CN115561188A

CN115561188A - Method for measuring trace silver in rock mineral sample

Info

Publication number: CN115561188A
Application number: CN202211235268.4A
Authority: CN
Inventors: 程先忠; 王又容; 周国庆
Original assignee: Wuhan Polytechnic University
Current assignee: Wuhan Polytechnic University
Priority date: 2022-10-10
Filing date: 2022-10-10
Publication date: 2023-01-03

Abstract

The invention discloses a method for measuring trace silver in a rock mineral sample, which adopts tetra-acid to dissolve the sample, adds complexing agent into the prepared sample solution, and leads the complexing agent to be mixed with high-valence metal ions such as Fe ³⁺ 、VO ²⁺ The (V), cr (VI) and Mn (VII) are subjected to complexation reaction to reduce the oxidation-reduction potential of the elements, thereby eliminating the oxidation of the elements on the adsorption group-SH on the sulfhydryl cotton and effectively protecting the combination of the sulfhydryl-SH on silver. The hydrosulfuryl cotton in the 4% nitric acid medium can adsorb elements such as silver, gold, platinum and palladium, other metal ions are not adsorbed, so that the interference of other elements, particularly transition metal elements, can be effectively eliminated, the adsorbed silver is completely desorbed by thiourea eluent after the silver is completely adsorbed, the solution is subjected to volume fixing and then is measured by an atomic absorption spectrometer, the result accuracy is good, and the data is reliable.

Description

Method for measuring trace silver in rock mineral sample

Technical Field

The invention relates to the field of chemical analysis and test of trace metal elements, in particular to a method for determining trace silver in a rock mineral sample.

Background

When the atomic absorption spectrometry is used for measuring polymetallic ore samples of rocks such as pyrite, chalcopyrite, manganese ore, silver vanadium ore and the like, a chemical separation method is generally adopted to remove matrix elements or interference elements, influence is eliminated, and then the measurement is carried out by combining with a corresponding analytical test instrument. In the chemical separation method, the mercapto cotton is usually used as an adsorption material, the mercapto cotton is generated by esterification of absorbent cotton and thioglycollic acid under the catalysis of sulfuric acid, and the method is widely used for separation and enrichment of trace elements such as copper, lead, zinc, chromium, nickel, cobalt, manganese, arsenic, mercury, selenium, tellurium and the like in environmental samples such as water samples and also used for treatment of trace gold, silver and palladium in rock minerals. However, the polymetallic mineral sample of the rock contains a large amount of high-valence metal elements such as iron, chromium, vanadium, manganese and the like, which can negatively affect the adsorption effect of silver, thereby reducing the accuracy and precision of the determination method and causing larger errors of analysis and test results. Therefore, the method for adsorbing, separating and enriching silver by the mercapto cotton and eliminating the adsorption influence of interference ions on the trace silver is provided, and the method for measuring the trace silver in the rock polymetallic ore by the atomic absorption spectrometry is particularly important.

Disclosure of Invention

The invention mainly aims to provide a method for measuring trace silver in a rock mineral sample, aiming at eliminating the influence of coexisting transition metal elements on the separation and enrichment of trace silver by hydrosulfuryl cotton, so as to improve the accuracy and precision of the measurement of trace silver in the rock polymetallic mineral sample.

In order to achieve the purpose, the invention provides a method for measuring trace silver in a rock mineral sample, which comprises the following steps:

s1, dissolving a sample by adopting a common tetra-acid method, weighing 0.1-0.3 g of the sample, putting the sample into a polytetrafluoroethylene plastic crucible (hereinafter referred to as a crucible for short), adding 5 drops of distilled water for wetting, sequentially adding perchloric acid, hydrochloric acid, nitric acid and hydrofluoric acid, then putting the sample into a fume hood, heating and dissolving the sample on a high-temperature electric heating plate, evaporating the perchloric acid until the perchloric acid is completely smoked, preparing sample dry slag, and meanwhile, making a sample blank.

S2, taking the crucible down from the electric hot plate, adding the complexing agent, the concentrated nitric acid and the hot water into the crucible while the crucible is hot, putting the crucible on the high-temperature electric hot plate again, heating and dissolving salts, taking down the crucible, and cooling the crucible to obtain a sample solution.

S3, adsorbing and separating the sample solution prepared in the step 2 in a sulfhydryl cotton exchange column (hereinafter referred to as sulfhydryl cotton column for short) to enrich trace silver, washing the sulfhydryl cotton column for multiple times by dilute nitric acid after the solution is drained to remove impurity ions, and then washing the exchange column for multiple times by distilled water until the pH value is 4-6.

And S4, eluting the trace silver adsorbed on the mercapto cotton into a colorimetric tube by using a hot stripping agent to prepare a solution to be detected.

And S5, measuring the content of silver in the liquid to be measured by using an atomic absorption spectrometer, preparing a standard curve, setting instrument conditions, detecting by using an atomic absorption method, using a graphite furnace atomic absorption method for a low-content sample, selecting a flame atomic absorption method for a high-content sample solution, and calculating the content of silver in the sample according to the concentration of the measured solution.

Optionally, in the step S1, 0.2 to 0.6mL of perchloric acid, 3 to 5mL of concentrated hydrochloric acid, 1 to 2mL of nitric acid, and 3 to 5mL of hydrofluoric acid are placed on a high-temperature electric hot plate at 200 to 250 ℃ to heat and decompose the sample, and the perchloric acid white smoke is evaporated to the end to obtain dry sample residues, and then the next operation is performed, and the whole operation process is completed in a fume hood.

Optionally, in step S1, a platinum forceps is used to take the crucible during the whole sample dissolving process, so as to prevent cross contamination of the sample.

Optionally, in step S2, the complexing agent is one of sulfosalicylic acid and 4- (2-pyridylazo) -resorcinol (hereinafter referred to as PAR).

Optionally, in the step S2, the mass concentration of the sulfosalicylic acid is 150 to 200g/L, and the adding amount is 6 to 10 drops.

Optionally, in step S2, the mass concentration of the PAR is 10 to 50g/L, and the addition amount is 1.0 to 2.0mL.

Optionally, in step S2, the amount of the concentrated nitric acid added is 0.3 to 0.6mL, the amount of the hot water added is 8 to 10mL, and the temperature of the hot water is 60 to 90 ℃, so as to prepare a sample solution.

Optionally, step S3 includes:

s31, weighing sulfhydryl cotton, and filling the sulfhydryl cotton into a short-neck funnel to prepare a sulfhydryl cotton column;

s32, washing the sulfhydryl cotton column by using distilled water, and then balancing the exchange column by using 4% nitric acid (v/v);

s33, separating and enriching the prepared sample solution through a sulfhydryl cotton column, and washing the crucible and the exchange column with 4% nitric acid (v/v) and distilled water in sequence after the sample solution is drained.

Optionally, in step S31, the insertion mass of the mercapto cotton is 95 to 105mg, and the neck end of the short-neck funnel is phi 4 to 6mm.

Alternatively, in step S32, the distilled water washes the column 2 to 3 times and the 4% nitric acid (v/v) equilibrates the column 2 to 3 times.

Alternatively, in step S33, the crucible and the mercaptocotton column are washed 2 to 4 times each with 4% nitric acid (v/v), and then the mercaptocotton column is washed 3 to 5 times with distilled water until the effluent has a pH of 4 to 6.

Alternatively, in steps S32 and S33, the solution flow rate is 1 to 3mL/min.

Optionally, step S4 includes:

s41, heating the solution of the release agent on an electric heating plate to a certain temperature;

s42, eluting the silver in the colorimetric tube by using a hot eluent for 5 times.

Alternatively, in step S41, the eluent solution is a mixed solution of 5g/L thiourea-0.5% HCl (v/v).

Optionally, in step S41, the heating temperature is 40 to 70 ℃.

Alternatively, in step S42, the volume of 5.0 or 10.0mL of silver is eluted 5 times by 5 times with hot eluent in a 10mL colorimetric tube.

Optionally, in step S42, the 5mL or 10mL cuvette for receiving the eluent is a cuvette selected according to the content of silver in the sample, and if the sample is a polymetallic ore sample with high content of silver, a 10mL cuvette is selected, and if the sample is a general rock sample, a 5mL cuvette is selected.

Optionally, in step S5, the working conditions of the apparatus are set, flame atomic absorption detection is performed first, and the graphite furnace atomic absorption detection is used for detecting the sample below the lower limit of flame detection.

Optionally, in step S5, a standard working curve of 0-80 ng/mL silver is selected for graphite oven atomic absorption spectroscopy for low concentration silver content, and 0-4.0 μ g/mL is selected for flame atomic absorption spectroscopy for high concentration silver content, the standard working solution of silver is diluted with a mixed solution of 5g/L thiourea-0.5% HCl (v/v).

Has the advantages that: the technology provided by the inventionIn the scheme, a complexing agent and high-valence metal ions such as Fe are firstly added into a prepared sample solution ³⁺ ，VO ₂ ⁺ And (V), cr (VI) and Mn (VII) are subjected to complexation reaction to reduce the oxidation-reduction potential of the elements and eliminate the oxidation of the elements on the adsorption group-SH on the mercapto cotton, namely eliminate the oxidation of high-valence metal ions on the mercapto cotton and avoid the reduction of the adsorption effect of silver. The method can ensure that the mercapto cotton can completely adsorb silver in a 5% nitric acid medium, thereby improving the accuracy and precision of the method for measuring the trace silver in the rock minerals.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings described herein are only some embodiments of the present invention, and that other drawings can be obtained by those skilled in the art without inventive efforts.

FIG. 1 effect of nitric acid concentration on silver adsorption rate according to the invention;

FIG. 2 the effect of the solution flow rate of the present invention on the silver adsorption rate;

FIG. 3 is a graph of the effect of eluent amount of the present invention on silver elution.

Detailed Description

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments or the prior art will be briefly introduced below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other related drawings can be obtained according to the drawings without creative efforts, and the chemical reagents used in the embodiments are analytical purity or superior purity.

A method for determining trace silver in a rock mineral sample, comprising:

in the step S1, decomposing a sample by using four mixed acids, forming aqua regia by nitric acid and hydrochloric acid, decomposing the sample, and volatilizing and removing silicon tetrafluoride generated by silicon in the sample by using hydrofluoric acid to destroy the structure of silicate rock so as to decompose the sample; a small amount of hydrochloric acid and hydrofluoric acid are remained in the crucible after the sample is decomposed to affect silver adsorption of the mercapto cotton, silver ions react with the residual chloride ions to generate silver chloride precipitates, and the residual hydrofluoric acid corrodes glassware, so that the silver chloride precipitates and the hydrofluoric acid must be cleaned, the hydrochloric acid and the hydrofluoric acid are heated to the temperature of more than 200 ℃ by virtue of perchloric acid to emit white smoke, and the hydrochloric acid and the hydrofluoric acid are volatilized and removed, so that the purpose is realized by only observing the white smoke generated in the later stage of the sample decomposition.

In the step S2, after the crucible is steamed until white smoke is exhausted, metal ions exist in dry slag in a salt form, the crucible is taken down and cooled to 30-60 ℃, and after a complexing agent solution and a concentrated nitric acid solution are added, a dark purple solution is immediately generated in the crucible, which shows that the complexing agent and high-valence metal ions are subjected to a complexing reaction to generate a complex. Sulfosalicylic acid is a white powder and PAR is a brown powder, both of which are readily soluble in water and are capable of forming red or purple chelates with many high-valence metal ions, particularly transition metal ions. After the high-valence metal ions and the complexing agent form a chelate, the oxidation state concentration of the metal ions is obviously reduced, the oxidation-reduction potential is reduced according to the Nernst equation, and the oxidation property of the metal ions is reduced along with the reduction of the oxidation-reduction potential, so that the sulfydryl (-SH) on the sulfydryl cotton is not oxidized by the high-valence metal ions, that is, the sulfydryl cotton can be effectively prevented from being damaged, and the sulfydryl cotton can be ensured to completely adsorb silver ions in the solution. Then adding 0.3-0.6 mL of concentrated nitric acid and 8-10 mL of hot water at 60-90 ℃, on one hand, the aim of effectively dissolving salt to form a sample solution is to facilitate the next adsorption operation; on the other hand, the acidity of the solution is controlled within the concentration range of 1-6% nitric acid (v/v), under the acidity condition, cu ²⁺ 、Co ²⁺ 、Cd ²⁺ 、Ni ²⁺ 、Pb ²⁺ 、Fe ³⁺ 、Fe ²⁺ V (V), mn (II, VII) and other transition metal ions are not adsorbed by the mercapto cotton, and only Ag ⁺ 、Au ³⁺ 、Pt ⁴⁺ 、Pd ⁴⁺ Noble metal elements are adsorbed, but Au ³⁺ 、Pt ⁴⁺ 、Pd ⁴⁺ The content is very little and does not interfere with the determination of the silver content.

In the step 3, 95-105mg of the mercapto cotton is weighed and uniformly stuffed into a short-neck funnel, the neck end of the short-neck funnel is phi 4-6 mm, the length of the mercapto cotton is 6-8 cm, and the mercapto cotton column is prepared. The method comprises the steps of washing sulfhydryl cotton in a sulfhydryl cotton column for 2-3 times by distilled water in advance, wherein the purpose is to wash free thioglycollic acid on the sulfhydryl cotton, balancing the sulfhydryl cotton column for 2-3 times by 4% nitric acid so as to keep the acidity of a sample solution basically consistent, and the experiment result of an acidity medium for adsorbing silver by the sulfhydryl cotton is shown in figure 1, wherein in a 1-6% nitric acid medium, the adsorption rate of the sulfhydryl cotton to the silver is 89.7-99.6%, in the embodiment, the 3-6% nitric acid medium is selected for carrying out silver separation and enrichment, and the adsorption rate of the silver is 99.5%. The flow rate of the sample solution also affects the adsorption rate of silver, the adsorption rate of silver decreases when the flow rate is too high, and the work efficiency is affected when the flow rate is too slow, as shown in fig. 2, the flow rate is controlled to be 1-3 mL/min, and the adsorption rate of silver is 99.8%.

In the step S3, after the sample solution is drained, 4% nitric acid solution is used for washing the crucible so as to recover silver ions adhered to the crucible and transfer the silver ions to the exchange column for adsorption, and meanwhile, 4% nitric acid solution is used for washing the exchange column so as to wash other metal ions, but the silver ions are continuously retained on the mercapto cotton column; after washing with 4% nitric acid solution, the exchange column turns from dark purple to white, and then is washed with distilled water for 3-5 times in order to remove residual nitric acid on the sulfhydryl cotton column, and when the pH of the effluent of the sulfhydryl cotton column is 5 +/-1, the next step of operation is carried out.

In step S4, the solution of 5g/L thiourea-0.5% HCl (v/v) as a stripping agent is prepared by dissolving 2.5g thiourea in 500mL distilled water, adding 2.5mL concentrated hydrochloric acid, and stirring well to obtain the final product, wherein the thiourea can be mixed with Ag ⁺ Forming a stable complex, dissolving the adsorbed silver into a solution, and desorbing from the mercaptocotton, 0.5% HCl (v/v) acting to stabilize thiourea, without affecting the silver, which preferentially forms a complex with thiourea. The amount of the stripping agent affects the stripping rate of silver, and as shown in fig. 3, for 0.5 μ g of silver, only 4-6 mL of stripping agent is needed to completely elute the adsorbed silver, and in the experiment, 5mL of stripping agent is used for a sample with low content. The adsorbed silver can be completely eluted even by 7-10 mL of the release agent for 20 mu gA rock mineral sample in an amount of 1-300. Mu.g/g is sufficient with 10mL of the stripping agent, and for higher content samples 25mL of the eluent is used and taken up with a 25mL cuvette.

When the silver is stripped, the stripping agent mixed solution needs to be heated to 40-70 ℃, and the hot thiourea solution can quickly carry out complex reaction with the silver; and (3) during stripping, adding 1mL of the solution into a mercaptocotton column by using a dropper each time to elute silver ions, carrying the eluent by using a 5 or 10mL colorimetric tube, taking down the colorimetric tube when the eluent reaches 5mL or 10mL, diluting the colorimetric tube to a 5mL or 10mL scale by using a stripping agent to obtain a solution to be detected, and shaking uniformly to detect by using an atomic absorption photometer.

In step S5, the working conditions of the instrument are set, 0-80 ng/mL standard solution of silver is prepared, the graphite furnace atomic absorption method is used for measuring low-content silver, 0-4 mu g/mL standard solution of silver is prepared, the flame atomic absorption spectrometry method is used for measuring high-content silver, and the standard solution of prepared silver is diluted by using a mixed solution of 5g/L thiourea-0.5 percent HCl (v/v), so that the consistency of the solution to be measured and the solution of the standard curve can be ensured, and the measurement error can not be generated.

Example 1

A method for determining trace silver in a rock mineral sample, comprising:

s1, weighing 0.3000g of sedimentary rock sample in a polytetrafluoroethylene plastic crucible (hereinafter referred to as a plastic crucible) by adopting a common four-acid sample dissolving method, wetting the sample with 5 drops of distilled water, adding 0.2 mL of perchloric acid, 3mL of hydrochloric acid, 1mL of nitric acid and 3mL of hydrofluoric acid respectively, heating and dissolving the sample by using a high-temperature electric heating plate at 200 ℃, preparing sample dry slag after white smoke is exhausted, simultaneously using the sample as a sample blank, and carrying out the whole operation in a fume hood.

S2, taking down the crucible from the electric hot plate, adding 6 drops of 150g/L sulfosalicylic acid into the crucible while the crucible is hot, adding 0.3mL of concentrated nitric acid and 8mL of distilled water at 60 ℃ after 3 minutes, putting the crucible on the high-temperature electric hot plate again, heating and dissolving dry residues, taking down and cooling to obtain a sample solution.

S3, plugging 95mg of mercapto cotton into a short-neck funnel, washing with distilled water for 2 times, and then balancing with 4% nitric acid (v/v) for 2 times, wherein the flow rate of the solution is 1mL/min; then pouring the sample solution into a pretreated sulfhydryl cotton column, wherein the flow rate of the solution is 1mL/min, after the sample solution is drained, washing the crucible and the sulfhydryl cotton column with 4% nitric acid for 2 times, and then washing the sulfhydryl cotton column with distilled water for 3 times until the pH value is 5.

S4, eluting the trace silver adsorbed on the mercaptocotton column into a 5mL colorimetric tube by using 5g/L thiourea-0.5% HCl (v/v) mixed solution at 40 ℃ to prepare a solution to be detected.

S5, preparing a silver standard working curve of 0-80 ng/mL, measuring the silver content in the liquid to be measured by using a graphite furnace atomic absorption spectrometry, wherein the sensitivity of the implementation method is 0.07ng/g, and obtaining a sample according to the measurement result of the instrument and the following calculation formula as shown in Table 1.

ω/(ng/g) = ρV/m；

In the formula, the unit of omega is ng/g; ρ is the measured concentration (ng/mL); v is assay volume (mL); m is sample mass (g).

Example 2

A method for determining trace silver in a rock mineral sample, comprising:

s1, weighing 0.10g of silver ore sample in a plastic crucible by adopting a common four-acid sample dissolving method, wetting the silver ore sample with 5 drops of distilled water, and adding the silver ore sample into the plastic crucible respectively. 0.6mL of perchloric acid, 5mL of hydrochloric acid, 2mL of nitric acid and 5mL of hydrofluoric acid, then placing the mixture on a high-temperature electric hot plate at 220 ℃ for heating and dissolving, preparing sample dry slag after white smoke is exhausted, and operating the sample dry slag in a fume hood.

S2, taking the plastic crucible down from the electric hot plate, adding 10 drops of complexing agent 200g/L sulfosalicylic acid into the crucible while the plastic crucible is hot, adding 0.6mL of concentrated nitric acid and 10mL of distilled water at 90 ℃ after 3 minutes, putting the crucible on the high-temperature electric hot plate again, heating and dissolving dry residues, taking down and cooling to obtain a sample solution.

S3, plugging 105mg of sulfhydryl cotton into a short-neck funnel, washing the sulfhydryl cotton for 3 times by using distilled water, balancing the sulfhydryl cotton for 3 times by using 4% nitric acid (v/v), wherein the flow rate of the solution is 3mL/min, and pretreating the sulfhydryl cotton for later use; then pouring the sample solution into a pretreated sulfhydryl cotton column, wherein the flow rate of the solution is 3mL/min, after the sample solution is drained, washing the crucible and the sulfhydryl cotton column with 4% nitric acid for 3 times, then washing the sulfhydryl cotton column with distilled water for 3 times, and the pH value of the effluent is 4.

S4, eluting the trace silver adsorbed on the mercaptocotton column into a 10mL colorimetric tube by using a 70 ℃ mixed solution of 5g/L thiourea-0.5% HCl (v/v), and preparing a solution to be detected.

S5, preparing 0-4.0 mu g/mL of silver for measuring the high-concentration silver content by using a flame atomic absorption spectrometry, wherein the sensitivity of the implementation method is 0.36 mu g/g, and the measured sample results are shown in Table 1 according to the concentration measured by an instrument and the following calculation formula.

ω/(μg/g) = ρV/m；

Wherein the unit of omega is mu g/g; ρ is the measured concentration (. Mu.g/mL); v is assay volume (mL); m is sample mass (g).

Example 3

A method for determining trace silver in a rock mineral sample, comprising:

s1, weighing 0.20g of copper ore sample in a plastic crucible by adopting a common tetraacid sample dissolving method, wetting the copper ore sample with 5 drops of distilled water, and adding the copper ore sample into the plastic crucible respectively. 0.4mL perchloric acid, 4mL hydrochloric acid, 1.5mL nitric acid and 3.5mL hydrofluoric acid, then placing the mixture on a high-temperature electric hot plate at 200 ℃ for heating and dissolving, preparing sample dry slag after white smoke is exhausted, and operating in a fume hood.

S2, taking the plastic crucible down from the electric hot plate, adding 8 drops of complexing agent 180g/L sulfosalicylic acid into the crucible while the plastic crucible is hot, adding 0.45mL of concentrated nitric acid and 9mL of distilled water at 70 ℃ after 3 minutes, putting the crucible on the high-temperature electric hot plate again, heating and dissolving dry residues, taking down and cooling to obtain a sample solution.

S3, plugging 100mg of sulfhydryl cotton into a short-neck funnel, washing the sulfhydryl cotton for 3 times by using distilled water, balancing the sulfhydryl cotton for 2 times by using 4% nitric acid (v/v), wherein the flow rate of the solution is 2mL/min, and pretreating the sulfhydryl cotton for later use; then pouring the sample solution into a pretreated sulfhydryl cotton column, wherein the flow rate of the solution is 2mL/min, after the sample solution completely flows out, washing the crucible and the sulfhydryl cotton column with 4% nitric acid for 3 times, then washing the sulfhydryl cotton column with distilled water for 3 times, and the pH value of an effluent liquid is 4.5.

S4, eluting the trace silver adsorbed on the mercaptocotton exchange column into a 5mL colorimetric tube by using 5g/L thiourea-0.5% HCl (v/v) mixed solution at the temperature of 55 ℃ to prepare a solution to be tested.

S5, preparing 0-4.0 mu g/mL of silver for measuring the content of high-concentration silver by using a flame atomic absorption spectrometry, and obtaining sample results according to the calculation formula of the example 2, wherein the measured sample results are shown in Table 1.

Example 4

A method for determining trace silver in a rock mineral sample, comprising:

s1, weighing 0.25g of an ore (iron-containing sample) sample in a plastic crucible by adopting a common tetraacid sample dissolving method, wetting the sample with 5 drops of distilled water, and adding the sample into the plastic crucible respectively. 0.3mL perchloric acid, 4.5mL hydrochloric acid, 2mL nitric acid and 4mL hydrofluoric acid, then placing the mixture on a high-temperature electric hot plate at 200 ℃ for heating and dissolving, preparing sample dry slag after white smoke is exhausted, and operating in a fume hood.

S2, taking the plastic crucible down from the electric hot plate, adding 8 drops of complexing agent of 150g/L sulfosalicylic acid into the crucible while the plastic crucible is hot, adding 0.3mL of concentrated nitric acid and 9mL of distilled water at 80 ℃ after 3 minutes, putting the crucible on the high-temperature electric hot plate again, heating and dissolving dry residues, taking down and cooling to obtain a sample solution.

S3, plugging 100mg of sulfhydryl cotton into a short-neck funnel, washing the sulfhydryl cotton for 3 times by using distilled water, balancing the sulfhydryl cotton for 3 times by using 4% nitric acid (v/v), wherein the flow rate of a solution is 2.5mL/min, and pretreating the sulfhydryl cotton for later use; then pouring the sample solution into a pretreated sulfhydryl cotton column, wherein the flow rate of the solution is 2mL/min, after the sample solution is drained, washing the crucible and the sulfhydryl cotton column with 4% nitric acid for 3 times, then washing the sulfhydryl cotton column with distilled water for 3 times, and the pH value of the effluent is 6.

S4, eluting the trace amount of silver adsorbed on the mercaptocotton column into a 10mL colorimetric tube by using a mixed solution of 5g/L thiourea-0.5% HCl (v/v) at 60 ℃ to prepare a test solution.

S5, preparing 0-4.0 mu g/mL of silver for measuring the content of high-concentration silver by using a flame atomic absorption spectrometry, obtaining the content of the silver in the sample according to the calculation formula of the example 2, and obtaining the sample results as shown in the table 1.

Example 5

The experimental operation steps are the same as those of example 1, except that 2.0mL of 10g/L PAR solution is adopted as the complexing agent in the step S2, the obtained solution to be tested is measured by graphite furnace atomic absorption spectrometry, the standard working curve of silver is 0-80 ng/mL, and the sample results are shown in Table 1.

Example 6

The experimental procedure is the same as example 2, except that 1.0mL of 50g/L PAR solution is used as the complexing agent in step S2 to obtain a sample solution, the sample solution is used for the flame atomic absorption spectrometry, the standard curve of silver is 0-4.0 μ g/mL, and the sample results are shown in Table 1.

Example 7

The experimental procedure is the same as example 3, except that 1.5mL of 40g/L PAR solution is used as the complexing agent in step S2 to obtain a sample solution, the sample solution is used for the flame atomic absorption spectrometry, the standard curve of silver is 0-4.0 μ g/mL, and the sample results are shown in Table 1.

Example 8

The experimental procedure is the same as example 4, except that 2.0mL of 35g/L PAR solution is used as the complexing agent in step S2 to obtain a sample solution, the sample solution is used for the flame atomic absorption spectrometry, the standard curve of silver is 0-4.0 μ g/mL, and the sample results are shown in Table 1.

Test example 1

The experimental operation steps are the same as example 4, 5 parts of 0.1000g pyrite sample is weighed, after dissolution, separation and enrichment of sulfhydryl cotton and desorption of thiourea are carried out, a flame atomic absorption spectrometry is adopted to determine that the standard curve of silver is 0-4.0 mu g/mL, the content of Ag in the pyrite sample is 372 mu g/g and RSD is 0.76%.

Test example 2

Experimental procedures were as in example 4, weighing 0.2000g of black shale (V) ₂ O ₅ 1.2%) of the sample, performing dissolution, separation and enrichment of sulfhydryl cotton, and desorption of thiourea, and determining by flame atomic absorption spectrometry, wherein the standard curve of silver is 0-4.0 mug/mL, and the content of Ag in the pyrite sample is 116 mug/g, and the RSD is 1.13%.

Comparative example 1

The procedure was the same as in example 1 except that no complexing agent was added in the step S2, and the results of measuring the sample content are shown in Table 1.

Comparative example 2

The procedure was the same as in example 2, except that no complexing agent was added in the step S2, and the results of measuring the sample content were as shown in Table 1.

Comparative example 3

The procedure was the same as in example 3, except that no complexing agent was added in the step S2, and the results of measuring the sample content were as shown in Table 1.

Comparative example 4

The procedure was the same as in example 4 except that no complexing agent was added in the step S2, and the results of measuring the sample content were as shown in Table 1.

TABLE 1 analysis results of silver content in samples

The measurement values are the average of 5 measurements; RSD n =5 relative standard deviation of assay calculation.

As can be seen from the results in Table 1, compared with the results of the samples obtained by measuring 1-8 by the method provided by the embodiment of the invention and the corresponding comparative examples 1-4, the deviation between the silver content in the rock mineral measured by the method provided by the embodiment of the invention and the standard value of the national standard sample is very small, which indicates that the result of the method for measuring the silver content in the sample provided by the embodiment of the invention is reliable; secondly, as can be seen from the results of the comparative examples 1 to 4, the addition of no complexing agent in the comparative examples affects the silver adsorption effect of the mercapto cotton, resulting in a larger relative standard deviation of the results, which indicates that the addition of the complexing agent in the present embodiment can significantly protect the silver adsorption effect of the mercapto cotton, eliminate the interference of coexisting metal ions on silver measurement, and ensure the accuracy of the results.

The above is only a preferred embodiment of the present invention, and it is not intended to limit the scope of the invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall be included in the scope of the present invention.

Claims

1. A method for measuring trace silver in a rock mineral sample is characterized by comprising the following steps:

s1, adopting a common four-acid method to dissolve a sample, weighing 0.1-0.30 g of the sample, putting the sample into a polytetrafluoroethylene plastic crucible (hereinafter referred to as a crucible for short), adding 5 drops of distilled water for wetting, respectively adding perchloric acid, hydrochloric acid, nitric acid and hydrofluoric acid, then putting the mixture into a fume hood, heating and dissolving the mixture by a high-temperature electric heating plate, and preparing dry residue of the sample after white smoke is exhausted;

s2, taking down the crucible from the electric hot plate, respectively adding a complexing agent, concentrated nitric acid and hot water into the crucible while the crucible is hot, putting the crucible on the high-temperature electric hot plate again, heating and dissolving dry slag, taking down the crucible, and cooling the crucible to obtain a sample solution;

s3, adsorbing and separating the sample solution prepared in the step 2 through a sulfhydryl cotton exchange column to enrich trace silver, washing the crucible and the exchange column for multiple times by using dilute nitric acid after the solution flows out to remove impurity ions, and then washing the exchange column for multiple times to be neutral by using distilled water;

s4, eluting the trace silver adsorbed on the mercaptocotton exchange column into a 10mL colorimetric tube by using a hot stripping agent to prepare a solution to be detected;

and S5, measuring the content of silver in the liquid to be measured prepared in the step 4 by using an atomic absorption spectrometer, simultaneously preparing a silver standard curve, setting instrument conditions, carrying out flame atomic absorption method detection, changing a sample lower than the lower limit of the flame atomic absorption method detection into a graphite furnace detection method, and finally calculating the content of silver in the sample according to the measured concentration.

2. The method according to claim 1, wherein in step S1, the amount of perchlorate used is 0.2 to 0.6mL, 3 to 5mL of concentrated hydrochloric acid, 1 to 2mL of nitric acid, and 3 to 5mL of hydrofluoric acid, and the sample is decomposed by heating on a high-temperature electric hot plate at 150 to 220 ℃ and evaporated to the end of perchloric acid white smoke to obtain dry residue of the sample.

3. The assay of claim 1, wherein in step S2, the complexing agent is one of sulfosalicylic acid, PAR.

4. The method according to claim 1, wherein in step S2, the sulfosalicylic acid is added in an amount of 6 to 10 drops at a mass concentration of 150 to 200 g/L.

5. The method according to claim 1, wherein in step S2, the PAR is added in an amount of 1 to 2.0mL at a mass concentration of 10 to 50 g/L.

6. The method according to claim 1, wherein in step S2, the concentrated nitric acid is added in an amount of 0.3 to 0.6mL, the hot water temperature is 60 to 90 ℃, and the amount of the concentrated nitric acid added is 8 to 10mL.

7. The method for measuring trace silver in a rock mineral sample according to claim 1, wherein in step S3, the loading amount of the mercapto cotton in the exchange column is 95 to 105mg, and the exchange column is washed with distilled water 2 to 3 times, followed by equilibration with 4% nitric acid (v/v) 2 to 3 times at a flow rate of 1 to 3mL/min, and the sample solution is ready for use.

8. The method according to claim 1, wherein in step S3, the sample solution is subjected to a flow rate of 1 to 3mL/min during the separation, enrichment and adsorption process.

9. The method according to claim 1, wherein in step S3, the crucible and the column are washed with the dilute nitric acid having a volume concentration of 4% (v/v), the crucible and the column are washed with 4% nitric acid (v/v) 2 to 4 times each, and then the column is washed with distilled water 2 to 3 times until the pH is 4 to 6.

10. The method of claim 1, wherein the releasing agent is a mixed solution of 5g/L thiourea-0.5% HCl (v/v) in step S4, and the releasing agent is heated to 40 to 70 ℃ for elution, and the amount used is 1 mL/time for elution, and the total amount used is 5mL or 10mL.