赤泥磷酸浸出液中稀土的萃取行为研究

Study on extraction behavior of rare earth elements from the red mud leaching solution with phosphoric acid

赤泥是铝土矿生产氧化铝过程中产生的固体残渣,含有铁、硅、铝、钛及稀土等多种有价组分。在已预先分离赤泥中大部分铁、硅、铝、钛的前提下,采取溶剂萃取的方式对赤泥磷酸浸出液中的稀土作进一步分离与纯化,研究了在中性磷型萃取剂TBP、酸性磷型萃取剂P204和P507分别作用下,稀土La、Ce、Sc、Y以及主要杂质组分Al、Fe、Ti、Ca的萃取行为,结果表明:TBP对稀土的萃取效果较差,P507对稀土Sc、Y及杂质Fe、Ti的萃取能力较强,P204萃取稀土的能力优于P507;采用质量分数2%P204作为萃取剂,在溶液pH为1.5、相比为1∶3的条件下,磷酸浸出液中Sc、Y的萃取率分别为90%、99%,La、Ce及杂质Fe、Al、Ti、Ca萃取率均低于5%;将P204质量分数升至20%,La、Ce萃取率可分别达到85%、95%。因此可通过采用P204分步萃取的方式有效分离磷酸浸出液中的稀土。

Red mud is a solid residue generated from the production of aluminum oxide with bauxite ore,which contains many valuable components such as iron,silicon,aluminum,titanium and rare earth.Upon completion of pre-separating most of the iron,silicon,aluminum,and titanium from the red mud,solvent extraction was employed to further separate and purify the rare earth elements contained in the leaching solution of red mud with phosphoric acid.The extraction behavior of rare earth elements like La,Ce,Sc,Y,and the major impurity components such as Al,Fe,Ti,Ca were studied under the action of neutral phosphorous-oxygen type extractant TBP,acidic phosphorous-oxygen type extractant P204 and P507 respectively.The results show that the extractant TBP exhibited low extraction efficiency on rare earth elements La,Ce,while P507 presented high extraction efficiency on rare earth elements Sc,Y and impurities like Fe and Ti.However the extractant P204 performed better than P507 when being used for extracting rare earth elements.Using 2%P204 as the extractant,the extraction rate of 90%Sc and 99%Y can be achieved from the leaching solution with phosphoric acid at a pH1.5 and a phase ratio of 1∶3.The extraction rate of element La,Ce or impurities like Fe,Al,Ti,and Ca was lower than 5%.When 20%P204 was applied in the extraction process,the extraction rates of element La and Ce reached 85%and 95%respectively.Therefore,application of extractant P204 in the step-by-step extraction process makes the efficient separation of rare earth elements from red mud leaching solution with phosphoric acid workable.