Spent coffee to carbon: blending with manganese zinc ferrite as a plasmonic photocatalysis for degradation of organic dyes

Abstract

ABSTRACT In this work, we introduce a new composite material consisting of Mn(1-x)ZnxFe2O4 (MZF) and wasted coffee grounds carbon (C). Crucially, the surface chemistry of the ‎composite, which lacks Zn2+ ions in octahedral locations, highlights its distinctive structural ‎characteristics. Before the integration of the carbon composite, the saturation magnetisation ‎of the sample was recorded as 53.073 emu/g. However, it decreased to 45.49 emu/g ‎after the composite was formed and the reaction processes occurred. UV-spectroscopy ‎enabled the measurement of band gap energies, which showed that the band gap energies for ‎ferrite were 2.93 eV and for the MZF/C composite were 2.12 eV. By utilising plasmonic ‎photocatalysis, the MZF/C composite has shown exceptional effectiveness as a high-temperature photocatalyst, specifically in the breakdown of methylene blue (MB) and Eosin (EO) dyes, ‎which are representative of basic and acidic dyes, respectively. The study demonstrated enhanced photocatalytic degradation kinetics under both visible light and sunlight, with sunlight showing superior performance. Over a 120-min period, the ferrite composite achieved a removal efficiency of 89% under sunlight, compared to 68% under artificial light. By utilising plasmonic photocatalysis principles, this work clarifies the structural and optical ‎properties of the MZF/C composite and emphasises its capacity to tackle environmental ‎issues through effective dye degradation mechanisms.‎