Method for detecting content of eutectic phosphorus in phosphogypsum

Abstract

The invention relates to the technical field of ardealite detection, in particular to a method for detecting the content of eutectic phosphorus in ardealite, which comprises the following steps: S1) extracting eutectic phosphorus from an ardealite sample by adopting a buffer solution combined horizontal oscillation method; the buffer solution comprises one of an oxalic acid-ammonium oxalate buffer solution, a citric acid-sodium citrate buffer solution, a citric acid-ammonium citrate buffer solution, a formic acid-ammonium formate buffer solution and a tartaric acid-ammonium tartrate buffer solution; and S2) detecting and calculating the content of the obtained eutectic phosphorus by adopting a phosphomolybdic acid quinoline gravimetric method. The key point of accurate detection of eutectic phosphorus is effective separation of insoluble phosphorus and eutectic phosphorus. According to the method, water-soluble phosphorus is removed firstly, and calcium sulfate dihydrate crystal lattices are destroyed through a specific buffer solution, so that eutectic phosphorus is dissolved out, and meanwhile insoluble phosphorus cannot be dissolved; the buffer solution has special specificity, and the detection method provided by the invention is high in accuracy, good in precision and suitable for popularization.

Description

Technical Field

[0001] The invention relates to the technical field of phosphogypsum detection, and in particular to a method for detecting the eutectic phosphorus content in phosphogypsum. Background Art

[0002] Phosphogypsum is a byproduct produced during the wet process of producing phosphoric acid from phosphate ore. It has a large stockpile and low utilization rate. Phosphogypsum contains a variety of harmful impurities such as phosphorus, fluorine, organic matter, and alkali metal salts. Among them, phosphorus is one of the impurities that has the greatest impact on the performance of phosphogypsum, which is specifically manifested in the extension of setting time and the reduction of hardened body strength. The phosphorus in phosphogypsum mainly exists in three forms: water-soluble phosphorus (free phosphorus), eutectic phosphorus, and insoluble phosphorus. The water-soluble phosphorus in phosphogypsum mainly exists in free form; the insoluble phosphorus mainly exists in the form of phosphate and incompletely decomposed phosphate ore; the eutectic phosphorus mainly exists in the form of CaHPO4·2H2O. Since CaHPO4·2H2O and CaSO4·2H2O belong to the monoclinic system, under certain conditions, CaHPO4·2H2O can enter the CaSO4·2H2O lattice to form a solid solution. Eutectic phosphorus is a harmful impurity second only to water-soluble phosphorus. During the hydration process of gypsum, eutectic phosphorus can be dissolved from the calcium sulfate dihydrate lattice and dissolved in the slurry as soluble phosphorus, thus affecting the quality of gypsum.

[0003] At present, although there are reports on the detection method of eutectic phosphorus content in phosphogypsum, there are doubts as to whether the detected phosphorus is the true value of eutectic phosphorus. The key point to accurately detect eutectic phosphorus lies in the effective separation of insoluble phosphorus and eutectic phosphorus.

[0004] The patent application document with application number 202110857534 discloses a method for detecting eutectic phosphorus by calcination combined with extraction. The phosphogypsum is first calcined into hemihydrate gypsum, and sulfuric acid in a slightly boiling state is added to the treated phosphogypsum. It is believed that the filtrate obtained after filtration is eutectic phosphorus. However, this method does not separate the water-soluble phosphorus in the phosphogypsum, and the extracted filtrate will contain water-soluble phosphorus, resulting in deviations in the detection results of eutectic phosphorus.

[0005] The patent application document with application number 202110862275 discloses a difference method for detecting the eutectic phosphorus content. The eutectic phosphorus content is obtained by subtracting the phosphorus content extracted from the phosphogypsum with an inorganic acid solution (the inorganic acid solution is nitric acid and hydrochloric acid) from the total phosphorus content in the phosphogypsum. This prior art believes that the inorganic acid solution can extract water-soluble phosphorus and insoluble phosphorus, but cannot extract eutectic phosphorus. In the method described in this prior art, in order to avoid the dissolution of calcium sulfate during the dissolution of impurities, it is necessary to detect the sulfate content while detecting the solution ion content. However, in the embodiment part, the sulfate content in the leachate of each embodiment is not mentioned, and it is impossible to determine whether the calcium sulfate is dissolved together, causing the eutectic phosphorus therein to enter the leachate together.

[0006] The existing document "Effect of eutectic phosphorus on gypsum performance and its mechanism of action" (Li Mei et al. Journal of Sichuan University (Engineering Science Edition), 2012, 44(03): 200-204.) adopts a solvent extraction method to remove water-soluble phosphorus, and then extract it with a potassium hydrogen phthalate buffer solution with a pH of 4.0 and a barium nitrate solution with a concentration of 10%. After solid-liquid separation, the phosphorus in the filtrate is the eutectic phosphorus. However, this method does not specify the concentration of the potassium hydrogen phthalate buffer solution, and the phosphorus content extracted by buffer solutions of different concentrations is different. In addition, barium nitrate is an explosive chemical with poor safety. Summary of the invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a method for detecting the eutectic phosphorus content in phosphogypsum, which can accurately detect the eutectic phosphorus content in phosphogypsum.

[0008] The present invention provides a method for detecting the eutectic phosphorus content in phosphogypsum, comprising the following steps:

[0009] S1) extracting eutectic phosphorus from the phosphogypsum sample using a buffer solution combined with a horizontal oscillation method;

[0010] The buffer solution comprises one of oxalic acid-ammonium oxalate buffer solution, citric acid-sodium citrate buffer solution, citric acid-ammonium citrate buffer solution, formic acid-ammonium formate and tartaric acid-ammonium tartrate buffer solution;

[0011] S2) using the quinoline phosphomolybdic acid weight method to detect and calculate the phosphorus content of the obtained eutectic.

[0012] Preferably, in step S1), the pH value of the buffer solution is 3.5 to 7.5.

[0013] Preferably, in step S1), the concentration of the buffer solution is 0.05 to 2.5 mol / L.

[0014] Preferably, in step S1), the solid-to-liquid ratio of the obtained sample to the buffer solution is 1:30-60.

[0015] Preferably, in step S1), the extraction temperature is 23-27° C., the extraction time is 90-135 min, and the oscillator frequency is 120-180 r / min.

[0016] Preferably, in step S1), before extracting eutectic phosphorus from the phosphogypsum sample using a buffer solution combined with a horizontal oscillation method, the method further comprises:

[0017] The phosphogypsum samples were subjected to the removal of water-soluble phosphorus.

[0018] Preferably, the phosphogypsum sample is a dry phosphogypsum sample.

[0019] Preferably, the method for removing water-soluble phosphorus comprises the following steps:

[0020] The phosphogypsum sample is mixed with water, horizontally shaken, and then the solid and liquid are separated to obtain a sample after removing the water-soluble phosphorus.

[0021] Preferably, the dosage ratio of the phosphogypsum sample to water is 0.8-1.2 g: 45-55 mL;

[0022] The temperature of the horizontal oscillation is 23-27° C., the time is 18-22 min, and the oscillator frequency is 145-155 r / min.

[0023] Preferably, in step S2), the calculation method includes:

[0024] Eutectic phosphorus content in phosphogypsum samples: Eutectic P2O5 is expressed as mass fraction and calculated according to formula (1):

[0025]

[0026] In formula (1):

[0027] ω——phosphorus pentoxide content in phosphogypsum sample, in percentage (%);

[0028] m——mass of phosphogypsum sample, in g;

[0029] m1——the mass of the crucible, in g;

[0030] m2——the mass of quinoline phosphomolybdate precipitate and crucible, in g;

[0031] m3——the mass of the blank test crucible, in g;

[0032] m4——the mass of blank test precipitate and crucible, in g;

[0033] 0.03207——The coefficient for converting the molar mass of quinoline phosphomolybdate to the molar mass of phosphorus pentoxide;

[0034] f——dilution multiple.

[0035] The present invention provides a method for detecting the content of eutectic phosphorus in phosphogypsum, comprising the following steps: S1) extracting eutectic phosphorus from a phosphogypsum sample by a buffer solution combined with a horizontal oscillation method; the buffer solution comprises one of an oxalic acid-ammonium oxalate buffer solution, a citric acid-sodium citrate buffer solution, a citric acid-ammonium citrate buffer solution, a formic acid-ammonium formate and a tartaric acid-ammonium tartrate buffer solution; S2) detecting and calculating the obtained eutectic phosphorus content by a quinoline phosphomolybdic acid weight method. The key point of accurately detecting eutectic phosphorus is the effective separation of insoluble phosphorus and eutectic phosphorus. The present invention first removes water-soluble phosphorus, and destroys the calcium sulfate dihydrate lattice by a specific buffer solution, so that the eutectic phosphorus is dissolved, while the insoluble phosphorus cannot be dissolved; the buffer solution has special specificity, and the detection method provided by the present invention has high accuracy and good precision, and is suitable for promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0037] Figure 1 This is a microscopic diagram of the particle crystal structure of the phosphogypsum sample before drying in Example 8 of the present invention;

[0038] Figure 2 The particle crystal microstructure diagram of the sample obtained in step (1) of Example 8 of the present invention;

[0039] Figure 3 This is a microscopic diagram of the particle crystal structure of the filter residue obtained after solid-liquid separation in step (3) of Example 8 of the present invention. DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The present invention provides a method for detecting the eutectic phosphorus content in phosphogypsum, comprising the following steps:

[0042] S1) extracting eutectic phosphorus from the phosphogypsum sample using a buffer solution combined with a horizontal oscillation method;

[0043] The buffer solution is selected from one of oxalic acid-ammonium oxalate buffer solution, citric acid-sodium citrate buffer solution, citric acid-ammonium citrate buffer solution, formic acid-ammonium formate and tartaric acid-ammonium tartrate buffer solution;

[0044] S2) using the quinoline phosphomolybdic acid weight method to detect and calculate the phosphorus content of the obtained eutectic.

[0045] Regarding step S1):

[0046] The eutectic phosphorus was extracted from the phosphogypsum sample using a buffer solution combined with a horizontal oscillation method.

[0047] In certain embodiments of the present invention, before extracting eutectic phosphorus from the phosphogypsum sample using a buffer solution in combination with a horizontal oscillation method, the method further comprises:

[0048] The phosphogypsum samples were subjected to the removal of water-soluble phosphorus.

[0049] In certain embodiments of the present invention, the phosphogypsum sample is a dry phosphogypsum sample.

[0050] The dried phosphogypsum sample can be obtained by drying the phosphogypsum sample. The drying temperature is 43-47° C. Specifically, the phosphogypsum sample is dried at 43-47° C. to a constant weight to obtain a dried phosphogypsum sample.

[0051] In certain embodiments of the present invention, the method for removing water-soluble phosphorus comprises the following steps:

[0052] The phosphogypsum sample is mixed with water, horizontally shaken, and then the solid and liquid are separated to obtain a sample after removing the water-soluble phosphorus.

[0053] The water is ultrapure water.

[0054] The dosage ratio of the phosphogypsum sample to water is 0.8-1.2 g:45-55 mL, for example, 1 g:50 mL.

[0055] The temperature of the horizontal oscillation is 23-27° C., such as 25° C.; the time is 18-22 min., such as 20 min.; and the oscillator frequency is 145-155 r / min.

[0056] After the solid-liquid separation, the phosphorus contained in the obtained filtrate is water-soluble phosphorus, and the phosphorus contained in the solid is insoluble phosphorus and eutectic phosphorus.

[0057] After removing the water-soluble phosphorus, the obtained sample was used to extract the eutectic phosphorus using a buffer solution combined with a horizontal oscillation method.

[0058] Specifically, after the obtained sample is mixed with a buffer solution, the eutectic phosphorus is extracted by a horizontal oscillation method.

[0059] The buffer solution is selected from one of oxalic acid-ammonium oxalate buffer solution, citric acid-sodium citrate buffer solution, citric acid-ammonium citrate buffer solution, formic acid-ammonium formate buffer solution and tartaric acid-ammonium tartrate buffer solution. Preferably, the buffer solution is citric acid-ammonium citrate buffer solution.

[0060] In certain embodiments of the present invention, the pH value of the buffer solution is 3.5-7.5, such as 5.5; the concentration of the buffer solution is 0.05-2.5 mol / L, such as 0.125 mol / L.

[0061] The solid-to-liquid ratio of the obtained sample to the buffer solution is 1:30-60, preferably 1:50.

[0062] The extraction temperature is 23-27° C., such as 25° C.; the extraction time is 90-135 min, such as 120 min; and the oscillator frequency is 120-180 r / min, such as 150 r / min.

[0063] After the extraction, the method further includes: solid-liquid separation. The filtrate obtained by the solid-liquid separation is the eutectic phosphorus extract.

[0064] The difficulty in accurately detecting the eutectic phosphorus content lies in whether the insoluble phosphorus and the eutectic phosphorus can be effectively separated. The present invention analyzes the phosphorus impurities in the phosphogypsum and the properties of the gypsum. The main component of the phosphogypsum is CaSO4·2H2O, and the eutectic phosphorus is a solid solution formed by CaHPO4·2H2O entering the CaSO4·2H2O lattice. The present invention uses a specific ammonium salt buffer solution, which can destroy the CaSO4·2H2O lattice to dissolve the CaHPO4·2H2O therein. The present invention further limits the conditions for extracting the buffer solution, so that the insoluble phosphorus cannot be dissolved in the buffer solution or only a small amount of insoluble phosphorus is dissolved as much as possible.

[0065] Regarding step S2):

[0066] The content of eutectic phosphorus in the obtained eutectic phosphorus extract was detected and calculated by the quinoline phosphomolybdic acid weight method.

[0067] The quinoline phosphomolybdic acid weight method is the quinoline phosphomolybdic acid weight method in "Determination Method of Phosphorus and Fluorine in Phosphogypsum" CJ / T2073-2011.

[0068] The specific calculation methods include:

[0069] Eutectic phosphorus content in the sample: Eutectic P2O5 is expressed as mass fraction and calculated according to formula (1): The sample is the phosphogypsum sample in step S1), measured at the first weighing without removing water-soluble phosphorus;

[0070]

[0071] In formula (1):

[0072] ω——phosphorus pentoxide content in the sample, in percentage (%);

[0073] m——sample mass, in g;

[0074] m1——the mass of the crucible, in g;

[0075] m2——the mass of quinoline phosphomolybdate precipitate and crucible, in g;

[0076] m3——the mass of the blank test crucible, in g;

[0077] m4——the mass of blank test precipitate and crucible, in g;

[0078] 0.03207——The coefficient for converting the molar mass of quinoline phosphomolybdate to the molar mass of phosphorus pentoxide;

[0079] f——dilution factor.

[0080] The detection method provided by the present invention first removes water-soluble phosphorus according to the types of phosphorus impurities in phosphogypsum and the properties of gypsum, and then selects a specific buffer solution to extract eutectic phosphorus, destroys the calcium sulfate dihydrate lattice, dissolves the eutectic phosphorus, and the sparingly soluble phosphorus cannot be dissolved in the buffer solution, and the eutectic phosphorus content in the phosphogypsum can be quantitatively obtained, and the detection accuracy can reach more than 95%.

[0081] The present invention has no particular limitation on the sources of the raw materials used above, and they can be generally commercially available.

[0082] In order to further illustrate the present invention, a method for detecting the eutectic phosphorus content in phosphogypsum provided by the present invention is described in detail below in conjunction with examples, but it should not be construed as limiting the scope of protection of the present invention.

[0083] Phosphogypsum contains water-soluble phosphorus, eutectic phosphorus and insoluble phosphorus (insoluble phosphorus can be mainly divided into Ca3(PO4)2 and insoluble phosphorus in undecomposed phosphate rock).

[0084] Example 1

[0085] A method for detecting the eutectic phosphorus content in phosphogypsum, the implementation steps are as follows:

[0086] (1) Sample preparation: Reference substance preparation: CaSO4·2H2O and Ca3(PO4)2 were used to precisely prepare a sparingly soluble phosphorus with a total phosphorus mass percentage of 1.4%, and this reference substance was recorded as A (simulating the Ca3(PO4)2 sparingly soluble phosphorus in phosphogypsum); CaSO4·2H2O and CaHPO4·2H2O were used to precisely prepare a eutectic phosphorus with a total phosphorus mass percentage of 1.4%, and this reference substance was recorded as B; CaSO4·2H2O and phosphate concentrate were used to precisely prepare a sparingly soluble phosphorus with a total phosphorus mass percentage of 1.4%, and this reference substance was recorded as C (simulating the sparingly soluble phosphorus in undecomposed phosphate rock), and the phosphate concentrate was the raw material for wet phosphoric acid production, and the total phosphorus mass content was 33.60%.

[0087] (2) Preparation of buffer solution: prepare a citric acid-ammonium citrate buffer solution with a pH value of 5.5 and a concentration of 0.125 mol / L.

[0088] (3) Extraction of eutectic phosphorus: The prepared reference substances A, B, and C were mixed with the buffer solution in a solid-liquid ratio of 1:50, and placed in an oscillator with an oscillation frequency of 150 r / min, and extracted with horizontal oscillation at 25°C for 120 min. Solid-liquid separation was performed, and the filtrate was the eutectic phosphorus extract.

[0089] (4) Eutectic phosphorus detection: The eutectic P2O5 content was determined using the quinoline phosphomolybdate weight method in the "Determination of phosphorus and fluorine in phosphogypsum" CJ / T2073-2011;

[0090] (5) Calculation of eutectic phosphorus content. Eutectic P2O5 is expressed as mass fraction and is calculated according to formula (1):

[0091]

[0092] In formula (1):

[0093] ω——phosphorus pentoxide content in the test material (sample), in percentage (%);

[0094] m——mass of the test material (sample), in g;

[0095] m1——the mass of the crucible, in g;

[0096] m2——the mass of quinoline phosphomolybdate precipitate and crucible, in g;

[0097] m3——the mass of the blank test crucible, in g;

[0098] m4——the mass of blank test precipitate and crucible, in g;

[0099] 0.03207——The coefficient for converting the molar mass of quinoline phosphomolybdate to the molar mass of phosphorus pentoxide;

[0100] f——dilution factor.

[0101] (6) The eutectic phosphorus extraction rate is calculated according to formula (2):

[0102]

[0103] (7) The extraction rate of insoluble phosphorus is calculated according to formula (3):

[0104]

[0105] Example 2

[0106] The difference from Example 1 is:

[0107] In step (2), the buffer solution is an oxalic acid-ammonium oxalate buffer solution with a pH value of 5.5 and a concentration of 0.125 mol / L.

[0108] Example 3

[0109] The difference from Example 1 is:

[0110] In step (2), the buffer solution is a citric acid-ammonium citrate buffer solution with a pH value of 4.5 and a concentration of 0.125 mol / L.

[0111] Example 4

[0112] The difference from Example 1 is:

[0113] In step (2), the buffer solution is a citric acid-ammonium citrate buffer solution with a pH value of 5.5 and a concentration of 0.1 mol / L.

[0114] Example 5

[0115] The difference from Example 1 is:

[0116] In step (3), the solid-liquid ratio is 1:30.

[0117] Example 6

[0118] The difference from Example 1 is:

[0119] In step (3), the oscillation frequency is 100 r / min.

[0120] Example 7

[0121] The difference from Example 1 is:

[0122] In step (3), the extraction is performed by horizontal shaking at 25° C. for 105 min.

[0123] The calculation results of Examples 1 to 7 are shown in Table 1.

[0124] Table 1 Calculation results of Examples 1 to 7

[0125]

[0126] The key point of accurately detecting eutectic phosphorus is the effective separation of eutectic phosphorus and insoluble phosphorus. As can be seen from Table 1, reference substances A and C represent insoluble phosphorus in phosphogypsum, and reference substance B represents eutectic phosphorus in phosphogypsum. That is, the lower the extraction rate of A and C, and the higher the extraction rate of B, the closer the detected result is to the true content of eutectic phosphorus in phosphogypsum. As can be seen from the above Examples 1 to 7, the result detected in Example 1 is closest to the true content of eutectic phosphorus in phosphogypsum.

[0127] Example 8

[0128] A method for detecting the eutectic phosphorus content in phosphogypsum, the implementation steps are as follows:

[0129] (1) Sample preparation:

[0130] The phosphogypsum sample was dried at 45°C to constant weight, ultrapure water was added according to the solid-liquid ratio of 1g phosphogypsum: 50mL ultrapure water, and horizontal oscillation was performed at 25°C for 20min with an oscillator frequency of 150r / min; solid-liquid separation was performed, and the phosphorus contained in the solid was insoluble phosphorus and eutectic phosphorus, which was the test sample.

[0131] Figure 1 This is a microscopic picture of the particle crystal structure of the phosphogypsum sample before drying in Example 8 of the present invention. Figure 1 It can be seen that there are a large number of irregular crystals in the untreated phosphogypsum slag.

[0132] Figure 2 This is a microscopic picture of the particle crystal structure of the sample obtained in step (1) of Example 8 of the present invention. Figure 2 It can be seen that after water washing to remove water-soluble phosphorus, a large number of irregular crystals still exist in the phosphogypsum. Water washing cannot destroy the CaSO4·2H2O lattice and the eutectic phosphorus cannot be dissolved.

[0133] (2) Preparation of buffer solution: prepare a citric acid-ammonium citrate buffer solution with a pH value of 5.5 and a concentration of 0.125 mol / L.

[0134] (3) Extraction of eutectic phosphorus: The prepared test sample was mixed with a buffer solution in a solid-liquid ratio of 1:50, and placed in an oscillator with an oscillation frequency of 150 r / min, and extracted with horizontal oscillation at 25°C for 120 min. Solid-liquid separation was performed, and the filtrate was the eutectic phosphorus.

[0135] Figure 3This is a microscopic view of the particle crystal structure of the filter residue obtained after solid-liquid separation in step (3) of Example 8 of the present invention. Figure 3 It can be seen that there is basically no crystal in the slag after the eutectic phosphorus is extracted by citric acid-ammonium citrate buffer solution. Under the action of this buffer solution, the CaSO4·2H2O lattice can be destroyed to dissolve CaHPO4·2H2O.

[0136] (4) Eutectic phosphorus detection: The eutectic P2O5 content was determined using the quinoline phosphomolybdate weight method in the "Determination of phosphorus and fluorine in phosphogypsum" CJ / T2073-2011;

[0137] (5) Calculation of eutectic phosphorus content: eutectic P2O5 is expressed as mass fraction and is calculated according to formula (1); wherein the sample is the phosphogypsum sample in step (1), and is calculated based on the first weighing before the removal of water-soluble phosphorus.

[0138] The test samples were tested 6 times in parallel to investigate their precision, as shown in Table 2.

[0139] Table 2 Effects of 6 parallel tests on the test products

[0140]

[0141] As can be seen from Table 2, the test samples are phosphogypsum produced from the same batch. The eutectic phosphorus in the same batch of phosphogypsum was tested six times in parallel, and the relative standard deviation was small, indicating that the detection method of the present invention has good stability.

[0142] Example 9

[0143] A method for detecting the eutectic phosphorus content in phosphogypsum, the implementation steps are as follows:

[0144] (1) Sample preparation:

[0145] Preparation of test sample + reference sample: Prepare reference sample A in Example 1 and the test sample in Example 8, mix them thoroughly at a mass ratio of 1:5, and record them as A-1; prepare reference sample C in Example 1 and the test sample in Example 8, mix them thoroughly at a mass ratio of 1:5, and record them as C-1.

[0146] (2) Preparation of buffer solution: prepare a citric acid-ammonium citrate buffer solution with a pH value of 5.5 and a concentration of 0.125 mol / L.

[0147] (3) Extraction of eutectic phosphorus: The prepared A-1 and C-1 were mixed with a buffer solution for solid-liquid separation, the solid-liquid ratio being 1:50, and placed in an oscillator with an oscillation frequency of 150 r / min, and extracted with horizontal oscillation at 25°C for 120 min. Solid-liquid separation was performed, and the filtrate was the eutectic phosphorus.

[0148] (4) Eutectic phosphorus detection: The eutectic P2O5 content was determined using the quinoline phosphomolybdate weight method in the "Determination of phosphorus and fluorine in phosphogypsum" CJ / T2073-2011;

[0149] (5) Calculation of eutectic phosphorus content: eutectic P2O5 is expressed as mass fraction and is calculated according to formula (1); wherein the sample is the phosphogypsum sample in step (1), and is calculated based on the first weighing before the removal of water-soluble phosphorus.

[0150] The samples were tested in parallel six times to demonstrate that the citric acid-ammonium citrate buffer solution with a pH value of 5.5 and a concentration of 0.125 mol / L was specific for the extraction of eutectic phosphorus, as shown in Table 3.

[0151] Table 3 Effect of 6 parallel tests on samples

[0152]

[0153] This example is intended to prove that the detection method of the present invention is specific for the extraction and detection of eutectic phosphorus, that is, it cannot extract and detect sparingly soluble phosphorus. As shown in Table 3, there is no significant difference between the results detected by the test sample and A-1 and C-1, proving that the detection method of the present invention is accurate and reliable.

[0154] Example 10

[0155] A method for detecting the eutectic phosphorus content in phosphogypsum, the implementation steps are as follows:

[0156] (1) Sample preparation:

[0157] Preparation of test sample + reference sample:

[0158] A reference substance C-2 with a P2O5 content of 0.5% was precisely prepared with CaSO4·2H2O and phosphate concentrate, and the test substance in Example 8 was used as the test substance, and the mixture was thoroughly mixed at a mass ratio of 2:3.

[0159] (2) Preparation of buffer solution: prepare a citric acid-ammonium citrate buffer solution with a pH value of 5.5 and a concentration of 0.125 mol / L.

[0160] (3) Extraction of eutectic phosphorus: The sample prepared in step (1) was mixed with a buffer solution in a solid-liquid ratio of 1:50, placed in an oscillator with an oscillation frequency of 150 r / min, and extracted with horizontal oscillation at 25° C. for 120 min. Solid-liquid separation was performed, and the filtrate was the eutectic phosphorus.

[0161] (4) Eutectic phosphorus detection: The eutectic P2O5 content was determined using the quinoline phosphomolybdate weight method in the "Determination of phosphorus and fluorine in phosphogypsum" CJ / T2073-2011;

[0162] (5) Calculation of eutectic phosphorus content: eutectic P2O5 is expressed as mass fraction and is calculated according to formula (1); wherein the sample is the phosphogypsum sample in step (1), and is calculated based on the first weighing before the removal of water-soluble phosphorus.

[0163] The samples were tested three times in parallel to calculate the spike recoveries, as shown in Table 4.

[0164] Table 4 Effect of 3 parallel tests on samples

[0165]

[0166] Table 4 shows that the detection method of the present invention has been subjected to a spike recovery test, and the spike recovery rate is 98.08% to 99.36%, which is a good result, proving that the detection method of the present invention is relatively ideal.

[0167] The description of the above embodiments is only used to help understand the method of the present invention and its core idea. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting the eutectic phosphorus content in phosphogypsum, comprising the following steps: S1) extracting eutectic phosphorus from the phosphogypsum sample using a buffer solution combined with a horizontal oscillation method; The buffer solution comprises one of oxalic acid-ammonium oxalate buffer solution, citric acid-sodium citrate buffer solution, citric acid-ammonium citrate buffer solution, formic acid-ammonium formate and tartaric acid-ammonium tartrate buffer solution; S2) using the quinoline phosphomolybdic acid weight method to detect and calculate the phosphorus content of the obtained eutectic.

2. The detection method according to claim 1, characterized in that: In step S1), the pH value of the buffer solution is 3.5-7.

5.

3. The detection method according to claim 1, characterized in that: In step S1), the concentration of the buffer solution is 0.05-2.5 mol / L.

4. The detection method according to claim 1, characterized in that: In step S1), the solid-to-liquid ratio of the obtained sample to the buffer solution is 1:30-60.

5. The detection method according to claim 1, characterized in that: In step S1), the extraction temperature is 23-27° C., the extraction time is 90-135 min, and the oscillator frequency is 120-180 r / min.

6. The detection method according to claim 1, characterized in that: In step S1), before extracting eutectic phosphorus from the phosphogypsum sample using a buffer solution combined with a horizontal oscillation method, the method further comprises: The phosphogypsum samples were subjected to the removal of water-soluble phosphorus.

7. The detection method according to claim 6, characterized in that: The phosphogypsum sample is a dry phosphogypsum sample.

8. The detection method according to claim 6, characterized in that: The method for removing water-soluble phosphorus comprises the following steps: The phosphogypsum sample is mixed with water, horizontally shaken, and then the solid and liquid are separated to obtain a sample after removing the water-soluble phosphorus.

9. The detection method according to claim 8, characterized in that: The dosage ratio of the phosphogypsum sample to water is 0.8-1.2 g: 45-55 mL; The temperature of the horizontal oscillation is 23-27° C., the time is 18-22 min, and the oscillator frequency is 145-155 r / min.

10. The detection method according to claim 1, characterized in that: In step S2), the calculation method includes: Eutectic phosphorus content in phosphogypsum samples: Eutectic P2O5 is expressed as mass fraction and calculated according to formula (1): In formula (1): ω——phosphorus pentoxide content in phosphogypsum sample, in percentage (%); m——mass of phosphogypsum sample, in g; m1——the mass of the crucible, in g; m2——the mass of quinoline phosphomolybdate precipitate and crucible, in g; m3——the mass of the blank test crucible, in g; m4——the mass of blank test precipitate and crucible, in g; 0.03207——Coefficient for converting the molar mass of quinoline phosphomolybdate to the molar mass of phosphorus pentoxide; f——dilution factor.

Images