Quick-acting phosphorus combined extraction method suitable for acidic, neutral and calcareous soil

Abstract

The invention belongs to the technical field of extraction, and discloses a combined extraction method of quick-acting phosphorus suitable for acidic, neutral and calcareous soil, which comprises the following steps: preparing a composite extraction agent which comprises the following components: citric acid-sodium citrate buffer solution, EDTA (Ethylene Diamine Tetraacetic Acid) disodium salt and ammonium oxalate; mixing the soil sample with the composite extracting agent; carrying out solid-liquid separation on a mixture of the soil sample and the composite extracting agent; and carrying out phosphorus determination on the filtrate obtained by solid-liquid separation. The citric acid-sodium citrate buffer solution is used for maintaining an acidic environment and dissolving iron / aluminum combined phosphorus; eDTA disodium salt is chelated with calcium ions, so that refixation of phosphorus in calcareous soil is prevented; according to the method, the leaching process is simple, the efficiency is high, the universality is high, the recovery rate is high, the method is suitable for the soil with the pH value of 4.0-8.5, the recovery rate is larger than or equal to 92%, the leaching cost is low, the method is environmentally friendly, the composite leaching agent is free of toxicity and harm and fluoride and strong acid components, waste is easy to treat, and the method meets the green chemical standard.

Description

Technical Field

[0001] This invention belongs to the field of leaching technology, specifically relating to a combined leaching method for fast-acting phosphorus suitable for acidic, neutral, and calcareous soils. Background Technology

[0002] Soil phosphorus extraction refers to the process of extracting phosphorus (including available and fixed phosphorus) from soil into a solution using chemical or physical methods in order to determine its content or assess the availability of phosphorus.

[0003] Traditional extraction methods include the Bray-1 method and the Olsen method. The Bray-1 method is suitable for acidic soils, while the Olsen method is suitable for alkaline soils. Traditional extraction methods cannot be adapted to multiple soil types simultaneously, requiring the selection of different methods based on soil pH. This process is cumbersome and also suffers from the following problems: low extraction efficiency, high reagent toxicity, and complex procedures. Regarding extraction efficiency, phosphorus in calcareous soils is easily fixed by calcium, and existing extraction agents have insufficient desorption capacity (recovery rate <80%). Regarding reagent toxicity, some extraction agents contain strong acids or fluorides (such as Mehlich-3 solution), posing an environmental pollution risk. Regarding the extraction process, multiple centrifugations or filtrations are required, and the processing time for a single sample exceeds 20 minutes.

[0004] The root cause of the above problems lies in the fact that the extractant formulation has not been optimized for the chemical characteristics of various soil types and lacks the comprehensive chelation ability for phosphorus fixation elements such as calcium, iron, and aluminum. Therefore, a fast-acting phosphorus combined extraction method suitable for acidic, neutral, and calcareous soils is provided. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a fast-acting phosphorus extraction method suitable for acidic, neutral and calcareous soils, which is applicable to agricultural soil fertility assessment, environmental monitoring and rapid laboratory testing.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A combined method for the extraction of fast-acting phosphorus suitable for acidic, neutral, and calcareous soils includes the following: (I) Prepare a compound extractant, the components of which include citrate-sodium citrate buffer, disodium EDTA, and ammonium oxalate; (II) Soil samples were mixed with the compound extractant; (III) Solid-liquid separation of the soil sample and the mixture of compound extractant; (IV) Determine the phosphorus content of the filtrate obtained from solid-liquid separation.

[0007] In this invention, citrate-sodium citrate buffer is used to maintain an acidic environment and dissolve iron / aluminum bound phosphorus; EDTA disodium salt chelates calcium ions to prevent phosphorus refixation in calcareous soils; ammonium oxalate enhances the release of occluded phosphorus; this invention has strong versatility, is suitable for soils with pH 4.0 to 8.5, has a recovery rate of ≥92%, is environmentally friendly, contains no fluorides or strong acid components, and its waste is easy to dispose of.

[0008] As a preferred technical solution of the present invention, in step (I), the concentration of the citrate-sodium citrate buffer solution is 0.25 mol / L, the pH of the citrate-sodium citrate buffer solution is 4.5-5.5, the concentration of the disodium EDTA solution is 0.05 mol / L, and the mass-volume percentage concentration of ammonium oxalate is 2%.

[0009] In some optional instances, the pH of the citrate-sodium citrate buffer solution is 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.0, 5.1, 5.2, 5.3, 5.4, and 5.5, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0010] As a preferred technical solution of the present invention, in step (II), the mixing ratio of soil sample and compound extractant is 1:20, and the soil sample and compound extractant are shaken at a temperature of 25℃±2℃.

[0011] In some optional instances, the mixing temperature conditions are 23°C, 24°C, 25°C, 26°C, and 27°C, but are not limited to the listed values; other unlisted values ​​within this range also apply. The required oscillation time for mixing is 5 to 30 minutes. For example, it can be 10 minutes, in which case a rotation speed of 250 r / min is used, or it can be 20 minutes, in which case a rotation speed of 180 r / min is used. However, it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0012] As a preferred technical solution of the present invention, in step (III), the mixture of soil sample and compound extractant is separated into solid and liquid by vacuum filtration machine, and the solid-liquid separation time of vacuum filtration machine is within two minutes.

[0013] In some optional examples, the pore size of the vacuum filter is 0.45 μm.

[0014] As a preferred technical solution of the present invention, in step (IV), the phosphorus content of the filtrate is determined by the molybdenum blue colorimetric method, and the quantitative analysis of phosphorus is achieved by a spectrophotometer.

[0015] In some optional instances, the light wavelength used in the molybdenum blue colorimetric method is 680–780 nm, for example, 700 nm, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0016] The beneficial effects of this invention are: 1. Citrate-sodium citrate buffer is used to maintain an acidic environment and dissolve iron / aluminum bound phosphorus; EDTA disodium salt chelates calcium ions to prevent phosphorus refixation in calcareous soils; ammonium oxalate enhances the release of occluded phosphorus. The extraction process of this invention is simple and efficient, reducing the single-sample processing time from 20 minutes in traditional extraction to 12 minutes. 2. High applicability and high recovery rate: This invention is suitable for soils with pH 4.0–8.5, with a recovery rate ≥92%. Specifically, the recovery rate is 95%–98% for acidic soils (pH 4.0–6.5) and 92%–94% for calcareous soils (pH 7.5–8.5). 3. The extraction cost is low and the environment is friendly. The compound extractant is non-toxic and harmless, free of fluorides and strong acid components, and the waste is easy to dispose of, which meets the standards of green chemistry. Attached Figure Description

[0017] The present invention can be further illustrated by the non-limiting embodiments given in the accompanying drawings; Figure 1 This is a flowchart of an embodiment of the present invention. Detailed Implementation

[0018] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein. Example

[0019] like Figure 1 As shown, this embodiment provides a method for combined extraction of fast-acting phosphorus suitable for acidic, neutral, and calcareous soils, including the following contents. (I) Prepare a compound extractant. The components of the compound extractant include a citrate-sodium citrate buffer solution with a pH of 5.0 and a solution concentration of 0.25 mol / L, a solution concentration of 0.05 mol / L EDTA disodium salt, and an ammonium oxalate solution with a mass-volume percentage concentration of 2%. (II) Select calcareous soil with pH 8.0 and pass it through a 2mm sieve to obtain 5g of soil sample. Mix the soil sample with the compound extractant at a mixing ratio of 1:20. Take 100mL of the compound extractant. When mixing the soil sample with the compound extractant, shake it in a constant temperature shaker at 25℃. The shaking speed is 180r / min and the shaking time is 20 minutes. (III) Solid-liquid separation of soil sample and compound extractant was carried out by vacuum filtration machine. The solid-liquid separation time of vacuum filtration machine was less than two minutes to avoid secondary precipitation. The filter pore size of vacuum filtration machine was 0.45μm. (IV) Take 10 mL of the filtrate and add it to the ammonium molybdate-potassium antimony tartrate mixed reagent. The phosphorus content of the filtrate is determined by the molybdenum blue colorimetric method. After standing and color development, the phosphorus is quantitatively analyzed by a spectrophotometer. The characteristic absorption wavelength of the light wave used in the molybdenum blue colorimetric method is 700 nm.

[0020] In this embodiment, a citrate-sodium citrate buffer solution is used to maintain an acidic environment and dissolve iron / aluminum bound phosphorus; disodium EDTA chelates calcium ions to prevent phosphorus refixation in calcareous soils; ammonium oxalate enhances the release of occluded phosphorus. The entire extraction process is simple and efficient, reducing the single-sample processing time from 20 minutes in traditional extraction to 12 minutes. This invention has strong versatility and is suitable for soils with pH 4.0–8.5, with a recovery rate ≥92%. Specifically, the recovery rate is 95%–98% for acidic soils (pH 4.0–6.5) and 92%–94% for calcareous soils (pH 7.5–8.5). In addition, the extraction cost of this invention is low and environmentally friendly. The composite extractant is non-toxic and harmless, free of fluorides and strong acid components, and the waste is easy to dispose of, meeting green chemistry standards.

[0021] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for combined extraction of fast-acting phosphorus suitable for acidic, neutral, and calcareous soils, characterized in that: Includes the following content: A compound extractant is prepared, the components of which include citrate-sodium citrate buffer, disodium EDTA, and ammonium oxalate. Soil samples were mixed with a compound extractant; Solid-liquid separation was performed on the mixture of soil samples and composite extractant; Phosphorus content was determined in the filtrate obtained from solid-liquid separation.

2. The method for combined extraction of fast-acting phosphorus suitable for acidic, neutral, and calcareous soils according to claim 1, characterized in that: In step (I), the concentration of the citrate-sodium citrate buffer solution is 0.25 mol / L, the concentration of the disodium EDTA solution is 0.05 mol / L, and the mass-volume percentage concentration of ammonium oxalate is 2%.

3. The method for combined extraction of fast-acting phosphorus suitable for acidic, neutral, and calcareous soils according to claim 2, characterized in that: In step (I), the pH of the citrate-sodium citrate buffer solution is 4.5 to 5.

5.

4. The method for combined extraction of fast-acting phosphorus suitable for acidic, neutral, and calcareous soils according to claim 1, characterized in that: In step (II), the mixing ratio of soil sample and compound extractant is 1:

20.

5. The method for combined extraction of fast-acting phosphorus suitable for acidic, neutral, and calcareous soils according to claim 4, characterized in that: In step (II), the soil sample is mixed with the composite extractant and shaken at a temperature of 25℃±2℃.

6. The method for combined extraction of fast-acting phosphorus suitable for acidic, neutral, and calcareous soils according to claim 1, characterized in that: In step (III), the mixture of soil sample and compound extractant is separated into solid and liquid components by vacuum filtration.

7. The method for combined extraction of fast-acting phosphorus suitable for acidic, neutral, and calcareous soils according to claim 6, characterized in that: In step (III), the solid-liquid separation time of the vacuum filter is within two minutes.

8. The method for combined extraction of fast-acting phosphorus suitable for acidic, neutral, and calcareous soils according to claim 1, characterized in that: In step (IV), the phosphorus content of the filtrate is determined by the molybdenum blue colorimetric method, and the quantitative analysis of phosphorus is achieved by a spectrophotometer.

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