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A number of effective coagulants from plant origin have been identified: Nirmali, Okra, red bean, sugar and red maize [8], Moringa oleifera [9], Cactus latifera, and seed powder of Prosopis juliflora [10].
What are the two most common coagulants?
Traditional chemical coagulation uses aluminum and iron coagulants. The most common aluminum coagulants are aluminum sulfate, aluminum chloride, and sodium aluminate. Iron coagulants include ferric sulfate, ferrous sulfate, ferric chloride, and ferric chloride sulfate [4].
What are examples of coagulants?
Examples of primary coagulants are metallic salts, such as aluminum sulfate (referred to as alum), ferric sulfate, and ferric chloride. Cationic polymers may also be used as primary coagulants.
Is Lime a coagulant?
Lime is a coagulant aid used to increase the alkalinity of the water. The increase in alkalinity results in an increase in ions (electrically charged particles) in the water, some of which are positively charged.
What are the characteristics of good coagulant?
There are three key properties of a coagulant : Trivalent cation : As indicated in the last section, the colloids most commonly found in natural waters are negatively charged, hence a cation is required to neutralize the charge. Nontoxic : This requirement is obvious for the production of a safe water.
What is coagulant in water treatment?
Coagulation is the chemical water treatment process used to remove solids from water, by manipulating electrostatic charges of particles suspended in water. This process introduces small, highly charged molecules into water to destabilize the charges on particles, colloids, or oily materials in suspension.
What are natural coagulants?
They are mainly composed of polymers of natural origin extracted from plants, algae or animals. Among these are polysaccharides and water soluble substances that act as coagulation and / or flocculation agents.
What makes a good coagulant?
The best coagulant is therefore a pre-hydrolysed species with a high basicity. PACl has been found to be very suitable for lime softening applications. The advantage of a low basicity coagulant is even more pronounced in full softening applications, and the non-sulphated PACl is the coagulant of choice.
Is na2so4 a coagulant?
Sodium sulfate is a well-known coagulant for PVA, and it is used in the coagulation bath of PVA before wet spinning of vinylon fibers.
How turbidity can be removed?
These options mechanically (through filtration) or chemically (through flocculation and settling of suspended material) remove particles and reduce turbidity.
What is the most commonly used coagulant in water treatment?
1. Alum (aluminum sulfate), Al2(SO4)3. Still, the most common coagulant in the United States, it is often used in conjunction with cationic polymers.
How does a flocculant work?
A flocculant is a chemical that can be added to the water to help colloids and any other suspended solids bind together and form heavier particles. The heavier particles then settle to the bottom of the container/tank and the water on the top is drained off.
What is coagulant made of?
Chemically, coagulant chemicals are either metallic salts (such as alum) or polymers. Polymers are man-made organic compounds made up of a long chain of smaller molecules. Polymers can be either cationic (positively charged), anionic (negatively charged), or nonionic (neutrally charged.)
What is meant by flocculant?
A flocculant is a compound or agent which is added to a vessel to make particles stick together and form larger particles. Flocculation involves the addition of a flocculant that causes the particles to stick together.
What are the side effects of alum?
If experienced, these tend to have a Severe expression i fluid accumulation around the eye. throat swelling. a feeling of throat tightness. a skin ulcer. hives. a shallow ulcer on the skin. fainting. puffy face from water retention.
What is the best coagulant?
Generally, alum is the first coagulant of choice because of its lower cost and its widespread availability. For coloured, low turbidity, low pH/alkalinity surface waters pre-treatment with lime, soda ash or caustic soda will normally be required to ensure that the optimum coagulation (dosed-water) pH is achieved.
Which coagulant is used for sewage treatment?
Ferric chloride is widely used for sewage treatment and Alum is widely used for water treatment.
Is gypsum a flocculant?
Gypsum can coagulate or bridge clay particles, which accelerates settling. Flocculants should be used to prevent damage to sensitive water resources such as ponds, lakes and trout streams or whenever turbidity control is required. The best thing to do is a jar or bucket test using slightly varying rates of gypsum.
What does a coagulant do?
Coagulants are a substance which cause particles in a liquid to curdle and clot together. Particles stay suspended in water rather than settling because they carry surface electrical charges that mutually repel each other.
What can be used as a flocculant?
The following natural products are used as flocculants: Chitosan. Isinglass. Moringa oleifera seeds (Horseradish Tree) Gelatin. Strychnos potatorum seeds (Nirmali nut tree) Guar gum. Alginates (brown seaweed extracts).
Why alum is used as coagulant?
When alum is added to water, it reacts with the water and results in positively charged ions. Coagulation removes colloids and suspended solids from the water. These particles have a negative charge, so the positively charged coagulant chemicals neutralize them during coagulation.
What is the most common used coagulant?
Aluminum sulfate (alum) is the most common coagulant used for water purification. Other chemicals, such as ferric sulfate or sodium aluminate, may also be used.
Does alum increase pH?
Ionic species present in alum solutions are highly dependent on the degree of reaction with hydroxyl ions. It is tempting to say that “the composition is pH-dependent.” However, in the vicinity of pH=4.3 the composition of alum solutions changes a great deal with very little change in pH.
What is the difference between flocculant and coagulant?
Flocculants differ from coagulants in that they are often polymers, whereas coagulants are typically salts. Generally speaking, anionic flocculants are used to catch mineral particles while cationic flocculants can capture organic particles.
Is alum positive or negative?
For example, the colloidal particles are negatively charged and alum is added as a coagulant to create positively charged ions. Once the repulsive charges have been neutralized (since opposite charges attract), van der Waals force will cause the particles to cling together (agglomerate) and form micro floc.
