The understanding of source and flow path of the groundwater provides important strategy for the environmental management of mines. Thus, groundwater samples from the shaft and level in the Shimokawa mine and the surrounding river water samples were taken and the stable isotopes of hydrogen and oxygen and water quality of the samples were analyzed. The results indicate that shallow groundwater starts mainly from mountain-sides and passes through rocks above ore bodies. The simulation of groundwater flow was also conducted. The distribution of velocity vector of the simulated result showed that down streamlines which flows more than 2×10-3 mper day from mountain-sides to the ore bodies were observed. By considering the altitudes of mountain-sides range from 300 to 550 m, these results correspond well with the altitudes estimated from δD and δ18O values of samples.
Mutual separation of rare earth ions is very difficult because of their similar chemical properties. In this study, extraction of Nd (III), Dy (III), and Pr (III) from hydrochloric acid solution and their back extraction have been investigated using the mixture of tributyl phosphate, TBP, and 1-alkyl-3-methylimidazoliumbis[ (trifluoromethyl) sulfonyl]imide, [Cnmim][Tf2N] (n, the alkyl chain length, was 2, 4, and 6), in order to clarify the possibility of mutual separation and recovery of these elements. Synergistic effect between TBP and [Cnmim][Tf2N] was found because the extraction was highly enhanced using their mixture, while the extraction by the individual reagent was very low. Although the extraction was increased with a decrease in the n value, mutual separation was difficult because the extraction behavior was similar to one another. Ammonium formate was found to be effective as a back extraction reagent because Pr (III) and Nd (III) were precipitated out as formates while Dy (III) was quantitatively back extracted without precipitation. Precipitation formation was faster in Pr (III) than Nd (III). Based on these results, a possibility of the mutual separation among these three ions was shown.