Six kinds of galena with different impurities were synthesized and the effects of impurities on the floatability of galena were investigated. The thermodynamic and kinetic parameters on the galena surface were measured using microcalorimetry, and the adsorption configuration and energy of butyl xanthate on the surfaces of galena with different impurities were simulated by density functional theory. Flotation experiments showed that Ag and Bi significantly promoted the recovery of galena, while Zn, Sb, Mn, and Cu reduced the recovery of the flotation. Microthermokinetic results indicated that the absolute value of xanthate adsorption heat was directly proportional to the flotation recovery of galena. Adsorption heat and reaction rate coefficients of xanthate on galena containing Ag or Bi were larger than those on pure galena, but smaller on galena containing Cu or Sb. Additionally, the relationship between the heat of unsaturated adsorption of xanthate and the adsorption energy of impurity atom on galena surface was investigated.
The electronic structure and properties of FeS2 with the space groups of Pa3 and P1 were studied by the density functional theory. The generalized-gradient approximation exchange-correlation functional was used in conjunction with a plane wave-ultrasoft pseudopotential representation. Calculation results show that differences are observed in electronic structures and properties between Pa3 and P1 crystals. The band gap and energy loss of P1 are smaller than those of Pa3 crystal, while the dielectric constant, conductivity, refractive index, extinction coefficient, and intensity of optical absorption of P1 are larger than those of Pa3. These behaviors are attributed to the differences in symmetry, atomic arrangement, and Mulliken bond population of each unit for Pa3 and P1 crystals.
Pseudo glycolythiourea acid（PGA） was synthesized and used as depressant for flotation separation of Cu and Mo.The results indicate that a low amount of PGA has strong depression effect on chalcopyrite.Mo grade of 26.17% and recovery of 89.83% were achieved with rougher and scavenger one time and cleaners twice,while the recovery of Mo was deceased by 2% when Na2S was used as depressant.Measurement on adsorption of PGA on the mineral surface indicates that PGA and xanthate were adsorbed on mineral surface by competition,and PGA was adsorbed on chalcopyrite surface much stronger than on molybdenite surface.FTIR results indicate a chemical absorption process for PGA on chalcopyrite surface and a physical adsorption process on molybdenite surface.The frontier orbital calculation shows that the S atom is an active center,and the depression of PGA can be explained with the Fermi level of energy based on the electrochemical mechanism.
First-principles calculations are performed to investigate the relaxation and electronic properties of sulfide minerals surfaces(MoS2, Sb2S3, Cu2 S, ZnS, PbS and FeS2) in presence of H2 O molecule. The calculated results show that the structure and electronic properties of sulfide minerals surfaces have been influenced in presence of H2 O molecule. The adsorption of the flotation reagent at the interface of mineral-water would be different from that of mineral surface due to the changes of surface structures and electronic properties caused by H2 O molecule. Hence, the influence of H2 O molecule on the reaction of flotation reagent with sulfide mineral surface will attract more attention.
Adsorption of water on sulfide surfaces and natural floatability of sulfide minerals were studied using density functional theory （DFT） method. All computational models were built in a vacuum environment to eliminate the effects of oxygen and other factors. H2O molecule prefers to stay with pyrite and sphalerite surfaces rather than water, whereas for galena, chalcocite, stibnite, and molybdenite, H2O molecule prefers to stay with water rather than the mineral surfaces. On the other hand, pyrite surface favors N2 more than water, while sphalerite surface cannot adsorb N2. These results show that galena, stibnite, chalcocite, and molybdenite are hydrophobic, while sphalerite is hydrophilic. Although pyrite has certain hydrophilicity, it tends to be aerophilic because the reaction of pyrite with H2O is weaker than pyrite with N2. Thus, pyrite, galena, chalcocite, stibnite and molybdenite all have natural floatability.
Electronic structures of complex mineral jamesonite were studied using density functional theory method together with their flotation behavior. The flotation behavior ofjamesonite is similar to that of stibnite, indicating good floatability at pH below 6 and easy depression with NaOH, especially with lime. In weak alkaline condition, the flotation behavior ofjamesonite is close to that of galena. The coordination structure of Pb for jamesonite is more complex than that for galena. Sb in jamesonite possesses two coordinated modes, whereas Sb of stibnite is only 3-coordinated. Pb in galena is more active than that in jamesonite. Sb （3-coordination） in jamesonite is inactive, in contrast with that in stibnite. However, 4-coordination Sb in jamesonite is more active than 3-coordination Sb. HOMO orbitals of jamesonite and stibnite contain metal atoms, which contribute to the formation of adsorption configuration of CaOH^＋ when there is lime; therefore, jamesonite and stibnite are easily depressed by lime.
The adsorption heat and reaction rate constant of potassium dichromate on the surface of galena were studied. The results indicate that potassium dichromate tends to adsorption on the galena surface. The reaction order is only 0.08385, suggesting that the concentration of potassium dichromate has little influence on its adsorption on the galena surface. In addition, the simulation of CrO2 4- adsorption on the PbS （100） surface in the absence and presence of O2 was carried out by density functional theory （DFT）. The calculated results show that CrO2 4- species adsorb energetically at the Pb-S bond site, and the presence of O2 can enhance this adsorption.
