Clay, colloidal deflocculation

Deflocculation, including its secondary effects, is a result of ion exchange on the surface of clay particles. The efficacy of this colloid-chemical adjustment is illustrated by the example reported by Norton (1952) addition of NaOH solution to mono-disperse fraction of H -kaolinite prepared by dialysis gives rise to an (approximately) 200-fold decrease in apparent viscosity, affected instantaneously in the region of pH 5-6, where complete exchange of ions for Na " has taken place. 

Hemstock GW, Swanson JW (1956) Clay Deflocculation and its Effect on the Flow Properties of Clay Slips. TAPPLTechnical Association of the Pulp Paper Industry Journal 39 35-39 Iler RK (1955) The Colloid Chemistry of SiUca and Sili-cates.Cornell Univ Press, Ithaca. New York Anderson PJ, Murray P (1959) Zeta Potentials in Relation to Rheological Properties of Oxide Slips. J Am Ceram Soc 42 70-74 Worrall WE (1956) The Organic Matter of Clays. J Trans Br Ceram Soc 55 689-705... 

Kuykendall and Thomas studied the photophysics of tetrakis(V-methylpyri-dyl)porphyrin adsorbed on colloidal smectite and proposed that the photophysics can be a convenient method to monitor the degree of dispersion or extent of deflocculation of a clay dispersion to produce primary particles or single sheets (156). 

Deflocculation. — This is a term employed to indicate an increase in the colloidal properties, and usually involves a lowering in the value of n. The principal defloculants for clays are alkalis, or salts that by hydrolysis give alkaline reactions. Chiefly among the latter are sodium, potassium, and ammonium carbonates, oxalates and phosphates. According to Ashley sodium carbonate may react as follows ... 

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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