Degradation on 2,4,6-Trinitrophenol by cold plasma technology
Abstract
Cold plasma exhibits many advantages in environmental treatment without additive reagent required. The 2,4,6- Trinitrophenol (TNP) might be degraded with high efficiency using cold plasma. The main factors influencing the TNP degradation have been studied. The kinetics of the TNP process proposed fits to the pseudo- first order reaction. The overall reaction rate expression was established to be - r= 0.024CTNP at low TNP concentration
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Introduction
Since the late of 20th century, plasma field as a new study filed has been interested in the great attention of many scientists in over the word [1]. The plasma chemistry is focused on studying about the energetic particles (electrons and ions) in plasma participated in chemical reactions. The plasma can be divided into two kinds such as thermal plasma and cold plasma depending on the electron temperature and ion temperature [1,2]. According this principle, thermal plasma has electron temperature equal to ion temperature, while for cold plasma, the electron temperature is higher than the ion temperature. The cold plasma produced in water solutions forms the basis of an innovative advanced oxidation technology of water treatment. So that recently cold plasma has been considered to be a useful method in environmental pollution treatment technology concluding solid, liquid and gas wastes [3,4]. Because, the degradation of these substances has been based on the strongly active species (free radicals) generated from cold plasma process. Cold plasma is produced by gas discharge or combined with air in atmosphere that results in highly oxidative species such as electrons, ions, radicals, excited atoms and molecules [5]. So that use of cold plasma technique is an environmentally friendly and cost – effective alternative due to without any additional chemical reagents used and therefore their disposal is not required. Cold plasma can be classified into many types in which dielectric barrier discharge (DBD) is one of these. In this paper cold plasma with DBP (shortly called cold plasma) used to degrade 2,4,6 –Trinitrophenol will be presented in detail.
2,4.6-Trinitro phenol TNP (picric acid) is an organic compound with the formula (O2N)3C6H2OH, mass molecule 229.10 g·mol− , pka = 0.38, which used in munitions explosives or in medicine and dyes [6]. 2,4.6-Trinitrophenol is toxic that causes headache, vertigo, nausea, vomiting, diarrhea, inflammation of kidney and acute hepatitis and red colored urine may be produced [7].
In this paper the 2,4,6-trinitrophenol in waste water treated by cold plasma (DBD) will be studied in detail including degradation efficiency and the experimental conditions under that provides the highest efficiency.
Conclusion
Cold plasma technology has been applied in environmental treatment with the many advantages. The main principle of cold plasma technology is based on the oxidative particles including free radical OH and active ions or molecules generating in situ under the high electric voltage to degrade pollutants from wastewater. The cold plasma has been used to degrade TNP in water samples resulting in high efficiency. The influence of main factors such as pH, reaction time, additive H2O2, TNP concentration was studied. The cold plasma used to degrade TNP yielded high efficiency at the range of pH 3.2-11 and its efficiency enhancing with additive H2O2. The kinetics of the TNP degradation under cold plasma has been suggested, following the pseudo - first order reaction at the low TNP concentration.