Recovery of Scandium from Hot Spring Water with Graft Adsorbent Containing Phosphoric Groups

Scandium (Sc) which is a kind of rare-earth element has dissolved at a low concentration into the Kusatsu Hot Spring, located in Gunma prefecture, Japan.If Sc can be recovered from hot spring water, it is possible to ensure a stable supply of Sc as a future resource.Therefore, an adsorbent for Sc recovery was developed with radiation-induced graft polymerization of phosphoric acids that have a high affinity for Sc onto a polyethylene fabric.Hot spring water in Kusatsu Town flows into the Yukawa River, so Sc is contained at the concentration of 17 g dm -3 in the Yukawa River.The adsorption performance of Sc was evaluated with the Sc recovery equipment, consisting of 155 mm internal diameter columns and a pump that were set up near Yukawa River.The adsorbent (1.5 dm 3 ) was packed into a column and water from the Yukawa River was pumped through the column at a space velocity of 250 h -1 .As a result of the adsorption test, approximately 60 mg of Sc was collected per column.In addition, to achieve a practical use of Sc recovery, the adsorbent needs to be able to be used repeatedly while maintaining its efficiency in terms of cost reduction.So, the reusability of the adsorbent was investigated by repeating adsorption and elution.The breakthrough curves of Sc adsorption showed similar behavior in all tests.The adsorbed Sc from the 19th adsorption test was 56 mg, which was a comparable capacity relative to the average.These results indicated that the adsorbent was used more than 19 times while maintaining high adsorption performance of Sc.