Treatment of Mine Wastewaters for Cyanide Destruction and Thiocyanate Removal with Ferrate(VI)

Symposium 2015 Rouyn-Noranda
Mr Thomas D.Waite (Florida Institute of Technology)
Ferrates are oxy-anions of iron in oxidation states of between two and eight (FeO22- and FeO52-). While several different ferrates have been studied for commercial exploitation, only Ferrate(VI), i.e. (FeO42-) has been utilized for environmental applications. Over 400 published studies have demonstrated the unique treatment capability of Ferrate(VI) for both water and wastewater, as it can simultaneously perform oxidation, and disinfection; and because it is unstable, it is quickly reduced to Fe3+which is a coagulant. Ferrate(VI) has not been utilized in the past because of the high cost of production. Recent advances in technology have allowed for the creation of on-site generation of an inexpensive ferrate product, suitable for environmental applications.

Recent studies and pilot tests have been undertaken on Ferrate(VI) treatment of various mine wastewaters, specifically for cyanide destruction, and toxic metal removal. Results have demonstrated that Ferrate(VI) reacts quickly with both free CN (forming cyanate), and thiocyanate, (forming sulfate and cyanate). The testing also demonstrated that essentially all toxic metals tested could be removed (co-precipitated on the ferric hydroxide) by Ferrate(VI) addition.
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