Lake sediment phosphorus-fixing granules and preparation method and application thereof

Abstract

The present invention relates to a lake sediment phosphorus-fixing granule and a preparation method and application thereof. The preparation method of the granule includes: preparation of iron-modified attapulgite, preparation of calcium nitrate-polyvinyl alcohol solution, preparation of BC700 biochar and preparation of phosphorus-fixing granule. The present invention achieves a good phosphorus-fixing effect by using iron-modified attapulgite and calcium nitrate to jointly treat phosphorus in lake sediments, controls the release of nitrate over time, and solves the problems of ineffective release of calcium nitrate and subsequent pollution caused by direct addition of calcium nitrate. The granules prepared by the present invention not only have obvious effects in phosphorus fixation in lake sediments, but also can greatly reduce other pollution such as antibiotics in water. The phosphorus-fixing granules of the present invention can be used for the comprehensive management of lake sediment restoration, and the materials used are all natural products or degradable materials, will not cause water pollution, and are green and environmentally friendly.

Description

Technical Field

[0001] The invention relates to the technical field of lake eutrophication treatment, in particular to lake bottom mud phosphorus-fixing particles and a preparation method and application thereof. Background Art

[0002] Eutrophication of lakes is accompanied by the outbreak of blue algae blooms, leading to the death of aquatic plants and animals due to lack of oxygen, economic losses and serious damage to the ecological environment of the water body. The main factor of eutrophication is phosphorus in lakes, and the soluble orthophosphate released by sediments is considered to be one of the main causes of eutrophication. In particular, shallow lakes (such as Wuliangsuhai, Chaohu Lake, Poyang Lake, etc.) are less than six meters deep, and the bottom mud is easily disturbed and releases endogenous phosphorus, further exacerbating eutrophication.

[0003] Nitrate addition as a method to inhibit the release of endogenous phosphorus in lakes is believed to directly fix phosphorus through oxidation reactions, oxidizing Fe 2+ Oxidized to Fe 3+ , by forming iron oxides, phosphorus in sediments and overlying water can be better fixed, thereby inhibiting the release of endogenous phosphorus in lakes. However, directly adding nitrates will cause the problem of ineffective nitrate release. Excessive nitrates often produce ecotoxicity in surface waters by converting into nitrites, causing subsequent pollution and bringing potential environmental risks.

[0004] Therefore, the existing methods for treating lake sediments have failed to effectively solve the problem of the release of endogenous phosphorus in lakes, and it is difficult to provide effective long-term endogenous phosphorus control measures while ensuring ecological safety. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is how to effectively reduce the release of endogenous phosphorus in lakes while avoiding ecological risks, and to provide lake sediment phosphorus-fixing particles and a preparation method and application thereof.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing lake sediment phosphorus-fixing particles, comprising the following steps:

[0008] (1) Preparation of iron-modified attapulgite:

[0009] 1-1. Prepare attapulgite:

[0010] Grind the attapulgite and sieve it;

[0011] 1-2. Iron modification of attapulgite:

[0012] The attapulgite treated in step 1-1 is mixed evenly with ferric chloride to obtain a mixture A; deionized water is added to the mixture A, and after shaking, a mixed solution is obtained;

[0013] 1-3. Treatment of modified attapulgite:

[0014] The mixed solution is centrifuged, and the precipitate after centrifugation is washed, then dried, ground again, and sieved to obtain iron-modified attapulgite for later use;

[0015] (2) Preparation of calcium nitrate-polyvinyl alcohol solution:

[0016] 2-1. Preparation of calcium nitrate solution:

[0017] Add deionized water to calcium nitrate, heat and dissolve to obtain a calcium nitrate solution;

[0018] 2-2. Preparation of calcium nitrate-polyvinyl alcohol solution:

[0019] Continue heating the calcium nitrate solution, add polyvinyl alcohol to the calcium nitrate solution when heating begins, heat to boiling, obtain a calcium nitrate-polyvinyl alcohol solution, maintain the solution temperature, and set aside;

[0020] (3) Preparation of biochar:

[0021] 3-1. Prepare biochar raw materials:

[0022] Corn cobs were used as raw materials, washed with deionized water, dried to constant weight, ground and sieved to obtain powder;

[0023] 3-2. Burning biochar:

[0024] The powder obtained in step 3-1 is fired, washed, filtered and dried to obtain biochar for later use;

[0025] (4) Preparation of fixed phosphorus granules:

[0026] 4-1. Mixed raw materials:

[0027] The iron-modified attapulgite and sodium carboxymethyl cellulose were mixed evenly to obtain a mixture B; the biochar and calcium peroxide were mixed evenly to obtain a mixture C; the mixture B was first added to the calcium nitrate-polyvinyl alcohol solution, and then added to the mixture C to obtain a mixture D;

[0028] 4-2. Preparation of phosphorus-fixing granules:

[0029] The mixture D is made into spherical particles and air-dried naturally to obtain the product.

[0030] Preferably, in step 1-1 of step (1), the sieving is through a 100-mesh sieve;

[0031] In step 1-2 of step (1), the ferric chloride is ferric chloride octahydrate; the oscillation temperature is 20-30° C., the rotation speed is 100-300 r / min, and the oscillation time is 22-26 h.

[0032] Preferably, in step 1-2 of step (1), the mass ratio of the attapulgite to ferric chloride octahydrate is 2:1; and the volume ratio of the mass of the mixture to deionized water is 30 g:50 mL.

[0033] Preferably, in steps 1-3 of step (1), the centrifugal speed is 5000-8000 r / min, and the centrifugal time is 10-15 min; the drying temperature is 100° C., and the drying time is 1 h; and after grinding again, the product is sieved through a 100-mesh screen.

[0034] Preferably, in step 2-1 of step (2), the calcium nitrate is calcium nitrate tetrahydrate; the mass ratio of the calcium nitrate tetrahydrate to the volume of deionized water is 7g:100mL; the heating temperature is 50-65°C, and the heating is maintained for 5-10 minutes after dissolution;

[0035] In step 2-2 of step (2), the mass ratio of polyvinyl alcohol to calcium nitrate tetrahydrate is 1:7; the mixture is allowed to stand for 10-15 minutes after boiling; and the heating rate during heating is 10°C / min.

[0036] Preferably, in step 3-1 of step (3), the drying temperature is 50° C. and the sieving is through a 50-mesh sieve;

[0037] In step 3-2 of step (3), the firing temperature is 700° C. and the firing time is 8 hours; deionized water and anhydrous ethanol are used for washing respectively; the drying temperature is 110° C. and the drying time is 24 hours.

[0038] Preferably, in step 4-1 of step (4), the mixing mass ratio of the iron-modified attapulgite and sodium carboxymethyl cellulose is 5:1; the mixing mass ratio of the biochar and calcium peroxide is 1:1; and the volume ratio of the mass of the mixture B, the mass of the mixture C and the calcium nitrate-polyvinyl alcohol solution is 12g:3g:100mL.

[0039] Preferably, in step 4-2 of step (4), the diameter of the spherical particles is 1-3 cm; and the natural air-drying time is 24 hours.

[0040] The invention provides lake sediment phosphorus-fixing particles, which are prepared by the preparation method.

[0041] The invention provides an application of the lake sediment phosphorus-fixing particles in lake sediment phosphorus-fixing.

[0042] The technical solution of the present invention achieves the following beneficial technical effects:

[0043] (1) The present invention achieves a good phosphorus fixation effect by using iron-modified clay (i.e., iron-modified attapulgite) and calcium nitrate to treat phosphorus in lake sediments. Among them, iron-modified clay, as a low-cost material with little impact on the environment, absorbs phosphorus in sediments to form Fe-P precipitates, thereby inhibiting the release of phosphorus after phosphorus fixation. Calcium nitrate and calcium peroxide react with water to generate Ca 2+ As a coexisting ion, it can improve the adsorption effect of iron-modified attapulgite on phosphorus. In addition, the oxidation of the two can convert Fe in lake sediment into 2+ Oxidized to Fe 3+ , further reducing the release of endogenous phosphorus.

[0044] (2) The present invention achieves the effect of slow release of calcium nitrate by preparing phosphorus-fixing particles, thereby solving the problems of ineffective release of calcium nitrate and subsequent pollution caused by direct addition of calcium nitrate, and solving the problems of ecological risks and insufficient control of phosphorus release in the prior art.

[0045] (3) The phosphorus-fixing particles of the present invention not only have a significant effect in fixing phosphorus in lake sediments, but can also significantly reduce other pollution such as antibiotics in water, such as tetracycline. The phosphorus-fixing particles of the present invention can be used for comprehensive management of lake sediment restoration.

[0046] (4) The materials used in the present invention are all natural products or degradable materials, will not cause water pollution, and are green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A schematic diagram of the process flow of the method for preparing the phosphorus-fixing particles of the present invention;

[0048] Figure 2 Physical appearance of the phosphorus-fixing particles obtained in Example 1 of the present invention;

[0049] Figure 3 A graph showing the change of phosphorus content in muddy water over time after adding the phosphorus-fixing particles obtained in Example 1 of the present invention;

[0050] Figure 4 Comparison of the phosphorus fixation effects of the phosphorus fixation particles obtained in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention;

[0051] Figure 5 A graph showing the change in nitric acid release of the phosphorus-fixing granules obtained in Example 1 of the present invention and bulk calcium nitrate with the same content in deionized water;

[0052] Figure 6 A graph showing the change of dissolved oxygen content in muddy water over time after adding the phosphorus-fixing particles obtained in Example 1 of the present invention;

[0053] Figure 7 A graph showing the change in antibiotic content in a tetracycline solution over time after adding the phosphorus-fixing granules obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical scheme and technical effect of the invention of this application clearer, the technical scheme in the embodiment of this application will be clearly and completely described below in conjunction with the drawings in the embodiment of this application. Obviously, the described embodiment is a part of the embodiment of this application, not all the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0055] In view of the technical problems existing in the prior art, the present invention provides a method for preparing lake sediment phosphorus-fixing particles, comprising the following steps:

[0056] (1) Preparation of iron-modified attapulgite:

[0057] 1-1. Prepare attapulgite:

[0058] Grind the attapulgite and sieve it;

[0059] 1-2. Iron modification of attapulgite:

[0060] The attapulgite treated in step 1-1 is mixed evenly with ferric chloride to obtain a mixture A; deionized water is added to the mixture A, and after shaking, a mixed solution is obtained;

[0061] 1-3. Treatment of modified attapulgite:

[0062] The mixed solution is centrifuged, and the precipitate after centrifugation is washed, then dried, ground again, and sieved to obtain iron-modified attapulgite for later use;

[0063] (2) Preparation of calcium nitrate-polyvinyl alcohol solution:

[0064] 2-1. Preparation of calcium nitrate solution:

[0065] Add deionized water to calcium nitrate, heat and dissolve to obtain a calcium nitrate solution;

[0066] 2-2. Preparation of calcium nitrate-polyvinyl alcohol solution:

[0067] Continue heating the calcium nitrate solution, add polyvinyl alcohol (PVA) to the calcium nitrate solution when heating begins, heat to boiling, and obtain a calcium nitrate-polyvinyl alcohol solution, maintain the solution temperature, and set aside;

[0068] (3) Preparation of BC700 biochar

[0069] 3-1. Prepare biochar raw materials:

[0070] Corn cobs were used as raw materials, washed with deionized water, dried to constant weight, ground and sieved to obtain powder;

[0071] 3-2. Burning biochar:

[0072] The powder obtained in step 3-1 is fired, washed, filtered and dried to obtain BC700 biochar for later use;

[0073] (4) Preparation of fixed phosphorus granules:

[0074] 4-1. Mixed raw materials:

[0075] The iron-modified attapulgite (i.e., iron-modified clay) and sodium carboxymethyl cellulose were mixed evenly to obtain a mixture B; the BC700 biochar and calcium peroxide were mixed evenly to obtain a mixture C; the mixture B was first added to the calcium nitrate-polyvinyl alcohol solution, and then added to the mixture C to obtain a mixture D;

[0076] 4-2. Preparation of phosphorus-fixing granules:

[0077] The mixture D is made into spherical particles and air-dried naturally to obtain the product.

[0078] Among them, sodium carboxymethyl cellulose and iron-modified attapulgite both have adhesive effects, which can make the particles form. At the same time, iron-modified attapulgite is the main phosphorus fixation adsorbent, so mixing the two first has a better wrapping effect. Then biochar and calcium peroxide are mixed in. The two materials are relatively on the outer layer of the particles, which increases the specific surface area of ​​the particles and improves the phosphorus adsorption. At the same time, calcium peroxide reacts with water in contact, on the one hand, calcium ions are produced, which improve the adsorption efficiency of iron-modified attapulgite as coexisting ions, and on the other hand, the dissolved oxygen content in the water is increased, which helps to improve water quality and the occurrence of phosphorus adsorption.

[0079] In a preferred embodiment of the present invention, in step 1-1 of step (1), the sieving is through a 100-mesh sieve;

[0080] In a preferred embodiment of the present invention, in step 1-2 of step (1), the ferric chloride is ferric chloride octahydrate; the mass ratio of the attapulgite to ferric chloride octahydrate is 2:1; the mass ratio of the mixture to the volume of deionized water is 30 g:50 mL;

[0081] The oscillation temperature is 20-30°C, the rotation speed is 100-300r / min, and the oscillation time is 22-26h.

[0082] In a preferred embodiment of the present invention, the oscillation temperature is 25°C, the rotation speed is 200r / min, and the oscillation time is 24h;

[0083] In a preferred embodiment of the present invention, in steps 1-3 of step (1), the centrifugal speed is 5000-8000 r / min, and the centrifugal time is 10-15 min;

[0084] The washing is performed with pure water until no precipitation occurs in the water after washing using silver nitrate solution, that is, the Cl - The drying temperature is 100°C and the drying time is 1h; the powder is ground again and passed through a 100-mesh sieve;

[0085] In a preferred embodiment of the present invention, the centrifugal speed is 8000r / min and the centrifugal time is 10min;

[0086] In a preferred embodiment of the present invention, in step 2-1 of step (2), the calcium nitrate is calcium nitrate tetrahydrate; the mass ratio of the calcium nitrate tetrahydrate to the volume of deionized water is 7g:100mL; the heating temperature is 50-65°C, and the heating is maintained for 5-10 minutes after dissolution;

[0087] In a preferred embodiment of the present invention, the heating temperature is 50°C, and the temperature is maintained for 5 minutes after heating and dissolving;

[0088] In a preferred embodiment of the present invention, in step 2-2 of step (2), the mass ratio of polyvinyl alcohol to calcium nitrate tetrahydrate is 1:7; the mixture is allowed to stand for 10-15 minutes after boiling; and the heating rate during heating is 10°C / min;

[0089] In a preferred embodiment of the present invention, in step 3-1 of step (3), the drying temperature is 50° C.; the sieving is through a 50-mesh sieve;

[0090] In a preferred embodiment of the present invention, in step 3-2 of step (3), the firing temperature is 700°C and the firing time is 8 hours; deionized water and anhydrous ethanol are used for washing respectively; the drying temperature is 110°C and the drying time is 24 hours;

[0091] In a preferred embodiment of the present invention, in step 4-1 of step (4), the mixing mass ratio of the iron-modified attapulgite to sodium carboxymethyl cellulose is 5:1; the mixing mass ratio of the BC700 biochar to calcium peroxide is 1:1; the mass of the mixture B, the mass of the mixture C, and the volume ratio of the calcium nitrate-polyvinyl alcohol solution are 12g:3g:100mL;

[0092] When adding mixture B and mixture C, the calcium nitrate-polyvinyl alcohol solution is in a slightly boiling state and is added while stirring; the mixture D is viscous and plastic;

[0093] In a preferred embodiment of the present invention, in step 4-2 of step (4), the diameter of the spherical particles is 1-3 cm; and the natural air-drying time is 24 hours.

[0094] The lake sediment phosphorus-fixing particles of the present invention and their preparation method and application are described in detail below through specific embodiments.

[0095] Example 1

[0096] This embodiment provides a method for preparing lake sediment phosphorus-fixing particles, comprising the following steps:

[0097] (1) Preparation of iron-modified attapulgite:

[0098] 1-1. Prepare attapulgite:

[0099] Grind 20 g of attapulgite and pass it through a 100-mesh stainless steel sieve;

[0100] 1-2. Iron modification of attapulgite:

[0101] The attapulgite treated in step 1-1 was mixed evenly with 10 g of ferric chloride octahydrate to obtain a mixture A; 50 mL of deionized water was added to 30 g of the mixture A, and the mixture was oscillated at a constant temperature of 200 r / min at 25° C. for 24 h using a constant temperature oscillator to obtain a mixed solution;

[0102] 1-3. Treatment of modified attapulgite:

[0103] After taking out the mixed solution, put it into a centrifuge tube and centrifuge it in a centrifuge at 8000r / min for 10 minutes. Then take out the centrifuge tube and pour out the supernatant. Wash with pure water until no precipitation can be seen in the washed water with silver nitrate solution, which means that Cl is completely removed. - ; After filtering, dry in a drying oven at 100°C for 1 hour, grind again and pass through a 100-mesh stainless steel sieve; iron-modified attapulgite is obtained and set aside;

[0104] (2) Preparation of calcium nitrate-polyvinyl alcohol solution:

[0105] 2-1. Preparation of calcium nitrate solution:

[0106] Add 100 mL of deionized water to 7 g of calcium nitrate tetrahydrate, heat to 50°C to completely dissolve the calcium nitrate, and maintain the temperature for 5 minutes after reaching the target temperature to obtain a calcium nitrate solution;

[0107] 2-2. Preparation of calcium nitrate-polyvinyl alcohol solution:

[0108] Continue to heat the calcium nitrate solution at a heating rate of 10°C / min. When heating begins, add 1g of polyvinyl alcohol (PVA) to the calcium nitrate solution and heat to boiling to obtain a calcium nitrate-polyvinyl alcohol solution. Keep the solution temperature (slightly boiling state) and let it stand for 15 minutes to allow the calcium nitrate and polyvinyl alcohol to fully contact and mix to obtain a calcium nitrate-polyvinyl alcohol solution for later use.

[0109] (3) Preparation of BC700 biochar

[0110] 3-1. Prepare biochar raw materials:

[0111] Corn cobs (agricultural waste from Liangping District, Chongqing) were used as raw materials. After being washed with deionized water, they were placed in a constant temperature drying oven for drying at 50°C until constant weight was reached. After being ground in a mortar, they were passed through a 50-mesh stainless steel sieve to obtain powder.

[0112] 3-2. Burning biochar:

[0113] Firing the powder obtained in step 3-1, placing the powder in a muffle furnace, calcining at 700°C for 8h, washing the obtained product three times with deionized water, washing the washed powder three times with anhydrous ethanol, filtering, and drying the filtered solid in a vacuum drying oven at 110°C for 24h to obtain BC700 biochar for standby use;

[0114] (4) Preparation of fixed phosphorus granules:

[0115] 4-1. Mixed raw materials:

[0116] 10g of iron-modified attapulgite and 2g of sodium carboxymethyl cellulose were mixed evenly to obtain mixture B; 1g of BC700 biochar and 1g of calcium peroxide were mixed evenly to obtain mixture C; 12g of mixture B was first added to 100mL of calcium nitrate-polyvinyl alcohol solution (slightly boiling state), and then 3g of mixture C was added while stirring to obtain mixture D (viscous and plastic);

[0117] 4-2. Preparation of phosphorus-fixing granules:

[0118] The mixture D was made into spherical particles with a diameter of 1-3 cm using a mold, placed in a ventilated and dry place, and naturally air-dried for 24 hours to obtain particles (the spheres were firm and maintained intact in shape), named particles A.

[0119] The appearance characteristics of the phosphorus-fixing particles obtained in this example are shown in Figure 2 .

[0120] The fixed phosphorus particles obtained in this example are complete, hard, and do not disperse in water; they are stable in water for 30 days.

[0121] Comparative Example 1

[0122] This comparative example provides a method for preparing lake sediment phosphorus-fixing particles, which is different from Example 1 in that the attapulgite in step (1) does not involve ferric chloride modification, that is, the 100-mesh attapulgite obtained by grinding in step 1-1 is directly used to prepare the phosphorus-fixing particles in step (4). The other steps and parameters are the same as those in Example 1. The lake sediment phosphorus-fixing particles are obtained and named as particles B.

[0123] The fixed phosphorus particles obtained in this comparative example are complete, hard, and do not disperse in water.

[0124] Comparative Example 2

[0125] This comparative example provides a method for preparing lake sediment phosphorus-fixing particles, which differs from Example 1 in that potassium nitrate is used instead of calcium nitrate in step (2). The other steps and parameters are the same as those in Example 1. Lake sediment phosphorus-fixing particles are obtained, named particles C.

[0126] The fixed phosphorus particles obtained in this comparative example are complete, hard, and do not disperse in water.

[0127] Comparative Example 3

[0128] This comparative example provides a method for preparing lake sediment phosphorus-fixing particles, which is different from Example 1 in that when preparing the calcium nitrate-polyvinyl alcohol solution in step (2), the mixing mass of polyvinyl alcohol and calcium nitrate tetrahydrate is different; when preparing mixture B in step (4), the mixing mass ratio of iron-modified attapulgite and sodium carboxymethyl cellulose is different;

[0129] In the preparation method of this comparative example: in step (2), the mass of calcium nitrate tetrahydrate is 8 g, and the mass of polyvinyl alcohol is 1 g; in step (4), the mass of iron-modified attapulgite is 9 g, and the mass of sodium carboxymethyl cellulose is 2 g; the other steps and parameters are the same as those in Example 1.

[0130] The solid phosphorus granules obtained in this comparative example do not form agglomerates when stirred, have a fixed shape after drying, and are dispersed in water in small amounts. The undispersed portion is stable in water for less than 1 day.

[0131] Comparative Example 4

[0132] This comparative example provides a method for preparing lake sediment phosphorus-fixing particles, which is different from Example 1 in that when preparing the calcium nitrate-polyvinyl alcohol solution in step (2), the mixing mass of polyvinyl alcohol and calcium nitrate tetrahydrate is different; when preparing mixture B in step (4), the mixing mass ratio of iron-modified attapulgite and sodium carboxymethyl cellulose is different;

[0133] In the preparation method of this comparative example: in step (2), the mass of calcium nitrate tetrahydrate is 6 g, and the mass of polyvinyl alcohol is 1 g; in step (4), the mass of iron-modified attapulgite is 12 g, and the mass of sodium carboxymethyl cellulose is 1 g; the other steps and parameters are the same as those in Example 1.

[0134] The solid phosphorus granules obtained in this comparative example can be stirred into agglomerates, have a stable shape, are tough, and are stable in water for 7 days without dispersing.

[0135] Comparative Example 5

[0136] This comparative example provides a method for preparing lake sediment phosphorus-fixing particles, which is different from Example 1 in that when preparing the calcium nitrate-polyvinyl alcohol solution in step (2), the mixing mass of polyvinyl alcohol and calcium nitrate tetrahydrate is different; when preparing mixture B in step (4), the mixing mass ratio of iron-modified attapulgite and sodium carboxymethyl cellulose is different;

[0137] In the preparation method of this comparative example: in step (2), the mass of calcium nitrate tetrahydrate is 7 g, and the mass of polyvinyl alcohol is 0 g; in step (4), the mass of iron-modified attapulgite is 10 g, and the mass of sodium carboxymethyl cellulose is 3 g; the other steps and parameters are the same as those in Example 1.

[0138] The fixed phosphorus particles obtained in this comparative example dispersed in water and could not exist stably.

[0139] Application Examples

[0140] The muddy water used in the following experiment was prepared with sediment and phosphate solution. The sediment was taken from the center of Wuliangsuhai Lake in Bayannur City, Inner Mongolia Autonomous Region. The grab sediment sampler was used for on-site sampling. The sampling thickness was about 5-10cm deep. The sediment was pretreated at the sampling site, and then stored in a polyethylene ziplock bag with a label and brought back to the laboratory within 2 hours. The collected fresh sediment was treated for impurities in the laboratory, and plastics, stones, garbage, plant debris and other large particles of impurities were screened. The collected sediment was then evenly spread on newspapers and dried naturally in a well-ventilated location for two weeks. Finally, the dried sediment was passed through a 100-mesh sieve, and 50g of sediment was added to 200mL of the prepared 1.5mg / L phosphate solution.

[0141] (1) 10 g of the phosphorus-fixing particles obtained in Example 1 were added to 200 mL of muddy water. According to the "Determination of total phosphorus in water quality - ammonium molybdate spectrophotometry" (GB 11893-89), the total phosphorus content in the water overlying the sediment was detected on days 0, 1, 2, 3, 4, 5, and 8. The results are shown in Figure 3 ,Depend on Figure 3 It can be seen that after the phosphorus-fixing particles were added to the muddy water, the total phosphorus content decreased significantly over time, proving that the particles played a role in fixing phosphorus in the sediment-water system.

[0142] Furthermore, 10 g of the phosphorus-fixing particles obtained in Example 1, Comparative Example 1, and Comparative Example 2 were respectively put into 200 mL of muddy water, and the total phosphorus content in the water overlying the sediment was detected on the 0th, 1st, 2nd, 3rd, and 4th day. Figure 4 ,Depend on Figure 4 It can be seen that the phosphorus-fixing effect of the phosphorus-fixing particles obtained in Example 1 is the best.

[0143] (2) 20 g of the phosphorus-fixing granules obtained in Example 1 (containing about 7 g of calcium nitrate) and 7 g of bulk calcium nitrate of the same content were added to 500 mL of deionized water, respectively. According to the "Surface Water Environmental Quality Standard" (GB3838-2002), the nitrate content in the water body was tested after dilution at 0, 1, 2, 3, 4, 5, and 8 days after adding the phosphorus-fixing granules or bulk calcium nitrate. The comparison results are shown in Figure 5 ,Depend on Figure 5 It can be seen that the half-life of nitrate release by the phosphorus-fixing particles of the present invention is extended by 91.2 hours, which proves that the phosphorus-fixing particles of the present invention play a role in the sustained release of nitrate.

[0144] (3) 10 g of the phosphorus-fixing particles obtained in Example 1 were added to 200 mL of muddy water. According to the technical requirements and detection methods of portable dissolved oxygen measuring instruments (HJ 925-2017), the dissolved oxygen content in the muddy water was detected on the 0th, 1st, 2nd, 3rd, 4th and 5th day after adding the phosphorus-fixing particles. The results are shown in Figure 6 ,Depend on Figure 6 It can be seen that the phosphorus-fixing particles of the present invention play a role in increasing the dissolved oxygen in the water body.

[0145] (4) 10 g of the phosphorus-fixing granules obtained in Example 1 were added to 250 mL of a 20 mg / L tetracycline solution, and the changes in tetracycline content at 0, 1, 2, 3, and 4 days after the addition of the phosphorus-fixing granules were detected. The results are as follows: Figure 7 As shown by Figure 7 It can be seen that the phosphorus-fixing particles of the present invention not only play a role in phosphorus fixation, but also have a certain removal effect on organic pollutants or antibiotics in sediment remediation projects.

[0146] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A method for preparing lake sediment phosphorus-fixing particles, characterized in that: The following steps are involved: (1) Preparation of iron-modified attapulgite: 1-1. Prepare attapulgite: Grind the attapulgite and sieve it; 1-2. Iron modification of attapulgite: The attapulgite treated in step 1-1 is mixed evenly with ferric chloride to obtain a mixture A; deionized water is added to the mixture A, and after shaking, a mixed solution is obtained; The ferric chloride is ferric chloride octahydrate; the mass ratio of the attapulgite to ferric chloride octahydrate is 2:1; the mass ratio of the mixture A to the volume of deionized water is 30g:50mL; 1-3. Treatment of modified attapulgite: The mixed solution is centrifuged, and the precipitate after centrifugation is washed, then dried, ground again, and sieved to obtain iron-modified attapulgite for later use; (2) Preparation of calcium nitrate-polyvinyl alcohol solution: 2-1. Preparation of calcium nitrate solution: Add deionized water to calcium nitrate, heat and dissolve to obtain a calcium nitrate solution; The calcium nitrate is calcium nitrate tetrahydrate; the mass and volume ratio of calcium nitrate tetrahydrate to deionized water is 7g: 100mL; 2-2. Preparation of calcium nitrate-polyvinyl alcohol solution: Continue heating the calcium nitrate solution, add polyvinyl alcohol to the calcium nitrate solution when heating begins, heat to boiling, obtain a calcium nitrate-polyvinyl alcohol solution, maintain the solution temperature, and set aside; The mass ratio of the polyvinyl alcohol to calcium nitrate tetrahydrate is 1:7; (3) Preparation of biochar: 3-1. Prepare biochar raw materials: Corn cobs were used as raw materials, washed with deionized water, dried to constant weight, ground and sieved to obtain powder; 3-2. Burning biochar: The powder obtained in step 3-1 is fired, washed, filtered and dried to obtain biochar for later use; (4) Preparation of phosphorus-fixing granules: 4-1. Mixed raw materials: The iron-modified attapulgite and sodium carboxymethyl cellulose were mixed evenly to obtain a mixture B; the biochar and calcium peroxide were mixed evenly to obtain a mixture C; the mixture B was first added to the calcium nitrate-polyvinyl alcohol solution, and then added to the mixture C to obtain a mixture D; The mixing mass ratio of the iron-modified attapulgite and sodium carboxymethyl cellulose is 5:1; the mixing mass ratio of the biochar and calcium peroxide is 1:1; the volume ratio of the mass of the mixture B, the mass of the mixture C and the calcium nitrate-polyvinyl alcohol solution is 12g:3g:100mL; 4-2. Preparation of phosphorus-fixing granules: The mixture D is made into spherical particles and naturally air-dried to obtain the product.

2. The preparation method according to claim 1, characterized in that: In step 1-1 of step (1), the sieving is through a 100-mesh sieve; In step 1-2 of step (1), the oscillation temperature is 20-30° C., the rotation speed is 100-300 r / min, and the oscillation time is 22-26 h.

3. The preparation method according to claim 1, characterized in that: In steps 1-3 of step (1), the centrifugal speed is 5000-8000 r / min, and the centrifugal time is 10-15 min; the drying temperature is 100° C., and the drying time is 1 h; and after grinding again, the product is passed through a 100-mesh sieve.

4. The preparation method according to claim 1, characterized in that: In step 2-1 of step (2), the heating temperature is 50-65° C. and the temperature is maintained for 5-10 minutes after heating and dissolving; In step 2-2 of step (2), the mixture is allowed to stand for 10-15 minutes after boiling; and the heating rate during heating is 10°C / min.

5. The preparation method according to claim 1, characterized in that: In step 3-1 of step (3), the drying temperature is 50° C. and the sieving is through a 50-mesh sieve; In step 3-2 of step (3), the firing temperature is 700° C. and the firing time is 8 hours; deionized water and anhydrous ethanol are used for washing respectively; the drying temperature is 110° C. and the drying time is 24 hours.

6. The preparation method according to claim 1, characterized in that: In step 4-2 of step (4), the diameter of the spherical particles is 1-3 cm; and the natural air-drying time is 24 hours.

7. A lake sediment phosphorus-fixing granule, characterized in that: The lake sediment phosphorus-fixing particles are prepared by the preparation method described in any one of claims 1-6.

8. Use of the lake sediment phosphorus-fixing particles as claimed in claim 7 in lake sediment phosphorus-fixing.

Images