Degradation of crystal violet in water solution using post discharge DBD plasma treatment: Factorial design experiment and modeling

Abstract

In this study, highly oxidative ozone species, generated through dielectric barrier discharge (DBD) plasma, were used to decolorize crystal violet (CV) in aqueous solutions. The solution was exposed to a post-discharge plasma with a mixture of oxygen and argon as carrier gas. The exhaust plasma gas was brought into contact with the solution to be treated in a bubbler by the post discharge configuration. The degradation of the contaminants would be improved by the enhancement of the reactive species diffusion in the solution in the post discharge configuration. The effects of different parameters including oxygen percentage in the carrier gas, discharge power, and total flow rate were investigated on the efficiency of CV removal. Further, the concentrations of ozone in the gas and liquid phases were measured via iodine and indigo methods, respectively. Under optimal conditions, the entire dissolved CV was degraded after 60 s of plasma treatment. Kinetic study revealed that the reaction between ozone and CV follows the behavior of a first-order reaction. After plasma treatment, the aromatic fragment and its intermediates completely disappeared. Analysis of variance with an excellent coefficient of determination of 0.988 ensured a satisfactory fit between second-order regression model and the experimental data. The high CV removal rate constant of 4.88 min^-1 obtained at a low discharge power of 5 W was of paramount importance in comparison with previous studies.

Keywords: Decoloration; Dye wastewater; Ozonation; Plasma treatment; Response surface methodology; Water treatment.