Preparation of titanium dioxide (TiO <inf>2</inf> ) from sludge produced by titanium tetrachloride (TiCl <inf>4</inf> ) flocculation of wastewater

Publication Type:
Journal Article
Citation:
Environmental Science and Technology, 2007, 41 (4), pp. 1372 - 1377
Issue Date:
2007-02-15
Full metadata record
Sludge disposal is one of the most costly and environmentally problematic challenges of modern wastewater treatment worldwide. In this study, a new process was developed, which has a significant potential for lower cost of waste disposal, protection of the environment and public health, and yield of economically useful byproducts. Titanium oxide (TiO 2 ), which is the most widely used metal oxide, was produced from the wastewater sludge generated by the flocculation of secondary wastewater with titanium tetrachloride (TiCl 4 ). Detailed analyses were conducted to compare TiCl 4 , ferric chloride (FeCl 3 ), and aluminum sulfate (Al 2 (SO 4 ) 3 ) flocculation. Removal of organic matter and different molecular sizes by Ti-salt flocculation was similar to that of the most widely used Fe- and Al-salt flocculation. The mean size of Ti-, Fe-, and Al-salt flocs was 47.5, 42.5, and 16.9 μm, respectively. The decantability of the settled flocs by TiCl 4 coagulant was similar to that by FeCl 3 coagulant and much higher than that of Al 2 (SO 4 ) 3 . The photocatalyst from wastewater (PFW) produced by TiCl 4 flocculation was characterized by X-ray diffraction, BET surface area, scanning electron microscopy/energy dispersive X-ray, transmission electron microscopy, photocatalytic activity, and X-ray photoelectron spectroscopy. The resulting PFW was found to be superior to commercial TiO 2 (P-25) in terms of photocatalytic activity and surface area. The PFW was also found to be mainly doped with C and P atoms. The atomic percentage of the PFW was TiO 1.42 C 0.44 P 0.14 . © 2007 American Chemical Society.
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