[Chemistry Class Notes] Flocculation Pdf for Exam

Flocculation meaning is a process that helps in forming large aggregates of particles. For this to occur, a chemical coagulant gets added to the liquid. This coagulant facilitates the bonding of the particles in the liquid. According to IUPAC, the flocculation definition states that it is a process of contact and adhesion through which the dispersed particles form large clusters. The particles that are together can easily loosen up due to the surface tension of the liquid. Flocculation has numerous applications. Sometimes flocculation may be undesirable for the process. Hence, the removal of flocculants takes place. Water supplies, water treatment plants, and even sample processing are some applications that require flocculation. 

Natural Flocculation

Natural processes of flocculation treat wastewater. Natural flocculants are environment-friendly. Seeds of plants like ovata, Oliveira, moringa, or Plantago are for this purpose. Starch is a natural product that can also act as a natural flocculant. Using natural resources like these makes the processes of waste management cost-effective. One of the main advantages of these flocculants is that they are biodegradable and can be renewed and used. Using these materials is preferable as they are non-toxic. No toxic reaction should affect the purification. Natural flocculants are very safe to use but their lifespan is less. 

Chemical Flocculation

The chemical flocculants ensure a very effective treatment in coagulation processes. As suggested by the name, they are chemically synthesized from various monomers from electrolytes, cationic, anionic as well as nonionic polymers. However, these chemical flocculants produce toxicity as suggested by many studies. They produce sludge with a high concentration of metal hydroxides that are harmful to living beings if released into the water bodies. 

Alum, Aluminium chlorohydrate, or aluminum sulfate are different kinds of organic flocculants used to treat water. The cationic flocculants are available in the largest number of varieties and hence are used the most. The chemical flocculants are mainly useful as they allow techniques like copolymerization to occur. The nonionic flocculants have very low surface charge and can only function through certain bridging mechanisms, in an aqueous medium. 

Application of Flocculation

There are several fields where the process of flocculation is applied. Some flocculation examples are given below:

• Flocculation helps in emulsion, where each droplet comes together to form a cluster. It has usage in mineral dressing or to design the physical properties of pharmaceutical products.

• Flocculation processes induce eutrophication through the adsorption of substances from underwater. It also maintains the freshwater quality under the soil. Thus the formation of colloids helps in these processes.

• Due to the hydrolysis of molecules and the micro peptides, flocculation is used extensively in the cheese industry. During the manufacture of cheese, this process determines the time required for the formation of the curd.

• During construction work, flocculation helps in the coagulation of clay particles and polymers by mechanical agitation. This process leads to the formation of structures spontaneously. It is due to the attraction of the positive and negative charges. Hence, these applications are important for civil engineering processes.

• Flocculation is used in many biological and biotechnological processes. The process of microfiltration and flocculation go hand in hand. Synthetic flocculants in the bioreactor increase in size and hence help in the purification process.

• Processes such as coagulation, flocculation sedimentation treat the stormwater, sewage, or industrial wastewater. Drinking water also requires such treatments.

• In the brewing industry, yeast gets flocculated. It helps in the fermentation of beer. The yeast gets sedimented and floats down to the base or the top, from where it can be separated. This yeast gets reused for fermentation. 

Questions and Answers

1. How Can Efficient Flocculation Be Carried Out?

Answer: Flocculation is an essential process in the purification of substances. It is a widely used process used in industries. One of the main things is that the phenomenon should be very cost-effective. Precious metals, particulate matter, fibers, and fillers, or even water impurities can be accumulated through efficient processes. These processes are:

• Flocculants are selected carefully. Natural flocculants have the lowest toxicity rate. Metals and other such substances require cationic and anionic flocculants.

• There are several parameters related to the process of flocculation like mixing intensity, time, shear stress, concentration, the particle size of the solid, and the dosing rate and location. The value will differ according to the requirement.

• There must be a downstream flow of the particles.

2. Describe the Floc Breakage Kinetics.

Answer: Stirring is an essential process in flocculation. Fast stirring can break the floc. It causes the number of particles to become of the same density and size as before flocculation. Therefore, a very gentle stirring is required. The different particles have varied flocculation strength. Hence the stirrer rpm is determined to understand which value is more suitable for which variety of floc. Slow stirring leaves most flocs intact. The intensity of the combination, if carefully set, prevents the breaking of the flocs, stopping the increase in filtration time as well.