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1、 The mechanism of action of flocculants
1. Condensation
Coagulation: mainly refers to the process of colloid destabilization and the generation of small aggregates. The mechanism of condensation generally includes four explanations: compression of the double electron layer, adsorption electrical neutralization, adsorption bridging effect, and net trapping sweeping effect.
1.1 Compression double layer effect
According to the DLVO theory, when an electrolyte containing high valence positively charged ions is added, the high valence positively charged ions enter the surface of the colloidal particles through electrostatic attraction, replacing the original low valence positively charged ions. This way, the double layer still maintains electrical neutrality, but the number of positive ions decreases, which means the thickness of the double layer becomes thinner and the sliding surface of the colloidal particles is replaced ξ The potential decreases.
When ξ When the potential drops to 0, it is called an isoelectric state, at which point the repulsive potential barrier completely disappears.
ξ When the potential drops to a certain value, the potential barrier Emax on the total potential energy curve of the colloidal particles is set to 0, and the colloidal particles undergo aggregation. At this point ξ The potential is called the critical potential ξ K.
1.2 Adsorption Electrical Neutralization
The surface of colloidal particles adsorbs heterologous ions, heterologous colloidal particles, or polymers with heterologous charges, thereby neutralizing some of the charges carried by the colloidal particles themselves, reducing the electrostatic attraction between the particles, and making the colloidal particles more prone to aggregation and sedimentation.
The driving forces include electrostatic attraction, hydrogen bonding, coordination bonding, and van der Waals forces. It can explain the phenomenon of colloidal particle re stabilization in water treatment.
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