Graphene-based adsorbents for the separation of f-metals from waste solutions: A review

There is tremendous pressure on the energy sector to meet the surging global demand and to lower the carbon footprint. Though the majority of the research is driven towards the development of clean energy initiatives, a sizable segment is working towards making the pre-existing technology, greener than ever. With a negligible carbon footprint, nuclear supersedes thermal in the energy output. The primary issue that lies with nuclear energy is the safe disposal of high-level nuclear waste solutions which requires utmost attention. In recent years, research work has been centered on making the technology clean and economical where fuel recovery and removal of short-lived radionuclides have been prioritized. Another form of waste that is now becoming a global threat is the waste electrical and electronic equipment (WEEE). The increasing demand and cost of rare earth elements (REEs) along with mismanagement of WEEE have forced researchers and separation scientists to explore newer possibilities for the separation and recovery of REEs. Carbon-based adsorbents with graphene or nanotubes (CNTs) as the basis have been extensively studied for pre-concentration and separation of REE5 and actinides from waste solutions. Previously, we reviewed studies dealing with f-metal recovery where the 3D morphology of CNTs was the restrictive feature leading to lower adsorption performances. This review has been focused around the application of graphene-based adsorbents for the separation of REEs and actinides. Detailed discussions on mechanisms of adsorption/de-sorption have been backed by various spectroscopic, microscopic, and theoretical studies. (C) 2019 Elsevier B.V. All rights reserved.