Redox-Active Nanohybrid Filter for Selective Recovery of Gold from Water

There is an increasing demand for the recovery of noble metals with high added value from complex matrices. Traditional strategies reported to date usually require toxic chemicals and complicated operation under extreme extraction conditions. With the aim of achieving effective and selective recovery of trace amounts of Au from water, herein, we developed a functional redox-active nanohybrid filter consisting of carbon nanotube (CNT) and three-dimensional molybdenum disulfide (MoS2) nanoflowers. The CNT-MoS2 nanohybrid filter demonstrated an ultrahigh recovery capacity of 2495 mg/g toward Au(III) which could be attributed to its sufficient exposed active sites, excellent stability, flow-through design, and redox-active capability. Extensive experimental studies and advanced characterizations confirmed that the recovery mechanism of Au(III) involved a two-step adsorption-reduction process between Au(III) and the MoS2 nanoflowers. Au(III) was first adsorbed by chelation to the S atoms of the MoS2 moiety and then spontaneously reduced to Au(0) via electron capture from Mo(IV). Notably, thanks to the high affinity with a binding energy of -1.523 eV for Au(III), the CNT-MoS2 nanohybrid filter exhibited superior selectivity (distribution coefficient of 5.6 x 105 mL/g) in the presence of several common anions and cations or even in actual Au(III)-containing industrial wastewater. This study provides a proof-of-concept demonstration of a redox-active nanohybrid filter for extracting noble metal from complex wastewater.