Photolytic degradation of chlorophenols from industrial wastewaters by organic oxidants peroxy acetic acid, para nitro benzoic acid and methyl ethyl ketone peroxide: identification of reaction products.
In this investigation, chlorophenol (CP) containing industrial wastewater was remediated by ultraviolet irradiation in conjunction with organic oxidants, peroxy acetic acid (PAA); para nitro benzoic acid (PNBA); and methyl ethyl ketone peroxide (MEKP). CP mineralization was studied with regard to chemical oxygen demand (COD) and chloride ion release under identical test conditions. COD depletion to the extent of 81% by PAA, 66% by PNBA, and 67% by MEKP was noted along with an upwardly mobile trend of chloride ion release upon irradiation of samples at 254 nm. A 90-99% decrease in CP concentration (as per high pressure liquid chromatography (HPLC) analysis) was achieved with an additional 15.0 ml of organic oxidant in all cases. Gas chromatography high resolution mass spectroscopy (GC-HRMS) results also indicated the formation of such reaction products as are free from chlorine substitutions. This treatment also leads to total decolorization of the collected samples.
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.
Interaction of Diclofop-Methyl and MCPA on Wild Oats (Avena fatua)
Diclofop-methyl {methyl 2-[4-(2,4-dichlorophenoxy)phenoxy] propanoate} loses part of its activity on wild oats (Avena fatua L.) when it is applied in combination with ester or amine formulations of MCPA {[4-chloro-o-tolyl)oxy] acetic acid.} Uptake of diclofop-methyl is reduced in the presence of commercial formulations of MCPA, particularly amine formulations, which are only partly compatible with the diclofop-methyl formulation. With added MCPA, regardless of formulation, hydrolysis of diclofop-methyl to the acid diclofop is slowed down, both in intact wild oat plants and in a crude leaf extract. At the same time, conversion of any acid formed to inactive conjugates is accelerated in the presence of MCPA. It is concluded that the loss of activity of diclofop-methyl by MCPA can be accounted for by the effects of MCPA on uptake and metabolic conversion of diclofop-methyl.