Removal of Fe(III) from leachate of spent FCC catalyst by HNO3 in order to purify rare earths

Abstract

Currently, Dung Quat refinery disposes about 10 ton/day of spent FCC catalyst. Recovery of valuable rare earth from the spent catalyst before disposing by landfill is important not only from the economic point of view but also for environmental reasons. The solution obtained by HNO₃ leaching of the spent FCC catalyst contained La(III), Ce(III), Al(III) and Fe(III) as major components. It was difficult purifying La(III) and Ce(III) with the presence of Fe(III). In this paper, separation of Fe(III) from a leachate of spent FCC catalyst containing Al(III), La(III), Ce(III) and Fe(III) had been studied. 2 methods were utilized for Fe removal,which were precipitation and solvent extraction. Results indicated that it was not possible to separate Fe from this solution by precipitation method while extracting with DiOPA showed high Fe removal efficiency (> 99%). Based on those results, extraction method was utilized on real leaching solution of spent FCC catalyst and a solution of La and Ce with purity of 99.6% was achieved.