Özet:

Magnetic and nonmagnetic activated carbons (ACs) were successfully prepared by using AC obtained from spent coffee grounds (SCGs) for use in CO$_{2}$ and CH$_{4}$ capture. SCGs were activated by chemical activation to produce ACs and a magnetic $\alpha $-Fe$_{2}$O$_{3}$/AC composite was prepared by coprecipitation method from the ACs produced. Magnetic and nonmagnetic samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive X-ray spectrometry (EDX) techniques. The textural properties of samples were determined by nitrogen adsorption-desorption using the Brunauer--Emmett--Teller (BET) and Barrett--Joyner--Halenda (BJH) methods. The results showed that the porosity of AC was not blocked by $\alpha $-Fe$_{2}$O$_{3}$ particles. According to adsorption-desorption experiments, the best results were obtained with the magnetic $\alpha $-Fe$_{2}$O$_{3}$/AC sample (1.68 mmol g$^{-1}$ for CO$_{2}$ and 0.65 mmol g$^{-1}$ for CH$_{4})$ at 0 \textdegree C and 120 kPa. Adsorption performances were evaluated using four isotherm models. The isosteric heats of adsorption calculated for both adsorbents were smaller than 80 kJ/mol and it revealed that CO$_{2}$ and CH$_{4}$ adsorption is dominated by the physical adsorption. The $\alpha $-Fe$_{2}$O$_{3}$/AC multicycle CO$_{2}$ adsorption tests showed that it can be successfully regenerated with high sorption capacity. The $\alpha $-Fe$_{2}$O$_{3}$/AC composite is a promising adsorbent for potential application.

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