Facile Preparation of Multifunctional Ag-Fe<sub>x</sub>O<sub>y</sub>/C Composite from Coffee Husk for Antibacterial and Catalytic Applications

In this research, FexOy/C was first prepared through one-step pyrolysis of FeCl3-coffee husk mixture. The surface of FexOy/C was then loaded with Ag particles using an ex-situ method, producing Ag-FexOy/C. XRD result indicates that different crystals of Fe3O4, Fe2O3, and FeO(OH) were formed on the surface of porous carbon. The existence of 0.41 wt% Ag and 3.13 wt% Fe was determined by AAS results. Subsequently, Ag-FexOy/C was primarily explored for its antibacterial and catalytic applications. According to the ASTM E2149-13a standard, the material killed 62% of Staphylococcus aureus within 60 min of contamination. For catalytic performance, 50 ppm sunset yellow FCF was decolorized by 240 ppm H2O2 using 0.40 g/L Ag-FexOy/C at pH 3.0. The results showed that Ag-FexOy/C had an adsorption capacity of 7.8 mg/g and an average decolorization rate of 41.6 mg.g-1.h-1. This rate was approximately 13-fold higher than that without a catalyst. Furthermore, Ag-FexOy/C with a saturation magnetization of 3.62 emu/g was separated and recovered easily from the treated mixture by a magnet bar. Overall, the findings initially prove that Ag-FexOy/C is a promisingly multifunctional material, thanks to its antibacterial activity, adsorption capacity, catalytic activity and magnetic recoverability.