Selective Extraction of U(VI) and Th(IV) from High Saline Matrices Using AXAD-16-BHBPD as Chelating Polymeric Matrix

A new chelating polymer has been developed for the selective preconcentration of actinide ions, using Amberlite XAD-16 (AXAD-16) polymeric matrix, chemically modified using (bis-2-hydroxy benzyl) p-phenylene diamine (BHBPD) through an azo spacer. The developed chelating resin matrix possessed superior metal sorption capacity, faster exchange kinetics, and exclusive ion-selectivity for U(VI) and Th(IV), over many common metal ions. Various physio-chemical parameters like the solution pH, kinetics of sorption, effect of competing cations and complexing anions, maximum metal sorption capacity, sample breakthrough volume, flow rate, etc., which influence the extent of metal ion sorption to the resin phase were studied and optimized by both static and dynamic method. The developed chelating resin exhibited high metal loading capacity values of 1.68 and 1.62 mmol g-1 for U(VI) and Th(IV) respectively. It also showed faster exchange kinetics between phases with a time duration of < 10 min for complete metal ion extraction with t 1/2 values of < 3 min for both the analytes. From the recovery studies, it was found that the sequential separation of U(VI) and Th(IV) were possible using 4 M and 1 M HCl respectively, with a quantitative metal ion recovery of > 99%. The metal extractive behavior of the resin matrix was tested using synthetic mixtures and real samples, which showed rsd ≤2.5%, for all analytical measurements showing its practical utility. The developed resin matrix showed a good mechanical stability and chemical durability even up to 30 cycles of repeated usage.