Polyelectrolytes as inhibitors of Fe(III) oxide precipitation

Abstract

Fe(III) oxide precipitation was studied in the presence of several polyelectrolytes. A rather specific inhibition of the synthesis of hematite in the presence of polyacrylic acid of molecular mass 4000 was observed. This effect occurs over a very narrow polyelectrolyte concentration range: 4.4 to 8.8 × 10 −5 N. When the molecular mass of the polyacrylic acid is changed to higher values (25,000, 125,000, and 250,000), the inhibitory influence disappears completely. Polymethacrylic acid of molecular mass 4000 has no retarding or inhibiting effect, indicating that the conformation of the polymeric chain is an important variable. Other polyelectrolytes, such as polystyrenesulfonic acid and polyvinylbenzyltrimethylammonium chloride, show no inhibiting effect. Possible explanations of these observations are discussed.