Enhanced trichloroethylene degradation in the presence of surfactant: Pivotal role of Fe(II)/nZVI catalytic synergy in persulfate system

Abstract

Trichloroethylene (TCE) removal performance in non-ionic surfactant Tween-80 (TW-80) and anionic surfactant sodium dodecyl sulfate (SDS) involved solution by Fe(II) activated persulfate (PS) was investigated through the strengthening of nanoscale zero valent iron (nZVI). 99.5% removal of TCE could be obtained at the PS/Fe(II)/nZVI/TCE molar ratio of 8/4/4/1 with 1.0 critical micelle concentration (CMC) of TW-80 presence (13 mg L−1), while this value was slightly decreased to 88.3% at the molar ratio of 40/20/20/1 with 1.0 CMC of SDS presence (2.3 g L−1) in 180 min. The addition of nZVI significantly promoted TCE degradation, while TW-80 or SDS definitely inhibited TCE removal. Further, TCE removal declined with TW-80 or SDS concentration increasing from 0 to 10 CMC, and continuously decreased at 20 CMC of TW-80 but elevated TCE removal at 20 CMC of SDS. Tests of radical scavengers revealed that HO and SO4− contributed a major part while O2− had less contribution to TCE degradation in PS/Fe(II)/nZVI system. The dichlorination of TCE in PS/Fe(II)/nZVI system was 94.5% with TW-80 and 97.2% with SDS. In addition, TCE (with TW-80) removal was decreased with the initial pH increase from 3.0 to 11.0, while TCE (with SDS) degradation was always beyond 83% in the initial pH change from 3.0 to 11.0. Moreover, the effects of inorganic anions (Cl−, HCO3−) in the solution were evaluated. Experimental results using the actual groundwater revealed the excellent availability of PS/Fe(II)/nZVI system in remediating TCE contaminated field involved with TW-80 or SDS surfactants. In summary, these findings provide a new direction in remediating groundwater from contaminated sites polluted by chlorinated organic solvents after pretreatment by surfactant solubilization.