Slow-release liquid water-soluble fertilizer containing peat-derived humic acid and preparation method thereof

Abstract

The present application relates to the technical field of liquid fertilizer, in particular to a slow-release liquid water-soluble fertilizer containing peat-derived humic acid and a preparation method thereof.The present application uses medium peat as raw material, obtains high-activity humic acid suspension through hot water countercurrent extraction after wet ultrafine ball milling; then adds nitrogen, phosphorus, potassium source and metal salt in sequence to realize constant-temperature complexation reaction and molecular-level anchoring of nutrient ions; finally, compounding double-component suspension stabilizer and dispersion wetting agent, the finished product is prepared through emulsification.The present application uses physical means to extract humic acid throughout the process, avoiding the damage of chemical reagents to active functional groups; the obtained product has multiple advantages of chemical slow-release nutrients, efficient heavy metal ion passivation and super-long room temperature storage stability.

Description

Technical Field

[0001] This invention relates to the field of liquid fertilizer technology, and in particular to a slow-release liquid water-soluble fertilizer containing peat-derived humic acid and its preparation method. Background Technology

[0002] Liquid water-soluble fertilizers are increasingly widely used in modern facility agriculture and fertigation due to their advantages such as high nutrient content, rapid absorption, and convenient application. Among them, humic acid-containing water-soluble fertilizers have become an important category in the liquid fertilizer field because they provide nutrients, improve soil, and stimulate crop growth.

[0003] However, the humic acid used in existing humic acid liquid fertilizers is mostly derived from weathered coal, lignite, and other raw materials. The extraction process often employs strong alkali and high-temperature treatment, which is not only energy-intensive but also causes irreversible damage to the active functional groups (carboxyl groups, phenolic hydroxyl groups, etc.) in the humic acid molecule structure, severely weakening its natural heavy metal complexing and nutrient regulation capabilities. Current technologies often involve simple physical mixing of the extracted humic acid solution with nitrogen, phosphorus, and potassium nutrients. The lack of stable chemical complexation / chelation bonds between humic acid and nutrient ions results in nutrients existing in the solution as free ions, which are easily fixed by the soil or leached after application. Furthermore, the active functional groups of humic acid are not fully utilized, significantly reducing its complexing, solubilizing, and slow-release regulation functions.

[0004] Currently, soil heavy metal pollution is becoming increasingly serious. The accumulation of heavy metal ions such as cadmium, lead, copper, nickel, and chromium in farmland not only endangers crop quality but also threatens human health through the food chain. While existing humic acid-containing liquid fertilizers possess a certain heavy metal complexing ability, their simultaneous and efficient adsorption capacity for multiple heavy metal ions is limited due to the destruction of the active functional groups of humic acid during the extraction process and insufficient content of effective active components. This makes it difficult to meet the increasingly stringent requirements for soil remediation and safe planting. Furthermore, existing technologies that achieve slow release by adding urea-formaldehyde condensates, nano-silica, or attapulgite either involve chemical synthesis, are costly, or have poor system stability, failing to form a comprehensive solution that simultaneously achieves "efficient heavy metal adsorption, slow-release of nutrients, and stable and controllable system." In addition, humic acid-containing liquid fertilizers, especially suspension liquid fertilizers containing insoluble components, are prone to problems such as stratification, precipitation, and clumping during storage, seriously affecting product quality and effectiveness.

[0005] Therefore, developing a liquid water-soluble fertilizer containing peat-based humic acid that combines slow-release chemical nutrients, high-efficiency heavy metal ion adsorption capacity, and long-term room-temperature storage stability is of great significance for improving fertilizer added value, remediating farmland polluted by heavy metals, and promoting green and sustainable agricultural development. Summary of the Invention

[0006] The purpose of this invention is to provide a slow-release liquid water-soluble fertilizer containing peat-derived humic acid and its preparation method. The slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared by the method of this invention has multiple characteristics, including slow-release chemical nutrients, high-efficiency heavy metal ion adsorption capacity, and long-term room temperature storage stability.

[0007] To achieve the above objectives, the present invention provides a method for preparing a slow-release liquid water-soluble fertilizer containing peat-derived humic acid, comprising the following steps: (1) Mix the medium-sized peat with water and wet ball mill to obtain peat slurry; (2) The peat slurry was extracted and centrifuged to obtain a humic acid suspension; (3) Mix the nitrogen source, phosphorus source, potassium source, metal salt and the humic acid suspension to obtain a humic acid complex solution; (4) Mix the suspension stabilizer, dispersant and wetting agent with the humic acid complex solution, emulsify, and adjust the pH to 6.5~7.5 to obtain a slow-release liquid water-soluble fertilizer containing peat source humic acid; The suspension stabilizer includes xanthan gum and guar gum; the mass ratio of xanthan gum to guar gum is 1:0.5~1; The extraction is a countercurrent extraction; the number of extraction stages is 1 to 3; the extraction temperature is 90 to 95°C, and the extraction time for each stage is 1.5 to 4 hours.

[0008] In this invention, the nitrogen source is preferably urea; the phosphorus source is preferably potassium dihydrogen phosphate; the potassium source is preferably potassium sulfate; the metal element of the metal salt preferably includes any two or more combinations of Fe, Zn, Mn, Cu, B, and Mo; the metal salt is preferably one or more of sulfate, chloride, and nitrate; and the dispersing and wetting agent is preferably tea saponin.

[0009] In this invention, the preferred mass ratio of the median peat, nitrogen source, phosphorus source, potassium source, metal salt, suspension stabilizer, and dispersing wetting agent is 80~120:80~120:50~80:40~60:3~8:0.8~2.5:0.2~0.8; specifically, it can be 100:100:65:50:3:1.6:0.5, 100:120:70:55:3.6:2.1:0.3, 100:90:55:45:6:1.5:0.6, 80:120:80:60:3.6:2.4:0.8, 110:100:60:50:3:1.6:0.6, 120:110:75:55:7.2:1.8:0.6; the amount of metal salt used is based on the mass of the metal element it contains.

[0010] In this invention, in step (1), the degree of decomposition of the median peat is preferably 25% to 40%, specifically 28%, 30%, 32%, 35%, or 38%; the organic matter content of the median peat is preferably ≥48%, specifically 52%, 54%, or 50%.

[0011] In this invention, in step (1), the median peat needs to be pretreated before use. The pretreatment process is preferably carried out sequentially by air drying and crushing. The air drying is preferably carried out until the moisture content of the median peat is ≤8%. The crushing is preferably carried out until the particle size of the median peat is crushed to ≤5mm.

[0012] In this invention, in step (1), the mass ratio of the median peat to water is preferably 1:2~3, specifically 1:2.5; the milling media is preferably corundum balls or ceramic balls, and the ball-to-material ratio is preferably 3~8:1, specifically 5:1, 6:1, or 7:1; the wet milling preferably includes a first milling and a second milling; the rotation speed of the first milling is preferably 250~300 rpm, specifically 280 rpm; the time is preferably 1.5~2.5 h, specifically 2 h; the first milling is preferably milled to 10 The mesh size is 0~200 mesh, specifically 130 mesh, 140 mesh, 150 mesh, or 160 mesh; the rotation speed of the second ball mill is preferably 350~450 rpm, specifically 380 rpm, 400 rpm, or 420 rpm; the time is preferably 3.5~5 h, specifically 4 h or 4.5 h; the second ball mill is preferably milled to 2000~2500 mesh, specifically 2200 mesh, 2300 mesh, or 2400 mesh; the wet ball milling process preferably includes filtration after completion; the filtration preferably uses a 200 mesh filter.

[0013] In this invention, in step (2), the mass ratio of water used for extraction to median peat is preferably 1:1~2, specifically 1:1.5; the number of extraction stages is preferably 1~3, specifically 2; the extraction temperature is preferably 90~95℃, specifically 92℃, 93℃, or 94℃; the extraction speed is preferably 60~80 rpm, specifically 70 rpm; and the extraction time for each stage is preferably 1.5~4h, specifically 2h or 3h.

[0014] In this invention, in step (2), the centrifugation speed is preferably 4000~6000 rpm, specifically 4500 rpm, 5000 rpm, or 5500 rpm; the time is preferably 15~30 min, specifically 20 min or 25 min.

[0015] In this invention, in step (3), the mixing method is preferably to add the nitrogen source, phosphorus source, potassium source and metal salt to the humic acid suspension in sequence; the interval between adding the nitrogen source, phosphorus source, potassium source and metal salt is preferably 3 to 5 minutes; the addition process is accompanied by stirring; the mixing speed is preferably 200 to 300 rpm; specifically, it can be 250 rpm; the temperature is preferably 40 to 50°C; specifically, it can be 45°C; the time is preferably 1 to 2 hours; specifically, it can be 1.5 hours.

[0016] In this invention, in step (4), the suspension stabilizer preferably includes xanthan gum and guar gum; the mass ratio of xanthan gum to guar gum is preferably 1:0.5~1, specifically 1:0.6 or 1:0.8.

[0017] In this invention, in step (4), the mixing method is preferably to add the suspension stabilizer and the dispersing wetting agent to the humic acid complex solution in sequence, and the addition interval of the suspension stabilizer and the dispersing wetting agent is preferably 3 to 5 minutes; the emulsification speed is preferably 2500 to 4500 rpm, specifically 3000 rpm, 3500 rpm, or 4000 rpm; the temperature is preferably 30 to 40°C, specifically 35°C; and the time is preferably 25 to 40 minutes, specifically 30 minutes or 35 minutes.

[0018] In this invention, the pH adjustment is preferably achieved using a potassium hydroxide solution or a phosphoric acid solution. The mass concentration of the potassium hydroxide solution is preferably 10-20%, and the mass concentration of the phosphoric acid solution is preferably 10-20%. The pH is preferably adjusted to 6.5-7.5, specifically 6.8, 7.0, or 7.2.

[0019] In this invention, after the pH adjustment is completed, cooling is preferably included. The cooling process is accompanied by stirring. The stirring speed is preferably 40-60 rpm, specifically 45 rpm or 50 rpm. The target temperature for cooling is preferably room temperature.

[0020] This invention provides a slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared by the above preparation method.

[0021] The present invention has the following beneficial effects: This invention uses peat as raw material and achieves the release and activation of humic acid through wet ball milling and countercurrent extraction, relying on purely physical means, thereby improving the humic acid release rate. At the same time, it fully preserves the high complexing activity of the active functional groups of humic acid molecules and uses it as a natural "complexing carrier" to achieve the chemical anchoring of nutrient molecules.

[0022] This invention utilizes the natural macromolecular structure and abundant active functional groups of peat-derived humic acid to achieve "molecular-level anchoring" and chemical controlled release of nutrients through a simple complexation reaction.

[0023] This invention constructs a dual-gum synergistic suspension system of xanthan gum and guar gum, which can synergistically achieve slow-release of nutrients in liquid fertilizer with humic acid-nutrient complex; at the same time, it solves the problem of liquid fertilizer storage stratification and improves the long-term room temperature storage stability of the product.

[0024] This invention also provides a slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared by the above-described method. In the product obtained by this invention, the active functional groups (carboxyl groups, phenolic hydroxyl groups, etc.) of the peat-derived humic acid are completely preserved. Numerous unoccupied active coordination sites on its molecular skeleton can continuously chelate and fix Pb in the soil through various forces such as ion exchange, coordination complexation, and electrostatic adsorption. 2+ Cd 2+ Cu 2+ Ni 2+ Cr 3+ The presence of heavy metal ions enhances the adsorption performance for heavy metal ions. Example data shows that the slow-release liquid water-soluble fertilizer containing peat-derived humic acid of the present invention effectively removes Pb ions. 2+ The adsorption rate reaches 97.90%~99.04%, and the adsorption rate for Cd is [missing information]. 2+ The adsorption rate reaches 96.44%~98.36%, for Cu 2+ The adsorption rate reaches 98.76%~99.44%, for Ni 2+ The adsorption rate reached 96.10%~98.10%, and the adsorption rate for Cr was... 3+ The adsorption rate reached 97.32%~98.56%, and the adsorption rates of each heavy metal ion were stable between 96%~99.5%, indicating that the slow-release liquid water-soluble fertilizer containing peat-derived humic acid of the present invention has a high-efficiency heavy metal ion adsorption capacity.

[0025] The product obtained by this invention, when applied to the soil, relies on the inhibitory effect of humic acid on urease activity to delay urea hydrolysis, and gradually releases nutrients through the progressive decomposition by soil microorganisms, thus matching the nutrient release with the crop absorption cycle. Example data shows that the nutrient release cycle (water immersion method) of the slow-release liquid water-soluble fertilizer containing peat-derived humic acid of this invention is 58-75 days, and the fertilizer utilization rate (pot experiment) is 60%-69%. Simultaneously, the product shows no obvious stratification or sedimentation after being stored at room temperature for more than 12 months, and the water-insoluble matter is ≤7g / L, meeting the requirements of NY / T 1106 standard, indicating that it has excellent chemical slow-release nutrient properties and long-term stable performance at room temperature. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the preparation process of the slow-release liquid water-soluble fertilizer containing peat-derived humic acid in Example 1. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0029] Example 1 This embodiment provides a method for preparing a slow-release liquid water-soluble fertilizer containing peat-derived humic acid. The raw materials used, by mass, include the following components: 100 parts of medium-grade peat (decomposition degree 32%, organic matter content ≥52%); 100 parts of urea; 65 parts of potassium dihydrogen phosphate; 50 parts of potassium sulfate; 0.5 parts each of ferric chloride, zinc sulfate, manganese sulfate, copper sulfate, boric acid, and ammonium molybdate (calculated based on the effective content of each metal element); 1.0 part of xanthan gum; 0.6 parts of guar gum; 0.5 parts of tea saponin; 450 parts of water.

[0030] (1) After air-drying the medium-sized peat to a moisture content of ≤8%, it is placed in a jaw crusher for coarse crushing to a peat coarse particle size of ≤5mm; the coarsely crushed peat particles are mixed with 250 parts of deionized water, stirred evenly, and then transferred to a planetary ball mill. Corundum balls are used as the ball milling medium (ball-to-material ratio of 5:1) for wet secondary ball milling; the first ball milling conditions are: rotation speed 300rpm, time 2h, and the peat coarse particles are ball milled to 150 mesh; the second ball milling conditions are: rotation speed 400rpm, ball milling for 4h, and ball milling is continued to 2500 mesh; after ball milling, the slurry is filtered with a 200-mesh sieve and the slurry under the sieve is collected to obtain ultrafine peat slurry; (2) Pump the ultrafine peat slurry into the three-stage countercurrent leaching device. Heat 200 parts of water to 90°C and add it from the third-stage leaching tank. The ultrafine peat slurry enters from the first stage and is subjected to three-stage countercurrent leaching. The leaching temperature is 90°C, the leaching speed is 60 rpm, and the leaching time for each stage is 1.5 h. After leaching, the slurry is centrifuged at 5000 rpm for 20 min. The bottom sediment is discarded, and the dark brown supernatant is collected to obtain humic acid suspension. (3) Transfer the humic acid suspension into the reactor. Under the conditions of 250 rpm and constant temperature of 45°C, add urea, potassium dihydrogen phosphate, potassium sulfate, ferric chloride, zinc sulfate, manganese sulfate, copper sulfate, boric acid and ammonium molybdate in sequence. The interval between each raw material addition is 5 min. After all raw materials are added, keep the stirring speed and temperature constant for 1.5 h to obtain humic acid complex solution. (4) Cool the humic acid complex solution to 35°C and transfer it to a high-speed shear emulsifier. Add xanthan gum, guar gum and tea saponin in sequence at a speed of 3000 rpm. The interval between each raw material addition is 3 min. After all raw materials are added, continue emulsification for 30 min. During the emulsification process, add 10% potassium hydroxide solution to adjust the pH to 7.0. After the emulsification is completed, stir and cool to room temperature at a speed of 50 rpm to obtain a slow-release liquid water-soluble fertilizer containing peat source humic acid.

[0031] The schematic diagram of the preparation process of the slow-release liquid water-soluble fertilizer containing peat-derived humic acid in this embodiment is shown below. Figure 1 As shown.

[0032] The core performance indicators of the slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Example 1 were tested, and the results are shown in Table 1.

[0033] Table 1 Performance indicators of slow-release liquid water-soluble fertilizer containing peat-derived humic acid in Example 1

[0034] As can be seen from Table 1, the nutrient release cycle of the product obtained in this embodiment is 72 days, and there is no obvious stratification after 12 months of storage at room temperature, indicating that it has excellent nutrient slow-release performance and storage stability.

[0035] The slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Example 1 was diluted 100 times, and then Pb-containing compounds were added to it. 2+ Cd 2+ Cu 2+ Ni 2+ Cr 3+ The heavy metal ion solutions (initial concentration of 50 mg / L) were shaken and adsorbed at 25℃ and pH 7.0 for 24 h. The residual concentration of heavy metal ions in the solution after adsorption was measured and the adsorption rate was calculated. The results are shown in Table 2.

[0036] Table 2 Adsorption results of heavy metal ions

[0037] As can be seen from Table 2, the product obtained in this embodiment has a positive effect on Pb. 2+ Cd 2+ Cu 2+ Ni2+ Cr 3+ They all have extremely high adsorption rates.

[0038] Example 2 This embodiment provides a method for preparing a slow-release liquid water-soluble fertilizer containing peat-derived humic acid. The raw materials used, by mass fraction, include the following components: 100 parts of medium-grade peat (35% decomposition, ≥54% organic matter content); 120 parts of urea; 70 parts of potassium dihydrogen phosphate; 55 parts of potassium sulfate; 0.6 parts each of ferric chloride, zinc sulfate, manganese sulfate, copper sulfate, boric acid, and ammonium molybdate (calculated based on the effective content of each metal element); 1.4 parts of xanthan gum; 0.7 parts of guar gum; 0.3 parts of tea saponin; and 300 parts of water.

[0039] This embodiment provides a method for preparing the above-mentioned slow-release liquid water-soluble fertilizer containing peat-derived humic acid, including the following steps: (1) After air-drying the medium-sized peat to a moisture content of ≤8%, it is placed in a jaw crusher for coarse crushing to a peat coarse particle size of ≤5mm. The coarsely crushed peat particles are mixed with 200 parts of deionized water, stirred evenly, and then transferred to a planetary ball mill. Corundum balls are used as the ball milling medium (ball-to-material ratio of 6:1) for wet secondary ball milling. The first ball milling conditions are: rotation speed 280rpm, time 2.5h, and the peat coarse particles are ball milled to 130 mesh. The second ball milling conditions are: rotation speed 380rpm, ball milling for 5h, and ball milling is continued to 2200 mesh. After ball milling, the slurry is filtered with a 200-mesh sieve and the slurry under the sieve is collected to obtain ultrafine peat slurry. (2) Pump the ultrafine peat slurry into a two-stage countercurrent leaching device. Heat 100 parts of water to 92°C and add it from the second-stage leaching tank. The ultrafine peat slurry enters from the first stage and is subjected to two-stage countercurrent leaching. The leaching temperature is 92°C, the leaching speed is 70 rpm, and the leaching time for each stage is 2 hours. After leaching, the slurry is centrifuged at 5500 rpm for 20 minutes. The bottom sediment is discarded, and the dark brown supernatant is collected to obtain a humic acid suspension. (3) Transfer the humic acid suspension into the reactor. Under the conditions of 250 rpm and constant temperature of 45°C, add urea, potassium dihydrogen phosphate, potassium sulfate, ferric chloride, zinc sulfate, manganese sulfate, copper sulfate, boric acid and ammonium molybdate in sequence. The interval between each raw material addition is 5 min. After all raw materials are added, keep the stirring speed and temperature constant for 2 h to obtain humic acid complex solution. (4) Cool the humic acid complex solution to 35°C and transfer it to a high-speed shear emulsifier. Add xanthan gum, guar gum and tea saponin in sequence at a speed of 4500 rpm. The interval between each raw material addition is 3 min. After all raw materials are added, continue shear emulsification for 35 min. During the emulsification process, add 10% potassium hydroxide solution to adjust the pH to 7.2. After the emulsification is completed, stir and cool to room temperature at a speed of 45 rpm to obtain a slow-release liquid water-soluble fertilizer containing peat source humic acid.

[0040] The core performance indicators of the slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Example 2 were tested, and the results are shown in Table 3.

[0041] Table 3 Performance indicators of slow-release liquid water-soluble fertilizer containing peat-derived humic acid in Example 2

[0042] The slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Example 2 was diluted 100 times, and then Pb-containing compounds were added to it. 2+ Cd 2+ Cu 2+ Ni 2+ Cr 3+ The heavy metal ion solutions (initial concentration of 50 mg / L) were shaken and adsorbed for 24 h at 25 °C and pH 7.0. The residual concentration of heavy metal ions in the solution after adsorption was measured and the adsorption rate was calculated. The results are shown in Table 4.

[0043] Table 4 Adsorption results of heavy metal ions

[0044] Example 3 This embodiment provides a method for preparing a slow-release liquid water-soluble fertilizer containing peat-derived humic acid. The raw materials used, by mass, include the following components: 100 parts of median peat (decomposition degree 28%, organic matter content ≥48%); 90 parts of urea; 55 parts of potassium dihydrogen phosphate; 45 parts of potassium sulfate; 1 part each of ferric chloride, zinc nitrate, manganese nitrate, copper nitrate, boric acid, and ammonium molybdate (calculated according to the effective content of each metal element); 1.0 part of xanthan gum; 0.5 part of guar gum; 0.6 parts of tea saponin; 350 parts of water.

[0045] This embodiment provides a method for preparing the above-mentioned slow-release liquid water-soluble fertilizer containing peat-derived humic acid, including the following steps: (1) After air-drying the medium-sized peat to a moisture content of ≤8%, it is placed in a jaw crusher for coarse crushing to a peat coarse particle size of ≤5mm; the coarsely crushed peat particles are mixed with 250 parts of deionized water, stirred evenly, and then transferred to a planetary ball mill. The ceramic balls are used as the ball milling medium (ball-to-material ratio of 6:1) for wet secondary ball milling; the first ball milling conditions are: rotation speed 300rpm, time 1.5h, and the peat coarse particles are ball milled to 140 mesh; the second ball milling conditions are: rotation speed 400rpm, ball milling for 3.5h, and ball milling is continued to 2300 mesh; after ball milling, the slurry is filtered with a 200-mesh sieve and the slurry under the sieve is collected to obtain ultrafine peat slurry; (2) Pump the ultrafine peat slurry into the extraction tank, add 100 parts of water (95℃), and extract for 4 hours at 95℃ and 80 rpm. Centrifuge the extracted slurry at 6000 rpm for 15 minutes, discard the bottom sediment, collect the dark brown supernatant, and obtain humic acid suspension. (3) Transfer the humic acid suspension into the reactor. Under the conditions of 200 rpm and constant temperature of 45°C, add urea, potassium dihydrogen phosphate, potassium sulfate, ferric chloride, zinc nitrate, manganese nitrate, copper nitrate, boric acid and ammonium molybdate in sequence. The time interval between each raw material addition is 5 min. After all raw materials are added, keep the stirring speed and temperature constant for 1.5 h to obtain humic acid complex solution. (4) Cool the humic acid complex solution to 35°C and transfer it to a high-speed shear emulsifier. Add xanthan gum, guar gum and tea saponin in sequence at a speed of 3500 rpm. The interval between each raw material addition is 3 min. After all raw materials are added, continue shear emulsification for 40 min. During the emulsification process, add 10% phosphoric acid solution to adjust the pH to 6.8. After the emulsification is completed, stir and cool to room temperature at a speed of 40 rpm to obtain a slow-release liquid water-soluble fertilizer containing peat source humic acid.

[0046] The core performance indicators of the slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Example 3 were tested, and the results are shown in Table 5.

[0047] Table 5 Performance indicators of slow-release liquid water-soluble fertilizer containing peat-derived humic acid in Example 3

[0048] The slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Example 3 was diluted 100 times, and then Pb-containing compounds were added to it. 2+ Cd 2+ Cu 2+ Ni 2+ Cr 3+The heavy metal ion solutions (initial concentration of 50 mg / L) were shaken and adsorbed for 24 h at 25 °C and pH 7.0. The residual concentration of heavy metal ions in the solution after adsorption was measured and the adsorption rate was calculated. The results are shown in Table 6.

[0049] Table 6 Adsorption results of heavy metal ions

[0050] Example 4 This embodiment provides a method for preparing a slow-release liquid water-soluble fertilizer containing peat-derived humic acid. The raw materials used, by mass, include the following components: 80 parts of median peat (decomposition degree 28%, organic matter content ≥48%); 120 parts of urea; 80 parts of potassium dihydrogen phosphate; 60 parts of potassium sulfate; 0.6 parts each of ferric chloride, zinc sulfate, manganese sulfate, copper sulfate, boric acid, and ammonium molybdate (calculated based on the effective content of each metal element); 1.6 parts of xanthan gum; 0.8 parts of guar gum; 0.8 parts of tea saponin; 320 parts of water.

[0051] This embodiment provides a method for preparing the above-mentioned slow-release liquid water-soluble fertilizer containing peat-derived humic acid, including the following steps: (1) After air-drying the medium-sized peat to a moisture content of ≤8%, it is placed in a jaw crusher for coarse crushing to a peat coarse particle size of ≤5mm; the coarsely crushed peat particles are mixed with 160 parts of deionized water, stirred evenly, and then transferred to a planetary ball mill. Corundum balls are used as the ball milling medium (ball-to-material ratio of 7:1) for wet secondary ball milling; the first ball milling conditions are: rotation speed 300rpm, time 2h, and the peat coarse particles are ball milled to 160 mesh; the second ball milling conditions are: rotation speed 420rpm, ball milling for 5h, and ball milling is continued to 2400 mesh; after ball milling, the slurry is filtered through a 200-mesh sieve and the slurry under the sieve is collected to obtain ultrafine peat slurry; (2) Pump the ultrafine peat slurry into a two-stage countercurrent leaching device. Heat 160 parts of water to 92°C and add it from the second-stage leaching tank. The ultrafine peat slurry enters from the first stage and is subjected to two-stage countercurrent leaching. The leaching temperature is 94°C, the leaching speed is 70 rpm, and the leaching time for each stage is 3 hours. Centrifuge the slurry after leaching at 5500 rpm for 20 minutes, discard the bottom sediment, and collect the dark brown supernatant to obtain a humic acid suspension. (3) Transfer the humic acid suspension into the reactor. Under the conditions of 250 rpm and constant temperature of 45°C, add urea, potassium dihydrogen phosphate, potassium sulfate, ferric chloride, zinc sulfate, manganese sulfate, copper sulfate, boric acid and ammonium molybdate in sequence. The interval between each raw material addition is 5 min. After all raw materials are added, keep the stirring speed and temperature constant for 2 h to obtain humic acid complex solution. (4) Cool the humic acid complex solution to 35°C and transfer it to a high-speed shear emulsifier. Add xanthan gum, guar gum and tea saponin in sequence at a speed of 4500 rpm. The interval between each raw material addition is 3 min. After all raw materials are added, continue shear emulsification for 40 min. During the emulsification process, add 10% potassium hydroxide solution to adjust the pH to 7.2. After the emulsification is completed, stir and cool to room temperature at a speed of 45 rpm to obtain a slow-release liquid water-soluble fertilizer containing peat source humic acid.

[0052] The core performance indicators of the slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Example 4 were tested, and the results are shown in Table 7.

[0053] Table 7 Performance Indicators of Slow-Release Liquid Water-Soluble Fertilizer Containing Peat-Based Humic Acid in Example 4

[0054] The slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Example 4 was diluted 100 times, and then Pb-containing compounds were added to it. 2+ Cd 2+ Cu 2+ Ni 2+ Cr 3+ The heavy metal ion solutions (initial concentration of 50 mg / L) were shaken and adsorbed for 24 h at 25 °C and pH 7.0. The residual concentration of heavy metal ions in the solution after adsorption was measured and the adsorption rate was calculated. The results are shown in Table 8.

[0055] Table 8. Adsorption results of heavy metal ions

[0056] Example 5 This embodiment provides a method for preparing a slow-release liquid water-soluble fertilizer containing peat-derived humic acid. The raw materials used, by mass, include the following components: 110 parts of median peat (30% decomposition, ≥48% organic matter content); 100 parts of urea; 60 parts of potassium dihydrogen phosphate; 50 parts of potassium sulfate; 0.5 parts each of ferric chloride, zinc sulfate, manganese sulfate, copper sulfate, boric acid, and ammonium molybdate (calculated based on the effective content of each metal element); 1.2 parts of xanthan gum; 0.6 parts of guar gum; 0.6 parts of tea saponin; and 440 parts of water.

[0057] This embodiment provides a method for preparing the above-mentioned slow-release liquid water-soluble fertilizer containing peat-derived humic acid, including the following steps: (1) After air-drying the medium-sized peat to a moisture content of ≤8%, it is placed in a jaw crusher for coarse crushing to a particle size of ≤5mm. The coarsely crushed peat particles are mixed with 220 parts of deionized water and stirred evenly before being transferred to a planetary ball mill. Corundum balls are used as the ball milling medium (ball-to-material ratio of 7:1) for wet secondary ball milling. The first ball milling conditions are: 300 rpm for 2 hours to mill the peat coarse particles to 150 mesh. The second ball milling conditions are: 400 rpm for 4.5 hours to continue milling to 2300 mesh. After the ball milling is completed, the slurry is filtered through a 200-mesh sieve and collected to obtain ultrafine peat slurry. (2) Pump the ultrafine peat slurry into the three-stage countercurrent leaching device. Heat 220 parts of water to 90°C and add it from the third-stage leaching tank. The ultrafine peat slurry enters from the first stage and is subjected to three-stage countercurrent leaching. The leaching temperature is 90°C, the leaching speed is 60 rpm, and the leaching time for each stage is 1.5 h. After leaching, the slurry is centrifuged at 5000 rpm for 25 min. The bottom sediment is discarded, and the dark brown supernatant is collected to obtain humic acid suspension. (3) Transfer the humic acid suspension into the reactor. Under the conditions of 250 rpm and constant temperature of 45°C, add urea, potassium dihydrogen phosphate, potassium sulfate, ferric chloride, zinc sulfate, manganese sulfate, copper sulfate, boric acid and ammonium molybdate in sequence. The interval between each raw material addition is 5 min. After all raw materials are added, keep the stirring speed and temperature constant for 1.5 h to obtain humic acid complex solution. (4) Cool the humic acid complex solution to 35°C and transfer it to a high-speed shear emulsifier. Add xanthan gum, guar gum and tea saponin in sequence at a speed of 4000 rpm. The interval between each addition of raw materials is 3 min. After all raw materials are added, continue shear emulsification for 30 min. During shear emulsification, add 10% potassium hydroxide solution to adjust the pH to 7. After shear emulsification, stir and cool to room temperature at a speed of 45 rpm to obtain a slow-release liquid water-soluble fertilizer containing peat source humic acid.

[0058] The core performance indicators of the slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Example 5 were tested, and the results are shown in Table 9.

[0059] Table 9 Performance Indicators of Slow-Release Liquid Water-Soluble Fertilizer Containing Peat-Based Humic Acid in Example 5

[0060] The slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Example 5 was diluted 100 times, and then Pb-containing compounds were added to it. 2+ Cd 2+ Cu 2+ Ni 2+ Cr 3+The heavy metal ion solutions (initial concentration of 50 mg / L) were shaken and adsorbed for 24 h at 25 °C and pH 7.0. The residual concentration of heavy metal ions in the solution after adsorption was measured and the adsorption rate was calculated. The results are shown in Table 10.

[0061] Table 10 Adsorption results of heavy metal ions

[0062] Example 6 This embodiment provides a method for preparing a slow-release liquid water-soluble fertilizer containing peat-derived humic acid. The raw materials used, by mass, include the following components: 120 parts of median peat (decomposition degree 38%, organic matter content ≥50%); 110 parts of urea; 75 parts of potassium dihydrogen phosphate; 55 parts of potassium sulfate; 1.2 parts each of ferric chloride, zinc sulfate, manganese sulfate, copper sulfate, boric acid, and ammonium molybdate (calculated according to the effective content of each metal element); 1 part of xanthan gum; 0.8 parts of guar gum; 0.6 parts of tea saponin; and 480 parts of water.

[0063] This embodiment provides a method for preparing the above-mentioned slow-release liquid water-soluble fertilizer containing peat-derived humic acid, including the following steps: (1) After air-drying the medium-sized peat to a moisture content of ≤8%, it is placed in a jaw crusher for coarse crushing to a peat coarse particle size of ≤5mm; the coarsely crushed peat particles are mixed with 300 parts of deionized water, stirred evenly, and then transferred to a planetary ball mill. Corundum balls are used as the ball milling medium (ball-to-material ratio of 7:1) for wet secondary ball milling; the first ball milling conditions are: rotation speed 300rpm, time 2h, and the peat coarse particles are ball milled to 150 mesh; the second ball milling conditions are: rotation speed 400rpm, ball milling for 4.5h, and ball milling is continued to 2300 mesh; after ball milling, the slurry is filtered with a 200-mesh sieve and the slurry under the sieve is collected to obtain ultrafine peat slurry; (2) Pump the ultrafine peat slurry into the three-stage countercurrent leaching device. Heat 180 parts of water to 90°C and add it from the third-stage leaching tank. The ultrafine peat slurry enters from the first stage and is subjected to three-stage countercurrent leaching. The leaching temperature is 90°C, the leaching speed is 60 rpm, and the leaching time for each stage is 2 hours. Centrifuge the slurry after leaching at 4500 rpm for 30 minutes, discard the bottom sediment, and collect the dark brown supernatant to obtain humic acid suspension. (3) Transfer the humic acid suspension into the reactor. Under the conditions of 250 rpm and constant temperature of 45°C, add urea, potassium dihydrogen phosphate, potassium sulfate, ferric chloride, zinc sulfate, manganese sulfate, copper sulfate, boric acid and ammonium molybdate in sequence. The interval between each raw material addition is 5 min. After all raw materials are added, keep the stirring speed and temperature constant for 1.5 h to obtain humic acid complex solution. (4) Cool the humic acid complex solution to 35°C and transfer it to a high-speed shear emulsifier. Add xanthan gum, guar gum and tea saponin in sequence at a speed of 4000 rpm. The interval between each raw material addition is 3 min. After all raw materials are added, continue shear emulsification for 35 min. During the emulsification process, add 10% potassium hydroxide solution to adjust the pH to 7. After the emulsification is completed, stir and cool to room temperature at a speed of 45 rpm to obtain a slow-release liquid water-soluble fertilizer containing peat source humic acid.

[0064] The core performance indicators of the slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Example 6 were tested, and the results are shown in Table 11.

[0065] Table 11 Performance Indicators of Slow-Release Liquid Water-Soluble Fertilizer Containing Peat-Based Humic Acid in Example 6

[0066] The slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Example 6 was diluted 100 times, and then Pb-containing compounds were added to it. 2+ Cd 2+ Cu 2+ Ni 2+ Cr 3+ The heavy metal ion solutions (initial concentration of 50 mg / L) were shaken and adsorbed at 25℃ and pH 7.0 for 24 h. The residual concentration of heavy metal ions in the solution after adsorption was measured and the adsorption rate was calculated. The results are shown in Table 12.

[0067] Table 12 Adsorption results of heavy metal ions

[0068] Comparative Example 1 The raw materials used in this comparative example are the same as those in Example 1.

[0069] The preparation method of the slow-release liquid water-soluble fertilizer containing peat-derived humic acid in this comparative example differs from that in Example 1 in that, in step (1), only the first ball milling is performed, and the second ball milling is not performed; the remaining steps are the same as in Example 1, and the slow-release liquid water-soluble fertilizer containing peat-derived humic acid is obtained.

[0070] The core performance indicators of the slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Comparative Example 1 were tested, and the results are shown in Table 13.

[0071] Table 13 Performance Indicators of Slow-Release Liquid Water-Soluble Fertilizer Containing Peat-Based Humic Acid (Comparative Example 1)

[0072] As shown in Table 13, the humic acid release rate of this comparative example was 32%, and the nutrient release cycle was 28 days. This indicates that ball milling only once significantly reduced the humic acid release rate and total content, and led to a significant increase in water-insoluble matter. At the same time, the nutrient release cycle and fertilizer utilization rate also decreased significantly.

[0073] The slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Comparative Example 1 was diluted 100 times, and then Pb-containing fertilizer was added to it. 2+ Cd 2+ Cu 2+ Ni 2+ Cr 3+ The heavy metal ion solutions (initial concentration of 50 mg / L) were shaken and adsorbed at 25℃ and pH 7.0 for 24 h. The residual concentration of heavy metal ions in the solution after adsorption was measured and the adsorption rate was calculated. The results are shown in Table 14.

[0074] Table 14 Adsorption results of heavy metal ions

[0075] As can be seen from Table 14, the adsorption rate of heavy metal ions of the product obtained by ball milling only once is significantly lower than that of the product obtained by ball milling twice in Example 1.

[0076] Comparative Example 2 The raw materials used in this comparative example are the same as those in Example 1.

[0077] The preparation method of the slow-release liquid water-soluble fertilizer containing peat-derived humic acid in this comparative example differs from that in Example 1 in that the extraction temperature in step (2) is 25°C; the remaining steps are the same as in Example 1, and a slow-release liquid water-soluble fertilizer containing peat-derived humic acid is obtained.

[0078] The core performance indicators of the slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Comparative Example 2 were tested, and the results are shown in Table 15.

[0079] Table 15 Performance indicators of slow-release liquid water-soluble fertilizer containing peat-derived humic acid (Comparative Example 2)

[0080] As shown in Table 15, the humic acid release rate of this comparative example is 28%, and the nutrient release cycle is 35 days. This indicates that extraction at room temperature leads to a significant reduction in the humic acid release rate and total content, as well as a significant decrease in fertilizer utilization and nutrient release cycle.

[0081] The slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Comparative Example 2 was diluted 100 times, and then Pb-containing fertilizer was added to it. 2+ Cd 2+ Cu 2+ Ni 2+Cr 3+ The heavy metal ion solutions (initial concentration of 50 mg / L) were shaken and adsorbed at 25℃ and pH 7.0 for 24 h. The residual concentration of heavy metal ions in the solution after adsorption was measured and the adsorption rate was calculated. The results are shown in Table 16.

[0082] Table 16 Adsorption results of heavy metal ions

[0083] As can be seen from Table 16, extraction at room temperature leads to a decrease in the release rate of humic acid, which in turn leads to a significant decrease in the adsorption rate of heavy metal ions by the product.

[0084] Comparative Example 3 The difference between the raw materials used in this comparative example and those in Example 1 is that guar gum was omitted.

[0085] The preparation method of the slow-release liquid water-soluble fertilizer containing peat-derived humic acid in this comparative example differs from that in Example 1 in that, in step (4), only xanthan gum and tea saponin are added, and guar gum is not added. The remaining steps are the same as in Example 1, and a slow-release liquid water-soluble fertilizer containing peat-derived humic acid is obtained.

[0086] The core performance indicators of the slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Comparative Example 3 were tested, and the results are shown in Table 17.

[0087] Table 17 Performance indicators of slow-release liquid water-soluble fertilizer containing peat-derived humic acid (Comparative Example 3)

[0088] As can be seen from Table 17, compared with Example 1, the room temperature storage stability of the product obtained in this comparative example decreased from 12 months to 6 months, indicating that the combination of xanthan gum and guar gum can improve the long-term room temperature storage stability of the product.

[0089] The slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared in Comparative Example 3 was diluted 100 times, and then Pb-containing fertilizer was added to it. 2+ Cd 2+ Cu 2+ Ni 2+ Cr 3+ The heavy metal ion solutions (initial concentration of 50 mg / L) were shaken and adsorbed at 25℃ and pH 7.0 for 24 h. The residual concentration of heavy metal ions in the solution after adsorption was measured and the adsorption rate was calculated. The results are shown in Table 18.

[0090] Table 18 Adsorption results of heavy metal ions

[0091] As can be seen from Table 18, the product obtained by wet secondary ball milling and hot water countercurrent extraction in this comparative example still maintains a high level of adsorption capacity for heavy metal ions.

[0092] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a slow-release liquid water-soluble fertilizer containing peat-derived humic acid, characterized in that, Includes the following steps: (1) Mix the medium-sized peat with water and wet ball mill to obtain peat slurry; (2) The peat slurry was extracted and centrifuged to obtain a humic acid suspension; (3) Mix the nitrogen source, phosphorus source, potassium source, metal salt and the humic acid suspension to obtain a humic acid complex solution; (4) Mix the suspension stabilizer, dispersant and wetting agent with the humic acid complex solution, emulsify, and adjust the pH to 6.5~7.5 to obtain a slow-release liquid water-soluble fertilizer containing peat source humic acid; The suspension stabilizer includes xanthan gum and guar gum; the mass ratio of xanthan gum to guar gum is 1:0.5~1; The extraction is a countercurrent extraction; the number of extraction stages is 1 to 3; the extraction temperature is 90 to 95°C, and the extraction time for each stage is 1.5 to 4 hours.

2. The method for preparing a slow-release liquid water-soluble fertilizer containing peat-derived humic acid according to claim 1, characterized in that, The nitrogen source is urea; the phosphorus source is potassium dihydrogen phosphate; the potassium source is potassium sulfate; the metal element of the metal salt includes any two or more combinations of Fe, Zn, Mn, Cu, B, and Mo; and the dispersing and wetting agent is tea saponin.

3. The method for preparing a slow-release liquid water-soluble fertilizer containing peat-derived humic acid according to claim 1, characterized in that, The mass ratio of the median peat, nitrogen source, phosphorus source, potassium source, metal salt, suspension stabilizer and dispersing wetting agent is 80~120:80~120:50~80:40~60:3~8:0.8~2.5:0.2~0.8; the mass of the metal salt is based on the mass of the metal element it contains.

4. The method for preparing a slow-release liquid water-soluble fertilizer containing peat-derived humic acid according to claim 1, characterized in that, In step (1), the degree of decomposition of the median peat is 25%~40%, and the organic matter content is ≥48%; the mass ratio of the median peat to water is 1:2~3.

5. The method for preparing a slow-release liquid water-soluble fertilizer containing peat-derived humic acid according to claim 1, characterized in that, In step (1), the wet ball milling includes a first ball milling and a second ball milling; the first ball milling is to 100~200 mesh; the second ball milling is to 2000~2500 mesh.

6. The method for preparing a slow-release liquid water-soluble fertilizer containing peat-derived humic acid according to claim 1, characterized in that, The mass ratio of water used for extraction to median peat is 1:1~2.

7. The method for preparing a slow-release liquid water-soluble fertilizer containing peat-derived humic acid according to claim 1, characterized in that, In step (2), the centrifugation speed is 4000~6000 rpm and the time is 15~30 min.

8. The method for preparing a slow-release liquid water-soluble fertilizer containing peat-derived humic acid according to claim 1, characterized in that, In step (3), the mixing temperature is 40~50℃ and the time is 1~2h.

9. The method for preparing a slow-release liquid water-soluble fertilizer containing peat-derived humic acid according to claim 1, characterized in that, In step (4), the emulsification speed is 2500~4500 rpm, the temperature is 30~40℃, and the time is 25~35 min.

10. A slow-release liquid water-soluble fertilizer containing peat-derived humic acid prepared by the preparation method of the slow-release liquid water-soluble fertilizer containing peat-derived humic acid as described in any one of claims 1 to 9.

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