Highly Mesoporous Hybrid Transition Metal Oxide Nanowires for Enhanced Adsorption of Rare Earth Elements from Wastewater

Abstract

Removal of rare earth elements (REEs) from industrial wastewater is a continual challenge. To date, several approaches to the synthesis of nanoadsorbants for this application have been reported, although these are characterized by insufficient adsorption capacity and limitations in cycling stability. The present work reports the fabrication and performance of hierarchical hybrid transition metal oxide (TMO) nanowires deposited on carbon fibers. An ordered assembly of hybrid TMO nanowires exhibits an outstanding adsorbance of 1000 mg·g-1 of REEs with 93% recyclability. This superior performance is attributed to the unique mesoporous architecture of the nanowires, which exhibits a high surface area of 122 cm3·g-1. Further, rapid adsorption/desorption of the REEs reveals minimal morphological alteration and hence high structural stability of these hybrid TMO nanowires after multiple cycles. The ready accessibility of the adsorption sites at crystallite boundaries and the surfaces as well as rapid adsorption of the REEs on the mesoporous nanostructure facilitate considerable adsorption capacity, improved structural stability, and extended cyclability, all of which suggest the potential for this material in REE extraction.