The aqueous chemistry of ferric iron is similar to that of aluminum. Subtle differences exist in the complexity of hy-drolytic reactions, the pH effects on intermediate soluble species, and the final precipitated floc.
An important property of ferric iron coagulant in waste-water applications is its ability to undergo reducing reactions to form ferrous iron. When raw municipal waste-water is treated, the absence of free molecular oxygen or any other oxidation agent results in a reducing environment. Research shows that precipitated ferric-iron hydrolysis species release iron as a reduced ferrous compound when they are maintained in an anaerobic environment. This property is significant in applications where removal of phosphorus compounds and the destabilization of colloidal pollutants is required. However, its significance for destabilization only is unknown.
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