Zinc xanthate

The flotation of sphalerite, the sulfidic mineral source of zinc, is next considered as an example to illustrate the role of activators. This mineral is not satisfactorily floated solely by the addition of the xanthate collector. This is due to the fact that the collector products formed, such as zinc xanthate, are soluble in water, and so do not furnish a hydrophobic film around the mineral particles. It is necessary to add copper sulfate which acts as an... 

Assuming the concentration of all dissolved species to be lO mol/L, the reaction potential are 0.37 V and 0.32 V respectively, corresponding to reactions (4-33) and (4-34) and the oxidation peak potential in Fig. 4.18. Therefore the upper limit potential of flotation of sphalerite may depend on reaction (4-33) or (4-34), i.e. the decomposition of zinc xanthate and the formation of zinc hydroxide or oxy-zinc species. 

However, the decomposition potential of zinc xanthate into dixanthogen is above 0.3 V according to reactions (4-33) or (4-34) and the upper potential limit of flotation of marmatite extends to 620 mV, which indicates the coexistence of dixanthogen on marmatite in this condition. The difference of flotation behavior and hydrophobic entity between sphalerite and marmatite may be due to the existence of iron in marmatite. 

Figure 4.41 presents the FTIR reflection spectra of ethyl xanthate adsorption on marmatite at different pH. The characteristic absorption peaks 1210, 1108, 1025 cm occurred. It has been reported that the characteristic absorption bands of dixanthogen are 1260, 1240, 1020 and 1105 cm and those bands of zinc xanthate are 1030, 1125 and 1212 cm (Mielezarski, 1986 Leppinen, 1990). It is derived from Fig.4.41 that there may exist the mixture of dixanthogen and zinc xanthate because both distinct peaks of dixanthogen and xanthate salt appeares in Fig. 4.41, which further confirms the results from the UV analysis in Fig. 4.36 and Fig. 4.37. It can also be seen from Fig. 4.41 that the intensity of the IR peaks is strong indicating the stronger adsorption of xanthate on marmatite accounting for its good floatability in weak pH media. When pH increased above 7, only a very weak peak appeared in the spectra indicating very weak or no adsorption of xanthate on marmatite accounting for its very poor floatability in alkaline pH media.

These compounds are used to separate valuable metallic compounds found in ores. Zinc-xanthates are also used as accelerators for natural rubber. 

The solubility products (pL) and the dissociation constants (p a) of zinc-xanthates as a function of chain length n) are illustrated in Fig. 5.5. The recovery of galena flotation using xanthates and fatty acids with various chain lengths is shown in Fig. 5.6 [1]. 

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