Non-thermal plasma coupled liquid-phase catalysis /Fe2+ for VOCs removal: Enhanced mechanism of protocatechuic acid

•Acetone removal efficiency reached 91% in PCA enhanced NTP-LC/ Fe2+ system.•O3 removal efficiency was 100% when PCA was added.•PCA formed complexes with Fe3+ to prevent its precipitation.•PCA enhanced the generation of OH and O2- by accelerating the Fe3+/Fe2+ cycle. Non-thermal plasma coupling Fe2+ containing liquid-phase catalysis (NTP-LC/ Fe2+) can effectively reuse the byproduct ozone (O3) of NTP in LC/ Fe2+ for volatile organic compounds (VOCs) degradation. However, the low recycling rate of Fe2+/Fe3+ resulted in poor catalytic effect of the coupling system. In this study, the chelator protocatechuic acid (PCA) was added to LC/Fe2+ to enhance the removal of representative VOC acetone. The results showed that adding PCA increased the acetone removal efficiency to 91% and kept O3 ∼ 100% removed within 180 min. The mechanism of PCA-enhanced acetone degradation was that PCA accelerated the Fe3+/Fe2+ cycle by generating PCA-Fe3+ chelates, which prevented the Fe3+ from precipitation and promoted the production of OH and O2- for acetone oxidation.