Validation of a fluidized bed thermogravimetric method with integrated gas analysis for CO2 capture by activated hydrochar from pistachio shells Kroiß, Christoph Al Afif, Rafat Pröll, Tobias Pfeifer, Christoph Weinberger, Christian Tondl, Gregor Hydrothermal carbonization Activated hydrochar CO2 adsorption Adsorption isotherms Thermogravimetric analysis Gas analysis Method validation Carbon capture Hydrothermal carbonization (HTC) of pistachio shells was performed in a high-pressure batch reactor at 200 °C for 2 h, yielding a carbon-enriched hydrochar. Elemental analysis shows an increase in carbon mass fraction from 44.76 % to 54.09 % and a decrease in atomic O/C and H/C ratios, confirming carbonization as visualized in a Van Krevelen diagram. The hydrochar was chemically activated by potassium hydroxide (KOH) impregnation and thermal treatment, yielding 16–28 wt.% activated hydrochar. Adsorption isotherms were determined in a thermogravimetric, fluidized-bed reactor using a stepwise CO2 concentration program limited to 50 vol.% CO2 in N2 (0–5–10–25–50–0 vol.% CO2 at 100 kPa total pressure). The setup was extended by integrating online gas analysis to provide an independent, time-resolved mass-balance cross-check. Validation was performed using Lewatit VP OC 1065 by an internal Langmuir parity check and comparison with literature-based Toth model representations; gas analysis is demonstrated using a representative low-concentration step and by comparing Langmuir models derived from gas-based versus gravimetric loadings at 50 °C. For activated hydrochar, equilibrium points were obtained up to 50 vol.% CO2 (pCO2 ≈ 50 kPa) and show decreasing loading with increasing temperature. For literature comparison and indicative saturation reporting, isotherm fits were extrapolated to pure CO2 at 100 kPa: the maximum loading derived from the raw weighing signal was 1.84 mmol/g; after buoyancy correction, the corresponding value is 1.45 mmol/g. Springer Science and Business Media LLC 2026 info:eu-repo/semantics/article doc-type:article text http://purl.org/coar/resource_type/c_6501 https://ris.uni-paderborn.de/record/66282 Kroiß C, Al Afif R, Pröll T, Pfeifer C, Weinberger C, Tondl G. Validation of a fluidized bed thermogravimetric method with integrated gas analysis for CO2 capture by activated hydrochar from pistachio shells. <i>Discover Applied Sciences</i>. Published online 2026. doi:<a href="https://doi.org/10.1007/s42452-026-09061-7">10.1007/s42452-026-09061-7</a> eng info:eu-repo/semantics/altIdentifier/doi/10.1007/s42452-026-09061-7 info:eu-repo/semantics/altIdentifier/issn/3004-9261 info:eu-repo/semantics/closedAccess