| Coal is the main energy in China and plays a leading role in the energy consumption system;China’s steam coal consumption accounts for more than 70%of the total coal consumption,which is the largest coal in China.Among them,lignite,long-flame coal and other low-grade coals account for about 40%of the discovered coal resources.Fine slime with a yield of about 10%or higher can be obtained after raw coal separation.Flotation is a more effective and economic technology for slime separation.However,due to the strong surface hydrophilicity of low-rank coal and the poor flotation effect of conventional collectors,the flotation and upgrading of low-rank slime has become a difficult problem in the field of mineral processing.In this paper,the flotation recovery and selectivity index are used as evaluation indicators,and the molecular structure descriptors of eight amine collectors are obtained by molecular simulation and experiment.The QSAR model between the molecular structure descriptors of collectors and the flotation recovery and selectivity index is established by genetic algorithm,forming the design and screening method of coal slime reverse flotation collectors.The research results have important guiding value for the design and synthesis of mining collectors.The quantum chemical calculation results of amine collectors show that the introduction of substituents in the dodecylamine group can increase the Connolly surface area of the collector molecule and the solvent contact surface area.The positive charge of each agent is mainly concentrated in the hydrophilic head group.After introducing substituents in the head group,the positive charge of the head group increases significantly.The LUMO orbital of the reagent molecule is mainly concentrated in the head group,while the HOMO orbital is distributed in the carbon chain.The LUMO orbital of the reagent is more likely to interact with the HOMO orbital of kaolinite.The introduction of nonpolar methyl in the head group of dodecylamine can not improve the dipole moment and electronegativity of the molecule.The introduction of polar functional groups such as ammonium group and oxygen atom can significantly enhance the dipole moment and electronegativity of the drug molecule.The DFT study of kaolinite surface adsorption showed that the H atom in the collector head group interacted with the O atom on the 001 surface of kaolinite.The introduction of oxygen atom in the head group could increase the interaction with the hydrogen atom on the 001 surface of kaolinite,but could not increase the interaction with the 001~—surface of kaolinite.The results of differential charge density show that the electron aggregation region is mainly located near the N atom of the collector head group,and the region between the collector head group and the surface of kaolinite,while the electron consumption is mainly located near the O atom of the surface of kaolinite,and near the H atom in the collector head group;The adsorption strength of the collector on the 001 surface of kaolinite is greater than that on the 001~—surface of kaolinite.The molecular dynamics study on the adsorption of collectors on the surface of kaolinite shows that the collectors 1227,1635,1432,1841 and 1738 can be adsorbed on the 001 surface of kaolinite under vacuum environment,while the collectors 1431,1534 and 2138 can not be adsorbed on the 001 surface of kaolinite.However,in the water environment,the 8 kinds of collectors can not be adsorbed on the 001 side of kaolinite,but can be adsorbed on the 001~—side of kaolinite.The order from strong to weak of the eight collectors on the water molecules on the surface of kaolinite is:1738>2138>1534>1431>1432>1841>1635>1227.The effective collectors 1738,2138and 1534 are the molecules with more branched chains in the head base and larger space volume of the head base.The flotation test results of single minerals of kaolinite and clean coal show that the flotation effect of four collectors with larger head base size,2138,1738,1841 and1534,is significantly better than the other four collectors with smaller head base size.The flotation results of single minerals of kaolinite are in good agreement with the previous molecular simulation results.Combined with the flotation results of the collector on kaolinite,2138 has the strongest flotation capacity for kaolinite and the weak flotation capacity for clean coal.Selecting 2138 collector can obtain the highest flotation efficiency.The quantitative structure-activity relationship between collector molecules and flotation performance shows that the linear model fitted by the Genetic Function Approximation method is more concise and accurate.Based on the existing flotation theory,the rationality analysis of the model found that the HOMO energy of the collector molecule,its own orbital energy difference,dipole moment and octanol-water partition coefficient have a significant impact on the flotation recovery of kaolinite.The solvent contactable surface of the collector molecule,the number of rotatable bonds,the octanol-water partition coefficient and the topological parameter Subgraph counts(0)have a significant impact on the selectivity index.The model is more practical and can provide a reference for the design of molecular structure of coal slime reverse flotation collectors in the future.Figure[28]Table[18]Reference[96]... |
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