Electrical Discharge in Water Treatment Technology for Micropollutant Decomposition

Hazardous micropollutants are increasingly detected worldwide in wastewater treatment plant effluent. As this indicates, their removal is insufficient by means of conventional modern water treatment techniques. In the search for a cost-effective solution, advanced oxidation processes have recently gained more attention since they are the most effective available techniques to decompose biorecalcitrant organics. As a main drawback, however, their energy costs are high up to now, preventing their implementation on large scale. For the specific case of water treatment by means of electrical discharge, further optimization is a complex task due to the wide variety in reactor design and materials, discharge types, and operational parameters. In this chapter, an extended overview is given on plasma reactor types, based on their design and materials. Influence of design and materials on energy efficiency is investigated, as well as the influence of operational parameters. The collected data can be used for the optimization of existing reactor types and for development of novel reactors

Abatement of VOCs using packed bed non-thermal plasma reactors : a review

Non thermal plasma (NTP) reactors packed with non-catalytic or catalytic packing material have been widely used for the abatement of volatile organic compounds such as toluene, benzene, etc. Packed bed reactors are single stage reactors where the packing material is placed directly in the plasma discharge region. The presence of packing material can alter the physical (such as discharge characteristics, power consumption, etc.) and chemical characteristics (oxidation and destruction pathway, formation of by-products, etc.) of the reactor. Thus, packed bed reactors can overcome the disadvantages of NTP reactors for abatement of volatile organic compounds (VOCs) such as lower energy efficiency and formation of unwanted toxic by-products. This paper aims at reviewing the effect of different packing materials on the abatement of different aliphatic, aromatic and chlorinated volatile organic compounds

Applications of plasma-liquid systems : a review

Plasma-liquid systems have attracted increasing attention in recent years, owing to their high potential in material processing and nanoscience, environmental remediation, sterilization, biomedicine, and food applications. Due to the multidisciplinary character of this scientific field and due to its broad range of established and promising applications, an updated overview is required, addressing the various applications of plasma-liquid systems till now. In the present review, after a brief historical introduction on this important research field, the authors aimed to bring together a wide range of applications of plasma-liquid systems, including nanomaterial processing, water analytical chemistry, water purification, plasma sterilization, plasma medicine, food preservation and agricultural processing, power transformers for high voltage switching, and polymer solution treatment. Although the general understanding of plasma-liquid interactions and their applications has grown significantly in recent decades, it is aimed here to give an updated overview on the possible applications of plasma-liquid systems. This review can be used as a guide for researchers from different fields to gain insight in the history and state-of-the-art of plasma-liquid interactions and to obtain an overview on the acquired knowledge in this field up to now

Katalüsaatorite toime lämmastikoksiidide oksüdeerimisel plasmaühenditega

Väitekirja elektrooniline versioon ei sisalda publikatsiooneÕhureostus on tihedalt asustatud piirkondades kasvav probleem ja seda põhjustav oluline saasteainete klass on lämmastikoksiidid – NO ja NO2. Nende gaaside üks tähtsamaid allikaid on kütuste põlemisprotsessid ja atmosfääri sattudes võivad nad tekitada happevihmasid ning avaldada otsest kahjulikku mõju inimeste tervisele. Seetõttu on vajalik nende ühendite eemaldamine gaasivoogudest enne atmosfääri jõudmist. Üks võimalus selleks on eemaldamine plasma abil, mis väldib mõningaid laiemalt kasutusel olevate meetodite puudusi. Plasmaga eemaldamise efektiivsust saab omakorda parandada katalüsaatorite abil ning sellele aspektile on pühendatud käesolev doktoritöö. Uuringute käigus leiti, et kogu gaasivoo otse läbi plasmareaktori juhtimise asemel on kasulikum plasma rakendamine osooni tekitamiseks ja sellega saastunud gaasivoo töötlemine. Uuritud katalüsaatoritest andis parima tulemuse raudoksiid Fe2O3, mis ühelt poolt suurendas protsessi efektiivsust kuni kolm korda ja teiselt poolt lagundas ülejäävat osooni, vältides selle õhku paiskamist. Katalüsaatori toime seisnes selle pinnal täiendavate ühendite ja reaktsioonikanalite tekkimises, mis parandasid kogu protsessi efektiivsust.Air pollution is a growing problem in densely populated areas and an important class of compounds that contribute to the pollution is nitrogen oxides – NO and NO2. A major source of these gases is fuel combustion and upon reaching the atmosphere they can be the precursors of acid rains and have direct adverse health effects. Because of this it is important to remove nitrogen oxides from exhaust gases before they enter the atmosphere. A possibility for that is removal by plasma, which avoids some drawbacks of more widely used methods. Removal by plasma can in turn be improved by catalysts and this aspect is dealt with in the current thesis. It was found that plasma is best used only for the production of ozone, instead of directing the whole polluted gas stream through the plasma reactor. Of the catalysts that were investigated, iron oxide (Fe2O3) lead to the best results, increasing the efficiency of the process up to three times and at the same time decomposing excessive ozone, which prevented its emission into the atmosphere. The effect of the catalysts was caused by additional compounds and reaction pathways on their surfaces, which improved the efficiency of the whole process.https://www.ester.ee/record=b524282

Influence of mixed-phase TiO2 on the activity of adsorption-plasma photocatalysis for total oxidation of toluene

Herein, the effects of different crystalline phases of TiO2 on the adsorption-plasma photocatalytic oxidation of toluene were investigated. First, photocatalysts loaded on a molecular sieve (MS) were characterised and the catalytic performance of toluene abatement was evaluated in a plasma system. The COx yield of the pure anatase (An) sample outperformed other samples in the adsorption-plasma photocatalytic oxidation process, especially for CO2 yield (69.1%). It was revealed that the highest space-time-yield of 2.35 gco(2)/Lcat.h was also achieved using plasma-An/MS. However, the highest total toluene abatement (99.5%) was achieved in the plasma-P25/MS system. The plasma-generated UV flux only played a minor role in photocatalyst activation because of the very low UV flux of 2.7 mu W/cm(2) generated by discharge. For the degradation pathway, compared with the plasma-MS system, byproducts of 1,3-Butadiyne (C4H2), guanidine, methyl-(C2H7N3) did not exist in the TiO2-assisted system, indicating a difference in the toluene degradation pathway. There were no obvious effects of different TiO2 samples on organic byproducts generation, and almost a complete mineralisation of all byproducts was observed after 30 min of treatment, with the exception of ethylamine (C2H7N) and acetaldehyde (C2H4O). Finally, a cycled adsorption-plasma study was conducted to reveal the sustainability of the process. A partial deactivation of plasma-An/MS with less than 7% decrease in CO2 selectivity after 7 cycles was revealed, which is a promising result for use in possible industrial applications