阅读说明：本技术 一种电位滴定法测定高锰粗制氢氧化钴中钴含量的方法 (Method for measuring cobalt content in high-manganese crude cobalt hydroxide by potentiometric titration ) 是由 张兴勋 李华荣 刘海波 叶志勇 黄兆驱 刘国锋 罗高峰 于 2021-09-06 设计创作，主要内容包括：本发明公开了一种电位滴定法测定高锰粗制氢氧化钴中钴含量的方法,称取试料于烧杯中,加入盐酸和硝酸加热溶解试料,直至剩余1mL溶液；在溶液中加入HNO-(3)和KClO-(3),加热直至剩余10mL溶液；用水冲洗杯壁和表面皿,加热溶解盐类,将溶液移入200mL容量瓶中,用水稀释至刻度；干过滤,舍去最初的10mL滤液；于200mL烧杯中,加入柠檬酸铵溶液和氨水,加入过量的铁氰化钾标准溶液；混匀后,加入滤液,继续混匀；在电位滴定仪上,将氧化还原电极放入200mL烧杯中,不断搅拌下用钴标准滴定溶液滴定过量的铁氰化钾,滴定至电位突跃最大即为终点；将沉淀用盐酸和硝酸溶解,所得溶液用原子吸收光谱仪测定钴量进行补正。本发明准确度、精密度和适用性好。(The invention discloses a method for measuring cobalt content in high-manganese crude cobalt hydroxide by a potentiometric titration method, which comprises the steps of weighing a test material in a beaker, adding hydrochloric acid and nitric acid, heating and dissolving the test material until 1mL of solution is remained; adding HNO into the solution 3 And KClO 3 Heating until 10mL of solution remains; washing the cup wall and the watch glass with water, heating to dissolve salts, transferring the solution into a 200mL volumetric flask, and diluting with water to a scale; dry filtration, discarding the first 10mL of filtrate; adding ammonium citrate solution and ammonia water into a 200mL beaker, and adding excessive potassium ferricyanide standard solution; mixing, adding the filtrate, and mixing; on a potentiometric titrator, putting an oxidation-reduction electrode into a 200mL beaker, titrating excessive potassium ferricyanide by using a cobalt standard titration solution under the condition of continuous stirring until the maximum potential jump is the end point; dissolving the precipitate with hydrochloric acid and nitric acid, and correcting the cobalt content of the obtained solution by measuring with atomic absorption spectrometer. The invention has good accuracy, precision and applicability.)

1. A method for measuring the cobalt content in high-manganese crude cobalt hydroxide by a potentiometric titration method is characterized by comprising the following specific steps:

s1, sample decomposition: 0.4g of a sample was weighed into a 400mL beaker, and 10mL of HCL and 5mL of HNO were added₃Heating to dissolve the sample until 1mL of solution remains;

s2, adding 15mL HNO into the solution obtained in the step S1₃And 1g of KClO₃Heating until 10mL of solution remains;

s3, washing the wall of the cup and the watch glass with water, continuously heating to dissolve all salts, transferring the solution into a 200mL volumetric flask, and diluting with water to a scale;

s4, dry filtering, and discarding the initial 10mL of filtrate;

s5, adding 30mL of ammonium citrate solution and 30mL of ammonia water into a 200mL beaker, and then adding excessive potassium ferricyanide standard solution; after uniformly mixing, adding 25mL of the filtrate obtained in the step S4 into the 200mL beaker, and continuously uniformly mixing;

s6, putting the redox electrode into the 200mL beaker of the step S5 on a potentiometric titrator, titrating the excessive potassium ferricyanide by using a cobalt standard titration solution under continuous stirring, and titrating until the maximum potential jump is the end point;

s7, dissolving the precipitate obtained by filtering in the step S4 with hydrochloric acid and nitric acid, and measuring the cobalt content of the obtained solution by using an atomic absorption spectrometer for correction;

and S8, calculating the final cobalt content according to the titration result of the step S6 and the measurement result of the step S7.

2. The method according to claim 1, wherein the specific process of step S8 is as follows:

the content of cobalt is in mass fraction omega_CoIn% by weight, the value is calculated as follows:

in the formula:

k is the conversion factor of the standard potassium ferricyanide solution to the standard cobalt titration solution;

V₀the total volume of the solution finally obtained in step S3, in mL;

V₁the number of milliliters of the standard cobalt solution consumed by the back titration is milliliter (mL);

V₂adding mL of the potassium ferricyanide standard solution, wherein the unit is mL;

V₃-dividing the volume of the test solution in mL;

ρ_Co-mass concentration of cobalt standard titration solution in milligrams per milliliter mg/mL;

m is the sample amount in grams g;

V₄-the volume of the solution obtained in step S7, in mL;

ρ₁the mass concentration of the element to be detected in the test solution is mg/L;

ρ₀the mass concentration of the element to be measured in the blank solution is mg/L.

Technical Field

The invention relates to the technical field of chemical determination, in particular to a method for determining cobalt content in high-manganese crude cobalt hydroxide by a potentiometric titration method.

Background

At present, according to the non-ferrous metal industry standard YS/T1157.1-2016 part 1 of the chemical analysis method of crude cobalt hydroxide: potentiometric titration of cobalt amounts ", there are two methods for this standard, specifically as follows:

the first method is masked manganese-potentiometric titration: the sample is oxidized to Mn in the presence of perchloric acid and phosphoric acid^{3 +}Manganese phosphate is formed to mask the interference of coexisting element manganese. In the presence of citrate in an ammoniacal solution, Co is mixed with a potassium ferricyanide solution²⁺Oxidation to Co³⁺Excess potassium ferricyanide was back titrated by potentiometric titration with a standard titration solution of cobalt.

The second method is a manganese reduction-potentiometric titration method: in the presence of citrate in an ammoniacal solution, Co is mixed with a potassium ferricyanide solution²⁺Oxidation to Co³⁺The excess potassium ferricyanide was potentiometrically titrated with a standard titration solution of cobalt using potentiometric titration. Mn is present in the sample²⁺In the coexistence, the manganese is quantitatively oxidized into Mn by potassium ferricyanide solution³⁺And correcting the manganese amount to the cobalt amount and then subtracting the cobalt amount to obtain the cobalt amount.

However, in the practical application process, when the content of manganese in the product is high, manganese influences the sudden jump of potentiometric titration in the titration process, so that the end point is not obvious, the titration end point is difficult to control, and the precision and accuracy of the detection result are poor. Therefore, it is of great significance to find a method for measuring the cobalt content in the high manganese crude cobalt hydroxide, which avoids the interference of manganese during potentiometric titration, has obvious titration leap and good accuracy and precision.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a method for measuring the cobalt content in high-manganese crude cobalt hydroxide by a potentiometric titration method, solves the problems that the potentiometric titration end point is not obvious and is difficult to control when the manganese is high, and has good accuracy, precision and applicability.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for measuring the cobalt content in high-manganese crude cobalt hydroxide by a potentiometric titration method comprises the following specific steps:

s1, sample decomposition: 0.4g of a sample was weighed into a 400mL beaker, and 10mL of HCL and 5mL of HNO were added₃Heating to dissolve the sample until 1mL of solution remains;

s2, adding 15mL HNO into the solution obtained in the step S1₃And 1g of KClO₃Heating until 10mL of solution remains;

s3, washing the wall of the cup and the watch glass with water, continuously heating to dissolve all salts, transferring the solution into a 200mL volumetric flask, and diluting with water to a scale;

s4, dry filtering, and discarding the initial 10mL of filtrate;

s5, adding 30mL of ammonium citrate solution and 30mL of ammonia water into a 200mL beaker, and then adding excessive potassium ferricyanide standard solution; after uniformly mixing, adding 25mL of the filtrate obtained in the step S4 into the 200mL beaker, and continuously uniformly mixing;

s6, putting the redox electrode into the 200mL beaker of the step S5 on a potentiometric titrator, titrating the excessive potassium ferricyanide by using a cobalt standard titration solution under continuous stirring, and titrating until the maximum potential jump is the end point;

s7, dissolving the precipitate obtained by filtering in the step S4 with hydrochloric acid and nitric acid, and measuring the cobalt content of the obtained solution by using an atomic absorption spectrometer for correction;

and S8, calculating the final cobalt content according to the titration result of the step S6 and the measurement result of the step S7.

Further, the specific process of step S8 is:

the content of cobalt is in mass fraction omega_CoIn% by weight, the value is calculated as follows:

in the formula:

k is the conversion factor of the standard potassium ferricyanide solution to the standard cobalt titration solution;

V₀the total volume of the solution finally obtained in step S3, in mL;

V₁the number of milliliters of the standard cobalt solution consumed by the back titration is milliliter (mL);

V₂adding mL of the potassium ferricyanide standard solution, wherein the unit is mL;

V₃-dividing the volume of the test solution in mL;

ρ_Co-mass concentration of cobalt standard titration solution in milligrams per milliliter mg/mL;

m is the sample amount in grams g;

V₄-the volume of the solution obtained in step S7, in mL;

ρ₁the mass concentration of the element to be detected in the test solution is mg/L;

ρ₀the mass concentration of the element to be measured in the blank solution is mg/L.

The invention has the beneficial effects that:

after potassium chlorate precipitation is carried out to separate manganese, a small amount of manganese does not interfere with titration under the action of a masking agent during potentiometric titration, and the potentiometric leap is obvious, thereby being beneficial to end point judgment.

② the method of the invention is applied to the residual amount (MnO)₂Cobalt included in the precipitate) for correctionThe problem of low system is solved;

the method solves the problems that the potentiometric titration end point is not obvious and the end point is difficult to control when the manganese content is high, and has better accuracy and precision compared with the method used by YS/T1157.1-2016.

And fourthly, the recovery rate of the cobalt in the crude cobalt hydroxide sample obtained by the method is 99 to 101 percent, and the requirement is met.

Drawings

FIG. 1 is a schematic flow chart of a method according to an embodiment of the present invention.

Detailed Description

The present invention will be further described with reference to the accompanying drawings, and it should be noted that the present embodiment is based on the technical solution, and the detailed implementation and the specific operation process are provided, but the protection scope of the present invention is not limited to the present embodiment.

The embodiment provides a method for measuring cobalt content in high-manganese crude cobalt hydroxide by a potentiometric titration method, as shown in fig. 1, the specific process is as follows:

s1, sample decomposition: 0.4g of a sample was weighed into a 400mL beaker, and 10mL of HCL and 5mL of HNO were added₃The cuvette was closed and the sample was dissolved by heating until about 1mL of the solution remained. The remaining solution required about 1mL, and if the remaining volume was too large, hydrochloric acid was still present in the solution, and after addition of potassium chloride, manganese precipitation was not completed completely, and the result was high due to the presence of manganese ions at the time of potentiometric titration.

S2, adding 15mL HNO into the solution obtained in the step S1₃And about 1g KClO₃Heat until about 10mL of solution remains.

S3, washing the wall of the beaker and the watch glass with water, continuously heating to completely dissolve the salts, transferring the solution into a 200mL volumetric flask, and diluting the solution to the scale with water.

S4, dry filtration, and discarding the first 10mL of filtrate.

S5, adding 30mL of ammonium citrate solution and 30mL of ammonia water into a 200mL beaker, and then adding a potassium ferricyanide standard solution, wherein the potassium ferricyanide standard solution is excessive by 2 mL-10 mL; after the mixture is mixed, the mixture obtained in step S4 is dividedAdding 25mL of the obtained filtrate into the 200mL beaker, continuously mixing uniformly, and adding Co²⁺Oxidation to Co³⁺(ii) a At this time, the electric potential is about 200mv, if the difference is larger, the amount of the potassium ferricyanide standard solution should be increased or decreased.

S6, putting the redox electrode into the 200mL beaker of the step S5 on a potentiometric titrator, titrating the excessive potassium ferricyanide by using a cobalt standard titration solution under continuous stirring, and titrating until the maximum potential jump is the end point;

s7, washing the precipitate obtained by filtration in the step S4, adding 15mL of hydrochloric acid and 5mL of nitric acid to dissolve the precipitate, and correcting the cobalt content of the obtained solution by measuring the cobalt content with an atomic absorption spectrometer.

Specifically, the precipitate is washed, dissolved with hydrochloric acid and nitric acid, transferred into a new volumetric flask, diluted to the scale with an aqueous solution, and settled for clarification. The resulting solution was zeroed at the wavelength of 240.7nm of an atomic absorption spectrometer using an air-acetylene flame with accompanying sample blanks, absorbance was measured, background absorption was subtracted, and the corresponding cobalt concentration was checked from the working curve.

S8, calculation of analysis results:

the content of cobalt is in mass fraction omega_CoIn% by weight, the value is calculated as follows:

in the formula:

k is the conversion factor of the standard potassium ferricyanide solution to the standard cobalt titration solution;

V₀the total volume of the solution finally obtained in step S3, in mL;

V₁the number of milliliters of the standard cobalt solution consumed by the back titration is milliliter (mL);

V₂adding mL of the potassium ferricyanide standard solution, wherein the unit is mL;

V₃-dividing the volume of the test solution in mL;

ρ_Co——the mass concentration of the cobalt standard titration solution is mg/mL;

m is the sample amount in grams g;

V₄-the volume of the solution obtained in step S7, in mL;

ρ₁the mass concentration of the element to be detected in the test solution is mg/L;

ρ₀the mass concentration of the element to be measured in the blank solution is mg/L.

Example 2

Three panelists analyzed 3 different high manganese crude cobalt hydroxide samples using the method described in example 1, and the results are shown in table 1:

TABLE 1

The data in table 1 show that the method described in example 1 is used to determine cobalt in high manganese crude cobalt hydroxide with a relative standard deviation of < 0.5%, which verifies the feasibility of the method described in example 1 and also shows that the method described in example 1 has better repeatability.

Example 3

Satisfactory results were obtained by performing a laboratory-to-laboratory comparison using the method described in example 1 and determining the cobalt content of the high manganese crude cobalt hydroxide, the results of which are given in table 2 below:

TABLE 2

The data in Table 2 show that when the Z ratio is < + > 2, the method in example 1 is satisfactory, the technology of the method is up to the state level when the method is applied to the determination of the cobalt content in the high-manganese crude cobalt hydroxide, and further shows that the method in example 1 is mature and can be applied to the detection and analysis of actual production.

Example 4

This example demonstrates the performance of the method described in example 1 by testing.

1. Interference test:

the results of parallel measurement of 5 samples by adopting a masking manganese-potentiometric titration method are respectively 28.11%, 28.35%, 28.65%, 29.21% and 28.98%, and the RSD is 1.56%, and the precision is poor, mainly because the end point jump is not obvious during potentiometric titration due to the interference of manganese, the judgment of the detection end point is difficult, and meanwhile, the masking agent cannot eliminate the interference of a large amount of manganese, so that the precision and the accuracy of the detection result are poor.

2. Precision test

The results of parallel measurements of 5 samples as described in example 1 were 28.32%, 28.36%, 28.45%, 28.21%, 28.30% and an RSD of 0.31%, respectively, from which it can be seen that the method of example 1 has a good precision.

3. Accuracy test

0.1120g of pure cobalt and 0.0402g of pure manganese, 0.1123g of pure cobalt and 0.0325g of pure manganese are respectively weighed and used as two test samples, and the test results are respectively 28.15% and 27.86% and the standard recovery rates are respectively 100.5% and 99.5% according to the method in example 1, so that the method in example 1 has good accuracy.

Various corresponding changes and modifications can be made by those skilled in the art based on the above technical solutions and concepts, and all such changes and modifications should be included in the protection scope of the present invention.