Electrochemical Cs removal and crystal formation from Fukushima weathered biotite in molten NaCl-CaCl2

Abstract

The possibility of removal and controlling crystal formation from weathered biotite (WB) in clay minerals were investigated using molten salt electrochemistry (EC) in molten NaCl-CaCl 2 under an electrochemical reductive reaction. Cyclic Voltammogram (CV) measurements were performed in the range of +0.5 V to −2.2 V. Several peaks were confirmed in the CV spectra. The peak at −1.4 V represents a reduction reaction of Fe in WB, so we conducted an experiment at −1.4 V for 2 h to reduce Iron (Fe). The Cs removal rate after EC treatment was determined by X-ray fluorescence analysis, and almost 100% Cs removal was confirmed. To understand the effect of the reductive reaction, we performed X-ray Adsorption Fine Structure (XAFS) analysis. Before EC treatment, the Fe in WB was present as a mixture of Fe 3+ and Fe 2+ . After EC treatment, the presence of Fe 2+ was confirmed by XAFS analysis. Based on this finding, EC treatment is effective for reducing Fe in WB. This result indicated that Fe 2 O 3 formation was suppressed, and the reduction reaction was effective for controlling crystal formation.