Removal of persistent organic pollutants from water using a newly developed atmospheric plasma reactor

Abstract

A new bench-top reactor employing a streamer discharge in air was developed and tested for potential use in an advanced oxidation stage in water treatment processes. The complex heterogeneous system and the ensuing chemical processes were characterized using an integrated approach to map the morphology of the plasma/gas/ liquid interface, identify the plasma short-lived excited species, determine the oxidants in solution and monitor the organic pollutants degradation. Three model pollutants were used in these experiments, rhodamine B, phenol and metolachlor. The first two are common standards used to evaluate the performance of advanced oxidation processes. Metolachlor is a widely used herbicide listed among the most important recalcitrant emerging organic pollutants. Energy efficiency, kinetics and products of our tests show a good performance of the reactor. Specifically, mineralization appears feasible also in the case of metolachlor.metolachlor, phenol, reactive oxygen species, streamer discharge, water treatment

Cold plasma oxidation of harmful algae and associated metabolite BMAA toxin in aqueous suspension

“…Figure (b) portrays Rhodamine B oxidative degradation kinetics with the present Ar/O 2 discharges, and with those in air reported by Tampieri at al . With appropriate caution regarding simplifying assumptions, we interpret the near‐identical slopes (up to ca.…”

“…(a) pH values of 15 mL distilled water samples after indicated exposure durations to air and Ar/O 2 HV AC discharge effluents; (b) Rhodamine B degradation versus Ar/O 2 plasma treatment time. The diamond symbols correspond to data reported by Tampieri et al using air discharges…”

“…This can be explained very simply as follows: in the case of Ar + O 2 , the (non‐degassed) water was in contact with the atmosphere, which permitted interaction with air and carbon dioxide, both of which might account for the observed slight acidification. On the other hand, it is well known and documented that air plasma generates NO x as major reaction products, in other words “RONS” (reactive oxygen and nitrogen species); in the presence of water these form nitrous and nitric acids, the reason for observed low pH values. Because those acids and other RONS can also partake in reactions with organic constituents in the water, we opted to use Ar/O 2 as feed gas for this study, one that yields only reactive oxygen species (ROS) for degrading the organic contaminants, hence leading to presumably less ambiguous interpretation of resulting data.…”

“…The reactor used in the present work was in several important aspects similar to the one recently described by Tampieri et al It consisted of a 50 mL Pyrex beaker with a top cover made of (electrically insulating) polytetrafluoroethylene, PTFE, traversed by a ca. 20 cm long stainless steel ( s.s .)…”

“…In a recent special issue of this journal, Plasma Processes and Polymers , which was devoted to the theme “plasma and liquids,” there were several articles that dealt with AP plasmas immersed in, or in direct contact with a liquid, water being the liquid of choice in most cases . We shall later be referring in more detail to one of those articles, namely that by Tampieri et al They reported a clever bench‐top AP plasma reactor system based on a hollow needle electrode in contact with (deliberately contaminated) water, through which the oxidant gas was fed. They then mapped the morphology of the plasma/gas/liquid interface, identified short‐lived excited species, determined oxidants in solution and monitored the degradation of their organic pollutants.…”