Oxidation of 2,6-dimethyl phenol in supercritical water: experimental and molecular dynamics simulation study

N Aghamohammadi and F Esmaeilzadeh and D Mowla and A Elhambakhsh, INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCE AND TECHNOLOGY, 20, 551-564 (2023).

DOI: 10.1007/s13762-022-04540-x

Supercritical water oxidation has emerged as a promising technique for the removal of aromatic compounds, which are difficult to remove by conventional wastewater treatment processes. In this study, supercritical water oxidation was used to investigate the decomposition mechanism of 2,6-dimethylphenol. 2,6-Dimethylphenol was listed as a priority pollutant by the US Environmental Protection Agency due to its toxicity, carcinogenicity and high solubility in water. To do so, different effective parameters such as initial pollutant concentration (40-500 ppm), degradation time (0-100 s), temperature (300-500 celcius) and oxidant coefficient (0.8-2) on the removal of 2,6-dimethylphenol were optimized using the response surface method. With respect to the obtained results, as an index for 2,6-dimethylphenol removal, the reduction efficiency of chemical oxygen demand reached up to 97.15% under optimal conditions (temperature of 497 degrees C, residence time of 76 s and oxidant coefficient of 1.99). Also, based on the high- performance liquid chromatography analysis, two compounds of formic acid (CH2O2) and glyoxylic acid (C2H2O3) were produced at the end of the reaction (pollutant degradation). In addition, the reaction mechanism for 2,6-dimethylphenol degradation was elucidated by molecular dynamics simulation and reactive force field. Ultimately, the reaction mechanism showed that the supercritical water oxidation followed the free radical mechanism that it is justified the high reaction rate in this technology.

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