The influence of various microplastics on PBDEs contaminated soil remediation by nZVI and sulfide-nZVI: Impedance, electron-accepting/-donating capacity and aging

The microplastics (MPs) existed in the environment widely has resulted in novel thinking about in-situ remediation techniques, such as nano-zero-valent iron (nZVI) and sulfided nZVI (S-nZVI), which were often compromised by various environmental factors. In this study, three common MPs such as polyvinyl chloride (PVC), polystyrene (PS), and polypropylene (PP) in soil were found to inhibit the degradation rate of decabromodiphenyl ether (BDE209) by nZVI and S-nZVI to different degrees due to MPs inhibiting of electron transfer which is the main way to degrade BDE209. The inhibition strength was related to its impedance (Z) and electron-accepting (EAC)/-donating capacity (EDC). Based on the explanation of the inhibition mechanism, the reason for different aging degrees of nZVI and S-nZVI in different MPs was illustrated, especially in PVC systems. Furthermore, the aging of reacted MPs, functionalization and fragmentation in particular, indicated that they were involved in the degradation process. Moreover, this work provided new insights into the field application of nZVI-based materials for removing persistent organic pollutants (POPs).