Recovery of yttrium oxide from titanium-aluminium based wastes

Abstract

Yttrium belongs to the rare earth elements and critical metals. Yttrium oxide is mostly used in fluoroscent lamps, production of electrodes, in electronic filters, lasers, superconductors and as additives in various titanium-aluminium materials to improve their properties. Recovery of yttrium oxide from secondary sources such as red mud, coatings from ceramic industry and phosphors is extremely important. The main aim of this study is to examine the selective recovery of yttrium oxide from Al-Ti based secondary materials using one combined method based mostly on leaching for selective recovery of yttrium containing:  crashing and grinding of materials, sieving, leaching of chosen fine fraction with hydrochloric acid, precipitation with oxalic acid in order to produce a pure yttrium oxalate, filtration and a final thermal decomposition of yttrium oxalate. The present study summarized mostly the influence of different reaction parameters such as leaching temperature, time and concentration of hydrochloric acid on yttrium dissolution from Al-Ti based secondary materials. An increase of dissolution time and temperature increases yttrium dissolution. An increase of pressure from an atmospheric pressure to 0.5 MPa at 150 °C leads to the maximum dissolution of yttrium (about 98.6 %). The final produced yttrium oxide after thermal decomposition of yttrium oxalate was analyzed using SEM and EDS-analysis.