Fe3O4@β-CD nanocomposite as heterogeneous Fenton-like catalyst for enhanced degradation of 4-chlorophenol (4-CP)

• Fe3O4@β-CD nanocomposites were fabricated via Fe ions and β-CD in one pot.
• Fe3O4@β-CD exhibits an enhancement effect than Fe3O4 toward H2O2 decomposition for 4-chlorophenol (4-CP) and chlorobenzene (CB).
• EPR spectra indicate that the scavenging influence of β-CD on the OH produced could be neglected using Fe3O4@β-CD.
• The enhancement effect may be ascribed to the construction of a ternary complex (Fe2+-β-CD-pollutant) that allowed OH to directly attack the contaminant.

The magnetic Fe3O4@β-cyclodextrin (β-CD) nanocomposites were fabricated via Fe ions and β-CD in one pot and characterized as a heterogeneous Fenton-like catalyst that may be used for the degradation of 4-chlorophenol (4-CP). The catalytic capacity of Fe3O4@β-CD was evaluated on the basis of various parameters, including pH, H2O2 concentration and catalyst loading, with regards to the pseudo-first-order kinetics of 4-CP degradation. In addition, iron leaching, the effect of radical scavengers and reusability of the Fe3O4@β-CD nanocomposite were also studied. The results showed that Fe3O4@β-CD exhibited a higher catalytic ability than that Fe3O4 toward 4-CP degradation, the observed rate constants (kobs) were 0.0373 min−1 for Fe3O4@β-CD, and 0.0162 min−1 for Fe3O4, which may be ascribed to the construction of a ternary complex (Fe2+–β-CD–pollutant) that allowed the produced hydroxyl radicals (·OH) to directly attack the contaminant and simultaneously enhanced the solubility of the organic pollutant. Fe3O4@β-CD also exhibited an enhancement effect for chlorobenzene (CB) degradation with the kobs of 0.0392 min−1 (kobs = 0.0099 min−1 for Fe3O4), which may be due to a synergistic effect in the Fe3O4@β-CD composite. Furthermore, Fe3O4@β-CD has an excellent catalytic activity, stable mechanical strength and adequate reusability. A possible reaction pathway of 4-CP degradation dominated by ·OH was proposed according to analyses of the degradation intermediates and chloride ions. The host-guest interaction between β-CD and 4-CP were examined with density functional theory (DFT) calculations, expounding the unicity of degraded intermediate owing to the specific spatial selectivity of β-CD. The findings of this study provide a novel material used in the Fenton-like process for the degradation of contaminants.

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