Mineral ethyl xanthate

Fig. 1. Effect of particle size on the flotation recovery of a sulfide mineral. Mineral chalcocite [2112-20-9J, CU2S reagent potassium ethyl xanthate,...

Table 1.2 Products of the interaction of sulphide minerals with potassium ethyl xanthate and the measured rest potential. Potassium ethyl xanthate (6.25 x 10 mol/L at pH = 7) reversible potential for oxidation to dixanthogen is 0.13 V (Allison et al., 1972)...

The influence of pulp potential on the floatability of chalcopyrite is shown in Fig. 4.4 for an initial concentration of 2x 10 mol/L ethyl XMthate and butyl xanthate. The lower flotation potential is -O.IV for KBX and OV for KEX. The hydrophobic entity is usually assumed to be dixanthogen (Allison et al., 1972 Woods, 1991 Wang et al, 1992) by the reaction (1-3). The calculated potential in terms of reaction (1-3), are, however, 0.217 V and 0.177 V, respectively, for ethyl and butyl xanthate oxidation to dixanthogen for a concentration of 2 x lO" mol/L, which corresponds to the region of maximum recovery but not to the lower limiting potential for flotation, indicating that some other surface hydrophobicity to the mineral. Richardson and Walker (1985) considered that ethyl xanthate flotation of chalcopyrite may be induced by the reaction ... 

Janetski et al. (1977) used voltammetry to study the oxidation of pyrite electrode in solution at different pH in the absence and presence of ethyl xanthate to demonstrate that the oxidation of pyrite itself increases as the pH is increased. At high pH condition, the oxidation of pyrite occurs at a potential cathodic to that for xanthate oxidation and hence, only the mineral will be oxidized at the mixed potential and flotation will be depressed. 

The depression by hydrosulphide ion is in a similar manner as hydroxyl depression, i.e. there is a critical pH for each HS ion concentration at a constant xanthate concentration above which no flotation is possible. In the case that the hydrophobic entity is disulphide, the mineral will be depressed when the reaction (3-5a) or (3-6a) occurs before the reaction (1-3). Thus for the pyrite /ethyl xanthate system, pyrite will be depressed if the oxidation reaction (3-5a) takes place prior to the oxidation reaction (4-35). 

Finkelstein, N. P., 1999. Addendum to The activation of sulphide minerals for flotation a review. Inter. J. Miner. Process, 55(4) 283 - 286 Fomasiero, D., Montalti, M., Ralston, J., 1995. Kinetics of adsorption of ethyl xanthate on pyrrhotite in situ UV and infiared spectroscopic studies. Langmuir, 11 467 - 478 Forssberg, K. S. E., Antti, B. M., Palsson, B., 1984. Computer-assisted calculations of thermodynamic equilibria in the chalcopyrite-ethyl xanthate system. In M. J. Jones and R. Oblatt (eds.). Reagents in the Minerals Industry. IMM, Rome, Italy, 251 - 264 Fuerstenau, M. C., Kuhn, M. C., Elgillani, D. A., 1968. The role of dixanthogen in xaomthate flotation ofpyrite. Trans. AIME, 241 437 Fuerstenau, M. C. and Sabacky, B. J., 1981. Inter. J. Miner. Process, 8 79 - 84 Fuerstenau, M. C., Misra, M., Palmer, B. R., Xanthate adsorption on selected sulphides in the presence of oxygen. Inter. J. Miner. Process... 

Miner. Process Extra. Metall. Rev., 2 203 - 234 Hayes, R. A. and Ralston, J., 1988. The collectorless flotation and separation of sulphide minerals by control. Inter. J. Miner. Process, 23 55 - 84 Hepel, T. and Pomianowski, A., 1977. Diagrams of electrochemical equilibria of the system copper-potassium ethyl xanthate-water at 25°C. Int. J. Miner. Process, 4 345 - 361 Heyes, G. W. and Trahar, W. J., 1977. The natural floatability of chalcopyrite. Int. J. Miner. Process, 4 317-344... 

Leppinen, J. 0., Basilio, C. I, Yoon, R. H., 1989. In-situ FTIR study of ethyl xanthate adsorption on sulphide minerals under conditions of controlled potential. Int. J. Miner. Process, 26 259 - 274... 

Pozzo, R. L., Malicsi, A. S., Iwasaki, L, 1988. Pyrite-pryyhotite-grinding media contact and its effect on flotation. Minerals Metallurgical Processing, 5(1) 16-21 Pozzo, R. L., Malicsi, A. S., Iwasaki, I., 1990. Pyrite-pyrrhotite-grinding media contact and its effect on flotation. Minerals Metallurgical Processing, 7(1) 16 - 21 Prestidge, C. A., Thiel, A. G., Ralston, J., Smart, R. S. C., 1994. The interaction of ethyl xanthate with copper (II)—activated zinc sulphide kinetic effects. Colloids Surfece, A. Physicochem. Eng. Aspects, 85 51 - 68... 

Pritzker, M. D. and Yoon, R. H., 1984a. Thermodynamic calculations on sulphide flotation systems I. galena-ethyl xanthate system in the absence of metastable species. Inter. J. Miner. Process, 12 95 - 125... 

Woods, R., 1996. Chemisorption of thiols on metal and metal sulphide. In J. O M Bockris, B. E. Conway, R. E. White (eds.). Modem Aspects of Electrochemistry. 29 401 - 453 Woods, R., Young, C. A., Yoon, R. H., 1990. Ethyl xanthate chemisorption isotherms andEh-pH diagrams for the copper/water/xanthate and chalcocite/water/xanthate systems. Inter. J. Miner. Process, 30 17 - 33... 

Grano, S. R., Prestidge, C. A., and Ralston, J. (1997) Solution interaction of ethyl xanthate and sulfite and its effect on galena flotation and xanthate adsorption, Int. J. Miner. Process., 52(2-3), 161-186. 

A significant development in this regard was the correlation of the solubility products of a series of heavy metal-ethyl xanthate salts with the floatability of corresponding sulfide minerals by (Kakovsky, 1980). He found the decrease in the order of the solubility product of sulfide minerals to be in line with the increase in the order of their floatability. From exchange reactions of lead-diethyl xanthate, the well-known Barsky equation can be derived ... 

Using Eq. (4.42), the pMe -pH diagrams given in Fig. 4.40 can be generated. In this diagram, the horizontal line at the bottom represents the minimum concentration of metallic ions which is necessary for the formation of ethyl xanthate salt the intersection point of horizontal and vertical lines gives the upper pH limit for the mineral flotation. 

Table 4.2 lists the values of rest potential for a few minerals in potassium ethyl xanthate solutions (6.25 X 10 mol/1, pH 7) and infrared identifications of surface reaction products (Allison et al., 1972). Only those minerals such as chalcopyrite and pyrite have surface reaction product of dixanthogen. 

In another technique, a polished surface of the specimen (metal, mineral, etc.) was dipped into a solution containing a radioactive reagent, which selectively reacts with one of the constituents of the surface. A mineral was dipped into potassium ethyl xanthate labeled with (jff" 87.5 d) the xanthate reacted selectively with sphalerite (zinc blende), ZnS, in the sample. The distribution of the xanthate, as shown by the autoradiograph, indicated the ZnS distribution in the mineral. The low j3-energy of 0.2 MeV, was an advantage to... 

Ethyl xanthate Potassium isobutyl xanthate Potassium isopropyl xanthate Sodium n-butyl xanthate Sodium s-butyl xanthate flotation agent, froth minerals Calcium cyanide flotation agent, herbicides Palmitamine... 

Persson et al. [385, 386, 484, 493] performed comparative DRIFTS studies of ethyl xanthate (EX) adsorption on fresh and oxidized natural minerals and sulfur-and metal-rich synthetic CU2S, ZnS, CdS, and PbS following different pretreatments of the absorbents. Only small amounts of Cu(I)EX were found on the... 

Figure 7.27. ATR spectra of pyrite particles after conditioning at two different concentrations of potassium ethyl xanthate (KEX). Reprinted, by permission, from J. O. Leppinen, Int. J. Miner. Process. 30,245 (1990), p. 251, Fig. 4. Copyright 1990 Elsevier Publishers B.V.

ATR on Mineral-Bed Electrodes. ATR at a mineral-bed electrode was employed to study the anodic oxidation of ethyl xanthate (EX) on chalcocite, chalcopyrite, pyrite, and galena [513, 514]. The optical scheme of the SEC cell is shown in Fig. 4.51. Prior to the addition of xanthate to the buffer, the electrode was polarized cathodically in order to remove any oxidation products that are formed during sample preparation. After a polarization period of 15 min at the selected potential, the electrode was pressed against a Ge IRE and the spectrum was measured while applying a potential less than or equal to -l-0.1 V. Otherwise, the spectra were recorded at open-circuit potential (OCP) just after the polarization to avoid corrosion of the Ge IRE. 

Flotation is a method of separating solids Irom streams by creating a froth to which they are attracted. Thus in a slurry circuit, flocculants are added to create a froth rich with the metal concentrate. The trick is to make mineral particles hydrophobic, or water repellant. Flotation involves the selected adsorption of hydrocarbons (e.g., ethyl xanthate) on liberated minerals (e.g., chalcopyrite), which can then be attached to and transported by air bubbles in the slurry to a so-called froth layer and then separated from the hydrophilic (wetted) particles. 

O Dell et extended voltammetry on the ethyl xanthate/chalco-cite system from conventional mineral electrodes to include studies on particle beds. A bed composed of 1.4 g of mineral particles in the size... 

The determination of flotation recovery using particulate sulfide mineral bed electrodes under potential control was refined by Richardson and co-workers and applied to the study of the interaction of ethyl xanthate with a range of sulfide minerals. " " The approach introduced by these authors was to employ relatively large particles (590-840 //m) and to keep the bed under positive pressure during potential conditioning. With this technique, they were able to combine flotation recovery determinations with voltammetry and with UV-vis spectroscopy of the solution phase. 

The Eh-pH diagrams shown in Fig. 29 portray the region of chemisorption as extending nearly 0.3 V below the stability zone of copper(I) xanthate. At high Eh values, chalcocite is oxidized to copper sulfides of progressively lower copper content. Chemisorbed xanthate will not coexist with these sulfides when CuO is formed since the oxide is expected to overlay the surface of the mineral. This implies that there is an upper potential limit to flotation of chalcocite with ethyl xanthate, and such behavior has been established for this system. ... 

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