Palladium impregnated activated carbon (Pd/C) filters play a major role in air quality management by the removal of toxic carbon monoxide from confined environments. However, Pd is an expensive metal and therefore, recovery and reuse of Pd from spent filter cartridges is highly desirable. The objective of the present study was to biosynthesise Pd nanoparticles (NPs) using green tea as a reducing agent. The source of Pd for the NP synthesis was spent Pd/C. Three different acid based Pd extraction protocols constituting of hydrochloric acid-hydrogen peroxide (HCl-H2O2), 2 M HCl and aqua regia were systematically explored. The Pd impregnated carbon was characterised using scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), ultraviolet-visible (UV-vis) spectroscopy, X-ray powder diffraction (XRD) and atomic absorption spectrometry (AAS) before and after Pd extraction. It was found that the aqua regia based extraction protocol was the most efficient among the three chosen acid or acid mixtures with an average absolute yield of 96%. Finally, an attempt was made towards one pot biosynthesis of Pd NPs from the recovered extract by using green tea as a reducing agent. The synthesised NPs were characterised using UV-vis spectroscopy, SEM and XRD.

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