Processing End-of-Life Tube Lights for Recovery of Rare Earth Oxides

Abstract

The investigation of secondary rare earth sources is attractive because of environmental concerns, economic benefits, and resource conservation. The present work investigates milling/mechanical activation, chemical and thermal (microwave) treatment for rare earth recovery from trichromatic phosphor of spent tubular lights. Ball milling prior to acid leaching of phosphor recovered 82% Y, 41% La, 33% Ce, 97% Eu, and 32% Tb. The activation energy for the thermal decomposition of the phosphor was determined as 498.9 kJ mol−1, 381.6 kJ mol−1, and 202.2 kJ mol−1 for Na2CO3, NaOH, and CaCl2, respectively. Mechanical activation with Na2CO3 reduced the decomposition temperature for microwave processing and yielded 99% Y, 97% La, 0.6% Ce, 99% Eu, and 80% Tb values. Direct leaching yielded 39 g Y-Eu oxide product; ball milling and the mechanical activation followed by acid leaching yielded 52 and 89 g of Y-Eu-La-Ce-Tb oxides, respectively, from the processing of 100 units of end-of-life tubular units.