MXene-Carbon Nanotube Hybrid Membrane for Robust Recovery of Au from Trace-Level Solution

The use of precious metals in many areas, such as printed circuit boards, catalysts, and targeted drugs, is increasing due to their unique physical and chemical properties, but their recovery remains a great challenge. Here, we report a sandwiched Ti₃C₂T_x MXene/carbon nanotube (CNT) hybrid membrane, where the CNT isolates and supports the MXene sheets, which act as a reducing agent. The hybrid membrane shows excellent ability to capture precious metal ions in solution with a high flux. The water permeability of the membrane reaches 437.6 L m^-2 h^-1 bar^-1 (2.46 × 10^-18 m²), about 202 times higher than that of a pure Ti₃C₂T_x membrane, and captures 99.8% Au(III) from a solution with an extremely low concentration of 20 ppm. The desirable precious metal trapping capability of the Ti₃C₂T_x-CNT film is due to the high redox activity of C-Ti-OH. This work provides an efficient way for the recovery of precious metal ions from wastewater.