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 polyac rylic acids (PAAs) (molecular weight (MW) 2000, 5000 and 90 000) on th e mercury surface by phase selective a.c. voltammetry at a potential o f - 0.6 V vs. Ag/AgCl reference electrode was investigated. The adsorp tion of these compounds was determined in the pH range 2-8, which is i mportant, because by changing the pH values the degree of neutralizati on of PAAs changes and influences adsorption. The adsorption of PAAs i s 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 polymeriz ation. No effect of ionic strength (0.01 M and 0.55 M NaCl) was detect ed for adsorption of PAA (MW 2000 at pH 1.8 and MW 5000 in the pH rang e 2-8) under the experimental conditions. The study of adsorption of a crylic acid and glutaric acid as possible monomers of PAAs at the merc ury electrode has shown that even at low pH glutaric acid is poorly ad sorbed, while acrylic acid is adsorbed more strongly than predicted fr om its hydrophobic properties defined through the octanol/water distri bution coefficient.