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

The effect of bisulfite (HSO3-) in nCaO(2)/Fe(III)/HSO3- system on improving HO center dot generation and trichloroethene (TCE) removal was innovatively reported. The enhancement mechanism of HSO3- for TCE removal in nCaO(2)/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 O-2 in water to produce SO4-center dot for accelerating TCE degradation. A double effect of nCaO(2) as an oxidant source to generate HO center dot and as a O-2 source to promote SO4-center dot 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 nCaO(2)/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 center dot, SO4-center dot, O-2(-)center dot and O-1(2) were generated, all contributed to TCE removal and HO center dot was the dominant one in nCaO(2)/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.

Automated summary

The role of bisulfite (HSO3-) in the nCaO(2)/Fe(III)/HSO3- system in promoting HO center dot generation and improving trichloroethene (TCE) removal was reported. The complexing and reducing effects of HSO3- on Fe(III) conversion to Fe(II), as well as the generation of SO4-center dot, were identified as the main mechanisms for enhancing TCE removal. Various reactive oxygen species (ROSs) were found to contribute to TCE degradation, with HO center dot being the dominant species in the nCaO(2)/Fe(III)/HSO3- system.