| Mineral flotation is one of the most important beneficiation methods, and the application of flotation reagent is the key to successful flotation, so the research on efficient and environmental friendly flotation reagents has an important significance. In this paper, pyrite, which is one of the typical sulfide minerals and andalusite,which is a silicate mineral and their flotation collectors methyl benzyl xanthate and alkyl hydroxamic acid was studied based on Density functional theory. The main results and conclusions are as follows:(1) Molecular design of methyl benzyl xanthate derivatives. Through checking, GGA-PBE was selected as exchange-correlation function and a cutoff energy of 267 e V was used for all calculation, the simulation results are agree with the experimental results. The band gap of pyrite is 0.954, Mulliken charge distributions indicate that Fe with-0.170 e negative charge, S with 0.090 e positive charge in the bulk, while Fe with 0.070 e positive charge, S with 0.100 e negative charge in pyrite(100) surface; The partial density of states of Fe(3d) in pyrite surface shift to the low energy and a new state density peak emerges near the Fermi level in the conduction band; Two S atoms of methyl benzyl xanthate near to the surface of Fe atoms, the distance of Fe and S is 2.256? and 2.359? respectively; fifteen new kinds of methyl benzyl xanthate derivatives were designed, and eight of them whose ability of collect had been improved, the maximum improvement is 18.00% and the lowest is 3.58%.(2) The quantitative calculation of electronic structure of andalusite. Through assessment, GGA-PW91 was chosed as exchange-correlation function and k point sampling densities was chosed as 4 × 4 × 5 and 410 e V was chosed as cutoff energy, the calculated lattice constants and atomic fraction coordinate of andalusite are in good agreement with the experimental values; The simulation results showed that less influence of pressure on the structure of andalusite and the ionicity of Al-O bond stronger than the Si-O bond in andalusite, when the bonds were broken, the surface will have more Al ions. After andalusite(001) surface relaxation, Al atoms are not directly exposed to the surface.(3) The quantitative calculation of property of alkyl hydroxamic acid. The reaction active region and the active center of hydroxamic acid molecule was studied by using DFT/B3 LYP method, and the DNP group. The results showed that-CONHOH was the reactive region of the anion and neutral molecule, the two oxygen atoms charged more negative charges than other atoms, and hense became their chemical reactivity center. The two O atoms carried more charges in anion molecule than in neutral molecule.(4) The mechanism for alkyl hydroxamic acid interacted with andalusite and molecular design of alkyl hydroxamic acid derivatives. The two O atoms in the alkyl hydroxamic acid ions interacted with the Al atom in the andalusite surface forming five-member ring.Increaseing polar groups in collector of hydroxamic acids may form multi-member ring chelate, which may enhance agent’s affinity curable, and hense the stability of the adsorption system would be strengthened. The octyl hydroxamic acid molecules were implanted –OH,-C(O)NH2 and-C(O)NHOH respectively, the computation results showed that after-C(O)NHOH and-C(O)NH2 implantated, the collectors’ collecting capacity had been significantly improved, and the optimal hydrophobic carbon chain length of the former is 10, while the most suitable straight-chain length of the latter ranges from 5 to 10, which is determined by hydrophilic- hydrophobic balance.Based on the analysis above, when the DFT method is applied to mineral flotation, it can be helpful for the profound understanding on mineral flotation separation process, thus, it could provide a theoretical basis for the production and development of novel technology and agents. |
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