Mainly used xanthate flotation of sulfide minerals ferrous metal, non-ferrous metals advanced xanthate flotation of oxide minerals can also be used. The mechanism of the action of xanthate and non-ferrous metal sulfides has been a long-standing problem. People have learned through practice and then re-recognize it. They have a certain understanding of Huangji’s harvester Gao Li, and selected some arguments. as follows.
(1) Chemical hypothesis
This argument is that xanthate can form insoluble xanthate precipitates with many metal cations. The cations on the mineral surface react with the xanthate to adsorb on the mineral surface. The hydrocarbon base of the xanthate is oriented outward, making the ore particles hydrophobic and floating. . Indeed, this hypothesis can explain some of the problems, the less soluble the xanthate, the better the flotation effect.
The solubility product of certain metal sulfides and xanthogenates
Metal cation | Ethyl xanthate | Sulfide |
Hg 2+ Ag + Bi 3+ Cu + Pb 2+ Sb 3+ Sn 2+ Cd 2+ Co 2+ Ni 2+ Zn 2+ Fe 2+ Mn 2+ Cu 2+ | 1.15×10 -38 0.85×10 -18 1.2×10 -31 5.2×10 -20 1.7×10 -17 ~×10 -15 ~×10 -14 2.6×10 -14 6×10 -13 1.4×10 -12 4.9×10 -9 0.8×10 -8 <10 -2 2×10 -14 | 1×10 -52 1×10 -49 - 10 -38 to 10 -44 1×10 -29 - - 3.6×10 -29 - 1.4×10 -24 1.2×10 -23 - 1.4×10 -15 1×10 -36 |
It can be seen from Table 1 that the solution product of the metal sulfide is much smaller than the solubility product of the corresponding xanthate, so it is impossible to form a precipitate of xanthate, that is, the chemical hypothesis cannot Explain this question. Since the hypothesis that chemical and thus a natural mineral surface more or less oxidized, the surface of said oxidation products may settle and xanthate xanthate generated, for example, galena basic medium or in acidic medium (NaHCO 3 or Na 2 CO 3 ) Lu will produce PbSO 4 or PbCO 3 , and the latter will react with the yellow drug to form a chemical reaction to produce lead xanthate:
Therefore, the mechanism of action of xanthate and mineral surface is considered to be that the xanthate ion reacts chemically with the surface of the oxidized sulfide ore, forming an insoluble xanthate film covering the surface, showing hydrophobicity and floating; if this statement is Yes, it is assumed that the natural lead (PbSO 4 ), white lead (PbSO 3 ) and other oxidized ore should be easier to float than the sulfide ore, but the opposite is true, but it is much more difficult to float. The chemical hypothesis cannot explain these topics. [next]
(2) Semi-oxidation hypothesis The semi-oxidation hypothesis is that PbSO 4 is formed on the surface of completely oxidized sulfide ore. Its solubility is higher than that of lead, and it is easily dissolved on the surface of the ore. Therefore, it is impossible to form lead xanthate. It is strongly bonded to the ore particles, so PbSO 4 or transition-oxidized PbS are difficult to float directly with xanthate; however, the surface is slightly oxidized by sulfide ore, and the surface of the sulfide ore is slightly oxidized to a close lattice. The combined sulfide-sulfate combination, the xanthate anion and the combination act to fix on the surface of the ore particles, making the ore particles hydrophobic and floating.
The semi-oxidation hypothesis complements the deficiencies of the chemical hypothesis.
(3) Moderate oxidation of sulfide surface is an important condition for flotation
Under normal pressure, one liter of water dissolves up to 9 ml of oxygen. The fresh surface of the sulfide mineral, whether in the air or in the water, is inevitably oxidized by contact with oxygen. The oxidation of the surface of the sulfide mineral and its buoyancy have been affected. For many years, the current consensus is that moderate oxidation of sulfide minerals is one of the important conditions for flotation. Here are some representative arguments.
1. The study of the surface oxidation of the other side lead ore shows that the oxidation process is divided into four stages. The first is to induce it. At this time, the oxygen molecules dissolved in the slurry rapidly adsorb to the surface of the galena, capturing electrons from the surface, causing surface cavities, and making the surface of the galena electrically n-type (electronically conductive) to P Type (hole conduction type) conversion; the second is the acceleration period, when the surface begins to form PbS 2 O 3 or PbSO 4 ; the third is the oxidation period at a fixed speed; the fourth is because the surface forms a separate phase of the oxide layer, Prevent further oxidation.
2. Another part of the research results show that when galena is treated with oxygen or oxidant, oxygen molecules are adsorbed on the surface of the mineral. Because of its strong affinity for electrons, the electrons are taken from the surface to increase the concentration of holes. O 2 is sufficient to convert the surface inversion, that is, the electron conduction into a hole conduction type. The xanthate anion can smoothly adsorb the anode region (ie, the empty space) on the surface of the ore particles, and the valence electrons on the anion are transferred to the positive charge center of the mineral surface to form a strong chemical bond.
3. By measuring the electrode potential (electrochemical potential) of the mineral and the differential capacitance of the surface electric double layer, the surface inversion theory is further linked with the electrochemical potential of the mineral, and it is found that in the oxygen-containing solution, the galena, the supply Hu electric potential than zinc ore in the oxygen-free solution of high concentration that this is a result of increased surface of the hole. The increase of electrochemical potential is of great significance for the oxidation of xanthate anion on the mineral surface to xanthate, and it is the main basis for explaining the mechanism of action of the agent and mineral surface.
4. The chemical mechanism of oxidation was studied, and the surface was oxidized by the other lead ore and sphalerite. Measurement and analysis of the amount of precipitation, the amount of oxygen adsorbed, and the change in the pH of the slurry found that in the anaerobic pulp, the mineral surface was essentially absent. Precipitate; when there is oxygen Precipitating, and when the oxygen content is 20% of its saturation value, The amount of precipitation is the largest. Furthermore, it was found that the lower the PH value, The more precipitation, the higher the oxygen content in the pulp, the higher the pH. Therefore, the reaction mechanism of the initial oxidation of mineral surface is proposed:
Measurement and analysis of the amount of precipitation, the amount of oxygen adsorbed, and the change in the pH of the slurry found that in the anaerobic pulp, the mineral surface was essentially absent. Precipitate; when there is oxygen Precipitating, and when the oxygen content is 20% of its saturation value, The amount of precipitation is the largest. Furthermore, it was found that the lower the PH value, The more precipitation, the higher the oxygen content in the pulp, the higher the pH. Therefore, the reaction mechanism of the initial oxidation of mineral surface is proposed: [next] (4) shows that oxidation causes changes in the surface electronic state, and at the same time, if the pH is not large, it will precipitate on the mineral surface. ,
The precipitation and its role as a surface hydrophobicity have often been overlooked in the past.
, The precipitation and its role as a surface hydrophobicity have often been overlooked in the past. The formula (4) shows that when the oxidation of sulfide minerals such as galena and the pH of the pulp are less than 6.5, the sulphur-oxygen ions formed by oxidation begin to prevent the adsorption of xanthate; when PH<3, the decomposition of xanthate (half-life is only 5.5) ). On the other hand, when PH>10～11, the surface of galena will form lead-acid ions and dissolve, and it is impossible to float at the concentration of common xanthate (10 -5 ~ 10 -4 mol / liter).
(4) Exchange adsorption theory
According to the exchange adsorption slang, the adsorption of xanthate on the surface of sulfide minerals is mainly ion exchange adsorption, that is, the oxidation products of mineral surface, such as thiosulfate, basic thiosulfate and the exchange of yellow anion (X - ). The above adsorption follows the principle of solubility product, and the adsorption product is a surface hydrophobic layer of xanthate or a basic metal salt. For example, the generated surface of galena xanthate lead, iron ore generated in the surface of the yellow [Fe (OH) 2 X] , CuX 2, etc. generated in the surface of the copper minerals. This view is really the development of the chemical hypothesis. This view denies that xanthate is oxidized in aqueous solution in the form of a bismuth to form a xanthate (X 2 ):
1
2X - + ——O 2 +H 2 O —→ X 2 +2OH -
2
At the same time, they deny the earlier recognized reactions from the thermodynamic point of view and through the study of electron paramagnetic resonance spectroscopy:
2CuX 2 —→ 2CuX+X 2
It is believed that since there is no X 2 production in both the mineral surface and the aqueous solution, it is clear that X 2 is not necessary for the hydrophobicity of the mineral surface.
(5) A total of the attached
In recent years, the propensity of propensity is the adsorption of ion exchange adsorption and the adsorption of double xanthate molecules. This view points out that the adsorption layer of the collector on the mineral surface is composed of chemical adsorption products (such as MeX, Me + is a metal ion). , X - is xanthate) and physically adsorbed X 2 grade. Taking pyrite as an example, when PH=4～5, the maximum adsorption amount of X 2 can account for 45% of the total adsorption amount of xanthate, and it is pointed out that in order to ensure galena, chalcopyrite, and yellow iron The effective flotation of the ore, molecular adsorption (ie, X 2 adsorption) should account for at least 10 to 36% of the adsorption amount. It has been determined that the surface of the galena is in a wide range of pH values ​​(4 to 12), and the X 2 is average. As an adsorption layer, the total amount is about 50%. It has also been pointed out that when the ratio of X- to X 2 molar (ion) is 3:1 in the co-adsorbed layer on the surface of galena, the galena flotation is the best.
Per capita views of co-adsorption emphasize the catalytic effect of metal ions and mineral surfaces on X - oxidation. It is believed that the catalytic effect of sulfide ore on X - oxidation is manifested in a wide range of pH values, except for galena, other sulfide minerals. The adsorption properties of xanthate depend on their ability to oxidize xanthate.
(6) The mechanism of action of xanthate varies with mineral properties
A large number of studies on the effects of sixteen different sulfide minerals and 1- 6 carbonaceous drugs have been reported, and several excerpts are listed in Table 2.
The product of the action of several sulfide minerals and xanthate
Drug | Mineral | ||||||||||||
Sphalerite | Glow mine (1) | Glow mine (2) | cinnabar | Galena | Copper ore | Copper ore | Tonglan | Pyrite | Pyrrhotite | Arsenic pyrite | Molybdenite | Chalcopyrite | |
Product | |||||||||||||
Xanthate Ding Huang Yao Elevant | 0 0 0 | 0 0 0 | MeX MeX MeX | 0 0 0 | MeX MeX MeX | 0 MeX MeX | 0 MeX MeX | X2 X2+MeX X2+MeX | X2 X2 X2 | X2 X2 X2 | X2 X2 X2 | X2+? X2+? X2+? | X2 X2 Multifunctional Comprehensive Trainer
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