Chitosan/hydroxyapatite/Fe3O4 magnetic composite for metal-complex dye AY220 removal: Recyclable metal-promoted Fenton-like degradation

Cross-linked Chitosan (CS) loaded with iron species has been widely used as heterogeneous Fenton catalysts for organic contaminant removal. In comparison with raw-CS based Fenton catalysts, it exhibited an improved degradation efficiency due to the stabilization of cross-linking agents. With cross-linking, however, most reactive sites of CS were occupied by cross-linking agents, making its capability decreased sharply for adsorbing the released metal ions from metal-complex dye degradation. In this work, in order to efficiently adsorb the released metal ions from metal-complex dyes and avoid a secondary pollution, a new CS-based heterogeneous Fenton catalyst (Chitosan/Hydroxyapatite/Fe 3 O 4 magnetic composite) was developed for AY220 (a model of metal-complex dyes) removal. Hydroxyapatite (HA), a well-known biocompatible material with strong ability for metal ion adsorption, was introduced to combine with CS for Fe 3 O 4 loading. The total removal efficiency of AY220 by the magnetic composite can reach as high as 95.0%, and the degradation efficiency of AY220 was greatly enhanced compared with a raw-CS based catalyst and bare Fe 3 O 4 . Meanwhile, the composite can efficiently adsorb Co 2   + released from AY220 degradation, which can further promote the degradation of AY220. After five recyclable runs of the composite, the degradation efficiency of AY220 increased from 25.1% to 45.6%, demonstrating its potential usefulness in recyclable degradation of metal-complex dyes.