Preparation and characterization of activated carbon from Posidonia Oceanica for CO2 capture

At the worldwide, there is an increasing interest in the environmental impact of greenhouse gases emissions and CO2 in particular. In this way, the production of activated carbon with the high internal surface area (1500-3000 m2/g) to CO2 capture has gained the attention of many researchers in the last years. This is due to the properties of activated carbons which have a large active surface and it can provide high adsorption capacity. The most common precursors used for the preparation of activated carbons are organic materials that are rich in carbon. Hence, use of biomass materials could represent a good opportunity to apply renewable feedstocks to produce porous carbon [1-2]. The goal of this study is to investigate the feasibility to use a local biomass (Posidonia Oceanica) as a raw precursor to the production of activated carbons with high surface area and noticeable CO2 adsorption properties. Posidonia Oceanica is a Mediterranean sea plant previously studied by authors as the potential feedstock for biofuels (bio-oil and biochar) production [3]. Pyrolysis experiments were carried out at 400°C with a heating rate of 5°C/min using a biomass particles size: 0.4-1.2 mm under a nitrogen atmosphere. Bio-chars with a surface area of 41.3 m2/g were obtained. Both physical (600°C with steam) and chemical (600-800°C after pre-treatment with H3PO4 or KOH) activation methodologies were carried out to obtain porous carbons with high surface area. Activated carbons with surface area rates of 199.4÷234.9 m2/g were obtained by steam and H3PO4 treatments while the activation in presence of KOH has led an increasing of the superficial area; depending also by particles size of the raw biomass material (2194 m2/g and 3000 m2/g from 0.8-1.2 mm and 0.4-0.8 mm, respectively). All porous carbons were characterized in terms of elemental analysis (CHNS-O), superficial area, SEM analysis and CO2 adsorption measurements performed by BET ASAP 2020 Micromeritics apparatus (ambient temperature, 1 atm of pressure). CO2 adsorption experiments carried out on KOH carbons activated highlighted an enhancing of CO2 capture properties with the increase of the surface area value from 1.9 mmol/g with 2194 m2/g to 3.4 mmol/g with 3000 m2/g