title: Photocatalytic degradation efficiency and mechanism of microcystin-RR by mesoporous Bi₂WO₆ under near ultraviolet light.
abstract: Microcystin-RR (MC-RR) is one of the most common cyanotoxin microcystins in fresh water and is of great concern due to its potential hepatotoxicity. In the present study, Bi(2)WO(6) was synthesized with a hydrothermal method by varying the pH of the reaction solution in the range of 1-11. The surface area of the catalysts decreased, but the crystallinity and crystal size increased with the pH. The adsorption and degradation capacities of the catalysts decreased with increasing the preparation solution pH. The Bi(2)WO(6) prepared at pH 1 (Bi(2)WO(6)-pH1) displayed the highest adsorption and degradation capacity to MC-RR even though it consisted of randomly aggregated particles. Nearly 100% of MC-RR at 10 mg L(-1) was removed after 30 min of irradiation of near-ultraviolet light (300-400 nm) in a solution with Bi(2)WO(6) concentration of 0.2 g L(-1). The photodegradation efficiency of Bi(2)WO(6)-pH1 was greater in acid medium than in basic solutions. Several intermediate products were observed and identified by liquid chromatography/mass spectrometry/mass spectrometry, and a unique photodegradation pathway was proposed. It was assumed that a photo-Kolbe process happened at the site carboxyl acid group of the d-Glu residue by the photogenerated holes, producing a hydroperoxyl product at m/z 513.8. This intermediate could be further decomposed to an alcohol product at m/z 505.8 and a ketone product at m/z 504.8. The aromatic ring and diene bond of the Adda chain could also be attacked by the holes and form phenol and diol products.
authors.affiliation: College of Environmental Science and Engineering, Key Laboratory of Pollution Processes and Environmental Criteria, Ministry of Education, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, Tianjin 300071, People's Republic of China.
authors.forename: Peng
authors.initials: P
authors.lastname: Chen
authors.forename: Lingyan
authors.initials: L
authors.lastname: Zhu
authors.forename: Shuhong
authors.initials: S
authors.lastname: Fang
authors.forename: Chunying
authors.initials: C
authors.lastname: Wang
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Shan
mesh_terms: D001729:Bismuth / Q000737:chemistry* / Q000528:radiation effects; D002384:Catalysis; D008387:Marine Toxins; D052998:Microcystins / Q000737:chemistry* / Q000528:radiation effects; D010782:Photolysis; D017973:Tungsten Compounds / Q000737:chemistry* / Q000528:radiation effects; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000528:radiation effects; D018508:Water Purification / Q000379:methods*
chemical_list: D008387:Marine Toxins; D052998:Microcystins; D017973:Tungsten Compounds; D014874:Water Pollutants, Chemical; C063855:microcystin RR; D001729:Bismuth