Performance of non-thermal plasma reactor for removal of organic and inorganic chemical residues in aqueous media

In this work, the performance of an atmospheric air-assisted plasma reactor was evaluated for the oxidative degradation of azo (orange G and congo red) and non-azo (crystal violet, and coomassie brilliant blue) textile dyes and removal of hardness in an aqueous medium. Dye degradation efficiency was evaluated at different applied voltages (2-6 kV), pH (2.85-11.44), and initial dye concentrations (5-25 ppm). Nearly 99% degradation efficiency (at 5 ppm concentration) could be achieved in 30 min treatment time for all dyes. Degradation effi-ciency showed a direct relationship with applied voltage and an inverse relationship with the initial dye con-centration. Moreover, higher degradation efficiencies were observed at neutral pH than in the acidic and alkaline ranges. The pseudo-first-order kinetic model exhibited a better correlation coefficient (R2 > 0.90) in explaining the degradation kinetics of dyes. The water hardness was dropped by 55.5% after 60 min of plasma treatment. Also, the crystalline structure and morphology of water samples containing salts before and after the treatments were analyzed using XRD and SEM. The average crystalline size of untreated and plasma-treated samples is calculated to be 197.9 nm and 98.1 nm respectively. The concentration of O-3, OH., H2O2, NO2-& nbsp;and ROS species increased linearly with increasing treatment time. The energy yield and energy consumption for degradation and water hardness removal were-0.016 g kW/h and-0.3932 g kW/h, 1.08*10(7) J/L, and 2.16*10(6) J/L respectively. Moreover, atmospheric pressure gliding arc discharge-based air plasma discharge was computationally modeled and electrical characteristics such as electron density, electric potential, electron temperature, absolute electron flux and charged species (positive and negative) density were examined at different applied voltages. Overall, the atmospheric air-assistant cold plasma process shows promising potential for the removal of chemical residues in water.