Modern societies depend strongly on electronic and electric equipment (EEE) which has a side effect result on the large production of electronic wastes (e-waste). This has been regarded as a worldwide issue, because of its environmental impact—namely due to non-adequate treatment and storage limitations. In particular, EEE is dependent on the availability of rare earth elements (REEs), considered as the “vitamins” of modern industry, due to their crucial role in the development of new cutting-edge technologies. High demand and limited resources of REEs in Europe, combined with potential environmental problems, enforce the development of innovative low-cost techniques and materials to recover these elements from e-waste and wastewaters. In this context, sorption methods have shown advantages to pre-concentrate REEs from wastewaters and several studies have reported the use of diverse nanomaterials for these purposes, although mostly describing the sorption of REEs from synthetic and mono-elemental solutions at unrealistic metal concentrations. This review is a one-stop-reference by bringing together recent research works in the scope of the application of carbon nanomaterials for the recovery of REEs from water.

Current environmental policies aim to reduce the levels of toxic substances in aquatic ecosystems and to promote the water reuse after appropriate treatment of wastewater.Chromium is a hazard element present in effluents of various industries that should be reduced to achieve the objectives of those policies. Most of the results reported in the literature concern the use of nanomaterials for chromium sorption dissolved either in synthetic or mono-elemental spiked solutions. The present work reviews the results of research undertaken in the last decade on the application of various nanomaterials to decrease chromium concentrations in contaminated waters. Major factors influencing the removal efficiency were examined. Because most of the published studies are based on simple experiments with deionised water and mono contamination further studies are suggested focused on effects of natural and artificial chelators, interferences of other trace elements competing with chromium sorption, reduction the sorbent mass per water volume.

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