Application of the Schulze-Hardy rule to haematite and haematite/humate colloid stability

The applicability of the Schulze-Hardy rule to haematite and haematite/humate mixtures has been investigated by measuring the rate of fast and slow coagulation after the addition of increasing concentrations of mono, di and trivalent ions. Haematite colloids follow the rule for mono, di and trivalent ions. Haematite colloids coated with humate generally follow the rule for mono and di valent ions with the exception of copper ions. Trivalent ions do not follow the Schulze-Hardy rule because of their relatively strong complexation with humate. The size of the counter ion has an effect on the de-stabilising ability of ions of the same charge. (C) 1999 Elsevier Science B.V. All rights reserved.