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

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-CaCl2 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 Fe3+ and Fe2+. After EC treatment, the presence of Fe2+ was confirmed by XAFS analysis. Based on this finding, EC treatment is effective for reducing Fe in WB. This result indicated that Fe2O3 formation was suppressed, and the reduction reaction was effective for controlling crystal formation. © 2019 the Author(s), licensee AIMS Press. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0)