The flotation separation of fine particles is relatively difficult, mainly due to the following two reasons:
(1) Fine particles have a large specific surface area, resulting in a significant increase in surface energy. Under certain conditions, non-selective agglomeration easily occurs between the surfaces of different minerals. Although fine particles have a high adsorption capacity for reagents, their selective adsorption is poor, making selective separation difficult.
(2) Fine particles have a small volume, reducing the likelihood of collision with air bubbles. Due to their small mass, fine particles are less likely to overcome the resistance of the hydration layer between the mineral particles and air bubbles when colliding, making it difficult to adhere to the air bubbles.
The technological measures to solve the problem of fine particle flotation are as follows:
(1) Selective flocculation flotation. Flocculants are used to selectively flocculate the target mineral particles or gangue mud, and then flotation is used for separation.
(2) Carrier flotation. Mineral particles of general flotation size are used as carriers, allowing the target mineral particles to adhere to the carrier and float. The carrier can be of the same type of mineral or different types of minerals. For example, pyrite can be used as a carrier to float fine-grained gold, and calcite can be used as a carrier to float away fine-grained iron and titanium impurities in kaolin.
(3) Agglomeration flotation, also known as emulsion flotation. After treatment with a collector, fine-grained minerals form an oily foam containing minerals under the action of neutral oil. The collector and neutral oil can be mixed into an emulsion before being added to the pulp, or neutral oil and collector can be added separately to a high-concentration pulp (solid content up to 70%), stirred vigorously, and the time controlled before skimming off the upper layer of foam. This method has been used for fine-grained manganese ore, ilmenite, and apatite, etc.