Synthesis of NaA and NaX Zeolites in Untreated Lead Tree Wood for Cu(II) Adsorption

This study addresses the challenge of separating powdered zeolite adsorbents by developing biomass-supported composites via in situ crystallization of zeolites NaA (LTA) and NaX (FAU) within lead tree wood. Wood was mixed with precursor gels and subjected to hydrothermal treatment, yielding composites and external zeolite powders. Phase formation and morphology were confirmed by X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The zeolite content in the composites was estimated from TGA to be approximately 10 wt.% for LTW–NaA and ~2 wt.% for LTW–NaX. Cu(II) adsorption was evaluated under controlled conditions and analyzed using Langmuir and Freundlich models together with Giles classification. The NaA powder showed the highest capacity (qₘ ≈ 210 mg g−1), while composite performance reflected zeolite loading. When normalized by zeolite mass, the composites exhibited comparable or enhanced capacities relative to powders, suggesting improved accessibility of active sites. NaA-based materials displayed H-type isotherms, whereas NaX-based materials showed L-type behavior, indicating different adsorption mechanisms. These results demonstrate that framework topology and biomass confinement jointly influence adsorption and that the composites are promising, easily recoverable adsorbents, with further work required to assess regeneration and long-term stability.