Degradation of Triton X-100 in Water Falling Film Dielectric Barrier Discharge Reactor

Abstract

The aim of this study was to investigate the degradation of the non-ionic surfactant Triton X-100 (TX-100) by using an advanced oxidation process in a non-thermal plasma reactor based on water falling film dielectric barrier discharge (DBD). The effects of two catalytic plasma systems, Fe2+/DBD and H2O2/DBD, were tested to improve the degradation of TX-100 and the mineralization efficiency in the DBD reactor. Both catalytic systems exhibited significant improvements in degradation efficiency, especially in the beginning of the treatment: the efficiency increased from 23 to 88 and 50%, for 5mgL-1 Fe2+/DBD and 10mmolL-1 H2O2/DBD, respectively. The mineralization efficiency of TX-100 in the non-catalytic DBD treatment was very low (1%), but with addition of catalysts, the mineralization efficiency was drastically improved, with H2O2/DBD at 4-34% (depending on the H2O2 concentration) and Fe2+/DBD at 2-21% (depending on the Fe2+ concentration). Degradation products of TX-100 in non-catalytic and two catalytic systems were identified using UHPLC-Orbitrap-MS. Based on the degradation products that were identified, a simple mechanistic scheme was proposed. MS analysis revealed that degradation of TX-100 in the DBD reactor occurred by shortening the ethoxy chain. In the presence of catalysts, there are additional reactions of cleavage of the alkyl chain followed by formation of polyethoxylated phenol (H2O2/DBD) and addition of OH• radicals onto the aromatic ring (Fe2+/DBD). The final degradation products did not cause any significant toxic effects to Vibrio fischeri or Artemia salina.