Adsorption of polyacrylic acid on hydrophobic and hydrophilic surfaces

Abstract

In this paper the adsorption of polyacrylic acid (MW=5000) on the hydrophobic mercury surface and on the hydrophilic γ-Al2O3 surface at pH=3–4 in 0.55 M sodium chloride solution was investigated. Measurements of change of the double layer capacitance by phase selective a.c. voltammetry were used for determination of the adsorption of polyacrylic acid on the mercury electrode. The same method was used for the determination of the polyacrylic acid remaining in the solution after the adsorption on hydrophilic particles (γ-Al2O3 particles). The results obtained for adsorption of polyacrylic acid were compared to the results of the adsorption of humic substance of similar molecular weight under similar experimental conditions. The study has shown that polyacrylic acid in acidic solution is strongly adsorbed on the mercury surface, which is comparable to the adsorption of humic substance on the mercury surface. At the same time, the adsorption/deposition of polyacrylic acid on the γ-Al2O3 surface is weaker compared to humic acid, indicating at a smaller degree of interaction of polyacrylic acid with aluminium ions and with hydrophilic surface.