| In this paper, based on the crystal structure of diaspore and kaolinite, as well as the designing theory of flotation reagents, six tertiary amines collectors were designed and synthesized. By means of micro-flotation tests of pure minerals, the flotation performances of six tertiary amines on diaspore and kaolinite were investigated and figured out. Using the measurements of zeta-potential and FT-IR, the calculations of solution chemistry and quantum chemistry, and the simulations of molecular dynamics, the interaction mechanisms between tertiary amines and minerals, as well as the relationship between performances of collectors and substituent groups in the molecule of amines, were studied and discussed. The main contents were briefly summarized as follow.(1) When being ground to particles, the liberation of diaspore takes place mainly along the (001) crystal planes, breaking Al-O bonds with high energy and stronger hydrophilicity. The liberation of kaolinite takes place along (001) completly, and along (110) and (010) planes incompletely. Besindes the Al-O bonds whit high energy, there are also the Si-O bonds on these liberation surfaces, which also exhibited the strong hydrophilicity. The surface charging mechanism of diaspore and kaolinite is similarly controlled mainly by the ionization of the surface O-H groups, and this part of charge is dominated by the pH of the pulp. In addition, the isomorphic exchange of kaolinite surface ions is responsible for the permanent negative charge of (001) planes. Under the aim of enhancing the collecting power and selectivity of new collecters on kaolinite, based on the basic structure of flotation reagents and surface characteristics of diaspore and kaolinite, N atom was determined to be the bonding atom of the polar group of new collectors; meanwhile, in order to enlarging the inductive effect of N atom, using the dodecyl amine as the matrix, the polar group was determined to be the tertiary amine group (-NR2), and the substituent groups included CH3, C2H5, C3H7 and C7H7.(2) By using aliphatic amines, aldehyde and formic acid as raw materials, two series and six tertiary amines including DRN12, DEN12, DPN12, DBN12, DRN16 and DEN16 were synthesized and prepared in lab by means of reduction and alkylation to primary amine. The synthetic yield of tertiary amines is considerable high, and near all these amines have the purity of more than 80%.(3) Flotation performances of tertiary amines on diaspore and kaolinite showed that the collecting powers of six tertiary amines on diaspore were weak, the recovery maximum were 52%,61%,6% and 62% respectively, when using DRN12, DPN12, DBN12 and DRN16, and were about 78% when using DEN12 and DEN16.When increasing the dosage of tertiary amines, recoveries of diaspore increased a little. Except for the DBN12, the collecting abilities of other tertiary amines on kaolinite were commonly better. The recoveries of kaolinite were almost more than 85% when using these collectors at pH=2-3.5. After increasing the dosage of these amines, recoveries of kaolinite increased gradually; when the concentration of amines was added up to 4×10-4mol/L, the recoveries of kaolinite were almost more than 95% except the DBN12. DRN12, DEN12 and DPN12 have the stronger selectively collecting power on kaolinite than diaspore, the differences of maximum recovery of kaolinite and diaspore(Rkaolinite-Rdiaspore) were 42%,41%和42%. The flotation performances of sery-12 tertiary amines on diaspore and kaolinite follow the same order of DEN12> DPN12> DRN12> DBN12.(4) Based on the calculation of solution chemistry and measurements of FT-IR and zeta potentials, the interaction mechanisms between tertiary amines and diaspore and kaolinite were investigated.The results showed that the interaction mode between collectors and minerals was physics adsorption controlled by electrostatic power. The physics adsorption between collectors and kaolinite was more remarkable, and that between collectors and diaspore was not remarkable enough. After adsorption on minerals, tertiary amines can increase the zeta potentials of diaspore and kaolinite. The changing amounts of potentials from tertiary amines were in the order of DEN>DPN>DRN>DBN. In the acid pulp, the surface of diaspore are mainly the Al-OH, leading to the cation of tertiary amines difficultly to adsorb onto the surface of diaspore; the surface of kaolinite are mainly the Al-OH and Si-OH, but its surface is partly charged negatively because of the isomorphous replacement, leading to the cation of tertiary amines easily to adsorb onto the surface of kaolinite. In the basic pulp, the surface of diaspore are mainly the Al-O, leading to the cation of tertiary amines easily to adsorb on to the surface of diaspore; and the surface of kaolinite are mainly the Al-O and Si-O, leading to the cation of tertiary amines easily to adsorb on the surface of kaolinite; however, because the negative charged kaolinite particles are extremely dispersed in the pulp, and the hydrophobic carbon chain of tertiary amines may be associated together for the hydrophobic power, the flotation recoveries of kaolinite are lower irregularly.(5) Based on the quantum chemistry and molecular dynamics simulation, the relationships between substituents effects and flotation performance were investigated. Being Influenced by the inductive effect of substituent groups, the EHOMO and net charge of N atom of tertiary amines follow the intensity sequence of DPN12>DEN12> DRN12>DBN12; and the positive charge of the head group of tertiary amines follow the same order of DPN12>DEN12> DRN12>DBN12. The space steric effects of the substituent groups in four tertiary amines follow the order of DBN12>DPN12>DEN12> DRN12. The electrostatic forces between four collectors and kaolinite (001) surface are in the order of DEN12>DPN12>DRN12>DBN12. In one word, these two aspects account for an increase in collecting power according to: DEN12>DPN12>DRN12>DBN12.
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