Demineralization of common ivy-derived biomass and biochar and its effect on the resulting activated carbon properties

Abstract

Biomass waste often contains high amounts of inorganic impurities, which is a limitation for developing high-quality bioproducts, e.g., high-purity activated carbons (ACs). Otherwise, these would be applicable to purify polluted water and air streams. Conventionally, AC’s are purified with non-sustainable and corrosive inorganic acids. This study illustrates the successful removal of the impurities from common ivy, Hedera helix L., through treatment with a natural deep eutectic solvent (NADES), namely choline chloride-malic acid (CCl:MA, 1:1 M). The demineralization efficiency is benchmarked against H2O and dilute hydrochloric acid (HCl). Moreover, the importance of the process sequence, pre- or post- pyrolysis demineralization, for AC-production was investigated. The three solvents showed different biomass (pre-pyrolysis) demineralization efficiencies, they were ranked, from best to worst, as follows: HCl > CCl:MA > H2O. However, demineralizing the biomass after pyrolysis yielded highly porous ACs, with a good mix of meso-and micropores. In this case, no differences in removal performance could be observed between HCl and CCl:MA. Lastly, the ACs phosphate adsorption capacity was highest after demineralizing biomass with either H2O or CCl:MA. Ultimately, this investigation demonstrated CCl:MA’s potential as a green demineralization agent to treat metal-contaminated biomass in future bio-refinery processes.