ChE 536L – Chemical Laboratory 1
Experiment No. 7
Sedimentation
INTRODUCTION
Sedimentation is the process of deposition of solid material from a fluid, usually air
or water, from a state of suspension. It is widely observed in nature in the formation of rocks
and ore deposits. One important branch of Geology, Sedimentology or Sedimentary
Petrology, studies the origin of rocks by this method. Sedimentation has also a great scientific
and industrial importance, especially in the mining and chemical industry. (Bustos, 1999)
The size and type of particles to be removed have a significant effect on the operation
of the sedimentation tank. Sand or silt can be removed very easily because of their density.
The velocity of the water-flow channel can be slowed to less than one foot per second and
most of the sand and silt will be removed by simple gravitational forces. In contrast, colloidal
material (small particles that stay in suspension and make the water seem cloudy) will not
settle until the material is coagulated and flocculated by adding a chemical, such as iron salt
or aluminum sulfate. The shape of the particle also affects its settling characteristics. A round
particle, for example, will settle much more readily than a particle that has ragged or irregular
edges. All particles also tend to have a slight electrical charge. Particles with the same charge
tend to repel each other. This repelling action keeps the particles from congregating into flocs
and settling (Kocamemi, n.d.).
APPARATUS/MATERIALS
Cornstarch
Water
Batch/Sedimentation Apparatus
Stirring Rod
