Xanthate system

Thiuram accelerators break down into the corresponding dithiocarbamate before becoming active. There is thus a delay in the onset of vulcanisation. Thiurams can be used over a wide range of sulphur systems. They can behave as system activators when used in combination with thiazoles, whilst acting as retarders for dithiocarbamate and xanthate systems. 

Silver oxide lead ores have much different flotation processing characteristics. Although this ore responds to sulphidization-xanthate system, silver recovery in the lead concentrate was usually poor and amounted to about 30 40%. Floatability of lead minerals also was not satisfactory. 

Abstract In the beginning, the mixed potential model, which is generally used to explain the adsorption of collectors on the sulphide minerals, is illustrated. And the collector flotation of several kinds of minerals such as copper sulphide minerals, lead sulphide minerals, zinc sulphide minerals and iron sulphide minerals is discussed in the aspect of pulp potential and the nature of hydrophobic entity is concluded from the dependence of flotation on pulp potential. In the following section, the electrochemical phase diagrams for butyl xanthate/water system and chalcocite/oxygen/xanthate system are all demonstrated from which some useful information about the hydrophobic species are obtained. And some instrumental methods including UV analysis, FTIR analysis and XPS analysis can also be used to investigated sulphide mineral-thio-collector sytem. And some examples about that are listed in the last part of this chapter. 

For the galena/ethyl xanthate system critical pH determined by Eqs. (2-22) and (4-12b) is... 

Therefore, the critical pH of hydroxyl depression of pyrite and galena could be calculated using Eqs. (5-4) to (5-8) or Eqs. (5-9) to (5-11). The results are given in Fig. 5.1 for the diethyl dithiophosphate system and in Fig. 5.2 for the ethyl xanthate system. Also shown in the same figures are the so-called contact curves (solid lines) from Sutherland and Wark (1955). The dashed lines are the calculated... 

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). 

For the galena/ethyl xanthate system, if the reaction Eq. (3-5a) occurs before the reaction (4-12a), the critical pH condition determined by the reaction Eqs. (3-5b) and (4-12a) is... 

Figure 7.12 is the EIS of pyrite under different xanthate concentration. Figure 7.12 exhibits two capacitive reactance loops existing in the pyrite-xanthate system... 

Baldauf, H. and Schubert, H., 1980. Fine Particles Processing, 1(39) 767 - 786 Ball, B. and Richard, R. S., 1976. The chemistry of pyrite flotation and depression. In Flotation, A. M. Gaudin Memorial volume, M. C. Fuerstanau(eds.), AIME, Inc., 1 458 - 484 Basiollio, C., Pritzker, M. D., Yoon, R. H., 1985. Thermodynamics, electrochemistry and flotation of the chalcocite-potassium ethyl xanthate system. SME-AIME Annual Meeting, New York, Preprint No. 85 - 86... 

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... 

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... 

Trahar, W. J., Senior, G. D., Heyes, G. W., Creed, M. D., 1997. The activation of sphalerite by lead—a flotation perspective. Inter. J. Miner. Process, 49 121 - 148 Usui, A. H. and Tolun, R., 1974. Electrochemical study of the pyrite-oxygen-xanthate system. Inter. J. Miner. Process, 1 135 - 140... 

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... 

Naklicki, M.L. et al.. Flotation and surface analysis of the nickel(II) oxide/amyl xanthate system, Int. J. Miner. Process., 65, 73, 2002. 

For galena-ethyl xanthate system, the reaction constants are ... 

Table 1 summarizes some representative solvents or solvent systems for cellulose. The xanthate system has been used for a longtime to make viscose rayon and sponge. However, rayon production, where H2S is released to varying amounts during the recovery system of spent solvent, is shrinking because of environmental issues. On the other hand, cellulose is soluble in aqueous NaOH alone under limited conditions. Microcrystalline cellulose with DP 200—300 is soluble in 6—9% NaOH by freezing and defrosting procedures. Pretreatments of cellulose such as steam explosion are necessary for complete dissolution in the aqueous NaOH for normal bleached wood pulp and cotton linters with DP of more than 500. ... 

Complementary to the traditional xanthate system used to make viscose rayon, films, and sponges, or the use of aqueous NaOH to dissolve cellulose under limited conditions, many nonaqueous solvent systems for cellulose have subsequently been developed. Apart from trifluoroacetic acid, which is the only volatile solvent known for cellulose, the others consist of reagents that react with the hydroxyl groups of cellulose in a polar aprotic solvent, such as dimethyl sulfoxide or A,A-dimethylacet-amide (DMAC). 

The XPS study of the galena/butyl xanthate system included investigations of surfaces treated under potential control. This approach more precisely defines the chemisorbed and metal xanthate states. At underpotentials to lead xanthate formation, the S(2p) spectrum displayed an additional doublet shifted by 1.5 eV from that of the substrate (Fig. 22) and no shifted Pb(4/) component. After the potential was held above the reversible value of the PbS/Pb(C4H90CS2)2 couple, two additional doublets were evident in the S(2p) spectrum, shifted by 1.35 and 1.8 eV (Fig. 22), as well as a Pb(4f) component shifted by -1 eV. The two additional S(2p) doublets were assigned to chemisorbed xanthate and lead xanthate, respectively. 

Figure 29. Eh-pH diagrams for the chalcocite/water/ethyl xanthate system for an initial xanthate concentration of 10 mol dm (A) and 10 mol dm (B). Sulfur-oxygen anions are not considered. Species designated Cu2.j(S cover the same range of stoichiometries...

---