Ferrate is cited as having a dual role in water treatment, both as oxidant and coagulant. Few studies have considered the coagulation effect in detail, mainly because of the difficulty of separating the oxidation and coagulation effects. This paper summarises some preliminary results from an ongoing laboratory-based project that is investigating the coagulation reaction, dynamically via a PDA instrument, between ferrate and a suspension of kaolin powder at different doses and pH values, and comparing the observations with the use of ferric chloride. The PDA output gives a comparative measure of the rate of floc growth and the magnitude of floc formation. The results of the tests show some similarities and significant differences in the pattern of behaviour between ferrate and ferric chloride. This paper presents and discusses these observations and provides some comparative information on the strength of flocs formed.
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