Modified phenolic resin for the removal and reduction of Au(III) and simultaneously as the nano-Au(0) immobilized carrier for catalysis

In this work, a new adsorbent resorcinol-formaldehyde-thiourea (RFT) was synthesized through the improved stöber method. Fourier transform infrared (FT-IR), Thermogravimetric (TGA), X-ray diffraction (XRD), Scanning electron micrograph (SEM), Transmission Electron Microscope (TEM), EDS mapping and X-ray photoelectron spectroscopy (XPS) were used to analyze the morphology and physical properties of RTF microspheres. RFT exhibits outstanding Au(III) adsorption performance, reaching 1088 mg/g of MAu/MRFT due to the abundant phenolic hydroxyl of resorcinol and thiourea functional groups. Owing to the reduction ability of sulfur group, Au(III) was reduced to Au(0) and deposited on RFT. DFT results illustrate that S from thiourea is the major adsorption site. Moreover, the RFT after adsorbing Au(III) can be used as a catalyst to reduce the hazard 4-nitrophenol to 4-aminophenol. This work provides an innovative strategy to deal with gold-bearing wastewater, designs a green route from gold recovery to reuse and broadens the applications of sulfur-rich nanomaterials in the recovery and reuse of precious metal.