Radiochim. Acta 94, 351–356 (2006) / DOI 10.1524/ract.2006.94.6.351  by Oldenbourg Wissenschaftsverlag, München BEHSA grafted polymer for selective extraction of U(VI), Th(IV) and La(III) from acidic matrices and environmental samples – a green process By Ch. Siva Kesava Raju 1 , M. S. Subramanian 1 , ∗ , T. G. Srinivasan 2 and P. R. Vasudeva Rao 2 1 Department of Chemistry, Indian Institute of Technology, Chennai 600 036, India 2 Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India (Received September 5, 2005; accepted in revised form January 31, 2006) Solid phase extraction / BEHSA ligand / Grafted polymer / Preconcentration / Sorption capacity / Acidic wastes Summary. A new class of polymeric resin called MCM- BEHSA, for extraction of U(VI), Th(IV) and La(III) was synthesized by grafting Merrifield chloromethylated polymer with N, N -bis-(2-ethyl-hexyl)-succinamic acid. The chemical modifications at each step of the grafting was confirmed by FT-IR spectroscopy, CPMAS solid state NMR spectroscopy, CHN elemental analysis and also by Thermo Gravimetric analysis. All the parameters influencing the quantitative metal ion extraction were optimized by both static and dynamic methods. The resin showed good extractability over a wide range of acidity (0.01–10 M) with fast exchange rate (satura- tion possible within 20 minutes) and high sorption capacities for U(VI), Th(IV) and La(III). Quantitative metal desorption was achieved by using 0.5M (NH 4 ) 2 CO 3 for all the analytes. A significant feature of this grafted polymer was its ability to extract Th(IV) from very high nitric acid concentrations. Interference studies with commonly encountered metal ions, rare earth ions and electrolytes showed very high tolerance limit for those ions. Enrichment factor values of 400, 550 and 350 with limit of quantification (LOQ) as 10 ng ml −1 , 10 ng ml −1 and 20 ng ml −1 were observed for U(VI), Th(IV) and La(III), respectively. All the analytical data were within 3.2% rsd, reflecting the reproducibility and reliability of the developed method. Introduction During nuclear fuel cycle, at different stages of utilization, actinides like uranium and thorium undergo neutron induced fission, thereby releasing valuable energy as well as produc- ing highly radioactive wastes in the form of fission products. Extraction and preconcentration of these valuable metal ions from such wastes are extremely important not only from the point of view of their limited resource availability, but also to reduce their quantum for disposal as radioactive wastes. Quantitative recovery of these metal ions at trace levels in the nuclear spent solutions is the most challenging task be- cause of the high acidic environment [1–4]. *Author for correspondence (E-mail: mssu@rediffmail.com). Solvent extraction (SE) is the widely used technique and many extractants are developed for selective extrac- tion of actinides and lanthanides. Simple organic acids are known to form weak complexes [5] with actinides. Trib- utylphosphate (TBP) was known to be popular for the re- covery of actinides under high acidic conditions, but it suf- fers from some major disadvantages like non-incinerable nature of the spent extractant, low resistance to hydroly- sis and radiolysis, leading to the formation of mono and dibutyl phosphoric acids which reduce the extraction effi- ciency for actinides by yielding large amount of secondary radio active wastes [6]. N, N-dialkyl aliphatic amides were found to be good alternative extractants to TBP in view of their harmless degradation products, high radiolytic stabil- ity and complete incinerability under the above said condi- tions. Furthermore, they show good selectivity for actinides in preference to other fission products and are easy to syn- thesize [7]. Many long chain dialkylamides and tetraalky- lamides with varying chain lengths were prepared and used extensively in SE for the extraction of actinides from acidic wastes [8–12]. The use of polymeric sorbents in solid phase extraction (SPE) has its own advantages like total insolu- bility in aqueous phase, low rate of physical degradation, no scope for third phase formation, no disposal of toxic or- ganic solvent etc., and can be reused up to 20–30 cycles without loss of extraction efficiency. These features make solid phase extraction using polymeric sorbents a green sep- aration technique [13, 14]. Many of such polymeric sor- bents have been reported for preconcentration and extrac- tion of U(VI) and Th(IV) [15–18]. In spite of the positive features of the amides, not much work has been reported in SPE using amides as extracting ligands in acidic me- dia [19]. In this work a new type of polymeric sorbent was synthesized by grafting Merrifield chloromethylated resin with BEHSA ligand. The significance of this ligand is that it contains both amide and carboxylic acid groups which make the grafted polymer to extract actinides and lanthanides in both acidic and neutral medium. The experi- mental parameters were optimized and their applicability was tested for the recovery of U(VI) and Th(IV) from syn- thetic mixtures mimicking nuclear spent fuel and monazite sand. Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 5/30/15 2:26 AM