Synergistic photosensitized removal of Cr(VI) and Rhodamine B dye on amorphous TiO2 under visible light irradiation

Amorphous TiO2 (Am-TiO2) was prepared at room temperature by hydrolysis of Ti(OBu)(4) in water without addition of strong acids or organic solvents. Results from XRD and TEM revealed that the as-prepared Am-TiO2 was composed of amorphous structure. For the simultaneous photosensitized removal of Cr(VI) and zwitterionic Rhodamine B (RhB) dye, Am-TiO2 exhibited more significant synergistic effect than commercial P25-TiO2. The removal efficiencies for RhB and Cr(VI) after 100 min visible light irradiation were 97.8% and 53.5% on Am-TiO2, respectively. While 88.2% RhB and 42.1% Cr(VI) were removed on P25-TiO2. Decreased synergistic activities as well as smaller surface areas were observed when Am-TiO2 was pretreated at high temperatures (200-700 degrees C). Thus, it was the larger specific surface area rather than better crystallinity dominated the synergistic degradation dynamics under visible light irradiation with lower pH (2), greater catalyst loading amount (2 g/L), proper RhB/Cr(VI) ratios (1:8) and higher light intensity (500W). Better synergistic performance was also obtained on Am-TiO2 than P25-TiO2 when Cr(VI) coexists with cationic dyes, while negligible difference was observed in the presence of anionic dyes. Superior stability and simplicity of Am-TiO2 was also exhibited in the cyclic runs. (C) 2012 Elsevier B.V. All rights reserved.