Recovery of Rare Earth Elements from High Alumina Fly Ash by Alkali-Solution Desilication Combined with Mechanochemical Extraction Method
Alkali-solution desilication combined with mechanochemical extraction method was applied to recover rare earth elements(REEs)from high alumina fly ash(HAFA),and high value-added aluminium-rich residue was obtained simultaneously.The results show that REEs in HAFA are mainly enriched in the glass phase.The alkali-solution desilication process can be used to efficiently and selectively dissolve the glass phase(retain the aluminium-rich mullite-corundum phase)in HAFA under mild conditions,and release the REEs into NaOH solution to be converted into rare earth hydroxide precipitates.Then,EDTA was used as leaching agent to efficiently and rapidly extract the REEs from the desilication residue by mechanochemical method.Under the optimal conditions of the leaching process,the extraction efficiencies of La,Ce,Pr and Nd are 85.99%,83.30%,82.03%and 88.71%,respectively,while aluminium-rich slag is obtained(mass fraction of Al2O3 is 68.23%,and Al/Si=2.517).This study can provide a new strategy for the green and high value-added recycling of HAFA.
high alumina fly ashalkali-solution desilicationrare earth element recoverymechanochemical extractionEDTA
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