Composition‐Tunable Lignocellulosic Aerogels From Eucalyptus spp. Bark for Oil and Cu 2+ Adsorption

Composition‐tunable lignocellulosic aerogels were produced from Eucalyptus spp. bark as adsorbents without additional chemical functionalization. Four formulations comprising cellulose, lignin, and microfibrillated cellulose (MFC) were freeze‐dried: cellulose (CEL), cellulose/MFC (CEL‐M), lignin/MFC (L‐M), and cellulose/lignin/MFC (CEL‐L‐M) aerogels. The samples were characterized by SEM, nitrogen physisorption, XRD, FTIR, density, and porosity. All aerogels exhibited ultralow density and porosity above 99%, with composition‐dependent fibrillar organization, crystallinity, and pore architecture. Bru nauer–Emmett–Teller (BET) surface areas ranged from 0.95 to 7.37 m 2 g −1 for as‐synthesized samples and reached 18.38 m 2 g −1 after Cu 2+ adsorption. CEL showed the highest used cooking‐oil uptake (approximately 40 g g −1 ), whereas CEL‐M performed best for used pump oil (38.81 g g −1 ). Cu 2+ adsorption increased from pH 2 to pH 4–5; CEL‐L‐M reached the highest capacity (1.1337 g g −1 ) at pH 5 after 30 min, while L‐M reached 0.8964 g g −1 within 15 min and remained above 1.06 g g −1 from 30 to 60 min. FTIR changes and Cu detection by EDS supported pH‐regulated binding at oxygen‐containing sites. Accordingly, cellulose, lignin, and MFC contributed differently: CEL maximized cooking‐oil uptake, CEL‐M maximized pump‐oil uptake, while L‐M and CEL‐L‐M provided the fastest Cu 2+ uptake and highest capacity, respectively.