Novel application of metal-free graphitic carbon nitride (g-C3N4) in photocatalytic reduction-Recovery of silver ions

Metal-free graphitic carbon nitride (g-C3N4) photocatalyst was synthesized by simple pyrolysis of urea without additive assistance. The prepared photocatalyst was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and UV-Visible diffuse reflectance spectroscopy (DRS). The photoreduction and recovery of the precious silver metal from aqueous solution, in the presence of formic acid as scarifying substance, has been carried out using the prepared material under simulated sunlight. Different photoreduction conditions have been investigated in order to determine the optimal conditions. The best efficiency of Ag+ photoreduction has been achieved using 100 ppm g-C3N4 photocatalyst and formic acid, as hole scavenger, when pH of the medium was set at 4. The low photocatalyst dose confirms that g-C3N4 is a promising photocatalyst for silver reduction and recovery.