Method for determining phosphorus content in iron alloy by gravimetric method

Abstract

The invention relates to a method for determining the content of phosphorus in an iron alloy by a gravimetric method, which is characterized in that the phosphorus element in the iron alloy is fully dissolved and separated from other impurities, so that the basis of subsequent quantitative analysis of the phosphorus element is ensured, and the interference of other impurities on the determination of the phosphorus element is avoided; then, the phosphorus element is precipitated in a stable form by adding a specific reagent, so that subsequent separation and weighing are facilitated, the completeness and purity of phosphorus element precipitation are ensured, and the accuracy of an experimental result is improved; and finally, the obtained phosphorus-containing precipitate is subjected to accurate ash content treatment, so that the accuracy of subsequent phosphorus content measurement is ensured. The measurement mode is low in cost and high in measurement accuracy, and a new measurement thought is provided for analysis of the phosphorus-containing element in the iron alloy.

Description

Technical Field

[0001] The present application relates to the technical field of ferroalloy element analysis, and in particular to a method for determining the phosphorus content in ferroalloys by weight. Background Art

[0002] Phosphorus is a harmful element in ferroalloys. It not only significantly reduces the toughness of ferroalloys but also causes segregation during solidification. Therefore, accurate determination of phosphorus in ferroalloys is of great significance.

[0003] Currently, the detection methods for determining phosphorus in ferroalloys mostly use fluorescence spectroscopy, inductively coupled plasma atomic emission spectroscopy, and spectrophotometry. Although these analytical methods are convenient and fast, the purchase cost of the equipment is high, which is not conducive to the production cost control of small enterprises. In addition, the phosphorus content gradient range in ferroalloy standard samples is small, which is not conducive to the drawing of standard curves, causing these instruments to produce large errors during measurement.

[0004] In view of this, it is necessary to design a method for determining the phosphorus content in ferroalloys by weight to solve the above problems. Summary of the Invention

[0005] The present application provides a method for determining the phosphorus content in ferroalloys by weight, so as to solve the problems of single method for measuring the phosphorus content in ferroalloys, low measurement accuracy and high measurement cost.

[0006] The present application provides a method for determining the phosphorus content in an iron alloy by gravimetric method, comprising the following steps:

[0007] Provide ferroalloy samples;

[0008] treating the ferroalloy sample with acid to completely dissolve phosphorus in the ferroalloy to obtain a first mixed solution, and filtering the first mixed solution to obtain a first filtrate;

[0009] adding ammonium citrate, a precipitant, and the first ammonia solution to the first filtrate in sequence to obtain a second mixed solution, and filtering the second mixed solution to obtain magnesium ammonium phosphate precipitate;

[0010] ashing the magnesium ammonium phosphate precipitate to obtain magnesium pyrophosphate;

[0011] The phosphorus content in the ferroalloy sample was calculated based on the mass of the magnesium pyrophosphate.

[0012] In some embodiments, the precipitant is a magnesium salt solution;

[0013] The preparation process of the magnesium salt solution includes: dissolving magnesium chloride hexahydrate and ammonium chloride in a third water, then adding the first ammonia water to adjust the pH to 8.5-9.5, letting it stand and filtering to remove precipitates to obtain a magnesium salt filtrate, and adding a second hydrochloric acid solution to the magnesium salt filtrate to adjust the pH to 5-6 to prepare the magnesium salt solution.

[0014] In some embodiments, the acid treatment process includes: adding hydrofluoric acid to the ferroalloy sample until the ferroalloy sample no longer dissolves; then adding nitric acid solution thereto until the dissolved ferroalloy sample no longer dissolves; then adding perchloric acid thereto and performing a first heating until no smoke is emitted, thereby obtaining the first mixed solution.

[0015] In some embodiments, the process of filtering the first mixed liquid includes: cooling the first mixed liquid, adding first water and performing a second heating until the soluble salt in the first mixed liquid is completely dissolved to obtain a soluble salt solution; performing a first filtration and a first washing treatment on the soluble salt solution, collecting the filtrate of the first filtration and the filtrate of the first washing to obtain the first filtrate.

[0016] In some embodiments, the particle size of the ferroalloy sample is no greater than 180 mesh; and / or,

[0017] The molar concentration of the hydrofluoric acid is 22.99 mol / L; and / or,

[0018] The molar concentration of the nitric acid solution is 0.29 mol / L; and / or,

[0019] The first heating temperature is 200° C. to 240° C.; and / or,

[0020] The volume ratio of the perchloric acid to the first water is (4-6):1; and / or,

[0021] The first mixed liquid is cooled to a temperature of 10° C. to 40° C.; and / or,

[0022] The second heating temperature is 100°C.

[0023] In some embodiments, the first washing process comprises: washing the soluble salt solution with a first hydrochloric acid solution and hot water in sequence;

[0024] The molar concentration of the first hydrochloric acid solution is 0.60 mol / L; the temperature of the hot water is 80° C. to 90° C.

[0025] In some embodiments, the process of sequentially adding ammonium citrate, a precipitant, and a first ammonia solution to the first filtrate comprises: adding the ammonium citrate to the first filtrate; adding the precipitant after the ammonium citrate is dissolved; adding the first ammonia solution until the pH is 8.5 to 9.5, then adding the second water, stirring until no precipitate is generated, to obtain a second mixed solution; and performing a second filtration treatment on the second mixed solution to obtain the magnesium ammonium phosphate precipitate;

[0026] The second filtration treatment process includes: sequentially allowing the second mixed liquid to stand, cooling, filtering, and collecting a first precipitate; then washing the first precipitate with a second ammonia solution until no chloride ions are left in the first precipitate to obtain the magnesium ammonium phosphate precipitate; the standing time during the second filtration treatment process is ≥3 hours; and the cooling temperature during the second filtration treatment process is 5°C to 10°C;

[0027] The concentration of the second ammonia solution is 0.714 mol / L.

[0028] In some embodiments, the molar concentration of the second hydrochloric acid solution is 2.32 mol / L; the ratio of the magnesium chloride hexahydrate, the ammonium chloride, and the third water is: 4 g:3 g:15 mL.

[0029] In some embodiments, the ratio of the ferroalloy sample, the ammonium citrate, and the magnesium salt solution is 0.3 g:(20 g-25 g):60 mL; the volume ratio of the magnesium salt solution to the second mixed solution is 2:5; and / or;

[0030] The concentration of the first ammonia solution is 0.90 g / mL.

[0031] In some embodiments, the ashing process includes: calcining the magnesium ammonium phosphate precipitate at 1000° C. to a constant weight.

[0032] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0033] The gravimetric method for determining phosphorus content in ferroalloys provided in the embodiments of the present application first fully dissolves the phosphorus in the ferroalloy and separates it from other impurities, ensuring the basis for subsequent quantitative analysis of the phosphorus element and preventing other impurities from interfering with the determination of the phosphorus element. Subsequently, a specific reagent is added to precipitate the phosphorus element in a stable form, facilitating subsequent separation and weighing, ensuring the completeness and purity of the phosphorus precipitation and improving the accuracy of the experimental results. Finally, the resulting phosphorus-containing precipitate is accurately ash-processed to ensure the accuracy of subsequent phosphorus content measurements. This gravimetric method provides a new measurement method for the analysis of phosphorus-containing elements in ferroalloys. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0035] The various embodiments of the present application may be presented in the form of a range. It should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the present application. Therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated in this application, it is intended to include any quoted number (fraction or integer) within the indicated range. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in this application can be purchased commercially or can be prepared by existing methods. In addition, in this application, the terms "including", "comprising" and the like mean "including but not limited to". In this application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this application, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. In this application, "at least one" means one or more, and "plurality" means two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0036] The present invention provides a method for determining the phosphorus content in an iron alloy by gravimetric method, comprising the following steps:

[0037] Obtaining the phosphorus content of ash in ferroalloys:

[0038] Adding an iron alloy sample with a mass of m into a polytetrafluoroethylene beaker, sequentially subjecting the iron alloy sample to acid treatment to completely dissolve the phosphorus element in the iron alloy to obtain a first mixed liquid, and filtering the first mixed liquid to obtain a first filtrate;

[0039] adding ammonium citrate, a precipitant, and the first ammonia solution to the first filtrate in sequence to obtain a second mixed solution, and filtering the second mixed solution to obtain magnesium ammonium phosphate precipitate;

[0040] The magnesium ammonium phosphate precipitate is placed in a first platinum crucible and calcined at 1000° C. to constant weight for ashing to obtain magnesium pyrophosphate; and the total weight m1 of the first platinum crucible and the substances therein is recorded. Before placing the second precipitate in the first platinum crucible for ashing, the first platinum crucible is dried at 105° C. to constant weight, and the mass m2 of the first platinum crucible dried to constant weight before ashing is recorded.

[0041] Get the blank ash content in the blank experiment:

[0042] In the blank experiment, except that the ferroalloy sample with a mass of m was not added to the polytetrafluoroethylene beaker, the remaining steps were consistent with the above-mentioned steps of obtaining the phosphorus ash content in the ferroalloy, wherein the mass of each chemical reagent added and other experimental parameters (such as heating time, temperature, etc.) were also kept consistent. The specific steps are not repeated here.

[0043] The total weight of the second platinum crucible and its contents after the ashing treatment is recorded at this time is m3; the weight of the second platinum crucible after being dried at 105°C to 110°C to a constant weight before the ashing treatment is recorded at m4;

[0044] The phosphorus content in the ferroalloy sample was calculated based on the mass of the magnesium pyrophosphate:

[0045]

[0046] M1=m1-m2;

[0047] M2=m3-m4;

[0048] Where: M1——mass of phosphorus-containing ash, g;

[0049] M2——mass of blank ash, g;

[0050] m is the mass of the ferroalloy sample, g.

[0051] m1 - the total mass of the first platinum crucible and its contents for ashing, g;

[0052] m2——the mass of the first platinum crucible dried to constant weight, g;

[0053] m3——the total mass of the second platinum crucible and the material therein for ashing, g;

[0054] m4——the mass of the second platinum crucible dried to constant weight, g;

[0055] 0.2786——The mass fraction of phosphorus in magnesium pyrophosphate (Mg2P2O7).

[0056] This method first fully dissolves the phosphorus in the ferroalloy and separates it from other impurities, ensuring the foundation for subsequent quantitative analysis of phosphorus and preventing interference from other impurities. Subsequently, by adding a specific reagent, the phosphorus is precipitated in a stable form, facilitating subsequent separation and weighing, ensuring the completeness and purity of the phosphorus precipitate and improving the accuracy of the experimental results. Finally, the resulting phosphorus precipitate is accurately ash-processed to ensure the accuracy of subsequent phosphorus content measurements. This gravimetric method provides a new measurement method for analyzing phosphorus in ferroalloys.

[0057] Furthermore, in the embodiment of the present application, the precipitant is a magnesium salt solution;

[0058] The preparation process of the magnesium salt solution includes: dissolving magnesium chloride hexahydrate and ammonium chloride in a third water, then adding the first ammonia water to adjust the pH to 8.5-9.5, letting it stand and filtering to remove precipitates to obtain a magnesium salt filtrate, and adding a second hydrochloric acid solution to the magnesium salt filtrate to adjust the pH to 5-6 to prepare the magnesium salt solution.

[0059] Furthermore, in an embodiment of the present application, the acid treatment process includes: adding hydrofluoric acid to the ferroalloy sample until the ferroalloy sample no longer dissolves; then adding nitric acid solution thereto until the dissolved ferroalloy sample no longer dissolves; then adding perchloric acid thereto and performing a first heating until no smoke is emitted, thereby obtaining the first mixed solution; wherein, the nitric acid solution is added dropwise to the partially dissolved ferroalloy sample using a dropper.

[0060] In this way, hydrofluoric acid is first used to react with the silicon and iron in the phosphorus-containing ferroalloy to generate gaseous silicon tetrafluoride, water, and ferrous fluoride; then nitric acid solution is added to further dissolve the Fe3P, Fe2P, FeP, and FeP2 in the ferroalloy; then perchloric acid is added and heated until white smoke is emitted to remove residual silicon and fluorine; in this way, the phosphorus element in the ferroalloy is fully dissolved and converted into a soluble salt, which facilitates the subsequent accurate measurement of the phosphorus element in the ferroalloy.

[0061] Furthermore, in an embodiment of the present application, the process of filtering the first mixed liquid includes: waiting for the first mixed liquid to cool (to avoid splashing due to the presence of strong acid in the first mixed liquid and the high temperature causing subsequent water addition, which affects the subsequent detection results), adding first water and performing a second heating until the soluble salt in the first mixed liquid is completely dissolved to obtain a soluble salt solution; performing a first filtration and a first washing treatment on the soluble salt solution, collecting the filtrate of the first filtration and the filtrate of the first washing to obtain the first filtrate.

[0062] In order to ensure that the phosphorus element in the ferroalloy can be fully converted into soluble salt, the particle size of the ferroalloy sample is not greater than 180 mesh.

[0063] Furthermore, in the embodiment of the present application, the molar concentration of the hydrofluoric acid is 22.99 mol / L; preferably, the ratio of the ferroalloy sample to the hydrofluoric acid is 0.3 g:4 mL to 0.3 g:5 mL;

[0064] The molar concentration of the nitric acid solution is 0.29 mol / L;

[0065] The first heating temperature is 200°C to 240°C;

[0066] The volume ratio of the perchloric acid to the first water is (4-6):1;

[0067] The temperature of the first mixed liquid cooling is 10-40°C;

[0068] The second heating temperature is 100°C.

[0069] Furthermore, in an embodiment of the present application, the first washing process includes: washing the soluble salt solution with a first hydrochloric acid solution and hot water in sequence;

[0070] The molar concentration of the first hydrochloric acid solution is 0.60 mol / L; the temperature of the hot water is 80° C. to 90° C.

[0071] Furthermore, in an embodiment of the present application, the process of sequentially adding ammonium citrate, a precipitant, and a first ammonia water to the first filtrate includes: adding the ammonium citrate to the first filtrate; adding the precipitant after the ammonium citrate is dissolved; adding the first ammonia water until the pH is 8.5 to 9.5, then adding the second water, stirring until no precipitate is generated, to obtain a second mixed solution; and performing a second filtration treatment on the second mixed solution to obtain the magnesium ammonium phosphate precipitate;

[0072] The second filtration treatment process includes: sequentially allowing the second mixed liquid to stand, cooling, filtering, and collecting a first precipitate; then washing the first precipitate with a second ammonia solution until no chloride ions are left in the first precipitate to obtain the magnesium ammonium phosphate precipitate; the standing time during the second filtration treatment process is ≥3 hours; and the cooling temperature during the second filtration treatment process is 5°C to 10°C;

[0073] The concentration of the second ammonia solution is 0.714 mol / L.

[0074] Wherein, a silver nitrate solution with a concentration of 10 g / L can be used to test whether the first precipitate contains chloride ions.

[0075] It is worth noting that if the magnesium salt mixed solution is added first and then ammonium citrate is added: when Mg 2+ When added, Fe 3+ 、Al 3+ Interfering ions such as OH have not yet been complexed and will preferentially react with — The reaction generates Fe(OH)3 and Al(OH)3 colloidal precipitates; these precipitates will adsorb PO4 3— Or MgNH4PO4, resulting in impurities mixed into the target precipitate (MgNH4PO4), and the result is too high during measurement.

[0076] In addition, the purpose of diluting with the second aqueous solution is to expand the buffer system (NH3·H2O / NH4 + ) capacity, prevent pH fluctuations caused by local acid-base changes, improve the buffering capacity of ammonia water, control the solution volume and ion concentration, optimize the precipitation conditions, ensure the complete precipitation of the target precipitate (magnesium ammonium phosphate) and the purity of the precipitate, reduce the initial ion concentration, avoid local oversaturation and the formation of fine precipitates; at the same time, reduce the ionic strength and reduce impurity adsorption.

[0077] Furthermore, in an embodiment of the present application, the molar concentration of the second hydrochloric acid solution is 2.32 mol / L; the ratio of the magnesium chloride hexahydrate, the ammonium chloride, and the third water is: 4 g:3 g:15 mL.

[0078] Furthermore, in the embodiment of the present application, the ratio of the ferroalloy sample, the ammonium citrate, and the magnesium salt mixed solution is 0.3 g:(20 g to 25 g):60 mL; the volume ratio of the magnesium salt mixed solution to the second mixed solution is 2:5;

[0079] The concentration of the first ammonia solution is 0.90 g / mL.

[0080] Furthermore, in the embodiment of the present application, the first water, the second water, and the third water all include deionized water.

[0081] The present application is further described below with reference to specific examples. Experimental methods in the following examples where specific conditions are not specified are generally determined in accordance with national standards. If no corresponding national standards exist, the methods are performed in accordance with commonly used international standards, conventional conditions, or conditions recommended by the manufacturer.

[0082] Example

[0083] This embodiment provides a method for determining the phosphorus content in an iron alloy by gravimetric method, comprising the following steps:

[0084] Obtaining the phosphorus content of ash in ferroalloys:

[0085] In a polytetrafluoroethylene beaker, add mass m=0.3000g and granularity is not more than 180 purpose ferroalloy samples, adding molar concentration is the hydrofluoric acid of 22.99mol / L again, until the ferroalloy sample no longer dissolves (the hydrofluoric acid volume consumed this moment is 1.20mL), and for ensuring complete reaction, continue to add excessive hydrofluoric acid, the total hydrofluoric acid volume consumed is 5mL; With a dropper, dripping the salpeter solution that molar concentration is 0.29mol / L again, until the described ferroalloy sample after the dissolving no longer dissolves (the salpeter solution consumed this moment is 17.10mL), and for ensuring complete reaction, continue to add excessive salpeter solution, the volume of the total salpeter solution consumed is 25mL; Then wherein add perchloric acid, and under 200 ℃, carry out the first heating, until no longer fuming, the perchloric acid of record consumption is 10mL, obtains the first mixed solution;

[0086] After the first mixed solution is cooled to room temperature, 50 mL of the first water is added, and the mixture is heated for a second time at 100° C. until the soluble salt in the first mixed solution is completely dissolved to obtain a soluble salt solution;

[0087] The soluble salt solution is subjected to a first filtration and a first washing process, and the filtrate of the first filtration and the filtrate of the first washing are collected to obtain the first filtrate; the first washing process comprises: washing the soluble salt solution with a first hydrochloric acid solution and hot water at a temperature of 80° C. in sequence;

[0088] 20 g of ammonium citrate granules were added to the first filtrate; after the ammonium citrate granules were dissolved, 60 mL of magnesium salt solution was added; the first ammonia solution was then added until the pH reached 9, and then the second water was added to dilute the volume to 150 mL; after stirring until no more precipitate was generated, a second filtration process was performed to obtain the magnesium ammonium phosphate precipitate;

[0089] The second filtration treatment process includes: standing for 3 hours, cooling to 5°C, filtering, and collecting the first precipitate; washing the first precipitate with a second ammonia solution having a concentration of 0.714 mol / L until no chloride ions are left in the first precipitate to obtain the magnesium ammonium phosphate precipitate; and testing the first precipitate for chloride ions using silver nitrate at a concentration of 10 g / L.

[0090] The preparation process of the magnesium salt solution includes: dissolving 400g of magnesium chloride hexahydrate and 300g of ammonium chloride in 1500mL of a third water, adding the first ammonia water with a concentration of 0.90g / mL to adjust the pH to 9, standing for 1h and filtering to remove the precipitate, and then adding a second hydrochloric acid solution with a molar concentration of 2.32mol / L to adjust the pH to 6 to prepare the magnesium salt solution.

[0091] The magnesium ammonium phosphate precipitate is placed in a first platinum crucible and burned at 1000°C to constant weight for ashing to obtain magnesium pyrophosphate; and the total weight m1 of the first platinum crucible and the substances therein is recorded. Before placing the second precipitate in the first platinum crucible for ashing, the first platinum crucible is dried at 110°C to constant weight, and the mass m2 of the first platinum crucible dried to constant weight before ashing is recorded;

[0092] Get the blank ash content in the blank experiment:

[0093] Except for not adding the iron alloy sample with a mass of m to the polytetrafluoroethylene beaker, the remaining steps are consistent with the above steps of obtaining the phosphorus ash content in the iron alloy, wherein the mass of each chemical reagent added and other experimental parameters (such as heating time, temperature, etc.) are also kept consistent. The specific steps are not repeated here.

[0094] The total weight of the second platinum crucible and its contents after the ashing treatment is recorded at this time is m3; the weight of the second platinum crucible after being dried at 110° C. to a constant weight before the ashing treatment is recorded at m4;

[0095] Calculating the phosphorus content in ferroalloys :

[0096]

[0097] M1=m1-m2;

[0098] M2=m3-m4;

[0099] Where: m1 is the total mass of the first platinum crucible and its contents for ashing, g;

[0100] m2——the mass of the first platinum crucible dried to constant weight, g;

[0101] m3——the total mass of the second platinum crucible and the material therein for ashing, g;

[0102] m4——the mass of the second platinum crucible dried to constant weight, g;

[0103] m——mass of ferroalloy sample, g;

[0104] 0.2786——The mass fraction of phosphorus in magnesium pyrophosphate (Mg2P2O7).

[0105] All reagents used in the experiment were of high-grade pure reagents.

[0106] The preparation process of nitric acid solution is as follows: mix high-grade pure nitric acid and water in a volume ratio of 2:98.

[0107] The first hydrochloric acid solution is prepared by uniformly mixing high-grade pure hydrochloric acid and water in a volume ratio of 5:95.

[0108] The second hydrochloric acid solution is prepared by uniformly mixing high-grade pure hydrochloric acid and water in a volume ratio of 1:4.

[0109] According to the above method, the two ferroalloy samples were measured eight times in parallel. The measurement results are shown in Table 1.

[0110] Table 1 The results of the determination of phosphorus content in two ferroalloy samples using the gravimetric method

[0111]

[0112] According to the above method, two standard samples were measured eight times in parallel. The standard sample numbers are YSBC 28661-2018 (phosphorus content: 27.23%) and YSBC 28662-2018 (phosphorus content: 26.78%). The measurement results are shown in Table 2.

[0113] Table 2 Determination results of phosphorus content in two standard ferroalloy samples using the gravimetric method

[0114]

[0115] The relative standard deviations (RSDs) obtained for the YSBC 28661-2018 (phosphorus content: 27.23%) and YSBC 28662-2018 (phosphorus content: 26.78%) standard samples in Table 2 were small, and the measured values ​​were close to the certified values ​​and within the allowable error range, demonstrating the high accuracy of this method. Furthermore, the RSDs obtained for each sample in Tables 1 and 2 were small, indicating the high precision and good repeatability of this method.

[0116] In summary, the present invention provides a gravimetric method for determining phosphorus content in ferroalloys. This method first fully dissolves the phosphorus in the ferroalloy and separates it from other impurities, ensuring the basis for subsequent quantitative analysis of the phosphorus element and preventing other impurities from interfering with the determination of the phosphorus element. Subsequently, a specific reagent is added to precipitate the phosphorus element in a stable form, facilitating subsequent separation and weighing, ensuring the completeness and purity of the phosphorus precipitate and improving the accuracy of the experimental results. Finally, the resulting phosphorus-containing precipitate is accurately ash-processed to ensure the accuracy of subsequent phosphorus content measurements. This gravimetric method provides a new measurement strategy for analyzing phosphorus in ferroalloys.

[0117] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but rather is intended to conform to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for determining the phosphorus content in ferroalloys by gravimetric method, characterized in that: The following steps are involved: Provide ferroalloy samples; treating the ferroalloy sample with acid to completely dissolve phosphorus in the ferroalloy to obtain a first mixed solution, and filtering the first mixed solution to obtain a first filtrate; adding ammonium citrate, a precipitant, and the first ammonia solution to the first filtrate in sequence to obtain a second mixed solution, and filtering the second mixed solution to obtain magnesium ammonium phosphate precipitate; ashing the magnesium ammonium phosphate precipitate to obtain magnesium pyrophosphate; The phosphorus content in the ferroalloy sample was calculated based on the mass of the magnesium pyrophosphate.

2. The method for determining the phosphorus content in ferroalloys by gravimetric method according to claim 1, characterized in that: The precipitant is a magnesium salt solution; The preparation process of the magnesium salt solution includes: dissolving magnesium chloride hexahydrate and ammonium chloride in a third water, then adding the first ammonia water to adjust the pH to 8.5-9.5, letting it stand and filtering to remove precipitates to obtain a magnesium salt filtrate, and adding a second hydrochloric acid solution to the magnesium salt filtrate to adjust the pH to 5-6 to prepare the magnesium salt solution.

3. The method for determining the phosphorus content in ferroalloys by gravimetric method according to claim 1, characterized in that: The acid treatment process includes: adding hydrofluoric acid to the ferroalloy sample until the ferroalloy sample no longer dissolves; then adding nitric acid solution thereto until the dissolved ferroalloy sample no longer dissolves; then adding perchloric acid thereto and performing a first heating until no smoke is emitted, thereby obtaining the first mixed solution.

4. The method for determining the phosphorus content in ferroalloys by gravimetric method according to claim 3, characterized in that: The process of filtering the first mixed liquid includes: cooling the first mixed liquid, adding first water and performing a second heating until the soluble salt in the first mixed liquid is completely dissolved to obtain a soluble salt solution; performing a first filtration and a first washing treatment on the soluble salt solution, collecting the filtrate of the first filtration and the filtrate of the first washing to obtain the first filtrate.

5. The method for determining the phosphorus content in ferroalloys by gravimetric method according to claim 4, characterized in that: The particle size of the ferroalloy sample is not greater than 180 mesh; and / or, The molar concentration of the hydrofluoric acid is 22.99 mol / L; and / or, The molar concentration of the nitric acid solution is 0.29 mol / L; and / or, The first heating temperature is 200° C. to 240° C.; and / or, The volume ratio of the perchloric acid to the first water is (4-6):1; and / or, The first mixed liquid is cooled to a temperature of 10° C. to 40° C.; and / or, The second heating temperature is 100°C.

6. The method for determining the phosphorus content in ferroalloys by gravimetric method according to claim 4, characterized in that: The first washing process includes: washing the soluble salt solution with a first hydrochloric acid solution and hot water in sequence; The molar concentration of the first hydrochloric acid solution is 0.60 mol / L; the temperature of the hot water is 80° C. to 90° C.

7. The method for determining the phosphorus content in ferroalloys by gravimetric method according to claim 1, characterized in that: The process of sequentially adding ammonium citrate, a precipitant, and a first ammonia solution to the first filtrate comprises: adding the ammonium citrate to the first filtrate; adding the precipitant after the ammonium citrate is dissolved; adding the first ammonia solution until the pH reaches 8.5 to 9.5, then adding the second water, stirring until no precipitate is generated, to obtain a second mixed solution; and performing a second filtration process on the second mixed solution to obtain the magnesium ammonium phosphate precipitate; The second filtration treatment process includes: sequentially allowing the second mixed liquid to stand, cooling, filtering, and collecting a first precipitate; then washing the first precipitate with a second ammonia solution until no chloride ions are left in the first precipitate to obtain the magnesium ammonium phosphate precipitate; the standing time during the second filtration treatment process is ≥3 hours; and the cooling temperature during the second filtration treatment process is 5°C to 10°C; The concentration of the second ammonia solution is 0.714 mol / L.

8. The method for determining the phosphorus content in ferroalloys by gravimetric method according to claim 2, characterized in that: The molar concentration of the second hydrochloric acid solution is 2.32 mol / L; the ratio of the magnesium chloride hexahydrate, the ammonium chloride, and the third water is: 4 g:3 g:15 mL.

9. The method for determining the phosphorus content in ferroalloys by gravimetric method according to claim 2, characterized in that: The ratio of the ferroalloy sample, the ammonium citrate, and the magnesium salt solution is 0.3 g:(20 g to 25 g):60 mL; the volume ratio of the magnesium salt solution to the second mixed solution is 2:5; and / or; The concentration of the first ammonia solution is 0.90 g / mL.

10. The method for determining the phosphorus content in ferroalloys by gravimetric method according to claim 1, characterized in that: The ashing process includes: calcining the magnesium ammonium phosphate precipitate at 1000° C. to a constant weight.

Images