Abstract

Certain undesired N-containing products like ammonia, nitrate, and organic-N species have become the roadblocks to supercritical water oxidation (SCWO) application. This study examined the mechanisms for total nitrogen (TN) removal by catalytic SCWO. By comparing pseudo-first order kinetic constants of TN removal, our findings showed that heteropolyacids took a significant part in TN removal for nitrobenzene, and Cu(NO3)2 achieved the best TN removal performance for aniline, nitrobenzene, and indole since both Cu(II) and NO3- could accelerate N2 formation via the reduction of nitrate and the oxidation of ammonia by NO2. and .OH. Distribution of N-containing species revealed that adding catalysts could generally facilitate the conversion of nitrogen gas from organic-N, while it cannot accelerate N2 production from ammonia and nitrate. According to the DFT result, conceivable degradation pathways of aniline, nitrobenzen, and indole were proposed involving denitrification, ring-open, and mineralization.

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