Magnetic Iron-Doped Filtered Coffee Bio-Waste Based Carbon for the Adsorption of Reactive Blue 21

Abstract: Intensive coffee consumption causes a high amount of coffee waste to be produced annually. In this study, the adsorption of Reactive Blue 21 (RB21) dye by using the magnetic iron-doped filtered coffee bio-waste (magnetic-FCW) was investigated in detail. Magnetic-FCW was characterised by SEM-EDX, mapping, FTIR, and Raman analysis and it was found that the material contains 3.4% Fe by weight. The highest RB21 removal was observed as 97.8% at pH 3 and 5 g/L magnetic-FCW concentration. It was determined that the adsorption of RB21 dye by magnetic-FCW was more describable by the pseudo second-order kinetic model, and k₂was calculated as 0.086 and 0.0016 g/mg min at 50 and 100 mg/L RB21 concentrations, respectively. In addition, RB21 dye removal with magnetic-FCW was more amenable to the Langmuir isotherm model and the q_maxwas calculated as 15.80 mg/g. In conclusion, the use of this bio-waste, which is formed as a result of the rapid increase in the consumption of filtered coffee, in the removal of dyes such as RB21 dye from wastewater, makes it possible to include magnetic-FCW in the field of waste management as a low-cost adsorbent material, which reduces operating costs and makes it possible to reuse these wastes in the waste sector. Collecting these bio-wastes, especially from cafes and restaurants and, reusing them could serve the circular economy as well.