Reduction of nitrobenzene by a zero-valent iron microspheres/polyvinylidene fluoride (mZVI/PVDF) membrane

Abstract Zero-valent iron microparticle (mZVI) is an excellent reductant for nitroaromatic compounds (NACs). However, it still faces severe challenges including easy agglomeration, oxidation, loss and difficult reuse. To overcome these drawbacks, a zero-valent iron microspheres/polyvinylidene fluoride (mZVI/PVDF) composite membrane using non-solvent induced phase separation (NIPS) method was constructed. Compared with bare mZVI, the mZVI/PVDF composite membrane limited agglomeration and oxidation of mZVI and slowed down the loss of mZVI and resultant iron (hydr)oxide, which made it maintain 100% nitrobenzene (NB) degradation in eight cycles. In the 1st use of mZVI/PVDF composite membrane, the NB degradation went through four steps dominated by adsorption, reduction by mZVI, formation of Fe2+ species associated with iron (hydr)oxide, reduction by Fe2+ species associated with iron (hydr)oxide. The captured iron (hydr)oxide by mZVI/PVDF composite membrane after 1st use accelerated the formation of Fe2+ species associated with iron (hydr)oxide, which made the NB degradation in 2nd-5th use faster than in 1st use. To promote NB diffusion, the cross-flow model was further applied and the NB removal amount was 11.63 times that in static model in 1st use. Our findings showed the NB degradation by mZVI/PVDF composite membrane in details, which would accelerate optimized use of mZVI.