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Common soil cations include sodium (Na+), potassium (K+), magnesium (Mg2+), and calcium (Ca2+). Cations can make clay particles stick together (flocculate).
What cations promote flocculation?
Clay particles usually possess net negative charge and therefore they electrostatically attract positively charged ions, such as Ca2+ cations, which form bridges, holding the particles together. Therefore, these cations can induce flocculation of clay particles.
Which ion causes flocculation?
Aggregate stability (dispersion and flocculation) depends on the balance (SAR) between (Ca2+ and Mg2+) and Na+ as well as the amount of soluble salts (EC) in the soil. Soil particles will flocculate if concentrations of (Ca2+ + Mg2+) are increased relative to the concentration of Na+ (SAR is decreased).
What causes soil dispersion?
What causes soil dispersion? Soils often disperse when they are sodic, which means they contain enough sodium to interfere with the structural stability of the soil.
Why does sodium ion cause dispersion?
The forces that bind clay particles together are disrupted when too many large sodium ions come between them. When this separation occurs, the clay particles expand, causing swelling and soil dispersion.
What is the purpose of the flocculation process?
Flocculation is a process by which a chemical coagulant added to the water acts to facilitate bonding between particles, creating larger aggregates which are easier to separate. The method is widely used in water treatment plants and can also be applied to sample processing for monitoring applications.
What is flocculant made of?
One of the most common flocculants used in water purification today is aluminum sulfate (also known as alum); its chemical composition is shown in Figure 3. Figure 3. The chemical structure of aluminum sulfate (alum). Aluminum sulfate is a white, solid (powder) with a chemical formula of Al2(SO4)3.
What is red soil made of?
It is formed by the weathering of ancient crystalline and metamorphic rocks, particularly acid granites and gneisses, quartzitic rocks, and felspathic rocks. Chemically, red soil is siliceous and aluminous, with free quartz as sand, but is rich in potassium, ranging from sand to clay with the majority being loamy.
What is grown in red soil?
Crops in Red Soils The red soils are mostly loamy and hence cannot retain water like the black soils. The red soils, with the proper use of fertilizers and irrigation techniques, give good yield of cotton, wheat, rice, pulses, millets, tobacco, oil seeds, potatoes and fruits.
What is soil coagulation?
Effective coagulation and separation of particles in a soil-washed solution is required for a successful soil washing process. The soil coagulation process was found to decrease with an increase in the pH of the suspension, and maximum coagulation was achieved with an acidic pH.
What is the pH of sodic soils?
The pH values of sodic soils exceed 8.5, rising to 10 or higher in some cases. (L) Soil with good structure (non-sodic soil); (R) Soil with poor and dense structure (sodic soil).
What does EC stand for in soil?
Soil electrical conductivity (EC) is a measure of the amount of salts in soil (salinity of soil). For certain non-saline soils, determining EC can be a convenient and economical way to estimate the amount of nitrogen (N) available for plant growth.
What defines a sodic soil?
Sodic soils are low in total soluble salts but high in exchangeable sodium, which tends to disperse soil particles and destroys soil structure (Management of Saline and Sodic Soils, Kansas State University, 1992).
What does salt do to the soil?
When salt concentrations in the soil are high, the movement of water from the soil to the root is slowed down. When the salt concentrations in the soil are higher than inside the root cells, the soil will draw water from the root, and the plant will wilt and die.
Why is salt bad for soil?
Salts in the soil can absorb water. This results in less water being available for uptake by the plants, increasing water stress and root dehydration. This is referred to as physiological drought, which, if not corrected, can lead to reduced plant growth.
Where does salt in the soil come from naturally?
Salts occur naturally within soils and water. Salination can be caused by natural processes such as mineral weathering or by the gradual withdrawal of an ocean. It can also come about through artificial processes such as irrigation and road salt.
Is alum a coagulant or flocculant?
To accomplish this, the water is treated with aluminum sulfate, commonly called alum, which serves as a flocculant. Raw water often holds tiny suspended particles that are very difficult for a filter to catch. Alum causes them to clump together so that they can settle out of the water or be easily trapped by a filter.
What is the difference between coagulant and flocculant?
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.
How can flocculation be prevented?
When particles of a suspension come close together they can form aggregates called flocculates which will settle more rapidly. To prevent that we often coat the particle with a charged surfactant. The charge (Zeta potential) acts to keep the particles separate and prevent flocculation.
Can you use too much flocculant?
Flocculant is aluminum sulfate, which is designed to clump with the particles you’re trying to remove. But if you add too much, the flocculant will start to agglomerate with itself instead of those particles. These flocculant clumps will not drop to the pool floor and can clog up your filter.
Is Lime a flocculant?
Yes you can use lime as a flocculant or to help your flocculate and settle. Additionally, the water’s pH can affect the performance of a flocculant. The pH scale is used to determine how acidic or basic the water is.
What is the best flocculant?
These compounds make up some of the most widely used flocculation agents on the market. Aluminum sulfate (Al2(SO4)3) is an aluminum salt that is also known by the name alum. Along with ferric chloride and ferric sulfate, it is the most widely used of all flocculant agents.
