Effect of plasmonic metal (Cu, Ag, and Au) loading over the physicochemical and photocatalytic properties of Mg-Al LDH towards degradation of tetracycline under LED light

This work focused on the enhancement of the photocatalytic activity of solvothermal synthesized Mg-0.667 Al-0.333 (OH)(2) (CO3)(0.167) (H2O)(0.5) layered double hydroxide (LDH) by plasmonic metal (Cu, Ag, and Au) photodeposition (1-3 wt%). HRTEM analysis confirmed the successful loading of plasmonic nanoparticles with varying sizes (Au (similar to 4-25 nm) > Ag (similar to 3-12 nm) > Cu (similar to 2-7 nm)) on the surface of LDH. The effect of different plasmonic metals and their size on the surface structural, optical, electrokinetic, and photocatalytic properties of LDH was investigated. The prepared catalysts were evaluated for the degradation of tetracycline under LED irradiation for 140 min and the photoactivity trend followed the order: pristine LDH < Cu@LDH < Ag@LDH < Au@LDH. The LC-MS studies revealed that the degradation occurred by the attack of various reactive species (O-2(center dot-), h(+), O(H) over dot) via four paths mainly including hydroxylation, functional group cleavage, and ring-opening reaction. A possible mechanism was proposed for the appreciable enhancement in performance caused by the formation of Schottky barriers and surface plasmon resonance of plasmonic nanoparticles. The results of total organic carbon (TOC) indicated the acceptable mineralization of about 84 %. Less than a 10 % fall in degradation efficiency was observed within four recycle runs.