Synergistic degradation and heat generation characteristics of dyeing wastewaters by plasma oxidation combined with residual ozone bubbling

The wastewater temperature is a key factor on the degradation of pollutants contained in wastewaters by plasma- driven advanced oxidation. The plasma-thermal conversion characteristics and the thermal effects on the degradation of methylene blue (MB) and tetracycline (TC) were initially explored in the plasma-driven oxidation system that combines a falling film plasma reactor (FFR) with in situ oxidation and a residual ozone bubbling reactor (BR). The synergistic factor of MB degradation by the FFR and BR was 1.14 at 25 degrees C. Meanwhile, the energy efficiency (Y), chemical oxygen demand COD removal, and total organic carbon TOC removal were 1.27, 1.05, 1.48 times than the plasma-driven FFR, respectively. The degradation rate constant k (0.0287 - 0.0489 min-1 ) and the Gibbs free energy change Delta G (77.367 - 84.862 kJ center dot mol-1) showed the increasing tendency with the temperature rising from 10 to 40 degrees C. 10 % electric energy was converted to the thermal energy of wastewater, while the wastewater temperature increased from 19.1 degrees C to 51.0 degrees C. On this basis, an equation was established to predict the degradation rate of MB (r) in the temperature rising process. This study provides the underlying insights to guide the considering and utilization of the thermal energy of wastewater in the plasma-driven advanced oxidation of pollutants contained in wastewaters.