Salicylic Acid Photodegradation On NiO/La/NaTaO₃ And Pt/TiO₂ Mixed Photocatalyst And Its Mechanism

TiO₂-based photocatalytic degradation of pollutions is attracting considerable attention as a promising technology for the application to environmental problems. However, low photocatalytic efficiency and large band gap (3.2eV) has seriously hindered its large-scale applications, but also inhibited sustainable development of photocatalysis science. Hence, increasing efficiency and revealing the nature of photocatalytic process have been a hot problem. It is very important for the fundament and application study of photocatalysis to open a new door to improving the efficiency and revealing the role mechanism of photocatalytic process.TiO₂ and La/NaTaO3 were prepared by the sol-gel and solid state reaction, respectively. NiO was loaded on La/NaTaO3 and Pt was loaded on TiO₂ by an impregnation method. The mixed photocatalyst was obtained by simply mechanically mixing the powder of Pt/TiO₂ with NiO/ La/NaTaO3. Photocatalytic performance between mixed photocatalyst and single photocatayst was investigation toward salicylic acid (SA) photodegradation under 254nm light irradiation. The effect of SA initial concentration, catalyst dosage and percentage of NiO/ La/NaTaO3 in mixed photocatalyst on the degradation and mineralization of SA was evaluated. Terephthalic acid photoluminescence probing technique (TA-PL) and GC-MS were used to determined the formation of the active oxidative species (HO?) and the intermediates during photodegradation process. The possible mechanism on mixed photocatalyst for SA degradation was also discussed.The results indicated that, (1) the mixed photocatalyst exhibited a superior photocatalytic activity to either of single photocatalyst for SA degradation under 254nm irradiation. Addition of 20wt% NiO/La/NaTaO3 to Pt/TiO₂ lead to a positive increase in the SA degradation from a value of 81.9% to 91.6% for 210min; meanwhile, the mineralization achieved 80.7% over mixed photocatalyst, as compared to 66.2% over Pt/TiO₂ alone for 240min. After the photocatalytic reaction for 6 runs, no deactivation of the mixed photocatalyst occurs. (2) An optimum percentage of NiO/La/NaTaO3 loading was achieved with a value of 20wt% in the mixed photocatalyst. The higher SA initial concentration, the more remarkable...