The coagulation principle in the water purification process is very complicated, and various types of flocculants will have various principles in the same water environment. At present, the principle of coagulation is roughly as follows:
1.Compression of electric double layer
Adding an electrolyte to water will create a double-electron layer with a reduced thickness on the surface of the solid particles, strengthen the van der Waals force, and adsorb and pull the two together. In addition, tiny solids with different charged types can be added In this way, these particles with heterogeneous charges can cause coagulation and aggregation under the electrostatic adsorption and traction.
Under normal circumstances, the polymer coagulant has a linear structure and a large degree of polymerization. Therefore, once one of these macromolecular substances adsorbs colloidal ions, and the other end also adsorbs other colloidal particles, in this case, it seems to be a bridge between different colloidal particles, so that Different colloidal particles are connected and gradually become larger, forming larger floes. This is the principle of adsorption and bridging between macromolecular coagulants and colloidal particles.
Coagulants (such as aluminum-based coagulants and iron-based coagulants) are introduced into the liquid through a series of complex hydrolysis phenomena to produce some alum flocculent substances, which will adsorb colloidal ions in the liquid when they sink. Traction, the two form a community, and continue to precipitate to form a precipitate, which is the net capture effect.