Magnetic field improves ozone production in an atmospheric pressure surface dielectric barrier discharge: understanding the physico-chemical mechanism behind low energy consumption.

Herein, we studied the combined effects of the magnetic field and the alternating current driven air surface dielectric barrier discharge on ozone production, and found that a 0.13 T perpendicular magnetic field introduced into the discharge area significantly enhanced the ozone generation performance with a 36-108% increase in ozone number density and 24-80% increase in ozone yield depending on discharge voltage and frequency differences. To reveal the micro physico-chemical mechanism of the influence of a magnetic field and discharge parameters of discharge voltage and frequency on ozone generation, a plasma chemical reaction network involving electron collision-chain reactions was considered. The results show that these parameters jointly influence ozone generation by affecting electron collision reactions and chain chemical reactions by changing the mean electron energy and plasma gas temperature. In this study, both the experimental results and mechanism analysis suggested that an optimal discharge parameter for ozone generation is the magnetic field assisted, low frequency, high voltage (6.5 kHz, 6.5 kV) surface dielectric barrier discharge. These insights provide guidance for optimizing the discharge parameters of the magnetic field assisted discharge to increase ozone production and reduce energy consumption.

Degradation of trimethoprim in aqueous by persulfate activated with nanosecond pulsed gas-liquid discharge plasma.

The persulfate activation by nanosecond pulsed gas-liquid discharge (NPG-LD) is employed to degrade the trimethoprim (TMP) in water. The results show that persulfate addition enhances the degradation of TMP by NPG-LD through an obvious synergetic effect. With treatment time of 50 min, the high removal efficiency and energy yield reach 94.6% and 0.57 gkWh-1 in air NPG-LD with the addition of persulfate, respectively, which is 13.5% and 0.09 gkWh-1 higher than that in solo air NPG-LD, respectively. Correspondingly, the calculated synergetic factor achieves 1.62, indicating the synergetic effect is established. The activation mechanism of persulfate by NPG-LD is analyzed by the measurement of reactive species and the effects of radical scavenger addition on TMP removal. It is found that the synergetic effect between NPG-LD and persulfate is attributed to the increased production of OH, H2O2, and . Besides, the TMP degradation by NPG-LD and persulfate synergetic system is influenced by discharge working gas, pulse voltage, addition dosage of persulfate, initial TMP concentration, and initial pH value. Subsequently, the degradation pathway of TMP is analyzed using LC-MS/MS.

Ultra-high synergetic intensity for humic acid removal by coupling bubble discharge with activated carbon.

Humic acid (HA) removal research focuses on the global water treatment industry. In this work, efficient HA degradation with an ultra-high synergetic intensity is achieved by combined bubble discharge with activated carbon (AC). Adding AC to the discharge greatly improves HA removal efficiency and degradation speed; the synergetic intensity reaches 651.52% in the combined system, and the adsorption residual on AC is 4.52%. After 90 min of treatment, the HA removal efficiency reaches 98.90%, 31.29%, and 7.61% in the plasma-AC combined, solo bubble discharge, and solo AC adsorption systems, respectively. During the plasma process, the number of pore structures and active sites and the amount of oxygen-containing functional groups on the AC surface increase, resulting in a higher adsorption capacity to reactive species (H2O2 and O3) and HA and promoting interactions on the AC surface. For HA mineralization, the presence of AC greatly promotes the destruction of aromatic structures and chromophoric HA functional groups.