Industrial wastewater (especially pharmaceutical industry) contains large quantities of volatile organic solvents and among them, chlorinated hydrocarbons such as chloroform and chlorobenzene raise serious concerns to human health and ecosystem due to their high toxicity and recalcitrance. Chloroform is a highly oxidized aliphatic compound while chlorobenzene is an aromatic hydrocarbon which possesses resonance structures resulting in its high stability. Pulsed streamer plasma is an advanced oxidation process (AOP) which produces both oxidizing and reductive species. Since chloroform is highly oxidized than chlorobenzene and has high reactivity with aqueous electrons(e-aq), chloroform is more prone to reductive degradation. In this work, the mechanism of plasma degradation of chloroform and chlorobenzene were evaluated by conducting reactive species scavenger studies. Effect of input voltage, initial concentration and mineralization potential of plasma were also studied. The degradation efficiency of chloroform and chlorobenzene increased with increase in input voltage. The behavior of chloroform and chlorobenzene degradation with respect to reactive species scavengers and initial concentration were exactly opposite to each other because of the differences in properties and structure of these two compounds. In case of scavenger studies, highest degradation efficiency of chloroform was obtained in presence of isopropanol which is hydroxyl radical scavenger whereas in case of chlorobenzene, highest rate of degradation was achieved when e-aq scavenger i.e., nitrate was present in solution. Since the volatility of chlorobenzene was less than that of chloroform, concentration of chlorobenzene in bulk solution was more and it took more time for degradation. The total organic carbon (TOC) removal was 91 % after 10 min of treatment in case of chloroform whereas in case of chlorobenzene it was 40.7 % after 18 min and this was because of the formation of short chain carboxylic acids such as formic acid, acetic acid and oxalic acid and other intermediates.

Degradation of chloroform and chlorobenzene by pulsed streamer plasma: A comparative study

2019 Spring National Meeting

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