Recovery of rare metal from the hot spring water

温泉水中有価金属の回収

瀬古 典明; 笠井 昇; 保科 宏行*; 玉田 正男; 市川 栄一*

Seko, Noriaki; Kasai, Noboru; Hoshina, Hiroyuki*; Tamada, Masao; Ichikawa, Eiichi*

放射線グラフト重合により作製した繊維状の吸着材は溶存する極低濃度の金属イオンを効率よく捕集することが可能である。この材料を用いて温泉水中に溶存するスカンジウムやヒ素などを回収するため、リン酸型の吸着材を作製し、吸着特性を評価した。温泉排水と同様なpH0.5から2の酸性域で、40ppbに調製したスカンジウム溶液中にリン酸型吸着材を浸漬撹拌させたところ、pH1から3の範囲で効率の良い吸着性能を示し、pH2では99%の回収率であった。また、吸着率は浸漬温度に影響し、92Cにおける吸着率は同様の試験で、わずか10分の接触で97%のスカンジウムが吸着可能であった。このことから、92Cで湧出する温泉源水での使用がより効果的であることがわかった。次に、リン酸型吸着材にジルコニウムを担持させて得られるヒ素回収用の吸着材を作製し、ヒ素の除去効率を評価したところ、市販品と比較して100倍の速度での処理が可能であることがわかった。

Adsorption method is attractive to collect the metal from the seawater and the ground water without any slag from the viewpoint of security of metal resources and environmental preservation. In this method, the adsorbent needs the high selectivity and capacity for metal adsorption from the solution. We found that the rare metals such as a scandium were solved in the hot spring water. The temperature of hot spring water is feasible for metal adsorption by means of the graft adsorbent. Noble adsorbent is necessary for collecting the scandium from hot spring water since pH of the hot spring water is less than 2. We have synthesized a fibrous phosphoric adsorbent for recovery of scandium by using graft technique. The phosphoric adsorbent has high performance for scandium even in highly acidic condition when the phosphoric adsorbent was dipped into the 100ppb scandium solution it was found that 99% of scandium ions could be adsorbed within 2 hours. Removal of toxic metals from streaming water and the groundwater is also important task to preserve environment. Hot spring water contains toxic metals such as arsenic. The arsenic adsorbent was synthesized by loading zirconium on the phosphoric adsorbent. The resulting adsorbent had 100 times faster rate of arsenic adsorption than that of commercial resin. Furthermore, the zirconium loading phosphoric adsorbent could be adapted to the removal of arsenic from the hot spring water. This adsorbent adsorbed 1g-arsenic/kg-adsorbent for 1 week soaking in hot spring.