Recovering Y and Eu from Waste Phosphors Using Chlorination Roasting—Water Leaching Process

Abstract

Recovering Y and Eu from waste phosphors using chlorination roasting followed by a water leaching process was investigated in this study. Firstly, by chlorination roasting and water leaching, Y and Eu elements present in waste phosphors were efficiently extracted into a leach solution. Secondly, the majority of the impurities in the solution can be removed by adjusting the pH to 4.5 using a Na 2 S and NH 3 ·H 2 O solution. Thirdly, the rare earths can be precipitated afterwards by adding a H 2 C 2 O 4 solution and adjusting the pH to 2.0. Then rare earth oxides (REOs) can be obtained after calcining at 800 • C for 1 h. The characterization study of the waste phosphors and the rare earth oxide products was performed by XRD, XRF, and SEM-EDS analysis to determine the phase and morphological features. Influences of the factors, such as roasting temperatures and time, the addition of ammonium chloride on the roasting of waste phosphors, as well as the pH and the amount of oxalates on the precipitation of Y and Eu, were investigated. The maximum grade (99.84%) of mixed rare earth oxides and recovery rate (87.35%) of Y and Eu were obtained at the optimized conditions.

Rare earth elements recovery from secondary wastes by solid-state chlorination and selective organic leaching

“…Other approaches work at higher temperature (400 °C, 2 h), yet lower yield (87.35%) after adding oxalic acid and subsequent calcination (Yu et al, 2016).…”

Leaching of rare earth elements from coal ash using low molecular weight organocarboxylic acids: Complexation overview and kinetic evaluation

“…22 The leaching kinetics of rare earths has been demonstrated to follow SCM from mixed rare earth concentrate and waste cathode ray tube phosphors where in most of them it is governed by a chemical control mechanism. [23][24][25] Another important study performed by Kumari et al 26 on leaching of REEs with hydrochloric acid from NdFeB magnets concluded the kinetic model to follow the mixed mechanism with activation energy (E a ) of 30.1 kJ/mol (temperature range 348-368 K). In nutshell, the kinetic mechanism for the leaching of REE varies with respect to the source.…”

“…In yet another study, the dissolution process for Nd, Sm, and Dy from bentonite clay was determined to follow pseudo second‐order kinetic model 22 . The leaching kinetics of rare earths has been demonstrated to follow SCM from mixed rare earth concentrate and waste cathode ray tube phosphors where in most of them it is governed by a chemical control mechanism 23–25 . Another important study performed by Kumari et al 26 .…”

Effective Enrichment of Low-Concentration Rare-Earth Ions by Three-Dimensional Thiostannate K2Sn2S5

“…Up to now, several techniques have been developed to recycle REEs in wastewater, including chemical precipitation, solvent extraction, and membrane filtration, and these techniques have been widely used in industrial practice. − In addition, ion exchange has also attracted much attention for the recycling of REEs in wastewater due to its characteristics of cost-effectiveness and environmental benignity. , In fact, the REE wastewater produced from industries contains various interfering ions, such as Al 3+ , Fe 3+ , etc . In addition, the large quantity of wastewater features low concentrations of REEs .…”

“…10 Taking account of the nonrenewable nature of REE resources, it is essential to develop novel materials and related technologies for efficient recycling of REEs in wastewaters to maintain the sustainable development of REE economies and ecological environment. 8,11,12 Up to now, several techniques have been developed to recycle REEs in wastewater, including chemical precipitation, 13 solvent extraction, 14 and membrane filtration, 15 and these techniques have been widely used in industrial practice. 16−19 In addition, ion exchange has also attracted much attention for the recycling of REEs in wastewater due to its characteristics of cost-effectiveness and environmental benignity.…”