Vitamin C promoted refractory organic contaminant elimination in the zero-valent iron/peracetic acid system: Efficiency, mechanism and effects of various parameters

The conventional zero-valent iron/peracetic acid (ZVI/PAA) system is severely limited owing to the passivation of ZVI and the low recovery of Fe2+. In this study, a reducing agent, vitamin C (H2A), was used for the first time to enhance the ZVI/PAA system as a way to improve its degradation performance. Under optimal conditions, the removal efficiency of the H2A/ZVI/PAA system was 82.9%, while that of the H2A/PAA and ZVI/PAA systems were only 19.0% and 25.6%. Free radical quenching and electron paramagnetic experiments (EPR) confirmed that CH3C(O)O•, •OH and CH3C(O)OO• were the major active species for acid orange 7 (AO7) degradation with contributions of 9.7%, 75% and 14.4%, respectively. The degradation mechanism was proposed through UV-vis full-wavelength scanning and chemical oxygen demand (COD) experiments. The removal of AO7 was not affected in the presence of Cl-, SO42- and HCO3-, while inhibition occurred with humic acid. ZVI exhibited excellent catalytic properties and stability, and the removal efficiency of AO7 exceeded 70% after three cycles. Additionally, the H2A/ZVI/PAA system showed good ability to remove AO7 in well water, lake water, river water and reservoir water, and the elimination efficiency of MO, DCF and ACE also exceeded 70%. Overall, this study contributes new cognition for enhancing the ZVI/PAA system to degrade contaminants, which is expected to achieve a cleaner water environment.

 

Comments：

This study proposes the use of vitamin C (H2A) as a reducing agent to improve the performance of the conventional zero-valent iron/peracetic acid (ZVI/PAA) system for the degradation of acid orange 7 (AO7) and other contaminants in water. The results indicate that the H2A/ZVI/PAA system exhibits significantly higher removal efficiency compared to the H2A/PAA and ZVI/PAA systems. The active species responsible for AO7 degradation are identified through free radical quenching and electron paramagnetic experiments (EPR), and the degradation mechanism is proposed through UV-vis full-wavelength scanning and chemical oxygen demand (COD) experiments.

The catalytic properties and stability of ZVI are found to be excellent, and the removal efficiency of AO7 is maintained even after three cycles. The system also shows good ability to remove other contaminants such as MO, DCF and ACE from different sources of water including well water, lake water, river water, and reservoir water. The presence of Cl-, SO42- and HCO3- does not affect the removal of AO7, while inhibition is observed in the presence of humic acid.

The study provides new insights into enhancing the ZVI/PAA system for the degradation of contaminants in water and highlights the potential of the H2A/ZVI/PAA system for achieving a cleaner water environment.

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S3114	Vitamin C	Vitamin C (L-Ascorbic acid) is a water-soluble vitamin indicated for the prevention and treatment of scurvy.

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