Article

Study of electrochemical bleaching of p-nitrosodimethylaniline and its role as hydroxyl radical probe compound

Journal of Applied Electrochemistry (Impact Factor: 1.84). 02/2011; 41(5):599-607. DOI: 10.1007/s10800-011-0268-1

ABSTRACT In the present paper, research on the electrochemical bleaching of p-nitrosodimethylaniline (RNO) in different electrolyte systems is presented with special attention to the role of RNO as a
selective hydroxyl radical probe compound. At a Ti/Pt90–Ir10 anode, RNO was found to be bleached in 0.050M sodium sulphate electrolyte due to lattice active oxygen without hydroxyl
radicals being intermediately present. In 0.050M sodium chloride, the bleaching rate was greatly enhanced due to indirect
bulk oxidation by active chlorine species, again without the presence of hydroxyl radicals in the oxidation mechanisms. Under
galvanostatic electrolysis, a linear relationship was found between the concentration of added chloride to a supporting sodium
sulphate electrolyte and the first order rate constant of the bleaching reaction, showing the importance of the indirect bulk
chlorine bleaching in chloride electrolyte systems. In this fashion both the chemically bonded active oxygen and the chemical
bulk oxidation by active chlorine species proved to be valid bleaching pathways of RNO that according to these findings cannot
be regarded as a fully selective hydroxyl radical probe compound. In addition, the difference in the mechanisms of chloride
electrolysis at Ti/Pt90–Ir10 and Si–BDD anodes was clearly demonstrated using t-BuOH as hydroxyl radical scavenger.

KeywordsElectrochemical oxidation–Bleaching of dye–Hydroxyl radical probe compound–
p-Nitrosodimethylaniline–RNO–
pNDA–Chlorine oxidation

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    ABSTRACT: This study investigated the potential use of oxidation in a photoelectrocatalytic cell for bleaching p-nitrosodimethylaniline. The Ti/TiO2 used as photo-anode was prepared by a pulsed laser deposition method. The TiO2 coatings were found to have rutile and anatase structures consisting of approximately 10 and 15 nm in diameter, respectively. A relatively high degradation rate of p-nitrosodimethylaniline was recorded using the photoelectrocatalytic cell, compared to those measured during conventional electrochemical oxidation, direct photolysis and photocatalysis processes. The influence of different parameters such as crystallographic structure of Ti/TiO2, type of cathode, potential applied, electrolysis time, UV irradiation and initial pH were investigated. The photoelectrocatalytic cell using Ti/TiO2 (anatase structure) as photo-anode and vitreous carbon as cathode operated at a current intensity of 0.1 A for 120 min with 254 nm of UV irradiation was found to have the best conditions to remove high amounts of p-nitrosodimethylaniline (22.6 × 10−3 mM h−1).
    Journal of Applied Electrochemistry 43(4). · 1.84 Impact Factor

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