ABSORBENT USING PEELINGS OF PERSIMMON AS RAW MATERIAL AND METHOD FOR SEPARATING URANIUM AND THORIUM

PROBLEM TO BE SOLVED : To provide a method for separating/removing uranium and thorium present in environment in low concentration using an inexpensive adsorbent, especially a method for separating/removing a very small amount of uranium and thorium coexisting in a rare-earth element. SOLUTION : This adsorbent is inexpensively prepared by grinding astringent persimmons, which are caused in large quantities at the time of production of dried persimmons as they are and crosslinking the ground persimmons using a crosslinking agent such as para-formaldehyde or the like before washing and drying them. This adsorbent thus prepared is stirred along with water containing uranium and thorium in an existing stirring device and subsequently filtered off to remove uranium and thorium in water. Alternatively, a column is filled with the adsorbent and water containing uranium and thorium is passed through the column to remove uranium and thorium in water. An acid aqueous solution with a pH of 1 or below is passed through the column after adsorption to concentrate adsorbed uranium and thorium to elute them. The adsorbent is regenerated by this method to be again subjected to adsorption/removal.