文献名：Enrichment of rare earths in magnesium sulfate leach solutions of ion-absorbed ores by extraction-precipitation 

作者：Xiang Su^abc, Yanliang Wang^ab, Jia Su^abc, Wei Lai^ac, Yun Gao^a, Xiaoqi Sun^acd 

^aCAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Key Laboratory of Nanomaterials, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, PR China

^bUniversity of Chinese Academy of Sciences, Beijing 100039, PR China

^cFujian Research Center for Rare Earth Engineering Technology, Xiamen Institute of Rare Earth Materials, Haixi Institute, Chinese Academy of Sciences, Xiamen 361021, PR China

^dGanzhou Rare Earth Group Co., Ltd., China Southern Rare Earth, Ganzhou 341000, PR China

摘要：Magnesium sulfate (MgSO4), a leaching agent for ion-absorption rare earth (RE) ores, can reduce the production of ammonia nitrogen wastewater and supply magnesium (Mg) for soil. Three novel solid extractants, i.e., 2,2′-(1,4-phenylenebis(oxy))dioctanoic acid (PPBOA), 2,2′-(1,2-phenylenebis(oxy))dioctanoic acid (OPBOA) and 2,2′-(1,3-phenylenebis(oxy))dioctanoic acid (MPBOA) were synthesized and used to enrich RE by extraction-precipitation strategy, which showed better selectivity and faster equilibrium. The precipitation rates of PPBOA, OPBOA and MPBOA on RE could reach 95.1%, 93.5% and 96.7% at the large liquid/solid phase ratio (450/1). Meanwhile, the purities of RE in the stripping solutions reached 96.1 wt%, 94.1 wt% and 96.2 wt%. Chemical oxygen demand (COD) values of raffinates from OPBOA and MPBOA were 56 mg/L and 69 mg/L, being lower than that of China national emission standard (100 mg/L). The concentration of enriched RE solution by MPBOA was 238.0 g/L, solid extractant and MgSO4 raffinate could be recycled.