In the field of chemical engineering, settling refers to the process by which solid particles separate from a liquid suspension under the influence of gravity. There are different types of settling mechanisms depending on the behavior of the particles in the suspension.


Zone settling occurs when particles in the suspension settle without any interference from neighboring particles. This type of settling is typically observed when the particles are well dispersed and the suspension has a low concentration of solids. In zone settling, the particles settle in distinct layers or zones based on their size and density.


Compression settling occurs when the particles in the suspension are compressed under the weight of the settling particles above them. This type of settling is commonly observed in concentrated suspensions where the particles are closely packed together. As the particles settle, they compress the particles beneath them, leading to a decrease in the volume occupied by the suspension.


Hindered settling occurs when the settling of particles is impeded or hindered by the presence of other particles in the suspension. In a dilute suspension, the particles are not closely packed together, allowing for a free flow of liquid between the particles. However, as the concentration of particles increases, the movement of particles becomes more restricted, leading to hindered settling.


Discrete settling refers to the settling of individual particles without any interaction or interference from neighboring particles. This type of settling is typically observed when the particles in the suspension are well dispersed and do not interact with each other.


The correct answer is option 'C' - Hindered settling. In a dilute suspension, the particles are not closely packed together, allowing for a free flow of liquid between the particles. However, as the concentration of particles increases, the movement of particles becomes more restricted, leading to hindered settling. In hindered settling, the settling of particles is impeded by the presence of other particles in the suspension. This type of settling is commonly observed in concentrated suspensions where the particles are closely packed together and interact with each other, causing hindered movement and settling.