In processing, one of the most widespread ways of separating minerals, based on their different wettability (floatability). The wettability of the grains of heifer with water is better than the wetness of the grains of ore or coal; when oil is added to the mash, it only covers the grains of ore that float to the surface while the heifer falls to the bottom (oil flotation).
The most important is foam flotation, which adds a small amount of foaming additives. These additives adhere to the little wetting grains (but not to the well-wetting heifer), at the same time they wrap a thin layer of air bubble in the water formed by the aeration of the mash, which is achieved by stirring or by blowing the air into the mash. The ore grains connect with air bubbles and are brought to the surface in the form of a foam.
Gold is hydrophobic compared to the parent material and the particles of gold seem to be trying to collect air bubbles in the aerated mash, climb them to the surface and concentrate in the mineralized foam
When floating it is important to change it; the particle size depends on their specific gravity. For grain, the grains are adjusted to a maximum of 0.1 to 0.4 mm, for coal and other lighter minerals not more than 0.5-1 mm; flotation time is up to 40 minutes for ores, for coal about 5 minutes. There is a distinction between basic flotation, clearing and control flotation.
Pure flotation is another flotation treatment of the foam product. Control flotation is a non-foam product. Other variants are collective and selective flotation.
Collective flotation is used for mineral resources that contain more utility components that migrate to a collective concentrate. Selective flotation yields the individual components in separate selective concentrates from the multi-component feedstock.
Flotation agents and their impact on the environment
Achieving successful flotation is to use this process so that the benefit of processing ore is the maximum. It requires the optimal interaction of all components in the flotation process. The leading role in this process is usually played by flotation collectors, which weigh in particular on an ordinarily unfiltered mineral and provide a “greasy” hydrocarbon film. The altered surface of the mineral becomes hydrophobic and preferably preferentially to the air bubbles formed in the flotation cell. The flotation pantographs should be:
Strong enough to provide the required yield
weak to ensure selectivity
Capable of providing the necessary flotation speed and good foam
insensitive to ores and water quality
well-storable and manipulable
Frequently used flotation pickers are alkaline xantogens and esters of a dithiophosphoric acid. These substances are thioderivatives of carbonic and phosphoric acids which derive from the flotation agents mentioned above a wide range of products found in agriculture, medicine, and other industries.
Xantogenan cellulose is an intermediate in the manufacture of artificial silk but also in sausage and salami intestine. The use of xantogens as active toxic heavy metal precipitants has recently been proposed to remove these pollutants from natural waters.
Xantogens are slightly toxic substances; for mammals insignificantly. More than 11,000 tons of xantogens (40% sodium isopropylxantogen, 30% sodium ethylxanthogenate, 15% sec sodium butyanthogenate and 10% potassium amylxantogenate) are consumed annually in the world with flotation separation of ores. From the published works devoted to determining the impact of the use of xanthate on the environment (aquatic flora and fauna) that the xantogens may be harmful to pollutants in water systems at concentrations above 2 mg / l. From the practice of the flotation treatment, it has been found that the untreated effluent may contain residual concentrations of xantogens at a level of 2 mg / l or less, only exceptionally above 4 mg / l.
Safely dispose of the potential effluent of residual values of xantoges is possible thanks to the fact, that xantogenes to reliably biodegrade to concentrations 20 – 25 mg/l. Operationally, this is achieved by conventional biological sewage treatment plants. The knowledge gained from long-term operation of the flotation finishing plants in the world (currently flotation adjusted 2 billion tons of mineral resources) also documented that the toxicity of flotation agents is not a significant risk factor in the environmental industry, mining and processing mineral resources. The experience with flotation plants in the Czech Republic (Nový Benešov, Kaňk, and others) is in line with this fact.
The reasons for this are as follows:
Flotation pantographs are used in the form of dilute solutions, and the dose of the flotation collectors are minimal (tens of ppm). The flotation pantograph is adsorbed on the surface of the foam product by the process principle. During the other processing, the decomposition of the reagent occurs, if the flotation pantograph is desorbed in small amounts to flotation waste which is caused by dissolution of the reagent, treatment effluent prior to cleaning contains residual concentrations of xantogenes which can be reliably purified in biological purifiers.