Sodium carbonate alkali melting method for measuring multiple elements of soil or sediment

Abstract

The invention discloses a sodium carbonate alkali melting method for measuring multiple elements of soil or sediment, which comprises the following steps: selecting anhydrous sodium carbonate as a flux, putting the flux and a substance to be measured into a platinum crucible, transferring into a muffle furnace for heating, taking out, rotating, shaking and shaping, putting into tap water at room temperature for cooling, adding deionized water, heating for pyrolysis, and filtering to obtain a filtrate; soaking overnight for 24 hours, fully stirring with a plastic rod, washing with deionized water, dropwise adding 2ml of diluted hydrochloric acid, heating at low temperature, mashing fallen substances, stirring, adding nitric acid-hydrochloric acid mixed acid, dissolving, transferring, fixing the volume, uniformly shaking, filtering, directly measuring the boron element, and detecting on a machine after measuring that other elements are diluted by a proper multiple.

Description

Technical Field

[0001] The invention relates to the technical field of environmental detection, in particular to a sodium carbonate alkali melting method for determining multiple elements in soil or sediment. Background Art

[0002] At present, the determination of inorganic elements in soil or sediment in my country mostly uses atomic absorption method, and the pretreatment adopts acid fusion method, but the acid fusion method cannot determine silicon. "Determination of 11 Elements in Soil or Sediment by Alkali Fusion-Inductively Coupled Plasma Optical Emission Spectrometry" (HJ 974-2018) fills the gap of alkali fusion-inductively coupled plasma optical emission spectrometry for the determination of inorganic elements in soil or sediment in my country, but the flux used in this method is sodium carbonate, lithium tetraborate and lithium metaborate, and the molten material is dissolved with a mixed acid of hydrochloric acid and nitric acid, and the fixed volume is 500mL, so the boron element cannot be measured at the same time. The research report on this method shows that compared with sodium carbonate, lithium tetraborate and lithium metaborate, the sodium carbonate flux has no significant difference in the determination of other elements except that the silicon element is larger. The alkali fusion-plasma optical emission spectrometry method for the determination of total boron in soil mentioned in Chapter 18.1 of "Technical Specifications for Soil Analysis" (Second Edition) uses sodium carbonate as a flux, dilute sulfuric acid to dissolve the molten material, and the fixed volume is 100mL. There are certain differences between the two standards in terms of flux mixing methods, melting time and temperature, but the differences are not significant. Both of them describe the process of dissolving the melt too simply, which may lead to problems such as the melt not being completely dissolved and silicon precipitation during dissolution when verifying the experiment.

[0003] The platinum crucibles used for alkali melting are expensive and scarce. If silicon, boron and other elements can be determined simultaneously with multiple metal elements after a single pretreatment, the detection efficiency can be greatly improved and manpower and material resources can be saved. Therefore, this project team was established to conduct in-depth research, integration and improvement of the two standards.

[0004] Therefore, a technical means is provided, sodium carbonate is selected as a flux, and a method is designed to determine the metal elements in soil or sediment, which can simultaneously determine elements such as silicon and boron while ensuring precision and accuracy, so that more than ten elements can be determined simultaneously after one alkali melting pretreatment of the sample, which greatly improves the detection efficiency while also saving time and labor costs. Summary of the invention

[0005] To achieve the above object, the present invention provides a sodium carbonate alkali melting method for determining multiple elements in soil or sediment.

[0006] The present invention provides a sodium carbonate alkali melting method for determining multiple elements in soil or sediment, including a melting extraction method for multiple elements in soil or sediment, and the melting extraction method comprises the following steps:

[0007] a. Place anhydrous sodium carbonate flux at the bottom of the crucible;

[0008] b. Place the soil or sediment sample to be tested evenly on the anhydrous sodium carbonate flux;

[0009] c. Add anhydrous sodium carbonate on top of the sample layer;

[0010] d. Cover the entire mixture with a layer of anhydrous sodium carbonate flux.

[0011] Furthermore, the soil or sediment sample to be tested is processed by removing foreign matter, air drying, grinding and passing through a nylon sieve;

[0012] Preferably, the nylon mesh has a pore size of 0.096 mm.

[0013] Furthermore, the method for melting and extracting elements from soil or sediment also includes the step of placing the crucible in a muffle furnace, heating it to 1000° C., and keeping it for 30 minutes before taking it out.

[0014] Furthermore, after taking out the crucible, take off the lid and put it into cold water while the sample is still in a molten state, and then shake the crucible in circles at a constant speed to allow the molten liquid to gradually solidify into a thin layer at the bottom of the crucible and 1 / 3 of the wall.

[0015] Furthermore, the method also includes placing the bottom of the crucible into room temperature tap water to cool it down, adding deionized water of about 1 / 2 the volume of the crucible after slight cracks appear, heating and pyrolysis at 90°C, soaking it overnight for 24 hours, and stirring it thoroughly with a plastic rod to remove as much of the molten material as possible from the pot.

[0016] Further, by weight, 0.4 parts by weight of the anhydrous sodium carbonate flux is placed at the bottom of the crucible, 0.2 parts by weight of the soil or sediment sample to be tested is evenly placed on the anhydrous sodium carbonate flux, 0.6 parts by weight of anhydrous sodium carbonate is added on the sample layer, and then covered with a layer of 0.4 parts by weight of anhydrous sodium carbonate flux;

[0017] Preferably, the crucible is a platinum crucible.

[0018] Further, the grinding step is carried out in a ball mill or a mortar;

[0019] Further, a method for determining the content of multiple elements in soil or sediment is included, and the method for determining the content of multiple elements in soil or sediment comprises the following steps:

[0020] a. dissolving the melt obtained by the melt extraction method according to any one of claims 3 to 7 and transferring it to a volumetric flask to a fixed volume;

[0021] b. After filtration, it is directly used for the determination of boron;

[0022] c. Dilute it 50 times and use it to determine silicon;

[0023] dFor other elements, perform preliminary determination on the test liquid using inductively coupled plasma emission spectrometer to understand the approximate concentration range of the elements, and adjust the dilution factor of the melt based on the results of the preliminary determination so that the concentration of the elements falls within the linear detection range of the instrument. Then re-determine the element content and record the results.

[0024] Furthermore, in step d of the method for determining the content of multiple elements in soil or sediment, the dilution factor can be adjusted according to the specific concentration of the element to be measured and the detection sensitivity of the instrument.

[0025] Furthermore, the method for determining the content of multiple elements in soil or sediment also includes the step of adding dilute hydrochloric acid and nitric acid-hydrochloric acid mixed acid during the dissolution of the melt to promote complete dissolution of the melt;

[0026] Preferably, the volume ratio of nitric acid to hydrochloric acid in the nitric acid-hydrochloric acid mixed acid is 1:4.

[0027] The sodium carbonate alkali melting method for determining multiple elements in soil or sediment proposed by the present invention has the following beneficial effects:

[0028] 1. Sodium carbonate is used as flux, which can simultaneously determine elements such as silicon and boron, so that more than ten elements can be determined simultaneously after one alkali melting pretreatment of the sample;

[0029] 2. While ensuring precision and accuracy, the detection efficiency is greatly improved. The preparation method is simple and easy to operate, suitable for large-scale industrial production;

[0030] 3. Anhydrous sodium carbonate is a commonly used alkali flux, which can effectively decompose silicates and other refractory compounds in soil or sediments, promote chemical reactions during the melting process, improve the efficiency of element extraction, and realize the efficient extraction of multiple elements in soil or sediments. It adopts a new combination and ratio of raw materials, and optimizes the proportion of each component and the preparation process to achieve efficient and accurate determination of multiple elements in soil or sediments, significantly improve the efficiency of element extraction, reduce errors and interference in the determination process, and is suitable for various types of soil or sediment samples, including refractory samples such as high silicon, high aluminum, and high calcium. DETAILED DESCRIPTION

[0031] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0032] Unless otherwise specified, the examples and comparative examples are parallel tests with the same components, component contents, preparation steps and preparation parameters. The experimental methods in the following examples are conventional methods unless otherwise specified. The experimental materials used in the following examples are purchased from commercial channels unless otherwise specified.

[0033] The sources of the materials mentioned in the present invention are as follows: soil samples were purchased from.

[0034] Unless otherwise stated, all reagents were used as received without further purification.

[0035] In the preparation examples and embodiments of the present invention, the “parts” are parts by weight unless otherwise specified, and the concentration percentages are concentrations by weight unless otherwise specified.

[0036] The parameters of the inductively coupled plasma emission spectrometer used in the on-machine test in the present invention are: plasma gas flow rate 20L / min; auxiliary gas flow rate 0.5L / min; nebulizer flow rate 0.8L / min; injection volume 2.5mL / min power 1500W; lamp current 30mA; carrier gas flow rate 400mL / min; shielding gas flow rate 800mL / min; and the detection wavelength is selected as 254.1nm.

[0037] Example 1

[0038] The soil or sediment sample to be tested is processed by removing foreign matter, air drying, grinding and passing through a nylon sieve with a pore size of 0.096mm. 0.4 parts by weight of anhydrous sodium carbonate flux is placed at the bottom of the platinum crucible, and 0.2 parts by weight of the soil or sediment sample to be tested is evenly placed on the anhydrous sodium carbonate flux. The main purpose of this layer is to allow the sample to initially contact the flux and prepare for the subsequent melting reaction. A layer of 0.6 parts by weight of anhydrous sodium carbonate is added on top of the sample layer. The function of this layer is to promote complete melting of the sample and ensure that all elements can be effectively extracted. A layer of 0.4 parts by weight of anhydrous sodium carbonate flux is covered on the entire mixture. The main function of this layer is to prevent the volatilization of the sample and solvent during the melting process, and it also helps to maintain the stability of the molten state.

[0039] Cover the crucible, put it in a muffle furnace and heat it to 1000℃, keep it for 30 minutes, stop heating, take out the crucible after 5 minutes, take off the lid while the sample is still in a molten state and put it in cold water, then shake the crucible in a circle at a constant speed to make the molten liquid gradually solidify into a thin layer at the bottom and 1 / 3 of the wall of the crucible. Put the bottom of the crucible into room temperature tap water to cool, and slight cracks will appear. Add 1 / 2 volume of deionized water of the crucible, heat and pyrolyze at 90℃, soak overnight for 24 hours, stir thoroughly with a plastic rod, remove as much of the molten material as possible from the pot, pour it into a plastic beaker at one time, and rinse it with a small amount of deionized water 1-2 times. Use a dropper to drip 2ml of dilute hydrochloric acid along the wall of the crucible, and heat at low temperature to dissolve the remaining molten material. Use a plastic rod to break up the large pieces of melt in the beaker, and use a dropper or pipette to quickly stir / shake while adding 10ml of 1+4 nitric acid-hydrochloric acid mixed acid at one time. This process will produce a lot of bubbles, and the melt will completely dissolve and slowly become a yellow transparent liquid. Repeat the operation several times. After the melt is completely dissolved, transfer it to a 100mL plastic volumetric flask, make up to volume and shake well. After filtering, it can be directly used to determine the boron element. After diluting it 50 times, it can be used to determine the silicon element. If other elements are determined, the liquid to be tested can be preliminarily determined according to the inductively coupled plasma emission spectrometer to understand the approximate concentration range of the element. According to the results of the preliminary determination, adjust the dilution multiple of the melt so that the concentration of the element falls within the linear detection range of the instrument. Only then can the machine be used for detection and the content of the element can be re-determined, and the results recorded.

[0040] Further, when the temperature is raised to 1000°C in a muffle furnace, 1000°C is used as the target temperature for target temperature control in the muffle furnace, including: gradient segmentation according to a preset gradient rule for the target temperature to obtain multiple temperature gradients, after the crucible cover is placed in the muffle furnace, temperature control is performed according to a first gradient heating rate, and when the overall temperature of the crucible reaches the first temperature gradient, the temperature control is adjusted, and the temperature control is performed according to a second gradient heating rate, and when the overall temperature of the crucible reaches the second temperature gradient, the temperature control is continued to be adjusted, and the temperature control is performed according to a third gradient heating rate, and the cycle is repeated multiple times until the overall temperature of the crucible reaches the target temperature, and then after the overall temperature of the crucible reaches the target temperature, the temperature control is adjusted to be kept at a constant temperature. Among them, in the preset gradient rule, the temperature difference of each temperature gradient is in an increasing sequence, and the heating rate of each gradient is also in an increasing form. The above technical solution performs gradient segmentation according to preset gradient rules for the target temperature, so that the muffle furnace can gradually achieve target temperature regulation during the heating process, thereby avoiding damage to the crucible caused by uneven heating of the crucible due to excessive temperature changes.

[0041] Furthermore, the plastic stirring rod is provided with a plurality of stirring blades, and an intelligent control system is configured for the plastic stirring rod. When the plastic stirring rod is fully stirred, the stirring blades are combined according to the start signal, and then the stirring blades after the combined processing are stirred according to the first preset power and the first preset time. When the stirring time reaches the first preset time, the first stirring mode is completed. At this time, the stirring blades after the combined processing are separated so that the stirring blades are restored to the initial state, and then the secondary stirring is continued according to the second preset power and the second preset time, until the secondary stirring time reaches the second preset time, the secondary stirring is completed. Among them, the first preset power is greater than the second preset power, and the first preset time and the second preset time can be the same or different. The above technical scheme realizes the intelligent stirring of the plastic stirring rod through the intelligent control system, which can not only save manpower consumption and enable rapid stirring, but also ensure the stirring effect, so that more molten materials are separated from the crucible. By dividing the stirring process into two stages, the molten material adhering to the crucible can be better removed, the removal effect of the molten material is guaranteed, the stirring efficiency is improved, and convenience is provided for the subsequent use of the molten material. Moreover, based on the stirring plate after the combined treatment, stirring is performed according to the first preset power and the first preset time, which can not only remove the molten material that adheres strongly to the crucible and avoid damage to the plastic stirring rod by the molten material, but also realize the simultaneous removal of large pieces of molten material from the crucible, thereby improving the removal efficiency. By continuing the secondary stirring according to the second preset power and the second preset time, the smaller residual molten material on the crucible can be removed, so that more molten material can be removed from the crucible as much as possible, thereby ensuring the stirring effect.

[0042] Performance Testing

[0043] The standard test samples with known element contents were tested using Example 1. The results are shown in Table 1.

[0044] Table 1

[0045]

[0046]

[0047] As shown in Table 1, the calculated results measured by Example 1 have a small deviation from the actual true value of the content of each element.

[0048] The specific embodiments of the present invention are described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions made to the present invention are also within the scope of the present invention. Therefore, the equalization changes and modifications made without departing from the spirit and scope of the present invention should be included in the scope of the present invention.

Claims

1. A sodium carbonate alkali fusion method for determining multiple elements in soil or sediment, characterized in that: The invention relates to a melting extraction method for multiple elements in soil or sediment, wherein the melting extraction method comprises the following steps: a. Place anhydrous sodium carbonate flux at the bottom of the crucible; b. Place the soil or sediment sample to be tested evenly on the anhydrous sodium carbonate flux; c. Add anhydrous sodium carbonate on top of the sample layer; d. Cover the entire mixture with a layer of anhydrous sodium carbonate flux.

2. The method for determining multiple elements in soil or sediment using sodium carbonate alkali fusion according to claim 1, characterized in that: The soil or sediment sample to be tested is processed by removing foreign matter, air drying, grinding and passing through a nylon sieve, and the aperture of the nylon sieve is 0.096 mm.

3. The method for determining multiple elements in soil or sediment using sodium carbonate alkali fusion according to claim 1, characterized in that: The method also includes placing the crucible in a muffle furnace, heating the temperature to 1000° C., maintaining the temperature for 30 minutes, and then taking out the crucible.

4. The method for determining multiple elements in soil or sediment using sodium carbonate alkali fusion according to claim 3, characterized in that: After taking out the crucible, take off the lid and put it into cold water while the sample is still in a molten state, and shake the crucible in circles to allow the molten liquid to gradually solidify into a thin layer at the bottom of the crucible and 1 / 3 of the wall.

5. The method for determining multiple elements in soil or sediment using sodium carbonate alkali fusion according to claim 4, characterized in that: The process also includes placing the bottom of the crucible in room temperature tap water to cool it down, adding 1 / 2 volume of deionized water to the crucible after slight cracks appear, heating and pyrolysis at 90°C, soaking it overnight for 24 hours, and stirring it with a plastic rod.

6. The method for determining multiple elements in soil or sediment using sodium carbonate alkali fusion according to claim 1, characterized in that: By weight, 0.4 parts by weight of the anhydrous sodium carbonate flux is placed at the bottom of the crucible, 0.2 parts by weight of the soil or sediment sample to be tested is placed on the anhydrous sodium carbonate flux, 0.6 parts by weight of anhydrous sodium carbonate is added on the sample layer, and a layer of 0.4 parts by weight of anhydrous sodium carbonate flux is covered. The crucible is a platinum crucible.

7. The method for determining multiple elements in soil or sediment using sodium carbonate alkali fusion according to claim 2, characterized in that: The grinding step is performed in a ball mill or a mortar.

8. The method for determining multiple elements in soil or sediment using sodium carbonate alkali fusion according to claim 1, characterized in that: The invention comprises a method for determining the content of multiple elements in soil or sediment, and the method for determining the content of multiple elements in soil or sediment comprises the following steps: a. dissolving the melt obtained by the melt extraction method according to any one of claims 3 to 7 and transferring it to a volumetric flask to a fixed volume; b. After filtration, it is directly used for the determination of boron; c. Dilute it 50 times and use it to determine silicon; dFor other elements, perform preliminary determination on the test liquid using inductively coupled plasma emission spectrometer to understand the approximate concentration range of the elements, and adjust the dilution factor of the melt based on the results of the preliminary determination so that the concentration of the elements falls within the linear detection range of the instrument. Then re-determine the element content and record the results.

9. The method for determining multiple elements in soil or sediment using sodium carbonate alkali fusion according to claim 8, characterized in that: In step d of the method for determining the content of multiple elements in soil or sediment, the dilution factor can be adjusted according to the specific concentration of the element to be measured and the detection sensitivity of the instrument.

10. The method for determining multiple elements in soil or sediment using sodium carbonate alkali fusion according to claim 8, characterized in that: The method for determining the content of multiple elements in soil or sediment also includes the step of adding dilute hydrochloric acid and nitric acid-hydrochloric acid mixed acid during the dissolution of the melt to promote the complete dissolution of the melt, and the volume ratio of nitric acid to hydrochloric acid in the nitric acid-hydrochloric acid mixed acid is 1:4.

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