Modification of biomass-derived activated carbon with magnetic α-Fe2O3 nanoparticles for CO2 and CH4 adsorption

Magnetic and nonmagnetic activated carbons (ACs) were successfully prepared by using AC obtained from spent coffee grounds (SCGs) for use in CO2 and CH4 capture. SCGs were activated by chemical activation to produce ACs and a magnetic alpha-Fe2O3 /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 (FTIR), 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-Fe2O3 particles. According to adsorption-desorption experiments, the best results were obtained with the magnetic alpha-Fe2O3/AC sample (1.68 mmol g(-1) for CO2 and 0.65 mmol g(-1) for CH4) at 0 degrees 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 CO2 and CH4 adsorption is dominated by the physical adsorption. The alpha-Fe2O3 alpha/AC multicycle CO2 adsorption tests showed that it can be successfully regenerated with high sorption capacity. The -Fe2O3/AC composite is a promising adsorbent for potential application.