醋酸浸出赤泥及P507萃取浸出液回收钇的实验研究

Experimental Study on Recovery of Y by Acetic Acid Leaching from Red Mud and Solvent Extraction by P507 from Leaching Solution

赤泥是生产氧化铝过程排放的固体废弃物,其中富含钇等稀有金属,是一种重要的二次矿产资源。针对目前赤泥浸出提钇过程存在杂质元素协同溶解显著的问题,利用醋酸选择性浸出赤泥中的钇,考察了醋酸浓度、液固比、浸出温度、浸出时间对赤泥中钇浸出率的影响。采用2–乙基己基磷酸单2–乙基己基酯(P507)萃取分离醋酸浸出液中钇,考察了P507浓度、萃取pH值、萃取时间和O/A等对钇萃取率及反萃率的影响。同时利用XRD、SEM−EDS等微观检测手段和浸出、萃取热力学理论分析选择性浸出和溶剂萃取过程。结果表明:在醋酸溶液pH值为0.1,液固比为10 mL/g,浸出温度为50℃,浸出时间为1 h的条件下,钇、铝、铁的浸出率分别为83%、54%和5%,而赤泥中钙、钠、钾几乎全部溶解。醋酸能够实现选择性破坏含钠、钾、钙、铝、硅的钙霞石晶体结构,赤泥中各氧化物的浸出反应吉布斯自由能变均小于0,其溶解顺序为氧化钠>氧化钾>氧化钙>氧化钇>氧化铝>氧化铁。在P507浓度为5%,溶液pH值为0.5、萃取时间为6 min和O/A为1∶5条件下,醋酸浸出液中钇的萃取率大于99%,而铝、铁萃取率小于10%,钠、钾和钙的萃取率接近于0。根据钇萃取的McCable−Thiele图谱分析,含钇醋酸浸出液采用P507经3级逆流萃取,可进一步实现浸出液中钇与铝、铁、钙、钠、钾等杂质离子的分离。负载钇有机相在硫酸体积浓度为8%和反萃时间为7 min的条件下进行反萃,钇反萃率接近100%,铁反萃率为29%,较好地实现了钇与铁的分离。

Red mud is a solid waste produced in alumina smelting process and was an important secondary mineral resource,which is rich in rare metals such as Y.Selective leaching of Y from red mud by acetic acid was used to solve the problem of collective dissolution of impurity elements in the process of yttrium extraction from red mud.The effects of acetic acid concentration,liquid to solid ratio,leaching temperature and leaching time on the leaching efficiency of Y were investigated.The solvent extraction was applied to separate Y from the acid leaching solution.The effects of P507 concentration,pH value,extraction time and O/A on the extraction efficiency of Y were studied.Furthermore,XRD,SEM-EDS and thermodynamic theory of leaching and extraction were used to analyze the selective process of leaching and solvent extraction.The results showed that the leaching efficiency of Y,Al and Fe was 83%,54% and 5%,respectively under the conditions of acetic acid solution pH value of 0.1,liquid to solid ratio of 10 mL/g,leaching temperature of 50℃ and leaching time of 1 h,while the Na,K and Ca in red mud were almost dissolved into the solution.Acetic acid could selectively destroy the crystal structure of cancrinite containing Na,K,Ca,Al and Si.The Gibbs free energy change of each metal oxide was less than 0,and the dissolution order was Na_(2)O>K_(2)O>CaO>Y_(2)O_(3)>Al_(2)O_(3)>Fe_(2)O_(3).The extraction efficiency of Y was more than 99%,and the extraction efficiency of Al and Fe was less than 10% under the condition of P507 concen tration of 5%,pH value of 0.5,extraction time of 6 min and O/A of 1∶5,while the extraction efficiency of Na,K and Ca was close to 0.According to the analysis of the McCable-Thiele diagram of Y extraction,Y was further separated from impurities such as Al,Fe,Ca,Na and K by threestage counter current extraction with P507.The stripping efficiency of Y was close to 100% and the stripping efficiency of Fe was only 29% under the conditions of sulfuric acid concentration of 8% and stripping time of 7 min,and the separation of yttrium and iron was achieved.