Bisulfite-assisted surface Fenton-like degradation of dimethyl phthalate by ferrihydrite-H2O2 system

As a common plasticizer, phthalic acid esters (PAEs) have been widely employed to improve the flexibility and workability of polymetric materials, thus leading to their widespread distribution in soils and wastewater. Moreover, PAEs raised great public concerns due to their endocrine-disrupting effects, which could damage reproductive system and body development at low exposure dose. In the present study, a ferrihydrite-H2O2-bisulfite ternary system was developed to achieve efficient degradation of dimethyl phthalate (DMP). Our results showed that 86.6 % of total DMP could be removed within 240 min by the ferrihydrite-H2O2-bisulfite ternary system, in which the respective optimum concentration of ferrihydrite, H2O2 and bisulfite was set as 1.0 g/L, 5.0 mM and 2.0 mM. For comparison, negligible DMP removal was observed in the binary systems of ferrihydrite-H2O2, ferrihydrite-bisulfite and H2O2-bisulfite. Hydroxyl radical (•OH) was identified as the dominant reactive species for DMP degradation based on the results of electron paramagnetic resonance (EPR) analysis and free radicals quenching experiments. By complexing with iron species, bisulfite could accelerate the reduction of Fe(III) to Fe(II), thus increasing the generation of •OH by ∼4 times in the heterogeneous ferrihydrite-H2O2 system. Furthermore, ferrihydrite exhibited excellent recyclability without any modification as indicated by the negligible decrease in the catalytic degradation efficiency of DMP. Thus, in addition to efficient degradation of PAEs in wastewater, our study would shed light on the in-situ soil remediation technology on the basis of bisulfite-assisted heterogeneous Fenton-like reactions.