Production of char from vacuum pyrolysis of South-African sugar cane bagasse and its characterization as activated carbon and biochar

International audience The potential of vacuum pyrolysis to convert sugar cane bagasse into char materials for wastewatertreatment and soil amendment is the focus of this research paper. Vacuum pyrolysis produces bothbio-oil and char in similar quantities. Vacuum pyrolysis has the potential to produce high quality charsfor wastewater treatment and soil amendment directly during the conversion process, with no furtherupgrading required. In the present study, chars with the required porous structure was obtained directlyfrom the vacuum pyrolysis process, making it very efficient as adsorbent both in terms of methylene blue(MB) adsorption with a N2-BET surface area of 418 m2 g−1. Further steam activation of the chars benefitedthe development of meso- and macroporosity, although this upgrading step was not essential to achievethe required performance of char as an MB adsorbent. The development of large pores during the vacuumpyrolysis favored physisorption of MB, rather than chemisorption. The chemical nature of the vacuumpyrolysis char resulted in a slightly acidic surface (pH 6.56). The biochar from vacuum pyrolysis can beconsidered as a highly beneficial soil amendment, as it would enhance soil nutrient and water holdingcapacity, due to its high cation exchange capacity (122 cmolc kg−1) and high surface area. It is also a goodsource of beneficial plant macro- and micronutrients and contains negligible levels of toxic elements.