Rapid microwave processing of discarded tubular lights for extraction of rare earth values

Abstract

In this study, recycling of spent tubular lights comprising about 40 % rare earth (Y, La, Ce, Eu, Tb) elements are explored. In this study, two different processing routes comprising leaching followed by microwave treatment, and vice versa are investigated. Leaching of Eu-Y values followed by microwave treatment of leach residue with sodium hydroxide was found promising for rare earth extraction. Different routes comprising one step, two-step, and acid baking in the microwave were compared based on the recovery of rare earth values. Two-step process consisting of acid leaching followed by NaOH microwave treatment of leach residue was found best concerning overall extraction and separation of Y-Eu and La-Ce-Tb oxides. The material balance shows that 50 g mixed oxide of Y, Eu, and ∼8 g of La, Ce, Eu, Tb, Y mixed oxide with purity over 97 % can be recovered from 100 units of discarded tubular lights. Finally, it is concluded that microwave processing can be employed for the recovery of rare earth values from abundantly available discarded tubular lights.