Temperature sensitivity of nitrogen-containing compounds decomposition during supercritical water oxidation (SCWO)

Supercritical water oxidation (SCWO) has sprung up as a promising technique to eliminate refractory compounds, which are difficult to be removed by conventional wastewater treatment processes. However, data is still sparse on SCWO of a series of N-containing compounds, such as TN removal, N-containing species distribution and molecular characteristics. In this work, decomposition of 44 nitrogen-containing compounds was investigated under temperature of 350-550 degrees C, resulted in total nitrogen (TN) removal from 55 to 94%. The N-containing products were primary N-2, nitrate and ammonium. The primary products were NO3- and NH4+ from nitro- and amino-group compounds, respectively. As for diazo and N-heterocyclic ones, NO3- and NH4+ were the main nitrogen containing products, respectively. Interestingly, in terms of aniline and its derivatives, the amount of N-2 followed the order: aniline > N-methylaniline (N-MA) > N,N-dimethylaniline (N,N-DMA). These experimental results were in agreement with the results of Fukui function. The correlationship between the temperature at TN removal rate of 50% (T-N50) and 17 molecular characteristics has been calculated, which resulted E-HOMO and Fukui indices could largely influence temperature behavior of TN removal. (C) 2018 Published by Elsevier B.V. on behalf of Taiwan Institute of Chemical Engineers.