AXAD-16-3,4-dihydroxy benzoyl methyl phosphonic acid: a selective preconcentrator for U and Th from acidic waste streams and environmental samples

A novel chelating ion-exchange extraction chromatographic technique has been developed using AXAD-16-3,4-dihydroxy benzoyl methyl phosphonic acid, as the stationary phase, for the selective extraction of uranium and thorium. The polymeric stationary phase was characterized by FT-IR spectroscopy, CHNPS elemental analysis and also by thermo gravimetric analysis. Various physio-chemical parameters influencing the quantitative metal ion extraction were optimized by both static and dynamic methods. The most notable feature of the developed resin matrix was its high distribution ratio values both under high acidities and pH conditions. The matrix showed superior metal sorption capacity values of 1.66 and 1.51 mmol g−1 for U(VI) and Th(IV), respectively. Kinetics studies revealed that time duration of <5 min was sufficient for complete resin phase metal ion saturation. A good enrichment factor of 333 was achieved, with the lower limits of analyte extraction being 10 ng cm−3 for both U(VI) and Th(IV). Sequential separation of Th(IV) and U(VI) was possible using 6 M HCl as eluant. In order to check the practical utility of the developed system, extraction studies were performed using simulated nuclear reprocessing mixture, synthetic seawater, real water and monazite sand samples. All the data obtained were within 3.9% rsd, reflecting the reliability and data reproducibility using the developed method.