Graphene modified iron sludge derived from homogeneous Fenton process as an efficient heterogeneous Fenton catalyst for degradation of organic pollutants

Abstract

Fenton process has emerged as one of the most promising alternative strategies for wastewater treatment. Unfortunately, it is still challenging to deal with iron sludge generated during the process, which is of great importance for practical application. Here, we report a green way to modify iron sludge with low amount (0–2 wt%) of graphene as a heterogeneous Fenton catalyst. XRD, FESEM, TEM, Raman and XPS results suggested that the iron sludge existed as FeOOH particles that were mainly entrapped inside the graphene sheet. BET results confirmed the mesoporous structure of the composites. Under the optimal conditions, the degradation rate of rhodamine B, acid red G and metronidazole by the iron sludge-graphene catalyst reached 99.0%, 98.5% and 91.8%, respectively, within 120 min. Moreover, the as-prepared catalyst exhibited wide pH operating range, excellent stability and reusability. The enhanced heterogeneous Fenton property of the composite as compared to bare iron sludge could be ascribed to the mesoporous structure, increased adsorption ability and the promoted ≡FeIII/≡FeII cycle. This work not only provides a new idea of fabricating heterogeneous Fenton catalysts, but may also promote the application of homogeneous Fenton process for wastewater treatment.