Synthesis of malonic acid-functionalized amberlite XAD-4 and its use in solid phase extraction/preconcentrative separation of thorium(IV)

A new chelating polymer has been developed wherein Amberlite XAD-4 has been functionalized by coupling it with diethylmalonate after acetylation. The resulting resin has been characterized by IR spectral and microanalysis studies and has been used for preconcentrative separation of thorium(IV) in the presence of alkali, alkaline earth, transition elements and lanthanides. Various physico-chemical parameters influencing the sorption of thorium(IV) onto the polymeric matrix was investigated and optimized by both batch and column methods. Quantitative extraction of thorium(IV) was obtained in the pH range 6.0-8.0. The sorption capacity of the malonic acid functionalized resin is 19.28 mg per g of polymer with an enrichment factor of 500. Moreover, the system showed faster exchange kinetics for extraction of thorium(IV) thus resulting in quantitative enrichment at flow rates as high as 16.0 cm3/min using 0.2 g of resin packed column (7 mm dia). Five replicate determinations of 10 μg of thorium(IV) present in 2.5 dm3 of sample solution gave a mean absorbance of 0.160 with a relative standard deviation of 2.54%. The detection limit corresponding to 3 times the standard deviation of the blank was found to be 0.2 μg dm3. The developed procedure has been successfully utilized for the estimation of thorium(IV) content of pure rare earth chloride solution collected from Indian Rare Earths Limited, Alwaye, India. (orig.)