Browsing by Subject "Activated carbon"

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    B,N‐doped activated carbon‐based electrodes from potato peels for energy storage applications
    (2025) Straten, Jan Willem; Alhnidi, Muhammad‐Jamal; Alchoumari, Ghassan; Sangam, Krishna; Kruse, Andrea
    Potato peels (PPs) as waste biomass were selected as the biobased carbon source for this study, using urea as N precursor and boron trioxide as B precursor for the “in situ doping” via hydrothermal carbonization (HTC). During HTC, the feedstocks decompose over a wide range of complex chemical degradation mechanisms that finally form single B‐ and N‐ as well as B,N‐co‐doped hydrochars (HCs). Upon chemical ZnCl2 activation, the single B‐doped activated carbon (AC) possessed a maximum B content of 0.2 wt%, whereas co‐doped B,N‐AC had the highest N content of 5.7 wt% with a B content of 0.1 wt%. The influence of single and B,N‐co‐doping on the physical‐chemical material properties of the AC electrodes was analyzed and compared, in combination with its effect on the electrochemical performance for energy storage application. Compared to pristine AC derived from PPs, the B‐doped and B,N‐co‐doped AC depicted increased electrical conductivity (EC) values of 50.3 S ⋅ m−1 and 34.0 S ⋅ m−1, respectively. In addition, the B,N‐co‐doped AC unveiled the highest average specific capacitances of 51.7 F ⋅ g−1 at 100 mV ⋅ s−1 and of 71.9 F ⋅ g−1 at 5 mV ⋅ s−1 outperforming the specific capacitance values of the reference material AC from peat.
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    From coffee waste to wastewater treatment: optimization of hydrothermal carbonization and H₃PO₄ activation for Cr(VI) adsorption
    (2026) Piccoli Miranda de Freitas, Caroline; De Freitas Batista, Gabriel; Dalmolin da Silva, Mariele; Checa Gomez, Manuel; Arauzo, Pablo J.; França da Cunha, Fernando; Kruse, Andrea
    Spent coffee grounds (SCG) are an abundant agro-industrial waste, and their valorization as activated carbon (AC) offers a sustainable approach for wastewater treatment and heavy-metal remediation. However, the high energy demand of SCG activation limits large-scale application. Hydrothermal carbonization (HTC) reduces energy consumption and enhances material properties. This study evaluated the performance of activated carbon (AC) derived from SCG via HTC, followed by H₃PO₄ activation for Cr(VI) removal, and compared it with non-activated carbon obtained by HTC and pyrolysis. The results highlight the effect of chemical activation on enhancing surface area, porosity, and adsorption efficiency. The predicted optimal IN was 1624.7 mg·g⁻¹, closely matching the experimental value of 1640.1 ± 15.5 mg·g⁻¹, achieved at 426 °C, 92 min, and a hydrochar-to-H₃PO₄ ratio of 1:1.6. The optimized AC exhibited a maximum adsorption capacity (Qₑ) of 33 ± 1.1 mg·g⁻¹ and 99.4 ± 0.1 % Cr(VI) removal under pH 2, 25 mg·L⁻¹ initial concentration, and 2 g·L⁻¹ adsorbent dose. In contrast, the non-activated carbon presented a lower iodine number (1411 ± 70 mg·g⁻¹) and inferior adsorption performance, confirming the key role of H₃PO₄ activation in improving surface reactivity and adsorption sites. Chemical activation proved essential for improving Cr(VI) adsorption, with the H₃PO₄-AC exhibiting the highest capacity. These results demonstrate the potential of SCG-derived AC as a low-cost adsorbent for heavy-metal-rich industrial effluents, supporting circular economy strategies.