O. N. Tchaikovskaya

The fluorescence analysis of laser photolysis of phenols in water

Photolysis of phenol and p-chlorophenol exposed to KrCl- and Nd-YAG laser light is studied by electron spectroscopy and fluorescence and quantum chemical techniques. The decrease of the quantum yield of phenol fluorescence with increase in the excitation energy is not related to dynamic changes in the intramolecular photophysical processes; rather this is a result of increased photoreaction efficiency. Chlorine substitution for para-state of phenol is shown to strengthen the OH-bond in excitation into the long wavelength absorption band.

Role of photochemical and microbial degradation of phenol in water

The present work is aimed at spectroscopic and luminescent investigations of the microbial cleavage efficiency of phenol in the water solution upon expose to UV light. With increasing time of irradiation of phenol in the saline solution,the absorption intensity increases throughout the spectrum. The efficiency of photoalteration of phenol in the saline solution is higher compared to that in water. The results obtained have shown that the efficiency of complex photobiological phenol destruction increases sharply compared to the photochemical or microbial destruction.

Fluorescence Investigations of Phenol Phototransformation in Aqueous Solutions

Absorption and fluorescence techniques were used to study special features of the XeCl laser-induced phototransformation of phenols in water and to compare the results obtained with those of photolysis of phenol solutions exposed to the UV radiation from mercury lamps. XeCl laser-induced phenol photolysis provided photoproducts not found on exposure to UV radiation. This is related to the two-photon population of highly excited phenol states under high-power laser pumping, which gives rise to a new phototransformation reaction pathway.

Photodegradation of 2-methyl-4-chlorophenol in a KrCl exciplex flow-through photoreactor: a kinetic study

AbstractThe removal of 2-methyl-4-chlorophenol (MC), the main photoproduct from 4-chloro-2-methylphenoxyacetic acid oxidation, has been studied with an advanced oxidation treatment and, for this purpose, a KrCl exciplex flow-through photoreactor was tested. Preliminary results show that the use of UV treatment leads to practically total MC degradation in 10, 60 or 90 min for the initial concentrations of 0.2, 1.0 or 2.0 mM, respectively. However, to attain higher elimination of the main photoproducts, 2-MH and 2-MB, addition of an oxidizing agent, such as hydrogen peroxide, is necessary. With molar ratios H2O2/MC/1 or higher, smaller concentrations of photoproducts are obtained after the treatment. Additional chemical analysis, such as chemical oxygen demand (COD) suggests that although COD is smaller after the treatment than before, for the highest H2O2 concentrations an excess of H2O2 remains in the medium, which increases this parameter, being required longer treatment times. Total phenols, pH, and res...

The role of UV‐irradiation pretreatment on the degradation of 2,4‐dichlorophenoxyacetic acid in water

The degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) in water by the combination process of UV-irradiation, humic acids and activated sludge treatment has been studied. The photoreaction rate of all irradiated samples was lowest for the sample irradiated at 308 nm (the XeCl excilamp) in the absence and in the presence of humic acids, and highest for the sample irradiated at 222 nm (the KrCl excilamp). Photolysis of 2,4-D has been shown to enhance the subsequent microbial degradation.

The use of modern UV radiation sources for the utilization of persistent toxic substances

The influence of KrCl excilamp UV radiation (7nr = 222 nm) on the biodegradation of polycyclic aromatic hydrocarbons (PAHs: anthracene, phenanthrene, and naphthalene) by activated sludge treatment has been investigated using electronic absorption and fluorescence spectrometry and chromatography methods. The revealed final photoreaction products of a quinine structure indicate that a hydroxylation reaction is involved in the mechanism of PAH photodegradation. The loss of separate PAHs in hexane after the action of the KrCl excilamp has been determined. Preliminary irradiation improves the efficiency of PAH biodegradation by activated sludge treatment in comparison with biodegradation.

The effect of UV radiation on the phenol photodegradation in the presence of humic and fulvic acids

Upon exposure to radiation in the presence of humic substances, phenol can be transformed by the mechanisms of direct and indirect photolysis. The addition of the humic fraction containing humic and fulvic acids to the aqueous phenol solution causes the efficiency of phenol degradation to decrease. The most efficient phenol degradation in the aqueous solution upon exposure to radiation at 222 nm is observed in the presence of fulvic acid.

Choice of Parameters and Stability of Nonlinear Vibration Isolation Device

Work of active vibration isolation devices with single-mass electromagnetic suspension taking into account of real characteristics of the voltage regulators is described. The analytical researches are carried out; the areas of stability of work of nonlinear vibration isolation device are defined.

Photolysis of water phenol solutions under UV excitation by KrCl laser and KrCl excilamp

Phenol and 4-chlorophenol water solutions photolysis under UV-excitation from KrCl-laser and capacitive discharge KrCl- excilamp are presented. The irradiated solutions have been investigated by spectroscopic methods. The comparison of the KrCl-excilamp and KrCl-laser irradiation effects has been realized for the first time.

Study interaction between humic acids and metal ions using fluorescence quenching approach

The interaction of humic acids (HA) isolated from oxidized and brown coals with copper, nickel, and cadmium ions is investigated. The complexation constant of HA with heavy metal ions is determined using the fluorescence quenching method. It is shown that preliminary mechanic activation of humic-containing substances increases the binding coefficients of HA with copper and nickel ions in 1.5 to 3.5 times, as compared to cadmium ions, for which the values of the fluorescence quenching constant КSV decrease. This is due not only to structural changes in HA after the mechanic activation, but also to the nature of metal ions.