21 st International Symposium on Plasma Chemistry (ISPC 21) Sunday 4 August – Friday 9 August 2013 Cairns Convention Centre, Queensland, Australia Effect of Micro- and Nano-particles on Submerged Arc Decomposition of Methylene N. Parkansky 1 , E. Faktorovich-Simon 1 , V. Yacubov 1 , B. Alterkop 1 , O. Berkh 2 , R.L. Boxman 1 , Z. Barkay 3 , Yu. Rosenberg 3 , L. Burstein 3 , A. Khatchtouriants 4 1 Electrical Discharge and Plasma Laboratory, 2 School of Electrical Engineering , 3 Wolfson Applied Materials Research Center, 4 The Center for Nanoscience and Nanotechnology, Tel Aviv University, POB 39040, Tel Aviv 69978, Israel Abstract: The pulsed submerged arc (SA) can decompose contaminant molecules in water. Recently, SA decomposition of Methylene Blue (MB) contamination in aqueous solutions was demonstrated. The particles eroded from the electrodes were shown to influence the decom- position efficiency. However, no comparative studies of effects of the particles eroded from Fe and Ti electrodes were conducted. The objective of this work was to determine the effects of Fe and Ti electrodes on the efficiency of MB decomposition in aqueous solutions. Elec- trode pairs of the same material (Fe or Ti) and combinations of these materials were used. Solutions were treated using a SA with Fe and Ti electrodes in the presence of H 2 O 2 and without it, and then aged. The treated solutions were examined by Raman and absorption spectroscopy. The produced particles were studied by SEM, XPS and XRD. In the absence of H 2 O 2 in the solutions, the decontamination ratio after SA treatment was higher with Fe/Fe than with Ti/Ti electrodes. In the presence of H 2 O 2 in the solutions, SA treatment with Ti/Ti electrodes was more effective than with Fe/Fe electrodes. One week ag- ing of the solutions treated in the presence of H 2 O 2 with all electrode pairs very effectively decontaminated the solutions, reaching a decontamination ratio close to 99 %). According to the XPS and Raman spectroscopy analysis, titanium peroxide was formed by SA treatment with Ti electrodes on the surface of particles eroded from the electrodes. We believe that Ti-peroxide forms on the surface of eroded particles during SA treatment and gradually oxi- dizes MB during aging. A similar processes can proceed on the surface of the particles eroded from Fe electrodes owing to Fe-peroxide compounds formed in Fenton chemistry during dis- charge. Keywords: Submerged pulsed arc, water treatment, micro- and nano-particles plasma, de- contamination. 1. Introduction Plasma processes to treat water proceed by several mechanisms such as radical reactions, shock waves, ul- tra-violet radiation, ionic reactions, electron processes and thermal dissociation [1-4]. The submerged pulsed high-current and high voltage electrical discharge, i.e. a discharge between two electrodes in a liquid, referred to as an electro-hydraulic discharge [1], has been shown to oxidize many organic compounds [5-9]. The pulsed low voltage submerged arc (SA) can decompose contaminant molecules in water. Recently, SA decomposition of Meth- ylene Blue (MB) contamination was demonstrated [2,9]. However, similarities and differences of the effects of particles eroded from different electrodes on decontami- nation efficiency have not been studied. The objectives of this research were determining and comparing these ef- fects for the particles eroded from Fe and Ti electrodes. Electrode pairs Fe a /Fe c , Ti a /Ti c , Ti a /Fe c and Fe a /Ti c (where the subscripts a and c designate the anode and cathode, respectively) were used. 2. Experimental Details Pulsed arcs were applied between low carbon (0.2%) steel (designated herein as Fe) and 99.5% Ti electrodes. Electrode pairs of the same material and combinations of these materials were used in a setup which was previously presented [2]. 40 ml samples of 10mg/l MB solutions, most containing 0.5% H 2 O 2 , were SA treated with the above electrodes. All solutions were prepared using de- ionized water. The SA comprised discharging a 15 F capacitor charged to 80 V, and hence storing an energy of 48 mJ, my momentarily contacting and separating the electrodes, which were submerged in the solution. This was accomplished by mounting one of the electrodes on a vibrator, which had a vibration amplitude of zz mm, and vibration frequency of 100 Hz. This produced arc pulses with a 100 Hz repetition frequency, which was applied to the solution for 2 min. The SA treatment was followed by aging of the treated