20.500.12556/DKUM-99727 Hydrothermal conversion of lignocellulosic biomass using deep eutectic solvents and iron salts for solid biofuel and chemical recovery Hydrothermal carbonization (HTC) of lignocellulosic waste (hemp oil cake) was investigated using a thermally stable choline chloride–glycolic acid deep eutectic solvent (DES) as an alternative reaction medium, in combination with iron salts (FeCl3 and FeSO4), to assess their synergistic effects on product properties. DES significantly enhanced biomass hydrolysis and solubilisation, while Fe salts modified reaction pathways and nutrient distribution. Compared to water-assisted HTC, DES-assisted HTC resulted in reduced hydrochar yields (50–72 wt%), particularly at higher temperatures and DES dosages, but promoted carbon enrichment. Carbon content increased from 49.6 wt% for water-derived hydrochar to 53.1–59.7 wt% for DES–Fe derived hydrochars, accompanied by a substantial reduction in nitrogen content. The combined DES–Fe HTC resulted in a notable improvement in fuel quality, with heating values reaching up to 26.6 MJ/kg. SEM showed increased porosity and spherical carbon structures. XPS and NMR confirmed enhanced aromatisation and nitrogen stabilization in heterocyclic and graphitic forms, with Fe salts accelerating graphitic-N formation. DES-assisted HTC enriched process liquids in organic carbon, phenolics and furfural, indicating enhanced extraction but also increased ecotoxicity. No genotoxicity was detected in the Vicia faba assay. This work introduces a novel DES–Fe-assisted HTC approach to tailor hydrochar properties for renewable energy applications. hydrothermal treatment deep eutectic solvent inorganic catalyst hydrochar properties liquid fraction properties hidrotermalna obdelava inorganski katalizator true false true Elsevier Ltd. Angleški jezik Slovenski jezik https://www.sciencedirect.com/journal/renewable-energy © 2026 The Authors Članek v reviji 2026-08-25 09:31:31 2026-08-25 09:31:32 2026-08-26 03:09:51 0000-00-00 00:00:00 2026 0 0 15 str. Vol. 247, [article no.] 126186 Oct. 2026 0000-00-00 Zaloznikova Objavljeno NiDoloceno 2026-01-08 2026-07-11 2026-07-13 66 287020547 10.1016/j.renene.2026.126186 1879-0682 https://www.sciencedirect.com/science/article/pii/S0960148126010128?via%3Dihub 1 ff17a630-a056-11f1-a977-00155d0001be https://dk.um.si/Dokument.php?lang=slv&id=210399 1-s2.0-S0960148126010128-main.pdf 1-s2.0-S0960148126010128-main.pdf 1 A16CCD906B39B7B588A6CA17547F33D3 3135a46d8664f03b9034aa4c1c9bd0956f70e8ab23441ba67b932ec33e4ff459 d49277ae-a057-11f1-a977-00155d0001be https://dk.um.si/Dokument.php?lang=slv&id=210400 Fakulteta za kemijo in kemijsko tehnologijo 0 0 0