CN112763431A - Method for quantifying content of hematite in sediment based on diffuse reflection spectrum - Google Patents

Abstract

The invention discloses a novel method for quantifying the content of hematite in a deposit based on diffuse reflection spectroscopy, which comprises the following steps: (1) selecting a typical kalimeris middle loess L1 and an ancient soil layer S1 in a loess plateau area as substrates, and grinding the substrates into powder; (2) adding and proportioning a loess layer L1 and an ancient soil layer S1 sample substrate and samples with different contents of hematite and goethite; (3) using Lambda 900 ultraviolet/visible light/near infrared spectrophotometer to measure the sample to obtain the original spectral data of 300-700 nm; (4) calculating original spectral data to obtain the data of the yellowness and the orange degree of each sample; (5) and carrying out regression analysis by utilizing the known ratio of the content of the hematite to the yellowness/orange degree to obtain the quantitative relation of the hematite. The method has the advantages of simple pretreatment, reliable quantification and weak substrate effect, is not interfered by the content of associated goethite, can rapidly, effectively and accurately quantify the content of the hematite in various sediments, saves time and cost, and is suitable for large-scale quantitative testing of the hematite in the sediments.

Description

Method for quantifying content of hematite in sediment based on diffuse reflection spectrum

Technical Field

The invention relates to a novel method for quantifying the content of hematite in a sediment based on diffuse reflection spectroscopy, and belongs to the field of environment.

Background

Hematite is an iron oxide which is widely distributed in nature, widely distributed in soil, glaciers, lakes and marine sediments, is also an important ironmaking raw material, and is generally known due to strong color-causing characteristics. Hematite is also an inorganic colloid, can adsorb substances such as organic pollutants, heavy metals and the like in soil, and is one of important minerals in soil remediation. Meanwhile, the hematite in the soil can also indicate the formed climate environment information, often accompanying with goethite, the hematite is inclined to be formed in a warm and dry environment, while the goethite likes a cold and wet environment, the ratio of the two represents the dry and wet change, and the goethite is widely applied to loess, lakes and marine sediment carriers and is used for reconstructing the past climate environment change. Therefore, the work of quantitatively measuring the hematite in the sediment has great requirements on scientific research and environmental remediation.

At present, the traditional method for testing the ratio of hematite in the sediment mainly comprises a diffuse reflection spectrum technology, and the main method comprises the following steps: the method comprises the steps of firstly utilizing Kubelka-Munk function conversion of diffuse reflection spectrum original data, then obtaining a second derivative to obtain a hematite/goethite ratio, then utilizing sodium citrate-sodium bicarbonate-sodium hydrosulfite to extract free iron of a sample, calculating the total amount of goethite and hematite, and obtaining the content of the hematite through two equations, wherein a large amount of amorphous iron exists in the free iron, so that the total amount of the hematite and the goethite can be greatly overestimated. And the other method is to obtain corresponding chromaticity values from the measured diffuse reflection spectrum and then perform simple polynomial regression fitting, and the method is only statistical analysis, and the result depends on the number of the adopted databases and is also strongly interfered by goethite. The method of quantifying hematite content by soil redness is also widely used, but since goethite content is also related to redness, it is disturbed by goethite content. In addition, X-ray diffraction is also commonly used for quantifying the content of hematite, but the detection line is high, and the requirement on the crystal form of the hematite in a sample is high, so that the method is widely considered as a qualitative and semi-quantitative method.

Disclosure of Invention

The purpose of the invention is as follows: in order to overcome the defects in the prior art, the invention provides a novel method for quantifying the content of hematite in sediment based on diffuse reflection spectrum, which has the advantages of simple pretreatment, convenient test, high efficiency, accurate quantification, no influence of sediment types and no interference of frequently associated goethite in sediment.

The technical scheme is as follows: in order to solve the technical problems, the novel method for quantifying the content of hematite in the sediment based on the diffuse reflection spectrum comprises the following steps:

(1) preparation of iron-free oxide substrates of loess plateau Lingtai section Malan loess middle loess and ancient soil layer samples. Selecting a loess layer LT-L1 sample and an ancient soil layer LT-S1 sample, weighing about 20 +/-1 g of the samples, grinding the samples into powder samples by using an agate mortar, putting the powder samples into a 500ml beaker, adding 250ml of 0.3mol/L sodium citrate solution and 35ml of 1mol/L sodium bicarbonate solution, adding 1 +/-0.1 g of sodium hydrosulfite, carrying out excessive reaction, putting the samples into ultrasonic waves at 80 ℃ for stirring and reacting for 90 minutes, transferring the samples into a 250ml centrifuge cup, putting the centrifuge cup into a low-speed centrifuge for centrifuging for 12 minutes at 5000r/min, pouring out supernatant, repeating the steps until the sediment is gray, namely completely reacting, cleaning the completely reacted samples for three times by using secondary distilled water, centrifuging, drying the residues at room temperature, grinding the residues into powder, and obtaining a substrate of the loess and ancient soil layer samples;

(2) adding loess or ancient soil sample base and samples with different contents of hematite and goethite: firstly, weighing a substrate sample by using a ten-thousand-position high-precision electronic balance, pouring the substrate sample into an agate mortar, weighing a hematite sample of the Pfizer R1599 international standard or a goethite sample of the Synox HY610 international standard, pouring the hematite sample or the goethite sample into the agate mortar with the substrate, grinding for more than 10 minutes to ensure that the hematite sample and the goethite sample are uniformly mixed without obvious color difference, and sequentially matching 43 samples with different contents of hematite and goethite to form a loess substrate LT-L1 and an ancient soil substrate LT-S1;

(3) testing the proportioned sample by using a Lambda 900 diffuse reflection spectrometer, wherein the scanning wavelength is 400-700nm, the interval is 2nm, when in testing, taking a proper amount of powder sample on a glass slide, adding a few drops of distilled water to mix the powder sample into paste, uniformly stirring and smearing the paste, slightly knocking the glass slide by a glass rod to enable the surface of the sample to be flat, and naturally drying the sample; then, testing on a computer, firstly testing a barium sulfate white board which is used as a color background, wherein the testing steps comprise that the barium sulfate white board is placed at a sample placing position of an instrument, a cover is covered, Lambda 900 software in the computer is clicked, the wavelength range is 400-700nm, the distance is 2nm, the sample number is modified, an AUTOZORO button is clicked, after the testing is finished, a START button is clicked again to test, the testing error is +/-1%, if the testing error does not reach the standard, the testing needs to be repeated, when the sample is tested, a glass slide coated with the sample is placed in a sample bin, the sample number is filled, the START button is clicked, the testing time of one sample is 2-3 minutes, and the data is automatically stored after the testing is finished;

(4) processing the original data of the diffuse reflection spectrometer by using EXCEL software of OFFICE OFFICE software of MICROSOFT to obtain the yellowness and the orange degree of each sample, wherein the yellowness Y is the ratio of the reflectivity of 560-;

(5) regression analysis was performed using the known goethite/hematite content to yellowness Y/orange O ratio with a quantitative relationship of hematite content 0.5336Y/O²-0.7680*Y/O+0.2783，R²0.95% RMSE, 0.1%;

(6) and obtaining the content of the hematite in the sediment by utilizing the quantitative relation between the content of the goethite/hematite and the yellowness degree Y/orange degree O.

Has the advantages that: the novel method for quantifying the content of the hematite in the sediment based on the diffuse reflection spectrum has the advantages of simple pretreatment, capability of quickly, effectively and accurately quantifying the content of the hematite in the sediment, time saving and cost saving, and suitability for large-scale quantitative test of the content of the hematite in the sediment.

Drawings

FIG. 1 is a graph showing the correlation between goethite and hematite standard minerals (a), goethite/hematite contents (b) and a yellowness/orange degree ratio, and the correlation between the content of hematite (c) added and the content of hematite calculated from the yellowness/orange degree

FIG. 2 is a schematic flow chart of the present invention.

Detailed Description

The present invention will be further described with reference to the accompanying drawings.

As shown in fig. 2, the method for quantifying the content of hematite in the deposit based on the diffuse reflection spectrum of the invention comprises the following steps:

(1) preparation of iron-free oxide substrates of loess plateau Lingtai section Malan loess middle loess and ancient soil layer samples. Selecting a loess layer and an ancient soil layer sample, weighing about 20 +/-1 g of the sample, grinding the sample into a powder sample by using an agate mortar, putting the powder sample into a 500ml beaker, adding 250ml of 0.3mol/L sodium citrate solution and 35ml of 1mol/L sodium bicarbonate solution, adding 1 +/-0.1 g of sodium hydrosulfite to enable the reaction to be excessive, putting the sample into a shaking table at 80 ℃ for oscillation reaction for 90 minutes, transferring the sample into a 250ml centrifuge cup, putting the centrifuge cup into a low-speed centrifuge for centrifugation for 10 minutes at 5000r/min, pouring out supernatant, repeating the steps until the sediment is grey white, namely the reaction is complete, cleaning the sample which is completely reacted by using secondary distilled water for three times, centrifuging, drying the residue at room temperature, and grinding the residue into powder to obtain a substrate of the loess and ancient soil layer samples;

(2) adding loess or ancient soil sample base and samples with different contents of hematite and goethite: firstly, weighing a substrate sample by using a ten-thousand-position high-precision electronic balance, pouring the substrate sample into an agate mortar, weighing a hematite sample of the Pfizer R1599 international standard or a goethite sample of the Synox HY610 international standard, pouring the hematite sample or the goethite sample into the agate mortar filled with the substrate, grinding for more than 10 minutes to ensure that the hematite sample and the goethite sample are uniformly mixed without obvious color difference, and sequentially matching 43 samples with different contents of hematite and goethite to form a loess substrate and an ancient soil substrate;

(3) testing the proportioned sample by using a Lambda 900 diffuse reflection spectrometer, wherein the scanning wavelength is 400-700nm, the interval is 2nm, when in testing, taking a proper amount of powder sample on a glass slide, adding a few drops of distilled water to mix the powder sample into paste, uniformly stirring and smearing the paste, slightly knocking the glass slide by a glass rod to enable the surface of the sample to be flat, and naturally drying the sample; then, testing on a computer, firstly testing a barium sulfate white board which is used as a color background, wherein the testing steps comprise that the barium sulfate white board is placed at a sample placing position of an instrument, a cover is covered, Lambda 900 software in the computer is clicked, the wavelength range is 400-700nm, the distance is 2nm, the sample number is modified, an AUTOZORO button is clicked, after the testing is finished, a START button is clicked again to test, the testing error is +/-1%, if the testing error does not reach the standard, the testing needs to be repeated, when the sample is tested, a glass slide coated with the sample is placed in a sample bin, the sample number is filled, the START button is clicked, the testing time of one sample is 2-3 minutes, and the data is automatically stored after the testing is finished;

(4) processing the original data of the diffuse reflection spectrometer by using EXCEL software of OFFICE OFFICE software of MICROSOFT to obtain the yellowness and the orange degree of each sample, wherein the yellowness Y is the ratio of the reflectivity of 560-;

(5) regression analysis is carried out by utilizing the known goethite/hematite content and the yellowness Y/orange degree O ratio, the fact that the goethite content is 0.1 to 2 percent, the yellowness/orange degree ratio is basically constant, meanwhile, whether pure hematite is added or a mixture of the hematite and the goethite is added, the yellowness/orange degree ratio is obviously related to the hematite content, the yellowness Y/orange degree O ratio is unrelated to the goethite content, and the quantitative relation is that the hematite content is 0.5336Y/O²-0.7680*Y/O+0.2783，R²0.95 RMSE, 0.1% as shown in figure 1;

(6) and obtaining the content of the hematite in the sediment by utilizing the quantitative relation between the content of the goethite/hematite and the yellowness degree Y/orange degree O.

The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.

Claims (1)

1. A novel method for quantifying the content of hematite in a deposit based on diffuse reflectance spectroscopy is characterized by comprising the following steps:

(1) preparing iron-free oxide substrate of loess plateau Lingtai section Malan loess middle loess layer and ancient soil layer samples. Selecting samples LT-L1 and LT-S1 of loess layer, weighing 20 +/-1 g of samples, grinding the samples with agate mortar to prepare powder samples, putting the powder samples into a 500ml beaker, adding 0.3mol/L sodium citrate solution 250ml and 1mol/L sodium bicarbonate solution 35ml, adding 1 + -0.1 g sodium dithionite for reaction to excess, placing the sample in 80 deg.C ultrasonic wave for reaction and stirring for 90 minutes, transferring the sample into 250ml centrifuge cup, centrifuging in a low-speed centrifuge at 5000r/min for 12 min, pouring out the supernatant, repeating the above steps until the precipitate is grey white, washing the sample with secondary distilled water for three times, centrifuging, drying the residue in a 40 ℃ oven, and grinding to powder to obtain loess and ancient soil layer sample substrates respectively;

(2) adding loess or ancient soil sample base and samples with different contents of hematite and goethite: firstly, weighing a substrate sample by using a ten-thousand-position high-precision electronic balance, pouring the substrate sample into an agate mortar, weighing a hematite sample of the Pfizer R1599 international standard and/or a goethite sample of the Synox HY610 international standard, pouring the hematite sample and/or the goethite sample into the agate mortar filled with the substrate, grinding for more than 10 minutes to ensure that the hematite sample and the goethite sample are uniformly mixed without obvious color difference, and sequentially matching 43 samples with different contents of hematite and goethite to form a loess substrate LT-L1 and an ancient soil substrate LT-S1;

(3) testing the proportioned sample by using a Lambda 900 diffuse reflection spectrometer, wherein the scanning wavelength is 400-700nm, the interval is 2nm, when in testing, taking a proper amount of powder sample on a glass slide, adding a few drops of distilled water to mix the powder sample into paste, uniformly stirring and smearing the paste, slightly knocking the glass slide by a glass rod to enable the surface of the sample to be flat, and naturally drying the sample; the method comprises the steps of firstly testing a barium sulfate white board which is used as a color background, placing the barium sulfate white board at a sample placing position of an instrument, covering a cover, clicking Lambda 900 software in a computer, setting the wavelength range to be 400-700nm and the interval to be 2nm, modifying a test number, clicking an AUTOZORO button, after the test is finished, clicking a START button to test, if the test error is +/-1%, repeatedly performing the test, placing a glass slide coated with a sample into a sample bin when the sample is tested, filling the sample number, clicking the START button, testing for 2-3 minutes for one sample, and automatically storing data after the test is finished;

(4) the raw diffuse reflectance spectrometer data was processed using EXCEL software from MICROSOFT's OFFICE OFFICE software to obtain the yellowness Y and orange-ness O of each sample. According to the division of the standard color band, the yellowness Y is the ratio of the reflectivity of 560-590nm to the sum of the reflectivities of 400-700nm, and the orange degree O is the ratio of the reflectivity of 590-630nm to the sum of the reflectivities of 400-700 nm;

(5) the known goethite/hematite content and the yellowness Y/orange degree O ratio are used for carrying out regression to obtain the quantitative relation that the hematite content is 0.5336Y/O²-0.7680*Y/O+0.2783，R²0.95% RMSE, 0.1%;

(6) and obtaining the content of the hematite in the sediment by utilizing the quantitative relation between the content of the goethite/hematite and the yellowness degree Y/orange degree O.

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