The Potential of Cold Atmospheric Pressure Plasmas for the Direct Degradation of Organic Pollutants Derived from the Food Production Industry.

Specialized chemicals are used for intensifying food production, including boosting meat and crop yields. Among the applied formulations, antibiotics and pesticides pose a severe threat to the natural balance of the ecosystem, as they either contribute to the development of multidrug resistance among pathogens or exhibit ecotoxic and mutagenic actions of a persistent character. Recently, cold atmospheric pressure plasmas (CAPPs) have emerged as promising technologies for degradation of these organic pollutants. CAPP-based technologies show eco-friendliness and potency for the removal of organic pollutants of diverse chemical formulas and different modes of action. For this reason, various types of CAPP-based systems are presented in this review and assessed in terms of their constructions, types of discharges, operating parameters, and efficiencies in the degradation of antibiotics and persistent organic pollutants. Additionally, the key role of reactive oxygen and nitrogen species (RONS) is highlighted. Moreover, optimization of the CAPP operating parameters seems crucial to effectively remove contaminants. Finally, the CAPP-related paths and technologies are further considered in terms of biological and environmental effects associated with the treatments, including changes in antibacterial properties and toxicity of the exposed solutions, as well as the potential of the CAPP-based strategies for limiting the spread of multidrug resistance.

Positive Effect Induced by Plasma Treatment of Seeds on the Agricultural Performance of Sunflower.

The need for efficient technologies to enhance productivity in agriculture strongly motivates research on plasma treatment of seeds and plants. In this study, the influence of plasma treatment on sunflower (Helianthus annuus L.) seeds was evidenced throughout the entire life span of the plants. The seeds were packed in a DBD reactor operated in air and treated in plasma for 10 min, using a sinusoidal voltage of 16 kV amplitude at 50 Hz frequency. Early growth observation of plants under laboratory conditions showed that, after a slower start, the plasma-treated seeds developed faster and produced taller seedlings with greater total mass as compared to the control samples. Results obtained from mature plants cultivated in the field revealed a positive effect of plasma exposure with respect to capitulum size, number of seeds per capitulum and mass per thousand seeds, resulting in a remarkable increase in crop yield. The plasma effect lasted for at least two weeks of seed storage; however, it was considerably affected by the sowing period.

Degradation of pharmaceutical compounds in water by non-thermal plasma treatment.

Pharmaceutical compounds became an important class of water pollutants due to their increasing consumption over the last years, as well as due to their persistence in the environment. Since conventional waste water treatment plants are unable to remove certain non-biodegradable pharmaceuticals, advanced oxidation processes was extensively studied for this purpose. Among them, non-thermal plasma was also recently investigated and promising results were obtained. This work reviews the recent research on the oxidative degradation of pharmaceuticals using non-thermal plasma in contact with liquid. As target compounds, several drugs belonging to different therapeutic groups were selected: antibiotics, anticonvulsants, anxiolytics, lipid regulators, vasodilatators, contrast media, antihypertensives and analgesics. It was found that these compounds were removed from water relatively fast, partly degraded, and partly even mineralized. In order to ensure the effluent is environmentally safe it is important to identify the degradation intermediates and to follow their evolution during treatment, which requires complex chemical analysis of the solutions. Based on this analysis, degradation pathways of the investigated pharmaceuticals under plasma conditions were suggested. After sufficient plasma treatment the final organic by-products present in the solutions were mainly small molecules in an advanced oxidation state.

Toluene oxidation by non-thermal plasma combined with palladium catalysts.

The oxidation of toluene in air was investigated using a dielectric barrier discharge (DBD) combined with a Pd/Al2O3 catalyst. When using only plasma, rather low selectivity toward CO2 was obtained: 32-35%. By filling the DBD reactor with Pd/Al2O3 catalyst the CO2 selectivity was significantly enhanced (80-90%), however, a large amount of toluene was desorbed from the catalyst when the discharge was operated. By filling a quarter of the discharge gap with catalyst and placing the rest of the catalyst downstream of the plasma reactor, an important increase of CO2 selectivity (~75%) and a 15% increase in toluene conversion were achieved as compared to the results with plasma alone. The catalyst exhibited a very good stability in this reaction.

Degradation of pharmaceutical compound pentoxifylline in water by non-thermal plasma treatment.

The decomposition of a model pharmaceutical compound, pentoxifylline, in aqueous solution was investigated using a dielectric barrier discharge (DBD) in coaxial configuration, operated in pulsed regime, at atmospheric pressure and room temperature. The solution was made to flow as a film over the surface of the inner electrode of the plasma reactor, so the discharge was generated at the gas-liquid interface. Oxygen was introduced with a flow rate of 600sccm. After 60min plasma treatment 92.5% removal of pentoxifylline was achieved and the corresponding decomposition yield was 16g/kWh. It was found that pentoxifylline degradation depended on the initial concentration of the compound, being faster for lower concentrations. Faster decomposition of pentoxifylline could be also achieved by increasing the pulse repetition rate, and implicitly the power introduced in the discharge, however, this had little effect on the decomposition yield. The degradation products were investigated by liquid chromatography-mass spectrometry technique (LC-MS). The evolution of the intermediates during plasma treatment showed a fast increase in the first 30min, followed by a slower decrease, so that these products are almost completely removed after 120min treatment time.