A novel neutral-base coupling synergistic extraction system of Cyanex923 and primary amine N1923 for the recovery of cerium(IV) and fluorine from sulfuric acid medium

[Display omitted] •Cyanex923-N1923 mixture achieved synergistic co-extraction of Ce(IV) and F−.•Maximum synergistic coefficients reached RCe(IV) = 4.39 and RF− = 4.33.•Synergistic extraction mechanisms and extracted complex structures were studied.•Extracted Ce(IV) and F− could be readily stripped obtaining CeF3 particles.•High industrial potential of Cyanex923-N1923 was proved in Bayan Obo H2SO4 liquor. Cyanex923 (A) and primary amine N1923 (B) mixture was developed as a novel neutral-base coupling extraction system for the recovery of cerium(IV) (Ce(IV)) and fluorine (F−) from sulfuric acid (H2SO4) medium. This system demonstrated excellent synergistic effects for both Ce(IV) and F− extraction. In Ce(IV) solution, the maximal synergistic coefficient (Rmax) for Ce(IV) was 2.93 at the Cyanex923 mole fraction (X) of 0.6. In Ce(IV)-F− solution, the presence of F− enhanced the synergistic extraction of Ce(IV) with the Rmax-Ce(IV) of 4.39 at XCyanex923 = 0.6, meanwhile the synergistic coefficient for F− (Rmax-F−) reached 4.33. The synergistic extraction mechanisms were systematically studied through multiple techniques including stoichiometry analysis, FT-IR and NMR characterizations. Equilibrium structures of extracted complexes were determined as Ce(SO4)2∙(A)1.5(B) and CeF(SO4)1.5∙(A)(B). Thermodynamic investigations revealed that the synergistic extraction processes were spontaneous. Specifically, the extraction process for Ce(IV) was endothermic and entropy driven, while the extraction process for Ce(IV)-F− was exothermic and enthalpy driven. The extracted Ce(IV) and F− can be almost stripped completely using HNO3 with additive H2O2, and CeF3 particles were obtained by reductive stripping from Ce(IV)-F− loaded organic phase as confirmed by XRD, SEM and DLS. The Cyanex923-N1923 system achieved comprehensive recovery of Ce(IV) and F− from the Bayan Obo mixed RE H2SO4 liquor and this excellent synergistic extraction performance suggests its high practical application potential.