Fabrication of highly efficient Au and layered double hydroxide modified g-C3N4 ternary composites for degradation of pharmaceutical drug: Pathways and mechanism

Abstract

Graphitic carbon nitride (CN), a conjugated polymer widely recognized as a chemically stable and low toxic catalyst for the degradation of organic molecules. But it acquires certain limitations like a limited visible light response, high recombination rate of charge carriers, and lower charge density. To overcome such drawbacks, we synthesized a series of Ni-Al layer double hydroxide (LDH)/CN composites by loading 5–15 wt% of Ni-Al LDH onto CN by electrostatic self-assembly method. Further, Au nanoparticles were deposited photochemically on LDH/CN nanocomposites. The Au/LDH/CN nanocomposites exhibited enhanced photocatalytic degradation of tetracycline (TCH) under visible light. Particularly, the Au/LDH/CN nanocomposite with LDH and Au contents of 10 and 1 wt%, sequentially, displayed the highest degradation, which was much better than that for pure CN. The face-to-face interface between LDH and CN and the electron-accepting capability of Au nanoparticles in Au@LDH/CN boosts the separation and transfer efficiencies of photogenerated charge carriers. The intermediate products formed after the degradation of TCH were detected by LCMS and possible degradation pathways were shown. Based on photoluminescence, scavenging experiments, and LC-MS analysis, a possible mechanism for degradation of TCH on Au@LDH/CN nanocomposite was proposed.