Abstract
A method for measuring the consecutive adsorption of phenolic acids was devised by using the batch technique. Both the consecutive adsorption and desorption characteristics of three phenolic compounds with one or two salicylic moiety and dierent molecular weights, salicylic acid, 2-hydroxy-3-naphthoic acid sodium salt and naphthochrome green, on allophanic clay were measured by changing pH and concentration.
The halloysitic and illitic clays were used as references. The amounts of adsorbed salicylic acid abruptly increased at relatively high pH conditions after the second repetition, which occured by chelating bondings with the surfaces of allophanic clay. The 2-hydroxy-3-naphthoic acid sodium salt and the naphthochrome green were, however, largely retained at low pH conditions, so the participation of other mechanisms than chelating bondings, such as ionic exchange, hydrogen bonding and/or physical bonding, were estimated.
The pH and concentration (C: M) dependency of the retention (n:μM/g) obeyed the following linearly multiple regression equation:
log (n)=a pH+b log (C)+c pH×log (C)+d pH2+e
where a, b, c, d and e were coefficient constants for a combination of a phenolic compounds and a clay sample at each repetition.
