XANTHATES
Xanthates can be obtained by reacting an alcohol with carbon disulphide and an alkali such as sodium hydroxide or potassium hydroxide. The reaction with ethyl alcohol is as follow,
C2H5OH + CS2 + KOH → C2H5 – O – SK + H2O
II
S
Xanthates are water-soluble chemicals that are used primarily in the mining industry. Other names for xanthates include xanthogenates, carbondithioates, and sodium or potassium salts of xanthanic (or dithiocarbonic) acids.
The alcohols employed are not unique. They can form ethyl, butyl (isobutyl, normal butyl, secondary butyl), propyl (isopropyl, normal propyl) and amyl (isoamyl, normal amyl, secondary amyl) xanthates, in dry forms, such as powder, granules, pellets, tablets or flakes.
Xanthate is the common name for chemical reagents used in the flotation of base and precious metals, which is the standard method for separating valuable minerals, such as gold, copper, lead or zinc minerals, from non-valuable minerals, such as limestone or quartz (gangue).
To extract values, conditioned ores are mixed in a solution of water and xanthates and then agitated in flotation cells. Xanthates may be added in liquid or solid form. The xanthates cause the minerals to attach themselves to air bubbles and then float to the top of the flotation cell. As values reach the surface, the bubbles form a froth that overflows into a trough for collection. The residual may be re-used for additional recovery or removed for disposal. Most of the xanthate is consumed in the process.
Several flotation processes are required for different ores. Since each ore is unique, there is no standard flotation procedure and no standard grade or type of xanthate used to extract specific values. Each producer has its own grades for xanthate composition, including purity, which is stated as a minimum percentage up to 100 per cent, and moisture. Four types of xanthates (ethyl, butyl, propyl and amyl) are produced in various combinations with sodium and potassium, which are stabilizers in the chemical formula.
Mine operators may use different xanthates to extract the same value. Certain xanthates are stronger than others, for example, potassium amyl xanthate (PAX) versus potassium ethyl xanthate (PEX). PAX is therefore used to produce high-grade concentrates or to promote the flotation of difficult-to-float minerals. A mine operator may however decide to use PEX if a cost benefit can be made.
Xanthates are also used as defoliants, herbicides, insecticides and fungicides in agricultural production and as additives in the curing and vulcanization of rubber and as high-pressure lubricant additives.
The key reagent is carbon disulphide. A special plant must be built for its production, in other words, a xanthate manufacturer must have two plants, one for carbon disulphide and other for xanthate production. So the production cost is influenced by carbon disulphide.
Carbon disulphide (CS2) is also known as carbon bisulphide and sometimes dithiocarbonic anhydride. It is a faintly yellow highly flammable liquid with a strong disagreeable odour.
Carbon disulphide is manufactured from hydrocarbons and sulfur and is a very flammable liquid which is therefore extremely hazardous to manufacture and transport.
Worldwide carbon disulfide is used to manufacture regenerated cellulose (viscose rayon and cellophane), carbon tetrachloride and organic sulfur compounds including xanthates used as flotation agents in mineral processing.
Xanthates can be kept in hermetic containers and maintain their properties for some time, generally one year. However, when the container is open, xanthates can be altered by oxygen, temperature, and humidity. For this reason is good practice prepare fresh solution (5 -10%) each day and much better if each production is consumed in each shift.
Hydrocone' Reduction Crusher Evidence model form Mining Glossary J – L Gypsum, Salt, Potash and Coal The Gravity Method Geochemistry Prospecting Organic Colloids Anorthite Composition, Crystallization & Structure Crusher Packing Cryptocrystalline Quartz Varieties Occurrence and Use Relationship Between Feed Size and Roll Diameter of Crusher Diamond Pipes Skipping Ore to the Surface Placer Deposits How to Sample a Drill Hole
