title: Photochemical removal of aniline in aqueous solutions: switching from photocatalytic degradation to photo-enhanced polymerization recovery.
abstract: Organic pollutants may be treated by either a degradation process or a recovery process in the view point of sustainable chemistry. Photocatalytic removal of aniline was investigated in aqueous solutions. It was found that the photocatalytic oxidation of aniline resulted in its degradation or polymerization, depending on its concentration. Hence a new treatment strategy was proposed in combination of photocatalytic degradation and polymerization, where the polymerization was in fact a recovery process. When aniline concentration was as low as 0.1 mmol L(-1), it was possible to photocatalytically degrade aniline, which could be further enhanced by increasing solution pH, modifying TiO(2) surface with the addition of anions, or coupling with the photoreduction of added oxidants. When aniline concentration was increased to about 1 mmol L(-1), the photocatalytic oxidation was observed to yield the polymerization of aniline, leading to nanocomposites of polyaniline (PAN) and TiO(2). Alternatively, the photo-enhanced chemical polymerization of aniline at higher concentrations (>or=50 mmol L(-1)) in the presence of chemical oxidants produced PAN nanostructures. The conversion of pollutant aniline to valuable PAN nanostructures or nano-PAN/TiO(2) composites is suggestive for possible applications in the treatment of aniline wastewaters as a sustainable environmental protection measure.
authors.affiliation: College of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China. hqtang62@yahoo.com.cn
authors.forename: Heqing
authors.initials: H
authors.lastname: Tang
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.forename: Yeqiang
authors.initials: Y
authors.lastname: Bie
authors.forename: Lihua
authors.initials: L
authors.lastname: Zhu
authors.forename: Jing
authors.initials: J
authors.lastname: Zou
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry / Q000302:isolation & purification*; D002384:Catalysis; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D046529:Microscopy, Electron, Transmission / Q000379:methods; D049329:Nanostructures / Q000737:chemistry; D036103:Nanotechnology / Q000379:methods; D010100:Oxygen / Q000737:chemistry; D010777:Photochemistry / Q000379:methods*; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D014025:Titanium / Q000737:chemistry; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification; D018508:Water Purification / Q000379:methods*
chemical_list: D000814:Aniline Compounds; D007220:Industrial Waste; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D014025:Titanium; D010100:Oxygen; C023650:aniline