Mechanism of trichloroethylene degradation in Fe(II)-activated peroxymonosulfate coupled with citric acid system in the presence of surfactants

This study demonstrated that peroxymonosulfate (PMS) activated by Fe(II)/citric acid (CA) could effectively degrade trichloroethylene (TCE) in the presence of Tween-80 (TW-80) or sodium dodecyl sulfate (SDS). Significant TCE removal of 91.6% (90.1%) with 1.3 g L-1 TW-80 (2.3 g L-1 SDS) were achieved at the PMS/Fe(II)/CA/TCE molar ratio of 4/4/4/1 (20/20/20/1). TCE degradation could be greatly elevated by Fe(II) and CA addition, while the existence of surfactants restrained TCE removal and the inhibitory effect increased with the higher surfactant concentration. The tests of the electron paramagnetic resonance (EPR) and reactive radicals scavenging experiments proved that sulfate radical (SO4-center dot), hydroxyl radical (HO center dot), and superoxide radical (O-2(-)center dot) were responsible for TCE degradation and SO4-center dot acted as the major one. The influences of initial solution pH and inorganic anions k(Cl- and HCO3-) on TCE removal were also investigated. Eventually, TCE removal in actual groundwater tests with surfactants confirmed that the PMS/Fe(II)/CA process has a huge potential of practical application in remediating the groundwater contaminated by TCE after the pretreatment by solubilization using surfactants.

Automated summary

This study demonstrated that peroxymonosulfate (PMS) activated by Fe(II)/citric acid (CA) could effectively degrade trichloroethylene (TCE) in the presence of surfactants, with the sulfate radical (SO4•−) identified as the major reactive species responsible for TCE degradation. The study also investigated the influence of pH and inorganic anions on TCE removal, and confirmed the practical potential of the PMS/Fe(II)/CA process in remediating TCE-contaminated groundwater.