Studies on the dissolution of haematite sol in mixtures containing complexing and reducing agents

Abstract

This study deals with the dissolution of monodispersed spherical haematite sol (particle size ̴130 nm) in a mixture of organic chelating and reducing agents, viz., EDTA, ascorbic acid and citric acid at <em>p</em>H 2.8 at 353 K and evaluation of the dependence of the dissolution rates on the concentration of each of the individual constituents of the mixture. The study based on the 'grain model' shows a linear dependence of dissolution rate on EDTA concentration; in the case of citric acid the concentration dependence is not linear but tends to level off at concentrations above 33 mol m^-3. The dissolution rate decreases as ascorbic acid concentration is increased from 11 - 22 mol m^-3 and reaches a limiting value with further increase in ascorbic acid concentration.