Interface-engineered Fe3O4/hydrophilic graphene as recyclable heterogeneous Fenton catalyst for dye degradation enhancement

The efficiency of heterogeneous Fenton catalysts is often constrained by poor mass transfer at the solid-liquid interface and challenges in catalyst recovery. To address this, a novel Fe 3 O 4 /hydrophilic graphene (Fe 3 O 4 /HG) nanocomposite was synthesized via a one-pot method involving the grafting of sodium dodecylbenzenesulfonate (SDBS) onto graphene oxide followed by in-situ deposition of Fe 3 O 4 nanoparticles (90 wt% loading). The material was thoroughly characterized by XRD, SEM, TEM, Raman, FT-IR, and contact angle measurements, while Density Functional Theory (DFT) calculations elucidated the interfacial interaction mechanisms. The introduced sulfonic acid groups drastically enhanced hydrophilicity, reducing the water contact angle to 15.0° (compared to 38.8° for Fe 3 O 4 /rGO) and improving aqueous dispersion. The optimal catalyst (FHG-W90) achieved 99% degradation of methyl orange (30 mg·L −1 ) within 60 min under optimal conditions ([Catalyst] = 2.0 g ·L −1 , [H 2 O 2 ] = 14.5 mmol·L −1 , pH=3), significantly outperforming control samples (Fe 3 O 4 NPs and Fe 3 O 4 /rGO). Meanwhile, the nanocomposite retained sufficient saturation magnetization (∼70 emu·g −1 ) for facile magnetic separation. DFT calculations quantitatively revealed that SDBS functionalization intensified the adsorption energy ( E ads ) of H 2 O (from -7.9 to -12.0 kcal·mol −1 ) and H 2 O 2 (from -8.2 to -13.2 kcal·mol −1 ) on the graphene surface. This work highlights interface engineering via hydrophilic modification as a highly effective strategy for developing high-performance and easily recyclable Fenton catalysts. The Fe 3 O 4 /HG nanocomposite shows great promise for practical wastewater treatment, and the design principle can be extended to other catalytic systems.