In this study we divided the experiment into two major parts, part one is about treating methylene blue (MB) solution by TiO2 powder photocatalysis. In part two, we prepared stainless steel with coated TiO2 catalyst for the photocatalytic oxidation of MB.
As for the part one of TiO2 powder, the results show that self-made and commercial TiO2 catalyst enabled over 95% color removal after 6hr of reaction in 10 ppm MB solution under the light source of 365nm with 0.75 g/L of catalyst loading. The efficacies of photocatalytic oxidation of MB increased with catalysts loading, but no significant increase when catalysts loading over 0.5g/L. The color removal after 6hr of reaction decreased as initial MB concentration increased. Self-made TiO2 was superior to Merck at the high MB concentration solutions. For initial pH, it was found both catalysts are favorable in non-acidic solutions.
In the part two of TiO2 catalyst dip-coated stainless steel of batch run, at the condition of TiO2 catalyst dip-coated stainless steel with 2 plates, a vertical plane to the light source of 365nm, enables 98.58% of color removal after 6hr of reaction in the 5ppm MB solution, showed the TiO2 plates valid for the UV irradiation. The efficacy of photocatalytic oxidation was relative to the number of dip-coated plate, which 2 and above plates was superior to one plate, and also vertical plane to the light source was more efficient than parallel plane. The reaction rate constant showed the color removal decreased as initial MB concentration is raised. As for efficiency of durability, it was found that TiO2 dip-coated stainless steel plate performed 95% color removal at 5 ppm MB even after 4 times repeated usage, which showed favorable durability. However, when the concentration up to 10 ppm, the color removal decreases as the used time is raised; As for efficiency of regeneration, the regenerated catalyst produced almost the same activity as the fresh catalyst, which indicated the method of regeneration for catalyst may prolong the usage time of catalyst steel plate.
As for the experiment of continuous flow, under the condition of 5ppm MB, a flow rate of 55 mL/min, with 2 plates, a vertical plane to the light source, the result showed that it performed only 37% of color removal, which is inferior to batch run. A possible reason was the MB solution circulated in the tank might shorten the time of irradiation, led the catalyst to poor activity. We suggest prolonging the time of irradiation and increasing number of steel plate to enhance performance.