Degradation characteristics and reaction mechanism of supercritical water oxidation of oily wastewater

With the continuous increase of oil and natural gas extraction, the amount of oily wastewater generated during the extraction process is increasing yearly. Oily wastewater will pollute the environment and water sources and jeopardize human life and health. Traditional treatment technology cannot achieve the minimization and harmlessness of the treatment process. Supercritical water oxidation (SCWO) technology is a promising technology for the harmless treatment of organic matter, which scholars at home and abroad are concerned. Therefore, supercritical water oxidation technology is used to degrade oily wastewater in this part. The effects of key parameters such as different times, secondary oxidant injection time, and secondary oxidant percentage on the degradation pattern of oily wastewater were explored. The changes in the organic matter composition before and after the reaction were obtained by analyzing the composition before and after the reaction, and pyridine was selected as a model compound to study its ring opening during the supercritical water oxidation process. The reaction mechanism of pyridine was investigated in the supercritical water oxidation process. The results showed that the optimal residence time was 10 min, the optimal secondary oxidant injection time was 7 min after the start of the reaction, the optimal secondary oxidant percentage was 0.2, and among the initial reaction sites between hydroxyl radicals and pyridine, 3C of 1C, 2C, and 3C of pyridine was the most susceptible to the attack of hydroxyl radicals.