Method for electrically enhanced recovery of phosphorus and fluorine from phosphogypsum

Abstract

The application provides a method for electrically strengthening recovery of phosphorus and fluorine in phosphogypsum, and belongs to the technical field of harmless treatment of phosphogypsum. In the method, the phosphogypsum is placed in a self-made electric treatment device, and strong acid salt or weak acid salt or water is used as an electrolyte; under the action of a low-voltage direct current electric field, phosphate ions and fluorine ions migrate into an anode chamber, and heavy metal cations migrate into a cathode chamber. The phosphorus and fluorine in the phosphogypsum are converted and directionally moved in the electric process, and then are enriched and recovered. Through the electric strengthening treatment of the phosphogypsum, the phosphorus and fluorine resources in the phosphogypsum are enriched and recovered, high-value calcium fluoride, calcium fluorophosphate and other products are obtained, high-value utilization of the phosphorus and fluorine is realized; meanwhile, the content of impurities such as Ti, Sr, P, Fe, Cr, Ba, Al and F in the phosphogypsum is reduced, and the harmless production of the phosphogypsum is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of harmless treatment of phosphogypsum, and particularly relates to a method for recovering phosphorus and fluorine in phosphogypsum by electro-enhanced method. BACKGROUND

[0002] At present, the main methods for the harmless treatment of phosphogypsum include water washing, acid-base leaching, high-temperature calcination and the like. However, the above processes are difficult to achieve the enrichment and recovery of valuable elements and the production of harmless phosphogypsum at the same time, and there is no suitable way to treat the large amount of phosphogypsum in situ. At present, the international community tends to prefer low-energy and low-cost in-situ site remediation for large amounts of slag or contaminated soil, and has made certain progress. There are still great challenges for the existing electro-treatment of phosphogypsum for the synergistic treatment of phosphogypsum harmless and phosphorus-fluorine resource recovery. The high-voltage and high-current mode used in the existing method is a high-energy treatment method, and the high liquid-solid ratio used makes it not applicable to in-situ remediation, but may cause secondary pollution, and the selectivity of the generated product is poor. SUMMARY

[0003] The present application aims to solve the above problems in the prior art, and provides a method for recovering phosphorus and fluorine in phosphogypsum by electro-enhanced method. The method combines electro-treatment technology with phosphogypsum, and performs the harmless treatment of phosphogypsum by applying direct current at both ends of the electrolytic cell. The method can move and enrich phosphorus and fluorine elements in phosphogypsum in a targeted manner, and simultaneously produce harmless phosphogypsum products.

[0004] To achieve the above object, the present application adopts the following technical scheme:

[0005] The first object of the present application is to provide a method for recovering phosphorus and fluorine in phosphogypsum by electro-enhanced method, comprising the following specific steps:

[0006] Step S1, crushing and sieving the phosphogypsum to obtain a first solid product;

[0007] Step S2, uniformly mixing the first solid product with an electrolyte according to a certain solid-liquid ratio, and standing to obtain a second solid-liquid mixture; the electrolyte includes any one of a strong acid salt solution, a weak acid salt solution or water;

[0008] Step S3, placing the second solid-liquid mixture into an electro-treatment device, and applying a constant current or constant voltage direct current power supply, and obtaining a phosphorus-fluorine-containing liquid product and a third solid-liquid mixture after electro-treatment for a predetermined time under predetermined conditions; the direct current power supply selects a constant voltage, and the constant voltage range is 0V-60V; the direct current power supply selects a constant current, and the constant current range is 0.01A-1.50A;

[0009] Step S4, the third solid-liquid mixture is subjected to suction filtration to obtain a fourth solid product and a phosphorus-fluorine-containing filtrate;

[0010] Step S5, the fourth solid product is placed in an oven and dried at a certain temperature for a certain time to obtain a purified phosphogypsum product;

[0011] The phosphorus-fluorine-containing filtrate and the filtrate after suction filtration are mixed, a certain amount of a calcium source is added thereto, a certain reaction temperature is controlled, and the mixture is reacted for a certain time under a certain stirring speed to obtain a fifth solid-liquid mixture.

[0012] Step S6, the fifth solid-liquid mixture is subjected to centrifugal recovery of a solid after centrifugation, and the solid is dried to obtain a purified phosphorus-fluorine crystal product.

[0013] Further, in step S1, the particle size of the first solid product is 50-400 mesh.

[0014] Further, the strong acid salt includes a sulfate, and the weak acid salt solution includes a citrate or an oxalate.

[0015] The cation in the sulfate, the citrate or the oxalate is one or more of an ammonium ion, a sodium ion, a calcium ion, a potassium ion, a zinc ion, a magnesium ion, and an aluminum ion.

[0016] Further, in step S2, the concentration of the electrolyte is 0-4 mol / L.

[0017] Further, in step S2, the solid ratio of the electrolyte to the first solid product mixture is 0.1-3.0.

[0018] Further, in step S2, the reaction temperature is 25-150°C, and the reaction time is 0.5-8.0 h.

[0019] Further, in step S3, the electric treatment device includes an electrolytic cell, the electrolytic cell is provided with an anode chamber, a sample chamber and a cathode chamber, electrode sheets are arranged in the anode chamber and the cathode chamber respectively, the two electrode sheets are electrically connected with a direct current power supply, and electric treatment can be realized by electrification, the anode chamber is communicated with an anode treatment tank through a pipeline, and the cathode chamber is communicated with a cathode treatment tank through a pipeline.

[0020] Further, in step S3, the electric treatment time is 1-108 h.

[0021] Further, in step S5, the content of the calcium source is determined according to the phosphorus and fluorine concentration content in the phosphorus-fluorine-containing liquid.

[0022] Further, in step S5, the calcium source includes any one of CaCl2, CaCO3 and Ca(OH)2.

[0023] Further, in step S5, the temperature of the reaction is 20℃-85℃, the stirring speed is 200rpm-500rpm, and the stirring reaction time is 5min-180min.

[0024] Further, the phosphorus-fluorine crystalline product includes calcium fluoride or calcium fluorophosphate.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] (1) The present application provides a method for recovering phosphorus and fluorine from phosphogypsum by electrically strengthening. The phosphogypsum is placed in a self-made electric treatment device, and strong acid salt or weak acid salt or water is used as the electrolyte. Under the action of low-voltage direct current electric field, phosphate ions and fluoride ions migrate to the anode chamber, and heavy metal cations migrate to the cathode chamber. The phosphorus and fluorine in the phosphogypsum are converted and directionally moved during the electric process, and then enriched and recovered. For 0.05M sodium citrate as electrolyte, the recovery rate of soluble fluorine reaches 83% after 60h of electric treatment of phosphogypsum, and the recovery rate of soluble phosphorus reaches 65%. For 0.05M potassium oxalate as electrolyte, the recovery rate of soluble fluorine reaches 74% after 60h of electric treatment of phosphogypsum, and the recovery rate of soluble phosphorus reaches 75%. For deionized water as electrolyte, the recovery rate of soluble fluorine reaches 63% after 60h of electric treatment of phosphogypsum, and the recovery rate of soluble phosphorus reaches 61%. For sodium sulfate as electrolyte, the recovery rate of soluble fluorine reaches 52% after 60h of electric treatment of phosphogypsum, and the recovery rate of soluble phosphorus reaches 42%. Through electric treatment of phosphogypsum, the phosphorus and fluorine resources in the phosphogypsum are enriched and recovered, and high-value calcium fluoride, calcium fluorophosphate and other products are obtained, realizing high-value utilization of phosphorus and fluorine. At the same time, the contents of Ti, Sr, P, Fe, Cr, Ba, Al, F and other impurities in the phosphogypsum are reduced, realizing harmless production of phosphogypsum.

[0027] (2) The present application significantly reduces the content of soluble fluorine and soluble phosphorus in the phosphogypsum, realizes the occurrence form regulation of fluorine in the phosphogypsum and the recovery of phosphorus and fluorine resources. The water-soluble fluorine content of the treated phosphogypsum meets the first level requirement of GB / T 23456-2018 for gypsum used in building materials. The phosphorus content of the treated phosphogypsum meets the first level requirement of GB / T 23456-2018 for gypsum used in building materials.

[0028] (3) The present application realizes the regulation of the current size in the electric process by regulating the type and concentration of the electrolyte, and realizes the enhanced recovery of phosphorus and fluorine.

[0029] (4) The present application enriches and recovers the phosphorus and fluorine resources in the phosphogypsum by electrically strengthening the treatment of the phosphogypsum, which provides support for the recovery and utilization of solid waste resources.

[0030] (5) The electric treatment method provided by the application has simple and easy-to-operate treatment process, does not need special protection during the electric process, and is environment-friendly and non-polluting.

[0031] (6) The electric treatment technology system of phosphogypsum is constructed, the phosphorus and fluorine resources in the phosphogypsum are extracted by the electric device, and the phosphorus and fluorine resources are recycled, so that the harmless production of the phosphogypsum is realized, and an effective means for recycling the phosphorus and fluorine resources is provided.

[0032] (7) The electric method provided by the application has low energy consumption, low liquid-solid ratio and weak acid salt as the electrolyte, has good in-situ treatment application prospect, and provides an effective means for solid waste resource utilization and green treatment. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The electric treatment device structure diagram used in the application is shown in the figure;

[0034] Figure 2 The contrastive diagram of the electric treatment for recycling fluorine and phosphorus under different voltages is shown in the figure;

[0035] Figure 3 The contrastive diagram of the electric treatment for recycling fluorine and phosphorus under different electrolytes is shown in the figure;

[0036] Figure 4 The XRD diagram of the product after adding calcium source into the anode treatment tank is shown in the figure;

[0037] Figure 5 The diagram of the change of the fluorine ion concentration in the anode chamber and the cathode chamber with time under the electric condition of Example 1 is shown in the figure;

[0038] Figure 6 The diagram of the change of the phosphorus concentration in the anode chamber and the cathode chamber with time under the electric condition of Example 1 is shown in the figure;

[0039] Figure 7 The diagram of the soluble fluorine content in the solid fluorine in the anode vicinity and the cathode vicinity after the electric treatment of Example 1 is shown in the figure;

[0040] Figure 8 The diagram of the soluble phosphorus content in the solid phosphorus in the anode vicinity and the cathode vicinity after the electric treatment of Example 1 is shown in the figure;

[0041] Figure 9 The diagram of the change of the fluorine ion concentration in the anode chamber and the cathode chamber with time under the electric condition of Example 2 is shown in the figure;

[0042] Figure 10 The diagram of the change of the phosphorus concentration in the anode chamber and the cathode chamber with time under the electric condition of Example 2 is shown in the figure;

[0043] Figure 11 Figure of soluble fluorine content in solid fluorine in the vicinity of the anode and the vicinity of the cathode after electrokinetic treatment for Example 2;

[0044] Figure 12 Figure of soluble phosphorus content in solid phosphorus in the vicinity of the anode and the vicinity of the cathode after electrokinetic treatment for Example 2;

[0045] Figure 13 Figure of the change of fluorine ion concentration in the anode chamber and the cathode chamber with time under electrokinetic conditions for Example 3;

[0046] Figure 14 Figure of the change of phosphorus concentration in the anode chamber and the cathode chamber with time under electrokinetic conditions for Example 3;

[0047] Figure 15 Figure of soluble fluorine content in solid fluorine in the vicinity of the anode and the vicinity of the cathode after electrokinetic treatment for Example 3;

[0048] Figure 16 Figure of soluble phosphorus content in solid phosphorus in the vicinity of the anode and the vicinity of the cathode after electrokinetic treatment for Example 3. DETAILED DESCRIPTION

[0049] In order to make the objects, technical solutions and advantages of the present application clearer, the embodiments of the present application are described in detail below, and the examples of the embodiments are shown in the drawings, in which the same or similar notations represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0050] REFERENCE Figure 1 , the structural schematic diagram of the electrokinetic treatment device used in the present application comprises an electrolytic cell, the electrolytic cell is composed of a rectangular polymethyl methacrylate flat plate organic glass box, and is divided into an anode chamber, a sample chamber and a cathode chamber; electrode sheets are arranged in the anode chamber and the cathode chamber respectively, and the electrode sheets are selected from copper electrodes, graphite electrodes or platinum electrodes; the two electrode sheets are electrically connected with a direct current power supply, the direct current power supply selects a constant voltage, and the constant voltage setting range is 0V-60V; the direct current power supply selects a constant current, and the constant current setting range is 0.01A-1.50A; the anode chamber is communicated with an anode treatment pool through a pipeline, a peristaltic pump can be arranged on the pipeline, a calcium source can be added into the anode treatment pool, and calcium fluoride or fluorophosphoric acid calcium product can be obtained after reaction; the cathode chamber is communicated with a cathode treatment pool through a pipeline, a peristaltic pump can be arranged on the pipeline, and heavy metal ions electrolyzed are recovered in the cathode treatment pool.

[0051] The phosphogypsum used in the present application is untreated phosphogypsum in the wet-process phosphoric acid process.

[0052] The electrokinetic strengthening treatment process in the following examples is completed by using the electrokinetic treatment device shown in Figure 1

[0053] Example 1

[0054] In this example, deionized water is added as an electrolyte for electrokinetic experiments.

[0055] (1) The phosphogypsum is crushed in a crusher for 5 minutes and then sieved through a 100-mesh sieve. A certain amount of the sieved phosphogypsum is weighed.

[0056] (2) The above phosphogypsum and deionized water are uniformly mixed in a ratio of 1:1, and then left to stand for 3 hours to obtain a second solid-liquid mixture.

[0057] (3) Graphite electrode plates with a size of 10 cm x 10 cm are uniformly drilled with holes, and placed in the clamping slots at both ends of the electrolytic cell.

[0058] (4) The second solid-liquid mixture obtained in step (2) is placed in the sample chamber.

[0059] (5) The electrodes in the electrode device of the sample chamber are connected to a direct current power supply to provide a constant voltage to the sample chamber. The constant voltage is set to 20 V. During the experiment, the current value displayed by the direct current power supply is recorded at 1 h, 3 h, 6 h, 9 h, 12 h, 15 h, 24 h, 30 h, 36 h, 48 h, and 60 h.

[0060] (6) During the experiment, the pH of the cathode chamber and the anode chamber is measured at 1 h, 3 h, 6 h, 9 h, 12 h, 15 h, 24 h, 30 h, 36 h, 48 h, and 60 h using a pH meter. Liquid samples are also taken from the cathode chamber and the anode chamber. The concentration of fluoride ions is determined using a fluoride ion selective electrode method, and the concentration of phosphorus in the solution is determined using an inductively coupled plasma emission spectrometer.

[0061] (7) After 60 hours of electrokinetic treatment, the electrolyte is collected from the anode chamber and the cathode chamber. The third solid-liquid mixture in the sample chamber is filtered, and the filtered solution is recovered as the electrolyte. The fourth solid product is dried in a blast drying oven at 45°C to remove moisture and purify the phosphogypsum product. Solid samples near the anode region and the cathode region are collected, and the form of fluorine elements is measured and analyzed.

[0062] (8) The recovered electrolyte is stirred at a speed of 250 rpm at 25°C. Ca(OH)2 is added as a calcium source to perform solid-phase synthesis of fluorine and phosphorus resources. The stirring time is 30 minutes. The fifth solid-liquid mixture obtained after stirring is centrifuged at 6000 rpm for 3 minutes and then dried at 60°C for 2 hours to obtain a purified phosphorus and fluorine crystal product. ​

[0063] Reference Figure 3 It can be seen that by using deionized water as electrolyte for electrokinetic treatment for 60h, the equilibrium is reached at 48h, and the concentrations of fluorine and phosphorus in the anode chamber are 403mg / L and 2321mg / L, respectively. After filtration, the recovered fluorine and phosphorus (in terms of P2O5) are 80.5mg and 354.5mg, respectively, and the recovery rates of soluble fluorine and soluble phosphorus are 63% and 61%, respectively.

[0064] Reference Figure 4 In order to add calcium source into the anode treatment tank, the XRD diagram of calcium fluoride or calcium fluorophosphate product can be obtained after reaction, which shows the crystalline phase of calcium fluoride and calcium fluorophosphate.

[0065] Reference Figure 5 The graph of the change of fluorine ion concentration in the anode chamber and the cathode chamber with time according to the electrokinetic experiment of the present embodiment shows that the fluorine ion concentration in the anode chamber gradually increases with time and reaches equilibrium at 48h.

[0066] Reference Figure 6 The graph of the change of phosphorus concentration in the anode chamber and the cathode chamber with time according to the electrokinetic experiment of the present embodiment shows that the phosphorus concentration in the anode chamber gradually increases with time and reaches equilibrium at 48h.

[0067] Reference Figure 7 The graph of the soluble fluorine content in the solid fluorine in the anode vicinity and the cathode vicinity after electrokinetic treatment according to the present embodiment shows that the soluble fluorine content in the solid fluorine in the anode vicinity and the cathode vicinity is greatly reduced, and the soluble fluorine content in the solid fluorine in the cathode vicinity is reduced more.

[0068] Reference Figure 8 The graph of the soluble phosphorus content in the solid phosphorus in the anode vicinity and the cathode vicinity after electrokinetic treatment according to the present embodiment shows that the soluble phosphorus content in the solid phosphorus in the anode vicinity and the cathode vicinity is greatly reduced, and the soluble phosphorus content in the solid phosphorus in the cathode vicinity is almost none.

[0069] Example 2

[0070] In the present embodiment, 0.05M sodium citrate is used as electrolyte for electrokinetic experiment.

[0071] (1) The phosphogypsum is crushed in a crusher for 5min and then sieved through a 100-mesh sieve, and a certain amount of sieved phosphogypsum is weighed.

[0072] (2) The above phosphogypsum and sodium citrate electrolyte are uniformly mixed in a ratio of 1:1.1, and then left to stand for 3h to obtain a second solid-liquid mixture.

[0073] (3) The graphite electrode plate with a size of 10 cm x 10 cm is uniformly punched with holes by drilling, and is placed in the clamping groove at both ends of the electrolytic cell.

[0074] (4) The second solid-liquid mixture obtained in step (2) is placed in the sample chamber.

[0075] (5) The electrodes in the electrode device of the sample chamber are connected to a direct current power supply to provide a constant voltage to the sample chamber, and the constant voltage is set to 20 V. During the experiment, the current value displayed by the direct current power supply is recorded at time points of 1 h, 3 h, 6 h, 9 h, 12 h, 15 h, 24 h, 30 h, 36 h, 48 h, and 60 h.

[0076] (6) During the experiment, the pH of the cathode chamber and the anode chamber is measured at time points of 1 h, 3 h, 6 h, 9 h, 12 h, 15 h, 24 h, 30 h, 36 h, 48 h, and 60 h using a pH meter, and liquid samples are taken from the cathode chamber and the anode chamber, respectively. The concentration of fluoride ions is determined using a fluoride ion selective electrode method, and the concentration of phosphorus in the solution is determined using an inductively coupled plasma emission spectrometer.

[0077] (7) After 60 h of electrokinetic treatment, the electrolyte is collected from the anode chamber and the cathode chamber, respectively, and the third solid-liquid mixture in the sample chamber is suction filtered. The filtered solution is recovered as the electrolyte, and the fourth solid product is dried in a blast drying oven at 45°C to remove moisture and purify the phosphogypsum product. Solid samples near the anode region and the cathode region are collected, and the forms of existence of fluorine and phosphorus elements are measured and analyzed.

[0078] (8) The recovered electrolyte is stirred at a speed of 250 rpm at 25°C, and Ca(OH)2 is added as a calcium source for solid-phase synthesis of fluorine and phosphorus resources. The stirring time is 30 min. The fifth solid-liquid mixture obtained after stirring is centrifuged at 6000 rpm for 3 min and then dried at 70°C for 2 h to obtain a purified phosphorus and fluorine crystal product.

[0079] Reference Figure 3 By using 0.05M sodium citrate as the electrolyte for 60 h of electrokinetic treatment, the concentration of fluorine reached equilibrium at 30 h, and the concentration of phosphorus reached equilibrium at 48 h. The concentrations of fluorine and phosphorus in the anode chamber were 585 mg / L and 2480 mg / L, respectively. After suction filtration, the mass of recovered fluorine and phosphorus (calculated as P2O5) was 105.7 mg and 378.8 mg, respectively. The recovery rate of soluble fluorine was 83%, and the recovery rate of soluble phosphorus was 65%.

[0080] By ICP analysis of the phosphogypsum before and after treatment, the results are shown in Table 1. Electrokinetic treatment reduced the content of elements such as Ti, Sr, P, Fe, Cr, Ba, Al, etc. in the phosphogypsum.

[0081] Table 1.

[0082]

[0083] refer to Figure 9 The figure shows the change of fluoride ion concentration in the anode and cathode chambers of the electric experiment conducted according to this embodiment over time. The results show that the fluoride ion concentration in the anode chamber gradually increases with time and reaches equilibrium at 30 hours.

[0084] See appendix Figure 10 The figure shows the change of phosphorus concentration in the anode and cathode chambers over time in the electric experiment conducted according to this embodiment. The results show that the phosphorus concentration in the anode chamber gradually increases with time and reaches equilibrium at 48 hours.

[0085] refer to Figure 11 The figure shows the soluble fluoride content in the solid fluoride near the anode and cathode regions after electro-electric treatment according to this embodiment. It can be seen that the soluble fluoride content in the solid fluoride near the anode and cathode is significantly reduced, with the reduction in the solid soluble fluoride near the cathode region being even greater.

[0086] refer to Figure 12 The figure shows the soluble phosphorus content in the solid phosphorus near the anode and cathode regions after electro-electric treatment according to this embodiment. It can be seen that the soluble phosphorus content in the solid phosphorus near the anode and cathode regions is significantly reduced, while the solid soluble phosphorus content near the cathode region is almost non-existent.

[0087] Example 3

[0088] In this embodiment, an electrokinetic experiment was conducted using 0.05M potassium oxalate as the electrolyte.

[0089] (1) Place the phosphogypsum in a crusher and crush it for 5 minutes. Then pass it through a 100-mesh sieve and weigh a certain amount of the sieved phosphogypsum.

[0090] (2) Mix the above phosphogypsum and potassium oxalate electrolyte in a ratio of 1:1.2 and let stand for 3 hours to obtain the second solid-liquid mixture.

[0091] (3) Drill holes evenly into the graphite electrode plate with a specification of 10cm×10cm and place it in the slots at both ends of the electrolytic cell.

[0092] (4) Place the second solid-liquid mixture obtained in step (2) into the sample chamber.

[0093] (5) The electrodes in the sample chamber electrode device were connected to a direct current power supply to provide a constant voltage to the sample chamber, which was set to 20 V. During the experiment, the current value displayed by the direct current power supply was recorded at 1 h, 3 h, 6 h, 9 h, 12 h, 15 h, 24 h, 30 h, 36 h, 48 h, and 60 h.

[0094] (6) During the experiment, the pH of the cathode chamber and the anode chamber was measured at 1 h, 3 h, 6 h, 9 h, 12 h, 15 h, 24 h, 30 h, 36 h, 48 h, and 60 h using a pH meter, and liquid samples were taken from the cathode chamber and the anode chamber. The concentration of fluoride ions was determined using a fluoride ion selective electrode method, and the concentration of phosphorus in the solution was determined using an inductively coupled plasma emission spectrometer.

[0095] (7) After 60 h of electrokinetic treatment, the electrolyte was collected from the anode chamber and the cathode chamber, and the third solid-liquid product from the sample chamber was suction filtered. The solution after suction filtration was recovered as the electrolyte, and the fourth solid product was dried in a blast drying oven at 45°C to remove moisture and purify the phosphogypsum product. Solid samples near the anode region and the cathode region were collected, and the forms of existence of fluorine and phosphorus were measured and analyzed.

[0096] (8) The recovered electrolyte was stirred at 500 rpm at 50°C, and Ca(OH)2 was added as a calcium source to synthesize CaF2. The stirring time was 10 min. The fifth solid-liquid product obtained after stirring was centrifuged at 6000 rpm for 3 min and then dried at 60°C for 2 h to obtain a purified phosphorus-fluorine crystal product.

[0097] Reference Figure 3 The concentration of fluorine in the anode chamber reached equilibrium at 30 h, and the concentration of phosphorus reached equilibrium at 36 h. The concentrations of fluorine and phosphorus in the anode chamber were 470.8 mg / L and 2847.9 mg / L, respectively. After suction filtration, the mass of recovered fluorine and phosphorus (calculated as P2O5) was 94.2 mg and 434.8 mg, respectively. The recovery rate of soluble fluorine was 74%, and the recovery rate of soluble phosphorus was 75%.

[0098] Reference Figure 13 Figure 2 is a graph showing the change in the concentration of fluorine ions in the anode chamber and the cathode chamber over time for the electrokinetic experiment according to the present embodiment. The results show that the concentration of fluorine ions in the anode chamber gradually increased over time and reached equilibrium at 30 h.

[0099] Reference Figure 14 Figure 3 is a graph showing the change in the concentration of phosphorus in the anode chamber and the cathode chamber over time for the electrokinetic experiment according to the present embodiment. The results show that the concentration of phosphorus in the anode chamber gradually increased over time and reached equilibrium at 36 h.

[0100] Reference Figure 15 For the graph of the soluble fluorine content in the solid fluorine in the vicinity of the anode and the vicinity of the cathode after the electrokinetic treatment according to the present embodiment, it can be seen that the soluble fluorine content of the solid fluorine in the vicinity of the anode and the vicinity of the cathode is greatly reduced, and the solid soluble fluorine content in the vicinity of the cathode is reduced more.

[0101] Reference Figure 16 For the graph of the soluble phosphorus content in the solid phosphorus in the vicinity of the anode and the vicinity of the cathode after the electrokinetic treatment according to the present embodiment, it can be seen that the soluble phosphorus content of the solid phosphorus in the vicinity of the anode and the vicinity of the cathode is greatly reduced, and the solid soluble phosphorus content in the vicinity of the cathode is almost none.

[0102] Example 4

[0103] The present embodiment carries out electrokinetic experiment by using 0.1M potassium oxalate as electrolyte.

[0104] (1) The phosphogypsum is placed in a crusher for 5 minutes and then sieved through a 100-mesh sieve, and a certain amount of sieved phosphogypsum is weighed.

[0105] (2) The above phosphogypsum and potassium oxalate electrolyte are uniformly mixed in a ratio of 1:1.3, and the second solid-liquid mixture is obtained after standing for 3 hours.

[0106] (3) The graphite electrode plate with a size of 10cm×10cm is uniformly drilled with holes and placed in the clamping groove at both ends of the electrolytic cell.

[0107] (4) The second solid-liquid mixture obtained in step (2) is placed in the sample chamber.

[0108] (5) The electrodes in the electrode device of the sample chamber are connected to a direct current power supply to provide a constant voltage to the sample chamber, and the constant voltage is set to 15V. During the experiment, the current value displayed by the direct current power supply is recorded at time 1h, 3h, 6h, 9h, 12h, 15h, 24h, 30h, 36h, 48h, 60h.

[0109] (6) During the experiment, the pH of the cathode chamber and the anode chamber is measured at time 1h, 3h, 6h, 9h, 12h, 15h, 24h, 30h, 36h, 48h, 60h using a pH meter, and liquid samples are taken in the cathode chamber and the anode chamber, respectively, and the fluorine ion concentration is determined using the fluorine ion selective electrode method, and the phosphorus concentration in the solution is determined using an inductively coupled plasma emission spectrometer.

[0110] (7) After 60h of electrokinetic treatment, the electrolyte was collected from the anode and cathode compartments, respectively, and the third solid-liquid mixture in the sample chamber was suction-filtered. The solution after suction-filtration was recovered as the electrolyte, and the fourth solid product was dried in a blast drying oven at 45°C to remove moisture and purify the phosphogypsum product. Solid samples near the anode and cathode regions were collected and analyzed for the presence of fluorine and phosphorus.

[0111] (8) The recovered electrolyte was stirred at 25°C at a rotation speed of 300 rpm, and CaO was added as a calcium source for solid-phase synthesis of fluorine and phosphorus resources. The stirring time was 40 min. The fifth solid-liquid mixture obtained after stirring was centrifuged at 5000 rpm for 4 min and then dried at 60°C for 6 h to obtain a purified phosphorus and fluorine crystalline product.

[0112] After 48h of electrokinetic treatment with 0.1M potassium oxalate as the electrolyte, the fluorine concentration reached equilibrium at 42h, and the phosphorus concentration reached equilibrium at 30h. The fluorine and phosphorus concentrations in the anode compartment were 430.5mg / L and 2718mg / L, respectively. After suction-filtration, the recovered fluorine and phosphorus masses were 81.3mg and 415mg, respectively. The recovery rate of soluble fluorine was 62%, and the recovery rate of soluble phosphorus was 70%. Through electrokinetic enrichment and impurity removal, fluorine resources were effectively recovered, and the production of phosphogypsum was simultaneously realized in a harmless manner.

[0113] Example 5

[0114] In this example, electrokinetic experiments were performed using 0.1M sodium citrate as the electrolyte.

[0115] (1) The phosphogypsum was crushed in a crusher for 5 min and then sieved through a 100-mesh sieve. A certain amount of the sieved phosphogypsum was weighed.

[0116] (2) The above phosphogypsum and sodium citrate electrolyte were uniformly mixed in a ratio of 1:1.2, and the mixture was allowed to stand for 10h to obtain a second solid-liquid mixture.

[0117] (3) Graphite electrode plates with a size of 10cm x 10cm were uniformly drilled with holes and placed in the clamping slots at both ends of the electrolytic cell.

[0118] (4) The second solid-liquid mixture obtained in step (2) was placed in the sample chamber.

[0119] (5) The electrodes in the electrode device of the sample chamber were connected to a direct current power supply to provide a constant current to the sample chamber. The constant current was set to 0.2A. During the experiment, the current value displayed by the direct current power supply was recorded at 1h, 3h, 6h, 9h, 12h, 15h, 24h, 30h, 36h, 48h, 60h, and 72h.

[0120] (6) In the experiment, the pH of the cathode chamber and the anode chamber was measured at 1h, 3h, 6h, 9h, 12h, 15h, 24h, 30h, 36h, 48h, 60h, 72h, respectively, using a pH meter, and liquid sampling was carried out in the cathode chamber and the anode chamber, respectively, and the fluorine ion concentration was determined by using a fluorine ion selective electrode method, and the phosphorus concentration in the solution was determined by using an inductively coupled plasma emission spectrometer.

[0121] (7) After 72h of electrokinetic treatment, the electrolyte was collected from the anode chamber and the cathode chamber, respectively, and the third solid-liquid mixture in the sample chamber was suction filtered, and the solution after suction filtration was recovered as the electrolyte, and the fourth solid product was dried in a blast drying oven at 35°C to remove moisture and purify the phosphogypsum product, and the solid samples near the anode region and the cathode region were collected, and the forms of existence of fluorine and phosphorus elements were measured and analyzed.

[0122] (8) The recovered electrolyte was stirred at 500rpm at 35°C, Ca(OH)2 was added as a calcium source, CaF2 synthesis was carried out, and the stirring time was 45min. The fifth solid-liquid product obtained after stirring was centrifuged at 6500rpm for 10min and then dried at 70°C for 1.5h to obtain a purified phosphorus-fluorine crystal product.

[0123] Through 72h of electrokinetic treatment with 0.1M sodium citrate as the electrolyte, the fluorine concentration reached equilibrium at 60h, and the phosphorus concentration reached equilibrium at 60h, and the fluorine and phosphorus concentrations in the anode chamber were 425.2mg / L and 2663.2mg / L, respectively, and after suction filtration treatment, the mass of recovered fluorine was 114.7mg, and the mass of recovered phosphorus was 406.7mg, and the recovery rate of soluble fluorine reached 66.9%, and the recovery rate of soluble phosphorus reached 69.9%. Through electrokinetic enrichment and impurity removal, fluorine resources were effectively recovered, and harmless production of phosphogypsum was simultaneously achieved.

[0124] Example 6

[0125] In this example, deionized water was used as the electrolyte for electrokinetic experiments.

[0126] (1) The phosphogypsum was crushed in a crusher for 5min and then sieved through a 100-mesh sieve, and a certain amount of sieved phosphogypsum was weighed.

[0127] (2) The above phosphogypsum and deionized water were uniformly mixed in a ratio of 1:1, and then left to stand for 3h to obtain a second solid-liquid mixture.

[0128] (3) The graphite electrode plate with a size of 10cm×10cm was uniformly drilled with holes, and placed in the clamping slots at both ends of the electrolytic cell.

[0129] (4) The second solid-liquid mixture obtained in step (2) is placed in the sample chamber.

[0130] (5) The electrodes in the electrode device of the sample chamber are connected to a direct current power supply to provide a constant voltage to the sample chamber, and the constant voltage is set to 10 V, 20 V and 40 V respectively. During the experiment, the current value displayed by the direct current power supply is recorded at 1 h, 3 h, 6 h, 9 h, 12 h, 15 h, 24 h, 30 h, 36 h, 48 h and 60 h respectively.

[0131] (6) During the experiment, the pH of the cathode chamber and the anode chamber is measured at 1 h, 3 h, 6 h, 9 h, 12 h, 15 h, 24 h, 30 h, 36 h, 48 h and 60 h respectively using a pH meter, and liquid samples are taken from the cathode chamber and the anode chamber respectively, and the fluorine ion concentration is determined using a fluorine ion selective electrode method, and the phosphorus concentration in the solution is determined using an inductively coupled plasma emission spectrometer.

[0132] (7) After 60 h of electrokinetic treatment, the electrolyte is collected from the anode chamber and the cathode chamber respectively, the third solid-liquid mixture of the sample chamber is suction filtered, the solution after suction filtration is used as electrolyte recovery, the fourth solid product is dried in a blast drying oven at 45°C to remove water, and the purified phosphogypsum product is obtained, and the solid samples near the anode region and the cathode region are collected to measure and analyze the form of fluorine element.

[0133] Reference Figure 2 By using deionized water as the electrolyte and different voltages for electrokinetic treatment for 60 h, the fluorine and phosphorus concentration contents in the anode chamber are 328 mg / L and 1548 mg / L at a voltage of 10 V, and after suction filtration treatment, the recovered fluorine and phosphorus mass is 65.3 mg and 236.3 mg (calculated as P2O5), and the recovery rate of soluble fluorine reaches 51%, and the recovery rate of soluble phosphorus reaches 40%, the fluorine and phosphorus concentration contents in the anode chamber are 403 mg / L and 2321 mg / L at a voltage of 20 V, and after suction filtration treatment, the recovered fluorine and phosphorus mass is 80.5 mg and 354.5 mg (calculated as P2O5), and the recovery rate of soluble fluorine reaches 63%, and the recovery rate of soluble phosphorus reaches 61%, the fluorine and phosphorus concentration contents in the anode chamber are 363 mg / L and 2012 mg / L at a voltage of 40 V, and after suction filtration treatment, the recovered fluorine and phosphorus mass is 72.8 mg and 307.2 mg (calculated as P2O5), and the recovery rate of soluble fluorine reaches 57%, and the recovery rate of soluble phosphorus reaches 52%. It can be seen that the recovery rate of soluble fluorine and soluble phosphorus is relatively the highest at a voltage of 20 V.

[0134] Example 7

[0135] In this example, 0.1 M sodium sulfate is added as the electrolyte for electrokinetic experiment.

[0136] (1) The phosphogypsum was placed in a crusher for 5 minutes and sieved through a 100-mesh sieve. A certain amount of the sieved phosphogypsum was weighed.

[0137] (2) The phosphogypsum and the sodium sulfate electrolyte were uniformly mixed in a ratio of 1:1.1, and left to stand for 3 hours to obtain a second solid-liquid mixture.

[0138] (3) A graphite electrode plate with a size of 10 cm x 10 cm was uniformly drilled with holes and placed in the clamping groove at both ends of the electrolytic cell.

[0139] (4) The second solid-liquid mixture obtained in step (2) was placed in the sample chamber.

[0140] (5) The electrodes in the sample chamber electrode device were connected to a direct current power supply to provide a constant voltage to the sample chamber. The constant voltage was set to 15 V. During the experiment, the current value displayed by the direct current power supply was recorded at 1 h, 3 h, 6 h, 9 h, 12 h, 15 h, 24 h, 30 h, 36 h, 48 h, and 60 h.

[0141] (6) During the experiment, the pH of the cathode chamber and the anode chamber was measured at 1 h, 3 h, 6 h, 9 h, 12 h, 15 h, 24 h, 30 h, 36 h, 48 h, and 60 h using a pH meter. Liquid samples were taken from the cathode chamber and the anode chamber, respectively. The concentration of fluoride ions was determined using a fluoride ion selective electrode method, and the concentration of phosphorus in the solution was determined using an inductively coupled plasma emission spectrometer.

[0142] (7) After 60 hours of electrochemical treatment, the electrolyte was collected from the anode chamber and the cathode chamber, respectively. The third solid-liquid mixture in the sample chamber was filtered, and the filtered solution was used as the recovered electrolyte. The fourth solid product was dried in a blast drying oven at 45°C to remove moisture and purify the phosphogypsum product. Solid samples near the anode region and the cathode region were collected, and the forms of fluorine and phosphorus elements were measured and analyzed.

[0143] (8) The recovered electrolyte was stirred at a speed of 300 rpm at 25°C for 40 minutes with the addition of CaO as a calcium source for solid-phase synthesis of fluorine and phosphorus resources. The fifth solid-liquid mixture obtained after stirring was centrifuged at 5000 rpm for 4 minutes and then dried at 60°C for 6 hours to obtain a purified phosphorus and fluorine crystal product.

[0144] The electrokinetic treatment is carried out for 60 h by using 0.1 M sodium sulfate as electrolyte, the fluorine concentration reaches equilibrium at 48 h, the phosphorus concentration reaches equilibrium at 40 h, the fluorine and phosphorus concentration contents in the anode chamber are 350.5 mg / L and 1606 mg / L, after the suction filtration treatment, the recovered fluorine and phosphorus mass are 66.3 mg and 245 mg, the recovery rate of soluble fluorine reaches 52%, the recovery rate of soluble phosphorus reaches 42%, the fluorine resource is effectively recovered by the electrokinetic enrichment and impurity removal, and the harmless production of phosphogypsum is simultaneously realized.

[0145] The above not involved, applicable to the prior art.

[0146] Although some specific embodiments of the present application have been described in detail by examples, those skilled in the art should understand that the above examples are only for illustration, not for limiting the scope of the present application, and those skilled in the art can make various modifications or supplements or use similar ways to replace the described specific embodiments, but will not deviate from the direction of the present application or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modification, equivalent replacement, improvement, etc. made to the above embodiments according to the technical essence of the present application shall be included in the protection scope of the present application.

Claims

1. A method for electro-enhanced recovery of phosphorus and fluorine from phosphogypsum, characterized in that, The specific steps include the following: S1. The phosphogypsum is crushed and sieved to obtain the first solid product; S2. The first solid product and the electrolyte are uniformly mixed according to a certain solid-liquid ratio, and allowed to stand to obtain a second solid-liquid mixture; the electrolyte is any one of a strong acid salt solution, a weak acid salt solution, or water; the concentration of the electrolyte is 0 mol / L to 4 mol / L, and the liquid-solid ratio of the electrolyte to the first solid product mixture is 0.1 to 3.

0. S3. The second solid-liquid mixture is placed in an electric processing device, which includes an electrolytic cell containing an anode chamber, a sample chamber, and a cathode chamber. Electrode plates are placed in the anode chamber and the cathode chamber, respectively. The two electrode plates are electrically connected to a DC power supply, and electric processing can be achieved when energized. The anode chamber is connected to an anode treatment tank through a pipe, and the cathode chamber is connected to a cathode treatment tank through a pipe, and a DC power supply with constant current or constant voltage is supplied. Under preset conditions, after electric processing for a certain period of time, the electrolyte is collected from the anode chamber and the cathode chamber, respectively, and the third solid-liquid mixture is collected from the sample chamber. The DC power supply is selected with a constant voltage, the constant voltage range being 15 V to 60 V, and the DC power supply is selected with a constant current, the constant current range being 0.01 A to 1.50 A. S4. Filter the third solid-liquid mixture to obtain the fourth solid product and phosphorus-fluorine-containing filtrate; S5. Place the fourth solid product in an oven and dry it at a certain temperature for a certain time to obtain the purified phosphogypsum product. The electrolyte collected from the anode and cathode chambers and the phosphorus-fluorine-containing filtrate obtained after filtration are mixed, a certain amount of calcium source is added, a certain reaction temperature is controlled, and the mixture is reacted for a period of time at a certain stirring speed to obtain the fifth solid-liquid mixture. S6. Centrifuge the fifth solid-liquid mixture to recover the solid after centrifugation, dry it, and obtain the purified phosphorus and fluorine crystal product; The strong acid salt is a sulfate, and the weak acid salt is a citrate or oxalate.

2. The method as described in claim 1, characterized in that, In step S1, the particle size of the first solid product is 50~400 mesh.

3. The method as described in claim 1, characterized in that, In step S3, the electric processing time is 1 h to 108 h.

4. The method as described in claim 1, characterized in that, In step S5, the content of the calcium source is determined based on the phosphorus and fluorine concentrations in the phosphorus-fluorine-containing liquid.

5. The method as described in claim 1, characterized in that, In step S5, the calcium source includes any one of CaCl2, CaCO3, and Ca(OH)2.

6. The method as described in claim 5, characterized in that, In step S5, the reaction temperature is 20 ℃~85 ℃, the stirring speed is 200 rpm~500 rpm, and the stirring reaction time is 5 min~180 min.

7. The method as described in claim 1, characterized in that, The phosphorus-fluorine crystal products include calcium fluoride or calcium fluorophosphate.

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