Diagnostics and applications of dielectric barrier discharge in contact with water.

Ova doktorska disertacija posvećena je istraţivanju dielektričnog barijernog praţnjenja u kontaktu sa vodom i njegovim primenama. U dielektričnom barijernom praţnjenju (DBP) sa padajućim vodenim filmom ispitana je interakcija plazme i tečnosti sa karakterizacijom fizičkih i hemijskih osobina gasne i tečne faze. Osnovni doprinos ovog istraţivanja je unapreĎenje razumevanja hemijskih procesa koje neravnoteţna plazma na atmosferskom pritisku indukuje u tečnostima. Plazma u DBP reaktoru ispitivana je uz pomoć emisione spektroskopije i električnih merenja. Ispitano je formiranje hidroksil radikala (˙OH) i dugoţivećih hemijskih vrsta (H2O2, O3, NO3 i NO2 ) u vodi i dimetil sulfoksidu koji su izloţeni delovanju neravnoteţne plazme u DBP reaktoru sa vodenim filmom u zavisnosti od gasne atmosfere (vazduh, azot, kiseonik, argon i helijum). U fokusu ovog istraţivanja bilo je formiranje hidroksil radikala i mogući uticaj njegovog zahvatanja hemijskom sondom (dimetil sulfoksid) na formiranje dugoţivećih vrsta. UtvrĎeno je da reakcija rekombinacije hidroksil radikala suštinski odreĎuje formiranje vodonik-peroksida u praţnjenjima u vazduhu, azotu i argonu. Za prostorno- vremensko istraţivanje interakcije plazme sa vodom korišćen je helijumov plazmeni mlaz u kontaktu sa vodom. Snimci razvoja praţnjenja dobijeni iCCD kamerom otkrivaju da interakcija praţnjenja sa tečnom metom moţe biti produţena nekoliko puta u zavisnosti od radnih parametara. Merene su raspodele emisije nekoliko ekscitovanih hemijskih vrsta da bi se identifikovao glavni mehanizam ekscitacije. Korišćenjem metoda Štarkove polarizacione spektroskopije, izmerena je raspodela jačine električnog polja u plazmenom mlazu koji interaguje sa tečnom metom. Ova merenja podrţana su Šlirenovom vizuelizacijom plazmenog mlaza i vodene mete. Pokazano je da neznatne promene neelektričnih parametara, kao što je udaljenost mete i brzina protoka gasa, mogu u potpunosti da promene prirodu praţnjenja. Merene vrednosti električnog polja su u opsegu 8-30 kV/cm, i zavise samo od protoka gasa i rastojanja mete, i saglasne su sa rezultatima modelovanja. Šlirenovom vizuelizacijom demonstrirana je interakcija izmeĎu protoka gasa i same plazme. Poseban doprinos ove studije je dokumentovan uticaj plazmenog mlaza na mešanje tečnosti. U okviru istraţivanja primena DBP sa vodenim filom ispitano je uklanjanje isparljivih ugljovodonika u gasnoj fazi. Demonstrirana je degradacija undekana i toluena sa smanjenom emisijom nusproizvoda kao i konverzija nerastvorljivih jedinjenja u rastvorljiva. Ispitana je inaktivacija različitih vrsta mikroorganizama u tečnostima. Pri uklanjanju zagaĎujućih supstanci u tečnoj fazi ispitan je uticaj različitih homogenih katalizatora i njihove doze na proces degradacije herbicida mezotriona, farmaceutskog jedinjenja ibuprofena i nikotina u DBP sa vodenim filmom i pokazana je visoka (do 99 %) efikasnost degradacije.The subject of the presented thesis is the study of dielectric barrier discharge in contact with water and its applications. In water falling film dielectric barrier discharge (DBD) plasma- liquid interaction has been studied, with characterization of physical and chemical properties of the gas phase and the liquid phase. The main contribution of this research is improvement of understanding of chemical processes induced in liquids by nonthermal atmospheric/pressure plasmas. Plasma in DBD reactor has been studied by optical emission spectroscopy and electrical measurements. The formation of hydroxyl radical (˙OH) and long-living chemical species (H2O2, O3, NO3 and NO2 ) generated in water and in dimethyl sulfoxide in water falling film DBD in dependence on the gas atmosphere (air, nitrogen, oxygen, argon and helium) was studied. The focus of this study was the formation of hydroxyl radical and the influence of ˙OH scavenging by dimethyl sulfoxide on the formation of long-living species. It was found that formation of hydrogen peroxide in air, nitrogen and argon discharges is determined by recombination reaction of hydroxyl radicals. For spatio-temporally resolved study of plasma-liquid interaction helium plasma jet with liquid target was used. ICCD recordings of the discharge development revealed that discharge interaction with the target can be elongated several times, depending on the operating parameters. Distributions of the emissions of several excited chemical species are measured in order to identify the main excitation mechanisms. Utilizing the method of Stark polarization spectroscopy, the electric field strength distribution measurements in helium plasma jet interacting with a liquid target are also obtained. Measurements are supported by simultaneous Schlieren imaging of both the effluent of plasma jet and water target. It was shown that the slight change of the non-electrical parameters, such as target distance and the gas flow rate can completely change the nature of the discharge. Measured electric field values are in range of 8-30 kV/cm, and depend only on the gas flow and the target distance, and they are in reasonable agreement with the modeling outcomes. Schlieren imaging demonstrated strong interaction between the gas flow and the plasma itself. Special outcome of this article is documented influence of the plasma jet discharge on the mixing of the liquid. As part of the research on the applications of water falling film DBD, the removal of volatile hydrocarbons in the gas phase was investigated. Degradation of undecane and toluene with reduced emission of by-products as well as conversion of insoluble compounds to soluble was demonstrated. Inactivation of different types of microorganisms in liquids was investigated. The influence of various homogeneous catalysts and their dosage on the degradation process of the mesotrione herbicide, the pharmaceutical compound ibuprofen and nicotine in water falling film DBD was examined and high degradation efficiency (up to 99%) was demonstrated