Low temperature-calcined TiO(2) for visible light assisted decontamination of 4-nitrophenol and hexavalent chromium from wastewater

In the present study, alkaline hydrothermally treated titania nanoparticles (TiO(2)-HT) are prepared and followed by calcination at different low temperatures to improve TiO(2) activity under visible light. The prepared photocatalysts (PCs) are characterized by different tools. TiO(2)-HT is scrutinized for decontamination of para-nitrophenol (PNP) and hexavalent chromium ions (Cr(6+) ions) under simulated sunlight. TiO(2)-HT-300 and TiO(2)-HT-400 PCs have nanosized particle with large surface area of 148 and 116.26 m(2)/g, respectively. Additionally, XRD and FTIR proved formation of nanocrystalline anatase TiO(2). The different calcined TiO(2)-HT materials show lower adsorption capacity for PNP and Cr(6+) ions. TiO(2)-HT-300 and HT-TiO(2)-400 PCs have higher reduction rate of PNP than that of uncalcined temperature titania (HT-TiO(2)-U) powder. Complete conversion of PNP is achieved at natural pH after 180 min over TiO(2)-HT-300. As well, TiO(2)-HT-300 exhibits a superior photocatalytic removal of Cr(6+) ions. The enhanced photocatalytic efficacy is ascribed to the synergism between higher surface area and particle size (quantum effect) of TiO(2)-HT-300. As results, HO· radicals are the main key active species for the photocatalytic degradation of PNP over TiO(2)- HT-300 PC but contribution of O(2)(–) and h(+) holes is minor. The used method for preparation of TiO(2)-HT-300 reduces the cost preparation as well as environmental impact reduction. Finally, low temperature-calcined TiO(2) is promising visible light active and an efficient photocatalyst with lower environmental impact for detoxification of PNP and Cr(6+) ions from water.