A screening method of phosphogypsum flotation collector

Abstract

The application discloses a screening method of a phosphogypsum flotation collector, and comprises the following steps: providing a molecular structure of the collector, and obtaining the composition of impurities in the phosphogypsum; constructing a molecular model of the collector and a unit cell model of the impurities respectively, and performing geometric optimization to obtain an optimized collector molecular model and an optimized impurity unit cell model; constructing a unit cell box of the impurities; constructing an adsorption model between the collector and the impurities based on the optimized collector molecular model and the unit cell box of the impurities; performing molecular dynamics simulation calculation on the adsorption model to obtain the adsorption energy between the collector and the impurities; and sorting the adsorption energy according to the size to screen out the collector with better collection effect. The application reveals the adsorption mechanism of the collector and the phosphogypsum impurities from the molecular and atomic scales, can more quickly select the optimal collector compounding scheme based on different regional phosphogypsum impurity phases, and provides theoretical support for phosphogypsum impurity removal.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of phosphogypsum impurity removal, and particularly relates to a screening method of a phosphogypsum flotation collector. BACKGROUND

[0002] Phosphogypsum is a solid waste discharged during the production of wet-process phosphoric acid. In 2019, the annual production of phosphogypsum in China was about 75 million tons, and the comprehensive utilization rate was about 40%. At present, the cumulative storage of phosphogypsum in China has reached 400 million tons, and the global cumulative storage has reached 6 billion tons. The main component of phosphogypsum is calcium sulfate dihydrate (CaSO4•2H2O), with a content of more than 80%, and other impurities are residual phosphate rock, phosphoric acid, fluorosilicate, metal oxide, carbon, organic matter, etc., which leads to low whiteness, generally light yellow, light gray or gray black. At present, although phosphogypsum can be used in the cement industry, chemical raw materials, soil conditioner, roadbed or industrial filler industries, etc., its low whiteness and high impurity content hinder its large-scale application in building materials and high-value application. Therefore, it is urgent to realize efficient whitening and impurity removal through technical research.

[0003] The methods for removing impurities and whitening phosphogypsum include water washing, acid dissolution, calcination and flotation. Among them, flotation is a low-cost and effective method for removing impurities. However, at present, the research on the mechanism of the interaction between the reagent and the phosphogypsum molecule in the flotation process is relatively lacking, which limits the further improvement of the method in terms of impurity removal efficiency and selectivity. Molecular simulation has become a promising tool for optimizing the exploration of the flotation mechanism of phosphogypsum and promoting the development of flotation reagents, which can effectively overcome this challenge. Molecular simulation is a computational method based on physical principles, which can simulate and predict chemical and physical processes at the molecular scale. By constructing the model of the surface of phosphogypsum and the reagent molecule, and applying molecular force fields and various simulation algorithms, the interaction between the reagent and phosphogypsum, solvent effects, ion exchange and other important phenomena in the flotation process can be simulated, and the interaction mechanism between the reagent and the phosphogypsum molecule can be revealed. In addition, molecular simulation can also be used to predict the structure and activity relationship of the reagent molecule, and optimize the structure of the reagent to improve its flotation performance.

[0004] Due to the lack of systematic simulation research on the flotation characteristics of minerals and impurities in phosphogypsum using cationic collectors, the existing collector development cycle is long, the development efficiency is low, and the development cost is high. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a screening method of a phosphogypsum flotation collector, which solves the technical defects of low development efficiency, long cycle and high cost of the existing phosphogypsum collector.

[0006] The technical solution of the present application is realized in the following way:

[0007] The application provides a screening method of a phosphogypsum flotation collector, comprising the following steps:

[0008] S1. providing a molecular structure of a collector and obtaining a composition of impurities in phosphogypsum;

[0009] S2. constructing a molecular model of the collector and a unit cell model of the impurities based on the molecular structure of the collector and the composition of the impurities, respectively;

[0010] S3. geometrically optimizing the molecular model of the collector and the unit cell model of the impurities to obtain an optimized molecular model of the collector and an optimized unit cell model of the impurities;

[0011] S4. constructing a unit cell box of the impurities according to the optimized unit cell model of the impurities;

[0012] S5. constructing an adsorption model between the collector and the impurities based on the optimized molecular model of the collector and the unit cell box of the impurities;

[0013] S6. performing molecular dynamics calculation on the adsorption model to obtain an adsorption energy between the collector and the impurities;

[0014] S7. sorting according to the size of the adsorption energy to screen out a collector with better collection effect.

[0015] Preferably, in step S2, the molecular model of the collector and the unit cell model of the impurities are constructed by using Materials Studio software, wherein the unit cell model of the impurities includes a mineral phase unit cell model and an organic matter unit cell model.

[0016] 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; and the organic matter unit cell model is an organic matter polymer amorphous unit cell model, including difluorodimethylsilane, difluorophosphoric acid, methylbenzenesulfonic anhydride and decanoic acid vinyl ester.

[0017] Preferably, in step S3, the method for geometrically optimizing the molecular model of the collector includes: using the PBE functional in the Dmol3 module of the Materials Studio software, optimizing the atomic position through the BFGS algorithm, and correcting the missing van der Waals interaction in the density functional calculation by using the Tkatchenko-Scheffler van der Waals correction method.

[0018] Preferably, when the molecular model of the collector is geometrically optimized, the convergence criteria for 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.

[0019] Preferably, in step S3, the method for geometric optimization of the unit cell model of the impurity comprises:

[0020] For mineral phase impurities, based on density functional theory, using the PBE functional in the Castep module of the Materials Studio software, the plane wave cutoff energy is 400 eV, the atomic positions are 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;

[0021] For organic impurities, the Forcite module of the Materials Studio software is used for geometric optimization, and the CompassII force field is selected as the force field.

[0022] Preferably, when the unit cell model of the mineral phase impurity is geometrically optimized, the convergence criteria for geometric 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, and self-consistent field tolerance 2.0 × 10 -6 eV / atom.

[0023] Preferably, in step S4, the method for constructing the unit cell box of the impurity comprises:

[0024] When the impurity is a mineral phase, the optimized unit cell model of the mineral phase is cut into a section, a supercell, and a vacuum layer is established to obtain a mineral phase unit cell box;

[0025] When the impurity is an 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. The purpose of establishing a vacuum layer for the unit cell box is to prevent the collector molecules from interacting with the bottom atoms.

[0026] Preferably, in step S5, the Build layers in the Materials Studio software is used to construct the adsorption model between the collector and the impurity, wherein the distance between the collector and the impurity is greater than 5 Å.

[0027] Preferably, in step S6, the Forcite module of the Materials Studio software is used to perform molecular dynamics calculation on the adsorption model, wherein the ensemble is selected as NVT, the initial velocity is selected as Random, the temperature is selected as 298 K, the temperature control method is selected as the Nosé-Hoover-Langevin method, and the Andersen method is used to couple and adjust the system pressure.

[0028] The beneficial effects of the present application are:

[0029] The present application aims at the demand of phosphogypsum flotation impurity removal, through interface adsorption chemistry, quantum mechanics and molecular dynamics simulation, the adsorption model between collector and phosphogypsum impurities is constructed, based on the adsorption model, the adsorption characteristics of different collectors on the interface of phosphogypsum is studied, and the adsorption process mechanism of the collector on each mineral phase and organic matter of phosphogypsum is explored, which is conducive to accelerating the development process of new green and efficient collector, and reducing the development cost.

[0030] The present application reveals the mechanism of collector and phosphogypsum impurity adsorption from the molecular and atomic scale, which can quickly select the optimal compounding scheme of collector based on different regional phosphogypsum impurity phase, and provide theoretical support for phosphogypsum impurity removal. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a phosphogypsum flotation collector screening method flow chart of the present application;

[0032] Figure 2 It is an optimized molecular model of the collector;

[0033] Figure 3 It is an optimized unit cell model of the mineral phase;

[0034] Figure 4 It is a polymer amorphous optimized unit cell model of the organic matter;

[0035] Figure 5 It is an adsorption model of the collector on the (111) surface of hemihydrate gypsum;

[0036] Figure 6 It is an adsorption model of the collector on the (001) surface of apatite;

[0037] Figure 7 It is an adsorption model of the collector on the (101) surface of quartz;

[0038] Figure 8 It is an adsorption model of the collector on the (111) surface of dihydrate gypsum

[0039] Figure 9 It is an adsorption model of the collector and organic matter;

[0040] Figure 10 It is a picture of phosphogypsum before and after flotation by the collector;

[0041] Figure 11 It is a SEM graph of black particles in the flotation tailings. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0043] As shown in the formula (I), the present embodiment provides a screening method of phosphogypsum flotation collector, comprising the following steps: Figure 1

[0044] S1. Provide the molecular structure of the collector, and based on the analysis of the physicochemical properties of the phosphogypsum, obtain the mineral phase and organic matter composition in the phosphogypsum.

[0045] S2. Based on the molecular structure of the collector, the mineral phase and the organic matter composition, use the Materials Studio software to construct the molecular model of the collector and the unit cell model of the impurities, i.e. the mineral phase unit cell model and the organic matter unit cell model, wherein the organic matter unit cell model is an organic matter polymer amorphous unit cell model.

[0046] S3. Geometrically optimize the molecular model of the collector and the unit cell model of the impurities to obtain the optimized molecular model of the collector and the optimized unit cell model of the impurities.

[0047] The method for geometrically optimizing the molecular model of the collector includes: using the PBE functional in the Dmol3 module of the Materials Studio software, optimizing the atomic position by the BFGS algorithm, and correcting the missing van der Waals interaction in the density functional calculation by the Tkatchenko-Scheffler van der Waals correction method. The convergence criteria for geometric optimization are: maximum displacement 0.05 Å, maximum force 0.02 Ha / Å, energy 1.0 × 10 -4 Ha, and self-consistent field tolerance 2.0 × 10 -6 eV / atom.

[0048] The method for geometrically optimizing the unit cell model of the impurities includes: for the mineral phase impurities, based on the density functional theory, using the PBE functional in the Castep module of the Materials Studio software, the plane wave cutoff energy is 400 eV, the interaction between the valence electrons and the ion core is described by the ultra-soft pseudo-potential, the atomic position is optimized by the BFGS algorithm, and the missing van der Waals interaction in the density functional calculation is corrected by the Tkatchenko-Scheffler van der Waals correction method. The convergence criteria for geometric optimization are: maximum displacement 2.0 × 10 -4 ​nm, maximum force 0.05 ev / A, maximum stress 0.1 x 10 3 MPa, energy 2.0 x 10 -5 eV / atom, self-consistent field tolerance 2.0 x 10 -6 eV / atom.

[0049] For organic impurities, the Forcite module of the Materials Studio software is used for geometry optimization, and the CompassII force field is selected as the force field.

[0050] 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 cut, supercellled, and a vacuum layer is established to obtain a mineral phase unit cell box; when the impurity is an 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.

[0051] S5. Based on the optimized molecular model of the collector and the unit cell box of the impurity, the Build layers in the Materials Studio software is used to construct an adsorption model between the collector and the impurity, wherein the distance between the collector and the impurity is greater than 5 Å.

[0052] S6. The Forcite module in the Materials Studio software is used for molecular dynamics calculation of the adsorption model, wherein the ensemble is selected as NVT, the initial velocity is selected as Random, the temperature is selected as 298 K, the temperature control method is selected as the Nosé-Hoover-Langevin method, and the Andersen method is used to couple and adjust the system pressure to obtain the adsorption energy between the collector and the impurity.

[0053] S7. According to the size of the adsorption energy, the collector with better collecting effect is screened out.

[0054] In order to make the purposes, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below in combination with the drawings of the present application.

[0055] Example 1

[0056] A screening method of a phosphogypsum flotation collector, comprising the following steps:

[0057] S1. Analysis of physicochemical properties

[0058] The chemical formula and molecular structure of cationic collectors dodecyl trimethyl ammonium chloride (DTAC), dodecyl amine (DDA), octadecyl dimethyl ethyl benzyl ammonium chloride (ODBC) and dodecyl dimethyl benzyl ammonium chloride (DDBAC) were obtained, respectively. The mineral phase composition of the phosphogypsum provided by a certain enterprise in Hubei was observed by XRD, and the chemical element composition of the phosphogypsum was obtained by XRF. After carbon tetrachloride cyclone extraction of the phosphogypsum, the composition and mass fraction of the organic matter in the phosphogypsum were obtained by LC-MS liquid chromatography-mass spectrometry analysis. It is found that the mineral phases existing in the phosphogypsum mainly include dihydrate gypsum, hemihydrate gypsum, apatite and quartz, and the organic matter includes difluorodimethylsilane 25.32%, difluorophosphoric acid 22.69%, methylbenzenesulfonic acid anhydride 39.82% and vinyl decanoate 12.17%.

[0059] S2. Modeling and optimization

[0060] Modeling and optimization of cationic collectors: taking DTAC as an example, the chemical formula of DTAC is C 15 H 34 ClN, the carbon chain is first drawn using the brush of 3D viewer in Material studio software, and then hydrogen is added, cleaned, to obtain the molecular model of DTAC. The molecular model of DDA, the molecular model of ODBC and the molecular model of DDBAC are obtained by the same method. Finally, the Dmol3 module of MS software is used, the PBE functional in the generalized gradient approximation GGA is used, the global orbital truncation scheme is selected, and the interaction between valence electrons and ion cores is described by DFT Semi-core Pseudopots pseudopotential. The atomic positions are optimized by 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 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, to obtain the optimized molecular models of the above four collectors, as shown in Figure 2 , wherein, Figure 2 (a)-(d) are the optimized molecular models of DTAC, DDBAC, ODBC and DDA, respectively.

[0061] Modeling and optimization of mineral phases: The various mineral phases in phosphogypsum were modeled using the Build module of the MS (Material studio) software. The modeling parameters were derived from the XRD specific active crystal face data and literature references, and the unit cell models of different mineral phases were obtained. Then, based on the density functional theory (DFT), the Castep module of the Materials Studio software was used. The PBE functional in the generalized gradient approximation (GGA) was used, the plane wave cutoff energy was 400 eV, the interaction between valence electrons and ion cores was described by the ultra-soft pseudo-potential, 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 interaction in the density functional calculation. The convergence criteria for geometric optimization were: 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 the optimized unit cell models of different mineral phases were obtained, as shown in Figure 3 Fig. 2, (a)-(d) are the optimized unit cell models of dihydrate gypsum, quartz, hemihydrate gypsum and apatite, respectively.

[0062] Modeling and optimization of organic matter: Based on the analysis of the physicochemical properties of phosphogypsum, there are difluorodimethylsilane, difluorophosphoric acid, methylbenzenesulfonic anhydride, and vinyl decanoate in the organic matter, and the average density of the organic matter is 1.2339 g / cm 3 . Accordingly, the Amorphous cell module of the Materials Studio software was used to construct the polymer amorphous unit cell of the organic matter in the phosphogypsum, and the Forcite module was used to optimize the geometry of the unit cell, and the Compass II force field was selected, and the polymer amorphous optimized unit cell model of the organic matter was obtained, as shown in Figure 4 Fig. 3.

[0063] S3. Constructing a unit cell box

[0064] Construction of mineral phase unit cell box: taking dihydrate gypsum as an example, the optimized unit cell model of dihydrate gypsum is cut, specifically: the experimental value of dihydrate gypsum space group is I12 / c1, using the Build function in MS, inputting vector coordinates a, b, c are 5.67, 15.201, 6.533, cutting the unit cell on the (111) cutting surface, selecting thickness 3.0 in the process of cutting the unit cell, then establishing a vacuum layer with a thickness of 50 Å, and performing supercell with 2x2x1 to obtain the unit cell box of the (111) surface of dihydrate gypsum. The same method is used to obtain the unit cell box of the (111) surface of hemihydrate gypsum, the (101) surface of quartz, and the (001) surface of apatite.

[0065] Construction of organic matter unit cell box: an optimized unit cell model of organic matter is established with a vacuum layer of 50 Å thickness to obtain an organic matter unit cell box.

[0066] S4. Construction of adsorption model

[0067] Based on the optimized molecular model of collector, the mineral phase unit cell box and the organic matter unit cell box, the Build layers module in Materials Studio 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, as shown in Figures 5~9 , wherein the distance between the collector and the impurities is 15 Å.

[0068] S5. Calculation of adsorption energy

[0069] The Forcite module in Materials Studio software is used to perform molecular dynamics simulation on the adsorption model obtained in S4, wherein the ensemble is selected as NVT, the initial velocity is selected as Random, the temperature is selected as 298 K, the temperature control method is selected as Nosé-Hoover-Langevin method, and the Andersen method is used to couple and adjust the system pressure; after the molecular dynamics simulation, the surface energy after relaxation of the adsorbed substance, the surface energy of only relaxation without adsorption, and the surface energy parameters of the adsorbed substance are obtained. Then the adsorption energy calculation formula Δ E = E surf+ads - E surf - E ads is calculated. In the formula, E surf+ads is the surface energy after relaxation of the adsorbed substance, E surf is the surface energy of only relaxation without adsorption, E ads is the surface energy of the adsorbed substance.

[0070] S6. Result analysis

[0071] Figure 5 For the adsorption model of collector on the (111) surface of hemihydrate gypsum, wherein, Figure 5 (a)~(d) are the adsorption models of DTAC, DDA, ODBC, DDBAC on the (111) surface of hemihydrate gypsum, respectively. From Figure 5 It can be seen that the adsorption of DTAC, DDA, ODBC, DDBAC on the (111) surface of hemihydrate gypsum is hydrogen bond adsorption, and the hydrogen bond lengths formed by DTAC and hemihydrate gypsum are 3.106, 3.249, 3.351 Å, respectively, the hydrogen bond lengths formed by DDA and hemihydrate gypsum are 3.253, 3.471 Å, respectively, the hydrogen bond lengths formed by ODBC and hemihydrate gypsum are 3.366, 3.121, 3.469 Å, respectively, and the hydrogen bond lengths formed by DDBAC and hemihydrate gypsum are 3.212, 3.344, 3.476 Å, respectively. At the same time, it is obtained through simulation calculation that the adsorption energies of DTAC, DDA, ODBC, DDBAC on the (111) surface of hemihydrate gypsum are-17.739 kcal / mol, -17.477 kcal / mol, -27.825 kcal / mol, and -22.156 kcal / mol, respectively. The more negative the adsorption energy is, the greater the adsorption force is. Therefore, it can be concluded that the adsorption effect of the collector on the (111) surface of hemihydrate gypsum is: DDA < DTAC < DDBAC < ODBC. Therefore, the collector ODBC has the best removal efficiency on hemihydrate gypsum in phosphogypsum, and ODBC can be preferentially selected as the collector when hemihydrate gypsum needs to be removed from phosphogypsum.

[0072] Figure 6 For the adsorption model of collector on the (001) surface of apatite, wherein, Figure 6 (a)~(d) are the adsorption models of DTAC, DDA, ODBC, DDBAC on the (001) surface of apatite, respectively. From Figure 6It can be seen that the adsorption of DTAC, DDA, ODBC, DDBAC on the (001) surface of apatite is hydrogen bond adsorption, the hydrogen bond lengths formed by DTAC and apatite are 3.325, 3.455, 3.129 Å respectively, the hydrogen bond lengths formed by DDA and apatite are 3.222, 3.256 Å respectively, the hydrogen bond lengths formed by ODBC and apatite are 3.191, 3.237, 3.218 Å respectively, and the hydrogen bond lengths formed by DDBAC and apatite are 3.317, 3.435, 3.301 Å respectively. Meanwhile, it is obtained through simulation calculation that the adsorption energies of DTAC, DDA, ODBC, DDBAC on the (001) surface of apatite are -317.713 kcal / mol, -135.997 kcal / mol, -274.225 kcal / mol, and -283.942 kcal / mol respectively. The more negative the adsorption energy is, the greater the adsorption force is. Therefore, it can be concluded that the adsorption effect of the reagents on the (001) surface of apatite is: DDA < ODBC < DDBAC < DTAC. Therefore, the collector DTAC has the best removal efficiency on apatite in phosphogypsum, and DTAC can be preferentially selected as a collector when apatite in phosphogypsum needs to be removed.

[0073] Figure 7 The adsorption model of the collector on the (101) surface of quartz is shown in Figure 6. Figure 7 (a)-(d) are the adsorption models of DTAC, DDA, ODBC, and DDBAC on the (101) surface of quartz respectively. Figure 7 It can be seen that the adsorption of DTAC, DDA, ODBC, and DDBAC on the (101) surface of quartz is hydrogen bond adsorption, the hydrogen bond lengths formed by DTAC and quartz are 3.301, 3.172, 3.264 Å respectively, the hydrogen bond lengths formed by DDA and quartz are 3.417, 3.372 Å respectively, the hydrogen bond lengths formed by ODBC and quartz are 3.192, 3.214, 3.208 Å respectively, and the hydrogen bond lengths formed by DDBAC and quartz are 3.221, 3.168, 3.184 Å respectively. Meanwhile, it is obtained through simulation calculation that the adsorption energies of DTAC, DDA, ODBC, and DDBAC on the (101) surface of quartz are -62.275 kcal / mol, -20.096 kcal / mol, -102.228 kcal / mol, and -88.131 kcal / mol respectively. The more negative the adsorption energy is, the greater the adsorption force is. Therefore, it can be concluded that the adsorption effect of the reagents on the (101) surface of quartz is: DDA < DTAC < DDBAC < ODBC. Therefore, the collector ODBC has the best removal efficiency on quartz in phosphogypsum, and ODBC can be preferentially selected as a collector when quartz in phosphogypsum needs to be removed.

[0074] Figure 8For the adsorption model of collector on the (111) surface of dihydrate gypsum, wherein, Figure 8 (a)-(d) are respectively the adsorption model of DTAC, DDA, ODBC, DDBAC on the (111) surface of dihydrate gypsum. From Figure 8 It can be seen that the adsorption of DTAC, DDA, ODBC, DDBAC on the (111) surface of dihydrate gypsum is hydrogen bond adsorption, the hydrogen bond length formed by DTAC and dihydrate gypsum is 3.278, 3.301 Å respectively, the hydrogen bond length formed by DDA and dihydrate gypsum is 3.453, 3.391 Å respectively, the hydrogen bond length formed by ODBC and dihydrate gypsum is 3.476, 3.212, 3.344 Å respectively, the hydrogen bond length formed by DDBAC and dihydrate gypsum is 3.229, 3.187, 3.211 Å respectively, and through simulation calculation, the adsorption energy of DTAC, DDA, ODBC, DDBAC on the (111) surface of dihydrate gypsum is-12.994 kcal / mol, -11.251 kcal / mol, -12.701 kcal / mol, -22.101 kcal / mol respectively, the more negative the adsorption energy, the greater the adsorption force, so it can be concluded that the adsorption effect of reagent on the (111) surface of dihydrate gypsum is: DDA<ODBC<DTAC<DDBAC, the main component of phosphogypsum is dihydrate gypsum, so when it is necessary to remove quartz, hemihydrate gypsum and apatite and other mineral phases in phosphogypsum, ODBC, DTAC or a complex of the two can be preferentially selected, which has strong adsorption effect on impurities and weak adsorption effect on dihydrate gypsum.

[0075] Figure 9 For the adsorption model of collector on the (111) surface of dihydrate gypsum, wherein, Figure 9 (a)-(d) are respectively the adsorption model of DTAC, DDA, ODBC, DDBAC on the (111) surface of dihydrate gypsum. From Figure 9It can be seen that the adsorption of DTAC, DDA, ODBC, DDBAC and 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, and the hydrogen bond lengths formed by DDBAC and organic matter are 2.931, 3.325, 3.639 and 3.587 Å respectively. Meanwhile, it is obtained through simulation calculation that the adsorption energies of DTAC, DDA, ODBC and DDBAC and organic matter are-115.308 kcal / mol, -91.362 kcal / mol, -141.056 kcal / mol and-124.091 kcal / mol respectively, so it can be concluded that the adsorption effect of the reagents and organic matter is: DDA < DTAC < DDBAC < ODBC, and therefore the removal efficiency of the collector ODBC on the organic matter in phosphogypsum is the best, and ODBC can be preferentially selected as the collector when the organic matter in phosphogypsum needs to be removed.

[0076] According to the calculation results of the adsorption energy, the removal difficulty of different impurities in the phosphogypsum by the cationic collector can be known. The adsorption energy of DTAC on the (111) surface of hemihydrate gypsum, the (001) surface of apatite, the (101) surface of quartz, the (111) surface of dihydrate gypsum and organic matter is-17.739 kcal / mol, -317.713 kcal / mol, -62.275 kcal / mol, -12.994 kcal / mol and -115.308 kcal / mol, respectively, and thus the collecting effect of DTAC on the mineral phase and organic matter is dihydrate gypsum < hemihydrate gypsum < quartz < organic matter < apatite. The adsorption energy of DDA on the (111) surface of hemihydrate gypsum, the (001) surface of apatite, the (101) surface of quartz, the (111) surface of dihydrate gypsum and organic matter is-17.477 kcal / mol, -135.997 kcal / mol, -20.096 kcal / mol, -11.251 kcal / mol and -91.362 kcal / mol, respectively, and thus the collecting effect of DDA on the mineral phase and organic matter is dihydrate gypsum < hemihydrate gypsum < quartz < organic matter < apatite. The adsorption energy of ODBC on the (111) surface of hemihydrate gypsum, the (001) surface of apatite, the (101) surface of quartz, the (111) surface of dihydrate gypsum and organic matter is-27.825 kcal / mol, -274.225 kcal / mol, -102.228 kcal / mol, -12.701 kcal / mol and -141.056 kcal / mol, respectively, and thus the collecting effect of ODBC on the mineral phase and organic matter is dihydrate gypsum < hemihydrate gypsum < quartz < organic matter < apatite. The adsorption energy of DDBAC on the (111) surface of hemihydrate gypsum, the (001) surface of apatite, the (101) surface of quartz, the (111) surface of dihydrate gypsum and organic matter is-22.156 kcal / mol, -283.942 kcal / mol, -88.131 kcal / mol, -22.101 kcal / mol and -124.091 kcal / mol, respectively, and thus the collecting effect of ODBC on the mineral phase and organic matter is dihydrate gypsum < hemihydrate gypsum < quartz < organic matter < apatite. It can be known from the above results that the adsorption effect of DTAC, DDA, ODBC and DDBAC on the mineral phase and organic matter is dihydrate gypsum < hemihydrate gypsum < quartz < organic matter < apatite, and thus the apatite and organic matter are preferentially removed in the flotation process, followed by the flotation of quartz, and finally the hemihydrate gypsum and dihydrate gypsum are difficult to float, so as to achieve the purpose of reverse flotation.

[0077] The results above show that different collectors have different collection effects on impurities in phosphogypsum. In the phosphogypsum impurity removal process, technicians can use the simulation calculation method provided by this invention to calculate the adsorption energy of the collector and the adsorption of phosphogypsum and its impurities, and thus select a suitable collector.

[0078] Experimental verification

[0079] Reverse flotation experiments were conducted using cationic collectors and phosphogypsum. The phosphogypsum sample used in the experiments was the same as that used in the simulation calculations, both produced by a company in Hubei Province. A 0.5 L single-cell XFD-Ⅳ flotation machine was used for reverse flotation of the phosphogypsum (MIBC dosage maintained at 300 g / t, pH 2.5, solid-liquid ratio S / L 1:4). After flotation, the phosphogypsum concentrate was filtered, washed, and then dried in a 101-2EBS vacuum drying oven at 338 K for 10 h. The whiteness of the dried phosphogypsum concentrate was measured using a YQ-Z-48A whiteness meter. The reverse flotation results of different collectors on phosphogypsum are shown in Table 1.

[0080] Table 1

[0081]

[0082] As shown in Table 1, the flotation effect of the collector on quartz in phosphogypsum is: DDA < DTAC < DDBAC < ODBC, which is consistent with the simulation calculation.

[0083] like Figure 10 As shown, the whiteness of the raw phosphogypsum ore is 29.72% ( Figure 10 a) The whiteness of the phosphogypsum concentrate after DDBAC treatment is 66.74% ( Figure 10 (b) After treatment, the whiteness of the phosphogypsum increased from 29% to 66%, the purity increased from 82% to 97%, the silicon content decreased from 7.17% to 1.1%, and the organic matter content decreased from 0.72% to 0.057%. After reverse flotation, black particles with a diameter of approximately 0.02~0.2 mm remained in the tailings. Analysis of the composition of these black particles revealed the presence of large amounts of quartz, organic matter, and apatite in the flotation tailings. Electron microscopy was performed on the black particles in the tailings, as shown... Figure 11 As shown, quartz in the tailings mainly exists in the form of particles, while apatite exists in the form of a massive structure. Organic matter not only adheres to the surface of apatite, but is also embedded in its internal structure, indicating that the flotation order is apatite > organic matter > quartz, which is consistent with the simulation calculation.

[0084] In summary, the application uses simulation software to build an adsorption model between the collector and the phosphogypsum impurities, and obtains the adsorption energy of different cationic collectors on the surface of specific materials through model calculation, so as to evaluate the adsorption effect of these collectors. In the phosphogypsum impurity removal process, the technical personnel can judge whether it is necessary to select the corresponding collector according to the results obtained by simulation calculation, so as to save the cost, or assist in research and development through simulation calculation. The simulation software is used in the embodiment of the application to calculate the adsorption energy of different cationic collectors and various impurities in the phosphogypsum, the removal efficiency of different collectors for the impurities in the phosphogypsum is predicted by using the calculated adsorption energy, so as to select the most effective collector, and the theoretical prediction result is consistent with the experimental verification result.

[0085] It should be noted that each of the above embodiments belongs to the same inventive concept, and the description of each embodiment has its own emphasis. If not described in detail in an individual embodiment, the description can be referred to in other embodiments.

[0086] The above-described embodiments only express the implementation of the application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which are all within the protection scope of the application. Therefore, the protection scope of the patent of the application should be subject to the appended claims.

Claims

1. A method of screening phosphogypsum flotation collectors, characterized by, The method comprises the following steps: S1. providing a molecular structure of a collector and obtaining a composition of impurities in phosphogypsum; S2. constructing a molecular model of the collector and a unit cell model of the impurities based on the molecular structure of the collector and the composition of the impurities, respectively; S3. performing geometric optimization on the molecular model of the collector and the unit cell model of the impurities to obtain an optimized molecular model of the collector and an optimized unit cell model of the impurities; S4. constructing a unit cell box of the impurities according to the optimized unit cell model of the impurities; S5. constructing an adsorption model between the collector and the impurities based on the optimized molecular model of the collector and the unit cell box of the impurities; S6. performing molecular dynamics simulation calculation on the adsorption model to obtain an adsorption energy between the collector and the impurities; S7. sorting according to the size of the adsorption energy to screen out a collector with better collecting effect. In step S2, the molecular model of the collector and the unit cell model of the impurities are constructed by using Materials Studio software, wherein the unit cell model of the impurities includes a mineral phase unit cell model and an organic matter unit cell model. The mineral phase unit cell model includes a hemihydrate gypsum unit cell model, a quartz unit cell model and an apatite unit cell model; and the organic matter unit cell model is an organic matter polymer amorphous unit cell model. In step S3, the method for performing geometric optimization on the molecular model of the collector includes: using the PBE functional in the Dmol3 module of the Materials Studio software, optimizing the atomic position by the BFGS algorithm, and using the Tkatchenko-Scheffler van der Waals correction method to correct the missing van der Waals interaction in the density functional calculation. When the molecular model of the collector is geometrically optimized, the convergence criteria for the geometric optimization are: maximum displacement 0.05 A, maximum force 0.02 Ha / A, energy 1.0 x 10 -4 -4 Hartree (Ha), and self-consistent field tolerance 2.0 x 10 -6 -4 eV / atom.

2. The method of screening for a phosphogypsum flotation collector according to claim 1, characterized in that, In step S3, the method for performing geometric optimization on the unit cell model of the impurities includes: For mineral phase impurities, based on the density functional theory, using the PBE functional in the Castep module of the Materials Studio software, the plane wave cutoff energy is 400 eV, 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. For organic matter impurities, the Forcite module of the Materials Studio software is used, and the Compass II force field is selected for geometric optimization.

3. The method of screening for a phosphogypsum flotation collector according to claim 2, characterized in that, When the cell model of the mineral phase impurity is geometrically optimized, the convergence criteria for the geometric optimization are: maximum displacement 2.0 x 10 -4 nm, maximum force 0.05 eV / A, maximum stress 0.1 x 10 3 MPa, energy 2.0 x 10 -5 eV / atom, self-consistent field tolerance 2.0 x 10 -6 eV / atom.

4. The method of screening for a phosphogypsum flotation collector according to claim 1, characterized in that, In step S4, the method for constructing the unit cell box of the impurities includes: When the impurity is a mineral phase, the optimized unit cell model of the mineral phase is cut, supercellled 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.

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

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

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