1. An extraction test method of carbonate crystal lattice phosphate is characterized by comprising the following steps:

dissolving a sample containing carbonate minerals by using an acetic acid solution, and centrifuging to obtain a dissolved solution and residual solids;

detecting the content of phosphate in the dissolved solution by using a malachite green-phosphomolybdic heteropoly acid spectrophotometry;

repeatedly washing the residual solid by using a sodium chloride buffer solution to release adsorbed phosphate, collecting the washing liquid, detecting the content of phosphate in the washing liquid by using a malachite green-phosphomolybdic heteropoly acid spectrophotometry, and summarizing the measured content of phosphate to obtain the content of carbonate lattice phosphate in the sample.

2. The carbonate lattice phosphate extraction test method of claim 1, wherein the volume concentration of acetic acid in the acetic acid solution is 2%.

3. The method for testing the extraction of carbonate lattice phosphate according to claim 1, wherein the carbonate mineral contained in the sample is one of calcite or dolomite.

4. The method for the extraction test of carbonate lattice phosphate according to claim 1, wherein the mass of carbonate mineral in the sample is made to be 0.1g ± 0.001g by sampling the mass of inorganic carbon (TIC) content of the sample, and 70% of carbonate mineral in the sample is dissolved when the sample containing carbonate mineral is dissolved.

5. The carbonate lattice phosphate extraction test method of claim 1, wherein the sodium chloride buffer solution is adjusted to pH 8 with sodium bicarbonate solution.

6. The carbonate lattice phosphate extraction test method of claim 1, wherein 4mL of 2% by volume acetic acid solution is added when the sample is limestone and 4.35mL of 2% by volume acetic acid solution is added when the sample is dolomite.

Background

At present, the research on the content level and the change of the seawater phosphate in the geological historical period is considered to have important significance for understanding the early life evolution and the change of the ancient marine environment, but the existing research method usually only extracts different phosphorus components in geological samples or detects the phosphorus content of the whole rock of the geological samples, so that the phosphorus cycle of the ancient marine is researched, and the direct indication on the content of the phosphate in the seawater is difficult to carry out.

Disclosure of Invention

An object of the present invention is to solve at least the above problems and to provide at least the advantages described later.

It is still another object of the present invention to provide a method for extracting carbonate lattice phosphate, comprising the steps of: dissolving a sample containing carbonate minerals by using an acetic acid solution, and centrifuging to obtain a dissolved solution and residual solids; detecting the content of phosphate in the dissolved solution by using a malachite green-phosphomolybdic heteropoly acid spectrophotometry; repeatedly washing the residual solid by using a sodium chloride buffer solution to release adsorbed phosphate, collecting the washing liquid, detecting the content of phosphate in the washing liquid by using a malachite green-phosphomolybdic heteropoly acid spectrophotometry, and summarizing the measured content of phosphate to obtain the content of carbonate lattice phosphate in the sample. The method uses malachite green-phosphomolybdic heteropoly acid spectrophotometry to detect the content of phosphate, effectively eliminates the interference of a large amount of calcium and magnesium ions released by dissolving carbonate, and effectively avoids the adsorption of residual solids on the phosphate by repeatedly washing the residual solids through sodium chloride buffer solution, thereby having the effects of safety, convenience and economy. The method directly extracts the phosphate of the carbonate crystal lattice in the geological sample, can effectively indicate the content and the change of the phosphate of the ancient seawater, and researches the content level and the change of the phosphate in the geological history period.

To achieve these objects and other advantages in accordance with the present invention, there is provided a carbonate lattice phosphate extraction test method comprising the steps of:

dissolving a sample containing carbonate minerals by using an acetic acid solution, and centrifuging to obtain a dissolved solution and residual solids;

detecting the content of phosphate in the dissolved solution by using a malachite green-phosphomolybdic heteropoly acid spectrophotometry;

repeatedly washing the residual solid by using a sodium chloride buffer solution to release adsorbed phosphate, collecting the washing liquid, detecting the content of the phosphate in the washing liquid by using a malachite green-phosphomolybdic heteropoly acid spectrophotometry, and summarizing the measured content of the phosphate to obtain the content of the carbonate lattice phosphate of the sample.

Preferably, the volume concentration of acetic acid in the acetic acid solution is 2%.

Preferably, the carbonate mineral contained in the sample is one of calcite or dolomite.

Preferably, the mass of the carbonate mineral in the sample is taken through the TIC content of the sample so that the mass of the carbonate mineral in the sample reaches 0.1 g. + -. 0.001g, and when the sample containing the carbonate mineral is dissolved, only 70% of the carbonate mineral in the sample is dissolved.

Preferably, the sodium chloride buffer solution is adjusted to a pH of 8 with sodium bicarbonate solution.

Preferably, when the sample is limestone, 4mL of 2% by volume acetic acid solution is added, and when the sample is dolomite, 4.35mL of 2% by volume acetic acid solution is added.

The invention at least comprises the following beneficial effects:

the method uses malachite green-phosphomolybdic heteropoly acid spectrophotometry to detect the content of phosphate, effectively eliminates the interference of a large amount of calcium and magnesium ions released by dissolving carbonate, and effectively avoids the adsorption of residual solids on the phosphate by repeatedly washing the residual solids through sodium chloride buffer solution, thereby having the effects of safety, convenience and economy;

the method can be used for directly extracting carbonate lattice phosphate from geological samples, can be used for effectively extracting and testing the carbonate lattice phosphate, directly indicating the phosphate content level of the ancient seawater, effectively indicating the phosphate content and change of the ancient seawater and researching the phosphate content level and change of geological historical periods, has the characteristics of easiness in obtaining experimental reagents, simplicity and convenience in operation and high detection precision, and provides an important research means for researching biogeochemical cycle of phosphorus, marine environment change and life synergistic evolution.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

Drawings

FIG. 1 is a schematic diagram of the carbonate lattice phosphate extraction test method of the present invention.

Detailed Description

The invention provides an extraction test method of carbonate crystal lattice phosphate, which comprises the following steps:

dissolving a sample containing carbonate minerals by using an acetic acid solution, and centrifuging to obtain a dissolved solution and residual solids;

detecting the content of phosphate in the dissolved solution by using a malachite green-phosphomolybdic heteropoly acid spectrophotometry;

repeatedly washing the residual solid by using a sodium chloride buffer solution to release adsorbed phosphate, collecting the washing liquid, detecting the content of the phosphate in the washing liquid by using a malachite green-phosphomolybdic heteropoly acid spectrophotometry, and summarizing the measured content of the phosphate to obtain the content of the carbonate lattice phosphate of the sample.

According to the technical method, the method for extracting the carbonate crystal lattice phosphate comprises the steps of dissolving a limestone or dolomite sample by using an acetic acid solution, cleaning phosphorus adsorbed on the surface of the sample by using a sodium chloride buffer solution, and detecting the content of the phosphate in the dissolved solution by using a malachite green-phosphomolybdic heteropoly acid spectrophotometry.

The volume concentration of acetic acid in the acetic acid solution was 2%.

The carbonate mineral contained in the sample is one of calcite or dolomite.

The sample mass was taken through the TIC content of the sample so that the mass of carbonate mineral in the sample became 0.1 g. + -. 0.001g, and when the sample containing carbonate mineral was dissolved, only 70% of the carbonate mineral in the sample was dissolved.

The pH value of the sodium chloride buffer solution is 8, and the pH value is adjusted by sodium bicarbonate solution.

The present invention is further described in detail below with reference to examples so that those skilled in the art can practice the invention with reference to the description.

It is to be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified.

The invention provides a specific embodiment of an extraction test method of carbonate crystal lattice phosphate, and the flow of the test method is shown in figure 1.

The method for extracting the carbonate crystal lattice phosphate is divided into seven steps.

Weighing samples containing carbonate minerals, firstly measuring the TIC content of the samples, and weighing the samples according to the TIC content of the samples to enable the carbonate mineral content in each sample to reach 0.1g +/-0.001 g;

the second step is to dissolve the sample, for different samples, using different doses of 2% strength by volume acetic acid solution to dissolve the sample in the test tube, for the sample is limestone, add 4mL of 2% strength by volume acetic acid solution, for the sample is dolomite, add 4.35mL of 2% strength by volume acetic acid solution, this step will dissolve 0.1g carbonate mineral 70%;

thirdly, placing the test tube containing the sample solution in a vortex instrument under the condition of normal temperature, vibrating for 40 minutes and then centrifuging;

the fourth step is that 200 mu L of supernatant is extracted from the centrifuged sample and added into a prepared centrifugal tube of 10mL nitric acid solution with the mass fraction of 2 percent, and the content of Ca and Mg elements in the solution is detected by ICP-OES;

and the fifth step is that 1mL of supernatant is extracted from the centrifuged sample solution, added into a 2mL test tube, added with 0.2mL of color developing agent, then added with 0.05mL of 4% polyvinyl alcohol (PVA) solution, and waits for 30 minutes until the color development is stable, and the measurement is carried out by an ultraviolet spectrophotometer at the wavelength of 636 nm. The upper limit of phosphorus measured by a malachite green-phosphomolybdic heteropoly acid spectrophotometry is 1ppm, and if the phosphorus content is more than 1ppm, the phosphorus is measured after being diluted by 0.174M calcium acetate solution;

and the sixth step is that residual supernatant in the test tube in the third step is carefully poured out to obtain residual solid, 10mL of sodium chloride buffer solution with the pH value of 8 is added into the residual solid, the residual solid is vibrated in a vortex instrument for 2 hours at normal temperature and then centrifuged, 1mL of supernatant is extracted and placed into a 4mL centrifuge tube, then 0.2mL of color developing agent is added, 0.05mL of 4% PVA solution is added, and the measurement is carried out by an ultraviolet spectrophotometer at the wavelength of 636 nm. The washing of the residual solid was repeated until the phosphorus concentration in the supernatant in the residual solid washed with sodium chloride buffer solution was <0.05 ppm. Most residual solids may only need to be washed 1 time, with the maximum number of washes being 5.

And step seven, summarizing the phosphate content in the step five and the phosphate content in the step six, and then calculating the phosphate content in the carbonate mineral.

For the above experiments, some reagents were formulated as follows:

malachite green solution: dissolving 0.14g of malachite green reagent in 50mL of 6MHCl solution;

ammonium molybdate solution: dissolving 5g of ammonium molybdate reagent in 50mL of ultrapure water;

polyvinyl alcohol (PVA) solution: dissolving 2g of polyvinyl alcohol reagent in 50mL of ultrapure water;

color developing agent: adding 2.5mL of ammonium molybdate solution into 10mL of malachite green solution;

calcium acetate solution: dissolving 13.76g of calcium acetate in 500mL of ultrapure water;

the reagents used in the above experiments are required to be of high-grade purity, and are all from chemical reagents of national drug group, ltd.

While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable to various fields of endeavor for which the invention may be embodied with additional modifications as would be readily apparent to those skilled in the art, and the invention is therefore not limited to the details given herein and to the embodiments shown and described without departing from the generic concept as defined by the claims and their equivalents.