Flocculation And Sedimentation Experiment

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Experiment 4
Suspension-sedimentation

Objective
To obtain a good formulation in controlling the rate of flocculation and sedimentation.

Introduction
In colloid chemistry, suspension is a heterogeneous mixture containing solid particles which are large enough to settle out from the liquid through sedimentation. The internal phase (solid) is dispersed throughout the external phase (fluid) through mechanical agitation, with the use of certain excipients or suspending agents and it will eventually settle. Suspension is considered as thermodynamically unstable because the properties of suspension is always changing with time as they will undergo sedimentation. Suspension may be flocculated or deflocculated.
Sedimentation is the tendency for particles
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In this process, particles in suspension can come together to form either floccules or aggregate. The flocculation process is reversible if the interaction forces between the floccules are not strong. Floccules form when weak van der Waals forces are holding the particles together. Floccules are easy to break apart. If floccules sediment they trap solvent and are easier to re-suspend than if the particles settle into a tighter aggregate without the trapped solvent. However, the large fluffy clumps that characterize a flocculated system settle…show more content…
First, bismuth subnitrate was added into the graduated cylinder. Bismuth subnitrate is a white powder which soluble in water. The purpose of adding bismuth subnitrate is to mix the solute (bismuth subnitrate) and solvent together. Methylcellulose is a hydrophilic white powder in pure form and dissolves in only cold water, forming a clear viscous solution or gel.
In the first boiling tube, the solution consists of 2 g of bismuth nitrate and water. Based on the results, the height of sediments was the same over time which the value kept constant at 0.4cm. This is because flocculating agent was absent in the boiling tube hence cannot undergo flocculation process.
For the second boiling tube, the solution consists of 2g of bismuth subnitate, 10 mL of flocculating agent and water. The height of sediments was the same as time goes on which the value kept constant at 1.1 cm. But supposingly, the height of sediments should increase over time due to the presence of flocculating agent. With flocculating agent, Zeta potential between the particles decrease and cause the van der waals forces become

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