Effect of steam activation of biochar produced from a giant Miscanthus on copper sorption and toxicity

This study aims to evaluate the physiochemical properties, sorption characteristics, and toxicity effects of biochar (BC) produced from Miscanthus sacchariflorus via slow pyrolysis at 500 °C and its steam activation product (ABC). Although BC has a much lower surface area than ABC (181 and 322 m2 g−1, respectively), the Cu sorption capacities of BC and ABC are not significantly different (p > 0.05). A two-compartment model successfully explains the sorption of BC and ABC as being dominated by fast and slow sorption processes, respectively. In addition, both BC and ABC efficiently eliminate the toxicity of Cu towards Daphnia magna. However, ABC itself induced acute toxicity to D. magna, which is possibly due to increased aromaticity upon steam activation. These findings suggest that activation of BC produced from M. sacchariflorus at a pyrolytic temperature of 500 °C may not be appropriate in terms of Cu sorption and toxicity reduction.