Ciprofloxacin (CIP) in natural waters has been taken as a serious pollutant because of its hazardous biological and ecotoxicological effects. Here, a 3D nanocomposite photocatalyst g-C₃N₄/La-N-TiO₂ (CN/La-N-TiO₂) was successfully synthesized by a simple and reproducible in-situ synthetic method. The obtained composite was characterized by XRD, SEM, BET, TEM, mapping, IR, and UV-vis spectra. The photocatalytic degradation of ciprofloxacin was investigated by using CN/La-N-TiO₂ nanocomposite. The main influential factors such as pH of the solution, initial CIP concentration, catalyst dosage, and coexisting ions were investigated in detail. The fastest degradation of CIP occurred at a pH of about 6.5, and CIP (5 mg/L starting concentration) was completely degraded in about 60 min after exposure to the simulated solar light. The removal rates were rarely affected by Na⁺ (10 mg·L⁻¹), Ca²⁺ (10 mg·L⁻¹), Mg²⁺ (10 mg·L⁻¹), and urea (5 mg·L⁻¹), but decreased in the presence of NO₃⁻ (10 mg·L⁻¹). The findings indicate that CN/La-N-TiO₂ nanocomposite is a green and promising photocatalyst for large-scale applications and would be a candidate for the removal of the emerging antibiotics present in the water environment.

The surface morphology, particle size and crystal structure have a great impact on the performance of materials. Therefore, it is necessary to explore a method for the controllable synthesis of materials. In this study, three-dimensional TiO₂ nanotube arrays (3D-TNAs) formed by electrochemical anodization over Ti meshes have been prepared. The TiO₂ nanotubes are oriented in all directions, and could harvest the incident light from any direction. 3D TiO₂ nanotube arrays decorated by TiO₂ nanoparticles (3D-TNAs/TiO₂) were successfully prepared by a combined dielectrophoresis (DEP)/sol–gel process. This method greatly shortens the time required for 3D-TNAs/TiO₂ preparation while increasing the density of electrode materials and particle size uniformity. Experimental results show that the morphology and size of 3D-TNAs/TiO₂ can be controlled using DEP technology. These mesh electrodes with an anatase/rutile heterojunction were applied in photoelectrocatalytic degradation of methylene blue (MB), and show a significant improvement in photoelectrocatalytic activity compared to unmodified 3D-TNAs and 3D-TNAs/TiO₂ fabricated through only a sol–gel process. The photocurrent density could reach 0.11 mA cm⁻². The superior photoelectrocatalytic activity and the photocurrent response of 3D-TNAs/TiO₂ were mainly attributed to the high specific surface area, strong light absorption, low electron–hole recombination rate and wide light-response range.