Enhancement of CO2 adsorption on biochar sorbent modified by metal incorporation

This work is scrutinizing the development of metallized biochar as a low-cost bio-sorbent for low temperature CO2 capture with high adsorption capacity. Accordingly, single-step pyrolysis process was carried out in order to synthesize biochar from rambutan peel (RP) at different temperatures. The biochar product was then subjected to wet impregnation with several magnesium salts including magnesium nitrate, magnesium sulphate, magnesium chloride and magnesium acetate which then subsequently heat-treated with N2. The impregnation of magnesium into the biochar structure improved the CO2 capture performance in the sequence of magnesium nitrate > magnesium sulphate > magnesium chloride > magnesium acetate. There is an enhancement in CO2 adsorption capacity of metallized biochar (76.80 mg g-1) compare with pristine biochar (68.74 mg g-1). It can be justified by the synergetic influences of physicochemical characteristics. Gas selectivity study verified the high affinity of biochar for CO2 capture compared with other gases such as air, methane, and nitrogen. This investigation also revealed a stable performance of the metallized biochar in 25 cycles of CO2 adsorption and desorption. Avrami kinetic model accurately predicted the dynamic CO2 adsorption performance for pristine and metallized biochar.