Immobilization of chitosan-templated MnO 2 nanoparticles onto filter paper by redox method as a retrievable Fenton-like dip catalyst.

By exploiting the hydrophilicity of cellulose filter paper (FP) and the excellent chelating property of chitosan (CH) for Mn ²⁺ , we have designed an efficient and retrievable dip catalyst MnO ₂ /CH-FP for Fenton-like degradation of methylene blue (MB) over a wide pH range from 2.8 to 11.2. The MnO ₂ nanoparticles were uniformly immobilized in the CH-FP matrix by in-situ redox precipitation method where Mn(NO ₃ ) ₂ was treated with KMnO ₄ at mild conditions. A series of MnO ₂ /CH-FP hybrids with different MnO ₂ loading were fabricated via varying concentration of Mn(NO ₃ ) ₂ solution, and their structure-function relationships were discussed based on detailed characterization. The optimal catalyst 1.0MnO ₂ /CH-FP could cooperate with multiple low-concentration dosages of H ₂ O ₂ to efficiently degrade 95.6% MB in 90 min (50 mg L ^-1 MB, 1 g L ^-1 catalyst, 30 mg L ^-1 H ₂ O ₂ , pH 7). It is also shown that 1.0MnO ₂ /CH-FP could still keep 83.3% degradation efficiency of MB after six cycles. Moreover, the activity of this composite greatly surpassed that of bare MnO ₂ for nearly 50%, owing to its larger surface area and more accessible active sites. This method for preparing MnO ₂ /CH-FP could effectively avoid the agglomeration of MnO ₂ nanoparticles and make the reaction turn on/off almost instantaneously by mere insertion/removal.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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