Oxidative removal of brilliant green by UV/S2O82‒, UV/HSO5‒ and UV/H2O2 processes in aqueous media: A comparative study

• Published in: Journal of hazardous materials 2018-09, Vol.357, p.506-514
• Main Authors: Rehman, Faiza, Sayed, Murtaza, Khan, Javed Ali, Shah, Noor S., Khan, Hasan M., Dionysiou, Dionysios D.
• Format: Article
• Language: English
• Subjects: Advanced oxidation processes (AOPs); Brilliant green; Degradation pathways; Dyes; Second order rate constant; Water treatment
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2018.06.012

[Display omitted] •Removal of brilliant green has been assessed by UV/S2O82−, UV/HSO5− and UV/H2O2 processes.•OH showed slightly higher reactivity than SO4− for the degradation of brilliant green.•Density functional theory was used to predict the attack sites of brilliant green by OH/SO4−.•Nine degradation products of brilliant green were detected experimentally using LC/MS/MS. The removal of brilliant green (BG), a toxic organic and cationic dye, has been examined by UV/S2O82− (PS), UV/HSO5− (PMS) and UV/H2O2 processes. BG showed insignificant direct photolysis at 254 nm (i.e., 8.6% after 30 min). However, enhanced BG degradation was observed in UV/PS, UV/PMS and UV/H2O2 systems as revealed from 63.1, 47.0 and 34.8% BG degradation, respectively, at 30 min of reaction time, using 0.05 mM BG and 1.0 mM oxidant initial concentration. The bimolecular rate constants of OH and SO4− with BG were determined to be 2.35 × 109 and 2.21 × 109 M−1 s−1, respectively. Electrical energy per order (EE/O) values for UV/PS, UV/PMS and UV/H2O2 processes were calculated to be 5.4, 6.8, and 7.8 KWh/m3/order, respectively. The addition of humic acid (HA) and inorganic anions inhibited the degradation of BG by UV/PS in the order of NO2− > HA > HCO3− > Cl−  > NO3− ≈ SO42−. The results of frontier electron densities (FEDs) showed that C-atom holding the three rings (C7), and C-atoms at para positions to N-alkyl groups of the two rings (C4 and C14) are the predominant sites for radical addition. Furthermore, nine degradation products (DPs) of BG were detected experimentally using LC/MS/MS.