Solubility lead xanthate

These properties impair the use of native cellulose in the manufacture of useful products, except those made of threads. Modifications of cellulose usually require the cellulose to be solubilised. In the viscose process, cellulose is treated with 18-20% aqueous sodium hydroxide. The mass is aged to allow oxidative degradation of the chains in order to reduce molecular weight. Then the alkali cellulose is treated with carbon disulfide, leading to the soluble sodium xanthate derivative of cellulose, as shown in Equation 3.23. 

In the 2nd period ranging from the 1930s to the 1950s, basic research on flotation was conducted widely in order to understand the principles of the flotation process. Taggart and co-workers (1930, 1945) proposed a chemical reaction hypothesis, based on which the flotation of sulphide minerals was explained by the solubility product of the metal-collector salts involved. It was plausible at that time that the floatability of copper, lead, and zinc sulphide minerals using xanthate as a collector decreased in the order of increase of the solubility product of their metal xanthate (Karkovsky, 1957). Sutherland and Wark (1955) paid attention to the fact that this model was not always consistent with the established values of the solubility products of the species involved. They believed that the interaction of thio-collectors with sulphides should be considered as adsorption and proposed a mechanism of competitive adsorption between xanthate and hydroxide ions, which explained the Barsky empirical relationship between the upper pH limit of flotation and collector concentration. Gaudin (1957) concurred with Wark s explanation of this phenomenon. Du Rietz... 

Quite frequently the natural surface of a mineral requires preliminary chemical treatment before it will form the surface film required for collection One of the commonest instances of this is with sphalerite (zinc sulphide), which does not float properly when treated with xanthates. If, however, it is given a preliminary treatment with dilute copper sulphate solution, a very small amount of copper sulphide is deposited on the surface and the ore becomes floatable, the surface being now capable of reaction with xanthates. Such treatment is usually termed activation in general, an activating solution for a sulphide mineral should contain a metallic ion whose sulphide is less soluble than that contained in the mineral for zinc sulphides, silver, copper, mercury, cadmium, and lead salts are all effective activators. 

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 ... 

The solubility product of lead ethyl xanthate is 4 x 10", and hence the reversible potential of reaction (3) for an ethyl xanthate concentration of 10 mol dm" (the conditions of Fig. 2) is 0.01 V. It can be seen from Fig. 2 that the anodic oxidation reaction commences at -0.2 V below the value at which reaction (3) is possible. The solubility product increase equivalent to a decrease in potential of 0.2 V is nearly seven orders of magnitude. Thus, the observed undeipotential chemisorption of xanthate conforms to the model proposed by Wark and Cox, in which flotation is induced by an adsorbed analog of the bulk metal-collector compound with a much lower solubility. 

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