Heavy metal removal and crude bio-oil upgrading from Sedum plumbizincicola harvest using hydrothermal upgrading process

The main aim of this study was to separate heavy metals and yield crude bio-oil from a heavy metals hyperaccumulator harvest, Sedum plumbizincicola, through hydrothermal upgrading process. Parameters such as granularity, temperature, pressure, and duration were examined for their effect on the removal efficiency of heavy metals and upgrading efficacy of crude bio-oil. Maximum heavy metal removal efficiency of >99% and crude bio-oil upgrading efficiency of >63% were attained with an 18 mesh (1 mm) granularity, and 22.1 MPa at 370 °C in the presence of 10 mg/L additives for 60 s. Under these optimized conditions, an oil phase (mostly composed of phenolic hydrocarbons and derivatives), a water phase raffinate containing Zn2+ (0.39 g/L), Pb2+ (0.10 g/L), Cu2+ (0.16 g/L), and a solid phase (the hydrothermal upgrading residue, which completely satisfies the limit set by China legislation related to biosolids disposal, were obtained).