尿素共沉淀法回收钕铁硼废料中的稀土及铁元素

Recycling Rare Earth and Fe Elements from NdFeB Waste by Urea Co-Precipitation Method

通过尿素共沉淀法从钕铁硼废料中回收稀土及Fe元素,并采用X射线衍射(XRD)分析其相组成,用扫描电镜(SEM)分析其微观结构,获得的产物由纳米尺寸的稀土或稀土与铁的混合氧化物以及微米尺寸的Fe2O3组成。研究了pH值与温度T对尿素水解及回收产物的影响。结果表明,随pH值从1增大至6,稀土元素回收率总体呈先升高后降低的趋势,Fe元素回收率呈持续升高趋势。4种稀土元素回收率随pH值的变化趋势略有差异。随温度升高,4种稀土元素回收率均先升高后降低,总回收率在温度为60~70℃时稳定在大于90%的水平。其中最佳沉淀条件为:pH=3,T=65℃。该条件下稀土元素和Fe元素回收率分别为94.92%和100.49%,总回收率为98.81%,产物纯度为98.86%。与现有共沉淀工艺相比,尿素共沉淀工艺可通过控制温度来控制反应速度,获得高的回收率及纯度。该方法流程短、操作简单、节能环保,是一种具有实用价值的钕铁硼废料回收工艺。

Rare earth(RE)and Fe elements were successfully recycled from NdFeB waste by co-precipitation method with urea.The products were conducted X-ray diffraction(XRD)and scanning electron microscope(SEM)to analysis compositions,phases and microstructure.The obtained products included the nano-sized RE or RE and Fe oxide particles and micro-sized Fe2 O3 powders.The influences of pH value and temperature T on the urea hydrolysis process and recycling products had been investigated.On the whole,RE elements’recovery yields lifted up firstly and subsequently decreased,Fe element’s always increased with the value of pH from 1 to 6.There were some differences among four RE elements in the changing tendency.The recovery yields of four RE elements kept above90%at 60~70℃with a continuously increasing trend following the rising temperature.The optimized precipitation parameters were detennined as pH value of 3 and T of 65℃.The recovery yields up to 94.92%and 100.94%were obtained for Fe and RE element,respectively.The total recovery yield was up to 98.81%,and the purity was up to 98.86%.Compared with the existing co-precipitation methods,urea co-precipitation method had the advantage of controlling reaction speed to achieved high recovery rate and purity by adjusting temperature.Hence,it was a practical method for recovering NdFeB waste with merits of short process,simple operation,energy saving and environmental protection.