Rare-Earth Recovery from Soda Lime Silicate Glass Cullet by P2O5 Addition

Abstract

Many rare-earth elements are incorporated into fine glass particles found in glass-polishing sludge and wasted without further exploitation. This study attempts to recover rare-earth element from simulated glass particles. For this purpose, a series of P2O5 concentrations were added to glass cullet doped with Eu2O3, followed by melting and cooling to room temperature. Recovery of rare-earth element was conducted by leaching into water. Europium was selected as dopant into the opaque samples, and its sensitive fluorescence spectrum utilized to estimate changes in the neighborhood of Eu3+ ions upon P2O5 addition. On the basis of fluorescence and infrared (IR) spectral analysis, it is estimated that significant amounts of Eu3+ ions began to coordinate with PO4 tetrahedral units when the concentration of P2O5 (P) was higher than the concentration of alkali and alkaline-earth metal oxides (A), expressed as A/P-ratio <1. In this condition, the recovery efficiency of europium element by leaching into water increased to 50–100 % relative to its initial concentration. IR spectra suggested that the increased leaching was promoted by the solubility of metaphosphate chains. This study suggests a process for recovery of rare-earth elements from glass particles found in glass-polishing sludge without use of acid treatment.