Enrichment of bio-oil after hydrothermal liquefaction (HTL) of microalgae C. vulgaris grown in wastewater: Bio-char and post HTL wastewater utilization studies

In this study, bio-oil was produced through hydrothermal liquefaction (HTL) of C. vulgaris biomass cultivated in wastewater and was enriched into transportation fuels. Bio-oil yield was 29.37% wt at 300 °C, 60 min, at 15 g/200 mL biomass loading rate with 3% wt nano ZnO catalyst loading. Applying catalyst reduced oxygen and nitrogen content in bio-oil and increased its calorific value (19.6 ± 0.8 MJ/Kg). Bio-oil was enriched through liquid-liquid extraction (LLE) and higher yield was obtained at 30 °C for dichloromethane solvent (18.2% wt). Compounds of enriched oil were within the petro-diesel range (C8-C21). Bio-char after HTL process was activated and used as adsorbent in wastewater treatment process to remove organic pollutants (COD, NO3, NH3 and PO4). Treated wastewater can be supplied as growth medium for microalgae cultivation in further experiments. Nearly 3-4 times the nanocatalyst can be reused in the HTL process.