Investigation of UV-assisted chlorophenol congeners’ degradation by organic oxidant p-nitrobenzoic acid in basic media

This research specifically addressed the photodegradation of selected model chlorophenol (CP) congeners, 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP), by an organic oxidant, p-nitrobenzoic acid (PNBA), in basic media. The reactions were followed by high-pressure liquid chromatography and gas chromatography–mass spectroscopy analysis for residual concentration and the identification of photodegraded products respectively. Initial degradation was confirmed by the formation of ring cleavage compounds, and subsequent mineralization was evidently marked by an increase in release of chloride ions in the time course profile. The presence of fewer/no chlorine atoms in the degraded compounds corroborated the mineralization by UV/PNBA action. The chemical oxygen demand (COD) was also observed to fall appreciably to the extent of 73% during all CP congeners’ degradation. The maximum COD decrease was observed in PNBA-assisted 4-CP degradation. The overall degradation kinetics conforming to second-order reaction is observed to follow the order 4-CP > 2,4,6-TCP ∼ PCP ∼ 2,4-DCP. The findings of this investigation elucidated the fact that PNBA was capable of successfully degrading/mineralizing the selected CP congeners.