20.500.12556/DKUM-96637 Conversion of waste from the vegetable oil industry into efficient adsorbents for dye removal thermo-chemical modification of hydrochar with green modifiers, adsorption kinetics and mechanisms The discharge of synthetic dyes into aquatic environments poses a significant environmental threat. Waste from the vegetable oil industry, such as hemp oil cake, offers a low-cost feedstock for the production of carbonaceous adsorbents for water purification due to its high carbon content and availability. In this study, hydrochars produced from hemp oil cake and cheese whey were thermo-chemically modified using natural vinegars and compared with conventional modifiers, then tested for adsorption of bromocresol green (BCG) and methylene blue (MB) dyes. According to FTIR, BET and SEM-EDS analyses, modifications with alcoholic and wine vinegar, acetic acid and KOH significantly altered the structural properties of the hydrochars, increasing the specific surface area from 1.60 to 234.35, 260.73, 71.32 and 582.84 m²/g, respectively. Among the acid-modified hydrochars, the hydrochar modified with alcoholic vinegar was the most effective, with an adsorption capacity of 15.45 mg/g for BCG and 62.16 mg/g for MB, as determined by Langmuir kinetic model, while the unmodified hydrochar had lower capacities. In comparison, the highest adsorption capacities for KOH-modified hydrochar were 640.15 mg/g for MB and 38.17 mg/g for BCG. Adsorption kinetics mostly followed a pseudo-second order model, indicating a combination of chemical and physical adsorption mechanisms driven byelectrostatic interactions, hydrogen bonding and π–π interactions. Isothermal kinetic modelling revealed heterogeneous adsorption behaviour, with the Redlich-Peterson and Freundlich models providing the best fit to the experimental data. The results emphasise the enhanced effectiveness of thermo-chemically modified hemp oil cake hydrochars for sustainable dye removal and water purification applications. hydrothermal carbonization hydrochar modification lignocellulosic biomass adsorption kinetics dyes hidrotermalna karbonizacija modifikacija ogljikovega oglja lignocelulozna biomasa adsorpcija kinetika barvila true false true Springer Nature Angleški jezik Slovenski jezik https://link.springer.com/journal/13399 © The Author(s) 2025 Članek v reviji 2026-01-21 16:23:58 2026-01-21 16:24:01 2026-01-22 03:35:11 0000-00-00 00:00:00 2026 0 0 22 str. Vol. 16, ǂart. number ǂ19 2026 0000-00-00 Zaloznikova Objavljeno NiDoloceno 2025-03-13 2025-10-27 2026-01-06 66.02 265370371 10.1007/s13399-025-07017-2 2190-6823 s13399-025-07017-2.pdf s13399-025-07017-2.pdf 1 3E59A1BE9F04930537E806201FED0183 bd4475c9fe2b6a312c7da145d97841fa3720c03c8b55ee76bdbed18618983d44 7873f138-f6dd-11f0-80d4-00155d580e02 https://dk.um.si/Dokument.php?lang=slv&id=202360 Fakulteta za kemijo in kemijsko tehnologijo 0 0 0