Understanding the relationship between the structure of the collector and the flotation performance is very important for exploring the flotation mechanism, guiding the design and synthesizing the new collector. This is an important direction for people to study the mechanism of flotation and flotation.
Hu Yuehua et al. applied molecular orbital theory and energy band theory to the research of sulfide ore flotation mechanism. It was found that the valence band and conduction band energy level in the surface electronic structure of sulfide minerals affect the final surface product form, and the frontier orbit of the drug molecule determines the drug selection. One of the key factors of sex.
Sun Wei et al., The relevant parameters as the frontier orbital selected depending brass ore collector to provide a new standard for the screening agent. The density functional theory is used to calculate the properties of the frontier orbit of the chalcopyrite collector—the highest occupied molecular orbital (HOMO) energy, the HO-M0 shape, and the HOMO density of the constituent atoms of the agent. The results show that the three parameters can be combined to evaluate the selectivity of the chalcopyrite collector.
Liu Guangyi et al. used the generalized emblem theory and density functional theory to analyze the mechanism of preferential copper selection in the medium-weak alkaline conditions of the new copper-selective collector (ECTC, etc.). Xu Bin's research on the geometry of collectors found that in terms of the bond length of the covalent bond of the carbonyl sulfide atom, the selectivity of copper capture by Dinghuang is not as good as that of N-ethyl-N'-isopropyloxycarbonyl sulfide. Urea (EICTU) and Z-200; in addition, the size of the dihedral angle is known as -NC(=S)-NC(=O)-O- of EICTU, -NC(=S)-O- of Z-200, The -OC(=S)-S-functional group of Dinghuang is easy to form a conjugate large π. It is calculated by quantum chemistry that the pyridyl benzothiazole (MBT) is more stable in the form of thioketone molecules. The nitrogen atom and the sulfur atom outside the five-membered ring have a negative Mulliken charge, and the electron-donating ability is strong. The Mulliken charge in the sulfur atom in the elementary ring is positive, and the electron donating ability is weak. Therefore, the reactive sites on the thione molecule are a nitrogen atom and an extra-ring sulfur atom.
H.Yekeler used the density functional first principle to study the quantitative properties of three mercaptobenzothiazoles (MBT). The activity of the drug molecule is determined by the HOMO position, HOMO energy, atomic Mulliken charge population and electrostatic potential. The nature is a good explanation of the capture performance of the three agents. B.Bag used quantum chemical calculation to study the interaction between ethyl xanthate, propyl ketone, isopropanol, isobutyl xanthate, pentoxanthin and copper ions, through total interaction energy, highest occupied orbital energy, charge density, Quantitative parameter analysis such as binding energy and dipole motion showed that the pentoxanthin was most likely to interact with copper ions and was consistent with the experimental results. Hailstörm studied the molecular structures of ethyl, heptyl sodium and potassium xanthate. It was found that using the local density approximation (LDA) function under density functional theory, the molecular optimization structure is closest to the experimental value.
2 Mechanism of action of minerals and agents
The mode of action of the agent on the mineral surface can be generally divided into the following categories:
(1) Molecular adsorption. It refers to the adsorption of the collector in the form of molecules on the surface of the mineral. Such oxidized ore collectors mainly include carboxylic acids, amines, etc. The molecular adsorption mainly depends on the hydrolysis of the agent in water to form weak base or weak acid molecules, and the hydrolyzed agents are adsorbed on the mineral surface by van der Waals force.
(2) Chemical adsorption. The chemisorption mechanism considers that the characteristic groups of the collector ions or molecules are bonded to the electrons of the ions, atoms or molecules on the surface of the mineral to form an alignment. It is characterized by high energy (about 1 electron/mol), or high adsorption heat (tens of kilojoules/mole), small distance between adsorbed molecules and mineral surface, electron relationship between chemical molecules and minerals, and adsorption force. Essentially chemical. Chemical adsorption is generally selective, the adsorption is relatively strong, and it is not easy to desorb, and the adsorption amount generally increases with increasing temperature (within a certain range).
(3) Surface chemical reaction. That is, chemisorption is further developed, and chemical reactions often occur on the surface of minerals. The main difference between surface chemical reaction and chemical adsorption is that the former reaction product constitutes an independent phase on the surface.
(4) Exchange adsorption of ions of the same name. This concept evolved from the ion exchange model proposed by Wacker and Kirks, mainly to show that the agent acts as an ion in the slurry and competes with the 0H - in the water to determine the flotation process. no.
(5) Adsorption of the reaction product of the agent on the mineral surface or in the slurry. Studies have found that the effects of flotation agents and mineral surfaces are not as simple as discussed above, not only the original components of the agent interact with the mineral itself, but in most cases also include a complex series of reactions. For example, minerals react with air components, react with oxygen in the pulp and various inevitable components to change the surface of the minerals; when flotation agents interact with minerals, they also include many side reactions, redox reactions, catalytic reactions, and minerals. Various types of reactions at different locations and at different stages of the surface.
(6) Double layer adsorption. The theory of electric double layer adsorption suggests that the cation layer and the anion layer are formed after the mineral-water interface is charged in the slurry system. The Stern double layer theory is widely accepted. In this adsorption model, when the concentration of the collector is low, it is adsorbed in a single ion state, and when the concentration is high, it is adsorbed in a semi-micelle state, and a part of the undissociated molecules are dependent on the van der Waals force between the intermetallic and non-polar groups. The collector ions are co-adsorbed on the surface of the mineral; when the collector has a large hydrocarbon chain, a strong interchain effect, or a chemical affinity between the polar group and the mineral, that is, when there is a so-called characteristic adsorption force, not only Adsorption in the dense layer, and the amount of adsorption can be large enough to exceed the opposite charge of the inner layer, thereby strongly changing the magnitude of the potential, causing a change in the surface charge sign.
3 Research methods for the effects of flotation reagents and mineral surfaces
There are many researches on the mechanism of action of minerals and agents, but most of them are studied by isothermal adsorption curve, potentiodynamic potential, contact angle, infrared spectrum, x-ray photoelectron spectroscopy, fluorescent probe, atomic force microscopy and other methods. None of the above methods can perform a complete real-time measurement of the entire process of adsorption of the agent on the mineral surface. Quartz crystal microbalance QCM-D agent may be adsorbed on the mineral surface measured embodiments the whole process, and the piezoelectric effect as a high-precision mass measurement technique in the measurement accuracy can be achieved QCM-D nanoscale. It not only can obtain the mass change and thickness change of the surface adsorption film, but also can obtain the viscoelastic property of the adsorption film and can presume the structural characteristics of the adsorption film, thereby obtaining the action adsorption mechanism and law of the drug. The results of Qi et al. show that QCM-D has more accurate and obvious determination of the adsorption difference of different amine collectors on the quartz surface than Zeta potential, so it has important reference value for studying the adsorption mechanism of flotation reagents.
Gao Zhiyong observed and studied the microscopic morphology of the common exposed faces of three calcium-containing mineral crystals by atomic force microscopy (AFM), and discussed the cleavage properties and dissolution behavior of the crystal faces. The wettability of the common exposed faces of the three calcium-containing mineral crystals was then investigated by contact angle measurement using three probes of liquid distilled water, formamide, and diiodomethane . By means of the fitting calculation method of several surface energies such as geometric mean equation, the surface free energy of common exposed surface is obtained, and the relationship between surface free energy and its component and surface chain bond properties is analyzed.
In recent years, quantum chemical calculation methods and dynamic simulation methods have been introduced to better understand the flotation and flotation mechanism. Wang et al., Molecular collector by performing molecular dynamics simulation found, mineral cleavage plane acts CPC cation molybdenum oxide {100}, {010} apatite adsorption capacity of the surface are 448.86kJ / mol and response 420.16kJ/mol, indicating that CPC cations are more likely to adsorb with molybdenum oxide particles. Guo Jingnan et al. Molecular dynamics simulation of molecular interaction with a diaspore and kaolinite, results show that the drug molecules with a crystallographic plane diaspore practice closely.
Andrw Hungl calculated characteristic structure and properties of the methyl xanthate ion, and studied it in Fes 2 {100} and {111} plane of the adsorption behavior, and easily results show that methyl xanthate pyrite {100} plane The tetracoordinate iron atom and the bridge sulfur atom on the {111} surface act, and the xanthate will chemically adsorb on the surface of the pyrite containing defects. Xu Bin by S- benzyl ester -N- ethoxycarbonyl diltiazem (BITCM) Molecular modeling studies of the mineral surface adsorption discovery: by adsorption can be seen comparing, BITCM molecule {100} plane in the galena, sphalerite The most stable adsorption configuration on the {110} surface of the ore and the {100} surface of pyrite is the simultaneous adsorption of carbonyl sulfide and carbonyl oxygen, and the adsorption of BITCM on the surface of galena is the most likely to occur.
Comprehensive diagnostic infrared reflection technology can intuitively measure the type and quantity of particles adsorbed on the mineral surface. When pyrite is in contact with sphalerite, the adsorption of xanthate on the surface of pyrite is completely inhibited, and the formation of lead xanthate on the surface of sphalerite is more than layer structure. When pyrite is in contact with chalcopyrite, the formation of the xanthate on the surface of the pyrite is inhibited, and the amount of the xanthate on the surface of the chalcopyrite is increased by a factor of 2.5.
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