Cu⁺-Ti Bimetallic Modified SiO₂ Nanospheres Synthesized by “One-Pot” In Situ Reduction Method for Efficiently Removing Tetracycline from Aqueous Solution

The control of emerging tetracycline organic pollutants in aquatic environments has been a recent challenge and research focus in the field of water pollution. This study presents a sol–gel method for synthesizing copper-titanium bimetallic doped silica microspheres as an effective adsorbent for removing tetracycline from aqueous solutions. The microspheres were characterized using SEM, TEM, FT-IR, XPS, and BET analysis, and the effects of pH, dosage, time, and ion strength on tetracycline adsorption were investigated. The maximum adsorption capacity of the material was found to be 99.96 mg/g, significantly higher than monometallic doped microspheres. The enhanced adsorption properties for tetracycline are a result of the larger specific surface area (421.49 m² g⁻¹), pore size (14.7819 nm), and new metal coordination sites of the copper-doped material. Kinetic and isotherm modeling confirmed the effectiveness of the adsorbent, and FT-IR and XPS analyses suggested hydrogen bonding and copper complex formation as the primary mechanisms for tetracycline adsorption. At the fifth reuse, it is still possible to achieve 60% removal rate. All the results suggest that Cu/Ti-SiO₂ composites can be a promising material for the removal of tetracycline from wastewater.