Ionic liquid (IL)-based extraction is a promising high-efficiency and environmentally benign separation technology. Imidazolium ILs lose their cations or anions to aqueous phase during extraction, the release lead to water pollution. To develop sustainable IL-based extraction system, we firstly investigate quaternary ammonium nitrate IL-based extraction strategy. Alkylated phosphine oxides (Cyanex925) in tricaprylmethylammonium nitrate ([A336][NO(3)]) are studied for separating Sc from Y and lanthanides. Distribution ratio and separation factor of the Cyanex925-[A336][NO(3)] system for Sc(3+) are by far larger than those achieved using Cyanex925-[C(8)mim][PF(6)] system. The stability and solvating mechanism of Cyanex925-[A336][NO(3)] extraction system can avoid release of [A336][NO(3)] to aqueous phase. The novel quaternary ammonium nitrate IL-based extraction system is an efficient and sustainable separation strategy. Published by Elsevier B.V.