Rare earth elements (REEs) have found applications in the aerospace, automotive, consumer electronics and lighting industries, among others. A special class of REEs known as heavy rare earths (HREEs) is of particular importance to energy applications. With the growing clean energy technologies incorporating HREEs, it is valuable to examine their environmental emissions and energy requirements. Currently, extraction of HREEs is mainly carried out in China, where they are extracted mainly via open pit mining of bastnasite and/or monazite and leaching of ion-adsorption clays. Leach mining varies significantly from open pit mining technique in that the ores have much lower REE content but REEs stay as cations thus there is no need for physical and chemical beneficiation. To date limited life cycle assessment (LCA) studies have been done on REEs production and all of them are for the bastnasite/monazite route. This paper presents the first LCA of in-situ leach mining of REEs from ion adsorption clays in southern China. The function unit was defined as production of 1 kg of mixed rare earth oxides (REOs) of purity 92%. Ecoinvent 3.0 database was adopted for inventory analysis with material and energy flow information gathered from Chinese literature. To facilitate the use of results in U.S. and EU, TRACI and ILCD in SimaPro 8 were used for environmental impact assessment and cumulative energy demand was also considered as one additional category. The results showed that the environmental impacts for REOs derived from ion adsorption clays are similar in

Rare-earth elements (REEs) are a group of 17 elements with similar chemical properties, including 15 in the lanthanide group, yttrium, and scandium. Due to their unique physical and chemical properties, REEs gain increasing importance in many new energy technologies and systems that contribute to reduce greenhouse gas emissions and fossil fuel depletion (e.g., wind turbine, electric vehicles, high efficiency lighting, batteries, and hydrogen storage). However, it is well known that production of REEs is far from environmentally sustainable as it requires significant material and energy consumption while generating large amounts of air/water emissions and solid waste. Although life-cycle assessment (LCA) has been accepted as the most comprehensive approach to quantify the environmental sustainability of a product or process, to date, there have been only very limited LCA studies on the production of REEs. With the continual growth of renewable energy and energy efficient technologies, global production of REEs will increase. Therefore, reducing environmental footprints of REE production becomes critical and identifying environmental hotspots based on a holistic and comprehensive assessment on environmental impacts serves as an important starting point. After providing an overview of LCA methodology and a high-level description of the major REE production routes used from 1990s to today, this paper reviews the published LCA studies on the production of REEs. To date, almost all the LCA studies are based on process information collected from the operation of Mountain Pass facility in U.S. in 1990s and the operation of facilities in Bayan Obo, China. Knowledge gaps are identified and future research efforts are suggested to advance understanding on environmental impacts of REE production from the life-cycle perspective.

A commercial soda-lime glass subjected to ion exchange with Ag' at different temperatures and times is studied by photoluminescence (PL), optical absorption (OA) and transmission electron microscopy (TEM). Some samples were reheated in air and in a reducing atmosphere (N,-HJ to favour the reduction of the Ag' ions.The evolution of the silver colloids with the exchange parameters is monitored by means of the caracteristic absorption band at 420 nm.PL spectra reveal that the samples exchanged with silver show a broad emission band centered around 600 nm upon excitation in the nearby ultraviolet, which intensity is very sensitive to temperature and exchange time. The excitation spectra exhibit a broad band with three peaks at about 360, 395 and 445 nm related to different types of silver centres.