EVIDENCE SUPPORTING SPECIFIC ADSORPTION OF BORON ON SYNTHETIC ALUMINUM HYDROXIDES

Aluminum hydroxide gels were precipitated in the presence of B. Both chemical and IR analyses were used to characterize the B adsorption sites on the Al(OH)3. The zero point of charge (ZPC) in a gel containing B was 1.6-2.1 pH units lower than a gel without B. This reduction was attributed to an increase in the negative charge of the hydroxide surface as a result of specific adsorption of B. Aging studies revealed that adsorbed B in gels retarded crystal growth of the Al(OH)3. The concentration of B in the total gel, in the electrical double layer and on the hydroxide surface was determined colorimetrically. Essentially all adsorbed B was held onto the hydroxide surface.