The coagulating behaviors of Fe(III) polymeric species—I. Preformed polymers by base addition

The hydrolysis-polymerization-precipitation processes of Fe(III) in solution with acid-base addition can be characterized by a parameter B∗ = OH/Fe ratio calculated by a method suggested in this paper. The classification of solutions by B∗ is self-consistent in their performances as pH evolution with time, absorption spectrum, chemical speciation and coagulating behaviors. The preformed Fe(III) solution of type B∗ = 0.5–1.0 exhibited the optimum ability to coagulate kaolinite suspensions.