Synthesis, characterization, evaluation and DFT investigation of novel amidophosphonic acid ligand for uranium and rare earths extraction from phosphoric acid medium

A new class of extractant namely amidophosphonic acid ligand has been synthesized, characterized and evaluated for uranium and rare earth extraction from phosphoric acid medium. This particular ligand was inspired from the most popular system D2EHPA-TOPO deployed for uranium extraction where one acidic and another neutral ligand was utilized for synergistic extraction of uranium from phosphoric acid medium. Here in this class of ligand the neutral component is provided by amide group whereas, the acid component is phosphoric ester. The synthesis involves the reaction of Diethyl phosphate sodium DEPNa(1) with chloroacetamide (ClCH₂CON(oct)₂) to obtain the amidophosphonic ester(2) . ¹H NMR (600 MHz, CDCl₃) (ppm): 0.75 - 0.76 (m, 6H, CH₃); 1.16 - 1.22 (m, 26H, CH₂,); 1.42 - 1.47 (m, 4H); 2.8-2.9 (d, 2H, COCH₂P); 3.14 - 3.26 (m, 4H, CH₂N); 3.9 - 4.0 (m, 4H, O-CH₂-CH₃). Further hydrolysis of 2 using trimethyl silyl bromide (TMSBr) yields the final product confirmed by titration analysis. The overall yield of reaction is found to be 95 %. The experimental results indicated that bifunctional amidophosphonic acid extractant has the potential to be used for the selective separation of uranium from phosphoric acid medium