Enhanced Manganese Uptake by BTCA‐Functionalized Lignocellulosic Felts

ABSTRACT Lignocellulosic felts derived from hemp and flax were investigated as sustainable biosorbents for manganese ions removal from aqueous solutions, both in their native form and after functionalization through 1,2,3,4‐butanetetracarboxylic acid (BTCA) grafting. Batch experiments were conducted to assess the influence of initial metal concentration, adsorbent dosage, pH, and ionic strength on biosorption performance. BTCA modification significantly enhanced Mn 2+ uptake, with flax‐based felts outperforming hemp due to their higher α‐cellulose content, finer fiber morphology, and larger effective surface area. Mn 2+ removal increased with adsorbent dosage and reached its maximum at pH values promoting deprotonation of BTCA carboxyl groups, confirming a complexation‐driven mechanism. Increasing the solution ionic strength (0.1‐0.5 M NaCl) reduced removal efficiency by competitive Na + interactions with cellulose, hemicellulose, and BTCA‐derived ‐COO − groups, though modified felts maintained superior performance. Adsorption isotherm modelling revealed distinct behaviors among materials: native felts fit moderately well to the Langmuir model, while BTCA‐modified flax showed excellent agreement with Langmuir and Dubinin–Radushkevich models. The mean free energy of 18 kJ mol −1 confirmed chemisorption via metal‐carboxylate coordination as the dominant mechanism. Overall, BTCA‐modified flax felts emerged as highly effective and environmentally friendly biosorbents, offering strong potential for Mn 2+ removal in industrial wastewater treatment applications.