title: Photodegradation of crystal violet in TiO(2) suspensions using UV-vis irradiation from two microwave-powered electrodeless discharge lamps (EDL(-2)): products, mechanism and feasibility.
abstract: Aqueous crystal violet (CV) solutions containing P25-TiO(2) photocatalyst were irradiated with ultraviolet-visible (UV-vis) light from two microwave-powered electrodeless discharge lamps (EDL(-2)). The results demonstrated that approximately 94.4% of CV was effectively removed after 3 min of irradiation, with a pseudo-first order kinetic constant of 0.838 min(-1). According to 32 kinds of products, a five-step degradation pathway of CV was proposed. Further investigations showed that (1) three kinds of N-demethylated products and 4-dimethylaminobenzophenone (DLBP) were the main intermediates; (2) malachite green (MG) and leuco-crystal violet could not be generated by N-demethylation and phototransformation reactions, respectively; (3) bis(4-(dimethylamino)phenyl)methanone preferentially generated via decomposition of the conjugated structure of CV could be further N-demethylated into DLBP. Moreover, the unique degradation pathways of CV and MG were ascribed to the different substituents on the conjugated structures. Additionally, the cost and kinetic constant of different processes was also evaluated, and the results indicated the feasibility of this method for treatment of CV in field situations.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, PR China.
authors.forename: Yongming
authors.initials: Y
authors.lastname: Ju
authors.forename: Jiande
authors.initials: J
authors.lastname: Fang
authors.forename: Xiaowen
authors.initials: X
authors.lastname: Liu
authors.forename: Zhencheng
authors.initials: Z
authors.lastname: Xu
authors.forename: Xiuwen
authors.initials: X
authors.lastname: Ren
authors.forename: Cheng
authors.initials: C
authors.lastname: Sun
authors.forename: Shaogui
authors.initials: S
authors.lastname: Yang
authors.forename: Qian
authors.initials: Q
authors.lastname: Ren
authors.forename: Youchao
authors.initials: Y
authors.lastname: Ding
authors.forename: Kai
authors.initials: K
authors.lastname: Yu
authors.forename: Lianhong
authors.initials: L
authors.lastname: Wang
authors.forename: Zhongbo
authors.initials: Z
authors.lastname: Wei
mesh_terms: D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid; D004566:Electrodes; D005240:Feasibility Studies; D008401:Gas Chromatography-Mass Spectrometry; D005840:Gentian Violet / Q000737:chemistry*; D008745:Methylation; D008872:Microwaves; D010782:Photolysis; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: C009495:titanium dioxide; D014025:Titanium; D005840:Gentian Violet