Titratable acidity of organo-mineral complexes as affected by mode of preparation, drying and stability of aggregates

Publisher Website
Google Scholar
Abstract
Hydroxy-aluminum-tannate-montomorillonite complexes, which were prepared at pH 4.5 by different addition sequences of hydroxy-Al, tannic acid and montomorillonite showed distinct differences in titratable acidity both before and after drying. Titratable acidity of the complexes depended on the feed rate of the base and on the presence and nature of neutral salts (KCl or CaCl2). The organo-mineral complexes showed acidity values in CaCl2 substantially higher than those determined in KCl or in water (in the order listed), probably because many weak acidic groups released H+ ions by complexation (tannate molecules) or adsorption (OH-Al-ions) of Ca2+ ions. The hydroxy-Al-tannate-montmorillonite complexes, which were washed differently (dialyzed or ultrafiltered) and dried (freeze-dried or air-dried) also showed remarkably different titratable acidity. All the complexes usually showed much lower acidity values when air-dried than when freeze-dried. After sonification the titratable acidity values of all the complexes increased, but some air-dried samples, even after four sonification treatments, showed titratable acidity lower than that of the same freeze-dried complexes before sonification. Key words: Organo-mineral complexes, aluminum, titratable acidity, potentiometric titrations

This publication has 0 references indexed in Scilit: