title: Microwave induced catalytic degradation of crystal violet in nano-nickel dioxide suspensions.
abstract: Nickel oxide catalyst was obtained by precipitation-oxidation method with the assistance of microwave irradiation. The samples were characterized by X-ray diffraction, Raman spectrophotometer, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, surface area and porosity analyzer. On the basis of the results, the as-prepared product was nano-NiO(2) with OH group and active oxygen. The catalytic activity of the as-prepared product might be attributed to its microwave absorbing property and the role of active oxygen, OH group under microwave irradiation. The microwave induced catalytic degradation process (MICD) with as-prepared product was further applied to degrade triphenylmethane dye crystal violet (CV). 97% of a 100 mg L(-1) sample of CV was rapidly degraded in 5 min with the corresponding 81% TOC removal. The main intermediates were separated and identified by LC-ESI-MS and GC-MS techniques. The LC-ESI-MS analytical results demonstrated that a series of N-de-methylation products were obtained in a stepwise manner, namely mono-, di-, tri-, tetra-, penta-, and hexa-de-methylated CV species. Nine organic acids with benzene ring and four low molecular acids were yielded with the assistance of GC-MS. The proposed degradation pathways were discussed in this study. The degradation processes might include N-de-methylation, destruction of conjugated structure and opening-benzene ring. MICD, as a potential technique with wide application perspective, can be used to purify triphenylmethane dye wastewater with nanosized nickel dioxide.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, PR China.
authors.forename: Huan
authors.initials: H
authors.lastname: He
authors.forename: Shaogui
authors.initials: S
authors.lastname: Yang
authors.forename: Kai
authors.initials: K
authors.lastname: Yu
authors.forename: Yongming
authors.initials: Y
authors.lastname: Ju
authors.forename: Cheng
authors.initials: C
authors.lastname: Sun
authors.forename: Lianhong
authors.initials: L
authors.lastname: Wang
mesh_terms: D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D004396:Coloring Agents / Q000737:chemistry* / Q000528:radiation effects*; D008401:Gas Chromatography-Mass Spectrometry; D005840:Gentian Violet / Q000737:chemistry* / Q000528:radiation effects*; D007220:Industrial Waste / Q000032:analysis; D013058:Mass Spectrometry; D008872:Microwaves; D053758:Nanoparticles; D009532:Nickel / Q000737:chemistry* / Q000528:radiation effects*; D010087:Oxides / Q000737:chemistry* / Q000528:radiation effects*; D021241:Spectrometry, Mass, Electrospray Ionization; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D013535:Suspensions; D013816:Thermodynamics; D014865:Waste Disposal, Fluid; D014961:X-Ray Diffraction
chemical_list: D004396:Coloring Agents; D007220:Industrial Waste; D010087:Oxides; D013535:Suspensions; C547128:nickel dioxide; D009532:Nickel; D005840:Gentian Violet