PNNL

Abstract

In previous studies, we have examined using sodium permanganate for selectively oxidizing and removing chromium from washed Hanford tank sludges. The conclusion from the previous work was that contact with sodium permanganate in a minimally caustic solution, i.e., 0.1 to 0.25 M [OH-] initially, provided maximum Cr dissolution while minimizing concomitant Pu dissolution. This report describes work focused on 1) developing simulants to be used in oxidative leaching tests, 2) developing methods for monitoring chromium oxidation by permanganate, and 3) identifying the Cr and Mn materials formed during the oxidative leaching process. The impact of such variables as the Cr compound used, agitation rate, temperature, hydroxide concentration, and initial MnO4-:Cr ratio on the rate and extent of chromate formation were examined.