Suspensions, deflocculated colloid

Garrido, L.B., Volzone, C., and Tones Sanchez, R.M., OH-Al polymers and HMP adsorption on kaolinite Experimental conditions and viscosity of deflocculated suspensions. Colloids Surf. A, 121, 163, 1997. 

In practice, therefore, the objective is to achieve an intermediate form by the addition of a controlled amount of electrolyte or surfactant. When the particles strongly repel each other, an electrolyte can be added. By decreasing the zeta-potential, the repulsive forces will decrease. When the particles attract each other too strongly a surfactant can be added. As the lyophobic part of the surfactant molecule adsorbs onto the surface of lyophobic colloids its lyophilic part will be oriented into the dispersion medium. By steric stabilisation, the attraction forces are decreased. The properties of flocculated and deflocculated suspensions are summarised in Table 18.18. 

Flocculation. The addition of a suitable electrolyte to a colloidal suspension to agglomerate the particles and so hasten their settling the sediment thus formed is usually more readily removed from the containing vessel than is the sediment from a deflocculated suspension. An example is the addition of up to 0.05% CaCl2 to flocculate slop glaze. 

The sodium gel is soluble and probably acts as a protective colloid, hence it is possible to have a suspension of clay formed that is relatively stable. However too great concentrations of the deflocculating agent may cause recoagulation and precipitation of the mixture. Tannin acts as a deflocculant for clays containing iron. It appears to take... 

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