Magnetite loaded on carbonized rice husk: low cost biomass-derived composites for CO2 capture

Recent studies of CO2 sorption on low-cost metal oxides strongly encourage their use as sorbents [Alfè, PROCI, 2015] in CO2 capture and storage (CCS) strategies. Magnetite (Fe3O4, FM) and CO2 interaction proceeds through acid-base interactions involving unsaturated metal and O sites exposed on FM surface. The FM sorption capacity is lowered by the tendency of magnetite particles to agglomerate causing a decrease of the exposed surface area. The dispersion of magnetic particles on carbon-based solid matrices has been proposed to face this limitation. Thanks to their low-cost, high surface area and porosity, carbonized biomasses are good candidates for supporting FM phase. Rice husk (RH) is an agricultural residue abundantly available in rice producing countries, obtained during the milling of paddy (22 wt. % of the weight of unmilled rice is received as husk). It presents a high ash content, which is 92 to 95% silica, highly porosity and a high surface area. RH is a green material that has a great potential for technological applications since it can be converted to different types of fuels and chemical feedstocks through a variety of thermochemical conversion processes. Following the same approach presented in our previous works on the CO2 capture performances of FM supported on a carbon-based reference material (carbon black) [Alfè, PROCI, 2015; Gargiulo, App. Surf. Sci. 2016], the synthesis and characterization of RH/FM composite materials were performed. A set of RH/FM composites were produced by varying the amount of carbonized RH from 20 to 80 wt.% in order to optimize the sorbent properties for CO2 adsorption applications. Preliminary data about the CO2 sorption capacity were also obtained.