Enhanced trichloroethene degradation performance in innovative nanoscale CaO2 coupled with bisulfite system and mechanism investigation

Abstract The effect of bisulfite (HSO3–) in nCaO2/Fe(III)/HSO3– system on improving HO• generation and trichloroethene (TCE) removal was innovatively reported. The enhancement mechanism of HSO3– for TCE removal in nCaO2/Fe(III)/HSO3– system was caused not only by the complexing and reducing effects on promoting the conversion of Fe(III) to Fe(II), but also due to the reaction with O2 in water to produce SO4–• for accelerating TCE degradation. A double effect of nCaO2 as an oxidant source to generate HO• and as a O2 source to promote SO4–• generation was revealed. A pseudo-second-order kinetic model of TCE removal was determined and 94.6% TCE degradation was achieved within 60 min at the nCaO2/Fe(III)/HSO3–/TCE molar ratio of 6/12/9/1, in which 82.8% TCE was dechlorinated. The scavenger test and EPR detection found that various kinds of reactive oxygen species (ROSs) including HO•, SO4–•, O2–• and 1O2 were generated, all contributed to TCE removal and HO• was the dominant one in nCaO2/Fe(III)/HSO3– system. The effects of surfactant presence and the complex matrix in the actual groundwater were evaluated. The experiments of high efficiency for chlorinated olefins and benzene series removals but low applicability for chlorinated alkanes provided an alternative technique to remedy groundwater based on the various kinds of contaminants performance.