological restoration, and particularly relates to a modified attapulgite, a riverbank ecological substrate and a preparation method thereof. BACKGROUND

[0002] With the rapid development of economy and society, the demand for natural resources by humans is increasing. However, this growth is accompanied by serious disturbance and destruction of the ecological environment. Due to the increasing frequency of human activities, the riparian zone and water environment have suffered serious pollution, especially factors such as agricultural activities, industrial emissions and urbanization, which have brought unprecedented pollution pressure to these environments. These activities not only deteriorate the ecological environment, but also affect water quality and flood control capacity, posing a threat to the health of aquatic ecosystems, so ecological protection technology has emerged as the times require. Ecological revetment is an important part of the river ecosystem, which not only enhances the landscape value of the riverbank, but also enhances the stability and erosion resistance of the bank slope. More importantly, ecological revetment has a significant effect on intercepting and purifying non-point source pollution. The mechanism of the river ecological revetment for controlling pollutants mainly includes interception of particulate matter in surface runoff and its attached pollutants by vegetation, absorption by plant roots, adsorption of pollutants by soil, and transformation and degradation of pollutants by soil microorganisms.

[0003] The ecological substrate refers to a composite material formed by mixing soil, cementing material, coarse aggregate, organic matter and plant seeds, etc., which has the characteristics of strong durability, stable structure and good permeability, and provides a suitable environment for plant growth. Its developed root system grows along the internal pores of the substrate until the deep part of the slope surface, connecting the ecological substrate and the bank slope into a whole, and has the effects of improving the stability of the bank slope, purifying the water body and perfecting the ecological system.

[0004] At present, the research on ecological substrate is still in its initial stage, mainly focusing on standardizing the mix proportion design of ecological substrate, preparation process, balancing the mechanical properties of ecological substrate and the needs of plant growth, etc., and less on the research on the erosion resistance and adsorption of ecological substrate. Therefore, it is crucial to further improve the adsorption and erosion resistance of the improved ecological substrate, effectively slow down the erosion of the riverbank and reduce non-point source pollution. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application aims to provide a modified attapulgite, a riverbank ecological substrate and a preparation method thereof. The modified attapulgite is used to prepare the ecological substrate in cooperation with the zeolite composite material, which has the effects of reducing soil density, increasing soil porosity and improving soil consistency, and enhances the performance of the ecological slope protection substrate in terms of fertilizer retention and water retention.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] A preparation method of modified attapulgite, comprising the following steps:

[0008] (1) taking biochar and potassium hydroxide, stirring after adding water, then suction filtration, the product is dried, ground and sieved in sequence to obtain a powder;

[0009] KOH mainly plays an activation role, reacts with active oxygen-containing substances in biochar, KOH is completely converted into K2CO3, resulting in the formation of a large amount of gaseous products and phenols, increasing the oxygen content and specific surface area of biochar.

[0010] (2) mixing the powder in step (1) with attapulgite powder, and performing pyrolysis reaction under a protective gas atmosphere, washing the product to pH=6.5-7.0 after the reaction is completed to obtain attapulgite-based biochar;

[0011] (3) adding ferric chloride solution and thiourea solution to the attapulgite-based biochar, then ultrasonic stirring and drying, calcining the product in a protective gas atmosphere, then mixing with water, adjusting the pH of the system to 6.5-7.5 and standing, and finally washing and drying to obtain the modified attapulgite, i.e. hydrothermal iron-modified attapulgite.

[0012] In step (3), thiourea and ferric chloride have a synergistic activation effect.

[0013] Preferably, in step (1), the mass ratio of biochar to potassium hydroxide is 1:3.

[0014] Preferably, in step (1), the mass ratio of the amount of water added to KOH is 5:3.

[0015] Preferably, in step (1), the drying temperature is 80°C.

[0016] Preferably, in step (1), the sieve aperture is 0.42 mm.

[0017] Preferably, in step (1), the biochar is prepared by high-temperature pyrolysis of at least one of rapeseed straw, potato, corn straw, coconut shell, walnut shell and chestnut shell; and the particle size of the biochar is 200-400 mesh.

[0018] Preferably, in step (2), the attapulgite powder is sieved through a sieve with an aperture of 0.42 mm before use.

[0019] Preferably, in step (2), the mass ratio of the attapulgite powder to the powder in step (1) is 1:1-2.

[0020] Preferably, in step (2), the protective gas is nitrogen.

[0021] Preferably, in step (2), the pyrolysis reaction is carried out at a temperature of 450-550℃ for 1h.

[0022] Preferably, in step (2), the washing is carried out using deionized water.

[0023] Preferably, in step (3), the mass ratio of the attapulgite-based biochar to the ferric chloride solution is 1.6-2:5.

[0024] Preferably, in step (3), the mass ratio of the attapulgite-based biochar to the thiourea solution is 1-2:5.

[0025] Preferably, in step (3), the concentration of the ferric chloride solution is 2 mol·L -1 .

[0026] Preferably, in step (3), the concentration of the thiourea solution is 1 mol·L -1 .

[0027] Preferably, in step (3), the temperature of the ultrasonic stirring is 80℃.

[0028] Preferably, in step (3), the temperature of the drying is 105℃.

[0029] Preferably, in step (3), the protective gas is nitrogen.

[0030] Preferably, in step (3), the calcination is carried out at a temperature of 700℃ for 2h.

[0031] Preferably, in step (3), the pH of the system is adjusted by adding a NaOH solution.

[0032] Preferably, in step (3), the standing time is 24h.

[0033] Preferably, in step (3), the temperature of the drying is 50-70℃.

[0034] The modified attapulgite prepared by the above method.

[0035] A riverbank ecological substrate prepared from components including 100-120 parts of planting soil, 3-6 parts of the modified attapulgite, 1-3 parts of zeolite-based composite material, 0-3 parts of biochar, 1-3 parts of cement, 1-2 parts of greening additive, and 5-10 parts of organic material.

[0036] Preferably, the zeolite-based composite material is prepared by the following method: grinding the zeolite and palygorskite, mixing after passing through a 2mm aperture sieve, incorporating cement and a foaming agent to form a blank, and curing in a steam box for 24 hours.

[0037] The zeolite-based composite material has the characteristics of large specific surface area, rich pores, many adsorption sites and good ion exchange performance, and can adsorb NH4 + -N effect is good.

[0038] Preferably, the foaming agent is a carbonate, and more preferably, the carbonate is at least one of calcium carbonate, magnesium carbonate and sodium bicarbonate. The foaming agent can adjust the porosity and pore size of the material, effectively reduce the surface tension of the liquid, and improve the surface activity of the target material.

[0039] Preferably, the amount of foaming agent added accounts for 0.10% to 0.15% of the total mass of the zeolite, cement and palygorskite.

[0040] Preferably, the curing environment temperature is 60℃ and the humidity is 90%.

[0041] Preferably, the preparation method of the biochar is as follows: at least one of rapeseed straw, potato, corn straw, coconut shell, walnut shell and chestnut shell is pyrolyzed to obtain the biochar; and the particle size of the biochar is 200-400 mesh.

[0042] Preferably, the cement is P.O 42.5 grade ordinary Portland cement.

[0043] Preferably, the greening additive is ferrous sulfate, which adjusts the alkaline environment generated by cement hydration without significantly affecting the strength of the substrate, so as to make it suitable for the survival and reproduction of plants and functional microorganisms.

[0044] Preferably, the organic material is soybean meal particles with a particle size of 2mm, and the main components include soybean meal, corn meal, fish bone meal and traditional Chinese medicine residue.

[0045] The preparation method of the above riverbank ecological substrate comprises the following steps: drying, crushing and sieving the planting soil to remove coarse particles; weighing the modified palygorskite, biochar, zeolite-based composite material, cement and greening additive according to the proportion, adding water and mixing with the planting soil to obtain an initial improved material; and finally adding the organic material.

[0046] Preferably, the amount of water added is determined according to the actual situation, and the water content of the riverbank ecological substrate after adding water is 15-20%.

[0047] Compared with the prior art, the beneficial effects of the present application include:

[0048] (1) The hydrothermal method iron modified attapulgite of the application has a unique layer chain structure and rod-shaped crystal, and can adsorb, complex and ion exchange pollutants in the environment. It is composed of a large amount of SiO2 and Al2O3 minerals, can have a secondary hydration reaction with Ca(OH)2 generated by cement hydration in the ecological slope protection substrate, generate low Ca / Si ratio hydrated calcium silicate, generate hydrated calcium silicate (C-S-H) and hydrated calcium aluminate (C-A-H), and produce secondary strengthening to the substrate, improve the bonding strength of the substrate; meanwhile, it can also improve the reactivity of attapulgite and the adverse effects of cement alkalinity on the growth of vegetation.

[0049] The application makes attapulgite uniformly dispersed on the surface of biochar through thermal co-decomposition with biochar, forms a composite material with high anion exchange capacity, and has strong adsorption and retention capacity for nitrogen and phosphorus in the soil.

[0050] (2) The particle size of the biomass charcoal is between 200-400 meshes, which can improve the maximum adsorption capacity of the soil to phosphorus, and reduce the soil phosphorus desorption rate. It has a strong filling effect, can enhance the aggregation effect of the ecological slope protection substrate, has the advantages of large specific surface area, rich pore structure and strong ion adsorption and exchange capacity. Biomass charcoal is considered as a potential soil modifier, which can reduce soil density, increase soil porosity and improve soil consistency, and enhance the fertilizer and water retention performance of the ecological slope protection substrate.

[0051] (3) The zeolite-based composite material further improves the adsorption capacity, pore ratio and specific surface area of zeolite, so that it has excellent adsorption performance of NH4 + -N, and is low in cost, widely distributed, non-toxic and harmless, and has good ion exchange performance. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 The statistical curve of planting days and germination rate of the riverbank ecological substrate prepared by using each example and comparative example for planting Cynodon dactylon.

[0053] Figure 2 The statistical graph of the total nitrogen adsorption efficiency of the riverbank ecological substrate prepared by using each example and comparative example for sewage, wherein 0%, 1%, 2%, 3% and 4% respectively correspond to different proportions of the content of biochar.

[0054] Figure 3 The statistical graph of the total phosphorus adsorption efficiency of the riverbank ecological substrate prepared by using each example and comparative example for sewage, wherein 0%, 1%, 2%, 3% and 4% respectively correspond to different proportions of the content of biochar.

[0055] Figure 4 The total nitrogen adsorption kinetics curve of No. 4 substrate, No. 14 substrate and No. 15 substrate.

[0056] Figure 5 Figure 4 is a total phosphorus adsorption kinetics curve graph of No. 4 substrate, No. 14 substrate and No. 15 substrate. DETAILED DESCRIPTION

[0057] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0058] The zeolite in the examples is zeolite, which is purchased from Hui Bang Mining Products Co., Ltd. in Lingshou County;

[0059] The attapulgite is purchased from Chengnuo Mining Products Co., Ltd. in Lingshou County; the biochar is purchased from Henan Coconut Carbon Environmental Protection Material Co., Ltd.; and the cement is P.O 42.5 grade ordinary portland cement.

[0060] The planting soil is selected from the south area test soil of the Ministry of Education Key Laboratory of River and Lake Health Intelligence Sensing and Ecological Restoration in Wuhan, Hubei Province; the greenery additive is ferrous sulfate; and the organic material is soybean powder particle, which is purchased from Tianbao Biological Engineering Co., Ltd.

[0061] The modified attapulgite in the examples and comparative examples is prepared according to the following steps:

[0062] (1) Take biochar and potassium hydroxide, add water and ultrasonically stir for 1 h (the mass ratio of biochar: potassium hydroxide: water = 1:3:5), then filter, and the product is sequentially dried, ground and passed through a 0.42 mm aperture sieve to obtain a powder;

[0063] (2) Mix 5 g of the powder in step (1) with 5 g of attapulgite powder (previously passed through a 0.42 mm aperture sieve), heat to 500℃ at a temperature increasing rate of 10℃·min -1 -1 under a nitrogen atmosphere for 1 h pyrolysis reaction, and after the reaction, wash the product with deionized water until pH = 6.5-7.0 to obtain attapulgite-based biochar;

[0064] (3) Add 10 g of ferric chloride solution (attapulgite-based biochar: ferric chloride solution = 2:5, actually introduced by FeCl3·6H2O, the concentration of the ferric chloride solution is 2 mol·L -1 -1 ) and 20 g of thiourea solution (the concentration is 1 mol·L -1 -1 ) to 4 g of attapulgite-based biochar, then ultrasonically stir at 80℃ and dry at 105℃, and calcine the product in a nitrogen atmosphere, the calcination temperature is 700℃ and the calcination time is 2 h. Then mix with water, and use NaOH solution (the concentration is 2 mol·L -1) The pH of the adjusting system is adjusted to 6.5-7.5 and is left for 24 hours, and finally, the modified palygorskite is prepared by washing with deionized water for multiple times and drying (the drying temperature is 60°C, and the drying time is 12 hours), namely, the hydrothermal iron modified palygorskite.

[0065] The zeolite-based composite material in the examples and comparative examples is prepared by the following method: grinding the zeolite and palygorskite, mixing after passing through a 2mm aperture sieve, incorporating cement (P.O 42.5 grade ordinary portland cement) and a foaming agent to make a blank, and curing in a steam box for 24 hours, wherein the mass ratio of the zeolite and palygorskite is 4:6, the cement is 10% of the total mass of the zeolite, cement and palygorskite, and the foaming agent is sodium bicarbonate, and the amount added is 0.10% of the total mass of the zeolite, cement and palygorskite.

[0066] Example 1

[0067] A riverbank ecological substrate is prepared from the following components by mass parts: 100 parts of planting soil, 3 parts of the modified palygorskite, 1 part of the zeolite-based composite material, 0 parts of biochar, 3 parts of cement, 1.5 parts of greening additives and 7 parts of organic materials.

[0068] The riverbank ecological substrate is prepared by the following method: drying, crushing and sieving the planting soil to remove coarse particles; weighing the modified palygorskite, zeolite-based composite material, cement and greening additives according to the proportion, adding water (the water content of the prepared riverbank ecological substrate is 15-20%) and mixing with the planting soil to obtain an initial improvement, and finally adding organic materials.

[0069] Example 2

[0070] A riverbank ecological substrate is prepared from the following components by mass parts: 100 parts of planting soil, 3 parts of the modified palygorskite, 1 part of the zeolite-based composite material, 2 parts of biochar, 3 parts of cement, 1.5 parts of greening additives and 7 parts of organic materials.

[0071] The riverbank ecological substrate is prepared by the following method: drying, crushing and sieving the planting soil to remove coarse particles; weighing the modified palygorskite, biochar, zeolite-based composite material, cement and greening additives according to the proportion, adding water (the water content of the prepared riverbank ecological substrate is 15-20%) and mixing with the planting soil to obtain an initial improvement, and finally adding organic materials.

[0072] Example 3

[0073] A riverbank ecological substrate is prepared from the following components by mass parts: 100 parts of planting soil, 5 parts of the modified palygorskite, 1 part of the zeolite-based composite material, 2 parts of biochar, 3 parts of cement, 1.5 parts of greening additives and 7 parts of organic materials.

[0074] The riverbank ecological substrate was prepared according to the method described in Example 1.

[0075] Comparative Example 1

[0076] Planting soil was used as the ecological substrate.

[0077] Comparative Example 2

[0078] This comparative example provides a riverbank ecological substrate, which is based on Example 1, and only the modified attapulgite is omitted, and the other raw materials remain unchanged. The preparation method of the riverbank ecological substrate is described in Example 1.

[0079] Comparative Example 3

[0080] This comparative example provides a riverbank ecological substrate, which is based on Example 1, and only the fraction of modified attapulgite is changed to "1 part", and the other raw materials remain unchanged. The preparation method of the riverbank ecological substrate is described in Example 1.

[0081] Comparative Example 4

[0082] This comparative example provides a riverbank ecological substrate, which is based on Example 1, and only the fraction of modified attapulgite is changed to "5 parts", and the other raw materials remain unchanged. The preparation method of the riverbank ecological substrate is described in Example 1.

[0083] Comparative Example 5

[0084] This comparative example provides a riverbank ecological substrate, which is based on Example 1, and only the fraction of modified attapulgite is changed to "7 parts", and the other raw materials remain unchanged. The preparation method of the riverbank ecological substrate is described in Example 1.

[0085] Comparative Examples 6-10

[0086] A riverbank ecological substrate was prepared from the following components in parts by mass: 100 parts of planting soil, the modified attapulgite described above, 1 part of zeolite-based composite material, 1 part of biochar, 3 parts of cement, 1.5 parts of greening additives, and 7 parts of organic material. Among them, the fraction of modified attapulgite is 0, 1, 3, 5 and 7 parts, respectively, corresponding to Comparative Example 6, Comparative Example 7, Comparative Example 8, Comparative Example 9 and Comparative Example 10.

[0087] The riverbank ecological substrate was prepared according to the method described in Example 1.

[0088] Comparative Example 11

[0089] This comparative example provides a riverbank ecological substrate, which is based on Example 2, and only the modified attapulgite is omitted, and the other raw materials remain unchanged. The preparation method of the riverbank ecological substrate is described in Example 2.

[0090] Comparative Example 12

[0091] The comparative example provides a riverbank ecological substrate, on the basis of Example 2, only the fraction of modified palygorskite is changed to "1 part", and other raw materials remain unchanged. The preparation method of the riverbank ecological substrate is described in Example 2.

[0092] Comparative Example 13

[0093] The comparative example provides a riverbank ecological substrate, on the basis of Example 2, only the fraction of modified palygorskite is changed to "7 parts", and other raw materials remain unchanged. The preparation method of the riverbank ecological substrate is described in Example 2.

[0094] Comparative Examples 14-18

[0095] A riverbank ecological substrate is prepared from the following components in parts by mass: 100 parts of planting soil, the modified palygorskite described above, 1 part of zeolite-based composite material, 3 parts of biochar, 3 parts of cement, 1.5 parts of greening additives, and 7 parts of organic materials. Among them, the fraction of modified palygorskite is 0, 1, 3, 5, and 7 parts, respectively, corresponding to Comparative Example 14, Comparative Example 15, Comparative Example 16, Comparative Example 17, and Comparative Example 18.

[0096] The riverbank ecological substrate is prepared according to the method described in Example 1.

[0097] Comparative Examples 19-23

[0098] A riverbank ecological substrate is prepared from the following components in parts by mass: 100 parts of planting soil, the modified palygorskite described above, 1 part of zeolite-based composite material, 4 parts of biochar, 3 parts of cement, 1.5 parts of greening additives, and 7 parts of organic materials. Among them, the fraction of modified palygorskite is 0, 1, 3, 5, and 7 parts, respectively, corresponding to Comparative Example 19, Comparative Example 20, Comparative Example 21, Comparative Example 22, and Comparative Example 23.

[0099] The riverbank ecological substrate is prepared according to the method described in Example 1.

[0100] The influence of the prepared ecological substrates on plant growth is evaluated, and the specific steps are as follows: 1500 seeds of Bermudagrass (20g / m 2 ) are sown, and after sowing, regular watering is maintained, the vegetation growth state is observed every day for the first 20 days, the soil is kept moist, and the germination rate of the plant samples is recorded every day for the first 20 days, and the average plant height of the samples is continuously observed and recorded every 5 days.

[0101]

[0102]

[0103] Figure 1Statistical curve of planting days and germination rate of Cynodon dactylon planted in the riverbank ecological substrate prepared by using each embodiment and comparative example. From Figure 1 It can be seen that the influence of the addition amount of modified attapulgite and biomass charcoal on seed germination showed different trends and effects at different stages of the test, and the germination details are shown in Table 1.

[0104] Referring to Figure 1 In the early stage of germination (1-4 days), it was observed that the influence of different proportions of modified attapulgite and biomass charcoal on the germination of Cynodon dactylon seeds was relatively small. In this period, the germination rate was not significantly different between groups, and the overall performance of seed germination was relatively balanced. In the middle stage (5-15 days), which is the key period of rapid seed germination, the influence of different proportions of ecological substrate on the germination rate of seeds became very obvious, and the modification of modified attapulgite and biomass charcoal had an inhibitory effect on seed germination. In the later stage (after 16 days), the number of observed seed germination was small, and the germination process basically stopped.

[0105] Specifically, when the proportion of modified attapulgite (i.e., the ratio of modified attapulgite to planting soil) is greater than 5% and the proportion of biomass charcoal (i.e., the ratio of biomass charcoal to planting soil) is greater than 2%, the addition amount of modified attapulgite and biomass charcoal has a significant inhibitory effect on seed germination, which may be due to the fact that modified attapulgite and biomass charcoal increase the pH of the soil, and when the soil is alkaline, it may inhibit the enzyme activity of the seeds, affecting the absorption of water and nutrients by the seeds, thereby inhibiting germination.

[0106] Plants, as an important part of ecological revetment, are very important to the erosion resistance of the soil on the bank slope. Plant roots can greatly improve the soil and sand fixation capacity of the bank slope, thereby reducing water and soil loss. The plant growth experiment of the riverbank ecological substrate prepared in Examples 1-3 proves that the substrate can provide a good environment for plant growth, and therefore, the riverbank ecological substrate has excellent erosion resistance.

[0107] Figure 2 Statistical graph of total nitrogen adsorption efficiency of sewage by the riverbank ecological substrate prepared in each embodiment and comparative example, wherein 0%, 1%, 2%, 3%, and 4% respectively correspond to different proportions of biomass charcoal content, and the nitrogen content of the sewage is 1 mg / L. Here, the substrate corresponding to Comparative Example 1 is not counted, so there are a total of 25 groups of samples. The specific operation of the statistics is as follows: total nitrogen determination is carried out in accordance with the “Determination of Total Nitrogen in Water - Alkaline Persulfate Digestion Ultraviolet Spectrophotometric Method” of the People's Republic of China National Environmental Protection Standard HJ 636-2012.

[0108] From Figure 2It can be seen that different substrate combinations have different effects on nitrogen adsorption. The substrate combinations with nitrogen adsorption efficiency exceeding 80% are 8# (1% modified attapulgite + 1% biochar), 9# (3% modified attapulgite + 1% biochar), 10# (5% modified attapulgite + 1% biochar), 11# (7% modified attapulgite + 1% biochar), 13# (1% modified attapulgite + 2% biochar), 14# (3% modified attapulgite + 2% biochar), 15# (5% modified attapulgite + 2% biochar), and 19# (3% modified attapulgite + 3% biochar, and 15# has the best nitrogen adsorption efficiency.

[0109] Figure 3 A statistical graph of the adsorption efficiency of the riverbank ecological substrate prepared for each example and comparative example on total phosphorus in sewage is shown, wherein 0%, 1%, 2%, 3% and 4% correspond to different proportions of biochar content, and the phosphorus content of the sewage is 1 mg / L. Here, the substrate corresponding to Comparative Example 1 is not counted, so there are 25 groups of samples in total. The specific operation of the statistics is as follows: total phosphorus determination is carried out according to the national environmental protection standard GB 11893-89 “Determination of total phosphorus in water by platinum acid spectrophotometry”.

[0110] From Figure 3 It can be seen that different substrate combinations have different effects on phosphorus adsorption. The substrate combinations with phosphorus adsorption efficiency exceeding 85% are 4# (3% modified attapulgite + 0% biochar), 10# (9% modified attapulgite + 1% biochar), 8# (1% modified attapulgite + 1% biochar), 9# (3% modified attapulgite + 1% biochar), 11# (7% modified attapulgite + 1% biochar), 12# (0% modified attapulgite + 2% biochar), 13# (1% modified attapulgite + 2% biochar), 14# (3% modified attapulgite + 2% biochar), 17# (0% modified attapulgite + 3% biochar), 18# (1% modified attapulgite + 3% biochar), and 22# (0% modified attapulgite + 4% biochar), and 14# has the best phosphorus adsorption efficiency.

[0111] Figure 4It is the total nitrogen adsorption kinetics curve of No. 4 substrate, No. 14 substrate and No. 15 substrate. The specific operation is: accurately weigh 1g of the combined substrate with different proportions by using an electronic balance, a total of 3 mass proportions, set 3 parallel samples for each substrate, put into a 100mL centrifuge tube, add 50mL of NH4Cl solution with a concentration of 5mg / L, cover the cover and put on the shaking table, run under the operating condition of 150r / min and 25℃ without interruption, set the shaking time as 0.5h, 1h, 2h, 3h, 5h, 7h, 9h, 12h and 24h respectively, take out the centrifuge tube after the shaking is completed, and measure the total nitrogen concentration of the solution by using HJ 636-2012 “Determination of total nitrogen in water - Alkaline potassium persulfate digestion-UV spectrophotometric method”. From Figure 4 It can be seen that: the adsorption process is mainly divided into three stages. In the early stage (0~5 hours), the adsorption rate of all substrates to TN (total nitrogen) is fast, and the adsorption amount increases significantly with the extension of time; in the middle stage (5~12 hours), the adsorption rate decreases; in the later stage (12~24 hours), the slope of the adsorption kinetics curve decreases to the minimum, indicating that the adsorption rate further slows down. After 24 hours, the adsorption amount of different proportion substrates to TN presents the rule of 14#>15#>4#.

[0112] Figure 5 It is the total phosphorus absorption kinetics curve of No. 4 substrate, No. 14 substrate and No. 15 substrate. The specific operation is: accurately weigh 1g of the combined substrate with different proportions by using an electronic balance, a total of 3 mass proportions, set 3 parallel samples for each substrate, put into a 100mL centrifuge tube, add 50ml of KH2PO4 solution with a concentration of 5mg / L respectively, cover the cover and put on the shaking table, run under the operating condition of 150r / min and 25℃ without interruption, set the shaking time as 0.5h, 1h, 2h, 3h, 5h, 7h, 9h, 12h and 24h respectively, take out the centrifuge tube after the shaking is completed, and measure the total phosphorus concentration of the solution by using GB 11893-89 “Determination of total phosphorus in water - Platinum acid spectrophotometric method”. From Figure 5 It can be seen that: the adsorption process is mainly divided into three stages. In the early stage (0~5 hours), the adsorption rate of all substrates to TP (total phosphorus) is fast, and the adsorption amount increases significantly with the extension of time; in the middle stage (5~12 hours), the adsorption rate decreases; in the later stage (12~24 hours), the slope of the adsorption kinetics curve decreases to the minimum, indicating that the adsorption rate further slows down. After 24 hours, the adsorption amount of different proportion substrates to TP presents the rule of 15#>14#>4#.

[0113] The specific embodiments of the application described above do not constitute a limitation on the protective scope of the application. Any various other corresponding changes and modifications made according to the technical concept of the application should be included in the protective scope of the claims of the application.

Claims

1. A method for preparing modified attapulgite, characterized in that, Includes the following steps: (1) Take biochar and potassium hydroxide, add water and stir, then filter. The product is dried, ground and sieved to obtain powder. (2) The powder is mixed with attapulgite powder and pyrolysis reaction is carried out under a protective gas atmosphere. After the reaction is completed, the product is washed until pH=6.5~7.0 to obtain attapulgite-based biochar. (3) Add ferric chloride solution and thiourea solution to the attapulgite-based biochar, stir and dry, calcine the product in a protective gas atmosphere, mix with water, adjust the pH of the system to 6.5~7.5 and let it stand, and finally wash and dry to obtain the modified attapulgite.

2. The method for preparing modified attapulgite according to claim 1, characterized in that, The mass ratio of biochar to potassium hydroxide in step (1) is 1:3; In step (1), the mass ratio of water to potassium hydroxide is 5:

3. The mass ratio of the attapulgite powder in step (2) to the powder in step (1) is 1:1~2.

3. The method for preparing modified attapulgite according to claim 1, characterized in that, The protective gas mentioned in steps (2) and (3) is nitrogen; The temperature of the pyrolysis reaction in step (2) is 450~550℃, and the reaction time is 1h; The method for adjusting the pH of the system in step (3) is to add NaOH solution; The calcination temperature in step (3) is 700℃, and the calcination time is 2 hours; The resting time in step (3) is 24 hours.

4. The method for preparing modified attapulgite according to claim 1, characterized in that, In step (3), the mass ratio of attapulgite-based biochar to ferric chloride solution is 1.6~2:5; In step (3), the mass ratio of attapulgite-based biochar to thiourea solution is 1~2:5; The concentration of the ferric chloride solution in step (3) is 2 mol·L⁻¹. -1 ; The concentration of the thiourea solution in step (3) is 1 mol·L⁻¹. -1 .

5. Modified attapulgite prepared by the method of any one of claims 1 to 4.

6. A riverbank ecological substrate, characterized in that, It is prepared from the following components in parts by weight: 100-120 parts planting soil, 3-6 parts modified attapulgite as described in claim 5, 1-3 parts zeolite-based composite material, 0-3 parts biochar, 1-3 parts cement, 1-2 parts greening additive and 5-10 parts organic material; The zeolite-based composite material is prepared by the following method: zeolite and attapulgite are ground, sieved, mixed, and then cement and foaming agent are added to form a blank, which is then cured in a steam box. The mass ratio of zeolite, cement and attapulgite is 5~10:1~3:1~3.

7. The riverbank ecological substrate according to claim 6, characterized in that, The foaming agent is a carbonate, and the cement is PO 42.5 grade ordinary Portland cement; The greening additive is ferrous sulfate; The organic material is soybean flour.

8. The riverbank ecological substrate according to claim 7, characterized in that, The carbonate is at least one of calcium carbonate, magnesium carbonate, and sodium bicarbonate; The amount of foaming agent added is 0.10% to 0.15% of the total mass of zeolite, cement, and attapulgite; The ambient temperature for the curing process is 60℃ and the humidity is 90%.

9. A method for preparing the riverbank ecological substrate according to any one of claims 6 to 8, characterized in that, Includes the following steps: Weigh the modified attapulgite, biochar, zeolite-based composite material, cement, and greening additives according to the specified proportions, add water and mix evenly with the planting soil to obtain the initial improved material, and then add organic materials.

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