3D MXene hybrid architectures for the cold-resistant, rapid and selective capture of precious metals from electronic waste and mineral

Abstract

Research into advanced adsorbents is one of the most promising ways to recycle precious metals from electronic wastes and minerals owing to their high uptake capacity, low maintenance requirements, and ease of use. Herein, a new adsorbent, MXene hybrid aerogels (MXGA), were successfully prepared by means of a hydrothermal reactor with the assistance of graphene oxide (GO) and a freezing-induced assembly method. The MXGA and pure MXene aerogel (MXA) displayed high selectivity to Au(III) (Kd = 2.61 × 106 for MXGA; Kd = 3.23 × 105 for MXA) and Ag(I) (Kd = 2.03 × 105 for MXGA; Kd = 1.76 × 108 for MXA) in a mixture of multiple metal ions. In addition, the trapping capability of MXGA (1063.8 mg/g) and MXA (1851.8 mg/g) for Au(III) was encouragingly high. The capture mechanism was investigated, where a surface complexation from oxygen-containing functional groups was proposed for Ag (I), and the sorption-redox process and electrostatic attraction in MXGA were proposed for Au(III) adsorption. A trapping efficiency of 99.9% for Au(III) by MXA was achieved within 1 min through the redox–capture process. Au(III) and Ag(I) captured on MXA and MXGA were rapidly trapped and the sorbent reused for more than five cycles, without a significant decrease in its capture capacity. Notably, compared with the capture ability at room temperature, MXGA architectures could also maintain superior capture and enrichment capabilities at temperatures as low as 0 °C. This unique property endowed the 3D MXene hybrid architectures with the promising ability to trap gold and silver from ores and electronic waste, providing a new method for the development of green platforms for noble metals regeneration.