III, Phosphate Adsorption by Clay and Bond Migration

The adsorption of monoaluminum phosphate on Florida plastic kaolin was found to be 13.3 m.e. per 100 gm., whereas North Carolina kaolin adsorbed 9.6 m.e. per 100 gm. The effects of time, solution concentration, and pH were slight. Ball milling of North Carolina kaolin for 98 hours reduced the particle size of the clay considerably and increased the adsorption to 92.5 m.e. per 100 gm. A logarithmic plot of adsorption of monodisperse fractions of the ground material vs. equivalent spherical diameter gave a straight line, indicating the phenomenon to be surface adsorption. The ground material had a higher adsorption capacity than unground material of the same particle size. The rate of drying and of migration of sodium chloride and monoaluminum phosphate with unground clay and clay ground 98 hours was determined. The rate of drying of sodium chloride solutions depended on the salt content and was similar for ground and unground materials, as was the final salt distribution. Ground monoaluminum phosphate having a high adsorption capacity showed almost no salt migration, a rate of drying like that of water, and no surface deposition of monoaluminum phosphate.