Screening method of ardealite flotation collecting agent

Abstract

The invention discloses a screening method of an ardealite flotation collecting agent, which comprises the following steps: providing a molecular structure of the collecting agent, and obtaining components of impurities in ardealite; respectively constructing a molecular model of the collecting agent and a unit cell model of the impurities, and carrying out geometric optimization to obtain an optimized molecular model of the collecting agent and an optimized unit cell model of the impurities; constructing a unit cell box of the impurities; on the basis of the optimized collecting agent molecular model and the impurity unit cell box, an adsorption model between the collecting agent and the impurities is built; performing molecular dynamics simulation calculation on the adsorption model to obtain adsorption energy between the collecting agent and the impurities; and sorting is conducted according to the size of the adsorption energy, and the collecting agent with the good collecting effect is screened out. The adsorption mechanism of the collecting agent and the ardealite impurities is disclosed from the molecular scale and the atomic scale, the optimal collecting agent compounding scheme based on ardealite impurity phases in different regions can be selected more quickly, and theoretical support is provided for ardealite impurity removal.

Description

Technical Field

[0001] The invention belongs to the technical field of phosphogypsum impurity removal, and in particular relates to a method for screening a phosphogypsum flotation collector. Background Art

[0002] Phosphogypsum is a solid waste discharged during the production of wet-process phosphoric acid. In 2019, my country's annual output of phosphogypsum was about 75 million tons, with a comprehensive utilization rate of about 40%. At present, the cumulative stockpile of phosphogypsum in China has reached 400 million tons, and the global cumulative stockpile has reached 6 billion tons. The large amount of phosphogypsum stockpiling not only occupies land and damages the environment, but also seriously restricts the healthy and sustainable development of phosphorus chemical companies. The main component of phosphogypsum is calcium sulfate dihydrate (CaSO4•2H2O), with a content of more than 80%. Other impurities are residual phosphate rock, phosphoric acid, fluorosilicate, metal oxides, carbonaceous matter, organic matter, etc., resulting in its low whiteness, generally light yellow, light gray or gray-black. At present, although phosphogypsum can be used in industries such as cement industry, chemical raw materials, soil conditioners, roadbeds or industrial fillers, its low whiteness and high impurity content have hindered its large-scale high-value application in building materials. Therefore, it is urgent to achieve its efficient whitening and impurity removal through technical breakthroughs.

[0003] Methods for removing impurities and whitening phosphogypsum include washing, acid dissolution, roasting, flotation, etc. Among them, flotation is a low-cost and effective impurity removal method. However, at present, there is a relative lack of research on the mechanism of action between reagents and phosphogypsum molecules in the flotation process, which limits the further improvement of this method in terms of impurity removal efficiency and selectivity. Molecular simulation has become a promising tool that can be used to optimize the exploration of the flotation mechanism of phosphogypsum and promote the development of flotation reagents, which can effectively overcome this challenge. Molecular simulation is a computational method based on physical principles that can simulate and predict chemical and physical processes at the molecular scale. By constructing models of phosphogypsum surfaces and reagent molecules, and applying molecular force fields and various simulation algorithms, important phenomena such as the interaction between reagents and phosphogypsum during flotation, solvent effects, and ion exchange can be simulated, revealing the interaction mechanism between reagents and phosphogypsum molecules. In addition, molecular simulation can also be used to predict the structure and activity relationship of reagent molecules and optimize the reagent structure to improve its flotation performance.

[0004] Regarding the reverse flotation desiliconization technology for phosphogypsum, due to the lack of systematic simulation research on the flotation characteristics of cationic collectors on minerals and impurities in phosphogypsum, the existing collectors have a long development cycle, low development efficiency and high development cost. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a method for screening a phosphogypsum flotation collector to solve the technical defects of the existing phosphogypsum collector development, such as low efficiency, long cycle and high cost.

[0006] The technical solution of the present invention is achieved in the following manner: The present invention provides a method for screening a phosphogypsum flotation collector, comprising the following steps: S1. Provide the molecular structure of the collector and obtain the composition of impurities in phosphogypsum; S2. Based on the molecular structure of the collector and the composition of the impurity, a molecular model of the collector and a unit cell model of the impurity are constructed respectively; S3. geometrically optimizing the molecular model of the collector and the unit cell model of the impurity to obtain an optimized molecular model of the collector and an optimized unit cell model of the impurity; S4. constructing a unit cell box of the impurity according to the optimized unit cell model of the impurity; S5. Based on the optimized molecular model of the collector and the unit cell box of the impurity, an adsorption model between the collector and the impurity is constructed; S6. Perform molecular dynamics calculation on the adsorption model to obtain the adsorption energy between the collector and the impurity; S7. Sort by adsorption energy and select collectors with better capture effects.

[0007] Preferably, in step S2, the molecular model of the collector and the unit cell model of the impurity are respectively constructed using Materials Studio software, wherein the unit cell model of the impurity includes a mineral phase unit cell model and an organic matter unit cell model.

[0008] Preferably, the mineral phase unit cell model includes a hemihydrate gypsum unit cell model, a quartz unit cell model and an apatite unit cell model; the organic unit cell model is an organic polymer amorphous unit cell model, including difluorodimethylsilane, difluorophosphoric acid, toluenesulfonic anhydride and vinyl decanoate.

[0009] Preferably, in step S3, the method for geometrically optimizing the molecular model of the collector includes: using the PBE functional in the Dmol3 module GGA of Materials Studio software, optimizing the atomic positions by the BFGS algorithm, and correcting the missing van der Waals interactions in the density functional calculation using the Tkatchenko-Scheffler van der Waals correction method.

[0010] Preferably, when the molecular model of the collector is geometrically optimized, the convergence criteria of the geometric optimization are: maximum displacement 0.05 Å, maximum force 0.02 Ha / Å, energy 1.0×10 -4 Ha, self-consistent field tolerance 2.0×10 -6 eV / atom.

[0011] Preferably, in step S3, the method for geometrically optimizing the unit cell model of the impurity includes: For mineral phase impurities, based on density functional theory, the PBE functional in the GGA module of the Materials Studio software Castap was used, with a plane wave cutoff energy of 400 eV. The atomic positions were optimized by the BFGS algorithm, and the Tkatchenko-Scheffler van der Waals correction method was used to correct the missing van der Waals interactions in the density functional calculation. For organic impurities, the Forcite module of Materials Studio software was used, and the CompassII force field was used for geometry optimization.

[0012] Preferably, when the unit cell model of the mineral phase impurity is geometrically optimized, the convergence criterion of the geometric optimization is: the maximum displacement is 2.0 × 10 -4 nm, maximum force 0.05 eV / Å, maximum stress 0.1× 10 3 MPa, energy 2.0 × 10 -5 eV / atom, self-consistent field tolerance 2.0 × 10 -6 eV / atom.

[0013] Preferably, in step S4, the method for constructing a unit cell box of the impurity comprises: When the impurity is a mineral phase, the optimized unit cell model of the mineral phase is sectioned and supercelled, and a vacuum layer is established to obtain a mineral phase unit cell box; When the impurities are organic matter, a vacuum layer is established for the optimized unit cell model of the organic matter to obtain an organic unit cell box. The purpose of establishing a vacuum layer for the unit cell box is to prevent the collector molecules from interacting with the bottom atoms.

[0014] Preferably, in step S5, the adsorption model between the collector and the impurity is constructed using Build layers in Materials Studio software, wherein the distance between the collector and the impurity is greater than 5 Å.

[0015] Preferably, in step S6, the Forcite module in the Materials Studio software is used to perform molecular dynamics calculations on the adsorption model, wherein the ensemble selects NVT, the initial velocity selects Random, the temperature selects 298 K, the temperature control method selects the Nosé-Hoover-Langevin method, and the Andersen method is used to couple and adjust the system pressure.

[0016] The beneficial effects of the present invention are: In response to the need for impurity removal during flotation of phosphogypsum, the present invention constructs an adsorption model between a collector and phosphogypsum impurities through interface adsorption chemistry, quantum mechanics and molecular dynamics simulations. Based on the adsorption model, the adsorption characteristics of different collectors at the interface of phosphogypsum are studied, and the mechanism of the adsorption process of the collector on various mineral phases and organic matter in phosphogypsum is explored, which is conducive to accelerating the development process of new green and efficient collectors and reducing development costs.

[0017] The present invention reveals the mechanism of adsorption of collectors and phosphogypsum impurities at the molecular and atomic scales, and can more quickly select the optimal compounding scheme of collectors based on the impurity phases of phosphogypsum in different regions, providing theoretical support for the removal of impurities from phosphogypsum. The method is convenient and practical, and has broad application prospects and guiding value in the field of phosphogypsum flotation agent development. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart of a method for screening a phosphogypsum flotation collector of the present invention; Figure 2 Optimized molecular model for collector; Figure 3 It is the optimized unit cell model of the mineral phase; Figure 4 Optimize the unit cell model for amorphous organic polymers; Figure 5 is the adsorption model of the collector on the (111) surface of hemihydrate gypsum; Figure 6 is the adsorption model of the collector on the apatite (001) surface; Figure 7 is the adsorption model of the collector on the quartz (101) surface; Figure 8 The adsorption model of the collector on the (111) surface of dihydrate gypsum is Fig. 9 It is the adsorption model of collector and organic matter; Fig.10 These are photos of phosphogypsum before and after flotation by collector; Fig.11 This is the SEM image of black particles in flotation tailings. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in 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.

[0020] like Figure 1As shown, the embodiment of the present invention provides a method for screening a phosphogypsum flotation collector, comprising the following steps: S1. Provide the molecular structure of the collector, and based on the physical and chemical properties of phosphogypsum, derive the mineral phase and organic matter components in phosphogypsum.

[0021] S2. Based on the molecular structure, mineral phase and organic matter composition of the collector, the molecular model of the collector and the unit cell model of the impurity, namely the mineral phase unit cell model and the organic unit cell model, are constructed respectively using Materials Studio software. The organic unit cell model is an organic polymer amorphous unit cell model.

[0022] S3. geometrically optimizing the molecular model of the collector and the unit cell model of the impurity to obtain an optimized molecular model of the collector and an optimized unit cell model of the impurity; Among them, the method for geometric optimization of the molecular model of the collector includes: using the PBE functional in the GGA of the Dmol3 module of Materials Studio software, optimizing the atomic positions by the BFGS algorithm, and using the Tkatchenko-Scheffler van der Waals correction method to correct the missing van der Waals interactions in the density functional calculation. The convergence criteria for geometry optimization are: maximum displacement 0.05 Å, maximum force 0.02 Ha / Å, energy 1.0×10 -4 Ha, self-consistent field tolerance 2.0×10 -6 eV / atom.

[0023] The method for geometric optimization of the unit cell model of impurities includes: for mineral phase impurities, based on density functional theory, using the PBE functional in the GGA module of the Materials Studio software Castap, the plane wave cutoff energy is 400 eV, the interaction between valence electrons and ion cores is described by ultrasoft pseudopotential, the atomic position is optimized by the BFGS algorithm, and the Tkatchenko-Scheffler van der Waals correction method is used to correct the missing van der Waals interaction in the density functional calculation. The convergence criteria for geometry optimization are: maximum displacement 2.0 × 10 -4 nm, maximum force 0.05 ev / Å, maximum stress 0.1× 10 3 MPa, energy 2.0 × 10 -5 eV / atom, self-consistent field tolerance 2.0 × 10 -6 eV / atom.

[0024] For organic impurities, the Forcite module of Materials Studio software was used, and the CompassII force field was used for geometry optimization.

[0025] S4. According to the optimized unit cell model of the impurity, a unit cell box of the impurity is constructed; when the impurity is a mineral phase, the optimized unit cell model of the mineral phase is sectioned, super-celled, and a vacuum layer is established to obtain a mineral phase unit cell box; when the impurity is organic matter, a vacuum layer is established for the optimized unit cell model of the organic matter to obtain an organic matter unit cell box.

[0026] S5. Based on the optimized molecular model of the collector and the unit cell box of the impurity, the adsorption model between the collector and the impurity was constructed using the Build layers in Materials Studio software, where the distance between the collector and the impurity was greater than 5 Å.

[0027] S6. The molecular dynamics calculation of the adsorption model was performed using the Forcite module in Materials Studio software. NVT was selected as the ensemble, Random as the initial velocity, 298 K as the temperature, and the Nosé-Hoover-Langevin method as the temperature control method. The Andersen method was used to couple the system pressure to obtain the adsorption energy between the collector and the impurity.

[0028] S7. Sort by adsorption energy and select collectors with better capture effects.

[0029] In order to make the implementation objectives, technical solutions and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be described in more detail below in conjunction with the accompanying drawings of the present invention.

[0030] Example 1 A method for screening a phosphogypsum flotation collector comprises the following steps: S1. Physicochemical properties analysis The chemical formula and molecular structure of cationic collectors dodecyltrimethylammonium chloride (DTAC), dodecylamine (DDA), octadecyldimethylethylbenzylammonium chloride (ODBC), and dodecyldimethylbenzylammonium chloride (DDBAC) were obtained respectively. XRD was used to observe the mineral phase composition of phosphogypsum provided by a Hubei enterprise, and XRF was used to obtain the chemical element composition of phosphogypsum. After carbon tetrachloride cyclone extraction, LC-MS liquid mass analysis was used to obtain the composition and mass fraction of organic matter in phosphogypsum. The mineral phases in phosphogypsum mainly included dihydrate gypsum, hemihydrate gypsum, apatite, and quartz, and the organic matter included 25.32% difluorodimethylsilane, 22.69% difluorophosphoric acid, 39.82% toluenesulfonic anhydride, and 12.17% vinyl decanoate.

[0031] S2. Modeling and Optimization Modeling and optimization of cationic collectors: Taking DTAC as an example, the chemical formula of DTAC is C15 H 34 ClN, use the brush of the 3D viewer in the Material studio software to first draw the carbon chain, then add hydrogen and clean to obtain the molecular model of DTAC. Use the same method to obtain the molecular models of DDA, ODBC and DDBAC respectively. Finally, use the Dmol3 module of the MS software, use the PBE functional in the generalized gradient approximation GGA, select Global for the orbital truncation scheme, and use the DFT Semi-core Pseudopots pseudopotential to describe the interaction between valence electrons and ion nuclei. Optimize the atomic positions using the BFGS algorithm, and use the Tkatchenko-Scheffler van der Waals correction method to correct the missing van der Waals interactions in the density functional calculation. The convergence criteria for geometry optimization are: maximum displacement 0.05 Å, maximum force 0.02 Ha / Å, energy 1.0×10 -4 Ha, self-consistent field tolerance 2.0×10 -6 eV / atom, and the optimized molecular models of the above four collectors were obtained. The results are as follows Figure 2 As shown, Figure 2 (a)~(d) are the optimized molecular models of DTAC, DDBAC, ODBC, and DDA, respectively.

[0032] Modeling and optimization of mineral phases: The Build module of MS (Material studio) software was used to model various mineral phases in phosphogypsum. The modeling parameters were derived from the specific active crystal surface data of XRD and literature references to obtain the unit cell models of different mineral phases. Then, based on density functional theory (DFT), the Castep module of Materials Studio software was used, and the PBE functional in the generalized gradient approximation GGA was used. The plane wave cutoff energy was 400 eV, and the interaction between valence electrons and ion nuclei was described by ultrasoft pseudopotentials. The atomic positions were optimized by the BFGS algorithm, and the Tkatchenko-Scheffler van der Waals correction method was used to correct the missing van der Waals interactions in the density functional calculation. The convergence criteria for geometry optimization are: maximum displacement 2.0 × 10 -4 nm, maximum force 0.05 eV / Å, maximum stress 0.1× 10 3 MPa, energy 2.0 × 10 -5 eV / atom, self-consistent field tolerance 2.0 × 10 -6 eV / atom, and obtain the optimized unit cell models of different mineral phases, such as Figure 3 As shown, (a) to (d) are the optimized unit cell models of dihydrate gypsum, quartz, hemihydrate gypsum and apatite respectively.

[0033] Modeling and optimization of organic matter: Based on the analysis of the physical and chemical properties of phosphogypsum, difluorodimethylsilane, difluorophosphoric acid, toluenesulfonic anhydride, and vinyl decanoate are present in the organic matter, and the average density of the organic matter is 1.2339 g / cm 3 Based on this, the Amorphous cell module of Materials Studio software is used to construct the polymer amorphous unit cell of organic matter in phosphogypsum, and the Forcite module is used to perform geometric optimization on the unit cell. The force field is Compass II force field, and the polymer amorphous optimized unit cell model of organic matter is obtained, as shown in the figure. Figure 4 shown.

[0034] S3. Constructing the unit cell box Construction of mineral phase unit cell box: Taking dihydrate gypsum as an example, the optimized unit cell model of dihydrate gypsum was sectioned. Specifically, the experimental value of the dihydrate gypsum space group was I12 / c1. Using the Build function in MS, the vector coordinates a, b, and c were input as 5.67, 15.201, and 6.533, respectively. The unit cell was cut on the (111) cutting plane. During the unit cell cutting process, the thickness was selected as 3.0. Then a vacuum layer with a thickness of 50 Å was established, and a supercell was performed with 2x2x1 to obtain the unit cell box of the dihydrate gypsum (111) plane. The unit cell box of the hemihydrate gypsum (111) plane, the unit cell box of the quartz (101) plane, and the unit cell box of the apatite (001) plane were obtained by the same method.

[0035] Construction of organic matter unit cell box: A vacuum layer with a thickness of 50 Å is established for the optimized unit cell model of organic matter to obtain an organic matter unit cell box.

[0036] S4. Construction of adsorption model Based on the optimized molecular model of the collector, the mineral phase unit cell box, and the organic matter unit cell box, the Build layers module in the MaterialsStudio software is used to construct the adsorption model between the collector and the mineral phase, and the adsorption model between the collector and the organic matter, such as Figures 5 to 9 As shown, the distance between the collector and the impurity is 15 Å.

[0037] S5. Calculation of adsorption energy The Forcite module in Materials Studio software was used to perform molecular dynamics simulation on the adsorption model obtained by S4, where NVT was selected as the ensemble, Random was selected as the initial velocity, 298 K was selected as the temperature, the Nosé-Hoover-Langevin method was selected as the temperature control method, and the Andersen method was used to couple and adjust the system pressure; after molecular dynamics simulation, the surface energy after relaxation after adsorption, the surface energy after relaxation without adsorption, and the surface energy parameters of the adsorbate were obtained. Then, according to the adsorption energy calculation formula Δ E = E surf+ads - E surf - E ads Calculate the adsorption energy; where, E surf+ads is the surface energy after relaxation after adsorption, E surf is the surface energy of the relaxed and unadsorbed surface, E ads is the surface energy of the adsorbate.

[0038] S6. Results and Analysis Figure 5 is the adsorption model of the collector on the (111) surface of hemihydrate gypsum, where: Figure 5 (a) to (d) are the adsorption models of DTAC, DDA, ODBC, and DDBAC on the (111) surface of hemihydrate gypsum. Figure 5 It can be seen that the adsorption of DTAC, DDA, ODBC, and DDBAC on the hemihydrate gypsum (111) surface is hydrogen bond adsorption. The hydrogen bond lengths formed by DTAC and hemihydrate gypsum are 3.106, 3.249, and 3.351 Å, respectively. The hydrogen bond lengths formed by DDA and hemihydrate gypsum are 3.253 and 3.471 Å, respectively. The hydrogen bond lengths formed by ODBC and hemihydrate gypsum are 3.366, 3.121, and 3.469 Å, respectively. The hydrogen bond lengths formed by DDBAC and hemihydrate gypsum are 3.212, 3.344, and 3.476 Å, respectively. At the same time, the simulation calculation shows that the adsorption energies of DTAC, DDA, ODBC, and DDBAC on the hemihydrate gypsum (111) surface are -17.739 kcal / mol, -17.477 kcal / mol, -27.825 kcal / mol, -22.156 kcal / mol, respectively. kcal / mol, the more negative the adsorption energy, the greater the adsorption force. Therefore, it can be concluded that the adsorption effect of the collector on hemihydrate gypsum (111) is: DDA<DTAC<DDBAC<ODBC. Therefore, the collector ODBC has the best removal efficiency for hemihydrate gypsum in phosphogypsum. When it is necessary to remove hemihydrate gypsum in phosphogypsum, ODBC can be preferred as the collector.

[0039] Figure 6 is the adsorption model of the collector on the apatite (001) surface, where Figure 6 (a) to (d) are the adsorption models of DTAC, DDA, ODBC, and DDBAC on the apatite (001) surface. Figure 6 It can be seen that the adsorption of DTAC, DDA, ODBC, and DDBAC on the apatite (001) surface is hydrogen bond adsorption. The hydrogen bond lengths of DTAC and apatite are 3.325, 3.455, and 3.129 Å, respectively. The hydrogen bond lengths of DDA and apatite are 3.222 and 3.256 Å, respectively. The hydrogen bond lengths of ODBC and apatite are 3.191, 3.237, and 3.218 Å, respectively. The hydrogen bond lengths of DDBAC and apatite are 3.317, 3.435, and 3.301 Å, respectively. At the same time, the adsorption energies of DTAC, DDA, ODBC, and DDBAC on the apatite (001) surface are calculated by simulation and are -317.713 kcal / mol, -135.997 kcal / mol, -274.225 kcal / mol, -283.942 kcal / mol, respectively. kcal / mol, the more negative the adsorption energy, the greater the adsorption force. Therefore, it can be concluded that the adsorption effect of the agent on apatite (001) is: DDA<ODBC<DDBAC<DTAC. Therefore, the collector DTAC has the best removal efficiency for apatite in phosphogypsum. When it is necessary to remove apatite in phosphogypsum, DTAC can be preferentially selected as the collector.

[0040] Figure 7 is the adsorption model of the collector on the quartz (101) surface, where Figure 7 (a) to (d) are the adsorption models of DTAC, DDA, ODBC, and DDBAC on the quartz (101) surface. Figure 7It can be seen that the adsorption of DTAC, DDA, ODBC, and DDBAC on the quartz (101) surface is hydrogen bond adsorption. The hydrogen bond lengths of DTAC and quartz are 3.301, 3.172, and 3.264 Å, respectively. The hydrogen bond lengths of DDA and quartz are 3.417 and 3.372 Å, respectively. The hydrogen bond lengths of ODBC and quartz are 3.192, 3.214, and 3.208 Å, respectively. The hydrogen bond lengths of DDBAC and quartz are 3.221, 3.168, and 3.184 Å, respectively. At the same time, the adsorption energies of DTAC, DDA, ODBC, and DDBAC on the quartz (101) surface are calculated by simulation and are -62.275 kcal / mol, -20.096 kcal / mol, -102.228 kcal / mol, -88.131 kcal / mol, respectively. kcal / mol, the more negative the adsorption energy, the greater the adsorption force. Therefore, it can be concluded that the adsorption effect of the agent on quartz (101) is: DDA<DTAC<DDBAC<ODBC. Therefore, the collector ODBC has the best removal efficiency for quartz in phosphogypsum. When it is necessary to remove quartz in phosphogypsum, ODBC can be selected as the collector.

[0041] Figure 8 is the adsorption model of the collector on the dihydrate gypsum (111) surface, where Figure 8 (a) to (d) are the adsorption models of DTAC, DDA, ODBC, and DDBAC on the (111) surface of dihydrate gypsum. Figure 8 It can be seen that the adsorption of DTAC, DDA, ODBC, and DDBAC on the dihydrate gypsum (111) surface is hydrogen bond adsorption. The hydrogen bond lengths formed by DTAC and dihydrate gypsum are 3.278 and 3.301 Å, respectively, the hydrogen bond lengths formed by DDA and dihydrate gypsum are 3.453 and 3.391 Å, respectively, the hydrogen bond lengths formed by ODBC and dihydrate gypsum are 3.476, 3.212, and 3.344 Å, respectively, and the hydrogen bond lengths formed by DDBAC and dihydrate gypsum are 3.229, 3.187, and 3.211 Å, respectively. At the same time, the simulation calculation shows that the adsorption energies of DTAC, DDA, ODBC, and DDBAC on the dihydrate gypsum (111) surface are -12.994 kcal / mol, -11.251 kcal / mol, -12.701 kcal / mol, -22.101 kcal / mol, respectively. kcal / mol, the more negative the adsorption energy, the greater the adsorption force. Therefore, it can be concluded that the adsorption effect of the agent on dihydrate gypsum (111) is: DDA<ODBC<DTAC<DDBAC. The main component of phosphogypsum is dihydrate gypsum. Therefore, when it is necessary to remove mineral phases such as quartz, hemihydrate gypsum and apatite in phosphogypsum, ODBC, DTAC or a combination of the two, which have strong adsorption effects on impurities but weak adsorption effects on dihydrate gypsum, can be preferentially selected.

[0042] Fig. 9 is the adsorption model of collector and organic matter, where Fig. 9 (a) to (d) are the adsorption models of DTAC, DDA, ODBC, DDBAC and organic matter, respectively. Fig. 9 It can be seen that the adsorption of DTAC, DDA, ODBC, and DDBAC to organic matter is hydrogen bond adsorption. The hydrogen bond lengths formed by DTAC and organic matter are 3.262, 3.367, and 3.618 Å, respectively; the hydrogen bond lengths formed by DDA and organic matter are 3.316, 3.255, and 3.545 Å, respectively; the hydrogen bond lengths formed by ODBC and organic matter are 2.716, 3.335, and 3.724 Å, respectively; the hydrogen bond lengths formed by DDBAC and organic matter are 2.931, 3.325, 3.639, and 3.587 Å, respectively. At the same time, the simulation calculation shows that the adsorption energies of DTAC, DDA, ODBC, and DDBAC to organic matter are -115.308 kcal / mol, -91.362 kcal / mol, -141.056 kcal / mol, and -124.091 kcal / mol, respectively. kcal / mol, so it can be concluded that the adsorption effect of the agent and organic matter is: DDA<DTAC<DDBAC<ODBC. Therefore, the collector ODBC has the best removal efficiency for organic matter in phosphogypsum. When it is necessary to remove organic matter in phosphogypsum, ODBC can be preferentially selected as the collector.

[0043] According to the calculation results of the above adsorption energy, we can also know the difficulty of cationic collectors in removing different impurities in phosphogypsum. The adsorption energies of DTAC on the hemihydrate gypsum (111) surface, apatite (001) surface, quartz (101) surface, dihydrate gypsum (111) surface and organic matter are -17.739 kcal / mol, -317.713 kcal / mol, -62.275 kcal / mol, -12.994 kcal / mol and -115.308 kcal / mol, respectively. Therefore, the collection effect of DTAC on mineral phases and organic matter is: dihydrate gypsum < hemihydrate gypsum < quartz < organic matter < apatite. The adsorption energies of DDA on hemihydrate gypsum (111) surface, apatite (001) surface, quartz (101) surface, dihydrate gypsum (111) surface and on organic matter are -17.477 kcal / mol, -135.997 kcal / mol, -20.096 kcal / mol, -11.251 kcal / mol and -91.362 kcal / mol, respectively. Therefore, the collection effect of DDA on mineral phase and organic matter is: dihydrate gypsum < hemihydrate gypsum < quartz < organic matter < apatite. The adsorption energies of ODBC on hemihydrate gypsum (111) surface, apatite (001) surface, quartz (101) surface, dihydrate gypsum (111) surface and organic matter are -27.825 kcal / mol, -274.225 kcal / mol, -102.228 kcal / mol, -12.701 kcal / mol and -141.056 kcal / mol, respectively. Therefore, the capture effect of ODBC on mineral phase and organic matter is: dihydrate gypsum < hemihydrate gypsum < quartz < organic matter < apatite. The adsorption energies of DDBAC on hemihydrate gypsum (111) surface, apatite (001) surface, quartz (101) surface, dihydrate gypsum (111) surface and organic matter are -22.156 kcal / mol, -283.942 kcal / mol, -88.131 kcal / mol, -22.101 kcal / mol, -124.091 kcal / mol, respectively. Therefore, the collection effect of ODBC on mineral phase and organic matter is: dihydrate gypsum < hemihydrate gypsum < quartz < organic matter < apatite. From the above results, it can be seen that the adsorption effects of DTAC, DDA, ODBC, and DDBAC on mineral phase and organic matter are all dihydrate gypsum < hemihydrate gypsum < quartz < organic matter < apatite. Therefore, in the flotation process, apatite and organic matter are removed first, followed by quartz, and finally the hemihydrate gypsum and dihydrate gypsum are more difficult to float out, thus achieving the purpose of reverse flotation.

[0044] It can be seen from the above results that different collectors have different capture effects on impurities in phosphogypsum. In the phosphogypsum impurity removal process, technicians can calculate the adsorption energy according to the simulation calculation method of the adsorption of collectors, phosphogypsum and its impurities provided by the present invention, so as to select a suitable collector.

[0045] Test verification The reverse flotation test of cationic collector and phosphogypsum was carried out. The phosphogypsum samples used in the test were the same as those used in the above simulation calculations. They were all produced by a Hubei enterprise. The phosphogypsum was reversely floated using an XFD-IV 0.5 L single-tank flotation machine (the dosage of the foaming agent MIBC was maintained at 300 g / t, the pH was 2.5, and the solid-liquid ratio S / L was 1:4.). The phosphogypsum concentrate after flotation was filtered and washed, and then placed in a 101-2EBS vacuum drying oven at 338 K for 10 hours. After the phosphogypsum concentrate was dried, its whiteness was measured using a YQ-Z-48A whiteness meter. The reverse flotation results of phosphogypsum with different collectors are shown in Table 1.

[0046] Table 1

[0047] It can be seen from Table 1 that the flotation effect of collector on quartz in phosphogypsum is: DDA<DTAC<DDBAC<ODBC, which is consistent with the simulation calculation.

[0048] like Fig.10 As shown, the whiteness of the phosphogypsum ore is 29.72% ( Fig.10 a), the whiteness of the concentrate of phosphogypsum after DDBAC treatment is 66.74% ( Fig.10 b) After treatment, the whiteness of the phosphogypsum can be increased from 29% to 66%, the purity from 82% to 97%, the silicon content from 7.17% to 1.1%, and the organic matter content from 0.72% to 0.057%. After reverse flotation treatment, black particles with a diameter of about 0.02 ~ 0.2 mm remain in the tailings. The composition of the black particles is analyzed, and it is found that there are a lot of quartz, organic matter and apatite in the flotation tailings. The black particles of the tailings are scanned by electron microscope, such as Fig.11 As shown, quartz in the tailings mainly exists in the form of particles, while apatite exists in a blocky structure. The organic matter is not only attached to the surface of apatite, but also embedded in its internal structure, indicating that the flotation order is apatite > organic matter > quartz, which is consistent with the simulation calculation.

[0049] In summary, the present invention uses simulation software to build an adsorption model between collectors and phosphogypsum impurities, and obtains the adsorption energy of different cationic collectors on the surface of specific materials through model calculation, thereby evaluating the adsorption effect of these collectors. In the process of removing impurities from phosphogypsum, technicians can use the results obtained by simulation calculation to determine whether it is necessary to select a corresponding collector, thereby saving costs, or assist in research and development through simulation calculation. The embodiment of the present invention uses simulation software to calculate the adsorption energy of different cationic collectors and various impurities in phosphogypsum, and uses the calculated adsorption energy to predict the removal efficiency of impurities in phosphogypsum by different collectors, thereby screening out the most effective collector, and the theoretical prediction results are consistent with the experimental verification results.

[0050] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For matters that are not described in detail in some embodiments, reference may be made to the description in other embodiments.

[0051] The above-mentioned embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for screening a phosphogypsum flotation collector, characterized in that: The steps include: S1. Provide the molecular structure of the collector and obtain the composition of impurities in phosphogypsum; S2. Based on the molecular structure of the collector and the composition of the impurities, a molecular model of the collector and a unit cell model of the impurities are constructed respectively; S3. geometrically optimizing the molecular model of the collector and the unit cell model of the impurity to obtain an optimized molecular model of the collector and an optimized unit cell model of the impurity; S4. Constructing a unit cell box of the impurity according to the optimized unit cell model of the impurity; S5. Based on the optimized molecular model of the collector and the unit cell box of the impurity, construct an adsorption model between the collector and the impurity; S6. Performing molecular dynamics simulation calculations on the adsorption model to obtain the adsorption energy between the collector and the impurity; S7. Sort by the size of the adsorption energy and select the collector with better capture effect.

2. The method for screening a phosphogypsum flotation collector according to claim 1, characterized in that: In step S2, the molecular model of the collector and the unit cell model of the impurity are constructed respectively using Materials Studio software, wherein the unit cell model of the impurity includes a mineral phase unit cell model and an organic matter unit cell model.

3. The method for screening phosphogypsum flotation collector according to claim 2, characterized in that: The mineral phase unit cell model includes a hemihydrate gypsum unit cell model, a quartz unit cell model and an apatite unit cell model; the organic unit cell model is an organic polymerized amorphous unit cell model.

4. The method for screening a phosphogypsum flotation collector according to claim 1, characterized in that: In step S3, the method for geometrically optimizing the molecular model of the collector includes: using the PBE functional in the GGA of the Dmol3 module of Materials Studio software, optimizing the atomic positions by the BFGS algorithm, and correcting the missing van der Waals interactions in the density functional calculation by the Tkatchenko-Scheffler van der Waals correction method.

5. The method for screening a phosphogypsum flotation collector according to claim 4, characterized in that: When the molecular model of the collector is geometrically optimized, the convergence criteria of the geometry optimization are: maximum displacement 0.05 Å, maximum force 0.02 Ha / Å, energy 1.0×10 -4 Ha, self-consistent field tolerance 2.0×10 -6 eV / atom.

6. The method for screening phosphogypsum flotation collector according to claim 1, characterized in that: In step S3, the method for geometrically optimizing the unit cell model of the impurity includes: For mineral phase impurities, based on density functional theory, the PBE functional in the GGA module of the Materials Studio software Castap was used, with a plane wave cutoff energy of 400 eV. The atomic positions were optimized by the BFGS algorithm, and the Tkatchenko-Scheffler van der Waals correction method was used to correct the missing van der Waals interactions in the density functional calculation. For organic impurities, the Forcite module of Materials Studio software was used, and the Compass II force field was used for geometry optimization.

7. The method for screening a phosphogypsum flotation collector according to claim 6, characterized in that: When the unit cell model of mineral phase impurities is geometrically optimized, the convergence criteria of the geometry optimization are: maximum displacement 2.0 × 10 -4 nm, maximum force 0.05 eV / Å, maximum stress 0.1× 10 3 MPa, energy 2.0 × 10 -5 eV / atom, self-consistent field tolerance 2.0 × 10 -6 eV / atom.

8. The method for screening phosphogypsum flotation collector according to claim 1, characterized in that: In step S4, the method for constructing a unit cell box of the impurity includes: When the impurity is a mineral phase, the optimized unit cell model of the mineral phase is sectioned and supercelled, and a vacuum layer is established to obtain a mineral phase unit cell box; When the impurities are organic matter, a vacuum layer is established for the optimized unit cell model of the organic matter to obtain an organic unit cell box.

9. The method for screening a phosphogypsum flotation collector according to claim 1, characterized in that: In step S5, the adsorption model between the collector and the impurity is constructed using the Build layers module in the Materials Studio software, wherein the distance between the collector and the impurity is greater than 5 Å.

10. The method for screening a phosphogypsum flotation collector according to claim 1, characterized in that: In step S6, the Forcite module in Materials Studio software is used to perform molecular dynamics simulation calculations on the adsorption model, wherein NVT is selected as the ensemble, Random is selected as the initial velocity, 298 K is selected as the temperature, the Nosé-Hoover-Langevin method is selected as the temperature control method, and the Andersen method is used to couple and adjust the system pressure.

Images