Impact of pore structure in pitch-based activated carbon fibers on Cr(VI) adsorption behaviors

Hexavalent chromium (Cr(VI)) is a highly toxic pollutant widely used in various industrial processes, posing serious threats to human health and the environment. Herein, pitch-based activated carbon fibers (PACFs) were synthesized via steam activation of pitch precursors to achieve efficient Cr(VI) removal from aqueous solutions. PACF_800, activated at 800 °C, exhibited an exceptionally high specific surface area (1768 m² g^–1) and a micropore volume of 0.872 cm³ g^–1, accounting for 63.5 % of the total pore volume. The maximum adsorption capacity reached 93.2 mg g^–1 at pH 3, attributed to the synergistic effects of a highly developed microporous network and abundant oxygen-containing functional groups. Adsorption isotherm analysis showed excellent agreement with the Langmuir model (R² > 0.99), indicating a predominant monolayer adsorption mechanism, while kinetic analysis revealed a shift toward pseudo-second-order behavior at higher activation temperatures, consistent with enhanced chemisorption. Furthermore, PACFs demonstrated outstanding reusability, retaining 94.9 % of their initial adsorption capacity after five regeneration cycles. These results highlight the strong potential of PACFs as high-performance adsorbents for Cr(VI) removal in industrial wastewater treatment.