Froth Flotation Method

Published time:20 December 2018

Gold flotation

The Froth Flotation Method is means separating minerals according to their different physical and chemical properties. According to classification, the flotability of gold and silver minerals is included in the first category of natural and non-ferrous heavy metal sulfides, characterized by low surface wettability and easy flotation, which can be flotation by xanthate collectors.

The froth flotation method is widely used to treat various veins of gold and silver ores for the following reasons:
(1) In most cases, the froth flotation process can enrich gold and silver in sulfide concentrate to the greatest extent and discard a large number of tailings, thus reducing the smelting cost.
(2) When the flotation machine is used to treat polymetallic gold and silver ores, concentrates containing gold, silver and non-ferrous heavy metals can be effectively separated, which is conducive to the comprehensive utilization of valuable mineral resources.
(3) For refractory gold and silver ores which cannot be treated directly by mercury amalgamation or cyanidation, a combined process including flotation is needed. However, there are some limitations in flotation, such as ores with gold particles larger than 0.2-0.3 mm or pure quartz gold ores without metal sulfides, which are difficult to deal with by flotation separation alone.

This paper introduces commonly used reagents and the flotation process of gold and silver ore for you.
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Gold and Silver Ore Flotation Processing Technology1
Gold and Silver Ore Flotation Processing Technology2

Commonly Used Froth Flotation Reagents

  1. Collectors: Collectors commonly used in the flotation process of gold and silver ores include xanthate, black powder and butylammonium black powder. Kerosene and transformer oil can be used as auxiliary collectors. Oleic acid can also be used as a collector for gold-copper oxide ores.
    The greater the difference of solubility of Metal Xanthate in a cyanide solution, that is, the greater the difference of Ki/n, the easier the separation of two metal minerals in the cyanide solution. Gold, silver and xanthate form insoluble xanthate. The order of solubility product is after Mercury and before bismuth and antimony, so it can be separated from other metal minerals.
    When flotation of gold and silver sulfide ores, the general xanthate dosage is 50-150 g/t. Usually, the dosage increases with the increase of metal grade and oxidation degree. Experience shows that the use of mixed collectors is better than that of single collectors, which not only improves the selectivity of the flotation separation process, but also saves the dosage of reagents.
    Butylammonium black powder is an anionic collector developed in recent years. It can strengthen the separation effect of gold-silver quartz vein ore and gold-silver ore associated with non-ferrous metals, and has the dual functions of collecting and foaming.
  2. Foaming agent: Foaming agent for separation of gold and silver ores, commonly used are 2 # oil, turpentine, camphor oil, dipyridine and formic acid, the amount of which is generally 20-100 g/t. Camphor oil has good selectivity and is mostly used to obtain high-quality concentrates and priority flotation operations.
    A tungsten-antimony gold mine in China has obtained good results with camphor oil in the priority flotation process of Antimony-Gold ore.
  3. Regulator: Lime is a commonly used medium regulator, and also an effective inhibitor of sludge coagulant and pyrite. It also has a certain inhibitory effect on gold sludge. Its dosage is 1-5 kg/t.
    Cyanide is a commonly used depressant in the flotation process of nonferrous sulfide ores. However, due to its strong inhibitory effect on gold and silver ores and its ability to dissolve precious metals such as gold and silver, it is better not to use.
    Sodium sulfide is not only an activator of Au-Ag oxides, but also can form a layer of metal sulfide film on the surface of Au-Ag minerals, which makes the refractory oxides float better. But it can inhibit natural gold. Therefore, the dosage should be strictly controlled in use, which is generally 20-200 g/t.
  4. In addition, the commonly used activators are lead nitrate, lead acetate and copper sulfate. Sulfur dioxide is also used as an activator in gold-bearing pyrite flotation abroad.
    The acidity and alkalinity of pulp often directly or indirectly affect the flotability of gold-bearing and silver-bearing minerals. The flotation of gold and silver minerals is mostly carried out in alkaline pulp medium, but for some gold-bearing pyrite and pyrrhotite, it is suitable for flotation in weak acid pulp medium.
    Oxygen has an effect on the flotation process of gold-silver sulfide ore oxidized to different degrees. For example, when a factory floatation contains gold and silver sulfide ore, the use of a large amount of organic matter and anoxic lake water, the flotation effect is not good, after mixing and aeration, the stable mineralization foam is obtained, the recovery rate of gold is increased by 10%.
Gold and Silver Ore Flotation Processing Technology

Gold and Silver Ore Froth Flotation Method

Froth Flotation Method is usually based on the properties of gold and silver ores and product specifications. Common principles and processes are as follows:

    1. Cyanidation of froth flotation + flotation concentrate
      A small amount of concentrate is obtained from gold-silver quartz vein sulfide ore by flotation, and then cyanide treatment is carried out. Compared with the whole slime cyanidation process, the froth flotation method concentrate process has the advantages of no fine grinding of all ores, saving power consumption, small plant area and less capital investment.
    2. Flotation+Concentrate Roasting+Calcination Cyanidation
      The process is often used to treat insoluble gold-arsenic ores, Gold-Antimony ores and gold-pyrite ores with high sulfide content. The purpose of roasting is to remove arsenic and antimony which are harmful to the cyanidation process.
    3. Thermal treatment of flotation + flotation concentrate
      The vast majority of polymetallic sulphide ores containing gold and silver are treated by this method. When flotation of such ores, gold and silver enter into the copper concentrate or lead concentrate closely associated with them. The products are called copper, gold and silver concentrate or lead, gold and silver concentrate, etc. Then they are sent to the smelter to recover gold and silver.
    4. Cyanidation of flotation + flotation tailings or middlings + in-situ roasting of flotation concentrates
      This froth flotation method is used to treat quartz sulfide ores or gold-silver-bearing pyrite and pyrrhotite containing gold telluride, pyrrhotite, chalcopyrite and other sulfide minerals. The floatable gold telluride in the ores is first produced as a concentrate, and then roasted and cyanided to expose gold and silver ores in sulfides and tellurides. Because the middle and tailings after flotation generally contain high gold and silver, they need to be recovered by cyanidation.
    5. Cyanidation of Raw Ore + Flotation of Cyanide Tailing
      When gold and silver cannot be recovered completely by cyanidation, the recovery of gold and silver can be improved by flotation after cyanidation treatment. Domestic and foreign examples of gold and silver recovery from cyanide-treated old tailings by flotation have been reported.
      Extraction of gold, extraction of silver, etc. The froth flotation method always combines with gold leaching, carbon in leaching, carbon in pulp, heap leaching. JXSC supply flotation machine in South Africa, Asia, South America for many years.
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