Question

Discuss the various processes used for the concentration of different types of ores.

Answer 1

Hydraulic Washing or Levigation or Gravity Separation: When the ore particles are heavier than the gangue particles, this procedure is employed. The idea behind this method of separating gangue particles from ore is based on the fact that the gangue particles and ore have different specific gravities. A water current is used to wash the powdered ore when the heavier ore particles are left behind after the lighter impurity particles are removed. Levigation is the name of this technique, which is typically applied to oxide ore concentrations.

Magnetic Separation: When a magnet attracts ore particles rather than gangue, this technique is employed. For instance, the concentration of the iron ore haematite can be determined using this technique. This method can be used to separate the magnetic ore particles in haematite from the silicious gangue.

As shown in the figure, this process involves causing powdered ore to fall onto a rubber belt that moves horizontally over two rollers, one of which is magnetic. While the non-magnetic gangue particles fly off and collect in a heap distant from the magnetic roller, the magnetic ore particles are drawn to it and fall closer to it.

This method can also be used to separate magnetic impurities from non-magnetic mineral particles. In this instance, the non-magnetic ore particles fall farther away, while the magnetic gangue particles gather close to the magnetic roller. For example, this method can be used to concentrate wolframite, a non-magnetic tungsten ore containing iron magnetic impurities.

Froth Floatation Process: This method is used for the concentration of ores where the gangue particles are preferentially wetted by water and the ore particles are preferentially wetted by oil. The method is often applied to sulphide ore concentration. This procedure involves placing the finely ground ore slurry (ore + water) in a sizable tank, as seen in Figure.

Following substances are also added to the slurry of the ore.

1. Frothing agents: Pine oil or eucalyptus oil is used as a frothing agent. It forms a stable froth which rises to the top of the tank.
2. Collectors: The collector is either potassium ethyl xanthate or ethyl xanthate. As a result, the froth and ore particles have a stronger binding force. In fact, it is attached to the mineral grains' polar groups. The ore particles enter the froth as a result of becoming water-repellent.
3. Activators or Depressants: These substances are employed when the ore contains many minerals and can either activate or repress the flotation property. These aid in separating the many minerals that are contained in the same ore.

Leaching: This chemical method is employed to concentrate ores. This process involves treating the ore with an appropriate reagent (base, acid, or another reagent) so that the impurities are insoluble in it but the ore is soluble. The contaminants are eliminated through filtration while remaining undissolved. An appropriate reagent is added to the ore's solution, causing the ore to precipitate. As a result, the ore is concentrated. This process concentrates the ores of several metals, including gold, silver, aluminium, and others.