Recent reports indicate that chars and other black carbon substances may have inherent reactivity towards certain compounds. In some cases this reactivity has been attributed to persistent free radicals in the solid that generate reactive oxygen species (ROS) derived from molecular oxygen (via H2O2), especially hydroxyl radical HO*. Other research has shown that chars possess reversible electron donor/acceptor capacity, like a battery. In this study, we investigated the ability of chars made anoxically from pure lignin and cellulose at 500 oC to transform p-nitrophenol (PNP) in water. PNP loss and H2O2 production and decay and were monitored as a function of char storage time in moist air at 20 oC prior to its submersion in the aqueous phase. We found that ROS played only a minor role, whereas direct reaction of sorbed PNP with non-radical (reducing) sites on the chars accounted for most of the reactivity. The lignin char was more reactive in every respect than the cellulose char. The results have important implications for the inherent reactivity of biochar and natural chars.

Inherent reactivity of chars from model feedstocks, lignin and cellulose: Persistent free radicals, reactive oxygen species, and non-radical direct reacting sites

255th National Meeting (2018)

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