Direct synthesis of a chelating carboxamide derivative and its application for thorium extraction from Abu Rusheid ore sample, South Eastern Desert, Egypt

Abstract

ABSTRACT Direct synthesis of Pyridine-2,6-dicarboxylic a-+cid bis-(3-hydroxy phenyl)]amide, (Pydca), chelating ligand was applied for Th(IV) extraction from Abu Rusheid Ore Sample, South Eastern Desert, Egypt, between latitudes 24° 37ʹ 16ʹʹ N and longitudes 34° 46 ʹ 35 ʹʹ E and far from the Red Sea coast by about 42 km west, using poly phosphoric acid catalyst (PPA). The synthesis of new amide via direct condensation of organic acid and aromatic amine was performed in DMF at 100°C. The immediate condensation reaction led to construct the carboxamide derivative in one easy step dismantling the hard activation, halogenation, step resulting in a good yield production. This cross-coupling reaction appears simple, convenient and has a wide scope of activities. This protocol could be extended to industrial large-scale production processes. Experimental measurements have been optimised such as diluent type, pH, contact time, initial Th(IV) concentration, temperature, pydca conc., co-existing ions and stripping agents. It was found that a maximum value of Th(IV) retention (0.86 × 10−3 mol/L) is observed with 0.015 mol/L pydca/CCl4 chelating ligand at room temperature. From kinetic aspects, it was found that Th(IV) extraction follows the pseudo-first order kinetic model. The thermodynamic parameters, ΔS, ΔH and ΔG were also evaluated indicating an endothermic and spontaneous extraction process with increasing the randomness of the extraction system. Th(IV) can be completely back extracted from the loaded pydca chelating ligand using 0.5 M HNO3, 1 M H2SO4 and 1 M HCl. Finally, the optimised factors have been applied for Th(IV) recovery from Abu Rusheid Ore Sample, South Eastern Desert, Egypt, producing a thorium oxide concentrate with Th(IV) content of 81.43% with a purity of 92.67%.