The working principle of PAC is mainly through the adsorption of electric neutralization, adsorption bridging, compression of double electric layer, sediment net and other mechanisms, so that edema fine suspended particles and colloidal ions are de-stabilized, aggregation, flocculation, coagulation, precipitation, to achieve the purification effect. Today, we will talk about the adsorption of polyaluminum chloride bridging effect.
The adsorption and bridging mechanism of PAC mainly refers to the adsorption and bridging between polymer and colloidal particles. It can also be understood that two large colloidal particles of the same size are connected together due to a different colloidal particle in the middle.
High polymer flocculant with linear structure, they have with parts play a role of colloidal particle surface functional groups, when high polymer contact with colloidal particles, groups with special reaction and colloidal particles surface adsorption, while the rest of the polymer molecules spread in solution, can have vacancy of colloidal particles with another surface adsorption, it ACTS as a bridge to connect the polymer.
If the colloidal particles are less, the extended part of the polymer does not adhere to the colloidal particles, then the extended part will be absorbed by the original colloidal particles in other parts sooner or later, the polymer can not play a bridging role, and the colloidal particles are in a stable state.
When the amount of polymer flocculant is too large, the surface of colloidal particles will be saturated and stabilized again. If the bridged flocculated colloidal particles are stirred violently for a long time, the bridging polymer may break off from the surface of another colloidal particle and roll back to the surface of the original one, resulting in a re-stable state.
The adsorption of polymer on colloidal surface comes from various physical and chemical actions, such as van der Waals attraction, electrostatic attraction, hydrogen bond, coordination bond, etc., which depends on the characteristics of the chemical structure of polymer and colloidal surface. This mechanism can explain the good flocculation effect of non-ionic or ionic polymer flocculants with the same electric number.