Hydrothermal Treatment of the Pristine and Contaminated Cd/Zn Hyperaccumulators for Bio-Oil Production and Heavy Metal Separation

Abstract

Hydrothermal conversion is a promising technology to dispose of biomass wastes. To achieve the harmless treatment of heavy metal (HM) hyperaccumulators and production of bio-oil, hydrothermal conversion of two types of Sedum alfredii [i.e., uncontaminated S. alfredii (SAL) and the harvested S. alfredii after phytoremediation (SAH)] at 210−300 °C was conducted in this study. Only 0.53−1.59% of Cd and 0.34−5.94% of Zn in SAH migrated to bio-oils, which were much lower than those in hydrochar and the aqueous products. High hydrothermal conversion temperature promoted the bio-oil yield, and the S. alfredii-derived bio-oils showed considerable higher heating values (32.07−33.83 MJ/kg). The main components of bio-oils were aliphatic hydrocarbons, followed by oxygen-containing compounds (e.g., alcohols, phenols, and ketones/aldehydes) and nitrogencontaining compounds. The bio-oils derived from SAL contained a higher content of aliphatic hydrocarbons (56.39−60.11%) and N-containing compounds (9.03−15.17%), while the SAH-derived bio-oils had more ketones/aldehydes (15.17−19.79%), which could be ascribed to the component difference of feedstocks and the catalytic effect of Zn. Moreover, the distillable fraction (boiling point <538 °C) in the bio-oils was up to 79.89−86.90%. These results suggest that hydrothermal conversion of S. alfredii could be a promising technique for the HM separation and value-added bio-oil production.

Speciation Evolution and Phase Migration of Phosphorus and Nitrogen during Subcritical Hydrothermal Recycling of Antibiotic Fermentation Residue

“…Recently, the subcritical hydrothermal liquefaction (HTL) technique has emerged as a sustainable treatment technique for biowastes. − Compared to other technologies such as pyrolysis and incineration, HTL can effectively control the release of pollutants and fully recycle the chemicals, hydrochar, and nutrients from biowastes. − Moreover, it has been proved that HTL with low energy consumption can effectively eliminate the residual antibiotics. ,− Although several studies have treated AR by HTL, the focus was primarily on improving the anaerobic fermentation, , degrading the antibiotics, , and removing the nitrogen. , Limited information is available on the synchronous recycling of the multiple nutrients (e.g., N and P) from AR with the HTL technology.…”

Selective Clipping of a Lignin-Derived Monomer by Plasma for Bio-Oil Upgrading

“…2 Biomass-derived bio-oils usually have a high oxygen content, resulting in limited heating value, poor thermal stability, and high viscosity. 3 These undesirable properties are an obstacle to direct use as an energy source; therefore, bio-oils have to be upgraded by removing oxygen atoms. Torrefaction is used to reduce moisture and oxygen contents as a pretreatment step of biomass pyrolysis.…”

“…Lignocellulosic biomass is one of the abundant renewable and sustainable resources for producing biofuels, which are an alternative to fossil fuels . Biomass-derived bio-oils usually have a high oxygen content, resulting in limited heating value, poor thermal stability, and high viscosity . These undesirable properties are an obstacle to direct use as an energy source; therefore, bio-oils have to be upgraded by removing oxygen atoms.…”