Facile Fabrication of Ag/g-C₃N₄ Photocatalyst with Visible Light Responsive Efficiency for Cr(VI) Reduction in Presence of EDTA

In order to enhance photocatalytic Cr(VI) reduction from aqueous solution, g-C₃N₄ was fabricated by Ag to synthesize Ag/g-C₃N₄ composite via a simple one-step calcination method from urea and AgNO₃. The properties of the as-synthesized Ag/g-C₃N₄ were examined by a series of characterization techniques. The obtained Ag/g-C₃N₄ composite exhibited apparently improved charge separation efficacy and optical absorption. Additionally, the influence of operating parameters, including Ag quantity in the composite, calcination temperature and time, amount of catalyst, initial Cr(VI) concentration, ethylenediaminetetraacetic acid (EDTA) concentration, and pH was studied to find an optimized condition for Cr(VI) reduction. The Ag/g-C₃N₄ composite containing 22 wt% of Ag displays 96% photocatalytic Cr(VI) reduction within 30 min in the presence of EDTA. The photocatalytic Cr(VI) reduction could follow pseudo-first-order kinetics, and the rate constant using the Ag/g-C₃N₄ composite (0.1054 min⁻¹) was 6 times higher than that using g-C₃N₄ (0.0177 min⁻¹) in the presence of EDTA. Furthermore, the composite showed high recyclability up to the fourth cycle.