Chapter 16 - Flotation

Abstract

Flotation is a separation process that treats complex or low grade ores where the average particle size for liberation is too small for efficient gravity separation or where the gravity difference between minerals is too small. This chapter focuses on this process highlighting its mechanism and usage. Flotation relies on the surface of the valuable mineral being hydrophobic while the surface of the gangue minerals is hydrophilic. The chemicals used in flotation are divided into three classes, such as collectors, frothers and modifiers. The chapter discusses all three classes illustrating their uses and differences. The equipment used in flotation can be divided into several categories according to the method of introducing air into the cell. These include mechanical, pneumatic, vacuum, electro-flotation, and dissolved air flotation. This chapter describes in detail all these methods. Flotation is carried out as a continuous operation in a series or bank of cells. This increases the floating time, allowing ample opportunity for particle-bubble attachment to occur. The chapter also provides a detailed technical description of flotation kinetics. The factors affecting the rate of flotation are impeller speed, air flow rate, particle size, and reagents. after the chapter discusses the application of kinetic equations in the froth flotation process and provides a brief description of some of the other mathematical approaches to the flotation phenomenon.