Two-stage selective recovery process of scandium from the group of rare earth elements in aqueous systems using activated carbon and silica composites: Dual applications by tailoring the ligand grafting approach

A steady, reliable and enhanced scale of scandium (Sc) supply is of paramount importance in the current industrial sector, specifically, in the production of solid oxide fuel cells and scandium based aluminum alloys. Despite an expensive price quote, the remarkable physical properties of Sc drive the need to foster alternate supply pools, including industrial wastes and stockpiles, to tackle the ever-increasing need in global markets. However, they are most often obtained as a combined by-product with other metals, Sc-Y silicate minerals or rare earth elements (REE). To achieve this, activated carbon (AC) was utilized together with nano silica to synthesize two groups of adsorbents varying in terms of the ligand grafting technique. The study revealed that the Method II composites were highly effective in REE recovery, even under the process conditions of high salinity and water hardness, and in the presence of oil and organic compounds. As a conclusive step, the REE adsorption process was also successfully validated with real acidic mine drainage (AMD). Additionally, the synthesized adsorbents were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), X-ray diffraction spectroscopy (XRD), organic elemental and zeta potential (ZP) analysis to gain a better insight into the underlying mechanism characterizing the adsorption process.