Photocatalytic degradation of ciprofloxacin by Gd-Co/g-C3N4 under low-power light source: Degradation pathways and mechanistic insights

Abstract

Ciprofloxacin hydrochloride (CIP) is remained in the natural environment. Photocatalysis is a promising technology for removing hard-to-degrade pollutants from water. For this purpose, we constructed a three-dimensional porous structure of graphitic-phase carbon nitride (3D g-C3N4) and doped rare earth element Gd and metal Co into 3D g-C3N4 to form a photocatalyst (Gd-Co/CN). We conducted photocatalytic experiments to evaluate its photocatalytic activity with CIP as the target pollutant. Experimental results showed that Gd-Co/CN had the best photocatalytic degradation of CIP under a 30 W LED lamp. The increase in photocatalytic activity is mainly attributed to the doping of Gd and Co expanding the specific surface area of 3D g-C3N4, and providing more reaction sites for photocatalytic reactions. Gd-Co/CN enhances O2 adsorption and activation and generates radicals (O2− and h+), allowing efficient degradation of CIP under low-power light sources. Furthermore, Gd-Co/CN also showed excellent stability and reusability in cycling experiments. This study explored the degradation pathways and mechanisms of CIP by using ultra-high-performance liquid chromatography and mass spectrometry (HPLC-MS) and density functional theory (DFT). It provides a more energy-efficient and environmentally friendly method for the treatment of antibiotic wastewater.