Effect of synthesis method on NS-TiO₂ photocatalytic performance

In this study, highly visible-light photoactive nitrogen and sulfur co-doped TiO2 nanoparticles and nanosheets were synthesized via sol-gel and hydrothermal methods, respectively. The photocatalytic activity of N,S-TiO2 photocatalysts were evaluated and compared by degradation of non-steroidal anti-inflammatory drugs, ibuprofen(IBP) and naproxen (NPX), under simulated solar light. The sol-gel method developed a mesoporous structure N,S-TiO2 nanoparticle which contains both anatase and rutile phases with large BET surface area (132 m²/g). N,S-TiO2 nanosheets with pure anatase phase, with larger mesoporous structure and a smaller BET surface area (64 m²/g) was formed via hydrothermal method. NS-TiO2 nanoparticles were coated on UVC-treated polycarbonate (PC) (NS-TiO2@PC) by simple deposition method. The results showed that under identical condition, N,S-TiO2 nanoparticles can degrade 85% and 99.3% of ibuprofen and naproxen while 71.6% of IBP and 99.1% of NPX were degraded by N,S-TiO2 nanosheets. Optimization results showed that maximum degradation efficiency was achieved at the optimum conditions: irradiation intensity 8.36 mW/cm² (for ibuprofen) and 10 mW/cm² (for naproxen), initial drugs concentration 10 mg/L and reaction time 121 min. Under this condition, the maximum degradation efficiency of 83% and 100% were achieved for ibuprofen and naproxen, respectively. The results of this study elucidate co-doped NS-TiO2 nanoparticles prepared by sol-gel methods are photocatalytically more effective and practically easier to reproduce for the practical application, both in terms of energy saving and cost reduction. The energy cost analysis indicated that sol-gel method for synthesis of N,S-TiO2 is more cost effective.