What is Xanthates
The name “xanthates” was adapted from the Greek word “xanthos” meaning yellow, and refers to the color of the copper salt rather than that of the alkali metal salts. From the time of their discovery by Zeise in 1822 until the beginning of the this century, xanthates found no commercial application. Shortly after 1900, the rubber industry used xanthates in the curing and vulcanization of rubber. Later, the compounds found some application in the manufacture of synthetic textiles and as fungicides.
In 1923, Cornelius H. Keller discovered what has become the largest scale application for xanthates – their use as collectors for flotation of sulfide minerals, as disclosed in a 1925 United States patent. While xanthates were not the first collector reagents of the so-called “chemical” type, the were among the first water-soluble organic collectors. Their adoption was immediate and widespread and it is generally recognized that xanthates, in conjunction with alkaline pulp circuits, have a major part in the development of selective mineral flotation.
The high collector efficiency and low cost of the xanthates have made them the standard of comparison – since 1923 – among sulfide mineral collectors.
Chemical Structure an Activity
Xanthates are dithiocarbonates corresponding to the structural formula
In which R represents the alkyl radical and X an alkali metal. One of the most commonly used xanthates is sodium isopropyl xanthates, which has the formula.
The xanthates used in flotation usually are prepared from a aliphatic alcohol, carbon disulfide, and caustic soda or caustic potash.
Oxidation of a xanthates results in the formation of the dixanthogen
The dixanthogen so formed is in itself a good collector but because of low water solubility is unsatisfactory unless used as a water emulsion. In this form, it is a superior collector for the flotation of copper, zinc, and molybdenum form some ores.
Emulsions ma be prepared by the oxidation of dilute (1-2 percent) xanthates solutions with a standard oxidizing agent such a sodium hypochlorite (NaOCI), potassium permanganate, or potassium persulfate.
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