What is the Difference Between Flocculant and Coagulant

Water treatment is the process of purifying water in order to use it for purposes such as cooking and drinking. Coagulants and flocculants are two substances useful in water treatment.

What is the difference between flocculant and coagulant? Flocculants promote the growth of small particles into larger particles, whereas coagulants neutralize the charge of suspended particles.

Key Areas Covered

1. What are Flocculants 
      – Definition, Features 
2. What are Coagulants
      – Definition, Features 
3. Similarities Between Flocculant and Coagulant
      – Outline of Common Features
4. Difference Between Flocculant and Coagulant
      – Comparison of Key Differences
5. FAQ: Flocculant and Coagulant
      – Answers to Frequently Asked Questions

Key Terms

Flocculant, Coagulant

What are Flocculants

Flocculants cause the particles suspended in a liquid to clump together, forming much larger particles. They promote the aggregation of small particles. As the particles are removed in this manner, the liquid becomes clearer and purer.

The molecular structure of flocculants is a long chain-like structure. When these are added to a liquid with suspended particles, these molecules bridge the gap between the particles. This, in turn, causes the particles to clump and aggregate together. Later, these clumps are removed using techniques like sedimentation and filtration.

There are two main types of flocculants: organic and inorganic.

Organic flocculants are derived from natural resources, or they are synthetically made polymers. Polyacrylamide is an example of a synthetic organic flocculant, while chitosan is an example of a natural organic flocculant. Inorganic flocculants, on the other hand, are mainly derived from minerals. Two examples are aluminum sulfate and ferric chloride. Furthermore, insoluble particles form by the reaction of these compounds with water.

There are many applications of flocculants. Moreover, they are useful in water treatment, wastewater treatment, mining, paper production, and food processing.

Figure 1: Coagulation Flocculation Process in Water Treatment

What are Coagulants

Coagulants are chemicals added to the water to remove suspended particles such as dirt, clay, bacteria, and algae.
There are a few steps in the process of coagulation.

1. Destabilization – A coagulant is added to water to neutralize the electrical charges on the suspended particles. (These charges repel the particles from each other, which keeps them suspended).
2. Floc formation – the particles that are now destabilized collide with each other and form larger clumps.
3. These floc particles could then be sedimented or filtered.

Two examples of coagulants are ferric sulfate and polyelectrolytes. Furthermore, factors such as the type of water being treated, required water quality, and cost of the coagulant affect the choice of the relevant coagulant.

Similarities Between Flocculant and Coagulant

• Both are useful in water treatment.
• Moreover, they improve water quality.

Difference Between Flocculant and Coagulant

Definition

• Flocculants are substances that cause the particles suspended in a liquid to clump together, forming much larger particles, whereas coagulants are chemicals added to the water to remove suspended particles such as dirt, clay, bacteria, and algae.

Function

• Coagulants neutralize the surface charge of suspended particles, while flocculants physically bridge the particles together to form larger flocs.

Nature

• Coagulants are mostly inorganic salts, while flocculants are synthetic polymers or natural organic substances.

Molecular Weight

• Coagulants have a relatively low molecular weight, while flocculants have a high molecular weight.

Conclusion

Flocculants and coagulants are both useful in water treatment. The main difference between flocculant and coagulant is that coagulants neutralize the charge of the particles and form clump, whereas flocculants bridge these clumps together.

FAQ: Flocculant and Coagulant

1. What are the coagulants used in water treatment?

Some common coagulants used in water treatment include aluminum sulfate (alum) and ferric chloride. Coagulation aids in the removal of impurities in the water.

2. What is a real-life example of coagulation?

Blood clotting is a real-life example of coagulation. When you get a cut on yourself, platelets and clotting factors work together to form a clot. This clot prevents further bleeding.

3. What is the most commonly used coagulant?

Aluminum sulfate (alum) is the most commonly used coagulant in water treatment. It neutralizes the negative charge of suspended particles.

4. What do flocculants do?

Flocculants are chemicals that cause particles in a liquid to clump together. They make the particles larger and heavier so that it would be easy to remove the impurities from the liquid.

5. What are natural coagulants?

Natural coagulants are substances present in nature that can help to purify water by causing particles to clump together and settle. A few examples are alum, iron sulfate, and chitosan.

Reference:

1. “Flocculant.” Science Direct. 
2. “Coagulation (Water Treatment).” Wikipedia. Wikipedia Foundation. 

Image Courtesy:

1. “The coagulation and filtration processes at a drinking water treatment plant” By USEPA Environmental-Protection-Agency – The coagulation and filtration processes at a drinking water treatment plant. (Public Domain) via Commons Wikimedia