ADSORPTION OF ACRYLIC AND POLYACRYLIC ACIDS ON THE MERCURY-ELECTRODE SODIUM-CHLORIDE SOLUTION INTERFACE

In this paper the adsorption of acrylic acid, glutaric acid and polyacrylic acids (PAAs) (molecular weight (MW) 2000, 5000 and 90 000) on the mercury surface by phase selective a.c. voltammetry at a potential of - 0.6 V vs. Ag/AgCl reference electrode was investigated. The adsorption of these compounds was determined in the pH range 2-8, which is important, because by changing the pH values the degree of neutralization of PAAs changes and influences adsorption. The adsorption of PAAs is pronounced at low pH values (pH 2.0), while at higher pH values (pH 7) they are not adsorbed at all, regardless of the degree of polymerization. No effect of ionic strength (0.01 M and 0.55 M NaCl) was detected for adsorption of PAA (MW 2000 at pH 1.8 and MW 5000 in the pH range 2-8) under the experimental conditions. The study of adsorption of acrylic acid and glutaric acid as possible monomers of PAAs at the mercury electrode has shown that even at low pH glutaric acid is poorly adsorbed, while acrylic acid is adsorbed more strongly than predicted from its hydrophobic properties defined through the octanol/water distribution coefficient.