Selective flocculation or coagulation flocculation is a process in which destabilized colloidal particles are brought together to form flocs. This process is used to separate particles of different sizes or densities. Selective flocculation is accomplished by adding a flocculant, such as a polyelectrolyte, across the surface of the suspension. The flocculant gradually binds together particles of similar size and shape, while repelling particles of different sizes or densities. This process can be automated and is used in a variety of industries, including mining, chemical processing, and wastewater treatment.
The history of selective flocculation dates back to the early 19th century, when it was first used to aid in the removal of gold ore from less dense particles such as sand, gypsum and clay. This process was later adapted to treat wastewater and mineral suspensions, eventually leading to its wide use in industrial applications. In 1919, German chemist Albert Bauer initiated the idea of polymer flocculation and opened the door to the development of modern processes.
Selective flocculation is typically used in wastewater treatment processes to separate suspended particles. In wastewater treatment, flocculants are added to water to bind suspended particles together and forming larger flocs that can be removed by settling or filtration. The process works by adding a cationic or anionic polyelectrolyte to the water. This polyelectrolyte binds to particles of the same charge and forms larger particles. As the particles become larger, the gravitational force eventually causes the particles to settle to the bottom of the settling tank. The flocculation process then creates smaller particles that are then filtered from the water.
Selective flocculation also has applications in mining operations. In mining, flocculants are added to suspension tanks that are filled with ore. The flocculants attract particles of similar density and size and bring them together to form flocs. These flocs are then separated from the ore by centrifuge or spiral classifiers. The process of selective flocculation used in mining results in the recovery of higher volumes of valuable minerals, while rejecting unwanted and harmful materials.
Selective flocculation has also proved useful in paper production. In the paper industry, paper pulp is treated with polyelectrolyte flocculants to reduce the amount of sludge that is created during the processing. The polyelectrolyte flocculants work by attracting particles of similar size and shape, helping the sludge and other suspended particles to settle. This reduces the amount of sludge that must be removed from the paper pulp and makes the process more efficient.
Selective flocculation is a versatile process that can be used in a variety of industries to separate particles of different densities and sizes. The process is effective and efficient, and can be automated for easier, faster operation. As technology advances, selective flocculation is becoming more widely used and is proving to be a valuable tool in industrial processes.
