School of Chemistry and Biological Engineering;
University of Science and Technology Beijing;
Beijing 100083;
China;
North China Rare Earth Hi-Tech Company Limited;
Baotou 014030;
China;
School of Chemistry and Chemical Engineering;
Inner Mangolia University of Science and Technology;
Baotou 014010;
China;
Rare; earth; Extraction; Back-extraction; N; N; N'; N'; Tetra-octyl-3-oxopentanediamide(TODGA); Enrichment;