Selective extraction of U(VI) over Th(IV) from acidic streams using di-bis(2-ethylhexyl) malonamide anchored chloromethylated polymeric matrix

A new chelatin polymeric sorbent has been developed using Merrifield chloromethylated resin anchored with di-bis (2-ethylhexyl) malonamide (DB2EHM). The modified resin was characterized by C-13 CPMAS NMR spectroscopy, FT-NIR-FIR spectroscopy, CHN elemental analysis and also by thermo gravimetric analysis. The fabricated sorbent showed superior binding affinity for U(VI) over Th(IV) and other diverse ions. even under high acidities. Various physio-chemical parameters, like solution acidity, phase exchange kinetics, metal sorption capacity. electrolyte tolerance studies, etc., influencing the resin's metal extractive behavior were Studied by both static and dynamic method. Batch extraction studies performed over a wide range of solution acidity (0.01-10M) revealed that selective extraction of U(VI) could be achieved even up to 4 M acidity with distribution ratios (D) in the order of similar to10(3). The phase exchange kinetics studies performed for U(VI) and Th(IV) revealed that time duration of <15 min was sufficient for >99.5% extraction. But similar studies when preformed for trivalent lanthanides gave very low D values (<50), with the extraction time extending up to 60 min. The metal sorption studies performed for U(VI) and Th(IV) at 5 M HNO3 was found to be 62.5 and 38.2 mg g(-1),. respectively. Extraction efficiency in the presence of inferring electrolyte species and inorganic cations were also examined. Metal ion desorption was effective using 10-15 mL of I M (NH4)(2)CO3 or 0.5 M a-hydroxy isobutyric acid (HIBA). Extraction studies performed on a chromatographic column at 5 M acidity were found to give enrichment factor values of 310 and 250 for U(VI) and Th(TV), respectively. The practical utility of the fabricated chelating sorbent and its efficiency to extract actinides from acidic waste streams was tested using a synthetic nuclear spent fuel Solution. The R.S.D. values obtained on triplicate measurements (n = 3) were within 5.2%. (C) 2004 Elsevier B.V. All rights reserved.