TREATMENT OF WASTEWATER CONTAINING 2,4-DICHLOROPHENOL IN DIELECTRIC BARRIER DISCHARGE PLASMA

Abstract

In the work, the processes of destruction of aqueous solutions of 2,4-dichlorophenol in a dielectric barrier discharge of atmospheric pressure in oxygen were studied. It has been experimentally shown that 2,4-dichlorophenol is destroyed in plasma quite efficiently (the degree of destruction reaches 80 %), which confirms the earlier studies on the decomposition of various organic pollutants in a dielectric barrier discharge plasma. The kinetic parameters were estimated and the main intermediate and final products of the decomposition of 2,4-dichlorophenol under the action of active plasma particles were determined. The destruction of the starting compound is described by a first order kinetic equation. The effective rate constant depends weakly on the experimental conditions and it equals to 0.56 s–1. The composition of the degradation products was studied by gas chromatography, as well as by fluorescence, spectrophotometric and potentiometric methods. Cl- in the liquid phase, as well as СО and СО2 in the gas phase, were identified as the final degradation products. And carboxylic acids and aldehydes were intermediate degradation products. But their concentrations are not high relative to СО and СО2. No molecular chlorine was detected in the gas phase. It was found that ozone does not make a significant contribution to the oxidative destruction of 2,4-dichlorophenol. The hydroxyl radicals and atomic oxygen are main active particles involved in oxidative processes. An increase in the frequency of the discharge current from 50 to 800 Hz, as well as the absence of a hydrophobic coating of the internal electrode, leads to a decrease in the decomposition rate by a factor of 1.7 (from 227 to 135 μmol/(l∙s)).