Precipitation supported slow-release carbon-based iron fertilizer and preparation method thereof

Abstract

The invention discloses a precipitation-supported slow-release carbon-based iron fertilizer and a preparation method thereof, and the preparation method specifically comprises the following steps: firstly, putting a biological carapace heavy metal adsorbent into a calcium hydroxide solution for dipping, drying, then putting the biological carapace heavy metal adsorbent into a ferrous sulfate solution for dipping in two times, and finally drying and granulating. Precipitated ferric hydroxide, a ferrous hydroxide mixture and excessive ferric sulfate are uniformly dispersed and attached to the interiors of pore channels of the porous adsorbent, and the excessive ferric sulfate can quickly provide iron ions for antagonistic cadmium and arsenic ion absorption in the early growth stage of rice. Precipitated ferric hydroxide and ferrous hydroxide wrapped by calcium sulfate in the porous adsorbent not only can realize long-acting slow release of iron ions, but also can reduce the oxygen content of soil, and iron ion antagonism and precipitation type adsorption loading modes are carried out in the whole growth process of rice, so that the release period of the iron ions is greatly prolonged, and the soil quality is improved. The iron fertilizer disclosed by the invention has an excellent rice cadmium-arsenic antagonism effect and has an excellent application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of safe rice production in paddy fields polluted by heavy metals, and in particular to a precipitation-loaded slow-release carbon-based iron fertilizer and a preparation method thereof. Background Art

[0002] In recent years, with the development of industry and the extensive use of agricultural inputs, the world is facing increasingly serious soil environmental safety issues, among which heavy metal pollution has received the most attention. At present, in order to implement the main responsibility for food security, continuous and extensive research has been carried out across the country on the safe use of contaminated farmland, especially cadmium and arsenic contaminated farmland, and certain results have been achieved.

[0003] In fact, heavy metal pollutants that enter the soil cannot be separated from the soil simply and quickly. For the treatment of contaminated soil, the chemical remediation technology of passivation / stabilization method is currently mainly used, that is, the total amount of heavy metals in the soil is not reduced, but through technical means, the chemical remediation agents added to the soil are used to react with pollutants to undergo oxidation, reduction, ion exchange and other chemical reactions to reduce the mobility and bioavailability of pollutants, thereby curbing their impact and ecological risks, reducing the absorption of heavy metals by crops such as rice, and achieving safe production of agricultural products. Carbon-based materials, due to their special pore structure, high surface negative charge density, and a large number of oxygen-containing functional groups, can adsorb and fix heavy metal ions, thereby reducing the effective content of heavy metals in the soil and reducing the toxicity of heavy metals to plants, and have received more attention. For example, the effective Cd leaching amount of soil under pig bone biochar treatment was reduced by 38%; the Cd concentration in soil pore water under Quercus biochar treatment decreased by 66.0%; the application of rice husk biochar can reduce the Cd content of rapeseed aboveground by 68.40% and the Cd content of underground by 60.62%.

[0004] However, due to the influence of raw material structure, composition and other factors, the fixation effect of biochar materials prepared from different raw materials on soil Cd is different. In addition, the existing carbon-based passivation materials generally have technical defects such as high cost, insufficient persistence, and large amount of passivation agent. The application amount usually needs to reach 200-300kg / mu. Therefore, it is necessary to design a carbon-based passivation agent material that can be used to reduce the biological effectiveness of cadmium and arsenic elements in the soil. This material should have long-term effectiveness, that is, long-term antagonism, and outstanding passivation effect. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a precipitation-loaded slow-release carbon-based iron fertilizer and a preparation method thereof. The preparation method is specifically as follows: firstly, a biological crustacean heavy metal adsorbent is immersed in a calcium hydroxide solution, and after drying, the biocrust heavy metal adsorbent is immersed in a ferrous sulfate solution twice, and finally dried and granulated. The slow-release iron fertilizer is loaded by precipitation, and the precipitated ferric hydroxide, ferrous hydroxide mixture and excess ferric sulfate are uniformly dispersed and attached to the pores of the porous adsorbent. Excess ferric sulfate can quickly provide iron ions to antagonize the absorption of cadmium and arsenic ions in the early stage of rice growth. Calcium sulfate encapsulates the precipitated ferric hydroxide and ferrous hydroxide, which can realize long-term slow-release of iron ions and reduce the oxygen content of soil. After application in the field, iron ion antagonism is carried out in the whole process of rice growth. The precipitation-type adsorption loading method greatly increases the release period of iron ions. Compared with traditional slow-release fertilizers, the iron fertilizer of the present invention has excellent cadmium and arsenic antagonism of rice and has excellent application prospects.

[0006] In order to achieve the above technical effects, the following technical solutions are adopted: A method for preparing a precipitation-loaded slow-release carbon-based iron fertilizer comprises the following steps: Step S1: crush the biocrust adsorbent into particles with a diameter not greater than 1 mm, impregnate with Ca(OH)2 solution, filter and dry at low temperature; Step S2: The biological crustacean adsorbent particles dried in step S1 are immersed in a FeSO4 solution, taken out, filtered, and directly dried at low temperature, and then crushed into particles with a diameter of no more than 1 mm to obtain iron-based loaded biological crustacean particles; Step S3: the iron-based biological shell particles dried in step S2 are immersed in the FeSO4 solution again, taken out, filtered and dried, and then directly dried at low temperature and crushed into particles with a diameter of no more than 1 mm to obtain iron-based biological shell particles with excess ferrous sulfate; Step S4: using an adhesive, granulating the iron-based loaded biological crustacean particles with excess ferrous sulfate in step S3 according to a mass ratio, drying at low temperature, and sieving after drying to obtain a precipitated loaded slow-release carbon-based iron fertilizer.

[0007] Furthermore, in step S1, the concentration of the Ca(OH)2 solution is 5% to 10%; and the immersion time is more than 4 hours.

[0008] Furthermore, in step S2, the concentration of the FeSO4 solution is 5% to 10%; the immersion time is more than 4 hours; in step S3, the concentration of the FeSO4 solution is 5% to 10%; the immersion time is more than 1 hour.

[0009] Furthermore, the ratio of the concentration of the FeSO4 solution to the concentration of the Ca(OH)2 solution is 1.1~1.5:1, the ratio of the volume of the Ca(OH)2 solution to the biological crustacean adsorbent particles in step S1 is 1~1.5:1; the ratio of the volume of the FeSO4 solution in step S2 to the biological crustacean adsorbent particles dried in step S1 is 1.5~2:1; the ratio of the volume of the FeSO4 solution in step S3 to the biological crustacean adsorbent particles dried in step S2 is 1~1.5:1.

[0010] Furthermore, the low-temperature drying temperature is 55-65°C.

[0011] Furthermore, the adhesive comprises one or more of gypsum, quicklime and slaked lime; the mass ratio of the adhesive to the iron-based biocrust particles with excess ferrous sulfate is 1:3-1:5, and water is added for bonding and granulation, and the amount of water added is 30-40% of the total mass of the adhesive; the low-temperature drying temperature in step S4 is 50-55°C, and the precipitated loaded slow-release carbon-based iron fertilizer in step S4 is filtered through a mesh screen, and the particle size is 2-3 mm.

[0012] Furthermore, the mass ratio of the raw gypsum to the iron-based biological crust particles with excess ferrous sulfate is 1:3, the mass ratio of the quicklime to the iron-based biological crust particles with excess ferrous sulfate is 1:3, and the mass ratio of the slaked lime to the iron-based biological crust particles with excess ferrous sulfate is 1:5.

[0013] Furthermore, the preparation method of the biological crustacean adsorbent is: Under the condition of isolating oxygen, treating the biological shell at a temperature of 300-600° C. for 2-3 hours, and modifying the treated biological shell to obtain the modified biological shell adsorbent; Modification of the treated biocrustacean includes the following steps: Carboxymethylation: reacting the treated biocrust with chloroacetic acid in an alkaline solution to obtain a carboxymethyl biocrust; the alkaline solution is a 10% to 60% NaOH solution; the mass ratio of the treated biocrust: alkali: chloroacetic acid is 1: (2-4): (1.2-3); Dialdehydeation: reacting carboxymethyl biocarapace with an oxidant to obtain dialdehyde carboxymethyl biocarapace; the oxidant is periodic acid and its salt; the mass ratio of the oxidant to the carboxymethyl biocarapace is (1-2):1; Schiff base reaction: reacting dialdehyde carboxymethyl biological crust with a water-soluble amino compound to obtain a dialdehyde carboxymethyl biological crust Schiff base; the water-soluble amino compound is one or more of aniline, benzylamine, phenylethylamine, m-aminophenol, n-hexylamine, n-octylamine, aminothiazole, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, aminobenzothiazole, and m-acetylaniline; the mass ratio of the water-soluble amino compound to the dialdehyde carboxymethyl biological crust is (1-5):1; the biological crust is one or more of shrimp shells, tortoise shells, crab shells, turtle shells, and fish scales.

[0014] A precipitation-loaded slow-release carbon-based iron fertilizer is prepared by any one of the above preparation methods.

[0015] The precipitation-loaded slow-release carbon-based iron fertilizer is used to reduce the absorption of cadmium ions by rice.

[0016] The beneficial effects of the present invention are: The invention discloses a precipitation-loaded slow-release carbon-based iron fertilizer and a preparation method thereof. The invention uniformly loads ferric hydroxide and ferrous hydroxide into a porous material by precipitation. The specific method is as follows: firstly, a biological crustacean heavy metal adsorbent is immersed in a calcium hydroxide solution, filtered and dried at low temperature, and then immersed again in a ferrous sulfate solution with a slightly higher concentration, filtered and dried to obtain particles, and then immersed again in a ferrous sulfate solution with a slightly higher concentration, filtered and dried to obtain particles, and then granulated to obtain a precipitation-loaded slow-release carbon-based iron fertilizer. The slow-release iron fertilizer is loaded by precipitation, and the precipitated ferric hydroxide and ferrous hydroxide thereof, and calcium sulfate particles mixed in the precipitate generated simultaneously with the precipitation of ferric hydroxide and ferrous hydroxide, and the excess ferric sulfate covered on the precipitate are uniformly dispersed and attached to the inside of the pores of the porous adsorbent to synergistically act, and the excess ferric sulfate can quickly provide iron ions for entry in the early stage of rice growth. Antagonize the absorption of cadmium and arsenic ions and reduce the expression of cadmium and arsenic ion transport proteins in rice roots; the biological crustacean adsorbent, precipitated ferric hydroxide and ferrous hydroxide, and calcium sulfate particles mixed with the precipitate generated at the same time as the precipitation work together synergistically to achieve long-term slow release of iron ions. After application in the field, iron ion antagonism is carried out throughout the growth process of rice to reduce the absorption of cadmium and arsenic ions by rice. The precipitated loading method and the mixed coating of the reaction product calcium sulfate greatly improve the release law and speed of iron ions through the adsorption and precipitation of porous materials, and greatly increase the release cycle of iron ions. Ferric hydroxide and ferrous hydroxide precipitates are alkaline precipitates, which can control the pH value of the soil and reduce the mobility of cadmium and arsenic. In addition, since the precipitate is generated in the porous material and has the covering and coating effect of the calcium sulfate particles, a part of the ferrous hydroxide precipitate can be retained while the ferric hydroxide precipitate is generated. After the ferrous hydroxide precipitate is released in the soil, it can quickly obtain oxygen in the soil, react itself to generate ferric hydroxide precipitate, and also consume oxygen in the soil, thereby reducing the oxygen content in the soil, reducing the oxygen content in the rhizosphere of rice, and reducing the ionic conversion of heavy metals from a reduced state to an oxidized state. The multiple effects work synergistically with each other. Compared with traditional slow-release fertilizers, the precipitated loaded slow-release carbon-based iron fertilizer of the present invention has an excellent antagonistic effect on cadmium and arsenic in rice, can achieve a significant reduction in the cadmium content in rice with a smaller dosage, and has an excellent application prospect. DETAILED DESCRIPTION

[0017] The present invention is further described below, and the protection scope of the present invention is not limited to the following: Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0018] Embodiment 1: In this embodiment, the preparation method of the biological crustacean adsorbent is: The biological crustaceans were treated at 300°C for 2h under oxygen-free conditions; Modifying the treated biological crust to obtain the modified biological crust adsorbent comprises the following steps: Carboxymethylation: reacting the treated biocrust with chloroacetic acid in an alkaline solution to obtain a carboxymethyl biocrust; the alkaline solution is a 10% NaOH solution; the mass ratio of the treated biocrust: alkali: chloroacetic acid is 1:2:1.2; Dialdehydeation: reacting carboxymethyl biocarapace with an oxidant to obtain dialdehyde carboxymethyl biocarapace; the oxidant is periodic acid; the mass ratio of the oxidant to the carboxymethyl biocarapace is 1:1; Schiff base reaction: reacting dialdehyde carboxymethyl biological crust with a water-soluble amino compound to obtain a dialdehyde carboxymethyl biological crust Schiff base; the water-soluble amino compound is aniline; the mass ratio of the water-soluble amino compound to the dialdehyde carboxymethyl biological crust is 1:1; the biological crust is a shrimp shell.

[0019] The preparation method of a precipitation-loaded slow-release carbon-based iron fertilizer of this embodiment is as follows, comprising the following steps: Step S1: crush the biological crustacean adsorbent into particles with a diameter not greater than 1 mm, soak them in a Ca(OH)2 solution, filter and dry them at a low temperature at 55°C; the concentration of the Ca(OH)2 solution is 5%; the soaking time is more than 4 hours; the volume ratio of the Ca(OH)2 solution to the biological crustacean adsorbent particles is 1:1; Step S2: The biological crustacean adsorbent particles dried in step S1 are immersed in a FeSO4 solution, taken out and filtered, and then directly dried at low temperature and crushed into particles with a diameter of no more than 1 mm at a temperature of 55°C to obtain iron-based loaded biological crustacean particles; the concentration of the FeSO4 solution is 5.5%; the immersion time is more than 4 hours; the volume ratio of the FeSO4 solution to the biological crustacean adsorbent particles dried in step S1 is 1.5:1; Step S3: The iron-based biological crustacean particles dried in step S2 are immersed in the FeSO4 solution again, and after being fished out and filtered, they are directly dried at low temperature and crushed into particles with a diameter not greater than 1 mm at a temperature of 55°C to obtain iron-based biological crustacean particles with excess ferrous sulfate; the concentration of the FeSO4 solution is 5.5%; the immersion time is more than 1 hour; the volume ratio of the FeSO4 solution to the biological crustacean adsorbent particles dried in step S2 is 1:1.

[0020] Step S4: using an adhesive, the adhesive includes gypsum, quicklime, and slaked lime; the mass ratio of quicklime to iron-based biological crust particles with excess ferrous sulfate is 1:3, the mass ratio of quicklime to iron-based biological crust particles with excess ferrous sulfate is 1:4, and the mass ratio of slaked lime to iron-based biological crust particles with excess ferrous sulfate is 1:5; adding water for bonding and then granulating, the amount of water added is 30% of the total mass of the adhesive; granulating the iron-based biological crust particles with excess ferrous sulfate in step S3 according to the mass ratio, drying at low temperature, the temperature is 50°C, and sieving after drying to obtain precipitation-loaded slow-release carbon-based iron fertilizer 1.

[0021] Embodiment 2: In this embodiment, the preparation method of the biological crustacean adsorbent is: The biological carapace was treated at 600°C for 3h under oxygen-free conditions; Modifying the treated biological crust to obtain the modified biological crust adsorbent comprises the following steps: Carboxymethylation: reacting the treated biocrust with chloroacetic acid in an alkaline solution to obtain a carboxymethyl biocrust; the alkaline solution is a 60% NaOH solution; the mass ratio of the treated biocrust: alkali: chloroacetic acid is 1:4:3; Dialdehydeation: reacting carboxymethyl biocarapace with an oxidant to obtain dialdehyde carboxymethyl biocarapace; the oxidant is periodic acid; the mass ratio of the oxidant to the carboxymethyl biocarapace is 2:1; Schiff base reaction: react dialdehyde carboxymethyl biological crust with a water-soluble amino compound to obtain a dialdehyde carboxymethyl biological crust Schiff base; the water-soluble amino compound is benzylamine; the mass ratio of the water-soluble amino compound to the dialdehyde carboxymethyl biological crust is 5:1; the biological crust is a crab shell.

[0022] The preparation method of a precipitation-loaded slow-release carbon-based iron fertilizer of this embodiment is as follows, comprising the following steps: Step S1: crush the biological crustacean adsorbent into particles with a diameter not greater than 1 mm, soak them in a Ca(OH)2 solution, filter and dry them at low temperature, the temperature is 65°C; the concentration of the Ca(OH)2 solution is 6.67%; the soaking time is more than 4 hours; the volume ratio of the Ca(OH)2 solution to the biological crustacean adsorbent particles is 1.5:1; Step S2: The biological crustacean adsorbent particles dried in step S1 are immersed in a FeSO4 solution, taken out, filtered and dried, and then directly dried at low temperature and crushed into particles with a diameter of no more than 1 mm at a temperature of 65°C to obtain iron-based loaded biological crustacean particles; the concentration of the FeSO4 solution is 10%; the immersion time is more than 4 hours; the volume ratio of the FeSO4 solution to the biological crustacean adsorbent particles dried in step S1 is 2:1; Step S3: The iron-based biological crustacean particles dried in step S2 are immersed in the FeSO4 solution again, and after being fished out and filtered, they are directly dried at low temperature and crushed into particles with a diameter not greater than 1 mm at a temperature of 65°C to obtain iron-based biological crustacean particles with excess ferrous sulfate; the concentration of the FeSO4 solution is 10%; the immersion time is more than 1 hour; the volume ratio of the FeSO4 solution to the biological crustacean adsorbent particles dried in step S2 is 1.5:1.

[0023] Step S4: using an adhesive, the adhesive includes raw gypsum, quicklime, and slaked lime; the mass ratio of raw gypsum to iron-based biological crust particles with excess ferrous sulfate is 1:3, the mass ratio of quicklime to iron-based biological crust particles with excess ferrous sulfate is 1:4, and the mass ratio of slaked lime to iron-based biological crust particles with excess ferrous sulfate is 1:5; adding water for bonding and then granulating, the amount of water added is 40% of the total mass of the adhesive; granulating the iron-based biological crust particles with excess ferrous sulfate in step S3 according to the mass ratio, drying at low temperature, the temperature is 55°C, and sieving after drying to obtain precipitation-loaded slow-release carbon-based iron fertilizer 2.

[0024] Embodiment 3: In this embodiment, the preparation method of the biological crustacean adsorbent is: The biological carapace was treated at 500°C for 2.5h under oxygen-free conditions; Modifying the treated biological crust to obtain the modified biological crust adsorbent comprises the following steps: Carboxymethylation: reacting the treated biocrust with chloroacetic acid in an alkaline solution to obtain a carboxymethyl biocrust; the alkaline solution is a 30% NaOH solution; the mass ratio of the treated biocrust: alkali: chloroacetic acid is 1:3:2; Dialdehydeation: reacting carboxymethyl biocarapace with an oxidant to obtain dialdehyde carboxymethyl biocarapace; the oxidant is periodic acid; the mass ratio of the oxidant to the carboxymethyl biocarapace is 1.5:1; Schiff base reaction: reacting dialdehyde carboxymethyl biological crust with a water-soluble amino compound to obtain a dialdehyde carboxymethyl biological crust Schiff base; the water-soluble amino compound is m-phenylenediamine; the mass ratio of the water-soluble amino compound to the dialdehyde carboxymethyl biological crust is 3:1; the biological crust is fish scales.

[0025] The preparation method of a precipitation-loaded slow-release carbon-based iron fertilizer of this embodiment is as follows, comprising the following steps: Step S1: crush the biological crustacean adsorbent into particles with a diameter not greater than 1 mm, soak them in a Ca(OH)2 solution, filter and dry them at low temperature, the temperature is 60°C; the concentration of the Ca(OH)2 solution is 6%; the soaking time is more than 4 hours; the volume ratio of the Ca(OH)2 solution to the biological crustacean adsorbent particles is 1.3:1; Step S2: The biological crustacean adsorbent particles dried in step S1 are immersed in a FeSO4 solution, taken out and filtered, and then directly dried at low temperature and crushed into particles with a diameter of no more than 1 mm at a temperature of 60°C to obtain iron-based loaded biological crustacean particles; the concentration of the FeSO4 solution is 9%; the immersion time is more than 4 hours; the volume ratio of the FeSO4 solution to the biological crustacean adsorbent particles dried in step S1 is 1.8:1; Step S3: The iron-based biological crustacean particles dried in step S2 are immersed in the FeSO4 solution again, and after being fished out and filtered, they are directly dried at low temperature and crushed into particles with a diameter not greater than 1 mm at a temperature of 60°C to obtain iron-based biological crustacean particles with excess ferrous sulfate; the concentration of the FeSO4 solution is 9%; the immersion time is more than 1 hour; the volume ratio of the FeSO4 solution to the biological crustacean adsorbent particles dried in step S2 is 1.3:1.

[0026] Step S4: using an adhesive, the adhesive includes one or more of raw gypsum, quicklime, and slaked lime; the mass ratio of raw gypsum to iron-based biocrust particles with excess ferrous sulfate is 1:3, the mass ratio of quicklime to iron-based biocrust particles with excess ferrous sulfate is 1:4, and the mass ratio of slaked lime to iron-based biocrust particles with excess ferrous sulfate is 1:5; adding water for bonding and then granulating, the amount of water added is 30% of the total mass of the adhesive; granulating the iron-based biocrust particles with excess ferrous sulfate in step S3 according to the mass ratio, drying at low temperature, the temperature is 55°C, and sieving after drying to obtain precipitation-loaded slow-release carbon-based iron fertilizer 3.

[0027] Comparative Example 1: Based on Example 1: In this comparative example, the preparation method of the biological crustacean adsorbent is consistent with that in Example 1.

[0028] The preparation method of a common loaded slow-release carbon-based iron fertilizer in this comparative example is as follows, comprising the following steps: Step S1: crush the biological crustacean adsorbent into particles with a diameter not greater than 1 mm, immerse in FeSO4 solution, remove and filter, directly dry at low temperature, and then crush into particles with a diameter not greater than 1 mm at a temperature of 55°C to obtain iron-based loaded biological crustacean particles; the concentration of FeSO4 solution is 5.5%; the immersion time is more than 4 hours; the volume ratio of FeSO4 solution to biological crustacean adsorbent particles is 1.5:1; Step S2: The iron-based loaded biological crust particles dried in step S1 are immersed in the FeSO4 solution again, and after being fished out and filtered, they are directly dried at low temperature and crushed into particles with a diameter not greater than 1 mm at a temperature of 55°C to obtain iron-based loaded biological crust particles; the concentration of the FeSO4 solution is 5.5%; the immersion time is more than 1 hour; the volume ratio of the FeSO4 solution to the biological crust adsorbent particles dried in step S1 is 1:1.

[0029] Step S3: using an adhesive, the adhesive includes raw gypsum, quicklime, and slaked lime; the mass ratio of raw gypsum to iron-based loaded biological crust particles is 1:3, the mass ratio of quicklime to iron-based loaded biological crust particles is 1:4, and the mass ratio of slaked lime to iron-based loaded biological crust particles is 1:5; adding water for bonding and then granulating, the amount of water added is 30% of the total mass of the adhesive; granulating the iron-based loaded biological crust particles in step S2 according to the mass ratio, drying at low temperature, the temperature is 50°C, and sieving after drying to obtain ordinary loaded slow-release carbon-based iron fertilizer 4.

[0030] Comparative Example 2: In this comparative example, the preparation method of the biological crustacean adsorbent is consistent with that in Example 1.

[0031] The preparation method of a common loaded slow-release carbon-based iron fertilizer in this comparative example is as follows, comprising the following steps: Step S1: loading with iron hydroxide powder: crush the biological crustacean adsorbent into particles with a diameter of no more than 1 mm, take 3 parts by weight of the biological crustacean adsorbent particles and 8 parts by weight of the iron hydroxide powder, mix the biological crustacean adsorbent particles and the iron hydroxide powder evenly, add them into a shaking device for shaking, and after the shaking is completed, use a screening device to separate the biological crustacean adsorbent particles loaded with iron hydroxide powder for later use; Step S2: using an adhesive, the adhesive includes raw gypsum, quicklime, and slaked lime; the mass ratio of raw gypsum to the biological shell adsorbent particles loaded with iron hydroxide powder is 1:3, the mass ratio of quicklime to the biological shell adsorbent particles loaded with iron hydroxide powder is 1:4, and the mass ratio of slaked lime to the biological shell adsorbent particles loaded with iron hydroxide powder is 1:5; adding water for bonding and then granulating, the amount of water added is 30% of the total mass of the adhesive; granulating the biological shell adsorbent particles loaded with iron hydroxide powder in step S1 according to the mass ratio, low-temperature drying at a temperature of 50°C, and sieving after drying to obtain ordinary loaded slow-release carbon-based iron fertilizer 5.

[0032] Comparative Example 3: In this comparative example, the preparation method of the biological crustacean adsorbent is consistent with that in Example 1.

[0033] The preparation method of a precipitated loaded slow-release carbon-based iron fertilizer of this comparative example is as follows, comprising the following steps: Step S1: crush the biological crustacean adsorbent into particles with a diameter of no more than 1 mm, impregnate with FeSO4 solution, filter and dry at low temperature, the temperature is 55°C; the concentration of FeSO4 solution is 5.5%; the impregnation time is more than 4 hours; the volume ratio of FeSO4 solution to biological crustacean adsorbent particles is 1:1; Step S2: The biological crustacean adsorbent particles dried in step S1 are immersed in a Ca(OH)2 solution, and after being taken out and filtered, they are directly dried at low temperature and crushed into particles with a diameter of no more than 1 mm at a temperature of 55°C to obtain iron-based loaded biological crustacean particles; the concentration of the Ca(OH)2 solution is 5%; the immersion time is more than 4 hours; the volume ratio of the Ca(OH)2 solution to the biological crustacean adsorbent particles dried in step S1 is 1.5:1; Step S3: using an adhesive, the adhesive includes raw gypsum, quicklime, and slaked lime; the mass ratio of raw gypsum to iron-based loaded biological crust particles is 1:3, the mass ratio of quicklime to iron-based loaded biological crust particles is 1:4, and the mass ratio of slaked lime to iron-based loaded biological crust particles is 1:5; adding water for bonding and then granulating, the amount of water added is 30% of the total mass of the adhesive; granulating the iron-based loaded biological crust particles in step S3 according to the mass ratio, drying at low temperature, the temperature is 50°C, and sieving after drying to obtain precipitation-loaded slow-release carbon-based iron fertilizer 6.

[0034] Comparative Example 4: In this comparative example, the preparation method of the biological crustacean adsorbent is consistent with that in Example 1.

[0035] The preparation method of a precipitated loaded slow-release carbon-based iron fertilizer of this comparative example is as follows, comprising the following steps: Step S1: crush the biological crustacean adsorbent into particles with a diameter not greater than 1 mm, soak them in a Ca(OH)2 solution, filter and dry them at a low temperature at 55°C; the concentration of the Ca(OH)2 solution is 5%; the soaking time is more than 4 hours; the volume ratio of the Ca(OH)2 solution to the biological crustacean adsorbent particles is 1:1; Step S2: The biological crustacean adsorbent particles dried in step S1 are immersed in a FeSO4 solution, taken out and filtered, and then directly dried at low temperature and crushed into particles with a diameter of no more than 1 mm at a temperature of 55°C to obtain iron-based loaded biological crustacean particles; the concentration of the FeSO4 solution is 5.5%; the immersion time is more than 4 hours; the volume ratio of the FeSO4 solution to the biological crustacean adsorbent particles dried in step S1 is 1.5:1; Step S3: using an adhesive, the adhesive includes raw gypsum, quicklime, and slaked lime; the mass ratio of raw gypsum to iron-based biocrust particles with a slight excess of ferrous sulfate is 1:3, the mass ratio of quicklime to iron-based biocrust particles with a slight excess of ferrous sulfate is 1:4, and the mass ratio of slaked lime to iron-based biocrust particles with a slight excess of ferrous sulfate is 1:5; adding water for bonding and then granulating, the amount of water added is 30% of the total mass of the adhesive; granulating the iron-based biocrust particles with a slight excess of ferrous sulfate in step S3 according to the mass ratio, drying at a low temperature of 50°C, and sieving after drying to obtain precipitation-loaded slow-release carbon-based iron fertilizer 7.

[0036] Comparative Example 5: In this comparative example, the preparation method of the biological crustacean adsorbent is consistent with that in Example 1.

[0037] The preparation method of a precipitated loaded slow-release carbon-based iron fertilizer of this comparative example is as follows, comprising the following steps: Step S1: crush the biological crustacean adsorbent into particles with a diameter not greater than 1 mm, soak them in a Ca(OH)2 solution, filter and dry them at a low temperature at 55°C; the concentration of the Ca(OH)2 solution is 5%; the soaking time is more than 4 hours; the volume ratio of the Ca(OH)2 solution to the biological crustacean adsorbent particles is 1:1; Step S2: The biological crustacean adsorbent particles dried in step S1 are immersed in a FeSO4 solution, the immersed biological crustacean adsorbent particles are taken out and filtered, and then immersed in clean water for more than 6 hours, taken out and filtered, and then low-temperature dried and crushed into particles with a diameter of no more than 1 mm at a temperature of 55°C to obtain iron-based loaded biological crustacean particles; the concentration of the FeSO4 solution is 5.5%; the immersion time is more than 4 hours; the volume ratio of the FeSO4 solution to the biological crustacean adsorbent particles dried in step S1 is 1.5:1; Step S3: using an adhesive, the adhesive includes raw gypsum, quicklime, and slaked lime; the mass ratio of raw gypsum to iron-based loaded biological crust particles is 1:3, the mass ratio of quicklime to iron-based loaded biological crust particles is 1:4, and the mass ratio of slaked lime to iron-based loaded biological crust particles is 1:5; adding water for bonding and then granulating, the amount of water added is 30% of the total mass of the adhesive; granulating the iron-based loaded biological crust particles in step S3 according to the mass ratio, drying at low temperature, the temperature is 50°C, and sieving after drying to obtain precipitation-loaded slow-release carbon-based iron fertilizer 8.

[0038] The slow-release carbon-based iron fertilizers in Examples 1-3 and Comparative Examples 1-5 are evaluated below: The experiment was conducted in a paddy field with a pH of 5.33, total cadmium of 0.71 mg / kg, total arsenic of 53 mg / kg, and organic matter content of 28.1 g / kg. The soil was a latent paddy soil with medium overall fertility. The entire field was divided into 27 plots, each with an area of ​​30 m 2 Every 3 plots were a treatment area, with a total of 9 treatment areas. Treatment area 1 was a blank control group CK (no slow-release carbon-based iron fertilizer passivator was applied), and treatment areas 2-9 were the slow-release carbon-based iron fertilizer passivators in Examples 1-3 and Comparative Examples 1-5, respectively; the same rice variety was planted in all of them, namely Taiyou 398.

[0039] Rice seedlings were raised in the field. Two days before rice transplanting, 45 kg / mu of compound fertilizer (total nutrient content 45%, of which N-P2O5-K2O=15-15-15) was applied. Different treatment areas were simultaneously applied with 50 kg / mu of iron fertilizer described in Examples 1-3 and Comparative Examples 1-5, respectively, and plowed once to ensure that the fertilizer and iron fertilizer were fully mixed with the soil. Manual transplanting or seedling throwing can be used in the transplanting process. After the rice turns green, 8 kg / mu of urea is applied during the tillering stage. Other field water and fertilizer management methods and pest and disease control methods are consistent with traditional methods. After the rice matures, each plot is harvested and measured for yield, and the cadmium and arsenic contents in the rice are determined.

[0040] The method for determining the cadmium and arsenic content of brown rice is as follows: take 0.1g brown rice powder sample, add 5mL nitric acid and 3.0mL hydrogen peroxide solution, cover and cold digest overnight, digest for 2h using a graphite digester and dilute to 25mL, and analyze and determine the cadmium and arsenic concentrations in the digestion solution using an inductively coupled plasma mass spectrometer. The test results are shown in Table 1: Table 1 Differences in rice yield and cadmium and arsenic content in brown rice among treatments Processing Area deal with Rice yield (kg / mu) Cadmium content in brown rice (mg / kg) Arsenic content in rice (mg / kg ( 1 Blank control CK 535±28 0.660±0.079 0.596±0.053 2 Example 1 550±15 0.146±0.023 0.241±0.011 3 Example 2 541±20 0.143±0.019 0.249±0.019 4 Example 3 538±16 0.146±0.013 0.243±0.025 5 Comparative Example 1 534±22 0.417±0.031 0.458±0.047 6 Comparative Example 2 533±13 0.378±0.029 0.426±0.033 7 Comparative Example 3 529±17 0.301±0.022 0.395±0.024 8 Comparative Example 4 537±19 0.268±0.017 0.361±0.022 9 Comparative Example 5 540±11 0.347±0.028 0.437±0.026 Note 1: Except for the different treatment methods, the other conventional cultivation methods of each group in the table are the same.

[0041] Note 2: According to the requirements of "GB 2762-2022 National Food Safety Standard Limits of Contaminants in Food", the cadmium content of qualified rice should be less than or equal to 0.2 mg / kg, and the arsenic content should be less than or equal to 0.35 mg / kg.

[0042] In summary, the present invention discloses a precipitation-loaded slow-release carbon-based iron fertilizer and a preparation method thereof. The present invention uniformly loads ferric hydroxide and ferrous hydroxide into a porous material by precipitation. The specific method is as follows: firstly, a biological crustacean heavy metal adsorbent is immersed in a calcium hydroxide solution, filtered and dried at low temperature, and then immersed again in a ferrous sulfate solution with a slightly higher concentration, filtered and dried to obtain particles, and then immersed again in a ferrous sulfate solution with a slightly higher concentration, filtered and dried to obtain particles, and granulated to obtain a precipitation-loaded slow-release carbon-based iron fertilizer. This slow-release iron fertilizer is loaded by precipitation, and its precipitated ferric hydroxide and ferrous hydroxide, and calcium sulfate particles mixed in the precipitate generated simultaneously with the precipitation of ferric hydroxide and ferrous hydroxide, and the excess ferric sulfate covered on the precipitate are uniformly dispersed and attached to the pores of the porous adsorbent to act synergistically, and the excess ferric sulfate can quickly provide iron in the early stage of rice growth. Ions antagonize the absorption of cadmium and arsenic ions and reduce the expression of cadmium and arsenic ion transporters in rice roots; the biological crustacean adsorbent, precipitated ferric hydroxide and ferrous hydroxide, and calcium sulfate particles generated simultaneously with the precipitation and mixed in the precipitate work together to achieve long-term slow release of iron ions. After application in the field, iron ions are antagonized throughout the growth process of rice to reduce the absorption of cadmium and arsenic ions by rice. The precipitated loading method and the mixed coating of the reaction product calcium sulfate greatly improve the release law and speed of iron ions through the adsorption and precipitation of porous materials, and greatly increase the release cycle of iron ions. Ferric hydroxide and ferrous hydroxide precipitates are alkaline precipitates, which can control the pH of the soil and reduce the mobility of cadmium and arsenic. In addition, since the precipitate is generated in the porous material and has the covering and coating effect of the calcium sulfate particles, a part of the ferrous hydroxide precipitate can be retained while the ferric hydroxide precipitate is generated. After the ferrous hydroxide precipitate is released in the soil, it can quickly obtain oxygen in the soil, react itself to generate ferric hydroxide precipitate, and also consume oxygen in the soil, thereby reducing the oxygen content in the soil, reducing the oxygen content in the rhizosphere of rice, and reducing the ionic conversion of heavy metals from a reduced state to an oxidized state. The multiple effects work synergistically with each other. Compared with traditional slow-release fertilizers, the precipitated loaded slow-release carbon-based iron fertilizer of the present invention has an excellent antagonistic effect on cadmium and arsenic in rice, can achieve a significant reduction in the cadmium content in rice with a smaller dosage, and has an excellent application prospect.

[0043] At this point, those skilled in the art recognize that, although the embodiments of the present invention have been shown and described in detail herein, many other variations or modifications that conform to the principles of the present invention can still be directly determined or derived based on the contents disclosed in the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and recognized as covering all such other variations or modifications.

Claims

1. A method for preparing a precipitation-loaded slow-release carbon-based iron fertilizer, characterized in that: The preparation method comprises the following steps: Step S1: crush the biocrust adsorbent into particles with a diameter not greater than 1 mm, impregnate with Ca(OH)2 solution, filter and dry at low temperature; Step S2: The biological crustacean adsorbent particles dried in step S1 are immersed in a FeSO4 solution, taken out, filtered, and directly dried at low temperature, and then crushed into particles with a diameter of no more than 1 mm to obtain iron-based loaded biological crustacean particles; Step S3: the iron-based biological shell particles dried in step S2 are immersed in the FeSO4 solution again, taken out, filtered and dried, and then directly dried at low temperature and crushed into particles with a diameter of no more than 1 mm to obtain iron-based biological shell particles with excess ferrous sulfate; Step S4: using an adhesive, granulating the iron-based loaded biological crustacean particles with excess ferrous sulfate in step S3 according to a mass ratio, drying at low temperature, and sieving after drying to obtain a precipitated loaded slow-release carbon-based iron fertilizer.

2. A method for preparing a precipitation-loaded slow-release carbon-based iron fertilizer as described in claim 1, characterized in that: The concentration of the Ca(OH)2 solution in step S1 is 5% to 10%; the immersion time is more than 4 hours.

3. A method for preparing a precipitation-loaded slow-release carbon-based iron fertilizer as claimed in claim 1, characterized in that: In step S2, the concentration of the FeSO4 solution is 5% to 10%; the immersion time is more than 4 hours; in step S3, the concentration of the FeSO4 solution is 5% to 10%; the immersion time is more than 1 hour.

4. A method for preparing a precipitation-loaded slow-release carbon-based iron fertilizer as claimed in claim 1, characterized in that: The ratio of the concentration of the FeSO4 solution to the concentration of the Ca(OH)2 solution is 1.1-1.5:1, and the ratio of the volume of the Ca(OH)2 solution to the biological crustacean adsorbent particles in step S1 is 1-1.5:1; the ratio of the volume of the FeSO4 solution in step S2 to the biological crustacean adsorbent particles dried in step S1 is 1.5-2:1; the ratio of the volume of the FeSO4 solution in step S3 to the biological crustacean adsorbent particles dried in step S2 is 1-1.5:

1.

5. A method for preparing a precipitation-loaded slow-release carbon-based iron fertilizer as claimed in claim 1, characterized in that: The low-temperature drying temperature is 55-65°C.

6. A method for preparing a precipitation-loaded slow-release carbon-based iron fertilizer as claimed in claim 1, characterized in that: The adhesive comprises one or more of gypsum, quicklime and slaked lime; water is added for bonding and then granulation is performed, and the amount of water added is 30-40% of the total mass of the adhesive; the mass ratio of the adhesive to the iron-based biological shell particles with excess ferrous sulfate is 1:3-1:5, the low-temperature drying temperature in step S4 is 50-55°C, and the precipitation-loaded slow-release carbon-based iron fertilizer in step S4 is filtered through a mesh screen, and the particle size is 2-3 mm.

7. A method for preparing a precipitation-loaded slow-release carbon-based iron fertilizer as claimed in claim 6, characterized in that: The mass ratio of the raw gypsum to the iron-based biological crust particles with excess ferrous sulfate is 1:3, the mass ratio of the quicklime to the iron-based biological crust particles with excess ferrous sulfate is 1:4, and the mass ratio of the slaked lime to the iron-based biological crust particles with excess ferrous sulfate is 1:

5.

8. A method for preparing a precipitation-loaded slow-release carbon-based iron fertilizer as claimed in claim 1, characterized in that: The preparation method of the biological crustacean adsorbent is: Under the condition of isolating oxygen, treating the biological shell at a temperature of 300-600° C. for 2-3 hours, and modifying the treated biological shell to obtain the modified biological shell adsorbent; Modification of the treated biocrustacean includes the following steps: Carboxymethylation: reacting the treated biocrust with chloroacetic acid in an alkaline solution to obtain a carboxymethyl biocrust; the alkaline solution is a 10% to 60% NaOH solution; the mass ratio of the treated biocrust: alkali: chloroacetic acid is 1: (2-4): (1.2-3); Dialdehydeation: reacting carboxymethyl biocarapace with an oxidant to obtain dialdehyde carboxymethyl biocarapace; the oxidant is periodic acid and its salt; the mass ratio of the oxidant to the carboxymethyl biocarapace is (1-2):1; Schiff base reaction: reacting dialdehyde carboxymethyl biological crust with a water-soluble amino compound to obtain a dialdehyde carboxymethyl biological crust Schiff base; the water-soluble amino compound is one or more of aniline, benzylamine, phenylethylamine, m-aminophenol, n-hexylamine, n-octylamine, aminothiazole, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, aminobenzothiazole, and m-acetylaniline; the mass ratio of the water-soluble amino compound to the dialdehyde carboxymethyl biological crust is (1-5):1; the biological crust is one or more of shrimp shells, tortoise shells, crab shells, turtle shells, and fish scales.

9. A precipitation-loaded slow-release carbon-based iron fertilizer, characterized in that: The iron fertilizer is prepared by the preparation method according to any one of claims 1 to 8.

10. A precipitation-loaded slow-release carbon-based iron fertilizer as claimed in claim 9, characterized in that: The precipitation-loaded slow-release carbon-based iron fertilizer is used to reduce the absorption of cadmium ions by rice.