Recovery and purification of rare earth elements from wastewater and sludge using a porous magnetic composite of β-cyclodextrin and silica doped with PC88A

Abstract

Global mining of rare earth elements (REEs) has increased exponentially because of their modern technologies' applications. The recovery of REEs from secondary sources such as industrial wastewater and industrial sludge can reduce the radioactive wastes and greenhouse gases generated during their mining and processing, as well as numerous environmental pollutions from REEs commercial products. In this work, β-cyclodextrin hybrid (P-CDP@Fe3O4) was functionalized with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl (PC88A) doped in silica. The synthesized composite, namely PCDP-M-SHM, performed better toward recovering REEs. The quantitative desorption of adsorbed REEs using dilute acidic solutions was achieved over five cycles without degradation in composite performance. More importantly, PCDP-M-SHM was found to selectively purify REEs from synthetic solutions and industrial wastewater in a continuous adsorption process with enrichment factors ranging from 10 to 30. Finally, the separation factor confirmed the effectiveness of PCDP-M-SHM to recover REEs from digested sludge with much higher distribution coefficients than coexisting elements. These results indicate that the synthesized adsorbent is a promising solution for REEs separation and purification from water.