Influences of nitrite on paracetamol degradation in dielectric barrier discharge reactor

摘要

The frequent detection of paracetamol in natural water increased environmental concerns. The dielectric barrier discharge (DBD) technology is an effective paracetamol removing method, however, this research showed that the removal of paracetamol using DBD technology at 30 min dropped from 100% to 53.3% as the initial paracetamol concentration increased from 10 mg/L to 100 mg/L, due to the formation of more competitive intermediate products at higher paracetamol concentration. The removal of TOC was found to be much slower than that of paracetamol, as paracetamol was removed completely after 5 min treatment, the removal rate of TOC was 46.3% after 20 min treatment under 500 W discharge power and 50 mL/min air flow rate. The orthogonal experiment showed that the removal of TOC was significantly influenced by the treatment time, discharge power and recirculating flow rate, while less influenced by the discharge frequency. In the removal process of paracetamol, nitrite ion that generated during DBD treatment reacted with paracetamol to form an intermediate product of 3-nitro-4-acetamidophenol. The presence of nitrite ion retarded the removal of 3-nitro-4-acetamidophenol and thus the TOC, however, the nitrate ion did not. The degradation of paracetamol followed a sequence of 3-nitro-4-acetamidophenol, nitrosophenol/acetamide, N-methylacetamide, acetamide and small molecule organic acids in the DBD reactor, and these intermediates were finally oxidized to CO2, H2O and NO3-.