Photocatalytic Recovery of Gold from a Non-Cyanide Gold Plating Solution as Au Nanoparticle-Decorated Semiconductors

Abstract

In this work, a photocatalytic process was carried out to recover gold (Au) from the simulated non-cyanide plating bath solution. Effects of semiconductor types (TiO 2 , WO 3 , Nb 2 O 3 , CeO 2 , and Bi 2 O 3 ), initial pH of the solution (3−10), and type of complexing agents (Na 2 S 2 O 3 and Na 2 SO 3 ) and their concentrations (1−4 mM each) on Au recovery were explored. Among all employed semiconductors, TiO 2 exhibited the highest photocatalytic activity to recover Au from the simulated spent plating bath solution both in the absence and presence of complexing agents, in which Au was completely recovered within 15 min at a pH of 6.5. The presence of complexing agents remarkably affected the size of deposited Au on the TiO 2 surface, the localized surface plasmon effect (LSPR) behavior, and the valence band (VB) edge position of the obtained Au/TiO 2 , without a significant change in the textural properties or the band gap energy. The photocatalytic activity of the obtained Au/TiO 2 tested via two photocatalytic processes depended on the common reduction mechanism rather than the textural or optical properties. As a result, the Au/TiO 2 NPs obtained from the proposed recovery process are recommended for use as a photocatalyst for the reactions occurring at the conduction band rather than at the valence band. Notably, they exhibited good stability after the fifth photocatalytic cycle for Au recovery from the actual cyanide plating bath solution.

Porous organic polycarbene nanotrap for efficient and selective gold stripping from electronic waste

“…As shown in Fig. 4 b and c , after adsorbing Au 3+ at lower concentrations of 10 ppm and 100 ppm, the peak assigned to Au 4 f was divided into two peaks corresponding to Au 0 : Au 4 f 5/2 at binding energies of 87.55/87.11 eV and Au 4 f 7/2 at 83.89/83.48 eV 37 , 38 . However, at higher Au 3+ concentrations of 300 ppm and 500 ppm, the XPS spectra of Ptriaz-CN-A-Au showed three similar oxidation states of gold.…”

“…Article https://doi.org/10.1038/s41467-023-35971-w to Au 0 : Au 4f 5/2 at binding energies of 87.55/87.11 eV and Au 4f 7/2 at 83.89/83.48 eV37,38 . However, at higher Au 3+ concentrations of 300 ppm and 500 ppm, the XPS spectra of Ptriaz-CN-A-Au showed three similar oxidation states of gold.…”

Methane conversion and hydrogen production over TiO2/WO3/Pt heterojunction photocatalysts

“…The clear lattice fringes with the spacings of 0.35 nm, 0.23 nm and 0.39 nm in a high-resolution TEM (HRTEM) image can be assigned to the (101), (111) and (020) crystal planes of TiO 2 , Pt and WO 3 nanoparticles, respectively. 35,36…”

“…The clear lattice fringes with the spacings of 0.35 nm, 0.23 nm and 0.39 nm in a highresolution TEM (HRTEM) image can be assigned to the (101), ( 111) and (020) crystal planes of TiO 2 , Pt and WO 3 nanoparticles, respectively. 35,36 The XPS analysis was used to determine the surface composition and the chemical valence state of the elements in the asprepared samples, as shown in Fig. 3a-d.…”

Photosynthesis of Au/TiO2 nanoparticles for photocatalytic gold recovery from industrial gold-cyanide plating wastewater

“…The high resolution XPS spectra of Ti2p components in the parental TiO 2 structure exhibited two symmetric spectra at binding energy of 458.3 and 464.1 eV (Fig. 4b), corresponding to the spin-orbital doublet of the Ti2p3/2 and Ti2p1/2 components 29,30 , which indicates the presence of Ti 4+ species in TiO 2 NPs 31 . The Ti2p XPS spectra of Au x /TiO 2 NPs also revealed the symmetric spectra of Ti2p3/2 and Ti2p1/2 components without any shifting of binding energy compared with those of parental TiO 2 NPs.…”