Ferrocene-modified chitosan as an efficient and green heterogeneous catalyst for sulfate-radical-based advanced oxidation process. (1st October 2017) - Lin, Kun-Yi Andrew
Highlights: CS is used a green support for immobilizing Fc to prepare Fc-CS via covalent bonds. Fc-CS exhibits a much higher catalytic activity than Fc to activate persulfate (PS). Amaranth (AMR) can be fully decomposed by Fc-CS activated PS (Fc-CS + PS). Mechanisms of PS activation and AMR degradation are proposed based on EPR. Fc-CS can be re-used to activate PS over multiple cycles without efficiency loss. Abstract: While ferrocene (Fc) is a promising heterogeneous catalyst for activating persulfate (PS) to degrade organic contaminants, chemical reagent-grade Fc is nanoscale and direct usage of Fc leads to operational and recovery issues. In this study, chitosan (CS) is selected as a support to immobilize Fc as CS is abundant, and environmental benign fishery waste. The amine group of CS also allows the formation of covalent bond between Fc-based reagent ( i.e., Fc-CHO) and CS to form Fc-modified CS (Fc-CS). This Fc-CS can be more advantageous than Fc because of its easier recovery by precipitation and filtration. To evaluate Fc-CS for PS activation, degradation of Amaranth (AMR) dye by PS is selected as a model test. The resulting Fc-CS exhibits a higher catalytic activity than pristine Fc possibly because Fc can be evenly dispersed on CS and CS can also exhibit affinity toward AMR. AMR can be also fully decomposed by Fc-CS activated PS. Through the Electron paramagnetic resonance (EPR) spectroscopic analysis, the AMR degradation can be attributed to both sulfate and hydroxyl radicals. Fc-CS had been also proven to activate PS for AMR degradation over multiple times without loss of catalytic activity. These features indicate that Fc-CS can be a promising catalyst and CS appears to be a naturally available and environmentally friendly waste-derived support for immobilizing Fc. The results and findings in this study are essential for CS-supported metal catalysts in environmental applications.